1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2018 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{} 1988-2018 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) 1988-2018 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
163 * In-Process Agent:: In-Process Agent
165 * GDB Bugs:: Reporting bugs in @value{GDBN}
167 @ifset SYSTEM_READLINE
168 * Command Line Editing: (rluserman). Command Line Editing
169 * Using History Interactively: (history). Using History Interactively
171 @ifclear SYSTEM_READLINE
172 * Command Line Editing:: Command Line Editing
173 * Using History Interactively:: Using History Interactively
175 * In Memoriam:: In Memoriam
176 * Formatting Documentation:: How to format and print @value{GDBN} documentation
177 * Installing GDB:: Installing GDB
178 * Maintenance Commands:: Maintenance Commands
179 * Remote Protocol:: GDB Remote Serial Protocol
180 * Agent Expressions:: The GDB Agent Expression Mechanism
181 * Target Descriptions:: How targets can describe themselves to
183 * Operating System Information:: Getting additional information from
185 * Trace File Format:: GDB trace file format
186 * Index Section Format:: .gdb_index section format
187 * Man Pages:: Manual pages
188 * Copying:: GNU General Public License says
189 how you can copy and share GDB
190 * GNU Free Documentation License:: The license for this documentation
191 * Concept Index:: Index of @value{GDBN} concepts
192 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
193 functions, and Python data types
201 @unnumbered Summary of @value{GDBN}
203 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
204 going on ``inside'' another program while it executes---or what another
205 program was doing at the moment it crashed.
207 @value{GDBN} can do four main kinds of things (plus other things in support of
208 these) to help you catch bugs in the act:
212 Start your program, specifying anything that might affect its behavior.
215 Make your program stop on specified conditions.
218 Examine what has happened, when your program has stopped.
221 Change things in your program, so you can experiment with correcting the
222 effects of one bug and go on to learn about another.
225 You can use @value{GDBN} to debug programs written in C and C@t{++}.
226 For more information, see @ref{Supported Languages,,Supported Languages}.
227 For more information, see @ref{C,,C and C++}.
229 Support for D is partial. For information on D, see
233 Support for Modula-2 is partial. For information on Modula-2, see
234 @ref{Modula-2,,Modula-2}.
236 Support for OpenCL C is partial. For information on OpenCL C, see
237 @ref{OpenCL C,,OpenCL C}.
240 Debugging Pascal programs which use sets, subranges, file variables, or
241 nested functions does not currently work. @value{GDBN} does not support
242 entering expressions, printing values, or similar features using Pascal
246 @value{GDBN} can be used to debug programs written in Fortran, although
247 it may be necessary to refer to some variables with a trailing
250 @value{GDBN} can be used to debug programs written in Objective-C,
251 using either the Apple/NeXT or the GNU Objective-C runtime.
254 * Free Software:: Freely redistributable software
255 * Free Documentation:: Free Software Needs Free Documentation
256 * Contributors:: Contributors to GDB
260 @unnumberedsec Free Software
262 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
263 General Public License
264 (GPL). The GPL gives you the freedom to copy or adapt a licensed
265 program---but every person getting a copy also gets with it the
266 freedom to modify that copy (which means that they must get access to
267 the source code), and the freedom to distribute further copies.
268 Typical software companies use copyrights to limit your freedoms; the
269 Free Software Foundation uses the GPL to preserve these freedoms.
271 Fundamentally, the General Public License is a license which says that
272 you have these freedoms and that you cannot take these freedoms away
275 @node Free Documentation
276 @unnumberedsec Free Software Needs Free Documentation
278 The biggest deficiency in the free software community today is not in
279 the software---it is the lack of good free documentation that we can
280 include with the free software. Many of our most important
281 programs do not come with free reference manuals and free introductory
282 texts. Documentation is an essential part of any software package;
283 when an important free software package does not come with a free
284 manual and a free tutorial, that is a major gap. We have many such
287 Consider Perl, for instance. The tutorial manuals that people
288 normally use are non-free. How did this come about? Because the
289 authors of those manuals published them with restrictive terms---no
290 copying, no modification, source files not available---which exclude
291 them from the free software world.
293 That wasn't the first time this sort of thing happened, and it was far
294 from the last. Many times we have heard a GNU user eagerly describe a
295 manual that he is writing, his intended contribution to the community,
296 only to learn that he had ruined everything by signing a publication
297 contract to make it non-free.
299 Free documentation, like free software, is a matter of freedom, not
300 price. The problem with the non-free manual is not that publishers
301 charge a price for printed copies---that in itself is fine. (The Free
302 Software Foundation sells printed copies of manuals, too.) The
303 problem is the restrictions on the use of the manual. Free manuals
304 are available in source code form, and give you permission to copy and
305 modify. Non-free manuals do not allow this.
307 The criteria of freedom for a free manual are roughly the same as for
308 free software. Redistribution (including the normal kinds of
309 commercial redistribution) must be permitted, so that the manual can
310 accompany every copy of the program, both on-line and on paper.
312 Permission for modification of the technical content is crucial too.
313 When people modify the software, adding or changing features, if they
314 are conscientious they will change the manual too---so they can
315 provide accurate and clear documentation for the modified program. A
316 manual that leaves you no choice but to write a new manual to document
317 a changed version of the program is not really available to our
320 Some kinds of limits on the way modification is handled are
321 acceptable. For example, requirements to preserve the original
322 author's copyright notice, the distribution terms, or the list of
323 authors, are ok. It is also no problem to require modified versions
324 to include notice that they were modified. Even entire sections that
325 may not be deleted or changed are acceptable, as long as they deal
326 with nontechnical topics (like this one). These kinds of restrictions
327 are acceptable because they don't obstruct the community's normal use
330 However, it must be possible to modify all the @emph{technical}
331 content of the manual, and then distribute the result in all the usual
332 media, through all the usual channels. Otherwise, the restrictions
333 obstruct the use of the manual, it is not free, and we need another
334 manual to replace it.
336 Please spread the word about this issue. Our community continues to
337 lose manuals to proprietary publishing. If we spread the word that
338 free software needs free reference manuals and free tutorials, perhaps
339 the next person who wants to contribute by writing documentation will
340 realize, before it is too late, that only free manuals contribute to
341 the free software community.
343 If you are writing documentation, please insist on publishing it under
344 the GNU Free Documentation License or another free documentation
345 license. Remember that this decision requires your approval---you
346 don't have to let the publisher decide. Some commercial publishers
347 will use a free license if you insist, but they will not propose the
348 option; it is up to you to raise the issue and say firmly that this is
349 what you want. If the publisher you are dealing with refuses, please
350 try other publishers. If you're not sure whether a proposed license
351 is free, write to @email{licensing@@gnu.org}.
353 You can encourage commercial publishers to sell more free, copylefted
354 manuals and tutorials by buying them, and particularly by buying
355 copies from the publishers that paid for their writing or for major
356 improvements. Meanwhile, try to avoid buying non-free documentation
357 at all. Check the distribution terms of a manual before you buy it,
358 and insist that whoever seeks your business must respect your freedom.
359 Check the history of the book, and try to reward the publishers that
360 have paid or pay the authors to work on it.
362 The Free Software Foundation maintains a list of free documentation
363 published by other publishers, at
364 @url{http://www.fsf.org/doc/other-free-books.html}.
367 @unnumberedsec Contributors to @value{GDBN}
369 Richard Stallman was the original author of @value{GDBN}, and of many
370 other @sc{gnu} programs. Many others have contributed to its
371 development. This section attempts to credit major contributors. One
372 of the virtues of free software is that everyone is free to contribute
373 to it; with regret, we cannot actually acknowledge everyone here. The
374 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
375 blow-by-blow account.
377 Changes much prior to version 2.0 are lost in the mists of time.
380 @emph{Plea:} Additions to this section are particularly welcome. If you
381 or your friends (or enemies, to be evenhanded) have been unfairly
382 omitted from this list, we would like to add your names!
385 So that they may not regard their many labors as thankless, we
386 particularly thank those who shepherded @value{GDBN} through major
388 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
389 Jim Blandy (release 4.18);
390 Jason Molenda (release 4.17);
391 Stan Shebs (release 4.14);
392 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
393 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
394 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
395 Jim Kingdon (releases 3.5, 3.4, and 3.3);
396 and Randy Smith (releases 3.2, 3.1, and 3.0).
398 Richard Stallman, assisted at various times by Peter TerMaat, Chris
399 Hanson, and Richard Mlynarik, handled releases through 2.8.
401 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
402 in @value{GDBN}, with significant additional contributions from Per
403 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
404 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
405 much general update work leading to release 3.0).
407 @value{GDBN} uses the BFD subroutine library to examine multiple
408 object-file formats; BFD was a joint project of David V.
409 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
411 David Johnson wrote the original COFF support; Pace Willison did
412 the original support for encapsulated COFF.
414 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
416 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
417 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
419 Jean-Daniel Fekete contributed Sun 386i support.
420 Chris Hanson improved the HP9000 support.
421 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
422 David Johnson contributed Encore Umax support.
423 Jyrki Kuoppala contributed Altos 3068 support.
424 Jeff Law contributed HP PA and SOM support.
425 Keith Packard contributed NS32K support.
426 Doug Rabson contributed Acorn Risc Machine support.
427 Bob Rusk contributed Harris Nighthawk CX-UX support.
428 Chris Smith contributed Convex support (and Fortran debugging).
429 Jonathan Stone contributed Pyramid support.
430 Michael Tiemann contributed SPARC support.
431 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
432 Pace Willison contributed Intel 386 support.
433 Jay Vosburgh contributed Symmetry support.
434 Marko Mlinar contributed OpenRISC 1000 support.
436 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
438 Rich Schaefer and Peter Schauer helped with support of SunOS shared
441 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
442 about several machine instruction sets.
444 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
445 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
446 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
447 and RDI targets, respectively.
449 Brian Fox is the author of the readline libraries providing
450 command-line editing and command history.
452 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
453 Modula-2 support, and contributed the Languages chapter of this manual.
455 Fred Fish wrote most of the support for Unix System Vr4.
456 He also enhanced the command-completion support to cover C@t{++} overloaded
459 Hitachi America (now Renesas America), Ltd. sponsored the support for
460 H8/300, H8/500, and Super-H processors.
462 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
464 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
467 Toshiba sponsored the support for the TX39 Mips processor.
469 Matsushita sponsored the support for the MN10200 and MN10300 processors.
471 Fujitsu sponsored the support for SPARClite and FR30 processors.
473 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
476 Michael Snyder added support for tracepoints.
478 Stu Grossman wrote gdbserver.
480 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
481 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
483 The following people at the Hewlett-Packard Company contributed
484 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
485 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
486 compiler, and the Text User Interface (nee Terminal User Interface):
487 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
488 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
489 provided HP-specific information in this manual.
491 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
492 Robert Hoehne made significant contributions to the DJGPP port.
494 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
495 development since 1991. Cygnus engineers who have worked on @value{GDBN}
496 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
497 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
498 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
499 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
500 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
501 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
502 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
503 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
504 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
505 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
506 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
507 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
508 Zuhn have made contributions both large and small.
510 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
511 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
513 Jim Blandy added support for preprocessor macros, while working for Red
516 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
517 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
518 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
519 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
520 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
521 with the migration of old architectures to this new framework.
523 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
524 unwinder framework, this consisting of a fresh new design featuring
525 frame IDs, independent frame sniffers, and the sentinel frame. Mark
526 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
527 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
528 trad unwinders. The architecture-specific changes, each involving a
529 complete rewrite of the architecture's frame code, were carried out by
530 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
531 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
532 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
533 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
536 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
537 Tensilica, Inc.@: contributed support for Xtensa processors. Others
538 who have worked on the Xtensa port of @value{GDBN} in the past include
539 Steve Tjiang, John Newlin, and Scott Foehner.
541 Michael Eager and staff of Xilinx, Inc., contributed support for the
542 Xilinx MicroBlaze architecture.
544 Initial support for the FreeBSD/mips target and native configuration
545 was developed by SRI International and the University of Cambridge
546 Computer Laboratory under DARPA/AFRL contract FA8750-10-C-0237
547 ("CTSRD"), as part of the DARPA CRASH research programme.
549 The original port to the OpenRISC 1000 is believed to be due to
550 Alessandro Forin and Per Bothner. More recent ports have been the work
551 of Jeremy Bennett, Franck Jullien, Stefan Wallentowitz and
555 @chapter A Sample @value{GDBN} Session
557 You can use this manual at your leisure to read all about @value{GDBN}.
558 However, a handful of commands are enough to get started using the
559 debugger. This chapter illustrates those commands.
562 In this sample session, we emphasize user input like this: @b{input},
563 to make it easier to pick out from the surrounding output.
566 @c FIXME: this example may not be appropriate for some configs, where
567 @c FIXME...primary interest is in remote use.
569 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
570 processor) exhibits the following bug: sometimes, when we change its
571 quote strings from the default, the commands used to capture one macro
572 definition within another stop working. In the following short @code{m4}
573 session, we define a macro @code{foo} which expands to @code{0000}; we
574 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
575 same thing. However, when we change the open quote string to
576 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
577 procedure fails to define a new synonym @code{baz}:
586 @b{define(bar,defn(`foo'))}
590 @b{changequote(<QUOTE>,<UNQUOTE>)}
592 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
595 m4: End of input: 0: fatal error: EOF in string
599 Let us use @value{GDBN} to try to see what is going on.
602 $ @b{@value{GDBP} m4}
603 @c FIXME: this falsifies the exact text played out, to permit smallbook
604 @c FIXME... format to come out better.
605 @value{GDBN} is free software and you are welcome to distribute copies
606 of it under certain conditions; type "show copying" to see
608 There is absolutely no warranty for @value{GDBN}; type "show warranty"
611 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
616 @value{GDBN} reads only enough symbol data to know where to find the
617 rest when needed; as a result, the first prompt comes up very quickly.
618 We now tell @value{GDBN} to use a narrower display width than usual, so
619 that examples fit in this manual.
622 (@value{GDBP}) @b{set width 70}
626 We need to see how the @code{m4} built-in @code{changequote} works.
627 Having looked at the source, we know the relevant subroutine is
628 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
629 @code{break} command.
632 (@value{GDBP}) @b{break m4_changequote}
633 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
637 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
638 control; as long as control does not reach the @code{m4_changequote}
639 subroutine, the program runs as usual:
642 (@value{GDBP}) @b{run}
643 Starting program: /work/Editorial/gdb/gnu/m4/m4
651 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
652 suspends execution of @code{m4}, displaying information about the
653 context where it stops.
656 @b{changequote(<QUOTE>,<UNQUOTE>)}
658 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
660 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
664 Now we use the command @code{n} (@code{next}) to advance execution to
665 the next line of the current function.
669 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
674 @code{set_quotes} looks like a promising subroutine. We can go into it
675 by using the command @code{s} (@code{step}) instead of @code{next}.
676 @code{step} goes to the next line to be executed in @emph{any}
677 subroutine, so it steps into @code{set_quotes}.
681 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
683 530 if (lquote != def_lquote)
687 The display that shows the subroutine where @code{m4} is now
688 suspended (and its arguments) is called a stack frame display. It
689 shows a summary of the stack. We can use the @code{backtrace}
690 command (which can also be spelled @code{bt}), to see where we are
691 in the stack as a whole: the @code{backtrace} command displays a
692 stack frame for each active subroutine.
695 (@value{GDBP}) @b{bt}
696 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
698 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
700 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
701 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
703 #4 0x79dc in expand_input () at macro.c:40
704 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
708 We step through a few more lines to see what happens. The first two
709 times, we can use @samp{s}; the next two times we use @code{n} to avoid
710 falling into the @code{xstrdup} subroutine.
714 0x3b5c 532 if (rquote != def_rquote)
716 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
717 def_lquote : xstrdup(lq);
719 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
722 538 len_lquote = strlen(rquote);
726 The last line displayed looks a little odd; we can examine the variables
727 @code{lquote} and @code{rquote} to see if they are in fact the new left
728 and right quotes we specified. We use the command @code{p}
729 (@code{print}) to see their values.
732 (@value{GDBP}) @b{p lquote}
733 $1 = 0x35d40 "<QUOTE>"
734 (@value{GDBP}) @b{p rquote}
735 $2 = 0x35d50 "<UNQUOTE>"
739 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
740 To look at some context, we can display ten lines of source
741 surrounding the current line with the @code{l} (@code{list}) command.
747 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
749 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
752 538 len_lquote = strlen(rquote);
753 539 len_rquote = strlen(lquote);
760 Let us step past the two lines that set @code{len_lquote} and
761 @code{len_rquote}, and then examine the values of those variables.
765 539 len_rquote = strlen(lquote);
768 (@value{GDBP}) @b{p len_lquote}
770 (@value{GDBP}) @b{p len_rquote}
775 That certainly looks wrong, assuming @code{len_lquote} and
776 @code{len_rquote} are meant to be the lengths of @code{lquote} and
777 @code{rquote} respectively. We can set them to better values using
778 the @code{p} command, since it can print the value of
779 any expression---and that expression can include subroutine calls and
783 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
785 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
790 Is that enough to fix the problem of using the new quotes with the
791 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
792 executing with the @code{c} (@code{continue}) command, and then try the
793 example that caused trouble initially:
799 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
806 Success! The new quotes now work just as well as the default ones. The
807 problem seems to have been just the two typos defining the wrong
808 lengths. We allow @code{m4} exit by giving it an EOF as input:
812 Program exited normally.
816 The message @samp{Program exited normally.} is from @value{GDBN}; it
817 indicates @code{m4} has finished executing. We can end our @value{GDBN}
818 session with the @value{GDBN} @code{quit} command.
821 (@value{GDBP}) @b{quit}
825 @chapter Getting In and Out of @value{GDBN}
827 This chapter discusses how to start @value{GDBN}, and how to get out of it.
831 type @samp{@value{GDBP}} to start @value{GDBN}.
833 type @kbd{quit} or @kbd{Ctrl-d} to exit.
837 * Invoking GDB:: How to start @value{GDBN}
838 * Quitting GDB:: How to quit @value{GDBN}
839 * Shell Commands:: How to use shell commands inside @value{GDBN}
840 * Logging Output:: How to log @value{GDBN}'s output to a file
844 @section Invoking @value{GDBN}
846 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
847 @value{GDBN} reads commands from the terminal until you tell it to exit.
849 You can also run @code{@value{GDBP}} with a variety of arguments and options,
850 to specify more of your debugging environment at the outset.
852 The command-line options described here are designed
853 to cover a variety of situations; in some environments, some of these
854 options may effectively be unavailable.
856 The most usual way to start @value{GDBN} is with one argument,
857 specifying an executable program:
860 @value{GDBP} @var{program}
864 You can also start with both an executable program and a core file
868 @value{GDBP} @var{program} @var{core}
871 You can, instead, specify a process ID as a second argument, if you want
872 to debug a running process:
875 @value{GDBP} @var{program} 1234
879 would attach @value{GDBN} to process @code{1234} (unless you also have a file
880 named @file{1234}; @value{GDBN} does check for a core file first).
882 Taking advantage of the second command-line argument requires a fairly
883 complete operating system; when you use @value{GDBN} as a remote
884 debugger attached to a bare board, there may not be any notion of
885 ``process'', and there is often no way to get a core dump. @value{GDBN}
886 will warn you if it is unable to attach or to read core dumps.
888 You can optionally have @code{@value{GDBP}} pass any arguments after the
889 executable file to the inferior using @code{--args}. This option stops
892 @value{GDBP} --args gcc -O2 -c foo.c
894 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
895 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
897 You can run @code{@value{GDBP}} without printing the front material, which describes
898 @value{GDBN}'s non-warranty, by specifying @code{--silent}
899 (or @code{-q}/@code{--quiet}):
902 @value{GDBP} --silent
906 You can further control how @value{GDBN} starts up by using command-line
907 options. @value{GDBN} itself can remind you of the options available.
917 to display all available options and briefly describe their use
918 (@samp{@value{GDBP} -h} is a shorter equivalent).
920 All options and command line arguments you give are processed
921 in sequential order. The order makes a difference when the
922 @samp{-x} option is used.
926 * File Options:: Choosing files
927 * Mode Options:: Choosing modes
928 * Startup:: What @value{GDBN} does during startup
932 @subsection Choosing Files
934 When @value{GDBN} starts, it reads any arguments other than options as
935 specifying an executable file and core file (or process ID). This is
936 the same as if the arguments were specified by the @samp{-se} and
937 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
938 first argument that does not have an associated option flag as
939 equivalent to the @samp{-se} option followed by that argument; and the
940 second argument that does not have an associated option flag, if any, as
941 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
942 If the second argument begins with a decimal digit, @value{GDBN} will
943 first attempt to attach to it as a process, and if that fails, attempt
944 to open it as a corefile. If you have a corefile whose name begins with
945 a digit, you can prevent @value{GDBN} from treating it as a pid by
946 prefixing it with @file{./}, e.g.@: @file{./12345}.
948 If @value{GDBN} has not been configured to included core file support,
949 such as for most embedded targets, then it will complain about a second
950 argument and ignore it.
952 Many options have both long and short forms; both are shown in the
953 following list. @value{GDBN} also recognizes the long forms if you truncate
954 them, so long as enough of the option is present to be unambiguous.
955 (If you prefer, you can flag option arguments with @samp{--} rather
956 than @samp{-}, though we illustrate the more usual convention.)
958 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
959 @c way, both those who look for -foo and --foo in the index, will find
963 @item -symbols @var{file}
965 @cindex @code{--symbols}
967 Read symbol table from file @var{file}.
969 @item -exec @var{file}
971 @cindex @code{--exec}
973 Use file @var{file} as the executable file to execute when appropriate,
974 and for examining pure data in conjunction with a core dump.
978 Read symbol table from file @var{file} and use it as the executable
981 @item -core @var{file}
983 @cindex @code{--core}
985 Use file @var{file} as a core dump to examine.
987 @item -pid @var{number}
988 @itemx -p @var{number}
991 Connect to process ID @var{number}, as with the @code{attach} command.
993 @item -command @var{file}
995 @cindex @code{--command}
997 Execute commands from file @var{file}. The contents of this file is
998 evaluated exactly as the @code{source} command would.
999 @xref{Command Files,, Command files}.
1001 @item -eval-command @var{command}
1002 @itemx -ex @var{command}
1003 @cindex @code{--eval-command}
1005 Execute a single @value{GDBN} command.
1007 This option may be used multiple times to call multiple commands. It may
1008 also be interleaved with @samp{-command} as required.
1011 @value{GDBP} -ex 'target sim' -ex 'load' \
1012 -x setbreakpoints -ex 'run' a.out
1015 @item -init-command @var{file}
1016 @itemx -ix @var{file}
1017 @cindex @code{--init-command}
1019 Execute commands from file @var{file} before loading the inferior (but
1020 after loading gdbinit files).
1023 @item -init-eval-command @var{command}
1024 @itemx -iex @var{command}
1025 @cindex @code{--init-eval-command}
1027 Execute a single @value{GDBN} command before loading the inferior (but
1028 after loading gdbinit files).
1031 @item -directory @var{directory}
1032 @itemx -d @var{directory}
1033 @cindex @code{--directory}
1035 Add @var{directory} to the path to search for source and script files.
1039 @cindex @code{--readnow}
1041 Read each symbol file's entire symbol table immediately, rather than
1042 the default, which is to read it incrementally as it is needed.
1043 This makes startup slower, but makes future operations faster.
1046 @anchor{--readnever}
1047 @cindex @code{--readnever}, command-line option
1048 Do not read each symbol file's symbolic debug information. This makes
1049 startup faster but at the expense of not being able to perform
1050 symbolic debugging. DWARF unwind information is also not read,
1051 meaning backtraces may become incomplete or inaccurate. One use of
1052 this is when a user simply wants to do the following sequence: attach,
1053 dump core, detach. Loading the debugging information in this case is
1054 an unnecessary cause of delay.
1058 @subsection Choosing Modes
1060 You can run @value{GDBN} in various alternative modes---for example, in
1061 batch mode or quiet mode.
1069 Do not execute commands found in any initialization file.
1070 There are three init files, loaded in the following order:
1073 @item @file{system.gdbinit}
1074 This is the system-wide init file.
1075 Its location is specified with the @code{--with-system-gdbinit}
1076 configure option (@pxref{System-wide configuration}).
1077 It is loaded first when @value{GDBN} starts, before command line options
1078 have been processed.
1079 @item @file{~/.gdbinit}
1080 This is the init file in your home directory.
1081 It is loaded next, after @file{system.gdbinit}, and before
1082 command options have been processed.
1083 @item @file{./.gdbinit}
1084 This is the init file in the current directory.
1085 It is loaded last, after command line options other than @code{-x} and
1086 @code{-ex} have been processed. Command line options @code{-x} and
1087 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1090 For further documentation on startup processing, @xref{Startup}.
1091 For documentation on how to write command files,
1092 @xref{Command Files,,Command Files}.
1097 Do not execute commands found in @file{~/.gdbinit}, the init file
1098 in your home directory.
1104 @cindex @code{--quiet}
1105 @cindex @code{--silent}
1107 ``Quiet''. Do not print the introductory and copyright messages. These
1108 messages are also suppressed in batch mode.
1111 @cindex @code{--batch}
1112 Run in batch mode. Exit with status @code{0} after processing all the
1113 command files specified with @samp{-x} (and all commands from
1114 initialization files, if not inhibited with @samp{-n}). Exit with
1115 nonzero status if an error occurs in executing the @value{GDBN} commands
1116 in the command files. Batch mode also disables pagination, sets unlimited
1117 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1118 off} were in effect (@pxref{Messages/Warnings}).
1120 Batch mode may be useful for running @value{GDBN} as a filter, for
1121 example to download and run a program on another computer; in order to
1122 make this more useful, the message
1125 Program exited normally.
1129 (which is ordinarily issued whenever a program running under
1130 @value{GDBN} control terminates) is not issued when running in batch
1134 @cindex @code{--batch-silent}
1135 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1136 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1137 unaffected). This is much quieter than @samp{-silent} and would be useless
1138 for an interactive session.
1140 This is particularly useful when using targets that give @samp{Loading section}
1141 messages, for example.
1143 Note that targets that give their output via @value{GDBN}, as opposed to
1144 writing directly to @code{stdout}, will also be made silent.
1146 @item -return-child-result
1147 @cindex @code{--return-child-result}
1148 The return code from @value{GDBN} will be the return code from the child
1149 process (the process being debugged), with the following exceptions:
1153 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1154 internal error. In this case the exit code is the same as it would have been
1155 without @samp{-return-child-result}.
1157 The user quits with an explicit value. E.g., @samp{quit 1}.
1159 The child process never runs, or is not allowed to terminate, in which case
1160 the exit code will be -1.
1163 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1164 when @value{GDBN} is being used as a remote program loader or simulator
1169 @cindex @code{--nowindows}
1171 ``No windows''. If @value{GDBN} comes with a graphical user interface
1172 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1173 interface. If no GUI is available, this option has no effect.
1177 @cindex @code{--windows}
1179 If @value{GDBN} includes a GUI, then this option requires it to be
1182 @item -cd @var{directory}
1184 Run @value{GDBN} using @var{directory} as its working directory,
1185 instead of the current directory.
1187 @item -data-directory @var{directory}
1188 @itemx -D @var{directory}
1189 @cindex @code{--data-directory}
1191 Run @value{GDBN} using @var{directory} as its data directory.
1192 The data directory is where @value{GDBN} searches for its
1193 auxiliary files. @xref{Data Files}.
1197 @cindex @code{--fullname}
1199 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1200 subprocess. It tells @value{GDBN} to output the full file name and line
1201 number in a standard, recognizable fashion each time a stack frame is
1202 displayed (which includes each time your program stops). This
1203 recognizable format looks like two @samp{\032} characters, followed by
1204 the file name, line number and character position separated by colons,
1205 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1206 @samp{\032} characters as a signal to display the source code for the
1209 @item -annotate @var{level}
1210 @cindex @code{--annotate}
1211 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1212 effect is identical to using @samp{set annotate @var{level}}
1213 (@pxref{Annotations}). The annotation @var{level} controls how much
1214 information @value{GDBN} prints together with its prompt, values of
1215 expressions, source lines, and other types of output. Level 0 is the
1216 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1217 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1218 that control @value{GDBN}, and level 2 has been deprecated.
1220 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1224 @cindex @code{--args}
1225 Change interpretation of command line so that arguments following the
1226 executable file are passed as command line arguments to the inferior.
1227 This option stops option processing.
1229 @item -baud @var{bps}
1231 @cindex @code{--baud}
1233 Set the line speed (baud rate or bits per second) of any serial
1234 interface used by @value{GDBN} for remote debugging.
1236 @item -l @var{timeout}
1238 Set the timeout (in seconds) of any communication used by @value{GDBN}
1239 for remote debugging.
1241 @item -tty @var{device}
1242 @itemx -t @var{device}
1243 @cindex @code{--tty}
1245 Run using @var{device} for your program's standard input and output.
1246 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1248 @c resolve the situation of these eventually
1250 @cindex @code{--tui}
1251 Activate the @dfn{Text User Interface} when starting. The Text User
1252 Interface manages several text windows on the terminal, showing
1253 source, assembly, registers and @value{GDBN} command outputs
1254 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1255 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1256 Using @value{GDBN} under @sc{gnu} Emacs}).
1258 @item -interpreter @var{interp}
1259 @cindex @code{--interpreter}
1260 Use the interpreter @var{interp} for interface with the controlling
1261 program or device. This option is meant to be set by programs which
1262 communicate with @value{GDBN} using it as a back end.
1263 @xref{Interpreters, , Command Interpreters}.
1265 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1266 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1267 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1268 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1269 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1270 @sc{gdb/mi} interfaces are no longer supported.
1273 @cindex @code{--write}
1274 Open the executable and core files for both reading and writing. This
1275 is equivalent to the @samp{set write on} command inside @value{GDBN}
1279 @cindex @code{--statistics}
1280 This option causes @value{GDBN} to print statistics about time and
1281 memory usage after it completes each command and returns to the prompt.
1284 @cindex @code{--version}
1285 This option causes @value{GDBN} to print its version number and
1286 no-warranty blurb, and exit.
1288 @item -configuration
1289 @cindex @code{--configuration}
1290 This option causes @value{GDBN} to print details about its build-time
1291 configuration parameters, and then exit. These details can be
1292 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1297 @subsection What @value{GDBN} Does During Startup
1298 @cindex @value{GDBN} startup
1300 Here's the description of what @value{GDBN} does during session startup:
1304 Sets up the command interpreter as specified by the command line
1305 (@pxref{Mode Options, interpreter}).
1309 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1310 used when building @value{GDBN}; @pxref{System-wide configuration,
1311 ,System-wide configuration and settings}) and executes all the commands in
1314 @anchor{Home Directory Init File}
1316 Reads the init file (if any) in your home directory@footnote{On
1317 DOS/Windows systems, the home directory is the one pointed to by the
1318 @code{HOME} environment variable.} and executes all the commands in
1321 @anchor{Option -init-eval-command}
1323 Executes commands and command files specified by the @samp{-iex} and
1324 @samp{-ix} options in their specified order. Usually you should use the
1325 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1326 settings before @value{GDBN} init files get executed and before inferior
1330 Processes command line options and operands.
1332 @anchor{Init File in the Current Directory during Startup}
1334 Reads and executes the commands from init file (if any) in the current
1335 working directory as long as @samp{set auto-load local-gdbinit} is set to
1336 @samp{on} (@pxref{Init File in the Current Directory}).
1337 This is only done if the current directory is
1338 different from your home directory. Thus, you can have more than one
1339 init file, one generic in your home directory, and another, specific
1340 to the program you are debugging, in the directory where you invoke
1344 If the command line specified a program to debug, or a process to
1345 attach to, or a core file, @value{GDBN} loads any auto-loaded
1346 scripts provided for the program or for its loaded shared libraries.
1347 @xref{Auto-loading}.
1349 If you wish to disable the auto-loading during startup,
1350 you must do something like the following:
1353 $ gdb -iex "set auto-load python-scripts off" myprogram
1356 Option @samp{-ex} does not work because the auto-loading is then turned
1360 Executes commands and command files specified by the @samp{-ex} and
1361 @samp{-x} options in their specified order. @xref{Command Files}, for
1362 more details about @value{GDBN} command files.
1365 Reads the command history recorded in the @dfn{history file}.
1366 @xref{Command History}, for more details about the command history and the
1367 files where @value{GDBN} records it.
1370 Init files use the same syntax as @dfn{command files} (@pxref{Command
1371 Files}) and are processed by @value{GDBN} in the same way. The init
1372 file in your home directory can set options (such as @samp{set
1373 complaints}) that affect subsequent processing of command line options
1374 and operands. Init files are not executed if you use the @samp{-nx}
1375 option (@pxref{Mode Options, ,Choosing Modes}).
1377 To display the list of init files loaded by gdb at startup, you
1378 can use @kbd{gdb --help}.
1380 @cindex init file name
1381 @cindex @file{.gdbinit}
1382 @cindex @file{gdb.ini}
1383 The @value{GDBN} init files are normally called @file{.gdbinit}.
1384 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1385 the limitations of file names imposed by DOS filesystems. The Windows
1386 port of @value{GDBN} uses the standard name, but if it finds a
1387 @file{gdb.ini} file in your home directory, it warns you about that
1388 and suggests to rename the file to the standard name.
1392 @section Quitting @value{GDBN}
1393 @cindex exiting @value{GDBN}
1394 @cindex leaving @value{GDBN}
1397 @kindex quit @r{[}@var{expression}@r{]}
1398 @kindex q @r{(@code{quit})}
1399 @item quit @r{[}@var{expression}@r{]}
1401 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1402 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1403 do not supply @var{expression}, @value{GDBN} will terminate normally;
1404 otherwise it will terminate using the result of @var{expression} as the
1409 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1410 terminates the action of any @value{GDBN} command that is in progress and
1411 returns to @value{GDBN} command level. It is safe to type the interrupt
1412 character at any time because @value{GDBN} does not allow it to take effect
1413 until a time when it is safe.
1415 If you have been using @value{GDBN} to control an attached process or
1416 device, you can release it with the @code{detach} command
1417 (@pxref{Attach, ,Debugging an Already-running Process}).
1419 @node Shell Commands
1420 @section Shell Commands
1422 If you need to execute occasional shell commands during your
1423 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1424 just use the @code{shell} command.
1429 @cindex shell escape
1430 @item shell @var{command-string}
1431 @itemx !@var{command-string}
1432 Invoke a standard shell to execute @var{command-string}.
1433 Note that no space is needed between @code{!} and @var{command-string}.
1434 If it exists, the environment variable @code{SHELL} determines which
1435 shell to run. Otherwise @value{GDBN} uses the default shell
1436 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1439 The utility @code{make} is often needed in development environments.
1440 You do not have to use the @code{shell} command for this purpose in
1445 @cindex calling make
1446 @item make @var{make-args}
1447 Execute the @code{make} program with the specified
1448 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1451 @node Logging Output
1452 @section Logging Output
1453 @cindex logging @value{GDBN} output
1454 @cindex save @value{GDBN} output to a file
1456 You may want to save the output of @value{GDBN} commands to a file.
1457 There are several commands to control @value{GDBN}'s logging.
1461 @item set logging on
1463 @item set logging off
1465 @cindex logging file name
1466 @item set logging file @var{file}
1467 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1468 @item set logging overwrite [on|off]
1469 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1470 you want @code{set logging on} to overwrite the logfile instead.
1471 @item set logging redirect [on|off]
1472 By default, @value{GDBN} output will go to both the terminal and the logfile.
1473 Set @code{redirect} if you want output to go only to the log file.
1474 @kindex show logging
1476 Show the current values of the logging settings.
1480 @chapter @value{GDBN} Commands
1482 You can abbreviate a @value{GDBN} command to the first few letters of the command
1483 name, if that abbreviation is unambiguous; and you can repeat certain
1484 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1485 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1486 show you the alternatives available, if there is more than one possibility).
1489 * Command Syntax:: How to give commands to @value{GDBN}
1490 * Completion:: Command completion
1491 * Help:: How to ask @value{GDBN} for help
1494 @node Command Syntax
1495 @section Command Syntax
1497 A @value{GDBN} command is a single line of input. There is no limit on
1498 how long it can be. It starts with a command name, which is followed by
1499 arguments whose meaning depends on the command name. For example, the
1500 command @code{step} accepts an argument which is the number of times to
1501 step, as in @samp{step 5}. You can also use the @code{step} command
1502 with no arguments. Some commands do not allow any arguments.
1504 @cindex abbreviation
1505 @value{GDBN} command names may always be truncated if that abbreviation is
1506 unambiguous. Other possible command abbreviations are listed in the
1507 documentation for individual commands. In some cases, even ambiguous
1508 abbreviations are allowed; for example, @code{s} is specially defined as
1509 equivalent to @code{step} even though there are other commands whose
1510 names start with @code{s}. You can test abbreviations by using them as
1511 arguments to the @code{help} command.
1513 @cindex repeating commands
1514 @kindex RET @r{(repeat last command)}
1515 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1516 repeat the previous command. Certain commands (for example, @code{run})
1517 will not repeat this way; these are commands whose unintentional
1518 repetition might cause trouble and which you are unlikely to want to
1519 repeat. User-defined commands can disable this feature; see
1520 @ref{Define, dont-repeat}.
1522 The @code{list} and @code{x} commands, when you repeat them with
1523 @key{RET}, construct new arguments rather than repeating
1524 exactly as typed. This permits easy scanning of source or memory.
1526 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1527 output, in a way similar to the common utility @code{more}
1528 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1529 @key{RET} too many in this situation, @value{GDBN} disables command
1530 repetition after any command that generates this sort of display.
1532 @kindex # @r{(a comment)}
1534 Any text from a @kbd{#} to the end of the line is a comment; it does
1535 nothing. This is useful mainly in command files (@pxref{Command
1536 Files,,Command Files}).
1538 @cindex repeating command sequences
1539 @kindex Ctrl-o @r{(operate-and-get-next)}
1540 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1541 commands. This command accepts the current line, like @key{RET}, and
1542 then fetches the next line relative to the current line from the history
1546 @section Command Completion
1549 @cindex word completion
1550 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1551 only one possibility; it can also show you what the valid possibilities
1552 are for the next word in a command, at any time. This works for @value{GDBN}
1553 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1555 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1556 of a word. If there is only one possibility, @value{GDBN} fills in the
1557 word, and waits for you to finish the command (or press @key{RET} to
1558 enter it). For example, if you type
1560 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1561 @c complete accuracy in these examples; space introduced for clarity.
1562 @c If texinfo enhancements make it unnecessary, it would be nice to
1563 @c replace " @key" by "@key" in the following...
1565 (@value{GDBP}) info bre @key{TAB}
1569 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1570 the only @code{info} subcommand beginning with @samp{bre}:
1573 (@value{GDBP}) info breakpoints
1577 You can either press @key{RET} at this point, to run the @code{info
1578 breakpoints} command, or backspace and enter something else, if
1579 @samp{breakpoints} does not look like the command you expected. (If you
1580 were sure you wanted @code{info breakpoints} in the first place, you
1581 might as well just type @key{RET} immediately after @samp{info bre},
1582 to exploit command abbreviations rather than command completion).
1584 If there is more than one possibility for the next word when you press
1585 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1586 characters and try again, or just press @key{TAB} a second time;
1587 @value{GDBN} displays all the possible completions for that word. For
1588 example, you might want to set a breakpoint on a subroutine whose name
1589 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1590 just sounds the bell. Typing @key{TAB} again displays all the
1591 function names in your program that begin with those characters, for
1595 (@value{GDBP}) b make_ @key{TAB}
1596 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1597 make_a_section_from_file make_environ
1598 make_abs_section make_function_type
1599 make_blockvector make_pointer_type
1600 make_cleanup make_reference_type
1601 make_command make_symbol_completion_list
1602 (@value{GDBP}) b make_
1606 After displaying the available possibilities, @value{GDBN} copies your
1607 partial input (@samp{b make_} in the example) so you can finish the
1610 If you just want to see the list of alternatives in the first place, you
1611 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1612 means @kbd{@key{META} ?}. You can type this either by holding down a
1613 key designated as the @key{META} shift on your keyboard (if there is
1614 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1616 If the number of possible completions is large, @value{GDBN} will
1617 print as much of the list as it has collected, as well as a message
1618 indicating that the list may be truncated.
1621 (@value{GDBP}) b m@key{TAB}@key{TAB}
1623 <... the rest of the possible completions ...>
1624 *** List may be truncated, max-completions reached. ***
1629 This behavior can be controlled with the following commands:
1632 @kindex set max-completions
1633 @item set max-completions @var{limit}
1634 @itemx set max-completions unlimited
1635 Set the maximum number of completion candidates. @value{GDBN} will
1636 stop looking for more completions once it collects this many candidates.
1637 This is useful when completing on things like function names as collecting
1638 all the possible candidates can be time consuming.
1639 The default value is 200. A value of zero disables tab-completion.
1640 Note that setting either no limit or a very large limit can make
1642 @kindex show max-completions
1643 @item show max-completions
1644 Show the maximum number of candidates that @value{GDBN} will collect and show
1648 @cindex quotes in commands
1649 @cindex completion of quoted strings
1650 Sometimes the string you need, while logically a ``word'', may contain
1651 parentheses or other characters that @value{GDBN} normally excludes from
1652 its notion of a word. To permit word completion to work in this
1653 situation, you may enclose words in @code{'} (single quote marks) in
1654 @value{GDBN} commands.
1656 A likely situation where you might need this is in typing an
1657 expression that involves a C@t{++} symbol name with template
1658 parameters. This is because when completing expressions, GDB treats
1659 the @samp{<} character as word delimiter, assuming that it's the
1660 less-than comparison operator (@pxref{C Operators, , C and C@t{++}
1663 For example, when you want to call a C@t{++} template function
1664 interactively using the @code{print} or @code{call} commands, you may
1665 need to distinguish whether you mean the version of @code{name} that
1666 was specialized for @code{int}, @code{name<int>()}, or the version
1667 that was specialized for @code{float}, @code{name<float>()}. To use
1668 the word-completion facilities in this situation, type a single quote
1669 @code{'} at the beginning of the function name. This alerts
1670 @value{GDBN} that it may need to consider more information than usual
1671 when you press @key{TAB} or @kbd{M-?} to request word completion:
1674 (@value{GDBP}) p 'func< @kbd{M-?}
1675 func<int>() func<float>()
1676 (@value{GDBP}) p 'func<
1679 When setting breakpoints however (@pxref{Specify Location}), you don't
1680 usually need to type a quote before the function name, because
1681 @value{GDBN} understands that you want to set a breakpoint on a
1685 (@value{GDBP}) b func< @kbd{M-?}
1686 func<int>() func<float>()
1687 (@value{GDBP}) b func<
1690 This is true even in the case of typing the name of C@t{++} overloaded
1691 functions (multiple definitions of the same function, distinguished by
1692 argument type). For example, when you want to set a breakpoint you
1693 don't need to distinguish whether you mean the version of @code{name}
1694 that takes an @code{int} parameter, @code{name(int)}, or the version
1695 that takes a @code{float} parameter, @code{name(float)}.
1698 (@value{GDBP}) b bubble( @kbd{M-?}
1699 bubble(int) bubble(double)
1700 (@value{GDBP}) b bubble(dou @kbd{M-?}
1704 See @ref{quoting names} for a description of other scenarios that
1707 For more information about overloaded functions, see @ref{C Plus Plus
1708 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1709 overload-resolution off} to disable overload resolution;
1710 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1712 @cindex completion of structure field names
1713 @cindex structure field name completion
1714 @cindex completion of union field names
1715 @cindex union field name completion
1716 When completing in an expression which looks up a field in a
1717 structure, @value{GDBN} also tries@footnote{The completer can be
1718 confused by certain kinds of invalid expressions. Also, it only
1719 examines the static type of the expression, not the dynamic type.} to
1720 limit completions to the field names available in the type of the
1724 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1725 magic to_fputs to_rewind
1726 to_data to_isatty to_write
1727 to_delete to_put to_write_async_safe
1732 This is because the @code{gdb_stdout} is a variable of the type
1733 @code{struct ui_file} that is defined in @value{GDBN} sources as
1740 ui_file_flush_ftype *to_flush;
1741 ui_file_write_ftype *to_write;
1742 ui_file_write_async_safe_ftype *to_write_async_safe;
1743 ui_file_fputs_ftype *to_fputs;
1744 ui_file_read_ftype *to_read;
1745 ui_file_delete_ftype *to_delete;
1746 ui_file_isatty_ftype *to_isatty;
1747 ui_file_rewind_ftype *to_rewind;
1748 ui_file_put_ftype *to_put;
1755 @section Getting Help
1756 @cindex online documentation
1759 You can always ask @value{GDBN} itself for information on its commands,
1760 using the command @code{help}.
1763 @kindex h @r{(@code{help})}
1766 You can use @code{help} (abbreviated @code{h}) with no arguments to
1767 display a short list of named classes of commands:
1771 List of classes of commands:
1773 aliases -- Aliases of other commands
1774 breakpoints -- Making program stop at certain points
1775 data -- Examining data
1776 files -- Specifying and examining files
1777 internals -- Maintenance commands
1778 obscure -- Obscure features
1779 running -- Running the program
1780 stack -- Examining the stack
1781 status -- Status inquiries
1782 support -- Support facilities
1783 tracepoints -- Tracing of program execution without
1784 stopping the program
1785 user-defined -- User-defined commands
1787 Type "help" followed by a class name for a list of
1788 commands in that class.
1789 Type "help" followed by command name for full
1791 Command name abbreviations are allowed if unambiguous.
1794 @c the above line break eliminates huge line overfull...
1796 @item help @var{class}
1797 Using one of the general help classes as an argument, you can get a
1798 list of the individual commands in that class. For example, here is the
1799 help display for the class @code{status}:
1802 (@value{GDBP}) help status
1807 @c Line break in "show" line falsifies real output, but needed
1808 @c to fit in smallbook page size.
1809 info -- Generic command for showing things
1810 about the program being debugged
1811 show -- Generic command for showing things
1814 Type "help" followed by command name for full
1816 Command name abbreviations are allowed if unambiguous.
1820 @item help @var{command}
1821 With a command name as @code{help} argument, @value{GDBN} displays a
1822 short paragraph on how to use that command.
1825 @item apropos @var{args}
1826 The @code{apropos} command searches through all of the @value{GDBN}
1827 commands, and their documentation, for the regular expression specified in
1828 @var{args}. It prints out all matches found. For example:
1839 alias -- Define a new command that is an alias of an existing command
1840 aliases -- Aliases of other commands
1841 d -- Delete some breakpoints or auto-display expressions
1842 del -- Delete some breakpoints or auto-display expressions
1843 delete -- Delete some breakpoints or auto-display expressions
1848 @item complete @var{args}
1849 The @code{complete @var{args}} command lists all the possible completions
1850 for the beginning of a command. Use @var{args} to specify the beginning of the
1851 command you want completed. For example:
1857 @noindent results in:
1868 @noindent This is intended for use by @sc{gnu} Emacs.
1871 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1872 and @code{show} to inquire about the state of your program, or the state
1873 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1874 manual introduces each of them in the appropriate context. The listings
1875 under @code{info} and under @code{show} in the Command, Variable, and
1876 Function Index point to all the sub-commands. @xref{Command and Variable
1882 @kindex i @r{(@code{info})}
1884 This command (abbreviated @code{i}) is for describing the state of your
1885 program. For example, you can show the arguments passed to a function
1886 with @code{info args}, list the registers currently in use with @code{info
1887 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1888 You can get a complete list of the @code{info} sub-commands with
1889 @w{@code{help info}}.
1893 You can assign the result of an expression to an environment variable with
1894 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1895 @code{set prompt $}.
1899 In contrast to @code{info}, @code{show} is for describing the state of
1900 @value{GDBN} itself.
1901 You can change most of the things you can @code{show}, by using the
1902 related command @code{set}; for example, you can control what number
1903 system is used for displays with @code{set radix}, or simply inquire
1904 which is currently in use with @code{show radix}.
1907 To display all the settable parameters and their current
1908 values, you can use @code{show} with no arguments; you may also use
1909 @code{info set}. Both commands produce the same display.
1910 @c FIXME: "info set" violates the rule that "info" is for state of
1911 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1912 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1916 Here are several miscellaneous @code{show} subcommands, all of which are
1917 exceptional in lacking corresponding @code{set} commands:
1920 @kindex show version
1921 @cindex @value{GDBN} version number
1923 Show what version of @value{GDBN} is running. You should include this
1924 information in @value{GDBN} bug-reports. If multiple versions of
1925 @value{GDBN} are in use at your site, you may need to determine which
1926 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1927 commands are introduced, and old ones may wither away. Also, many
1928 system vendors ship variant versions of @value{GDBN}, and there are
1929 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1930 The version number is the same as the one announced when you start
1933 @kindex show copying
1934 @kindex info copying
1935 @cindex display @value{GDBN} copyright
1938 Display information about permission for copying @value{GDBN}.
1940 @kindex show warranty
1941 @kindex info warranty
1943 @itemx info warranty
1944 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1945 if your version of @value{GDBN} comes with one.
1947 @kindex show configuration
1948 @item show configuration
1949 Display detailed information about the way @value{GDBN} was configured
1950 when it was built. This displays the optional arguments passed to the
1951 @file{configure} script and also configuration parameters detected
1952 automatically by @command{configure}. When reporting a @value{GDBN}
1953 bug (@pxref{GDB Bugs}), it is important to include this information in
1959 @chapter Running Programs Under @value{GDBN}
1961 When you run a program under @value{GDBN}, you must first generate
1962 debugging information when you compile it.
1964 You may start @value{GDBN} with its arguments, if any, in an environment
1965 of your choice. If you are doing native debugging, you may redirect
1966 your program's input and output, debug an already running process, or
1967 kill a child process.
1970 * Compilation:: Compiling for debugging
1971 * Starting:: Starting your program
1972 * Arguments:: Your program's arguments
1973 * Environment:: Your program's environment
1975 * Working Directory:: Your program's working directory
1976 * Input/Output:: Your program's input and output
1977 * Attach:: Debugging an already-running process
1978 * Kill Process:: Killing the child process
1980 * Inferiors and Programs:: Debugging multiple inferiors and programs
1981 * Threads:: Debugging programs with multiple threads
1982 * Forks:: Debugging forks
1983 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1987 @section Compiling for Debugging
1989 In order to debug a program effectively, you need to generate
1990 debugging information when you compile it. This debugging information
1991 is stored in the object file; it describes the data type of each
1992 variable or function and the correspondence between source line numbers
1993 and addresses in the executable code.
1995 To request debugging information, specify the @samp{-g} option when you run
1998 Programs that are to be shipped to your customers are compiled with
1999 optimizations, using the @samp{-O} compiler option. However, some
2000 compilers are unable to handle the @samp{-g} and @samp{-O} options
2001 together. Using those compilers, you cannot generate optimized
2002 executables containing debugging information.
2004 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
2005 without @samp{-O}, making it possible to debug optimized code. We
2006 recommend that you @emph{always} use @samp{-g} whenever you compile a
2007 program. You may think your program is correct, but there is no sense
2008 in pushing your luck. For more information, see @ref{Optimized Code}.
2010 Older versions of the @sc{gnu} C compiler permitted a variant option
2011 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
2012 format; if your @sc{gnu} C compiler has this option, do not use it.
2014 @value{GDBN} knows about preprocessor macros and can show you their
2015 expansion (@pxref{Macros}). Most compilers do not include information
2016 about preprocessor macros in the debugging information if you specify
2017 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
2018 the @sc{gnu} C compiler, provides macro information if you are using
2019 the DWARF debugging format, and specify the option @option{-g3}.
2021 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
2022 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
2023 information on @value{NGCC} options affecting debug information.
2025 You will have the best debugging experience if you use the latest
2026 version of the DWARF debugging format that your compiler supports.
2027 DWARF is currently the most expressive and best supported debugging
2028 format in @value{GDBN}.
2032 @section Starting your Program
2038 @kindex r @r{(@code{run})}
2041 Use the @code{run} command to start your program under @value{GDBN}.
2042 You must first specify the program name with an argument to
2043 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2044 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2045 command (@pxref{Files, ,Commands to Specify Files}).
2049 If you are running your program in an execution environment that
2050 supports processes, @code{run} creates an inferior process and makes
2051 that process run your program. In some environments without processes,
2052 @code{run} jumps to the start of your program. Other targets,
2053 like @samp{remote}, are always running. If you get an error
2054 message like this one:
2057 The "remote" target does not support "run".
2058 Try "help target" or "continue".
2062 then use @code{continue} to run your program. You may need @code{load}
2063 first (@pxref{load}).
2065 The execution of a program is affected by certain information it
2066 receives from its superior. @value{GDBN} provides ways to specify this
2067 information, which you must do @emph{before} starting your program. (You
2068 can change it after starting your program, but such changes only affect
2069 your program the next time you start it.) This information may be
2070 divided into four categories:
2073 @item The @emph{arguments.}
2074 Specify the arguments to give your program as the arguments of the
2075 @code{run} command. If a shell is available on your target, the shell
2076 is used to pass the arguments, so that you may use normal conventions
2077 (such as wildcard expansion or variable substitution) in describing
2079 In Unix systems, you can control which shell is used with the
2080 @code{SHELL} environment variable. If you do not define @code{SHELL},
2081 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2082 use of any shell with the @code{set startup-with-shell} command (see
2085 @item The @emph{environment.}
2086 Your program normally inherits its environment from @value{GDBN}, but you can
2087 use the @value{GDBN} commands @code{set environment} and @code{unset
2088 environment} to change parts of the environment that affect
2089 your program. @xref{Environment, ,Your Program's Environment}.
2091 @item The @emph{working directory.}
2092 You can set your program's working directory with the command
2093 @kbd{set cwd}. If you do not set any working directory with this
2094 command, your program will inherit @value{GDBN}'s working directory if
2095 native debugging, or the remote server's working directory if remote
2096 debugging. @xref{Working Directory, ,Your Program's Working
2099 @item The @emph{standard input and output.}
2100 Your program normally uses the same device for standard input and
2101 standard output as @value{GDBN} is using. You can redirect input and output
2102 in the @code{run} command line, or you can use the @code{tty} command to
2103 set a different device for your program.
2104 @xref{Input/Output, ,Your Program's Input and Output}.
2107 @emph{Warning:} While input and output redirection work, you cannot use
2108 pipes to pass the output of the program you are debugging to another
2109 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2113 When you issue the @code{run} command, your program begins to execute
2114 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2115 of how to arrange for your program to stop. Once your program has
2116 stopped, you may call functions in your program, using the @code{print}
2117 or @code{call} commands. @xref{Data, ,Examining Data}.
2119 If the modification time of your symbol file has changed since the last
2120 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2121 table, and reads it again. When it does this, @value{GDBN} tries to retain
2122 your current breakpoints.
2127 @cindex run to main procedure
2128 The name of the main procedure can vary from language to language.
2129 With C or C@t{++}, the main procedure name is always @code{main}, but
2130 other languages such as Ada do not require a specific name for their
2131 main procedure. The debugger provides a convenient way to start the
2132 execution of the program and to stop at the beginning of the main
2133 procedure, depending on the language used.
2135 The @samp{start} command does the equivalent of setting a temporary
2136 breakpoint at the beginning of the main procedure and then invoking
2137 the @samp{run} command.
2139 @cindex elaboration phase
2140 Some programs contain an @dfn{elaboration} phase where some startup code is
2141 executed before the main procedure is called. This depends on the
2142 languages used to write your program. In C@t{++}, for instance,
2143 constructors for static and global objects are executed before
2144 @code{main} is called. It is therefore possible that the debugger stops
2145 before reaching the main procedure. However, the temporary breakpoint
2146 will remain to halt execution.
2148 Specify the arguments to give to your program as arguments to the
2149 @samp{start} command. These arguments will be given verbatim to the
2150 underlying @samp{run} command. Note that the same arguments will be
2151 reused if no argument is provided during subsequent calls to
2152 @samp{start} or @samp{run}.
2154 It is sometimes necessary to debug the program during elaboration. In
2155 these cases, using the @code{start} command would stop the execution
2156 of your program too late, as the program would have already completed
2157 the elaboration phase. Under these circumstances, either insert
2158 breakpoints in your elaboration code before running your program or
2159 use the @code{starti} command.
2163 @cindex run to first instruction
2164 The @samp{starti} command does the equivalent of setting a temporary
2165 breakpoint at the first instruction of a program's execution and then
2166 invoking the @samp{run} command. For programs containing an
2167 elaboration phase, the @code{starti} command will stop execution at
2168 the start of the elaboration phase.
2170 @anchor{set exec-wrapper}
2171 @kindex set exec-wrapper
2172 @item set exec-wrapper @var{wrapper}
2173 @itemx show exec-wrapper
2174 @itemx unset exec-wrapper
2175 When @samp{exec-wrapper} is set, the specified wrapper is used to
2176 launch programs for debugging. @value{GDBN} starts your program
2177 with a shell command of the form @kbd{exec @var{wrapper}
2178 @var{program}}. Quoting is added to @var{program} and its
2179 arguments, but not to @var{wrapper}, so you should add quotes if
2180 appropriate for your shell. The wrapper runs until it executes
2181 your program, and then @value{GDBN} takes control.
2183 You can use any program that eventually calls @code{execve} with
2184 its arguments as a wrapper. Several standard Unix utilities do
2185 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2186 with @code{exec "$@@"} will also work.
2188 For example, you can use @code{env} to pass an environment variable to
2189 the debugged program, without setting the variable in your shell's
2193 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2197 This command is available when debugging locally on most targets, excluding
2198 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2200 @kindex set startup-with-shell
2201 @anchor{set startup-with-shell}
2202 @item set startup-with-shell
2203 @itemx set startup-with-shell on
2204 @itemx set startup-with-shell off
2205 @itemx show startup-with-shell
2206 On Unix systems, by default, if a shell is available on your target,
2207 @value{GDBN}) uses it to start your program. Arguments of the
2208 @code{run} command are passed to the shell, which does variable
2209 substitution, expands wildcard characters and performs redirection of
2210 I/O. In some circumstances, it may be useful to disable such use of a
2211 shell, for example, when debugging the shell itself or diagnosing
2212 startup failures such as:
2216 Starting program: ./a.out
2217 During startup program terminated with signal SIGSEGV, Segmentation fault.
2221 which indicates the shell or the wrapper specified with
2222 @samp{exec-wrapper} crashed, not your program. Most often, this is
2223 caused by something odd in your shell's non-interactive mode
2224 initialization file---such as @file{.cshrc} for C-shell,
2225 $@file{.zshenv} for the Z shell, or the file specified in the
2226 @samp{BASH_ENV} environment variable for BASH.
2228 @anchor{set auto-connect-native-target}
2229 @kindex set auto-connect-native-target
2230 @item set auto-connect-native-target
2231 @itemx set auto-connect-native-target on
2232 @itemx set auto-connect-native-target off
2233 @itemx show auto-connect-native-target
2235 By default, if not connected to any target yet (e.g., with
2236 @code{target remote}), the @code{run} command starts your program as a
2237 native process under @value{GDBN}, on your local machine. If you're
2238 sure you don't want to debug programs on your local machine, you can
2239 tell @value{GDBN} to not connect to the native target automatically
2240 with the @code{set auto-connect-native-target off} command.
2242 If @code{on}, which is the default, and if @value{GDBN} is not
2243 connected to a target already, the @code{run} command automaticaly
2244 connects to the native target, if one is available.
2246 If @code{off}, and if @value{GDBN} is not connected to a target
2247 already, the @code{run} command fails with an error:
2251 Don't know how to run. Try "help target".
2254 If @value{GDBN} is already connected to a target, @value{GDBN} always
2255 uses it with the @code{run} command.
2257 In any case, you can explicitly connect to the native target with the
2258 @code{target native} command. For example,
2261 (@value{GDBP}) set auto-connect-native-target off
2263 Don't know how to run. Try "help target".
2264 (@value{GDBP}) target native
2266 Starting program: ./a.out
2267 [Inferior 1 (process 10421) exited normally]
2270 In case you connected explicitly to the @code{native} target,
2271 @value{GDBN} remains connected even if all inferiors exit, ready for
2272 the next @code{run} command. Use the @code{disconnect} command to
2275 Examples of other commands that likewise respect the
2276 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2277 proc}, @code{info os}.
2279 @kindex set disable-randomization
2280 @item set disable-randomization
2281 @itemx set disable-randomization on
2282 This option (enabled by default in @value{GDBN}) will turn off the native
2283 randomization of the virtual address space of the started program. This option
2284 is useful for multiple debugging sessions to make the execution better
2285 reproducible and memory addresses reusable across debugging sessions.
2287 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2288 On @sc{gnu}/Linux you can get the same behavior using
2291 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2294 @item set disable-randomization off
2295 Leave the behavior of the started executable unchanged. Some bugs rear their
2296 ugly heads only when the program is loaded at certain addresses. If your bug
2297 disappears when you run the program under @value{GDBN}, that might be because
2298 @value{GDBN} by default disables the address randomization on platforms, such
2299 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2300 disable-randomization off} to try to reproduce such elusive bugs.
2302 On targets where it is available, virtual address space randomization
2303 protects the programs against certain kinds of security attacks. In these
2304 cases the attacker needs to know the exact location of a concrete executable
2305 code. Randomizing its location makes it impossible to inject jumps misusing
2306 a code at its expected addresses.
2308 Prelinking shared libraries provides a startup performance advantage but it
2309 makes addresses in these libraries predictable for privileged processes by
2310 having just unprivileged access at the target system. Reading the shared
2311 library binary gives enough information for assembling the malicious code
2312 misusing it. Still even a prelinked shared library can get loaded at a new
2313 random address just requiring the regular relocation process during the
2314 startup. Shared libraries not already prelinked are always loaded at
2315 a randomly chosen address.
2317 Position independent executables (PIE) contain position independent code
2318 similar to the shared libraries and therefore such executables get loaded at
2319 a randomly chosen address upon startup. PIE executables always load even
2320 already prelinked shared libraries at a random address. You can build such
2321 executable using @command{gcc -fPIE -pie}.
2323 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2324 (as long as the randomization is enabled).
2326 @item show disable-randomization
2327 Show the current setting of the explicit disable of the native randomization of
2328 the virtual address space of the started program.
2333 @section Your Program's Arguments
2335 @cindex arguments (to your program)
2336 The arguments to your program can be specified by the arguments of the
2338 They are passed to a shell, which expands wildcard characters and
2339 performs redirection of I/O, and thence to your program. Your
2340 @code{SHELL} environment variable (if it exists) specifies what shell
2341 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2342 the default shell (@file{/bin/sh} on Unix).
2344 On non-Unix systems, the program is usually invoked directly by
2345 @value{GDBN}, which emulates I/O redirection via the appropriate system
2346 calls, and the wildcard characters are expanded by the startup code of
2347 the program, not by the shell.
2349 @code{run} with no arguments uses the same arguments used by the previous
2350 @code{run}, or those set by the @code{set args} command.
2355 Specify the arguments to be used the next time your program is run. If
2356 @code{set args} has no arguments, @code{run} executes your program
2357 with no arguments. Once you have run your program with arguments,
2358 using @code{set args} before the next @code{run} is the only way to run
2359 it again without arguments.
2363 Show the arguments to give your program when it is started.
2367 @section Your Program's Environment
2369 @cindex environment (of your program)
2370 The @dfn{environment} consists of a set of environment variables and
2371 their values. Environment variables conventionally record such things as
2372 your user name, your home directory, your terminal type, and your search
2373 path for programs to run. Usually you set up environment variables with
2374 the shell and they are inherited by all the other programs you run. When
2375 debugging, it can be useful to try running your program with a modified
2376 environment without having to start @value{GDBN} over again.
2380 @item path @var{directory}
2381 Add @var{directory} to the front of the @code{PATH} environment variable
2382 (the search path for executables) that will be passed to your program.
2383 The value of @code{PATH} used by @value{GDBN} does not change.
2384 You may specify several directory names, separated by whitespace or by a
2385 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2386 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2387 is moved to the front, so it is searched sooner.
2389 You can use the string @samp{$cwd} to refer to whatever is the current
2390 working directory at the time @value{GDBN} searches the path. If you
2391 use @samp{.} instead, it refers to the directory where you executed the
2392 @code{path} command. @value{GDBN} replaces @samp{.} in the
2393 @var{directory} argument (with the current path) before adding
2394 @var{directory} to the search path.
2395 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2396 @c document that, since repeating it would be a no-op.
2400 Display the list of search paths for executables (the @code{PATH}
2401 environment variable).
2403 @kindex show environment
2404 @item show environment @r{[}@var{varname}@r{]}
2405 Print the value of environment variable @var{varname} to be given to
2406 your program when it starts. If you do not supply @var{varname},
2407 print the names and values of all environment variables to be given to
2408 your program. You can abbreviate @code{environment} as @code{env}.
2410 @kindex set environment
2411 @anchor{set environment}
2412 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2413 Set environment variable @var{varname} to @var{value}. The value
2414 changes for your program (and the shell @value{GDBN} uses to launch
2415 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2416 values of environment variables are just strings, and any
2417 interpretation is supplied by your program itself. The @var{value}
2418 parameter is optional; if it is eliminated, the variable is set to a
2420 @c "any string" here does not include leading, trailing
2421 @c blanks. Gnu asks: does anyone care?
2423 For example, this command:
2430 tells the debugged program, when subsequently run, that its user is named
2431 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2432 are not actually required.)
2434 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2435 which also inherits the environment set with @code{set environment}.
2436 If necessary, you can avoid that by using the @samp{env} program as a
2437 wrapper instead of using @code{set environment}. @xref{set
2438 exec-wrapper}, for an example doing just that.
2440 Environment variables that are set by the user are also transmitted to
2441 @command{gdbserver} to be used when starting the remote inferior.
2442 @pxref{QEnvironmentHexEncoded}.
2444 @kindex unset environment
2445 @anchor{unset environment}
2446 @item unset environment @var{varname}
2447 Remove variable @var{varname} from the environment to be passed to your
2448 program. This is different from @samp{set env @var{varname} =};
2449 @code{unset environment} removes the variable from the environment,
2450 rather than assigning it an empty value.
2452 Environment variables that are unset by the user are also unset on
2453 @command{gdbserver} when starting the remote inferior.
2454 @pxref{QEnvironmentUnset}.
2457 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2458 the shell indicated by your @code{SHELL} environment variable if it
2459 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2460 names a shell that runs an initialization file when started
2461 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2462 for the Z shell, or the file specified in the @samp{BASH_ENV}
2463 environment variable for BASH---any variables you set in that file
2464 affect your program. You may wish to move setting of environment
2465 variables to files that are only run when you sign on, such as
2466 @file{.login} or @file{.profile}.
2468 @node Working Directory
2469 @section Your Program's Working Directory
2471 @cindex working directory (of your program)
2472 Each time you start your program with @code{run}, the inferior will be
2473 initialized with the current working directory specified by the
2474 @kbd{set cwd} command. If no directory has been specified by this
2475 command, then the inferior will inherit @value{GDBN}'s current working
2476 directory as its working directory if native debugging, or it will
2477 inherit the remote server's current working directory if remote
2482 @cindex change inferior's working directory
2483 @anchor{set cwd command}
2484 @item set cwd @r{[}@var{directory}@r{]}
2485 Set the inferior's working directory to @var{directory}, which will be
2486 @code{glob}-expanded in order to resolve tildes (@file{~}). If no
2487 argument has been specified, the command clears the setting and resets
2488 it to an empty state. This setting has no effect on @value{GDBN}'s
2489 working directory, and it only takes effect the next time you start
2490 the inferior. The @file{~} in @var{directory} is a short for the
2491 @dfn{home directory}, usually pointed to by the @env{HOME} environment
2492 variable. On MS-Windows, if @env{HOME} is not defined, @value{GDBN}
2493 uses the concatenation of @env{HOMEDRIVE} and @env{HOMEPATH} as
2496 You can also change @value{GDBN}'s current working directory by using
2497 the @code{cd} command.
2501 @cindex show inferior's working directory
2503 Show the inferior's working directory. If no directory has been
2504 specified by @kbd{set cwd}, then the default inferior's working
2505 directory is the same as @value{GDBN}'s working directory.
2508 @cindex change @value{GDBN}'s working directory
2510 @item cd @r{[}@var{directory}@r{]}
2511 Set the @value{GDBN} working directory to @var{directory}. If not
2512 given, @var{directory} uses @file{'~'}.
2514 The @value{GDBN} working directory serves as a default for the
2515 commands that specify files for @value{GDBN} to operate on.
2516 @xref{Files, ,Commands to Specify Files}.
2517 @xref{set cwd command}
2521 Print the @value{GDBN} working directory.
2524 It is generally impossible to find the current working directory of
2525 the process being debugged (since a program can change its directory
2526 during its run). If you work on a system where @value{GDBN} supports
2527 the @code {info proc} command (@pxref{Process Information}), you can
2528 use the @code{info proc} command to find out the
2529 current working directory of the debuggee.
2532 @section Your Program's Input and Output
2537 By default, the program you run under @value{GDBN} does input and output to
2538 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2539 to its own terminal modes to interact with you, but it records the terminal
2540 modes your program was using and switches back to them when you continue
2541 running your program.
2544 @kindex info terminal
2546 Displays information recorded by @value{GDBN} about the terminal modes your
2550 You can redirect your program's input and/or output using shell
2551 redirection with the @code{run} command. For example,
2558 starts your program, diverting its output to the file @file{outfile}.
2561 @cindex controlling terminal
2562 Another way to specify where your program should do input and output is
2563 with the @code{tty} command. This command accepts a file name as
2564 argument, and causes this file to be the default for future @code{run}
2565 commands. It also resets the controlling terminal for the child
2566 process, for future @code{run} commands. For example,
2573 directs that processes started with subsequent @code{run} commands
2574 default to do input and output on the terminal @file{/dev/ttyb} and have
2575 that as their controlling terminal.
2577 An explicit redirection in @code{run} overrides the @code{tty} command's
2578 effect on the input/output device, but not its effect on the controlling
2581 When you use the @code{tty} command or redirect input in the @code{run}
2582 command, only the input @emph{for your program} is affected. The input
2583 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2584 for @code{set inferior-tty}.
2586 @cindex inferior tty
2587 @cindex set inferior controlling terminal
2588 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2589 display the name of the terminal that will be used for future runs of your
2593 @item set inferior-tty [ @var{tty} ]
2594 @kindex set inferior-tty
2595 Set the tty for the program being debugged to @var{tty}. Omitting @var{tty}
2596 restores the default behavior, which is to use the same terminal as
2599 @item show inferior-tty
2600 @kindex show inferior-tty
2601 Show the current tty for the program being debugged.
2605 @section Debugging an Already-running Process
2610 @item attach @var{process-id}
2611 This command attaches to a running process---one that was started
2612 outside @value{GDBN}. (@code{info files} shows your active
2613 targets.) The command takes as argument a process ID. The usual way to
2614 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2615 or with the @samp{jobs -l} shell command.
2617 @code{attach} does not repeat if you press @key{RET} a second time after
2618 executing the command.
2621 To use @code{attach}, your program must be running in an environment
2622 which supports processes; for example, @code{attach} does not work for
2623 programs on bare-board targets that lack an operating system. You must
2624 also have permission to send the process a signal.
2626 When you use @code{attach}, the debugger finds the program running in
2627 the process first by looking in the current working directory, then (if
2628 the program is not found) by using the source file search path
2629 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2630 the @code{file} command to load the program. @xref{Files, ,Commands to
2633 The first thing @value{GDBN} does after arranging to debug the specified
2634 process is to stop it. You can examine and modify an attached process
2635 with all the @value{GDBN} commands that are ordinarily available when
2636 you start processes with @code{run}. You can insert breakpoints; you
2637 can step and continue; you can modify storage. If you would rather the
2638 process continue running, you may use the @code{continue} command after
2639 attaching @value{GDBN} to the process.
2644 When you have finished debugging the attached process, you can use the
2645 @code{detach} command to release it from @value{GDBN} control. Detaching
2646 the process continues its execution. After the @code{detach} command,
2647 that process and @value{GDBN} become completely independent once more, and you
2648 are ready to @code{attach} another process or start one with @code{run}.
2649 @code{detach} does not repeat if you press @key{RET} again after
2650 executing the command.
2653 If you exit @value{GDBN} while you have an attached process, you detach
2654 that process. If you use the @code{run} command, you kill that process.
2655 By default, @value{GDBN} asks for confirmation if you try to do either of these
2656 things; you can control whether or not you need to confirm by using the
2657 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2661 @section Killing the Child Process
2666 Kill the child process in which your program is running under @value{GDBN}.
2669 This command is useful if you wish to debug a core dump instead of a
2670 running process. @value{GDBN} ignores any core dump file while your program
2673 On some operating systems, a program cannot be executed outside @value{GDBN}
2674 while you have breakpoints set on it inside @value{GDBN}. You can use the
2675 @code{kill} command in this situation to permit running your program
2676 outside the debugger.
2678 The @code{kill} command is also useful if you wish to recompile and
2679 relink your program, since on many systems it is impossible to modify an
2680 executable file while it is running in a process. In this case, when you
2681 next type @code{run}, @value{GDBN} notices that the file has changed, and
2682 reads the symbol table again (while trying to preserve your current
2683 breakpoint settings).
2685 @node Inferiors and Programs
2686 @section Debugging Multiple Inferiors and Programs
2688 @value{GDBN} lets you run and debug multiple programs in a single
2689 session. In addition, @value{GDBN} on some systems may let you run
2690 several programs simultaneously (otherwise you have to exit from one
2691 before starting another). In the most general case, you can have
2692 multiple threads of execution in each of multiple processes, launched
2693 from multiple executables.
2696 @value{GDBN} represents the state of each program execution with an
2697 object called an @dfn{inferior}. An inferior typically corresponds to
2698 a process, but is more general and applies also to targets that do not
2699 have processes. Inferiors may be created before a process runs, and
2700 may be retained after a process exits. Inferiors have unique
2701 identifiers that are different from process ids. Usually each
2702 inferior will also have its own distinct address space, although some
2703 embedded targets may have several inferiors running in different parts
2704 of a single address space. Each inferior may in turn have multiple
2705 threads running in it.
2707 To find out what inferiors exist at any moment, use @w{@code{info
2711 @kindex info inferiors
2712 @item info inferiors
2713 Print a list of all inferiors currently being managed by @value{GDBN}.
2715 @value{GDBN} displays for each inferior (in this order):
2719 the inferior number assigned by @value{GDBN}
2722 the target system's inferior identifier
2725 the name of the executable the inferior is running.
2730 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2731 indicates the current inferior.
2735 @c end table here to get a little more width for example
2738 (@value{GDBP}) info inferiors
2739 Num Description Executable
2740 2 process 2307 hello
2741 * 1 process 3401 goodbye
2744 To switch focus between inferiors, use the @code{inferior} command:
2747 @kindex inferior @var{infno}
2748 @item inferior @var{infno}
2749 Make inferior number @var{infno} the current inferior. The argument
2750 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2751 in the first field of the @samp{info inferiors} display.
2754 @vindex $_inferior@r{, convenience variable}
2755 The debugger convenience variable @samp{$_inferior} contains the
2756 number of the current inferior. You may find this useful in writing
2757 breakpoint conditional expressions, command scripts, and so forth.
2758 @xref{Convenience Vars,, Convenience Variables}, for general
2759 information on convenience variables.
2761 You can get multiple executables into a debugging session via the
2762 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2763 systems @value{GDBN} can add inferiors to the debug session
2764 automatically by following calls to @code{fork} and @code{exec}. To
2765 remove inferiors from the debugging session use the
2766 @w{@code{remove-inferiors}} command.
2769 @kindex add-inferior
2770 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2771 Adds @var{n} inferiors to be run using @var{executable} as the
2772 executable; @var{n} defaults to 1. If no executable is specified,
2773 the inferiors begins empty, with no program. You can still assign or
2774 change the program assigned to the inferior at any time by using the
2775 @code{file} command with the executable name as its argument.
2777 @kindex clone-inferior
2778 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2779 Adds @var{n} inferiors ready to execute the same program as inferior
2780 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2781 number of the current inferior. This is a convenient command when you
2782 want to run another instance of the inferior you are debugging.
2785 (@value{GDBP}) info inferiors
2786 Num Description Executable
2787 * 1 process 29964 helloworld
2788 (@value{GDBP}) clone-inferior
2791 (@value{GDBP}) info inferiors
2792 Num Description Executable
2794 * 1 process 29964 helloworld
2797 You can now simply switch focus to inferior 2 and run it.
2799 @kindex remove-inferiors
2800 @item remove-inferiors @var{infno}@dots{}
2801 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2802 possible to remove an inferior that is running with this command. For
2803 those, use the @code{kill} or @code{detach} command first.
2807 To quit debugging one of the running inferiors that is not the current
2808 inferior, you can either detach from it by using the @w{@code{detach
2809 inferior}} command (allowing it to run independently), or kill it
2810 using the @w{@code{kill inferiors}} command:
2813 @kindex detach inferiors @var{infno}@dots{}
2814 @item detach inferior @var{infno}@dots{}
2815 Detach from the inferior or inferiors identified by @value{GDBN}
2816 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2817 still stays on the list of inferiors shown by @code{info inferiors},
2818 but its Description will show @samp{<null>}.
2820 @kindex kill inferiors @var{infno}@dots{}
2821 @item kill inferiors @var{infno}@dots{}
2822 Kill the inferior or inferiors identified by @value{GDBN} inferior
2823 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2824 stays on the list of inferiors shown by @code{info inferiors}, but its
2825 Description will show @samp{<null>}.
2828 After the successful completion of a command such as @code{detach},
2829 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2830 a normal process exit, the inferior is still valid and listed with
2831 @code{info inferiors}, ready to be restarted.
2834 To be notified when inferiors are started or exit under @value{GDBN}'s
2835 control use @w{@code{set print inferior-events}}:
2838 @kindex set print inferior-events
2839 @cindex print messages on inferior start and exit
2840 @item set print inferior-events
2841 @itemx set print inferior-events on
2842 @itemx set print inferior-events off
2843 The @code{set print inferior-events} command allows you to enable or
2844 disable printing of messages when @value{GDBN} notices that new
2845 inferiors have started or that inferiors have exited or have been
2846 detached. By default, these messages will not be printed.
2848 @kindex show print inferior-events
2849 @item show print inferior-events
2850 Show whether messages will be printed when @value{GDBN} detects that
2851 inferiors have started, exited or have been detached.
2854 Many commands will work the same with multiple programs as with a
2855 single program: e.g., @code{print myglobal} will simply display the
2856 value of @code{myglobal} in the current inferior.
2859 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2860 get more info about the relationship of inferiors, programs, address
2861 spaces in a debug session. You can do that with the @w{@code{maint
2862 info program-spaces}} command.
2865 @kindex maint info program-spaces
2866 @item maint info program-spaces
2867 Print a list of all program spaces currently being managed by
2870 @value{GDBN} displays for each program space (in this order):
2874 the program space number assigned by @value{GDBN}
2877 the name of the executable loaded into the program space, with e.g.,
2878 the @code{file} command.
2883 An asterisk @samp{*} preceding the @value{GDBN} program space number
2884 indicates the current program space.
2886 In addition, below each program space line, @value{GDBN} prints extra
2887 information that isn't suitable to display in tabular form. For
2888 example, the list of inferiors bound to the program space.
2891 (@value{GDBP}) maint info program-spaces
2895 Bound inferiors: ID 1 (process 21561)
2898 Here we can see that no inferior is running the program @code{hello},
2899 while @code{process 21561} is running the program @code{goodbye}. On
2900 some targets, it is possible that multiple inferiors are bound to the
2901 same program space. The most common example is that of debugging both
2902 the parent and child processes of a @code{vfork} call. For example,
2905 (@value{GDBP}) maint info program-spaces
2908 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2911 Here, both inferior 2 and inferior 1 are running in the same program
2912 space as a result of inferior 1 having executed a @code{vfork} call.
2916 @section Debugging Programs with Multiple Threads
2918 @cindex threads of execution
2919 @cindex multiple threads
2920 @cindex switching threads
2921 In some operating systems, such as GNU/Linux and Solaris, a single program
2922 may have more than one @dfn{thread} of execution. The precise semantics
2923 of threads differ from one operating system to another, but in general
2924 the threads of a single program are akin to multiple processes---except
2925 that they share one address space (that is, they can all examine and
2926 modify the same variables). On the other hand, each thread has its own
2927 registers and execution stack, and perhaps private memory.
2929 @value{GDBN} provides these facilities for debugging multi-thread
2933 @item automatic notification of new threads
2934 @item @samp{thread @var{thread-id}}, a command to switch among threads
2935 @item @samp{info threads}, a command to inquire about existing threads
2936 @item @samp{thread apply [@var{thread-id-list}] [@var{all}] @var{args}},
2937 a command to apply a command to a list of threads
2938 @item thread-specific breakpoints
2939 @item @samp{set print thread-events}, which controls printing of
2940 messages on thread start and exit.
2941 @item @samp{set libthread-db-search-path @var{path}}, which lets
2942 the user specify which @code{libthread_db} to use if the default choice
2943 isn't compatible with the program.
2946 @cindex focus of debugging
2947 @cindex current thread
2948 The @value{GDBN} thread debugging facility allows you to observe all
2949 threads while your program runs---but whenever @value{GDBN} takes
2950 control, one thread in particular is always the focus of debugging.
2951 This thread is called the @dfn{current thread}. Debugging commands show
2952 program information from the perspective of the current thread.
2954 @cindex @code{New} @var{systag} message
2955 @cindex thread identifier (system)
2956 @c FIXME-implementors!! It would be more helpful if the [New...] message
2957 @c included GDB's numeric thread handle, so you could just go to that
2958 @c thread without first checking `info threads'.
2959 Whenever @value{GDBN} detects a new thread in your program, it displays
2960 the target system's identification for the thread with a message in the
2961 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2962 whose form varies depending on the particular system. For example, on
2963 @sc{gnu}/Linux, you might see
2966 [New Thread 0x41e02940 (LWP 25582)]
2970 when @value{GDBN} notices a new thread. In contrast, on other systems,
2971 the @var{systag} is simply something like @samp{process 368}, with no
2974 @c FIXME!! (1) Does the [New...] message appear even for the very first
2975 @c thread of a program, or does it only appear for the
2976 @c second---i.e.@: when it becomes obvious we have a multithread
2978 @c (2) *Is* there necessarily a first thread always? Or do some
2979 @c multithread systems permit starting a program with multiple
2980 @c threads ab initio?
2982 @anchor{thread numbers}
2983 @cindex thread number, per inferior
2984 @cindex thread identifier (GDB)
2985 For debugging purposes, @value{GDBN} associates its own thread number
2986 ---always a single integer---with each thread of an inferior. This
2987 number is unique between all threads of an inferior, but not unique
2988 between threads of different inferiors.
2990 @cindex qualified thread ID
2991 You can refer to a given thread in an inferior using the qualified
2992 @var{inferior-num}.@var{thread-num} syntax, also known as
2993 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
2994 number and @var{thread-num} being the thread number of the given
2995 inferior. For example, thread @code{2.3} refers to thread number 3 of
2996 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
2997 then @value{GDBN} infers you're referring to a thread of the current
3000 Until you create a second inferior, @value{GDBN} does not show the
3001 @var{inferior-num} part of thread IDs, even though you can always use
3002 the full @var{inferior-num}.@var{thread-num} form to refer to threads
3003 of inferior 1, the initial inferior.
3005 @anchor{thread ID lists}
3006 @cindex thread ID lists
3007 Some commands accept a space-separated @dfn{thread ID list} as
3008 argument. A list element can be:
3012 A thread ID as shown in the first field of the @samp{info threads}
3013 display, with or without an inferior qualifier. E.g., @samp{2.1} or
3017 A range of thread numbers, again with or without an inferior
3018 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
3019 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
3022 All threads of an inferior, specified with a star wildcard, with or
3023 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
3024 @samp{1.*}) or @code{*}. The former refers to all threads of the
3025 given inferior, and the latter form without an inferior qualifier
3026 refers to all threads of the current inferior.
3030 For example, if the current inferior is 1, and inferior 7 has one
3031 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
3032 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
3033 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
3034 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
3038 @anchor{global thread numbers}
3039 @cindex global thread number
3040 @cindex global thread identifier (GDB)
3041 In addition to a @emph{per-inferior} number, each thread is also
3042 assigned a unique @emph{global} number, also known as @dfn{global
3043 thread ID}, a single integer. Unlike the thread number component of
3044 the thread ID, no two threads have the same global ID, even when
3045 you're debugging multiple inferiors.
3047 From @value{GDBN}'s perspective, a process always has at least one
3048 thread. In other words, @value{GDBN} assigns a thread number to the
3049 program's ``main thread'' even if the program is not multi-threaded.
3051 @vindex $_thread@r{, convenience variable}
3052 @vindex $_gthread@r{, convenience variable}
3053 The debugger convenience variables @samp{$_thread} and
3054 @samp{$_gthread} contain, respectively, the per-inferior thread number
3055 and the global thread number of the current thread. You may find this
3056 useful in writing breakpoint conditional expressions, command scripts,
3057 and so forth. @xref{Convenience Vars,, Convenience Variables}, for
3058 general information on convenience variables.
3060 If @value{GDBN} detects the program is multi-threaded, it augments the
3061 usual message about stopping at a breakpoint with the ID and name of
3062 the thread that hit the breakpoint.
3065 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
3068 Likewise when the program receives a signal:
3071 Thread 1 "main" received signal SIGINT, Interrupt.
3075 @kindex info threads
3076 @item info threads @r{[}@var{thread-id-list}@r{]}
3078 Display information about one or more threads. With no arguments
3079 displays information about all threads. You can specify the list of
3080 threads that you want to display using the thread ID list syntax
3081 (@pxref{thread ID lists}).
3083 @value{GDBN} displays for each thread (in this order):
3087 the per-inferior thread number assigned by @value{GDBN}
3090 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
3091 option was specified
3094 the target system's thread identifier (@var{systag})
3097 the thread's name, if one is known. A thread can either be named by
3098 the user (see @code{thread name}, below), or, in some cases, by the
3102 the current stack frame summary for that thread
3106 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3107 indicates the current thread.
3111 @c end table here to get a little more width for example
3114 (@value{GDBP}) info threads
3116 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3117 2 process 35 thread 23 0x34e5 in sigpause ()
3118 3 process 35 thread 27 0x34e5 in sigpause ()
3122 If you're debugging multiple inferiors, @value{GDBN} displays thread
3123 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3124 Otherwise, only @var{thread-num} is shown.
3126 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3127 indicating each thread's global thread ID:
3130 (@value{GDBP}) info threads
3131 Id GId Target Id Frame
3132 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3133 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3134 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3135 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3138 On Solaris, you can display more information about user threads with a
3139 Solaris-specific command:
3142 @item maint info sol-threads
3143 @kindex maint info sol-threads
3144 @cindex thread info (Solaris)
3145 Display info on Solaris user threads.
3149 @kindex thread @var{thread-id}
3150 @item thread @var{thread-id}
3151 Make thread ID @var{thread-id} the current thread. The command
3152 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3153 the first field of the @samp{info threads} display, with or without an
3154 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3156 @value{GDBN} responds by displaying the system identifier of the
3157 thread you selected, and its current stack frame summary:
3160 (@value{GDBP}) thread 2
3161 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3162 #0 some_function (ignore=0x0) at example.c:8
3163 8 printf ("hello\n");
3167 As with the @samp{[New @dots{}]} message, the form of the text after
3168 @samp{Switching to} depends on your system's conventions for identifying
3171 @kindex thread apply
3172 @cindex apply command to several threads
3173 @item thread apply [@var{thread-id-list} | all [-ascending]] @var{command}
3174 The @code{thread apply} command allows you to apply the named
3175 @var{command} to one or more threads. Specify the threads that you
3176 want affected using the thread ID list syntax (@pxref{thread ID
3177 lists}), or specify @code{all} to apply to all threads. To apply a
3178 command to all threads in descending order, type @kbd{thread apply all
3179 @var{command}}. To apply a command to all threads in ascending order,
3180 type @kbd{thread apply all -ascending @var{command}}.
3184 @cindex name a thread
3185 @item thread name [@var{name}]
3186 This command assigns a name to the current thread. If no argument is
3187 given, any existing user-specified name is removed. The thread name
3188 appears in the @samp{info threads} display.
3190 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3191 determine the name of the thread as given by the OS. On these
3192 systems, a name specified with @samp{thread name} will override the
3193 system-give name, and removing the user-specified name will cause
3194 @value{GDBN} to once again display the system-specified name.
3197 @cindex search for a thread
3198 @item thread find [@var{regexp}]
3199 Search for and display thread ids whose name or @var{systag}
3200 matches the supplied regular expression.
3202 As well as being the complement to the @samp{thread name} command,
3203 this command also allows you to identify a thread by its target
3204 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3208 (@value{GDBN}) thread find 26688
3209 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3210 (@value{GDBN}) info thread 4
3212 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3215 @kindex set print thread-events
3216 @cindex print messages on thread start and exit
3217 @item set print thread-events
3218 @itemx set print thread-events on
3219 @itemx set print thread-events off
3220 The @code{set print thread-events} command allows you to enable or
3221 disable printing of messages when @value{GDBN} notices that new threads have
3222 started or that threads have exited. By default, these messages will
3223 be printed if detection of these events is supported by the target.
3224 Note that these messages cannot be disabled on all targets.
3226 @kindex show print thread-events
3227 @item show print thread-events
3228 Show whether messages will be printed when @value{GDBN} detects that threads
3229 have started and exited.
3232 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3233 more information about how @value{GDBN} behaves when you stop and start
3234 programs with multiple threads.
3236 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3237 watchpoints in programs with multiple threads.
3239 @anchor{set libthread-db-search-path}
3241 @kindex set libthread-db-search-path
3242 @cindex search path for @code{libthread_db}
3243 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3244 If this variable is set, @var{path} is a colon-separated list of
3245 directories @value{GDBN} will use to search for @code{libthread_db}.
3246 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3247 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3248 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3251 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3252 @code{libthread_db} library to obtain information about threads in the
3253 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3254 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3255 specific thread debugging library loading is enabled
3256 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3258 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3259 refers to the default system directories that are
3260 normally searched for loading shared libraries. The @samp{$sdir} entry
3261 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3262 (@pxref{libthread_db.so.1 file}).
3264 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3265 refers to the directory from which @code{libpthread}
3266 was loaded in the inferior process.
3268 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3269 @value{GDBN} attempts to initialize it with the current inferior process.
3270 If this initialization fails (which could happen because of a version
3271 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3272 will unload @code{libthread_db}, and continue with the next directory.
3273 If none of @code{libthread_db} libraries initialize successfully,
3274 @value{GDBN} will issue a warning and thread debugging will be disabled.
3276 Setting @code{libthread-db-search-path} is currently implemented
3277 only on some platforms.
3279 @kindex show libthread-db-search-path
3280 @item show libthread-db-search-path
3281 Display current libthread_db search path.
3283 @kindex set debug libthread-db
3284 @kindex show debug libthread-db
3285 @cindex debugging @code{libthread_db}
3286 @item set debug libthread-db
3287 @itemx show debug libthread-db
3288 Turns on or off display of @code{libthread_db}-related events.
3289 Use @code{1} to enable, @code{0} to disable.
3293 @section Debugging Forks
3295 @cindex fork, debugging programs which call
3296 @cindex multiple processes
3297 @cindex processes, multiple
3298 On most systems, @value{GDBN} has no special support for debugging
3299 programs which create additional processes using the @code{fork}
3300 function. When a program forks, @value{GDBN} will continue to debug the
3301 parent process and the child process will run unimpeded. If you have
3302 set a breakpoint in any code which the child then executes, the child
3303 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3304 will cause it to terminate.
3306 However, if you want to debug the child process there is a workaround
3307 which isn't too painful. Put a call to @code{sleep} in the code which
3308 the child process executes after the fork. It may be useful to sleep
3309 only if a certain environment variable is set, or a certain file exists,
3310 so that the delay need not occur when you don't want to run @value{GDBN}
3311 on the child. While the child is sleeping, use the @code{ps} program to
3312 get its process ID. Then tell @value{GDBN} (a new invocation of
3313 @value{GDBN} if you are also debugging the parent process) to attach to
3314 the child process (@pxref{Attach}). From that point on you can debug
3315 the child process just like any other process which you attached to.
3317 On some systems, @value{GDBN} provides support for debugging programs
3318 that create additional processes using the @code{fork} or @code{vfork}
3319 functions. On @sc{gnu}/Linux platforms, this feature is supported
3320 with kernel version 2.5.46 and later.
3322 The fork debugging commands are supported in native mode and when
3323 connected to @code{gdbserver} in either @code{target remote} mode or
3324 @code{target extended-remote} mode.
3326 By default, when a program forks, @value{GDBN} will continue to debug
3327 the parent process and the child process will run unimpeded.
3329 If you want to follow the child process instead of the parent process,
3330 use the command @w{@code{set follow-fork-mode}}.
3333 @kindex set follow-fork-mode
3334 @item set follow-fork-mode @var{mode}
3335 Set the debugger response to a program call of @code{fork} or
3336 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3337 process. The @var{mode} argument can be:
3341 The original process is debugged after a fork. The child process runs
3342 unimpeded. This is the default.
3345 The new process is debugged after a fork. The parent process runs
3350 @kindex show follow-fork-mode
3351 @item show follow-fork-mode
3352 Display the current debugger response to a @code{fork} or @code{vfork} call.
3355 @cindex debugging multiple processes
3356 On Linux, if you want to debug both the parent and child processes, use the
3357 command @w{@code{set detach-on-fork}}.
3360 @kindex set detach-on-fork
3361 @item set detach-on-fork @var{mode}
3362 Tells gdb whether to detach one of the processes after a fork, or
3363 retain debugger control over them both.
3367 The child process (or parent process, depending on the value of
3368 @code{follow-fork-mode}) will be detached and allowed to run
3369 independently. This is the default.
3372 Both processes will be held under the control of @value{GDBN}.
3373 One process (child or parent, depending on the value of
3374 @code{follow-fork-mode}) is debugged as usual, while the other
3379 @kindex show detach-on-fork
3380 @item show detach-on-fork
3381 Show whether detach-on-fork mode is on/off.
3384 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3385 will retain control of all forked processes (including nested forks).
3386 You can list the forked processes under the control of @value{GDBN} by
3387 using the @w{@code{info inferiors}} command, and switch from one fork
3388 to another by using the @code{inferior} command (@pxref{Inferiors and
3389 Programs, ,Debugging Multiple Inferiors and Programs}).
3391 To quit debugging one of the forked processes, you can either detach
3392 from it by using the @w{@code{detach inferiors}} command (allowing it
3393 to run independently), or kill it using the @w{@code{kill inferiors}}
3394 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3397 If you ask to debug a child process and a @code{vfork} is followed by an
3398 @code{exec}, @value{GDBN} executes the new target up to the first
3399 breakpoint in the new target. If you have a breakpoint set on
3400 @code{main} in your original program, the breakpoint will also be set on
3401 the child process's @code{main}.
3403 On some systems, when a child process is spawned by @code{vfork}, you
3404 cannot debug the child or parent until an @code{exec} call completes.
3406 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3407 call executes, the new target restarts. To restart the parent
3408 process, use the @code{file} command with the parent executable name
3409 as its argument. By default, after an @code{exec} call executes,
3410 @value{GDBN} discards the symbols of the previous executable image.
3411 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3415 @kindex set follow-exec-mode
3416 @item set follow-exec-mode @var{mode}
3418 Set debugger response to a program call of @code{exec}. An
3419 @code{exec} call replaces the program image of a process.
3421 @code{follow-exec-mode} can be:
3425 @value{GDBN} creates a new inferior and rebinds the process to this
3426 new inferior. The program the process was running before the
3427 @code{exec} call can be restarted afterwards by restarting the
3433 (@value{GDBP}) info inferiors
3435 Id Description Executable
3438 process 12020 is executing new program: prog2
3439 Program exited normally.
3440 (@value{GDBP}) info inferiors
3441 Id Description Executable
3447 @value{GDBN} keeps the process bound to the same inferior. The new
3448 executable image replaces the previous executable loaded in the
3449 inferior. Restarting the inferior after the @code{exec} call, with
3450 e.g., the @code{run} command, restarts the executable the process was
3451 running after the @code{exec} call. This is the default mode.
3456 (@value{GDBP}) info inferiors
3457 Id Description Executable
3460 process 12020 is executing new program: prog2
3461 Program exited normally.
3462 (@value{GDBP}) info inferiors
3463 Id Description Executable
3470 @code{follow-exec-mode} is supported in native mode and
3471 @code{target extended-remote} mode.
3473 You can use the @code{catch} command to make @value{GDBN} stop whenever
3474 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3475 Catchpoints, ,Setting Catchpoints}.
3477 @node Checkpoint/Restart
3478 @section Setting a @emph{Bookmark} to Return to Later
3483 @cindex snapshot of a process
3484 @cindex rewind program state
3486 On certain operating systems@footnote{Currently, only
3487 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3488 program's state, called a @dfn{checkpoint}, and come back to it
3491 Returning to a checkpoint effectively undoes everything that has
3492 happened in the program since the @code{checkpoint} was saved. This
3493 includes changes in memory, registers, and even (within some limits)
3494 system state. Effectively, it is like going back in time to the
3495 moment when the checkpoint was saved.
3497 Thus, if you're stepping thru a program and you think you're
3498 getting close to the point where things go wrong, you can save
3499 a checkpoint. Then, if you accidentally go too far and miss
3500 the critical statement, instead of having to restart your program
3501 from the beginning, you can just go back to the checkpoint and
3502 start again from there.
3504 This can be especially useful if it takes a lot of time or
3505 steps to reach the point where you think the bug occurs.
3507 To use the @code{checkpoint}/@code{restart} method of debugging:
3512 Save a snapshot of the debugged program's current execution state.
3513 The @code{checkpoint} command takes no arguments, but each checkpoint
3514 is assigned a small integer id, similar to a breakpoint id.
3516 @kindex info checkpoints
3517 @item info checkpoints
3518 List the checkpoints that have been saved in the current debugging
3519 session. For each checkpoint, the following information will be
3526 @item Source line, or label
3529 @kindex restart @var{checkpoint-id}
3530 @item restart @var{checkpoint-id}
3531 Restore the program state that was saved as checkpoint number
3532 @var{checkpoint-id}. All program variables, registers, stack frames
3533 etc.@: will be returned to the values that they had when the checkpoint
3534 was saved. In essence, gdb will ``wind back the clock'' to the point
3535 in time when the checkpoint was saved.
3537 Note that breakpoints, @value{GDBN} variables, command history etc.
3538 are not affected by restoring a checkpoint. In general, a checkpoint
3539 only restores things that reside in the program being debugged, not in
3542 @kindex delete checkpoint @var{checkpoint-id}
3543 @item delete checkpoint @var{checkpoint-id}
3544 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3548 Returning to a previously saved checkpoint will restore the user state
3549 of the program being debugged, plus a significant subset of the system
3550 (OS) state, including file pointers. It won't ``un-write'' data from
3551 a file, but it will rewind the file pointer to the previous location,
3552 so that the previously written data can be overwritten. For files
3553 opened in read mode, the pointer will also be restored so that the
3554 previously read data can be read again.
3556 Of course, characters that have been sent to a printer (or other
3557 external device) cannot be ``snatched back'', and characters received
3558 from eg.@: a serial device can be removed from internal program buffers,
3559 but they cannot be ``pushed back'' into the serial pipeline, ready to
3560 be received again. Similarly, the actual contents of files that have
3561 been changed cannot be restored (at this time).
3563 However, within those constraints, you actually can ``rewind'' your
3564 program to a previously saved point in time, and begin debugging it
3565 again --- and you can change the course of events so as to debug a
3566 different execution path this time.
3568 @cindex checkpoints and process id
3569 Finally, there is one bit of internal program state that will be
3570 different when you return to a checkpoint --- the program's process
3571 id. Each checkpoint will have a unique process id (or @var{pid}),
3572 and each will be different from the program's original @var{pid}.
3573 If your program has saved a local copy of its process id, this could
3574 potentially pose a problem.
3576 @subsection A Non-obvious Benefit of Using Checkpoints
3578 On some systems such as @sc{gnu}/Linux, address space randomization
3579 is performed on new processes for security reasons. This makes it
3580 difficult or impossible to set a breakpoint, or watchpoint, on an
3581 absolute address if you have to restart the program, since the
3582 absolute location of a symbol will change from one execution to the
3585 A checkpoint, however, is an @emph{identical} copy of a process.
3586 Therefore if you create a checkpoint at (eg.@:) the start of main,
3587 and simply return to that checkpoint instead of restarting the
3588 process, you can avoid the effects of address randomization and
3589 your symbols will all stay in the same place.
3592 @chapter Stopping and Continuing
3594 The principal purposes of using a debugger are so that you can stop your
3595 program before it terminates; or so that, if your program runs into
3596 trouble, you can investigate and find out why.
3598 Inside @value{GDBN}, your program may stop for any of several reasons,
3599 such as a signal, a breakpoint, or reaching a new line after a
3600 @value{GDBN} command such as @code{step}. You may then examine and
3601 change variables, set new breakpoints or remove old ones, and then
3602 continue execution. Usually, the messages shown by @value{GDBN} provide
3603 ample explanation of the status of your program---but you can also
3604 explicitly request this information at any time.
3607 @kindex info program
3609 Display information about the status of your program: whether it is
3610 running or not, what process it is, and why it stopped.
3614 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3615 * Continuing and Stepping:: Resuming execution
3616 * Skipping Over Functions and Files::
3617 Skipping over functions and files
3619 * Thread Stops:: Stopping and starting multi-thread programs
3623 @section Breakpoints, Watchpoints, and Catchpoints
3626 A @dfn{breakpoint} makes your program stop whenever a certain point in
3627 the program is reached. For each breakpoint, you can add conditions to
3628 control in finer detail whether your program stops. You can set
3629 breakpoints with the @code{break} command and its variants (@pxref{Set
3630 Breaks, ,Setting Breakpoints}), to specify the place where your program
3631 should stop by line number, function name or exact address in the
3634 On some systems, you can set breakpoints in shared libraries before
3635 the executable is run.
3638 @cindex data breakpoints
3639 @cindex memory tracing
3640 @cindex breakpoint on memory address
3641 @cindex breakpoint on variable modification
3642 A @dfn{watchpoint} is a special breakpoint that stops your program
3643 when the value of an expression changes. The expression may be a value
3644 of a variable, or it could involve values of one or more variables
3645 combined by operators, such as @samp{a + b}. This is sometimes called
3646 @dfn{data breakpoints}. You must use a different command to set
3647 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3648 from that, you can manage a watchpoint like any other breakpoint: you
3649 enable, disable, and delete both breakpoints and watchpoints using the
3652 You can arrange to have values from your program displayed automatically
3653 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3657 @cindex breakpoint on events
3658 A @dfn{catchpoint} is another special breakpoint that stops your program
3659 when a certain kind of event occurs, such as the throwing of a C@t{++}
3660 exception or the loading of a library. As with watchpoints, you use a
3661 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3662 Catchpoints}), but aside from that, you can manage a catchpoint like any
3663 other breakpoint. (To stop when your program receives a signal, use the
3664 @code{handle} command; see @ref{Signals, ,Signals}.)
3666 @cindex breakpoint numbers
3667 @cindex numbers for breakpoints
3668 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3669 catchpoint when you create it; these numbers are successive integers
3670 starting with one. In many of the commands for controlling various
3671 features of breakpoints you use the breakpoint number to say which
3672 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3673 @dfn{disabled}; if disabled, it has no effect on your program until you
3676 @cindex breakpoint ranges
3677 @cindex breakpoint lists
3678 @cindex ranges of breakpoints
3679 @cindex lists of breakpoints
3680 Some @value{GDBN} commands accept a space-separated list of breakpoints
3681 on which to operate. A list element can be either a single breakpoint number,
3682 like @samp{5}, or a range of such numbers, like @samp{5-7}.
3683 When a breakpoint list is given to a command, all breakpoints in that list
3687 * Set Breaks:: Setting breakpoints
3688 * Set Watchpoints:: Setting watchpoints
3689 * Set Catchpoints:: Setting catchpoints
3690 * Delete Breaks:: Deleting breakpoints
3691 * Disabling:: Disabling breakpoints
3692 * Conditions:: Break conditions
3693 * Break Commands:: Breakpoint command lists
3694 * Dynamic Printf:: Dynamic printf
3695 * Save Breakpoints:: How to save breakpoints in a file
3696 * Static Probe Points:: Listing static probe points
3697 * Error in Breakpoints:: ``Cannot insert breakpoints''
3698 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3702 @subsection Setting Breakpoints
3704 @c FIXME LMB what does GDB do if no code on line of breakpt?
3705 @c consider in particular declaration with/without initialization.
3707 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3710 @kindex b @r{(@code{break})}
3711 @vindex $bpnum@r{, convenience variable}
3712 @cindex latest breakpoint
3713 Breakpoints are set with the @code{break} command (abbreviated
3714 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3715 number of the breakpoint you've set most recently; see @ref{Convenience
3716 Vars,, Convenience Variables}, for a discussion of what you can do with
3717 convenience variables.
3720 @item break @var{location}
3721 Set a breakpoint at the given @var{location}, which can specify a
3722 function name, a line number, or an address of an instruction.
3723 (@xref{Specify Location}, for a list of all the possible ways to
3724 specify a @var{location}.) The breakpoint will stop your program just
3725 before it executes any of the code in the specified @var{location}.
3727 When using source languages that permit overloading of symbols, such as
3728 C@t{++}, a function name may refer to more than one possible place to break.
3729 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3732 It is also possible to insert a breakpoint that will stop the program
3733 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3734 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3737 When called without any arguments, @code{break} sets a breakpoint at
3738 the next instruction to be executed in the selected stack frame
3739 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3740 innermost, this makes your program stop as soon as control
3741 returns to that frame. This is similar to the effect of a
3742 @code{finish} command in the frame inside the selected frame---except
3743 that @code{finish} does not leave an active breakpoint. If you use
3744 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3745 the next time it reaches the current location; this may be useful
3748 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3749 least one instruction has been executed. If it did not do this, you
3750 would be unable to proceed past a breakpoint without first disabling the
3751 breakpoint. This rule applies whether or not the breakpoint already
3752 existed when your program stopped.
3754 @item break @dots{} if @var{cond}
3755 Set a breakpoint with condition @var{cond}; evaluate the expression
3756 @var{cond} each time the breakpoint is reached, and stop only if the
3757 value is nonzero---that is, if @var{cond} evaluates as true.
3758 @samp{@dots{}} stands for one of the possible arguments described
3759 above (or no argument) specifying where to break. @xref{Conditions,
3760 ,Break Conditions}, for more information on breakpoint conditions.
3763 @item tbreak @var{args}
3764 Set a breakpoint enabled only for one stop. The @var{args} are the
3765 same as for the @code{break} command, and the breakpoint is set in the same
3766 way, but the breakpoint is automatically deleted after the first time your
3767 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3770 @cindex hardware breakpoints
3771 @item hbreak @var{args}
3772 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3773 @code{break} command and the breakpoint is set in the same way, but the
3774 breakpoint requires hardware support and some target hardware may not
3775 have this support. The main purpose of this is EPROM/ROM code
3776 debugging, so you can set a breakpoint at an instruction without
3777 changing the instruction. This can be used with the new trap-generation
3778 provided by SPARClite DSU and most x86-based targets. These targets
3779 will generate traps when a program accesses some data or instruction
3780 address that is assigned to the debug registers. However the hardware
3781 breakpoint registers can take a limited number of breakpoints. For
3782 example, on the DSU, only two data breakpoints can be set at a time, and
3783 @value{GDBN} will reject this command if more than two are used. Delete
3784 or disable unused hardware breakpoints before setting new ones
3785 (@pxref{Disabling, ,Disabling Breakpoints}).
3786 @xref{Conditions, ,Break Conditions}.
3787 For remote targets, you can restrict the number of hardware
3788 breakpoints @value{GDBN} will use, see @ref{set remote
3789 hardware-breakpoint-limit}.
3792 @item thbreak @var{args}
3793 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3794 are the same as for the @code{hbreak} command and the breakpoint is set in
3795 the same way. However, like the @code{tbreak} command,
3796 the breakpoint is automatically deleted after the
3797 first time your program stops there. Also, like the @code{hbreak}
3798 command, the breakpoint requires hardware support and some target hardware
3799 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3800 See also @ref{Conditions, ,Break Conditions}.
3803 @cindex regular expression
3804 @cindex breakpoints at functions matching a regexp
3805 @cindex set breakpoints in many functions
3806 @item rbreak @var{regex}
3807 Set breakpoints on all functions matching the regular expression
3808 @var{regex}. This command sets an unconditional breakpoint on all
3809 matches, printing a list of all breakpoints it set. Once these
3810 breakpoints are set, they are treated just like the breakpoints set with
3811 the @code{break} command. You can delete them, disable them, or make
3812 them conditional the same way as any other breakpoint.
3814 The syntax of the regular expression is the standard one used with tools
3815 like @file{grep}. Note that this is different from the syntax used by
3816 shells, so for instance @code{foo*} matches all functions that include
3817 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3818 @code{.*} leading and trailing the regular expression you supply, so to
3819 match only functions that begin with @code{foo}, use @code{^foo}.
3821 @cindex non-member C@t{++} functions, set breakpoint in
3822 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3823 breakpoints on overloaded functions that are not members of any special
3826 @cindex set breakpoints on all functions
3827 The @code{rbreak} command can be used to set breakpoints in
3828 @strong{all} the functions in a program, like this:
3831 (@value{GDBP}) rbreak .
3834 @item rbreak @var{file}:@var{regex}
3835 If @code{rbreak} is called with a filename qualification, it limits
3836 the search for functions matching the given regular expression to the
3837 specified @var{file}. This can be used, for example, to set breakpoints on
3838 every function in a given file:
3841 (@value{GDBP}) rbreak file.c:.
3844 The colon separating the filename qualifier from the regex may
3845 optionally be surrounded by spaces.
3847 @kindex info breakpoints
3848 @cindex @code{$_} and @code{info breakpoints}
3849 @item info breakpoints @r{[}@var{list}@dots{}@r{]}
3850 @itemx info break @r{[}@var{list}@dots{}@r{]}
3851 Print a table of all breakpoints, watchpoints, and catchpoints set and
3852 not deleted. Optional argument @var{n} means print information only
3853 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3854 For each breakpoint, following columns are printed:
3857 @item Breakpoint Numbers
3859 Breakpoint, watchpoint, or catchpoint.
3861 Whether the breakpoint is marked to be disabled or deleted when hit.
3862 @item Enabled or Disabled
3863 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3864 that are not enabled.
3866 Where the breakpoint is in your program, as a memory address. For a
3867 pending breakpoint whose address is not yet known, this field will
3868 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3869 library that has the symbol or line referred by breakpoint is loaded.
3870 See below for details. A breakpoint with several locations will
3871 have @samp{<MULTIPLE>} in this field---see below for details.
3873 Where the breakpoint is in the source for your program, as a file and
3874 line number. For a pending breakpoint, the original string passed to
3875 the breakpoint command will be listed as it cannot be resolved until
3876 the appropriate shared library is loaded in the future.
3880 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3881 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3882 @value{GDBN} on the host's side. If it is ``target'', then the condition
3883 is evaluated by the target. The @code{info break} command shows
3884 the condition on the line following the affected breakpoint, together with
3885 its condition evaluation mode in between parentheses.
3887 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3888 allowed to have a condition specified for it. The condition is not parsed for
3889 validity until a shared library is loaded that allows the pending
3890 breakpoint to resolve to a valid location.
3893 @code{info break} with a breakpoint
3894 number @var{n} as argument lists only that breakpoint. The
3895 convenience variable @code{$_} and the default examining-address for
3896 the @code{x} command are set to the address of the last breakpoint
3897 listed (@pxref{Memory, ,Examining Memory}).
3900 @code{info break} displays a count of the number of times the breakpoint
3901 has been hit. This is especially useful in conjunction with the
3902 @code{ignore} command. You can ignore a large number of breakpoint
3903 hits, look at the breakpoint info to see how many times the breakpoint
3904 was hit, and then run again, ignoring one less than that number. This
3905 will get you quickly to the last hit of that breakpoint.
3908 For a breakpoints with an enable count (xref) greater than 1,
3909 @code{info break} also displays that count.
3913 @value{GDBN} allows you to set any number of breakpoints at the same place in
3914 your program. There is nothing silly or meaningless about this. When
3915 the breakpoints are conditional, this is even useful
3916 (@pxref{Conditions, ,Break Conditions}).
3918 @cindex multiple locations, breakpoints
3919 @cindex breakpoints, multiple locations
3920 It is possible that a breakpoint corresponds to several locations
3921 in your program. Examples of this situation are:
3925 Multiple functions in the program may have the same name.
3928 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3929 instances of the function body, used in different cases.
3932 For a C@t{++} template function, a given line in the function can
3933 correspond to any number of instantiations.
3936 For an inlined function, a given source line can correspond to
3937 several places where that function is inlined.
3940 In all those cases, @value{GDBN} will insert a breakpoint at all
3941 the relevant locations.
3943 A breakpoint with multiple locations is displayed in the breakpoint
3944 table using several rows---one header row, followed by one row for
3945 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3946 address column. The rows for individual locations contain the actual
3947 addresses for locations, and show the functions to which those
3948 locations belong. The number column for a location is of the form
3949 @var{breakpoint-number}.@var{location-number}.
3954 Num Type Disp Enb Address What
3955 1 breakpoint keep y <MULTIPLE>
3957 breakpoint already hit 1 time
3958 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3959 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3962 You cannot delete the individual locations from a breakpoint. However,
3963 each location can be individually enabled or disabled by passing
3964 @var{breakpoint-number}.@var{location-number} as argument to the
3965 @code{enable} and @code{disable} commands. It's also possible to
3966 @code{enable} and @code{disable} a range of @var{location-number}
3967 locations using a @var{breakpoint-number} and two @var{location-number}s,
3968 in increasing order, separated by a hyphen, like
3969 @kbd{@var{breakpoint-number}.@var{location-number1}-@var{location-number2}},
3970 in which case @value{GDBN} acts on all the locations in the range (inclusive).
3971 Disabling or enabling the parent breakpoint (@pxref{Disabling}) affects
3972 all of the locations that belong to that breakpoint.
3974 @cindex pending breakpoints
3975 It's quite common to have a breakpoint inside a shared library.
3976 Shared libraries can be loaded and unloaded explicitly,
3977 and possibly repeatedly, as the program is executed. To support
3978 this use case, @value{GDBN} updates breakpoint locations whenever
3979 any shared library is loaded or unloaded. Typically, you would
3980 set a breakpoint in a shared library at the beginning of your
3981 debugging session, when the library is not loaded, and when the
3982 symbols from the library are not available. When you try to set
3983 breakpoint, @value{GDBN} will ask you if you want to set
3984 a so called @dfn{pending breakpoint}---breakpoint whose address
3985 is not yet resolved.
3987 After the program is run, whenever a new shared library is loaded,
3988 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3989 shared library contains the symbol or line referred to by some
3990 pending breakpoint, that breakpoint is resolved and becomes an
3991 ordinary breakpoint. When a library is unloaded, all breakpoints
3992 that refer to its symbols or source lines become pending again.
3994 This logic works for breakpoints with multiple locations, too. For
3995 example, if you have a breakpoint in a C@t{++} template function, and
3996 a newly loaded shared library has an instantiation of that template,
3997 a new location is added to the list of locations for the breakpoint.
3999 Except for having unresolved address, pending breakpoints do not
4000 differ from regular breakpoints. You can set conditions or commands,
4001 enable and disable them and perform other breakpoint operations.
4003 @value{GDBN} provides some additional commands for controlling what
4004 happens when the @samp{break} command cannot resolve breakpoint
4005 address specification to an address:
4007 @kindex set breakpoint pending
4008 @kindex show breakpoint pending
4010 @item set breakpoint pending auto
4011 This is the default behavior. When @value{GDBN} cannot find the breakpoint
4012 location, it queries you whether a pending breakpoint should be created.
4014 @item set breakpoint pending on
4015 This indicates that an unrecognized breakpoint location should automatically
4016 result in a pending breakpoint being created.
4018 @item set breakpoint pending off
4019 This indicates that pending breakpoints are not to be created. Any
4020 unrecognized breakpoint location results in an error. This setting does
4021 not affect any pending breakpoints previously created.
4023 @item show breakpoint pending
4024 Show the current behavior setting for creating pending breakpoints.
4027 The settings above only affect the @code{break} command and its
4028 variants. Once breakpoint is set, it will be automatically updated
4029 as shared libraries are loaded and unloaded.
4031 @cindex automatic hardware breakpoints
4032 For some targets, @value{GDBN} can automatically decide if hardware or
4033 software breakpoints should be used, depending on whether the
4034 breakpoint address is read-only or read-write. This applies to
4035 breakpoints set with the @code{break} command as well as to internal
4036 breakpoints set by commands like @code{next} and @code{finish}. For
4037 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
4040 You can control this automatic behaviour with the following commands:
4042 @kindex set breakpoint auto-hw
4043 @kindex show breakpoint auto-hw
4045 @item set breakpoint auto-hw on
4046 This is the default behavior. When @value{GDBN} sets a breakpoint, it
4047 will try to use the target memory map to decide if software or hardware
4048 breakpoint must be used.
4050 @item set breakpoint auto-hw off
4051 This indicates @value{GDBN} should not automatically select breakpoint
4052 type. If the target provides a memory map, @value{GDBN} will warn when
4053 trying to set software breakpoint at a read-only address.
4056 @value{GDBN} normally implements breakpoints by replacing the program code
4057 at the breakpoint address with a special instruction, which, when
4058 executed, given control to the debugger. By default, the program
4059 code is so modified only when the program is resumed. As soon as
4060 the program stops, @value{GDBN} restores the original instructions. This
4061 behaviour guards against leaving breakpoints inserted in the
4062 target should gdb abrubptly disconnect. However, with slow remote
4063 targets, inserting and removing breakpoint can reduce the performance.
4064 This behavior can be controlled with the following commands::
4066 @kindex set breakpoint always-inserted
4067 @kindex show breakpoint always-inserted
4069 @item set breakpoint always-inserted off
4070 All breakpoints, including newly added by the user, are inserted in
4071 the target only when the target is resumed. All breakpoints are
4072 removed from the target when it stops. This is the default mode.
4074 @item set breakpoint always-inserted on
4075 Causes all breakpoints to be inserted in the target at all times. If
4076 the user adds a new breakpoint, or changes an existing breakpoint, the
4077 breakpoints in the target are updated immediately. A breakpoint is
4078 removed from the target only when breakpoint itself is deleted.
4081 @value{GDBN} handles conditional breakpoints by evaluating these conditions
4082 when a breakpoint breaks. If the condition is true, then the process being
4083 debugged stops, otherwise the process is resumed.
4085 If the target supports evaluating conditions on its end, @value{GDBN} may
4086 download the breakpoint, together with its conditions, to it.
4088 This feature can be controlled via the following commands:
4090 @kindex set breakpoint condition-evaluation
4091 @kindex show breakpoint condition-evaluation
4093 @item set breakpoint condition-evaluation host
4094 This option commands @value{GDBN} to evaluate the breakpoint
4095 conditions on the host's side. Unconditional breakpoints are sent to
4096 the target which in turn receives the triggers and reports them back to GDB
4097 for condition evaluation. This is the standard evaluation mode.
4099 @item set breakpoint condition-evaluation target
4100 This option commands @value{GDBN} to download breakpoint conditions
4101 to the target at the moment of their insertion. The target
4102 is responsible for evaluating the conditional expression and reporting
4103 breakpoint stop events back to @value{GDBN} whenever the condition
4104 is true. Due to limitations of target-side evaluation, some conditions
4105 cannot be evaluated there, e.g., conditions that depend on local data
4106 that is only known to the host. Examples include
4107 conditional expressions involving convenience variables, complex types
4108 that cannot be handled by the agent expression parser and expressions
4109 that are too long to be sent over to the target, specially when the
4110 target is a remote system. In these cases, the conditions will be
4111 evaluated by @value{GDBN}.
4113 @item set breakpoint condition-evaluation auto
4114 This is the default mode. If the target supports evaluating breakpoint
4115 conditions on its end, @value{GDBN} will download breakpoint conditions to
4116 the target (limitations mentioned previously apply). If the target does
4117 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4118 to evaluating all these conditions on the host's side.
4122 @cindex negative breakpoint numbers
4123 @cindex internal @value{GDBN} breakpoints
4124 @value{GDBN} itself sometimes sets breakpoints in your program for
4125 special purposes, such as proper handling of @code{longjmp} (in C
4126 programs). These internal breakpoints are assigned negative numbers,
4127 starting with @code{-1}; @samp{info breakpoints} does not display them.
4128 You can see these breakpoints with the @value{GDBN} maintenance command
4129 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4132 @node Set Watchpoints
4133 @subsection Setting Watchpoints
4135 @cindex setting watchpoints
4136 You can use a watchpoint to stop execution whenever the value of an
4137 expression changes, without having to predict a particular place where
4138 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4139 The expression may be as simple as the value of a single variable, or
4140 as complex as many variables combined by operators. Examples include:
4144 A reference to the value of a single variable.
4147 An address cast to an appropriate data type. For example,
4148 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4149 address (assuming an @code{int} occupies 4 bytes).
4152 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4153 expression can use any operators valid in the program's native
4154 language (@pxref{Languages}).
4157 You can set a watchpoint on an expression even if the expression can
4158 not be evaluated yet. For instance, you can set a watchpoint on
4159 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4160 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4161 the expression produces a valid value. If the expression becomes
4162 valid in some other way than changing a variable (e.g.@: if the memory
4163 pointed to by @samp{*global_ptr} becomes readable as the result of a
4164 @code{malloc} call), @value{GDBN} may not stop until the next time
4165 the expression changes.
4167 @cindex software watchpoints
4168 @cindex hardware watchpoints
4169 Depending on your system, watchpoints may be implemented in software or
4170 hardware. @value{GDBN} does software watchpointing by single-stepping your
4171 program and testing the variable's value each time, which is hundreds of
4172 times slower than normal execution. (But this may still be worth it, to
4173 catch errors where you have no clue what part of your program is the
4176 On some systems, such as most PowerPC or x86-based targets,
4177 @value{GDBN} includes support for hardware watchpoints, which do not
4178 slow down the running of your program.
4182 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4183 Set a watchpoint for an expression. @value{GDBN} will break when the
4184 expression @var{expr} is written into by the program and its value
4185 changes. The simplest (and the most popular) use of this command is
4186 to watch the value of a single variable:
4189 (@value{GDBP}) watch foo
4192 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4193 argument, @value{GDBN} breaks only when the thread identified by
4194 @var{thread-id} changes the value of @var{expr}. If any other threads
4195 change the value of @var{expr}, @value{GDBN} will not break. Note
4196 that watchpoints restricted to a single thread in this way only work
4197 with Hardware Watchpoints.
4199 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4200 (see below). The @code{-location} argument tells @value{GDBN} to
4201 instead watch the memory referred to by @var{expr}. In this case,
4202 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4203 and watch the memory at that address. The type of the result is used
4204 to determine the size of the watched memory. If the expression's
4205 result does not have an address, then @value{GDBN} will print an
4208 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4209 of masked watchpoints, if the current architecture supports this
4210 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4211 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4212 to an address to watch. The mask specifies that some bits of an address
4213 (the bits which are reset in the mask) should be ignored when matching
4214 the address accessed by the inferior against the watchpoint address.
4215 Thus, a masked watchpoint watches many addresses simultaneously---those
4216 addresses whose unmasked bits are identical to the unmasked bits in the
4217 watchpoint address. The @code{mask} argument implies @code{-location}.
4221 (@value{GDBP}) watch foo mask 0xffff00ff
4222 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4226 @item rwatch @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 the value of @var{expr} is read
4231 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4232 Set a watchpoint that will break when @var{expr} is either read from
4233 or written into by the program.
4235 @kindex info watchpoints @r{[}@var{list}@dots{}@r{]}
4236 @item info watchpoints @r{[}@var{list}@dots{}@r{]}
4237 This command prints a list of watchpoints, using the same format as
4238 @code{info break} (@pxref{Set Breaks}).
4241 If you watch for a change in a numerically entered address you need to
4242 dereference it, as the address itself is just a constant number which will
4243 never change. @value{GDBN} refuses to create a watchpoint that watches
4244 a never-changing value:
4247 (@value{GDBP}) watch 0x600850
4248 Cannot watch constant value 0x600850.
4249 (@value{GDBP}) watch *(int *) 0x600850
4250 Watchpoint 1: *(int *) 6293584
4253 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4254 watchpoints execute very quickly, and the debugger reports a change in
4255 value at the exact instruction where the change occurs. If @value{GDBN}
4256 cannot set a hardware watchpoint, it sets a software watchpoint, which
4257 executes more slowly and reports the change in value at the next
4258 @emph{statement}, not the instruction, after the change occurs.
4260 @cindex use only software watchpoints
4261 You can force @value{GDBN} to use only software watchpoints with the
4262 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4263 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4264 the underlying system supports them. (Note that hardware-assisted
4265 watchpoints that were set @emph{before} setting
4266 @code{can-use-hw-watchpoints} to zero will still use the hardware
4267 mechanism of watching expression values.)
4270 @item set can-use-hw-watchpoints
4271 @kindex set can-use-hw-watchpoints
4272 Set whether or not to use hardware watchpoints.
4274 @item show can-use-hw-watchpoints
4275 @kindex show can-use-hw-watchpoints
4276 Show the current mode of using hardware watchpoints.
4279 For remote targets, you can restrict the number of hardware
4280 watchpoints @value{GDBN} will use, see @ref{set remote
4281 hardware-breakpoint-limit}.
4283 When you issue the @code{watch} command, @value{GDBN} reports
4286 Hardware watchpoint @var{num}: @var{expr}
4290 if it was able to set a hardware watchpoint.
4292 Currently, the @code{awatch} and @code{rwatch} commands can only set
4293 hardware watchpoints, because accesses to data that don't change the
4294 value of the watched expression cannot be detected without examining
4295 every instruction as it is being executed, and @value{GDBN} does not do
4296 that currently. If @value{GDBN} finds that it is unable to set a
4297 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4298 will print a message like this:
4301 Expression cannot be implemented with read/access watchpoint.
4304 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4305 data type of the watched expression is wider than what a hardware
4306 watchpoint on the target machine can handle. For example, some systems
4307 can only watch regions that are up to 4 bytes wide; on such systems you
4308 cannot set hardware watchpoints for an expression that yields a
4309 double-precision floating-point number (which is typically 8 bytes
4310 wide). As a work-around, it might be possible to break the large region
4311 into a series of smaller ones and watch them with separate watchpoints.
4313 If you set too many hardware watchpoints, @value{GDBN} might be unable
4314 to insert all of them when you resume the execution of your program.
4315 Since the precise number of active watchpoints is unknown until such
4316 time as the program is about to be resumed, @value{GDBN} might not be
4317 able to warn you about this when you set the watchpoints, and the
4318 warning will be printed only when the program is resumed:
4321 Hardware watchpoint @var{num}: Could not insert watchpoint
4325 If this happens, delete or disable some of the watchpoints.
4327 Watching complex expressions that reference many variables can also
4328 exhaust the resources available for hardware-assisted watchpoints.
4329 That's because @value{GDBN} needs to watch every variable in the
4330 expression with separately allocated resources.
4332 If you call a function interactively using @code{print} or @code{call},
4333 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4334 kind of breakpoint or the call completes.
4336 @value{GDBN} automatically deletes watchpoints that watch local
4337 (automatic) variables, or expressions that involve such variables, when
4338 they go out of scope, that is, when the execution leaves the block in
4339 which these variables were defined. In particular, when the program
4340 being debugged terminates, @emph{all} local variables go out of scope,
4341 and so only watchpoints that watch global variables remain set. If you
4342 rerun the program, you will need to set all such watchpoints again. One
4343 way of doing that would be to set a code breakpoint at the entry to the
4344 @code{main} function and when it breaks, set all the watchpoints.
4346 @cindex watchpoints and threads
4347 @cindex threads and watchpoints
4348 In multi-threaded programs, watchpoints will detect changes to the
4349 watched expression from every thread.
4352 @emph{Warning:} In multi-threaded programs, software watchpoints
4353 have only limited usefulness. If @value{GDBN} creates a software
4354 watchpoint, it can only watch the value of an expression @emph{in a
4355 single thread}. If you are confident that the expression can only
4356 change due to the current thread's activity (and if you are also
4357 confident that no other thread can become current), then you can use
4358 software watchpoints as usual. However, @value{GDBN} may not notice
4359 when a non-current thread's activity changes the expression. (Hardware
4360 watchpoints, in contrast, watch an expression in all threads.)
4363 @xref{set remote hardware-watchpoint-limit}.
4365 @node Set Catchpoints
4366 @subsection Setting Catchpoints
4367 @cindex catchpoints, setting
4368 @cindex exception handlers
4369 @cindex event handling
4371 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4372 kinds of program events, such as C@t{++} exceptions or the loading of a
4373 shared library. Use the @code{catch} command to set a catchpoint.
4377 @item catch @var{event}
4378 Stop when @var{event} occurs. The @var{event} can be any of the following:
4381 @item throw @r{[}@var{regexp}@r{]}
4382 @itemx rethrow @r{[}@var{regexp}@r{]}
4383 @itemx catch @r{[}@var{regexp}@r{]}
4385 @kindex catch rethrow
4387 @cindex stop on C@t{++} exceptions
4388 The throwing, re-throwing, or catching of a C@t{++} exception.
4390 If @var{regexp} is given, then only exceptions whose type matches the
4391 regular expression will be caught.
4393 @vindex $_exception@r{, convenience variable}
4394 The convenience variable @code{$_exception} is available at an
4395 exception-related catchpoint, on some systems. This holds the
4396 exception being thrown.
4398 There are currently some limitations to C@t{++} exception handling in
4403 The support for these commands is system-dependent. Currently, only
4404 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4408 The regular expression feature and the @code{$_exception} convenience
4409 variable rely on the presence of some SDT probes in @code{libstdc++}.
4410 If these probes are not present, then these features cannot be used.
4411 These probes were first available in the GCC 4.8 release, but whether
4412 or not they are available in your GCC also depends on how it was
4416 The @code{$_exception} convenience variable is only valid at the
4417 instruction at which an exception-related catchpoint is set.
4420 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4421 location in the system library which implements runtime exception
4422 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4423 (@pxref{Selection}) to get to your code.
4426 If you call a function interactively, @value{GDBN} normally returns
4427 control to you when the function has finished executing. If the call
4428 raises an exception, however, the call may bypass the mechanism that
4429 returns control to you and cause your program either to abort or to
4430 simply continue running until it hits a breakpoint, catches a signal
4431 that @value{GDBN} is listening for, or exits. This is the case even if
4432 you set a catchpoint for the exception; catchpoints on exceptions are
4433 disabled within interactive calls. @xref{Calling}, for information on
4434 controlling this with @code{set unwind-on-terminating-exception}.
4437 You cannot raise an exception interactively.
4440 You cannot install an exception handler interactively.
4444 @kindex catch exception
4445 @cindex Ada exception catching
4446 @cindex catch Ada exceptions
4447 An Ada exception being raised. If an exception name is specified
4448 at the end of the command (eg @code{catch exception Program_Error}),
4449 the debugger will stop only when this specific exception is raised.
4450 Otherwise, the debugger stops execution when any Ada exception is raised.
4452 When inserting an exception catchpoint on a user-defined exception whose
4453 name is identical to one of the exceptions defined by the language, the
4454 fully qualified name must be used as the exception name. Otherwise,
4455 @value{GDBN} will assume that it should stop on the pre-defined exception
4456 rather than the user-defined one. For instance, assuming an exception
4457 called @code{Constraint_Error} is defined in package @code{Pck}, then
4458 the command to use to catch such exceptions is @kbd{catch exception
4459 Pck.Constraint_Error}.
4462 @kindex catch handlers
4463 @cindex Ada exception handlers catching
4464 @cindex catch Ada exceptions when handled
4465 An Ada exception being handled. If an exception name is
4466 specified at the end of the command
4467 (eg @kbd{catch handlers Program_Error}), the debugger will stop
4468 only when this specific exception is handled.
4469 Otherwise, the debugger stops execution when any Ada exception is handled.
4471 When inserting a handlers catchpoint on a user-defined
4472 exception whose name is identical to one of the exceptions
4473 defined by the language, the fully qualified name must be used
4474 as the exception name. Otherwise, @value{GDBN} will assume that it
4475 should stop on the pre-defined exception rather than the
4476 user-defined one. For instance, assuming an exception called
4477 @code{Constraint_Error} is defined in package @code{Pck}, then the
4478 command to use to catch such exceptions handling is
4479 @kbd{catch handlers Pck.Constraint_Error}.
4481 @item exception unhandled
4482 @kindex catch exception unhandled
4483 An exception that was raised but is not handled by the program.
4486 @kindex catch assert
4487 A failed Ada assertion.
4491 @cindex break on fork/exec
4492 A call to @code{exec}.
4495 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
4496 @kindex catch syscall
4497 @cindex break on a system call.
4498 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4499 syscall is a mechanism for application programs to request a service
4500 from the operating system (OS) or one of the OS system services.
4501 @value{GDBN} can catch some or all of the syscalls issued by the
4502 debuggee, and show the related information for each syscall. If no
4503 argument is specified, calls to and returns from all system calls
4506 @var{name} can be any system call name that is valid for the
4507 underlying OS. Just what syscalls are valid depends on the OS. On
4508 GNU and Unix systems, you can find the full list of valid syscall
4509 names on @file{/usr/include/asm/unistd.h}.
4511 @c For MS-Windows, the syscall names and the corresponding numbers
4512 @c can be found, e.g., on this URL:
4513 @c http://www.metasploit.com/users/opcode/syscalls.html
4514 @c but we don't support Windows syscalls yet.
4516 Normally, @value{GDBN} knows in advance which syscalls are valid for
4517 each OS, so you can use the @value{GDBN} command-line completion
4518 facilities (@pxref{Completion,, command completion}) to list the
4521 You may also specify the system call numerically. A syscall's
4522 number is the value passed to the OS's syscall dispatcher to
4523 identify the requested service. When you specify the syscall by its
4524 name, @value{GDBN} uses its database of syscalls to convert the name
4525 into the corresponding numeric code, but using the number directly
4526 may be useful if @value{GDBN}'s database does not have the complete
4527 list of syscalls on your system (e.g., because @value{GDBN} lags
4528 behind the OS upgrades).
4530 You may specify a group of related syscalls to be caught at once using
4531 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
4532 instance, on some platforms @value{GDBN} allows you to catch all
4533 network related syscalls, by passing the argument @code{group:network}
4534 to @code{catch syscall}. Note that not all syscall groups are
4535 available in every system. You can use the command completion
4536 facilities (@pxref{Completion,, command completion}) to list the
4537 syscall groups available on your environment.
4539 The example below illustrates how this command works if you don't provide
4543 (@value{GDBP}) catch syscall
4544 Catchpoint 1 (syscall)
4546 Starting program: /tmp/catch-syscall
4548 Catchpoint 1 (call to syscall 'close'), \
4549 0xffffe424 in __kernel_vsyscall ()
4553 Catchpoint 1 (returned from syscall 'close'), \
4554 0xffffe424 in __kernel_vsyscall ()
4558 Here is an example of catching a system call by name:
4561 (@value{GDBP}) catch syscall chroot
4562 Catchpoint 1 (syscall 'chroot' [61])
4564 Starting program: /tmp/catch-syscall
4566 Catchpoint 1 (call to syscall 'chroot'), \
4567 0xffffe424 in __kernel_vsyscall ()
4571 Catchpoint 1 (returned from syscall 'chroot'), \
4572 0xffffe424 in __kernel_vsyscall ()
4576 An example of specifying a system call numerically. In the case
4577 below, the syscall number has a corresponding entry in the XML
4578 file, so @value{GDBN} finds its name and prints it:
4581 (@value{GDBP}) catch syscall 252
4582 Catchpoint 1 (syscall(s) 'exit_group')
4584 Starting program: /tmp/catch-syscall
4586 Catchpoint 1 (call to syscall 'exit_group'), \
4587 0xffffe424 in __kernel_vsyscall ()
4591 Program exited normally.
4595 Here is an example of catching a syscall group:
4598 (@value{GDBP}) catch syscall group:process
4599 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
4600 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
4601 'exit_group' [252] 'waitid' [284] 'unshare' [310])
4603 Starting program: /tmp/catch-syscall
4605 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
4606 from /lib64/ld-linux-x86-64.so.2
4612 However, there can be situations when there is no corresponding name
4613 in XML file for that syscall number. In this case, @value{GDBN} prints
4614 a warning message saying that it was not able to find the syscall name,
4615 but the catchpoint will be set anyway. See the example below:
4618 (@value{GDBP}) catch syscall 764
4619 warning: The number '764' does not represent a known syscall.
4620 Catchpoint 2 (syscall 764)
4624 If you configure @value{GDBN} using the @samp{--without-expat} option,
4625 it will not be able to display syscall names. Also, if your
4626 architecture does not have an XML file describing its system calls,
4627 you will not be able to see the syscall names. It is important to
4628 notice that these two features are used for accessing the syscall
4629 name database. In either case, you will see a warning like this:
4632 (@value{GDBP}) catch syscall
4633 warning: Could not open "syscalls/i386-linux.xml"
4634 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4635 GDB will not be able to display syscall names.
4636 Catchpoint 1 (syscall)
4640 Of course, the file name will change depending on your architecture and system.
4642 Still using the example above, you can also try to catch a syscall by its
4643 number. In this case, you would see something like:
4646 (@value{GDBP}) catch syscall 252
4647 Catchpoint 1 (syscall(s) 252)
4650 Again, in this case @value{GDBN} would not be able to display syscall's names.
4654 A call to @code{fork}.
4658 A call to @code{vfork}.
4660 @item load @r{[}regexp@r{]}
4661 @itemx unload @r{[}regexp@r{]}
4663 @kindex catch unload
4664 The loading or unloading of a shared library. If @var{regexp} is
4665 given, then the catchpoint will stop only if the regular expression
4666 matches one of the affected libraries.
4668 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4669 @kindex catch signal
4670 The delivery of a signal.
4672 With no arguments, this catchpoint will catch any signal that is not
4673 used internally by @value{GDBN}, specifically, all signals except
4674 @samp{SIGTRAP} and @samp{SIGINT}.
4676 With the argument @samp{all}, all signals, including those used by
4677 @value{GDBN}, will be caught. This argument cannot be used with other
4680 Otherwise, the arguments are a list of signal names as given to
4681 @code{handle} (@pxref{Signals}). Only signals specified in this list
4684 One reason that @code{catch signal} can be more useful than
4685 @code{handle} is that you can attach commands and conditions to the
4688 When a signal is caught by a catchpoint, the signal's @code{stop} and
4689 @code{print} settings, as specified by @code{handle}, are ignored.
4690 However, whether the signal is still delivered to the inferior depends
4691 on the @code{pass} setting; this can be changed in the catchpoint's
4696 @item tcatch @var{event}
4698 Set a catchpoint that is enabled only for one stop. The catchpoint is
4699 automatically deleted after the first time the event is caught.
4703 Use the @code{info break} command to list the current catchpoints.
4707 @subsection Deleting Breakpoints
4709 @cindex clearing breakpoints, watchpoints, catchpoints
4710 @cindex deleting breakpoints, watchpoints, catchpoints
4711 It is often necessary to eliminate a breakpoint, watchpoint, or
4712 catchpoint once it has done its job and you no longer want your program
4713 to stop there. This is called @dfn{deleting} the breakpoint. A
4714 breakpoint that has been deleted no longer exists; it is forgotten.
4716 With the @code{clear} command you can delete breakpoints according to
4717 where they are in your program. With the @code{delete} command you can
4718 delete individual breakpoints, watchpoints, or catchpoints by specifying
4719 their breakpoint numbers.
4721 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4722 automatically ignores breakpoints on the first instruction to be executed
4723 when you continue execution without changing the execution address.
4728 Delete any breakpoints at the next instruction to be executed in the
4729 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4730 the innermost frame is selected, this is a good way to delete a
4731 breakpoint where your program just stopped.
4733 @item clear @var{location}
4734 Delete any breakpoints set at the specified @var{location}.
4735 @xref{Specify Location}, for the various forms of @var{location}; the
4736 most useful ones are listed below:
4739 @item clear @var{function}
4740 @itemx clear @var{filename}:@var{function}
4741 Delete any breakpoints set at entry to the named @var{function}.
4743 @item clear @var{linenum}
4744 @itemx clear @var{filename}:@var{linenum}
4745 Delete any breakpoints set at or within the code of the specified
4746 @var{linenum} of the specified @var{filename}.
4749 @cindex delete breakpoints
4751 @kindex d @r{(@code{delete})}
4752 @item delete @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4753 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4754 list specified as argument. If no argument is specified, delete all
4755 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4756 confirm off}). You can abbreviate this command as @code{d}.
4760 @subsection Disabling Breakpoints
4762 @cindex enable/disable a breakpoint
4763 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4764 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4765 it had been deleted, but remembers the information on the breakpoint so
4766 that you can @dfn{enable} it again later.
4768 You disable and enable breakpoints, watchpoints, and catchpoints with
4769 the @code{enable} and @code{disable} commands, optionally specifying
4770 one or more breakpoint numbers as arguments. Use @code{info break} to
4771 print a list of all breakpoints, watchpoints, and catchpoints if you
4772 do not know which numbers to use.
4774 Disabling and enabling a breakpoint that has multiple locations
4775 affects all of its locations.
4777 A breakpoint, watchpoint, or catchpoint can have any of several
4778 different states of enablement:
4782 Enabled. The breakpoint stops your program. A breakpoint set
4783 with the @code{break} command starts out in this state.
4785 Disabled. The breakpoint has no effect on your program.
4787 Enabled once. The breakpoint stops your program, but then becomes
4790 Enabled for a count. The breakpoint stops your program for the next
4791 N times, then becomes disabled.
4793 Enabled for deletion. The breakpoint stops your program, but
4794 immediately after it does so it is deleted permanently. A breakpoint
4795 set with the @code{tbreak} command starts out in this state.
4798 You can use the following commands to enable or disable breakpoints,
4799 watchpoints, and catchpoints:
4803 @kindex dis @r{(@code{disable})}
4804 @item disable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4805 Disable the specified breakpoints---or all breakpoints, if none are
4806 listed. A disabled breakpoint has no effect but is not forgotten. All
4807 options such as ignore-counts, conditions and commands are remembered in
4808 case the breakpoint is enabled again later. You may abbreviate
4809 @code{disable} as @code{dis}.
4812 @item enable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4813 Enable the specified breakpoints (or all defined breakpoints). They
4814 become effective once again in stopping your program.
4816 @item enable @r{[}breakpoints@r{]} once @var{list}@dots{}
4817 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4818 of these breakpoints immediately after stopping your program.
4820 @item enable @r{[}breakpoints@r{]} count @var{count} @var{list}@dots{}
4821 Enable the specified breakpoints temporarily. @value{GDBN} records
4822 @var{count} with each of the specified breakpoints, and decrements a
4823 breakpoint's count when it is hit. When any count reaches 0,
4824 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4825 count (@pxref{Conditions, ,Break Conditions}), that will be
4826 decremented to 0 before @var{count} is affected.
4828 @item enable @r{[}breakpoints@r{]} delete @var{list}@dots{}
4829 Enable the specified breakpoints to work once, then die. @value{GDBN}
4830 deletes any of these breakpoints as soon as your program stops there.
4831 Breakpoints set by the @code{tbreak} command start out in this state.
4834 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4835 @c confusing: tbreak is also initially enabled.
4836 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4837 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4838 subsequently, they become disabled or enabled only when you use one of
4839 the commands above. (The command @code{until} can set and delete a
4840 breakpoint of its own, but it does not change the state of your other
4841 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4845 @subsection Break Conditions
4846 @cindex conditional breakpoints
4847 @cindex breakpoint conditions
4849 @c FIXME what is scope of break condition expr? Context where wanted?
4850 @c in particular for a watchpoint?
4851 The simplest sort of breakpoint breaks every time your program reaches a
4852 specified place. You can also specify a @dfn{condition} for a
4853 breakpoint. A condition is just a Boolean expression in your
4854 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4855 a condition evaluates the expression each time your program reaches it,
4856 and your program stops only if the condition is @emph{true}.
4858 This is the converse of using assertions for program validation; in that
4859 situation, you want to stop when the assertion is violated---that is,
4860 when the condition is false. In C, if you want to test an assertion expressed
4861 by the condition @var{assert}, you should set the condition
4862 @samp{! @var{assert}} on the appropriate breakpoint.
4864 Conditions are also accepted for watchpoints; you may not need them,
4865 since a watchpoint is inspecting the value of an expression anyhow---but
4866 it might be simpler, say, to just set a watchpoint on a variable name,
4867 and specify a condition that tests whether the new value is an interesting
4870 Break conditions can have side effects, and may even call functions in
4871 your program. This can be useful, for example, to activate functions
4872 that log program progress, or to use your own print functions to
4873 format special data structures. The effects are completely predictable
4874 unless there is another enabled breakpoint at the same address. (In
4875 that case, @value{GDBN} might see the other breakpoint first and stop your
4876 program without checking the condition of this one.) Note that
4877 breakpoint commands are usually more convenient and flexible than break
4879 purpose of performing side effects when a breakpoint is reached
4880 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4882 Breakpoint conditions can also be evaluated on the target's side if
4883 the target supports it. Instead of evaluating the conditions locally,
4884 @value{GDBN} encodes the expression into an agent expression
4885 (@pxref{Agent Expressions}) suitable for execution on the target,
4886 independently of @value{GDBN}. Global variables become raw memory
4887 locations, locals become stack accesses, and so forth.
4889 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4890 when its condition evaluates to true. This mechanism may provide faster
4891 response times depending on the performance characteristics of the target
4892 since it does not need to keep @value{GDBN} informed about
4893 every breakpoint trigger, even those with false conditions.
4895 Break conditions can be specified when a breakpoint is set, by using
4896 @samp{if} in the arguments to the @code{break} command. @xref{Set
4897 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4898 with the @code{condition} command.
4900 You can also use the @code{if} keyword with the @code{watch} command.
4901 The @code{catch} command does not recognize the @code{if} keyword;
4902 @code{condition} is the only way to impose a further condition on a
4907 @item condition @var{bnum} @var{expression}
4908 Specify @var{expression} as the break condition for breakpoint,
4909 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4910 breakpoint @var{bnum} stops your program only if the value of
4911 @var{expression} is true (nonzero, in C). When you use
4912 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4913 syntactic correctness, and to determine whether symbols in it have
4914 referents in the context of your breakpoint. If @var{expression} uses
4915 symbols not referenced in the context of the breakpoint, @value{GDBN}
4916 prints an error message:
4919 No symbol "foo" in current context.
4924 not actually evaluate @var{expression} at the time the @code{condition}
4925 command (or a command that sets a breakpoint with a condition, like
4926 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4928 @item condition @var{bnum}
4929 Remove the condition from breakpoint number @var{bnum}. It becomes
4930 an ordinary unconditional breakpoint.
4933 @cindex ignore count (of breakpoint)
4934 A special case of a breakpoint condition is to stop only when the
4935 breakpoint has been reached a certain number of times. This is so
4936 useful that there is a special way to do it, using the @dfn{ignore
4937 count} of the breakpoint. Every breakpoint has an ignore count, which
4938 is an integer. Most of the time, the ignore count is zero, and
4939 therefore has no effect. But if your program reaches a breakpoint whose
4940 ignore count is positive, then instead of stopping, it just decrements
4941 the ignore count by one and continues. As a result, if the ignore count
4942 value is @var{n}, the breakpoint does not stop the next @var{n} times
4943 your program reaches it.
4947 @item ignore @var{bnum} @var{count}
4948 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4949 The next @var{count} times the breakpoint is reached, your program's
4950 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4953 To make the breakpoint stop the next time it is reached, specify
4956 When you use @code{continue} to resume execution of your program from a
4957 breakpoint, you can specify an ignore count directly as an argument to
4958 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4959 Stepping,,Continuing and Stepping}.
4961 If a breakpoint has a positive ignore count and a condition, the
4962 condition is not checked. Once the ignore count reaches zero,
4963 @value{GDBN} resumes checking the condition.
4965 You could achieve the effect of the ignore count with a condition such
4966 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4967 is decremented each time. @xref{Convenience Vars, ,Convenience
4971 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4974 @node Break Commands
4975 @subsection Breakpoint Command Lists
4977 @cindex breakpoint commands
4978 You can give any breakpoint (or watchpoint or catchpoint) a series of
4979 commands to execute when your program stops due to that breakpoint. For
4980 example, you might want to print the values of certain expressions, or
4981 enable other breakpoints.
4985 @kindex end@r{ (breakpoint commands)}
4986 @item commands @r{[}@var{list}@dots{}@r{]}
4987 @itemx @dots{} @var{command-list} @dots{}
4989 Specify a list of commands for the given breakpoints. The commands
4990 themselves appear on the following lines. Type a line containing just
4991 @code{end} to terminate the commands.
4993 To remove all commands from a breakpoint, type @code{commands} and
4994 follow it immediately with @code{end}; that is, give no commands.
4996 With no argument, @code{commands} refers to the last breakpoint,
4997 watchpoint, or catchpoint set (not to the breakpoint most recently
4998 encountered). If the most recent breakpoints were set with a single
4999 command, then the @code{commands} will apply to all the breakpoints
5000 set by that command. This applies to breakpoints set by
5001 @code{rbreak}, and also applies when a single @code{break} command
5002 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
5006 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
5007 disabled within a @var{command-list}.
5009 You can use breakpoint commands to start your program up again. Simply
5010 use the @code{continue} command, or @code{step}, or any other command
5011 that resumes execution.
5013 Any other commands in the command list, after a command that resumes
5014 execution, are ignored. This is because any time you resume execution
5015 (even with a simple @code{next} or @code{step}), you may encounter
5016 another breakpoint---which could have its own command list, leading to
5017 ambiguities about which list to execute.
5020 If the first command you specify in a command list is @code{silent}, the
5021 usual message about stopping at a breakpoint is not printed. This may
5022 be desirable for breakpoints that are to print a specific message and
5023 then continue. If none of the remaining commands print anything, you
5024 see no sign that the breakpoint was reached. @code{silent} is
5025 meaningful only at the beginning of a breakpoint command list.
5027 The commands @code{echo}, @code{output}, and @code{printf} allow you to
5028 print precisely controlled output, and are often useful in silent
5029 breakpoints. @xref{Output, ,Commands for Controlled Output}.
5031 For example, here is how you could use breakpoint commands to print the
5032 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
5038 printf "x is %d\n",x
5043 One application for breakpoint commands is to compensate for one bug so
5044 you can test for another. Put a breakpoint just after the erroneous line
5045 of code, give it a condition to detect the case in which something
5046 erroneous has been done, and give it commands to assign correct values
5047 to any variables that need them. End with the @code{continue} command
5048 so that your program does not stop, and start with the @code{silent}
5049 command so that no output is produced. Here is an example:
5060 @node Dynamic Printf
5061 @subsection Dynamic Printf
5063 @cindex dynamic printf
5065 The dynamic printf command @code{dprintf} combines a breakpoint with
5066 formatted printing of your program's data to give you the effect of
5067 inserting @code{printf} calls into your program on-the-fly, without
5068 having to recompile it.
5070 In its most basic form, the output goes to the GDB console. However,
5071 you can set the variable @code{dprintf-style} for alternate handling.
5072 For instance, you can ask to format the output by calling your
5073 program's @code{printf} function. This has the advantage that the
5074 characters go to the program's output device, so they can recorded in
5075 redirects to files and so forth.
5077 If you are doing remote debugging with a stub or agent, you can also
5078 ask to have the printf handled by the remote agent. In addition to
5079 ensuring that the output goes to the remote program's device along
5080 with any other output the program might produce, you can also ask that
5081 the dprintf remain active even after disconnecting from the remote
5082 target. Using the stub/agent is also more efficient, as it can do
5083 everything without needing to communicate with @value{GDBN}.
5087 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
5088 Whenever execution reaches @var{location}, print the values of one or
5089 more @var{expressions} under the control of the string @var{template}.
5090 To print several values, separate them with commas.
5092 @item set dprintf-style @var{style}
5093 Set the dprintf output to be handled in one of several different
5094 styles enumerated below. A change of style affects all existing
5095 dynamic printfs immediately. (If you need individual control over the
5096 print commands, simply define normal breakpoints with
5097 explicitly-supplied command lists.)
5101 @kindex dprintf-style gdb
5102 Handle the output using the @value{GDBN} @code{printf} command.
5105 @kindex dprintf-style call
5106 Handle the output by calling a function in your program (normally
5110 @kindex dprintf-style agent
5111 Have the remote debugging agent (such as @code{gdbserver}) handle
5112 the output itself. This style is only available for agents that
5113 support running commands on the target.
5116 @item set dprintf-function @var{function}
5117 Set the function to call if the dprintf style is @code{call}. By
5118 default its value is @code{printf}. You may set it to any expression.
5119 that @value{GDBN} can evaluate to a function, as per the @code{call}
5122 @item set dprintf-channel @var{channel}
5123 Set a ``channel'' for dprintf. If set to a non-empty value,
5124 @value{GDBN} will evaluate it as an expression and pass the result as
5125 a first argument to the @code{dprintf-function}, in the manner of
5126 @code{fprintf} and similar functions. Otherwise, the dprintf format
5127 string will be the first argument, in the manner of @code{printf}.
5129 As an example, if you wanted @code{dprintf} output to go to a logfile
5130 that is a standard I/O stream assigned to the variable @code{mylog},
5131 you could do the following:
5134 (gdb) set dprintf-style call
5135 (gdb) set dprintf-function fprintf
5136 (gdb) set dprintf-channel mylog
5137 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
5138 Dprintf 1 at 0x123456: file main.c, line 25.
5140 1 dprintf keep y 0x00123456 in main at main.c:25
5141 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5146 Note that the @code{info break} displays the dynamic printf commands
5147 as normal breakpoint commands; you can thus easily see the effect of
5148 the variable settings.
5150 @item set disconnected-dprintf on
5151 @itemx set disconnected-dprintf off
5152 @kindex set disconnected-dprintf
5153 Choose whether @code{dprintf} commands should continue to run if
5154 @value{GDBN} has disconnected from the target. This only applies
5155 if the @code{dprintf-style} is @code{agent}.
5157 @item show disconnected-dprintf off
5158 @kindex show disconnected-dprintf
5159 Show the current choice for disconnected @code{dprintf}.
5163 @value{GDBN} does not check the validity of function and channel,
5164 relying on you to supply values that are meaningful for the contexts
5165 in which they are being used. For instance, the function and channel
5166 may be the values of local variables, but if that is the case, then
5167 all enabled dynamic prints must be at locations within the scope of
5168 those locals. If evaluation fails, @value{GDBN} will report an error.
5170 @node Save Breakpoints
5171 @subsection How to save breakpoints to a file
5173 To save breakpoint definitions to a file use the @w{@code{save
5174 breakpoints}} command.
5177 @kindex save breakpoints
5178 @cindex save breakpoints to a file for future sessions
5179 @item save breakpoints [@var{filename}]
5180 This command saves all current breakpoint definitions together with
5181 their commands and ignore counts, into a file @file{@var{filename}}
5182 suitable for use in a later debugging session. This includes all
5183 types of breakpoints (breakpoints, watchpoints, catchpoints,
5184 tracepoints). To read the saved breakpoint definitions, use the
5185 @code{source} command (@pxref{Command Files}). Note that watchpoints
5186 with expressions involving local variables may fail to be recreated
5187 because it may not be possible to access the context where the
5188 watchpoint is valid anymore. Because the saved breakpoint definitions
5189 are simply a sequence of @value{GDBN} commands that recreate the
5190 breakpoints, you can edit the file in your favorite editing program,
5191 and remove the breakpoint definitions you're not interested in, or
5192 that can no longer be recreated.
5195 @node Static Probe Points
5196 @subsection Static Probe Points
5198 @cindex static probe point, SystemTap
5199 @cindex static probe point, DTrace
5200 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5201 for Statically Defined Tracing, and the probes are designed to have a tiny
5202 runtime code and data footprint, and no dynamic relocations.
5204 Currently, the following types of probes are supported on
5205 ELF-compatible systems:
5209 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5210 @acronym{SDT} probes@footnote{See
5211 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5212 for more information on how to add @code{SystemTap} @acronym{SDT}
5213 probes in your applications.}. @code{SystemTap} probes are usable
5214 from assembly, C and C@t{++} languages@footnote{See
5215 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5216 for a good reference on how the @acronym{SDT} probes are implemented.}.
5218 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5219 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5223 @cindex semaphores on static probe points
5224 Some @code{SystemTap} probes have an associated semaphore variable;
5225 for instance, this happens automatically if you defined your probe
5226 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5227 @value{GDBN} will automatically enable it when you specify a
5228 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5229 breakpoint at a probe's location by some other method (e.g.,
5230 @code{break file:line}), then @value{GDBN} will not automatically set
5231 the semaphore. @code{DTrace} probes do not support semaphores.
5233 You can examine the available static static probes using @code{info
5234 probes}, with optional arguments:
5238 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5239 If given, @var{type} is either @code{stap} for listing
5240 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5241 probes. If omitted all probes are listed regardless of their types.
5243 If given, @var{provider} is a regular expression used to match against provider
5244 names when selecting which probes to list. If omitted, probes by all
5245 probes from all providers are listed.
5247 If given, @var{name} is a regular expression to match against probe names
5248 when selecting which probes to list. If omitted, probe names are not
5249 considered when deciding whether to display them.
5251 If given, @var{objfile} is a regular expression used to select which
5252 object files (executable or shared libraries) to examine. If not
5253 given, all object files are considered.
5255 @item info probes all
5256 List the available static probes, from all types.
5259 @cindex enabling and disabling probes
5260 Some probe points can be enabled and/or disabled. The effect of
5261 enabling or disabling a probe depends on the type of probe being
5262 handled. Some @code{DTrace} probes can be enabled or
5263 disabled, but @code{SystemTap} probes cannot be disabled.
5265 You can enable (or disable) one or more probes using the following
5266 commands, with optional arguments:
5269 @kindex enable probes
5270 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5271 If given, @var{provider} is a regular expression used to match against
5272 provider names when selecting which probes to enable. If omitted,
5273 all probes from all providers are enabled.
5275 If given, @var{name} is a regular expression to match against probe
5276 names when selecting which probes to enable. If omitted, probe names
5277 are not considered when deciding whether to enable them.
5279 If given, @var{objfile} is a regular expression used to select which
5280 object files (executable or shared libraries) to examine. If not
5281 given, all object files are considered.
5283 @kindex disable probes
5284 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5285 See the @code{enable probes} command above for a description of the
5286 optional arguments accepted by this command.
5289 @vindex $_probe_arg@r{, convenience variable}
5290 A probe may specify up to twelve arguments. These are available at the
5291 point at which the probe is defined---that is, when the current PC is
5292 at the probe's location. The arguments are available using the
5293 convenience variables (@pxref{Convenience Vars})
5294 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5295 probes each probe argument is an integer of the appropriate size;
5296 types are not preserved. In @code{DTrace} probes types are preserved
5297 provided that they are recognized as such by @value{GDBN}; otherwise
5298 the value of the probe argument will be a long integer. The
5299 convenience variable @code{$_probe_argc} holds the number of arguments
5300 at the current probe point.
5302 These variables are always available, but attempts to access them at
5303 any location other than a probe point will cause @value{GDBN} to give
5307 @c @ifclear BARETARGET
5308 @node Error in Breakpoints
5309 @subsection ``Cannot insert breakpoints''
5311 If you request too many active hardware-assisted breakpoints and
5312 watchpoints, you will see this error message:
5314 @c FIXME: the precise wording of this message may change; the relevant
5315 @c source change is not committed yet (Sep 3, 1999).
5317 Stopped; cannot insert breakpoints.
5318 You may have requested too many hardware breakpoints and watchpoints.
5322 This message is printed when you attempt to resume the program, since
5323 only then @value{GDBN} knows exactly how many hardware breakpoints and
5324 watchpoints it needs to insert.
5326 When this message is printed, you need to disable or remove some of the
5327 hardware-assisted breakpoints and watchpoints, and then continue.
5329 @node Breakpoint-related Warnings
5330 @subsection ``Breakpoint address adjusted...''
5331 @cindex breakpoint address adjusted
5333 Some processor architectures place constraints on the addresses at
5334 which breakpoints may be placed. For architectures thus constrained,
5335 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5336 with the constraints dictated by the architecture.
5338 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5339 a VLIW architecture in which a number of RISC-like instructions may be
5340 bundled together for parallel execution. The FR-V architecture
5341 constrains the location of a breakpoint instruction within such a
5342 bundle to the instruction with the lowest address. @value{GDBN}
5343 honors this constraint by adjusting a breakpoint's address to the
5344 first in the bundle.
5346 It is not uncommon for optimized code to have bundles which contain
5347 instructions from different source statements, thus it may happen that
5348 a breakpoint's address will be adjusted from one source statement to
5349 another. Since this adjustment may significantly alter @value{GDBN}'s
5350 breakpoint related behavior from what the user expects, a warning is
5351 printed when the breakpoint is first set and also when the breakpoint
5354 A warning like the one below is printed when setting a breakpoint
5355 that's been subject to address adjustment:
5358 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5361 Such warnings are printed both for user settable and @value{GDBN}'s
5362 internal breakpoints. If you see one of these warnings, you should
5363 verify that a breakpoint set at the adjusted address will have the
5364 desired affect. If not, the breakpoint in question may be removed and
5365 other breakpoints may be set which will have the desired behavior.
5366 E.g., it may be sufficient to place the breakpoint at a later
5367 instruction. A conditional breakpoint may also be useful in some
5368 cases to prevent the breakpoint from triggering too often.
5370 @value{GDBN} will also issue a warning when stopping at one of these
5371 adjusted breakpoints:
5374 warning: Breakpoint 1 address previously adjusted from 0x00010414
5378 When this warning is encountered, it may be too late to take remedial
5379 action except in cases where the breakpoint is hit earlier or more
5380 frequently than expected.
5382 @node Continuing and Stepping
5383 @section Continuing and Stepping
5387 @cindex resuming execution
5388 @dfn{Continuing} means resuming program execution until your program
5389 completes normally. In contrast, @dfn{stepping} means executing just
5390 one more ``step'' of your program, where ``step'' may mean either one
5391 line of source code, or one machine instruction (depending on what
5392 particular command you use). Either when continuing or when stepping,
5393 your program may stop even sooner, due to a breakpoint or a signal. (If
5394 it stops due to a signal, you may want to use @code{handle}, or use
5395 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5396 or you may step into the signal's handler (@pxref{stepping and signal
5401 @kindex c @r{(@code{continue})}
5402 @kindex fg @r{(resume foreground execution)}
5403 @item continue @r{[}@var{ignore-count}@r{]}
5404 @itemx c @r{[}@var{ignore-count}@r{]}
5405 @itemx fg @r{[}@var{ignore-count}@r{]}
5406 Resume program execution, at the address where your program last stopped;
5407 any breakpoints set at that address are bypassed. The optional argument
5408 @var{ignore-count} allows you to specify a further number of times to
5409 ignore a breakpoint at this location; its effect is like that of
5410 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5412 The argument @var{ignore-count} is meaningful only when your program
5413 stopped due to a breakpoint. At other times, the argument to
5414 @code{continue} is ignored.
5416 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5417 debugged program is deemed to be the foreground program) are provided
5418 purely for convenience, and have exactly the same behavior as
5422 To resume execution at a different place, you can use @code{return}
5423 (@pxref{Returning, ,Returning from a Function}) to go back to the
5424 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5425 Different Address}) to go to an arbitrary location in your program.
5427 A typical technique for using stepping is to set a breakpoint
5428 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5429 beginning of the function or the section of your program where a problem
5430 is believed to lie, run your program until it stops at that breakpoint,
5431 and then step through the suspect area, examining the variables that are
5432 interesting, until you see the problem happen.
5436 @kindex s @r{(@code{step})}
5438 Continue running your program until control reaches a different source
5439 line, then stop it and return control to @value{GDBN}. This command is
5440 abbreviated @code{s}.
5443 @c "without debugging information" is imprecise; actually "without line
5444 @c numbers in the debugging information". (gcc -g1 has debugging info but
5445 @c not line numbers). But it seems complex to try to make that
5446 @c distinction here.
5447 @emph{Warning:} If you use the @code{step} command while control is
5448 within a function that was compiled without debugging information,
5449 execution proceeds until control reaches a function that does have
5450 debugging information. Likewise, it will not step into a function which
5451 is compiled without debugging information. To step through functions
5452 without debugging information, use the @code{stepi} command, described
5456 The @code{step} command only stops at the first instruction of a source
5457 line. This prevents the multiple stops that could otherwise occur in
5458 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5459 to stop if a function that has debugging information is called within
5460 the line. In other words, @code{step} @emph{steps inside} any functions
5461 called within the line.
5463 Also, the @code{step} command only enters a function if there is line
5464 number information for the function. Otherwise it acts like the
5465 @code{next} command. This avoids problems when using @code{cc -gl}
5466 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5467 was any debugging information about the routine.
5469 @item step @var{count}
5470 Continue running as in @code{step}, but do so @var{count} times. If a
5471 breakpoint is reached, or a signal not related to stepping occurs before
5472 @var{count} steps, stepping stops right away.
5475 @kindex n @r{(@code{next})}
5476 @item next @r{[}@var{count}@r{]}
5477 Continue to the next source line in the current (innermost) stack frame.
5478 This is similar to @code{step}, but function calls that appear within
5479 the line of code are executed without stopping. Execution stops when
5480 control reaches a different line of code at the original stack level
5481 that was executing when you gave the @code{next} command. This command
5482 is abbreviated @code{n}.
5484 An argument @var{count} is a repeat count, as for @code{step}.
5487 @c FIX ME!! Do we delete this, or is there a way it fits in with
5488 @c the following paragraph? --- Vctoria
5490 @c @code{next} within a function that lacks debugging information acts like
5491 @c @code{step}, but any function calls appearing within the code of the
5492 @c function are executed without stopping.
5494 The @code{next} command only stops at the first instruction of a
5495 source line. This prevents multiple stops that could otherwise occur in
5496 @code{switch} statements, @code{for} loops, etc.
5498 @kindex set step-mode
5500 @cindex functions without line info, and stepping
5501 @cindex stepping into functions with no line info
5502 @itemx set step-mode on
5503 The @code{set step-mode on} command causes the @code{step} command to
5504 stop at the first instruction of a function which contains no debug line
5505 information rather than stepping over it.
5507 This is useful in cases where you may be interested in inspecting the
5508 machine instructions of a function which has no symbolic info and do not
5509 want @value{GDBN} to automatically skip over this function.
5511 @item set step-mode off
5512 Causes the @code{step} command to step over any functions which contains no
5513 debug information. This is the default.
5515 @item show step-mode
5516 Show whether @value{GDBN} will stop in or step over functions without
5517 source line debug information.
5520 @kindex fin @r{(@code{finish})}
5522 Continue running until just after function in the selected stack frame
5523 returns. Print the returned value (if any). This command can be
5524 abbreviated as @code{fin}.
5526 Contrast this with the @code{return} command (@pxref{Returning,
5527 ,Returning from a Function}).
5530 @kindex u @r{(@code{until})}
5531 @cindex run until specified location
5534 Continue running until a source line past the current line, in the
5535 current stack frame, is reached. This command is used to avoid single
5536 stepping through a loop more than once. It is like the @code{next}
5537 command, except that when @code{until} encounters a jump, it
5538 automatically continues execution until the program counter is greater
5539 than the address of the jump.
5541 This means that when you reach the end of a loop after single stepping
5542 though it, @code{until} makes your program continue execution until it
5543 exits the loop. In contrast, a @code{next} command at the end of a loop
5544 simply steps back to the beginning of the loop, which forces you to step
5545 through the next iteration.
5547 @code{until} always stops your program if it attempts to exit the current
5550 @code{until} may produce somewhat counterintuitive results if the order
5551 of machine code does not match the order of the source lines. For
5552 example, in the following excerpt from a debugging session, the @code{f}
5553 (@code{frame}) command shows that execution is stopped at line
5554 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5558 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5560 (@value{GDBP}) until
5561 195 for ( ; argc > 0; NEXTARG) @{
5564 This happened because, for execution efficiency, the compiler had
5565 generated code for the loop closure test at the end, rather than the
5566 start, of the loop---even though the test in a C @code{for}-loop is
5567 written before the body of the loop. The @code{until} command appeared
5568 to step back to the beginning of the loop when it advanced to this
5569 expression; however, it has not really gone to an earlier
5570 statement---not in terms of the actual machine code.
5572 @code{until} with no argument works by means of single
5573 instruction stepping, and hence is slower than @code{until} with an
5576 @item until @var{location}
5577 @itemx u @var{location}
5578 Continue running your program until either the specified @var{location} is
5579 reached, or the current stack frame returns. The location is any of
5580 the forms described in @ref{Specify Location}.
5581 This form of the command uses temporary breakpoints, and
5582 hence is quicker than @code{until} without an argument. The specified
5583 location is actually reached only if it is in the current frame. This
5584 implies that @code{until} can be used to skip over recursive function
5585 invocations. For instance in the code below, if the current location is
5586 line @code{96}, issuing @code{until 99} will execute the program up to
5587 line @code{99} in the same invocation of factorial, i.e., after the inner
5588 invocations have returned.
5591 94 int factorial (int value)
5593 96 if (value > 1) @{
5594 97 value *= factorial (value - 1);
5601 @kindex advance @var{location}
5602 @item advance @var{location}
5603 Continue running the program up to the given @var{location}. An argument is
5604 required, which should be of one of the forms described in
5605 @ref{Specify Location}.
5606 Execution will also stop upon exit from the current stack
5607 frame. This command is similar to @code{until}, but @code{advance} will
5608 not skip over recursive function calls, and the target location doesn't
5609 have to be in the same frame as the current one.
5613 @kindex si @r{(@code{stepi})}
5615 @itemx stepi @var{arg}
5617 Execute one machine instruction, then stop and return to the debugger.
5619 It is often useful to do @samp{display/i $pc} when stepping by machine
5620 instructions. This makes @value{GDBN} automatically display the next
5621 instruction to be executed, each time your program stops. @xref{Auto
5622 Display,, Automatic Display}.
5624 An argument is a repeat count, as in @code{step}.
5628 @kindex ni @r{(@code{nexti})}
5630 @itemx nexti @var{arg}
5632 Execute one machine instruction, but if it is a function call,
5633 proceed until the function returns.
5635 An argument is a repeat count, as in @code{next}.
5639 @anchor{range stepping}
5640 @cindex range stepping
5641 @cindex target-assisted range stepping
5642 By default, and if available, @value{GDBN} makes use of
5643 target-assisted @dfn{range stepping}. In other words, whenever you
5644 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5645 tells the target to step the corresponding range of instruction
5646 addresses instead of issuing multiple single-steps. This speeds up
5647 line stepping, particularly for remote targets. Ideally, there should
5648 be no reason you would want to turn range stepping off. However, it's
5649 possible that a bug in the debug info, a bug in the remote stub (for
5650 remote targets), or even a bug in @value{GDBN} could make line
5651 stepping behave incorrectly when target-assisted range stepping is
5652 enabled. You can use the following command to turn off range stepping
5656 @kindex set range-stepping
5657 @kindex show range-stepping
5658 @item set range-stepping
5659 @itemx show range-stepping
5660 Control whether range stepping is enabled.
5662 If @code{on}, and the target supports it, @value{GDBN} tells the
5663 target to step a range of addresses itself, instead of issuing
5664 multiple single-steps. If @code{off}, @value{GDBN} always issues
5665 single-steps, even if range stepping is supported by the target. The
5666 default is @code{on}.
5670 @node Skipping Over Functions and Files
5671 @section Skipping Over Functions and Files
5672 @cindex skipping over functions and files
5674 The program you are debugging may contain some functions which are
5675 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
5676 skip a function, all functions in a file or a particular function in
5677 a particular file when stepping.
5679 For example, consider the following C function:
5690 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5691 are not interested in stepping through @code{boring}. If you run @code{step}
5692 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5693 step over both @code{foo} and @code{boring}!
5695 One solution is to @code{step} into @code{boring} and use the @code{finish}
5696 command to immediately exit it. But this can become tedious if @code{boring}
5697 is called from many places.
5699 A more flexible solution is to execute @kbd{skip boring}. This instructs
5700 @value{GDBN} never to step into @code{boring}. Now when you execute
5701 @code{step} at line 103, you'll step over @code{boring} and directly into
5704 Functions may be skipped by providing either a function name, linespec
5705 (@pxref{Specify Location}), regular expression that matches the function's
5706 name, file name or a @code{glob}-style pattern that matches the file name.
5708 On Posix systems the form of the regular expression is
5709 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
5710 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
5711 expression is whatever is provided by the @code{regcomp} function of
5712 the underlying system.
5713 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
5714 description of @code{glob}-style patterns.
5718 @item skip @r{[}@var{options}@r{]}
5719 The basic form of the @code{skip} command takes zero or more options
5720 that specify what to skip.
5721 The @var{options} argument is any useful combination of the following:
5724 @item -file @var{file}
5725 @itemx -fi @var{file}
5726 Functions in @var{file} will be skipped over when stepping.
5728 @item -gfile @var{file-glob-pattern}
5729 @itemx -gfi @var{file-glob-pattern}
5730 @cindex skipping over files via glob-style patterns
5731 Functions in files matching @var{file-glob-pattern} will be skipped
5735 (gdb) skip -gfi utils/*.c
5738 @item -function @var{linespec}
5739 @itemx -fu @var{linespec}
5740 Functions named by @var{linespec} or the function containing the line
5741 named by @var{linespec} will be skipped over when stepping.
5742 @xref{Specify Location}.
5744 @item -rfunction @var{regexp}
5745 @itemx -rfu @var{regexp}
5746 @cindex skipping over functions via regular expressions
5747 Functions whose name matches @var{regexp} will be skipped over when stepping.
5749 This form is useful for complex function names.
5750 For example, there is generally no need to step into C@t{++} @code{std::string}
5751 constructors or destructors. Plus with C@t{++} templates it can be hard to
5752 write out the full name of the function, and often it doesn't matter what
5753 the template arguments are. Specifying the function to be skipped as a
5754 regular expression makes this easier.
5757 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
5760 If you want to skip every templated C@t{++} constructor and destructor
5761 in the @code{std} namespace you can do:
5764 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
5768 If no options are specified, the function you're currently debugging
5771 @kindex skip function
5772 @item skip function @r{[}@var{linespec}@r{]}
5773 After running this command, the function named by @var{linespec} or the
5774 function containing the line named by @var{linespec} will be skipped over when
5775 stepping. @xref{Specify Location}.
5777 If you do not specify @var{linespec}, the function you're currently debugging
5780 (If you have a function called @code{file} that you want to skip, use
5781 @kbd{skip function file}.)
5784 @item skip file @r{[}@var{filename}@r{]}
5785 After running this command, any function whose source lives in @var{filename}
5786 will be skipped over when stepping.
5789 (gdb) skip file boring.c
5790 File boring.c will be skipped when stepping.
5793 If you do not specify @var{filename}, functions whose source lives in the file
5794 you're currently debugging will be skipped.
5797 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5798 These are the commands for managing your list of skips:
5802 @item info skip @r{[}@var{range}@r{]}
5803 Print details about the specified skip(s). If @var{range} is not specified,
5804 print a table with details about all functions and files marked for skipping.
5805 @code{info skip} prints the following information about each skip:
5809 A number identifying this skip.
5810 @item Enabled or Disabled
5811 Enabled skips are marked with @samp{y}.
5812 Disabled skips are marked with @samp{n}.
5814 If the file name is a @samp{glob} pattern this is @samp{y}.
5815 Otherwise it is @samp{n}.
5817 The name or @samp{glob} pattern of the file to be skipped.
5818 If no file is specified this is @samp{<none>}.
5820 If the function name is a @samp{regular expression} this is @samp{y}.
5821 Otherwise it is @samp{n}.
5823 The name or regular expression of the function to skip.
5824 If no function is specified this is @samp{<none>}.
5828 @item skip delete @r{[}@var{range}@r{]}
5829 Delete the specified skip(s). If @var{range} is not specified, delete all
5833 @item skip enable @r{[}@var{range}@r{]}
5834 Enable the specified skip(s). If @var{range} is not specified, enable all
5837 @kindex skip disable
5838 @item skip disable @r{[}@var{range}@r{]}
5839 Disable the specified skip(s). If @var{range} is not specified, disable all
5848 A signal is an asynchronous event that can happen in a program. The
5849 operating system defines the possible kinds of signals, and gives each
5850 kind a name and a number. For example, in Unix @code{SIGINT} is the
5851 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5852 @code{SIGSEGV} is the signal a program gets from referencing a place in
5853 memory far away from all the areas in use; @code{SIGALRM} occurs when
5854 the alarm clock timer goes off (which happens only if your program has
5855 requested an alarm).
5857 @cindex fatal signals
5858 Some signals, including @code{SIGALRM}, are a normal part of the
5859 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5860 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5861 program has not specified in advance some other way to handle the signal.
5862 @code{SIGINT} does not indicate an error in your program, but it is normally
5863 fatal so it can carry out the purpose of the interrupt: to kill the program.
5865 @value{GDBN} has the ability to detect any occurrence of a signal in your
5866 program. You can tell @value{GDBN} in advance what to do for each kind of
5869 @cindex handling signals
5870 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5871 @code{SIGALRM} be silently passed to your program
5872 (so as not to interfere with their role in the program's functioning)
5873 but to stop your program immediately whenever an error signal happens.
5874 You can change these settings with the @code{handle} command.
5877 @kindex info signals
5881 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5882 handle each one. You can use this to see the signal numbers of all
5883 the defined types of signals.
5885 @item info signals @var{sig}
5886 Similar, but print information only about the specified signal number.
5888 @code{info handle} is an alias for @code{info signals}.
5890 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5891 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5892 for details about this command.
5895 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5896 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5897 can be the number of a signal or its name (with or without the
5898 @samp{SIG} at the beginning); a list of signal numbers of the form
5899 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5900 known signals. Optional arguments @var{keywords}, described below,
5901 say what change to make.
5905 The keywords allowed by the @code{handle} command can be abbreviated.
5906 Their full names are:
5910 @value{GDBN} should not stop your program when this signal happens. It may
5911 still print a message telling you that the signal has come in.
5914 @value{GDBN} should stop your program when this signal happens. This implies
5915 the @code{print} keyword as well.
5918 @value{GDBN} should print a message when this signal happens.
5921 @value{GDBN} should not mention the occurrence of the signal at all. This
5922 implies the @code{nostop} keyword as well.
5926 @value{GDBN} should allow your program to see this signal; your program
5927 can handle the signal, or else it may terminate if the signal is fatal
5928 and not handled. @code{pass} and @code{noignore} are synonyms.
5932 @value{GDBN} should not allow your program to see this signal.
5933 @code{nopass} and @code{ignore} are synonyms.
5937 When a signal stops your program, the signal is not visible to the
5939 continue. Your program sees the signal then, if @code{pass} is in
5940 effect for the signal in question @emph{at that time}. In other words,
5941 after @value{GDBN} reports a signal, you can use the @code{handle}
5942 command with @code{pass} or @code{nopass} to control whether your
5943 program sees that signal when you continue.
5945 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5946 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5947 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5950 You can also use the @code{signal} command to prevent your program from
5951 seeing a signal, or cause it to see a signal it normally would not see,
5952 or to give it any signal at any time. For example, if your program stopped
5953 due to some sort of memory reference error, you might store correct
5954 values into the erroneous variables and continue, hoping to see more
5955 execution; but your program would probably terminate immediately as
5956 a result of the fatal signal once it saw the signal. To prevent this,
5957 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5960 @cindex stepping and signal handlers
5961 @anchor{stepping and signal handlers}
5963 @value{GDBN} optimizes for stepping the mainline code. If a signal
5964 that has @code{handle nostop} and @code{handle pass} set arrives while
5965 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
5966 in progress, @value{GDBN} lets the signal handler run and then resumes
5967 stepping the mainline code once the signal handler returns. In other
5968 words, @value{GDBN} steps over the signal handler. This prevents
5969 signals that you've specified as not interesting (with @code{handle
5970 nostop}) from changing the focus of debugging unexpectedly. Note that
5971 the signal handler itself may still hit a breakpoint, stop for another
5972 signal that has @code{handle stop} in effect, or for any other event
5973 that normally results in stopping the stepping command sooner. Also
5974 note that @value{GDBN} still informs you that the program received a
5975 signal if @code{handle print} is set.
5977 @anchor{stepping into signal handlers}
5979 If you set @code{handle pass} for a signal, and your program sets up a
5980 handler for it, then issuing a stepping command, such as @code{step}
5981 or @code{stepi}, when your program is stopped due to the signal will
5982 step @emph{into} the signal handler (if the target supports that).
5984 Likewise, if you use the @code{queue-signal} command to queue a signal
5985 to be delivered to the current thread when execution of the thread
5986 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
5987 stepping command will step into the signal handler.
5989 Here's an example, using @code{stepi} to step to the first instruction
5990 of @code{SIGUSR1}'s handler:
5993 (@value{GDBP}) handle SIGUSR1
5994 Signal Stop Print Pass to program Description
5995 SIGUSR1 Yes Yes Yes User defined signal 1
5999 Program received signal SIGUSR1, User defined signal 1.
6000 main () sigusr1.c:28
6003 sigusr1_handler () at sigusr1.c:9
6007 The same, but using @code{queue-signal} instead of waiting for the
6008 program to receive the signal first:
6013 (@value{GDBP}) queue-signal SIGUSR1
6015 sigusr1_handler () at sigusr1.c:9
6020 @cindex extra signal information
6021 @anchor{extra signal information}
6023 On some targets, @value{GDBN} can inspect extra signal information
6024 associated with the intercepted signal, before it is actually
6025 delivered to the program being debugged. This information is exported
6026 by the convenience variable @code{$_siginfo}, and consists of data
6027 that is passed by the kernel to the signal handler at the time of the
6028 receipt of a signal. The data type of the information itself is
6029 target dependent. You can see the data type using the @code{ptype
6030 $_siginfo} command. On Unix systems, it typically corresponds to the
6031 standard @code{siginfo_t} type, as defined in the @file{signal.h}
6034 Here's an example, on a @sc{gnu}/Linux system, printing the stray
6035 referenced address that raised a segmentation fault.
6039 (@value{GDBP}) continue
6040 Program received signal SIGSEGV, Segmentation fault.
6041 0x0000000000400766 in main ()
6043 (@value{GDBP}) ptype $_siginfo
6050 struct @{...@} _kill;
6051 struct @{...@} _timer;
6053 struct @{...@} _sigchld;
6054 struct @{...@} _sigfault;
6055 struct @{...@} _sigpoll;
6058 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
6062 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
6063 $1 = (void *) 0x7ffff7ff7000
6067 Depending on target support, @code{$_siginfo} may also be writable.
6069 @cindex Intel MPX boundary violations
6070 @cindex boundary violations, Intel MPX
6071 On some targets, a @code{SIGSEGV} can be caused by a boundary
6072 violation, i.e., accessing an address outside of the allowed range.
6073 In those cases @value{GDBN} may displays additional information,
6074 depending on how @value{GDBN} has been told to handle the signal.
6075 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
6076 kind: "Upper" or "Lower", the memory address accessed and the
6077 bounds, while with @code{handle nostop SIGSEGV} no additional
6078 information is displayed.
6080 The usual output of a segfault is:
6082 Program received signal SIGSEGV, Segmentation fault
6083 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6084 68 value = *(p + len);
6087 While a bound violation is presented as:
6089 Program received signal SIGSEGV, Segmentation fault
6090 Upper bound violation while accessing address 0x7fffffffc3b3
6091 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
6092 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6093 68 value = *(p + len);
6097 @section Stopping and Starting Multi-thread Programs
6099 @cindex stopped threads
6100 @cindex threads, stopped
6102 @cindex continuing threads
6103 @cindex threads, continuing
6105 @value{GDBN} supports debugging programs with multiple threads
6106 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
6107 are two modes of controlling execution of your program within the
6108 debugger. In the default mode, referred to as @dfn{all-stop mode},
6109 when any thread in your program stops (for example, at a breakpoint
6110 or while being stepped), all other threads in the program are also stopped by
6111 @value{GDBN}. On some targets, @value{GDBN} also supports
6112 @dfn{non-stop mode}, in which other threads can continue to run freely while
6113 you examine the stopped thread in the debugger.
6116 * All-Stop Mode:: All threads stop when GDB takes control
6117 * Non-Stop Mode:: Other threads continue to execute
6118 * Background Execution:: Running your program asynchronously
6119 * Thread-Specific Breakpoints:: Controlling breakpoints
6120 * Interrupted System Calls:: GDB may interfere with system calls
6121 * Observer Mode:: GDB does not alter program behavior
6125 @subsection All-Stop Mode
6127 @cindex all-stop mode
6129 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6130 @emph{all} threads of execution stop, not just the current thread. This
6131 allows you to examine the overall state of the program, including
6132 switching between threads, without worrying that things may change
6135 Conversely, whenever you restart the program, @emph{all} threads start
6136 executing. @emph{This is true even when single-stepping} with commands
6137 like @code{step} or @code{next}.
6139 In particular, @value{GDBN} cannot single-step all threads in lockstep.
6140 Since thread scheduling is up to your debugging target's operating
6141 system (not controlled by @value{GDBN}), other threads may
6142 execute more than one statement while the current thread completes a
6143 single step. Moreover, in general other threads stop in the middle of a
6144 statement, rather than at a clean statement boundary, when the program
6147 You might even find your program stopped in another thread after
6148 continuing or even single-stepping. This happens whenever some other
6149 thread runs into a breakpoint, a signal, or an exception before the
6150 first thread completes whatever you requested.
6152 @cindex automatic thread selection
6153 @cindex switching threads automatically
6154 @cindex threads, automatic switching
6155 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6156 signal, it automatically selects the thread where that breakpoint or
6157 signal happened. @value{GDBN} alerts you to the context switch with a
6158 message such as @samp{[Switching to Thread @var{n}]} to identify the
6161 On some OSes, you can modify @value{GDBN}'s default behavior by
6162 locking the OS scheduler to allow only a single thread to run.
6165 @item set scheduler-locking @var{mode}
6166 @cindex scheduler locking mode
6167 @cindex lock scheduler
6168 Set the scheduler locking mode. It applies to normal execution,
6169 record mode, and replay mode. If it is @code{off}, then there is no
6170 locking and any thread may run at any time. If @code{on}, then only
6171 the current thread may run when the inferior is resumed. The
6172 @code{step} mode optimizes for single-stepping; it prevents other
6173 threads from preempting the current thread while you are stepping, so
6174 that the focus of debugging does not change unexpectedly. Other
6175 threads never get a chance to run when you step, and they are
6176 completely free to run when you use commands like @samp{continue},
6177 @samp{until}, or @samp{finish}. However, unless another thread hits a
6178 breakpoint during its timeslice, @value{GDBN} does not change the
6179 current thread away from the thread that you are debugging. The
6180 @code{replay} mode behaves like @code{off} in record mode and like
6181 @code{on} in replay mode.
6183 @item show scheduler-locking
6184 Display the current scheduler locking mode.
6187 @cindex resume threads of multiple processes simultaneously
6188 By default, when you issue one of the execution commands such as
6189 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6190 threads of the current inferior to run. For example, if @value{GDBN}
6191 is attached to two inferiors, each with two threads, the
6192 @code{continue} command resumes only the two threads of the current
6193 inferior. This is useful, for example, when you debug a program that
6194 forks and you want to hold the parent stopped (so that, for instance,
6195 it doesn't run to exit), while you debug the child. In other
6196 situations, you may not be interested in inspecting the current state
6197 of any of the processes @value{GDBN} is attached to, and you may want
6198 to resume them all until some breakpoint is hit. In the latter case,
6199 you can instruct @value{GDBN} to allow all threads of all the
6200 inferiors to run with the @w{@code{set schedule-multiple}} command.
6203 @kindex set schedule-multiple
6204 @item set schedule-multiple
6205 Set the mode for allowing threads of multiple processes to be resumed
6206 when an execution command is issued. When @code{on}, all threads of
6207 all processes are allowed to run. When @code{off}, only the threads
6208 of the current process are resumed. The default is @code{off}. The
6209 @code{scheduler-locking} mode takes precedence when set to @code{on},
6210 or while you are stepping and set to @code{step}.
6212 @item show schedule-multiple
6213 Display the current mode for resuming the execution of threads of
6218 @subsection Non-Stop Mode
6220 @cindex non-stop mode
6222 @c This section is really only a place-holder, and needs to be expanded
6223 @c with more details.
6225 For some multi-threaded targets, @value{GDBN} supports an optional
6226 mode of operation in which you can examine stopped program threads in
6227 the debugger while other threads continue to execute freely. This
6228 minimizes intrusion when debugging live systems, such as programs
6229 where some threads have real-time constraints or must continue to
6230 respond to external events. This is referred to as @dfn{non-stop} mode.
6232 In non-stop mode, when a thread stops to report a debugging event,
6233 @emph{only} that thread is stopped; @value{GDBN} does not stop other
6234 threads as well, in contrast to the all-stop mode behavior. Additionally,
6235 execution commands such as @code{continue} and @code{step} apply by default
6236 only to the current thread in non-stop mode, rather than all threads as
6237 in all-stop mode. This allows you to control threads explicitly in
6238 ways that are not possible in all-stop mode --- for example, stepping
6239 one thread while allowing others to run freely, stepping
6240 one thread while holding all others stopped, or stepping several threads
6241 independently and simultaneously.
6243 To enter non-stop mode, use this sequence of commands before you run
6244 or attach to your program:
6247 # If using the CLI, pagination breaks non-stop.
6250 # Finally, turn it on!
6254 You can use these commands to manipulate the non-stop mode setting:
6257 @kindex set non-stop
6258 @item set non-stop on
6259 Enable selection of non-stop mode.
6260 @item set non-stop off
6261 Disable selection of non-stop mode.
6262 @kindex show non-stop
6264 Show the current non-stop enablement setting.
6267 Note these commands only reflect whether non-stop mode is enabled,
6268 not whether the currently-executing program is being run in non-stop mode.
6269 In particular, the @code{set non-stop} preference is only consulted when
6270 @value{GDBN} starts or connects to the target program, and it is generally
6271 not possible to switch modes once debugging has started. Furthermore,
6272 since not all targets support non-stop mode, even when you have enabled
6273 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
6276 In non-stop mode, all execution commands apply only to the current thread
6277 by default. That is, @code{continue} only continues one thread.
6278 To continue all threads, issue @code{continue -a} or @code{c -a}.
6280 You can use @value{GDBN}'s background execution commands
6281 (@pxref{Background Execution}) to run some threads in the background
6282 while you continue to examine or step others from @value{GDBN}.
6283 The MI execution commands (@pxref{GDB/MI Program Execution}) are
6284 always executed asynchronously in non-stop mode.
6286 Suspending execution is done with the @code{interrupt} command when
6287 running in the background, or @kbd{Ctrl-c} during foreground execution.
6288 In all-stop mode, this stops the whole process;
6289 but in non-stop mode the interrupt applies only to the current thread.
6290 To stop the whole program, use @code{interrupt -a}.
6292 Other execution commands do not currently support the @code{-a} option.
6294 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
6295 that thread current, as it does in all-stop mode. This is because the
6296 thread stop notifications are asynchronous with respect to @value{GDBN}'s
6297 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
6298 changed to a different thread just as you entered a command to operate on the
6299 previously current thread.
6301 @node Background Execution
6302 @subsection Background Execution
6304 @cindex foreground execution
6305 @cindex background execution
6306 @cindex asynchronous execution
6307 @cindex execution, foreground, background and asynchronous
6309 @value{GDBN}'s execution commands have two variants: the normal
6310 foreground (synchronous) behavior, and a background
6311 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
6312 the program to report that some thread has stopped before prompting for
6313 another command. In background execution, @value{GDBN} immediately gives
6314 a command prompt so that you can issue other commands while your program runs.
6316 If the target doesn't support async mode, @value{GDBN} issues an error
6317 message if you attempt to use the background execution commands.
6319 To specify background execution, add a @code{&} to the command. For example,
6320 the background form of the @code{continue} command is @code{continue&}, or
6321 just @code{c&}. The execution commands that accept background execution
6327 @xref{Starting, , Starting your Program}.
6331 @xref{Attach, , Debugging an Already-running Process}.
6335 @xref{Continuing and Stepping, step}.
6339 @xref{Continuing and Stepping, stepi}.
6343 @xref{Continuing and Stepping, next}.
6347 @xref{Continuing and Stepping, nexti}.
6351 @xref{Continuing and Stepping, continue}.
6355 @xref{Continuing and Stepping, finish}.
6359 @xref{Continuing and Stepping, until}.
6363 Background execution is especially useful in conjunction with non-stop
6364 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6365 However, you can also use these commands in the normal all-stop mode with
6366 the restriction that you cannot issue another execution command until the
6367 previous one finishes. Examples of commands that are valid in all-stop
6368 mode while the program is running include @code{help} and @code{info break}.
6370 You can interrupt your program while it is running in the background by
6371 using the @code{interrupt} command.
6378 Suspend execution of the running program. In all-stop mode,
6379 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6380 only the current thread. To stop the whole program in non-stop mode,
6381 use @code{interrupt -a}.
6384 @node Thread-Specific Breakpoints
6385 @subsection Thread-Specific Breakpoints
6387 When your program has multiple threads (@pxref{Threads,, Debugging
6388 Programs with Multiple Threads}), you can choose whether to set
6389 breakpoints on all threads, or on a particular thread.
6392 @cindex breakpoints and threads
6393 @cindex thread breakpoints
6394 @kindex break @dots{} thread @var{thread-id}
6395 @item break @var{location} thread @var{thread-id}
6396 @itemx break @var{location} thread @var{thread-id} if @dots{}
6397 @var{location} specifies source lines; there are several ways of
6398 writing them (@pxref{Specify Location}), but the effect is always to
6399 specify some source line.
6401 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
6402 to specify that you only want @value{GDBN} to stop the program when a
6403 particular thread reaches this breakpoint. The @var{thread-id} specifier
6404 is one of the thread identifiers assigned by @value{GDBN}, shown
6405 in the first column of the @samp{info threads} display.
6407 If you do not specify @samp{thread @var{thread-id}} when you set a
6408 breakpoint, the breakpoint applies to @emph{all} threads of your
6411 You can use the @code{thread} qualifier on conditional breakpoints as
6412 well; in this case, place @samp{thread @var{thread-id}} before or
6413 after the breakpoint condition, like this:
6416 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6421 Thread-specific breakpoints are automatically deleted when
6422 @value{GDBN} detects the corresponding thread is no longer in the
6423 thread list. For example:
6427 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6430 There are several ways for a thread to disappear, such as a regular
6431 thread exit, but also when you detach from the process with the
6432 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6433 Process}), or if @value{GDBN} loses the remote connection
6434 (@pxref{Remote Debugging}), etc. Note that with some targets,
6435 @value{GDBN} is only able to detect a thread has exited when the user
6436 explictly asks for the thread list with the @code{info threads}
6439 @node Interrupted System Calls
6440 @subsection Interrupted System Calls
6442 @cindex thread breakpoints and system calls
6443 @cindex system calls and thread breakpoints
6444 @cindex premature return from system calls
6445 There is an unfortunate side effect when using @value{GDBN} to debug
6446 multi-threaded programs. If one thread stops for a
6447 breakpoint, or for some other reason, and another thread is blocked in a
6448 system call, then the system call may return prematurely. This is a
6449 consequence of the interaction between multiple threads and the signals
6450 that @value{GDBN} uses to implement breakpoints and other events that
6453 To handle this problem, your program should check the return value of
6454 each system call and react appropriately. This is good programming
6457 For example, do not write code like this:
6463 The call to @code{sleep} will return early if a different thread stops
6464 at a breakpoint or for some other reason.
6466 Instead, write this:
6471 unslept = sleep (unslept);
6474 A system call is allowed to return early, so the system is still
6475 conforming to its specification. But @value{GDBN} does cause your
6476 multi-threaded program to behave differently than it would without
6479 Also, @value{GDBN} uses internal breakpoints in the thread library to
6480 monitor certain events such as thread creation and thread destruction.
6481 When such an event happens, a system call in another thread may return
6482 prematurely, even though your program does not appear to stop.
6485 @subsection Observer Mode
6487 If you want to build on non-stop mode and observe program behavior
6488 without any chance of disruption by @value{GDBN}, you can set
6489 variables to disable all of the debugger's attempts to modify state,
6490 whether by writing memory, inserting breakpoints, etc. These operate
6491 at a low level, intercepting operations from all commands.
6493 When all of these are set to @code{off}, then @value{GDBN} is said to
6494 be @dfn{observer mode}. As a convenience, the variable
6495 @code{observer} can be set to disable these, plus enable non-stop
6498 Note that @value{GDBN} will not prevent you from making nonsensical
6499 combinations of these settings. For instance, if you have enabled
6500 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6501 then breakpoints that work by writing trap instructions into the code
6502 stream will still not be able to be placed.
6507 @item set observer on
6508 @itemx set observer off
6509 When set to @code{on}, this disables all the permission variables
6510 below (except for @code{insert-fast-tracepoints}), plus enables
6511 non-stop debugging. Setting this to @code{off} switches back to
6512 normal debugging, though remaining in non-stop mode.
6515 Show whether observer mode is on or off.
6517 @kindex may-write-registers
6518 @item set may-write-registers on
6519 @itemx set may-write-registers off
6520 This controls whether @value{GDBN} will attempt to alter the values of
6521 registers, such as with assignment expressions in @code{print}, or the
6522 @code{jump} command. It defaults to @code{on}.
6524 @item show may-write-registers
6525 Show the current permission to write registers.
6527 @kindex may-write-memory
6528 @item set may-write-memory on
6529 @itemx set may-write-memory off
6530 This controls whether @value{GDBN} will attempt to alter the contents
6531 of memory, such as with assignment expressions in @code{print}. It
6532 defaults to @code{on}.
6534 @item show may-write-memory
6535 Show the current permission to write memory.
6537 @kindex may-insert-breakpoints
6538 @item set may-insert-breakpoints on
6539 @itemx set may-insert-breakpoints off
6540 This controls whether @value{GDBN} will attempt to insert breakpoints.
6541 This affects all breakpoints, including internal breakpoints defined
6542 by @value{GDBN}. It defaults to @code{on}.
6544 @item show may-insert-breakpoints
6545 Show the current permission to insert breakpoints.
6547 @kindex may-insert-tracepoints
6548 @item set may-insert-tracepoints on
6549 @itemx set may-insert-tracepoints off
6550 This controls whether @value{GDBN} will attempt to insert (regular)
6551 tracepoints at the beginning of a tracing experiment. It affects only
6552 non-fast tracepoints, fast tracepoints being under the control of
6553 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6555 @item show may-insert-tracepoints
6556 Show the current permission to insert tracepoints.
6558 @kindex may-insert-fast-tracepoints
6559 @item set may-insert-fast-tracepoints on
6560 @itemx set may-insert-fast-tracepoints off
6561 This controls whether @value{GDBN} will attempt to insert fast
6562 tracepoints at the beginning of a tracing experiment. It affects only
6563 fast tracepoints, regular (non-fast) tracepoints being under the
6564 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6566 @item show may-insert-fast-tracepoints
6567 Show the current permission to insert fast tracepoints.
6569 @kindex may-interrupt
6570 @item set may-interrupt on
6571 @itemx set may-interrupt off
6572 This controls whether @value{GDBN} will attempt to interrupt or stop
6573 program execution. When this variable is @code{off}, the
6574 @code{interrupt} command will have no effect, nor will
6575 @kbd{Ctrl-c}. It defaults to @code{on}.
6577 @item show may-interrupt
6578 Show the current permission to interrupt or stop the program.
6582 @node Reverse Execution
6583 @chapter Running programs backward
6584 @cindex reverse execution
6585 @cindex running programs backward
6587 When you are debugging a program, it is not unusual to realize that
6588 you have gone too far, and some event of interest has already happened.
6589 If the target environment supports it, @value{GDBN} can allow you to
6590 ``rewind'' the program by running it backward.
6592 A target environment that supports reverse execution should be able
6593 to ``undo'' the changes in machine state that have taken place as the
6594 program was executing normally. Variables, registers etc.@: should
6595 revert to their previous values. Obviously this requires a great
6596 deal of sophistication on the part of the target environment; not
6597 all target environments can support reverse execution.
6599 When a program is executed in reverse, the instructions that
6600 have most recently been executed are ``un-executed'', in reverse
6601 order. The program counter runs backward, following the previous
6602 thread of execution in reverse. As each instruction is ``un-executed'',
6603 the values of memory and/or registers that were changed by that
6604 instruction are reverted to their previous states. After executing
6605 a piece of source code in reverse, all side effects of that code
6606 should be ``undone'', and all variables should be returned to their
6607 prior values@footnote{
6608 Note that some side effects are easier to undo than others. For instance,
6609 memory and registers are relatively easy, but device I/O is hard. Some
6610 targets may be able undo things like device I/O, and some may not.
6612 The contract between @value{GDBN} and the reverse executing target
6613 requires only that the target do something reasonable when
6614 @value{GDBN} tells it to execute backwards, and then report the
6615 results back to @value{GDBN}. Whatever the target reports back to
6616 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6617 assumes that the memory and registers that the target reports are in a
6618 consistant state, but @value{GDBN} accepts whatever it is given.
6621 If you are debugging in a target environment that supports
6622 reverse execution, @value{GDBN} provides the following commands.
6625 @kindex reverse-continue
6626 @kindex rc @r{(@code{reverse-continue})}
6627 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6628 @itemx rc @r{[}@var{ignore-count}@r{]}
6629 Beginning at the point where your program last stopped, start executing
6630 in reverse. Reverse execution will stop for breakpoints and synchronous
6631 exceptions (signals), just like normal execution. Behavior of
6632 asynchronous signals depends on the target environment.
6634 @kindex reverse-step
6635 @kindex rs @r{(@code{step})}
6636 @item reverse-step @r{[}@var{count}@r{]}
6637 Run the program backward until control reaches the start of a
6638 different source line; then stop it, and return control to @value{GDBN}.
6640 Like the @code{step} command, @code{reverse-step} will only stop
6641 at the beginning of a source line. It ``un-executes'' the previously
6642 executed source line. If the previous source line included calls to
6643 debuggable functions, @code{reverse-step} will step (backward) into
6644 the called function, stopping at the beginning of the @emph{last}
6645 statement in the called function (typically a return statement).
6647 Also, as with the @code{step} command, if non-debuggable functions are
6648 called, @code{reverse-step} will run thru them backward without stopping.
6650 @kindex reverse-stepi
6651 @kindex rsi @r{(@code{reverse-stepi})}
6652 @item reverse-stepi @r{[}@var{count}@r{]}
6653 Reverse-execute one machine instruction. Note that the instruction
6654 to be reverse-executed is @emph{not} the one pointed to by the program
6655 counter, but the instruction executed prior to that one. For instance,
6656 if the last instruction was a jump, @code{reverse-stepi} will take you
6657 back from the destination of the jump to the jump instruction itself.
6659 @kindex reverse-next
6660 @kindex rn @r{(@code{reverse-next})}
6661 @item reverse-next @r{[}@var{count}@r{]}
6662 Run backward to the beginning of the previous line executed in
6663 the current (innermost) stack frame. If the line contains function
6664 calls, they will be ``un-executed'' without stopping. Starting from
6665 the first line of a function, @code{reverse-next} will take you back
6666 to the caller of that function, @emph{before} the function was called,
6667 just as the normal @code{next} command would take you from the last
6668 line of a function back to its return to its caller
6669 @footnote{Unless the code is too heavily optimized.}.
6671 @kindex reverse-nexti
6672 @kindex rni @r{(@code{reverse-nexti})}
6673 @item reverse-nexti @r{[}@var{count}@r{]}
6674 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6675 in reverse, except that called functions are ``un-executed'' atomically.
6676 That is, if the previously executed instruction was a return from
6677 another function, @code{reverse-nexti} will continue to execute
6678 in reverse until the call to that function (from the current stack
6681 @kindex reverse-finish
6682 @item reverse-finish
6683 Just as the @code{finish} command takes you to the point where the
6684 current function returns, @code{reverse-finish} takes you to the point
6685 where it was called. Instead of ending up at the end of the current
6686 function invocation, you end up at the beginning.
6688 @kindex set exec-direction
6689 @item set exec-direction
6690 Set the direction of target execution.
6691 @item set exec-direction reverse
6692 @cindex execute forward or backward in time
6693 @value{GDBN} will perform all execution commands in reverse, until the
6694 exec-direction mode is changed to ``forward''. Affected commands include
6695 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6696 command cannot be used in reverse mode.
6697 @item set exec-direction forward
6698 @value{GDBN} will perform all execution commands in the normal fashion.
6699 This is the default.
6703 @node Process Record and Replay
6704 @chapter Recording Inferior's Execution and Replaying It
6705 @cindex process record and replay
6706 @cindex recording inferior's execution and replaying it
6708 On some platforms, @value{GDBN} provides a special @dfn{process record
6709 and replay} target that can record a log of the process execution, and
6710 replay it later with both forward and reverse execution commands.
6713 When this target is in use, if the execution log includes the record
6714 for the next instruction, @value{GDBN} will debug in @dfn{replay
6715 mode}. In the replay mode, the inferior does not really execute code
6716 instructions. Instead, all the events that normally happen during
6717 code execution are taken from the execution log. While code is not
6718 really executed in replay mode, the values of registers (including the
6719 program counter register) and the memory of the inferior are still
6720 changed as they normally would. Their contents are taken from the
6724 If the record for the next instruction is not in the execution log,
6725 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6726 inferior executes normally, and @value{GDBN} records the execution log
6729 The process record and replay target supports reverse execution
6730 (@pxref{Reverse Execution}), even if the platform on which the
6731 inferior runs does not. However, the reverse execution is limited in
6732 this case by the range of the instructions recorded in the execution
6733 log. In other words, reverse execution on platforms that don't
6734 support it directly can only be done in the replay mode.
6736 When debugging in the reverse direction, @value{GDBN} will work in
6737 replay mode as long as the execution log includes the record for the
6738 previous instruction; otherwise, it will work in record mode, if the
6739 platform supports reverse execution, or stop if not.
6741 For architecture environments that support process record and replay,
6742 @value{GDBN} provides the following commands:
6745 @kindex target record
6746 @kindex target record-full
6747 @kindex target record-btrace
6750 @kindex record btrace
6751 @kindex record btrace bts
6752 @kindex record btrace pt
6758 @kindex rec btrace bts
6759 @kindex rec btrace pt
6762 @item record @var{method}
6763 This command starts the process record and replay target. The
6764 recording method can be specified as parameter. Without a parameter
6765 the command uses the @code{full} recording method. The following
6766 recording methods are available:
6770 Full record/replay recording using @value{GDBN}'s software record and
6771 replay implementation. This method allows replaying and reverse
6774 @item btrace @var{format}
6775 Hardware-supported instruction recording. This method does not record
6776 data. Further, the data is collected in a ring buffer so old data will
6777 be overwritten when the buffer is full. It allows limited reverse
6778 execution. Variables and registers are not available during reverse
6779 execution. In remote debugging, recording continues on disconnect.
6780 Recorded data can be inspected after reconnecting. The recording may
6781 be stopped using @code{record stop}.
6783 The recording format can be specified as parameter. Without a parameter
6784 the command chooses the recording format. The following recording
6785 formats are available:
6789 @cindex branch trace store
6790 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6791 this format, the processor stores a from/to record for each executed
6792 branch in the btrace ring buffer.
6795 @cindex Intel Processor Trace
6796 Use the @dfn{Intel Processor Trace} recording format. In this
6797 format, the processor stores the execution trace in a compressed form
6798 that is afterwards decoded by @value{GDBN}.
6800 The trace can be recorded with very low overhead. The compressed
6801 trace format also allows small trace buffers to already contain a big
6802 number of instructions compared to @acronym{BTS}.
6804 Decoding the recorded execution trace, on the other hand, is more
6805 expensive than decoding @acronym{BTS} trace. This is mostly due to the
6806 increased number of instructions to process. You should increase the
6807 buffer-size with care.
6810 Not all recording formats may be available on all processors.
6813 The process record and replay target can only debug a process that is
6814 already running. Therefore, you need first to start the process with
6815 the @kbd{run} or @kbd{start} commands, and then start the recording
6816 with the @kbd{record @var{method}} command.
6818 @cindex displaced stepping, and process record and replay
6819 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6820 will be automatically disabled when process record and replay target
6821 is started. That's because the process record and replay target
6822 doesn't support displaced stepping.
6824 @cindex non-stop mode, and process record and replay
6825 @cindex asynchronous execution, and process record and replay
6826 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6827 the asynchronous execution mode (@pxref{Background Execution}), not
6828 all recording methods are available. The @code{full} recording method
6829 does not support these two modes.
6834 Stop the process record and replay target. When process record and
6835 replay target stops, the entire execution log will be deleted and the
6836 inferior will either be terminated, or will remain in its final state.
6838 When you stop the process record and replay target in record mode (at
6839 the end of the execution log), the inferior will be stopped at the
6840 next instruction that would have been recorded. In other words, if
6841 you record for a while and then stop recording, the inferior process
6842 will be left in the same state as if the recording never happened.
6844 On the other hand, if the process record and replay target is stopped
6845 while in replay mode (that is, not at the end of the execution log,
6846 but at some earlier point), the inferior process will become ``live''
6847 at that earlier state, and it will then be possible to continue the
6848 usual ``live'' debugging of the process from that state.
6850 When the inferior process exits, or @value{GDBN} detaches from it,
6851 process record and replay target will automatically stop itself.
6855 Go to a specific location in the execution log. There are several
6856 ways to specify the location to go to:
6859 @item record goto begin
6860 @itemx record goto start
6861 Go to the beginning of the execution log.
6863 @item record goto end
6864 Go to the end of the execution log.
6866 @item record goto @var{n}
6867 Go to instruction number @var{n} in the execution log.
6871 @item record save @var{filename}
6872 Save the execution log to a file @file{@var{filename}}.
6873 Default filename is @file{gdb_record.@var{process_id}}, where
6874 @var{process_id} is the process ID of the inferior.
6876 This command may not be available for all recording methods.
6878 @kindex record restore
6879 @item record restore @var{filename}
6880 Restore the execution log from a file @file{@var{filename}}.
6881 File must have been created with @code{record save}.
6883 @kindex set record full
6884 @item set record full insn-number-max @var{limit}
6885 @itemx set record full insn-number-max unlimited
6886 Set the limit of instructions to be recorded for the @code{full}
6887 recording method. Default value is 200000.
6889 If @var{limit} is a positive number, then @value{GDBN} will start
6890 deleting instructions from the log once the number of the record
6891 instructions becomes greater than @var{limit}. For every new recorded
6892 instruction, @value{GDBN} will delete the earliest recorded
6893 instruction to keep the number of recorded instructions at the limit.
6894 (Since deleting recorded instructions loses information, @value{GDBN}
6895 lets you control what happens when the limit is reached, by means of
6896 the @code{stop-at-limit} option, described below.)
6898 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6899 delete recorded instructions from the execution log. The number of
6900 recorded instructions is limited only by the available memory.
6902 @kindex show record full
6903 @item show record full insn-number-max
6904 Show the limit of instructions to be recorded with the @code{full}
6907 @item set record full stop-at-limit
6908 Control the behavior of the @code{full} recording method when the
6909 number of recorded instructions reaches the limit. If ON (the
6910 default), @value{GDBN} will stop when the limit is reached for the
6911 first time and ask you whether you want to stop the inferior or
6912 continue running it and recording the execution log. If you decide
6913 to continue recording, each new recorded instruction will cause the
6914 oldest one to be deleted.
6916 If this option is OFF, @value{GDBN} will automatically delete the
6917 oldest record to make room for each new one, without asking.
6919 @item show record full stop-at-limit
6920 Show the current setting of @code{stop-at-limit}.
6922 @item set record full memory-query
6923 Control the behavior when @value{GDBN} is unable to record memory
6924 changes caused by an instruction for the @code{full} recording method.
6925 If ON, @value{GDBN} will query whether to stop the inferior in that
6928 If this option is OFF (the default), @value{GDBN} will automatically
6929 ignore the effect of such instructions on memory. Later, when
6930 @value{GDBN} replays this execution log, it will mark the log of this
6931 instruction as not accessible, and it will not affect the replay
6934 @item show record full memory-query
6935 Show the current setting of @code{memory-query}.
6937 @kindex set record btrace
6938 The @code{btrace} record target does not trace data. As a
6939 convenience, when replaying, @value{GDBN} reads read-only memory off
6940 the live program directly, assuming that the addresses of the
6941 read-only areas don't change. This for example makes it possible to
6942 disassemble code while replaying, but not to print variables.
6943 In some cases, being able to inspect variables might be useful.
6944 You can use the following command for that:
6946 @item set record btrace replay-memory-access
6947 Control the behavior of the @code{btrace} recording method when
6948 accessing memory during replay. If @code{read-only} (the default),
6949 @value{GDBN} will only allow accesses to read-only memory.
6950 If @code{read-write}, @value{GDBN} will allow accesses to read-only
6951 and to read-write memory. Beware that the accessed memory corresponds
6952 to the live target and not necessarily to the current replay
6955 @kindex show record btrace
6956 @item show record btrace replay-memory-access
6957 Show the current setting of @code{replay-memory-access}.
6959 @kindex set record btrace bts
6960 @item set record btrace bts buffer-size @var{size}
6961 @itemx set record btrace bts buffer-size unlimited
6962 Set the requested ring buffer size for branch tracing in @acronym{BTS}
6963 format. Default is 64KB.
6965 If @var{size} is a positive number, then @value{GDBN} will try to
6966 allocate a buffer of at least @var{size} bytes for each new thread
6967 that uses the btrace recording method and the @acronym{BTS} format.
6968 The actually obtained buffer size may differ from the requested
6969 @var{size}. Use the @code{info record} command to see the actual
6970 buffer size for each thread that uses the btrace recording method and
6971 the @acronym{BTS} format.
6973 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6974 allocate a buffer of 4MB.
6976 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6977 also need longer to process the branch trace data before it can be used.
6979 @item show record btrace bts buffer-size @var{size}
6980 Show the current setting of the requested ring buffer size for branch
6981 tracing in @acronym{BTS} format.
6983 @kindex set record btrace pt
6984 @item set record btrace pt buffer-size @var{size}
6985 @itemx set record btrace pt buffer-size unlimited
6986 Set the requested ring buffer size for branch tracing in Intel
6987 Processor Trace format. Default is 16KB.
6989 If @var{size} is a positive number, then @value{GDBN} will try to
6990 allocate a buffer of at least @var{size} bytes for each new thread
6991 that uses the btrace recording method and the Intel Processor Trace
6992 format. The actually obtained buffer size may differ from the
6993 requested @var{size}. Use the @code{info record} command to see the
6994 actual buffer size for each thread.
6996 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6997 allocate a buffer of 4MB.
6999 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7000 also need longer to process the branch trace data before it can be used.
7002 @item show record btrace pt buffer-size @var{size}
7003 Show the current setting of the requested ring buffer size for branch
7004 tracing in Intel Processor Trace format.
7008 Show various statistics about the recording depending on the recording
7013 For the @code{full} recording method, it shows the state of process
7014 record and its in-memory execution log buffer, including:
7018 Whether in record mode or replay mode.
7020 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
7022 Highest recorded instruction number.
7024 Current instruction about to be replayed (if in replay mode).
7026 Number of instructions contained in the execution log.
7028 Maximum number of instructions that may be contained in the execution log.
7032 For the @code{btrace} recording method, it shows:
7038 Number of instructions that have been recorded.
7040 Number of blocks of sequential control-flow formed by the recorded
7043 Whether in record mode or replay mode.
7046 For the @code{bts} recording format, it also shows:
7049 Size of the perf ring buffer.
7052 For the @code{pt} recording format, it also shows:
7055 Size of the perf ring buffer.
7059 @kindex record delete
7062 When record target runs in replay mode (``in the past''), delete the
7063 subsequent execution log and begin to record a new execution log starting
7064 from the current address. This means you will abandon the previously
7065 recorded ``future'' and begin recording a new ``future''.
7067 @kindex record instruction-history
7068 @kindex rec instruction-history
7069 @item record instruction-history
7070 Disassembles instructions from the recorded execution log. By
7071 default, ten instructions are disassembled. This can be changed using
7072 the @code{set record instruction-history-size} command. Instructions
7073 are printed in execution order.
7075 It can also print mixed source+disassembly if you specify the the
7076 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
7077 as well as in symbolic form by specifying the @code{/r} modifier.
7079 The current position marker is printed for the instruction at the
7080 current program counter value. This instruction can appear multiple
7081 times in the trace and the current position marker will be printed
7082 every time. To omit the current position marker, specify the
7085 To better align the printed instructions when the trace contains
7086 instructions from more than one function, the function name may be
7087 omitted by specifying the @code{/f} modifier.
7089 Speculatively executed instructions are prefixed with @samp{?}. This
7090 feature is not available for all recording formats.
7092 There are several ways to specify what part of the execution log to
7096 @item record instruction-history @var{insn}
7097 Disassembles ten instructions starting from instruction number
7100 @item record instruction-history @var{insn}, +/-@var{n}
7101 Disassembles @var{n} instructions around instruction number
7102 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
7103 @var{n} instructions after instruction number @var{insn}. If
7104 @var{n} is preceded with @code{-}, disassembles @var{n}
7105 instructions before instruction number @var{insn}.
7107 @item record instruction-history
7108 Disassembles ten more instructions after the last disassembly.
7110 @item record instruction-history -
7111 Disassembles ten more instructions before the last disassembly.
7113 @item record instruction-history @var{begin}, @var{end}
7114 Disassembles instructions beginning with instruction number
7115 @var{begin} until instruction number @var{end}. The instruction
7116 number @var{end} is included.
7119 This command may not be available for all recording methods.
7122 @item set record instruction-history-size @var{size}
7123 @itemx set record instruction-history-size unlimited
7124 Define how many instructions to disassemble in the @code{record
7125 instruction-history} command. The default value is 10.
7126 A @var{size} of @code{unlimited} means unlimited instructions.
7129 @item show record instruction-history-size
7130 Show how many instructions to disassemble in the @code{record
7131 instruction-history} command.
7133 @kindex record function-call-history
7134 @kindex rec function-call-history
7135 @item record function-call-history
7136 Prints the execution history at function granularity. It prints one
7137 line for each sequence of instructions that belong to the same
7138 function giving the name of that function, the source lines
7139 for this instruction sequence (if the @code{/l} modifier is
7140 specified), and the instructions numbers that form the sequence (if
7141 the @code{/i} modifier is specified). The function names are indented
7142 to reflect the call stack depth if the @code{/c} modifier is
7143 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
7147 (@value{GDBP}) @b{list 1, 10}
7158 (@value{GDBP}) @b{record function-call-history /ilc}
7159 1 bar inst 1,4 at foo.c:6,8
7160 2 foo inst 5,10 at foo.c:2,3
7161 3 bar inst 11,13 at foo.c:9,10
7164 By default, ten lines are printed. This can be changed using the
7165 @code{set record function-call-history-size} command. Functions are
7166 printed in execution order. There are several ways to specify what
7170 @item record function-call-history @var{func}
7171 Prints ten functions starting from function number @var{func}.
7173 @item record function-call-history @var{func}, +/-@var{n}
7174 Prints @var{n} functions around function number @var{func}. If
7175 @var{n} is preceded with @code{+}, prints @var{n} functions after
7176 function number @var{func}. If @var{n} is preceded with @code{-},
7177 prints @var{n} functions before function number @var{func}.
7179 @item record function-call-history
7180 Prints ten more functions after the last ten-line print.
7182 @item record function-call-history -
7183 Prints ten more functions before the last ten-line print.
7185 @item record function-call-history @var{begin}, @var{end}
7186 Prints functions beginning with function number @var{begin} until
7187 function number @var{end}. The function number @var{end} is included.
7190 This command may not be available for all recording methods.
7192 @item set record function-call-history-size @var{size}
7193 @itemx set record function-call-history-size unlimited
7194 Define how many lines to print in the
7195 @code{record function-call-history} command. The default value is 10.
7196 A size of @code{unlimited} means unlimited lines.
7198 @item show record function-call-history-size
7199 Show how many lines to print in the
7200 @code{record function-call-history} command.
7205 @chapter Examining the Stack
7207 When your program has stopped, the first thing you need to know is where it
7208 stopped and how it got there.
7211 Each time your program performs a function call, information about the call
7213 That information includes the location of the call in your program,
7214 the arguments of the call,
7215 and the local variables of the function being called.
7216 The information is saved in a block of data called a @dfn{stack frame}.
7217 The stack frames are allocated in a region of memory called the @dfn{call
7220 When your program stops, the @value{GDBN} commands for examining the
7221 stack allow you to see all of this information.
7223 @cindex selected frame
7224 One of the stack frames is @dfn{selected} by @value{GDBN} and many
7225 @value{GDBN} commands refer implicitly to the selected frame. In
7226 particular, whenever you ask @value{GDBN} for the value of a variable in
7227 your program, the value is found in the selected frame. There are
7228 special @value{GDBN} commands to select whichever frame you are
7229 interested in. @xref{Selection, ,Selecting a Frame}.
7231 When your program stops, @value{GDBN} automatically selects the
7232 currently executing frame and describes it briefly, similar to the
7233 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
7236 * Frames:: Stack frames
7237 * Backtrace:: Backtraces
7238 * Selection:: Selecting a frame
7239 * Frame Info:: Information on a frame
7240 * Frame Filter Management:: Managing frame filters
7245 @section Stack Frames
7247 @cindex frame, definition
7249 The call stack is divided up into contiguous pieces called @dfn{stack
7250 frames}, or @dfn{frames} for short; each frame is the data associated
7251 with one call to one function. The frame contains the arguments given
7252 to the function, the function's local variables, and the address at
7253 which the function is executing.
7255 @cindex initial frame
7256 @cindex outermost frame
7257 @cindex innermost frame
7258 When your program is started, the stack has only one frame, that of the
7259 function @code{main}. This is called the @dfn{initial} frame or the
7260 @dfn{outermost} frame. Each time a function is called, a new frame is
7261 made. Each time a function returns, the frame for that function invocation
7262 is eliminated. If a function is recursive, there can be many frames for
7263 the same function. The frame for the function in which execution is
7264 actually occurring is called the @dfn{innermost} frame. This is the most
7265 recently created of all the stack frames that still exist.
7267 @cindex frame pointer
7268 Inside your program, stack frames are identified by their addresses. A
7269 stack frame consists of many bytes, each of which has its own address; each
7270 kind of computer has a convention for choosing one byte whose
7271 address serves as the address of the frame. Usually this address is kept
7272 in a register called the @dfn{frame pointer register}
7273 (@pxref{Registers, $fp}) while execution is going on in that frame.
7275 @cindex frame number
7276 @value{GDBN} assigns numbers to all existing stack frames, starting with
7277 zero for the innermost frame, one for the frame that called it,
7278 and so on upward. These numbers do not really exist in your program;
7279 they are assigned by @value{GDBN} to give you a way of designating stack
7280 frames in @value{GDBN} commands.
7282 @c The -fomit-frame-pointer below perennially causes hbox overflow
7283 @c underflow problems.
7284 @cindex frameless execution
7285 Some compilers provide a way to compile functions so that they operate
7286 without stack frames. (For example, the @value{NGCC} option
7288 @samp{-fomit-frame-pointer}
7290 generates functions without a frame.)
7291 This is occasionally done with heavily used library functions to save
7292 the frame setup time. @value{GDBN} has limited facilities for dealing
7293 with these function invocations. If the innermost function invocation
7294 has no stack frame, @value{GDBN} nevertheless regards it as though
7295 it had a separate frame, which is numbered zero as usual, allowing
7296 correct tracing of the function call chain. However, @value{GDBN} has
7297 no provision for frameless functions elsewhere in the stack.
7303 @cindex call stack traces
7304 A backtrace is a summary of how your program got where it is. It shows one
7305 line per frame, for many frames, starting with the currently executing
7306 frame (frame zero), followed by its caller (frame one), and on up the
7309 @anchor{backtrace-command}
7312 @kindex bt @r{(@code{backtrace})}
7315 Print a backtrace of the entire stack: one line per frame for all
7316 frames in the stack.
7318 You can stop the backtrace at any time by typing the system interrupt
7319 character, normally @kbd{Ctrl-c}.
7321 @item backtrace @var{n}
7323 Similar, but print only the innermost @var{n} frames.
7325 @item backtrace -@var{n}
7327 Similar, but print only the outermost @var{n} frames.
7329 @item backtrace full
7331 @itemx bt full @var{n}
7332 @itemx bt full -@var{n}
7333 Print the values of the local variables also. As described above,
7334 @var{n} specifies the number of frames to print.
7336 @item backtrace no-filters
7337 @itemx bt no-filters
7338 @itemx bt no-filters @var{n}
7339 @itemx bt no-filters -@var{n}
7340 @itemx bt no-filters full
7341 @itemx bt no-filters full @var{n}
7342 @itemx bt no-filters full -@var{n}
7343 Do not run Python frame filters on this backtrace. @xref{Frame
7344 Filter API}, for more information. Additionally use @ref{disable
7345 frame-filter all} to turn off all frame filters. This is only
7346 relevant when @value{GDBN} has been configured with @code{Python}
7352 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7353 are additional aliases for @code{backtrace}.
7355 @cindex multiple threads, backtrace
7356 In a multi-threaded program, @value{GDBN} by default shows the
7357 backtrace only for the current thread. To display the backtrace for
7358 several or all of the threads, use the command @code{thread apply}
7359 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7360 apply all backtrace}, @value{GDBN} will display the backtrace for all
7361 the threads; this is handy when you debug a core dump of a
7362 multi-threaded program.
7364 Each line in the backtrace shows the frame number and the function name.
7365 The program counter value is also shown---unless you use @code{set
7366 print address off}. The backtrace also shows the source file name and
7367 line number, as well as the arguments to the function. The program
7368 counter value is omitted if it is at the beginning of the code for that
7371 Here is an example of a backtrace. It was made with the command
7372 @samp{bt 3}, so it shows the innermost three frames.
7376 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7378 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7379 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7381 (More stack frames follow...)
7386 The display for frame zero does not begin with a program counter
7387 value, indicating that your program has stopped at the beginning of the
7388 code for line @code{993} of @code{builtin.c}.
7391 The value of parameter @code{data} in frame 1 has been replaced by
7392 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7393 only if it is a scalar (integer, pointer, enumeration, etc). See command
7394 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7395 on how to configure the way function parameter values are printed.
7397 @cindex optimized out, in backtrace
7398 @cindex function call arguments, optimized out
7399 If your program was compiled with optimizations, some compilers will
7400 optimize away arguments passed to functions if those arguments are
7401 never used after the call. Such optimizations generate code that
7402 passes arguments through registers, but doesn't store those arguments
7403 in the stack frame. @value{GDBN} has no way of displaying such
7404 arguments in stack frames other than the innermost one. Here's what
7405 such a backtrace might look like:
7409 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7411 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7412 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7414 (More stack frames follow...)
7419 The values of arguments that were not saved in their stack frames are
7420 shown as @samp{<optimized out>}.
7422 If you need to display the values of such optimized-out arguments,
7423 either deduce that from other variables whose values depend on the one
7424 you are interested in, or recompile without optimizations.
7426 @cindex backtrace beyond @code{main} function
7427 @cindex program entry point
7428 @cindex startup code, and backtrace
7429 Most programs have a standard user entry point---a place where system
7430 libraries and startup code transition into user code. For C this is
7431 @code{main}@footnote{
7432 Note that embedded programs (the so-called ``free-standing''
7433 environment) are not required to have a @code{main} function as the
7434 entry point. They could even have multiple entry points.}.
7435 When @value{GDBN} finds the entry function in a backtrace
7436 it will terminate the backtrace, to avoid tracing into highly
7437 system-specific (and generally uninteresting) code.
7439 If you need to examine the startup code, or limit the number of levels
7440 in a backtrace, you can change this behavior:
7443 @item set backtrace past-main
7444 @itemx set backtrace past-main on
7445 @kindex set backtrace
7446 Backtraces will continue past the user entry point.
7448 @item set backtrace past-main off
7449 Backtraces will stop when they encounter the user entry point. This is the
7452 @item show backtrace past-main
7453 @kindex show backtrace
7454 Display the current user entry point backtrace policy.
7456 @item set backtrace past-entry
7457 @itemx set backtrace past-entry on
7458 Backtraces will continue past the internal entry point of an application.
7459 This entry point is encoded by the linker when the application is built,
7460 and is likely before the user entry point @code{main} (or equivalent) is called.
7462 @item set backtrace past-entry off
7463 Backtraces will stop when they encounter the internal entry point of an
7464 application. This is the default.
7466 @item show backtrace past-entry
7467 Display the current internal entry point backtrace policy.
7469 @item set backtrace limit @var{n}
7470 @itemx set backtrace limit 0
7471 @itemx set backtrace limit unlimited
7472 @cindex backtrace limit
7473 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7474 or zero means unlimited levels.
7476 @item show backtrace limit
7477 Display the current limit on backtrace levels.
7480 You can control how file names are displayed.
7483 @item set filename-display
7484 @itemx set filename-display relative
7485 @cindex filename-display
7486 Display file names relative to the compilation directory. This is the default.
7488 @item set filename-display basename
7489 Display only basename of a filename.
7491 @item set filename-display absolute
7492 Display an absolute filename.
7494 @item show filename-display
7495 Show the current way to display filenames.
7499 @section Selecting a Frame
7501 Most commands for examining the stack and other data in your program work on
7502 whichever stack frame is selected at the moment. Here are the commands for
7503 selecting a stack frame; all of them finish by printing a brief description
7504 of the stack frame just selected.
7507 @kindex frame@r{, selecting}
7508 @kindex f @r{(@code{frame})}
7511 Select frame number @var{n}. Recall that frame zero is the innermost
7512 (currently executing) frame, frame one is the frame that called the
7513 innermost one, and so on. The highest-numbered frame is the one for
7516 @item frame @var{stack-addr} [ @var{pc-addr} ]
7517 @itemx f @var{stack-addr} [ @var{pc-addr} ]
7518 Select the frame at address @var{stack-addr}. This is useful mainly if the
7519 chaining of stack frames has been damaged by a bug, making it
7520 impossible for @value{GDBN} to assign numbers properly to all frames. In
7521 addition, this can be useful when your program has multiple stacks and
7522 switches between them. The optional @var{pc-addr} can also be given to
7523 specify the value of PC for the stack frame.
7527 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7528 numbers @var{n}, this advances toward the outermost frame, to higher
7529 frame numbers, to frames that have existed longer.
7532 @kindex do @r{(@code{down})}
7534 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7535 positive numbers @var{n}, this advances toward the innermost frame, to
7536 lower frame numbers, to frames that were created more recently.
7537 You may abbreviate @code{down} as @code{do}.
7540 All of these commands end by printing two lines of output describing the
7541 frame. The first line shows the frame number, the function name, the
7542 arguments, and the source file and line number of execution in that
7543 frame. The second line shows the text of that source line.
7551 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7553 10 read_input_file (argv[i]);
7557 After such a printout, the @code{list} command with no arguments
7558 prints ten lines centered on the point of execution in the frame.
7559 You can also edit the program at the point of execution with your favorite
7560 editing program by typing @code{edit}.
7561 @xref{List, ,Printing Source Lines},
7565 @kindex select-frame
7567 The @code{select-frame} command is a variant of @code{frame} that does
7568 not display the new frame after selecting it. This command is
7569 intended primarily for use in @value{GDBN} command scripts, where the
7570 output might be unnecessary and distracting.
7572 @kindex down-silently
7574 @item up-silently @var{n}
7575 @itemx down-silently @var{n}
7576 These two commands are variants of @code{up} and @code{down},
7577 respectively; they differ in that they do their work silently, without
7578 causing display of the new frame. They are intended primarily for use
7579 in @value{GDBN} command scripts, where the output might be unnecessary and
7584 @section Information About a Frame
7586 There are several other commands to print information about the selected
7592 When used without any argument, this command does not change which
7593 frame is selected, but prints a brief description of the currently
7594 selected stack frame. It can be abbreviated @code{f}. With an
7595 argument, this command is used to select a stack frame.
7596 @xref{Selection, ,Selecting a Frame}.
7599 @kindex info f @r{(@code{info frame})}
7602 This command prints a verbose description of the selected stack frame,
7607 the address of the frame
7609 the address of the next frame down (called by this frame)
7611 the address of the next frame up (caller of this frame)
7613 the language in which the source code corresponding to this frame is written
7615 the address of the frame's arguments
7617 the address of the frame's local variables
7619 the program counter saved in it (the address of execution in the caller frame)
7621 which registers were saved in the frame
7624 @noindent The verbose description is useful when
7625 something has gone wrong that has made the stack format fail to fit
7626 the usual conventions.
7628 @item info frame @var{addr}
7629 @itemx info f @var{addr}
7630 Print a verbose description of the frame at address @var{addr}, without
7631 selecting that frame. The selected frame remains unchanged by this
7632 command. This requires the same kind of address (more than one for some
7633 architectures) that you specify in the @code{frame} command.
7634 @xref{Selection, ,Selecting a Frame}.
7638 Print the arguments of the selected frame, each on a separate line.
7642 Print the local variables of the selected frame, each on a separate
7643 line. These are all variables (declared either static or automatic)
7644 accessible at the point of execution of the selected frame.
7648 @node Frame Filter Management
7649 @section Management of Frame Filters.
7650 @cindex managing frame filters
7652 Frame filters are Python based utilities to manage and decorate the
7653 output of frames. @xref{Frame Filter API}, for further information.
7655 Managing frame filters is performed by several commands available
7656 within @value{GDBN}, detailed here.
7659 @kindex info frame-filter
7660 @item info frame-filter
7661 Print a list of installed frame filters from all dictionaries, showing
7662 their name, priority and enabled status.
7664 @kindex disable frame-filter
7665 @anchor{disable frame-filter all}
7666 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
7667 Disable a frame filter in the dictionary matching
7668 @var{filter-dictionary} and @var{filter-name}. The
7669 @var{filter-dictionary} may be @code{all}, @code{global},
7670 @code{progspace}, or the name of the object file where the frame filter
7671 dictionary resides. When @code{all} is specified, all frame filters
7672 across all dictionaries are disabled. The @var{filter-name} is the name
7673 of the frame filter and is used when @code{all} is not the option for
7674 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
7675 may be enabled again later.
7677 @kindex enable frame-filter
7678 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
7679 Enable a frame filter in the dictionary matching
7680 @var{filter-dictionary} and @var{filter-name}. The
7681 @var{filter-dictionary} may be @code{all}, @code{global},
7682 @code{progspace} or the name of the object file where the frame filter
7683 dictionary resides. When @code{all} is specified, all frame filters across
7684 all dictionaries are enabled. The @var{filter-name} is the name of the frame
7685 filter and is used when @code{all} is not the option for
7686 @var{filter-dictionary}.
7691 (gdb) info frame-filter
7693 global frame-filters:
7694 Priority Enabled Name
7695 1000 No PrimaryFunctionFilter
7698 progspace /build/test frame-filters:
7699 Priority Enabled Name
7700 100 Yes ProgspaceFilter
7702 objfile /build/test frame-filters:
7703 Priority Enabled Name
7704 999 Yes BuildProgra Filter
7706 (gdb) disable frame-filter /build/test BuildProgramFilter
7707 (gdb) info frame-filter
7709 global frame-filters:
7710 Priority Enabled Name
7711 1000 No PrimaryFunctionFilter
7714 progspace /build/test frame-filters:
7715 Priority Enabled Name
7716 100 Yes ProgspaceFilter
7718 objfile /build/test frame-filters:
7719 Priority Enabled Name
7720 999 No BuildProgramFilter
7722 (gdb) enable frame-filter global PrimaryFunctionFilter
7723 (gdb) info frame-filter
7725 global frame-filters:
7726 Priority Enabled Name
7727 1000 Yes PrimaryFunctionFilter
7730 progspace /build/test frame-filters:
7731 Priority Enabled Name
7732 100 Yes ProgspaceFilter
7734 objfile /build/test frame-filters:
7735 Priority Enabled Name
7736 999 No BuildProgramFilter
7739 @kindex set frame-filter priority
7740 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7741 Set the @var{priority} of a frame filter in the dictionary matching
7742 @var{filter-dictionary}, and the frame filter name matching
7743 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7744 @code{progspace} or the name of the object file where the frame filter
7745 dictionary resides. The @var{priority} is an integer.
7747 @kindex show frame-filter priority
7748 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7749 Show the @var{priority} of a frame filter in the dictionary matching
7750 @var{filter-dictionary}, and the frame filter name matching
7751 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7752 @code{progspace} or the name of the object file where the frame filter
7758 (gdb) info frame-filter
7760 global frame-filters:
7761 Priority Enabled Name
7762 1000 Yes PrimaryFunctionFilter
7765 progspace /build/test frame-filters:
7766 Priority Enabled Name
7767 100 Yes ProgspaceFilter
7769 objfile /build/test frame-filters:
7770 Priority Enabled Name
7771 999 No BuildProgramFilter
7773 (gdb) set frame-filter priority global Reverse 50
7774 (gdb) info frame-filter
7776 global frame-filters:
7777 Priority Enabled Name
7778 1000 Yes PrimaryFunctionFilter
7781 progspace /build/test frame-filters:
7782 Priority Enabled Name
7783 100 Yes ProgspaceFilter
7785 objfile /build/test frame-filters:
7786 Priority Enabled Name
7787 999 No BuildProgramFilter
7792 @chapter Examining Source Files
7794 @value{GDBN} can print parts of your program's source, since the debugging
7795 information recorded in the program tells @value{GDBN} what source files were
7796 used to build it. When your program stops, @value{GDBN} spontaneously prints
7797 the line where it stopped. Likewise, when you select a stack frame
7798 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7799 execution in that frame has stopped. You can print other portions of
7800 source files by explicit command.
7802 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7803 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7804 @value{GDBN} under @sc{gnu} Emacs}.
7807 * List:: Printing source lines
7808 * Specify Location:: How to specify code locations
7809 * Edit:: Editing source files
7810 * Search:: Searching source files
7811 * Source Path:: Specifying source directories
7812 * Machine Code:: Source and machine code
7816 @section Printing Source Lines
7819 @kindex l @r{(@code{list})}
7820 To print lines from a source file, use the @code{list} command
7821 (abbreviated @code{l}). By default, ten lines are printed.
7822 There are several ways to specify what part of the file you want to
7823 print; see @ref{Specify Location}, for the full list.
7825 Here are the forms of the @code{list} command most commonly used:
7828 @item list @var{linenum}
7829 Print lines centered around line number @var{linenum} in the
7830 current source file.
7832 @item list @var{function}
7833 Print lines centered around the beginning of function
7837 Print more lines. If the last lines printed were printed with a
7838 @code{list} command, this prints lines following the last lines
7839 printed; however, if the last line printed was a solitary line printed
7840 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7841 Stack}), this prints lines centered around that line.
7844 Print lines just before the lines last printed.
7847 @cindex @code{list}, how many lines to display
7848 By default, @value{GDBN} prints ten source lines with any of these forms of
7849 the @code{list} command. You can change this using @code{set listsize}:
7852 @kindex set listsize
7853 @item set listsize @var{count}
7854 @itemx set listsize unlimited
7855 Make the @code{list} command display @var{count} source lines (unless
7856 the @code{list} argument explicitly specifies some other number).
7857 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7859 @kindex show listsize
7861 Display the number of lines that @code{list} prints.
7864 Repeating a @code{list} command with @key{RET} discards the argument,
7865 so it is equivalent to typing just @code{list}. This is more useful
7866 than listing the same lines again. An exception is made for an
7867 argument of @samp{-}; that argument is preserved in repetition so that
7868 each repetition moves up in the source file.
7870 In general, the @code{list} command expects you to supply zero, one or two
7871 @dfn{locations}. Locations specify source lines; there are several ways
7872 of writing them (@pxref{Specify Location}), but the effect is always
7873 to specify some source line.
7875 Here is a complete description of the possible arguments for @code{list}:
7878 @item list @var{location}
7879 Print lines centered around the line specified by @var{location}.
7881 @item list @var{first},@var{last}
7882 Print lines from @var{first} to @var{last}. Both arguments are
7883 locations. When a @code{list} command has two locations, and the
7884 source file of the second location is omitted, this refers to
7885 the same source file as the first location.
7887 @item list ,@var{last}
7888 Print lines ending with @var{last}.
7890 @item list @var{first},
7891 Print lines starting with @var{first}.
7894 Print lines just after the lines last printed.
7897 Print lines just before the lines last printed.
7900 As described in the preceding table.
7903 @node Specify Location
7904 @section Specifying a Location
7905 @cindex specifying location
7907 @cindex source location
7910 * Linespec Locations:: Linespec locations
7911 * Explicit Locations:: Explicit locations
7912 * Address Locations:: Address locations
7915 Several @value{GDBN} commands accept arguments that specify a location
7916 of your program's code. Since @value{GDBN} is a source-level
7917 debugger, a location usually specifies some line in the source code.
7918 Locations may be specified using three different formats:
7919 linespec locations, explicit locations, or address locations.
7921 @node Linespec Locations
7922 @subsection Linespec Locations
7923 @cindex linespec locations
7925 A @dfn{linespec} is a colon-separated list of source location parameters such
7926 as file name, function name, etc. Here are all the different ways of
7927 specifying a linespec:
7931 Specifies the line number @var{linenum} of the current source file.
7934 @itemx +@var{offset}
7935 Specifies the line @var{offset} lines before or after the @dfn{current
7936 line}. For the @code{list} command, the current line is the last one
7937 printed; for the breakpoint commands, this is the line at which
7938 execution stopped in the currently selected @dfn{stack frame}
7939 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7940 used as the second of the two linespecs in a @code{list} command,
7941 this specifies the line @var{offset} lines up or down from the first
7944 @item @var{filename}:@var{linenum}
7945 Specifies the line @var{linenum} in the source file @var{filename}.
7946 If @var{filename} is a relative file name, then it will match any
7947 source file name with the same trailing components. For example, if
7948 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7949 name of @file{/build/trunk/gcc/expr.c}, but not
7950 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7952 @item @var{function}
7953 Specifies the line that begins the body of the function @var{function}.
7954 For example, in C, this is the line with the open brace.
7956 By default, in C@t{++} and Ada, @var{function} is interpreted as
7957 specifying all functions named @var{function} in all scopes. For
7958 C@t{++}, this means in all namespaces and classes. For Ada, this
7959 means in all packages.
7961 For example, assuming a program with C@t{++} symbols named
7962 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
7963 func}} and @w{@kbd{break B::func}} set a breakpoint on both symbols.
7965 Commands that accept a linespec let you override this with the
7966 @code{-qualified} option. For example, @w{@kbd{break -qualified
7967 func}} sets a breakpoint on a free-function named @code{func} ignoring
7968 any C@t{++} class methods and namespace functions called @code{func}.
7970 @xref{Explicit Locations}.
7972 @item @var{function}:@var{label}
7973 Specifies the line where @var{label} appears in @var{function}.
7975 @item @var{filename}:@var{function}
7976 Specifies the line that begins the body of the function @var{function}
7977 in the file @var{filename}. You only need the file name with a
7978 function name to avoid ambiguity when there are identically named
7979 functions in different source files.
7982 Specifies the line at which the label named @var{label} appears
7983 in the function corresponding to the currently selected stack frame.
7984 If there is no current selected stack frame (for instance, if the inferior
7985 is not running), then @value{GDBN} will not search for a label.
7987 @cindex breakpoint at static probe point
7988 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7989 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7990 applications to embed static probes. @xref{Static Probe Points}, for more
7991 information on finding and using static probes. This form of linespec
7992 specifies the location of such a static probe.
7994 If @var{objfile} is given, only probes coming from that shared library
7995 or executable matching @var{objfile} as a regular expression are considered.
7996 If @var{provider} is given, then only probes from that provider are considered.
7997 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7998 each one of those probes.
8001 @node Explicit Locations
8002 @subsection Explicit Locations
8003 @cindex explicit locations
8005 @dfn{Explicit locations} allow the user to directly specify the source
8006 location's parameters using option-value pairs.
8008 Explicit locations are useful when several functions, labels, or
8009 file names have the same name (base name for files) in the program's
8010 sources. In these cases, explicit locations point to the source
8011 line you meant more accurately and unambiguously. Also, using
8012 explicit locations might be faster in large programs.
8014 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
8015 defined in the file named @file{foo} or the label @code{bar} in a function
8016 named @code{foo}. @value{GDBN} must search either the file system or
8017 the symbol table to know.
8019 The list of valid explicit location options is summarized in the
8023 @item -source @var{filename}
8024 The value specifies the source file name. To differentiate between
8025 files with the same base name, prepend as many directories as is necessary
8026 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
8027 @value{GDBN} will use the first file it finds with the given base
8028 name. This option requires the use of either @code{-function} or @code{-line}.
8030 @item -function @var{function}
8031 The value specifies the name of a function. Operations
8032 on function locations unmodified by other options (such as @code{-label}
8033 or @code{-line}) refer to the line that begins the body of the function.
8034 In C, for example, this is the line with the open brace.
8036 By default, in C@t{++} and Ada, @var{function} is interpreted as
8037 specifying all functions named @var{function} in all scopes. For
8038 C@t{++}, this means in all namespaces and classes. For Ada, this
8039 means in all packages.
8041 For example, assuming a program with C@t{++} symbols named
8042 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8043 -function func}} and @w{@kbd{break -function B::func}} set a
8044 breakpoint on both symbols.
8046 You can use the @kbd{-qualified} flag to override this (see below).
8050 This flag makes @value{GDBN} interpret a function name specified with
8051 @kbd{-function} as a complete fully-qualified name.
8053 For example, assuming a C@t{++} program with symbols named
8054 @code{A::B::func} and @code{B::func}, the @w{@kbd{break -qualified
8055 -function B::func}} command sets a breakpoint on @code{B::func}, only.
8057 (Note: the @kbd{-qualified} option can precede a linespec as well
8058 (@pxref{Linespec Locations}), so the particular example above could be
8059 simplified as @w{@kbd{break -qualified B::func}}.)
8061 @item -label @var{label}
8062 The value specifies the name of a label. When the function
8063 name is not specified, the label is searched in the function of the currently
8064 selected stack frame.
8066 @item -line @var{number}
8067 The value specifies a line offset for the location. The offset may either
8068 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
8069 the command. When specified without any other options, the line offset is
8070 relative to the current line.
8073 Explicit location options may be abbreviated by omitting any non-unique
8074 trailing characters from the option name, e.g., @w{@kbd{break -s main.c -li 3}}.
8076 @node Address Locations
8077 @subsection Address Locations
8078 @cindex address locations
8080 @dfn{Address locations} indicate a specific program address. They have
8081 the generalized form *@var{address}.
8083 For line-oriented commands, such as @code{list} and @code{edit}, this
8084 specifies a source line that contains @var{address}. For @code{break} and
8085 other breakpoint-oriented commands, this can be used to set breakpoints in
8086 parts of your program which do not have debugging information or
8089 Here @var{address} may be any expression valid in the current working
8090 language (@pxref{Languages, working language}) that specifies a code
8091 address. In addition, as a convenience, @value{GDBN} extends the
8092 semantics of expressions used in locations to cover several situations
8093 that frequently occur during debugging. Here are the various forms
8097 @item @var{expression}
8098 Any expression valid in the current working language.
8100 @item @var{funcaddr}
8101 An address of a function or procedure derived from its name. In C,
8102 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
8103 simply the function's name @var{function} (and actually a special case
8104 of a valid expression). In Pascal and Modula-2, this is
8105 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
8106 (although the Pascal form also works).
8108 This form specifies the address of the function's first instruction,
8109 before the stack frame and arguments have been set up.
8111 @item '@var{filename}':@var{funcaddr}
8112 Like @var{funcaddr} above, but also specifies the name of the source
8113 file explicitly. This is useful if the name of the function does not
8114 specify the function unambiguously, e.g., if there are several
8115 functions with identical names in different source files.
8119 @section Editing Source Files
8120 @cindex editing source files
8123 @kindex e @r{(@code{edit})}
8124 To edit the lines in a source file, use the @code{edit} command.
8125 The editing program of your choice
8126 is invoked with the current line set to
8127 the active line in the program.
8128 Alternatively, there are several ways to specify what part of the file you
8129 want to print if you want to see other parts of the program:
8132 @item edit @var{location}
8133 Edit the source file specified by @code{location}. Editing starts at
8134 that @var{location}, e.g., at the specified source line of the
8135 specified file. @xref{Specify Location}, for all the possible forms
8136 of the @var{location} argument; here are the forms of the @code{edit}
8137 command most commonly used:
8140 @item edit @var{number}
8141 Edit the current source file with @var{number} as the active line number.
8143 @item edit @var{function}
8144 Edit the file containing @var{function} at the beginning of its definition.
8149 @subsection Choosing your Editor
8150 You can customize @value{GDBN} to use any editor you want
8152 The only restriction is that your editor (say @code{ex}), recognizes the
8153 following command-line syntax:
8155 ex +@var{number} file
8157 The optional numeric value +@var{number} specifies the number of the line in
8158 the file where to start editing.}.
8159 By default, it is @file{@value{EDITOR}}, but you can change this
8160 by setting the environment variable @code{EDITOR} before using
8161 @value{GDBN}. For example, to configure @value{GDBN} to use the
8162 @code{vi} editor, you could use these commands with the @code{sh} shell:
8168 or in the @code{csh} shell,
8170 setenv EDITOR /usr/bin/vi
8175 @section Searching Source Files
8176 @cindex searching source files
8178 There are two commands for searching through the current source file for a
8183 @kindex forward-search
8184 @kindex fo @r{(@code{forward-search})}
8185 @item forward-search @var{regexp}
8186 @itemx search @var{regexp}
8187 The command @samp{forward-search @var{regexp}} checks each line,
8188 starting with the one following the last line listed, for a match for
8189 @var{regexp}. It lists the line that is found. You can use the
8190 synonym @samp{search @var{regexp}} or abbreviate the command name as
8193 @kindex reverse-search
8194 @item reverse-search @var{regexp}
8195 The command @samp{reverse-search @var{regexp}} checks each line, starting
8196 with the one before the last line listed and going backward, for a match
8197 for @var{regexp}. It lists the line that is found. You can abbreviate
8198 this command as @code{rev}.
8202 @section Specifying Source Directories
8205 @cindex directories for source files
8206 Executable programs sometimes do not record the directories of the source
8207 files from which they were compiled, just the names. Even when they do,
8208 the directories could be moved between the compilation and your debugging
8209 session. @value{GDBN} has a list of directories to search for source files;
8210 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
8211 it tries all the directories in the list, in the order they are present
8212 in the list, until it finds a file with the desired name.
8214 For example, suppose an executable references the file
8215 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
8216 @file{/mnt/cross}. The file is first looked up literally; if this
8217 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
8218 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
8219 message is printed. @value{GDBN} does not look up the parts of the
8220 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
8221 Likewise, the subdirectories of the source path are not searched: if
8222 the source path is @file{/mnt/cross}, and the binary refers to
8223 @file{foo.c}, @value{GDBN} would not find it under
8224 @file{/mnt/cross/usr/src/foo-1.0/lib}.
8226 Plain file names, relative file names with leading directories, file
8227 names containing dots, etc.@: are all treated as described above; for
8228 instance, if the source path is @file{/mnt/cross}, and the source file
8229 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
8230 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
8231 that---@file{/mnt/cross/foo.c}.
8233 Note that the executable search path is @emph{not} used to locate the
8236 Whenever you reset or rearrange the source path, @value{GDBN} clears out
8237 any information it has cached about where source files are found and where
8238 each line is in the file.
8242 When you start @value{GDBN}, its source path includes only @samp{cdir}
8243 and @samp{cwd}, in that order.
8244 To add other directories, use the @code{directory} command.
8246 The search path is used to find both program source files and @value{GDBN}
8247 script files (read using the @samp{-command} option and @samp{source} command).
8249 In addition to the source path, @value{GDBN} provides a set of commands
8250 that manage a list of source path substitution rules. A @dfn{substitution
8251 rule} specifies how to rewrite source directories stored in the program's
8252 debug information in case the sources were moved to a different
8253 directory between compilation and debugging. A rule is made of
8254 two strings, the first specifying what needs to be rewritten in
8255 the path, and the second specifying how it should be rewritten.
8256 In @ref{set substitute-path}, we name these two parts @var{from} and
8257 @var{to} respectively. @value{GDBN} does a simple string replacement
8258 of @var{from} with @var{to} at the start of the directory part of the
8259 source file name, and uses that result instead of the original file
8260 name to look up the sources.
8262 Using the previous example, suppose the @file{foo-1.0} tree has been
8263 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
8264 @value{GDBN} to replace @file{/usr/src} in all source path names with
8265 @file{/mnt/cross}. The first lookup will then be
8266 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
8267 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
8268 substitution rule, use the @code{set substitute-path} command
8269 (@pxref{set substitute-path}).
8271 To avoid unexpected substitution results, a rule is applied only if the
8272 @var{from} part of the directory name ends at a directory separator.
8273 For instance, a rule substituting @file{/usr/source} into
8274 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
8275 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
8276 is applied only at the beginning of the directory name, this rule will
8277 not be applied to @file{/root/usr/source/baz.c} either.
8279 In many cases, you can achieve the same result using the @code{directory}
8280 command. However, @code{set substitute-path} can be more efficient in
8281 the case where the sources are organized in a complex tree with multiple
8282 subdirectories. With the @code{directory} command, you need to add each
8283 subdirectory of your project. If you moved the entire tree while
8284 preserving its internal organization, then @code{set substitute-path}
8285 allows you to direct the debugger to all the sources with one single
8288 @code{set substitute-path} is also more than just a shortcut command.
8289 The source path is only used if the file at the original location no
8290 longer exists. On the other hand, @code{set substitute-path} modifies
8291 the debugger behavior to look at the rewritten location instead. So, if
8292 for any reason a source file that is not relevant to your executable is
8293 located at the original location, a substitution rule is the only
8294 method available to point @value{GDBN} at the new location.
8296 @cindex @samp{--with-relocated-sources}
8297 @cindex default source path substitution
8298 You can configure a default source path substitution rule by
8299 configuring @value{GDBN} with the
8300 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
8301 should be the name of a directory under @value{GDBN}'s configured
8302 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
8303 directory names in debug information under @var{dir} will be adjusted
8304 automatically if the installed @value{GDBN} is moved to a new
8305 location. This is useful if @value{GDBN}, libraries or executables
8306 with debug information and corresponding source code are being moved
8310 @item directory @var{dirname} @dots{}
8311 @item dir @var{dirname} @dots{}
8312 Add directory @var{dirname} to the front of the source path. Several
8313 directory names may be given to this command, separated by @samp{:}
8314 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
8315 part of absolute file names) or
8316 whitespace. You may specify a directory that is already in the source
8317 path; this moves it forward, so @value{GDBN} searches it sooner.
8321 @vindex $cdir@r{, convenience variable}
8322 @vindex $cwd@r{, convenience variable}
8323 @cindex compilation directory
8324 @cindex current directory
8325 @cindex working directory
8326 @cindex directory, current
8327 @cindex directory, compilation
8328 You can use the string @samp{$cdir} to refer to the compilation
8329 directory (if one is recorded), and @samp{$cwd} to refer to the current
8330 working directory. @samp{$cwd} is not the same as @samp{.}---the former
8331 tracks the current working directory as it changes during your @value{GDBN}
8332 session, while the latter is immediately expanded to the current
8333 directory at the time you add an entry to the source path.
8336 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
8338 @c RET-repeat for @code{directory} is explicitly disabled, but since
8339 @c repeating it would be a no-op we do not say that. (thanks to RMS)
8341 @item set directories @var{path-list}
8342 @kindex set directories
8343 Set the source path to @var{path-list}.
8344 @samp{$cdir:$cwd} are added if missing.
8346 @item show directories
8347 @kindex show directories
8348 Print the source path: show which directories it contains.
8350 @anchor{set substitute-path}
8351 @item set substitute-path @var{from} @var{to}
8352 @kindex set substitute-path
8353 Define a source path substitution rule, and add it at the end of the
8354 current list of existing substitution rules. If a rule with the same
8355 @var{from} was already defined, then the old rule is also deleted.
8357 For example, if the file @file{/foo/bar/baz.c} was moved to
8358 @file{/mnt/cross/baz.c}, then the command
8361 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
8365 will tell @value{GDBN} to replace @samp{/foo/bar} with
8366 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
8367 @file{baz.c} even though it was moved.
8369 In the case when more than one substitution rule have been defined,
8370 the rules are evaluated one by one in the order where they have been
8371 defined. The first one matching, if any, is selected to perform
8374 For instance, if we had entered the following commands:
8377 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
8378 (@value{GDBP}) set substitute-path /usr/src /mnt/src
8382 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
8383 @file{/mnt/include/defs.h} by using the first rule. However, it would
8384 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
8385 @file{/mnt/src/lib/foo.c}.
8388 @item unset substitute-path [path]
8389 @kindex unset substitute-path
8390 If a path is specified, search the current list of substitution rules
8391 for a rule that would rewrite that path. Delete that rule if found.
8392 A warning is emitted by the debugger if no rule could be found.
8394 If no path is specified, then all substitution rules are deleted.
8396 @item show substitute-path [path]
8397 @kindex show substitute-path
8398 If a path is specified, then print the source path substitution rule
8399 which would rewrite that path, if any.
8401 If no path is specified, then print all existing source path substitution
8406 If your source path is cluttered with directories that are no longer of
8407 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
8408 versions of source. You can correct the situation as follows:
8412 Use @code{directory} with no argument to reset the source path to its default value.
8415 Use @code{directory} with suitable arguments to reinstall the
8416 directories you want in the source path. You can add all the
8417 directories in one command.
8421 @section Source and Machine Code
8422 @cindex source line and its code address
8424 You can use the command @code{info line} to map source lines to program
8425 addresses (and vice versa), and the command @code{disassemble} to display
8426 a range of addresses as machine instructions. You can use the command
8427 @code{set disassemble-next-line} to set whether to disassemble next
8428 source line when execution stops. When run under @sc{gnu} Emacs
8429 mode, the @code{info line} command causes the arrow to point to the
8430 line specified. Also, @code{info line} prints addresses in symbolic form as
8435 @item info line @var{location}
8436 Print the starting and ending addresses of the compiled code for
8437 source line @var{location}. You can specify source lines in any of
8438 the ways documented in @ref{Specify Location}.
8441 For example, we can use @code{info line} to discover the location of
8442 the object code for the first line of function
8443 @code{m4_changequote}:
8445 @c FIXME: I think this example should also show the addresses in
8446 @c symbolic form, as they usually would be displayed.
8448 (@value{GDBP}) info line m4_changequote
8449 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
8453 @cindex code address and its source line
8454 We can also inquire (using @code{*@var{addr}} as the form for
8455 @var{location}) what source line covers a particular address:
8457 (@value{GDBP}) info line *0x63ff
8458 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
8461 @cindex @code{$_} and @code{info line}
8462 @cindex @code{x} command, default address
8463 @kindex x@r{(examine), and} info line
8464 After @code{info line}, the default address for the @code{x} command
8465 is changed to the starting address of the line, so that @samp{x/i} is
8466 sufficient to begin examining the machine code (@pxref{Memory,
8467 ,Examining Memory}). Also, this address is saved as the value of the
8468 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
8473 @cindex assembly instructions
8474 @cindex instructions, assembly
8475 @cindex machine instructions
8476 @cindex listing machine instructions
8478 @itemx disassemble /m
8479 @itemx disassemble /s
8480 @itemx disassemble /r
8481 This specialized command dumps a range of memory as machine
8482 instructions. It can also print mixed source+disassembly by specifying
8483 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
8484 as well as in symbolic form by specifying the @code{/r} modifier.
8485 The default memory range is the function surrounding the
8486 program counter of the selected frame. A single argument to this
8487 command is a program counter value; @value{GDBN} dumps the function
8488 surrounding this value. When two arguments are given, they should
8489 be separated by a comma, possibly surrounded by whitespace. The
8490 arguments specify a range of addresses to dump, in one of two forms:
8493 @item @var{start},@var{end}
8494 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8495 @item @var{start},+@var{length}
8496 the addresses from @var{start} (inclusive) to
8497 @code{@var{start}+@var{length}} (exclusive).
8501 When 2 arguments are specified, the name of the function is also
8502 printed (since there could be several functions in the given range).
8504 The argument(s) can be any expression yielding a numeric value, such as
8505 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8507 If the range of memory being disassembled contains current program counter,
8508 the instruction at that location is shown with a @code{=>} marker.
8511 The following example shows the disassembly of a range of addresses of
8512 HP PA-RISC 2.0 code:
8515 (@value{GDBP}) disas 0x32c4, 0x32e4
8516 Dump of assembler code from 0x32c4 to 0x32e4:
8517 0x32c4 <main+204>: addil 0,dp
8518 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8519 0x32cc <main+212>: ldil 0x3000,r31
8520 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8521 0x32d4 <main+220>: ldo 0(r31),rp
8522 0x32d8 <main+224>: addil -0x800,dp
8523 0x32dc <main+228>: ldo 0x588(r1),r26
8524 0x32e0 <main+232>: ldil 0x3000,r31
8525 End of assembler dump.
8528 Here is an example showing mixed source+assembly for Intel x86
8529 with @code{/m} or @code{/s}, when the program is stopped just after
8530 function prologue in a non-optimized function with no inline code.
8533 (@value{GDBP}) disas /m main
8534 Dump of assembler code for function main:
8536 0x08048330 <+0>: push %ebp
8537 0x08048331 <+1>: mov %esp,%ebp
8538 0x08048333 <+3>: sub $0x8,%esp
8539 0x08048336 <+6>: and $0xfffffff0,%esp
8540 0x08048339 <+9>: sub $0x10,%esp
8542 6 printf ("Hello.\n");
8543 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8544 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8548 0x08048348 <+24>: mov $0x0,%eax
8549 0x0804834d <+29>: leave
8550 0x0804834e <+30>: ret
8552 End of assembler dump.
8555 The @code{/m} option is deprecated as its output is not useful when
8556 there is either inlined code or re-ordered code.
8557 The @code{/s} option is the preferred choice.
8558 Here is an example for AMD x86-64 showing the difference between
8559 @code{/m} output and @code{/s} output.
8560 This example has one inline function defined in a header file,
8561 and the code is compiled with @samp{-O2} optimization.
8562 Note how the @code{/m} output is missing the disassembly of
8563 several instructions that are present in the @code{/s} output.
8593 (@value{GDBP}) disas /m main
8594 Dump of assembler code for function main:
8598 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8599 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8603 0x000000000040041d <+29>: xor %eax,%eax
8604 0x000000000040041f <+31>: retq
8605 0x0000000000400420 <+32>: add %eax,%eax
8606 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8608 End of assembler dump.
8609 (@value{GDBP}) disas /s main
8610 Dump of assembler code for function main:
8614 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8618 0x0000000000400406 <+6>: test %eax,%eax
8619 0x0000000000400408 <+8>: js 0x400420 <main+32>
8624 0x000000000040040a <+10>: lea 0xa(%rax),%edx
8625 0x000000000040040d <+13>: test %eax,%eax
8626 0x000000000040040f <+15>: mov $0x1,%eax
8627 0x0000000000400414 <+20>: cmovne %edx,%eax
8631 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8635 0x000000000040041d <+29>: xor %eax,%eax
8636 0x000000000040041f <+31>: retq
8640 0x0000000000400420 <+32>: add %eax,%eax
8641 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8642 End of assembler dump.
8645 Here is another example showing raw instructions in hex for AMD x86-64,
8648 (gdb) disas /r 0x400281,+10
8649 Dump of assembler code from 0x400281 to 0x40028b:
8650 0x0000000000400281: 38 36 cmp %dh,(%rsi)
8651 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
8652 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
8653 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
8654 End of assembler dump.
8657 Addresses cannot be specified as a location (@pxref{Specify Location}).
8658 So, for example, if you want to disassemble function @code{bar}
8659 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
8660 and not @samp{disassemble foo.c:bar}.
8662 Some architectures have more than one commonly-used set of instruction
8663 mnemonics or other syntax.
8665 For programs that were dynamically linked and use shared libraries,
8666 instructions that call functions or branch to locations in the shared
8667 libraries might show a seemingly bogus location---it's actually a
8668 location of the relocation table. On some architectures, @value{GDBN}
8669 might be able to resolve these to actual function names.
8672 @kindex set disassembler-options
8673 @cindex disassembler options
8674 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
8675 This command controls the passing of target specific information to
8676 the disassembler. For a list of valid options, please refer to the
8677 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
8678 manual and/or the output of @kbd{objdump --help}
8679 (@pxref{objdump,,objdump,binutils.info,The GNU Binary Utilities}).
8680 The default value is the empty string.
8682 If it is necessary to specify more than one disassembler option, then
8683 multiple options can be placed together into a comma separated list.
8684 Currently this command is only supported on targets ARM, PowerPC
8687 @kindex show disassembler-options
8688 @item show disassembler-options
8689 Show the current setting of the disassembler options.
8693 @kindex set disassembly-flavor
8694 @cindex Intel disassembly flavor
8695 @cindex AT&T disassembly flavor
8696 @item set disassembly-flavor @var{instruction-set}
8697 Select the instruction set to use when disassembling the
8698 program via the @code{disassemble} or @code{x/i} commands.
8700 Currently this command is only defined for the Intel x86 family. You
8701 can set @var{instruction-set} to either @code{intel} or @code{att}.
8702 The default is @code{att}, the AT&T flavor used by default by Unix
8703 assemblers for x86-based targets.
8705 @kindex show disassembly-flavor
8706 @item show disassembly-flavor
8707 Show the current setting of the disassembly flavor.
8711 @kindex set disassemble-next-line
8712 @kindex show disassemble-next-line
8713 @item set disassemble-next-line
8714 @itemx show disassemble-next-line
8715 Control whether or not @value{GDBN} will disassemble the next source
8716 line or instruction when execution stops. If ON, @value{GDBN} will
8717 display disassembly of the next source line when execution of the
8718 program being debugged stops. This is @emph{in addition} to
8719 displaying the source line itself, which @value{GDBN} always does if
8720 possible. If the next source line cannot be displayed for some reason
8721 (e.g., if @value{GDBN} cannot find the source file, or there's no line
8722 info in the debug info), @value{GDBN} will display disassembly of the
8723 next @emph{instruction} instead of showing the next source line. If
8724 AUTO, @value{GDBN} will display disassembly of next instruction only
8725 if the source line cannot be displayed. This setting causes
8726 @value{GDBN} to display some feedback when you step through a function
8727 with no line info or whose source file is unavailable. The default is
8728 OFF, which means never display the disassembly of the next line or
8734 @chapter Examining Data
8736 @cindex printing data
8737 @cindex examining data
8740 The usual way to examine data in your program is with the @code{print}
8741 command (abbreviated @code{p}), or its synonym @code{inspect}. It
8742 evaluates and prints the value of an expression of the language your
8743 program is written in (@pxref{Languages, ,Using @value{GDBN} with
8744 Different Languages}). It may also print the expression using a
8745 Python-based pretty-printer (@pxref{Pretty Printing}).
8748 @item print @var{expr}
8749 @itemx print /@var{f} @var{expr}
8750 @var{expr} is an expression (in the source language). By default the
8751 value of @var{expr} is printed in a format appropriate to its data type;
8752 you can choose a different format by specifying @samp{/@var{f}}, where
8753 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
8757 @itemx print /@var{f}
8758 @cindex reprint the last value
8759 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
8760 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
8761 conveniently inspect the same value in an alternative format.
8764 A more low-level way of examining data is with the @code{x} command.
8765 It examines data in memory at a specified address and prints it in a
8766 specified format. @xref{Memory, ,Examining Memory}.
8768 If you are interested in information about types, or about how the
8769 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
8770 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
8773 @cindex exploring hierarchical data structures
8775 Another way of examining values of expressions and type information is
8776 through the Python extension command @code{explore} (available only if
8777 the @value{GDBN} build is configured with @code{--with-python}). It
8778 offers an interactive way to start at the highest level (or, the most
8779 abstract level) of the data type of an expression (or, the data type
8780 itself) and explore all the way down to leaf scalar values/fields
8781 embedded in the higher level data types.
8784 @item explore @var{arg}
8785 @var{arg} is either an expression (in the source language), or a type
8786 visible in the current context of the program being debugged.
8789 The working of the @code{explore} command can be illustrated with an
8790 example. If a data type @code{struct ComplexStruct} is defined in your
8800 struct ComplexStruct
8802 struct SimpleStruct *ss_p;
8808 followed by variable declarations as
8811 struct SimpleStruct ss = @{ 10, 1.11 @};
8812 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8816 then, the value of the variable @code{cs} can be explored using the
8817 @code{explore} command as follows.
8821 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8822 the following fields:
8824 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8825 arr = <Enter 1 to explore this field of type `int [10]'>
8827 Enter the field number of choice:
8831 Since the fields of @code{cs} are not scalar values, you are being
8832 prompted to chose the field you want to explore. Let's say you choose
8833 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8834 pointer, you will be asked if it is pointing to a single value. From
8835 the declaration of @code{cs} above, it is indeed pointing to a single
8836 value, hence you enter @code{y}. If you enter @code{n}, then you will
8837 be asked if it were pointing to an array of values, in which case this
8838 field will be explored as if it were an array.
8841 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8842 Continue exploring it as a pointer to a single value [y/n]: y
8843 The value of `*(cs.ss_p)' is a struct/class of type `struct
8844 SimpleStruct' with the following fields:
8846 i = 10 .. (Value of type `int')
8847 d = 1.1100000000000001 .. (Value of type `double')
8849 Press enter to return to parent value:
8853 If the field @code{arr} of @code{cs} was chosen for exploration by
8854 entering @code{1} earlier, then since it is as array, you will be
8855 prompted to enter the index of the element in the array that you want
8859 `cs.arr' is an array of `int'.
8860 Enter the index of the element you want to explore in `cs.arr': 5
8862 `(cs.arr)[5]' is a scalar value of type `int'.
8866 Press enter to return to parent value:
8869 In general, at any stage of exploration, you can go deeper towards the
8870 leaf values by responding to the prompts appropriately, or hit the
8871 return key to return to the enclosing data structure (the @i{higher}
8872 level data structure).
8874 Similar to exploring values, you can use the @code{explore} command to
8875 explore types. Instead of specifying a value (which is typically a
8876 variable name or an expression valid in the current context of the
8877 program being debugged), you specify a type name. If you consider the
8878 same example as above, your can explore the type
8879 @code{struct ComplexStruct} by passing the argument
8880 @code{struct ComplexStruct} to the @code{explore} command.
8883 (gdb) explore struct ComplexStruct
8887 By responding to the prompts appropriately in the subsequent interactive
8888 session, you can explore the type @code{struct ComplexStruct} in a
8889 manner similar to how the value @code{cs} was explored in the above
8892 The @code{explore} command also has two sub-commands,
8893 @code{explore value} and @code{explore type}. The former sub-command is
8894 a way to explicitly specify that value exploration of the argument is
8895 being invoked, while the latter is a way to explicitly specify that type
8896 exploration of the argument is being invoked.
8899 @item explore value @var{expr}
8900 @cindex explore value
8901 This sub-command of @code{explore} explores the value of the
8902 expression @var{expr} (if @var{expr} is an expression valid in the
8903 current context of the program being debugged). The behavior of this
8904 command is identical to that of the behavior of the @code{explore}
8905 command being passed the argument @var{expr}.
8907 @item explore type @var{arg}
8908 @cindex explore type
8909 This sub-command of @code{explore} explores the type of @var{arg} (if
8910 @var{arg} is a type visible in the current context of program being
8911 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8912 is an expression valid in the current context of the program being
8913 debugged). If @var{arg} is a type, then the behavior of this command is
8914 identical to that of the @code{explore} command being passed the
8915 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8916 this command will be identical to that of the @code{explore} command
8917 being passed the type of @var{arg} as the argument.
8921 * Expressions:: Expressions
8922 * Ambiguous Expressions:: Ambiguous Expressions
8923 * Variables:: Program variables
8924 * Arrays:: Artificial arrays
8925 * Output Formats:: Output formats
8926 * Memory:: Examining memory
8927 * Auto Display:: Automatic display
8928 * Print Settings:: Print settings
8929 * Pretty Printing:: Python pretty printing
8930 * Value History:: Value history
8931 * Convenience Vars:: Convenience variables
8932 * Convenience Funs:: Convenience functions
8933 * Registers:: Registers
8934 * Floating Point Hardware:: Floating point hardware
8935 * Vector Unit:: Vector Unit
8936 * OS Information:: Auxiliary data provided by operating system
8937 * Memory Region Attributes:: Memory region attributes
8938 * Dump/Restore Files:: Copy between memory and a file
8939 * Core File Generation:: Cause a program dump its core
8940 * Character Sets:: Debugging programs that use a different
8941 character set than GDB does
8942 * Caching Target Data:: Data caching for targets
8943 * Searching Memory:: Searching memory for a sequence of bytes
8944 * Value Sizes:: Managing memory allocated for values
8948 @section Expressions
8951 @code{print} and many other @value{GDBN} commands accept an expression and
8952 compute its value. Any kind of constant, variable or operator defined
8953 by the programming language you are using is valid in an expression in
8954 @value{GDBN}. This includes conditional expressions, function calls,
8955 casts, and string constants. It also includes preprocessor macros, if
8956 you compiled your program to include this information; see
8959 @cindex arrays in expressions
8960 @value{GDBN} supports array constants in expressions input by
8961 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8962 you can use the command @code{print @{1, 2, 3@}} to create an array
8963 of three integers. If you pass an array to a function or assign it
8964 to a program variable, @value{GDBN} copies the array to memory that
8965 is @code{malloc}ed in the target program.
8967 Because C is so widespread, most of the expressions shown in examples in
8968 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8969 Languages}, for information on how to use expressions in other
8972 In this section, we discuss operators that you can use in @value{GDBN}
8973 expressions regardless of your programming language.
8975 @cindex casts, in expressions
8976 Casts are supported in all languages, not just in C, because it is so
8977 useful to cast a number into a pointer in order to examine a structure
8978 at that address in memory.
8979 @c FIXME: casts supported---Mod2 true?
8981 @value{GDBN} supports these operators, in addition to those common
8982 to programming languages:
8986 @samp{@@} is a binary operator for treating parts of memory as arrays.
8987 @xref{Arrays, ,Artificial Arrays}, for more information.
8990 @samp{::} allows you to specify a variable in terms of the file or
8991 function where it is defined. @xref{Variables, ,Program Variables}.
8993 @cindex @{@var{type}@}
8994 @cindex type casting memory
8995 @cindex memory, viewing as typed object
8996 @cindex casts, to view memory
8997 @item @{@var{type}@} @var{addr}
8998 Refers to an object of type @var{type} stored at address @var{addr} in
8999 memory. The address @var{addr} may be any expression whose value is
9000 an integer or pointer (but parentheses are required around binary
9001 operators, just as in a cast). This construct is allowed regardless
9002 of what kind of data is normally supposed to reside at @var{addr}.
9005 @node Ambiguous Expressions
9006 @section Ambiguous Expressions
9007 @cindex ambiguous expressions
9009 Expressions can sometimes contain some ambiguous elements. For instance,
9010 some programming languages (notably Ada, C@t{++} and Objective-C) permit
9011 a single function name to be defined several times, for application in
9012 different contexts. This is called @dfn{overloading}. Another example
9013 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
9014 templates and is typically instantiated several times, resulting in
9015 the same function name being defined in different contexts.
9017 In some cases and depending on the language, it is possible to adjust
9018 the expression to remove the ambiguity. For instance in C@t{++}, you
9019 can specify the signature of the function you want to break on, as in
9020 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
9021 qualified name of your function often makes the expression unambiguous
9024 When an ambiguity that needs to be resolved is detected, the debugger
9025 has the capability to display a menu of numbered choices for each
9026 possibility, and then waits for the selection with the prompt @samp{>}.
9027 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
9028 aborts the current command. If the command in which the expression was
9029 used allows more than one choice to be selected, the next option in the
9030 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
9033 For example, the following session excerpt shows an attempt to set a
9034 breakpoint at the overloaded symbol @code{String::after}.
9035 We choose three particular definitions of that function name:
9037 @c FIXME! This is likely to change to show arg type lists, at least
9040 (@value{GDBP}) b String::after
9043 [2] file:String.cc; line number:867
9044 [3] file:String.cc; line number:860
9045 [4] file:String.cc; line number:875
9046 [5] file:String.cc; line number:853
9047 [6] file:String.cc; line number:846
9048 [7] file:String.cc; line number:735
9050 Breakpoint 1 at 0xb26c: file String.cc, line 867.
9051 Breakpoint 2 at 0xb344: file String.cc, line 875.
9052 Breakpoint 3 at 0xafcc: file String.cc, line 846.
9053 Multiple breakpoints were set.
9054 Use the "delete" command to delete unwanted
9061 @kindex set multiple-symbols
9062 @item set multiple-symbols @var{mode}
9063 @cindex multiple-symbols menu
9065 This option allows you to adjust the debugger behavior when an expression
9068 By default, @var{mode} is set to @code{all}. If the command with which
9069 the expression is used allows more than one choice, then @value{GDBN}
9070 automatically selects all possible choices. For instance, inserting
9071 a breakpoint on a function using an ambiguous name results in a breakpoint
9072 inserted on each possible match. However, if a unique choice must be made,
9073 then @value{GDBN} uses the menu to help you disambiguate the expression.
9074 For instance, printing the address of an overloaded function will result
9075 in the use of the menu.
9077 When @var{mode} is set to @code{ask}, the debugger always uses the menu
9078 when an ambiguity is detected.
9080 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
9081 an error due to the ambiguity and the command is aborted.
9083 @kindex show multiple-symbols
9084 @item show multiple-symbols
9085 Show the current value of the @code{multiple-symbols} setting.
9089 @section Program Variables
9091 The most common kind of expression to use is the name of a variable
9094 Variables in expressions are understood in the selected stack frame
9095 (@pxref{Selection, ,Selecting a Frame}); they must be either:
9099 global (or file-static)
9106 visible according to the scope rules of the
9107 programming language from the point of execution in that frame
9110 @noindent This means that in the function
9125 you can examine and use the variable @code{a} whenever your program is
9126 executing within the function @code{foo}, but you can only use or
9127 examine the variable @code{b} while your program is executing inside
9128 the block where @code{b} is declared.
9130 @cindex variable name conflict
9131 There is an exception: you can refer to a variable or function whose
9132 scope is a single source file even if the current execution point is not
9133 in this file. But it is possible to have more than one such variable or
9134 function with the same name (in different source files). If that
9135 happens, referring to that name has unpredictable effects. If you wish,
9136 you can specify a static variable in a particular function or file by
9137 using the colon-colon (@code{::}) notation:
9139 @cindex colon-colon, context for variables/functions
9141 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
9142 @cindex @code{::}, context for variables/functions
9145 @var{file}::@var{variable}
9146 @var{function}::@var{variable}
9150 Here @var{file} or @var{function} is the name of the context for the
9151 static @var{variable}. In the case of file names, you can use quotes to
9152 make sure @value{GDBN} parses the file name as a single word---for example,
9153 to print a global value of @code{x} defined in @file{f2.c}:
9156 (@value{GDBP}) p 'f2.c'::x
9159 The @code{::} notation is normally used for referring to
9160 static variables, since you typically disambiguate uses of local variables
9161 in functions by selecting the appropriate frame and using the
9162 simple name of the variable. However, you may also use this notation
9163 to refer to local variables in frames enclosing the selected frame:
9172 process (a); /* Stop here */
9183 For example, if there is a breakpoint at the commented line,
9184 here is what you might see
9185 when the program stops after executing the call @code{bar(0)}:
9190 (@value{GDBP}) p bar::a
9193 #2 0x080483d0 in foo (a=5) at foobar.c:12
9196 (@value{GDBP}) p bar::a
9200 @cindex C@t{++} scope resolution
9201 These uses of @samp{::} are very rarely in conflict with the very
9202 similar use of the same notation in C@t{++}. When they are in
9203 conflict, the C@t{++} meaning takes precedence; however, this can be
9204 overridden by quoting the file or function name with single quotes.
9206 For example, suppose the program is stopped in a method of a class
9207 that has a field named @code{includefile}, and there is also an
9208 include file named @file{includefile} that defines a variable,
9212 (@value{GDBP}) p includefile
9214 (@value{GDBP}) p includefile::some_global
9215 A syntax error in expression, near `'.
9216 (@value{GDBP}) p 'includefile'::some_global
9220 @cindex wrong values
9221 @cindex variable values, wrong
9222 @cindex function entry/exit, wrong values of variables
9223 @cindex optimized code, wrong values of variables
9225 @emph{Warning:} Occasionally, a local variable may appear to have the
9226 wrong value at certain points in a function---just after entry to a new
9227 scope, and just before exit.
9229 You may see this problem when you are stepping by machine instructions.
9230 This is because, on most machines, it takes more than one instruction to
9231 set up a stack frame (including local variable definitions); if you are
9232 stepping by machine instructions, variables may appear to have the wrong
9233 values until the stack frame is completely built. On exit, it usually
9234 also takes more than one machine instruction to destroy a stack frame;
9235 after you begin stepping through that group of instructions, local
9236 variable definitions may be gone.
9238 This may also happen when the compiler does significant optimizations.
9239 To be sure of always seeing accurate values, turn off all optimization
9242 @cindex ``No symbol "foo" in current context''
9243 Another possible effect of compiler optimizations is to optimize
9244 unused variables out of existence, or assign variables to registers (as
9245 opposed to memory addresses). Depending on the support for such cases
9246 offered by the debug info format used by the compiler, @value{GDBN}
9247 might not be able to display values for such local variables. If that
9248 happens, @value{GDBN} will print a message like this:
9251 No symbol "foo" in current context.
9254 To solve such problems, either recompile without optimizations, or use a
9255 different debug info format, if the compiler supports several such
9256 formats. @xref{Compilation}, for more information on choosing compiler
9257 options. @xref{C, ,C and C@t{++}}, for more information about debug
9258 info formats that are best suited to C@t{++} programs.
9260 If you ask to print an object whose contents are unknown to
9261 @value{GDBN}, e.g., because its data type is not completely specified
9262 by the debug information, @value{GDBN} will say @samp{<incomplete
9263 type>}. @xref{Symbols, incomplete type}, for more about this.
9265 @cindex no debug info variables
9266 If you try to examine or use the value of a (global) variable for
9267 which @value{GDBN} has no type information, e.g., because the program
9268 includes no debug information, @value{GDBN} displays an error message.
9269 @xref{Symbols, unknown type}, for more about unknown types. If you
9270 cast the variable to its declared type, @value{GDBN} gets the
9271 variable's value using the cast-to type as the variable's type. For
9272 example, in a C program:
9275 (@value{GDBP}) p var
9276 'var' has unknown type; cast it to its declared type
9277 (@value{GDBP}) p (float) var
9281 If you append @kbd{@@entry} string to a function parameter name you get its
9282 value at the time the function got called. If the value is not available an
9283 error message is printed. Entry values are available only with some compilers.
9284 Entry values are normally also printed at the function parameter list according
9285 to @ref{set print entry-values}.
9288 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
9294 (gdb) print i@@entry
9298 Strings are identified as arrays of @code{char} values without specified
9299 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
9300 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
9301 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
9302 defines literal string type @code{"char"} as @code{char} without a sign.
9307 signed char var1[] = "A";
9310 You get during debugging
9315 $2 = @{65 'A', 0 '\0'@}
9319 @section Artificial Arrays
9321 @cindex artificial array
9323 @kindex @@@r{, referencing memory as an array}
9324 It is often useful to print out several successive objects of the
9325 same type in memory; a section of an array, or an array of
9326 dynamically determined size for which only a pointer exists in the
9329 You can do this by referring to a contiguous span of memory as an
9330 @dfn{artificial array}, using the binary operator @samp{@@}. The left
9331 operand of @samp{@@} should be the first element of the desired array
9332 and be an individual object. The right operand should be the desired length
9333 of the array. The result is an array value whose elements are all of
9334 the type of the left argument. The first element is actually the left
9335 argument; the second element comes from bytes of memory immediately
9336 following those that hold the first element, and so on. Here is an
9337 example. If a program says
9340 int *array = (int *) malloc (len * sizeof (int));
9344 you can print the contents of @code{array} with
9350 The left operand of @samp{@@} must reside in memory. Array values made
9351 with @samp{@@} in this way behave just like other arrays in terms of
9352 subscripting, and are coerced to pointers when used in expressions.
9353 Artificial arrays most often appear in expressions via the value history
9354 (@pxref{Value History, ,Value History}), after printing one out.
9356 Another way to create an artificial array is to use a cast.
9357 This re-interprets a value as if it were an array.
9358 The value need not be in memory:
9360 (@value{GDBP}) p/x (short[2])0x12345678
9361 $1 = @{0x1234, 0x5678@}
9364 As a convenience, if you leave the array length out (as in
9365 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
9366 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
9368 (@value{GDBP}) p/x (short[])0x12345678
9369 $2 = @{0x1234, 0x5678@}
9372 Sometimes the artificial array mechanism is not quite enough; in
9373 moderately complex data structures, the elements of interest may not
9374 actually be adjacent---for example, if you are interested in the values
9375 of pointers in an array. One useful work-around in this situation is
9376 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
9377 Variables}) as a counter in an expression that prints the first
9378 interesting value, and then repeat that expression via @key{RET}. For
9379 instance, suppose you have an array @code{dtab} of pointers to
9380 structures, and you are interested in the values of a field @code{fv}
9381 in each structure. Here is an example of what you might type:
9391 @node Output Formats
9392 @section Output Formats
9394 @cindex formatted output
9395 @cindex output formats
9396 By default, @value{GDBN} prints a value according to its data type. Sometimes
9397 this is not what you want. For example, you might want to print a number
9398 in hex, or a pointer in decimal. Or you might want to view data in memory
9399 at a certain address as a character string or as an instruction. To do
9400 these things, specify an @dfn{output format} when you print a value.
9402 The simplest use of output formats is to say how to print a value
9403 already computed. This is done by starting the arguments of the
9404 @code{print} command with a slash and a format letter. The format
9405 letters supported are:
9409 Regard the bits of the value as an integer, and print the integer in
9413 Print as integer in signed decimal.
9416 Print as integer in unsigned decimal.
9419 Print as integer in octal.
9422 Print as integer in binary. The letter @samp{t} stands for ``two''.
9423 @footnote{@samp{b} cannot be used because these format letters are also
9424 used with the @code{x} command, where @samp{b} stands for ``byte'';
9425 see @ref{Memory,,Examining Memory}.}
9428 @cindex unknown address, locating
9429 @cindex locate address
9430 Print as an address, both absolute in hexadecimal and as an offset from
9431 the nearest preceding symbol. You can use this format used to discover
9432 where (in what function) an unknown address is located:
9435 (@value{GDBP}) p/a 0x54320
9436 $3 = 0x54320 <_initialize_vx+396>
9440 The command @code{info symbol 0x54320} yields similar results.
9441 @xref{Symbols, info symbol}.
9444 Regard as an integer and print it as a character constant. This
9445 prints both the numerical value and its character representation. The
9446 character representation is replaced with the octal escape @samp{\nnn}
9447 for characters outside the 7-bit @sc{ascii} range.
9449 Without this format, @value{GDBN} displays @code{char},
9450 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
9451 constants. Single-byte members of vectors are displayed as integer
9455 Regard the bits of the value as a floating point number and print
9456 using typical floating point syntax.
9459 @cindex printing strings
9460 @cindex printing byte arrays
9461 Regard as a string, if possible. With this format, pointers to single-byte
9462 data are displayed as null-terminated strings and arrays of single-byte data
9463 are displayed as fixed-length strings. Other values are displayed in their
9466 Without this format, @value{GDBN} displays pointers to and arrays of
9467 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
9468 strings. Single-byte members of a vector are displayed as an integer
9472 Like @samp{x} formatting, the value is treated as an integer and
9473 printed as hexadecimal, but leading zeros are printed to pad the value
9474 to the size of the integer type.
9477 @cindex raw printing
9478 Print using the @samp{raw} formatting. By default, @value{GDBN} will
9479 use a Python-based pretty-printer, if one is available (@pxref{Pretty
9480 Printing}). This typically results in a higher-level display of the
9481 value's contents. The @samp{r} format bypasses any Python
9482 pretty-printer which might exist.
9485 For example, to print the program counter in hex (@pxref{Registers}), type
9492 Note that no space is required before the slash; this is because command
9493 names in @value{GDBN} cannot contain a slash.
9495 To reprint the last value in the value history with a different format,
9496 you can use the @code{print} command with just a format and no
9497 expression. For example, @samp{p/x} reprints the last value in hex.
9500 @section Examining Memory
9502 You can use the command @code{x} (for ``examine'') to examine memory in
9503 any of several formats, independently of your program's data types.
9505 @cindex examining memory
9507 @kindex x @r{(examine memory)}
9508 @item x/@var{nfu} @var{addr}
9511 Use the @code{x} command to examine memory.
9514 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
9515 much memory to display and how to format it; @var{addr} is an
9516 expression giving the address where you want to start displaying memory.
9517 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
9518 Several commands set convenient defaults for @var{addr}.
9521 @item @var{n}, the repeat count
9522 The repeat count is a decimal integer; the default is 1. It specifies
9523 how much memory (counting by units @var{u}) to display. If a negative
9524 number is specified, memory is examined backward from @var{addr}.
9525 @c This really is **decimal**; unaffected by 'set radix' as of GDB
9528 @item @var{f}, the display format
9529 The display format is one of the formats used by @code{print}
9530 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
9531 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
9532 The default is @samp{x} (hexadecimal) initially. The default changes
9533 each time you use either @code{x} or @code{print}.
9535 @item @var{u}, the unit size
9536 The unit size is any of
9542 Halfwords (two bytes).
9544 Words (four bytes). This is the initial default.
9546 Giant words (eight bytes).
9549 Each time you specify a unit size with @code{x}, that size becomes the
9550 default unit the next time you use @code{x}. For the @samp{i} format,
9551 the unit size is ignored and is normally not written. For the @samp{s} format,
9552 the unit size defaults to @samp{b}, unless it is explicitly given.
9553 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
9554 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
9555 Note that the results depend on the programming language of the
9556 current compilation unit. If the language is C, the @samp{s}
9557 modifier will use the UTF-16 encoding while @samp{w} will use
9558 UTF-32. The encoding is set by the programming language and cannot
9561 @item @var{addr}, starting display address
9562 @var{addr} is the address where you want @value{GDBN} to begin displaying
9563 memory. The expression need not have a pointer value (though it may);
9564 it is always interpreted as an integer address of a byte of memory.
9565 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
9566 @var{addr} is usually just after the last address examined---but several
9567 other commands also set the default address: @code{info breakpoints} (to
9568 the address of the last breakpoint listed), @code{info line} (to the
9569 starting address of a line), and @code{print} (if you use it to display
9570 a value from memory).
9573 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
9574 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
9575 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
9576 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
9577 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
9579 You can also specify a negative repeat count to examine memory backward
9580 from the given address. For example, @samp{x/-3uh 0x54320} prints three
9581 halfwords (@code{h}) at @code{0x54314}, @code{0x54328}, and @code{0x5431c}.
9583 Since the letters indicating unit sizes are all distinct from the
9584 letters specifying output formats, you do not have to remember whether
9585 unit size or format comes first; either order works. The output
9586 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
9587 (However, the count @var{n} must come first; @samp{wx4} does not work.)
9589 Even though the unit size @var{u} is ignored for the formats @samp{s}
9590 and @samp{i}, you might still want to use a count @var{n}; for example,
9591 @samp{3i} specifies that you want to see three machine instructions,
9592 including any operands. For convenience, especially when used with
9593 the @code{display} command, the @samp{i} format also prints branch delay
9594 slot instructions, if any, beyond the count specified, which immediately
9595 follow the last instruction that is within the count. The command
9596 @code{disassemble} gives an alternative way of inspecting machine
9597 instructions; see @ref{Machine Code,,Source and Machine Code}.
9599 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
9600 the command displays null-terminated strings or instructions before the given
9601 address as many as the absolute value of the given number. For the @samp{i}
9602 format, we use line number information in the debug info to accurately locate
9603 instruction boundaries while disassembling backward. If line info is not
9604 available, the command stops examining memory with an error message.
9606 All the defaults for the arguments to @code{x} are designed to make it
9607 easy to continue scanning memory with minimal specifications each time
9608 you use @code{x}. For example, after you have inspected three machine
9609 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
9610 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
9611 the repeat count @var{n} is used again; the other arguments default as
9612 for successive uses of @code{x}.
9614 When examining machine instructions, the instruction at current program
9615 counter is shown with a @code{=>} marker. For example:
9618 (@value{GDBP}) x/5i $pc-6
9619 0x804837f <main+11>: mov %esp,%ebp
9620 0x8048381 <main+13>: push %ecx
9621 0x8048382 <main+14>: sub $0x4,%esp
9622 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
9623 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
9626 @cindex @code{$_}, @code{$__}, and value history
9627 The addresses and contents printed by the @code{x} command are not saved
9628 in the value history because there is often too much of them and they
9629 would get in the way. Instead, @value{GDBN} makes these values available for
9630 subsequent use in expressions as values of the convenience variables
9631 @code{$_} and @code{$__}. After an @code{x} command, the last address
9632 examined is available for use in expressions in the convenience variable
9633 @code{$_}. The contents of that address, as examined, are available in
9634 the convenience variable @code{$__}.
9636 If the @code{x} command has a repeat count, the address and contents saved
9637 are from the last memory unit printed; this is not the same as the last
9638 address printed if several units were printed on the last line of output.
9640 @anchor{addressable memory unit}
9641 @cindex addressable memory unit
9642 Most targets have an addressable memory unit size of 8 bits. This means
9643 that to each memory address are associated 8 bits of data. Some
9644 targets, however, have other addressable memory unit sizes.
9645 Within @value{GDBN} and this document, the term
9646 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
9647 when explicitly referring to a chunk of data of that size. The word
9648 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
9649 the addressable memory unit size of the target. For most systems,
9650 addressable memory unit is a synonym of byte.
9652 @cindex remote memory comparison
9653 @cindex target memory comparison
9654 @cindex verify remote memory image
9655 @cindex verify target memory image
9656 When you are debugging a program running on a remote target machine
9657 (@pxref{Remote Debugging}), you may wish to verify the program's image
9658 in the remote machine's memory against the executable file you
9659 downloaded to the target. Or, on any target, you may want to check
9660 whether the program has corrupted its own read-only sections. The
9661 @code{compare-sections} command is provided for such situations.
9664 @kindex compare-sections
9665 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
9666 Compare the data of a loadable section @var{section-name} in the
9667 executable file of the program being debugged with the same section in
9668 the target machine's memory, and report any mismatches. With no
9669 arguments, compares all loadable sections. With an argument of
9670 @code{-r}, compares all loadable read-only sections.
9672 Note: for remote targets, this command can be accelerated if the
9673 target supports computing the CRC checksum of a block of memory
9674 (@pxref{qCRC packet}).
9678 @section Automatic Display
9679 @cindex automatic display
9680 @cindex display of expressions
9682 If you find that you want to print the value of an expression frequently
9683 (to see how it changes), you might want to add it to the @dfn{automatic
9684 display list} so that @value{GDBN} prints its value each time your program stops.
9685 Each expression added to the list is given a number to identify it;
9686 to remove an expression from the list, you specify that number.
9687 The automatic display looks like this:
9691 3: bar[5] = (struct hack *) 0x3804
9695 This display shows item numbers, expressions and their current values. As with
9696 displays you request manually using @code{x} or @code{print}, you can
9697 specify the output format you prefer; in fact, @code{display} decides
9698 whether to use @code{print} or @code{x} depending your format
9699 specification---it uses @code{x} if you specify either the @samp{i}
9700 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
9704 @item display @var{expr}
9705 Add the expression @var{expr} to the list of expressions to display
9706 each time your program stops. @xref{Expressions, ,Expressions}.
9708 @code{display} does not repeat if you press @key{RET} again after using it.
9710 @item display/@var{fmt} @var{expr}
9711 For @var{fmt} specifying only a display format and not a size or
9712 count, add the expression @var{expr} to the auto-display list but
9713 arrange to display it each time in the specified format @var{fmt}.
9714 @xref{Output Formats,,Output Formats}.
9716 @item display/@var{fmt} @var{addr}
9717 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
9718 number of units, add the expression @var{addr} as a memory address to
9719 be examined each time your program stops. Examining means in effect
9720 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
9723 For example, @samp{display/i $pc} can be helpful, to see the machine
9724 instruction about to be executed each time execution stops (@samp{$pc}
9725 is a common name for the program counter; @pxref{Registers, ,Registers}).
9728 @kindex delete display
9730 @item undisplay @var{dnums}@dots{}
9731 @itemx delete display @var{dnums}@dots{}
9732 Remove items from the list of expressions to display. Specify the
9733 numbers of the displays that you want affected with the command
9734 argument @var{dnums}. It can be a single display number, one of the
9735 numbers shown in the first field of the @samp{info display} display;
9736 or it could be a range of display numbers, as in @code{2-4}.
9738 @code{undisplay} does not repeat if you press @key{RET} after using it.
9739 (Otherwise you would just get the error @samp{No display number @dots{}}.)
9741 @kindex disable display
9742 @item disable display @var{dnums}@dots{}
9743 Disable the display of item numbers @var{dnums}. A disabled display
9744 item is not printed automatically, but is not forgotten. It may be
9745 enabled again later. Specify the numbers of the displays that you
9746 want affected with the command argument @var{dnums}. It can be a
9747 single display number, one of the numbers shown in the first field of
9748 the @samp{info display} display; or it could be a range of display
9749 numbers, as in @code{2-4}.
9751 @kindex enable display
9752 @item enable display @var{dnums}@dots{}
9753 Enable display of item numbers @var{dnums}. It becomes effective once
9754 again in auto display of its expression, until you specify otherwise.
9755 Specify the numbers of the displays that you want affected with the
9756 command argument @var{dnums}. It can be a single display number, one
9757 of the numbers shown in the first field of the @samp{info display}
9758 display; or it could be a range of display numbers, as in @code{2-4}.
9761 Display the current values of the expressions on the list, just as is
9762 done when your program stops.
9764 @kindex info display
9766 Print the list of expressions previously set up to display
9767 automatically, each one with its item number, but without showing the
9768 values. This includes disabled expressions, which are marked as such.
9769 It also includes expressions which would not be displayed right now
9770 because they refer to automatic variables not currently available.
9773 @cindex display disabled out of scope
9774 If a display expression refers to local variables, then it does not make
9775 sense outside the lexical context for which it was set up. Such an
9776 expression is disabled when execution enters a context where one of its
9777 variables is not defined. For example, if you give the command
9778 @code{display last_char} while inside a function with an argument
9779 @code{last_char}, @value{GDBN} displays this argument while your program
9780 continues to stop inside that function. When it stops elsewhere---where
9781 there is no variable @code{last_char}---the display is disabled
9782 automatically. The next time your program stops where @code{last_char}
9783 is meaningful, you can enable the display expression once again.
9785 @node Print Settings
9786 @section Print Settings
9788 @cindex format options
9789 @cindex print settings
9790 @value{GDBN} provides the following ways to control how arrays, structures,
9791 and symbols are printed.
9794 These settings are useful for debugging programs in any language:
9798 @item set print address
9799 @itemx set print address on
9800 @cindex print/don't print memory addresses
9801 @value{GDBN} prints memory addresses showing the location of stack
9802 traces, structure values, pointer values, breakpoints, and so forth,
9803 even when it also displays the contents of those addresses. The default
9804 is @code{on}. For example, this is what a stack frame display looks like with
9805 @code{set print address on}:
9810 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
9812 530 if (lquote != def_lquote)
9816 @item set print address off
9817 Do not print addresses when displaying their contents. For example,
9818 this is the same stack frame displayed with @code{set print address off}:
9822 (@value{GDBP}) set print addr off
9824 #0 set_quotes (lq="<<", rq=">>") at input.c:530
9825 530 if (lquote != def_lquote)
9829 You can use @samp{set print address off} to eliminate all machine
9830 dependent displays from the @value{GDBN} interface. For example, with
9831 @code{print address off}, you should get the same text for backtraces on
9832 all machines---whether or not they involve pointer arguments.
9835 @item show print address
9836 Show whether or not addresses are to be printed.
9839 When @value{GDBN} prints a symbolic address, it normally prints the
9840 closest earlier symbol plus an offset. If that symbol does not uniquely
9841 identify the address (for example, it is a name whose scope is a single
9842 source file), you may need to clarify. One way to do this is with
9843 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9844 you can set @value{GDBN} to print the source file and line number when
9845 it prints a symbolic address:
9848 @item set print symbol-filename on
9849 @cindex source file and line of a symbol
9850 @cindex symbol, source file and line
9851 Tell @value{GDBN} to print the source file name and line number of a
9852 symbol in the symbolic form of an address.
9854 @item set print symbol-filename off
9855 Do not print source file name and line number of a symbol. This is the
9858 @item show print symbol-filename
9859 Show whether or not @value{GDBN} will print the source file name and
9860 line number of a symbol in the symbolic form of an address.
9863 Another situation where it is helpful to show symbol filenames and line
9864 numbers is when disassembling code; @value{GDBN} shows you the line
9865 number and source file that corresponds to each instruction.
9867 Also, you may wish to see the symbolic form only if the address being
9868 printed is reasonably close to the closest earlier symbol:
9871 @item set print max-symbolic-offset @var{max-offset}
9872 @itemx set print max-symbolic-offset unlimited
9873 @cindex maximum value for offset of closest symbol
9874 Tell @value{GDBN} to only display the symbolic form of an address if the
9875 offset between the closest earlier symbol and the address is less than
9876 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9877 to always print the symbolic form of an address if any symbol precedes
9878 it. Zero is equivalent to @code{unlimited}.
9880 @item show print max-symbolic-offset
9881 Ask how large the maximum offset is that @value{GDBN} prints in a
9885 @cindex wild pointer, interpreting
9886 @cindex pointer, finding referent
9887 If you have a pointer and you are not sure where it points, try
9888 @samp{set print symbol-filename on}. Then you can determine the name
9889 and source file location of the variable where it points, using
9890 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9891 For example, here @value{GDBN} shows that a variable @code{ptt} points
9892 at another variable @code{t}, defined in @file{hi2.c}:
9895 (@value{GDBP}) set print symbol-filename on
9896 (@value{GDBP}) p/a ptt
9897 $4 = 0xe008 <t in hi2.c>
9901 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9902 does not show the symbol name and filename of the referent, even with
9903 the appropriate @code{set print} options turned on.
9906 You can also enable @samp{/a}-like formatting all the time using
9907 @samp{set print symbol on}:
9910 @item set print symbol on
9911 Tell @value{GDBN} to print the symbol corresponding to an address, if
9914 @item set print symbol off
9915 Tell @value{GDBN} not to print the symbol corresponding to an
9916 address. In this mode, @value{GDBN} will still print the symbol
9917 corresponding to pointers to functions. This is the default.
9919 @item show print symbol
9920 Show whether @value{GDBN} will display the symbol corresponding to an
9924 Other settings control how different kinds of objects are printed:
9927 @item set print array
9928 @itemx set print array on
9929 @cindex pretty print arrays
9930 Pretty print arrays. This format is more convenient to read,
9931 but uses more space. The default is off.
9933 @item set print array off
9934 Return to compressed format for arrays.
9936 @item show print array
9937 Show whether compressed or pretty format is selected for displaying
9940 @cindex print array indexes
9941 @item set print array-indexes
9942 @itemx set print array-indexes on
9943 Print the index of each element when displaying arrays. May be more
9944 convenient to locate a given element in the array or quickly find the
9945 index of a given element in that printed array. The default is off.
9947 @item set print array-indexes off
9948 Stop printing element indexes when displaying arrays.
9950 @item show print array-indexes
9951 Show whether the index of each element is printed when displaying
9954 @item set print elements @var{number-of-elements}
9955 @itemx set print elements unlimited
9956 @cindex number of array elements to print
9957 @cindex limit on number of printed array elements
9958 Set a limit on how many elements of an array @value{GDBN} will print.
9959 If @value{GDBN} is printing a large array, it stops printing after it has
9960 printed the number of elements set by the @code{set print elements} command.
9961 This limit also applies to the display of strings.
9962 When @value{GDBN} starts, this limit is set to 200.
9963 Setting @var{number-of-elements} to @code{unlimited} or zero means
9964 that the number of elements to print is unlimited.
9966 @item show print elements
9967 Display the number of elements of a large array that @value{GDBN} will print.
9968 If the number is 0, then the printing is unlimited.
9970 @item set print frame-arguments @var{value}
9971 @kindex set print frame-arguments
9972 @cindex printing frame argument values
9973 @cindex print all frame argument values
9974 @cindex print frame argument values for scalars only
9975 @cindex do not print frame argument values
9976 This command allows to control how the values of arguments are printed
9977 when the debugger prints a frame (@pxref{Frames}). The possible
9982 The values of all arguments are printed.
9985 Print the value of an argument only if it is a scalar. The value of more
9986 complex arguments such as arrays, structures, unions, etc, is replaced
9987 by @code{@dots{}}. This is the default. Here is an example where
9988 only scalar arguments are shown:
9991 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9996 None of the argument values are printed. Instead, the value of each argument
9997 is replaced by @code{@dots{}}. In this case, the example above now becomes:
10000 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
10005 By default, only scalar arguments are printed. This command can be used
10006 to configure the debugger to print the value of all arguments, regardless
10007 of their type. However, it is often advantageous to not print the value
10008 of more complex parameters. For instance, it reduces the amount of
10009 information printed in each frame, making the backtrace more readable.
10010 Also, it improves performance when displaying Ada frames, because
10011 the computation of large arguments can sometimes be CPU-intensive,
10012 especially in large applications. Setting @code{print frame-arguments}
10013 to @code{scalars} (the default) or @code{none} avoids this computation,
10014 thus speeding up the display of each Ada frame.
10016 @item show print frame-arguments
10017 Show how the value of arguments should be displayed when printing a frame.
10019 @item set print raw frame-arguments on
10020 Print frame arguments in raw, non pretty-printed, form.
10022 @item set print raw frame-arguments off
10023 Print frame arguments in pretty-printed form, if there is a pretty-printer
10024 for the value (@pxref{Pretty Printing}),
10025 otherwise print the value in raw form.
10026 This is the default.
10028 @item show print raw frame-arguments
10029 Show whether to print frame arguments in raw form.
10031 @anchor{set print entry-values}
10032 @item set print entry-values @var{value}
10033 @kindex set print entry-values
10034 Set printing of frame argument values at function entry. In some cases
10035 @value{GDBN} can determine the value of function argument which was passed by
10036 the function caller, even if the value was modified inside the called function
10037 and therefore is different. With optimized code, the current value could be
10038 unavailable, but the entry value may still be known.
10040 The default value is @code{default} (see below for its description). Older
10041 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
10042 this feature will behave in the @code{default} setting the same way as with the
10045 This functionality is currently supported only by DWARF 2 debugging format and
10046 the compiler has to produce @samp{DW_TAG_call_site} tags. With
10047 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10050 The @var{value} parameter can be one of the following:
10054 Print only actual parameter values, never print values from function entry
10058 #0 different (val=6)
10059 #0 lost (val=<optimized out>)
10061 #0 invalid (val=<optimized out>)
10065 Print only parameter values from function entry point. The actual parameter
10066 values are never printed.
10068 #0 equal (val@@entry=5)
10069 #0 different (val@@entry=5)
10070 #0 lost (val@@entry=5)
10071 #0 born (val@@entry=<optimized out>)
10072 #0 invalid (val@@entry=<optimized out>)
10076 Print only parameter values from function entry point. If value from function
10077 entry point is not known while the actual value is known, print the actual
10078 value for such parameter.
10080 #0 equal (val@@entry=5)
10081 #0 different (val@@entry=5)
10082 #0 lost (val@@entry=5)
10084 #0 invalid (val@@entry=<optimized out>)
10088 Print actual parameter values. If actual parameter value is not known while
10089 value from function entry point is known, print the entry point value for such
10093 #0 different (val=6)
10094 #0 lost (val@@entry=5)
10096 #0 invalid (val=<optimized out>)
10100 Always print both the actual parameter value and its value from function entry
10101 point, even if values of one or both are not available due to compiler
10104 #0 equal (val=5, val@@entry=5)
10105 #0 different (val=6, val@@entry=5)
10106 #0 lost (val=<optimized out>, val@@entry=5)
10107 #0 born (val=10, val@@entry=<optimized out>)
10108 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
10112 Print the actual parameter value if it is known and also its value from
10113 function entry point if it is known. If neither is known, print for the actual
10114 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
10115 values are known and identical, print the shortened
10116 @code{param=param@@entry=VALUE} notation.
10118 #0 equal (val=val@@entry=5)
10119 #0 different (val=6, val@@entry=5)
10120 #0 lost (val@@entry=5)
10122 #0 invalid (val=<optimized out>)
10126 Always print the actual parameter value. Print also its value from function
10127 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
10128 if both values are known and identical, print the shortened
10129 @code{param=param@@entry=VALUE} notation.
10131 #0 equal (val=val@@entry=5)
10132 #0 different (val=6, val@@entry=5)
10133 #0 lost (val=<optimized out>, val@@entry=5)
10135 #0 invalid (val=<optimized out>)
10139 For analysis messages on possible failures of frame argument values at function
10140 entry resolution see @ref{set debug entry-values}.
10142 @item show print entry-values
10143 Show the method being used for printing of frame argument values at function
10146 @item set print repeats @var{number-of-repeats}
10147 @itemx set print repeats unlimited
10148 @cindex repeated array elements
10149 Set the threshold for suppressing display of repeated array
10150 elements. When the number of consecutive identical elements of an
10151 array exceeds the threshold, @value{GDBN} prints the string
10152 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
10153 identical repetitions, instead of displaying the identical elements
10154 themselves. Setting the threshold to @code{unlimited} or zero will
10155 cause all elements to be individually printed. The default threshold
10158 @item show print repeats
10159 Display the current threshold for printing repeated identical
10162 @item set print null-stop
10163 @cindex @sc{null} elements in arrays
10164 Cause @value{GDBN} to stop printing the characters of an array when the first
10165 @sc{null} is encountered. This is useful when large arrays actually
10166 contain only short strings.
10167 The default is off.
10169 @item show print null-stop
10170 Show whether @value{GDBN} stops printing an array on the first
10171 @sc{null} character.
10173 @item set print pretty on
10174 @cindex print structures in indented form
10175 @cindex indentation in structure display
10176 Cause @value{GDBN} to print structures in an indented format with one member
10177 per line, like this:
10192 @item set print pretty off
10193 Cause @value{GDBN} to print structures in a compact format, like this:
10197 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
10198 meat = 0x54 "Pork"@}
10203 This is the default format.
10205 @item show print pretty
10206 Show which format @value{GDBN} is using to print structures.
10208 @item set print sevenbit-strings on
10209 @cindex eight-bit characters in strings
10210 @cindex octal escapes in strings
10211 Print using only seven-bit characters; if this option is set,
10212 @value{GDBN} displays any eight-bit characters (in strings or
10213 character values) using the notation @code{\}@var{nnn}. This setting is
10214 best if you are working in English (@sc{ascii}) and you use the
10215 high-order bit of characters as a marker or ``meta'' bit.
10217 @item set print sevenbit-strings off
10218 Print full eight-bit characters. This allows the use of more
10219 international character sets, and is the default.
10221 @item show print sevenbit-strings
10222 Show whether or not @value{GDBN} is printing only seven-bit characters.
10224 @item set print union on
10225 @cindex unions in structures, printing
10226 Tell @value{GDBN} to print unions which are contained in structures
10227 and other unions. This is the default setting.
10229 @item set print union off
10230 Tell @value{GDBN} not to print unions which are contained in
10231 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
10234 @item show print union
10235 Ask @value{GDBN} whether or not it will print unions which are contained in
10236 structures and other unions.
10238 For example, given the declarations
10241 typedef enum @{Tree, Bug@} Species;
10242 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
10243 typedef enum @{Caterpillar, Cocoon, Butterfly@}
10254 struct thing foo = @{Tree, @{Acorn@}@};
10258 with @code{set print union on} in effect @samp{p foo} would print
10261 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
10265 and with @code{set print union off} in effect it would print
10268 $1 = @{it = Tree, form = @{...@}@}
10272 @code{set print union} affects programs written in C-like languages
10278 These settings are of interest when debugging C@t{++} programs:
10281 @cindex demangling C@t{++} names
10282 @item set print demangle
10283 @itemx set print demangle on
10284 Print C@t{++} names in their source form rather than in the encoded
10285 (``mangled'') form passed to the assembler and linker for type-safe
10286 linkage. The default is on.
10288 @item show print demangle
10289 Show whether C@t{++} names are printed in mangled or demangled form.
10291 @item set print asm-demangle
10292 @itemx set print asm-demangle on
10293 Print C@t{++} names in their source form rather than their mangled form, even
10294 in assembler code printouts such as instruction disassemblies.
10295 The default is off.
10297 @item show print asm-demangle
10298 Show whether C@t{++} names in assembly listings are printed in mangled
10301 @cindex C@t{++} symbol decoding style
10302 @cindex symbol decoding style, C@t{++}
10303 @kindex set demangle-style
10304 @item set demangle-style @var{style}
10305 Choose among several encoding schemes used by different compilers to
10306 represent C@t{++} names. The choices for @var{style} are currently:
10310 Allow @value{GDBN} to choose a decoding style by inspecting your program.
10311 This is the default.
10314 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
10317 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
10320 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
10323 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
10324 @strong{Warning:} this setting alone is not sufficient to allow
10325 debugging @code{cfront}-generated executables. @value{GDBN} would
10326 require further enhancement to permit that.
10329 If you omit @var{style}, you will see a list of possible formats.
10331 @item show demangle-style
10332 Display the encoding style currently in use for decoding C@t{++} symbols.
10334 @item set print object
10335 @itemx set print object on
10336 @cindex derived type of an object, printing
10337 @cindex display derived types
10338 When displaying a pointer to an object, identify the @emph{actual}
10339 (derived) type of the object rather than the @emph{declared} type, using
10340 the virtual function table. Note that the virtual function table is
10341 required---this feature can only work for objects that have run-time
10342 type identification; a single virtual method in the object's declared
10343 type is sufficient. Note that this setting is also taken into account when
10344 working with variable objects via MI (@pxref{GDB/MI}).
10346 @item set print object off
10347 Display only the declared type of objects, without reference to the
10348 virtual function table. This is the default setting.
10350 @item show print object
10351 Show whether actual, or declared, object types are displayed.
10353 @item set print static-members
10354 @itemx set print static-members on
10355 @cindex static members of C@t{++} objects
10356 Print static members when displaying a C@t{++} object. The default is on.
10358 @item set print static-members off
10359 Do not print static members when displaying a C@t{++} object.
10361 @item show print static-members
10362 Show whether C@t{++} static members are printed or not.
10364 @item set print pascal_static-members
10365 @itemx set print pascal_static-members on
10366 @cindex static members of Pascal objects
10367 @cindex Pascal objects, static members display
10368 Print static members when displaying a Pascal object. The default is on.
10370 @item set print pascal_static-members off
10371 Do not print static members when displaying a Pascal object.
10373 @item show print pascal_static-members
10374 Show whether Pascal static members are printed or not.
10376 @c These don't work with HP ANSI C++ yet.
10377 @item set print vtbl
10378 @itemx set print vtbl on
10379 @cindex pretty print C@t{++} virtual function tables
10380 @cindex virtual functions (C@t{++}) display
10381 @cindex VTBL display
10382 Pretty print C@t{++} virtual function tables. The default is off.
10383 (The @code{vtbl} commands do not work on programs compiled with the HP
10384 ANSI C@t{++} compiler (@code{aCC}).)
10386 @item set print vtbl off
10387 Do not pretty print C@t{++} virtual function tables.
10389 @item show print vtbl
10390 Show whether C@t{++} virtual function tables are pretty printed, or not.
10393 @node Pretty Printing
10394 @section Pretty Printing
10396 @value{GDBN} provides a mechanism to allow pretty-printing of values using
10397 Python code. It greatly simplifies the display of complex objects. This
10398 mechanism works for both MI and the CLI.
10401 * Pretty-Printer Introduction:: Introduction to pretty-printers
10402 * Pretty-Printer Example:: An example pretty-printer
10403 * Pretty-Printer Commands:: Pretty-printer commands
10406 @node Pretty-Printer Introduction
10407 @subsection Pretty-Printer Introduction
10409 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
10410 registered for the value. If there is then @value{GDBN} invokes the
10411 pretty-printer to print the value. Otherwise the value is printed normally.
10413 Pretty-printers are normally named. This makes them easy to manage.
10414 The @samp{info pretty-printer} command will list all the installed
10415 pretty-printers with their names.
10416 If a pretty-printer can handle multiple data types, then its
10417 @dfn{subprinters} are the printers for the individual data types.
10418 Each such subprinter has its own name.
10419 The format of the name is @var{printer-name};@var{subprinter-name}.
10421 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
10422 Typically they are automatically loaded and registered when the corresponding
10423 debug information is loaded, thus making them available without having to
10424 do anything special.
10426 There are three places where a pretty-printer can be registered.
10430 Pretty-printers registered globally are available when debugging
10434 Pretty-printers registered with a program space are available only
10435 when debugging that program.
10436 @xref{Progspaces In Python}, for more details on program spaces in Python.
10439 Pretty-printers registered with an objfile are loaded and unloaded
10440 with the corresponding objfile (e.g., shared library).
10441 @xref{Objfiles In Python}, for more details on objfiles in Python.
10444 @xref{Selecting Pretty-Printers}, for further information on how
10445 pretty-printers are selected,
10447 @xref{Writing a Pretty-Printer}, for implementing pretty printers
10450 @node Pretty-Printer Example
10451 @subsection Pretty-Printer Example
10453 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
10456 (@value{GDBP}) print s
10458 static npos = 4294967295,
10460 <std::allocator<char>> = @{
10461 <__gnu_cxx::new_allocator<char>> = @{
10462 <No data fields>@}, <No data fields>
10464 members of std::basic_string<char, std::char_traits<char>,
10465 std::allocator<char> >::_Alloc_hider:
10466 _M_p = 0x804a014 "abcd"
10471 With a pretty-printer for @code{std::string} only the contents are printed:
10474 (@value{GDBP}) print s
10478 @node Pretty-Printer Commands
10479 @subsection Pretty-Printer Commands
10480 @cindex pretty-printer commands
10483 @kindex info pretty-printer
10484 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10485 Print the list of installed pretty-printers.
10486 This includes disabled pretty-printers, which are marked as such.
10488 @var{object-regexp} is a regular expression matching the objects
10489 whose pretty-printers to list.
10490 Objects can be @code{global}, the program space's file
10491 (@pxref{Progspaces In Python}),
10492 and the object files within that program space (@pxref{Objfiles In Python}).
10493 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
10494 looks up a printer from these three objects.
10496 @var{name-regexp} is a regular expression matching the name of the printers
10499 @kindex disable pretty-printer
10500 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10501 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10502 A disabled pretty-printer is not forgotten, it may be enabled again later.
10504 @kindex enable pretty-printer
10505 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10506 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10511 Suppose we have three pretty-printers installed: one from library1.so
10512 named @code{foo} that prints objects of type @code{foo}, and
10513 another from library2.so named @code{bar} that prints two types of objects,
10514 @code{bar1} and @code{bar2}.
10517 (gdb) info pretty-printer
10524 (gdb) info pretty-printer library2
10529 (gdb) disable pretty-printer library1
10531 2 of 3 printers enabled
10532 (gdb) info pretty-printer
10539 (gdb) disable pretty-printer library2 bar:bar1
10541 1 of 3 printers enabled
10542 (gdb) info pretty-printer library2
10549 (gdb) disable pretty-printer library2 bar
10551 0 of 3 printers enabled
10552 (gdb) info pretty-printer library2
10561 Note that for @code{bar} the entire printer can be disabled,
10562 as can each individual subprinter.
10564 @node Value History
10565 @section Value History
10567 @cindex value history
10568 @cindex history of values printed by @value{GDBN}
10569 Values printed by the @code{print} command are saved in the @value{GDBN}
10570 @dfn{value history}. This allows you to refer to them in other expressions.
10571 Values are kept until the symbol table is re-read or discarded
10572 (for example with the @code{file} or @code{symbol-file} commands).
10573 When the symbol table changes, the value history is discarded,
10574 since the values may contain pointers back to the types defined in the
10579 @cindex history number
10580 The values printed are given @dfn{history numbers} by which you can
10581 refer to them. These are successive integers starting with one.
10582 @code{print} shows you the history number assigned to a value by
10583 printing @samp{$@var{num} = } before the value; here @var{num} is the
10586 To refer to any previous value, use @samp{$} followed by the value's
10587 history number. The way @code{print} labels its output is designed to
10588 remind you of this. Just @code{$} refers to the most recent value in
10589 the history, and @code{$$} refers to the value before that.
10590 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
10591 is the value just prior to @code{$$}, @code{$$1} is equivalent to
10592 @code{$$}, and @code{$$0} is equivalent to @code{$}.
10594 For example, suppose you have just printed a pointer to a structure and
10595 want to see the contents of the structure. It suffices to type
10601 If you have a chain of structures where the component @code{next} points
10602 to the next one, you can print the contents of the next one with this:
10609 You can print successive links in the chain by repeating this
10610 command---which you can do by just typing @key{RET}.
10612 Note that the history records values, not expressions. If the value of
10613 @code{x} is 4 and you type these commands:
10621 then the value recorded in the value history by the @code{print} command
10622 remains 4 even though the value of @code{x} has changed.
10625 @kindex show values
10627 Print the last ten values in the value history, with their item numbers.
10628 This is like @samp{p@ $$9} repeated ten times, except that @code{show
10629 values} does not change the history.
10631 @item show values @var{n}
10632 Print ten history values centered on history item number @var{n}.
10634 @item show values +
10635 Print ten history values just after the values last printed. If no more
10636 values are available, @code{show values +} produces no display.
10639 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
10640 same effect as @samp{show values +}.
10642 @node Convenience Vars
10643 @section Convenience Variables
10645 @cindex convenience variables
10646 @cindex user-defined variables
10647 @value{GDBN} provides @dfn{convenience variables} that you can use within
10648 @value{GDBN} to hold on to a value and refer to it later. These variables
10649 exist entirely within @value{GDBN}; they are not part of your program, and
10650 setting a convenience variable has no direct effect on further execution
10651 of your program. That is why you can use them freely.
10653 Convenience variables are prefixed with @samp{$}. Any name preceded by
10654 @samp{$} can be used for a convenience variable, unless it is one of
10655 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
10656 (Value history references, in contrast, are @emph{numbers} preceded
10657 by @samp{$}. @xref{Value History, ,Value History}.)
10659 You can save a value in a convenience variable with an assignment
10660 expression, just as you would set a variable in your program.
10664 set $foo = *object_ptr
10668 would save in @code{$foo} the value contained in the object pointed to by
10671 Using a convenience variable for the first time creates it, but its
10672 value is @code{void} until you assign a new value. You can alter the
10673 value with another assignment at any time.
10675 Convenience variables have no fixed types. You can assign a convenience
10676 variable any type of value, including structures and arrays, even if
10677 that variable already has a value of a different type. The convenience
10678 variable, when used as an expression, has the type of its current value.
10681 @kindex show convenience
10682 @cindex show all user variables and functions
10683 @item show convenience
10684 Print a list of convenience variables used so far, and their values,
10685 as well as a list of the convenience functions.
10686 Abbreviated @code{show conv}.
10688 @kindex init-if-undefined
10689 @cindex convenience variables, initializing
10690 @item init-if-undefined $@var{variable} = @var{expression}
10691 Set a convenience variable if it has not already been set. This is useful
10692 for user-defined commands that keep some state. It is similar, in concept,
10693 to using local static variables with initializers in C (except that
10694 convenience variables are global). It can also be used to allow users to
10695 override default values used in a command script.
10697 If the variable is already defined then the expression is not evaluated so
10698 any side-effects do not occur.
10701 One of the ways to use a convenience variable is as a counter to be
10702 incremented or a pointer to be advanced. For example, to print
10703 a field from successive elements of an array of structures:
10707 print bar[$i++]->contents
10711 Repeat that command by typing @key{RET}.
10713 Some convenience variables are created automatically by @value{GDBN} and given
10714 values likely to be useful.
10717 @vindex $_@r{, convenience variable}
10719 The variable @code{$_} is automatically set by the @code{x} command to
10720 the last address examined (@pxref{Memory, ,Examining Memory}). Other
10721 commands which provide a default address for @code{x} to examine also
10722 set @code{$_} to that address; these commands include @code{info line}
10723 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
10724 except when set by the @code{x} command, in which case it is a pointer
10725 to the type of @code{$__}.
10727 @vindex $__@r{, convenience variable}
10729 The variable @code{$__} is automatically set by the @code{x} command
10730 to the value found in the last address examined. Its type is chosen
10731 to match the format in which the data was printed.
10734 @vindex $_exitcode@r{, convenience variable}
10735 When the program being debugged terminates normally, @value{GDBN}
10736 automatically sets this variable to the exit code of the program, and
10737 resets @code{$_exitsignal} to @code{void}.
10740 @vindex $_exitsignal@r{, convenience variable}
10741 When the program being debugged dies due to an uncaught signal,
10742 @value{GDBN} automatically sets this variable to that signal's number,
10743 and resets @code{$_exitcode} to @code{void}.
10745 To distinguish between whether the program being debugged has exited
10746 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
10747 @code{$_exitsignal} is not @code{void}), the convenience function
10748 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
10749 Functions}). For example, considering the following source code:
10752 #include <signal.h>
10755 main (int argc, char *argv[])
10762 A valid way of telling whether the program being debugged has exited
10763 or signalled would be:
10766 (@value{GDBP}) define has_exited_or_signalled
10767 Type commands for definition of ``has_exited_or_signalled''.
10768 End with a line saying just ``end''.
10769 >if $_isvoid ($_exitsignal)
10770 >echo The program has exited\n
10772 >echo The program has signalled\n
10778 Program terminated with signal SIGALRM, Alarm clock.
10779 The program no longer exists.
10780 (@value{GDBP}) has_exited_or_signalled
10781 The program has signalled
10784 As can be seen, @value{GDBN} correctly informs that the program being
10785 debugged has signalled, since it calls @code{raise} and raises a
10786 @code{SIGALRM} signal. If the program being debugged had not called
10787 @code{raise}, then @value{GDBN} would report a normal exit:
10790 (@value{GDBP}) has_exited_or_signalled
10791 The program has exited
10795 The variable @code{$_exception} is set to the exception object being
10796 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
10799 @itemx $_probe_arg0@dots{}$_probe_arg11
10800 Arguments to a static probe. @xref{Static Probe Points}.
10803 @vindex $_sdata@r{, inspect, convenience variable}
10804 The variable @code{$_sdata} contains extra collected static tracepoint
10805 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
10806 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
10807 if extra static tracepoint data has not been collected.
10810 @vindex $_siginfo@r{, convenience variable}
10811 The variable @code{$_siginfo} contains extra signal information
10812 (@pxref{extra signal information}). Note that @code{$_siginfo}
10813 could be empty, if the application has not yet received any signals.
10814 For example, it will be empty before you execute the @code{run} command.
10817 @vindex $_tlb@r{, convenience variable}
10818 The variable @code{$_tlb} is automatically set when debugging
10819 applications running on MS-Windows in native mode or connected to
10820 gdbserver that supports the @code{qGetTIBAddr} request.
10821 @xref{General Query Packets}.
10822 This variable contains the address of the thread information block.
10825 The number of the current inferior. @xref{Inferiors and
10826 Programs, ,Debugging Multiple Inferiors and Programs}.
10829 The thread number of the current thread. @xref{thread numbers}.
10832 The global number of the current thread. @xref{global thread numbers}.
10836 @node Convenience Funs
10837 @section Convenience Functions
10839 @cindex convenience functions
10840 @value{GDBN} also supplies some @dfn{convenience functions}. These
10841 have a syntax similar to convenience variables. A convenience
10842 function can be used in an expression just like an ordinary function;
10843 however, a convenience function is implemented internally to
10846 These functions do not require @value{GDBN} to be configured with
10847 @code{Python} support, which means that they are always available.
10851 @item $_isvoid (@var{expr})
10852 @findex $_isvoid@r{, convenience function}
10853 Return one if the expression @var{expr} is @code{void}. Otherwise it
10856 A @code{void} expression is an expression where the type of the result
10857 is @code{void}. For example, you can examine a convenience variable
10858 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10862 (@value{GDBP}) print $_exitcode
10864 (@value{GDBP}) print $_isvoid ($_exitcode)
10867 Starting program: ./a.out
10868 [Inferior 1 (process 29572) exited normally]
10869 (@value{GDBP}) print $_exitcode
10871 (@value{GDBP}) print $_isvoid ($_exitcode)
10875 In the example above, we used @code{$_isvoid} to check whether
10876 @code{$_exitcode} is @code{void} before and after the execution of the
10877 program being debugged. Before the execution there is no exit code to
10878 be examined, therefore @code{$_exitcode} is @code{void}. After the
10879 execution the program being debugged returned zero, therefore
10880 @code{$_exitcode} is zero, which means that it is not @code{void}
10883 The @code{void} expression can also be a call of a function from the
10884 program being debugged. For example, given the following function:
10893 The result of calling it inside @value{GDBN} is @code{void}:
10896 (@value{GDBP}) print foo ()
10898 (@value{GDBP}) print $_isvoid (foo ())
10900 (@value{GDBP}) set $v = foo ()
10901 (@value{GDBP}) print $v
10903 (@value{GDBP}) print $_isvoid ($v)
10909 These functions require @value{GDBN} to be configured with
10910 @code{Python} support.
10914 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10915 @findex $_memeq@r{, convenience function}
10916 Returns one if the @var{length} bytes at the addresses given by
10917 @var{buf1} and @var{buf2} are equal.
10918 Otherwise it returns zero.
10920 @item $_regex(@var{str}, @var{regex})
10921 @findex $_regex@r{, convenience function}
10922 Returns one if the string @var{str} matches the regular expression
10923 @var{regex}. Otherwise it returns zero.
10924 The syntax of the regular expression is that specified by @code{Python}'s
10925 regular expression support.
10927 @item $_streq(@var{str1}, @var{str2})
10928 @findex $_streq@r{, convenience function}
10929 Returns one if the strings @var{str1} and @var{str2} are equal.
10930 Otherwise it returns zero.
10932 @item $_strlen(@var{str})
10933 @findex $_strlen@r{, convenience function}
10934 Returns the length of string @var{str}.
10936 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10937 @findex $_caller_is@r{, convenience function}
10938 Returns one if the calling function's name is equal to @var{name}.
10939 Otherwise it returns zero.
10941 If the optional argument @var{number_of_frames} is provided,
10942 it is the number of frames up in the stack to look.
10950 at testsuite/gdb.python/py-caller-is.c:21
10951 #1 0x00000000004005a0 in middle_func ()
10952 at testsuite/gdb.python/py-caller-is.c:27
10953 #2 0x00000000004005ab in top_func ()
10954 at testsuite/gdb.python/py-caller-is.c:33
10955 #3 0x00000000004005b6 in main ()
10956 at testsuite/gdb.python/py-caller-is.c:39
10957 (gdb) print $_caller_is ("middle_func")
10959 (gdb) print $_caller_is ("top_func", 2)
10963 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10964 @findex $_caller_matches@r{, convenience function}
10965 Returns one if the calling function's name matches the regular expression
10966 @var{regexp}. Otherwise it returns zero.
10968 If the optional argument @var{number_of_frames} is provided,
10969 it is the number of frames up in the stack to look.
10972 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10973 @findex $_any_caller_is@r{, convenience function}
10974 Returns one if any calling function's name is equal to @var{name}.
10975 Otherwise it returns zero.
10977 If the optional argument @var{number_of_frames} is provided,
10978 it is the number of frames up in the stack to look.
10981 This function differs from @code{$_caller_is} in that this function
10982 checks all stack frames from the immediate caller to the frame specified
10983 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
10984 frame specified by @var{number_of_frames}.
10986 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10987 @findex $_any_caller_matches@r{, convenience function}
10988 Returns one if any calling function's name matches the regular expression
10989 @var{regexp}. Otherwise it returns zero.
10991 If the optional argument @var{number_of_frames} is provided,
10992 it is the number of frames up in the stack to look.
10995 This function differs from @code{$_caller_matches} in that this function
10996 checks all stack frames from the immediate caller to the frame specified
10997 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
10998 frame specified by @var{number_of_frames}.
11000 @item $_as_string(@var{value})
11001 @findex $_as_string@r{, convenience function}
11002 Return the string representation of @var{value}.
11004 This function is useful to obtain the textual label (enumerator) of an
11005 enumeration value. For example, assuming the variable @var{node} is of
11006 an enumerated type:
11009 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
11010 Visiting node of type NODE_INTEGER
11015 @value{GDBN} provides the ability to list and get help on
11016 convenience functions.
11019 @item help function
11020 @kindex help function
11021 @cindex show all convenience functions
11022 Print a list of all convenience functions.
11029 You can refer to machine register contents, in expressions, as variables
11030 with names starting with @samp{$}. The names of registers are different
11031 for each machine; use @code{info registers} to see the names used on
11035 @kindex info registers
11036 @item info registers
11037 Print the names and values of all registers except floating-point
11038 and vector registers (in the selected stack frame).
11040 @kindex info all-registers
11041 @cindex floating point registers
11042 @item info all-registers
11043 Print the names and values of all registers, including floating-point
11044 and vector registers (in the selected stack frame).
11046 @item info registers @var{reggroup} @dots{}
11047 Print the name and value of the registers in each of the specified
11048 @var{reggroup}s. The @var{reggoup} can be any of those returned by
11049 @code{maint print reggroups} (@pxref{Maintenance Commands}).
11051 @item info registers @var{regname} @dots{}
11052 Print the @dfn{relativized} value of each specified register @var{regname}.
11053 As discussed in detail below, register values are normally relative to
11054 the selected stack frame. The @var{regname} may be any register name valid on
11055 the machine you are using, with or without the initial @samp{$}.
11058 @anchor{standard registers}
11059 @cindex stack pointer register
11060 @cindex program counter register
11061 @cindex process status register
11062 @cindex frame pointer register
11063 @cindex standard registers
11064 @value{GDBN} has four ``standard'' register names that are available (in
11065 expressions) on most machines---whenever they do not conflict with an
11066 architecture's canonical mnemonics for registers. The register names
11067 @code{$pc} and @code{$sp} are used for the program counter register and
11068 the stack pointer. @code{$fp} is used for a register that contains a
11069 pointer to the current stack frame, and @code{$ps} is used for a
11070 register that contains the processor status. For example,
11071 you could print the program counter in hex with
11078 or print the instruction to be executed next with
11085 or add four to the stack pointer@footnote{This is a way of removing
11086 one word from the stack, on machines where stacks grow downward in
11087 memory (most machines, nowadays). This assumes that the innermost
11088 stack frame is selected; setting @code{$sp} is not allowed when other
11089 stack frames are selected. To pop entire frames off the stack,
11090 regardless of machine architecture, use @code{return};
11091 see @ref{Returning, ,Returning from a Function}.} with
11097 Whenever possible, these four standard register names are available on
11098 your machine even though the machine has different canonical mnemonics,
11099 so long as there is no conflict. The @code{info registers} command
11100 shows the canonical names. For example, on the SPARC, @code{info
11101 registers} displays the processor status register as @code{$psr} but you
11102 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
11103 is an alias for the @sc{eflags} register.
11105 @value{GDBN} always considers the contents of an ordinary register as an
11106 integer when the register is examined in this way. Some machines have
11107 special registers which can hold nothing but floating point; these
11108 registers are considered to have floating point values. There is no way
11109 to refer to the contents of an ordinary register as floating point value
11110 (although you can @emph{print} it as a floating point value with
11111 @samp{print/f $@var{regname}}).
11113 Some registers have distinct ``raw'' and ``virtual'' data formats. This
11114 means that the data format in which the register contents are saved by
11115 the operating system is not the same one that your program normally
11116 sees. For example, the registers of the 68881 floating point
11117 coprocessor are always saved in ``extended'' (raw) format, but all C
11118 programs expect to work with ``double'' (virtual) format. In such
11119 cases, @value{GDBN} normally works with the virtual format only (the format
11120 that makes sense for your program), but the @code{info registers} command
11121 prints the data in both formats.
11123 @cindex SSE registers (x86)
11124 @cindex MMX registers (x86)
11125 Some machines have special registers whose contents can be interpreted
11126 in several different ways. For example, modern x86-based machines
11127 have SSE and MMX registers that can hold several values packed
11128 together in several different formats. @value{GDBN} refers to such
11129 registers in @code{struct} notation:
11132 (@value{GDBP}) print $xmm1
11134 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
11135 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
11136 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
11137 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
11138 v4_int32 = @{0, 20657912, 11, 13@},
11139 v2_int64 = @{88725056443645952, 55834574859@},
11140 uint128 = 0x0000000d0000000b013b36f800000000
11145 To set values of such registers, you need to tell @value{GDBN} which
11146 view of the register you wish to change, as if you were assigning
11147 value to a @code{struct} member:
11150 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
11153 Normally, register values are relative to the selected stack frame
11154 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
11155 value that the register would contain if all stack frames farther in
11156 were exited and their saved registers restored. In order to see the
11157 true contents of hardware registers, you must select the innermost
11158 frame (with @samp{frame 0}).
11160 @cindex caller-saved registers
11161 @cindex call-clobbered registers
11162 @cindex volatile registers
11163 @cindex <not saved> values
11164 Usually ABIs reserve some registers as not needed to be saved by the
11165 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
11166 registers). It may therefore not be possible for @value{GDBN} to know
11167 the value a register had before the call (in other words, in the outer
11168 frame), if the register value has since been changed by the callee.
11169 @value{GDBN} tries to deduce where the inner frame saved
11170 (``callee-saved'') registers, from the debug info, unwind info, or the
11171 machine code generated by your compiler. If some register is not
11172 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
11173 its own knowledge of the ABI, or because the debug/unwind info
11174 explicitly says the register's value is undefined), @value{GDBN}
11175 displays @w{@samp{<not saved>}} as the register's value. With targets
11176 that @value{GDBN} has no knowledge of the register saving convention,
11177 if a register was not saved by the callee, then its value and location
11178 in the outer frame are assumed to be the same of the inner frame.
11179 This is usually harmless, because if the register is call-clobbered,
11180 the caller either does not care what is in the register after the
11181 call, or has code to restore the value that it does care about. Note,
11182 however, that if you change such a register in the outer frame, you
11183 may also be affecting the inner frame. Also, the more ``outer'' the
11184 frame is you're looking at, the more likely a call-clobbered
11185 register's value is to be wrong, in the sense that it doesn't actually
11186 represent the value the register had just before the call.
11188 @node Floating Point Hardware
11189 @section Floating Point Hardware
11190 @cindex floating point
11192 Depending on the configuration, @value{GDBN} may be able to give
11193 you more information about the status of the floating point hardware.
11198 Display hardware-dependent information about the floating
11199 point unit. The exact contents and layout vary depending on the
11200 floating point chip. Currently, @samp{info float} is supported on
11201 the ARM and x86 machines.
11205 @section Vector Unit
11206 @cindex vector unit
11208 Depending on the configuration, @value{GDBN} may be able to give you
11209 more information about the status of the vector unit.
11212 @kindex info vector
11214 Display information about the vector unit. The exact contents and
11215 layout vary depending on the hardware.
11218 @node OS Information
11219 @section Operating System Auxiliary Information
11220 @cindex OS information
11222 @value{GDBN} provides interfaces to useful OS facilities that can help
11223 you debug your program.
11225 @cindex auxiliary vector
11226 @cindex vector, auxiliary
11227 Some operating systems supply an @dfn{auxiliary vector} to programs at
11228 startup. This is akin to the arguments and environment that you
11229 specify for a program, but contains a system-dependent variety of
11230 binary values that tell system libraries important details about the
11231 hardware, operating system, and process. Each value's purpose is
11232 identified by an integer tag; the meanings are well-known but system-specific.
11233 Depending on the configuration and operating system facilities,
11234 @value{GDBN} may be able to show you this information. For remote
11235 targets, this functionality may further depend on the remote stub's
11236 support of the @samp{qXfer:auxv:read} packet, see
11237 @ref{qXfer auxiliary vector read}.
11242 Display the auxiliary vector of the inferior, which can be either a
11243 live process or a core dump file. @value{GDBN} prints each tag value
11244 numerically, and also shows names and text descriptions for recognized
11245 tags. Some values in the vector are numbers, some bit masks, and some
11246 pointers to strings or other data. @value{GDBN} displays each value in the
11247 most appropriate form for a recognized tag, and in hexadecimal for
11248 an unrecognized tag.
11251 On some targets, @value{GDBN} can access operating system-specific
11252 information and show it to you. The types of information available
11253 will differ depending on the type of operating system running on the
11254 target. The mechanism used to fetch the data is described in
11255 @ref{Operating System Information}. For remote targets, this
11256 functionality depends on the remote stub's support of the
11257 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
11261 @item info os @var{infotype}
11263 Display OS information of the requested type.
11265 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
11267 @anchor{linux info os infotypes}
11269 @kindex info os cpus
11271 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
11272 the available fields from /proc/cpuinfo. For each supported architecture
11273 different fields are available. Two common entries are processor which gives
11274 CPU number and bogomips; a system constant that is calculated during
11275 kernel initialization.
11277 @kindex info os files
11279 Display the list of open file descriptors on the target. For each
11280 file descriptor, @value{GDBN} prints the identifier of the process
11281 owning the descriptor, the command of the owning process, the value
11282 of the descriptor, and the target of the descriptor.
11284 @kindex info os modules
11286 Display the list of all loaded kernel modules on the target. For each
11287 module, @value{GDBN} prints the module name, the size of the module in
11288 bytes, the number of times the module is used, the dependencies of the
11289 module, the status of the module, and the address of the loaded module
11292 @kindex info os msg
11294 Display the list of all System V message queues on the target. For each
11295 message queue, @value{GDBN} prints the message queue key, the message
11296 queue identifier, the access permissions, the current number of bytes
11297 on the queue, the current number of messages on the queue, the processes
11298 that last sent and received a message on the queue, the user and group
11299 of the owner and creator of the message queue, the times at which a
11300 message was last sent and received on the queue, and the time at which
11301 the message queue was last changed.
11303 @kindex info os processes
11305 Display the list of processes on the target. For each process,
11306 @value{GDBN} prints the process identifier, the name of the user, the
11307 command corresponding to the process, and the list of processor cores
11308 that the process is currently running on. (To understand what these
11309 properties mean, for this and the following info types, please consult
11310 the general @sc{gnu}/Linux documentation.)
11312 @kindex info os procgroups
11314 Display the list of process groups on the target. For each process,
11315 @value{GDBN} prints the identifier of the process group that it belongs
11316 to, the command corresponding to the process group leader, the process
11317 identifier, and the command line of the process. The list is sorted
11318 first by the process group identifier, then by the process identifier,
11319 so that processes belonging to the same process group are grouped together
11320 and the process group leader is listed first.
11322 @kindex info os semaphores
11324 Display the list of all System V semaphore sets on the target. For each
11325 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
11326 set identifier, the access permissions, the number of semaphores in the
11327 set, the user and group of the owner and creator of the semaphore set,
11328 and the times at which the semaphore set was operated upon and changed.
11330 @kindex info os shm
11332 Display the list of all System V shared-memory regions on the target.
11333 For each shared-memory region, @value{GDBN} prints the region key,
11334 the shared-memory identifier, the access permissions, the size of the
11335 region, the process that created the region, the process that last
11336 attached to or detached from the region, the current number of live
11337 attaches to the region, and the times at which the region was last
11338 attached to, detach from, and changed.
11340 @kindex info os sockets
11342 Display the list of Internet-domain sockets on the target. For each
11343 socket, @value{GDBN} prints the address and port of the local and
11344 remote endpoints, the current state of the connection, the creator of
11345 the socket, the IP address family of the socket, and the type of the
11348 @kindex info os threads
11350 Display the list of threads running on the target. For each thread,
11351 @value{GDBN} prints the identifier of the process that the thread
11352 belongs to, the command of the process, the thread identifier, and the
11353 processor core that it is currently running on. The main thread of a
11354 process is not listed.
11358 If @var{infotype} is omitted, then list the possible values for
11359 @var{infotype} and the kind of OS information available for each
11360 @var{infotype}. If the target does not return a list of possible
11361 types, this command will report an error.
11364 @node Memory Region Attributes
11365 @section Memory Region Attributes
11366 @cindex memory region attributes
11368 @dfn{Memory region attributes} allow you to describe special handling
11369 required by regions of your target's memory. @value{GDBN} uses
11370 attributes to determine whether to allow certain types of memory
11371 accesses; whether to use specific width accesses; and whether to cache
11372 target memory. By default the description of memory regions is
11373 fetched from the target (if the current target supports this), but the
11374 user can override the fetched regions.
11376 Defined memory regions can be individually enabled and disabled. When a
11377 memory region is disabled, @value{GDBN} uses the default attributes when
11378 accessing memory in that region. Similarly, if no memory regions have
11379 been defined, @value{GDBN} uses the default attributes when accessing
11382 When a memory region is defined, it is given a number to identify it;
11383 to enable, disable, or remove a memory region, you specify that number.
11387 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
11388 Define a memory region bounded by @var{lower} and @var{upper} with
11389 attributes @var{attributes}@dots{}, and add it to the list of regions
11390 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
11391 case: it is treated as the target's maximum memory address.
11392 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
11395 Discard any user changes to the memory regions and use target-supplied
11396 regions, if available, or no regions if the target does not support.
11399 @item delete mem @var{nums}@dots{}
11400 Remove memory regions @var{nums}@dots{} from the list of regions
11401 monitored by @value{GDBN}.
11403 @kindex disable mem
11404 @item disable mem @var{nums}@dots{}
11405 Disable monitoring of memory regions @var{nums}@dots{}.
11406 A disabled memory region is not forgotten.
11407 It may be enabled again later.
11410 @item enable mem @var{nums}@dots{}
11411 Enable monitoring of memory regions @var{nums}@dots{}.
11415 Print a table of all defined memory regions, with the following columns
11419 @item Memory Region Number
11420 @item Enabled or Disabled.
11421 Enabled memory regions are marked with @samp{y}.
11422 Disabled memory regions are marked with @samp{n}.
11425 The address defining the inclusive lower bound of the memory region.
11428 The address defining the exclusive upper bound of the memory region.
11431 The list of attributes set for this memory region.
11436 @subsection Attributes
11438 @subsubsection Memory Access Mode
11439 The access mode attributes set whether @value{GDBN} may make read or
11440 write accesses to a memory region.
11442 While these attributes prevent @value{GDBN} from performing invalid
11443 memory accesses, they do nothing to prevent the target system, I/O DMA,
11444 etc.@: from accessing memory.
11448 Memory is read only.
11450 Memory is write only.
11452 Memory is read/write. This is the default.
11455 @subsubsection Memory Access Size
11456 The access size attribute tells @value{GDBN} to use specific sized
11457 accesses in the memory region. Often memory mapped device registers
11458 require specific sized accesses. If no access size attribute is
11459 specified, @value{GDBN} may use accesses of any size.
11463 Use 8 bit memory accesses.
11465 Use 16 bit memory accesses.
11467 Use 32 bit memory accesses.
11469 Use 64 bit memory accesses.
11472 @c @subsubsection Hardware/Software Breakpoints
11473 @c The hardware/software breakpoint attributes set whether @value{GDBN}
11474 @c will use hardware or software breakpoints for the internal breakpoints
11475 @c used by the step, next, finish, until, etc. commands.
11479 @c Always use hardware breakpoints
11480 @c @item swbreak (default)
11483 @subsubsection Data Cache
11484 The data cache attributes set whether @value{GDBN} will cache target
11485 memory. While this generally improves performance by reducing debug
11486 protocol overhead, it can lead to incorrect results because @value{GDBN}
11487 does not know about volatile variables or memory mapped device
11492 Enable @value{GDBN} to cache target memory.
11494 Disable @value{GDBN} from caching target memory. This is the default.
11497 @subsection Memory Access Checking
11498 @value{GDBN} can be instructed to refuse accesses to memory that is
11499 not explicitly described. This can be useful if accessing such
11500 regions has undesired effects for a specific target, or to provide
11501 better error checking. The following commands control this behaviour.
11504 @kindex set mem inaccessible-by-default
11505 @item set mem inaccessible-by-default [on|off]
11506 If @code{on} is specified, make @value{GDBN} treat memory not
11507 explicitly described by the memory ranges as non-existent and refuse accesses
11508 to such memory. The checks are only performed if there's at least one
11509 memory range defined. If @code{off} is specified, make @value{GDBN}
11510 treat the memory not explicitly described by the memory ranges as RAM.
11511 The default value is @code{on}.
11512 @kindex show mem inaccessible-by-default
11513 @item show mem inaccessible-by-default
11514 Show the current handling of accesses to unknown memory.
11518 @c @subsubsection Memory Write Verification
11519 @c The memory write verification attributes set whether @value{GDBN}
11520 @c will re-reads data after each write to verify the write was successful.
11524 @c @item noverify (default)
11527 @node Dump/Restore Files
11528 @section Copy Between Memory and a File
11529 @cindex dump/restore files
11530 @cindex append data to a file
11531 @cindex dump data to a file
11532 @cindex restore data from a file
11534 You can use the commands @code{dump}, @code{append}, and
11535 @code{restore} to copy data between target memory and a file. The
11536 @code{dump} and @code{append} commands write data to a file, and the
11537 @code{restore} command reads data from a file back into the inferior's
11538 memory. Files may be in binary, Motorola S-record, Intel hex,
11539 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
11540 append to binary files, and cannot read from Verilog Hex files.
11545 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11546 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
11547 Dump the contents of memory from @var{start_addr} to @var{end_addr},
11548 or the value of @var{expr}, to @var{filename} in the given format.
11550 The @var{format} parameter may be any one of:
11557 Motorola S-record format.
11559 Tektronix Hex format.
11561 Verilog Hex format.
11564 @value{GDBN} uses the same definitions of these formats as the
11565 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
11566 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
11570 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11571 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
11572 Append the contents of memory from @var{start_addr} to @var{end_addr},
11573 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
11574 (@value{GDBN} can only append data to files in raw binary form.)
11577 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
11578 Restore the contents of file @var{filename} into memory. The
11579 @code{restore} command can automatically recognize any known @sc{bfd}
11580 file format, except for raw binary. To restore a raw binary file you
11581 must specify the optional keyword @code{binary} after the filename.
11583 If @var{bias} is non-zero, its value will be added to the addresses
11584 contained in the file. Binary files always start at address zero, so
11585 they will be restored at address @var{bias}. Other bfd files have
11586 a built-in location; they will be restored at offset @var{bias}
11587 from that location.
11589 If @var{start} and/or @var{end} are non-zero, then only data between
11590 file offset @var{start} and file offset @var{end} will be restored.
11591 These offsets are relative to the addresses in the file, before
11592 the @var{bias} argument is applied.
11596 @node Core File Generation
11597 @section How to Produce a Core File from Your Program
11598 @cindex dump core from inferior
11600 A @dfn{core file} or @dfn{core dump} is a file that records the memory
11601 image of a running process and its process status (register values
11602 etc.). Its primary use is post-mortem debugging of a program that
11603 crashed while it ran outside a debugger. A program that crashes
11604 automatically produces a core file, unless this feature is disabled by
11605 the user. @xref{Files}, for information on invoking @value{GDBN} in
11606 the post-mortem debugging mode.
11608 Occasionally, you may wish to produce a core file of the program you
11609 are debugging in order to preserve a snapshot of its state.
11610 @value{GDBN} has a special command for that.
11614 @kindex generate-core-file
11615 @item generate-core-file [@var{file}]
11616 @itemx gcore [@var{file}]
11617 Produce a core dump of the inferior process. The optional argument
11618 @var{file} specifies the file name where to put the core dump. If not
11619 specified, the file name defaults to @file{core.@var{pid}}, where
11620 @var{pid} is the inferior process ID.
11622 Note that this command is implemented only for some systems (as of
11623 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
11625 On @sc{gnu}/Linux, this command can take into account the value of the
11626 file @file{/proc/@var{pid}/coredump_filter} when generating the core
11627 dump (@pxref{set use-coredump-filter}), and by default honors the
11628 @code{VM_DONTDUMP} flag for mappings where it is present in the file
11629 @file{/proc/@var{pid}/smaps} (@pxref{set dump-excluded-mappings}).
11631 @kindex set use-coredump-filter
11632 @anchor{set use-coredump-filter}
11633 @item set use-coredump-filter on
11634 @itemx set use-coredump-filter off
11635 Enable or disable the use of the file
11636 @file{/proc/@var{pid}/coredump_filter} when generating core dump
11637 files. This file is used by the Linux kernel to decide what types of
11638 memory mappings will be dumped or ignored when generating a core dump
11639 file. @var{pid} is the process ID of a currently running process.
11641 To make use of this feature, you have to write in the
11642 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
11643 which is a bit mask representing the memory mapping types. If a bit
11644 is set in the bit mask, then the memory mappings of the corresponding
11645 types will be dumped; otherwise, they will be ignored. This
11646 configuration is inherited by child processes. For more information
11647 about the bits that can be set in the
11648 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
11649 manpage of @code{core(5)}.
11651 By default, this option is @code{on}. If this option is turned
11652 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
11653 and instead uses the same default value as the Linux kernel in order
11654 to decide which pages will be dumped in the core dump file. This
11655 value is currently @code{0x33}, which means that bits @code{0}
11656 (anonymous private mappings), @code{1} (anonymous shared mappings),
11657 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
11658 This will cause these memory mappings to be dumped automatically.
11660 @kindex set dump-excluded-mappings
11661 @anchor{set dump-excluded-mappings}
11662 @item set dump-excluded-mappings on
11663 @itemx set dump-excluded-mappings off
11664 If @code{on} is specified, @value{GDBN} will dump memory mappings
11665 marked with the @code{VM_DONTDUMP} flag. This flag is represented in
11666 the file @file{/proc/@var{pid}/smaps} with the acronym @code{dd}.
11668 The default value is @code{off}.
11671 @node Character Sets
11672 @section Character Sets
11673 @cindex character sets
11675 @cindex translating between character sets
11676 @cindex host character set
11677 @cindex target character set
11679 If the program you are debugging uses a different character set to
11680 represent characters and strings than the one @value{GDBN} uses itself,
11681 @value{GDBN} can automatically translate between the character sets for
11682 you. The character set @value{GDBN} uses we call the @dfn{host
11683 character set}; the one the inferior program uses we call the
11684 @dfn{target character set}.
11686 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
11687 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
11688 remote protocol (@pxref{Remote Debugging}) to debug a program
11689 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
11690 then the host character set is Latin-1, and the target character set is
11691 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
11692 target-charset EBCDIC-US}, then @value{GDBN} translates between
11693 @sc{ebcdic} and Latin 1 as you print character or string values, or use
11694 character and string literals in expressions.
11696 @value{GDBN} has no way to automatically recognize which character set
11697 the inferior program uses; you must tell it, using the @code{set
11698 target-charset} command, described below.
11700 Here are the commands for controlling @value{GDBN}'s character set
11704 @item set target-charset @var{charset}
11705 @kindex set target-charset
11706 Set the current target character set to @var{charset}. To display the
11707 list of supported target character sets, type
11708 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
11710 @item set host-charset @var{charset}
11711 @kindex set host-charset
11712 Set the current host character set to @var{charset}.
11714 By default, @value{GDBN} uses a host character set appropriate to the
11715 system it is running on; you can override that default using the
11716 @code{set host-charset} command. On some systems, @value{GDBN} cannot
11717 automatically determine the appropriate host character set. In this
11718 case, @value{GDBN} uses @samp{UTF-8}.
11720 @value{GDBN} can only use certain character sets as its host character
11721 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
11722 @value{GDBN} will list the host character sets it supports.
11724 @item set charset @var{charset}
11725 @kindex set charset
11726 Set the current host and target character sets to @var{charset}. As
11727 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
11728 @value{GDBN} will list the names of the character sets that can be used
11729 for both host and target.
11732 @kindex show charset
11733 Show the names of the current host and target character sets.
11735 @item show host-charset
11736 @kindex show host-charset
11737 Show the name of the current host character set.
11739 @item show target-charset
11740 @kindex show target-charset
11741 Show the name of the current target character set.
11743 @item set target-wide-charset @var{charset}
11744 @kindex set target-wide-charset
11745 Set the current target's wide character set to @var{charset}. This is
11746 the character set used by the target's @code{wchar_t} type. To
11747 display the list of supported wide character sets, type
11748 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
11750 @item show target-wide-charset
11751 @kindex show target-wide-charset
11752 Show the name of the current target's wide character set.
11755 Here is an example of @value{GDBN}'s character set support in action.
11756 Assume that the following source code has been placed in the file
11757 @file{charset-test.c}:
11763 = @{72, 101, 108, 108, 111, 44, 32, 119,
11764 111, 114, 108, 100, 33, 10, 0@};
11765 char ibm1047_hello[]
11766 = @{200, 133, 147, 147, 150, 107, 64, 166,
11767 150, 153, 147, 132, 90, 37, 0@};
11771 printf ("Hello, world!\n");
11775 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
11776 containing the string @samp{Hello, world!} followed by a newline,
11777 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
11779 We compile the program, and invoke the debugger on it:
11782 $ gcc -g charset-test.c -o charset-test
11783 $ gdb -nw charset-test
11784 GNU gdb 2001-12-19-cvs
11785 Copyright 2001 Free Software Foundation, Inc.
11790 We can use the @code{show charset} command to see what character sets
11791 @value{GDBN} is currently using to interpret and display characters and
11795 (@value{GDBP}) show charset
11796 The current host and target character set is `ISO-8859-1'.
11800 For the sake of printing this manual, let's use @sc{ascii} as our
11801 initial character set:
11803 (@value{GDBP}) set charset ASCII
11804 (@value{GDBP}) show charset
11805 The current host and target character set is `ASCII'.
11809 Let's assume that @sc{ascii} is indeed the correct character set for our
11810 host system --- in other words, let's assume that if @value{GDBN} prints
11811 characters using the @sc{ascii} character set, our terminal will display
11812 them properly. Since our current target character set is also
11813 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
11816 (@value{GDBP}) print ascii_hello
11817 $1 = 0x401698 "Hello, world!\n"
11818 (@value{GDBP}) print ascii_hello[0]
11823 @value{GDBN} uses the target character set for character and string
11824 literals you use in expressions:
11827 (@value{GDBP}) print '+'
11832 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
11835 @value{GDBN} relies on the user to tell it which character set the
11836 target program uses. If we print @code{ibm1047_hello} while our target
11837 character set is still @sc{ascii}, we get jibberish:
11840 (@value{GDBP}) print ibm1047_hello
11841 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
11842 (@value{GDBP}) print ibm1047_hello[0]
11847 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
11848 @value{GDBN} tells us the character sets it supports:
11851 (@value{GDBP}) set target-charset
11852 ASCII EBCDIC-US IBM1047 ISO-8859-1
11853 (@value{GDBP}) set target-charset
11856 We can select @sc{ibm1047} as our target character set, and examine the
11857 program's strings again. Now the @sc{ascii} string is wrong, but
11858 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
11859 target character set, @sc{ibm1047}, to the host character set,
11860 @sc{ascii}, and they display correctly:
11863 (@value{GDBP}) set target-charset IBM1047
11864 (@value{GDBP}) show charset
11865 The current host character set is `ASCII'.
11866 The current target character set is `IBM1047'.
11867 (@value{GDBP}) print ascii_hello
11868 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
11869 (@value{GDBP}) print ascii_hello[0]
11871 (@value{GDBP}) print ibm1047_hello
11872 $8 = 0x4016a8 "Hello, world!\n"
11873 (@value{GDBP}) print ibm1047_hello[0]
11878 As above, @value{GDBN} uses the target character set for character and
11879 string literals you use in expressions:
11882 (@value{GDBP}) print '+'
11887 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
11890 @node Caching Target Data
11891 @section Caching Data of Targets
11892 @cindex caching data of targets
11894 @value{GDBN} caches data exchanged between the debugger and a target.
11895 Each cache is associated with the address space of the inferior.
11896 @xref{Inferiors and Programs}, about inferior and address space.
11897 Such caching generally improves performance in remote debugging
11898 (@pxref{Remote Debugging}), because it reduces the overhead of the
11899 remote protocol by bundling memory reads and writes into large chunks.
11900 Unfortunately, simply caching everything would lead to incorrect results,
11901 since @value{GDBN} does not necessarily know anything about volatile
11902 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
11903 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
11905 Therefore, by default, @value{GDBN} only caches data
11906 known to be on the stack@footnote{In non-stop mode, it is moderately
11907 rare for a running thread to modify the stack of a stopped thread
11908 in a way that would interfere with a backtrace, and caching of
11909 stack reads provides a significant speed up of remote backtraces.} or
11910 in the code segment.
11911 Other regions of memory can be explicitly marked as
11912 cacheable; @pxref{Memory Region Attributes}.
11915 @kindex set remotecache
11916 @item set remotecache on
11917 @itemx set remotecache off
11918 This option no longer does anything; it exists for compatibility
11921 @kindex show remotecache
11922 @item show remotecache
11923 Show the current state of the obsolete remotecache flag.
11925 @kindex set stack-cache
11926 @item set stack-cache on
11927 @itemx set stack-cache off
11928 Enable or disable caching of stack accesses. When @code{on}, use
11929 caching. By default, this option is @code{on}.
11931 @kindex show stack-cache
11932 @item show stack-cache
11933 Show the current state of data caching for memory accesses.
11935 @kindex set code-cache
11936 @item set code-cache on
11937 @itemx set code-cache off
11938 Enable or disable caching of code segment accesses. When @code{on},
11939 use caching. By default, this option is @code{on}. This improves
11940 performance of disassembly in remote debugging.
11942 @kindex show code-cache
11943 @item show code-cache
11944 Show the current state of target memory cache for code segment
11947 @kindex info dcache
11948 @item info dcache @r{[}line@r{]}
11949 Print the information about the performance of data cache of the
11950 current inferior's address space. The information displayed
11951 includes the dcache width and depth, and for each cache line, its
11952 number, address, and how many times it was referenced. This
11953 command is useful for debugging the data cache operation.
11955 If a line number is specified, the contents of that line will be
11958 @item set dcache size @var{size}
11959 @cindex dcache size
11960 @kindex set dcache size
11961 Set maximum number of entries in dcache (dcache depth above).
11963 @item set dcache line-size @var{line-size}
11964 @cindex dcache line-size
11965 @kindex set dcache line-size
11966 Set number of bytes each dcache entry caches (dcache width above).
11967 Must be a power of 2.
11969 @item show dcache size
11970 @kindex show dcache size
11971 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
11973 @item show dcache line-size
11974 @kindex show dcache line-size
11975 Show default size of dcache lines.
11979 @node Searching Memory
11980 @section Search Memory
11981 @cindex searching memory
11983 Memory can be searched for a particular sequence of bytes with the
11984 @code{find} command.
11988 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11989 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11990 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
11991 etc. The search begins at address @var{start_addr} and continues for either
11992 @var{len} bytes or through to @var{end_addr} inclusive.
11995 @var{s} and @var{n} are optional parameters.
11996 They may be specified in either order, apart or together.
11999 @item @var{s}, search query size
12000 The size of each search query value.
12006 halfwords (two bytes)
12010 giant words (eight bytes)
12013 All values are interpreted in the current language.
12014 This means, for example, that if the current source language is C/C@t{++}
12015 then searching for the string ``hello'' includes the trailing '\0'.
12016 The null terminator can be removed from searching by using casts,
12017 e.g.: @samp{@{char[5]@}"hello"}.
12019 If the value size is not specified, it is taken from the
12020 value's type in the current language.
12021 This is useful when one wants to specify the search
12022 pattern as a mixture of types.
12023 Note that this means, for example, that in the case of C-like languages
12024 a search for an untyped 0x42 will search for @samp{(int) 0x42}
12025 which is typically four bytes.
12027 @item @var{n}, maximum number of finds
12028 The maximum number of matches to print. The default is to print all finds.
12031 You can use strings as search values. Quote them with double-quotes
12033 The string value is copied into the search pattern byte by byte,
12034 regardless of the endianness of the target and the size specification.
12036 The address of each match found is printed as well as a count of the
12037 number of matches found.
12039 The address of the last value found is stored in convenience variable
12041 A count of the number of matches is stored in @samp{$numfound}.
12043 For example, if stopped at the @code{printf} in this function:
12049 static char hello[] = "hello-hello";
12050 static struct @{ char c; short s; int i; @}
12051 __attribute__ ((packed)) mixed
12052 = @{ 'c', 0x1234, 0x87654321 @};
12053 printf ("%s\n", hello);
12058 you get during debugging:
12061 (gdb) find &hello[0], +sizeof(hello), "hello"
12062 0x804956d <hello.1620+6>
12064 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
12065 0x8049567 <hello.1620>
12066 0x804956d <hello.1620+6>
12068 (gdb) find &hello[0], +sizeof(hello), @{char[5]@}"hello"
12069 0x8049567 <hello.1620>
12070 0x804956d <hello.1620+6>
12072 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
12073 0x8049567 <hello.1620>
12075 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
12076 0x8049560 <mixed.1625>
12078 (gdb) print $numfound
12081 $2 = (void *) 0x8049560
12085 @section Value Sizes
12087 Whenever @value{GDBN} prints a value memory will be allocated within
12088 @value{GDBN} to hold the contents of the value. It is possible in
12089 some languages with dynamic typing systems, that an invalid program
12090 may indicate a value that is incorrectly large, this in turn may cause
12091 @value{GDBN} to try and allocate an overly large ammount of memory.
12094 @kindex set max-value-size
12095 @item set max-value-size @var{bytes}
12096 @itemx set max-value-size unlimited
12097 Set the maximum size of memory that @value{GDBN} will allocate for the
12098 contents of a value to @var{bytes}, trying to display a value that
12099 requires more memory than that will result in an error.
12101 Setting this variable does not effect values that have already been
12102 allocated within @value{GDBN}, only future allocations.
12104 There's a minimum size that @code{max-value-size} can be set to in
12105 order that @value{GDBN} can still operate correctly, this minimum is
12106 currently 16 bytes.
12108 The limit applies to the results of some subexpressions as well as to
12109 complete expressions. For example, an expression denoting a simple
12110 integer component, such as @code{x.y.z}, may fail if the size of
12111 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
12112 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
12113 @var{A} is an array variable with non-constant size, will generally
12114 succeed regardless of the bounds on @var{A}, as long as the component
12115 size is less than @var{bytes}.
12117 The default value of @code{max-value-size} is currently 64k.
12119 @kindex show max-value-size
12120 @item show max-value-size
12121 Show the maximum size of memory, in bytes, that @value{GDBN} will
12122 allocate for the contents of a value.
12125 @node Optimized Code
12126 @chapter Debugging Optimized Code
12127 @cindex optimized code, debugging
12128 @cindex debugging optimized code
12130 Almost all compilers support optimization. With optimization
12131 disabled, the compiler generates assembly code that corresponds
12132 directly to your source code, in a simplistic way. As the compiler
12133 applies more powerful optimizations, the generated assembly code
12134 diverges from your original source code. With help from debugging
12135 information generated by the compiler, @value{GDBN} can map from
12136 the running program back to constructs from your original source.
12138 @value{GDBN} is more accurate with optimization disabled. If you
12139 can recompile without optimization, it is easier to follow the
12140 progress of your program during debugging. But, there are many cases
12141 where you may need to debug an optimized version.
12143 When you debug a program compiled with @samp{-g -O}, remember that the
12144 optimizer has rearranged your code; the debugger shows you what is
12145 really there. Do not be too surprised when the execution path does not
12146 exactly match your source file! An extreme example: if you define a
12147 variable, but never use it, @value{GDBN} never sees that
12148 variable---because the compiler optimizes it out of existence.
12150 Some things do not work as well with @samp{-g -O} as with just
12151 @samp{-g}, particularly on machines with instruction scheduling. If in
12152 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
12153 please report it to us as a bug (including a test case!).
12154 @xref{Variables}, for more information about debugging optimized code.
12157 * Inline Functions:: How @value{GDBN} presents inlining
12158 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
12161 @node Inline Functions
12162 @section Inline Functions
12163 @cindex inline functions, debugging
12165 @dfn{Inlining} is an optimization that inserts a copy of the function
12166 body directly at each call site, instead of jumping to a shared
12167 routine. @value{GDBN} displays inlined functions just like
12168 non-inlined functions. They appear in backtraces. You can view their
12169 arguments and local variables, step into them with @code{step}, skip
12170 them with @code{next}, and escape from them with @code{finish}.
12171 You can check whether a function was inlined by using the
12172 @code{info frame} command.
12174 For @value{GDBN} to support inlined functions, the compiler must
12175 record information about inlining in the debug information ---
12176 @value{NGCC} using the @sc{dwarf 2} format does this, and several
12177 other compilers do also. @value{GDBN} only supports inlined functions
12178 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
12179 do not emit two required attributes (@samp{DW_AT_call_file} and
12180 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
12181 function calls with earlier versions of @value{NGCC}. It instead
12182 displays the arguments and local variables of inlined functions as
12183 local variables in the caller.
12185 The body of an inlined function is directly included at its call site;
12186 unlike a non-inlined function, there are no instructions devoted to
12187 the call. @value{GDBN} still pretends that the call site and the
12188 start of the inlined function are different instructions. Stepping to
12189 the call site shows the call site, and then stepping again shows
12190 the first line of the inlined function, even though no additional
12191 instructions are executed.
12193 This makes source-level debugging much clearer; you can see both the
12194 context of the call and then the effect of the call. Only stepping by
12195 a single instruction using @code{stepi} or @code{nexti} does not do
12196 this; single instruction steps always show the inlined body.
12198 There are some ways that @value{GDBN} does not pretend that inlined
12199 function calls are the same as normal calls:
12203 Setting breakpoints at the call site of an inlined function may not
12204 work, because the call site does not contain any code. @value{GDBN}
12205 may incorrectly move the breakpoint to the next line of the enclosing
12206 function, after the call. This limitation will be removed in a future
12207 version of @value{GDBN}; until then, set a breakpoint on an earlier line
12208 or inside the inlined function instead.
12211 @value{GDBN} cannot locate the return value of inlined calls after
12212 using the @code{finish} command. This is a limitation of compiler-generated
12213 debugging information; after @code{finish}, you can step to the next line
12214 and print a variable where your program stored the return value.
12218 @node Tail Call Frames
12219 @section Tail Call Frames
12220 @cindex tail call frames, debugging
12222 Function @code{B} can call function @code{C} in its very last statement. In
12223 unoptimized compilation the call of @code{C} is immediately followed by return
12224 instruction at the end of @code{B} code. Optimizing compiler may replace the
12225 call and return in function @code{B} into one jump to function @code{C}
12226 instead. Such use of a jump instruction is called @dfn{tail call}.
12228 During execution of function @code{C}, there will be no indication in the
12229 function call stack frames that it was tail-called from @code{B}. If function
12230 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
12231 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
12232 some cases @value{GDBN} can determine that @code{C} was tail-called from
12233 @code{B}, and it will then create fictitious call frame for that, with the
12234 return address set up as if @code{B} called @code{C} normally.
12236 This functionality is currently supported only by DWARF 2 debugging format and
12237 the compiler has to produce @samp{DW_TAG_call_site} tags. With
12238 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
12241 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
12242 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
12246 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
12248 Stack level 1, frame at 0x7fffffffda30:
12249 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
12250 tail call frame, caller of frame at 0x7fffffffda30
12251 source language c++.
12252 Arglist at unknown address.
12253 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
12256 The detection of all the possible code path executions can find them ambiguous.
12257 There is no execution history stored (possible @ref{Reverse Execution} is never
12258 used for this purpose) and the last known caller could have reached the known
12259 callee by multiple different jump sequences. In such case @value{GDBN} still
12260 tries to show at least all the unambiguous top tail callers and all the
12261 unambiguous bottom tail calees, if any.
12264 @anchor{set debug entry-values}
12265 @item set debug entry-values
12266 @kindex set debug entry-values
12267 When set to on, enables printing of analysis messages for both frame argument
12268 values at function entry and tail calls. It will show all the possible valid
12269 tail calls code paths it has considered. It will also print the intersection
12270 of them with the final unambiguous (possibly partial or even empty) code path
12273 @item show debug entry-values
12274 @kindex show debug entry-values
12275 Show the current state of analysis messages printing for both frame argument
12276 values at function entry and tail calls.
12279 The analysis messages for tail calls can for example show why the virtual tail
12280 call frame for function @code{c} has not been recognized (due to the indirect
12281 reference by variable @code{x}):
12284 static void __attribute__((noinline, noclone)) c (void);
12285 void (*x) (void) = c;
12286 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12287 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
12288 int main (void) @{ x (); return 0; @}
12290 Breakpoint 1, DW_OP_entry_value resolving cannot find
12291 DW_TAG_call_site 0x40039a in main
12293 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12296 #1 0x000000000040039a in main () at t.c:5
12299 Another possibility is an ambiguous virtual tail call frames resolution:
12303 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
12304 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
12305 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
12306 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
12307 static void __attribute__((noinline, noclone)) b (void)
12308 @{ if (i) c (); else e (); @}
12309 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
12310 int main (void) @{ a (); return 0; @}
12312 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
12313 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
12314 tailcall: reduced: 0x4004d2(a) |
12317 #1 0x00000000004004d2 in a () at t.c:8
12318 #2 0x0000000000400395 in main () at t.c:9
12321 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
12322 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
12324 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
12325 @ifset HAVE_MAKEINFO_CLICK
12326 @set ARROW @click{}
12327 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
12328 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
12330 @ifclear HAVE_MAKEINFO_CLICK
12332 @set CALLSEQ1B @value{CALLSEQ1A}
12333 @set CALLSEQ2B @value{CALLSEQ2A}
12336 Frames #0 and #2 are real, #1 is a virtual tail call frame.
12337 The code can have possible execution paths @value{CALLSEQ1B} or
12338 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
12340 @code{initial:} state shows some random possible calling sequence @value{GDBN}
12341 has found. It then finds another possible calling sequcen - that one is
12342 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
12343 printed as the @code{reduced:} calling sequence. That one could have many
12344 futher @code{compare:} and @code{reduced:} statements as long as there remain
12345 any non-ambiguous sequence entries.
12347 For the frame of function @code{b} in both cases there are different possible
12348 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
12349 also ambigous. The only non-ambiguous frame is the one for function @code{a},
12350 therefore this one is displayed to the user while the ambiguous frames are
12353 There can be also reasons why printing of frame argument values at function
12358 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
12359 static void __attribute__((noinline, noclone)) a (int i);
12360 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
12361 static void __attribute__((noinline, noclone)) a (int i)
12362 @{ if (i) b (i - 1); else c (0); @}
12363 int main (void) @{ a (5); return 0; @}
12366 #0 c (i=i@@entry=0) at t.c:2
12367 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
12368 function "a" at 0x400420 can call itself via tail calls
12369 i=<optimized out>) at t.c:6
12370 #2 0x000000000040036e in main () at t.c:7
12373 @value{GDBN} cannot find out from the inferior state if and how many times did
12374 function @code{a} call itself (via function @code{b}) as these calls would be
12375 tail calls. Such tail calls would modify thue @code{i} variable, therefore
12376 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
12377 prints @code{<optimized out>} instead.
12380 @chapter C Preprocessor Macros
12382 Some languages, such as C and C@t{++}, provide a way to define and invoke
12383 ``preprocessor macros'' which expand into strings of tokens.
12384 @value{GDBN} can evaluate expressions containing macro invocations, show
12385 the result of macro expansion, and show a macro's definition, including
12386 where it was defined.
12388 You may need to compile your program specially to provide @value{GDBN}
12389 with information about preprocessor macros. Most compilers do not
12390 include macros in their debugging information, even when you compile
12391 with the @option{-g} flag. @xref{Compilation}.
12393 A program may define a macro at one point, remove that definition later,
12394 and then provide a different definition after that. Thus, at different
12395 points in the program, a macro may have different definitions, or have
12396 no definition at all. If there is a current stack frame, @value{GDBN}
12397 uses the macros in scope at that frame's source code line. Otherwise,
12398 @value{GDBN} uses the macros in scope at the current listing location;
12401 Whenever @value{GDBN} evaluates an expression, it always expands any
12402 macro invocations present in the expression. @value{GDBN} also provides
12403 the following commands for working with macros explicitly.
12407 @kindex macro expand
12408 @cindex macro expansion, showing the results of preprocessor
12409 @cindex preprocessor macro expansion, showing the results of
12410 @cindex expanding preprocessor macros
12411 @item macro expand @var{expression}
12412 @itemx macro exp @var{expression}
12413 Show the results of expanding all preprocessor macro invocations in
12414 @var{expression}. Since @value{GDBN} simply expands macros, but does
12415 not parse the result, @var{expression} need not be a valid expression;
12416 it can be any string of tokens.
12419 @item macro expand-once @var{expression}
12420 @itemx macro exp1 @var{expression}
12421 @cindex expand macro once
12422 @i{(This command is not yet implemented.)} Show the results of
12423 expanding those preprocessor macro invocations that appear explicitly in
12424 @var{expression}. Macro invocations appearing in that expansion are
12425 left unchanged. This command allows you to see the effect of a
12426 particular macro more clearly, without being confused by further
12427 expansions. Since @value{GDBN} simply expands macros, but does not
12428 parse the result, @var{expression} need not be a valid expression; it
12429 can be any string of tokens.
12432 @cindex macro definition, showing
12433 @cindex definition of a macro, showing
12434 @cindex macros, from debug info
12435 @item info macro [-a|-all] [--] @var{macro}
12436 Show the current definition or all definitions of the named @var{macro},
12437 and describe the source location or compiler command-line where that
12438 definition was established. The optional double dash is to signify the end of
12439 argument processing and the beginning of @var{macro} for non C-like macros where
12440 the macro may begin with a hyphen.
12442 @kindex info macros
12443 @item info macros @var{location}
12444 Show all macro definitions that are in effect at the location specified
12445 by @var{location}, and describe the source location or compiler
12446 command-line where those definitions were established.
12448 @kindex macro define
12449 @cindex user-defined macros
12450 @cindex defining macros interactively
12451 @cindex macros, user-defined
12452 @item macro define @var{macro} @var{replacement-list}
12453 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
12454 Introduce a definition for a preprocessor macro named @var{macro},
12455 invocations of which are replaced by the tokens given in
12456 @var{replacement-list}. The first form of this command defines an
12457 ``object-like'' macro, which takes no arguments; the second form
12458 defines a ``function-like'' macro, which takes the arguments given in
12461 A definition introduced by this command is in scope in every
12462 expression evaluated in @value{GDBN}, until it is removed with the
12463 @code{macro undef} command, described below. The definition overrides
12464 all definitions for @var{macro} present in the program being debugged,
12465 as well as any previous user-supplied definition.
12467 @kindex macro undef
12468 @item macro undef @var{macro}
12469 Remove any user-supplied definition for the macro named @var{macro}.
12470 This command only affects definitions provided with the @code{macro
12471 define} command, described above; it cannot remove definitions present
12472 in the program being debugged.
12476 List all the macros defined using the @code{macro define} command.
12479 @cindex macros, example of debugging with
12480 Here is a transcript showing the above commands in action. First, we
12481 show our source files:
12486 #include "sample.h"
12489 #define ADD(x) (M + x)
12494 printf ("Hello, world!\n");
12496 printf ("We're so creative.\n");
12498 printf ("Goodbye, world!\n");
12505 Now, we compile the program using the @sc{gnu} C compiler,
12506 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
12507 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
12508 and @option{-gdwarf-4}; we recommend always choosing the most recent
12509 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
12510 includes information about preprocessor macros in the debugging
12514 $ gcc -gdwarf-2 -g3 sample.c -o sample
12518 Now, we start @value{GDBN} on our sample program:
12522 GNU gdb 2002-05-06-cvs
12523 Copyright 2002 Free Software Foundation, Inc.
12524 GDB is free software, @dots{}
12528 We can expand macros and examine their definitions, even when the
12529 program is not running. @value{GDBN} uses the current listing position
12530 to decide which macro definitions are in scope:
12533 (@value{GDBP}) list main
12536 5 #define ADD(x) (M + x)
12541 10 printf ("Hello, world!\n");
12543 12 printf ("We're so creative.\n");
12544 (@value{GDBP}) info macro ADD
12545 Defined at /home/jimb/gdb/macros/play/sample.c:5
12546 #define ADD(x) (M + x)
12547 (@value{GDBP}) info macro Q
12548 Defined at /home/jimb/gdb/macros/play/sample.h:1
12549 included at /home/jimb/gdb/macros/play/sample.c:2
12551 (@value{GDBP}) macro expand ADD(1)
12552 expands to: (42 + 1)
12553 (@value{GDBP}) macro expand-once ADD(1)
12554 expands to: once (M + 1)
12558 In the example above, note that @code{macro expand-once} expands only
12559 the macro invocation explicit in the original text --- the invocation of
12560 @code{ADD} --- but does not expand the invocation of the macro @code{M},
12561 which was introduced by @code{ADD}.
12563 Once the program is running, @value{GDBN} uses the macro definitions in
12564 force at the source line of the current stack frame:
12567 (@value{GDBP}) break main
12568 Breakpoint 1 at 0x8048370: file sample.c, line 10.
12570 Starting program: /home/jimb/gdb/macros/play/sample
12572 Breakpoint 1, main () at sample.c:10
12573 10 printf ("Hello, world!\n");
12577 At line 10, the definition of the macro @code{N} at line 9 is in force:
12580 (@value{GDBP}) info macro N
12581 Defined at /home/jimb/gdb/macros/play/sample.c:9
12583 (@value{GDBP}) macro expand N Q M
12584 expands to: 28 < 42
12585 (@value{GDBP}) print N Q M
12590 As we step over directives that remove @code{N}'s definition, and then
12591 give it a new definition, @value{GDBN} finds the definition (or lack
12592 thereof) in force at each point:
12595 (@value{GDBP}) next
12597 12 printf ("We're so creative.\n");
12598 (@value{GDBP}) info macro N
12599 The symbol `N' has no definition as a C/C++ preprocessor macro
12600 at /home/jimb/gdb/macros/play/sample.c:12
12601 (@value{GDBP}) next
12603 14 printf ("Goodbye, world!\n");
12604 (@value{GDBP}) info macro N
12605 Defined at /home/jimb/gdb/macros/play/sample.c:13
12607 (@value{GDBP}) macro expand N Q M
12608 expands to: 1729 < 42
12609 (@value{GDBP}) print N Q M
12614 In addition to source files, macros can be defined on the compilation command
12615 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
12616 such a way, @value{GDBN} displays the location of their definition as line zero
12617 of the source file submitted to the compiler.
12620 (@value{GDBP}) info macro __STDC__
12621 Defined at /home/jimb/gdb/macros/play/sample.c:0
12628 @chapter Tracepoints
12629 @c This chapter is based on the documentation written by Michael
12630 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
12632 @cindex tracepoints
12633 In some applications, it is not feasible for the debugger to interrupt
12634 the program's execution long enough for the developer to learn
12635 anything helpful about its behavior. If the program's correctness
12636 depends on its real-time behavior, delays introduced by a debugger
12637 might cause the program to change its behavior drastically, or perhaps
12638 fail, even when the code itself is correct. It is useful to be able
12639 to observe the program's behavior without interrupting it.
12641 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
12642 specify locations in the program, called @dfn{tracepoints}, and
12643 arbitrary expressions to evaluate when those tracepoints are reached.
12644 Later, using the @code{tfind} command, you can examine the values
12645 those expressions had when the program hit the tracepoints. The
12646 expressions may also denote objects in memory---structures or arrays,
12647 for example---whose values @value{GDBN} should record; while visiting
12648 a particular tracepoint, you may inspect those objects as if they were
12649 in memory at that moment. However, because @value{GDBN} records these
12650 values without interacting with you, it can do so quickly and
12651 unobtrusively, hopefully not disturbing the program's behavior.
12653 The tracepoint facility is currently available only for remote
12654 targets. @xref{Targets}. In addition, your remote target must know
12655 how to collect trace data. This functionality is implemented in the
12656 remote stub; however, none of the stubs distributed with @value{GDBN}
12657 support tracepoints as of this writing. The format of the remote
12658 packets used to implement tracepoints are described in @ref{Tracepoint
12661 It is also possible to get trace data from a file, in a manner reminiscent
12662 of corefiles; you specify the filename, and use @code{tfind} to search
12663 through the file. @xref{Trace Files}, for more details.
12665 This chapter describes the tracepoint commands and features.
12668 * Set Tracepoints::
12669 * Analyze Collected Data::
12670 * Tracepoint Variables::
12674 @node Set Tracepoints
12675 @section Commands to Set Tracepoints
12677 Before running such a @dfn{trace experiment}, an arbitrary number of
12678 tracepoints can be set. A tracepoint is actually a special type of
12679 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
12680 standard breakpoint commands. For instance, as with breakpoints,
12681 tracepoint numbers are successive integers starting from one, and many
12682 of the commands associated with tracepoints take the tracepoint number
12683 as their argument, to identify which tracepoint to work on.
12685 For each tracepoint, you can specify, in advance, some arbitrary set
12686 of data that you want the target to collect in the trace buffer when
12687 it hits that tracepoint. The collected data can include registers,
12688 local variables, or global data. Later, you can use @value{GDBN}
12689 commands to examine the values these data had at the time the
12690 tracepoint was hit.
12692 Tracepoints do not support every breakpoint feature. Ignore counts on
12693 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
12694 commands when they are hit. Tracepoints may not be thread-specific
12697 @cindex fast tracepoints
12698 Some targets may support @dfn{fast tracepoints}, which are inserted in
12699 a different way (such as with a jump instead of a trap), that is
12700 faster but possibly restricted in where they may be installed.
12702 @cindex static tracepoints
12703 @cindex markers, static tracepoints
12704 @cindex probing markers, static tracepoints
12705 Regular and fast tracepoints are dynamic tracing facilities, meaning
12706 that they can be used to insert tracepoints at (almost) any location
12707 in the target. Some targets may also support controlling @dfn{static
12708 tracepoints} from @value{GDBN}. With static tracing, a set of
12709 instrumentation points, also known as @dfn{markers}, are embedded in
12710 the target program, and can be activated or deactivated by name or
12711 address. These are usually placed at locations which facilitate
12712 investigating what the target is actually doing. @value{GDBN}'s
12713 support for static tracing includes being able to list instrumentation
12714 points, and attach them with @value{GDBN} defined high level
12715 tracepoints that expose the whole range of convenience of
12716 @value{GDBN}'s tracepoints support. Namely, support for collecting
12717 registers values and values of global or local (to the instrumentation
12718 point) variables; tracepoint conditions and trace state variables.
12719 The act of installing a @value{GDBN} static tracepoint on an
12720 instrumentation point, or marker, is referred to as @dfn{probing} a
12721 static tracepoint marker.
12723 @code{gdbserver} supports tracepoints on some target systems.
12724 @xref{Server,,Tracepoints support in @code{gdbserver}}.
12726 This section describes commands to set tracepoints and associated
12727 conditions and actions.
12730 * Create and Delete Tracepoints::
12731 * Enable and Disable Tracepoints::
12732 * Tracepoint Passcounts::
12733 * Tracepoint Conditions::
12734 * Trace State Variables::
12735 * Tracepoint Actions::
12736 * Listing Tracepoints::
12737 * Listing Static Tracepoint Markers::
12738 * Starting and Stopping Trace Experiments::
12739 * Tracepoint Restrictions::
12742 @node Create and Delete Tracepoints
12743 @subsection Create and Delete Tracepoints
12746 @cindex set tracepoint
12748 @item trace @var{location}
12749 The @code{trace} command is very similar to the @code{break} command.
12750 Its argument @var{location} can be any valid location.
12751 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
12752 which is a point in the target program where the debugger will briefly stop,
12753 collect some data, and then allow the program to continue. Setting a tracepoint
12754 or changing its actions takes effect immediately if the remote stub
12755 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
12757 If remote stub doesn't support the @samp{InstallInTrace} feature, all
12758 these changes don't take effect until the next @code{tstart}
12759 command, and once a trace experiment is running, further changes will
12760 not have any effect until the next trace experiment starts. In addition,
12761 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
12762 address is not yet resolved. (This is similar to pending breakpoints.)
12763 Pending tracepoints are not downloaded to the target and not installed
12764 until they are resolved. The resolution of pending tracepoints requires
12765 @value{GDBN} support---when debugging with the remote target, and
12766 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
12767 tracing}), pending tracepoints can not be resolved (and downloaded to
12768 the remote stub) while @value{GDBN} is disconnected.
12770 Here are some examples of using the @code{trace} command:
12773 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
12775 (@value{GDBP}) @b{trace +2} // 2 lines forward
12777 (@value{GDBP}) @b{trace my_function} // first source line of function
12779 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
12781 (@value{GDBP}) @b{trace *0x2117c4} // an address
12785 You can abbreviate @code{trace} as @code{tr}.
12787 @item trace @var{location} if @var{cond}
12788 Set a tracepoint with condition @var{cond}; evaluate the expression
12789 @var{cond} each time the tracepoint is reached, and collect data only
12790 if the value is nonzero---that is, if @var{cond} evaluates as true.
12791 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
12792 information on tracepoint conditions.
12794 @item ftrace @var{location} [ if @var{cond} ]
12795 @cindex set fast tracepoint
12796 @cindex fast tracepoints, setting
12798 The @code{ftrace} command sets a fast tracepoint. For targets that
12799 support them, fast tracepoints will use a more efficient but possibly
12800 less general technique to trigger data collection, such as a jump
12801 instruction instead of a trap, or some sort of hardware support. It
12802 may not be possible to create a fast tracepoint at the desired
12803 location, in which case the command will exit with an explanatory
12806 @value{GDBN} handles arguments to @code{ftrace} exactly as for
12809 On 32-bit x86-architecture systems, fast tracepoints normally need to
12810 be placed at an instruction that is 5 bytes or longer, but can be
12811 placed at 4-byte instructions if the low 64K of memory of the target
12812 program is available to install trampolines. Some Unix-type systems,
12813 such as @sc{gnu}/Linux, exclude low addresses from the program's
12814 address space; but for instance with the Linux kernel it is possible
12815 to let @value{GDBN} use this area by doing a @command{sysctl} command
12816 to set the @code{mmap_min_addr} kernel parameter, as in
12819 sudo sysctl -w vm.mmap_min_addr=32768
12823 which sets the low address to 32K, which leaves plenty of room for
12824 trampolines. The minimum address should be set to a page boundary.
12826 @item strace @var{location} [ if @var{cond} ]
12827 @cindex set static tracepoint
12828 @cindex static tracepoints, setting
12829 @cindex probe static tracepoint marker
12831 The @code{strace} command sets a static tracepoint. For targets that
12832 support it, setting a static tracepoint probes a static
12833 instrumentation point, or marker, found at @var{location}. It may not
12834 be possible to set a static tracepoint at the desired location, in
12835 which case the command will exit with an explanatory message.
12837 @value{GDBN} handles arguments to @code{strace} exactly as for
12838 @code{trace}, with the addition that the user can also specify
12839 @code{-m @var{marker}} as @var{location}. This probes the marker
12840 identified by the @var{marker} string identifier. This identifier
12841 depends on the static tracepoint backend library your program is
12842 using. You can find all the marker identifiers in the @samp{ID} field
12843 of the @code{info static-tracepoint-markers} command output.
12844 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
12845 Markers}. For example, in the following small program using the UST
12851 trace_mark(ust, bar33, "str %s", "FOOBAZ");
12856 the marker id is composed of joining the first two arguments to the
12857 @code{trace_mark} call with a slash, which translates to:
12860 (@value{GDBP}) info static-tracepoint-markers
12861 Cnt Enb ID Address What
12862 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
12868 so you may probe the marker above with:
12871 (@value{GDBP}) strace -m ust/bar33
12874 Static tracepoints accept an extra collect action --- @code{collect
12875 $_sdata}. This collects arbitrary user data passed in the probe point
12876 call to the tracing library. In the UST example above, you'll see
12877 that the third argument to @code{trace_mark} is a printf-like format
12878 string. The user data is then the result of running that formating
12879 string against the following arguments. Note that @code{info
12880 static-tracepoint-markers} command output lists that format string in
12881 the @samp{Data:} field.
12883 You can inspect this data when analyzing the trace buffer, by printing
12884 the $_sdata variable like any other variable available to
12885 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
12888 @cindex last tracepoint number
12889 @cindex recent tracepoint number
12890 @cindex tracepoint number
12891 The convenience variable @code{$tpnum} records the tracepoint number
12892 of the most recently set tracepoint.
12894 @kindex delete tracepoint
12895 @cindex tracepoint deletion
12896 @item delete tracepoint @r{[}@var{num}@r{]}
12897 Permanently delete one or more tracepoints. With no argument, the
12898 default is to delete all tracepoints. Note that the regular
12899 @code{delete} command can remove tracepoints also.
12904 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
12906 (@value{GDBP}) @b{delete trace} // remove all tracepoints
12910 You can abbreviate this command as @code{del tr}.
12913 @node Enable and Disable Tracepoints
12914 @subsection Enable and Disable Tracepoints
12916 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
12919 @kindex disable tracepoint
12920 @item disable tracepoint @r{[}@var{num}@r{]}
12921 Disable tracepoint @var{num}, or all tracepoints if no argument
12922 @var{num} is given. A disabled tracepoint will have no effect during
12923 a trace experiment, but it is not forgotten. You can re-enable
12924 a disabled tracepoint using the @code{enable tracepoint} command.
12925 If the command is issued during a trace experiment and the debug target
12926 has support for disabling tracepoints during a trace experiment, then the
12927 change will be effective immediately. Otherwise, it will be applied to the
12928 next trace experiment.
12930 @kindex enable tracepoint
12931 @item enable tracepoint @r{[}@var{num}@r{]}
12932 Enable tracepoint @var{num}, or all tracepoints. If this command is
12933 issued during a trace experiment and the debug target supports enabling
12934 tracepoints during a trace experiment, then the enabled tracepoints will
12935 become effective immediately. Otherwise, they will become effective the
12936 next time a trace experiment is run.
12939 @node Tracepoint Passcounts
12940 @subsection Tracepoint Passcounts
12944 @cindex tracepoint pass count
12945 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
12946 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
12947 automatically stop a trace experiment. If a tracepoint's passcount is
12948 @var{n}, then the trace experiment will be automatically stopped on
12949 the @var{n}'th time that tracepoint is hit. If the tracepoint number
12950 @var{num} is not specified, the @code{passcount} command sets the
12951 passcount of the most recently defined tracepoint. If no passcount is
12952 given, the trace experiment will run until stopped explicitly by the
12958 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
12959 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
12961 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
12962 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
12963 (@value{GDBP}) @b{trace foo}
12964 (@value{GDBP}) @b{pass 3}
12965 (@value{GDBP}) @b{trace bar}
12966 (@value{GDBP}) @b{pass 2}
12967 (@value{GDBP}) @b{trace baz}
12968 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
12969 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
12970 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
12971 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
12975 @node Tracepoint Conditions
12976 @subsection Tracepoint Conditions
12977 @cindex conditional tracepoints
12978 @cindex tracepoint conditions
12980 The simplest sort of tracepoint collects data every time your program
12981 reaches a specified place. You can also specify a @dfn{condition} for
12982 a tracepoint. A condition is just a Boolean expression in your
12983 programming language (@pxref{Expressions, ,Expressions}). A
12984 tracepoint with a condition evaluates the expression each time your
12985 program reaches it, and data collection happens only if the condition
12988 Tracepoint conditions can be specified when a tracepoint is set, by
12989 using @samp{if} in the arguments to the @code{trace} command.
12990 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
12991 also be set or changed at any time with the @code{condition} command,
12992 just as with breakpoints.
12994 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
12995 the conditional expression itself. Instead, @value{GDBN} encodes the
12996 expression into an agent expression (@pxref{Agent Expressions})
12997 suitable for execution on the target, independently of @value{GDBN}.
12998 Global variables become raw memory locations, locals become stack
12999 accesses, and so forth.
13001 For instance, suppose you have a function that is usually called
13002 frequently, but should not be called after an error has occurred. You
13003 could use the following tracepoint command to collect data about calls
13004 of that function that happen while the error code is propagating
13005 through the program; an unconditional tracepoint could end up
13006 collecting thousands of useless trace frames that you would have to
13010 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
13013 @node Trace State Variables
13014 @subsection Trace State Variables
13015 @cindex trace state variables
13017 A @dfn{trace state variable} is a special type of variable that is
13018 created and managed by target-side code. The syntax is the same as
13019 that for GDB's convenience variables (a string prefixed with ``$''),
13020 but they are stored on the target. They must be created explicitly,
13021 using a @code{tvariable} command. They are always 64-bit signed
13024 Trace state variables are remembered by @value{GDBN}, and downloaded
13025 to the target along with tracepoint information when the trace
13026 experiment starts. There are no intrinsic limits on the number of
13027 trace state variables, beyond memory limitations of the target.
13029 @cindex convenience variables, and trace state variables
13030 Although trace state variables are managed by the target, you can use
13031 them in print commands and expressions as if they were convenience
13032 variables; @value{GDBN} will get the current value from the target
13033 while the trace experiment is running. Trace state variables share
13034 the same namespace as other ``$'' variables, which means that you
13035 cannot have trace state variables with names like @code{$23} or
13036 @code{$pc}, nor can you have a trace state variable and a convenience
13037 variable with the same name.
13041 @item tvariable $@var{name} [ = @var{expression} ]
13043 The @code{tvariable} command creates a new trace state variable named
13044 @code{$@var{name}}, and optionally gives it an initial value of
13045 @var{expression}. The @var{expression} is evaluated when this command is
13046 entered; the result will be converted to an integer if possible,
13047 otherwise @value{GDBN} will report an error. A subsequent
13048 @code{tvariable} command specifying the same name does not create a
13049 variable, but instead assigns the supplied initial value to the
13050 existing variable of that name, overwriting any previous initial
13051 value. The default initial value is 0.
13053 @item info tvariables
13054 @kindex info tvariables
13055 List all the trace state variables along with their initial values.
13056 Their current values may also be displayed, if the trace experiment is
13059 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
13060 @kindex delete tvariable
13061 Delete the given trace state variables, or all of them if no arguments
13066 @node Tracepoint Actions
13067 @subsection Tracepoint Action Lists
13071 @cindex tracepoint actions
13072 @item actions @r{[}@var{num}@r{]}
13073 This command will prompt for a list of actions to be taken when the
13074 tracepoint is hit. If the tracepoint number @var{num} is not
13075 specified, this command sets the actions for the one that was most
13076 recently defined (so that you can define a tracepoint and then say
13077 @code{actions} without bothering about its number). You specify the
13078 actions themselves on the following lines, one action at a time, and
13079 terminate the actions list with a line containing just @code{end}. So
13080 far, the only defined actions are @code{collect}, @code{teval}, and
13081 @code{while-stepping}.
13083 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
13084 Commands, ,Breakpoint Command Lists}), except that only the defined
13085 actions are allowed; any other @value{GDBN} command is rejected.
13087 @cindex remove actions from a tracepoint
13088 To remove all actions from a tracepoint, type @samp{actions @var{num}}
13089 and follow it immediately with @samp{end}.
13092 (@value{GDBP}) @b{collect @var{data}} // collect some data
13094 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
13096 (@value{GDBP}) @b{end} // signals the end of actions.
13099 In the following example, the action list begins with @code{collect}
13100 commands indicating the things to be collected when the tracepoint is
13101 hit. Then, in order to single-step and collect additional data
13102 following the tracepoint, a @code{while-stepping} command is used,
13103 followed by the list of things to be collected after each step in a
13104 sequence of single steps. The @code{while-stepping} command is
13105 terminated by its own separate @code{end} command. Lastly, the action
13106 list is terminated by an @code{end} command.
13109 (@value{GDBP}) @b{trace foo}
13110 (@value{GDBP}) @b{actions}
13111 Enter actions for tracepoint 1, one per line:
13114 > while-stepping 12
13115 > collect $pc, arr[i]
13120 @kindex collect @r{(tracepoints)}
13121 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
13122 Collect values of the given expressions when the tracepoint is hit.
13123 This command accepts a comma-separated list of any valid expressions.
13124 In addition to global, static, or local variables, the following
13125 special arguments are supported:
13129 Collect all registers.
13132 Collect all function arguments.
13135 Collect all local variables.
13138 Collect the return address. This is helpful if you want to see more
13141 @emph{Note:} The return address location can not always be reliably
13142 determined up front, and the wrong address / registers may end up
13143 collected instead. On some architectures the reliability is higher
13144 for tracepoints at function entry, while on others it's the opposite.
13145 When this happens, backtracing will stop because the return address is
13146 found unavailable (unless another collect rule happened to match it).
13149 Collects the number of arguments from the static probe at which the
13150 tracepoint is located.
13151 @xref{Static Probe Points}.
13153 @item $_probe_arg@var{n}
13154 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
13155 from the static probe at which the tracepoint is located.
13156 @xref{Static Probe Points}.
13159 @vindex $_sdata@r{, collect}
13160 Collect static tracepoint marker specific data. Only available for
13161 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
13162 Lists}. On the UST static tracepoints library backend, an
13163 instrumentation point resembles a @code{printf} function call. The
13164 tracing library is able to collect user specified data formatted to a
13165 character string using the format provided by the programmer that
13166 instrumented the program. Other backends have similar mechanisms.
13167 Here's an example of a UST marker call:
13170 const char master_name[] = "$your_name";
13171 trace_mark(channel1, marker1, "hello %s", master_name)
13174 In this case, collecting @code{$_sdata} collects the string
13175 @samp{hello $yourname}. When analyzing the trace buffer, you can
13176 inspect @samp{$_sdata} like any other variable available to
13180 You can give several consecutive @code{collect} commands, each one
13181 with a single argument, or one @code{collect} command with several
13182 arguments separated by commas; the effect is the same.
13184 The optional @var{mods} changes the usual handling of the arguments.
13185 @code{s} requests that pointers to chars be handled as strings, in
13186 particular collecting the contents of the memory being pointed at, up
13187 to the first zero. The upper bound is by default the value of the
13188 @code{print elements} variable; if @code{s} is followed by a decimal
13189 number, that is the upper bound instead. So for instance
13190 @samp{collect/s25 mystr} collects as many as 25 characters at
13193 The command @code{info scope} (@pxref{Symbols, info scope}) is
13194 particularly useful for figuring out what data to collect.
13196 @kindex teval @r{(tracepoints)}
13197 @item teval @var{expr1}, @var{expr2}, @dots{}
13198 Evaluate the given expressions when the tracepoint is hit. This
13199 command accepts a comma-separated list of expressions. The results
13200 are discarded, so this is mainly useful for assigning values to trace
13201 state variables (@pxref{Trace State Variables}) without adding those
13202 values to the trace buffer, as would be the case if the @code{collect}
13205 @kindex while-stepping @r{(tracepoints)}
13206 @item while-stepping @var{n}
13207 Perform @var{n} single-step instruction traces after the tracepoint,
13208 collecting new data after each step. The @code{while-stepping}
13209 command is followed by the list of what to collect while stepping
13210 (followed by its own @code{end} command):
13213 > while-stepping 12
13214 > collect $regs, myglobal
13220 Note that @code{$pc} is not automatically collected by
13221 @code{while-stepping}; you need to explicitly collect that register if
13222 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
13225 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
13226 @kindex set default-collect
13227 @cindex default collection action
13228 This variable is a list of expressions to collect at each tracepoint
13229 hit. It is effectively an additional @code{collect} action prepended
13230 to every tracepoint action list. The expressions are parsed
13231 individually for each tracepoint, so for instance a variable named
13232 @code{xyz} may be interpreted as a global for one tracepoint, and a
13233 local for another, as appropriate to the tracepoint's location.
13235 @item show default-collect
13236 @kindex show default-collect
13237 Show the list of expressions that are collected by default at each
13242 @node Listing Tracepoints
13243 @subsection Listing Tracepoints
13246 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
13247 @kindex info tp @r{[}@var{n}@dots{}@r{]}
13248 @cindex information about tracepoints
13249 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
13250 Display information about the tracepoint @var{num}. If you don't
13251 specify a tracepoint number, displays information about all the
13252 tracepoints defined so far. The format is similar to that used for
13253 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
13254 command, simply restricting itself to tracepoints.
13256 A tracepoint's listing may include additional information specific to
13261 its passcount as given by the @code{passcount @var{n}} command
13264 the state about installed on target of each location
13268 (@value{GDBP}) @b{info trace}
13269 Num Type Disp Enb Address What
13270 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
13272 collect globfoo, $regs
13277 2 tracepoint keep y <MULTIPLE>
13279 2.1 y 0x0804859c in func4 at change-loc.h:35
13280 installed on target
13281 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
13282 installed on target
13283 2.3 y <PENDING> set_tracepoint
13284 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
13285 not installed on target
13290 This command can be abbreviated @code{info tp}.
13293 @node Listing Static Tracepoint Markers
13294 @subsection Listing Static Tracepoint Markers
13297 @kindex info static-tracepoint-markers
13298 @cindex information about static tracepoint markers
13299 @item info static-tracepoint-markers
13300 Display information about all static tracepoint markers defined in the
13303 For each marker, the following columns are printed:
13307 An incrementing counter, output to help readability. This is not a
13310 The marker ID, as reported by the target.
13311 @item Enabled or Disabled
13312 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
13313 that are not enabled.
13315 Where the marker is in your program, as a memory address.
13317 Where the marker is in the source for your program, as a file and line
13318 number. If the debug information included in the program does not
13319 allow @value{GDBN} to locate the source of the marker, this column
13320 will be left blank.
13324 In addition, the following information may be printed for each marker:
13328 User data passed to the tracing library by the marker call. In the
13329 UST backend, this is the format string passed as argument to the
13331 @item Static tracepoints probing the marker
13332 The list of static tracepoints attached to the marker.
13336 (@value{GDBP}) info static-tracepoint-markers
13337 Cnt ID Enb Address What
13338 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
13339 Data: number1 %d number2 %d
13340 Probed by static tracepoints: #2
13341 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
13347 @node Starting and Stopping Trace Experiments
13348 @subsection Starting and Stopping Trace Experiments
13351 @kindex tstart [ @var{notes} ]
13352 @cindex start a new trace experiment
13353 @cindex collected data discarded
13355 This command starts the trace experiment, and begins collecting data.
13356 It has the side effect of discarding all the data collected in the
13357 trace buffer during the previous trace experiment. If any arguments
13358 are supplied, they are taken as a note and stored with the trace
13359 experiment's state. The notes may be arbitrary text, and are
13360 especially useful with disconnected tracing in a multi-user context;
13361 the notes can explain what the trace is doing, supply user contact
13362 information, and so forth.
13364 @kindex tstop [ @var{notes} ]
13365 @cindex stop a running trace experiment
13367 This command stops the trace experiment. If any arguments are
13368 supplied, they are recorded with the experiment as a note. This is
13369 useful if you are stopping a trace started by someone else, for
13370 instance if the trace is interfering with the system's behavior and
13371 needs to be stopped quickly.
13373 @strong{Note}: a trace experiment and data collection may stop
13374 automatically if any tracepoint's passcount is reached
13375 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
13378 @cindex status of trace data collection
13379 @cindex trace experiment, status of
13381 This command displays the status of the current trace data
13385 Here is an example of the commands we described so far:
13388 (@value{GDBP}) @b{trace gdb_c_test}
13389 (@value{GDBP}) @b{actions}
13390 Enter actions for tracepoint #1, one per line.
13391 > collect $regs,$locals,$args
13392 > while-stepping 11
13396 (@value{GDBP}) @b{tstart}
13397 [time passes @dots{}]
13398 (@value{GDBP}) @b{tstop}
13401 @anchor{disconnected tracing}
13402 @cindex disconnected tracing
13403 You can choose to continue running the trace experiment even if
13404 @value{GDBN} disconnects from the target, voluntarily or
13405 involuntarily. For commands such as @code{detach}, the debugger will
13406 ask what you want to do with the trace. But for unexpected
13407 terminations (@value{GDBN} crash, network outage), it would be
13408 unfortunate to lose hard-won trace data, so the variable
13409 @code{disconnected-tracing} lets you decide whether the trace should
13410 continue running without @value{GDBN}.
13413 @item set disconnected-tracing on
13414 @itemx set disconnected-tracing off
13415 @kindex set disconnected-tracing
13416 Choose whether a tracing run should continue to run if @value{GDBN}
13417 has disconnected from the target. Note that @code{detach} or
13418 @code{quit} will ask you directly what to do about a running trace no
13419 matter what this variable's setting, so the variable is mainly useful
13420 for handling unexpected situations, such as loss of the network.
13422 @item show disconnected-tracing
13423 @kindex show disconnected-tracing
13424 Show the current choice for disconnected tracing.
13428 When you reconnect to the target, the trace experiment may or may not
13429 still be running; it might have filled the trace buffer in the
13430 meantime, or stopped for one of the other reasons. If it is running,
13431 it will continue after reconnection.
13433 Upon reconnection, the target will upload information about the
13434 tracepoints in effect. @value{GDBN} will then compare that
13435 information to the set of tracepoints currently defined, and attempt
13436 to match them up, allowing for the possibility that the numbers may
13437 have changed due to creation and deletion in the meantime. If one of
13438 the target's tracepoints does not match any in @value{GDBN}, the
13439 debugger will create a new tracepoint, so that you have a number with
13440 which to specify that tracepoint. This matching-up process is
13441 necessarily heuristic, and it may result in useless tracepoints being
13442 created; you may simply delete them if they are of no use.
13444 @cindex circular trace buffer
13445 If your target agent supports a @dfn{circular trace buffer}, then you
13446 can run a trace experiment indefinitely without filling the trace
13447 buffer; when space runs out, the agent deletes already-collected trace
13448 frames, oldest first, until there is enough room to continue
13449 collecting. This is especially useful if your tracepoints are being
13450 hit too often, and your trace gets terminated prematurely because the
13451 buffer is full. To ask for a circular trace buffer, simply set
13452 @samp{circular-trace-buffer} to on. You can set this at any time,
13453 including during tracing; if the agent can do it, it will change
13454 buffer handling on the fly, otherwise it will not take effect until
13458 @item set circular-trace-buffer on
13459 @itemx set circular-trace-buffer off
13460 @kindex set circular-trace-buffer
13461 Choose whether a tracing run should use a linear or circular buffer
13462 for trace data. A linear buffer will not lose any trace data, but may
13463 fill up prematurely, while a circular buffer will discard old trace
13464 data, but it will have always room for the latest tracepoint hits.
13466 @item show circular-trace-buffer
13467 @kindex show circular-trace-buffer
13468 Show the current choice for the trace buffer. Note that this may not
13469 match the agent's current buffer handling, nor is it guaranteed to
13470 match the setting that might have been in effect during a past run,
13471 for instance if you are looking at frames from a trace file.
13476 @item set trace-buffer-size @var{n}
13477 @itemx set trace-buffer-size unlimited
13478 @kindex set trace-buffer-size
13479 Request that the target use a trace buffer of @var{n} bytes. Not all
13480 targets will honor the request; they may have a compiled-in size for
13481 the trace buffer, or some other limitation. Set to a value of
13482 @code{unlimited} or @code{-1} to let the target use whatever size it
13483 likes. This is also the default.
13485 @item show trace-buffer-size
13486 @kindex show trace-buffer-size
13487 Show the current requested size for the trace buffer. Note that this
13488 will only match the actual size if the target supports size-setting,
13489 and was able to handle the requested size. For instance, if the
13490 target can only change buffer size between runs, this variable will
13491 not reflect the change until the next run starts. Use @code{tstatus}
13492 to get a report of the actual buffer size.
13496 @item set trace-user @var{text}
13497 @kindex set trace-user
13499 @item show trace-user
13500 @kindex show trace-user
13502 @item set trace-notes @var{text}
13503 @kindex set trace-notes
13504 Set the trace run's notes.
13506 @item show trace-notes
13507 @kindex show trace-notes
13508 Show the trace run's notes.
13510 @item set trace-stop-notes @var{text}
13511 @kindex set trace-stop-notes
13512 Set the trace run's stop notes. The handling of the note is as for
13513 @code{tstop} arguments; the set command is convenient way to fix a
13514 stop note that is mistaken or incomplete.
13516 @item show trace-stop-notes
13517 @kindex show trace-stop-notes
13518 Show the trace run's stop notes.
13522 @node Tracepoint Restrictions
13523 @subsection Tracepoint Restrictions
13525 @cindex tracepoint restrictions
13526 There are a number of restrictions on the use of tracepoints. As
13527 described above, tracepoint data gathering occurs on the target
13528 without interaction from @value{GDBN}. Thus the full capabilities of
13529 the debugger are not available during data gathering, and then at data
13530 examination time, you will be limited by only having what was
13531 collected. The following items describe some common problems, but it
13532 is not exhaustive, and you may run into additional difficulties not
13538 Tracepoint expressions are intended to gather objects (lvalues). Thus
13539 the full flexibility of GDB's expression evaluator is not available.
13540 You cannot call functions, cast objects to aggregate types, access
13541 convenience variables or modify values (except by assignment to trace
13542 state variables). Some language features may implicitly call
13543 functions (for instance Objective-C fields with accessors), and therefore
13544 cannot be collected either.
13547 Collection of local variables, either individually or in bulk with
13548 @code{$locals} or @code{$args}, during @code{while-stepping} may
13549 behave erratically. The stepping action may enter a new scope (for
13550 instance by stepping into a function), or the location of the variable
13551 may change (for instance it is loaded into a register). The
13552 tracepoint data recorded uses the location information for the
13553 variables that is correct for the tracepoint location. When the
13554 tracepoint is created, it is not possible, in general, to determine
13555 where the steps of a @code{while-stepping} sequence will advance the
13556 program---particularly if a conditional branch is stepped.
13559 Collection of an incompletely-initialized or partially-destroyed object
13560 may result in something that @value{GDBN} cannot display, or displays
13561 in a misleading way.
13564 When @value{GDBN} displays a pointer to character it automatically
13565 dereferences the pointer to also display characters of the string
13566 being pointed to. However, collecting the pointer during tracing does
13567 not automatically collect the string. You need to explicitly
13568 dereference the pointer and provide size information if you want to
13569 collect not only the pointer, but the memory pointed to. For example,
13570 @code{*ptr@@50} can be used to collect the 50 element array pointed to
13574 It is not possible to collect a complete stack backtrace at a
13575 tracepoint. Instead, you may collect the registers and a few hundred
13576 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
13577 (adjust to use the name of the actual stack pointer register on your
13578 target architecture, and the amount of stack you wish to capture).
13579 Then the @code{backtrace} command will show a partial backtrace when
13580 using a trace frame. The number of stack frames that can be examined
13581 depends on the sizes of the frames in the collected stack. Note that
13582 if you ask for a block so large that it goes past the bottom of the
13583 stack, the target agent may report an error trying to read from an
13587 If you do not collect registers at a tracepoint, @value{GDBN} can
13588 infer that the value of @code{$pc} must be the same as the address of
13589 the tracepoint and use that when you are looking at a trace frame
13590 for that tracepoint. However, this cannot work if the tracepoint has
13591 multiple locations (for instance if it was set in a function that was
13592 inlined), or if it has a @code{while-stepping} loop. In those cases
13593 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
13598 @node Analyze Collected Data
13599 @section Using the Collected Data
13601 After the tracepoint experiment ends, you use @value{GDBN} commands
13602 for examining the trace data. The basic idea is that each tracepoint
13603 collects a trace @dfn{snapshot} every time it is hit and another
13604 snapshot every time it single-steps. All these snapshots are
13605 consecutively numbered from zero and go into a buffer, and you can
13606 examine them later. The way you examine them is to @dfn{focus} on a
13607 specific trace snapshot. When the remote stub is focused on a trace
13608 snapshot, it will respond to all @value{GDBN} requests for memory and
13609 registers by reading from the buffer which belongs to that snapshot,
13610 rather than from @emph{real} memory or registers of the program being
13611 debugged. This means that @strong{all} @value{GDBN} commands
13612 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
13613 behave as if we were currently debugging the program state as it was
13614 when the tracepoint occurred. Any requests for data that are not in
13615 the buffer will fail.
13618 * tfind:: How to select a trace snapshot
13619 * tdump:: How to display all data for a snapshot
13620 * save tracepoints:: How to save tracepoints for a future run
13624 @subsection @code{tfind @var{n}}
13627 @cindex select trace snapshot
13628 @cindex find trace snapshot
13629 The basic command for selecting a trace snapshot from the buffer is
13630 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
13631 counting from zero. If no argument @var{n} is given, the next
13632 snapshot is selected.
13634 Here are the various forms of using the @code{tfind} command.
13638 Find the first snapshot in the buffer. This is a synonym for
13639 @code{tfind 0} (since 0 is the number of the first snapshot).
13642 Stop debugging trace snapshots, resume @emph{live} debugging.
13645 Same as @samp{tfind none}.
13648 No argument means find the next trace snapshot or find the first
13649 one if no trace snapshot is selected.
13652 Find the previous trace snapshot before the current one. This permits
13653 retracing earlier steps.
13655 @item tfind tracepoint @var{num}
13656 Find the next snapshot associated with tracepoint @var{num}. Search
13657 proceeds forward from the last examined trace snapshot. If no
13658 argument @var{num} is given, it means find the next snapshot collected
13659 for the same tracepoint as the current snapshot.
13661 @item tfind pc @var{addr}
13662 Find the next snapshot associated with the value @var{addr} of the
13663 program counter. Search proceeds forward from the last examined trace
13664 snapshot. If no argument @var{addr} is given, it means find the next
13665 snapshot with the same value of PC as the current snapshot.
13667 @item tfind outside @var{addr1}, @var{addr2}
13668 Find the next snapshot whose PC is outside the given range of
13669 addresses (exclusive).
13671 @item tfind range @var{addr1}, @var{addr2}
13672 Find the next snapshot whose PC is between @var{addr1} and
13673 @var{addr2} (inclusive).
13675 @item tfind line @r{[}@var{file}:@r{]}@var{n}
13676 Find the next snapshot associated with the source line @var{n}. If
13677 the optional argument @var{file} is given, refer to line @var{n} in
13678 that source file. Search proceeds forward from the last examined
13679 trace snapshot. If no argument @var{n} is given, it means find the
13680 next line other than the one currently being examined; thus saying
13681 @code{tfind line} repeatedly can appear to have the same effect as
13682 stepping from line to line in a @emph{live} debugging session.
13685 The default arguments for the @code{tfind} commands are specifically
13686 designed to make it easy to scan through the trace buffer. For
13687 instance, @code{tfind} with no argument selects the next trace
13688 snapshot, and @code{tfind -} with no argument selects the previous
13689 trace snapshot. So, by giving one @code{tfind} command, and then
13690 simply hitting @key{RET} repeatedly you can examine all the trace
13691 snapshots in order. Or, by saying @code{tfind -} and then hitting
13692 @key{RET} repeatedly you can examine the snapshots in reverse order.
13693 The @code{tfind line} command with no argument selects the snapshot
13694 for the next source line executed. The @code{tfind pc} command with
13695 no argument selects the next snapshot with the same program counter
13696 (PC) as the current frame. The @code{tfind tracepoint} command with
13697 no argument selects the next trace snapshot collected by the same
13698 tracepoint as the current one.
13700 In addition to letting you scan through the trace buffer manually,
13701 these commands make it easy to construct @value{GDBN} scripts that
13702 scan through the trace buffer and print out whatever collected data
13703 you are interested in. Thus, if we want to examine the PC, FP, and SP
13704 registers from each trace frame in the buffer, we can say this:
13707 (@value{GDBP}) @b{tfind start}
13708 (@value{GDBP}) @b{while ($trace_frame != -1)}
13709 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
13710 $trace_frame, $pc, $sp, $fp
13714 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
13715 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
13716 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
13717 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
13718 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
13719 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
13720 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
13721 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
13722 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
13723 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
13724 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
13727 Or, if we want to examine the variable @code{X} at each source line in
13731 (@value{GDBP}) @b{tfind start}
13732 (@value{GDBP}) @b{while ($trace_frame != -1)}
13733 > printf "Frame %d, X == %d\n", $trace_frame, X
13743 @subsection @code{tdump}
13745 @cindex dump all data collected at tracepoint
13746 @cindex tracepoint data, display
13748 This command takes no arguments. It prints all the data collected at
13749 the current trace snapshot.
13752 (@value{GDBP}) @b{trace 444}
13753 (@value{GDBP}) @b{actions}
13754 Enter actions for tracepoint #2, one per line:
13755 > collect $regs, $locals, $args, gdb_long_test
13758 (@value{GDBP}) @b{tstart}
13760 (@value{GDBP}) @b{tfind line 444}
13761 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
13763 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
13765 (@value{GDBP}) @b{tdump}
13766 Data collected at tracepoint 2, trace frame 1:
13767 d0 0xc4aa0085 -995491707
13771 d4 0x71aea3d 119204413
13774 d7 0x380035 3670069
13775 a0 0x19e24a 1696330
13776 a1 0x3000668 50333288
13778 a3 0x322000 3284992
13779 a4 0x3000698 50333336
13780 a5 0x1ad3cc 1758156
13781 fp 0x30bf3c 0x30bf3c
13782 sp 0x30bf34 0x30bf34
13784 pc 0x20b2c8 0x20b2c8
13788 p = 0x20e5b4 "gdb-test"
13795 gdb_long_test = 17 '\021'
13800 @code{tdump} works by scanning the tracepoint's current collection
13801 actions and printing the value of each expression listed. So
13802 @code{tdump} can fail, if after a run, you change the tracepoint's
13803 actions to mention variables that were not collected during the run.
13805 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
13806 uses the collected value of @code{$pc} to distinguish between trace
13807 frames that were collected at the tracepoint hit, and frames that were
13808 collected while stepping. This allows it to correctly choose whether
13809 to display the basic list of collections, or the collections from the
13810 body of the while-stepping loop. However, if @code{$pc} was not collected,
13811 then @code{tdump} will always attempt to dump using the basic collection
13812 list, and may fail if a while-stepping frame does not include all the
13813 same data that is collected at the tracepoint hit.
13814 @c This is getting pretty arcane, example would be good.
13816 @node save tracepoints
13817 @subsection @code{save tracepoints @var{filename}}
13818 @kindex save tracepoints
13819 @kindex save-tracepoints
13820 @cindex save tracepoints for future sessions
13822 This command saves all current tracepoint definitions together with
13823 their actions and passcounts, into a file @file{@var{filename}}
13824 suitable for use in a later debugging session. To read the saved
13825 tracepoint definitions, use the @code{source} command (@pxref{Command
13826 Files}). The @w{@code{save-tracepoints}} command is a deprecated
13827 alias for @w{@code{save tracepoints}}
13829 @node Tracepoint Variables
13830 @section Convenience Variables for Tracepoints
13831 @cindex tracepoint variables
13832 @cindex convenience variables for tracepoints
13835 @vindex $trace_frame
13836 @item (int) $trace_frame
13837 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
13838 snapshot is selected.
13840 @vindex $tracepoint
13841 @item (int) $tracepoint
13842 The tracepoint for the current trace snapshot.
13844 @vindex $trace_line
13845 @item (int) $trace_line
13846 The line number for the current trace snapshot.
13848 @vindex $trace_file
13849 @item (char []) $trace_file
13850 The source file for the current trace snapshot.
13852 @vindex $trace_func
13853 @item (char []) $trace_func
13854 The name of the function containing @code{$tracepoint}.
13857 Note: @code{$trace_file} is not suitable for use in @code{printf},
13858 use @code{output} instead.
13860 Here's a simple example of using these convenience variables for
13861 stepping through all the trace snapshots and printing some of their
13862 data. Note that these are not the same as trace state variables,
13863 which are managed by the target.
13866 (@value{GDBP}) @b{tfind start}
13868 (@value{GDBP}) @b{while $trace_frame != -1}
13869 > output $trace_file
13870 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
13876 @section Using Trace Files
13877 @cindex trace files
13879 In some situations, the target running a trace experiment may no
13880 longer be available; perhaps it crashed, or the hardware was needed
13881 for a different activity. To handle these cases, you can arrange to
13882 dump the trace data into a file, and later use that file as a source
13883 of trace data, via the @code{target tfile} command.
13888 @item tsave [ -r ] @var{filename}
13889 @itemx tsave [-ctf] @var{dirname}
13890 Save the trace data to @var{filename}. By default, this command
13891 assumes that @var{filename} refers to the host filesystem, so if
13892 necessary @value{GDBN} will copy raw trace data up from the target and
13893 then save it. If the target supports it, you can also supply the
13894 optional argument @code{-r} (``remote'') to direct the target to save
13895 the data directly into @var{filename} in its own filesystem, which may be
13896 more efficient if the trace buffer is very large. (Note, however, that
13897 @code{target tfile} can only read from files accessible to the host.)
13898 By default, this command will save trace frame in tfile format.
13899 You can supply the optional argument @code{-ctf} to save data in CTF
13900 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
13901 that can be shared by multiple debugging and tracing tools. Please go to
13902 @indicateurl{http://www.efficios.com/ctf} to get more information.
13904 @kindex target tfile
13908 @item target tfile @var{filename}
13909 @itemx target ctf @var{dirname}
13910 Use the file named @var{filename} or directory named @var{dirname} as
13911 a source of trace data. Commands that examine data work as they do with
13912 a live target, but it is not possible to run any new trace experiments.
13913 @code{tstatus} will report the state of the trace run at the moment
13914 the data was saved, as well as the current trace frame you are examining.
13915 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
13919 (@value{GDBP}) target ctf ctf.ctf
13920 (@value{GDBP}) tfind
13921 Found trace frame 0, tracepoint 2
13922 39 ++a; /* set tracepoint 1 here */
13923 (@value{GDBP}) tdump
13924 Data collected at tracepoint 2, trace frame 0:
13928 c = @{"123", "456", "789", "123", "456", "789"@}
13929 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
13937 @chapter Debugging Programs That Use Overlays
13940 If your program is too large to fit completely in your target system's
13941 memory, you can sometimes use @dfn{overlays} to work around this
13942 problem. @value{GDBN} provides some support for debugging programs that
13946 * How Overlays Work:: A general explanation of overlays.
13947 * Overlay Commands:: Managing overlays in @value{GDBN}.
13948 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
13949 mapped by asking the inferior.
13950 * Overlay Sample Program:: A sample program using overlays.
13953 @node How Overlays Work
13954 @section How Overlays Work
13955 @cindex mapped overlays
13956 @cindex unmapped overlays
13957 @cindex load address, overlay's
13958 @cindex mapped address
13959 @cindex overlay area
13961 Suppose you have a computer whose instruction address space is only 64
13962 kilobytes long, but which has much more memory which can be accessed by
13963 other means: special instructions, segment registers, or memory
13964 management hardware, for example. Suppose further that you want to
13965 adapt a program which is larger than 64 kilobytes to run on this system.
13967 One solution is to identify modules of your program which are relatively
13968 independent, and need not call each other directly; call these modules
13969 @dfn{overlays}. Separate the overlays from the main program, and place
13970 their machine code in the larger memory. Place your main program in
13971 instruction memory, but leave at least enough space there to hold the
13972 largest overlay as well.
13974 Now, to call a function located in an overlay, you must first copy that
13975 overlay's machine code from the large memory into the space set aside
13976 for it in the instruction memory, and then jump to its entry point
13979 @c NB: In the below the mapped area's size is greater or equal to the
13980 @c size of all overlays. This is intentional to remind the developer
13981 @c that overlays don't necessarily need to be the same size.
13985 Data Instruction Larger
13986 Address Space Address Space Address Space
13987 +-----------+ +-----------+ +-----------+
13989 +-----------+ +-----------+ +-----------+<-- overlay 1
13990 | program | | main | .----| overlay 1 | load address
13991 | variables | | program | | +-----------+
13992 | and heap | | | | | |
13993 +-----------+ | | | +-----------+<-- overlay 2
13994 | | +-----------+ | | | load address
13995 +-----------+ | | | .-| overlay 2 |
13997 mapped --->+-----------+ | | +-----------+
13998 address | | | | | |
13999 | overlay | <-' | | |
14000 | area | <---' +-----------+<-- overlay 3
14001 | | <---. | | load address
14002 +-----------+ `--| overlay 3 |
14009 @anchor{A code overlay}A code overlay
14013 The diagram (@pxref{A code overlay}) shows a system with separate data
14014 and instruction address spaces. To map an overlay, the program copies
14015 its code from the larger address space to the instruction address space.
14016 Since the overlays shown here all use the same mapped address, only one
14017 may be mapped at a time. For a system with a single address space for
14018 data and instructions, the diagram would be similar, except that the
14019 program variables and heap would share an address space with the main
14020 program and the overlay area.
14022 An overlay loaded into instruction memory and ready for use is called a
14023 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
14024 instruction memory. An overlay not present (or only partially present)
14025 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
14026 is its address in the larger memory. The mapped address is also called
14027 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
14028 called the @dfn{load memory address}, or @dfn{LMA}.
14030 Unfortunately, overlays are not a completely transparent way to adapt a
14031 program to limited instruction memory. They introduce a new set of
14032 global constraints you must keep in mind as you design your program:
14037 Before calling or returning to a function in an overlay, your program
14038 must make sure that overlay is actually mapped. Otherwise, the call or
14039 return will transfer control to the right address, but in the wrong
14040 overlay, and your program will probably crash.
14043 If the process of mapping an overlay is expensive on your system, you
14044 will need to choose your overlays carefully to minimize their effect on
14045 your program's performance.
14048 The executable file you load onto your system must contain each
14049 overlay's instructions, appearing at the overlay's load address, not its
14050 mapped address. However, each overlay's instructions must be relocated
14051 and its symbols defined as if the overlay were at its mapped address.
14052 You can use GNU linker scripts to specify different load and relocation
14053 addresses for pieces of your program; see @ref{Overlay Description,,,
14054 ld.info, Using ld: the GNU linker}.
14057 The procedure for loading executable files onto your system must be able
14058 to load their contents into the larger address space as well as the
14059 instruction and data spaces.
14063 The overlay system described above is rather simple, and could be
14064 improved in many ways:
14069 If your system has suitable bank switch registers or memory management
14070 hardware, you could use those facilities to make an overlay's load area
14071 contents simply appear at their mapped address in instruction space.
14072 This would probably be faster than copying the overlay to its mapped
14073 area in the usual way.
14076 If your overlays are small enough, you could set aside more than one
14077 overlay area, and have more than one overlay mapped at a time.
14080 You can use overlays to manage data, as well as instructions. In
14081 general, data overlays are even less transparent to your design than
14082 code overlays: whereas code overlays only require care when you call or
14083 return to functions, data overlays require care every time you access
14084 the data. Also, if you change the contents of a data overlay, you
14085 must copy its contents back out to its load address before you can copy a
14086 different data overlay into the same mapped area.
14091 @node Overlay Commands
14092 @section Overlay Commands
14094 To use @value{GDBN}'s overlay support, each overlay in your program must
14095 correspond to a separate section of the executable file. The section's
14096 virtual memory address and load memory address must be the overlay's
14097 mapped and load addresses. Identifying overlays with sections allows
14098 @value{GDBN} to determine the appropriate address of a function or
14099 variable, depending on whether the overlay is mapped or not.
14101 @value{GDBN}'s overlay commands all start with the word @code{overlay};
14102 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
14107 Disable @value{GDBN}'s overlay support. When overlay support is
14108 disabled, @value{GDBN} assumes that all functions and variables are
14109 always present at their mapped addresses. By default, @value{GDBN}'s
14110 overlay support is disabled.
14112 @item overlay manual
14113 @cindex manual overlay debugging
14114 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
14115 relies on you to tell it which overlays are mapped, and which are not,
14116 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
14117 commands described below.
14119 @item overlay map-overlay @var{overlay}
14120 @itemx overlay map @var{overlay}
14121 @cindex map an overlay
14122 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
14123 be the name of the object file section containing the overlay. When an
14124 overlay is mapped, @value{GDBN} assumes it can find the overlay's
14125 functions and variables at their mapped addresses. @value{GDBN} assumes
14126 that any other overlays whose mapped ranges overlap that of
14127 @var{overlay} are now unmapped.
14129 @item overlay unmap-overlay @var{overlay}
14130 @itemx overlay unmap @var{overlay}
14131 @cindex unmap an overlay
14132 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
14133 must be the name of the object file section containing the overlay.
14134 When an overlay is unmapped, @value{GDBN} assumes it can find the
14135 overlay's functions and variables at their load addresses.
14138 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
14139 consults a data structure the overlay manager maintains in the inferior
14140 to see which overlays are mapped. For details, see @ref{Automatic
14141 Overlay Debugging}.
14143 @item overlay load-target
14144 @itemx overlay load
14145 @cindex reloading the overlay table
14146 Re-read the overlay table from the inferior. Normally, @value{GDBN}
14147 re-reads the table @value{GDBN} automatically each time the inferior
14148 stops, so this command should only be necessary if you have changed the
14149 overlay mapping yourself using @value{GDBN}. This command is only
14150 useful when using automatic overlay debugging.
14152 @item overlay list-overlays
14153 @itemx overlay list
14154 @cindex listing mapped overlays
14155 Display a list of the overlays currently mapped, along with their mapped
14156 addresses, load addresses, and sizes.
14160 Normally, when @value{GDBN} prints a code address, it includes the name
14161 of the function the address falls in:
14164 (@value{GDBP}) print main
14165 $3 = @{int ()@} 0x11a0 <main>
14168 When overlay debugging is enabled, @value{GDBN} recognizes code in
14169 unmapped overlays, and prints the names of unmapped functions with
14170 asterisks around them. For example, if @code{foo} is a function in an
14171 unmapped overlay, @value{GDBN} prints it this way:
14174 (@value{GDBP}) overlay list
14175 No sections are mapped.
14176 (@value{GDBP}) print foo
14177 $5 = @{int (int)@} 0x100000 <*foo*>
14180 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
14184 (@value{GDBP}) overlay list
14185 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
14186 mapped at 0x1016 - 0x104a
14187 (@value{GDBP}) print foo
14188 $6 = @{int (int)@} 0x1016 <foo>
14191 When overlay debugging is enabled, @value{GDBN} can find the correct
14192 address for functions and variables in an overlay, whether or not the
14193 overlay is mapped. This allows most @value{GDBN} commands, like
14194 @code{break} and @code{disassemble}, to work normally, even on unmapped
14195 code. However, @value{GDBN}'s breakpoint support has some limitations:
14199 @cindex breakpoints in overlays
14200 @cindex overlays, setting breakpoints in
14201 You can set breakpoints in functions in unmapped overlays, as long as
14202 @value{GDBN} can write to the overlay at its load address.
14204 @value{GDBN} can not set hardware or simulator-based breakpoints in
14205 unmapped overlays. However, if you set a breakpoint at the end of your
14206 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
14207 you are using manual overlay management), @value{GDBN} will re-set its
14208 breakpoints properly.
14212 @node Automatic Overlay Debugging
14213 @section Automatic Overlay Debugging
14214 @cindex automatic overlay debugging
14216 @value{GDBN} can automatically track which overlays are mapped and which
14217 are not, given some simple co-operation from the overlay manager in the
14218 inferior. If you enable automatic overlay debugging with the
14219 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
14220 looks in the inferior's memory for certain variables describing the
14221 current state of the overlays.
14223 Here are the variables your overlay manager must define to support
14224 @value{GDBN}'s automatic overlay debugging:
14228 @item @code{_ovly_table}:
14229 This variable must be an array of the following structures:
14234 /* The overlay's mapped address. */
14237 /* The size of the overlay, in bytes. */
14238 unsigned long size;
14240 /* The overlay's load address. */
14243 /* Non-zero if the overlay is currently mapped;
14245 unsigned long mapped;
14249 @item @code{_novlys}:
14250 This variable must be a four-byte signed integer, holding the total
14251 number of elements in @code{_ovly_table}.
14255 To decide whether a particular overlay is mapped or not, @value{GDBN}
14256 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
14257 @code{lma} members equal the VMA and LMA of the overlay's section in the
14258 executable file. When @value{GDBN} finds a matching entry, it consults
14259 the entry's @code{mapped} member to determine whether the overlay is
14262 In addition, your overlay manager may define a function called
14263 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
14264 will silently set a breakpoint there. If the overlay manager then
14265 calls this function whenever it has changed the overlay table, this
14266 will enable @value{GDBN} to accurately keep track of which overlays
14267 are in program memory, and update any breakpoints that may be set
14268 in overlays. This will allow breakpoints to work even if the
14269 overlays are kept in ROM or other non-writable memory while they
14270 are not being executed.
14272 @node Overlay Sample Program
14273 @section Overlay Sample Program
14274 @cindex overlay example program
14276 When linking a program which uses overlays, you must place the overlays
14277 at their load addresses, while relocating them to run at their mapped
14278 addresses. To do this, you must write a linker script (@pxref{Overlay
14279 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
14280 since linker scripts are specific to a particular host system, target
14281 architecture, and target memory layout, this manual cannot provide
14282 portable sample code demonstrating @value{GDBN}'s overlay support.
14284 However, the @value{GDBN} source distribution does contain an overlaid
14285 program, with linker scripts for a few systems, as part of its test
14286 suite. The program consists of the following files from
14287 @file{gdb/testsuite/gdb.base}:
14291 The main program file.
14293 A simple overlay manager, used by @file{overlays.c}.
14298 Overlay modules, loaded and used by @file{overlays.c}.
14301 Linker scripts for linking the test program on the @code{d10v-elf}
14302 and @code{m32r-elf} targets.
14305 You can build the test program using the @code{d10v-elf} GCC
14306 cross-compiler like this:
14309 $ d10v-elf-gcc -g -c overlays.c
14310 $ d10v-elf-gcc -g -c ovlymgr.c
14311 $ d10v-elf-gcc -g -c foo.c
14312 $ d10v-elf-gcc -g -c bar.c
14313 $ d10v-elf-gcc -g -c baz.c
14314 $ d10v-elf-gcc -g -c grbx.c
14315 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
14316 baz.o grbx.o -Wl,-Td10v.ld -o overlays
14319 The build process is identical for any other architecture, except that
14320 you must substitute the appropriate compiler and linker script for the
14321 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
14325 @chapter Using @value{GDBN} with Different Languages
14328 Although programming languages generally have common aspects, they are
14329 rarely expressed in the same manner. For instance, in ANSI C,
14330 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
14331 Modula-2, it is accomplished by @code{p^}. Values can also be
14332 represented (and displayed) differently. Hex numbers in C appear as
14333 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
14335 @cindex working language
14336 Language-specific information is built into @value{GDBN} for some languages,
14337 allowing you to express operations like the above in your program's
14338 native language, and allowing @value{GDBN} to output values in a manner
14339 consistent with the syntax of your program's native language. The
14340 language you use to build expressions is called the @dfn{working
14344 * Setting:: Switching between source languages
14345 * Show:: Displaying the language
14346 * Checks:: Type and range checks
14347 * Supported Languages:: Supported languages
14348 * Unsupported Languages:: Unsupported languages
14352 @section Switching Between Source Languages
14354 There are two ways to control the working language---either have @value{GDBN}
14355 set it automatically, or select it manually yourself. You can use the
14356 @code{set language} command for either purpose. On startup, @value{GDBN}
14357 defaults to setting the language automatically. The working language is
14358 used to determine how expressions you type are interpreted, how values
14361 In addition to the working language, every source file that
14362 @value{GDBN} knows about has its own working language. For some object
14363 file formats, the compiler might indicate which language a particular
14364 source file is in. However, most of the time @value{GDBN} infers the
14365 language from the name of the file. The language of a source file
14366 controls whether C@t{++} names are demangled---this way @code{backtrace} can
14367 show each frame appropriately for its own language. There is no way to
14368 set the language of a source file from within @value{GDBN}, but you can
14369 set the language associated with a filename extension. @xref{Show, ,
14370 Displaying the Language}.
14372 This is most commonly a problem when you use a program, such
14373 as @code{cfront} or @code{f2c}, that generates C but is written in
14374 another language. In that case, make the
14375 program use @code{#line} directives in its C output; that way
14376 @value{GDBN} will know the correct language of the source code of the original
14377 program, and will display that source code, not the generated C code.
14380 * Filenames:: Filename extensions and languages.
14381 * Manually:: Setting the working language manually
14382 * Automatically:: Having @value{GDBN} infer the source language
14386 @subsection List of Filename Extensions and Languages
14388 If a source file name ends in one of the following extensions, then
14389 @value{GDBN} infers that its language is the one indicated.
14407 C@t{++} source file
14413 Objective-C source file
14417 Fortran source file
14420 Modula-2 source file
14424 Assembler source file. This actually behaves almost like C, but
14425 @value{GDBN} does not skip over function prologues when stepping.
14428 In addition, you may set the language associated with a filename
14429 extension. @xref{Show, , Displaying the Language}.
14432 @subsection Setting the Working Language
14434 If you allow @value{GDBN} to set the language automatically,
14435 expressions are interpreted the same way in your debugging session and
14438 @kindex set language
14439 If you wish, you may set the language manually. To do this, issue the
14440 command @samp{set language @var{lang}}, where @var{lang} is the name of
14441 a language, such as
14442 @code{c} or @code{modula-2}.
14443 For a list of the supported languages, type @samp{set language}.
14445 Setting the language manually prevents @value{GDBN} from updating the working
14446 language automatically. This can lead to confusion if you try
14447 to debug a program when the working language is not the same as the
14448 source language, when an expression is acceptable to both
14449 languages---but means different things. For instance, if the current
14450 source file were written in C, and @value{GDBN} was parsing Modula-2, a
14458 might not have the effect you intended. In C, this means to add
14459 @code{b} and @code{c} and place the result in @code{a}. The result
14460 printed would be the value of @code{a}. In Modula-2, this means to compare
14461 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
14463 @node Automatically
14464 @subsection Having @value{GDBN} Infer the Source Language
14466 To have @value{GDBN} set the working language automatically, use
14467 @samp{set language local} or @samp{set language auto}. @value{GDBN}
14468 then infers the working language. That is, when your program stops in a
14469 frame (usually by encountering a breakpoint), @value{GDBN} sets the
14470 working language to the language recorded for the function in that
14471 frame. If the language for a frame is unknown (that is, if the function
14472 or block corresponding to the frame was defined in a source file that
14473 does not have a recognized extension), the current working language is
14474 not changed, and @value{GDBN} issues a warning.
14476 This may not seem necessary for most programs, which are written
14477 entirely in one source language. However, program modules and libraries
14478 written in one source language can be used by a main program written in
14479 a different source language. Using @samp{set language auto} in this
14480 case frees you from having to set the working language manually.
14483 @section Displaying the Language
14485 The following commands help you find out which language is the
14486 working language, and also what language source files were written in.
14489 @item show language
14490 @anchor{show language}
14491 @kindex show language
14492 Display the current working language. This is the
14493 language you can use with commands such as @code{print} to
14494 build and compute expressions that may involve variables in your program.
14497 @kindex info frame@r{, show the source language}
14498 Display the source language for this frame. This language becomes the
14499 working language if you use an identifier from this frame.
14500 @xref{Frame Info, ,Information about a Frame}, to identify the other
14501 information listed here.
14504 @kindex info source@r{, show the source language}
14505 Display the source language of this source file.
14506 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
14507 information listed here.
14510 In unusual circumstances, you may have source files with extensions
14511 not in the standard list. You can then set the extension associated
14512 with a language explicitly:
14515 @item set extension-language @var{ext} @var{language}
14516 @kindex set extension-language
14517 Tell @value{GDBN} that source files with extension @var{ext} are to be
14518 assumed as written in the source language @var{language}.
14520 @item info extensions
14521 @kindex info extensions
14522 List all the filename extensions and the associated languages.
14526 @section Type and Range Checking
14528 Some languages are designed to guard you against making seemingly common
14529 errors through a series of compile- and run-time checks. These include
14530 checking the type of arguments to functions and operators and making
14531 sure mathematical overflows are caught at run time. Checks such as
14532 these help to ensure a program's correctness once it has been compiled
14533 by eliminating type mismatches and providing active checks for range
14534 errors when your program is running.
14536 By default @value{GDBN} checks for these errors according to the
14537 rules of the current source language. Although @value{GDBN} does not check
14538 the statements in your program, it can check expressions entered directly
14539 into @value{GDBN} for evaluation via the @code{print} command, for example.
14542 * Type Checking:: An overview of type checking
14543 * Range Checking:: An overview of range checking
14546 @cindex type checking
14547 @cindex checks, type
14548 @node Type Checking
14549 @subsection An Overview of Type Checking
14551 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
14552 arguments to operators and functions have to be of the correct type,
14553 otherwise an error occurs. These checks prevent type mismatch
14554 errors from ever causing any run-time problems. For example,
14557 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
14559 (@value{GDBP}) print obj.my_method (0)
14562 (@value{GDBP}) print obj.my_method (0x1234)
14563 Cannot resolve method klass::my_method to any overloaded instance
14566 The second example fails because in C@t{++} the integer constant
14567 @samp{0x1234} is not type-compatible with the pointer parameter type.
14569 For the expressions you use in @value{GDBN} commands, you can tell
14570 @value{GDBN} to not enforce strict type checking or
14571 to treat any mismatches as errors and abandon the expression;
14572 When type checking is disabled, @value{GDBN} successfully evaluates
14573 expressions like the second example above.
14575 Even if type checking is off, there may be other reasons
14576 related to type that prevent @value{GDBN} from evaluating an expression.
14577 For instance, @value{GDBN} does not know how to add an @code{int} and
14578 a @code{struct foo}. These particular type errors have nothing to do
14579 with the language in use and usually arise from expressions which make
14580 little sense to evaluate anyway.
14582 @value{GDBN} provides some additional commands for controlling type checking:
14584 @kindex set check type
14585 @kindex show check type
14587 @item set check type on
14588 @itemx set check type off
14589 Set strict type checking on or off. If any type mismatches occur in
14590 evaluating an expression while type checking is on, @value{GDBN} prints a
14591 message and aborts evaluation of the expression.
14593 @item show check type
14594 Show the current setting of type checking and whether @value{GDBN}
14595 is enforcing strict type checking rules.
14598 @cindex range checking
14599 @cindex checks, range
14600 @node Range Checking
14601 @subsection An Overview of Range Checking
14603 In some languages (such as Modula-2), it is an error to exceed the
14604 bounds of a type; this is enforced with run-time checks. Such range
14605 checking is meant to ensure program correctness by making sure
14606 computations do not overflow, or indices on an array element access do
14607 not exceed the bounds of the array.
14609 For expressions you use in @value{GDBN} commands, you can tell
14610 @value{GDBN} to treat range errors in one of three ways: ignore them,
14611 always treat them as errors and abandon the expression, or issue
14612 warnings but evaluate the expression anyway.
14614 A range error can result from numerical overflow, from exceeding an
14615 array index bound, or when you type a constant that is not a member
14616 of any type. Some languages, however, do not treat overflows as an
14617 error. In many implementations of C, mathematical overflow causes the
14618 result to ``wrap around'' to lower values---for example, if @var{m} is
14619 the largest integer value, and @var{s} is the smallest, then
14622 @var{m} + 1 @result{} @var{s}
14625 This, too, is specific to individual languages, and in some cases
14626 specific to individual compilers or machines. @xref{Supported Languages, ,
14627 Supported Languages}, for further details on specific languages.
14629 @value{GDBN} provides some additional commands for controlling the range checker:
14631 @kindex set check range
14632 @kindex show check range
14634 @item set check range auto
14635 Set range checking on or off based on the current working language.
14636 @xref{Supported Languages, ,Supported Languages}, for the default settings for
14639 @item set check range on
14640 @itemx set check range off
14641 Set range checking on or off, overriding the default setting for the
14642 current working language. A warning is issued if the setting does not
14643 match the language default. If a range error occurs and range checking is on,
14644 then a message is printed and evaluation of the expression is aborted.
14646 @item set check range warn
14647 Output messages when the @value{GDBN} range checker detects a range error,
14648 but attempt to evaluate the expression anyway. Evaluating the
14649 expression may still be impossible for other reasons, such as accessing
14650 memory that the process does not own (a typical example from many Unix
14654 Show the current setting of the range checker, and whether or not it is
14655 being set automatically by @value{GDBN}.
14658 @node Supported Languages
14659 @section Supported Languages
14661 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
14662 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
14663 @c This is false ...
14664 Some @value{GDBN} features may be used in expressions regardless of the
14665 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
14666 and the @samp{@{type@}addr} construct (@pxref{Expressions,
14667 ,Expressions}) can be used with the constructs of any supported
14670 The following sections detail to what degree each source language is
14671 supported by @value{GDBN}. These sections are not meant to be language
14672 tutorials or references, but serve only as a reference guide to what the
14673 @value{GDBN} expression parser accepts, and what input and output
14674 formats should look like for different languages. There are many good
14675 books written on each of these languages; please look to these for a
14676 language reference or tutorial.
14679 * C:: C and C@t{++}
14682 * Objective-C:: Objective-C
14683 * OpenCL C:: OpenCL C
14684 * Fortran:: Fortran
14687 * Modula-2:: Modula-2
14692 @subsection C and C@t{++}
14694 @cindex C and C@t{++}
14695 @cindex expressions in C or C@t{++}
14697 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
14698 to both languages. Whenever this is the case, we discuss those languages
14702 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
14703 @cindex @sc{gnu} C@t{++}
14704 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
14705 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
14706 effectively, you must compile your C@t{++} programs with a supported
14707 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
14708 compiler (@code{aCC}).
14711 * C Operators:: C and C@t{++} operators
14712 * C Constants:: C and C@t{++} constants
14713 * C Plus Plus Expressions:: C@t{++} expressions
14714 * C Defaults:: Default settings for C and C@t{++}
14715 * C Checks:: C and C@t{++} type and range checks
14716 * Debugging C:: @value{GDBN} and C
14717 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
14718 * Decimal Floating Point:: Numbers in Decimal Floating Point format
14722 @subsubsection C and C@t{++} Operators
14724 @cindex C and C@t{++} operators
14726 Operators must be defined on values of specific types. For instance,
14727 @code{+} is defined on numbers, but not on structures. Operators are
14728 often defined on groups of types.
14730 For the purposes of C and C@t{++}, the following definitions hold:
14735 @emph{Integral types} include @code{int} with any of its storage-class
14736 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
14739 @emph{Floating-point types} include @code{float}, @code{double}, and
14740 @code{long double} (if supported by the target platform).
14743 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
14746 @emph{Scalar types} include all of the above.
14751 The following operators are supported. They are listed here
14752 in order of increasing precedence:
14756 The comma or sequencing operator. Expressions in a comma-separated list
14757 are evaluated from left to right, with the result of the entire
14758 expression being the last expression evaluated.
14761 Assignment. The value of an assignment expression is the value
14762 assigned. Defined on scalar types.
14765 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
14766 and translated to @w{@code{@var{a} = @var{a op b}}}.
14767 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
14768 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
14769 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
14772 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
14773 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
14774 should be of an integral type.
14777 Logical @sc{or}. Defined on integral types.
14780 Logical @sc{and}. Defined on integral types.
14783 Bitwise @sc{or}. Defined on integral types.
14786 Bitwise exclusive-@sc{or}. Defined on integral types.
14789 Bitwise @sc{and}. Defined on integral types.
14792 Equality and inequality. Defined on scalar types. The value of these
14793 expressions is 0 for false and non-zero for true.
14795 @item <@r{, }>@r{, }<=@r{, }>=
14796 Less than, greater than, less than or equal, greater than or equal.
14797 Defined on scalar types. The value of these expressions is 0 for false
14798 and non-zero for true.
14801 left shift, and right shift. Defined on integral types.
14804 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14807 Addition and subtraction. Defined on integral types, floating-point types and
14810 @item *@r{, }/@r{, }%
14811 Multiplication, division, and modulus. Multiplication and division are
14812 defined on integral and floating-point types. Modulus is defined on
14816 Increment and decrement. When appearing before a variable, the
14817 operation is performed before the variable is used in an expression;
14818 when appearing after it, the variable's value is used before the
14819 operation takes place.
14822 Pointer dereferencing. Defined on pointer types. Same precedence as
14826 Address operator. Defined on variables. Same precedence as @code{++}.
14828 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
14829 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
14830 to examine the address
14831 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
14835 Negative. Defined on integral and floating-point types. Same
14836 precedence as @code{++}.
14839 Logical negation. Defined on integral types. Same precedence as
14843 Bitwise complement operator. Defined on integral types. Same precedence as
14848 Structure member, and pointer-to-structure member. For convenience,
14849 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
14850 pointer based on the stored type information.
14851 Defined on @code{struct} and @code{union} data.
14854 Dereferences of pointers to members.
14857 Array indexing. @code{@var{a}[@var{i}]} is defined as
14858 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
14861 Function parameter list. Same precedence as @code{->}.
14864 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
14865 and @code{class} types.
14868 Doubled colons also represent the @value{GDBN} scope operator
14869 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
14873 If an operator is redefined in the user code, @value{GDBN} usually
14874 attempts to invoke the redefined version instead of using the operator's
14875 predefined meaning.
14878 @subsubsection C and C@t{++} Constants
14880 @cindex C and C@t{++} constants
14882 @value{GDBN} allows you to express the constants of C and C@t{++} in the
14887 Integer constants are a sequence of digits. Octal constants are
14888 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
14889 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
14890 @samp{l}, specifying that the constant should be treated as a
14894 Floating point constants are a sequence of digits, followed by a decimal
14895 point, followed by a sequence of digits, and optionally followed by an
14896 exponent. An exponent is of the form:
14897 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
14898 sequence of digits. The @samp{+} is optional for positive exponents.
14899 A floating-point constant may also end with a letter @samp{f} or
14900 @samp{F}, specifying that the constant should be treated as being of
14901 the @code{float} (as opposed to the default @code{double}) type; or with
14902 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
14906 Enumerated constants consist of enumerated identifiers, or their
14907 integral equivalents.
14910 Character constants are a single character surrounded by single quotes
14911 (@code{'}), or a number---the ordinal value of the corresponding character
14912 (usually its @sc{ascii} value). Within quotes, the single character may
14913 be represented by a letter or by @dfn{escape sequences}, which are of
14914 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
14915 of the character's ordinal value; or of the form @samp{\@var{x}}, where
14916 @samp{@var{x}} is a predefined special character---for example,
14917 @samp{\n} for newline.
14919 Wide character constants can be written by prefixing a character
14920 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
14921 form of @samp{x}. The target wide character set is used when
14922 computing the value of this constant (@pxref{Character Sets}).
14925 String constants are a sequence of character constants surrounded by
14926 double quotes (@code{"}). Any valid character constant (as described
14927 above) may appear. Double quotes within the string must be preceded by
14928 a backslash, so for instance @samp{"a\"b'c"} is a string of five
14931 Wide string constants can be written by prefixing a string constant
14932 with @samp{L}, as in C. The target wide character set is used when
14933 computing the value of this constant (@pxref{Character Sets}).
14936 Pointer constants are an integral value. You can also write pointers
14937 to constants using the C operator @samp{&}.
14940 Array constants are comma-separated lists surrounded by braces @samp{@{}
14941 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
14942 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
14943 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
14946 @node C Plus Plus Expressions
14947 @subsubsection C@t{++} Expressions
14949 @cindex expressions in C@t{++}
14950 @value{GDBN} expression handling can interpret most C@t{++} expressions.
14952 @cindex debugging C@t{++} programs
14953 @cindex C@t{++} compilers
14954 @cindex debug formats and C@t{++}
14955 @cindex @value{NGCC} and C@t{++}
14957 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
14958 the proper compiler and the proper debug format. Currently,
14959 @value{GDBN} works best when debugging C@t{++} code that is compiled
14960 with the most recent version of @value{NGCC} possible. The DWARF
14961 debugging format is preferred; @value{NGCC} defaults to this on most
14962 popular platforms. Other compilers and/or debug formats are likely to
14963 work badly or not at all when using @value{GDBN} to debug C@t{++}
14964 code. @xref{Compilation}.
14969 @cindex member functions
14971 Member function calls are allowed; you can use expressions like
14974 count = aml->GetOriginal(x, y)
14977 @vindex this@r{, inside C@t{++} member functions}
14978 @cindex namespace in C@t{++}
14980 While a member function is active (in the selected stack frame), your
14981 expressions have the same namespace available as the member function;
14982 that is, @value{GDBN} allows implicit references to the class instance
14983 pointer @code{this} following the same rules as C@t{++}. @code{using}
14984 declarations in the current scope are also respected by @value{GDBN}.
14986 @cindex call overloaded functions
14987 @cindex overloaded functions, calling
14988 @cindex type conversions in C@t{++}
14990 You can call overloaded functions; @value{GDBN} resolves the function
14991 call to the right definition, with some restrictions. @value{GDBN} does not
14992 perform overload resolution involving user-defined type conversions,
14993 calls to constructors, or instantiations of templates that do not exist
14994 in the program. It also cannot handle ellipsis argument lists or
14997 It does perform integral conversions and promotions, floating-point
14998 promotions, arithmetic conversions, pointer conversions, conversions of
14999 class objects to base classes, and standard conversions such as those of
15000 functions or arrays to pointers; it requires an exact match on the
15001 number of function arguments.
15003 Overload resolution is always performed, unless you have specified
15004 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
15005 ,@value{GDBN} Features for C@t{++}}.
15007 You must specify @code{set overload-resolution off} in order to use an
15008 explicit function signature to call an overloaded function, as in
15010 p 'foo(char,int)'('x', 13)
15013 The @value{GDBN} command-completion facility can simplify this;
15014 see @ref{Completion, ,Command Completion}.
15016 @cindex reference declarations
15018 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
15019 references; you can use them in expressions just as you do in C@t{++}
15020 source---they are automatically dereferenced.
15022 In the parameter list shown when @value{GDBN} displays a frame, the values of
15023 reference variables are not displayed (unlike other variables); this
15024 avoids clutter, since references are often used for large structures.
15025 The @emph{address} of a reference variable is always shown, unless
15026 you have specified @samp{set print address off}.
15029 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
15030 expressions can use it just as expressions in your program do. Since
15031 one scope may be defined in another, you can use @code{::} repeatedly if
15032 necessary, for example in an expression like
15033 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
15034 resolving name scope by reference to source files, in both C and C@t{++}
15035 debugging (@pxref{Variables, ,Program Variables}).
15038 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
15043 @subsubsection C and C@t{++} Defaults
15045 @cindex C and C@t{++} defaults
15047 If you allow @value{GDBN} to set range checking automatically, it
15048 defaults to @code{off} whenever the working language changes to
15049 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
15050 selects the working language.
15052 If you allow @value{GDBN} to set the language automatically, it
15053 recognizes source files whose names end with @file{.c}, @file{.C}, or
15054 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
15055 these files, it sets the working language to C or C@t{++}.
15056 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
15057 for further details.
15060 @subsubsection C and C@t{++} Type and Range Checks
15062 @cindex C and C@t{++} checks
15064 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
15065 checking is used. However, if you turn type checking off, @value{GDBN}
15066 will allow certain non-standard conversions, such as promoting integer
15067 constants to pointers.
15069 Range checking, if turned on, is done on mathematical operations. Array
15070 indices are not checked, since they are often used to index a pointer
15071 that is not itself an array.
15074 @subsubsection @value{GDBN} and C
15076 The @code{set print union} and @code{show print union} commands apply to
15077 the @code{union} type. When set to @samp{on}, any @code{union} that is
15078 inside a @code{struct} or @code{class} is also printed. Otherwise, it
15079 appears as @samp{@{...@}}.
15081 The @code{@@} operator aids in the debugging of dynamic arrays, formed
15082 with pointers and a memory allocation function. @xref{Expressions,
15085 @node Debugging C Plus Plus
15086 @subsubsection @value{GDBN} Features for C@t{++}
15088 @cindex commands for C@t{++}
15090 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
15091 designed specifically for use with C@t{++}. Here is a summary:
15094 @cindex break in overloaded functions
15095 @item @r{breakpoint menus}
15096 When you want a breakpoint in a function whose name is overloaded,
15097 @value{GDBN} has the capability to display a menu of possible breakpoint
15098 locations to help you specify which function definition you want.
15099 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
15101 @cindex overloading in C@t{++}
15102 @item rbreak @var{regex}
15103 Setting breakpoints using regular expressions is helpful for setting
15104 breakpoints on overloaded functions that are not members of any special
15106 @xref{Set Breaks, ,Setting Breakpoints}.
15108 @cindex C@t{++} exception handling
15110 @itemx catch rethrow
15112 Debug C@t{++} exception handling using these commands. @xref{Set
15113 Catchpoints, , Setting Catchpoints}.
15115 @cindex inheritance
15116 @item ptype @var{typename}
15117 Print inheritance relationships as well as other information for type
15119 @xref{Symbols, ,Examining the Symbol Table}.
15121 @item info vtbl @var{expression}.
15122 The @code{info vtbl} command can be used to display the virtual
15123 method tables of the object computed by @var{expression}. This shows
15124 one entry per virtual table; there may be multiple virtual tables when
15125 multiple inheritance is in use.
15127 @cindex C@t{++} demangling
15128 @item demangle @var{name}
15129 Demangle @var{name}.
15130 @xref{Symbols}, for a more complete description of the @code{demangle} command.
15132 @cindex C@t{++} symbol display
15133 @item set print demangle
15134 @itemx show print demangle
15135 @itemx set print asm-demangle
15136 @itemx show print asm-demangle
15137 Control whether C@t{++} symbols display in their source form, both when
15138 displaying code as C@t{++} source and when displaying disassemblies.
15139 @xref{Print Settings, ,Print Settings}.
15141 @item set print object
15142 @itemx show print object
15143 Choose whether to print derived (actual) or declared types of objects.
15144 @xref{Print Settings, ,Print Settings}.
15146 @item set print vtbl
15147 @itemx show print vtbl
15148 Control the format for printing virtual function tables.
15149 @xref{Print Settings, ,Print Settings}.
15150 (The @code{vtbl} commands do not work on programs compiled with the HP
15151 ANSI C@t{++} compiler (@code{aCC}).)
15153 @kindex set overload-resolution
15154 @cindex overloaded functions, overload resolution
15155 @item set overload-resolution on
15156 Enable overload resolution for C@t{++} expression evaluation. The default
15157 is on. For overloaded functions, @value{GDBN} evaluates the arguments
15158 and searches for a function whose signature matches the argument types,
15159 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
15160 Expressions, ,C@t{++} Expressions}, for details).
15161 If it cannot find a match, it emits a message.
15163 @item set overload-resolution off
15164 Disable overload resolution for C@t{++} expression evaluation. For
15165 overloaded functions that are not class member functions, @value{GDBN}
15166 chooses the first function of the specified name that it finds in the
15167 symbol table, whether or not its arguments are of the correct type. For
15168 overloaded functions that are class member functions, @value{GDBN}
15169 searches for a function whose signature @emph{exactly} matches the
15172 @kindex show overload-resolution
15173 @item show overload-resolution
15174 Show the current setting of overload resolution.
15176 @item @r{Overloaded symbol names}
15177 You can specify a particular definition of an overloaded symbol, using
15178 the same notation that is used to declare such symbols in C@t{++}: type
15179 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
15180 also use the @value{GDBN} command-line word completion facilities to list the
15181 available choices, or to finish the type list for you.
15182 @xref{Completion,, Command Completion}, for details on how to do this.
15184 @item @r{Breakpoints in functions with ABI tags}
15186 The GNU C@t{++} compiler introduced the notion of ABI ``tags'', which
15187 correspond to changes in the ABI of a type, function, or variable that
15188 would not otherwise be reflected in a mangled name. See
15189 @url{https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/}
15192 The ABI tags are visible in C@t{++} demangled names. For example, a
15193 function that returns a std::string:
15196 std::string function(int);
15200 when compiled for the C++11 ABI is marked with the @code{cxx11} ABI
15201 tag, and @value{GDBN} displays the symbol like this:
15204 function[abi:cxx11](int)
15207 You can set a breakpoint on such functions simply as if they had no
15211 (gdb) b function(int)
15212 Breakpoint 2 at 0x40060d: file main.cc, line 10.
15213 (gdb) info breakpoints
15214 Num Type Disp Enb Address What
15215 1 breakpoint keep y 0x0040060d in function[abi:cxx11](int)
15219 On the rare occasion you need to disambiguate between different ABI
15220 tags, you can do so by simply including the ABI tag in the function
15224 (@value{GDBP}) b ambiguous[abi:other_tag](int)
15228 @node Decimal Floating Point
15229 @subsubsection Decimal Floating Point format
15230 @cindex decimal floating point format
15232 @value{GDBN} can examine, set and perform computations with numbers in
15233 decimal floating point format, which in the C language correspond to the
15234 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
15235 specified by the extension to support decimal floating-point arithmetic.
15237 There are two encodings in use, depending on the architecture: BID (Binary
15238 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
15239 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
15242 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
15243 to manipulate decimal floating point numbers, it is not possible to convert
15244 (using a cast, for example) integers wider than 32-bit to decimal float.
15246 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
15247 point computations, error checking in decimal float operations ignores
15248 underflow, overflow and divide by zero exceptions.
15250 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
15251 to inspect @code{_Decimal128} values stored in floating point registers.
15252 See @ref{PowerPC,,PowerPC} for more details.
15258 @value{GDBN} can be used to debug programs written in D and compiled with
15259 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
15260 specific feature --- dynamic arrays.
15265 @cindex Go (programming language)
15266 @value{GDBN} can be used to debug programs written in Go and compiled with
15267 @file{gccgo} or @file{6g} compilers.
15269 Here is a summary of the Go-specific features and restrictions:
15272 @cindex current Go package
15273 @item The current Go package
15274 The name of the current package does not need to be specified when
15275 specifying global variables and functions.
15277 For example, given the program:
15281 var myglob = "Shall we?"
15287 When stopped inside @code{main} either of these work:
15291 (gdb) p main.myglob
15294 @cindex builtin Go types
15295 @item Builtin Go types
15296 The @code{string} type is recognized by @value{GDBN} and is printed
15299 @cindex builtin Go functions
15300 @item Builtin Go functions
15301 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
15302 function and handles it internally.
15304 @cindex restrictions on Go expressions
15305 @item Restrictions on Go expressions
15306 All Go operators are supported except @code{&^}.
15307 The Go @code{_} ``blank identifier'' is not supported.
15308 Automatic dereferencing of pointers is not supported.
15312 @subsection Objective-C
15314 @cindex Objective-C
15315 This section provides information about some commands and command
15316 options that are useful for debugging Objective-C code. See also
15317 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
15318 few more commands specific to Objective-C support.
15321 * Method Names in Commands::
15322 * The Print Command with Objective-C::
15325 @node Method Names in Commands
15326 @subsubsection Method Names in Commands
15328 The following commands have been extended to accept Objective-C method
15329 names as line specifications:
15331 @kindex clear@r{, and Objective-C}
15332 @kindex break@r{, and Objective-C}
15333 @kindex info line@r{, and Objective-C}
15334 @kindex jump@r{, and Objective-C}
15335 @kindex list@r{, and Objective-C}
15339 @item @code{info line}
15344 A fully qualified Objective-C method name is specified as
15347 -[@var{Class} @var{methodName}]
15350 where the minus sign is used to indicate an instance method and a
15351 plus sign (not shown) is used to indicate a class method. The class
15352 name @var{Class} and method name @var{methodName} are enclosed in
15353 brackets, similar to the way messages are specified in Objective-C
15354 source code. For example, to set a breakpoint at the @code{create}
15355 instance method of class @code{Fruit} in the program currently being
15359 break -[Fruit create]
15362 To list ten program lines around the @code{initialize} class method,
15366 list +[NSText initialize]
15369 In the current version of @value{GDBN}, the plus or minus sign is
15370 required. In future versions of @value{GDBN}, the plus or minus
15371 sign will be optional, but you can use it to narrow the search. It
15372 is also possible to specify just a method name:
15378 You must specify the complete method name, including any colons. If
15379 your program's source files contain more than one @code{create} method,
15380 you'll be presented with a numbered list of classes that implement that
15381 method. Indicate your choice by number, or type @samp{0} to exit if
15384 As another example, to clear a breakpoint established at the
15385 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
15388 clear -[NSWindow makeKeyAndOrderFront:]
15391 @node The Print Command with Objective-C
15392 @subsubsection The Print Command With Objective-C
15393 @cindex Objective-C, print objects
15394 @kindex print-object
15395 @kindex po @r{(@code{print-object})}
15397 The print command has also been extended to accept methods. For example:
15400 print -[@var{object} hash]
15403 @cindex print an Objective-C object description
15404 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
15406 will tell @value{GDBN} to send the @code{hash} message to @var{object}
15407 and print the result. Also, an additional command has been added,
15408 @code{print-object} or @code{po} for short, which is meant to print
15409 the description of an object. However, this command may only work
15410 with certain Objective-C libraries that have a particular hook
15411 function, @code{_NSPrintForDebugger}, defined.
15414 @subsection OpenCL C
15417 This section provides information about @value{GDBN}s OpenCL C support.
15420 * OpenCL C Datatypes::
15421 * OpenCL C Expressions::
15422 * OpenCL C Operators::
15425 @node OpenCL C Datatypes
15426 @subsubsection OpenCL C Datatypes
15428 @cindex OpenCL C Datatypes
15429 @value{GDBN} supports the builtin scalar and vector datatypes specified
15430 by OpenCL 1.1. In addition the half- and double-precision floating point
15431 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
15432 extensions are also known to @value{GDBN}.
15434 @node OpenCL C Expressions
15435 @subsubsection OpenCL C Expressions
15437 @cindex OpenCL C Expressions
15438 @value{GDBN} supports accesses to vector components including the access as
15439 lvalue where possible. Since OpenCL C is based on C99 most C expressions
15440 supported by @value{GDBN} can be used as well.
15442 @node OpenCL C Operators
15443 @subsubsection OpenCL C Operators
15445 @cindex OpenCL C Operators
15446 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
15450 @subsection Fortran
15451 @cindex Fortran-specific support in @value{GDBN}
15453 @value{GDBN} can be used to debug programs written in Fortran, but it
15454 currently supports only the features of Fortran 77 language.
15456 @cindex trailing underscore, in Fortran symbols
15457 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
15458 among them) append an underscore to the names of variables and
15459 functions. When you debug programs compiled by those compilers, you
15460 will need to refer to variables and functions with a trailing
15464 * Fortran Operators:: Fortran operators and expressions
15465 * Fortran Defaults:: Default settings for Fortran
15466 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
15469 @node Fortran Operators
15470 @subsubsection Fortran Operators and Expressions
15472 @cindex Fortran operators and expressions
15474 Operators must be defined on values of specific types. For instance,
15475 @code{+} is defined on numbers, but not on characters or other non-
15476 arithmetic types. Operators are often defined on groups of types.
15480 The exponentiation operator. It raises the first operand to the power
15484 The range operator. Normally used in the form of array(low:high) to
15485 represent a section of array.
15488 The access component operator. Normally used to access elements in derived
15489 types. Also suitable for unions. As unions aren't part of regular Fortran,
15490 this can only happen when accessing a register that uses a gdbarch-defined
15494 @node Fortran Defaults
15495 @subsubsection Fortran Defaults
15497 @cindex Fortran Defaults
15499 Fortran symbols are usually case-insensitive, so @value{GDBN} by
15500 default uses case-insensitive matches for Fortran symbols. You can
15501 change that with the @samp{set case-insensitive} command, see
15502 @ref{Symbols}, for the details.
15504 @node Special Fortran Commands
15505 @subsubsection Special Fortran Commands
15507 @cindex Special Fortran commands
15509 @value{GDBN} has some commands to support Fortran-specific features,
15510 such as displaying common blocks.
15513 @cindex @code{COMMON} blocks, Fortran
15514 @kindex info common
15515 @item info common @r{[}@var{common-name}@r{]}
15516 This command prints the values contained in the Fortran @code{COMMON}
15517 block whose name is @var{common-name}. With no argument, the names of
15518 all @code{COMMON} blocks visible at the current program location are
15525 @cindex Pascal support in @value{GDBN}, limitations
15526 Debugging Pascal programs which use sets, subranges, file variables, or
15527 nested functions does not currently work. @value{GDBN} does not support
15528 entering expressions, printing values, or similar features using Pascal
15531 The Pascal-specific command @code{set print pascal_static-members}
15532 controls whether static members of Pascal objects are displayed.
15533 @xref{Print Settings, pascal_static-members}.
15538 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
15539 Programming Language}. Type- and value-printing, and expression
15540 parsing, are reasonably complete. However, there are a few
15541 peculiarities and holes to be aware of.
15545 Linespecs (@pxref{Specify Location}) are never relative to the current
15546 crate. Instead, they act as if there were a global namespace of
15547 crates, somewhat similar to the way @code{extern crate} behaves.
15549 That is, if @value{GDBN} is stopped at a breakpoint in a function in
15550 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
15551 to set a breakpoint in a function named @samp{f} in a crate named
15554 As a consequence of this approach, linespecs also cannot refer to
15555 items using @samp{self::} or @samp{super::}.
15558 Because @value{GDBN} implements Rust name-lookup semantics in
15559 expressions, it will sometimes prepend the current crate to a name.
15560 For example, if @value{GDBN} is stopped at a breakpoint in the crate
15561 @samp{K}, then @code{print ::x::y} will try to find the symbol
15564 However, since it is useful to be able to refer to other crates when
15565 debugging, @value{GDBN} provides the @code{extern} extension to
15566 circumvent this. To use the extension, just put @code{extern} before
15567 a path expression to refer to the otherwise unavailable ``global''
15570 In the above example, if you wanted to refer to the symbol @samp{y} in
15571 the crate @samp{x}, you would use @code{print extern x::y}.
15574 The Rust expression evaluator does not support ``statement-like''
15575 expressions such as @code{if} or @code{match}, or lambda expressions.
15578 Tuple expressions are not implemented.
15581 The Rust expression evaluator does not currently implement the
15582 @code{Drop} trait. Objects that may be created by the evaluator will
15583 never be destroyed.
15586 @value{GDBN} does not implement type inference for generics. In order
15587 to call generic functions or otherwise refer to generic items, you
15588 will have to specify the type parameters manually.
15591 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
15592 cases this does not cause any problems. However, in an expression
15593 context, completing a generic function name will give syntactically
15594 invalid results. This happens because Rust requires the @samp{::}
15595 operator between the function name and its generic arguments. For
15596 example, @value{GDBN} might provide a completion like
15597 @code{crate::f<u32>}, where the parser would require
15598 @code{crate::f::<u32>}.
15601 As of this writing, the Rust compiler (version 1.8) has a few holes in
15602 the debugging information it generates. These holes prevent certain
15603 features from being implemented by @value{GDBN}:
15607 Method calls cannot be made via traits.
15610 Operator overloading is not implemented.
15613 When debugging in a monomorphized function, you cannot use the generic
15617 The type @code{Self} is not available.
15620 @code{use} statements are not available, so some names may not be
15621 available in the crate.
15626 @subsection Modula-2
15628 @cindex Modula-2, @value{GDBN} support
15630 The extensions made to @value{GDBN} to support Modula-2 only support
15631 output from the @sc{gnu} Modula-2 compiler (which is currently being
15632 developed). Other Modula-2 compilers are not currently supported, and
15633 attempting to debug executables produced by them is most likely
15634 to give an error as @value{GDBN} reads in the executable's symbol
15637 @cindex expressions in Modula-2
15639 * M2 Operators:: Built-in operators
15640 * Built-In Func/Proc:: Built-in functions and procedures
15641 * M2 Constants:: Modula-2 constants
15642 * M2 Types:: Modula-2 types
15643 * M2 Defaults:: Default settings for Modula-2
15644 * Deviations:: Deviations from standard Modula-2
15645 * M2 Checks:: Modula-2 type and range checks
15646 * M2 Scope:: The scope operators @code{::} and @code{.}
15647 * GDB/M2:: @value{GDBN} and Modula-2
15651 @subsubsection Operators
15652 @cindex Modula-2 operators
15654 Operators must be defined on values of specific types. For instance,
15655 @code{+} is defined on numbers, but not on structures. Operators are
15656 often defined on groups of types. For the purposes of Modula-2, the
15657 following definitions hold:
15662 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
15666 @emph{Character types} consist of @code{CHAR} and its subranges.
15669 @emph{Floating-point types} consist of @code{REAL}.
15672 @emph{Pointer types} consist of anything declared as @code{POINTER TO
15676 @emph{Scalar types} consist of all of the above.
15679 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
15682 @emph{Boolean types} consist of @code{BOOLEAN}.
15686 The following operators are supported, and appear in order of
15687 increasing precedence:
15691 Function argument or array index separator.
15694 Assignment. The value of @var{var} @code{:=} @var{value} is
15698 Less than, greater than on integral, floating-point, or enumerated
15702 Less than or equal to, greater than or equal to
15703 on integral, floating-point and enumerated types, or set inclusion on
15704 set types. Same precedence as @code{<}.
15706 @item =@r{, }<>@r{, }#
15707 Equality and two ways of expressing inequality, valid on scalar types.
15708 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
15709 available for inequality, since @code{#} conflicts with the script
15713 Set membership. Defined on set types and the types of their members.
15714 Same precedence as @code{<}.
15717 Boolean disjunction. Defined on boolean types.
15720 Boolean conjunction. Defined on boolean types.
15723 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15726 Addition and subtraction on integral and floating-point types, or union
15727 and difference on set types.
15730 Multiplication on integral and floating-point types, or set intersection
15734 Division on floating-point types, or symmetric set difference on set
15735 types. Same precedence as @code{*}.
15738 Integer division and remainder. Defined on integral types. Same
15739 precedence as @code{*}.
15742 Negative. Defined on @code{INTEGER} and @code{REAL} data.
15745 Pointer dereferencing. Defined on pointer types.
15748 Boolean negation. Defined on boolean types. Same precedence as
15752 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
15753 precedence as @code{^}.
15756 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
15759 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
15763 @value{GDBN} and Modula-2 scope operators.
15767 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
15768 treats the use of the operator @code{IN}, or the use of operators
15769 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
15770 @code{<=}, and @code{>=} on sets as an error.
15774 @node Built-In Func/Proc
15775 @subsubsection Built-in Functions and Procedures
15776 @cindex Modula-2 built-ins
15778 Modula-2 also makes available several built-in procedures and functions.
15779 In describing these, the following metavariables are used:
15784 represents an @code{ARRAY} variable.
15787 represents a @code{CHAR} constant or variable.
15790 represents a variable or constant of integral type.
15793 represents an identifier that belongs to a set. Generally used in the
15794 same function with the metavariable @var{s}. The type of @var{s} should
15795 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
15798 represents a variable or constant of integral or floating-point type.
15801 represents a variable or constant of floating-point type.
15807 represents a variable.
15810 represents a variable or constant of one of many types. See the
15811 explanation of the function for details.
15814 All Modula-2 built-in procedures also return a result, described below.
15818 Returns the absolute value of @var{n}.
15821 If @var{c} is a lower case letter, it returns its upper case
15822 equivalent, otherwise it returns its argument.
15825 Returns the character whose ordinal value is @var{i}.
15828 Decrements the value in the variable @var{v} by one. Returns the new value.
15830 @item DEC(@var{v},@var{i})
15831 Decrements the value in the variable @var{v} by @var{i}. Returns the
15834 @item EXCL(@var{m},@var{s})
15835 Removes the element @var{m} from the set @var{s}. Returns the new
15838 @item FLOAT(@var{i})
15839 Returns the floating point equivalent of the integer @var{i}.
15841 @item HIGH(@var{a})
15842 Returns the index of the last member of @var{a}.
15845 Increments the value in the variable @var{v} by one. Returns the new value.
15847 @item INC(@var{v},@var{i})
15848 Increments the value in the variable @var{v} by @var{i}. Returns the
15851 @item INCL(@var{m},@var{s})
15852 Adds the element @var{m} to the set @var{s} if it is not already
15853 there. Returns the new set.
15856 Returns the maximum value of the type @var{t}.
15859 Returns the minimum value of the type @var{t}.
15862 Returns boolean TRUE if @var{i} is an odd number.
15865 Returns the ordinal value of its argument. For example, the ordinal
15866 value of a character is its @sc{ascii} value (on machines supporting
15867 the @sc{ascii} character set). The argument @var{x} must be of an
15868 ordered type, which include integral, character and enumerated types.
15870 @item SIZE(@var{x})
15871 Returns the size of its argument. The argument @var{x} can be a
15872 variable or a type.
15874 @item TRUNC(@var{r})
15875 Returns the integral part of @var{r}.
15877 @item TSIZE(@var{x})
15878 Returns the size of its argument. The argument @var{x} can be a
15879 variable or a type.
15881 @item VAL(@var{t},@var{i})
15882 Returns the member of the type @var{t} whose ordinal value is @var{i}.
15886 @emph{Warning:} Sets and their operations are not yet supported, so
15887 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
15891 @cindex Modula-2 constants
15893 @subsubsection Constants
15895 @value{GDBN} allows you to express the constants of Modula-2 in the following
15901 Integer constants are simply a sequence of digits. When used in an
15902 expression, a constant is interpreted to be type-compatible with the
15903 rest of the expression. Hexadecimal integers are specified by a
15904 trailing @samp{H}, and octal integers by a trailing @samp{B}.
15907 Floating point constants appear as a sequence of digits, followed by a
15908 decimal point and another sequence of digits. An optional exponent can
15909 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
15910 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
15911 digits of the floating point constant must be valid decimal (base 10)
15915 Character constants consist of a single character enclosed by a pair of
15916 like quotes, either single (@code{'}) or double (@code{"}). They may
15917 also be expressed by their ordinal value (their @sc{ascii} value, usually)
15918 followed by a @samp{C}.
15921 String constants consist of a sequence of characters enclosed by a
15922 pair of like quotes, either single (@code{'}) or double (@code{"}).
15923 Escape sequences in the style of C are also allowed. @xref{C
15924 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
15928 Enumerated constants consist of an enumerated identifier.
15931 Boolean constants consist of the identifiers @code{TRUE} and
15935 Pointer constants consist of integral values only.
15938 Set constants are not yet supported.
15942 @subsubsection Modula-2 Types
15943 @cindex Modula-2 types
15945 Currently @value{GDBN} can print the following data types in Modula-2
15946 syntax: array types, record types, set types, pointer types, procedure
15947 types, enumerated types, subrange types and base types. You can also
15948 print the contents of variables declared using these type.
15949 This section gives a number of simple source code examples together with
15950 sample @value{GDBN} sessions.
15952 The first example contains the following section of code:
15961 and you can request @value{GDBN} to interrogate the type and value of
15962 @code{r} and @code{s}.
15965 (@value{GDBP}) print s
15967 (@value{GDBP}) ptype s
15969 (@value{GDBP}) print r
15971 (@value{GDBP}) ptype r
15976 Likewise if your source code declares @code{s} as:
15980 s: SET ['A'..'Z'] ;
15984 then you may query the type of @code{s} by:
15987 (@value{GDBP}) ptype s
15988 type = SET ['A'..'Z']
15992 Note that at present you cannot interactively manipulate set
15993 expressions using the debugger.
15995 The following example shows how you might declare an array in Modula-2
15996 and how you can interact with @value{GDBN} to print its type and contents:
16000 s: ARRAY [-10..10] OF CHAR ;
16004 (@value{GDBP}) ptype s
16005 ARRAY [-10..10] OF CHAR
16008 Note that the array handling is not yet complete and although the type
16009 is printed correctly, expression handling still assumes that all
16010 arrays have a lower bound of zero and not @code{-10} as in the example
16013 Here are some more type related Modula-2 examples:
16017 colour = (blue, red, yellow, green) ;
16018 t = [blue..yellow] ;
16026 The @value{GDBN} interaction shows how you can query the data type
16027 and value of a variable.
16030 (@value{GDBP}) print s
16032 (@value{GDBP}) ptype t
16033 type = [blue..yellow]
16037 In this example a Modula-2 array is declared and its contents
16038 displayed. Observe that the contents are written in the same way as
16039 their @code{C} counterparts.
16043 s: ARRAY [1..5] OF CARDINAL ;
16049 (@value{GDBP}) print s
16050 $1 = @{1, 0, 0, 0, 0@}
16051 (@value{GDBP}) ptype s
16052 type = ARRAY [1..5] OF CARDINAL
16055 The Modula-2 language interface to @value{GDBN} also understands
16056 pointer types as shown in this example:
16060 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
16067 and you can request that @value{GDBN} describes the type of @code{s}.
16070 (@value{GDBP}) ptype s
16071 type = POINTER TO ARRAY [1..5] OF CARDINAL
16074 @value{GDBN} handles compound types as we can see in this example.
16075 Here we combine array types, record types, pointer types and subrange
16086 myarray = ARRAY myrange OF CARDINAL ;
16087 myrange = [-2..2] ;
16089 s: POINTER TO ARRAY myrange OF foo ;
16093 and you can ask @value{GDBN} to describe the type of @code{s} as shown
16097 (@value{GDBP}) ptype s
16098 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
16101 f3 : ARRAY [-2..2] OF CARDINAL;
16106 @subsubsection Modula-2 Defaults
16107 @cindex Modula-2 defaults
16109 If type and range checking are set automatically by @value{GDBN}, they
16110 both default to @code{on} whenever the working language changes to
16111 Modula-2. This happens regardless of whether you or @value{GDBN}
16112 selected the working language.
16114 If you allow @value{GDBN} to set the language automatically, then entering
16115 code compiled from a file whose name ends with @file{.mod} sets the
16116 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
16117 Infer the Source Language}, for further details.
16120 @subsubsection Deviations from Standard Modula-2
16121 @cindex Modula-2, deviations from
16123 A few changes have been made to make Modula-2 programs easier to debug.
16124 This is done primarily via loosening its type strictness:
16128 Unlike in standard Modula-2, pointer constants can be formed by
16129 integers. This allows you to modify pointer variables during
16130 debugging. (In standard Modula-2, the actual address contained in a
16131 pointer variable is hidden from you; it can only be modified
16132 through direct assignment to another pointer variable or expression that
16133 returned a pointer.)
16136 C escape sequences can be used in strings and characters to represent
16137 non-printable characters. @value{GDBN} prints out strings with these
16138 escape sequences embedded. Single non-printable characters are
16139 printed using the @samp{CHR(@var{nnn})} format.
16142 The assignment operator (@code{:=}) returns the value of its right-hand
16146 All built-in procedures both modify @emph{and} return their argument.
16150 @subsubsection Modula-2 Type and Range Checks
16151 @cindex Modula-2 checks
16154 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
16157 @c FIXME remove warning when type/range checks added
16159 @value{GDBN} considers two Modula-2 variables type equivalent if:
16163 They are of types that have been declared equivalent via a @code{TYPE
16164 @var{t1} = @var{t2}} statement
16167 They have been declared on the same line. (Note: This is true of the
16168 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
16171 As long as type checking is enabled, any attempt to combine variables
16172 whose types are not equivalent is an error.
16174 Range checking is done on all mathematical operations, assignment, array
16175 index bounds, and all built-in functions and procedures.
16178 @subsubsection The Scope Operators @code{::} and @code{.}
16180 @cindex @code{.}, Modula-2 scope operator
16181 @cindex colon, doubled as scope operator
16183 @vindex colon-colon@r{, in Modula-2}
16184 @c Info cannot handle :: but TeX can.
16187 @vindex ::@r{, in Modula-2}
16190 There are a few subtle differences between the Modula-2 scope operator
16191 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
16196 @var{module} . @var{id}
16197 @var{scope} :: @var{id}
16201 where @var{scope} is the name of a module or a procedure,
16202 @var{module} the name of a module, and @var{id} is any declared
16203 identifier within your program, except another module.
16205 Using the @code{::} operator makes @value{GDBN} search the scope
16206 specified by @var{scope} for the identifier @var{id}. If it is not
16207 found in the specified scope, then @value{GDBN} searches all scopes
16208 enclosing the one specified by @var{scope}.
16210 Using the @code{.} operator makes @value{GDBN} search the current scope for
16211 the identifier specified by @var{id} that was imported from the
16212 definition module specified by @var{module}. With this operator, it is
16213 an error if the identifier @var{id} was not imported from definition
16214 module @var{module}, or if @var{id} is not an identifier in
16218 @subsubsection @value{GDBN} and Modula-2
16220 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
16221 Five subcommands of @code{set print} and @code{show print} apply
16222 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
16223 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
16224 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
16225 analogue in Modula-2.
16227 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
16228 with any language, is not useful with Modula-2. Its
16229 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
16230 created in Modula-2 as they can in C or C@t{++}. However, because an
16231 address can be specified by an integral constant, the construct
16232 @samp{@{@var{type}@}@var{adrexp}} is still useful.
16234 @cindex @code{#} in Modula-2
16235 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
16236 interpreted as the beginning of a comment. Use @code{<>} instead.
16242 The extensions made to @value{GDBN} for Ada only support
16243 output from the @sc{gnu} Ada (GNAT) compiler.
16244 Other Ada compilers are not currently supported, and
16245 attempting to debug executables produced by them is most likely
16249 @cindex expressions in Ada
16251 * Ada Mode Intro:: General remarks on the Ada syntax
16252 and semantics supported by Ada mode
16254 * Omissions from Ada:: Restrictions on the Ada expression syntax.
16255 * Additions to Ada:: Extensions of the Ada expression syntax.
16256 * Overloading support for Ada:: Support for expressions involving overloaded
16258 * Stopping Before Main Program:: Debugging the program during elaboration.
16259 * Ada Exceptions:: Ada Exceptions
16260 * Ada Tasks:: Listing and setting breakpoints in tasks.
16261 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
16262 * Ravenscar Profile:: Tasking Support when using the Ravenscar
16264 * Ada Glitches:: Known peculiarities of Ada mode.
16267 @node Ada Mode Intro
16268 @subsubsection Introduction
16269 @cindex Ada mode, general
16271 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
16272 syntax, with some extensions.
16273 The philosophy behind the design of this subset is
16277 That @value{GDBN} should provide basic literals and access to operations for
16278 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
16279 leaving more sophisticated computations to subprograms written into the
16280 program (which therefore may be called from @value{GDBN}).
16283 That type safety and strict adherence to Ada language restrictions
16284 are not particularly important to the @value{GDBN} user.
16287 That brevity is important to the @value{GDBN} user.
16290 Thus, for brevity, the debugger acts as if all names declared in
16291 user-written packages are directly visible, even if they are not visible
16292 according to Ada rules, thus making it unnecessary to fully qualify most
16293 names with their packages, regardless of context. Where this causes
16294 ambiguity, @value{GDBN} asks the user's intent.
16296 The debugger will start in Ada mode if it detects an Ada main program.
16297 As for other languages, it will enter Ada mode when stopped in a program that
16298 was translated from an Ada source file.
16300 While in Ada mode, you may use `@t{--}' for comments. This is useful
16301 mostly for documenting command files. The standard @value{GDBN} comment
16302 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
16303 middle (to allow based literals).
16305 @node Omissions from Ada
16306 @subsubsection Omissions from Ada
16307 @cindex Ada, omissions from
16309 Here are the notable omissions from the subset:
16313 Only a subset of the attributes are supported:
16317 @t{'First}, @t{'Last}, and @t{'Length}
16318 on array objects (not on types and subtypes).
16321 @t{'Min} and @t{'Max}.
16324 @t{'Pos} and @t{'Val}.
16330 @t{'Range} on array objects (not subtypes), but only as the right
16331 operand of the membership (@code{in}) operator.
16334 @t{'Access}, @t{'Unchecked_Access}, and
16335 @t{'Unrestricted_Access} (a GNAT extension).
16343 @code{Characters.Latin_1} are not available and
16344 concatenation is not implemented. Thus, escape characters in strings are
16345 not currently available.
16348 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
16349 equality of representations. They will generally work correctly
16350 for strings and arrays whose elements have integer or enumeration types.
16351 They may not work correctly for arrays whose element
16352 types have user-defined equality, for arrays of real values
16353 (in particular, IEEE-conformant floating point, because of negative
16354 zeroes and NaNs), and for arrays whose elements contain unused bits with
16355 indeterminate values.
16358 The other component-by-component array operations (@code{and}, @code{or},
16359 @code{xor}, @code{not}, and relational tests other than equality)
16360 are not implemented.
16363 @cindex array aggregates (Ada)
16364 @cindex record aggregates (Ada)
16365 @cindex aggregates (Ada)
16366 There is limited support for array and record aggregates. They are
16367 permitted only on the right sides of assignments, as in these examples:
16370 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
16371 (@value{GDBP}) set An_Array := (1, others => 0)
16372 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
16373 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
16374 (@value{GDBP}) set A_Record := (1, "Peter", True);
16375 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
16379 discriminant's value by assigning an aggregate has an
16380 undefined effect if that discriminant is used within the record.
16381 However, you can first modify discriminants by directly assigning to
16382 them (which normally would not be allowed in Ada), and then performing an
16383 aggregate assignment. For example, given a variable @code{A_Rec}
16384 declared to have a type such as:
16387 type Rec (Len : Small_Integer := 0) is record
16389 Vals : IntArray (1 .. Len);
16393 you can assign a value with a different size of @code{Vals} with two
16397 (@value{GDBP}) set A_Rec.Len := 4
16398 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
16401 As this example also illustrates, @value{GDBN} is very loose about the usual
16402 rules concerning aggregates. You may leave out some of the
16403 components of an array or record aggregate (such as the @code{Len}
16404 component in the assignment to @code{A_Rec} above); they will retain their
16405 original values upon assignment. You may freely use dynamic values as
16406 indices in component associations. You may even use overlapping or
16407 redundant component associations, although which component values are
16408 assigned in such cases is not defined.
16411 Calls to dispatching subprograms are not implemented.
16414 The overloading algorithm is much more limited (i.e., less selective)
16415 than that of real Ada. It makes only limited use of the context in
16416 which a subexpression appears to resolve its meaning, and it is much
16417 looser in its rules for allowing type matches. As a result, some
16418 function calls will be ambiguous, and the user will be asked to choose
16419 the proper resolution.
16422 The @code{new} operator is not implemented.
16425 Entry calls are not implemented.
16428 Aside from printing, arithmetic operations on the native VAX floating-point
16429 formats are not supported.
16432 It is not possible to slice a packed array.
16435 The names @code{True} and @code{False}, when not part of a qualified name,
16436 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
16438 Should your program
16439 redefine these names in a package or procedure (at best a dubious practice),
16440 you will have to use fully qualified names to access their new definitions.
16443 @node Additions to Ada
16444 @subsubsection Additions to Ada
16445 @cindex Ada, deviations from
16447 As it does for other languages, @value{GDBN} makes certain generic
16448 extensions to Ada (@pxref{Expressions}):
16452 If the expression @var{E} is a variable residing in memory (typically
16453 a local variable or array element) and @var{N} is a positive integer,
16454 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
16455 @var{N}-1 adjacent variables following it in memory as an array. In
16456 Ada, this operator is generally not necessary, since its prime use is
16457 in displaying parts of an array, and slicing will usually do this in
16458 Ada. However, there are occasional uses when debugging programs in
16459 which certain debugging information has been optimized away.
16462 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
16463 appears in function or file @var{B}.'' When @var{B} is a file name,
16464 you must typically surround it in single quotes.
16467 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
16468 @var{type} that appears at address @var{addr}.''
16471 A name starting with @samp{$} is a convenience variable
16472 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
16475 In addition, @value{GDBN} provides a few other shortcuts and outright
16476 additions specific to Ada:
16480 The assignment statement is allowed as an expression, returning
16481 its right-hand operand as its value. Thus, you may enter
16484 (@value{GDBP}) set x := y + 3
16485 (@value{GDBP}) print A(tmp := y + 1)
16489 The semicolon is allowed as an ``operator,'' returning as its value
16490 the value of its right-hand operand.
16491 This allows, for example,
16492 complex conditional breaks:
16495 (@value{GDBP}) break f
16496 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
16500 Rather than use catenation and symbolic character names to introduce special
16501 characters into strings, one may instead use a special bracket notation,
16502 which is also used to print strings. A sequence of characters of the form
16503 @samp{["@var{XX}"]} within a string or character literal denotes the
16504 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
16505 sequence of characters @samp{["""]} also denotes a single quotation mark
16506 in strings. For example,
16508 "One line.["0a"]Next line.["0a"]"
16511 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
16515 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
16516 @t{'Max} is optional (and is ignored in any case). For example, it is valid
16520 (@value{GDBP}) print 'max(x, y)
16524 When printing arrays, @value{GDBN} uses positional notation when the
16525 array has a lower bound of 1, and uses a modified named notation otherwise.
16526 For example, a one-dimensional array of three integers with a lower bound
16527 of 3 might print as
16534 That is, in contrast to valid Ada, only the first component has a @code{=>}
16538 You may abbreviate attributes in expressions with any unique,
16539 multi-character subsequence of
16540 their names (an exact match gets preference).
16541 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
16542 in place of @t{a'length}.
16545 @cindex quoting Ada internal identifiers
16546 Since Ada is case-insensitive, the debugger normally maps identifiers you type
16547 to lower case. The GNAT compiler uses upper-case characters for
16548 some of its internal identifiers, which are normally of no interest to users.
16549 For the rare occasions when you actually have to look at them,
16550 enclose them in angle brackets to avoid the lower-case mapping.
16553 (@value{GDBP}) print <JMPBUF_SAVE>[0]
16557 Printing an object of class-wide type or dereferencing an
16558 access-to-class-wide value will display all the components of the object's
16559 specific type (as indicated by its run-time tag). Likewise, component
16560 selection on such a value will operate on the specific type of the
16565 @node Overloading support for Ada
16566 @subsubsection Overloading support for Ada
16567 @cindex overloading, Ada
16569 The debugger supports limited overloading. Given a subprogram call in which
16570 the function symbol has multiple definitions, it will use the number of
16571 actual parameters and some information about their types to attempt to narrow
16572 the set of definitions. It also makes very limited use of context, preferring
16573 procedures to functions in the context of the @code{call} command, and
16574 functions to procedures elsewhere.
16576 If, after narrowing, the set of matching definitions still contains more than
16577 one definition, @value{GDBN} will display a menu to query which one it should
16581 (@value{GDBP}) print f(1)
16582 Multiple matches for f
16584 [1] foo.f (integer) return boolean at foo.adb:23
16585 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
16589 In this case, just select one menu entry either to cancel expression evaluation
16590 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
16591 instance (type the corresponding number and press @key{RET}).
16593 Here are a couple of commands to customize @value{GDBN}'s behavior in this
16598 @kindex set ada print-signatures
16599 @item set ada print-signatures
16600 Control whether parameter types and return types are displayed in overloads
16601 selection menus. It is @code{on} by default.
16602 @xref{Overloading support for Ada}.
16604 @kindex show ada print-signatures
16605 @item show ada print-signatures
16606 Show the current setting for displaying parameter types and return types in
16607 overloads selection menu.
16608 @xref{Overloading support for Ada}.
16612 @node Stopping Before Main Program
16613 @subsubsection Stopping at the Very Beginning
16615 @cindex breakpointing Ada elaboration code
16616 It is sometimes necessary to debug the program during elaboration, and
16617 before reaching the main procedure.
16618 As defined in the Ada Reference
16619 Manual, the elaboration code is invoked from a procedure called
16620 @code{adainit}. To run your program up to the beginning of
16621 elaboration, simply use the following two commands:
16622 @code{tbreak adainit} and @code{run}.
16624 @node Ada Exceptions
16625 @subsubsection Ada Exceptions
16627 A command is provided to list all Ada exceptions:
16630 @kindex info exceptions
16631 @item info exceptions
16632 @itemx info exceptions @var{regexp}
16633 The @code{info exceptions} command allows you to list all Ada exceptions
16634 defined within the program being debugged, as well as their addresses.
16635 With a regular expression, @var{regexp}, as argument, only those exceptions
16636 whose names match @var{regexp} are listed.
16639 Below is a small example, showing how the command can be used, first
16640 without argument, and next with a regular expression passed as an
16644 (@value{GDBP}) info exceptions
16645 All defined Ada exceptions:
16646 constraint_error: 0x613da0
16647 program_error: 0x613d20
16648 storage_error: 0x613ce0
16649 tasking_error: 0x613ca0
16650 const.aint_global_e: 0x613b00
16651 (@value{GDBP}) info exceptions const.aint
16652 All Ada exceptions matching regular expression "const.aint":
16653 constraint_error: 0x613da0
16654 const.aint_global_e: 0x613b00
16657 It is also possible to ask @value{GDBN} to stop your program's execution
16658 when an exception is raised. For more details, see @ref{Set Catchpoints}.
16661 @subsubsection Extensions for Ada Tasks
16662 @cindex Ada, tasking
16664 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
16665 @value{GDBN} provides the following task-related commands:
16670 This command shows a list of current Ada tasks, as in the following example:
16677 (@value{GDBP}) info tasks
16678 ID TID P-ID Pri State Name
16679 1 8088000 0 15 Child Activation Wait main_task
16680 2 80a4000 1 15 Accept Statement b
16681 3 809a800 1 15 Child Activation Wait a
16682 * 4 80ae800 3 15 Runnable c
16687 In this listing, the asterisk before the last task indicates it to be the
16688 task currently being inspected.
16692 Represents @value{GDBN}'s internal task number.
16698 The parent's task ID (@value{GDBN}'s internal task number).
16701 The base priority of the task.
16704 Current state of the task.
16708 The task has been created but has not been activated. It cannot be
16712 The task is not blocked for any reason known to Ada. (It may be waiting
16713 for a mutex, though.) It is conceptually "executing" in normal mode.
16716 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
16717 that were waiting on terminate alternatives have been awakened and have
16718 terminated themselves.
16720 @item Child Activation Wait
16721 The task is waiting for created tasks to complete activation.
16723 @item Accept Statement
16724 The task is waiting on an accept or selective wait statement.
16726 @item Waiting on entry call
16727 The task is waiting on an entry call.
16729 @item Async Select Wait
16730 The task is waiting to start the abortable part of an asynchronous
16734 The task is waiting on a select statement with only a delay
16737 @item Child Termination Wait
16738 The task is sleeping having completed a master within itself, and is
16739 waiting for the tasks dependent on that master to become terminated or
16740 waiting on a terminate Phase.
16742 @item Wait Child in Term Alt
16743 The task is sleeping waiting for tasks on terminate alternatives to
16744 finish terminating.
16746 @item Accepting RV with @var{taskno}
16747 The task is accepting a rendez-vous with the task @var{taskno}.
16751 Name of the task in the program.
16755 @kindex info task @var{taskno}
16756 @item info task @var{taskno}
16757 This command shows detailled informations on the specified task, as in
16758 the following example:
16763 (@value{GDBP}) info tasks
16764 ID TID P-ID Pri State Name
16765 1 8077880 0 15 Child Activation Wait main_task
16766 * 2 807c468 1 15 Runnable task_1
16767 (@value{GDBP}) info task 2
16768 Ada Task: 0x807c468
16771 Parent: 1 (main_task)
16777 @kindex task@r{ (Ada)}
16778 @cindex current Ada task ID
16779 This command prints the ID of the current task.
16785 (@value{GDBP}) info tasks
16786 ID TID P-ID Pri State Name
16787 1 8077870 0 15 Child Activation Wait main_task
16788 * 2 807c458 1 15 Runnable t
16789 (@value{GDBP}) task
16790 [Current task is 2]
16793 @item task @var{taskno}
16794 @cindex Ada task switching
16795 This command is like the @code{thread @var{thread-id}}
16796 command (@pxref{Threads}). It switches the context of debugging
16797 from the current task to the given task.
16803 (@value{GDBP}) info tasks
16804 ID TID P-ID Pri State Name
16805 1 8077870 0 15 Child Activation Wait main_task
16806 * 2 807c458 1 15 Runnable t
16807 (@value{GDBP}) task 1
16808 [Switching to task 1]
16809 #0 0x8067726 in pthread_cond_wait ()
16811 #0 0x8067726 in pthread_cond_wait ()
16812 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
16813 #2 0x805cb63 in system.task_primitives.operations.sleep ()
16814 #3 0x806153e in system.tasking.stages.activate_tasks ()
16815 #4 0x804aacc in un () at un.adb:5
16818 @item break @var{location} task @var{taskno}
16819 @itemx break @var{location} task @var{taskno} if @dots{}
16820 @cindex breakpoints and tasks, in Ada
16821 @cindex task breakpoints, in Ada
16822 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
16823 These commands are like the @code{break @dots{} thread @dots{}}
16824 command (@pxref{Thread Stops}). The
16825 @var{location} argument specifies source lines, as described
16826 in @ref{Specify Location}.
16828 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
16829 to specify that you only want @value{GDBN} to stop the program when a
16830 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
16831 numeric task identifiers assigned by @value{GDBN}, shown in the first
16832 column of the @samp{info tasks} display.
16834 If you do not specify @samp{task @var{taskno}} when you set a
16835 breakpoint, the breakpoint applies to @emph{all} tasks of your
16838 You can use the @code{task} qualifier on conditional breakpoints as
16839 well; in this case, place @samp{task @var{taskno}} before the
16840 breakpoint condition (before the @code{if}).
16848 (@value{GDBP}) info tasks
16849 ID TID P-ID Pri State Name
16850 1 140022020 0 15 Child Activation Wait main_task
16851 2 140045060 1 15 Accept/Select Wait t2
16852 3 140044840 1 15 Runnable t1
16853 * 4 140056040 1 15 Runnable t3
16854 (@value{GDBP}) b 15 task 2
16855 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
16856 (@value{GDBP}) cont
16861 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
16863 (@value{GDBP}) info tasks
16864 ID TID P-ID Pri State Name
16865 1 140022020 0 15 Child Activation Wait main_task
16866 * 2 140045060 1 15 Runnable t2
16867 3 140044840 1 15 Runnable t1
16868 4 140056040 1 15 Delay Sleep t3
16872 @node Ada Tasks and Core Files
16873 @subsubsection Tasking Support when Debugging Core Files
16874 @cindex Ada tasking and core file debugging
16876 When inspecting a core file, as opposed to debugging a live program,
16877 tasking support may be limited or even unavailable, depending on
16878 the platform being used.
16879 For instance, on x86-linux, the list of tasks is available, but task
16880 switching is not supported.
16882 On certain platforms, the debugger needs to perform some
16883 memory writes in order to provide Ada tasking support. When inspecting
16884 a core file, this means that the core file must be opened with read-write
16885 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
16886 Under these circumstances, you should make a backup copy of the core
16887 file before inspecting it with @value{GDBN}.
16889 @node Ravenscar Profile
16890 @subsubsection Tasking Support when using the Ravenscar Profile
16891 @cindex Ravenscar Profile
16893 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
16894 specifically designed for systems with safety-critical real-time
16898 @kindex set ravenscar task-switching on
16899 @cindex task switching with program using Ravenscar Profile
16900 @item set ravenscar task-switching on
16901 Allows task switching when debugging a program that uses the Ravenscar
16902 Profile. This is the default.
16904 @kindex set ravenscar task-switching off
16905 @item set ravenscar task-switching off
16906 Turn off task switching when debugging a program that uses the Ravenscar
16907 Profile. This is mostly intended to disable the code that adds support
16908 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
16909 the Ravenscar runtime is preventing @value{GDBN} from working properly.
16910 To be effective, this command should be run before the program is started.
16912 @kindex show ravenscar task-switching
16913 @item show ravenscar task-switching
16914 Show whether it is possible to switch from task to task in a program
16915 using the Ravenscar Profile.
16920 @subsubsection Known Peculiarities of Ada Mode
16921 @cindex Ada, problems
16923 Besides the omissions listed previously (@pxref{Omissions from Ada}),
16924 we know of several problems with and limitations of Ada mode in
16926 some of which will be fixed with planned future releases of the debugger
16927 and the GNU Ada compiler.
16931 Static constants that the compiler chooses not to materialize as objects in
16932 storage are invisible to the debugger.
16935 Named parameter associations in function argument lists are ignored (the
16936 argument lists are treated as positional).
16939 Many useful library packages are currently invisible to the debugger.
16942 Fixed-point arithmetic, conversions, input, and output is carried out using
16943 floating-point arithmetic, and may give results that only approximate those on
16947 The GNAT compiler never generates the prefix @code{Standard} for any of
16948 the standard symbols defined by the Ada language. @value{GDBN} knows about
16949 this: it will strip the prefix from names when you use it, and will never
16950 look for a name you have so qualified among local symbols, nor match against
16951 symbols in other packages or subprograms. If you have
16952 defined entities anywhere in your program other than parameters and
16953 local variables whose simple names match names in @code{Standard},
16954 GNAT's lack of qualification here can cause confusion. When this happens,
16955 you can usually resolve the confusion
16956 by qualifying the problematic names with package
16957 @code{Standard} explicitly.
16960 Older versions of the compiler sometimes generate erroneous debugging
16961 information, resulting in the debugger incorrectly printing the value
16962 of affected entities. In some cases, the debugger is able to work
16963 around an issue automatically. In other cases, the debugger is able
16964 to work around the issue, but the work-around has to be specifically
16967 @kindex set ada trust-PAD-over-XVS
16968 @kindex show ada trust-PAD-over-XVS
16971 @item set ada trust-PAD-over-XVS on
16972 Configure GDB to strictly follow the GNAT encoding when computing the
16973 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
16974 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
16975 a complete description of the encoding used by the GNAT compiler).
16976 This is the default.
16978 @item set ada trust-PAD-over-XVS off
16979 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
16980 sometimes prints the wrong value for certain entities, changing @code{ada
16981 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
16982 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
16983 @code{off}, but this incurs a slight performance penalty, so it is
16984 recommended to leave this setting to @code{on} unless necessary.
16988 @cindex GNAT descriptive types
16989 @cindex GNAT encoding
16990 Internally, the debugger also relies on the compiler following a number
16991 of conventions known as the @samp{GNAT Encoding}, all documented in
16992 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
16993 how the debugging information should be generated for certain types.
16994 In particular, this convention makes use of @dfn{descriptive types},
16995 which are artificial types generated purely to help the debugger.
16997 These encodings were defined at a time when the debugging information
16998 format used was not powerful enough to describe some of the more complex
16999 types available in Ada. Since DWARF allows us to express nearly all
17000 Ada features, the long-term goal is to slowly replace these descriptive
17001 types by their pure DWARF equivalent. To facilitate that transition,
17002 a new maintenance option is available to force the debugger to ignore
17003 those descriptive types. It allows the user to quickly evaluate how
17004 well @value{GDBN} works without them.
17008 @kindex maint ada set ignore-descriptive-types
17009 @item maintenance ada set ignore-descriptive-types [on|off]
17010 Control whether the debugger should ignore descriptive types.
17011 The default is not to ignore descriptives types (@code{off}).
17013 @kindex maint ada show ignore-descriptive-types
17014 @item maintenance ada show ignore-descriptive-types
17015 Show if descriptive types are ignored by @value{GDBN}.
17019 @node Unsupported Languages
17020 @section Unsupported Languages
17022 @cindex unsupported languages
17023 @cindex minimal language
17024 In addition to the other fully-supported programming languages,
17025 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
17026 It does not represent a real programming language, but provides a set
17027 of capabilities close to what the C or assembly languages provide.
17028 This should allow most simple operations to be performed while debugging
17029 an application that uses a language currently not supported by @value{GDBN}.
17031 If the language is set to @code{auto}, @value{GDBN} will automatically
17032 select this language if the current frame corresponds to an unsupported
17036 @chapter Examining the Symbol Table
17038 The commands described in this chapter allow you to inquire about the
17039 symbols (names of variables, functions and types) defined in your
17040 program. This information is inherent in the text of your program and
17041 does not change as your program executes. @value{GDBN} finds it in your
17042 program's symbol table, in the file indicated when you started @value{GDBN}
17043 (@pxref{File Options, ,Choosing Files}), or by one of the
17044 file-management commands (@pxref{Files, ,Commands to Specify Files}).
17046 @cindex symbol names
17047 @cindex names of symbols
17048 @cindex quoting names
17049 @anchor{quoting names}
17050 Occasionally, you may need to refer to symbols that contain unusual
17051 characters, which @value{GDBN} ordinarily treats as word delimiters. The
17052 most frequent case is in referring to static variables in other
17053 source files (@pxref{Variables,,Program Variables}). File names
17054 are recorded in object files as debugging symbols, but @value{GDBN} would
17055 ordinarily parse a typical file name, like @file{foo.c}, as the three words
17056 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
17057 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
17064 looks up the value of @code{x} in the scope of the file @file{foo.c}.
17067 @cindex case-insensitive symbol names
17068 @cindex case sensitivity in symbol names
17069 @kindex set case-sensitive
17070 @item set case-sensitive on
17071 @itemx set case-sensitive off
17072 @itemx set case-sensitive auto
17073 Normally, when @value{GDBN} looks up symbols, it matches their names
17074 with case sensitivity determined by the current source language.
17075 Occasionally, you may wish to control that. The command @code{set
17076 case-sensitive} lets you do that by specifying @code{on} for
17077 case-sensitive matches or @code{off} for case-insensitive ones. If
17078 you specify @code{auto}, case sensitivity is reset to the default
17079 suitable for the source language. The default is case-sensitive
17080 matches for all languages except for Fortran, for which the default is
17081 case-insensitive matches.
17083 @kindex show case-sensitive
17084 @item show case-sensitive
17085 This command shows the current setting of case sensitivity for symbols
17088 @kindex set print type methods
17089 @item set print type methods
17090 @itemx set print type methods on
17091 @itemx set print type methods off
17092 Normally, when @value{GDBN} prints a class, it displays any methods
17093 declared in that class. You can control this behavior either by
17094 passing the appropriate flag to @code{ptype}, or using @command{set
17095 print type methods}. Specifying @code{on} will cause @value{GDBN} to
17096 display the methods; this is the default. Specifying @code{off} will
17097 cause @value{GDBN} to omit the methods.
17099 @kindex show print type methods
17100 @item show print type methods
17101 This command shows the current setting of method display when printing
17104 @kindex set print type nested-type-limit
17105 @item set print type nested-type-limit @var{limit}
17106 @itemx set print type nested-type-limit unlimited
17107 Set the limit of displayed nested types that the type printer will
17108 show. A @var{limit} of @code{unlimited} or @code{-1} will show all
17109 nested definitions. By default, the type printer will not show any nested
17110 types defined in classes.
17112 @kindex show print type nested-type-limit
17113 @item show print type nested-type-limit
17114 This command shows the current display limit of nested types when
17117 @kindex set print type typedefs
17118 @item set print type typedefs
17119 @itemx set print type typedefs on
17120 @itemx set print type typedefs off
17122 Normally, when @value{GDBN} prints a class, it displays any typedefs
17123 defined in that class. You can control this behavior either by
17124 passing the appropriate flag to @code{ptype}, or using @command{set
17125 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
17126 display the typedef definitions; this is the default. Specifying
17127 @code{off} will cause @value{GDBN} to omit the typedef definitions.
17128 Note that this controls whether the typedef definition itself is
17129 printed, not whether typedef names are substituted when printing other
17132 @kindex show print type typedefs
17133 @item show print type typedefs
17134 This command shows the current setting of typedef display when
17137 @kindex info address
17138 @cindex address of a symbol
17139 @item info address @var{symbol}
17140 Describe where the data for @var{symbol} is stored. For a register
17141 variable, this says which register it is kept in. For a non-register
17142 local variable, this prints the stack-frame offset at which the variable
17145 Note the contrast with @samp{print &@var{symbol}}, which does not work
17146 at all for a register variable, and for a stack local variable prints
17147 the exact address of the current instantiation of the variable.
17149 @kindex info symbol
17150 @cindex symbol from address
17151 @cindex closest symbol and offset for an address
17152 @item info symbol @var{addr}
17153 Print the name of a symbol which is stored at the address @var{addr}.
17154 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
17155 nearest symbol and an offset from it:
17158 (@value{GDBP}) info symbol 0x54320
17159 _initialize_vx + 396 in section .text
17163 This is the opposite of the @code{info address} command. You can use
17164 it to find out the name of a variable or a function given its address.
17166 For dynamically linked executables, the name of executable or shared
17167 library containing the symbol is also printed:
17170 (@value{GDBP}) info symbol 0x400225
17171 _start + 5 in section .text of /tmp/a.out
17172 (@value{GDBP}) info symbol 0x2aaaac2811cf
17173 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
17178 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
17179 Demangle @var{name}.
17180 If @var{language} is provided it is the name of the language to demangle
17181 @var{name} in. Otherwise @var{name} is demangled in the current language.
17183 The @samp{--} option specifies the end of options,
17184 and is useful when @var{name} begins with a dash.
17186 The parameter @code{demangle-style} specifies how to interpret the kind
17187 of mangling used. @xref{Print Settings}.
17190 @item whatis[/@var{flags}] [@var{arg}]
17191 Print the data type of @var{arg}, which can be either an expression
17192 or a name of a data type. With no argument, print the data type of
17193 @code{$}, the last value in the value history.
17195 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
17196 is not actually evaluated, and any side-effecting operations (such as
17197 assignments or function calls) inside it do not take place.
17199 If @var{arg} is a variable or an expression, @code{whatis} prints its
17200 literal type as it is used in the source code. If the type was
17201 defined using a @code{typedef}, @code{whatis} will @emph{not} print
17202 the data type underlying the @code{typedef}. If the type of the
17203 variable or the expression is a compound data type, such as
17204 @code{struct} or @code{class}, @code{whatis} never prints their
17205 fields or methods. It just prints the @code{struct}/@code{class}
17206 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
17207 such a compound data type, use @code{ptype}.
17209 If @var{arg} is a type name that was defined using @code{typedef},
17210 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
17211 Unrolling means that @code{whatis} will show the underlying type used
17212 in the @code{typedef} declaration of @var{arg}. However, if that
17213 underlying type is also a @code{typedef}, @code{whatis} will not
17216 For C code, the type names may also have the form @samp{class
17217 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
17218 @var{union-tag}} or @samp{enum @var{enum-tag}}.
17220 @var{flags} can be used to modify how the type is displayed.
17221 Available flags are:
17225 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
17226 parameters and typedefs defined in a class when printing the class'
17227 members. The @code{/r} flag disables this.
17230 Do not print methods defined in the class.
17233 Print methods defined in the class. This is the default, but the flag
17234 exists in case you change the default with @command{set print type methods}.
17237 Do not print typedefs defined in the class. Note that this controls
17238 whether the typedef definition itself is printed, not whether typedef
17239 names are substituted when printing other types.
17242 Print typedefs defined in the class. This is the default, but the flag
17243 exists in case you change the default with @command{set print type typedefs}.
17246 Print the offsets and sizes of fields in a struct, similar to what the
17247 @command{pahole} tool does. This option implies the @code{/tm} flags.
17249 For example, given the following declarations:
17285 Issuing a @kbd{ptype /o struct tuv} command would print:
17288 (@value{GDBP}) ptype /o struct tuv
17289 /* offset | size */ type = struct tuv @{
17290 /* 0 | 4 */ int a1;
17291 /* XXX 4-byte hole */
17292 /* 8 | 8 */ char *a2;
17293 /* 16 | 4 */ int a3;
17295 /* total size (bytes): 24 */
17299 Notice the format of the first column of comments. There, you can
17300 find two parts separated by the @samp{|} character: the @emph{offset},
17301 which indicates where the field is located inside the struct, in
17302 bytes, and the @emph{size} of the field. Another interesting line is
17303 the marker of a @emph{hole} in the struct, indicating that it may be
17304 possible to pack the struct and make it use less space by reorganizing
17307 It is also possible to print offsets inside an union:
17310 (@value{GDBP}) ptype /o union qwe
17311 /* offset | size */ type = union qwe @{
17312 /* 24 */ struct tuv @{
17313 /* 0 | 4 */ int a1;
17314 /* XXX 4-byte hole */
17315 /* 8 | 8 */ char *a2;
17316 /* 16 | 4 */ int a3;
17318 /* total size (bytes): 24 */
17320 /* 40 */ struct xyz @{
17321 /* 0 | 4 */ int f1;
17322 /* 4 | 1 */ char f2;
17323 /* XXX 3-byte hole */
17324 /* 8 | 8 */ void *f3;
17325 /* 16 | 24 */ struct tuv @{
17326 /* 16 | 4 */ int a1;
17327 /* XXX 4-byte hole */
17328 /* 24 | 8 */ char *a2;
17329 /* 32 | 4 */ int a3;
17331 /* total size (bytes): 24 */
17334 /* total size (bytes): 40 */
17337 /* total size (bytes): 40 */
17341 In this case, since @code{struct tuv} and @code{struct xyz} occupy the
17342 same space (because we are dealing with an union), the offset is not
17343 printed for them. However, you can still examine the offset of each
17344 of these structures' fields.
17346 Another useful scenario is printing the offsets of a struct containing
17350 (@value{GDBP}) ptype /o struct tyu
17351 /* offset | size */ type = struct tyu @{
17352 /* 0:31 | 4 */ int a1 : 1;
17353 /* 0:28 | 4 */ int a2 : 3;
17354 /* 0: 5 | 4 */ int a3 : 23;
17355 /* 3: 3 | 1 */ signed char a4 : 2;
17356 /* XXX 3-bit hole */
17357 /* XXX 4-byte hole */
17358 /* 8 | 8 */ int64_t a5;
17359 /* 16:27 | 4 */ int a6 : 5;
17360 /* 16:56 | 8 */ int64_t a7 : 3;
17362 /* total size (bytes): 24 */
17366 Note how the offset information is now extended to also include how
17367 many bits are left to be used in each bitfield.
17371 @item ptype[/@var{flags}] [@var{arg}]
17372 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
17373 detailed description of the type, instead of just the name of the type.
17374 @xref{Expressions, ,Expressions}.
17376 Contrary to @code{whatis}, @code{ptype} always unrolls any
17377 @code{typedef}s in its argument declaration, whether the argument is
17378 a variable, expression, or a data type. This means that @code{ptype}
17379 of a variable or an expression will not print literally its type as
17380 present in the source code---use @code{whatis} for that. @code{typedef}s at
17381 the pointer or reference targets are also unrolled. Only @code{typedef}s of
17382 fields, methods and inner @code{class typedef}s of @code{struct}s,
17383 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
17385 For example, for this variable declaration:
17388 typedef double real_t;
17389 struct complex @{ real_t real; double imag; @};
17390 typedef struct complex complex_t;
17392 real_t *real_pointer_var;
17396 the two commands give this output:
17400 (@value{GDBP}) whatis var
17402 (@value{GDBP}) ptype var
17403 type = struct complex @{
17407 (@value{GDBP}) whatis complex_t
17408 type = struct complex
17409 (@value{GDBP}) whatis struct complex
17410 type = struct complex
17411 (@value{GDBP}) ptype struct complex
17412 type = struct complex @{
17416 (@value{GDBP}) whatis real_pointer_var
17418 (@value{GDBP}) ptype real_pointer_var
17424 As with @code{whatis}, using @code{ptype} without an argument refers to
17425 the type of @code{$}, the last value in the value history.
17427 @cindex incomplete type
17428 Sometimes, programs use opaque data types or incomplete specifications
17429 of complex data structure. If the debug information included in the
17430 program does not allow @value{GDBN} to display a full declaration of
17431 the data type, it will say @samp{<incomplete type>}. For example,
17432 given these declarations:
17436 struct foo *fooptr;
17440 but no definition for @code{struct foo} itself, @value{GDBN} will say:
17443 (@value{GDBP}) ptype foo
17444 $1 = <incomplete type>
17448 ``Incomplete type'' is C terminology for data types that are not
17449 completely specified.
17451 @cindex unknown type
17452 Othertimes, information about a variable's type is completely absent
17453 from the debug information included in the program. This most often
17454 happens when the program or library where the variable is defined
17455 includes no debug information at all. @value{GDBN} knows the variable
17456 exists from inspecting the linker/loader symbol table (e.g., the ELF
17457 dynamic symbol table), but such symbols do not contain type
17458 information. Inspecting the type of a (global) variable for which
17459 @value{GDBN} has no type information shows:
17462 (@value{GDBP}) ptype var
17463 type = <data variable, no debug info>
17466 @xref{Variables, no debug info variables}, for how to print the values
17470 @item info types @var{regexp}
17472 Print a brief description of all types whose names match the regular
17473 expression @var{regexp} (or all types in your program, if you supply
17474 no argument). Each complete typename is matched as though it were a
17475 complete line; thus, @samp{i type value} gives information on all
17476 types in your program whose names include the string @code{value}, but
17477 @samp{i type ^value$} gives information only on types whose complete
17478 name is @code{value}.
17480 This command differs from @code{ptype} in two ways: first, like
17481 @code{whatis}, it does not print a detailed description; second, it
17482 lists all source files where a type is defined.
17484 @kindex info type-printers
17485 @item info type-printers
17486 Versions of @value{GDBN} that ship with Python scripting enabled may
17487 have ``type printers'' available. When using @command{ptype} or
17488 @command{whatis}, these printers are consulted when the name of a type
17489 is needed. @xref{Type Printing API}, for more information on writing
17492 @code{info type-printers} displays all the available type printers.
17494 @kindex enable type-printer
17495 @kindex disable type-printer
17496 @item enable type-printer @var{name}@dots{}
17497 @item disable type-printer @var{name}@dots{}
17498 These commands can be used to enable or disable type printers.
17501 @cindex local variables
17502 @item info scope @var{location}
17503 List all the variables local to a particular scope. This command
17504 accepts a @var{location} argument---a function name, a source line, or
17505 an address preceded by a @samp{*}, and prints all the variables local
17506 to the scope defined by that location. (@xref{Specify Location}, for
17507 details about supported forms of @var{location}.) For example:
17510 (@value{GDBP}) @b{info scope command_line_handler}
17511 Scope for command_line_handler:
17512 Symbol rl is an argument at stack/frame offset 8, length 4.
17513 Symbol linebuffer is in static storage at address 0x150a18, length 4.
17514 Symbol linelength is in static storage at address 0x150a1c, length 4.
17515 Symbol p is a local variable in register $esi, length 4.
17516 Symbol p1 is a local variable in register $ebx, length 4.
17517 Symbol nline is a local variable in register $edx, length 4.
17518 Symbol repeat is a local variable at frame offset -8, length 4.
17522 This command is especially useful for determining what data to collect
17523 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
17526 @kindex info source
17528 Show information about the current source file---that is, the source file for
17529 the function containing the current point of execution:
17532 the name of the source file, and the directory containing it,
17534 the directory it was compiled in,
17536 its length, in lines,
17538 which programming language it is written in,
17540 if the debug information provides it, the program that compiled the file
17541 (which may include, e.g., the compiler version and command line arguments),
17543 whether the executable includes debugging information for that file, and
17544 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
17546 whether the debugging information includes information about
17547 preprocessor macros.
17551 @kindex info sources
17553 Print the names of all source files in your program for which there is
17554 debugging information, organized into two lists: files whose symbols
17555 have already been read, and files whose symbols will be read when needed.
17557 @kindex info functions
17558 @item info functions
17559 Print the names and data types of all defined functions.
17561 @item info functions @var{regexp}
17562 Print the names and data types of all defined functions
17563 whose names contain a match for regular expression @var{regexp}.
17564 Thus, @samp{info fun step} finds all functions whose names
17565 include @code{step}; @samp{info fun ^step} finds those whose names
17566 start with @code{step}. If a function name contains characters
17567 that conflict with the regular expression language (e.g.@:
17568 @samp{operator*()}), they may be quoted with a backslash.
17570 @kindex info variables
17571 @item info variables
17572 Print the names and data types of all variables that are defined
17573 outside of functions (i.e.@: excluding local variables).
17575 @item info variables @var{regexp}
17576 Print the names and data types of all variables (except for local
17577 variables) whose names contain a match for regular expression
17580 @kindex info classes
17581 @cindex Objective-C, classes and selectors
17583 @itemx info classes @var{regexp}
17584 Display all Objective-C classes in your program, or
17585 (with the @var{regexp} argument) all those matching a particular regular
17588 @kindex info selectors
17589 @item info selectors
17590 @itemx info selectors @var{regexp}
17591 Display all Objective-C selectors in your program, or
17592 (with the @var{regexp} argument) all those matching a particular regular
17596 This was never implemented.
17597 @kindex info methods
17599 @itemx info methods @var{regexp}
17600 The @code{info methods} command permits the user to examine all defined
17601 methods within C@t{++} program, or (with the @var{regexp} argument) a
17602 specific set of methods found in the various C@t{++} classes. Many
17603 C@t{++} classes provide a large number of methods. Thus, the output
17604 from the @code{ptype} command can be overwhelming and hard to use. The
17605 @code{info-methods} command filters the methods, printing only those
17606 which match the regular-expression @var{regexp}.
17609 @cindex opaque data types
17610 @kindex set opaque-type-resolution
17611 @item set opaque-type-resolution on
17612 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
17613 declared as a pointer to a @code{struct}, @code{class}, or
17614 @code{union}---for example, @code{struct MyType *}---that is used in one
17615 source file although the full declaration of @code{struct MyType} is in
17616 another source file. The default is on.
17618 A change in the setting of this subcommand will not take effect until
17619 the next time symbols for a file are loaded.
17621 @item set opaque-type-resolution off
17622 Tell @value{GDBN} not to resolve opaque types. In this case, the type
17623 is printed as follows:
17625 @{<no data fields>@}
17628 @kindex show opaque-type-resolution
17629 @item show opaque-type-resolution
17630 Show whether opaque types are resolved or not.
17632 @kindex set print symbol-loading
17633 @cindex print messages when symbols are loaded
17634 @item set print symbol-loading
17635 @itemx set print symbol-loading full
17636 @itemx set print symbol-loading brief
17637 @itemx set print symbol-loading off
17638 The @code{set print symbol-loading} command allows you to control the
17639 printing of messages when @value{GDBN} loads symbol information.
17640 By default a message is printed for the executable and one for each
17641 shared library, and normally this is what you want. However, when
17642 debugging apps with large numbers of shared libraries these messages
17644 When set to @code{brief} a message is printed for each executable,
17645 and when @value{GDBN} loads a collection of shared libraries at once
17646 it will only print one message regardless of the number of shared
17647 libraries. When set to @code{off} no messages are printed.
17649 @kindex show print symbol-loading
17650 @item show print symbol-loading
17651 Show whether messages will be printed when a @value{GDBN} command
17652 entered from the keyboard causes symbol information to be loaded.
17654 @kindex maint print symbols
17655 @cindex symbol dump
17656 @kindex maint print psymbols
17657 @cindex partial symbol dump
17658 @kindex maint print msymbols
17659 @cindex minimal symbol dump
17660 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
17661 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17662 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17663 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17664 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17665 Write a dump of debugging symbol data into the file @var{filename} or
17666 the terminal if @var{filename} is unspecified.
17667 If @code{-objfile @var{objfile}} is specified, only dump symbols for
17669 If @code{-pc @var{address}} is specified, only dump symbols for the file
17670 with code at that address. Note that @var{address} may be a symbol like
17672 If @code{-source @var{source}} is specified, only dump symbols for that
17675 These commands are used to debug the @value{GDBN} symbol-reading code.
17676 These commands do not modify internal @value{GDBN} state, therefore
17677 @samp{maint print symbols} will only print symbols for already expanded symbol
17679 You can use the command @code{info sources} to find out which files these are.
17680 If you use @samp{maint print psymbols} instead, the dump shows information
17681 about symbols that @value{GDBN} only knows partially---that is, symbols
17682 defined in files that @value{GDBN} has skimmed, but not yet read completely.
17683 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
17686 @xref{Files, ,Commands to Specify Files}, for a discussion of how
17687 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
17689 @kindex maint info symtabs
17690 @kindex maint info psymtabs
17691 @cindex listing @value{GDBN}'s internal symbol tables
17692 @cindex symbol tables, listing @value{GDBN}'s internal
17693 @cindex full symbol tables, listing @value{GDBN}'s internal
17694 @cindex partial symbol tables, listing @value{GDBN}'s internal
17695 @item maint info symtabs @r{[} @var{regexp} @r{]}
17696 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
17698 List the @code{struct symtab} or @code{struct partial_symtab}
17699 structures whose names match @var{regexp}. If @var{regexp} is not
17700 given, list them all. The output includes expressions which you can
17701 copy into a @value{GDBN} debugging this one to examine a particular
17702 structure in more detail. For example:
17705 (@value{GDBP}) maint info psymtabs dwarf2read
17706 @{ objfile /home/gnu/build/gdb/gdb
17707 ((struct objfile *) 0x82e69d0)
17708 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
17709 ((struct partial_symtab *) 0x8474b10)
17712 text addresses 0x814d3c8 -- 0x8158074
17713 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
17714 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
17715 dependencies (none)
17718 (@value{GDBP}) maint info symtabs
17722 We see that there is one partial symbol table whose filename contains
17723 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
17724 and we see that @value{GDBN} has not read in any symtabs yet at all.
17725 If we set a breakpoint on a function, that will cause @value{GDBN} to
17726 read the symtab for the compilation unit containing that function:
17729 (@value{GDBP}) break dwarf2_psymtab_to_symtab
17730 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
17732 (@value{GDBP}) maint info symtabs
17733 @{ objfile /home/gnu/build/gdb/gdb
17734 ((struct objfile *) 0x82e69d0)
17735 @{ symtab /home/gnu/src/gdb/dwarf2read.c
17736 ((struct symtab *) 0x86c1f38)
17739 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
17740 linetable ((struct linetable *) 0x8370fa0)
17741 debugformat DWARF 2
17747 @kindex maint info line-table
17748 @cindex listing @value{GDBN}'s internal line tables
17749 @cindex line tables, listing @value{GDBN}'s internal
17750 @item maint info line-table @r{[} @var{regexp} @r{]}
17752 List the @code{struct linetable} from all @code{struct symtab}
17753 instances whose name matches @var{regexp}. If @var{regexp} is not
17754 given, list the @code{struct linetable} from all @code{struct symtab}.
17756 @kindex maint set symbol-cache-size
17757 @cindex symbol cache size
17758 @item maint set symbol-cache-size @var{size}
17759 Set the size of the symbol cache to @var{size}.
17760 The default size is intended to be good enough for debugging
17761 most applications. This option exists to allow for experimenting
17762 with different sizes.
17764 @kindex maint show symbol-cache-size
17765 @item maint show symbol-cache-size
17766 Show the size of the symbol cache.
17768 @kindex maint print symbol-cache
17769 @cindex symbol cache, printing its contents
17770 @item maint print symbol-cache
17771 Print the contents of the symbol cache.
17772 This is useful when debugging symbol cache issues.
17774 @kindex maint print symbol-cache-statistics
17775 @cindex symbol cache, printing usage statistics
17776 @item maint print symbol-cache-statistics
17777 Print symbol cache usage statistics.
17778 This helps determine how well the cache is being utilized.
17780 @kindex maint flush-symbol-cache
17781 @cindex symbol cache, flushing
17782 @item maint flush-symbol-cache
17783 Flush the contents of the symbol cache, all entries are removed.
17784 This command is useful when debugging the symbol cache.
17785 It is also useful when collecting performance data.
17790 @chapter Altering Execution
17792 Once you think you have found an error in your program, you might want to
17793 find out for certain whether correcting the apparent error would lead to
17794 correct results in the rest of the run. You can find the answer by
17795 experiment, using the @value{GDBN} features for altering execution of the
17798 For example, you can store new values into variables or memory
17799 locations, give your program a signal, restart it at a different
17800 address, or even return prematurely from a function.
17803 * Assignment:: Assignment to variables
17804 * Jumping:: Continuing at a different address
17805 * Signaling:: Giving your program a signal
17806 * Returning:: Returning from a function
17807 * Calling:: Calling your program's functions
17808 * Patching:: Patching your program
17809 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
17813 @section Assignment to Variables
17816 @cindex setting variables
17817 To alter the value of a variable, evaluate an assignment expression.
17818 @xref{Expressions, ,Expressions}. For example,
17825 stores the value 4 into the variable @code{x}, and then prints the
17826 value of the assignment expression (which is 4).
17827 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
17828 information on operators in supported languages.
17830 @kindex set variable
17831 @cindex variables, setting
17832 If you are not interested in seeing the value of the assignment, use the
17833 @code{set} command instead of the @code{print} command. @code{set} is
17834 really the same as @code{print} except that the expression's value is
17835 not printed and is not put in the value history (@pxref{Value History,
17836 ,Value History}). The expression is evaluated only for its effects.
17838 If the beginning of the argument string of the @code{set} command
17839 appears identical to a @code{set} subcommand, use the @code{set
17840 variable} command instead of just @code{set}. This command is identical
17841 to @code{set} except for its lack of subcommands. For example, if your
17842 program has a variable @code{width}, you get an error if you try to set
17843 a new value with just @samp{set width=13}, because @value{GDBN} has the
17844 command @code{set width}:
17847 (@value{GDBP}) whatis width
17849 (@value{GDBP}) p width
17851 (@value{GDBP}) set width=47
17852 Invalid syntax in expression.
17856 The invalid expression, of course, is @samp{=47}. In
17857 order to actually set the program's variable @code{width}, use
17860 (@value{GDBP}) set var width=47
17863 Because the @code{set} command has many subcommands that can conflict
17864 with the names of program variables, it is a good idea to use the
17865 @code{set variable} command instead of just @code{set}. For example, if
17866 your program has a variable @code{g}, you run into problems if you try
17867 to set a new value with just @samp{set g=4}, because @value{GDBN} has
17868 the command @code{set gnutarget}, abbreviated @code{set g}:
17872 (@value{GDBP}) whatis g
17876 (@value{GDBP}) set g=4
17880 The program being debugged has been started already.
17881 Start it from the beginning? (y or n) y
17882 Starting program: /home/smith/cc_progs/a.out
17883 "/home/smith/cc_progs/a.out": can't open to read symbols:
17884 Invalid bfd target.
17885 (@value{GDBP}) show g
17886 The current BFD target is "=4".
17891 The program variable @code{g} did not change, and you silently set the
17892 @code{gnutarget} to an invalid value. In order to set the variable
17896 (@value{GDBP}) set var g=4
17899 @value{GDBN} allows more implicit conversions in assignments than C; you can
17900 freely store an integer value into a pointer variable or vice versa,
17901 and you can convert any structure to any other structure that is the
17902 same length or shorter.
17903 @comment FIXME: how do structs align/pad in these conversions?
17904 @comment /doc@cygnus.com 18dec1990
17906 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
17907 construct to generate a value of specified type at a specified address
17908 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
17909 to memory location @code{0x83040} as an integer (which implies a certain size
17910 and representation in memory), and
17913 set @{int@}0x83040 = 4
17917 stores the value 4 into that memory location.
17920 @section Continuing at a Different Address
17922 Ordinarily, when you continue your program, you do so at the place where
17923 it stopped, with the @code{continue} command. You can instead continue at
17924 an address of your own choosing, with the following commands:
17928 @kindex j @r{(@code{jump})}
17929 @item jump @var{location}
17930 @itemx j @var{location}
17931 Resume execution at @var{location}. Execution stops again immediately
17932 if there is a breakpoint there. @xref{Specify Location}, for a description
17933 of the different forms of @var{location}. It is common
17934 practice to use the @code{tbreak} command in conjunction with
17935 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
17937 The @code{jump} command does not change the current stack frame, or
17938 the stack pointer, or the contents of any memory location or any
17939 register other than the program counter. If @var{location} is in
17940 a different function from the one currently executing, the results may
17941 be bizarre if the two functions expect different patterns of arguments or
17942 of local variables. For this reason, the @code{jump} command requests
17943 confirmation if the specified line is not in the function currently
17944 executing. However, even bizarre results are predictable if you are
17945 well acquainted with the machine-language code of your program.
17948 On many systems, you can get much the same effect as the @code{jump}
17949 command by storing a new value into the register @code{$pc}. The
17950 difference is that this does not start your program running; it only
17951 changes the address of where it @emph{will} run when you continue. For
17959 makes the next @code{continue} command or stepping command execute at
17960 address @code{0x485}, rather than at the address where your program stopped.
17961 @xref{Continuing and Stepping, ,Continuing and Stepping}.
17963 The most common occasion to use the @code{jump} command is to back
17964 up---perhaps with more breakpoints set---over a portion of a program
17965 that has already executed, in order to examine its execution in more
17970 @section Giving your Program a Signal
17971 @cindex deliver a signal to a program
17975 @item signal @var{signal}
17976 Resume execution where your program is stopped, but immediately give it the
17977 signal @var{signal}. The @var{signal} can be the name or the number of a
17978 signal. For example, on many systems @code{signal 2} and @code{signal
17979 SIGINT} are both ways of sending an interrupt signal.
17981 Alternatively, if @var{signal} is zero, continue execution without
17982 giving a signal. This is useful when your program stopped on account of
17983 a signal and would ordinarily see the signal when resumed with the
17984 @code{continue} command; @samp{signal 0} causes it to resume without a
17987 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
17988 delivered to the currently selected thread, not the thread that last
17989 reported a stop. This includes the situation where a thread was
17990 stopped due to a signal. So if you want to continue execution
17991 suppressing the signal that stopped a thread, you should select that
17992 same thread before issuing the @samp{signal 0} command. If you issue
17993 the @samp{signal 0} command with another thread as the selected one,
17994 @value{GDBN} detects that and asks for confirmation.
17996 Invoking the @code{signal} command is not the same as invoking the
17997 @code{kill} utility from the shell. Sending a signal with @code{kill}
17998 causes @value{GDBN} to decide what to do with the signal depending on
17999 the signal handling tables (@pxref{Signals}). The @code{signal} command
18000 passes the signal directly to your program.
18002 @code{signal} does not repeat when you press @key{RET} a second time
18003 after executing the command.
18005 @kindex queue-signal
18006 @item queue-signal @var{signal}
18007 Queue @var{signal} to be delivered immediately to the current thread
18008 when execution of the thread resumes. The @var{signal} can be the name or
18009 the number of a signal. For example, on many systems @code{signal 2} and
18010 @code{signal SIGINT} are both ways of sending an interrupt signal.
18011 The handling of the signal must be set to pass the signal to the program,
18012 otherwise @value{GDBN} will report an error.
18013 You can control the handling of signals from @value{GDBN} with the
18014 @code{handle} command (@pxref{Signals}).
18016 Alternatively, if @var{signal} is zero, any currently queued signal
18017 for the current thread is discarded and when execution resumes no signal
18018 will be delivered. This is useful when your program stopped on account
18019 of a signal and would ordinarily see the signal when resumed with the
18020 @code{continue} command.
18022 This command differs from the @code{signal} command in that the signal
18023 is just queued, execution is not resumed. And @code{queue-signal} cannot
18024 be used to pass a signal whose handling state has been set to @code{nopass}
18029 @xref{stepping into signal handlers}, for information on how stepping
18030 commands behave when the thread has a signal queued.
18033 @section Returning from a Function
18036 @cindex returning from a function
18039 @itemx return @var{expression}
18040 You can cancel execution of a function call with the @code{return}
18041 command. If you give an
18042 @var{expression} argument, its value is used as the function's return
18046 When you use @code{return}, @value{GDBN} discards the selected stack frame
18047 (and all frames within it). You can think of this as making the
18048 discarded frame return prematurely. If you wish to specify a value to
18049 be returned, give that value as the argument to @code{return}.
18051 This pops the selected stack frame (@pxref{Selection, ,Selecting a
18052 Frame}), and any other frames inside of it, leaving its caller as the
18053 innermost remaining frame. That frame becomes selected. The
18054 specified value is stored in the registers used for returning values
18057 The @code{return} command does not resume execution; it leaves the
18058 program stopped in the state that would exist if the function had just
18059 returned. In contrast, the @code{finish} command (@pxref{Continuing
18060 and Stepping, ,Continuing and Stepping}) resumes execution until the
18061 selected stack frame returns naturally.
18063 @value{GDBN} needs to know how the @var{expression} argument should be set for
18064 the inferior. The concrete registers assignment depends on the OS ABI and the
18065 type being returned by the selected stack frame. For example it is common for
18066 OS ABI to return floating point values in FPU registers while integer values in
18067 CPU registers. Still some ABIs return even floating point values in CPU
18068 registers. Larger integer widths (such as @code{long long int}) also have
18069 specific placement rules. @value{GDBN} already knows the OS ABI from its
18070 current target so it needs to find out also the type being returned to make the
18071 assignment into the right register(s).
18073 Normally, the selected stack frame has debug info. @value{GDBN} will always
18074 use the debug info instead of the implicit type of @var{expression} when the
18075 debug info is available. For example, if you type @kbd{return -1}, and the
18076 function in the current stack frame is declared to return a @code{long long
18077 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
18078 into a @code{long long int}:
18081 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
18083 (@value{GDBP}) return -1
18084 Make func return now? (y or n) y
18085 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
18086 43 printf ("result=%lld\n", func ());
18090 However, if the selected stack frame does not have a debug info, e.g., if the
18091 function was compiled without debug info, @value{GDBN} has to find out the type
18092 to return from user. Specifying a different type by mistake may set the value
18093 in different inferior registers than the caller code expects. For example,
18094 typing @kbd{return -1} with its implicit type @code{int} would set only a part
18095 of a @code{long long int} result for a debug info less function (on 32-bit
18096 architectures). Therefore the user is required to specify the return type by
18097 an appropriate cast explicitly:
18100 Breakpoint 2, 0x0040050b in func ()
18101 (@value{GDBP}) return -1
18102 Return value type not available for selected stack frame.
18103 Please use an explicit cast of the value to return.
18104 (@value{GDBP}) return (long long int) -1
18105 Make selected stack frame return now? (y or n) y
18106 #0 0x00400526 in main ()
18111 @section Calling Program Functions
18114 @cindex calling functions
18115 @cindex inferior functions, calling
18116 @item print @var{expr}
18117 Evaluate the expression @var{expr} and display the resulting value.
18118 The expression may include calls to functions in the program being
18122 @item call @var{expr}
18123 Evaluate the expression @var{expr} without displaying @code{void}
18126 You can use this variant of the @code{print} command if you want to
18127 execute a function from your program that does not return anything
18128 (a.k.a.@: @dfn{a void function}), but without cluttering the output
18129 with @code{void} returned values that @value{GDBN} will otherwise
18130 print. If the result is not void, it is printed and saved in the
18134 It is possible for the function you call via the @code{print} or
18135 @code{call} command to generate a signal (e.g., if there's a bug in
18136 the function, or if you passed it incorrect arguments). What happens
18137 in that case is controlled by the @code{set unwindonsignal} command.
18139 Similarly, with a C@t{++} program it is possible for the function you
18140 call via the @code{print} or @code{call} command to generate an
18141 exception that is not handled due to the constraints of the dummy
18142 frame. In this case, any exception that is raised in the frame, but has
18143 an out-of-frame exception handler will not be found. GDB builds a
18144 dummy-frame for the inferior function call, and the unwinder cannot
18145 seek for exception handlers outside of this dummy-frame. What happens
18146 in that case is controlled by the
18147 @code{set unwind-on-terminating-exception} command.
18150 @item set unwindonsignal
18151 @kindex set unwindonsignal
18152 @cindex unwind stack in called functions
18153 @cindex call dummy stack unwinding
18154 Set unwinding of the stack if a signal is received while in a function
18155 that @value{GDBN} called in the program being debugged. If set to on,
18156 @value{GDBN} unwinds the stack it created for the call and restores
18157 the context to what it was before the call. If set to off (the
18158 default), @value{GDBN} stops in the frame where the signal was
18161 @item show unwindonsignal
18162 @kindex show unwindonsignal
18163 Show the current setting of stack unwinding in the functions called by
18166 @item set unwind-on-terminating-exception
18167 @kindex set unwind-on-terminating-exception
18168 @cindex unwind stack in called functions with unhandled exceptions
18169 @cindex call dummy stack unwinding on unhandled exception.
18170 Set unwinding of the stack if a C@t{++} exception is raised, but left
18171 unhandled while in a function that @value{GDBN} called in the program being
18172 debugged. If set to on (the default), @value{GDBN} unwinds the stack
18173 it created for the call and restores the context to what it was before
18174 the call. If set to off, @value{GDBN} the exception is delivered to
18175 the default C@t{++} exception handler and the inferior terminated.
18177 @item show unwind-on-terminating-exception
18178 @kindex show unwind-on-terminating-exception
18179 Show the current setting of stack unwinding in the functions called by
18184 @subsection Calling functions with no debug info
18186 @cindex no debug info functions
18187 Sometimes, a function you wish to call is missing debug information.
18188 In such case, @value{GDBN} does not know the type of the function,
18189 including the types of the function's parameters. To avoid calling
18190 the inferior function incorrectly, which could result in the called
18191 function functioning erroneously and even crash, @value{GDBN} refuses
18192 to call the function unless you tell it the type of the function.
18194 For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
18195 to do that. The simplest is to cast the call to the function's
18196 declared return type. For example:
18199 (@value{GDBP}) p getenv ("PATH")
18200 'getenv' has unknown return type; cast the call to its declared return type
18201 (@value{GDBP}) p (char *) getenv ("PATH")
18202 $1 = 0x7fffffffe7ba "/usr/local/bin:/"...
18205 Casting the return type of a no-debug function is equivalent to
18206 casting the function to a pointer to a prototyped function that has a
18207 prototype that matches the types of the passed-in arguments, and
18208 calling that. I.e., the call above is equivalent to:
18211 (@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
18215 and given this prototyped C or C++ function with float parameters:
18218 float multiply (float v1, float v2) @{ return v1 * v2; @}
18222 these calls are equivalent:
18225 (@value{GDBP}) p (float) multiply (2.0f, 3.0f)
18226 (@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
18229 If the function you wish to call is declared as unprototyped (i.e.@:
18230 old K&R style), you must use the cast-to-function-pointer syntax, so
18231 that @value{GDBN} knows that it needs to apply default argument
18232 promotions (promote float arguments to double). @xref{ABI, float
18233 promotion}. For example, given this unprototyped C function with
18234 float parameters, and no debug info:
18238 multiply_noproto (v1, v2)
18246 you call it like this:
18249 (@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
18253 @section Patching Programs
18255 @cindex patching binaries
18256 @cindex writing into executables
18257 @cindex writing into corefiles
18259 By default, @value{GDBN} opens the file containing your program's
18260 executable code (or the corefile) read-only. This prevents accidental
18261 alterations to machine code; but it also prevents you from intentionally
18262 patching your program's binary.
18264 If you'd like to be able to patch the binary, you can specify that
18265 explicitly with the @code{set write} command. For example, you might
18266 want to turn on internal debugging flags, or even to make emergency
18272 @itemx set write off
18273 If you specify @samp{set write on}, @value{GDBN} opens executable and
18274 core files for both reading and writing; if you specify @kbd{set write
18275 off} (the default), @value{GDBN} opens them read-only.
18277 If you have already loaded a file, you must load it again (using the
18278 @code{exec-file} or @code{core-file} command) after changing @code{set
18279 write}, for your new setting to take effect.
18283 Display whether executable files and core files are opened for writing
18284 as well as reading.
18287 @node Compiling and Injecting Code
18288 @section Compiling and injecting code in @value{GDBN}
18289 @cindex injecting code
18290 @cindex writing into executables
18291 @cindex compiling code
18293 @value{GDBN} supports on-demand compilation and code injection into
18294 programs running under @value{GDBN}. GCC 5.0 or higher built with
18295 @file{libcc1.so} must be installed for this functionality to be enabled.
18296 This functionality is implemented with the following commands.
18299 @kindex compile code
18300 @item compile code @var{source-code}
18301 @itemx compile code -raw @var{--} @var{source-code}
18302 Compile @var{source-code} with the compiler language found as the current
18303 language in @value{GDBN} (@pxref{Languages}). If compilation and
18304 injection is not supported with the current language specified in
18305 @value{GDBN}, or the compiler does not support this feature, an error
18306 message will be printed. If @var{source-code} compiles and links
18307 successfully, @value{GDBN} will load the object-code emitted,
18308 and execute it within the context of the currently selected inferior.
18309 It is important to note that the compiled code is executed immediately.
18310 After execution, the compiled code is removed from @value{GDBN} and any
18311 new types or variables you have defined will be deleted.
18313 The command allows you to specify @var{source-code} in two ways.
18314 The simplest method is to provide a single line of code to the command.
18318 compile code printf ("hello world\n");
18321 If you specify options on the command line as well as source code, they
18322 may conflict. The @samp{--} delimiter can be used to separate options
18323 from actual source code. E.g.:
18326 compile code -r -- printf ("hello world\n");
18329 Alternatively you can enter source code as multiple lines of text. To
18330 enter this mode, invoke the @samp{compile code} command without any text
18331 following the command. This will start the multiple-line editor and
18332 allow you to type as many lines of source code as required. When you
18333 have completed typing, enter @samp{end} on its own line to exit the
18338 >printf ("hello\n");
18339 >printf ("world\n");
18343 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
18344 provided @var{source-code} in a callable scope. In this case, you must
18345 specify the entry point of the code by defining a function named
18346 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
18347 inferior. Using @samp{-raw} option may be needed for example when
18348 @var{source-code} requires @samp{#include} lines which may conflict with
18349 inferior symbols otherwise.
18351 @kindex compile file
18352 @item compile file @var{filename}
18353 @itemx compile file -raw @var{filename}
18354 Like @code{compile code}, but take the source code from @var{filename}.
18357 compile file /home/user/example.c
18362 @item compile print @var{expr}
18363 @itemx compile print /@var{f} @var{expr}
18364 Compile and execute @var{expr} with the compiler language found as the
18365 current language in @value{GDBN} (@pxref{Languages}). By default the
18366 value of @var{expr} is printed in a format appropriate to its data type;
18367 you can choose a different format by specifying @samp{/@var{f}}, where
18368 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
18371 @item compile print
18372 @itemx compile print /@var{f}
18373 @cindex reprint the last value
18374 Alternatively you can enter the expression (source code producing it) as
18375 multiple lines of text. To enter this mode, invoke the @samp{compile print}
18376 command without any text following the command. This will start the
18377 multiple-line editor.
18381 The process of compiling and injecting the code can be inspected using:
18384 @anchor{set debug compile}
18385 @item set debug compile
18386 @cindex compile command debugging info
18387 Turns on or off display of @value{GDBN} process of compiling and
18388 injecting the code. The default is off.
18390 @item show debug compile
18391 Displays the current state of displaying @value{GDBN} process of
18392 compiling and injecting the code.
18395 @subsection Compilation options for the @code{compile} command
18397 @value{GDBN} needs to specify the right compilation options for the code
18398 to be injected, in part to make its ABI compatible with the inferior
18399 and in part to make the injected code compatible with @value{GDBN}'s
18403 The options used, in increasing precedence:
18406 @item target architecture and OS options (@code{gdbarch})
18407 These options depend on target processor type and target operating
18408 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
18409 (@code{-m64}) compilation option.
18411 @item compilation options recorded in the target
18412 @value{NGCC} (since version 4.7) stores the options used for compilation
18413 into @code{DW_AT_producer} part of DWARF debugging information according
18414 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
18415 explicitly specify @code{-g} during inferior compilation otherwise
18416 @value{NGCC} produces no DWARF. This feature is only relevant for
18417 platforms where @code{-g} produces DWARF by default, otherwise one may
18418 try to enforce DWARF by using @code{-gdwarf-4}.
18420 @item compilation options set by @code{set compile-args}
18424 You can override compilation options using the following command:
18427 @item set compile-args
18428 @cindex compile command options override
18429 Set compilation options used for compiling and injecting code with the
18430 @code{compile} commands. These options override any conflicting ones
18431 from the target architecture and/or options stored during inferior
18434 @item show compile-args
18435 Displays the current state of compilation options override.
18436 This does not show all the options actually used during compilation,
18437 use @ref{set debug compile} for that.
18440 @subsection Caveats when using the @code{compile} command
18442 There are a few caveats to keep in mind when using the @code{compile}
18443 command. As the caveats are different per language, the table below
18444 highlights specific issues on a per language basis.
18447 @item C code examples and caveats
18448 When the language in @value{GDBN} is set to @samp{C}, the compiler will
18449 attempt to compile the source code with a @samp{C} compiler. The source
18450 code provided to the @code{compile} command will have much the same
18451 access to variables and types as it normally would if it were part of
18452 the program currently being debugged in @value{GDBN}.
18454 Below is a sample program that forms the basis of the examples that
18455 follow. This program has been compiled and loaded into @value{GDBN},
18456 much like any other normal debugging session.
18459 void function1 (void)
18462 printf ("function 1\n");
18465 void function2 (void)
18480 For the purposes of the examples in this section, the program above has
18481 been compiled, loaded into @value{GDBN}, stopped at the function
18482 @code{main}, and @value{GDBN} is awaiting input from the user.
18484 To access variables and types for any program in @value{GDBN}, the
18485 program must be compiled and packaged with debug information. The
18486 @code{compile} command is not an exception to this rule. Without debug
18487 information, you can still use the @code{compile} command, but you will
18488 be very limited in what variables and types you can access.
18490 So with that in mind, the example above has been compiled with debug
18491 information enabled. The @code{compile} command will have access to
18492 all variables and types (except those that may have been optimized
18493 out). Currently, as @value{GDBN} has stopped the program in the
18494 @code{main} function, the @code{compile} command would have access to
18495 the variable @code{k}. You could invoke the @code{compile} command
18496 and type some source code to set the value of @code{k}. You can also
18497 read it, or do anything with that variable you would normally do in
18498 @code{C}. Be aware that changes to inferior variables in the
18499 @code{compile} command are persistent. In the following example:
18502 compile code k = 3;
18506 the variable @code{k} is now 3. It will retain that value until
18507 something else in the example program changes it, or another
18508 @code{compile} command changes it.
18510 Normal scope and access rules apply to source code compiled and
18511 injected by the @code{compile} command. In the example, the variables
18512 @code{j} and @code{k} are not accessible yet, because the program is
18513 currently stopped in the @code{main} function, where these variables
18514 are not in scope. Therefore, the following command
18517 compile code j = 3;
18521 will result in a compilation error message.
18523 Once the program is continued, execution will bring these variables in
18524 scope, and they will become accessible; then the code you specify via
18525 the @code{compile} command will be able to access them.
18527 You can create variables and types with the @code{compile} command as
18528 part of your source code. Variables and types that are created as part
18529 of the @code{compile} command are not visible to the rest of the program for
18530 the duration of its run. This example is valid:
18533 compile code int ff = 5; printf ("ff is %d\n", ff);
18536 However, if you were to type the following into @value{GDBN} after that
18537 command has completed:
18540 compile code printf ("ff is %d\n'', ff);
18544 a compiler error would be raised as the variable @code{ff} no longer
18545 exists. Object code generated and injected by the @code{compile}
18546 command is removed when its execution ends. Caution is advised
18547 when assigning to program variables values of variables created by the
18548 code submitted to the @code{compile} command. This example is valid:
18551 compile code int ff = 5; k = ff;
18554 The value of the variable @code{ff} is assigned to @code{k}. The variable
18555 @code{k} does not require the existence of @code{ff} to maintain the value
18556 it has been assigned. However, pointers require particular care in
18557 assignment. If the source code compiled with the @code{compile} command
18558 changed the address of a pointer in the example program, perhaps to a
18559 variable created in the @code{compile} command, that pointer would point
18560 to an invalid location when the command exits. The following example
18561 would likely cause issues with your debugged program:
18564 compile code int ff = 5; p = &ff;
18567 In this example, @code{p} would point to @code{ff} when the
18568 @code{compile} command is executing the source code provided to it.
18569 However, as variables in the (example) program persist with their
18570 assigned values, the variable @code{p} would point to an invalid
18571 location when the command exists. A general rule should be followed
18572 in that you should either assign @code{NULL} to any assigned pointers,
18573 or restore a valid location to the pointer before the command exits.
18575 Similar caution must be exercised with any structs, unions, and typedefs
18576 defined in @code{compile} command. Types defined in the @code{compile}
18577 command will no longer be available in the next @code{compile} command.
18578 Therefore, if you cast a variable to a type defined in the
18579 @code{compile} command, care must be taken to ensure that any future
18580 need to resolve the type can be achieved.
18583 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
18584 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
18585 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
18586 Compilation failed.
18587 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
18591 Variables that have been optimized away by the compiler are not
18592 accessible to the code submitted to the @code{compile} command.
18593 Access to those variables will generate a compiler error which @value{GDBN}
18594 will print to the console.
18597 @subsection Compiler search for the @code{compile} command
18599 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
18600 which may not be obvious for remote targets of different architecture
18601 than where @value{GDBN} is running. Environment variable @code{PATH} on
18602 @value{GDBN} host is searched for @value{NGCC} binary matching the
18603 target architecture and operating system. This search can be overriden
18604 by @code{set compile-gcc} @value{GDBN} command below. @code{PATH} is
18605 taken from shell that executed @value{GDBN}, it is not the value set by
18606 @value{GDBN} command @code{set environment}). @xref{Environment}.
18609 Specifically @code{PATH} is searched for binaries matching regular expression
18610 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
18611 debugged. @var{arch} is processor name --- multiarch is supported, so for
18612 example both @code{i386} and @code{x86_64} targets look for pattern
18613 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
18614 for pattern @code{s390x?}. @var{os} is currently supported only for
18615 pattern @code{linux(-gnu)?}.
18617 On Posix hosts the compiler driver @value{GDBN} needs to find also
18618 shared library @file{libcc1.so} from the compiler. It is searched in
18619 default shared library search path (overridable with usual environment
18620 variable @code{LD_LIBRARY_PATH}), unrelated to @code{PATH} or @code{set
18621 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
18622 according to the installation of the found compiler --- as possibly
18623 specified by the @code{set compile-gcc} command.
18626 @item set compile-gcc
18627 @cindex compile command driver filename override
18628 Set compilation command used for compiling and injecting code with the
18629 @code{compile} commands. If this option is not set (it is set to
18630 an empty string), the search described above will occur --- that is the
18633 @item show compile-gcc
18634 Displays the current compile command @value{NGCC} driver filename.
18635 If set, it is the main command @command{gcc}, found usually for example
18636 under name @file{x86_64-linux-gnu-gcc}.
18640 @chapter @value{GDBN} Files
18642 @value{GDBN} needs to know the file name of the program to be debugged,
18643 both in order to read its symbol table and in order to start your
18644 program. To debug a core dump of a previous run, you must also tell
18645 @value{GDBN} the name of the core dump file.
18648 * Files:: Commands to specify files
18649 * File Caching:: Information about @value{GDBN}'s file caching
18650 * Separate Debug Files:: Debugging information in separate files
18651 * MiniDebugInfo:: Debugging information in a special section
18652 * Index Files:: Index files speed up GDB
18653 * Symbol Errors:: Errors reading symbol files
18654 * Data Files:: GDB data files
18658 @section Commands to Specify Files
18660 @cindex symbol table
18661 @cindex core dump file
18663 You may want to specify executable and core dump file names. The usual
18664 way to do this is at start-up time, using the arguments to
18665 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
18666 Out of @value{GDBN}}).
18668 Occasionally it is necessary to change to a different file during a
18669 @value{GDBN} session. Or you may run @value{GDBN} and forget to
18670 specify a file you want to use. Or you are debugging a remote target
18671 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
18672 Program}). In these situations the @value{GDBN} commands to specify
18673 new files are useful.
18676 @cindex executable file
18678 @item file @var{filename}
18679 Use @var{filename} as the program to be debugged. It is read for its
18680 symbols and for the contents of pure memory. It is also the program
18681 executed when you use the @code{run} command. If you do not specify a
18682 directory and the file is not found in the @value{GDBN} working directory,
18683 @value{GDBN} uses the environment variable @code{PATH} as a list of
18684 directories to search, just as the shell does when looking for a program
18685 to run. You can change the value of this variable, for both @value{GDBN}
18686 and your program, using the @code{path} command.
18688 @cindex unlinked object files
18689 @cindex patching object files
18690 You can load unlinked object @file{.o} files into @value{GDBN} using
18691 the @code{file} command. You will not be able to ``run'' an object
18692 file, but you can disassemble functions and inspect variables. Also,
18693 if the underlying BFD functionality supports it, you could use
18694 @kbd{gdb -write} to patch object files using this technique. Note
18695 that @value{GDBN} can neither interpret nor modify relocations in this
18696 case, so branches and some initialized variables will appear to go to
18697 the wrong place. But this feature is still handy from time to time.
18700 @code{file} with no argument makes @value{GDBN} discard any information it
18701 has on both executable file and the symbol table.
18704 @item exec-file @r{[} @var{filename} @r{]}
18705 Specify that the program to be run (but not the symbol table) is found
18706 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
18707 if necessary to locate your program. Omitting @var{filename} means to
18708 discard information on the executable file.
18710 @kindex symbol-file
18711 @item symbol-file @r{[} @var{filename} @r{]}
18712 Read symbol table information from file @var{filename}. @code{PATH} is
18713 searched when necessary. Use the @code{file} command to get both symbol
18714 table and program to run from the same file.
18716 @code{symbol-file} with no argument clears out @value{GDBN} information on your
18717 program's symbol table.
18719 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
18720 some breakpoints and auto-display expressions. This is because they may
18721 contain pointers to the internal data recording symbols and data types,
18722 which are part of the old symbol table data being discarded inside
18725 @code{symbol-file} does not repeat if you press @key{RET} again after
18728 When @value{GDBN} is configured for a particular environment, it
18729 understands debugging information in whatever format is the standard
18730 generated for that environment; you may use either a @sc{gnu} compiler, or
18731 other compilers that adhere to the local conventions.
18732 Best results are usually obtained from @sc{gnu} compilers; for example,
18733 using @code{@value{NGCC}} you can generate debugging information for
18736 For most kinds of object files, with the exception of old SVR3 systems
18737 using COFF, the @code{symbol-file} command does not normally read the
18738 symbol table in full right away. Instead, it scans the symbol table
18739 quickly to find which source files and which symbols are present. The
18740 details are read later, one source file at a time, as they are needed.
18742 The purpose of this two-stage reading strategy is to make @value{GDBN}
18743 start up faster. For the most part, it is invisible except for
18744 occasional pauses while the symbol table details for a particular source
18745 file are being read. (The @code{set verbose} command can turn these
18746 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
18747 Warnings and Messages}.)
18749 We have not implemented the two-stage strategy for COFF yet. When the
18750 symbol table is stored in COFF format, @code{symbol-file} reads the
18751 symbol table data in full right away. Note that ``stabs-in-COFF''
18752 still does the two-stage strategy, since the debug info is actually
18756 @cindex reading symbols immediately
18757 @cindex symbols, reading immediately
18758 @item symbol-file @r{[} -readnow @r{]} @var{filename}
18759 @itemx file @r{[} -readnow @r{]} @var{filename}
18760 You can override the @value{GDBN} two-stage strategy for reading symbol
18761 tables by using the @samp{-readnow} option with any of the commands that
18762 load symbol table information, if you want to be sure @value{GDBN} has the
18763 entire symbol table available.
18765 @cindex @code{-readnever}, option for symbol-file command
18766 @cindex never read symbols
18767 @cindex symbols, never read
18768 @item symbol-file @r{[} -readnever @r{]} @var{filename}
18769 @itemx file @r{[} -readnever @r{]} @var{filename}
18770 You can instruct @value{GDBN} to never read the symbolic information
18771 contained in @var{filename} by using the @samp{-readnever} option.
18772 @xref{--readnever}.
18774 @c FIXME: for now no mention of directories, since this seems to be in
18775 @c flux. 13mar1992 status is that in theory GDB would look either in
18776 @c current dir or in same dir as myprog; but issues like competing
18777 @c GDB's, or clutter in system dirs, mean that in practice right now
18778 @c only current dir is used. FFish says maybe a special GDB hierarchy
18779 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
18783 @item core-file @r{[}@var{filename}@r{]}
18785 Specify the whereabouts of a core dump file to be used as the ``contents
18786 of memory''. Traditionally, core files contain only some parts of the
18787 address space of the process that generated them; @value{GDBN} can access the
18788 executable file itself for other parts.
18790 @code{core-file} with no argument specifies that no core file is
18793 Note that the core file is ignored when your program is actually running
18794 under @value{GDBN}. So, if you have been running your program and you
18795 wish to debug a core file instead, you must kill the subprocess in which
18796 the program is running. To do this, use the @code{kill} command
18797 (@pxref{Kill Process, ,Killing the Child Process}).
18799 @kindex add-symbol-file
18800 @cindex dynamic linking
18801 @item add-symbol-file @var{filename} @var{address}
18802 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{|} -readnever @r{]}
18803 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
18804 The @code{add-symbol-file} command reads additional symbol table
18805 information from the file @var{filename}. You would use this command
18806 when @var{filename} has been dynamically loaded (by some other means)
18807 into the program that is running. The @var{address} should give the memory
18808 address at which the file has been loaded; @value{GDBN} cannot figure
18809 this out for itself. You can additionally specify an arbitrary number
18810 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
18811 section name and base address for that section. You can specify any
18812 @var{address} as an expression.
18814 The symbol table of the file @var{filename} is added to the symbol table
18815 originally read with the @code{symbol-file} command. You can use the
18816 @code{add-symbol-file} command any number of times; the new symbol data
18817 thus read is kept in addition to the old.
18819 Changes can be reverted using the command @code{remove-symbol-file}.
18821 @cindex relocatable object files, reading symbols from
18822 @cindex object files, relocatable, reading symbols from
18823 @cindex reading symbols from relocatable object files
18824 @cindex symbols, reading from relocatable object files
18825 @cindex @file{.o} files, reading symbols from
18826 Although @var{filename} is typically a shared library file, an
18827 executable file, or some other object file which has been fully
18828 relocated for loading into a process, you can also load symbolic
18829 information from relocatable @file{.o} files, as long as:
18833 the file's symbolic information refers only to linker symbols defined in
18834 that file, not to symbols defined by other object files,
18836 every section the file's symbolic information refers to has actually
18837 been loaded into the inferior, as it appears in the file, and
18839 you can determine the address at which every section was loaded, and
18840 provide these to the @code{add-symbol-file} command.
18844 Some embedded operating systems, like Sun Chorus and VxWorks, can load
18845 relocatable files into an already running program; such systems
18846 typically make the requirements above easy to meet. However, it's
18847 important to recognize that many native systems use complex link
18848 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
18849 assembly, for example) that make the requirements difficult to meet. In
18850 general, one cannot assume that using @code{add-symbol-file} to read a
18851 relocatable object file's symbolic information will have the same effect
18852 as linking the relocatable object file into the program in the normal
18855 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
18857 @kindex remove-symbol-file
18858 @item remove-symbol-file @var{filename}
18859 @item remove-symbol-file -a @var{address}
18860 Remove a symbol file added via the @code{add-symbol-file} command. The
18861 file to remove can be identified by its @var{filename} or by an @var{address}
18862 that lies within the boundaries of this symbol file in memory. Example:
18865 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
18866 add symbol table from file "/home/user/gdb/mylib.so" at
18867 .text_addr = 0x7ffff7ff9480
18869 Reading symbols from /home/user/gdb/mylib.so...done.
18870 (gdb) remove-symbol-file -a 0x7ffff7ff9480
18871 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
18876 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
18878 @kindex add-symbol-file-from-memory
18879 @cindex @code{syscall DSO}
18880 @cindex load symbols from memory
18881 @item add-symbol-file-from-memory @var{address}
18882 Load symbols from the given @var{address} in a dynamically loaded
18883 object file whose image is mapped directly into the inferior's memory.
18884 For example, the Linux kernel maps a @code{syscall DSO} into each
18885 process's address space; this DSO provides kernel-specific code for
18886 some system calls. The argument can be any expression whose
18887 evaluation yields the address of the file's shared object file header.
18888 For this command to work, you must have used @code{symbol-file} or
18889 @code{exec-file} commands in advance.
18892 @item section @var{section} @var{addr}
18893 The @code{section} command changes the base address of the named
18894 @var{section} of the exec file to @var{addr}. This can be used if the
18895 exec file does not contain section addresses, (such as in the
18896 @code{a.out} format), or when the addresses specified in the file
18897 itself are wrong. Each section must be changed separately. The
18898 @code{info files} command, described below, lists all the sections and
18902 @kindex info target
18905 @code{info files} and @code{info target} are synonymous; both print the
18906 current target (@pxref{Targets, ,Specifying a Debugging Target}),
18907 including the names of the executable and core dump files currently in
18908 use by @value{GDBN}, and the files from which symbols were loaded. The
18909 command @code{help target} lists all possible targets rather than
18912 @kindex maint info sections
18913 @item maint info sections
18914 Another command that can give you extra information about program sections
18915 is @code{maint info sections}. In addition to the section information
18916 displayed by @code{info files}, this command displays the flags and file
18917 offset of each section in the executable and core dump files. In addition,
18918 @code{maint info sections} provides the following command options (which
18919 may be arbitrarily combined):
18923 Display sections for all loaded object files, including shared libraries.
18924 @item @var{sections}
18925 Display info only for named @var{sections}.
18926 @item @var{section-flags}
18927 Display info only for sections for which @var{section-flags} are true.
18928 The section flags that @value{GDBN} currently knows about are:
18931 Section will have space allocated in the process when loaded.
18932 Set for all sections except those containing debug information.
18934 Section will be loaded from the file into the child process memory.
18935 Set for pre-initialized code and data, clear for @code{.bss} sections.
18937 Section needs to be relocated before loading.
18939 Section cannot be modified by the child process.
18941 Section contains executable code only.
18943 Section contains data only (no executable code).
18945 Section will reside in ROM.
18947 Section contains data for constructor/destructor lists.
18949 Section is not empty.
18951 An instruction to the linker to not output the section.
18952 @item COFF_SHARED_LIBRARY
18953 A notification to the linker that the section contains
18954 COFF shared library information.
18956 Section contains common symbols.
18959 @kindex set trust-readonly-sections
18960 @cindex read-only sections
18961 @item set trust-readonly-sections on
18962 Tell @value{GDBN} that readonly sections in your object file
18963 really are read-only (i.e.@: that their contents will not change).
18964 In that case, @value{GDBN} can fetch values from these sections
18965 out of the object file, rather than from the target program.
18966 For some targets (notably embedded ones), this can be a significant
18967 enhancement to debugging performance.
18969 The default is off.
18971 @item set trust-readonly-sections off
18972 Tell @value{GDBN} not to trust readonly sections. This means that
18973 the contents of the section might change while the program is running,
18974 and must therefore be fetched from the target when needed.
18976 @item show trust-readonly-sections
18977 Show the current setting of trusting readonly sections.
18980 All file-specifying commands allow both absolute and relative file names
18981 as arguments. @value{GDBN} always converts the file name to an absolute file
18982 name and remembers it that way.
18984 @cindex shared libraries
18985 @anchor{Shared Libraries}
18986 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
18987 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
18988 DSBT (TIC6X) shared libraries.
18990 On MS-Windows @value{GDBN} must be linked with the Expat library to support
18991 shared libraries. @xref{Expat}.
18993 @value{GDBN} automatically loads symbol definitions from shared libraries
18994 when you use the @code{run} command, or when you examine a core file.
18995 (Before you issue the @code{run} command, @value{GDBN} does not understand
18996 references to a function in a shared library, however---unless you are
18997 debugging a core file).
18999 @c FIXME: some @value{GDBN} release may permit some refs to undef
19000 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
19001 @c FIXME...lib; check this from time to time when updating manual
19003 There are times, however, when you may wish to not automatically load
19004 symbol definitions from shared libraries, such as when they are
19005 particularly large or there are many of them.
19007 To control the automatic loading of shared library symbols, use the
19011 @kindex set auto-solib-add
19012 @item set auto-solib-add @var{mode}
19013 If @var{mode} is @code{on}, symbols from all shared object libraries
19014 will be loaded automatically when the inferior begins execution, you
19015 attach to an independently started inferior, or when the dynamic linker
19016 informs @value{GDBN} that a new library has been loaded. If @var{mode}
19017 is @code{off}, symbols must be loaded manually, using the
19018 @code{sharedlibrary} command. The default value is @code{on}.
19020 @cindex memory used for symbol tables
19021 If your program uses lots of shared libraries with debug info that
19022 takes large amounts of memory, you can decrease the @value{GDBN}
19023 memory footprint by preventing it from automatically loading the
19024 symbols from shared libraries. To that end, type @kbd{set
19025 auto-solib-add off} before running the inferior, then load each
19026 library whose debug symbols you do need with @kbd{sharedlibrary
19027 @var{regexp}}, where @var{regexp} is a regular expression that matches
19028 the libraries whose symbols you want to be loaded.
19030 @kindex show auto-solib-add
19031 @item show auto-solib-add
19032 Display the current autoloading mode.
19035 @cindex load shared library
19036 To explicitly load shared library symbols, use the @code{sharedlibrary}
19040 @kindex info sharedlibrary
19042 @item info share @var{regex}
19043 @itemx info sharedlibrary @var{regex}
19044 Print the names of the shared libraries which are currently loaded
19045 that match @var{regex}. If @var{regex} is omitted then print
19046 all shared libraries that are loaded.
19049 @item info dll @var{regex}
19050 This is an alias of @code{info sharedlibrary}.
19052 @kindex sharedlibrary
19054 @item sharedlibrary @var{regex}
19055 @itemx share @var{regex}
19056 Load shared object library symbols for files matching a
19057 Unix regular expression.
19058 As with files loaded automatically, it only loads shared libraries
19059 required by your program for a core file or after typing @code{run}. If
19060 @var{regex} is omitted all shared libraries required by your program are
19063 @item nosharedlibrary
19064 @kindex nosharedlibrary
19065 @cindex unload symbols from shared libraries
19066 Unload all shared object library symbols. This discards all symbols
19067 that have been loaded from all shared libraries. Symbols from shared
19068 libraries that were loaded by explicit user requests are not
19072 Sometimes you may wish that @value{GDBN} stops and gives you control
19073 when any of shared library events happen. The best way to do this is
19074 to use @code{catch load} and @code{catch unload} (@pxref{Set
19077 @value{GDBN} also supports the the @code{set stop-on-solib-events}
19078 command for this. This command exists for historical reasons. It is
19079 less useful than setting a catchpoint, because it does not allow for
19080 conditions or commands as a catchpoint does.
19083 @item set stop-on-solib-events
19084 @kindex set stop-on-solib-events
19085 This command controls whether @value{GDBN} should give you control
19086 when the dynamic linker notifies it about some shared library event.
19087 The most common event of interest is loading or unloading of a new
19090 @item show stop-on-solib-events
19091 @kindex show stop-on-solib-events
19092 Show whether @value{GDBN} stops and gives you control when shared
19093 library events happen.
19096 Shared libraries are also supported in many cross or remote debugging
19097 configurations. @value{GDBN} needs to have access to the target's libraries;
19098 this can be accomplished either by providing copies of the libraries
19099 on the host system, or by asking @value{GDBN} to automatically retrieve the
19100 libraries from the target. If copies of the target libraries are
19101 provided, they need to be the same as the target libraries, although the
19102 copies on the target can be stripped as long as the copies on the host are
19105 @cindex where to look for shared libraries
19106 For remote debugging, you need to tell @value{GDBN} where the target
19107 libraries are, so that it can load the correct copies---otherwise, it
19108 may try to load the host's libraries. @value{GDBN} has two variables
19109 to specify the search directories for target libraries.
19112 @cindex prefix for executable and shared library file names
19113 @cindex system root, alternate
19114 @kindex set solib-absolute-prefix
19115 @kindex set sysroot
19116 @item set sysroot @var{path}
19117 Use @var{path} as the system root for the program being debugged. Any
19118 absolute shared library paths will be prefixed with @var{path}; many
19119 runtime loaders store the absolute paths to the shared library in the
19120 target program's memory. When starting processes remotely, and when
19121 attaching to already-running processes (local or remote), their
19122 executable filenames will be prefixed with @var{path} if reported to
19123 @value{GDBN} as absolute by the operating system. If you use
19124 @code{set sysroot} to find executables and shared libraries, they need
19125 to be laid out in the same way that they are on the target, with
19126 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
19129 If @var{path} starts with the sequence @file{target:} and the target
19130 system is remote then @value{GDBN} will retrieve the target binaries
19131 from the remote system. This is only supported when using a remote
19132 target that supports the @code{remote get} command (@pxref{File
19133 Transfer,,Sending files to a remote system}). The part of @var{path}
19134 following the initial @file{target:} (if present) is used as system
19135 root prefix on the remote file system. If @var{path} starts with the
19136 sequence @file{remote:} this is converted to the sequence
19137 @file{target:} by @code{set sysroot}@footnote{Historically the
19138 functionality to retrieve binaries from the remote system was
19139 provided by prefixing @var{path} with @file{remote:}}. If you want
19140 to specify a local system root using a directory that happens to be
19141 named @file{target:} or @file{remote:}, you need to use some
19142 equivalent variant of the name like @file{./target:}.
19144 For targets with an MS-DOS based filesystem, such as MS-Windows and
19145 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
19146 absolute file name with @var{path}. But first, on Unix hosts,
19147 @value{GDBN} converts all backslash directory separators into forward
19148 slashes, because the backslash is not a directory separator on Unix:
19151 c:\foo\bar.dll @result{} c:/foo/bar.dll
19154 Then, @value{GDBN} attempts prefixing the target file name with
19155 @var{path}, and looks for the resulting file name in the host file
19159 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
19162 If that does not find the binary, @value{GDBN} tries removing
19163 the @samp{:} character from the drive spec, both for convenience, and,
19164 for the case of the host file system not supporting file names with
19168 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
19171 This makes it possible to have a system root that mirrors a target
19172 with more than one drive. E.g., you may want to setup your local
19173 copies of the target system shared libraries like so (note @samp{c} vs
19177 @file{/path/to/sysroot/c/sys/bin/foo.dll}
19178 @file{/path/to/sysroot/c/sys/bin/bar.dll}
19179 @file{/path/to/sysroot/z/sys/bin/bar.dll}
19183 and point the system root at @file{/path/to/sysroot}, so that
19184 @value{GDBN} can find the correct copies of both
19185 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
19187 If that still does not find the binary, @value{GDBN} tries
19188 removing the whole drive spec from the target file name:
19191 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
19194 This last lookup makes it possible to not care about the drive name,
19195 if you don't want or need to.
19197 The @code{set solib-absolute-prefix} command is an alias for @code{set
19200 @cindex default system root
19201 @cindex @samp{--with-sysroot}
19202 You can set the default system root by using the configure-time
19203 @samp{--with-sysroot} option. If the system root is inside
19204 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19205 @samp{--exec-prefix}), then the default system root will be updated
19206 automatically if the installed @value{GDBN} is moved to a new
19209 @kindex show sysroot
19211 Display the current executable and shared library prefix.
19213 @kindex set solib-search-path
19214 @item set solib-search-path @var{path}
19215 If this variable is set, @var{path} is a colon-separated list of
19216 directories to search for shared libraries. @samp{solib-search-path}
19217 is used after @samp{sysroot} fails to locate the library, or if the
19218 path to the library is relative instead of absolute. If you want to
19219 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
19220 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
19221 finding your host's libraries. @samp{sysroot} is preferred; setting
19222 it to a nonexistent directory may interfere with automatic loading
19223 of shared library symbols.
19225 @kindex show solib-search-path
19226 @item show solib-search-path
19227 Display the current shared library search path.
19229 @cindex DOS file-name semantics of file names.
19230 @kindex set target-file-system-kind (unix|dos-based|auto)
19231 @kindex show target-file-system-kind
19232 @item set target-file-system-kind @var{kind}
19233 Set assumed file system kind for target reported file names.
19235 Shared library file names as reported by the target system may not
19236 make sense as is on the system @value{GDBN} is running on. For
19237 example, when remote debugging a target that has MS-DOS based file
19238 system semantics, from a Unix host, the target may be reporting to
19239 @value{GDBN} a list of loaded shared libraries with file names such as
19240 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
19241 drive letters, so the @samp{c:\} prefix is not normally understood as
19242 indicating an absolute file name, and neither is the backslash
19243 normally considered a directory separator character. In that case,
19244 the native file system would interpret this whole absolute file name
19245 as a relative file name with no directory components. This would make
19246 it impossible to point @value{GDBN} at a copy of the remote target's
19247 shared libraries on the host using @code{set sysroot}, and impractical
19248 with @code{set solib-search-path}. Setting
19249 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
19250 to interpret such file names similarly to how the target would, and to
19251 map them to file names valid on @value{GDBN}'s native file system
19252 semantics. The value of @var{kind} can be @code{"auto"}, in addition
19253 to one of the supported file system kinds. In that case, @value{GDBN}
19254 tries to determine the appropriate file system variant based on the
19255 current target's operating system (@pxref{ABI, ,Configuring the
19256 Current ABI}). The supported file system settings are:
19260 Instruct @value{GDBN} to assume the target file system is of Unix
19261 kind. Only file names starting the forward slash (@samp{/}) character
19262 are considered absolute, and the directory separator character is also
19266 Instruct @value{GDBN} to assume the target file system is DOS based.
19267 File names starting with either a forward slash, or a drive letter
19268 followed by a colon (e.g., @samp{c:}), are considered absolute, and
19269 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
19270 considered directory separators.
19273 Instruct @value{GDBN} to use the file system kind associated with the
19274 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
19275 This is the default.
19279 @cindex file name canonicalization
19280 @cindex base name differences
19281 When processing file names provided by the user, @value{GDBN}
19282 frequently needs to compare them to the file names recorded in the
19283 program's debug info. Normally, @value{GDBN} compares just the
19284 @dfn{base names} of the files as strings, which is reasonably fast
19285 even for very large programs. (The base name of a file is the last
19286 portion of its name, after stripping all the leading directories.)
19287 This shortcut in comparison is based upon the assumption that files
19288 cannot have more than one base name. This is usually true, but
19289 references to files that use symlinks or similar filesystem
19290 facilities violate that assumption. If your program records files
19291 using such facilities, or if you provide file names to @value{GDBN}
19292 using symlinks etc., you can set @code{basenames-may-differ} to
19293 @code{true} to instruct @value{GDBN} to completely canonicalize each
19294 pair of file names it needs to compare. This will make file-name
19295 comparisons accurate, but at a price of a significant slowdown.
19298 @item set basenames-may-differ
19299 @kindex set basenames-may-differ
19300 Set whether a source file may have multiple base names.
19302 @item show basenames-may-differ
19303 @kindex show basenames-may-differ
19304 Show whether a source file may have multiple base names.
19308 @section File Caching
19309 @cindex caching of opened files
19310 @cindex caching of bfd objects
19312 To speed up file loading, and reduce memory usage, @value{GDBN} will
19313 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
19314 BFD, bfd, The Binary File Descriptor Library}. The following commands
19315 allow visibility and control of the caching behavior.
19318 @kindex maint info bfds
19319 @item maint info bfds
19320 This prints information about each @code{bfd} object that is known to
19323 @kindex maint set bfd-sharing
19324 @kindex maint show bfd-sharing
19325 @kindex bfd caching
19326 @item maint set bfd-sharing
19327 @item maint show bfd-sharing
19328 Control whether @code{bfd} objects can be shared. When sharing is
19329 enabled @value{GDBN} reuses already open @code{bfd} objects rather
19330 than reopening the same file. Turning sharing off does not cause
19331 already shared @code{bfd} objects to be unshared, but all future files
19332 that are opened will create a new @code{bfd} object. Similarly,
19333 re-enabling sharing does not cause multiple existing @code{bfd}
19334 objects to be collapsed into a single shared @code{bfd} object.
19336 @kindex set debug bfd-cache @var{level}
19337 @kindex bfd caching
19338 @item set debug bfd-cache @var{level}
19339 Turns on debugging of the bfd cache, setting the level to @var{level}.
19341 @kindex show debug bfd-cache
19342 @kindex bfd caching
19343 @item show debug bfd-cache
19344 Show the current debugging level of the bfd cache.
19347 @node Separate Debug Files
19348 @section Debugging Information in Separate Files
19349 @cindex separate debugging information files
19350 @cindex debugging information in separate files
19351 @cindex @file{.debug} subdirectories
19352 @cindex debugging information directory, global
19353 @cindex global debugging information directories
19354 @cindex build ID, and separate debugging files
19355 @cindex @file{.build-id} directory
19357 @value{GDBN} allows you to put a program's debugging information in a
19358 file separate from the executable itself, in a way that allows
19359 @value{GDBN} to find and load the debugging information automatically.
19360 Since debugging information can be very large---sometimes larger
19361 than the executable code itself---some systems distribute debugging
19362 information for their executables in separate files, which users can
19363 install only when they need to debug a problem.
19365 @value{GDBN} supports two ways of specifying the separate debug info
19370 The executable contains a @dfn{debug link} that specifies the name of
19371 the separate debug info file. The separate debug file's name is
19372 usually @file{@var{executable}.debug}, where @var{executable} is the
19373 name of the corresponding executable file without leading directories
19374 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
19375 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
19376 checksum for the debug file, which @value{GDBN} uses to validate that
19377 the executable and the debug file came from the same build.
19380 The executable contains a @dfn{build ID}, a unique bit string that is
19381 also present in the corresponding debug info file. (This is supported
19382 only on some operating systems, when using the ELF or PE file formats
19383 for binary files and the @sc{gnu} Binutils.) For more details about
19384 this feature, see the description of the @option{--build-id}
19385 command-line option in @ref{Options, , Command Line Options, ld.info,
19386 The GNU Linker}. The debug info file's name is not specified
19387 explicitly by the build ID, but can be computed from the build ID, see
19391 Depending on the way the debug info file is specified, @value{GDBN}
19392 uses two different methods of looking for the debug file:
19396 For the ``debug link'' method, @value{GDBN} looks up the named file in
19397 the directory of the executable file, then in a subdirectory of that
19398 directory named @file{.debug}, and finally under each one of the global debug
19399 directories, in a subdirectory whose name is identical to the leading
19400 directories of the executable's absolute file name.
19403 For the ``build ID'' method, @value{GDBN} looks in the
19404 @file{.build-id} subdirectory of each one of the global debug directories for
19405 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
19406 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
19407 are the rest of the bit string. (Real build ID strings are 32 or more
19408 hex characters, not 10.)
19411 So, for example, suppose you ask @value{GDBN} to debug
19412 @file{/usr/bin/ls}, which has a debug link that specifies the
19413 file @file{ls.debug}, and a build ID whose value in hex is
19414 @code{abcdef1234}. If the list of the global debug directories includes
19415 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
19416 debug information files, in the indicated order:
19420 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
19422 @file{/usr/bin/ls.debug}
19424 @file{/usr/bin/.debug/ls.debug}
19426 @file{/usr/lib/debug/usr/bin/ls.debug}.
19429 @anchor{debug-file-directory}
19430 Global debugging info directories default to what is set by @value{GDBN}
19431 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
19432 you can also set the global debugging info directories, and view the list
19433 @value{GDBN} is currently using.
19437 @kindex set debug-file-directory
19438 @item set debug-file-directory @var{directories}
19439 Set the directories which @value{GDBN} searches for separate debugging
19440 information files to @var{directory}. Multiple path components can be set
19441 concatenating them by a path separator.
19443 @kindex show debug-file-directory
19444 @item show debug-file-directory
19445 Show the directories @value{GDBN} searches for separate debugging
19450 @cindex @code{.gnu_debuglink} sections
19451 @cindex debug link sections
19452 A debug link is a special section of the executable file named
19453 @code{.gnu_debuglink}. The section must contain:
19457 A filename, with any leading directory components removed, followed by
19460 zero to three bytes of padding, as needed to reach the next four-byte
19461 boundary within the section, and
19463 a four-byte CRC checksum, stored in the same endianness used for the
19464 executable file itself. The checksum is computed on the debugging
19465 information file's full contents by the function given below, passing
19466 zero as the @var{crc} argument.
19469 Any executable file format can carry a debug link, as long as it can
19470 contain a section named @code{.gnu_debuglink} with the contents
19473 @cindex @code{.note.gnu.build-id} sections
19474 @cindex build ID sections
19475 The build ID is a special section in the executable file (and in other
19476 ELF binary files that @value{GDBN} may consider). This section is
19477 often named @code{.note.gnu.build-id}, but that name is not mandatory.
19478 It contains unique identification for the built files---the ID remains
19479 the same across multiple builds of the same build tree. The default
19480 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
19481 content for the build ID string. The same section with an identical
19482 value is present in the original built binary with symbols, in its
19483 stripped variant, and in the separate debugging information file.
19485 The debugging information file itself should be an ordinary
19486 executable, containing a full set of linker symbols, sections, and
19487 debugging information. The sections of the debugging information file
19488 should have the same names, addresses, and sizes as the original file,
19489 but they need not contain any data---much like a @code{.bss} section
19490 in an ordinary executable.
19492 The @sc{gnu} binary utilities (Binutils) package includes the
19493 @samp{objcopy} utility that can produce
19494 the separated executable / debugging information file pairs using the
19495 following commands:
19498 @kbd{objcopy --only-keep-debug foo foo.debug}
19503 These commands remove the debugging
19504 information from the executable file @file{foo} and place it in the file
19505 @file{foo.debug}. You can use the first, second or both methods to link the
19510 The debug link method needs the following additional command to also leave
19511 behind a debug link in @file{foo}:
19514 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
19517 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
19518 a version of the @code{strip} command such that the command @kbd{strip foo -f
19519 foo.debug} has the same functionality as the two @code{objcopy} commands and
19520 the @code{ln -s} command above, together.
19523 Build ID gets embedded into the main executable using @code{ld --build-id} or
19524 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
19525 compatibility fixes for debug files separation are present in @sc{gnu} binary
19526 utilities (Binutils) package since version 2.18.
19531 @cindex CRC algorithm definition
19532 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
19533 IEEE 802.3 using the polynomial:
19535 @c TexInfo requires naked braces for multi-digit exponents for Tex
19536 @c output, but this causes HTML output to barf. HTML has to be set using
19537 @c raw commands. So we end up having to specify this equation in 2
19542 <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>
19543 + <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
19549 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
19550 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
19554 The function is computed byte at a time, taking the least
19555 significant bit of each byte first. The initial pattern
19556 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
19557 the final result is inverted to ensure trailing zeros also affect the
19560 @emph{Note:} This is the same CRC polynomial as used in handling the
19561 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
19562 However in the case of the Remote Serial Protocol, the CRC is computed
19563 @emph{most} significant bit first, and the result is not inverted, so
19564 trailing zeros have no effect on the CRC value.
19566 To complete the description, we show below the code of the function
19567 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
19568 initially supplied @code{crc} argument means that an initial call to
19569 this function passing in zero will start computing the CRC using
19572 @kindex gnu_debuglink_crc32
19575 gnu_debuglink_crc32 (unsigned long crc,
19576 unsigned char *buf, size_t len)
19578 static const unsigned long crc32_table[256] =
19580 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
19581 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
19582 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
19583 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
19584 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
19585 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
19586 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
19587 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
19588 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
19589 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
19590 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
19591 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
19592 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
19593 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
19594 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
19595 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
19596 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
19597 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
19598 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
19599 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
19600 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
19601 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
19602 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
19603 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
19604 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
19605 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
19606 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
19607 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
19608 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
19609 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
19610 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
19611 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
19612 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
19613 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
19614 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
19615 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
19616 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
19617 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
19618 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
19619 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
19620 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
19621 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
19622 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
19623 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
19624 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
19625 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
19626 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
19627 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
19628 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
19629 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
19630 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
19633 unsigned char *end;
19635 crc = ~crc & 0xffffffff;
19636 for (end = buf + len; buf < end; ++buf)
19637 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
19638 return ~crc & 0xffffffff;
19643 This computation does not apply to the ``build ID'' method.
19645 @node MiniDebugInfo
19646 @section Debugging information in a special section
19647 @cindex separate debug sections
19648 @cindex @samp{.gnu_debugdata} section
19650 Some systems ship pre-built executables and libraries that have a
19651 special @samp{.gnu_debugdata} section. This feature is called
19652 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
19653 is used to supply extra symbols for backtraces.
19655 The intent of this section is to provide extra minimal debugging
19656 information for use in simple backtraces. It is not intended to be a
19657 replacement for full separate debugging information (@pxref{Separate
19658 Debug Files}). The example below shows the intended use; however,
19659 @value{GDBN} does not currently put restrictions on what sort of
19660 debugging information might be included in the section.
19662 @value{GDBN} has support for this extension. If the section exists,
19663 then it is used provided that no other source of debugging information
19664 can be found, and that @value{GDBN} was configured with LZMA support.
19666 This section can be easily created using @command{objcopy} and other
19667 standard utilities:
19670 # Extract the dynamic symbols from the main binary, there is no need
19671 # to also have these in the normal symbol table.
19672 nm -D @var{binary} --format=posix --defined-only \
19673 | awk '@{ print $1 @}' | sort > dynsyms
19675 # Extract all the text (i.e. function) symbols from the debuginfo.
19676 # (Note that we actually also accept "D" symbols, for the benefit
19677 # of platforms like PowerPC64 that use function descriptors.)
19678 nm @var{binary} --format=posix --defined-only \
19679 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
19682 # Keep all the function symbols not already in the dynamic symbol
19684 comm -13 dynsyms funcsyms > keep_symbols
19686 # Separate full debug info into debug binary.
19687 objcopy --only-keep-debug @var{binary} debug
19689 # Copy the full debuginfo, keeping only a minimal set of symbols and
19690 # removing some unnecessary sections.
19691 objcopy -S --remove-section .gdb_index --remove-section .comment \
19692 --keep-symbols=keep_symbols debug mini_debuginfo
19694 # Drop the full debug info from the original binary.
19695 strip --strip-all -R .comment @var{binary}
19697 # Inject the compressed data into the .gnu_debugdata section of the
19700 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
19704 @section Index Files Speed Up @value{GDBN}
19705 @cindex index files
19706 @cindex @samp{.gdb_index} section
19708 When @value{GDBN} finds a symbol file, it scans the symbols in the
19709 file in order to construct an internal symbol table. This lets most
19710 @value{GDBN} operations work quickly---at the cost of a delay early
19711 on. For large programs, this delay can be quite lengthy, so
19712 @value{GDBN} provides a way to build an index, which speeds up
19715 The index is stored as a section in the symbol file. @value{GDBN} can
19716 write the index to a file, then you can put it into the symbol file
19717 using @command{objcopy}.
19719 To create an index file, use the @code{save gdb-index} command:
19722 @item save gdb-index [-dwarf-5] @var{directory}
19723 @kindex save gdb-index
19724 Create index files for all symbol files currently known by
19725 @value{GDBN}. For each known @var{symbol-file}, this command by
19726 default creates it produces a single file
19727 @file{@var{symbol-file}.gdb-index}. If you invoke this command with
19728 the @option{-dwarf-5} option, it produces 2 files:
19729 @file{@var{symbol-file}.debug_names} and
19730 @file{@var{symbol-file}.debug_str}. The files are created in the
19731 given @var{directory}.
19734 Once you have created an index file you can merge it into your symbol
19735 file, here named @file{symfile}, using @command{objcopy}:
19738 $ objcopy --add-section .gdb_index=symfile.gdb-index \
19739 --set-section-flags .gdb_index=readonly symfile symfile
19742 Or for @code{-dwarf-5}:
19745 $ objcopy --dump-section .debug_str=symfile.debug_str.new symfile
19746 $ cat symfile.debug_str >>symfile.debug_str.new
19747 $ objcopy --add-section .debug_names=symfile.gdb-index \
19748 --set-section-flags .debug_names=readonly \
19749 --update-section .debug_str=symfile.debug_str.new symfile symfile
19752 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
19753 sections that have been deprecated. Usually they are deprecated because
19754 they are missing a new feature or have performance issues.
19755 To tell @value{GDBN} to use a deprecated index section anyway
19756 specify @code{set use-deprecated-index-sections on}.
19757 The default is @code{off}.
19758 This can speed up startup, but may result in some functionality being lost.
19759 @xref{Index Section Format}.
19761 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
19762 must be done before gdb reads the file. The following will not work:
19765 $ gdb -ex "set use-deprecated-index-sections on" <program>
19768 Instead you must do, for example,
19771 $ gdb -iex "set use-deprecated-index-sections on" <program>
19774 There are currently some limitation on indices. They only work when
19775 for DWARF debugging information, not stabs. And, they do not
19776 currently work for programs using Ada.
19778 @node Symbol Errors
19779 @section Errors Reading Symbol Files
19781 While reading a symbol file, @value{GDBN} occasionally encounters problems,
19782 such as symbol types it does not recognize, or known bugs in compiler
19783 output. By default, @value{GDBN} does not notify you of such problems, since
19784 they are relatively common and primarily of interest to people
19785 debugging compilers. If you are interested in seeing information
19786 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
19787 only one message about each such type of problem, no matter how many
19788 times the problem occurs; or you can ask @value{GDBN} to print more messages,
19789 to see how many times the problems occur, with the @code{set
19790 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
19793 The messages currently printed, and their meanings, include:
19796 @item inner block not inside outer block in @var{symbol}
19798 The symbol information shows where symbol scopes begin and end
19799 (such as at the start of a function or a block of statements). This
19800 error indicates that an inner scope block is not fully contained
19801 in its outer scope blocks.
19803 @value{GDBN} circumvents the problem by treating the inner block as if it had
19804 the same scope as the outer block. In the error message, @var{symbol}
19805 may be shown as ``@code{(don't know)}'' if the outer block is not a
19808 @item block at @var{address} out of order
19810 The symbol information for symbol scope blocks should occur in
19811 order of increasing addresses. This error indicates that it does not
19814 @value{GDBN} does not circumvent this problem, and has trouble
19815 locating symbols in the source file whose symbols it is reading. (You
19816 can often determine what source file is affected by specifying
19817 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
19820 @item bad block start address patched
19822 The symbol information for a symbol scope block has a start address
19823 smaller than the address of the preceding source line. This is known
19824 to occur in the SunOS 4.1.1 (and earlier) C compiler.
19826 @value{GDBN} circumvents the problem by treating the symbol scope block as
19827 starting on the previous source line.
19829 @item bad string table offset in symbol @var{n}
19832 Symbol number @var{n} contains a pointer into the string table which is
19833 larger than the size of the string table.
19835 @value{GDBN} circumvents the problem by considering the symbol to have the
19836 name @code{foo}, which may cause other problems if many symbols end up
19839 @item unknown symbol type @code{0x@var{nn}}
19841 The symbol information contains new data types that @value{GDBN} does
19842 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
19843 uncomprehended information, in hexadecimal.
19845 @value{GDBN} circumvents the error by ignoring this symbol information.
19846 This usually allows you to debug your program, though certain symbols
19847 are not accessible. If you encounter such a problem and feel like
19848 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
19849 on @code{complain}, then go up to the function @code{read_dbx_symtab}
19850 and examine @code{*bufp} to see the symbol.
19852 @item stub type has NULL name
19854 @value{GDBN} could not find the full definition for a struct or class.
19856 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
19857 The symbol information for a C@t{++} member function is missing some
19858 information that recent versions of the compiler should have output for
19861 @item info mismatch between compiler and debugger
19863 @value{GDBN} could not parse a type specification output by the compiler.
19868 @section GDB Data Files
19870 @cindex prefix for data files
19871 @value{GDBN} will sometimes read an auxiliary data file. These files
19872 are kept in a directory known as the @dfn{data directory}.
19874 You can set the data directory's name, and view the name @value{GDBN}
19875 is currently using.
19878 @kindex set data-directory
19879 @item set data-directory @var{directory}
19880 Set the directory which @value{GDBN} searches for auxiliary data files
19881 to @var{directory}.
19883 @kindex show data-directory
19884 @item show data-directory
19885 Show the directory @value{GDBN} searches for auxiliary data files.
19888 @cindex default data directory
19889 @cindex @samp{--with-gdb-datadir}
19890 You can set the default data directory by using the configure-time
19891 @samp{--with-gdb-datadir} option. If the data directory is inside
19892 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19893 @samp{--exec-prefix}), then the default data directory will be updated
19894 automatically if the installed @value{GDBN} is moved to a new
19897 The data directory may also be specified with the
19898 @code{--data-directory} command line option.
19899 @xref{Mode Options}.
19902 @chapter Specifying a Debugging Target
19904 @cindex debugging target
19905 A @dfn{target} is the execution environment occupied by your program.
19907 Often, @value{GDBN} runs in the same host environment as your program;
19908 in that case, the debugging target is specified as a side effect when
19909 you use the @code{file} or @code{core} commands. When you need more
19910 flexibility---for example, running @value{GDBN} on a physically separate
19911 host, or controlling a standalone system over a serial port or a
19912 realtime system over a TCP/IP connection---you can use the @code{target}
19913 command to specify one of the target types configured for @value{GDBN}
19914 (@pxref{Target Commands, ,Commands for Managing Targets}).
19916 @cindex target architecture
19917 It is possible to build @value{GDBN} for several different @dfn{target
19918 architectures}. When @value{GDBN} is built like that, you can choose
19919 one of the available architectures with the @kbd{set architecture}
19923 @kindex set architecture
19924 @kindex show architecture
19925 @item set architecture @var{arch}
19926 This command sets the current target architecture to @var{arch}. The
19927 value of @var{arch} can be @code{"auto"}, in addition to one of the
19928 supported architectures.
19930 @item show architecture
19931 Show the current target architecture.
19933 @item set processor
19935 @kindex set processor
19936 @kindex show processor
19937 These are alias commands for, respectively, @code{set architecture}
19938 and @code{show architecture}.
19942 * Active Targets:: Active targets
19943 * Target Commands:: Commands for managing targets
19944 * Byte Order:: Choosing target byte order
19947 @node Active Targets
19948 @section Active Targets
19950 @cindex stacking targets
19951 @cindex active targets
19952 @cindex multiple targets
19954 There are multiple classes of targets such as: processes, executable files or
19955 recording sessions. Core files belong to the process class, making core file
19956 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
19957 on multiple active targets, one in each class. This allows you to (for
19958 example) start a process and inspect its activity, while still having access to
19959 the executable file after the process finishes. Or if you start process
19960 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
19961 presented a virtual layer of the recording target, while the process target
19962 remains stopped at the chronologically last point of the process execution.
19964 Use the @code{core-file} and @code{exec-file} commands to select a new core
19965 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
19966 specify as a target a process that is already running, use the @code{attach}
19967 command (@pxref{Attach, ,Debugging an Already-running Process}).
19969 @node Target Commands
19970 @section Commands for Managing Targets
19973 @item target @var{type} @var{parameters}
19974 Connects the @value{GDBN} host environment to a target machine or
19975 process. A target is typically a protocol for talking to debugging
19976 facilities. You use the argument @var{type} to specify the type or
19977 protocol of the target machine.
19979 Further @var{parameters} are interpreted by the target protocol, but
19980 typically include things like device names or host names to connect
19981 with, process numbers, and baud rates.
19983 The @code{target} command does not repeat if you press @key{RET} again
19984 after executing the command.
19986 @kindex help target
19988 Displays the names of all targets available. To display targets
19989 currently selected, use either @code{info target} or @code{info files}
19990 (@pxref{Files, ,Commands to Specify Files}).
19992 @item help target @var{name}
19993 Describe a particular target, including any parameters necessary to
19996 @kindex set gnutarget
19997 @item set gnutarget @var{args}
19998 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
19999 knows whether it is reading an @dfn{executable},
20000 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
20001 with the @code{set gnutarget} command. Unlike most @code{target} commands,
20002 with @code{gnutarget} the @code{target} refers to a program, not a machine.
20005 @emph{Warning:} To specify a file format with @code{set gnutarget},
20006 you must know the actual BFD name.
20010 @xref{Files, , Commands to Specify Files}.
20012 @kindex show gnutarget
20013 @item show gnutarget
20014 Use the @code{show gnutarget} command to display what file format
20015 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
20016 @value{GDBN} will determine the file format for each file automatically,
20017 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
20020 @cindex common targets
20021 Here are some common targets (available, or not, depending on the GDB
20026 @item target exec @var{program}
20027 @cindex executable file target
20028 An executable file. @samp{target exec @var{program}} is the same as
20029 @samp{exec-file @var{program}}.
20031 @item target core @var{filename}
20032 @cindex core dump file target
20033 A core dump file. @samp{target core @var{filename}} is the same as
20034 @samp{core-file @var{filename}}.
20036 @item target remote @var{medium}
20037 @cindex remote target
20038 A remote system connected to @value{GDBN} via a serial line or network
20039 connection. This command tells @value{GDBN} to use its own remote
20040 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
20042 For example, if you have a board connected to @file{/dev/ttya} on the
20043 machine running @value{GDBN}, you could say:
20046 target remote /dev/ttya
20049 @code{target remote} supports the @code{load} command. This is only
20050 useful if you have some other way of getting the stub to the target
20051 system, and you can put it somewhere in memory where it won't get
20052 clobbered by the download.
20054 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20055 @cindex built-in simulator target
20056 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
20064 works; however, you cannot assume that a specific memory map, device
20065 drivers, or even basic I/O is available, although some simulators do
20066 provide these. For info about any processor-specific simulator details,
20067 see the appropriate section in @ref{Embedded Processors, ,Embedded
20070 @item target native
20071 @cindex native target
20072 Setup for local/native process debugging. Useful to make the
20073 @code{run} command spawn native processes (likewise @code{attach},
20074 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
20075 (@pxref{set auto-connect-native-target}).
20079 Different targets are available on different configurations of @value{GDBN};
20080 your configuration may have more or fewer targets.
20082 Many remote targets require you to download the executable's code once
20083 you've successfully established a connection. You may wish to control
20084 various aspects of this process.
20089 @kindex set hash@r{, for remote monitors}
20090 @cindex hash mark while downloading
20091 This command controls whether a hash mark @samp{#} is displayed while
20092 downloading a file to the remote monitor. If on, a hash mark is
20093 displayed after each S-record is successfully downloaded to the
20097 @kindex show hash@r{, for remote monitors}
20098 Show the current status of displaying the hash mark.
20100 @item set debug monitor
20101 @kindex set debug monitor
20102 @cindex display remote monitor communications
20103 Enable or disable display of communications messages between
20104 @value{GDBN} and the remote monitor.
20106 @item show debug monitor
20107 @kindex show debug monitor
20108 Show the current status of displaying communications between
20109 @value{GDBN} and the remote monitor.
20114 @kindex load @var{filename} @var{offset}
20115 @item load @var{filename} @var{offset}
20117 Depending on what remote debugging facilities are configured into
20118 @value{GDBN}, the @code{load} command may be available. Where it exists, it
20119 is meant to make @var{filename} (an executable) available for debugging
20120 on the remote system---by downloading, or dynamic linking, for example.
20121 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
20122 the @code{add-symbol-file} command.
20124 If your @value{GDBN} does not have a @code{load} command, attempting to
20125 execute it gets the error message ``@code{You can't do that when your
20126 target is @dots{}}''
20128 The file is loaded at whatever address is specified in the executable.
20129 For some object file formats, you can specify the load address when you
20130 link the program; for other formats, like a.out, the object file format
20131 specifies a fixed address.
20132 @c FIXME! This would be a good place for an xref to the GNU linker doc.
20134 It is also possible to tell @value{GDBN} to load the executable file at a
20135 specific offset described by the optional argument @var{offset}. When
20136 @var{offset} is provided, @var{filename} must also be provided.
20138 Depending on the remote side capabilities, @value{GDBN} may be able to
20139 load programs into flash memory.
20141 @code{load} does not repeat if you press @key{RET} again after using it.
20146 @kindex flash-erase
20148 @anchor{flash-erase}
20150 Erases all known flash memory regions on the target.
20155 @section Choosing Target Byte Order
20157 @cindex choosing target byte order
20158 @cindex target byte order
20160 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
20161 offer the ability to run either big-endian or little-endian byte
20162 orders. Usually the executable or symbol will include a bit to
20163 designate the endian-ness, and you will not need to worry about
20164 which to use. However, you may still find it useful to adjust
20165 @value{GDBN}'s idea of processor endian-ness manually.
20169 @item set endian big
20170 Instruct @value{GDBN} to assume the target is big-endian.
20172 @item set endian little
20173 Instruct @value{GDBN} to assume the target is little-endian.
20175 @item set endian auto
20176 Instruct @value{GDBN} to use the byte order associated with the
20180 Display @value{GDBN}'s current idea of the target byte order.
20184 Note that these commands merely adjust interpretation of symbolic
20185 data on the host, and that they have absolutely no effect on the
20189 @node Remote Debugging
20190 @chapter Debugging Remote Programs
20191 @cindex remote debugging
20193 If you are trying to debug a program running on a machine that cannot run
20194 @value{GDBN} in the usual way, it is often useful to use remote debugging.
20195 For example, you might use remote debugging on an operating system kernel,
20196 or on a small system which does not have a general purpose operating system
20197 powerful enough to run a full-featured debugger.
20199 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
20200 to make this work with particular debugging targets. In addition,
20201 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
20202 but not specific to any particular target system) which you can use if you
20203 write the remote stubs---the code that runs on the remote system to
20204 communicate with @value{GDBN}.
20206 Other remote targets may be available in your
20207 configuration of @value{GDBN}; use @code{help target} to list them.
20210 * Connecting:: Connecting to a remote target
20211 * File Transfer:: Sending files to a remote system
20212 * Server:: Using the gdbserver program
20213 * Remote Configuration:: Remote configuration
20214 * Remote Stub:: Implementing a remote stub
20218 @section Connecting to a Remote Target
20219 @cindex remote debugging, connecting
20220 @cindex @code{gdbserver}, connecting
20221 @cindex remote debugging, types of connections
20222 @cindex @code{gdbserver}, types of connections
20223 @cindex @code{gdbserver}, @code{target remote} mode
20224 @cindex @code{gdbserver}, @code{target extended-remote} mode
20226 This section describes how to connect to a remote target, including the
20227 types of connections and their differences, how to set up executable and
20228 symbol files on the host and target, and the commands used for
20229 connecting to and disconnecting from the remote target.
20231 @subsection Types of Remote Connections
20233 @value{GDBN} supports two types of remote connections, @code{target remote}
20234 mode and @code{target extended-remote} mode. Note that many remote targets
20235 support only @code{target remote} mode. There are several major
20236 differences between the two types of connections, enumerated here:
20240 @cindex remote debugging, detach and program exit
20241 @item Result of detach or program exit
20242 @strong{With target remote mode:} When the debugged program exits or you
20243 detach from it, @value{GDBN} disconnects from the target. When using
20244 @code{gdbserver}, @code{gdbserver} will exit.
20246 @strong{With target extended-remote mode:} When the debugged program exits or
20247 you detach from it, @value{GDBN} remains connected to the target, even
20248 though no program is running. You can rerun the program, attach to a
20249 running program, or use @code{monitor} commands specific to the target.
20251 When using @code{gdbserver} in this case, it does not exit unless it was
20252 invoked using the @option{--once} option. If the @option{--once} option
20253 was not used, you can ask @code{gdbserver} to exit using the
20254 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
20256 @item Specifying the program to debug
20257 For both connection types you use the @code{file} command to specify the
20258 program on the host system. If you are using @code{gdbserver} there are
20259 some differences in how to specify the location of the program on the
20262 @strong{With target remote mode:} You must either specify the program to debug
20263 on the @code{gdbserver} command line or use the @option{--attach} option
20264 (@pxref{Attaching to a program,,Attaching to a Running Program}).
20266 @cindex @option{--multi}, @code{gdbserver} option
20267 @strong{With target extended-remote mode:} You may specify the program to debug
20268 on the @code{gdbserver} command line, or you can load the program or attach
20269 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
20271 @anchor{--multi Option in Types of Remote Connnections}
20272 You can start @code{gdbserver} without supplying an initial command to run
20273 or process ID to attach. To do this, use the @option{--multi} command line
20274 option. Then you can connect using @code{target extended-remote} and start
20275 the program you want to debug (see below for details on using the
20276 @code{run} command in this scenario). Note that the conditions under which
20277 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
20278 (@code{target remote} or @code{target extended-remote}). The
20279 @option{--multi} option to @code{gdbserver} has no influence on that.
20281 @item The @code{run} command
20282 @strong{With target remote mode:} The @code{run} command is not
20283 supported. Once a connection has been established, you can use all
20284 the usual @value{GDBN} commands to examine and change data. The
20285 remote program is already running, so you can use commands like
20286 @kbd{step} and @kbd{continue}.
20288 @strong{With target extended-remote mode:} The @code{run} command is
20289 supported. The @code{run} command uses the value set by
20290 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
20291 the program to run. Command line arguments are supported, except for
20292 wildcard expansion and I/O redirection (@pxref{Arguments}).
20294 If you specify the program to debug on the command line, then the
20295 @code{run} command is not required to start execution, and you can
20296 resume using commands like @kbd{step} and @kbd{continue} as with
20297 @code{target remote} mode.
20299 @anchor{Attaching in Types of Remote Connections}
20301 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
20302 not supported. To attach to a running program using @code{gdbserver}, you
20303 must use the @option{--attach} option (@pxref{Running gdbserver}).
20305 @strong{With target extended-remote mode:} To attach to a running program,
20306 you may use the @code{attach} command after the connection has been
20307 established. If you are using @code{gdbserver}, you may also invoke
20308 @code{gdbserver} using the @option{--attach} option
20309 (@pxref{Running gdbserver}).
20313 @anchor{Host and target files}
20314 @subsection Host and Target Files
20315 @cindex remote debugging, symbol files
20316 @cindex symbol files, remote debugging
20318 @value{GDBN}, running on the host, needs access to symbol and debugging
20319 information for your program running on the target. This requires
20320 access to an unstripped copy of your program, and possibly any associated
20321 symbol files. Note that this section applies equally to both @code{target
20322 remote} mode and @code{target extended-remote} mode.
20324 Some remote targets (@pxref{qXfer executable filename read}, and
20325 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
20326 the same connection used to communicate with @value{GDBN}. With such a
20327 target, if the remote program is unstripped, the only command you need is
20328 @code{target remote} (or @code{target extended-remote}).
20330 If the remote program is stripped, or the target does not support remote
20331 program file access, start up @value{GDBN} using the name of the local
20332 unstripped copy of your program as the first argument, or use the
20333 @code{file} command. Use @code{set sysroot} to specify the location (on
20334 the host) of target libraries (unless your @value{GDBN} was compiled with
20335 the correct sysroot using @code{--with-sysroot}). Alternatively, you
20336 may use @code{set solib-search-path} to specify how @value{GDBN} locates
20339 The symbol file and target libraries must exactly match the executable
20340 and libraries on the target, with one exception: the files on the host
20341 system should not be stripped, even if the files on the target system
20342 are. Mismatched or missing files will lead to confusing results
20343 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
20344 files may also prevent @code{gdbserver} from debugging multi-threaded
20347 @subsection Remote Connection Commands
20348 @cindex remote connection commands
20349 @value{GDBN} can communicate with the target over a serial line, or
20350 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
20351 each case, @value{GDBN} uses the same protocol for debugging your
20352 program; only the medium carrying the debugging packets varies. The
20353 @code{target remote} and @code{target extended-remote} commands
20354 establish a connection to the target. Both commands accept the same
20355 arguments, which indicate the medium to use:
20359 @item target remote @var{serial-device}
20360 @itemx target extended-remote @var{serial-device}
20361 @cindex serial line, @code{target remote}
20362 Use @var{serial-device} to communicate with the target. For example,
20363 to use a serial line connected to the device named @file{/dev/ttyb}:
20366 target remote /dev/ttyb
20369 If you're using a serial line, you may want to give @value{GDBN} the
20370 @samp{--baud} option, or use the @code{set serial baud} command
20371 (@pxref{Remote Configuration, set serial baud}) before the
20372 @code{target} command.
20374 @item target remote @code{@var{host}:@var{port}}
20375 @itemx target remote @code{tcp:@var{host}:@var{port}}
20376 @itemx target extended-remote @code{@var{host}:@var{port}}
20377 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
20378 @cindex @acronym{TCP} port, @code{target remote}
20379 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
20380 The @var{host} may be either a host name or a numeric @acronym{IP}
20381 address; @var{port} must be a decimal number. The @var{host} could be
20382 the target machine itself, if it is directly connected to the net, or
20383 it might be a terminal server which in turn has a serial line to the
20386 For example, to connect to port 2828 on a terminal server named
20390 target remote manyfarms:2828
20393 If your remote target is actually running on the same machine as your
20394 debugger session (e.g.@: a simulator for your target running on the
20395 same host), you can omit the hostname. For example, to connect to
20396 port 1234 on your local machine:
20399 target remote :1234
20403 Note that the colon is still required here.
20405 @item target remote @code{udp:@var{host}:@var{port}}
20406 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
20407 @cindex @acronym{UDP} port, @code{target remote}
20408 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
20409 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
20412 target remote udp:manyfarms:2828
20415 When using a @acronym{UDP} connection for remote debugging, you should
20416 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
20417 can silently drop packets on busy or unreliable networks, which will
20418 cause havoc with your debugging session.
20420 @item target remote | @var{command}
20421 @itemx target extended-remote | @var{command}
20422 @cindex pipe, @code{target remote} to
20423 Run @var{command} in the background and communicate with it using a
20424 pipe. The @var{command} is a shell command, to be parsed and expanded
20425 by the system's command shell, @code{/bin/sh}; it should expect remote
20426 protocol packets on its standard input, and send replies on its
20427 standard output. You could use this to run a stand-alone simulator
20428 that speaks the remote debugging protocol, to make net connections
20429 using programs like @code{ssh}, or for other similar tricks.
20431 If @var{command} closes its standard output (perhaps by exiting),
20432 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
20433 program has already exited, this will have no effect.)
20437 @cindex interrupting remote programs
20438 @cindex remote programs, interrupting
20439 Whenever @value{GDBN} is waiting for the remote program, if you type the
20440 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
20441 program. This may or may not succeed, depending in part on the hardware
20442 and the serial drivers the remote system uses. If you type the
20443 interrupt character once again, @value{GDBN} displays this prompt:
20446 Interrupted while waiting for the program.
20447 Give up (and stop debugging it)? (y or n)
20450 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
20451 the remote debugging session. (If you decide you want to try again later,
20452 you can use @kbd{target remote} again to connect once more.) If you type
20453 @kbd{n}, @value{GDBN} goes back to waiting.
20455 In @code{target extended-remote} mode, typing @kbd{n} will leave
20456 @value{GDBN} connected to the target.
20459 @kindex detach (remote)
20461 When you have finished debugging the remote program, you can use the
20462 @code{detach} command to release it from @value{GDBN} control.
20463 Detaching from the target normally resumes its execution, but the results
20464 will depend on your particular remote stub. After the @code{detach}
20465 command in @code{target remote} mode, @value{GDBN} is free to connect to
20466 another target. In @code{target extended-remote} mode, @value{GDBN} is
20467 still connected to the target.
20471 The @code{disconnect} command closes the connection to the target, and
20472 the target is generally not resumed. It will wait for @value{GDBN}
20473 (this instance or another one) to connect and continue debugging. After
20474 the @code{disconnect} command, @value{GDBN} is again free to connect to
20477 @cindex send command to remote monitor
20478 @cindex extend @value{GDBN} for remote targets
20479 @cindex add new commands for external monitor
20481 @item monitor @var{cmd}
20482 This command allows you to send arbitrary commands directly to the
20483 remote monitor. Since @value{GDBN} doesn't care about the commands it
20484 sends like this, this command is the way to extend @value{GDBN}---you
20485 can add new commands that only the external monitor will understand
20489 @node File Transfer
20490 @section Sending files to a remote system
20491 @cindex remote target, file transfer
20492 @cindex file transfer
20493 @cindex sending files to remote systems
20495 Some remote targets offer the ability to transfer files over the same
20496 connection used to communicate with @value{GDBN}. This is convenient
20497 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
20498 running @code{gdbserver} over a network interface. For other targets,
20499 e.g.@: embedded devices with only a single serial port, this may be
20500 the only way to upload or download files.
20502 Not all remote targets support these commands.
20506 @item remote put @var{hostfile} @var{targetfile}
20507 Copy file @var{hostfile} from the host system (the machine running
20508 @value{GDBN}) to @var{targetfile} on the target system.
20511 @item remote get @var{targetfile} @var{hostfile}
20512 Copy file @var{targetfile} from the target system to @var{hostfile}
20513 on the host system.
20515 @kindex remote delete
20516 @item remote delete @var{targetfile}
20517 Delete @var{targetfile} from the target system.
20522 @section Using the @code{gdbserver} Program
20525 @cindex remote connection without stubs
20526 @code{gdbserver} is a control program for Unix-like systems, which
20527 allows you to connect your program with a remote @value{GDBN} via
20528 @code{target remote} or @code{target extended-remote}---but without
20529 linking in the usual debugging stub.
20531 @code{gdbserver} is not a complete replacement for the debugging stubs,
20532 because it requires essentially the same operating-system facilities
20533 that @value{GDBN} itself does. In fact, a system that can run
20534 @code{gdbserver} to connect to a remote @value{GDBN} could also run
20535 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
20536 because it is a much smaller program than @value{GDBN} itself. It is
20537 also easier to port than all of @value{GDBN}, so you may be able to get
20538 started more quickly on a new system by using @code{gdbserver}.
20539 Finally, if you develop code for real-time systems, you may find that
20540 the tradeoffs involved in real-time operation make it more convenient to
20541 do as much development work as possible on another system, for example
20542 by cross-compiling. You can use @code{gdbserver} to make a similar
20543 choice for debugging.
20545 @value{GDBN} and @code{gdbserver} communicate via either a serial line
20546 or a TCP connection, using the standard @value{GDBN} remote serial
20550 @emph{Warning:} @code{gdbserver} does not have any built-in security.
20551 Do not run @code{gdbserver} connected to any public network; a
20552 @value{GDBN} connection to @code{gdbserver} provides access to the
20553 target system with the same privileges as the user running
20557 @anchor{Running gdbserver}
20558 @subsection Running @code{gdbserver}
20559 @cindex arguments, to @code{gdbserver}
20560 @cindex @code{gdbserver}, command-line arguments
20562 Run @code{gdbserver} on the target system. You need a copy of the
20563 program you want to debug, including any libraries it requires.
20564 @code{gdbserver} does not need your program's symbol table, so you can
20565 strip the program if necessary to save space. @value{GDBN} on the host
20566 system does all the symbol handling.
20568 To use the server, you must tell it how to communicate with @value{GDBN};
20569 the name of your program; and the arguments for your program. The usual
20573 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
20576 @var{comm} is either a device name (to use a serial line), or a TCP
20577 hostname and portnumber, or @code{-} or @code{stdio} to use
20578 stdin/stdout of @code{gdbserver}.
20579 For example, to debug Emacs with the argument
20580 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
20584 target> gdbserver /dev/com1 emacs foo.txt
20587 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
20590 To use a TCP connection instead of a serial line:
20593 target> gdbserver host:2345 emacs foo.txt
20596 The only difference from the previous example is the first argument,
20597 specifying that you are communicating with the host @value{GDBN} via
20598 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
20599 expect a TCP connection from machine @samp{host} to local TCP port 2345.
20600 (Currently, the @samp{host} part is ignored.) You can choose any number
20601 you want for the port number as long as it does not conflict with any
20602 TCP ports already in use on the target system (for example, @code{23} is
20603 reserved for @code{telnet}).@footnote{If you choose a port number that
20604 conflicts with another service, @code{gdbserver} prints an error message
20605 and exits.} You must use the same port number with the host @value{GDBN}
20606 @code{target remote} command.
20608 The @code{stdio} connection is useful when starting @code{gdbserver}
20612 (gdb) target remote | ssh -T hostname gdbserver - hello
20615 The @samp{-T} option to ssh is provided because we don't need a remote pty,
20616 and we don't want escape-character handling. Ssh does this by default when
20617 a command is provided, the flag is provided to make it explicit.
20618 You could elide it if you want to.
20620 Programs started with stdio-connected gdbserver have @file{/dev/null} for
20621 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
20622 display through a pipe connected to gdbserver.
20623 Both @code{stdout} and @code{stderr} use the same pipe.
20625 @anchor{Attaching to a program}
20626 @subsubsection Attaching to a Running Program
20627 @cindex attach to a program, @code{gdbserver}
20628 @cindex @option{--attach}, @code{gdbserver} option
20630 On some targets, @code{gdbserver} can also attach to running programs.
20631 This is accomplished via the @code{--attach} argument. The syntax is:
20634 target> gdbserver --attach @var{comm} @var{pid}
20637 @var{pid} is the process ID of a currently running process. It isn't
20638 necessary to point @code{gdbserver} at a binary for the running process.
20640 In @code{target extended-remote} mode, you can also attach using the
20641 @value{GDBN} attach command
20642 (@pxref{Attaching in Types of Remote Connections}).
20645 You can debug processes by name instead of process ID if your target has the
20646 @code{pidof} utility:
20649 target> gdbserver --attach @var{comm} `pidof @var{program}`
20652 In case more than one copy of @var{program} is running, or @var{program}
20653 has multiple threads, most versions of @code{pidof} support the
20654 @code{-s} option to only return the first process ID.
20656 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
20658 This section applies only when @code{gdbserver} is run to listen on a TCP
20661 @code{gdbserver} normally terminates after all of its debugged processes have
20662 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
20663 extended-remote}, @code{gdbserver} stays running even with no processes left.
20664 @value{GDBN} normally terminates the spawned debugged process on its exit,
20665 which normally also terminates @code{gdbserver} in the @kbd{target remote}
20666 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
20667 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
20668 stays running even in the @kbd{target remote} mode.
20670 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
20671 Such reconnecting is useful for features like @ref{disconnected tracing}. For
20672 completeness, at most one @value{GDBN} can be connected at a time.
20674 @cindex @option{--once}, @code{gdbserver} option
20675 By default, @code{gdbserver} keeps the listening TCP port open, so that
20676 subsequent connections are possible. However, if you start @code{gdbserver}
20677 with the @option{--once} option, it will stop listening for any further
20678 connection attempts after connecting to the first @value{GDBN} session. This
20679 means no further connections to @code{gdbserver} will be possible after the
20680 first one. It also means @code{gdbserver} will terminate after the first
20681 connection with remote @value{GDBN} has closed, even for unexpectedly closed
20682 connections and even in the @kbd{target extended-remote} mode. The
20683 @option{--once} option allows reusing the same port number for connecting to
20684 multiple instances of @code{gdbserver} running on the same host, since each
20685 instance closes its port after the first connection.
20687 @anchor{Other Command-Line Arguments for gdbserver}
20688 @subsubsection Other Command-Line Arguments for @code{gdbserver}
20690 You can use the @option{--multi} option to start @code{gdbserver} without
20691 specifying a program to debug or a process to attach to. Then you can
20692 attach in @code{target extended-remote} mode and run or attach to a
20693 program. For more information,
20694 @pxref{--multi Option in Types of Remote Connnections}.
20696 @cindex @option{--debug}, @code{gdbserver} option
20697 The @option{--debug} option tells @code{gdbserver} to display extra
20698 status information about the debugging process.
20699 @cindex @option{--remote-debug}, @code{gdbserver} option
20700 The @option{--remote-debug} option tells @code{gdbserver} to display
20701 remote protocol debug output. These options are intended for
20702 @code{gdbserver} development and for bug reports to the developers.
20704 @cindex @option{--debug-format}, @code{gdbserver} option
20705 The @option{--debug-format=option1[,option2,...]} option tells
20706 @code{gdbserver} to include additional information in each output.
20707 Possible options are:
20711 Turn off all extra information in debugging output.
20713 Turn on all extra information in debugging output.
20715 Include a timestamp in each line of debugging output.
20718 Options are processed in order. Thus, for example, if @option{none}
20719 appears last then no additional information is added to debugging output.
20721 @cindex @option{--wrapper}, @code{gdbserver} option
20722 The @option{--wrapper} option specifies a wrapper to launch programs
20723 for debugging. The option should be followed by the name of the
20724 wrapper, then any command-line arguments to pass to the wrapper, then
20725 @kbd{--} indicating the end of the wrapper arguments.
20727 @code{gdbserver} runs the specified wrapper program with a combined
20728 command line including the wrapper arguments, then the name of the
20729 program to debug, then any arguments to the program. The wrapper
20730 runs until it executes your program, and then @value{GDBN} gains control.
20732 You can use any program that eventually calls @code{execve} with
20733 its arguments as a wrapper. Several standard Unix utilities do
20734 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
20735 with @code{exec "$@@"} will also work.
20737 For example, you can use @code{env} to pass an environment variable to
20738 the debugged program, without setting the variable in @code{gdbserver}'s
20742 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
20745 @cindex @option{--selftest}
20746 The @option{--selftest} option runs the self tests in @code{gdbserver}:
20749 $ gdbserver --selftest
20750 Ran 2 unit tests, 0 failed
20753 These tests are disabled in release.
20754 @subsection Connecting to @code{gdbserver}
20756 The basic procedure for connecting to the remote target is:
20760 Run @value{GDBN} on the host system.
20763 Make sure you have the necessary symbol files
20764 (@pxref{Host and target files}).
20765 Load symbols for your application using the @code{file} command before you
20766 connect. Use @code{set sysroot} to locate target libraries (unless your
20767 @value{GDBN} was compiled with the correct sysroot using
20768 @code{--with-sysroot}).
20771 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
20772 For TCP connections, you must start up @code{gdbserver} prior to using
20773 the @code{target} command. Otherwise you may get an error whose
20774 text depends on the host system, but which usually looks something like
20775 @samp{Connection refused}. Don't use the @code{load}
20776 command in @value{GDBN} when using @code{target remote} mode, since the
20777 program is already on the target.
20781 @anchor{Monitor Commands for gdbserver}
20782 @subsection Monitor Commands for @code{gdbserver}
20783 @cindex monitor commands, for @code{gdbserver}
20785 During a @value{GDBN} session using @code{gdbserver}, you can use the
20786 @code{monitor} command to send special requests to @code{gdbserver}.
20787 Here are the available commands.
20791 List the available monitor commands.
20793 @item monitor set debug 0
20794 @itemx monitor set debug 1
20795 Disable or enable general debugging messages.
20797 @item monitor set remote-debug 0
20798 @itemx monitor set remote-debug 1
20799 Disable or enable specific debugging messages associated with the remote
20800 protocol (@pxref{Remote Protocol}).
20802 @item monitor set debug-format option1@r{[},option2,...@r{]}
20803 Specify additional text to add to debugging messages.
20804 Possible options are:
20808 Turn off all extra information in debugging output.
20810 Turn on all extra information in debugging output.
20812 Include a timestamp in each line of debugging output.
20815 Options are processed in order. Thus, for example, if @option{none}
20816 appears last then no additional information is added to debugging output.
20818 @item monitor set libthread-db-search-path [PATH]
20819 @cindex gdbserver, search path for @code{libthread_db}
20820 When this command is issued, @var{path} is a colon-separated list of
20821 directories to search for @code{libthread_db} (@pxref{Threads,,set
20822 libthread-db-search-path}). If you omit @var{path},
20823 @samp{libthread-db-search-path} will be reset to its default value.
20825 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
20826 not supported in @code{gdbserver}.
20829 Tell gdbserver to exit immediately. This command should be followed by
20830 @code{disconnect} to close the debugging session. @code{gdbserver} will
20831 detach from any attached processes and kill any processes it created.
20832 Use @code{monitor exit} to terminate @code{gdbserver} at the end
20833 of a multi-process mode debug session.
20837 @subsection Tracepoints support in @code{gdbserver}
20838 @cindex tracepoints support in @code{gdbserver}
20840 On some targets, @code{gdbserver} supports tracepoints, fast
20841 tracepoints and static tracepoints.
20843 For fast or static tracepoints to work, a special library called the
20844 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
20845 This library is built and distributed as an integral part of
20846 @code{gdbserver}. In addition, support for static tracepoints
20847 requires building the in-process agent library with static tracepoints
20848 support. At present, the UST (LTTng Userspace Tracer,
20849 @url{http://lttng.org/ust}) tracing engine is supported. This support
20850 is automatically available if UST development headers are found in the
20851 standard include path when @code{gdbserver} is built, or if
20852 @code{gdbserver} was explicitly configured using @option{--with-ust}
20853 to point at such headers. You can explicitly disable the support
20854 using @option{--with-ust=no}.
20856 There are several ways to load the in-process agent in your program:
20859 @item Specifying it as dependency at link time
20861 You can link your program dynamically with the in-process agent
20862 library. On most systems, this is accomplished by adding
20863 @code{-linproctrace} to the link command.
20865 @item Using the system's preloading mechanisms
20867 You can force loading the in-process agent at startup time by using
20868 your system's support for preloading shared libraries. Many Unixes
20869 support the concept of preloading user defined libraries. In most
20870 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
20871 in the environment. See also the description of @code{gdbserver}'s
20872 @option{--wrapper} command line option.
20874 @item Using @value{GDBN} to force loading the agent at run time
20876 On some systems, you can force the inferior to load a shared library,
20877 by calling a dynamic loader function in the inferior that takes care
20878 of dynamically looking up and loading a shared library. On most Unix
20879 systems, the function is @code{dlopen}. You'll use the @code{call}
20880 command for that. For example:
20883 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
20886 Note that on most Unix systems, for the @code{dlopen} function to be
20887 available, the program needs to be linked with @code{-ldl}.
20890 On systems that have a userspace dynamic loader, like most Unix
20891 systems, when you connect to @code{gdbserver} using @code{target
20892 remote}, you'll find that the program is stopped at the dynamic
20893 loader's entry point, and no shared library has been loaded in the
20894 program's address space yet, including the in-process agent. In that
20895 case, before being able to use any of the fast or static tracepoints
20896 features, you need to let the loader run and load the shared
20897 libraries. The simplest way to do that is to run the program to the
20898 main procedure. E.g., if debugging a C or C@t{++} program, start
20899 @code{gdbserver} like so:
20902 $ gdbserver :9999 myprogram
20905 Start GDB and connect to @code{gdbserver} like so, and run to main:
20909 (@value{GDBP}) target remote myhost:9999
20910 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
20911 (@value{GDBP}) b main
20912 (@value{GDBP}) continue
20915 The in-process tracing agent library should now be loaded into the
20916 process; you can confirm it with the @code{info sharedlibrary}
20917 command, which will list @file{libinproctrace.so} as loaded in the
20918 process. You are now ready to install fast tracepoints, list static
20919 tracepoint markers, probe static tracepoints markers, and start
20922 @node Remote Configuration
20923 @section Remote Configuration
20926 @kindex show remote
20927 This section documents the configuration options available when
20928 debugging remote programs. For the options related to the File I/O
20929 extensions of the remote protocol, see @ref{system,
20930 system-call-allowed}.
20933 @item set remoteaddresssize @var{bits}
20934 @cindex address size for remote targets
20935 @cindex bits in remote address
20936 Set the maximum size of address in a memory packet to the specified
20937 number of bits. @value{GDBN} will mask off the address bits above
20938 that number, when it passes addresses to the remote target. The
20939 default value is the number of bits in the target's address.
20941 @item show remoteaddresssize
20942 Show the current value of remote address size in bits.
20944 @item set serial baud @var{n}
20945 @cindex baud rate for remote targets
20946 Set the baud rate for the remote serial I/O to @var{n} baud. The
20947 value is used to set the speed of the serial port used for debugging
20950 @item show serial baud
20951 Show the current speed of the remote connection.
20953 @item set serial parity @var{parity}
20954 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
20955 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
20957 @item show serial parity
20958 Show the current parity of the serial port.
20960 @item set remotebreak
20961 @cindex interrupt remote programs
20962 @cindex BREAK signal instead of Ctrl-C
20963 @anchor{set remotebreak}
20964 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
20965 when you type @kbd{Ctrl-c} to interrupt the program running
20966 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
20967 character instead. The default is off, since most remote systems
20968 expect to see @samp{Ctrl-C} as the interrupt signal.
20970 @item show remotebreak
20971 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
20972 interrupt the remote program.
20974 @item set remoteflow on
20975 @itemx set remoteflow off
20976 @kindex set remoteflow
20977 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
20978 on the serial port used to communicate to the remote target.
20980 @item show remoteflow
20981 @kindex show remoteflow
20982 Show the current setting of hardware flow control.
20984 @item set remotelogbase @var{base}
20985 Set the base (a.k.a.@: radix) of logging serial protocol
20986 communications to @var{base}. Supported values of @var{base} are:
20987 @code{ascii}, @code{octal}, and @code{hex}. The default is
20990 @item show remotelogbase
20991 Show the current setting of the radix for logging remote serial
20994 @item set remotelogfile @var{file}
20995 @cindex record serial communications on file
20996 Record remote serial communications on the named @var{file}. The
20997 default is not to record at all.
20999 @item show remotelogfile.
21000 Show the current setting of the file name on which to record the
21001 serial communications.
21003 @item set remotetimeout @var{num}
21004 @cindex timeout for serial communications
21005 @cindex remote timeout
21006 Set the timeout limit to wait for the remote target to respond to
21007 @var{num} seconds. The default is 2 seconds.
21009 @item show remotetimeout
21010 Show the current number of seconds to wait for the remote target
21013 @cindex limit hardware breakpoints and watchpoints
21014 @cindex remote target, limit break- and watchpoints
21015 @anchor{set remote hardware-watchpoint-limit}
21016 @anchor{set remote hardware-breakpoint-limit}
21017 @item set remote hardware-watchpoint-limit @var{limit}
21018 @itemx set remote hardware-breakpoint-limit @var{limit}
21019 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
21020 watchpoints. A limit of -1, the default, is treated as unlimited.
21022 @cindex limit hardware watchpoints length
21023 @cindex remote target, limit watchpoints length
21024 @anchor{set remote hardware-watchpoint-length-limit}
21025 @item set remote hardware-watchpoint-length-limit @var{limit}
21026 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
21027 a remote hardware watchpoint. A limit of -1, the default, is treated
21030 @item show remote hardware-watchpoint-length-limit
21031 Show the current limit (in bytes) of the maximum length of
21032 a remote hardware watchpoint.
21034 @item set remote exec-file @var{filename}
21035 @itemx show remote exec-file
21036 @anchor{set remote exec-file}
21037 @cindex executable file, for remote target
21038 Select the file used for @code{run} with @code{target
21039 extended-remote}. This should be set to a filename valid on the
21040 target system. If it is not set, the target will use a default
21041 filename (e.g.@: the last program run).
21043 @item set remote interrupt-sequence
21044 @cindex interrupt remote programs
21045 @cindex select Ctrl-C, BREAK or BREAK-g
21046 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
21047 @samp{BREAK-g} as the
21048 sequence to the remote target in order to interrupt the execution.
21049 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
21050 is high level of serial line for some certain time.
21051 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
21052 It is @code{BREAK} signal followed by character @code{g}.
21054 @item show interrupt-sequence
21055 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
21056 is sent by @value{GDBN} to interrupt the remote program.
21057 @code{BREAK-g} is BREAK signal followed by @code{g} and
21058 also known as Magic SysRq g.
21060 @item set remote interrupt-on-connect
21061 @cindex send interrupt-sequence on start
21062 Specify whether interrupt-sequence is sent to remote target when
21063 @value{GDBN} connects to it. This is mostly needed when you debug
21064 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
21065 which is known as Magic SysRq g in order to connect @value{GDBN}.
21067 @item show interrupt-on-connect
21068 Show whether interrupt-sequence is sent
21069 to remote target when @value{GDBN} connects to it.
21073 @item set tcp auto-retry on
21074 @cindex auto-retry, for remote TCP target
21075 Enable auto-retry for remote TCP connections. This is useful if the remote
21076 debugging agent is launched in parallel with @value{GDBN}; there is a race
21077 condition because the agent may not become ready to accept the connection
21078 before @value{GDBN} attempts to connect. When auto-retry is
21079 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
21080 to establish the connection using the timeout specified by
21081 @code{set tcp connect-timeout}.
21083 @item set tcp auto-retry off
21084 Do not auto-retry failed TCP connections.
21086 @item show tcp auto-retry
21087 Show the current auto-retry setting.
21089 @item set tcp connect-timeout @var{seconds}
21090 @itemx set tcp connect-timeout unlimited
21091 @cindex connection timeout, for remote TCP target
21092 @cindex timeout, for remote target connection
21093 Set the timeout for establishing a TCP connection to the remote target to
21094 @var{seconds}. The timeout affects both polling to retry failed connections
21095 (enabled by @code{set tcp auto-retry on}) and waiting for connections
21096 that are merely slow to complete, and represents an approximate cumulative
21097 value. If @var{seconds} is @code{unlimited}, there is no timeout and
21098 @value{GDBN} will keep attempting to establish a connection forever,
21099 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
21101 @item show tcp connect-timeout
21102 Show the current connection timeout setting.
21105 @cindex remote packets, enabling and disabling
21106 The @value{GDBN} remote protocol autodetects the packets supported by
21107 your debugging stub. If you need to override the autodetection, you
21108 can use these commands to enable or disable individual packets. Each
21109 packet can be set to @samp{on} (the remote target supports this
21110 packet), @samp{off} (the remote target does not support this packet),
21111 or @samp{auto} (detect remote target support for this packet). They
21112 all default to @samp{auto}. For more information about each packet,
21113 see @ref{Remote Protocol}.
21115 During normal use, you should not have to use any of these commands.
21116 If you do, that may be a bug in your remote debugging stub, or a bug
21117 in @value{GDBN}. You may want to report the problem to the
21118 @value{GDBN} developers.
21120 For each packet @var{name}, the command to enable or disable the
21121 packet is @code{set remote @var{name}-packet}. The available settings
21124 @multitable @columnfractions 0.28 0.32 0.25
21127 @tab Related Features
21129 @item @code{fetch-register}
21131 @tab @code{info registers}
21133 @item @code{set-register}
21137 @item @code{binary-download}
21139 @tab @code{load}, @code{set}
21141 @item @code{read-aux-vector}
21142 @tab @code{qXfer:auxv:read}
21143 @tab @code{info auxv}
21145 @item @code{symbol-lookup}
21146 @tab @code{qSymbol}
21147 @tab Detecting multiple threads
21149 @item @code{attach}
21150 @tab @code{vAttach}
21153 @item @code{verbose-resume}
21155 @tab Stepping or resuming multiple threads
21161 @item @code{software-breakpoint}
21165 @item @code{hardware-breakpoint}
21169 @item @code{write-watchpoint}
21173 @item @code{read-watchpoint}
21177 @item @code{access-watchpoint}
21181 @item @code{pid-to-exec-file}
21182 @tab @code{qXfer:exec-file:read}
21183 @tab @code{attach}, @code{run}
21185 @item @code{target-features}
21186 @tab @code{qXfer:features:read}
21187 @tab @code{set architecture}
21189 @item @code{library-info}
21190 @tab @code{qXfer:libraries:read}
21191 @tab @code{info sharedlibrary}
21193 @item @code{memory-map}
21194 @tab @code{qXfer:memory-map:read}
21195 @tab @code{info mem}
21197 @item @code{read-sdata-object}
21198 @tab @code{qXfer:sdata:read}
21199 @tab @code{print $_sdata}
21201 @item @code{read-spu-object}
21202 @tab @code{qXfer:spu:read}
21203 @tab @code{info spu}
21205 @item @code{write-spu-object}
21206 @tab @code{qXfer:spu:write}
21207 @tab @code{info spu}
21209 @item @code{read-siginfo-object}
21210 @tab @code{qXfer:siginfo:read}
21211 @tab @code{print $_siginfo}
21213 @item @code{write-siginfo-object}
21214 @tab @code{qXfer:siginfo:write}
21215 @tab @code{set $_siginfo}
21217 @item @code{threads}
21218 @tab @code{qXfer:threads:read}
21219 @tab @code{info threads}
21221 @item @code{get-thread-local-@*storage-address}
21222 @tab @code{qGetTLSAddr}
21223 @tab Displaying @code{__thread} variables
21225 @item @code{get-thread-information-block-address}
21226 @tab @code{qGetTIBAddr}
21227 @tab Display MS-Windows Thread Information Block.
21229 @item @code{search-memory}
21230 @tab @code{qSearch:memory}
21233 @item @code{supported-packets}
21234 @tab @code{qSupported}
21235 @tab Remote communications parameters
21237 @item @code{catch-syscalls}
21238 @tab @code{QCatchSyscalls}
21239 @tab @code{catch syscall}
21241 @item @code{pass-signals}
21242 @tab @code{QPassSignals}
21243 @tab @code{handle @var{signal}}
21245 @item @code{program-signals}
21246 @tab @code{QProgramSignals}
21247 @tab @code{handle @var{signal}}
21249 @item @code{hostio-close-packet}
21250 @tab @code{vFile:close}
21251 @tab @code{remote get}, @code{remote put}
21253 @item @code{hostio-open-packet}
21254 @tab @code{vFile:open}
21255 @tab @code{remote get}, @code{remote put}
21257 @item @code{hostio-pread-packet}
21258 @tab @code{vFile:pread}
21259 @tab @code{remote get}, @code{remote put}
21261 @item @code{hostio-pwrite-packet}
21262 @tab @code{vFile:pwrite}
21263 @tab @code{remote get}, @code{remote put}
21265 @item @code{hostio-unlink-packet}
21266 @tab @code{vFile:unlink}
21267 @tab @code{remote delete}
21269 @item @code{hostio-readlink-packet}
21270 @tab @code{vFile:readlink}
21273 @item @code{hostio-fstat-packet}
21274 @tab @code{vFile:fstat}
21277 @item @code{hostio-setfs-packet}
21278 @tab @code{vFile:setfs}
21281 @item @code{noack-packet}
21282 @tab @code{QStartNoAckMode}
21283 @tab Packet acknowledgment
21285 @item @code{osdata}
21286 @tab @code{qXfer:osdata:read}
21287 @tab @code{info os}
21289 @item @code{query-attached}
21290 @tab @code{qAttached}
21291 @tab Querying remote process attach state.
21293 @item @code{trace-buffer-size}
21294 @tab @code{QTBuffer:size}
21295 @tab @code{set trace-buffer-size}
21297 @item @code{trace-status}
21298 @tab @code{qTStatus}
21299 @tab @code{tstatus}
21301 @item @code{traceframe-info}
21302 @tab @code{qXfer:traceframe-info:read}
21303 @tab Traceframe info
21305 @item @code{install-in-trace}
21306 @tab @code{InstallInTrace}
21307 @tab Install tracepoint in tracing
21309 @item @code{disable-randomization}
21310 @tab @code{QDisableRandomization}
21311 @tab @code{set disable-randomization}
21313 @item @code{startup-with-shell}
21314 @tab @code{QStartupWithShell}
21315 @tab @code{set startup-with-shell}
21317 @item @code{environment-hex-encoded}
21318 @tab @code{QEnvironmentHexEncoded}
21319 @tab @code{set environment}
21321 @item @code{environment-unset}
21322 @tab @code{QEnvironmentUnset}
21323 @tab @code{unset environment}
21325 @item @code{environment-reset}
21326 @tab @code{QEnvironmentReset}
21327 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
21329 @item @code{set-working-dir}
21330 @tab @code{QSetWorkingDir}
21331 @tab @code{set cwd}
21333 @item @code{conditional-breakpoints-packet}
21334 @tab @code{Z0 and Z1}
21335 @tab @code{Support for target-side breakpoint condition evaluation}
21337 @item @code{multiprocess-extensions}
21338 @tab @code{multiprocess extensions}
21339 @tab Debug multiple processes and remote process PID awareness
21341 @item @code{swbreak-feature}
21342 @tab @code{swbreak stop reason}
21345 @item @code{hwbreak-feature}
21346 @tab @code{hwbreak stop reason}
21349 @item @code{fork-event-feature}
21350 @tab @code{fork stop reason}
21353 @item @code{vfork-event-feature}
21354 @tab @code{vfork stop reason}
21357 @item @code{exec-event-feature}
21358 @tab @code{exec stop reason}
21361 @item @code{thread-events}
21362 @tab @code{QThreadEvents}
21363 @tab Tracking thread lifetime.
21365 @item @code{no-resumed-stop-reply}
21366 @tab @code{no resumed thread left stop reply}
21367 @tab Tracking thread lifetime.
21372 @section Implementing a Remote Stub
21374 @cindex debugging stub, example
21375 @cindex remote stub, example
21376 @cindex stub example, remote debugging
21377 The stub files provided with @value{GDBN} implement the target side of the
21378 communication protocol, and the @value{GDBN} side is implemented in the
21379 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
21380 these subroutines to communicate, and ignore the details. (If you're
21381 implementing your own stub file, you can still ignore the details: start
21382 with one of the existing stub files. @file{sparc-stub.c} is the best
21383 organized, and therefore the easiest to read.)
21385 @cindex remote serial debugging, overview
21386 To debug a program running on another machine (the debugging
21387 @dfn{target} machine), you must first arrange for all the usual
21388 prerequisites for the program to run by itself. For example, for a C
21393 A startup routine to set up the C runtime environment; these usually
21394 have a name like @file{crt0}. The startup routine may be supplied by
21395 your hardware supplier, or you may have to write your own.
21398 A C subroutine library to support your program's
21399 subroutine calls, notably managing input and output.
21402 A way of getting your program to the other machine---for example, a
21403 download program. These are often supplied by the hardware
21404 manufacturer, but you may have to write your own from hardware
21408 The next step is to arrange for your program to use a serial port to
21409 communicate with the machine where @value{GDBN} is running (the @dfn{host}
21410 machine). In general terms, the scheme looks like this:
21414 @value{GDBN} already understands how to use this protocol; when everything
21415 else is set up, you can simply use the @samp{target remote} command
21416 (@pxref{Targets,,Specifying a Debugging Target}).
21418 @item On the target,
21419 you must link with your program a few special-purpose subroutines that
21420 implement the @value{GDBN} remote serial protocol. The file containing these
21421 subroutines is called a @dfn{debugging stub}.
21423 On certain remote targets, you can use an auxiliary program
21424 @code{gdbserver} instead of linking a stub into your program.
21425 @xref{Server,,Using the @code{gdbserver} Program}, for details.
21428 The debugging stub is specific to the architecture of the remote
21429 machine; for example, use @file{sparc-stub.c} to debug programs on
21432 @cindex remote serial stub list
21433 These working remote stubs are distributed with @value{GDBN}:
21438 @cindex @file{i386-stub.c}
21441 For Intel 386 and compatible architectures.
21444 @cindex @file{m68k-stub.c}
21445 @cindex Motorola 680x0
21447 For Motorola 680x0 architectures.
21450 @cindex @file{sh-stub.c}
21453 For Renesas SH architectures.
21456 @cindex @file{sparc-stub.c}
21458 For @sc{sparc} architectures.
21460 @item sparcl-stub.c
21461 @cindex @file{sparcl-stub.c}
21464 For Fujitsu @sc{sparclite} architectures.
21468 The @file{README} file in the @value{GDBN} distribution may list other
21469 recently added stubs.
21472 * Stub Contents:: What the stub can do for you
21473 * Bootstrapping:: What you must do for the stub
21474 * Debug Session:: Putting it all together
21477 @node Stub Contents
21478 @subsection What the Stub Can Do for You
21480 @cindex remote serial stub
21481 The debugging stub for your architecture supplies these three
21485 @item set_debug_traps
21486 @findex set_debug_traps
21487 @cindex remote serial stub, initialization
21488 This routine arranges for @code{handle_exception} to run when your
21489 program stops. You must call this subroutine explicitly in your
21490 program's startup code.
21492 @item handle_exception
21493 @findex handle_exception
21494 @cindex remote serial stub, main routine
21495 This is the central workhorse, but your program never calls it
21496 explicitly---the setup code arranges for @code{handle_exception} to
21497 run when a trap is triggered.
21499 @code{handle_exception} takes control when your program stops during
21500 execution (for example, on a breakpoint), and mediates communications
21501 with @value{GDBN} on the host machine. This is where the communications
21502 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
21503 representative on the target machine. It begins by sending summary
21504 information on the state of your program, then continues to execute,
21505 retrieving and transmitting any information @value{GDBN} needs, until you
21506 execute a @value{GDBN} command that makes your program resume; at that point,
21507 @code{handle_exception} returns control to your own code on the target
21511 @cindex @code{breakpoint} subroutine, remote
21512 Use this auxiliary subroutine to make your program contain a
21513 breakpoint. Depending on the particular situation, this may be the only
21514 way for @value{GDBN} to get control. For instance, if your target
21515 machine has some sort of interrupt button, you won't need to call this;
21516 pressing the interrupt button transfers control to
21517 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
21518 simply receiving characters on the serial port may also trigger a trap;
21519 again, in that situation, you don't need to call @code{breakpoint} from
21520 your own program---simply running @samp{target remote} from the host
21521 @value{GDBN} session gets control.
21523 Call @code{breakpoint} if none of these is true, or if you simply want
21524 to make certain your program stops at a predetermined point for the
21525 start of your debugging session.
21528 @node Bootstrapping
21529 @subsection What You Must Do for the Stub
21531 @cindex remote stub, support routines
21532 The debugging stubs that come with @value{GDBN} are set up for a particular
21533 chip architecture, but they have no information about the rest of your
21534 debugging target machine.
21536 First of all you need to tell the stub how to communicate with the
21540 @item int getDebugChar()
21541 @findex getDebugChar
21542 Write this subroutine to read a single character from the serial port.
21543 It may be identical to @code{getchar} for your target system; a
21544 different name is used to allow you to distinguish the two if you wish.
21546 @item void putDebugChar(int)
21547 @findex putDebugChar
21548 Write this subroutine to write a single character to the serial port.
21549 It may be identical to @code{putchar} for your target system; a
21550 different name is used to allow you to distinguish the two if you wish.
21553 @cindex control C, and remote debugging
21554 @cindex interrupting remote targets
21555 If you want @value{GDBN} to be able to stop your program while it is
21556 running, you need to use an interrupt-driven serial driver, and arrange
21557 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
21558 character). That is the character which @value{GDBN} uses to tell the
21559 remote system to stop.
21561 Getting the debugging target to return the proper status to @value{GDBN}
21562 probably requires changes to the standard stub; one quick and dirty way
21563 is to just execute a breakpoint instruction (the ``dirty'' part is that
21564 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
21566 Other routines you need to supply are:
21569 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
21570 @findex exceptionHandler
21571 Write this function to install @var{exception_address} in the exception
21572 handling tables. You need to do this because the stub does not have any
21573 way of knowing what the exception handling tables on your target system
21574 are like (for example, the processor's table might be in @sc{rom},
21575 containing entries which point to a table in @sc{ram}).
21576 The @var{exception_number} specifies the exception which should be changed;
21577 its meaning is architecture-dependent (for example, different numbers
21578 might represent divide by zero, misaligned access, etc). When this
21579 exception occurs, control should be transferred directly to
21580 @var{exception_address}, and the processor state (stack, registers,
21581 and so on) should be just as it is when a processor exception occurs. So if
21582 you want to use a jump instruction to reach @var{exception_address}, it
21583 should be a simple jump, not a jump to subroutine.
21585 For the 386, @var{exception_address} should be installed as an interrupt
21586 gate so that interrupts are masked while the handler runs. The gate
21587 should be at privilege level 0 (the most privileged level). The
21588 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
21589 help from @code{exceptionHandler}.
21591 @item void flush_i_cache()
21592 @findex flush_i_cache
21593 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
21594 instruction cache, if any, on your target machine. If there is no
21595 instruction cache, this subroutine may be a no-op.
21597 On target machines that have instruction caches, @value{GDBN} requires this
21598 function to make certain that the state of your program is stable.
21602 You must also make sure this library routine is available:
21605 @item void *memset(void *, int, int)
21607 This is the standard library function @code{memset} that sets an area of
21608 memory to a known value. If you have one of the free versions of
21609 @code{libc.a}, @code{memset} can be found there; otherwise, you must
21610 either obtain it from your hardware manufacturer, or write your own.
21613 If you do not use the GNU C compiler, you may need other standard
21614 library subroutines as well; this varies from one stub to another,
21615 but in general the stubs are likely to use any of the common library
21616 subroutines which @code{@value{NGCC}} generates as inline code.
21619 @node Debug Session
21620 @subsection Putting it All Together
21622 @cindex remote serial debugging summary
21623 In summary, when your program is ready to debug, you must follow these
21628 Make sure you have defined the supporting low-level routines
21629 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
21631 @code{getDebugChar}, @code{putDebugChar},
21632 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
21636 Insert these lines in your program's startup code, before the main
21637 procedure is called:
21644 On some machines, when a breakpoint trap is raised, the hardware
21645 automatically makes the PC point to the instruction after the
21646 breakpoint. If your machine doesn't do that, you may need to adjust
21647 @code{handle_exception} to arrange for it to return to the instruction
21648 after the breakpoint on this first invocation, so that your program
21649 doesn't keep hitting the initial breakpoint instead of making
21653 For the 680x0 stub only, you need to provide a variable called
21654 @code{exceptionHook}. Normally you just use:
21657 void (*exceptionHook)() = 0;
21661 but if before calling @code{set_debug_traps}, you set it to point to a
21662 function in your program, that function is called when
21663 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
21664 error). The function indicated by @code{exceptionHook} is called with
21665 one parameter: an @code{int} which is the exception number.
21668 Compile and link together: your program, the @value{GDBN} debugging stub for
21669 your target architecture, and the supporting subroutines.
21672 Make sure you have a serial connection between your target machine and
21673 the @value{GDBN} host, and identify the serial port on the host.
21676 @c The "remote" target now provides a `load' command, so we should
21677 @c document that. FIXME.
21678 Download your program to your target machine (or get it there by
21679 whatever means the manufacturer provides), and start it.
21682 Start @value{GDBN} on the host, and connect to the target
21683 (@pxref{Connecting,,Connecting to a Remote Target}).
21687 @node Configurations
21688 @chapter Configuration-Specific Information
21690 While nearly all @value{GDBN} commands are available for all native and
21691 cross versions of the debugger, there are some exceptions. This chapter
21692 describes things that are only available in certain configurations.
21694 There are three major categories of configurations: native
21695 configurations, where the host and target are the same, embedded
21696 operating system configurations, which are usually the same for several
21697 different processor architectures, and bare embedded processors, which
21698 are quite different from each other.
21703 * Embedded Processors::
21710 This section describes details specific to particular native
21714 * BSD libkvm Interface:: Debugging BSD kernel memory images
21715 * Process Information:: Process information
21716 * DJGPP Native:: Features specific to the DJGPP port
21717 * Cygwin Native:: Features specific to the Cygwin port
21718 * Hurd Native:: Features specific to @sc{gnu} Hurd
21719 * Darwin:: Features specific to Darwin
21722 @node BSD libkvm Interface
21723 @subsection BSD libkvm Interface
21726 @cindex kernel memory image
21727 @cindex kernel crash dump
21729 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
21730 interface that provides a uniform interface for accessing kernel virtual
21731 memory images, including live systems and crash dumps. @value{GDBN}
21732 uses this interface to allow you to debug live kernels and kernel crash
21733 dumps on many native BSD configurations. This is implemented as a
21734 special @code{kvm} debugging target. For debugging a live system, load
21735 the currently running kernel into @value{GDBN} and connect to the
21739 (@value{GDBP}) @b{target kvm}
21742 For debugging crash dumps, provide the file name of the crash dump as an
21746 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
21749 Once connected to the @code{kvm} target, the following commands are
21755 Set current context from the @dfn{Process Control Block} (PCB) address.
21758 Set current context from proc address. This command isn't available on
21759 modern FreeBSD systems.
21762 @node Process Information
21763 @subsection Process Information
21765 @cindex examine process image
21766 @cindex process info via @file{/proc}
21768 Some operating systems provide interfaces to fetch additional
21769 information about running processes beyond memory and per-thread
21770 register state. If @value{GDBN} is configured for an operating system
21771 with a supported interface, the command @code{info proc} is available
21772 to report information about the process running your program, or about
21773 any process running on your system.
21775 One supported interface is a facility called @samp{/proc} that can be
21776 used to examine the image of a running process using file-system
21777 subroutines. This facility is supported on @sc{gnu}/Linux and Solaris
21780 On FreeBSD systems, system control nodes are used to query process
21783 In addition, some systems may provide additional process information
21784 in core files. Note that a core file may include a subset of the
21785 information available from a live process. Process information is
21786 currently avaiable from cores created on @sc{gnu}/Linux and FreeBSD
21793 @itemx info proc @var{process-id}
21794 Summarize available information about any running process. If a
21795 process ID is specified by @var{process-id}, display information about
21796 that process; otherwise display information about the program being
21797 debugged. The summary includes the debugged process ID, the command
21798 line used to invoke it, its current working directory, and its
21799 executable file's absolute file name.
21801 On some systems, @var{process-id} can be of the form
21802 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
21803 within a process. If the optional @var{pid} part is missing, it means
21804 a thread from the process being debugged (the leading @samp{/} still
21805 needs to be present, or else @value{GDBN} will interpret the number as
21806 a process ID rather than a thread ID).
21808 @item info proc cmdline
21809 @cindex info proc cmdline
21810 Show the original command line of the process. This command is
21811 supported on @sc{gnu}/Linux and FreeBSD.
21813 @item info proc cwd
21814 @cindex info proc cwd
21815 Show the current working directory of the process. This command is
21816 supported on @sc{gnu}/Linux and FreeBSD.
21818 @item info proc exe
21819 @cindex info proc exe
21820 Show the name of executable of the process. This command is supported
21821 on @sc{gnu}/Linux and FreeBSD.
21823 @item info proc mappings
21824 @cindex memory address space mappings
21825 Report the memory address space ranges accessible in the program. On
21826 Solaris and FreeBSD systems, each memory range includes information on
21827 whether the process has read, write, or execute access rights to each
21828 range. On @sc{gnu}/Linux and FreeBSD systems, each memory range
21829 includes the object file which is mapped to that range.
21831 @item info proc stat
21832 @itemx info proc status
21833 @cindex process detailed status information
21834 Show additional process-related information, including the user ID and
21835 group ID; virtual memory usage; the signals that are pending, blocked,
21836 and ignored; its TTY; its consumption of system and user time; its
21837 stack size; its @samp{nice} value; etc. These commands are supported
21838 on @sc{gnu}/Linux and FreeBSD.
21840 For @sc{gnu}/Linux systems, see the @samp{proc} man page for more
21841 information (type @kbd{man 5 proc} from your shell prompt).
21843 For FreeBSD systems, @code{info proc stat} is an alias for @code{info
21846 @item info proc all
21847 Show all the information about the process described under all of the
21848 above @code{info proc} subcommands.
21851 @comment These sub-options of 'info proc' were not included when
21852 @comment procfs.c was re-written. Keep their descriptions around
21853 @comment against the day when someone finds the time to put them back in.
21854 @kindex info proc times
21855 @item info proc times
21856 Starting time, user CPU time, and system CPU time for your program and
21859 @kindex info proc id
21861 Report on the process IDs related to your program: its own process ID,
21862 the ID of its parent, the process group ID, and the session ID.
21865 @item set procfs-trace
21866 @kindex set procfs-trace
21867 @cindex @code{procfs} API calls
21868 This command enables and disables tracing of @code{procfs} API calls.
21870 @item show procfs-trace
21871 @kindex show procfs-trace
21872 Show the current state of @code{procfs} API call tracing.
21874 @item set procfs-file @var{file}
21875 @kindex set procfs-file
21876 Tell @value{GDBN} to write @code{procfs} API trace to the named
21877 @var{file}. @value{GDBN} appends the trace info to the previous
21878 contents of the file. The default is to display the trace on the
21881 @item show procfs-file
21882 @kindex show procfs-file
21883 Show the file to which @code{procfs} API trace is written.
21885 @item proc-trace-entry
21886 @itemx proc-trace-exit
21887 @itemx proc-untrace-entry
21888 @itemx proc-untrace-exit
21889 @kindex proc-trace-entry
21890 @kindex proc-trace-exit
21891 @kindex proc-untrace-entry
21892 @kindex proc-untrace-exit
21893 These commands enable and disable tracing of entries into and exits
21894 from the @code{syscall} interface.
21897 @kindex info pidlist
21898 @cindex process list, QNX Neutrino
21899 For QNX Neutrino only, this command displays the list of all the
21900 processes and all the threads within each process.
21903 @kindex info meminfo
21904 @cindex mapinfo list, QNX Neutrino
21905 For QNX Neutrino only, this command displays the list of all mapinfos.
21909 @subsection Features for Debugging @sc{djgpp} Programs
21910 @cindex @sc{djgpp} debugging
21911 @cindex native @sc{djgpp} debugging
21912 @cindex MS-DOS-specific commands
21915 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
21916 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
21917 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
21918 top of real-mode DOS systems and their emulations.
21920 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
21921 defines a few commands specific to the @sc{djgpp} port. This
21922 subsection describes those commands.
21927 This is a prefix of @sc{djgpp}-specific commands which print
21928 information about the target system and important OS structures.
21931 @cindex MS-DOS system info
21932 @cindex free memory information (MS-DOS)
21933 @item info dos sysinfo
21934 This command displays assorted information about the underlying
21935 platform: the CPU type and features, the OS version and flavor, the
21936 DPMI version, and the available conventional and DPMI memory.
21941 @cindex segment descriptor tables
21942 @cindex descriptor tables display
21944 @itemx info dos ldt
21945 @itemx info dos idt
21946 These 3 commands display entries from, respectively, Global, Local,
21947 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
21948 tables are data structures which store a descriptor for each segment
21949 that is currently in use. The segment's selector is an index into a
21950 descriptor table; the table entry for that index holds the
21951 descriptor's base address and limit, and its attributes and access
21954 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
21955 segment (used for both data and the stack), and a DOS segment (which
21956 allows access to DOS/BIOS data structures and absolute addresses in
21957 conventional memory). However, the DPMI host will usually define
21958 additional segments in order to support the DPMI environment.
21960 @cindex garbled pointers
21961 These commands allow to display entries from the descriptor tables.
21962 Without an argument, all entries from the specified table are
21963 displayed. An argument, which should be an integer expression, means
21964 display a single entry whose index is given by the argument. For
21965 example, here's a convenient way to display information about the
21966 debugged program's data segment:
21969 @exdent @code{(@value{GDBP}) info dos ldt $ds}
21970 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
21974 This comes in handy when you want to see whether a pointer is outside
21975 the data segment's limit (i.e.@: @dfn{garbled}).
21977 @cindex page tables display (MS-DOS)
21979 @itemx info dos pte
21980 These two commands display entries from, respectively, the Page
21981 Directory and the Page Tables. Page Directories and Page Tables are
21982 data structures which control how virtual memory addresses are mapped
21983 into physical addresses. A Page Table includes an entry for every
21984 page of memory that is mapped into the program's address space; there
21985 may be several Page Tables, each one holding up to 4096 entries. A
21986 Page Directory has up to 4096 entries, one each for every Page Table
21987 that is currently in use.
21989 Without an argument, @kbd{info dos pde} displays the entire Page
21990 Directory, and @kbd{info dos pte} displays all the entries in all of
21991 the Page Tables. An argument, an integer expression, given to the
21992 @kbd{info dos pde} command means display only that entry from the Page
21993 Directory table. An argument given to the @kbd{info dos pte} command
21994 means display entries from a single Page Table, the one pointed to by
21995 the specified entry in the Page Directory.
21997 @cindex direct memory access (DMA) on MS-DOS
21998 These commands are useful when your program uses @dfn{DMA} (Direct
21999 Memory Access), which needs physical addresses to program the DMA
22002 These commands are supported only with some DPMI servers.
22004 @cindex physical address from linear address
22005 @item info dos address-pte @var{addr}
22006 This command displays the Page Table entry for a specified linear
22007 address. The argument @var{addr} is a linear address which should
22008 already have the appropriate segment's base address added to it,
22009 because this command accepts addresses which may belong to @emph{any}
22010 segment. For example, here's how to display the Page Table entry for
22011 the page where a variable @code{i} is stored:
22014 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
22015 @exdent @code{Page Table entry for address 0x11a00d30:}
22016 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
22020 This says that @code{i} is stored at offset @code{0xd30} from the page
22021 whose physical base address is @code{0x02698000}, and shows all the
22022 attributes of that page.
22024 Note that you must cast the addresses of variables to a @code{char *},
22025 since otherwise the value of @code{__djgpp_base_address}, the base
22026 address of all variables and functions in a @sc{djgpp} program, will
22027 be added using the rules of C pointer arithmetics: if @code{i} is
22028 declared an @code{int}, @value{GDBN} will add 4 times the value of
22029 @code{__djgpp_base_address} to the address of @code{i}.
22031 Here's another example, it displays the Page Table entry for the
22035 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
22036 @exdent @code{Page Table entry for address 0x29110:}
22037 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
22041 (The @code{+ 3} offset is because the transfer buffer's address is the
22042 3rd member of the @code{_go32_info_block} structure.) The output
22043 clearly shows that this DPMI server maps the addresses in conventional
22044 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
22045 linear (@code{0x29110}) addresses are identical.
22047 This command is supported only with some DPMI servers.
22050 @cindex DOS serial data link, remote debugging
22051 In addition to native debugging, the DJGPP port supports remote
22052 debugging via a serial data link. The following commands are specific
22053 to remote serial debugging in the DJGPP port of @value{GDBN}.
22056 @kindex set com1base
22057 @kindex set com1irq
22058 @kindex set com2base
22059 @kindex set com2irq
22060 @kindex set com3base
22061 @kindex set com3irq
22062 @kindex set com4base
22063 @kindex set com4irq
22064 @item set com1base @var{addr}
22065 This command sets the base I/O port address of the @file{COM1} serial
22068 @item set com1irq @var{irq}
22069 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
22070 for the @file{COM1} serial port.
22072 There are similar commands @samp{set com2base}, @samp{set com3irq},
22073 etc.@: for setting the port address and the @code{IRQ} lines for the
22076 @kindex show com1base
22077 @kindex show com1irq
22078 @kindex show com2base
22079 @kindex show com2irq
22080 @kindex show com3base
22081 @kindex show com3irq
22082 @kindex show com4base
22083 @kindex show com4irq
22084 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
22085 display the current settings of the base address and the @code{IRQ}
22086 lines used by the COM ports.
22089 @kindex info serial
22090 @cindex DOS serial port status
22091 This command prints the status of the 4 DOS serial ports. For each
22092 port, it prints whether it's active or not, its I/O base address and
22093 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
22094 counts of various errors encountered so far.
22098 @node Cygwin Native
22099 @subsection Features for Debugging MS Windows PE Executables
22100 @cindex MS Windows debugging
22101 @cindex native Cygwin debugging
22102 @cindex Cygwin-specific commands
22104 @value{GDBN} supports native debugging of MS Windows programs, including
22105 DLLs with and without symbolic debugging information.
22107 @cindex Ctrl-BREAK, MS-Windows
22108 @cindex interrupt debuggee on MS-Windows
22109 MS-Windows programs that call @code{SetConsoleMode} to switch off the
22110 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
22111 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
22112 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
22113 sequence, which can be used to interrupt the debuggee even if it
22116 There are various additional Cygwin-specific commands, described in
22117 this section. Working with DLLs that have no debugging symbols is
22118 described in @ref{Non-debug DLL Symbols}.
22123 This is a prefix of MS Windows-specific commands which print
22124 information about the target system and important OS structures.
22126 @item info w32 selector
22127 This command displays information returned by
22128 the Win32 API @code{GetThreadSelectorEntry} function.
22129 It takes an optional argument that is evaluated to
22130 a long value to give the information about this given selector.
22131 Without argument, this command displays information
22132 about the six segment registers.
22134 @item info w32 thread-information-block
22135 This command displays thread specific information stored in the
22136 Thread Information Block (readable on the X86 CPU family using @code{$fs}
22137 selector for 32-bit programs and @code{$gs} for 64-bit programs).
22139 @kindex signal-event
22140 @item signal-event @var{id}
22141 This command signals an event with user-provided @var{id}. Used to resume
22142 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
22144 To use it, create or edit the following keys in
22145 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
22146 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
22147 (for x86_64 versions):
22151 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
22152 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
22153 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
22155 The first @code{%ld} will be replaced by the process ID of the
22156 crashing process, the second @code{%ld} will be replaced by the ID of
22157 the event that blocks the crashing process, waiting for @value{GDBN}
22161 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
22162 make the system run debugger specified by the Debugger key
22163 automatically, @code{0} will cause a dialog box with ``OK'' and
22164 ``Cancel'' buttons to appear, which allows the user to either
22165 terminate the crashing process (OK) or debug it (Cancel).
22168 @kindex set cygwin-exceptions
22169 @cindex debugging the Cygwin DLL
22170 @cindex Cygwin DLL, debugging
22171 @item set cygwin-exceptions @var{mode}
22172 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
22173 happen inside the Cygwin DLL. If @var{mode} is @code{off},
22174 @value{GDBN} will delay recognition of exceptions, and may ignore some
22175 exceptions which seem to be caused by internal Cygwin DLL
22176 ``bookkeeping''. This option is meant primarily for debugging the
22177 Cygwin DLL itself; the default value is @code{off} to avoid annoying
22178 @value{GDBN} users with false @code{SIGSEGV} signals.
22180 @kindex show cygwin-exceptions
22181 @item show cygwin-exceptions
22182 Displays whether @value{GDBN} will break on exceptions that happen
22183 inside the Cygwin DLL itself.
22185 @kindex set new-console
22186 @item set new-console @var{mode}
22187 If @var{mode} is @code{on} the debuggee will
22188 be started in a new console on next start.
22189 If @var{mode} is @code{off}, the debuggee will
22190 be started in the same console as the debugger.
22192 @kindex show new-console
22193 @item show new-console
22194 Displays whether a new console is used
22195 when the debuggee is started.
22197 @kindex set new-group
22198 @item set new-group @var{mode}
22199 This boolean value controls whether the debuggee should
22200 start a new group or stay in the same group as the debugger.
22201 This affects the way the Windows OS handles
22204 @kindex show new-group
22205 @item show new-group
22206 Displays current value of new-group boolean.
22208 @kindex set debugevents
22209 @item set debugevents
22210 This boolean value adds debug output concerning kernel events related
22211 to the debuggee seen by the debugger. This includes events that
22212 signal thread and process creation and exit, DLL loading and
22213 unloading, console interrupts, and debugging messages produced by the
22214 Windows @code{OutputDebugString} API call.
22216 @kindex set debugexec
22217 @item set debugexec
22218 This boolean value adds debug output concerning execute events
22219 (such as resume thread) seen by the debugger.
22221 @kindex set debugexceptions
22222 @item set debugexceptions
22223 This boolean value adds debug output concerning exceptions in the
22224 debuggee seen by the debugger.
22226 @kindex set debugmemory
22227 @item set debugmemory
22228 This boolean value adds debug output concerning debuggee memory reads
22229 and writes by the debugger.
22233 This boolean values specifies whether the debuggee is called
22234 via a shell or directly (default value is on).
22238 Displays if the debuggee will be started with a shell.
22243 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
22246 @node Non-debug DLL Symbols
22247 @subsubsection Support for DLLs without Debugging Symbols
22248 @cindex DLLs with no debugging symbols
22249 @cindex Minimal symbols and DLLs
22251 Very often on windows, some of the DLLs that your program relies on do
22252 not include symbolic debugging information (for example,
22253 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
22254 symbols in a DLL, it relies on the minimal amount of symbolic
22255 information contained in the DLL's export table. This section
22256 describes working with such symbols, known internally to @value{GDBN} as
22257 ``minimal symbols''.
22259 Note that before the debugged program has started execution, no DLLs
22260 will have been loaded. The easiest way around this problem is simply to
22261 start the program --- either by setting a breakpoint or letting the
22262 program run once to completion.
22264 @subsubsection DLL Name Prefixes
22266 In keeping with the naming conventions used by the Microsoft debugging
22267 tools, DLL export symbols are made available with a prefix based on the
22268 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
22269 also entered into the symbol table, so @code{CreateFileA} is often
22270 sufficient. In some cases there will be name clashes within a program
22271 (particularly if the executable itself includes full debugging symbols)
22272 necessitating the use of the fully qualified name when referring to the
22273 contents of the DLL. Use single-quotes around the name to avoid the
22274 exclamation mark (``!'') being interpreted as a language operator.
22276 Note that the internal name of the DLL may be all upper-case, even
22277 though the file name of the DLL is lower-case, or vice-versa. Since
22278 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
22279 some confusion. If in doubt, try the @code{info functions} and
22280 @code{info variables} commands or even @code{maint print msymbols}
22281 (@pxref{Symbols}). Here's an example:
22284 (@value{GDBP}) info function CreateFileA
22285 All functions matching regular expression "CreateFileA":
22287 Non-debugging symbols:
22288 0x77e885f4 CreateFileA
22289 0x77e885f4 KERNEL32!CreateFileA
22293 (@value{GDBP}) info function !
22294 All functions matching regular expression "!":
22296 Non-debugging symbols:
22297 0x6100114c cygwin1!__assert
22298 0x61004034 cygwin1!_dll_crt0@@0
22299 0x61004240 cygwin1!dll_crt0(per_process *)
22303 @subsubsection Working with Minimal Symbols
22305 Symbols extracted from a DLL's export table do not contain very much
22306 type information. All that @value{GDBN} can do is guess whether a symbol
22307 refers to a function or variable depending on the linker section that
22308 contains the symbol. Also note that the actual contents of the memory
22309 contained in a DLL are not available unless the program is running. This
22310 means that you cannot examine the contents of a variable or disassemble
22311 a function within a DLL without a running program.
22313 Variables are generally treated as pointers and dereferenced
22314 automatically. For this reason, it is often necessary to prefix a
22315 variable name with the address-of operator (``&'') and provide explicit
22316 type information in the command. Here's an example of the type of
22320 (@value{GDBP}) print 'cygwin1!__argv'
22321 'cygwin1!__argv' has unknown type; cast it to its declared type
22325 (@value{GDBP}) x 'cygwin1!__argv'
22326 'cygwin1!__argv' has unknown type; cast it to its declared type
22329 And two possible solutions:
22332 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
22333 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
22337 (@value{GDBP}) x/2x &'cygwin1!__argv'
22338 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
22339 (@value{GDBP}) x/x 0x10021608
22340 0x10021608: 0x0022fd98
22341 (@value{GDBP}) x/s 0x0022fd98
22342 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
22345 Setting a break point within a DLL is possible even before the program
22346 starts execution. However, under these circumstances, @value{GDBN} can't
22347 examine the initial instructions of the function in order to skip the
22348 function's frame set-up code. You can work around this by using ``*&''
22349 to set the breakpoint at a raw memory address:
22352 (@value{GDBP}) break *&'python22!PyOS_Readline'
22353 Breakpoint 1 at 0x1e04eff0
22356 The author of these extensions is not entirely convinced that setting a
22357 break point within a shared DLL like @file{kernel32.dll} is completely
22361 @subsection Commands Specific to @sc{gnu} Hurd Systems
22362 @cindex @sc{gnu} Hurd debugging
22364 This subsection describes @value{GDBN} commands specific to the
22365 @sc{gnu} Hurd native debugging.
22370 @kindex set signals@r{, Hurd command}
22371 @kindex set sigs@r{, Hurd command}
22372 This command toggles the state of inferior signal interception by
22373 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
22374 affected by this command. @code{sigs} is a shorthand alias for
22379 @kindex show signals@r{, Hurd command}
22380 @kindex show sigs@r{, Hurd command}
22381 Show the current state of intercepting inferior's signals.
22383 @item set signal-thread
22384 @itemx set sigthread
22385 @kindex set signal-thread
22386 @kindex set sigthread
22387 This command tells @value{GDBN} which thread is the @code{libc} signal
22388 thread. That thread is run when a signal is delivered to a running
22389 process. @code{set sigthread} is the shorthand alias of @code{set
22392 @item show signal-thread
22393 @itemx show sigthread
22394 @kindex show signal-thread
22395 @kindex show sigthread
22396 These two commands show which thread will run when the inferior is
22397 delivered a signal.
22400 @kindex set stopped@r{, Hurd command}
22401 This commands tells @value{GDBN} that the inferior process is stopped,
22402 as with the @code{SIGSTOP} signal. The stopped process can be
22403 continued by delivering a signal to it.
22406 @kindex show stopped@r{, Hurd command}
22407 This command shows whether @value{GDBN} thinks the debuggee is
22410 @item set exceptions
22411 @kindex set exceptions@r{, Hurd command}
22412 Use this command to turn off trapping of exceptions in the inferior.
22413 When exception trapping is off, neither breakpoints nor
22414 single-stepping will work. To restore the default, set exception
22417 @item show exceptions
22418 @kindex show exceptions@r{, Hurd command}
22419 Show the current state of trapping exceptions in the inferior.
22421 @item set task pause
22422 @kindex set task@r{, Hurd commands}
22423 @cindex task attributes (@sc{gnu} Hurd)
22424 @cindex pause current task (@sc{gnu} Hurd)
22425 This command toggles task suspension when @value{GDBN} has control.
22426 Setting it to on takes effect immediately, and the task is suspended
22427 whenever @value{GDBN} gets control. Setting it to off will take
22428 effect the next time the inferior is continued. If this option is set
22429 to off, you can use @code{set thread default pause on} or @code{set
22430 thread pause on} (see below) to pause individual threads.
22432 @item show task pause
22433 @kindex show task@r{, Hurd commands}
22434 Show the current state of task suspension.
22436 @item set task detach-suspend-count
22437 @cindex task suspend count
22438 @cindex detach from task, @sc{gnu} Hurd
22439 This command sets the suspend count the task will be left with when
22440 @value{GDBN} detaches from it.
22442 @item show task detach-suspend-count
22443 Show the suspend count the task will be left with when detaching.
22445 @item set task exception-port
22446 @itemx set task excp
22447 @cindex task exception port, @sc{gnu} Hurd
22448 This command sets the task exception port to which @value{GDBN} will
22449 forward exceptions. The argument should be the value of the @dfn{send
22450 rights} of the task. @code{set task excp} is a shorthand alias.
22452 @item set noninvasive
22453 @cindex noninvasive task options
22454 This command switches @value{GDBN} to a mode that is the least
22455 invasive as far as interfering with the inferior is concerned. This
22456 is the same as using @code{set task pause}, @code{set exceptions}, and
22457 @code{set signals} to values opposite to the defaults.
22459 @item info send-rights
22460 @itemx info receive-rights
22461 @itemx info port-rights
22462 @itemx info port-sets
22463 @itemx info dead-names
22466 @cindex send rights, @sc{gnu} Hurd
22467 @cindex receive rights, @sc{gnu} Hurd
22468 @cindex port rights, @sc{gnu} Hurd
22469 @cindex port sets, @sc{gnu} Hurd
22470 @cindex dead names, @sc{gnu} Hurd
22471 These commands display information about, respectively, send rights,
22472 receive rights, port rights, port sets, and dead names of a task.
22473 There are also shorthand aliases: @code{info ports} for @code{info
22474 port-rights} and @code{info psets} for @code{info port-sets}.
22476 @item set thread pause
22477 @kindex set thread@r{, Hurd command}
22478 @cindex thread properties, @sc{gnu} Hurd
22479 @cindex pause current thread (@sc{gnu} Hurd)
22480 This command toggles current thread suspension when @value{GDBN} has
22481 control. Setting it to on takes effect immediately, and the current
22482 thread is suspended whenever @value{GDBN} gets control. Setting it to
22483 off will take effect the next time the inferior is continued.
22484 Normally, this command has no effect, since when @value{GDBN} has
22485 control, the whole task is suspended. However, if you used @code{set
22486 task pause off} (see above), this command comes in handy to suspend
22487 only the current thread.
22489 @item show thread pause
22490 @kindex show thread@r{, Hurd command}
22491 This command shows the state of current thread suspension.
22493 @item set thread run
22494 This command sets whether the current thread is allowed to run.
22496 @item show thread run
22497 Show whether the current thread is allowed to run.
22499 @item set thread detach-suspend-count
22500 @cindex thread suspend count, @sc{gnu} Hurd
22501 @cindex detach from thread, @sc{gnu} Hurd
22502 This command sets the suspend count @value{GDBN} will leave on a
22503 thread when detaching. This number is relative to the suspend count
22504 found by @value{GDBN} when it notices the thread; use @code{set thread
22505 takeover-suspend-count} to force it to an absolute value.
22507 @item show thread detach-suspend-count
22508 Show the suspend count @value{GDBN} will leave on the thread when
22511 @item set thread exception-port
22512 @itemx set thread excp
22513 Set the thread exception port to which to forward exceptions. This
22514 overrides the port set by @code{set task exception-port} (see above).
22515 @code{set thread excp} is the shorthand alias.
22517 @item set thread takeover-suspend-count
22518 Normally, @value{GDBN}'s thread suspend counts are relative to the
22519 value @value{GDBN} finds when it notices each thread. This command
22520 changes the suspend counts to be absolute instead.
22522 @item set thread default
22523 @itemx show thread default
22524 @cindex thread default settings, @sc{gnu} Hurd
22525 Each of the above @code{set thread} commands has a @code{set thread
22526 default} counterpart (e.g., @code{set thread default pause}, @code{set
22527 thread default exception-port}, etc.). The @code{thread default}
22528 variety of commands sets the default thread properties for all
22529 threads; you can then change the properties of individual threads with
22530 the non-default commands.
22537 @value{GDBN} provides the following commands specific to the Darwin target:
22540 @item set debug darwin @var{num}
22541 @kindex set debug darwin
22542 When set to a non zero value, enables debugging messages specific to
22543 the Darwin support. Higher values produce more verbose output.
22545 @item show debug darwin
22546 @kindex show debug darwin
22547 Show the current state of Darwin messages.
22549 @item set debug mach-o @var{num}
22550 @kindex set debug mach-o
22551 When set to a non zero value, enables debugging messages while
22552 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
22553 file format used on Darwin for object and executable files.) Higher
22554 values produce more verbose output. This is a command to diagnose
22555 problems internal to @value{GDBN} and should not be needed in normal
22558 @item show debug mach-o
22559 @kindex show debug mach-o
22560 Show the current state of Mach-O file messages.
22562 @item set mach-exceptions on
22563 @itemx set mach-exceptions off
22564 @kindex set mach-exceptions
22565 On Darwin, faults are first reported as a Mach exception and are then
22566 mapped to a Posix signal. Use this command to turn on trapping of
22567 Mach exceptions in the inferior. This might be sometimes useful to
22568 better understand the cause of a fault. The default is off.
22570 @item show mach-exceptions
22571 @kindex show mach-exceptions
22572 Show the current state of exceptions trapping.
22577 @section Embedded Operating Systems
22579 This section describes configurations involving the debugging of
22580 embedded operating systems that are available for several different
22583 @value{GDBN} includes the ability to debug programs running on
22584 various real-time operating systems.
22586 @node Embedded Processors
22587 @section Embedded Processors
22589 This section goes into details specific to particular embedded
22592 @cindex send command to simulator
22593 Whenever a specific embedded processor has a simulator, @value{GDBN}
22594 allows to send an arbitrary command to the simulator.
22597 @item sim @var{command}
22598 @kindex sim@r{, a command}
22599 Send an arbitrary @var{command} string to the simulator. Consult the
22600 documentation for the specific simulator in use for information about
22601 acceptable commands.
22606 * ARC:: Synopsys ARC
22608 * M68K:: Motorola M68K
22609 * MicroBlaze:: Xilinx MicroBlaze
22610 * MIPS Embedded:: MIPS Embedded
22611 * OpenRISC 1000:: OpenRISC 1000 (or1k)
22612 * PowerPC Embedded:: PowerPC Embedded
22615 * Super-H:: Renesas Super-H
22619 @subsection Synopsys ARC
22620 @cindex Synopsys ARC
22621 @cindex ARC specific commands
22627 @value{GDBN} provides the following ARC-specific commands:
22630 @item set debug arc
22631 @kindex set debug arc
22632 Control the level of ARC specific debug messages. Use 0 for no messages (the
22633 default), 1 for debug messages, and 2 for even more debug messages.
22635 @item show debug arc
22636 @kindex show debug arc
22637 Show the level of ARC specific debugging in operation.
22639 @item maint print arc arc-instruction @var{address}
22640 @kindex maint print arc arc-instruction
22641 Print internal disassembler information about instruction at a given address.
22648 @value{GDBN} provides the following ARM-specific commands:
22651 @item set arm disassembler
22653 This commands selects from a list of disassembly styles. The
22654 @code{"std"} style is the standard style.
22656 @item show arm disassembler
22658 Show the current disassembly style.
22660 @item set arm apcs32
22661 @cindex ARM 32-bit mode
22662 This command toggles ARM operation mode between 32-bit and 26-bit.
22664 @item show arm apcs32
22665 Display the current usage of the ARM 32-bit mode.
22667 @item set arm fpu @var{fputype}
22668 This command sets the ARM floating-point unit (FPU) type. The
22669 argument @var{fputype} can be one of these:
22673 Determine the FPU type by querying the OS ABI.
22675 Software FPU, with mixed-endian doubles on little-endian ARM
22678 GCC-compiled FPA co-processor.
22680 Software FPU with pure-endian doubles.
22686 Show the current type of the FPU.
22689 This command forces @value{GDBN} to use the specified ABI.
22692 Show the currently used ABI.
22694 @item set arm fallback-mode (arm|thumb|auto)
22695 @value{GDBN} uses the symbol table, when available, to determine
22696 whether instructions are ARM or Thumb. This command controls
22697 @value{GDBN}'s default behavior when the symbol table is not
22698 available. The default is @samp{auto}, which causes @value{GDBN} to
22699 use the current execution mode (from the @code{T} bit in the @code{CPSR}
22702 @item show arm fallback-mode
22703 Show the current fallback instruction mode.
22705 @item set arm force-mode (arm|thumb|auto)
22706 This command overrides use of the symbol table to determine whether
22707 instructions are ARM or Thumb. The default is @samp{auto}, which
22708 causes @value{GDBN} to use the symbol table and then the setting
22709 of @samp{set arm fallback-mode}.
22711 @item show arm force-mode
22712 Show the current forced instruction mode.
22714 @item set debug arm
22715 Toggle whether to display ARM-specific debugging messages from the ARM
22716 target support subsystem.
22718 @item show debug arm
22719 Show whether ARM-specific debugging messages are enabled.
22723 @item target sim @r{[}@var{simargs}@r{]} @dots{}
22724 The @value{GDBN} ARM simulator accepts the following optional arguments.
22727 @item --swi-support=@var{type}
22728 Tell the simulator which SWI interfaces to support. The argument
22729 @var{type} may be a comma separated list of the following values.
22730 The default value is @code{all}.
22745 The Motorola m68k configuration includes ColdFire support.
22748 @subsection MicroBlaze
22749 @cindex Xilinx MicroBlaze
22750 @cindex XMD, Xilinx Microprocessor Debugger
22752 The MicroBlaze is a soft-core processor supported on various Xilinx
22753 FPGAs, such as Spartan or Virtex series. Boards with these processors
22754 usually have JTAG ports which connect to a host system running the Xilinx
22755 Embedded Development Kit (EDK) or Software Development Kit (SDK).
22756 This host system is used to download the configuration bitstream to
22757 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
22758 communicates with the target board using the JTAG interface and
22759 presents a @code{gdbserver} interface to the board. By default
22760 @code{xmd} uses port @code{1234}. (While it is possible to change
22761 this default port, it requires the use of undocumented @code{xmd}
22762 commands. Contact Xilinx support if you need to do this.)
22764 Use these GDB commands to connect to the MicroBlaze target processor.
22767 @item target remote :1234
22768 Use this command to connect to the target if you are running @value{GDBN}
22769 on the same system as @code{xmd}.
22771 @item target remote @var{xmd-host}:1234
22772 Use this command to connect to the target if it is connected to @code{xmd}
22773 running on a different system named @var{xmd-host}.
22776 Use this command to download a program to the MicroBlaze target.
22778 @item set debug microblaze @var{n}
22779 Enable MicroBlaze-specific debugging messages if non-zero.
22781 @item show debug microblaze @var{n}
22782 Show MicroBlaze-specific debugging level.
22785 @node MIPS Embedded
22786 @subsection @acronym{MIPS} Embedded
22789 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
22792 @item set mipsfpu double
22793 @itemx set mipsfpu single
22794 @itemx set mipsfpu none
22795 @itemx set mipsfpu auto
22796 @itemx show mipsfpu
22797 @kindex set mipsfpu
22798 @kindex show mipsfpu
22799 @cindex @acronym{MIPS} remote floating point
22800 @cindex floating point, @acronym{MIPS} remote
22801 If your target board does not support the @acronym{MIPS} floating point
22802 coprocessor, you should use the command @samp{set mipsfpu none} (if you
22803 need this, you may wish to put the command in your @value{GDBN} init
22804 file). This tells @value{GDBN} how to find the return value of
22805 functions which return floating point values. It also allows
22806 @value{GDBN} to avoid saving the floating point registers when calling
22807 functions on the board. If you are using a floating point coprocessor
22808 with only single precision floating point support, as on the @sc{r4650}
22809 processor, use the command @samp{set mipsfpu single}. The default
22810 double precision floating point coprocessor may be selected using
22811 @samp{set mipsfpu double}.
22813 In previous versions the only choices were double precision or no
22814 floating point, so @samp{set mipsfpu on} will select double precision
22815 and @samp{set mipsfpu off} will select no floating point.
22817 As usual, you can inquire about the @code{mipsfpu} variable with
22818 @samp{show mipsfpu}.
22821 @node OpenRISC 1000
22822 @subsection OpenRISC 1000
22823 @cindex OpenRISC 1000
22826 The OpenRISC 1000 provides a free RISC instruction set architecture. It is
22827 mainly provided as a soft-core which can run on Xilinx, Altera and other
22830 @value{GDBN} for OpenRISC supports the below commands when connecting to
22838 Runs the builtin CPU simulator which can run very basic
22839 programs but does not support most hardware functions like MMU.
22840 For more complex use cases the user is advised to run an external
22841 target, and connect using @samp{target remote}.
22843 Example: @code{target sim}
22845 @item set debug or1k
22846 Toggle whether to display OpenRISC-specific debugging messages from the
22847 OpenRISC target support subsystem.
22849 @item show debug or1k
22850 Show whether OpenRISC-specific debugging messages are enabled.
22853 @node PowerPC Embedded
22854 @subsection PowerPC Embedded
22856 @cindex DVC register
22857 @value{GDBN} supports using the DVC (Data Value Compare) register to
22858 implement in hardware simple hardware watchpoint conditions of the form:
22861 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
22862 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
22865 The DVC register will be automatically used when @value{GDBN} detects
22866 such pattern in a condition expression, and the created watchpoint uses one
22867 debug register (either the @code{exact-watchpoints} option is on and the
22868 variable is scalar, or the variable has a length of one byte). This feature
22869 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
22872 When running on PowerPC embedded processors, @value{GDBN} automatically uses
22873 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
22874 in which case watchpoints using only one debug register are created when
22875 watching variables of scalar types.
22877 You can create an artificial array to watch an arbitrary memory
22878 region using one of the following commands (@pxref{Expressions}):
22881 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
22882 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
22885 PowerPC embedded processors support masked watchpoints. See the discussion
22886 about the @code{mask} argument in @ref{Set Watchpoints}.
22888 @cindex ranged breakpoint
22889 PowerPC embedded processors support hardware accelerated
22890 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
22891 the inferior whenever it executes an instruction at any address within
22892 the range it specifies. To set a ranged breakpoint in @value{GDBN},
22893 use the @code{break-range} command.
22895 @value{GDBN} provides the following PowerPC-specific commands:
22898 @kindex break-range
22899 @item break-range @var{start-location}, @var{end-location}
22900 Set a breakpoint for an address range given by
22901 @var{start-location} and @var{end-location}, which can specify a function name,
22902 a line number, an offset of lines from the current line or from the start
22903 location, or an address of an instruction (see @ref{Specify Location},
22904 for a list of all the possible ways to specify a @var{location}.)
22905 The breakpoint will stop execution of the inferior whenever it
22906 executes an instruction at any address within the specified range,
22907 (including @var{start-location} and @var{end-location}.)
22909 @kindex set powerpc
22910 @item set powerpc soft-float
22911 @itemx show powerpc soft-float
22912 Force @value{GDBN} to use (or not use) a software floating point calling
22913 convention. By default, @value{GDBN} selects the calling convention based
22914 on the selected architecture and the provided executable file.
22916 @item set powerpc vector-abi
22917 @itemx show powerpc vector-abi
22918 Force @value{GDBN} to use the specified calling convention for vector
22919 arguments and return values. The valid options are @samp{auto};
22920 @samp{generic}, to avoid vector registers even if they are present;
22921 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
22922 registers. By default, @value{GDBN} selects the calling convention
22923 based on the selected architecture and the provided executable file.
22925 @item set powerpc exact-watchpoints
22926 @itemx show powerpc exact-watchpoints
22927 Allow @value{GDBN} to use only one debug register when watching a variable
22928 of scalar type, thus assuming that the variable is accessed through the
22929 address of its first byte.
22934 @subsection Atmel AVR
22937 When configured for debugging the Atmel AVR, @value{GDBN} supports the
22938 following AVR-specific commands:
22941 @item info io_registers
22942 @kindex info io_registers@r{, AVR}
22943 @cindex I/O registers (Atmel AVR)
22944 This command displays information about the AVR I/O registers. For
22945 each register, @value{GDBN} prints its number and value.
22952 When configured for debugging CRIS, @value{GDBN} provides the
22953 following CRIS-specific commands:
22956 @item set cris-version @var{ver}
22957 @cindex CRIS version
22958 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
22959 The CRIS version affects register names and sizes. This command is useful in
22960 case autodetection of the CRIS version fails.
22962 @item show cris-version
22963 Show the current CRIS version.
22965 @item set cris-dwarf2-cfi
22966 @cindex DWARF-2 CFI and CRIS
22967 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
22968 Change to @samp{off} when using @code{gcc-cris} whose version is below
22971 @item show cris-dwarf2-cfi
22972 Show the current state of using DWARF-2 CFI.
22974 @item set cris-mode @var{mode}
22976 Set the current CRIS mode to @var{mode}. It should only be changed when
22977 debugging in guru mode, in which case it should be set to
22978 @samp{guru} (the default is @samp{normal}).
22980 @item show cris-mode
22981 Show the current CRIS mode.
22985 @subsection Renesas Super-H
22988 For the Renesas Super-H processor, @value{GDBN} provides these
22992 @item set sh calling-convention @var{convention}
22993 @kindex set sh calling-convention
22994 Set the calling-convention used when calling functions from @value{GDBN}.
22995 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
22996 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
22997 convention. If the DWARF-2 information of the called function specifies
22998 that the function follows the Renesas calling convention, the function
22999 is called using the Renesas calling convention. If the calling convention
23000 is set to @samp{renesas}, the Renesas calling convention is always used,
23001 regardless of the DWARF-2 information. This can be used to override the
23002 default of @samp{gcc} if debug information is missing, or the compiler
23003 does not emit the DWARF-2 calling convention entry for a function.
23005 @item show sh calling-convention
23006 @kindex show sh calling-convention
23007 Show the current calling convention setting.
23012 @node Architectures
23013 @section Architectures
23015 This section describes characteristics of architectures that affect
23016 all uses of @value{GDBN} with the architecture, both native and cross.
23023 * HPPA:: HP PA architecture
23024 * SPU:: Cell Broadband Engine SPU architecture
23031 @subsection AArch64
23032 @cindex AArch64 support
23034 When @value{GDBN} is debugging the AArch64 architecture, it provides the
23035 following special commands:
23038 @item set debug aarch64
23039 @kindex set debug aarch64
23040 This command determines whether AArch64 architecture-specific debugging
23041 messages are to be displayed.
23043 @item show debug aarch64
23044 Show whether AArch64 debugging messages are displayed.
23049 @subsection x86 Architecture-specific Issues
23052 @item set struct-convention @var{mode}
23053 @kindex set struct-convention
23054 @cindex struct return convention
23055 @cindex struct/union returned in registers
23056 Set the convention used by the inferior to return @code{struct}s and
23057 @code{union}s from functions to @var{mode}. Possible values of
23058 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
23059 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
23060 are returned on the stack, while @code{"reg"} means that a
23061 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
23062 be returned in a register.
23064 @item show struct-convention
23065 @kindex show struct-convention
23066 Show the current setting of the convention to return @code{struct}s
23071 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
23072 @cindex Intel Memory Protection Extensions (MPX).
23074 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
23075 @footnote{The register named with capital letters represent the architecture
23076 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
23077 which are the lower bound and upper bound. Bounds are effective addresses or
23078 memory locations. The upper bounds are architecturally represented in 1's
23079 complement form. A bound having lower bound = 0, and upper bound = 0
23080 (1's complement of all bits set) will allow access to the entire address space.
23082 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
23083 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
23084 display the upper bound performing the complement of one operation on the
23085 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
23086 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
23087 can also be noted that the upper bounds are inclusive.
23089 As an example, assume that the register BND0 holds bounds for a pointer having
23090 access allowed for the range between 0x32 and 0x71. The values present on
23091 bnd0raw and bnd registers are presented as follows:
23094 bnd0raw = @{0x32, 0xffffffff8e@}
23095 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
23098 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
23099 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
23100 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
23101 Python, the display includes the memory size, in bits, accessible to
23104 Bounds can also be stored in bounds tables, which are stored in
23105 application memory. These tables store bounds for pointers by specifying
23106 the bounds pointer's value along with its bounds. Evaluating and changing
23107 bounds located in bound tables is therefore interesting while investigating
23108 bugs on MPX context. @value{GDBN} provides commands for this purpose:
23111 @item show mpx bound @var{pointer}
23112 @kindex show mpx bound
23113 Display bounds of the given @var{pointer}.
23115 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
23116 @kindex set mpx bound
23117 Set the bounds of a pointer in the bound table.
23118 This command takes three parameters: @var{pointer} is the pointers
23119 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
23120 for lower and upper bounds respectively.
23123 When you call an inferior function on an Intel MPX enabled program,
23124 GDB sets the inferior's bound registers to the init (disabled) state
23125 before calling the function. As a consequence, bounds checks for the
23126 pointer arguments passed to the function will always pass.
23128 This is necessary because when you call an inferior function, the
23129 program is usually in the middle of the execution of other function.
23130 Since at that point bound registers are in an arbitrary state, not
23131 clearing them would lead to random bound violations in the called
23134 You can still examine the influence of the bound registers on the
23135 execution of the called function by stopping the execution of the
23136 called function at its prologue, setting bound registers, and
23137 continuing the execution. For example:
23141 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
23142 $ print upper (a, b, c, d, 1)
23143 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
23145 @{lbound = 0x0, ubound = ffffffff@} : size -1
23148 At this last step the value of bnd0 can be changed for investigation of bound
23149 violations caused along the execution of the call. In order to know how to
23150 set the bound registers or bound table for the call consult the ABI.
23155 See the following section.
23158 @subsection @acronym{MIPS}
23160 @cindex stack on Alpha
23161 @cindex stack on @acronym{MIPS}
23162 @cindex Alpha stack
23163 @cindex @acronym{MIPS} stack
23164 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
23165 sometimes requires @value{GDBN} to search backward in the object code to
23166 find the beginning of a function.
23168 @cindex response time, @acronym{MIPS} debugging
23169 To improve response time (especially for embedded applications, where
23170 @value{GDBN} may be restricted to a slow serial line for this search)
23171 you may want to limit the size of this search, using one of these
23175 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
23176 @item set heuristic-fence-post @var{limit}
23177 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
23178 search for the beginning of a function. A value of @var{0} (the
23179 default) means there is no limit. However, except for @var{0}, the
23180 larger the limit the more bytes @code{heuristic-fence-post} must search
23181 and therefore the longer it takes to run. You should only need to use
23182 this command when debugging a stripped executable.
23184 @item show heuristic-fence-post
23185 Display the current limit.
23189 These commands are available @emph{only} when @value{GDBN} is configured
23190 for debugging programs on Alpha or @acronym{MIPS} processors.
23192 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
23196 @item set mips abi @var{arg}
23197 @kindex set mips abi
23198 @cindex set ABI for @acronym{MIPS}
23199 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
23200 values of @var{arg} are:
23204 The default ABI associated with the current binary (this is the
23214 @item show mips abi
23215 @kindex show mips abi
23216 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
23218 @item set mips compression @var{arg}
23219 @kindex set mips compression
23220 @cindex code compression, @acronym{MIPS}
23221 Tell @value{GDBN} which @acronym{MIPS} compressed
23222 @acronym{ISA, Instruction Set Architecture} encoding is used by the
23223 inferior. @value{GDBN} uses this for code disassembly and other
23224 internal interpretation purposes. This setting is only referred to
23225 when no executable has been associated with the debugging session or
23226 the executable does not provide information about the encoding it uses.
23227 Otherwise this setting is automatically updated from information
23228 provided by the executable.
23230 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
23231 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
23232 executables containing @acronym{MIPS16} code frequently are not
23233 identified as such.
23235 This setting is ``sticky''; that is, it retains its value across
23236 debugging sessions until reset either explicitly with this command or
23237 implicitly from an executable.
23239 The compiler and/or assembler typically add symbol table annotations to
23240 identify functions compiled for the @acronym{MIPS16} or
23241 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
23242 are present, @value{GDBN} uses them in preference to the global
23243 compressed @acronym{ISA} encoding setting.
23245 @item show mips compression
23246 @kindex show mips compression
23247 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
23248 @value{GDBN} to debug the inferior.
23251 @itemx show mipsfpu
23252 @xref{MIPS Embedded, set mipsfpu}.
23254 @item set mips mask-address @var{arg}
23255 @kindex set mips mask-address
23256 @cindex @acronym{MIPS} addresses, masking
23257 This command determines whether the most-significant 32 bits of 64-bit
23258 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
23259 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
23260 setting, which lets @value{GDBN} determine the correct value.
23262 @item show mips mask-address
23263 @kindex show mips mask-address
23264 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
23267 @item set remote-mips64-transfers-32bit-regs
23268 @kindex set remote-mips64-transfers-32bit-regs
23269 This command controls compatibility with 64-bit @acronym{MIPS} targets that
23270 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
23271 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
23272 and 64 bits for other registers, set this option to @samp{on}.
23274 @item show remote-mips64-transfers-32bit-regs
23275 @kindex show remote-mips64-transfers-32bit-regs
23276 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
23278 @item set debug mips
23279 @kindex set debug mips
23280 This command turns on and off debugging messages for the @acronym{MIPS}-specific
23281 target code in @value{GDBN}.
23283 @item show debug mips
23284 @kindex show debug mips
23285 Show the current setting of @acronym{MIPS} debugging messages.
23291 @cindex HPPA support
23293 When @value{GDBN} is debugging the HP PA architecture, it provides the
23294 following special commands:
23297 @item set debug hppa
23298 @kindex set debug hppa
23299 This command determines whether HPPA architecture-specific debugging
23300 messages are to be displayed.
23302 @item show debug hppa
23303 Show whether HPPA debugging messages are displayed.
23305 @item maint print unwind @var{address}
23306 @kindex maint print unwind@r{, HPPA}
23307 This command displays the contents of the unwind table entry at the
23308 given @var{address}.
23314 @subsection Cell Broadband Engine SPU architecture
23315 @cindex Cell Broadband Engine
23318 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
23319 it provides the following special commands:
23322 @item info spu event
23324 Display SPU event facility status. Shows current event mask
23325 and pending event status.
23327 @item info spu signal
23328 Display SPU signal notification facility status. Shows pending
23329 signal-control word and signal notification mode of both signal
23330 notification channels.
23332 @item info spu mailbox
23333 Display SPU mailbox facility status. Shows all pending entries,
23334 in order of processing, in each of the SPU Write Outbound,
23335 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
23338 Display MFC DMA status. Shows all pending commands in the MFC
23339 DMA queue. For each entry, opcode, tag, class IDs, effective
23340 and local store addresses and transfer size are shown.
23342 @item info spu proxydma
23343 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
23344 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
23345 and local store addresses and transfer size are shown.
23349 When @value{GDBN} is debugging a combined PowerPC/SPU application
23350 on the Cell Broadband Engine, it provides in addition the following
23354 @item set spu stop-on-load @var{arg}
23356 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
23357 will give control to the user when a new SPE thread enters its @code{main}
23358 function. The default is @code{off}.
23360 @item show spu stop-on-load
23362 Show whether to stop for new SPE threads.
23364 @item set spu auto-flush-cache @var{arg}
23365 Set whether to automatically flush the software-managed cache. When set to
23366 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
23367 cache to be flushed whenever SPE execution stops. This provides a consistent
23368 view of PowerPC memory that is accessed via the cache. If an application
23369 does not use the software-managed cache, this option has no effect.
23371 @item show spu auto-flush-cache
23372 Show whether to automatically flush the software-managed cache.
23377 @subsection PowerPC
23378 @cindex PowerPC architecture
23380 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
23381 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
23382 numbers stored in the floating point registers. These values must be stored
23383 in two consecutive registers, always starting at an even register like
23384 @code{f0} or @code{f2}.
23386 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
23387 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
23388 @code{f2} and @code{f3} for @code{$dl1} and so on.
23390 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
23391 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
23394 @subsection Nios II
23395 @cindex Nios II architecture
23397 When @value{GDBN} is debugging the Nios II architecture,
23398 it provides the following special commands:
23402 @item set debug nios2
23403 @kindex set debug nios2
23404 This command turns on and off debugging messages for the Nios II
23405 target code in @value{GDBN}.
23407 @item show debug nios2
23408 @kindex show debug nios2
23409 Show the current setting of Nios II debugging messages.
23413 @subsection Sparc64
23414 @cindex Sparc64 support
23415 @cindex Application Data Integrity
23416 @subsubsection ADI Support
23418 The M7 processor supports an Application Data Integrity (ADI) feature that
23419 detects invalid data accesses. When software allocates memory and enables
23420 ADI on the allocated memory, it chooses a 4-bit version number, sets the
23421 version in the upper 4 bits of the 64-bit pointer to that data, and stores
23422 the 4-bit version in every cacheline of that data. Hardware saves the latter
23423 in spare bits in the cache and memory hierarchy. On each load and store,
23424 the processor compares the upper 4 VA (virtual address) bits to the
23425 cacheline's version. If there is a mismatch, the processor generates a
23426 version mismatch trap which can be either precise or disrupting. The trap
23427 is an error condition which the kernel delivers to the process as a SIGSEGV
23430 Note that only 64-bit applications can use ADI and need to be built with
23433 Values of the ADI version tags, which are in granularity of a
23434 cacheline (64 bytes), can be viewed or modified.
23438 @kindex adi examine
23439 @item adi (examine | x) [ / @var{n} ] @var{addr}
23441 The @code{adi examine} command displays the value of one ADI version tag per
23444 @var{n} is a decimal integer specifying the number in bytes; the default
23445 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
23446 block size, to display.
23448 @var{addr} is the address in user address space where you want @value{GDBN}
23449 to begin displaying the ADI version tags.
23451 Below is an example of displaying ADI versions of variable "shmaddr".
23454 (@value{GDBP}) adi x/100 shmaddr
23455 0xfff800010002c000: 0 0
23459 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
23461 The @code{adi assign} command is used to assign new ADI version tag
23464 @var{n} is a decimal integer specifying the number in bytes;
23465 the default is 1. It specifies how much ADI version information, at the
23466 ratio of 1:ADI block size, to modify.
23468 @var{addr} is the address in user address space where you want @value{GDBN}
23469 to begin modifying the ADI version tags.
23471 @var{tag} is the new ADI version tag.
23473 For example, do the following to modify then verify ADI versions of
23474 variable "shmaddr":
23477 (@value{GDBP}) adi a/100 shmaddr = 7
23478 (@value{GDBP}) adi x/100 shmaddr
23479 0xfff800010002c000: 7 7
23484 @node Controlling GDB
23485 @chapter Controlling @value{GDBN}
23487 You can alter the way @value{GDBN} interacts with you by using the
23488 @code{set} command. For commands controlling how @value{GDBN} displays
23489 data, see @ref{Print Settings, ,Print Settings}. Other settings are
23494 * Editing:: Command editing
23495 * Command History:: Command history
23496 * Screen Size:: Screen size
23497 * Numbers:: Numbers
23498 * ABI:: Configuring the current ABI
23499 * Auto-loading:: Automatically loading associated files
23500 * Messages/Warnings:: Optional warnings and messages
23501 * Debugging Output:: Optional messages about internal happenings
23502 * Other Misc Settings:: Other Miscellaneous Settings
23510 @value{GDBN} indicates its readiness to read a command by printing a string
23511 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
23512 can change the prompt string with the @code{set prompt} command. For
23513 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
23514 the prompt in one of the @value{GDBN} sessions so that you can always tell
23515 which one you are talking to.
23517 @emph{Note:} @code{set prompt} does not add a space for you after the
23518 prompt you set. This allows you to set a prompt which ends in a space
23519 or a prompt that does not.
23523 @item set prompt @var{newprompt}
23524 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
23526 @kindex show prompt
23528 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
23531 Versions of @value{GDBN} that ship with Python scripting enabled have
23532 prompt extensions. The commands for interacting with these extensions
23536 @kindex set extended-prompt
23537 @item set extended-prompt @var{prompt}
23538 Set an extended prompt that allows for substitutions.
23539 @xref{gdb.prompt}, for a list of escape sequences that can be used for
23540 substitution. Any escape sequences specified as part of the prompt
23541 string are replaced with the corresponding strings each time the prompt
23547 set extended-prompt Current working directory: \w (gdb)
23550 Note that when an extended-prompt is set, it takes control of the
23551 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
23553 @kindex show extended-prompt
23554 @item show extended-prompt
23555 Prints the extended prompt. Any escape sequences specified as part of
23556 the prompt string with @code{set extended-prompt}, are replaced with the
23557 corresponding strings each time the prompt is displayed.
23561 @section Command Editing
23563 @cindex command line editing
23565 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
23566 @sc{gnu} library provides consistent behavior for programs which provide a
23567 command line interface to the user. Advantages are @sc{gnu} Emacs-style
23568 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
23569 substitution, and a storage and recall of command history across
23570 debugging sessions.
23572 You may control the behavior of command line editing in @value{GDBN} with the
23573 command @code{set}.
23576 @kindex set editing
23579 @itemx set editing on
23580 Enable command line editing (enabled by default).
23582 @item set editing off
23583 Disable command line editing.
23585 @kindex show editing
23587 Show whether command line editing is enabled.
23590 @ifset SYSTEM_READLINE
23591 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
23593 @ifclear SYSTEM_READLINE
23594 @xref{Command Line Editing},
23596 for more details about the Readline
23597 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
23598 encouraged to read that chapter.
23600 @node Command History
23601 @section Command History
23602 @cindex command history
23604 @value{GDBN} can keep track of the commands you type during your
23605 debugging sessions, so that you can be certain of precisely what
23606 happened. Use these commands to manage the @value{GDBN} command
23609 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
23610 package, to provide the history facility.
23611 @ifset SYSTEM_READLINE
23612 @xref{Using History Interactively, , , history, GNU History Library},
23614 @ifclear SYSTEM_READLINE
23615 @xref{Using History Interactively},
23617 for the detailed description of the History library.
23619 To issue a command to @value{GDBN} without affecting certain aspects of
23620 the state which is seen by users, prefix it with @samp{server }
23621 (@pxref{Server Prefix}). This
23622 means that this command will not affect the command history, nor will it
23623 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
23624 pressed on a line by itself.
23626 @cindex @code{server}, command prefix
23627 The server prefix does not affect the recording of values into the value
23628 history; to print a value without recording it into the value history,
23629 use the @code{output} command instead of the @code{print} command.
23631 Here is the description of @value{GDBN} commands related to command
23635 @cindex history substitution
23636 @cindex history file
23637 @kindex set history filename
23638 @cindex @env{GDBHISTFILE}, environment variable
23639 @item set history filename @var{fname}
23640 Set the name of the @value{GDBN} command history file to @var{fname}.
23641 This is the file where @value{GDBN} reads an initial command history
23642 list, and where it writes the command history from this session when it
23643 exits. You can access this list through history expansion or through
23644 the history command editing characters listed below. This file defaults
23645 to the value of the environment variable @code{GDBHISTFILE}, or to
23646 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
23649 @cindex save command history
23650 @kindex set history save
23651 @item set history save
23652 @itemx set history save on
23653 Record command history in a file, whose name may be specified with the
23654 @code{set history filename} command. By default, this option is disabled.
23656 @item set history save off
23657 Stop recording command history in a file.
23659 @cindex history size
23660 @kindex set history size
23661 @cindex @env{GDBHISTSIZE}, environment variable
23662 @item set history size @var{size}
23663 @itemx set history size unlimited
23664 Set the number of commands which @value{GDBN} keeps in its history list.
23665 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
23666 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
23667 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
23668 either a negative number or the empty string, then the number of commands
23669 @value{GDBN} keeps in the history list is unlimited.
23671 @cindex remove duplicate history
23672 @kindex set history remove-duplicates
23673 @item set history remove-duplicates @var{count}
23674 @itemx set history remove-duplicates unlimited
23675 Control the removal of duplicate history entries in the command history list.
23676 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
23677 history entries and remove the first entry that is a duplicate of the current
23678 entry being added to the command history list. If @var{count} is
23679 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
23680 removal of duplicate history entries is disabled.
23682 Only history entries added during the current session are considered for
23683 removal. This option is set to 0 by default.
23687 History expansion assigns special meaning to the character @kbd{!}.
23688 @ifset SYSTEM_READLINE
23689 @xref{Event Designators, , , history, GNU History Library},
23691 @ifclear SYSTEM_READLINE
23692 @xref{Event Designators},
23696 @cindex history expansion, turn on/off
23697 Since @kbd{!} is also the logical not operator in C, history expansion
23698 is off by default. If you decide to enable history expansion with the
23699 @code{set history expansion on} command, you may sometimes need to
23700 follow @kbd{!} (when it is used as logical not, in an expression) with
23701 a space or a tab to prevent it from being expanded. The readline
23702 history facilities do not attempt substitution on the strings
23703 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
23705 The commands to control history expansion are:
23708 @item set history expansion on
23709 @itemx set history expansion
23710 @kindex set history expansion
23711 Enable history expansion. History expansion is off by default.
23713 @item set history expansion off
23714 Disable history expansion.
23717 @kindex show history
23719 @itemx show history filename
23720 @itemx show history save
23721 @itemx show history size
23722 @itemx show history expansion
23723 These commands display the state of the @value{GDBN} history parameters.
23724 @code{show history} by itself displays all four states.
23729 @kindex show commands
23730 @cindex show last commands
23731 @cindex display command history
23732 @item show commands
23733 Display the last ten commands in the command history.
23735 @item show commands @var{n}
23736 Print ten commands centered on command number @var{n}.
23738 @item show commands +
23739 Print ten commands just after the commands last printed.
23743 @section Screen Size
23744 @cindex size of screen
23745 @cindex screen size
23748 @cindex pauses in output
23750 Certain commands to @value{GDBN} may produce large amounts of
23751 information output to the screen. To help you read all of it,
23752 @value{GDBN} pauses and asks you for input at the end of each page of
23753 output. Type @key{RET} when you want to continue the output, or @kbd{q}
23754 to discard the remaining output. Also, the screen width setting
23755 determines when to wrap lines of output. Depending on what is being
23756 printed, @value{GDBN} tries to break the line at a readable place,
23757 rather than simply letting it overflow onto the following line.
23759 Normally @value{GDBN} knows the size of the screen from the terminal
23760 driver software. For example, on Unix @value{GDBN} uses the termcap data base
23761 together with the value of the @code{TERM} environment variable and the
23762 @code{stty rows} and @code{stty cols} settings. If this is not correct,
23763 you can override it with the @code{set height} and @code{set
23770 @kindex show height
23771 @item set height @var{lpp}
23772 @itemx set height unlimited
23774 @itemx set width @var{cpl}
23775 @itemx set width unlimited
23777 These @code{set} commands specify a screen height of @var{lpp} lines and
23778 a screen width of @var{cpl} characters. The associated @code{show}
23779 commands display the current settings.
23781 If you specify a height of either @code{unlimited} or zero lines,
23782 @value{GDBN} does not pause during output no matter how long the
23783 output is. This is useful if output is to a file or to an editor
23786 Likewise, you can specify @samp{set width unlimited} or @samp{set
23787 width 0} to prevent @value{GDBN} from wrapping its output.
23789 @item set pagination on
23790 @itemx set pagination off
23791 @kindex set pagination
23792 Turn the output pagination on or off; the default is on. Turning
23793 pagination off is the alternative to @code{set height unlimited}. Note that
23794 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
23795 Options, -batch}) also automatically disables pagination.
23797 @item show pagination
23798 @kindex show pagination
23799 Show the current pagination mode.
23804 @cindex number representation
23805 @cindex entering numbers
23807 You can always enter numbers in octal, decimal, or hexadecimal in
23808 @value{GDBN} by the usual conventions: octal numbers begin with
23809 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
23810 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
23811 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
23812 10; likewise, the default display for numbers---when no particular
23813 format is specified---is base 10. You can change the default base for
23814 both input and output with the commands described below.
23817 @kindex set input-radix
23818 @item set input-radix @var{base}
23819 Set the default base for numeric input. Supported choices
23820 for @var{base} are decimal 8, 10, or 16. The base must itself be
23821 specified either unambiguously or using the current input radix; for
23825 set input-radix 012
23826 set input-radix 10.
23827 set input-radix 0xa
23831 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
23832 leaves the input radix unchanged, no matter what it was, since
23833 @samp{10}, being without any leading or trailing signs of its base, is
23834 interpreted in the current radix. Thus, if the current radix is 16,
23835 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
23838 @kindex set output-radix
23839 @item set output-radix @var{base}
23840 Set the default base for numeric display. Supported choices
23841 for @var{base} are decimal 8, 10, or 16. The base must itself be
23842 specified either unambiguously or using the current input radix.
23844 @kindex show input-radix
23845 @item show input-radix
23846 Display the current default base for numeric input.
23848 @kindex show output-radix
23849 @item show output-radix
23850 Display the current default base for numeric display.
23852 @item set radix @r{[}@var{base}@r{]}
23856 These commands set and show the default base for both input and output
23857 of numbers. @code{set radix} sets the radix of input and output to
23858 the same base; without an argument, it resets the radix back to its
23859 default value of 10.
23864 @section Configuring the Current ABI
23866 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
23867 application automatically. However, sometimes you need to override its
23868 conclusions. Use these commands to manage @value{GDBN}'s view of the
23874 @cindex Newlib OS ABI and its influence on the longjmp handling
23876 One @value{GDBN} configuration can debug binaries for multiple operating
23877 system targets, either via remote debugging or native emulation.
23878 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
23879 but you can override its conclusion using the @code{set osabi} command.
23880 One example where this is useful is in debugging of binaries which use
23881 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
23882 not have the same identifying marks that the standard C library for your
23885 When @value{GDBN} is debugging the AArch64 architecture, it provides a
23886 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
23887 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
23888 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
23892 Show the OS ABI currently in use.
23895 With no argument, show the list of registered available OS ABI's.
23897 @item set osabi @var{abi}
23898 Set the current OS ABI to @var{abi}.
23901 @cindex float promotion
23903 Generally, the way that an argument of type @code{float} is passed to a
23904 function depends on whether the function is prototyped. For a prototyped
23905 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
23906 according to the architecture's convention for @code{float}. For unprototyped
23907 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
23908 @code{double} and then passed.
23910 Unfortunately, some forms of debug information do not reliably indicate whether
23911 a function is prototyped. If @value{GDBN} calls a function that is not marked
23912 as prototyped, it consults @kbd{set coerce-float-to-double}.
23915 @kindex set coerce-float-to-double
23916 @item set coerce-float-to-double
23917 @itemx set coerce-float-to-double on
23918 Arguments of type @code{float} will be promoted to @code{double} when passed
23919 to an unprototyped function. This is the default setting.
23921 @item set coerce-float-to-double off
23922 Arguments of type @code{float} will be passed directly to unprototyped
23925 @kindex show coerce-float-to-double
23926 @item show coerce-float-to-double
23927 Show the current setting of promoting @code{float} to @code{double}.
23931 @kindex show cp-abi
23932 @value{GDBN} needs to know the ABI used for your program's C@t{++}
23933 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
23934 used to build your application. @value{GDBN} only fully supports
23935 programs with a single C@t{++} ABI; if your program contains code using
23936 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
23937 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
23938 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
23939 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
23940 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
23941 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
23946 Show the C@t{++} ABI currently in use.
23949 With no argument, show the list of supported C@t{++} ABI's.
23951 @item set cp-abi @var{abi}
23952 @itemx set cp-abi auto
23953 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
23957 @section Automatically loading associated files
23958 @cindex auto-loading
23960 @value{GDBN} sometimes reads files with commands and settings automatically,
23961 without being explicitly told so by the user. We call this feature
23962 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
23963 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
23964 results or introduce security risks (e.g., if the file comes from untrusted
23968 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
23969 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
23971 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
23972 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
23975 There are various kinds of files @value{GDBN} can automatically load.
23976 In addition to these files, @value{GDBN} supports auto-loading code written
23977 in various extension languages. @xref{Auto-loading extensions}.
23979 Note that loading of these associated files (including the local @file{.gdbinit}
23980 file) requires accordingly configured @code{auto-load safe-path}
23981 (@pxref{Auto-loading safe path}).
23983 For these reasons, @value{GDBN} includes commands and options to let you
23984 control when to auto-load files and which files should be auto-loaded.
23987 @anchor{set auto-load off}
23988 @kindex set auto-load off
23989 @item set auto-load off
23990 Globally disable loading of all auto-loaded files.
23991 You may want to use this command with the @samp{-iex} option
23992 (@pxref{Option -init-eval-command}) such as:
23994 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
23997 Be aware that system init file (@pxref{System-wide configuration})
23998 and init files from your home directory (@pxref{Home Directory Init File})
23999 still get read (as they come from generally trusted directories).
24000 To prevent @value{GDBN} from auto-loading even those init files, use the
24001 @option{-nx} option (@pxref{Mode Options}), in addition to
24002 @code{set auto-load no}.
24004 @anchor{show auto-load}
24005 @kindex show auto-load
24006 @item show auto-load
24007 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
24011 (gdb) show auto-load
24012 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
24013 libthread-db: Auto-loading of inferior specific libthread_db is on.
24014 local-gdbinit: Auto-loading of .gdbinit script from current directory
24016 python-scripts: Auto-loading of Python scripts is on.
24017 safe-path: List of directories from which it is safe to auto-load files
24018 is $debugdir:$datadir/auto-load.
24019 scripts-directory: List of directories from which to load auto-loaded scripts
24020 is $debugdir:$datadir/auto-load.
24023 @anchor{info auto-load}
24024 @kindex info auto-load
24025 @item info auto-load
24026 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
24030 (gdb) info auto-load
24033 Yes /home/user/gdb/gdb-gdb.gdb
24034 libthread-db: No auto-loaded libthread-db.
24035 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
24039 Yes /home/user/gdb/gdb-gdb.py
24043 These are @value{GDBN} control commands for the auto-loading:
24045 @multitable @columnfractions .5 .5
24046 @item @xref{set auto-load off}.
24047 @tab Disable auto-loading globally.
24048 @item @xref{show auto-load}.
24049 @tab Show setting of all kinds of files.
24050 @item @xref{info auto-load}.
24051 @tab Show state of all kinds of files.
24052 @item @xref{set auto-load gdb-scripts}.
24053 @tab Control for @value{GDBN} command scripts.
24054 @item @xref{show auto-load gdb-scripts}.
24055 @tab Show setting of @value{GDBN} command scripts.
24056 @item @xref{info auto-load gdb-scripts}.
24057 @tab Show state of @value{GDBN} command scripts.
24058 @item @xref{set auto-load python-scripts}.
24059 @tab Control for @value{GDBN} Python scripts.
24060 @item @xref{show auto-load python-scripts}.
24061 @tab Show setting of @value{GDBN} Python scripts.
24062 @item @xref{info auto-load python-scripts}.
24063 @tab Show state of @value{GDBN} Python scripts.
24064 @item @xref{set auto-load guile-scripts}.
24065 @tab Control for @value{GDBN} Guile scripts.
24066 @item @xref{show auto-load guile-scripts}.
24067 @tab Show setting of @value{GDBN} Guile scripts.
24068 @item @xref{info auto-load guile-scripts}.
24069 @tab Show state of @value{GDBN} Guile scripts.
24070 @item @xref{set auto-load scripts-directory}.
24071 @tab Control for @value{GDBN} auto-loaded scripts location.
24072 @item @xref{show auto-load scripts-directory}.
24073 @tab Show @value{GDBN} auto-loaded scripts location.
24074 @item @xref{add-auto-load-scripts-directory}.
24075 @tab Add directory for auto-loaded scripts location list.
24076 @item @xref{set auto-load local-gdbinit}.
24077 @tab Control for init file in the current directory.
24078 @item @xref{show auto-load local-gdbinit}.
24079 @tab Show setting of init file in the current directory.
24080 @item @xref{info auto-load local-gdbinit}.
24081 @tab Show state of init file in the current directory.
24082 @item @xref{set auto-load libthread-db}.
24083 @tab Control for thread debugging library.
24084 @item @xref{show auto-load libthread-db}.
24085 @tab Show setting of thread debugging library.
24086 @item @xref{info auto-load libthread-db}.
24087 @tab Show state of thread debugging library.
24088 @item @xref{set auto-load safe-path}.
24089 @tab Control directories trusted for automatic loading.
24090 @item @xref{show auto-load safe-path}.
24091 @tab Show directories trusted for automatic loading.
24092 @item @xref{add-auto-load-safe-path}.
24093 @tab Add directory trusted for automatic loading.
24096 @node Init File in the Current Directory
24097 @subsection Automatically loading init file in the current directory
24098 @cindex auto-loading init file in the current directory
24100 By default, @value{GDBN} reads and executes the canned sequences of commands
24101 from init file (if any) in the current working directory,
24102 see @ref{Init File in the Current Directory during Startup}.
24104 Note that loading of this local @file{.gdbinit} file also requires accordingly
24105 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24108 @anchor{set auto-load local-gdbinit}
24109 @kindex set auto-load local-gdbinit
24110 @item set auto-load local-gdbinit [on|off]
24111 Enable or disable the auto-loading of canned sequences of commands
24112 (@pxref{Sequences}) found in init file in the current directory.
24114 @anchor{show auto-load local-gdbinit}
24115 @kindex show auto-load local-gdbinit
24116 @item show auto-load local-gdbinit
24117 Show whether auto-loading of canned sequences of commands from init file in the
24118 current directory is enabled or disabled.
24120 @anchor{info auto-load local-gdbinit}
24121 @kindex info auto-load local-gdbinit
24122 @item info auto-load local-gdbinit
24123 Print whether canned sequences of commands from init file in the
24124 current directory have been auto-loaded.
24127 @node libthread_db.so.1 file
24128 @subsection Automatically loading thread debugging library
24129 @cindex auto-loading libthread_db.so.1
24131 This feature is currently present only on @sc{gnu}/Linux native hosts.
24133 @value{GDBN} reads in some cases thread debugging library from places specific
24134 to the inferior (@pxref{set libthread-db-search-path}).
24136 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
24137 without checking this @samp{set auto-load libthread-db} switch as system
24138 libraries have to be trusted in general. In all other cases of
24139 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
24140 auto-load libthread-db} is enabled before trying to open such thread debugging
24143 Note that loading of this debugging library also requires accordingly configured
24144 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24147 @anchor{set auto-load libthread-db}
24148 @kindex set auto-load libthread-db
24149 @item set auto-load libthread-db [on|off]
24150 Enable or disable the auto-loading of inferior specific thread debugging library.
24152 @anchor{show auto-load libthread-db}
24153 @kindex show auto-load libthread-db
24154 @item show auto-load libthread-db
24155 Show whether auto-loading of inferior specific thread debugging library is
24156 enabled or disabled.
24158 @anchor{info auto-load libthread-db}
24159 @kindex info auto-load libthread-db
24160 @item info auto-load libthread-db
24161 Print the list of all loaded inferior specific thread debugging libraries and
24162 for each such library print list of inferior @var{pid}s using it.
24165 @node Auto-loading safe path
24166 @subsection Security restriction for auto-loading
24167 @cindex auto-loading safe-path
24169 As the files of inferior can come from untrusted source (such as submitted by
24170 an application user) @value{GDBN} does not always load any files automatically.
24171 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
24172 directories trusted for loading files not explicitly requested by user.
24173 Each directory can also be a shell wildcard pattern.
24175 If the path is not set properly you will see a warning and the file will not
24180 Reading symbols from /home/user/gdb/gdb...done.
24181 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
24182 declined by your `auto-load safe-path' set
24183 to "$debugdir:$datadir/auto-load".
24184 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
24185 declined by your `auto-load safe-path' set
24186 to "$debugdir:$datadir/auto-load".
24190 To instruct @value{GDBN} to go ahead and use the init files anyway,
24191 invoke @value{GDBN} like this:
24194 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
24197 The list of trusted directories is controlled by the following commands:
24200 @anchor{set auto-load safe-path}
24201 @kindex set auto-load safe-path
24202 @item set auto-load safe-path @r{[}@var{directories}@r{]}
24203 Set the list of directories (and their subdirectories) trusted for automatic
24204 loading and execution of scripts. You can also enter a specific trusted file.
24205 Each directory can also be a shell wildcard pattern; wildcards do not match
24206 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
24207 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
24208 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
24209 its default value as specified during @value{GDBN} compilation.
24211 The list of directories uses path separator (@samp{:} on GNU and Unix
24212 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
24213 to the @env{PATH} environment variable.
24215 @anchor{show auto-load safe-path}
24216 @kindex show auto-load safe-path
24217 @item show auto-load safe-path
24218 Show the list of directories trusted for automatic loading and execution of
24221 @anchor{add-auto-load-safe-path}
24222 @kindex add-auto-load-safe-path
24223 @item add-auto-load-safe-path
24224 Add an entry (or list of entries) to the list of directories trusted for
24225 automatic loading and execution of scripts. Multiple entries may be delimited
24226 by the host platform path separator in use.
24229 This variable defaults to what @code{--with-auto-load-dir} has been configured
24230 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
24231 substitution applies the same as for @ref{set auto-load scripts-directory}.
24232 The default @code{set auto-load safe-path} value can be also overriden by
24233 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
24235 Setting this variable to @file{/} disables this security protection,
24236 corresponding @value{GDBN} configuration option is
24237 @option{--without-auto-load-safe-path}.
24238 This variable is supposed to be set to the system directories writable by the
24239 system superuser only. Users can add their source directories in init files in
24240 their home directories (@pxref{Home Directory Init File}). See also deprecated
24241 init file in the current directory
24242 (@pxref{Init File in the Current Directory during Startup}).
24244 To force @value{GDBN} to load the files it declined to load in the previous
24245 example, you could use one of the following ways:
24248 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
24249 Specify this trusted directory (or a file) as additional component of the list.
24250 You have to specify also any existing directories displayed by
24251 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
24253 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
24254 Specify this directory as in the previous case but just for a single
24255 @value{GDBN} session.
24257 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
24258 Disable auto-loading safety for a single @value{GDBN} session.
24259 This assumes all the files you debug during this @value{GDBN} session will come
24260 from trusted sources.
24262 @item @kbd{./configure --without-auto-load-safe-path}
24263 During compilation of @value{GDBN} you may disable any auto-loading safety.
24264 This assumes all the files you will ever debug with this @value{GDBN} come from
24268 On the other hand you can also explicitly forbid automatic files loading which
24269 also suppresses any such warning messages:
24272 @item @kbd{gdb -iex "set auto-load no" @dots{}}
24273 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
24275 @item @file{~/.gdbinit}: @samp{set auto-load no}
24276 Disable auto-loading globally for the user
24277 (@pxref{Home Directory Init File}). While it is improbable, you could also
24278 use system init file instead (@pxref{System-wide configuration}).
24281 This setting applies to the file names as entered by user. If no entry matches
24282 @value{GDBN} tries as a last resort to also resolve all the file names into
24283 their canonical form (typically resolving symbolic links) and compare the
24284 entries again. @value{GDBN} already canonicalizes most of the filenames on its
24285 own before starting the comparison so a canonical form of directories is
24286 recommended to be entered.
24288 @node Auto-loading verbose mode
24289 @subsection Displaying files tried for auto-load
24290 @cindex auto-loading verbose mode
24292 For better visibility of all the file locations where you can place scripts to
24293 be auto-loaded with inferior --- or to protect yourself against accidental
24294 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
24295 all the files attempted to be loaded. Both existing and non-existing files may
24298 For example the list of directories from which it is safe to auto-load files
24299 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
24300 may not be too obvious while setting it up.
24303 (gdb) set debug auto-load on
24304 (gdb) file ~/src/t/true
24305 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
24306 for objfile "/tmp/true".
24307 auto-load: Updating directories of "/usr:/opt".
24308 auto-load: Using directory "/usr".
24309 auto-load: Using directory "/opt".
24310 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
24311 by your `auto-load safe-path' set to "/usr:/opt".
24315 @anchor{set debug auto-load}
24316 @kindex set debug auto-load
24317 @item set debug auto-load [on|off]
24318 Set whether to print the filenames attempted to be auto-loaded.
24320 @anchor{show debug auto-load}
24321 @kindex show debug auto-load
24322 @item show debug auto-load
24323 Show whether printing of the filenames attempted to be auto-loaded is turned
24327 @node Messages/Warnings
24328 @section Optional Warnings and Messages
24330 @cindex verbose operation
24331 @cindex optional warnings
24332 By default, @value{GDBN} is silent about its inner workings. If you are
24333 running on a slow machine, you may want to use the @code{set verbose}
24334 command. This makes @value{GDBN} tell you when it does a lengthy
24335 internal operation, so you will not think it has crashed.
24337 Currently, the messages controlled by @code{set verbose} are those
24338 which announce that the symbol table for a source file is being read;
24339 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
24342 @kindex set verbose
24343 @item set verbose on
24344 Enables @value{GDBN} output of certain informational messages.
24346 @item set verbose off
24347 Disables @value{GDBN} output of certain informational messages.
24349 @kindex show verbose
24351 Displays whether @code{set verbose} is on or off.
24354 By default, if @value{GDBN} encounters bugs in the symbol table of an
24355 object file, it is silent; but if you are debugging a compiler, you may
24356 find this information useful (@pxref{Symbol Errors, ,Errors Reading
24361 @kindex set complaints
24362 @item set complaints @var{limit}
24363 Permits @value{GDBN} to output @var{limit} complaints about each type of
24364 unusual symbols before becoming silent about the problem. Set
24365 @var{limit} to zero to suppress all complaints; set it to a large number
24366 to prevent complaints from being suppressed.
24368 @kindex show complaints
24369 @item show complaints
24370 Displays how many symbol complaints @value{GDBN} is permitted to produce.
24374 @anchor{confirmation requests}
24375 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
24376 lot of stupid questions to confirm certain commands. For example, if
24377 you try to run a program which is already running:
24381 The program being debugged has been started already.
24382 Start it from the beginning? (y or n)
24385 If you are willing to unflinchingly face the consequences of your own
24386 commands, you can disable this ``feature'':
24390 @kindex set confirm
24392 @cindex confirmation
24393 @cindex stupid questions
24394 @item set confirm off
24395 Disables confirmation requests. Note that running @value{GDBN} with
24396 the @option{--batch} option (@pxref{Mode Options, -batch}) also
24397 automatically disables confirmation requests.
24399 @item set confirm on
24400 Enables confirmation requests (the default).
24402 @kindex show confirm
24404 Displays state of confirmation requests.
24408 @cindex command tracing
24409 If you need to debug user-defined commands or sourced files you may find it
24410 useful to enable @dfn{command tracing}. In this mode each command will be
24411 printed as it is executed, prefixed with one or more @samp{+} symbols, the
24412 quantity denoting the call depth of each command.
24415 @kindex set trace-commands
24416 @cindex command scripts, debugging
24417 @item set trace-commands on
24418 Enable command tracing.
24419 @item set trace-commands off
24420 Disable command tracing.
24421 @item show trace-commands
24422 Display the current state of command tracing.
24425 @node Debugging Output
24426 @section Optional Messages about Internal Happenings
24427 @cindex optional debugging messages
24429 @value{GDBN} has commands that enable optional debugging messages from
24430 various @value{GDBN} subsystems; normally these commands are of
24431 interest to @value{GDBN} maintainers, or when reporting a bug. This
24432 section documents those commands.
24435 @kindex set exec-done-display
24436 @item set exec-done-display
24437 Turns on or off the notification of asynchronous commands'
24438 completion. When on, @value{GDBN} will print a message when an
24439 asynchronous command finishes its execution. The default is off.
24440 @kindex show exec-done-display
24441 @item show exec-done-display
24442 Displays the current setting of asynchronous command completion
24445 @cindex ARM AArch64
24446 @item set debug aarch64
24447 Turns on or off display of debugging messages related to ARM AArch64.
24448 The default is off.
24450 @item show debug aarch64
24451 Displays the current state of displaying debugging messages related to
24453 @cindex gdbarch debugging info
24454 @cindex architecture debugging info
24455 @item set debug arch
24456 Turns on or off display of gdbarch debugging info. The default is off
24457 @item show debug arch
24458 Displays the current state of displaying gdbarch debugging info.
24459 @item set debug aix-solib
24460 @cindex AIX shared library debugging
24461 Control display of debugging messages from the AIX shared library
24462 support module. The default is off.
24463 @item show debug aix-thread
24464 Show the current state of displaying AIX shared library debugging messages.
24465 @item set debug aix-thread
24466 @cindex AIX threads
24467 Display debugging messages about inner workings of the AIX thread
24469 @item show debug aix-thread
24470 Show the current state of AIX thread debugging info display.
24471 @item set debug check-physname
24473 Check the results of the ``physname'' computation. When reading DWARF
24474 debugging information for C@t{++}, @value{GDBN} attempts to compute
24475 each entity's name. @value{GDBN} can do this computation in two
24476 different ways, depending on exactly what information is present.
24477 When enabled, this setting causes @value{GDBN} to compute the names
24478 both ways and display any discrepancies.
24479 @item show debug check-physname
24480 Show the current state of ``physname'' checking.
24481 @item set debug coff-pe-read
24482 @cindex COFF/PE exported symbols
24483 Control display of debugging messages related to reading of COFF/PE
24484 exported symbols. The default is off.
24485 @item show debug coff-pe-read
24486 Displays the current state of displaying debugging messages related to
24487 reading of COFF/PE exported symbols.
24488 @item set debug dwarf-die
24490 Dump DWARF DIEs after they are read in.
24491 The value is the number of nesting levels to print.
24492 A value of zero turns off the display.
24493 @item show debug dwarf-die
24494 Show the current state of DWARF DIE debugging.
24495 @item set debug dwarf-line
24496 @cindex DWARF Line Tables
24497 Turns on or off display of debugging messages related to reading
24498 DWARF line tables. The default is 0 (off).
24499 A value of 1 provides basic information.
24500 A value greater than 1 provides more verbose information.
24501 @item show debug dwarf-line
24502 Show the current state of DWARF line table debugging.
24503 @item set debug dwarf-read
24504 @cindex DWARF Reading
24505 Turns on or off display of debugging messages related to reading
24506 DWARF debug info. The default is 0 (off).
24507 A value of 1 provides basic information.
24508 A value greater than 1 provides more verbose information.
24509 @item show debug dwarf-read
24510 Show the current state of DWARF reader debugging.
24511 @item set debug displaced
24512 @cindex displaced stepping debugging info
24513 Turns on or off display of @value{GDBN} debugging info for the
24514 displaced stepping support. The default is off.
24515 @item show debug displaced
24516 Displays the current state of displaying @value{GDBN} debugging info
24517 related to displaced stepping.
24518 @item set debug event
24519 @cindex event debugging info
24520 Turns on or off display of @value{GDBN} event debugging info. The
24522 @item show debug event
24523 Displays the current state of displaying @value{GDBN} event debugging
24525 @item set debug expression
24526 @cindex expression debugging info
24527 Turns on or off display of debugging info about @value{GDBN}
24528 expression parsing. The default is off.
24529 @item show debug expression
24530 Displays the current state of displaying debugging info about
24531 @value{GDBN} expression parsing.
24532 @item set debug fbsd-lwp
24533 @cindex FreeBSD LWP debug messages
24534 Turns on or off debugging messages from the FreeBSD LWP debug support.
24535 @item show debug fbsd-lwp
24536 Show the current state of FreeBSD LWP debugging messages.
24537 @item set debug frame
24538 @cindex frame debugging info
24539 Turns on or off display of @value{GDBN} frame debugging info. The
24541 @item show debug frame
24542 Displays the current state of displaying @value{GDBN} frame debugging
24544 @item set debug gnu-nat
24545 @cindex @sc{gnu}/Hurd debug messages
24546 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
24547 @item show debug gnu-nat
24548 Show the current state of @sc{gnu}/Hurd debugging messages.
24549 @item set debug infrun
24550 @cindex inferior debugging info
24551 Turns on or off display of @value{GDBN} debugging info for running the inferior.
24552 The default is off. @file{infrun.c} contains GDB's runtime state machine used
24553 for implementing operations such as single-stepping the inferior.
24554 @item show debug infrun
24555 Displays the current state of @value{GDBN} inferior debugging.
24556 @item set debug jit
24557 @cindex just-in-time compilation, debugging messages
24558 Turn on or off debugging messages from JIT debug support.
24559 @item show debug jit
24560 Displays the current state of @value{GDBN} JIT debugging.
24561 @item set debug lin-lwp
24562 @cindex @sc{gnu}/Linux LWP debug messages
24563 @cindex Linux lightweight processes
24564 Turn on or off debugging messages from the Linux LWP debug support.
24565 @item show debug lin-lwp
24566 Show the current state of Linux LWP debugging messages.
24567 @item set debug linux-namespaces
24568 @cindex @sc{gnu}/Linux namespaces debug messages
24569 Turn on or off debugging messages from the Linux namespaces debug support.
24570 @item show debug linux-namespaces
24571 Show the current state of Linux namespaces debugging messages.
24572 @item set debug mach-o
24573 @cindex Mach-O symbols processing
24574 Control display of debugging messages related to Mach-O symbols
24575 processing. The default is off.
24576 @item show debug mach-o
24577 Displays the current state of displaying debugging messages related to
24578 reading of COFF/PE exported symbols.
24579 @item set debug notification
24580 @cindex remote async notification debugging info
24581 Turn on or off debugging messages about remote async notification.
24582 The default is off.
24583 @item show debug notification
24584 Displays the current state of remote async notification debugging messages.
24585 @item set debug observer
24586 @cindex observer debugging info
24587 Turns on or off display of @value{GDBN} observer debugging. This
24588 includes info such as the notification of observable events.
24589 @item show debug observer
24590 Displays the current state of observer debugging.
24591 @item set debug overload
24592 @cindex C@t{++} overload debugging info
24593 Turns on or off display of @value{GDBN} C@t{++} overload debugging
24594 info. This includes info such as ranking of functions, etc. The default
24596 @item show debug overload
24597 Displays the current state of displaying @value{GDBN} C@t{++} overload
24599 @cindex expression parser, debugging info
24600 @cindex debug expression parser
24601 @item set debug parser
24602 Turns on or off the display of expression parser debugging output.
24603 Internally, this sets the @code{yydebug} variable in the expression
24604 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
24605 details. The default is off.
24606 @item show debug parser
24607 Show the current state of expression parser debugging.
24608 @cindex packets, reporting on stdout
24609 @cindex serial connections, debugging
24610 @cindex debug remote protocol
24611 @cindex remote protocol debugging
24612 @cindex display remote packets
24613 @item set debug remote
24614 Turns on or off display of reports on all packets sent back and forth across
24615 the serial line to the remote machine. The info is printed on the
24616 @value{GDBN} standard output stream. The default is off.
24617 @item show debug remote
24618 Displays the state of display of remote packets.
24620 @item set debug separate-debug-file
24621 Turns on or off display of debug output about separate debug file search.
24622 @item show debug separate-debug-file
24623 Displays the state of separate debug file search debug output.
24625 @item set debug serial
24626 Turns on or off display of @value{GDBN} serial debugging info. The
24628 @item show debug serial
24629 Displays the current state of displaying @value{GDBN} serial debugging
24631 @item set debug solib-frv
24632 @cindex FR-V shared-library debugging
24633 Turn on or off debugging messages for FR-V shared-library code.
24634 @item show debug solib-frv
24635 Display the current state of FR-V shared-library code debugging
24637 @item set debug symbol-lookup
24638 @cindex symbol lookup
24639 Turns on or off display of debugging messages related to symbol lookup.
24640 The default is 0 (off).
24641 A value of 1 provides basic information.
24642 A value greater than 1 provides more verbose information.
24643 @item show debug symbol-lookup
24644 Show the current state of symbol lookup debugging messages.
24645 @item set debug symfile
24646 @cindex symbol file functions
24647 Turns on or off display of debugging messages related to symbol file functions.
24648 The default is off. @xref{Files}.
24649 @item show debug symfile
24650 Show the current state of symbol file debugging messages.
24651 @item set debug symtab-create
24652 @cindex symbol table creation
24653 Turns on or off display of debugging messages related to symbol table creation.
24654 The default is 0 (off).
24655 A value of 1 provides basic information.
24656 A value greater than 1 provides more verbose information.
24657 @item show debug symtab-create
24658 Show the current state of symbol table creation debugging.
24659 @item set debug target
24660 @cindex target debugging info
24661 Turns on or off display of @value{GDBN} target debugging info. This info
24662 includes what is going on at the target level of GDB, as it happens. The
24663 default is 0. Set it to 1 to track events, and to 2 to also track the
24664 value of large memory transfers.
24665 @item show debug target
24666 Displays the current state of displaying @value{GDBN} target debugging
24668 @item set debug timestamp
24669 @cindex timestampping debugging info
24670 Turns on or off display of timestamps with @value{GDBN} debugging info.
24671 When enabled, seconds and microseconds are displayed before each debugging
24673 @item show debug timestamp
24674 Displays the current state of displaying timestamps with @value{GDBN}
24676 @item set debug varobj
24677 @cindex variable object debugging info
24678 Turns on or off display of @value{GDBN} variable object debugging
24679 info. The default is off.
24680 @item show debug varobj
24681 Displays the current state of displaying @value{GDBN} variable object
24683 @item set debug xml
24684 @cindex XML parser debugging
24685 Turn on or off debugging messages for built-in XML parsers.
24686 @item show debug xml
24687 Displays the current state of XML debugging messages.
24690 @node Other Misc Settings
24691 @section Other Miscellaneous Settings
24692 @cindex miscellaneous settings
24695 @kindex set interactive-mode
24696 @item set interactive-mode
24697 If @code{on}, forces @value{GDBN} to assume that GDB was started
24698 in a terminal. In practice, this means that @value{GDBN} should wait
24699 for the user to answer queries generated by commands entered at
24700 the command prompt. If @code{off}, forces @value{GDBN} to operate
24701 in the opposite mode, and it uses the default answers to all queries.
24702 If @code{auto} (the default), @value{GDBN} tries to determine whether
24703 its standard input is a terminal, and works in interactive-mode if it
24704 is, non-interactively otherwise.
24706 In the vast majority of cases, the debugger should be able to guess
24707 correctly which mode should be used. But this setting can be useful
24708 in certain specific cases, such as running a MinGW @value{GDBN}
24709 inside a cygwin window.
24711 @kindex show interactive-mode
24712 @item show interactive-mode
24713 Displays whether the debugger is operating in interactive mode or not.
24716 @node Extending GDB
24717 @chapter Extending @value{GDBN}
24718 @cindex extending GDB
24720 @value{GDBN} provides several mechanisms for extension.
24721 @value{GDBN} also provides the ability to automatically load
24722 extensions when it reads a file for debugging. This allows the
24723 user to automatically customize @value{GDBN} for the program
24727 * Sequences:: Canned Sequences of @value{GDBN} Commands
24728 * Python:: Extending @value{GDBN} using Python
24729 * Guile:: Extending @value{GDBN} using Guile
24730 * Auto-loading extensions:: Automatically loading extensions
24731 * Multiple Extension Languages:: Working with multiple extension languages
24732 * Aliases:: Creating new spellings of existing commands
24735 To facilitate the use of extension languages, @value{GDBN} is capable
24736 of evaluating the contents of a file. When doing so, @value{GDBN}
24737 can recognize which extension language is being used by looking at
24738 the filename extension. Files with an unrecognized filename extension
24739 are always treated as a @value{GDBN} Command Files.
24740 @xref{Command Files,, Command files}.
24742 You can control how @value{GDBN} evaluates these files with the following
24746 @kindex set script-extension
24747 @kindex show script-extension
24748 @item set script-extension off
24749 All scripts are always evaluated as @value{GDBN} Command Files.
24751 @item set script-extension soft
24752 The debugger determines the scripting language based on filename
24753 extension. If this scripting language is supported, @value{GDBN}
24754 evaluates the script using that language. Otherwise, it evaluates
24755 the file as a @value{GDBN} Command File.
24757 @item set script-extension strict
24758 The debugger determines the scripting language based on filename
24759 extension, and evaluates the script using that language. If the
24760 language is not supported, then the evaluation fails.
24762 @item show script-extension
24763 Display the current value of the @code{script-extension} option.
24768 @section Canned Sequences of Commands
24770 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
24771 Command Lists}), @value{GDBN} provides two ways to store sequences of
24772 commands for execution as a unit: user-defined commands and command
24776 * Define:: How to define your own commands
24777 * Hooks:: Hooks for user-defined commands
24778 * Command Files:: How to write scripts of commands to be stored in a file
24779 * Output:: Commands for controlled output
24780 * Auto-loading sequences:: Controlling auto-loaded command files
24784 @subsection User-defined Commands
24786 @cindex user-defined command
24787 @cindex arguments, to user-defined commands
24788 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
24789 which you assign a new name as a command. This is done with the
24790 @code{define} command. User commands may accept an unlimited number of arguments
24791 separated by whitespace. Arguments are accessed within the user command
24792 via @code{$arg0@dots{}$argN}. A trivial example:
24796 print $arg0 + $arg1 + $arg2
24801 To execute the command use:
24808 This defines the command @code{adder}, which prints the sum of
24809 its three arguments. Note the arguments are text substitutions, so they may
24810 reference variables, use complex expressions, or even perform inferior
24813 @cindex argument count in user-defined commands
24814 @cindex how many arguments (user-defined commands)
24815 In addition, @code{$argc} may be used to find out how many arguments have
24821 print $arg0 + $arg1
24824 print $arg0 + $arg1 + $arg2
24829 Combining with the @code{eval} command (@pxref{eval}) makes it easier
24830 to process a variable number of arguments:
24837 eval "set $sum = $sum + $arg%d", $i
24847 @item define @var{commandname}
24848 Define a command named @var{commandname}. If there is already a command
24849 by that name, you are asked to confirm that you want to redefine it.
24850 The argument @var{commandname} may be a bare command name consisting of letters,
24851 numbers, dashes, and underscores. It may also start with any predefined
24852 prefix command. For example, @samp{define target my-target} creates
24853 a user-defined @samp{target my-target} command.
24855 The definition of the command is made up of other @value{GDBN} command lines,
24856 which are given following the @code{define} command. The end of these
24857 commands is marked by a line containing @code{end}.
24860 @kindex end@r{ (user-defined commands)}
24861 @item document @var{commandname}
24862 Document the user-defined command @var{commandname}, so that it can be
24863 accessed by @code{help}. The command @var{commandname} must already be
24864 defined. This command reads lines of documentation just as @code{define}
24865 reads the lines of the command definition, ending with @code{end}.
24866 After the @code{document} command is finished, @code{help} on command
24867 @var{commandname} displays the documentation you have written.
24869 You may use the @code{document} command again to change the
24870 documentation of a command. Redefining the command with @code{define}
24871 does not change the documentation.
24873 @kindex dont-repeat
24874 @cindex don't repeat command
24876 Used inside a user-defined command, this tells @value{GDBN} that this
24877 command should not be repeated when the user hits @key{RET}
24878 (@pxref{Command Syntax, repeat last command}).
24880 @kindex help user-defined
24881 @item help user-defined
24882 List all user-defined commands and all python commands defined in class
24883 COMAND_USER. The first line of the documentation or docstring is
24888 @itemx show user @var{commandname}
24889 Display the @value{GDBN} commands used to define @var{commandname} (but
24890 not its documentation). If no @var{commandname} is given, display the
24891 definitions for all user-defined commands.
24892 This does not work for user-defined python commands.
24894 @cindex infinite recursion in user-defined commands
24895 @kindex show max-user-call-depth
24896 @kindex set max-user-call-depth
24897 @item show max-user-call-depth
24898 @itemx set max-user-call-depth
24899 The value of @code{max-user-call-depth} controls how many recursion
24900 levels are allowed in user-defined commands before @value{GDBN} suspects an
24901 infinite recursion and aborts the command.
24902 This does not apply to user-defined python commands.
24905 In addition to the above commands, user-defined commands frequently
24906 use control flow commands, described in @ref{Command Files}.
24908 When user-defined commands are executed, the
24909 commands of the definition are not printed. An error in any command
24910 stops execution of the user-defined command.
24912 If used interactively, commands that would ask for confirmation proceed
24913 without asking when used inside a user-defined command. Many @value{GDBN}
24914 commands that normally print messages to say what they are doing omit the
24915 messages when used in a user-defined command.
24918 @subsection User-defined Command Hooks
24919 @cindex command hooks
24920 @cindex hooks, for commands
24921 @cindex hooks, pre-command
24924 You may define @dfn{hooks}, which are a special kind of user-defined
24925 command. Whenever you run the command @samp{foo}, if the user-defined
24926 command @samp{hook-foo} exists, it is executed (with no arguments)
24927 before that command.
24929 @cindex hooks, post-command
24931 A hook may also be defined which is run after the command you executed.
24932 Whenever you run the command @samp{foo}, if the user-defined command
24933 @samp{hookpost-foo} exists, it is executed (with no arguments) after
24934 that command. Post-execution hooks may exist simultaneously with
24935 pre-execution hooks, for the same command.
24937 It is valid for a hook to call the command which it hooks. If this
24938 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
24940 @c It would be nice if hookpost could be passed a parameter indicating
24941 @c if the command it hooks executed properly or not. FIXME!
24943 @kindex stop@r{, a pseudo-command}
24944 In addition, a pseudo-command, @samp{stop} exists. Defining
24945 (@samp{hook-stop}) makes the associated commands execute every time
24946 execution stops in your program: before breakpoint commands are run,
24947 displays are printed, or the stack frame is printed.
24949 For example, to ignore @code{SIGALRM} signals while
24950 single-stepping, but treat them normally during normal execution,
24955 handle SIGALRM nopass
24959 handle SIGALRM pass
24962 define hook-continue
24963 handle SIGALRM pass
24967 As a further example, to hook at the beginning and end of the @code{echo}
24968 command, and to add extra text to the beginning and end of the message,
24976 define hookpost-echo
24980 (@value{GDBP}) echo Hello World
24981 <<<---Hello World--->>>
24986 You can define a hook for any single-word command in @value{GDBN}, but
24987 not for command aliases; you should define a hook for the basic command
24988 name, e.g.@: @code{backtrace} rather than @code{bt}.
24989 @c FIXME! So how does Joe User discover whether a command is an alias
24991 You can hook a multi-word command by adding @code{hook-} or
24992 @code{hookpost-} to the last word of the command, e.g.@:
24993 @samp{define target hook-remote} to add a hook to @samp{target remote}.
24995 If an error occurs during the execution of your hook, execution of
24996 @value{GDBN} commands stops and @value{GDBN} issues a prompt
24997 (before the command that you actually typed had a chance to run).
24999 If you try to define a hook which does not match any known command, you
25000 get a warning from the @code{define} command.
25002 @node Command Files
25003 @subsection Command Files
25005 @cindex command files
25006 @cindex scripting commands
25007 A command file for @value{GDBN} is a text file made of lines that are
25008 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
25009 also be included. An empty line in a command file does nothing; it
25010 does not mean to repeat the last command, as it would from the
25013 You can request the execution of a command file with the @code{source}
25014 command. Note that the @code{source} command is also used to evaluate
25015 scripts that are not Command Files. The exact behavior can be configured
25016 using the @code{script-extension} setting.
25017 @xref{Extending GDB,, Extending GDB}.
25021 @cindex execute commands from a file
25022 @item source [-s] [-v] @var{filename}
25023 Execute the command file @var{filename}.
25026 The lines in a command file are generally executed sequentially,
25027 unless the order of execution is changed by one of the
25028 @emph{flow-control commands} described below. The commands are not
25029 printed as they are executed. An error in any command terminates
25030 execution of the command file and control is returned to the console.
25032 @value{GDBN} first searches for @var{filename} in the current directory.
25033 If the file is not found there, and @var{filename} does not specify a
25034 directory, then @value{GDBN} also looks for the file on the source search path
25035 (specified with the @samp{directory} command);
25036 except that @file{$cdir} is not searched because the compilation directory
25037 is not relevant to scripts.
25039 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
25040 on the search path even if @var{filename} specifies a directory.
25041 The search is done by appending @var{filename} to each element of the
25042 search path. So, for example, if @var{filename} is @file{mylib/myscript}
25043 and the search path contains @file{/home/user} then @value{GDBN} will
25044 look for the script @file{/home/user/mylib/myscript}.
25045 The search is also done if @var{filename} is an absolute path.
25046 For example, if @var{filename} is @file{/tmp/myscript} and
25047 the search path contains @file{/home/user} then @value{GDBN} will
25048 look for the script @file{/home/user/tmp/myscript}.
25049 For DOS-like systems, if @var{filename} contains a drive specification,
25050 it is stripped before concatenation. For example, if @var{filename} is
25051 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
25052 will look for the script @file{c:/tmp/myscript}.
25054 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
25055 each command as it is executed. The option must be given before
25056 @var{filename}, and is interpreted as part of the filename anywhere else.
25058 Commands that would ask for confirmation if used interactively proceed
25059 without asking when used in a command file. Many @value{GDBN} commands that
25060 normally print messages to say what they are doing omit the messages
25061 when called from command files.
25063 @value{GDBN} also accepts command input from standard input. In this
25064 mode, normal output goes to standard output and error output goes to
25065 standard error. Errors in a command file supplied on standard input do
25066 not terminate execution of the command file---execution continues with
25070 gdb < cmds > log 2>&1
25073 (The syntax above will vary depending on the shell used.) This example
25074 will execute commands from the file @file{cmds}. All output and errors
25075 would be directed to @file{log}.
25077 Since commands stored on command files tend to be more general than
25078 commands typed interactively, they frequently need to deal with
25079 complicated situations, such as different or unexpected values of
25080 variables and symbols, changes in how the program being debugged is
25081 built, etc. @value{GDBN} provides a set of flow-control commands to
25082 deal with these complexities. Using these commands, you can write
25083 complex scripts that loop over data structures, execute commands
25084 conditionally, etc.
25091 This command allows to include in your script conditionally executed
25092 commands. The @code{if} command takes a single argument, which is an
25093 expression to evaluate. It is followed by a series of commands that
25094 are executed only if the expression is true (its value is nonzero).
25095 There can then optionally be an @code{else} line, followed by a series
25096 of commands that are only executed if the expression was false. The
25097 end of the list is marked by a line containing @code{end}.
25101 This command allows to write loops. Its syntax is similar to
25102 @code{if}: the command takes a single argument, which is an expression
25103 to evaluate, and must be followed by the commands to execute, one per
25104 line, terminated by an @code{end}. These commands are called the
25105 @dfn{body} of the loop. The commands in the body of @code{while} are
25106 executed repeatedly as long as the expression evaluates to true.
25110 This command exits the @code{while} loop in whose body it is included.
25111 Execution of the script continues after that @code{while}s @code{end}
25114 @kindex loop_continue
25115 @item loop_continue
25116 This command skips the execution of the rest of the body of commands
25117 in the @code{while} loop in whose body it is included. Execution
25118 branches to the beginning of the @code{while} loop, where it evaluates
25119 the controlling expression.
25121 @kindex end@r{ (if/else/while commands)}
25123 Terminate the block of commands that are the body of @code{if},
25124 @code{else}, or @code{while} flow-control commands.
25129 @subsection Commands for Controlled Output
25131 During the execution of a command file or a user-defined command, normal
25132 @value{GDBN} output is suppressed; the only output that appears is what is
25133 explicitly printed by the commands in the definition. This section
25134 describes three commands useful for generating exactly the output you
25139 @item echo @var{text}
25140 @c I do not consider backslash-space a standard C escape sequence
25141 @c because it is not in ANSI.
25142 Print @var{text}. Nonprinting characters can be included in
25143 @var{text} using C escape sequences, such as @samp{\n} to print a
25144 newline. @strong{No newline is printed unless you specify one.}
25145 In addition to the standard C escape sequences, a backslash followed
25146 by a space stands for a space. This is useful for displaying a
25147 string with spaces at the beginning or the end, since leading and
25148 trailing spaces are otherwise trimmed from all arguments.
25149 To print @samp{@w{ }and foo =@w{ }}, use the command
25150 @samp{echo \@w{ }and foo = \@w{ }}.
25152 A backslash at the end of @var{text} can be used, as in C, to continue
25153 the command onto subsequent lines. For example,
25156 echo This is some text\n\
25157 which is continued\n\
25158 onto several lines.\n
25161 produces the same output as
25164 echo This is some text\n
25165 echo which is continued\n
25166 echo onto several lines.\n
25170 @item output @var{expression}
25171 Print the value of @var{expression} and nothing but that value: no
25172 newlines, no @samp{$@var{nn} = }. The value is not entered in the
25173 value history either. @xref{Expressions, ,Expressions}, for more information
25176 @item output/@var{fmt} @var{expression}
25177 Print the value of @var{expression} in format @var{fmt}. You can use
25178 the same formats as for @code{print}. @xref{Output Formats,,Output
25179 Formats}, for more information.
25182 @item printf @var{template}, @var{expressions}@dots{}
25183 Print the values of one or more @var{expressions} under the control of
25184 the string @var{template}. To print several values, make
25185 @var{expressions} be a comma-separated list of individual expressions,
25186 which may be either numbers or pointers. Their values are printed as
25187 specified by @var{template}, exactly as a C program would do by
25188 executing the code below:
25191 printf (@var{template}, @var{expressions}@dots{});
25194 As in @code{C} @code{printf}, ordinary characters in @var{template}
25195 are printed verbatim, while @dfn{conversion specification} introduced
25196 by the @samp{%} character cause subsequent @var{expressions} to be
25197 evaluated, their values converted and formatted according to type and
25198 style information encoded in the conversion specifications, and then
25201 For example, you can print two values in hex like this:
25204 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
25207 @code{printf} supports all the standard @code{C} conversion
25208 specifications, including the flags and modifiers between the @samp{%}
25209 character and the conversion letter, with the following exceptions:
25213 The argument-ordering modifiers, such as @samp{2$}, are not supported.
25216 The modifier @samp{*} is not supported for specifying precision or
25220 The @samp{'} flag (for separation of digits into groups according to
25221 @code{LC_NUMERIC'}) is not supported.
25224 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
25228 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
25231 The conversion letters @samp{a} and @samp{A} are not supported.
25235 Note that the @samp{ll} type modifier is supported only if the
25236 underlying @code{C} implementation used to build @value{GDBN} supports
25237 the @code{long long int} type, and the @samp{L} type modifier is
25238 supported only if @code{long double} type is available.
25240 As in @code{C}, @code{printf} supports simple backslash-escape
25241 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
25242 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
25243 single character. Octal and hexadecimal escape sequences are not
25246 Additionally, @code{printf} supports conversion specifications for DFP
25247 (@dfn{Decimal Floating Point}) types using the following length modifiers
25248 together with a floating point specifier.
25253 @samp{H} for printing @code{Decimal32} types.
25256 @samp{D} for printing @code{Decimal64} types.
25259 @samp{DD} for printing @code{Decimal128} types.
25262 If the underlying @code{C} implementation used to build @value{GDBN} has
25263 support for the three length modifiers for DFP types, other modifiers
25264 such as width and precision will also be available for @value{GDBN} to use.
25266 In case there is no such @code{C} support, no additional modifiers will be
25267 available and the value will be printed in the standard way.
25269 Here's an example of printing DFP types using the above conversion letters:
25271 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
25276 @item eval @var{template}, @var{expressions}@dots{}
25277 Convert the values of one or more @var{expressions} under the control of
25278 the string @var{template} to a command line, and call it.
25282 @node Auto-loading sequences
25283 @subsection Controlling auto-loading native @value{GDBN} scripts
25284 @cindex native script auto-loading
25286 When a new object file is read (for example, due to the @code{file}
25287 command, or because the inferior has loaded a shared library),
25288 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
25289 @xref{Auto-loading extensions}.
25291 Auto-loading can be enabled or disabled,
25292 and the list of auto-loaded scripts can be printed.
25295 @anchor{set auto-load gdb-scripts}
25296 @kindex set auto-load gdb-scripts
25297 @item set auto-load gdb-scripts [on|off]
25298 Enable or disable the auto-loading of canned sequences of commands scripts.
25300 @anchor{show auto-load gdb-scripts}
25301 @kindex show auto-load gdb-scripts
25302 @item show auto-load gdb-scripts
25303 Show whether auto-loading of canned sequences of commands scripts is enabled or
25306 @anchor{info auto-load gdb-scripts}
25307 @kindex info auto-load gdb-scripts
25308 @cindex print list of auto-loaded canned sequences of commands scripts
25309 @item info auto-load gdb-scripts [@var{regexp}]
25310 Print the list of all canned sequences of commands scripts that @value{GDBN}
25314 If @var{regexp} is supplied only canned sequences of commands scripts with
25315 matching names are printed.
25317 @c Python docs live in a separate file.
25318 @include python.texi
25320 @c Guile docs live in a separate file.
25321 @include guile.texi
25323 @node Auto-loading extensions
25324 @section Auto-loading extensions
25325 @cindex auto-loading extensions
25327 @value{GDBN} provides two mechanisms for automatically loading extensions
25328 when a new object file is read (for example, due to the @code{file}
25329 command, or because the inferior has loaded a shared library):
25330 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
25331 section of modern file formats like ELF.
25334 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
25335 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
25336 * Which flavor to choose?::
25339 The auto-loading feature is useful for supplying application-specific
25340 debugging commands and features.
25342 Auto-loading can be enabled or disabled,
25343 and the list of auto-loaded scripts can be printed.
25344 See the @samp{auto-loading} section of each extension language
25345 for more information.
25346 For @value{GDBN} command files see @ref{Auto-loading sequences}.
25347 For Python files see @ref{Python Auto-loading}.
25349 Note that loading of this script file also requires accordingly configured
25350 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25352 @node objfile-gdbdotext file
25353 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
25354 @cindex @file{@var{objfile}-gdb.gdb}
25355 @cindex @file{@var{objfile}-gdb.py}
25356 @cindex @file{@var{objfile}-gdb.scm}
25358 When a new object file is read, @value{GDBN} looks for a file named
25359 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
25360 where @var{objfile} is the object file's name and
25361 where @var{ext} is the file extension for the extension language:
25364 @item @file{@var{objfile}-gdb.gdb}
25365 GDB's own command language
25366 @item @file{@var{objfile}-gdb.py}
25368 @item @file{@var{objfile}-gdb.scm}
25372 @var{script-name} is formed by ensuring that the file name of @var{objfile}
25373 is absolute, following all symlinks, and resolving @code{.} and @code{..}
25374 components, and appending the @file{-gdb.@var{ext}} suffix.
25375 If this file exists and is readable, @value{GDBN} will evaluate it as a
25376 script in the specified extension language.
25378 If this file does not exist, then @value{GDBN} will look for
25379 @var{script-name} file in all of the directories as specified below.
25381 Note that loading of these files requires an accordingly configured
25382 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25384 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
25385 scripts normally according to its @file{.exe} filename. But if no scripts are
25386 found @value{GDBN} also tries script filenames matching the object file without
25387 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
25388 is attempted on any platform. This makes the script filenames compatible
25389 between Unix and MS-Windows hosts.
25392 @anchor{set auto-load scripts-directory}
25393 @kindex set auto-load scripts-directory
25394 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
25395 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
25396 may be delimited by the host platform path separator in use
25397 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
25399 Each entry here needs to be covered also by the security setting
25400 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
25402 @anchor{with-auto-load-dir}
25403 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
25404 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
25405 configuration option @option{--with-auto-load-dir}.
25407 Any reference to @file{$debugdir} will get replaced by
25408 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
25409 reference to @file{$datadir} will get replaced by @var{data-directory} which is
25410 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
25411 @file{$datadir} must be placed as a directory component --- either alone or
25412 delimited by @file{/} or @file{\} directory separators, depending on the host
25415 The list of directories uses path separator (@samp{:} on GNU and Unix
25416 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
25417 to the @env{PATH} environment variable.
25419 @anchor{show auto-load scripts-directory}
25420 @kindex show auto-load scripts-directory
25421 @item show auto-load scripts-directory
25422 Show @value{GDBN} auto-loaded scripts location.
25424 @anchor{add-auto-load-scripts-directory}
25425 @kindex add-auto-load-scripts-directory
25426 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
25427 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
25428 Multiple entries may be delimited by the host platform path separator in use.
25431 @value{GDBN} does not track which files it has already auto-loaded this way.
25432 @value{GDBN} will load the associated script every time the corresponding
25433 @var{objfile} is opened.
25434 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
25435 is evaluated more than once.
25437 @node dotdebug_gdb_scripts section
25438 @subsection The @code{.debug_gdb_scripts} section
25439 @cindex @code{.debug_gdb_scripts} section
25441 For systems using file formats like ELF and COFF,
25442 when @value{GDBN} loads a new object file
25443 it will look for a special section named @code{.debug_gdb_scripts}.
25444 If this section exists, its contents is a list of null-terminated entries
25445 specifying scripts to load. Each entry begins with a non-null prefix byte that
25446 specifies the kind of entry, typically the extension language and whether the
25447 script is in a file or inlined in @code{.debug_gdb_scripts}.
25449 The following entries are supported:
25452 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
25453 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
25454 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
25455 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
25458 @subsubsection Script File Entries
25460 If the entry specifies a file, @value{GDBN} will look for the file first
25461 in the current directory and then along the source search path
25462 (@pxref{Source Path, ,Specifying Source Directories}),
25463 except that @file{$cdir} is not searched, since the compilation
25464 directory is not relevant to scripts.
25466 File entries can be placed in section @code{.debug_gdb_scripts} with,
25467 for example, this GCC macro for Python scripts.
25470 /* Note: The "MS" section flags are to remove duplicates. */
25471 #define DEFINE_GDB_PY_SCRIPT(script_name) \
25473 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
25474 .byte 1 /* Python */\n\
25475 .asciz \"" script_name "\"\n\
25481 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
25482 Then one can reference the macro in a header or source file like this:
25485 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
25488 The script name may include directories if desired.
25490 Note that loading of this script file also requires accordingly configured
25491 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25493 If the macro invocation is put in a header, any application or library
25494 using this header will get a reference to the specified script,
25495 and with the use of @code{"MS"} attributes on the section, the linker
25496 will remove duplicates.
25498 @subsubsection Script Text Entries
25500 Script text entries allow to put the executable script in the entry
25501 itself instead of loading it from a file.
25502 The first line of the entry, everything after the prefix byte and up to
25503 the first newline (@code{0xa}) character, is the script name, and must not
25504 contain any kind of space character, e.g., spaces or tabs.
25505 The rest of the entry, up to the trailing null byte, is the script to
25506 execute in the specified language. The name needs to be unique among
25507 all script names, as @value{GDBN} executes each script only once based
25510 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
25514 #include "symcat.h"
25515 #include "gdb/section-scripts.h"
25517 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
25518 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
25519 ".ascii \"gdb.inlined-script\\n\"\n"
25520 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
25521 ".ascii \" def __init__ (self):\\n\"\n"
25522 ".ascii \" super (test_cmd, self).__init__ ("
25523 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
25524 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
25525 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
25526 ".ascii \"test_cmd ()\\n\"\n"
25532 Loading of inlined scripts requires a properly configured
25533 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25534 The path to specify in @code{auto-load safe-path} is the path of the file
25535 containing the @code{.debug_gdb_scripts} section.
25537 @node Which flavor to choose?
25538 @subsection Which flavor to choose?
25540 Given the multiple ways of auto-loading extensions, it might not always
25541 be clear which one to choose. This section provides some guidance.
25544 Benefits of the @file{-gdb.@var{ext}} way:
25548 Can be used with file formats that don't support multiple sections.
25551 Ease of finding scripts for public libraries.
25553 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
25554 in the source search path.
25555 For publicly installed libraries, e.g., @file{libstdc++}, there typically
25556 isn't a source directory in which to find the script.
25559 Doesn't require source code additions.
25563 Benefits of the @code{.debug_gdb_scripts} way:
25567 Works with static linking.
25569 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
25570 trigger their loading. When an application is statically linked the only
25571 objfile available is the executable, and it is cumbersome to attach all the
25572 scripts from all the input libraries to the executable's
25573 @file{-gdb.@var{ext}} script.
25576 Works with classes that are entirely inlined.
25578 Some classes can be entirely inlined, and thus there may not be an associated
25579 shared library to attach a @file{-gdb.@var{ext}} script to.
25582 Scripts needn't be copied out of the source tree.
25584 In some circumstances, apps can be built out of large collections of internal
25585 libraries, and the build infrastructure necessary to install the
25586 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
25587 cumbersome. It may be easier to specify the scripts in the
25588 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
25589 top of the source tree to the source search path.
25592 @node Multiple Extension Languages
25593 @section Multiple Extension Languages
25595 The Guile and Python extension languages do not share any state,
25596 and generally do not interfere with each other.
25597 There are some things to be aware of, however.
25599 @subsection Python comes first
25601 Python was @value{GDBN}'s first extension language, and to avoid breaking
25602 existing behaviour Python comes first. This is generally solved by the
25603 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
25604 extension languages, and when it makes a call to an extension language,
25605 (say to pretty-print a value), it tries each in turn until an extension
25606 language indicates it has performed the request (e.g., has returned the
25607 pretty-printed form of a value).
25608 This extends to errors while performing such requests: If an error happens
25609 while, for example, trying to pretty-print an object then the error is
25610 reported and any following extension languages are not tried.
25613 @section Creating new spellings of existing commands
25614 @cindex aliases for commands
25616 It is often useful to define alternate spellings of existing commands.
25617 For example, if a new @value{GDBN} command defined in Python has
25618 a long name to type, it is handy to have an abbreviated version of it
25619 that involves less typing.
25621 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
25622 of the @samp{step} command even though it is otherwise an ambiguous
25623 abbreviation of other commands like @samp{set} and @samp{show}.
25625 Aliases are also used to provide shortened or more common versions
25626 of multi-word commands. For example, @value{GDBN} provides the
25627 @samp{tty} alias of the @samp{set inferior-tty} command.
25629 You can define a new alias with the @samp{alias} command.
25634 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
25638 @var{ALIAS} specifies the name of the new alias.
25639 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
25642 @var{COMMAND} specifies the name of an existing command
25643 that is being aliased.
25645 The @samp{-a} option specifies that the new alias is an abbreviation
25646 of the command. Abbreviations are not shown in command
25647 lists displayed by the @samp{help} command.
25649 The @samp{--} option specifies the end of options,
25650 and is useful when @var{ALIAS} begins with a dash.
25652 Here is a simple example showing how to make an abbreviation
25653 of a command so that there is less to type.
25654 Suppose you were tired of typing @samp{disas}, the current
25655 shortest unambiguous abbreviation of the @samp{disassemble} command
25656 and you wanted an even shorter version named @samp{di}.
25657 The following will accomplish this.
25660 (gdb) alias -a di = disas
25663 Note that aliases are different from user-defined commands.
25664 With a user-defined command, you also need to write documentation
25665 for it with the @samp{document} command.
25666 An alias automatically picks up the documentation of the existing command.
25668 Here is an example where we make @samp{elms} an abbreviation of
25669 @samp{elements} in the @samp{set print elements} command.
25670 This is to show that you can make an abbreviation of any part
25674 (gdb) alias -a set print elms = set print elements
25675 (gdb) alias -a show print elms = show print elements
25676 (gdb) set p elms 20
25678 Limit on string chars or array elements to print is 200.
25681 Note that if you are defining an alias of a @samp{set} command,
25682 and you want to have an alias for the corresponding @samp{show}
25683 command, then you need to define the latter separately.
25685 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
25686 @var{ALIAS}, just as they are normally.
25689 (gdb) alias -a set pr elms = set p ele
25692 Finally, here is an example showing the creation of a one word
25693 alias for a more complex command.
25694 This creates alias @samp{spe} of the command @samp{set print elements}.
25697 (gdb) alias spe = set print elements
25702 @chapter Command Interpreters
25703 @cindex command interpreters
25705 @value{GDBN} supports multiple command interpreters, and some command
25706 infrastructure to allow users or user interface writers to switch
25707 between interpreters or run commands in other interpreters.
25709 @value{GDBN} currently supports two command interpreters, the console
25710 interpreter (sometimes called the command-line interpreter or @sc{cli})
25711 and the machine interface interpreter (or @sc{gdb/mi}). This manual
25712 describes both of these interfaces in great detail.
25714 By default, @value{GDBN} will start with the console interpreter.
25715 However, the user may choose to start @value{GDBN} with another
25716 interpreter by specifying the @option{-i} or @option{--interpreter}
25717 startup options. Defined interpreters include:
25721 @cindex console interpreter
25722 The traditional console or command-line interpreter. This is the most often
25723 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
25724 @value{GDBN} will use this interpreter.
25727 @cindex mi interpreter
25728 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
25729 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
25730 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
25734 @cindex mi2 interpreter
25735 The current @sc{gdb/mi} interface.
25738 @cindex mi1 interpreter
25739 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
25743 @cindex invoke another interpreter
25745 @kindex interpreter-exec
25746 You may execute commands in any interpreter from the current
25747 interpreter using the appropriate command. If you are running the
25748 console interpreter, simply use the @code{interpreter-exec} command:
25751 interpreter-exec mi "-data-list-register-names"
25754 @sc{gdb/mi} has a similar command, although it is only available in versions of
25755 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
25757 Note that @code{interpreter-exec} only changes the interpreter for the
25758 duration of the specified command. It does not change the interpreter
25761 @cindex start a new independent interpreter
25763 Although you may only choose a single interpreter at startup, it is
25764 possible to run an independent interpreter on a specified input/output
25765 device (usually a tty).
25767 For example, consider a debugger GUI or IDE that wants to provide a
25768 @value{GDBN} console view. It may do so by embedding a terminal
25769 emulator widget in its GUI, starting @value{GDBN} in the traditional
25770 command-line mode with stdin/stdout/stderr redirected to that
25771 terminal, and then creating an MI interpreter running on a specified
25772 input/output device. The console interpreter created by @value{GDBN}
25773 at startup handles commands the user types in the terminal widget,
25774 while the GUI controls and synchronizes state with @value{GDBN} using
25775 the separate MI interpreter.
25777 To start a new secondary @dfn{user interface} running MI, use the
25778 @code{new-ui} command:
25781 @cindex new user interface
25783 new-ui @var{interpreter} @var{tty}
25786 The @var{interpreter} parameter specifies the interpreter to run.
25787 This accepts the same values as the @code{interpreter-exec} command.
25788 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
25789 @var{tty} parameter specifies the name of the bidirectional file the
25790 interpreter uses for input/output, usually the name of a
25791 pseudoterminal slave on Unix systems. For example:
25794 (@value{GDBP}) new-ui mi /dev/pts/9
25798 runs an MI interpreter on @file{/dev/pts/9}.
25801 @chapter @value{GDBN} Text User Interface
25803 @cindex Text User Interface
25806 * TUI Overview:: TUI overview
25807 * TUI Keys:: TUI key bindings
25808 * TUI Single Key Mode:: TUI single key mode
25809 * TUI Commands:: TUI-specific commands
25810 * TUI Configuration:: TUI configuration variables
25813 The @value{GDBN} Text User Interface (TUI) is a terminal
25814 interface which uses the @code{curses} library to show the source
25815 file, the assembly output, the program registers and @value{GDBN}
25816 commands in separate text windows. The TUI mode is supported only
25817 on platforms where a suitable version of the @code{curses} library
25820 The TUI mode is enabled by default when you invoke @value{GDBN} as
25821 @samp{@value{GDBP} -tui}.
25822 You can also switch in and out of TUI mode while @value{GDBN} runs by
25823 using various TUI commands and key bindings, such as @command{tui
25824 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
25825 @ref{TUI Keys, ,TUI Key Bindings}.
25828 @section TUI Overview
25830 In TUI mode, @value{GDBN} can display several text windows:
25834 This window is the @value{GDBN} command window with the @value{GDBN}
25835 prompt and the @value{GDBN} output. The @value{GDBN} input is still
25836 managed using readline.
25839 The source window shows the source file of the program. The current
25840 line and active breakpoints are displayed in this window.
25843 The assembly window shows the disassembly output of the program.
25846 This window shows the processor registers. Registers are highlighted
25847 when their values change.
25850 The source and assembly windows show the current program position
25851 by highlighting the current line and marking it with a @samp{>} marker.
25852 Breakpoints are indicated with two markers. The first marker
25853 indicates the breakpoint type:
25857 Breakpoint which was hit at least once.
25860 Breakpoint which was never hit.
25863 Hardware breakpoint which was hit at least once.
25866 Hardware breakpoint which was never hit.
25869 The second marker indicates whether the breakpoint is enabled or not:
25873 Breakpoint is enabled.
25876 Breakpoint is disabled.
25879 The source, assembly and register windows are updated when the current
25880 thread changes, when the frame changes, or when the program counter
25883 These windows are not all visible at the same time. The command
25884 window is always visible. The others can be arranged in several
25895 source and assembly,
25898 source and registers, or
25901 assembly and registers.
25904 A status line above the command window shows the following information:
25908 Indicates the current @value{GDBN} target.
25909 (@pxref{Targets, ,Specifying a Debugging Target}).
25912 Gives the current process or thread number.
25913 When no process is being debugged, this field is set to @code{No process}.
25916 Gives the current function name for the selected frame.
25917 The name is demangled if demangling is turned on (@pxref{Print Settings}).
25918 When there is no symbol corresponding to the current program counter,
25919 the string @code{??} is displayed.
25922 Indicates the current line number for the selected frame.
25923 When the current line number is not known, the string @code{??} is displayed.
25926 Indicates the current program counter address.
25930 @section TUI Key Bindings
25931 @cindex TUI key bindings
25933 The TUI installs several key bindings in the readline keymaps
25934 @ifset SYSTEM_READLINE
25935 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
25937 @ifclear SYSTEM_READLINE
25938 (@pxref{Command Line Editing}).
25940 The following key bindings are installed for both TUI mode and the
25941 @value{GDBN} standard mode.
25950 Enter or leave the TUI mode. When leaving the TUI mode,
25951 the curses window management stops and @value{GDBN} operates using
25952 its standard mode, writing on the terminal directly. When reentering
25953 the TUI mode, control is given back to the curses windows.
25954 The screen is then refreshed.
25958 Use a TUI layout with only one window. The layout will
25959 either be @samp{source} or @samp{assembly}. When the TUI mode
25960 is not active, it will switch to the TUI mode.
25962 Think of this key binding as the Emacs @kbd{C-x 1} binding.
25966 Use a TUI layout with at least two windows. When the current
25967 layout already has two windows, the next layout with two windows is used.
25968 When a new layout is chosen, one window will always be common to the
25969 previous layout and the new one.
25971 Think of it as the Emacs @kbd{C-x 2} binding.
25975 Change the active window. The TUI associates several key bindings
25976 (like scrolling and arrow keys) with the active window. This command
25977 gives the focus to the next TUI window.
25979 Think of it as the Emacs @kbd{C-x o} binding.
25983 Switch in and out of the TUI SingleKey mode that binds single
25984 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
25987 The following key bindings only work in the TUI mode:
25992 Scroll the active window one page up.
25996 Scroll the active window one page down.
26000 Scroll the active window one line up.
26004 Scroll the active window one line down.
26008 Scroll the active window one column left.
26012 Scroll the active window one column right.
26016 Refresh the screen.
26019 Because the arrow keys scroll the active window in the TUI mode, they
26020 are not available for their normal use by readline unless the command
26021 window has the focus. When another window is active, you must use
26022 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
26023 and @kbd{C-f} to control the command window.
26025 @node TUI Single Key Mode
26026 @section TUI Single Key Mode
26027 @cindex TUI single key mode
26029 The TUI also provides a @dfn{SingleKey} mode, which binds several
26030 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
26031 switch into this mode, where the following key bindings are used:
26034 @kindex c @r{(SingleKey TUI key)}
26038 @kindex d @r{(SingleKey TUI key)}
26042 @kindex f @r{(SingleKey TUI key)}
26046 @kindex n @r{(SingleKey TUI key)}
26050 @kindex o @r{(SingleKey TUI key)}
26052 nexti. The shortcut letter @samp{o} stands for ``step Over''.
26054 @kindex q @r{(SingleKey TUI key)}
26056 exit the SingleKey mode.
26058 @kindex r @r{(SingleKey TUI key)}
26062 @kindex s @r{(SingleKey TUI key)}
26066 @kindex i @r{(SingleKey TUI key)}
26068 stepi. The shortcut letter @samp{i} stands for ``step Into''.
26070 @kindex u @r{(SingleKey TUI key)}
26074 @kindex v @r{(SingleKey TUI key)}
26078 @kindex w @r{(SingleKey TUI key)}
26083 Other keys temporarily switch to the @value{GDBN} command prompt.
26084 The key that was pressed is inserted in the editing buffer so that
26085 it is possible to type most @value{GDBN} commands without interaction
26086 with the TUI SingleKey mode. Once the command is entered the TUI
26087 SingleKey mode is restored. The only way to permanently leave
26088 this mode is by typing @kbd{q} or @kbd{C-x s}.
26092 @section TUI-specific Commands
26093 @cindex TUI commands
26095 The TUI has specific commands to control the text windows.
26096 These commands are always available, even when @value{GDBN} is not in
26097 the TUI mode. When @value{GDBN} is in the standard mode, most
26098 of these commands will automatically switch to the TUI mode.
26100 Note that if @value{GDBN}'s @code{stdout} is not connected to a
26101 terminal, or @value{GDBN} has been started with the machine interface
26102 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
26103 these commands will fail with an error, because it would not be
26104 possible or desirable to enable curses window management.
26109 Activate TUI mode. The last active TUI window layout will be used if
26110 TUI mode has prevsiouly been used in the current debugging session,
26111 otherwise a default layout is used.
26114 @kindex tui disable
26115 Disable TUI mode, returning to the console interpreter.
26119 List and give the size of all displayed windows.
26121 @item layout @var{name}
26123 Changes which TUI windows are displayed. In each layout the command
26124 window is always displayed, the @var{name} parameter controls which
26125 additional windows are displayed, and can be any of the following:
26129 Display the next layout.
26132 Display the previous layout.
26135 Display the source and command windows.
26138 Display the assembly and command windows.
26141 Display the source, assembly, and command windows.
26144 When in @code{src} layout display the register, source, and command
26145 windows. When in @code{asm} or @code{split} layout display the
26146 register, assembler, and command windows.
26149 @item focus @var{name}
26151 Changes which TUI window is currently active for scrolling. The
26152 @var{name} parameter can be any of the following:
26156 Make the next window active for scrolling.
26159 Make the previous window active for scrolling.
26162 Make the source window active for scrolling.
26165 Make the assembly window active for scrolling.
26168 Make the register window active for scrolling.
26171 Make the command window active for scrolling.
26176 Refresh the screen. This is similar to typing @kbd{C-L}.
26178 @item tui reg @var{group}
26180 Changes the register group displayed in the tui register window to
26181 @var{group}. If the register window is not currently displayed this
26182 command will cause the register window to be displayed. The list of
26183 register groups, as well as their order is target specific. The
26184 following groups are available on most targets:
26187 Repeatedly selecting this group will cause the display to cycle
26188 through all of the available register groups.
26191 Repeatedly selecting this group will cause the display to cycle
26192 through all of the available register groups in the reverse order to
26196 Display the general registers.
26198 Display the floating point registers.
26200 Display the system registers.
26202 Display the vector registers.
26204 Display all registers.
26209 Update the source window and the current execution point.
26211 @item winheight @var{name} +@var{count}
26212 @itemx winheight @var{name} -@var{count}
26214 Change the height of the window @var{name} by @var{count}
26215 lines. Positive counts increase the height, while negative counts
26216 decrease it. The @var{name} parameter can be one of @code{src} (the
26217 source window), @code{cmd} (the command window), @code{asm} (the
26218 disassembly window), or @code{regs} (the register display window).
26220 @item tabset @var{nchars}
26222 Set the width of tab stops to be @var{nchars} characters. This
26223 setting affects the display of TAB characters in the source and
26227 @node TUI Configuration
26228 @section TUI Configuration Variables
26229 @cindex TUI configuration variables
26231 Several configuration variables control the appearance of TUI windows.
26234 @item set tui border-kind @var{kind}
26235 @kindex set tui border-kind
26236 Select the border appearance for the source, assembly and register windows.
26237 The possible values are the following:
26240 Use a space character to draw the border.
26243 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
26246 Use the Alternate Character Set to draw the border. The border is
26247 drawn using character line graphics if the terminal supports them.
26250 @item set tui border-mode @var{mode}
26251 @kindex set tui border-mode
26252 @itemx set tui active-border-mode @var{mode}
26253 @kindex set tui active-border-mode
26254 Select the display attributes for the borders of the inactive windows
26255 or the active window. The @var{mode} can be one of the following:
26258 Use normal attributes to display the border.
26264 Use reverse video mode.
26267 Use half bright mode.
26269 @item half-standout
26270 Use half bright and standout mode.
26273 Use extra bright or bold mode.
26275 @item bold-standout
26276 Use extra bright or bold and standout mode.
26281 @chapter Using @value{GDBN} under @sc{gnu} Emacs
26284 @cindex @sc{gnu} Emacs
26285 A special interface allows you to use @sc{gnu} Emacs to view (and
26286 edit) the source files for the program you are debugging with
26289 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
26290 executable file you want to debug as an argument. This command starts
26291 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
26292 created Emacs buffer.
26293 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
26295 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
26300 All ``terminal'' input and output goes through an Emacs buffer, called
26303 This applies both to @value{GDBN} commands and their output, and to the input
26304 and output done by the program you are debugging.
26306 This is useful because it means that you can copy the text of previous
26307 commands and input them again; you can even use parts of the output
26310 All the facilities of Emacs' Shell mode are available for interacting
26311 with your program. In particular, you can send signals the usual
26312 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
26316 @value{GDBN} displays source code through Emacs.
26318 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
26319 source file for that frame and puts an arrow (@samp{=>}) at the
26320 left margin of the current line. Emacs uses a separate buffer for
26321 source display, and splits the screen to show both your @value{GDBN} session
26324 Explicit @value{GDBN} @code{list} or search commands still produce output as
26325 usual, but you probably have no reason to use them from Emacs.
26328 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
26329 a graphical mode, enabled by default, which provides further buffers
26330 that can control the execution and describe the state of your program.
26331 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
26333 If you specify an absolute file name when prompted for the @kbd{M-x
26334 gdb} argument, then Emacs sets your current working directory to where
26335 your program resides. If you only specify the file name, then Emacs
26336 sets your current working directory to the directory associated
26337 with the previous buffer. In this case, @value{GDBN} may find your
26338 program by searching your environment's @code{PATH} variable, but on
26339 some operating systems it might not find the source. So, although the
26340 @value{GDBN} input and output session proceeds normally, the auxiliary
26341 buffer does not display the current source and line of execution.
26343 The initial working directory of @value{GDBN} is printed on the top
26344 line of the GUD buffer and this serves as a default for the commands
26345 that specify files for @value{GDBN} to operate on. @xref{Files,
26346 ,Commands to Specify Files}.
26348 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
26349 need to call @value{GDBN} by a different name (for example, if you
26350 keep several configurations around, with different names) you can
26351 customize the Emacs variable @code{gud-gdb-command-name} to run the
26354 In the GUD buffer, you can use these special Emacs commands in
26355 addition to the standard Shell mode commands:
26359 Describe the features of Emacs' GUD Mode.
26362 Execute to another source line, like the @value{GDBN} @code{step} command; also
26363 update the display window to show the current file and location.
26366 Execute to next source line in this function, skipping all function
26367 calls, like the @value{GDBN} @code{next} command. Then update the display window
26368 to show the current file and location.
26371 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
26372 display window accordingly.
26375 Execute until exit from the selected stack frame, like the @value{GDBN}
26376 @code{finish} command.
26379 Continue execution of your program, like the @value{GDBN} @code{continue}
26383 Go up the number of frames indicated by the numeric argument
26384 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
26385 like the @value{GDBN} @code{up} command.
26388 Go down the number of frames indicated by the numeric argument, like the
26389 @value{GDBN} @code{down} command.
26392 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
26393 tells @value{GDBN} to set a breakpoint on the source line point is on.
26395 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
26396 separate frame which shows a backtrace when the GUD buffer is current.
26397 Move point to any frame in the stack and type @key{RET} to make it
26398 become the current frame and display the associated source in the
26399 source buffer. Alternatively, click @kbd{Mouse-2} to make the
26400 selected frame become the current one. In graphical mode, the
26401 speedbar displays watch expressions.
26403 If you accidentally delete the source-display buffer, an easy way to get
26404 it back is to type the command @code{f} in the @value{GDBN} buffer, to
26405 request a frame display; when you run under Emacs, this recreates
26406 the source buffer if necessary to show you the context of the current
26409 The source files displayed in Emacs are in ordinary Emacs buffers
26410 which are visiting the source files in the usual way. You can edit
26411 the files with these buffers if you wish; but keep in mind that @value{GDBN}
26412 communicates with Emacs in terms of line numbers. If you add or
26413 delete lines from the text, the line numbers that @value{GDBN} knows cease
26414 to correspond properly with the code.
26416 A more detailed description of Emacs' interaction with @value{GDBN} is
26417 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
26421 @chapter The @sc{gdb/mi} Interface
26423 @unnumberedsec Function and Purpose
26425 @cindex @sc{gdb/mi}, its purpose
26426 @sc{gdb/mi} is a line based machine oriented text interface to
26427 @value{GDBN} and is activated by specifying using the
26428 @option{--interpreter} command line option (@pxref{Mode Options}). It
26429 is specifically intended to support the development of systems which
26430 use the debugger as just one small component of a larger system.
26432 This chapter is a specification of the @sc{gdb/mi} interface. It is written
26433 in the form of a reference manual.
26435 Note that @sc{gdb/mi} is still under construction, so some of the
26436 features described below are incomplete and subject to change
26437 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
26439 @unnumberedsec Notation and Terminology
26441 @cindex notational conventions, for @sc{gdb/mi}
26442 This chapter uses the following notation:
26446 @code{|} separates two alternatives.
26449 @code{[ @var{something} ]} indicates that @var{something} is optional:
26450 it may or may not be given.
26453 @code{( @var{group} )*} means that @var{group} inside the parentheses
26454 may repeat zero or more times.
26457 @code{( @var{group} )+} means that @var{group} inside the parentheses
26458 may repeat one or more times.
26461 @code{"@var{string}"} means a literal @var{string}.
26465 @heading Dependencies
26469 * GDB/MI General Design::
26470 * GDB/MI Command Syntax::
26471 * GDB/MI Compatibility with CLI::
26472 * GDB/MI Development and Front Ends::
26473 * GDB/MI Output Records::
26474 * GDB/MI Simple Examples::
26475 * GDB/MI Command Description Format::
26476 * GDB/MI Breakpoint Commands::
26477 * GDB/MI Catchpoint Commands::
26478 * GDB/MI Program Context::
26479 * GDB/MI Thread Commands::
26480 * GDB/MI Ada Tasking Commands::
26481 * GDB/MI Program Execution::
26482 * GDB/MI Stack Manipulation::
26483 * GDB/MI Variable Objects::
26484 * GDB/MI Data Manipulation::
26485 * GDB/MI Tracepoint Commands::
26486 * GDB/MI Symbol Query::
26487 * GDB/MI File Commands::
26489 * GDB/MI Kod Commands::
26490 * GDB/MI Memory Overlay Commands::
26491 * GDB/MI Signal Handling Commands::
26493 * GDB/MI Target Manipulation::
26494 * GDB/MI File Transfer Commands::
26495 * GDB/MI Ada Exceptions Commands::
26496 * GDB/MI Support Commands::
26497 * GDB/MI Miscellaneous Commands::
26500 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26501 @node GDB/MI General Design
26502 @section @sc{gdb/mi} General Design
26503 @cindex GDB/MI General Design
26505 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
26506 parts---commands sent to @value{GDBN}, responses to those commands
26507 and notifications. Each command results in exactly one response,
26508 indicating either successful completion of the command, or an error.
26509 For the commands that do not resume the target, the response contains the
26510 requested information. For the commands that resume the target, the
26511 response only indicates whether the target was successfully resumed.
26512 Notifications is the mechanism for reporting changes in the state of the
26513 target, or in @value{GDBN} state, that cannot conveniently be associated with
26514 a command and reported as part of that command response.
26516 The important examples of notifications are:
26520 Exec notifications. These are used to report changes in
26521 target state---when a target is resumed, or stopped. It would not
26522 be feasible to include this information in response of resuming
26523 commands, because one resume commands can result in multiple events in
26524 different threads. Also, quite some time may pass before any event
26525 happens in the target, while a frontend needs to know whether the resuming
26526 command itself was successfully executed.
26529 Console output, and status notifications. Console output
26530 notifications are used to report output of CLI commands, as well as
26531 diagnostics for other commands. Status notifications are used to
26532 report the progress of a long-running operation. Naturally, including
26533 this information in command response would mean no output is produced
26534 until the command is finished, which is undesirable.
26537 General notifications. Commands may have various side effects on
26538 the @value{GDBN} or target state beyond their official purpose. For example,
26539 a command may change the selected thread. Although such changes can
26540 be included in command response, using notification allows for more
26541 orthogonal frontend design.
26545 There's no guarantee that whenever an MI command reports an error,
26546 @value{GDBN} or the target are in any specific state, and especially,
26547 the state is not reverted to the state before the MI command was
26548 processed. Therefore, whenever an MI command results in an error,
26549 we recommend that the frontend refreshes all the information shown in
26550 the user interface.
26554 * Context management::
26555 * Asynchronous and non-stop modes::
26559 @node Context management
26560 @subsection Context management
26562 @subsubsection Threads and Frames
26564 In most cases when @value{GDBN} accesses the target, this access is
26565 done in context of a specific thread and frame (@pxref{Frames}).
26566 Often, even when accessing global data, the target requires that a thread
26567 be specified. The CLI interface maintains the selected thread and frame,
26568 and supplies them to target on each command. This is convenient,
26569 because a command line user would not want to specify that information
26570 explicitly on each command, and because user interacts with
26571 @value{GDBN} via a single terminal, so no confusion is possible as
26572 to what thread and frame are the current ones.
26574 In the case of MI, the concept of selected thread and frame is less
26575 useful. First, a frontend can easily remember this information
26576 itself. Second, a graphical frontend can have more than one window,
26577 each one used for debugging a different thread, and the frontend might
26578 want to access additional threads for internal purposes. This
26579 increases the risk that by relying on implicitly selected thread, the
26580 frontend may be operating on a wrong one. Therefore, each MI command
26581 should explicitly specify which thread and frame to operate on. To
26582 make it possible, each MI command accepts the @samp{--thread} and
26583 @samp{--frame} options, the value to each is @value{GDBN} global
26584 identifier for thread and frame to operate on.
26586 Usually, each top-level window in a frontend allows the user to select
26587 a thread and a frame, and remembers the user selection for further
26588 operations. However, in some cases @value{GDBN} may suggest that the
26589 current thread or frame be changed. For example, when stopping on a
26590 breakpoint it is reasonable to switch to the thread where breakpoint is
26591 hit. For another example, if the user issues the CLI @samp{thread} or
26592 @samp{frame} commands via the frontend, it is desirable to change the
26593 frontend's selection to the one specified by user. @value{GDBN}
26594 communicates the suggestion to change current thread and frame using the
26595 @samp{=thread-selected} notification.
26597 Note that historically, MI shares the selected thread with CLI, so
26598 frontends used the @code{-thread-select} to execute commands in the
26599 right context. However, getting this to work right is cumbersome. The
26600 simplest way is for frontend to emit @code{-thread-select} command
26601 before every command. This doubles the number of commands that need
26602 to be sent. The alternative approach is to suppress @code{-thread-select}
26603 if the selected thread in @value{GDBN} is supposed to be identical to the
26604 thread the frontend wants to operate on. However, getting this
26605 optimization right can be tricky. In particular, if the frontend
26606 sends several commands to @value{GDBN}, and one of the commands changes the
26607 selected thread, then the behaviour of subsequent commands will
26608 change. So, a frontend should either wait for response from such
26609 problematic commands, or explicitly add @code{-thread-select} for
26610 all subsequent commands. No frontend is known to do this exactly
26611 right, so it is suggested to just always pass the @samp{--thread} and
26612 @samp{--frame} options.
26614 @subsubsection Language
26616 The execution of several commands depends on which language is selected.
26617 By default, the current language (@pxref{show language}) is used.
26618 But for commands known to be language-sensitive, it is recommended
26619 to use the @samp{--language} option. This option takes one argument,
26620 which is the name of the language to use while executing the command.
26624 -data-evaluate-expression --language c "sizeof (void*)"
26629 The valid language names are the same names accepted by the
26630 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
26631 @samp{local} or @samp{unknown}.
26633 @node Asynchronous and non-stop modes
26634 @subsection Asynchronous command execution and non-stop mode
26636 On some targets, @value{GDBN} is capable of processing MI commands
26637 even while the target is running. This is called @dfn{asynchronous
26638 command execution} (@pxref{Background Execution}). The frontend may
26639 specify a preferrence for asynchronous execution using the
26640 @code{-gdb-set mi-async 1} command, which should be emitted before
26641 either running the executable or attaching to the target. After the
26642 frontend has started the executable or attached to the target, it can
26643 find if asynchronous execution is enabled using the
26644 @code{-list-target-features} command.
26647 @item -gdb-set mi-async on
26648 @item -gdb-set mi-async off
26649 Set whether MI is in asynchronous mode.
26651 When @code{off}, which is the default, MI execution commands (e.g.,
26652 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
26653 for the program to stop before processing further commands.
26655 When @code{on}, MI execution commands are background execution
26656 commands (e.g., @code{-exec-continue} becomes the equivalent of the
26657 @code{c&} CLI command), and so @value{GDBN} is capable of processing
26658 MI commands even while the target is running.
26660 @item -gdb-show mi-async
26661 Show whether MI asynchronous mode is enabled.
26664 Note: In @value{GDBN} version 7.7 and earlier, this option was called
26665 @code{target-async} instead of @code{mi-async}, and it had the effect
26666 of both putting MI in asynchronous mode and making CLI background
26667 commands possible. CLI background commands are now always possible
26668 ``out of the box'' if the target supports them. The old spelling is
26669 kept as a deprecated alias for backwards compatibility.
26671 Even if @value{GDBN} can accept a command while target is running,
26672 many commands that access the target do not work when the target is
26673 running. Therefore, asynchronous command execution is most useful
26674 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
26675 it is possible to examine the state of one thread, while other threads
26678 When a given thread is running, MI commands that try to access the
26679 target in the context of that thread may not work, or may work only on
26680 some targets. In particular, commands that try to operate on thread's
26681 stack will not work, on any target. Commands that read memory, or
26682 modify breakpoints, may work or not work, depending on the target. Note
26683 that even commands that operate on global state, such as @code{print},
26684 @code{set}, and breakpoint commands, still access the target in the
26685 context of a specific thread, so frontend should try to find a
26686 stopped thread and perform the operation on that thread (using the
26687 @samp{--thread} option).
26689 Which commands will work in the context of a running thread is
26690 highly target dependent. However, the two commands
26691 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
26692 to find the state of a thread, will always work.
26694 @node Thread groups
26695 @subsection Thread groups
26696 @value{GDBN} may be used to debug several processes at the same time.
26697 On some platfroms, @value{GDBN} may support debugging of several
26698 hardware systems, each one having several cores with several different
26699 processes running on each core. This section describes the MI
26700 mechanism to support such debugging scenarios.
26702 The key observation is that regardless of the structure of the
26703 target, MI can have a global list of threads, because most commands that
26704 accept the @samp{--thread} option do not need to know what process that
26705 thread belongs to. Therefore, it is not necessary to introduce
26706 neither additional @samp{--process} option, nor an notion of the
26707 current process in the MI interface. The only strictly new feature
26708 that is required is the ability to find how the threads are grouped
26711 To allow the user to discover such grouping, and to support arbitrary
26712 hierarchy of machines/cores/processes, MI introduces the concept of a
26713 @dfn{thread group}. Thread group is a collection of threads and other
26714 thread groups. A thread group always has a string identifier, a type,
26715 and may have additional attributes specific to the type. A new
26716 command, @code{-list-thread-groups}, returns the list of top-level
26717 thread groups, which correspond to processes that @value{GDBN} is
26718 debugging at the moment. By passing an identifier of a thread group
26719 to the @code{-list-thread-groups} command, it is possible to obtain
26720 the members of specific thread group.
26722 To allow the user to easily discover processes, and other objects, he
26723 wishes to debug, a concept of @dfn{available thread group} is
26724 introduced. Available thread group is an thread group that
26725 @value{GDBN} is not debugging, but that can be attached to, using the
26726 @code{-target-attach} command. The list of available top-level thread
26727 groups can be obtained using @samp{-list-thread-groups --available}.
26728 In general, the content of a thread group may be only retrieved only
26729 after attaching to that thread group.
26731 Thread groups are related to inferiors (@pxref{Inferiors and
26732 Programs}). Each inferior corresponds to a thread group of a special
26733 type @samp{process}, and some additional operations are permitted on
26734 such thread groups.
26736 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26737 @node GDB/MI Command Syntax
26738 @section @sc{gdb/mi} Command Syntax
26741 * GDB/MI Input Syntax::
26742 * GDB/MI Output Syntax::
26745 @node GDB/MI Input Syntax
26746 @subsection @sc{gdb/mi} Input Syntax
26748 @cindex input syntax for @sc{gdb/mi}
26749 @cindex @sc{gdb/mi}, input syntax
26751 @item @var{command} @expansion{}
26752 @code{@var{cli-command} | @var{mi-command}}
26754 @item @var{cli-command} @expansion{}
26755 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
26756 @var{cli-command} is any existing @value{GDBN} CLI command.
26758 @item @var{mi-command} @expansion{}
26759 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
26760 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
26762 @item @var{token} @expansion{}
26763 "any sequence of digits"
26765 @item @var{option} @expansion{}
26766 @code{"-" @var{parameter} [ " " @var{parameter} ]}
26768 @item @var{parameter} @expansion{}
26769 @code{@var{non-blank-sequence} | @var{c-string}}
26771 @item @var{operation} @expansion{}
26772 @emph{any of the operations described in this chapter}
26774 @item @var{non-blank-sequence} @expansion{}
26775 @emph{anything, provided it doesn't contain special characters such as
26776 "-", @var{nl}, """ and of course " "}
26778 @item @var{c-string} @expansion{}
26779 @code{""" @var{seven-bit-iso-c-string-content} """}
26781 @item @var{nl} @expansion{}
26790 The CLI commands are still handled by the @sc{mi} interpreter; their
26791 output is described below.
26794 The @code{@var{token}}, when present, is passed back when the command
26798 Some @sc{mi} commands accept optional arguments as part of the parameter
26799 list. Each option is identified by a leading @samp{-} (dash) and may be
26800 followed by an optional argument parameter. Options occur first in the
26801 parameter list and can be delimited from normal parameters using
26802 @samp{--} (this is useful when some parameters begin with a dash).
26809 We want easy access to the existing CLI syntax (for debugging).
26812 We want it to be easy to spot a @sc{mi} operation.
26815 @node GDB/MI Output Syntax
26816 @subsection @sc{gdb/mi} Output Syntax
26818 @cindex output syntax of @sc{gdb/mi}
26819 @cindex @sc{gdb/mi}, output syntax
26820 The output from @sc{gdb/mi} consists of zero or more out-of-band records
26821 followed, optionally, by a single result record. This result record
26822 is for the most recent command. The sequence of output records is
26823 terminated by @samp{(gdb)}.
26825 If an input command was prefixed with a @code{@var{token}} then the
26826 corresponding output for that command will also be prefixed by that same
26830 @item @var{output} @expansion{}
26831 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
26833 @item @var{result-record} @expansion{}
26834 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
26836 @item @var{out-of-band-record} @expansion{}
26837 @code{@var{async-record} | @var{stream-record}}
26839 @item @var{async-record} @expansion{}
26840 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
26842 @item @var{exec-async-output} @expansion{}
26843 @code{[ @var{token} ] "*" @var{async-output nl}}
26845 @item @var{status-async-output} @expansion{}
26846 @code{[ @var{token} ] "+" @var{async-output nl}}
26848 @item @var{notify-async-output} @expansion{}
26849 @code{[ @var{token} ] "=" @var{async-output nl}}
26851 @item @var{async-output} @expansion{}
26852 @code{@var{async-class} ( "," @var{result} )*}
26854 @item @var{result-class} @expansion{}
26855 @code{"done" | "running" | "connected" | "error" | "exit"}
26857 @item @var{async-class} @expansion{}
26858 @code{"stopped" | @var{others}} (where @var{others} will be added
26859 depending on the needs---this is still in development).
26861 @item @var{result} @expansion{}
26862 @code{ @var{variable} "=" @var{value}}
26864 @item @var{variable} @expansion{}
26865 @code{ @var{string} }
26867 @item @var{value} @expansion{}
26868 @code{ @var{const} | @var{tuple} | @var{list} }
26870 @item @var{const} @expansion{}
26871 @code{@var{c-string}}
26873 @item @var{tuple} @expansion{}
26874 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
26876 @item @var{list} @expansion{}
26877 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
26878 @var{result} ( "," @var{result} )* "]" }
26880 @item @var{stream-record} @expansion{}
26881 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
26883 @item @var{console-stream-output} @expansion{}
26884 @code{"~" @var{c-string nl}}
26886 @item @var{target-stream-output} @expansion{}
26887 @code{"@@" @var{c-string nl}}
26889 @item @var{log-stream-output} @expansion{}
26890 @code{"&" @var{c-string nl}}
26892 @item @var{nl} @expansion{}
26895 @item @var{token} @expansion{}
26896 @emph{any sequence of digits}.
26904 All output sequences end in a single line containing a period.
26907 The @code{@var{token}} is from the corresponding request. Note that
26908 for all async output, while the token is allowed by the grammar and
26909 may be output by future versions of @value{GDBN} for select async
26910 output messages, it is generally omitted. Frontends should treat
26911 all async output as reporting general changes in the state of the
26912 target and there should be no need to associate async output to any
26916 @cindex status output in @sc{gdb/mi}
26917 @var{status-async-output} contains on-going status information about the
26918 progress of a slow operation. It can be discarded. All status output is
26919 prefixed by @samp{+}.
26922 @cindex async output in @sc{gdb/mi}
26923 @var{exec-async-output} contains asynchronous state change on the target
26924 (stopped, started, disappeared). All async output is prefixed by
26928 @cindex notify output in @sc{gdb/mi}
26929 @var{notify-async-output} contains supplementary information that the
26930 client should handle (e.g., a new breakpoint information). All notify
26931 output is prefixed by @samp{=}.
26934 @cindex console output in @sc{gdb/mi}
26935 @var{console-stream-output} is output that should be displayed as is in the
26936 console. It is the textual response to a CLI command. All the console
26937 output is prefixed by @samp{~}.
26940 @cindex target output in @sc{gdb/mi}
26941 @var{target-stream-output} is the output produced by the target program.
26942 All the target output is prefixed by @samp{@@}.
26945 @cindex log output in @sc{gdb/mi}
26946 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
26947 instance messages that should be displayed as part of an error log. All
26948 the log output is prefixed by @samp{&}.
26951 @cindex list output in @sc{gdb/mi}
26952 New @sc{gdb/mi} commands should only output @var{lists} containing
26958 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
26959 details about the various output records.
26961 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26962 @node GDB/MI Compatibility with CLI
26963 @section @sc{gdb/mi} Compatibility with CLI
26965 @cindex compatibility, @sc{gdb/mi} and CLI
26966 @cindex @sc{gdb/mi}, compatibility with CLI
26968 For the developers convenience CLI commands can be entered directly,
26969 but there may be some unexpected behaviour. For example, commands
26970 that query the user will behave as if the user replied yes, breakpoint
26971 command lists are not executed and some CLI commands, such as
26972 @code{if}, @code{when} and @code{define}, prompt for further input with
26973 @samp{>}, which is not valid MI output.
26975 This feature may be removed at some stage in the future and it is
26976 recommended that front ends use the @code{-interpreter-exec} command
26977 (@pxref{-interpreter-exec}).
26979 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26980 @node GDB/MI Development and Front Ends
26981 @section @sc{gdb/mi} Development and Front Ends
26982 @cindex @sc{gdb/mi} development
26984 The application which takes the MI output and presents the state of the
26985 program being debugged to the user is called a @dfn{front end}.
26987 Although @sc{gdb/mi} is still incomplete, it is currently being used
26988 by a variety of front ends to @value{GDBN}. This makes it difficult
26989 to introduce new functionality without breaking existing usage. This
26990 section tries to minimize the problems by describing how the protocol
26993 Some changes in MI need not break a carefully designed front end, and
26994 for these the MI version will remain unchanged. The following is a
26995 list of changes that may occur within one level, so front ends should
26996 parse MI output in a way that can handle them:
27000 New MI commands may be added.
27003 New fields may be added to the output of any MI command.
27006 The range of values for fields with specified values, e.g.,
27007 @code{in_scope} (@pxref{-var-update}) may be extended.
27009 @c The format of field's content e.g type prefix, may change so parse it
27010 @c at your own risk. Yes, in general?
27012 @c The order of fields may change? Shouldn't really matter but it might
27013 @c resolve inconsistencies.
27016 If the changes are likely to break front ends, the MI version level
27017 will be increased by one. This will allow the front end to parse the
27018 output according to the MI version. Apart from mi0, new versions of
27019 @value{GDBN} will not support old versions of MI and it will be the
27020 responsibility of the front end to work with the new one.
27022 @c Starting with mi3, add a new command -mi-version that prints the MI
27025 The best way to avoid unexpected changes in MI that might break your front
27026 end is to make your project known to @value{GDBN} developers and
27027 follow development on @email{gdb@@sourceware.org} and
27028 @email{gdb-patches@@sourceware.org}.
27029 @cindex mailing lists
27031 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27032 @node GDB/MI Output Records
27033 @section @sc{gdb/mi} Output Records
27036 * GDB/MI Result Records::
27037 * GDB/MI Stream Records::
27038 * GDB/MI Async Records::
27039 * GDB/MI Breakpoint Information::
27040 * GDB/MI Frame Information::
27041 * GDB/MI Thread Information::
27042 * GDB/MI Ada Exception Information::
27045 @node GDB/MI Result Records
27046 @subsection @sc{gdb/mi} Result Records
27048 @cindex result records in @sc{gdb/mi}
27049 @cindex @sc{gdb/mi}, result records
27050 In addition to a number of out-of-band notifications, the response to a
27051 @sc{gdb/mi} command includes one of the following result indications:
27055 @item "^done" [ "," @var{results} ]
27056 The synchronous operation was successful, @code{@var{results}} are the return
27061 This result record is equivalent to @samp{^done}. Historically, it
27062 was output instead of @samp{^done} if the command has resumed the
27063 target. This behaviour is maintained for backward compatibility, but
27064 all frontends should treat @samp{^done} and @samp{^running}
27065 identically and rely on the @samp{*running} output record to determine
27066 which threads are resumed.
27070 @value{GDBN} has connected to a remote target.
27072 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
27074 The operation failed. The @code{msg=@var{c-string}} variable contains
27075 the corresponding error message.
27077 If present, the @code{code=@var{c-string}} variable provides an error
27078 code on which consumers can rely on to detect the corresponding
27079 error condition. At present, only one error code is defined:
27082 @item "undefined-command"
27083 Indicates that the command causing the error does not exist.
27088 @value{GDBN} has terminated.
27092 @node GDB/MI Stream Records
27093 @subsection @sc{gdb/mi} Stream Records
27095 @cindex @sc{gdb/mi}, stream records
27096 @cindex stream records in @sc{gdb/mi}
27097 @value{GDBN} internally maintains a number of output streams: the console, the
27098 target, and the log. The output intended for each of these streams is
27099 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
27101 Each stream record begins with a unique @dfn{prefix character} which
27102 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
27103 Syntax}). In addition to the prefix, each stream record contains a
27104 @code{@var{string-output}}. This is either raw text (with an implicit new
27105 line) or a quoted C string (which does not contain an implicit newline).
27108 @item "~" @var{string-output}
27109 The console output stream contains text that should be displayed in the
27110 CLI console window. It contains the textual responses to CLI commands.
27112 @item "@@" @var{string-output}
27113 The target output stream contains any textual output from the running
27114 target. This is only present when GDB's event loop is truly
27115 asynchronous, which is currently only the case for remote targets.
27117 @item "&" @var{string-output}
27118 The log stream contains debugging messages being produced by @value{GDBN}'s
27122 @node GDB/MI Async Records
27123 @subsection @sc{gdb/mi} Async Records
27125 @cindex async records in @sc{gdb/mi}
27126 @cindex @sc{gdb/mi}, async records
27127 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
27128 additional changes that have occurred. Those changes can either be a
27129 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
27130 target activity (e.g., target stopped).
27132 The following is the list of possible async records:
27136 @item *running,thread-id="@var{thread}"
27137 The target is now running. The @var{thread} field can be the global
27138 thread ID of the the thread that is now running, and it can be
27139 @samp{all} if all threads are running. The frontend should assume
27140 that no interaction with a running thread is possible after this
27141 notification is produced. The frontend should not assume that this
27142 notification is output only once for any command. @value{GDBN} may
27143 emit this notification several times, either for different threads,
27144 because it cannot resume all threads together, or even for a single
27145 thread, if the thread must be stepped though some code before letting
27148 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
27149 The target has stopped. The @var{reason} field can have one of the
27153 @item breakpoint-hit
27154 A breakpoint was reached.
27155 @item watchpoint-trigger
27156 A watchpoint was triggered.
27157 @item read-watchpoint-trigger
27158 A read watchpoint was triggered.
27159 @item access-watchpoint-trigger
27160 An access watchpoint was triggered.
27161 @item function-finished
27162 An -exec-finish or similar CLI command was accomplished.
27163 @item location-reached
27164 An -exec-until or similar CLI command was accomplished.
27165 @item watchpoint-scope
27166 A watchpoint has gone out of scope.
27167 @item end-stepping-range
27168 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
27169 similar CLI command was accomplished.
27170 @item exited-signalled
27171 The inferior exited because of a signal.
27173 The inferior exited.
27174 @item exited-normally
27175 The inferior exited normally.
27176 @item signal-received
27177 A signal was received by the inferior.
27179 The inferior has stopped due to a library being loaded or unloaded.
27180 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
27181 set or when a @code{catch load} or @code{catch unload} catchpoint is
27182 in use (@pxref{Set Catchpoints}).
27184 The inferior has forked. This is reported when @code{catch fork}
27185 (@pxref{Set Catchpoints}) has been used.
27187 The inferior has vforked. This is reported in when @code{catch vfork}
27188 (@pxref{Set Catchpoints}) has been used.
27189 @item syscall-entry
27190 The inferior entered a system call. This is reported when @code{catch
27191 syscall} (@pxref{Set Catchpoints}) has been used.
27192 @item syscall-return
27193 The inferior returned from a system call. This is reported when
27194 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
27196 The inferior called @code{exec}. This is reported when @code{catch exec}
27197 (@pxref{Set Catchpoints}) has been used.
27200 The @var{id} field identifies the global thread ID of the thread
27201 that directly caused the stop -- for example by hitting a breakpoint.
27202 Depending on whether all-stop
27203 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
27204 stop all threads, or only the thread that directly triggered the stop.
27205 If all threads are stopped, the @var{stopped} field will have the
27206 value of @code{"all"}. Otherwise, the value of the @var{stopped}
27207 field will be a list of thread identifiers. Presently, this list will
27208 always include a single thread, but frontend should be prepared to see
27209 several threads in the list. The @var{core} field reports the
27210 processor core on which the stop event has happened. This field may be absent
27211 if such information is not available.
27213 @item =thread-group-added,id="@var{id}"
27214 @itemx =thread-group-removed,id="@var{id}"
27215 A thread group was either added or removed. The @var{id} field
27216 contains the @value{GDBN} identifier of the thread group. When a thread
27217 group is added, it generally might not be associated with a running
27218 process. When a thread group is removed, its id becomes invalid and
27219 cannot be used in any way.
27221 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
27222 A thread group became associated with a running program,
27223 either because the program was just started or the thread group
27224 was attached to a program. The @var{id} field contains the
27225 @value{GDBN} identifier of the thread group. The @var{pid} field
27226 contains process identifier, specific to the operating system.
27228 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
27229 A thread group is no longer associated with a running program,
27230 either because the program has exited, or because it was detached
27231 from. The @var{id} field contains the @value{GDBN} identifier of the
27232 thread group. The @var{code} field is the exit code of the inferior; it exists
27233 only when the inferior exited with some code.
27235 @item =thread-created,id="@var{id}",group-id="@var{gid}"
27236 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
27237 A thread either was created, or has exited. The @var{id} field
27238 contains the global @value{GDBN} identifier of the thread. The @var{gid}
27239 field identifies the thread group this thread belongs to.
27241 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
27242 Informs that the selected thread or frame were changed. This notification
27243 is not emitted as result of the @code{-thread-select} or
27244 @code{-stack-select-frame} commands, but is emitted whenever an MI command
27245 that is not documented to change the selected thread and frame actually
27246 changes them. In particular, invoking, directly or indirectly
27247 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
27248 will generate this notification. Changing the thread or frame from another
27249 user interface (see @ref{Interpreters}) will also generate this notification.
27251 The @var{frame} field is only present if the newly selected thread is
27252 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
27254 We suggest that in response to this notification, front ends
27255 highlight the selected thread and cause subsequent commands to apply to
27258 @item =library-loaded,...
27259 Reports that a new library file was loaded by the program. This
27260 notification has 5 fields---@var{id}, @var{target-name},
27261 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
27262 opaque identifier of the library. For remote debugging case,
27263 @var{target-name} and @var{host-name} fields give the name of the
27264 library file on the target, and on the host respectively. For native
27265 debugging, both those fields have the same value. The
27266 @var{symbols-loaded} field is emitted only for backward compatibility
27267 and should not be relied on to convey any useful information. The
27268 @var{thread-group} field, if present, specifies the id of the thread
27269 group in whose context the library was loaded. If the field is
27270 absent, it means the library was loaded in the context of all present
27271 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
27274 @item =library-unloaded,...
27275 Reports that a library was unloaded by the program. This notification
27276 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
27277 the same meaning as for the @code{=library-loaded} notification.
27278 The @var{thread-group} field, if present, specifies the id of the
27279 thread group in whose context the library was unloaded. If the field is
27280 absent, it means the library was unloaded in the context of all present
27283 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
27284 @itemx =traceframe-changed,end
27285 Reports that the trace frame was changed and its new number is
27286 @var{tfnum}. The number of the tracepoint associated with this trace
27287 frame is @var{tpnum}.
27289 @item =tsv-created,name=@var{name},initial=@var{initial}
27290 Reports that the new trace state variable @var{name} is created with
27291 initial value @var{initial}.
27293 @item =tsv-deleted,name=@var{name}
27294 @itemx =tsv-deleted
27295 Reports that the trace state variable @var{name} is deleted or all
27296 trace state variables are deleted.
27298 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
27299 Reports that the trace state variable @var{name} is modified with
27300 the initial value @var{initial}. The current value @var{current} of
27301 trace state variable is optional and is reported if the current
27302 value of trace state variable is known.
27304 @item =breakpoint-created,bkpt=@{...@}
27305 @itemx =breakpoint-modified,bkpt=@{...@}
27306 @itemx =breakpoint-deleted,id=@var{number}
27307 Reports that a breakpoint was created, modified, or deleted,
27308 respectively. Only user-visible breakpoints are reported to the MI
27311 The @var{bkpt} argument is of the same form as returned by the various
27312 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
27313 @var{number} is the ordinal number of the breakpoint.
27315 Note that if a breakpoint is emitted in the result record of a
27316 command, then it will not also be emitted in an async record.
27318 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
27319 @itemx =record-stopped,thread-group="@var{id}"
27320 Execution log recording was either started or stopped on an
27321 inferior. The @var{id} is the @value{GDBN} identifier of the thread
27322 group corresponding to the affected inferior.
27324 The @var{method} field indicates the method used to record execution. If the
27325 method in use supports multiple recording formats, @var{format} will be present
27326 and contain the currently used format. @xref{Process Record and Replay},
27327 for existing method and format values.
27329 @item =cmd-param-changed,param=@var{param},value=@var{value}
27330 Reports that a parameter of the command @code{set @var{param}} is
27331 changed to @var{value}. In the multi-word @code{set} command,
27332 the @var{param} is the whole parameter list to @code{set} command.
27333 For example, In command @code{set check type on}, @var{param}
27334 is @code{check type} and @var{value} is @code{on}.
27336 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
27337 Reports that bytes from @var{addr} to @var{data} + @var{len} were
27338 written in an inferior. The @var{id} is the identifier of the
27339 thread group corresponding to the affected inferior. The optional
27340 @code{type="code"} part is reported if the memory written to holds
27344 @node GDB/MI Breakpoint Information
27345 @subsection @sc{gdb/mi} Breakpoint Information
27347 When @value{GDBN} reports information about a breakpoint, a
27348 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
27353 The breakpoint number. For a breakpoint that represents one location
27354 of a multi-location breakpoint, this will be a dotted pair, like
27358 The type of the breakpoint. For ordinary breakpoints this will be
27359 @samp{breakpoint}, but many values are possible.
27362 If the type of the breakpoint is @samp{catchpoint}, then this
27363 indicates the exact type of catchpoint.
27366 This is the breakpoint disposition---either @samp{del}, meaning that
27367 the breakpoint will be deleted at the next stop, or @samp{keep},
27368 meaning that the breakpoint will not be deleted.
27371 This indicates whether the breakpoint is enabled, in which case the
27372 value is @samp{y}, or disabled, in which case the value is @samp{n}.
27373 Note that this is not the same as the field @code{enable}.
27376 The address of the breakpoint. This may be a hexidecimal number,
27377 giving the address; or the string @samp{<PENDING>}, for a pending
27378 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
27379 multiple locations. This field will not be present if no address can
27380 be determined. For example, a watchpoint does not have an address.
27383 If known, the function in which the breakpoint appears.
27384 If not known, this field is not present.
27387 The name of the source file which contains this function, if known.
27388 If not known, this field is not present.
27391 The full file name of the source file which contains this function, if
27392 known. If not known, this field is not present.
27395 The line number at which this breakpoint appears, if known.
27396 If not known, this field is not present.
27399 If the source file is not known, this field may be provided. If
27400 provided, this holds the address of the breakpoint, possibly followed
27404 If this breakpoint is pending, this field is present and holds the
27405 text used to set the breakpoint, as entered by the user.
27408 Where this breakpoint's condition is evaluated, either @samp{host} or
27412 If this is a thread-specific breakpoint, then this identifies the
27413 thread in which the breakpoint can trigger.
27416 If this breakpoint is restricted to a particular Ada task, then this
27417 field will hold the task identifier.
27420 If the breakpoint is conditional, this is the condition expression.
27423 The ignore count of the breakpoint.
27426 The enable count of the breakpoint.
27428 @item traceframe-usage
27431 @item static-tracepoint-marker-string-id
27432 For a static tracepoint, the name of the static tracepoint marker.
27435 For a masked watchpoint, this is the mask.
27438 A tracepoint's pass count.
27440 @item original-location
27441 The location of the breakpoint as originally specified by the user.
27442 This field is optional.
27445 The number of times the breakpoint has been hit.
27448 This field is only given for tracepoints. This is either @samp{y},
27449 meaning that the tracepoint is installed, or @samp{n}, meaning that it
27453 Some extra data, the exact contents of which are type-dependent.
27457 For example, here is what the output of @code{-break-insert}
27458 (@pxref{GDB/MI Breakpoint Commands}) might be:
27461 -> -break-insert main
27462 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27463 enabled="y",addr="0x08048564",func="main",file="myprog.c",
27464 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
27469 @node GDB/MI Frame Information
27470 @subsection @sc{gdb/mi} Frame Information
27472 Response from many MI commands includes an information about stack
27473 frame. This information is a tuple that may have the following
27478 The level of the stack frame. The innermost frame has the level of
27479 zero. This field is always present.
27482 The name of the function corresponding to the frame. This field may
27483 be absent if @value{GDBN} is unable to determine the function name.
27486 The code address for the frame. This field is always present.
27489 The name of the source files that correspond to the frame's code
27490 address. This field may be absent.
27493 The source line corresponding to the frames' code address. This field
27497 The name of the binary file (either executable or shared library) the
27498 corresponds to the frame's code address. This field may be absent.
27502 @node GDB/MI Thread Information
27503 @subsection @sc{gdb/mi} Thread Information
27505 Whenever @value{GDBN} has to report an information about a thread, it
27506 uses a tuple with the following fields. The fields are always present unless
27511 The global numeric id assigned to the thread by @value{GDBN}.
27514 The target-specific string identifying the thread.
27517 Additional information about the thread provided by the target.
27518 It is supposed to be human-readable and not interpreted by the
27519 frontend. This field is optional.
27522 The name of the thread. If the user specified a name using the
27523 @code{thread name} command, then this name is given. Otherwise, if
27524 @value{GDBN} can extract the thread name from the target, then that
27525 name is given. If @value{GDBN} cannot find the thread name, then this
27529 The execution state of the thread, either @samp{stopped} or @samp{running},
27530 depending on whether the thread is presently running.
27533 The stack frame currently executing in the thread. This field is only present
27534 if the thread is stopped. Its format is documented in
27535 @ref{GDB/MI Frame Information}.
27538 The value of this field is an integer number of the processor core the
27539 thread was last seen on. This field is optional.
27542 @node GDB/MI Ada Exception Information
27543 @subsection @sc{gdb/mi} Ada Exception Information
27545 Whenever a @code{*stopped} record is emitted because the program
27546 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
27547 @value{GDBN} provides the name of the exception that was raised via
27548 the @code{exception-name} field. Also, for exceptions that were raised
27549 with an exception message, @value{GDBN} provides that message via
27550 the @code{exception-message} field.
27552 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27553 @node GDB/MI Simple Examples
27554 @section Simple Examples of @sc{gdb/mi} Interaction
27555 @cindex @sc{gdb/mi}, simple examples
27557 This subsection presents several simple examples of interaction using
27558 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
27559 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
27560 the output received from @sc{gdb/mi}.
27562 Note the line breaks shown in the examples are here only for
27563 readability, they don't appear in the real output.
27565 @subheading Setting a Breakpoint
27567 Setting a breakpoint generates synchronous output which contains detailed
27568 information of the breakpoint.
27571 -> -break-insert main
27572 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27573 enabled="y",addr="0x08048564",func="main",file="myprog.c",
27574 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
27579 @subheading Program Execution
27581 Program execution generates asynchronous records and MI gives the
27582 reason that execution stopped.
27588 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
27589 frame=@{addr="0x08048564",func="main",
27590 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
27591 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
27596 <- *stopped,reason="exited-normally"
27600 @subheading Quitting @value{GDBN}
27602 Quitting @value{GDBN} just prints the result class @samp{^exit}.
27610 Please note that @samp{^exit} is printed immediately, but it might
27611 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
27612 performs necessary cleanups, including killing programs being debugged
27613 or disconnecting from debug hardware, so the frontend should wait till
27614 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
27615 fails to exit in reasonable time.
27617 @subheading A Bad Command
27619 Here's what happens if you pass a non-existent command:
27623 <- ^error,msg="Undefined MI command: rubbish"
27628 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27629 @node GDB/MI Command Description Format
27630 @section @sc{gdb/mi} Command Description Format
27632 The remaining sections describe blocks of commands. Each block of
27633 commands is laid out in a fashion similar to this section.
27635 @subheading Motivation
27637 The motivation for this collection of commands.
27639 @subheading Introduction
27641 A brief introduction to this collection of commands as a whole.
27643 @subheading Commands
27645 For each command in the block, the following is described:
27647 @subsubheading Synopsis
27650 -command @var{args}@dots{}
27653 @subsubheading Result
27655 @subsubheading @value{GDBN} Command
27657 The corresponding @value{GDBN} CLI command(s), if any.
27659 @subsubheading Example
27661 Example(s) formatted for readability. Some of the described commands have
27662 not been implemented yet and these are labeled N.A.@: (not available).
27665 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27666 @node GDB/MI Breakpoint Commands
27667 @section @sc{gdb/mi} Breakpoint Commands
27669 @cindex breakpoint commands for @sc{gdb/mi}
27670 @cindex @sc{gdb/mi}, breakpoint commands
27671 This section documents @sc{gdb/mi} commands for manipulating
27674 @subheading The @code{-break-after} Command
27675 @findex -break-after
27677 @subsubheading Synopsis
27680 -break-after @var{number} @var{count}
27683 The breakpoint number @var{number} is not in effect until it has been
27684 hit @var{count} times. To see how this is reflected in the output of
27685 the @samp{-break-list} command, see the description of the
27686 @samp{-break-list} command below.
27688 @subsubheading @value{GDBN} Command
27690 The corresponding @value{GDBN} command is @samp{ignore}.
27692 @subsubheading Example
27697 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27698 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27699 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
27707 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27708 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27709 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27710 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27711 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27712 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27713 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27714 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27715 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27716 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
27721 @subheading The @code{-break-catch} Command
27722 @findex -break-catch
27725 @subheading The @code{-break-commands} Command
27726 @findex -break-commands
27728 @subsubheading Synopsis
27731 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
27734 Specifies the CLI commands that should be executed when breakpoint
27735 @var{number} is hit. The parameters @var{command1} to @var{commandN}
27736 are the commands. If no command is specified, any previously-set
27737 commands are cleared. @xref{Break Commands}. Typical use of this
27738 functionality is tracing a program, that is, printing of values of
27739 some variables whenever breakpoint is hit and then continuing.
27741 @subsubheading @value{GDBN} Command
27743 The corresponding @value{GDBN} command is @samp{commands}.
27745 @subsubheading Example
27750 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27751 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27752 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
27755 -break-commands 1 "print v" "continue"
27760 @subheading The @code{-break-condition} Command
27761 @findex -break-condition
27763 @subsubheading Synopsis
27766 -break-condition @var{number} @var{expr}
27769 Breakpoint @var{number} will stop the program only if the condition in
27770 @var{expr} is true. The condition becomes part of the
27771 @samp{-break-list} output (see the description of the @samp{-break-list}
27774 @subsubheading @value{GDBN} Command
27776 The corresponding @value{GDBN} command is @samp{condition}.
27778 @subsubheading Example
27782 -break-condition 1 1
27786 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27787 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27788 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27789 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27790 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27791 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27792 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27793 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27794 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27795 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
27799 @subheading The @code{-break-delete} Command
27800 @findex -break-delete
27802 @subsubheading Synopsis
27805 -break-delete ( @var{breakpoint} )+
27808 Delete the breakpoint(s) whose number(s) are specified in the argument
27809 list. This is obviously reflected in the breakpoint list.
27811 @subsubheading @value{GDBN} Command
27813 The corresponding @value{GDBN} command is @samp{delete}.
27815 @subsubheading Example
27823 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27824 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27825 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27826 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27827 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27828 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27829 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27834 @subheading The @code{-break-disable} Command
27835 @findex -break-disable
27837 @subsubheading Synopsis
27840 -break-disable ( @var{breakpoint} )+
27843 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
27844 break list is now set to @samp{n} for the named @var{breakpoint}(s).
27846 @subsubheading @value{GDBN} Command
27848 The corresponding @value{GDBN} command is @samp{disable}.
27850 @subsubheading Example
27858 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27859 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27860 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27861 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27862 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27863 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27864 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27865 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
27866 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27867 line="5",thread-groups=["i1"],times="0"@}]@}
27871 @subheading The @code{-break-enable} Command
27872 @findex -break-enable
27874 @subsubheading Synopsis
27877 -break-enable ( @var{breakpoint} )+
27880 Enable (previously disabled) @var{breakpoint}(s).
27882 @subsubheading @value{GDBN} Command
27884 The corresponding @value{GDBN} command is @samp{enable}.
27886 @subsubheading Example
27894 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27895 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27896 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27897 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27898 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27899 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27900 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27901 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27902 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27903 line="5",thread-groups=["i1"],times="0"@}]@}
27907 @subheading The @code{-break-info} Command
27908 @findex -break-info
27910 @subsubheading Synopsis
27913 -break-info @var{breakpoint}
27917 Get information about a single breakpoint.
27919 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
27920 Information}, for details on the format of each breakpoint in the
27923 @subsubheading @value{GDBN} Command
27925 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
27927 @subsubheading Example
27930 @subheading The @code{-break-insert} Command
27931 @findex -break-insert
27932 @anchor{-break-insert}
27934 @subsubheading Synopsis
27937 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
27938 [ -c @var{condition} ] [ -i @var{ignore-count} ]
27939 [ -p @var{thread-id} ] [ @var{location} ]
27943 If specified, @var{location}, can be one of:
27946 @item linespec location
27947 A linespec location. @xref{Linespec Locations}.
27949 @item explicit location
27950 An explicit location. @sc{gdb/mi} explicit locations are
27951 analogous to the CLI's explicit locations using the option names
27952 listed below. @xref{Explicit Locations}.
27955 @item --source @var{filename}
27956 The source file name of the location. This option requires the use
27957 of either @samp{--function} or @samp{--line}.
27959 @item --function @var{function}
27960 The name of a function or method.
27962 @item --label @var{label}
27963 The name of a label.
27965 @item --line @var{lineoffset}
27966 An absolute or relative line offset from the start of the location.
27969 @item address location
27970 An address location, *@var{address}. @xref{Address Locations}.
27974 The possible optional parameters of this command are:
27978 Insert a temporary breakpoint.
27980 Insert a hardware breakpoint.
27982 If @var{location} cannot be parsed (for example if it
27983 refers to unknown files or functions), create a pending
27984 breakpoint. Without this flag, @value{GDBN} will report
27985 an error, and won't create a breakpoint, if @var{location}
27988 Create a disabled breakpoint.
27990 Create a tracepoint. @xref{Tracepoints}. When this parameter
27991 is used together with @samp{-h}, a fast tracepoint is created.
27992 @item -c @var{condition}
27993 Make the breakpoint conditional on @var{condition}.
27994 @item -i @var{ignore-count}
27995 Initialize the @var{ignore-count}.
27996 @item -p @var{thread-id}
27997 Restrict the breakpoint to the thread with the specified global
28001 @subsubheading Result
28003 @xref{GDB/MI Breakpoint Information}, for details on the format of the
28004 resulting breakpoint.
28006 Note: this format is open to change.
28007 @c An out-of-band breakpoint instead of part of the result?
28009 @subsubheading @value{GDBN} Command
28011 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
28012 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
28014 @subsubheading Example
28019 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
28020 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
28023 -break-insert -t foo
28024 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
28025 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
28029 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28030 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28031 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28032 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28033 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28034 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28035 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28036 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28037 addr="0x0001072c", func="main",file="recursive2.c",
28038 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
28040 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
28041 addr="0x00010774",func="foo",file="recursive2.c",
28042 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28045 @c -break-insert -r foo.*
28046 @c ~int foo(int, int);
28047 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
28048 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28053 @subheading The @code{-dprintf-insert} Command
28054 @findex -dprintf-insert
28056 @subsubheading Synopsis
28059 -dprintf-insert [ -t ] [ -f ] [ -d ]
28060 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28061 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
28066 If supplied, @var{location} may be specified the same way as for
28067 the @code{-break-insert} command. @xref{-break-insert}.
28069 The possible optional parameters of this command are:
28073 Insert a temporary breakpoint.
28075 If @var{location} cannot be parsed (for example, if it
28076 refers to unknown files or functions), create a pending
28077 breakpoint. Without this flag, @value{GDBN} will report
28078 an error, and won't create a breakpoint, if @var{location}
28081 Create a disabled breakpoint.
28082 @item -c @var{condition}
28083 Make the breakpoint conditional on @var{condition}.
28084 @item -i @var{ignore-count}
28085 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
28086 to @var{ignore-count}.
28087 @item -p @var{thread-id}
28088 Restrict the breakpoint to the thread with the specified global
28092 @subsubheading Result
28094 @xref{GDB/MI Breakpoint Information}, for details on the format of the
28095 resulting breakpoint.
28097 @c An out-of-band breakpoint instead of part of the result?
28099 @subsubheading @value{GDBN} Command
28101 The corresponding @value{GDBN} command is @samp{dprintf}.
28103 @subsubheading Example
28107 4-dprintf-insert foo "At foo entry\n"
28108 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
28109 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
28110 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
28111 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
28112 original-location="foo"@}
28114 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
28115 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
28116 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
28117 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
28118 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
28119 original-location="mi-dprintf.c:26"@}
28123 @subheading The @code{-break-list} Command
28124 @findex -break-list
28126 @subsubheading Synopsis
28132 Displays the list of inserted breakpoints, showing the following fields:
28136 number of the breakpoint
28138 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
28140 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
28143 is the breakpoint enabled or no: @samp{y} or @samp{n}
28145 memory location at which the breakpoint is set
28147 logical location of the breakpoint, expressed by function name, file
28149 @item Thread-groups
28150 list of thread groups to which this breakpoint applies
28152 number of times the breakpoint has been hit
28155 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
28156 @code{body} field is an empty list.
28158 @subsubheading @value{GDBN} Command
28160 The corresponding @value{GDBN} command is @samp{info break}.
28162 @subsubheading Example
28167 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28168 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28169 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28170 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28171 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28172 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28173 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28174 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28175 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
28177 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28178 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
28179 line="13",thread-groups=["i1"],times="0"@}]@}
28183 Here's an example of the result when there are no breakpoints:
28188 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28189 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28190 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28191 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28192 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28193 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28194 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28199 @subheading The @code{-break-passcount} Command
28200 @findex -break-passcount
28202 @subsubheading Synopsis
28205 -break-passcount @var{tracepoint-number} @var{passcount}
28208 Set the passcount for tracepoint @var{tracepoint-number} to
28209 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
28210 is not a tracepoint, error is emitted. This corresponds to CLI
28211 command @samp{passcount}.
28213 @subheading The @code{-break-watch} Command
28214 @findex -break-watch
28216 @subsubheading Synopsis
28219 -break-watch [ -a | -r ]
28222 Create a watchpoint. With the @samp{-a} option it will create an
28223 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
28224 read from or on a write to the memory location. With the @samp{-r}
28225 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
28226 trigger only when the memory location is accessed for reading. Without
28227 either of the options, the watchpoint created is a regular watchpoint,
28228 i.e., it will trigger when the memory location is accessed for writing.
28229 @xref{Set Watchpoints, , Setting Watchpoints}.
28231 Note that @samp{-break-list} will report a single list of watchpoints and
28232 breakpoints inserted.
28234 @subsubheading @value{GDBN} Command
28236 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
28239 @subsubheading Example
28241 Setting a watchpoint on a variable in the @code{main} function:
28246 ^done,wpt=@{number="2",exp="x"@}
28251 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
28252 value=@{old="-268439212",new="55"@},
28253 frame=@{func="main",args=[],file="recursive2.c",
28254 fullname="/home/foo/bar/recursive2.c",line="5"@}
28258 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
28259 the program execution twice: first for the variable changing value, then
28260 for the watchpoint going out of scope.
28265 ^done,wpt=@{number="5",exp="C"@}
28270 *stopped,reason="watchpoint-trigger",
28271 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
28272 frame=@{func="callee4",args=[],
28273 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28274 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28279 *stopped,reason="watchpoint-scope",wpnum="5",
28280 frame=@{func="callee3",args=[@{name="strarg",
28281 value="0x11940 \"A string argument.\""@}],
28282 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28283 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28287 Listing breakpoints and watchpoints, at different points in the program
28288 execution. Note that once the watchpoint goes out of scope, it is
28294 ^done,wpt=@{number="2",exp="C"@}
28297 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28298 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28299 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28300 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28301 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28302 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28303 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28304 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28305 addr="0x00010734",func="callee4",
28306 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28307 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
28309 bkpt=@{number="2",type="watchpoint",disp="keep",
28310 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
28315 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
28316 value=@{old="-276895068",new="3"@},
28317 frame=@{func="callee4",args=[],
28318 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28319 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28322 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28323 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28324 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28325 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28326 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28327 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28328 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28329 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28330 addr="0x00010734",func="callee4",
28331 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28332 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
28334 bkpt=@{number="2",type="watchpoint",disp="keep",
28335 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
28339 ^done,reason="watchpoint-scope",wpnum="2",
28340 frame=@{func="callee3",args=[@{name="strarg",
28341 value="0x11940 \"A string argument.\""@}],
28342 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28343 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28346 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28347 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28348 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28349 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28350 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28351 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28352 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28353 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28354 addr="0x00010734",func="callee4",
28355 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28356 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
28357 thread-groups=["i1"],times="1"@}]@}
28362 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28363 @node GDB/MI Catchpoint Commands
28364 @section @sc{gdb/mi} Catchpoint Commands
28366 This section documents @sc{gdb/mi} commands for manipulating
28370 * Shared Library GDB/MI Catchpoint Commands::
28371 * Ada Exception GDB/MI Catchpoint Commands::
28374 @node Shared Library GDB/MI Catchpoint Commands
28375 @subsection Shared Library @sc{gdb/mi} Catchpoints
28377 @subheading The @code{-catch-load} Command
28378 @findex -catch-load
28380 @subsubheading Synopsis
28383 -catch-load [ -t ] [ -d ] @var{regexp}
28386 Add a catchpoint for library load events. If the @samp{-t} option is used,
28387 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
28388 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
28389 in a disabled state. The @samp{regexp} argument is a regular
28390 expression used to match the name of the loaded library.
28393 @subsubheading @value{GDBN} Command
28395 The corresponding @value{GDBN} command is @samp{catch load}.
28397 @subsubheading Example
28400 -catch-load -t foo.so
28401 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
28402 what="load of library matching foo.so",catch-type="load",times="0"@}
28407 @subheading The @code{-catch-unload} Command
28408 @findex -catch-unload
28410 @subsubheading Synopsis
28413 -catch-unload [ -t ] [ -d ] @var{regexp}
28416 Add a catchpoint for library unload events. If the @samp{-t} option is
28417 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
28418 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
28419 created in a disabled state. The @samp{regexp} argument is a regular
28420 expression used to match the name of the unloaded library.
28422 @subsubheading @value{GDBN} Command
28424 The corresponding @value{GDBN} command is @samp{catch unload}.
28426 @subsubheading Example
28429 -catch-unload -d bar.so
28430 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
28431 what="load of library matching bar.so",catch-type="unload",times="0"@}
28435 @node Ada Exception GDB/MI Catchpoint Commands
28436 @subsection Ada Exception @sc{gdb/mi} Catchpoints
28438 The following @sc{gdb/mi} commands can be used to create catchpoints
28439 that stop the execution when Ada exceptions are being raised.
28441 @subheading The @code{-catch-assert} Command
28442 @findex -catch-assert
28444 @subsubheading Synopsis
28447 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
28450 Add a catchpoint for failed Ada assertions.
28452 The possible optional parameters for this command are:
28455 @item -c @var{condition}
28456 Make the catchpoint conditional on @var{condition}.
28458 Create a disabled catchpoint.
28460 Create a temporary catchpoint.
28463 @subsubheading @value{GDBN} Command
28465 The corresponding @value{GDBN} command is @samp{catch assert}.
28467 @subsubheading Example
28471 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
28472 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
28473 thread-groups=["i1"],times="0",
28474 original-location="__gnat_debug_raise_assert_failure"@}
28478 @subheading The @code{-catch-exception} Command
28479 @findex -catch-exception
28481 @subsubheading Synopsis
28484 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
28488 Add a catchpoint stopping when Ada exceptions are raised.
28489 By default, the command stops the program when any Ada exception
28490 gets raised. But it is also possible, by using some of the
28491 optional parameters described below, to create more selective
28494 The possible optional parameters for this command are:
28497 @item -c @var{condition}
28498 Make the catchpoint conditional on @var{condition}.
28500 Create a disabled catchpoint.
28501 @item -e @var{exception-name}
28502 Only stop when @var{exception-name} is raised. This option cannot
28503 be used combined with @samp{-u}.
28505 Create a temporary catchpoint.
28507 Stop only when an unhandled exception gets raised. This option
28508 cannot be used combined with @samp{-e}.
28511 @subsubheading @value{GDBN} Command
28513 The corresponding @value{GDBN} commands are @samp{catch exception}
28514 and @samp{catch exception unhandled}.
28516 @subsubheading Example
28519 -catch-exception -e Program_Error
28520 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
28521 enabled="y",addr="0x0000000000404874",
28522 what="`Program_Error' Ada exception", thread-groups=["i1"],
28523 times="0",original-location="__gnat_debug_raise_exception"@}
28527 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28528 @node GDB/MI Program Context
28529 @section @sc{gdb/mi} Program Context
28531 @subheading The @code{-exec-arguments} Command
28532 @findex -exec-arguments
28535 @subsubheading Synopsis
28538 -exec-arguments @var{args}
28541 Set the inferior program arguments, to be used in the next
28544 @subsubheading @value{GDBN} Command
28546 The corresponding @value{GDBN} command is @samp{set args}.
28548 @subsubheading Example
28552 -exec-arguments -v word
28559 @subheading The @code{-exec-show-arguments} Command
28560 @findex -exec-show-arguments
28562 @subsubheading Synopsis
28565 -exec-show-arguments
28568 Print the arguments of the program.
28570 @subsubheading @value{GDBN} Command
28572 The corresponding @value{GDBN} command is @samp{show args}.
28574 @subsubheading Example
28579 @subheading The @code{-environment-cd} Command
28580 @findex -environment-cd
28582 @subsubheading Synopsis
28585 -environment-cd @var{pathdir}
28588 Set @value{GDBN}'s working directory.
28590 @subsubheading @value{GDBN} Command
28592 The corresponding @value{GDBN} command is @samp{cd}.
28594 @subsubheading Example
28598 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
28604 @subheading The @code{-environment-directory} Command
28605 @findex -environment-directory
28607 @subsubheading Synopsis
28610 -environment-directory [ -r ] [ @var{pathdir} ]+
28613 Add directories @var{pathdir} to beginning of search path for source files.
28614 If the @samp{-r} option is used, the search path is reset to the default
28615 search path. If directories @var{pathdir} are supplied in addition to the
28616 @samp{-r} option, the search path is first reset and then addition
28618 Multiple directories may be specified, separated by blanks. Specifying
28619 multiple directories in a single command
28620 results in the directories added to the beginning of the
28621 search path in the same order they were presented in the command.
28622 If blanks are needed as
28623 part of a directory name, double-quotes should be used around
28624 the name. In the command output, the path will show up separated
28625 by the system directory-separator character. The directory-separator
28626 character must not be used
28627 in any directory name.
28628 If no directories are specified, the current search path is displayed.
28630 @subsubheading @value{GDBN} Command
28632 The corresponding @value{GDBN} command is @samp{dir}.
28634 @subsubheading Example
28638 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
28639 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
28641 -environment-directory ""
28642 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
28644 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
28645 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
28647 -environment-directory -r
28648 ^done,source-path="$cdir:$cwd"
28653 @subheading The @code{-environment-path} Command
28654 @findex -environment-path
28656 @subsubheading Synopsis
28659 -environment-path [ -r ] [ @var{pathdir} ]+
28662 Add directories @var{pathdir} to beginning of search path for object files.
28663 If the @samp{-r} option is used, the search path is reset to the original
28664 search path that existed at gdb start-up. If directories @var{pathdir} are
28665 supplied in addition to the
28666 @samp{-r} option, the search path is first reset and then addition
28668 Multiple directories may be specified, separated by blanks. Specifying
28669 multiple directories in a single command
28670 results in the directories added to the beginning of the
28671 search path in the same order they were presented in the command.
28672 If blanks are needed as
28673 part of a directory name, double-quotes should be used around
28674 the name. In the command output, the path will show up separated
28675 by the system directory-separator character. The directory-separator
28676 character must not be used
28677 in any directory name.
28678 If no directories are specified, the current path is displayed.
28681 @subsubheading @value{GDBN} Command
28683 The corresponding @value{GDBN} command is @samp{path}.
28685 @subsubheading Example
28690 ^done,path="/usr/bin"
28692 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
28693 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
28695 -environment-path -r /usr/local/bin
28696 ^done,path="/usr/local/bin:/usr/bin"
28701 @subheading The @code{-environment-pwd} Command
28702 @findex -environment-pwd
28704 @subsubheading Synopsis
28710 Show the current working directory.
28712 @subsubheading @value{GDBN} Command
28714 The corresponding @value{GDBN} command is @samp{pwd}.
28716 @subsubheading Example
28721 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
28725 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28726 @node GDB/MI Thread Commands
28727 @section @sc{gdb/mi} Thread Commands
28730 @subheading The @code{-thread-info} Command
28731 @findex -thread-info
28733 @subsubheading Synopsis
28736 -thread-info [ @var{thread-id} ]
28739 Reports information about either a specific thread, if the
28740 @var{thread-id} parameter is present, or about all threads.
28741 @var{thread-id} is the thread's global thread ID. When printing
28742 information about all threads, also reports the global ID of the
28745 @subsubheading @value{GDBN} Command
28747 The @samp{info thread} command prints the same information
28750 @subsubheading Result
28752 The result contains the following attributes:
28756 A list of threads. The format of the elements of the list is described in
28757 @ref{GDB/MI Thread Information}.
28759 @item current-thread-id
28760 The global id of the currently selected thread. This field is omitted if there
28761 is no selected thread (for example, when the selected inferior is not running,
28762 and therefore has no threads) or if a @var{thread-id} argument was passed to
28767 @subsubheading Example
28772 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
28773 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
28774 args=[]@},state="running"@},
28775 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
28776 frame=@{level="0",addr="0x0804891f",func="foo",
28777 args=[@{name="i",value="10"@}],
28778 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
28779 state="running"@}],
28780 current-thread-id="1"
28784 @subheading The @code{-thread-list-ids} Command
28785 @findex -thread-list-ids
28787 @subsubheading Synopsis
28793 Produces a list of the currently known global @value{GDBN} thread ids.
28794 At the end of the list it also prints the total number of such
28797 This command is retained for historical reasons, the
28798 @code{-thread-info} command should be used instead.
28800 @subsubheading @value{GDBN} Command
28802 Part of @samp{info threads} supplies the same information.
28804 @subsubheading Example
28809 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28810 current-thread-id="1",number-of-threads="3"
28815 @subheading The @code{-thread-select} Command
28816 @findex -thread-select
28818 @subsubheading Synopsis
28821 -thread-select @var{thread-id}
28824 Make thread with global thread number @var{thread-id} the current
28825 thread. It prints the number of the new current thread, and the
28826 topmost frame for that thread.
28828 This command is deprecated in favor of explicitly using the
28829 @samp{--thread} option to each command.
28831 @subsubheading @value{GDBN} Command
28833 The corresponding @value{GDBN} command is @samp{thread}.
28835 @subsubheading Example
28842 *stopped,reason="end-stepping-range",thread-id="2",line="187",
28843 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
28847 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28848 number-of-threads="3"
28851 ^done,new-thread-id="3",
28852 frame=@{level="0",func="vprintf",
28853 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
28854 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
28858 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28859 @node GDB/MI Ada Tasking Commands
28860 @section @sc{gdb/mi} Ada Tasking Commands
28862 @subheading The @code{-ada-task-info} Command
28863 @findex -ada-task-info
28865 @subsubheading Synopsis
28868 -ada-task-info [ @var{task-id} ]
28871 Reports information about either a specific Ada task, if the
28872 @var{task-id} parameter is present, or about all Ada tasks.
28874 @subsubheading @value{GDBN} Command
28876 The @samp{info tasks} command prints the same information
28877 about all Ada tasks (@pxref{Ada Tasks}).
28879 @subsubheading Result
28881 The result is a table of Ada tasks. The following columns are
28882 defined for each Ada task:
28886 This field exists only for the current thread. It has the value @samp{*}.
28889 The identifier that @value{GDBN} uses to refer to the Ada task.
28892 The identifier that the target uses to refer to the Ada task.
28895 The global thread identifier of the thread corresponding to the Ada
28898 This field should always exist, as Ada tasks are always implemented
28899 on top of a thread. But if @value{GDBN} cannot find this corresponding
28900 thread for any reason, the field is omitted.
28903 This field exists only when the task was created by another task.
28904 In this case, it provides the ID of the parent task.
28907 The base priority of the task.
28910 The current state of the task. For a detailed description of the
28911 possible states, see @ref{Ada Tasks}.
28914 The name of the task.
28918 @subsubheading Example
28922 ^done,tasks=@{nr_rows="3",nr_cols="8",
28923 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
28924 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
28925 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
28926 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
28927 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
28928 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
28929 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
28930 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
28931 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
28932 state="Child Termination Wait",name="main_task"@}]@}
28936 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28937 @node GDB/MI Program Execution
28938 @section @sc{gdb/mi} Program Execution
28940 These are the asynchronous commands which generate the out-of-band
28941 record @samp{*stopped}. Currently @value{GDBN} only really executes
28942 asynchronously with remote targets and this interaction is mimicked in
28945 @subheading The @code{-exec-continue} Command
28946 @findex -exec-continue
28948 @subsubheading Synopsis
28951 -exec-continue [--reverse] [--all|--thread-group N]
28954 Resumes the execution of the inferior program, which will continue
28955 to execute until it reaches a debugger stop event. If the
28956 @samp{--reverse} option is specified, execution resumes in reverse until
28957 it reaches a stop event. Stop events may include
28960 breakpoints or watchpoints
28962 signals or exceptions
28964 the end of the process (or its beginning under @samp{--reverse})
28966 the end or beginning of a replay log if one is being used.
28968 In all-stop mode (@pxref{All-Stop
28969 Mode}), may resume only one thread, or all threads, depending on the
28970 value of the @samp{scheduler-locking} variable. If @samp{--all} is
28971 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
28972 ignored in all-stop mode. If the @samp{--thread-group} options is
28973 specified, then all threads in that thread group are resumed.
28975 @subsubheading @value{GDBN} Command
28977 The corresponding @value{GDBN} corresponding is @samp{continue}.
28979 @subsubheading Example
28986 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
28987 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
28993 @subheading The @code{-exec-finish} Command
28994 @findex -exec-finish
28996 @subsubheading Synopsis
28999 -exec-finish [--reverse]
29002 Resumes the execution of the inferior program until the current
29003 function is exited. Displays the results returned by the function.
29004 If the @samp{--reverse} option is specified, resumes the reverse
29005 execution of the inferior program until the point where current
29006 function was called.
29008 @subsubheading @value{GDBN} Command
29010 The corresponding @value{GDBN} command is @samp{finish}.
29012 @subsubheading Example
29014 Function returning @code{void}.
29021 *stopped,reason="function-finished",frame=@{func="main",args=[],
29022 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
29026 Function returning other than @code{void}. The name of the internal
29027 @value{GDBN} variable storing the result is printed, together with the
29034 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
29035 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
29036 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29037 gdb-result-var="$1",return-value="0"
29042 @subheading The @code{-exec-interrupt} Command
29043 @findex -exec-interrupt
29045 @subsubheading Synopsis
29048 -exec-interrupt [--all|--thread-group N]
29051 Interrupts the background execution of the target. Note how the token
29052 associated with the stop message is the one for the execution command
29053 that has been interrupted. The token for the interrupt itself only
29054 appears in the @samp{^done} output. If the user is trying to
29055 interrupt a non-running program, an error message will be printed.
29057 Note that when asynchronous execution is enabled, this command is
29058 asynchronous just like other execution commands. That is, first the
29059 @samp{^done} response will be printed, and the target stop will be
29060 reported after that using the @samp{*stopped} notification.
29062 In non-stop mode, only the context thread is interrupted by default.
29063 All threads (in all inferiors) will be interrupted if the
29064 @samp{--all} option is specified. If the @samp{--thread-group}
29065 option is specified, all threads in that group will be interrupted.
29067 @subsubheading @value{GDBN} Command
29069 The corresponding @value{GDBN} command is @samp{interrupt}.
29071 @subsubheading Example
29082 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
29083 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
29084 fullname="/home/foo/bar/try.c",line="13"@}
29089 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
29093 @subheading The @code{-exec-jump} Command
29096 @subsubheading Synopsis
29099 -exec-jump @var{location}
29102 Resumes execution of the inferior program at the location specified by
29103 parameter. @xref{Specify Location}, for a description of the
29104 different forms of @var{location}.
29106 @subsubheading @value{GDBN} Command
29108 The corresponding @value{GDBN} command is @samp{jump}.
29110 @subsubheading Example
29113 -exec-jump foo.c:10
29114 *running,thread-id="all"
29119 @subheading The @code{-exec-next} Command
29122 @subsubheading Synopsis
29125 -exec-next [--reverse]
29128 Resumes execution of the inferior program, stopping when the beginning
29129 of the next source line is reached.
29131 If the @samp{--reverse} option is specified, resumes reverse execution
29132 of the inferior program, stopping at the beginning of the previous
29133 source line. If you issue this command on the first line of a
29134 function, it will take you back to the caller of that function, to the
29135 source line where the function was called.
29138 @subsubheading @value{GDBN} Command
29140 The corresponding @value{GDBN} command is @samp{next}.
29142 @subsubheading Example
29148 *stopped,reason="end-stepping-range",line="8",file="hello.c"
29153 @subheading The @code{-exec-next-instruction} Command
29154 @findex -exec-next-instruction
29156 @subsubheading Synopsis
29159 -exec-next-instruction [--reverse]
29162 Executes one machine instruction. If the instruction is a function
29163 call, continues until the function returns. If the program stops at an
29164 instruction in the middle of a source line, the address will be
29167 If the @samp{--reverse} option is specified, resumes reverse execution
29168 of the inferior program, stopping at the previous instruction. If the
29169 previously executed instruction was a return from another function,
29170 it will continue to execute in reverse until the call to that function
29171 (from the current stack frame) is reached.
29173 @subsubheading @value{GDBN} Command
29175 The corresponding @value{GDBN} command is @samp{nexti}.
29177 @subsubheading Example
29181 -exec-next-instruction
29185 *stopped,reason="end-stepping-range",
29186 addr="0x000100d4",line="5",file="hello.c"
29191 @subheading The @code{-exec-return} Command
29192 @findex -exec-return
29194 @subsubheading Synopsis
29200 Makes current function return immediately. Doesn't execute the inferior.
29201 Displays the new current frame.
29203 @subsubheading @value{GDBN} Command
29205 The corresponding @value{GDBN} command is @samp{return}.
29207 @subsubheading Example
29211 200-break-insert callee4
29212 200^done,bkpt=@{number="1",addr="0x00010734",
29213 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29218 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29219 frame=@{func="callee4",args=[],
29220 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29221 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29227 111^done,frame=@{level="0",func="callee3",
29228 args=[@{name="strarg",
29229 value="0x11940 \"A string argument.\""@}],
29230 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29231 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29236 @subheading The @code{-exec-run} Command
29239 @subsubheading Synopsis
29242 -exec-run [ --all | --thread-group N ] [ --start ]
29245 Starts execution of the inferior from the beginning. The inferior
29246 executes until either a breakpoint is encountered or the program
29247 exits. In the latter case the output will include an exit code, if
29248 the program has exited exceptionally.
29250 When neither the @samp{--all} nor the @samp{--thread-group} option
29251 is specified, the current inferior is started. If the
29252 @samp{--thread-group} option is specified, it should refer to a thread
29253 group of type @samp{process}, and that thread group will be started.
29254 If the @samp{--all} option is specified, then all inferiors will be started.
29256 Using the @samp{--start} option instructs the debugger to stop
29257 the execution at the start of the inferior's main subprogram,
29258 following the same behavior as the @code{start} command
29259 (@pxref{Starting}).
29261 @subsubheading @value{GDBN} Command
29263 The corresponding @value{GDBN} command is @samp{run}.
29265 @subsubheading Examples
29270 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
29275 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29276 frame=@{func="main",args=[],file="recursive2.c",
29277 fullname="/home/foo/bar/recursive2.c",line="4"@}
29282 Program exited normally:
29290 *stopped,reason="exited-normally"
29295 Program exited exceptionally:
29303 *stopped,reason="exited",exit-code="01"
29307 Another way the program can terminate is if it receives a signal such as
29308 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
29312 *stopped,reason="exited-signalled",signal-name="SIGINT",
29313 signal-meaning="Interrupt"
29317 @c @subheading -exec-signal
29320 @subheading The @code{-exec-step} Command
29323 @subsubheading Synopsis
29326 -exec-step [--reverse]
29329 Resumes execution of the inferior program, stopping when the beginning
29330 of the next source line is reached, if the next source line is not a
29331 function call. If it is, stop at the first instruction of the called
29332 function. If the @samp{--reverse} option is specified, resumes reverse
29333 execution of the inferior program, stopping at the beginning of the
29334 previously executed source line.
29336 @subsubheading @value{GDBN} Command
29338 The corresponding @value{GDBN} command is @samp{step}.
29340 @subsubheading Example
29342 Stepping into a function:
29348 *stopped,reason="end-stepping-range",
29349 frame=@{func="foo",args=[@{name="a",value="10"@},
29350 @{name="b",value="0"@}],file="recursive2.c",
29351 fullname="/home/foo/bar/recursive2.c",line="11"@}
29361 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
29366 @subheading The @code{-exec-step-instruction} Command
29367 @findex -exec-step-instruction
29369 @subsubheading Synopsis
29372 -exec-step-instruction [--reverse]
29375 Resumes the inferior which executes one machine instruction. If the
29376 @samp{--reverse} option is specified, resumes reverse execution of the
29377 inferior program, stopping at the previously executed instruction.
29378 The output, once @value{GDBN} has stopped, will vary depending on
29379 whether we have stopped in the middle of a source line or not. In the
29380 former case, the address at which the program stopped will be printed
29383 @subsubheading @value{GDBN} Command
29385 The corresponding @value{GDBN} command is @samp{stepi}.
29387 @subsubheading Example
29391 -exec-step-instruction
29395 *stopped,reason="end-stepping-range",
29396 frame=@{func="foo",args=[],file="try.c",
29397 fullname="/home/foo/bar/try.c",line="10"@}
29399 -exec-step-instruction
29403 *stopped,reason="end-stepping-range",
29404 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
29405 fullname="/home/foo/bar/try.c",line="10"@}
29410 @subheading The @code{-exec-until} Command
29411 @findex -exec-until
29413 @subsubheading Synopsis
29416 -exec-until [ @var{location} ]
29419 Executes the inferior until the @var{location} specified in the
29420 argument is reached. If there is no argument, the inferior executes
29421 until a source line greater than the current one is reached. The
29422 reason for stopping in this case will be @samp{location-reached}.
29424 @subsubheading @value{GDBN} Command
29426 The corresponding @value{GDBN} command is @samp{until}.
29428 @subsubheading Example
29432 -exec-until recursive2.c:6
29436 *stopped,reason="location-reached",frame=@{func="main",args=[],
29437 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
29442 @subheading -file-clear
29443 Is this going away????
29446 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29447 @node GDB/MI Stack Manipulation
29448 @section @sc{gdb/mi} Stack Manipulation Commands
29450 @subheading The @code{-enable-frame-filters} Command
29451 @findex -enable-frame-filters
29454 -enable-frame-filters
29457 @value{GDBN} allows Python-based frame filters to affect the output of
29458 the MI commands relating to stack traces. As there is no way to
29459 implement this in a fully backward-compatible way, a front end must
29460 request that this functionality be enabled.
29462 Once enabled, this feature cannot be disabled.
29464 Note that if Python support has not been compiled into @value{GDBN},
29465 this command will still succeed (and do nothing).
29467 @subheading The @code{-stack-info-frame} Command
29468 @findex -stack-info-frame
29470 @subsubheading Synopsis
29476 Get info on the selected frame.
29478 @subsubheading @value{GDBN} Command
29480 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
29481 (without arguments).
29483 @subsubheading Example
29488 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
29489 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29490 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
29494 @subheading The @code{-stack-info-depth} Command
29495 @findex -stack-info-depth
29497 @subsubheading Synopsis
29500 -stack-info-depth [ @var{max-depth} ]
29503 Return the depth of the stack. If the integer argument @var{max-depth}
29504 is specified, do not count beyond @var{max-depth} frames.
29506 @subsubheading @value{GDBN} Command
29508 There's no equivalent @value{GDBN} command.
29510 @subsubheading Example
29512 For a stack with frame levels 0 through 11:
29519 -stack-info-depth 4
29522 -stack-info-depth 12
29525 -stack-info-depth 11
29528 -stack-info-depth 13
29533 @anchor{-stack-list-arguments}
29534 @subheading The @code{-stack-list-arguments} Command
29535 @findex -stack-list-arguments
29537 @subsubheading Synopsis
29540 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29541 [ @var{low-frame} @var{high-frame} ]
29544 Display a list of the arguments for the frames between @var{low-frame}
29545 and @var{high-frame} (inclusive). If @var{low-frame} and
29546 @var{high-frame} are not provided, list the arguments for the whole
29547 call stack. If the two arguments are equal, show the single frame
29548 at the corresponding level. It is an error if @var{low-frame} is
29549 larger than the actual number of frames. On the other hand,
29550 @var{high-frame} may be larger than the actual number of frames, in
29551 which case only existing frames will be returned.
29553 If @var{print-values} is 0 or @code{--no-values}, print only the names of
29554 the variables; if it is 1 or @code{--all-values}, print also their
29555 values; and if it is 2 or @code{--simple-values}, print the name,
29556 type and value for simple data types, and the name and type for arrays,
29557 structures and unions. If the option @code{--no-frame-filters} is
29558 supplied, then Python frame filters will not be executed.
29560 If the @code{--skip-unavailable} option is specified, arguments that
29561 are not available are not listed. Partially available arguments
29562 are still displayed, however.
29564 Use of this command to obtain arguments in a single frame is
29565 deprecated in favor of the @samp{-stack-list-variables} command.
29567 @subsubheading @value{GDBN} Command
29569 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
29570 @samp{gdb_get_args} command which partially overlaps with the
29571 functionality of @samp{-stack-list-arguments}.
29573 @subsubheading Example
29580 frame=@{level="0",addr="0x00010734",func="callee4",
29581 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29582 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
29583 frame=@{level="1",addr="0x0001076c",func="callee3",
29584 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29585 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
29586 frame=@{level="2",addr="0x0001078c",func="callee2",
29587 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29588 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
29589 frame=@{level="3",addr="0x000107b4",func="callee1",
29590 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29591 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
29592 frame=@{level="4",addr="0x000107e0",func="main",
29593 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29594 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
29596 -stack-list-arguments 0
29599 frame=@{level="0",args=[]@},
29600 frame=@{level="1",args=[name="strarg"]@},
29601 frame=@{level="2",args=[name="intarg",name="strarg"]@},
29602 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
29603 frame=@{level="4",args=[]@}]
29605 -stack-list-arguments 1
29608 frame=@{level="0",args=[]@},
29610 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
29611 frame=@{level="2",args=[
29612 @{name="intarg",value="2"@},
29613 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
29614 @{frame=@{level="3",args=[
29615 @{name="intarg",value="2"@},
29616 @{name="strarg",value="0x11940 \"A string argument.\""@},
29617 @{name="fltarg",value="3.5"@}]@},
29618 frame=@{level="4",args=[]@}]
29620 -stack-list-arguments 0 2 2
29621 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
29623 -stack-list-arguments 1 2 2
29624 ^done,stack-args=[frame=@{level="2",
29625 args=[@{name="intarg",value="2"@},
29626 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
29630 @c @subheading -stack-list-exception-handlers
29633 @anchor{-stack-list-frames}
29634 @subheading The @code{-stack-list-frames} Command
29635 @findex -stack-list-frames
29637 @subsubheading Synopsis
29640 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
29643 List the frames currently on the stack. For each frame it displays the
29648 The frame number, 0 being the topmost frame, i.e., the innermost function.
29650 The @code{$pc} value for that frame.
29654 File name of the source file where the function lives.
29655 @item @var{fullname}
29656 The full file name of the source file where the function lives.
29658 Line number corresponding to the @code{$pc}.
29660 The shared library where this function is defined. This is only given
29661 if the frame's function is not known.
29664 If invoked without arguments, this command prints a backtrace for the
29665 whole stack. If given two integer arguments, it shows the frames whose
29666 levels are between the two arguments (inclusive). If the two arguments
29667 are equal, it shows the single frame at the corresponding level. It is
29668 an error if @var{low-frame} is larger than the actual number of
29669 frames. On the other hand, @var{high-frame} may be larger than the
29670 actual number of frames, in which case only existing frames will be
29671 returned. If the option @code{--no-frame-filters} is supplied, then
29672 Python frame filters will not be executed.
29674 @subsubheading @value{GDBN} Command
29676 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
29678 @subsubheading Example
29680 Full stack backtrace:
29686 [frame=@{level="0",addr="0x0001076c",func="foo",
29687 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
29688 frame=@{level="1",addr="0x000107a4",func="foo",
29689 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29690 frame=@{level="2",addr="0x000107a4",func="foo",
29691 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29692 frame=@{level="3",addr="0x000107a4",func="foo",
29693 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29694 frame=@{level="4",addr="0x000107a4",func="foo",
29695 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29696 frame=@{level="5",addr="0x000107a4",func="foo",
29697 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29698 frame=@{level="6",addr="0x000107a4",func="foo",
29699 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29700 frame=@{level="7",addr="0x000107a4",func="foo",
29701 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29702 frame=@{level="8",addr="0x000107a4",func="foo",
29703 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29704 frame=@{level="9",addr="0x000107a4",func="foo",
29705 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29706 frame=@{level="10",addr="0x000107a4",func="foo",
29707 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29708 frame=@{level="11",addr="0x00010738",func="main",
29709 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
29713 Show frames between @var{low_frame} and @var{high_frame}:
29717 -stack-list-frames 3 5
29719 [frame=@{level="3",addr="0x000107a4",func="foo",
29720 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29721 frame=@{level="4",addr="0x000107a4",func="foo",
29722 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29723 frame=@{level="5",addr="0x000107a4",func="foo",
29724 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29728 Show a single frame:
29732 -stack-list-frames 3 3
29734 [frame=@{level="3",addr="0x000107a4",func="foo",
29735 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29740 @subheading The @code{-stack-list-locals} Command
29741 @findex -stack-list-locals
29742 @anchor{-stack-list-locals}
29744 @subsubheading Synopsis
29747 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29750 Display the local variable names for the selected frame. If
29751 @var{print-values} is 0 or @code{--no-values}, print only the names of
29752 the variables; if it is 1 or @code{--all-values}, print also their
29753 values; and if it is 2 or @code{--simple-values}, print the name,
29754 type and value for simple data types, and the name and type for arrays,
29755 structures and unions. In this last case, a frontend can immediately
29756 display the value of simple data types and create variable objects for
29757 other data types when the user wishes to explore their values in
29758 more detail. If the option @code{--no-frame-filters} is supplied, then
29759 Python frame filters will not be executed.
29761 If the @code{--skip-unavailable} option is specified, local variables
29762 that are not available are not listed. Partially available local
29763 variables are still displayed, however.
29765 This command is deprecated in favor of the
29766 @samp{-stack-list-variables} command.
29768 @subsubheading @value{GDBN} Command
29770 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
29772 @subsubheading Example
29776 -stack-list-locals 0
29777 ^done,locals=[name="A",name="B",name="C"]
29779 -stack-list-locals --all-values
29780 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
29781 @{name="C",value="@{1, 2, 3@}"@}]
29782 -stack-list-locals --simple-values
29783 ^done,locals=[@{name="A",type="int",value="1"@},
29784 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
29788 @anchor{-stack-list-variables}
29789 @subheading The @code{-stack-list-variables} Command
29790 @findex -stack-list-variables
29792 @subsubheading Synopsis
29795 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29798 Display the names of local variables and function arguments for the selected frame. If
29799 @var{print-values} is 0 or @code{--no-values}, print only the names of
29800 the variables; if it is 1 or @code{--all-values}, print also their
29801 values; and if it is 2 or @code{--simple-values}, print the name,
29802 type and value for simple data types, and the name and type for arrays,
29803 structures and unions. If the option @code{--no-frame-filters} is
29804 supplied, then Python frame filters will not be executed.
29806 If the @code{--skip-unavailable} option is specified, local variables
29807 and arguments that are not available are not listed. Partially
29808 available arguments and local variables are still displayed, however.
29810 @subsubheading Example
29814 -stack-list-variables --thread 1 --frame 0 --all-values
29815 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
29820 @subheading The @code{-stack-select-frame} Command
29821 @findex -stack-select-frame
29823 @subsubheading Synopsis
29826 -stack-select-frame @var{framenum}
29829 Change the selected frame. Select a different frame @var{framenum} on
29832 This command in deprecated in favor of passing the @samp{--frame}
29833 option to every command.
29835 @subsubheading @value{GDBN} Command
29837 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
29838 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
29840 @subsubheading Example
29844 -stack-select-frame 2
29849 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29850 @node GDB/MI Variable Objects
29851 @section @sc{gdb/mi} Variable Objects
29855 @subheading Motivation for Variable Objects in @sc{gdb/mi}
29857 For the implementation of a variable debugger window (locals, watched
29858 expressions, etc.), we are proposing the adaptation of the existing code
29859 used by @code{Insight}.
29861 The two main reasons for that are:
29865 It has been proven in practice (it is already on its second generation).
29868 It will shorten development time (needless to say how important it is
29872 The original interface was designed to be used by Tcl code, so it was
29873 slightly changed so it could be used through @sc{gdb/mi}. This section
29874 describes the @sc{gdb/mi} operations that will be available and gives some
29875 hints about their use.
29877 @emph{Note}: In addition to the set of operations described here, we
29878 expect the @sc{gui} implementation of a variable window to require, at
29879 least, the following operations:
29882 @item @code{-gdb-show} @code{output-radix}
29883 @item @code{-stack-list-arguments}
29884 @item @code{-stack-list-locals}
29885 @item @code{-stack-select-frame}
29890 @subheading Introduction to Variable Objects
29892 @cindex variable objects in @sc{gdb/mi}
29894 Variable objects are "object-oriented" MI interface for examining and
29895 changing values of expressions. Unlike some other MI interfaces that
29896 work with expressions, variable objects are specifically designed for
29897 simple and efficient presentation in the frontend. A variable object
29898 is identified by string name. When a variable object is created, the
29899 frontend specifies the expression for that variable object. The
29900 expression can be a simple variable, or it can be an arbitrary complex
29901 expression, and can even involve CPU registers. After creating a
29902 variable object, the frontend can invoke other variable object
29903 operations---for example to obtain or change the value of a variable
29904 object, or to change display format.
29906 Variable objects have hierarchical tree structure. Any variable object
29907 that corresponds to a composite type, such as structure in C, has
29908 a number of child variable objects, for example corresponding to each
29909 element of a structure. A child variable object can itself have
29910 children, recursively. Recursion ends when we reach
29911 leaf variable objects, which always have built-in types. Child variable
29912 objects are created only by explicit request, so if a frontend
29913 is not interested in the children of a particular variable object, no
29914 child will be created.
29916 For a leaf variable object it is possible to obtain its value as a
29917 string, or set the value from a string. String value can be also
29918 obtained for a non-leaf variable object, but it's generally a string
29919 that only indicates the type of the object, and does not list its
29920 contents. Assignment to a non-leaf variable object is not allowed.
29922 A frontend does not need to read the values of all variable objects each time
29923 the program stops. Instead, MI provides an update command that lists all
29924 variable objects whose values has changed since the last update
29925 operation. This considerably reduces the amount of data that must
29926 be transferred to the frontend. As noted above, children variable
29927 objects are created on demand, and only leaf variable objects have a
29928 real value. As result, gdb will read target memory only for leaf
29929 variables that frontend has created.
29931 The automatic update is not always desirable. For example, a frontend
29932 might want to keep a value of some expression for future reference,
29933 and never update it. For another example, fetching memory is
29934 relatively slow for embedded targets, so a frontend might want
29935 to disable automatic update for the variables that are either not
29936 visible on the screen, or ``closed''. This is possible using so
29937 called ``frozen variable objects''. Such variable objects are never
29938 implicitly updated.
29940 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
29941 fixed variable object, the expression is parsed when the variable
29942 object is created, including associating identifiers to specific
29943 variables. The meaning of expression never changes. For a floating
29944 variable object the values of variables whose names appear in the
29945 expressions are re-evaluated every time in the context of the current
29946 frame. Consider this example:
29951 struct work_state state;
29958 If a fixed variable object for the @code{state} variable is created in
29959 this function, and we enter the recursive call, the variable
29960 object will report the value of @code{state} in the top-level
29961 @code{do_work} invocation. On the other hand, a floating variable
29962 object will report the value of @code{state} in the current frame.
29964 If an expression specified when creating a fixed variable object
29965 refers to a local variable, the variable object becomes bound to the
29966 thread and frame in which the variable object is created. When such
29967 variable object is updated, @value{GDBN} makes sure that the
29968 thread/frame combination the variable object is bound to still exists,
29969 and re-evaluates the variable object in context of that thread/frame.
29971 The following is the complete set of @sc{gdb/mi} operations defined to
29972 access this functionality:
29974 @multitable @columnfractions .4 .6
29975 @item @strong{Operation}
29976 @tab @strong{Description}
29978 @item @code{-enable-pretty-printing}
29979 @tab enable Python-based pretty-printing
29980 @item @code{-var-create}
29981 @tab create a variable object
29982 @item @code{-var-delete}
29983 @tab delete the variable object and/or its children
29984 @item @code{-var-set-format}
29985 @tab set the display format of this variable
29986 @item @code{-var-show-format}
29987 @tab show the display format of this variable
29988 @item @code{-var-info-num-children}
29989 @tab tells how many children this object has
29990 @item @code{-var-list-children}
29991 @tab return a list of the object's children
29992 @item @code{-var-info-type}
29993 @tab show the type of this variable object
29994 @item @code{-var-info-expression}
29995 @tab print parent-relative expression that this variable object represents
29996 @item @code{-var-info-path-expression}
29997 @tab print full expression that this variable object represents
29998 @item @code{-var-show-attributes}
29999 @tab is this variable editable? does it exist here?
30000 @item @code{-var-evaluate-expression}
30001 @tab get the value of this variable
30002 @item @code{-var-assign}
30003 @tab set the value of this variable
30004 @item @code{-var-update}
30005 @tab update the variable and its children
30006 @item @code{-var-set-frozen}
30007 @tab set frozeness attribute
30008 @item @code{-var-set-update-range}
30009 @tab set range of children to display on update
30012 In the next subsection we describe each operation in detail and suggest
30013 how it can be used.
30015 @subheading Description And Use of Operations on Variable Objects
30017 @subheading The @code{-enable-pretty-printing} Command
30018 @findex -enable-pretty-printing
30021 -enable-pretty-printing
30024 @value{GDBN} allows Python-based visualizers to affect the output of the
30025 MI variable object commands. However, because there was no way to
30026 implement this in a fully backward-compatible way, a front end must
30027 request that this functionality be enabled.
30029 Once enabled, this feature cannot be disabled.
30031 Note that if Python support has not been compiled into @value{GDBN},
30032 this command will still succeed (and do nothing).
30034 This feature is currently (as of @value{GDBN} 7.0) experimental, and
30035 may work differently in future versions of @value{GDBN}.
30037 @subheading The @code{-var-create} Command
30038 @findex -var-create
30040 @subsubheading Synopsis
30043 -var-create @{@var{name} | "-"@}
30044 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
30047 This operation creates a variable object, which allows the monitoring of
30048 a variable, the result of an expression, a memory cell or a CPU
30051 The @var{name} parameter is the string by which the object can be
30052 referenced. It must be unique. If @samp{-} is specified, the varobj
30053 system will generate a string ``varNNNNNN'' automatically. It will be
30054 unique provided that one does not specify @var{name} of that format.
30055 The command fails if a duplicate name is found.
30057 The frame under which the expression should be evaluated can be
30058 specified by @var{frame-addr}. A @samp{*} indicates that the current
30059 frame should be used. A @samp{@@} indicates that a floating variable
30060 object must be created.
30062 @var{expression} is any expression valid on the current language set (must not
30063 begin with a @samp{*}), or one of the following:
30067 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
30070 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
30073 @samp{$@var{regname}} --- a CPU register name
30076 @cindex dynamic varobj
30077 A varobj's contents may be provided by a Python-based pretty-printer. In this
30078 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
30079 have slightly different semantics in some cases. If the
30080 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
30081 will never create a dynamic varobj. This ensures backward
30082 compatibility for existing clients.
30084 @subsubheading Result
30086 This operation returns attributes of the newly-created varobj. These
30091 The name of the varobj.
30094 The number of children of the varobj. This number is not necessarily
30095 reliable for a dynamic varobj. Instead, you must examine the
30096 @samp{has_more} attribute.
30099 The varobj's scalar value. For a varobj whose type is some sort of
30100 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
30101 will not be interesting.
30104 The varobj's type. This is a string representation of the type, as
30105 would be printed by the @value{GDBN} CLI. If @samp{print object}
30106 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30107 @emph{actual} (derived) type of the object is shown rather than the
30108 @emph{declared} one.
30111 If a variable object is bound to a specific thread, then this is the
30112 thread's global identifier.
30115 For a dynamic varobj, this indicates whether there appear to be any
30116 children available. For a non-dynamic varobj, this will be 0.
30119 This attribute will be present and have the value @samp{1} if the
30120 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30121 then this attribute will not be present.
30124 A dynamic varobj can supply a display hint to the front end. The
30125 value comes directly from the Python pretty-printer object's
30126 @code{display_hint} method. @xref{Pretty Printing API}.
30129 Typical output will look like this:
30132 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
30133 has_more="@var{has_more}"
30137 @subheading The @code{-var-delete} Command
30138 @findex -var-delete
30140 @subsubheading Synopsis
30143 -var-delete [ -c ] @var{name}
30146 Deletes a previously created variable object and all of its children.
30147 With the @samp{-c} option, just deletes the children.
30149 Returns an error if the object @var{name} is not found.
30152 @subheading The @code{-var-set-format} Command
30153 @findex -var-set-format
30155 @subsubheading Synopsis
30158 -var-set-format @var{name} @var{format-spec}
30161 Sets the output format for the value of the object @var{name} to be
30164 @anchor{-var-set-format}
30165 The syntax for the @var{format-spec} is as follows:
30168 @var{format-spec} @expansion{}
30169 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
30172 The natural format is the default format choosen automatically
30173 based on the variable type (like decimal for an @code{int}, hex
30174 for pointers, etc.).
30176 The zero-hexadecimal format has a representation similar to hexadecimal
30177 but with padding zeroes to the left of the value. For example, a 32-bit
30178 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
30179 zero-hexadecimal format.
30181 For a variable with children, the format is set only on the
30182 variable itself, and the children are not affected.
30184 @subheading The @code{-var-show-format} Command
30185 @findex -var-show-format
30187 @subsubheading Synopsis
30190 -var-show-format @var{name}
30193 Returns the format used to display the value of the object @var{name}.
30196 @var{format} @expansion{}
30201 @subheading The @code{-var-info-num-children} Command
30202 @findex -var-info-num-children
30204 @subsubheading Synopsis
30207 -var-info-num-children @var{name}
30210 Returns the number of children of a variable object @var{name}:
30216 Note that this number is not completely reliable for a dynamic varobj.
30217 It will return the current number of children, but more children may
30221 @subheading The @code{-var-list-children} Command
30222 @findex -var-list-children
30224 @subsubheading Synopsis
30227 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
30229 @anchor{-var-list-children}
30231 Return a list of the children of the specified variable object and
30232 create variable objects for them, if they do not already exist. With
30233 a single argument or if @var{print-values} has a value of 0 or
30234 @code{--no-values}, print only the names of the variables; if
30235 @var{print-values} is 1 or @code{--all-values}, also print their
30236 values; and if it is 2 or @code{--simple-values} print the name and
30237 value for simple data types and just the name for arrays, structures
30240 @var{from} and @var{to}, if specified, indicate the range of children
30241 to report. If @var{from} or @var{to} is less than zero, the range is
30242 reset and all children will be reported. Otherwise, children starting
30243 at @var{from} (zero-based) and up to and excluding @var{to} will be
30246 If a child range is requested, it will only affect the current call to
30247 @code{-var-list-children}, but not future calls to @code{-var-update}.
30248 For this, you must instead use @code{-var-set-update-range}. The
30249 intent of this approach is to enable a front end to implement any
30250 update approach it likes; for example, scrolling a view may cause the
30251 front end to request more children with @code{-var-list-children}, and
30252 then the front end could call @code{-var-set-update-range} with a
30253 different range to ensure that future updates are restricted to just
30256 For each child the following results are returned:
30261 Name of the variable object created for this child.
30264 The expression to be shown to the user by the front end to designate this child.
30265 For example this may be the name of a structure member.
30267 For a dynamic varobj, this value cannot be used to form an
30268 expression. There is no way to do this at all with a dynamic varobj.
30270 For C/C@t{++} structures there are several pseudo children returned to
30271 designate access qualifiers. For these pseudo children @var{exp} is
30272 @samp{public}, @samp{private}, or @samp{protected}. In this case the
30273 type and value are not present.
30275 A dynamic varobj will not report the access qualifying
30276 pseudo-children, regardless of the language. This information is not
30277 available at all with a dynamic varobj.
30280 Number of children this child has. For a dynamic varobj, this will be
30284 The type of the child. If @samp{print object}
30285 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30286 @emph{actual} (derived) type of the object is shown rather than the
30287 @emph{declared} one.
30290 If values were requested, this is the value.
30293 If this variable object is associated with a thread, this is the
30294 thread's global thread id. Otherwise this result is not present.
30297 If the variable object is frozen, this variable will be present with a value of 1.
30300 A dynamic varobj can supply a display hint to the front end. The
30301 value comes directly from the Python pretty-printer object's
30302 @code{display_hint} method. @xref{Pretty Printing API}.
30305 This attribute will be present and have the value @samp{1} if the
30306 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30307 then this attribute will not be present.
30311 The result may have its own attributes:
30315 A dynamic varobj can supply a display hint to the front end. The
30316 value comes directly from the Python pretty-printer object's
30317 @code{display_hint} method. @xref{Pretty Printing API}.
30320 This is an integer attribute which is nonzero if there are children
30321 remaining after the end of the selected range.
30324 @subsubheading Example
30328 -var-list-children n
30329 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30330 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
30332 -var-list-children --all-values n
30333 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30334 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
30338 @subheading The @code{-var-info-type} Command
30339 @findex -var-info-type
30341 @subsubheading Synopsis
30344 -var-info-type @var{name}
30347 Returns the type of the specified variable @var{name}. The type is
30348 returned as a string in the same format as it is output by the
30352 type=@var{typename}
30356 @subheading The @code{-var-info-expression} Command
30357 @findex -var-info-expression
30359 @subsubheading Synopsis
30362 -var-info-expression @var{name}
30365 Returns a string that is suitable for presenting this
30366 variable object in user interface. The string is generally
30367 not valid expression in the current language, and cannot be evaluated.
30369 For example, if @code{a} is an array, and variable object
30370 @code{A} was created for @code{a}, then we'll get this output:
30373 (gdb) -var-info-expression A.1
30374 ^done,lang="C",exp="1"
30378 Here, the value of @code{lang} is the language name, which can be
30379 found in @ref{Supported Languages}.
30381 Note that the output of the @code{-var-list-children} command also
30382 includes those expressions, so the @code{-var-info-expression} command
30385 @subheading The @code{-var-info-path-expression} Command
30386 @findex -var-info-path-expression
30388 @subsubheading Synopsis
30391 -var-info-path-expression @var{name}
30394 Returns an expression that can be evaluated in the current
30395 context and will yield the same value that a variable object has.
30396 Compare this with the @code{-var-info-expression} command, which
30397 result can be used only for UI presentation. Typical use of
30398 the @code{-var-info-path-expression} command is creating a
30399 watchpoint from a variable object.
30401 This command is currently not valid for children of a dynamic varobj,
30402 and will give an error when invoked on one.
30404 For example, suppose @code{C} is a C@t{++} class, derived from class
30405 @code{Base}, and that the @code{Base} class has a member called
30406 @code{m_size}. Assume a variable @code{c} is has the type of
30407 @code{C} and a variable object @code{C} was created for variable
30408 @code{c}. Then, we'll get this output:
30410 (gdb) -var-info-path-expression C.Base.public.m_size
30411 ^done,path_expr=((Base)c).m_size)
30414 @subheading The @code{-var-show-attributes} Command
30415 @findex -var-show-attributes
30417 @subsubheading Synopsis
30420 -var-show-attributes @var{name}
30423 List attributes of the specified variable object @var{name}:
30426 status=@var{attr} [ ( ,@var{attr} )* ]
30430 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
30432 @subheading The @code{-var-evaluate-expression} Command
30433 @findex -var-evaluate-expression
30435 @subsubheading Synopsis
30438 -var-evaluate-expression [-f @var{format-spec}] @var{name}
30441 Evaluates the expression that is represented by the specified variable
30442 object and returns its value as a string. The format of the string
30443 can be specified with the @samp{-f} option. The possible values of
30444 this option are the same as for @code{-var-set-format}
30445 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
30446 the current display format will be used. The current display format
30447 can be changed using the @code{-var-set-format} command.
30453 Note that one must invoke @code{-var-list-children} for a variable
30454 before the value of a child variable can be evaluated.
30456 @subheading The @code{-var-assign} Command
30457 @findex -var-assign
30459 @subsubheading Synopsis
30462 -var-assign @var{name} @var{expression}
30465 Assigns the value of @var{expression} to the variable object specified
30466 by @var{name}. The object must be @samp{editable}. If the variable's
30467 value is altered by the assign, the variable will show up in any
30468 subsequent @code{-var-update} list.
30470 @subsubheading Example
30478 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
30482 @subheading The @code{-var-update} Command
30483 @findex -var-update
30485 @subsubheading Synopsis
30488 -var-update [@var{print-values}] @{@var{name} | "*"@}
30491 Reevaluate the expressions corresponding to the variable object
30492 @var{name} and all its direct and indirect children, and return the
30493 list of variable objects whose values have changed; @var{name} must
30494 be a root variable object. Here, ``changed'' means that the result of
30495 @code{-var-evaluate-expression} before and after the
30496 @code{-var-update} is different. If @samp{*} is used as the variable
30497 object names, all existing variable objects are updated, except
30498 for frozen ones (@pxref{-var-set-frozen}). The option
30499 @var{print-values} determines whether both names and values, or just
30500 names are printed. The possible values of this option are the same
30501 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
30502 recommended to use the @samp{--all-values} option, to reduce the
30503 number of MI commands needed on each program stop.
30505 With the @samp{*} parameter, if a variable object is bound to a
30506 currently running thread, it will not be updated, without any
30509 If @code{-var-set-update-range} was previously used on a varobj, then
30510 only the selected range of children will be reported.
30512 @code{-var-update} reports all the changed varobjs in a tuple named
30515 Each item in the change list is itself a tuple holding:
30519 The name of the varobj.
30522 If values were requested for this update, then this field will be
30523 present and will hold the value of the varobj.
30526 @anchor{-var-update}
30527 This field is a string which may take one of three values:
30531 The variable object's current value is valid.
30534 The variable object does not currently hold a valid value but it may
30535 hold one in the future if its associated expression comes back into
30539 The variable object no longer holds a valid value.
30540 This can occur when the executable file being debugged has changed,
30541 either through recompilation or by using the @value{GDBN} @code{file}
30542 command. The front end should normally choose to delete these variable
30546 In the future new values may be added to this list so the front should
30547 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
30550 This is only present if the varobj is still valid. If the type
30551 changed, then this will be the string @samp{true}; otherwise it will
30554 When a varobj's type changes, its children are also likely to have
30555 become incorrect. Therefore, the varobj's children are automatically
30556 deleted when this attribute is @samp{true}. Also, the varobj's update
30557 range, when set using the @code{-var-set-update-range} command, is
30561 If the varobj's type changed, then this field will be present and will
30564 @item new_num_children
30565 For a dynamic varobj, if the number of children changed, or if the
30566 type changed, this will be the new number of children.
30568 The @samp{numchild} field in other varobj responses is generally not
30569 valid for a dynamic varobj -- it will show the number of children that
30570 @value{GDBN} knows about, but because dynamic varobjs lazily
30571 instantiate their children, this will not reflect the number of
30572 children which may be available.
30574 The @samp{new_num_children} attribute only reports changes to the
30575 number of children known by @value{GDBN}. This is the only way to
30576 detect whether an update has removed children (which necessarily can
30577 only happen at the end of the update range).
30580 The display hint, if any.
30583 This is an integer value, which will be 1 if there are more children
30584 available outside the varobj's update range.
30587 This attribute will be present and have the value @samp{1} if the
30588 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30589 then this attribute will not be present.
30592 If new children were added to a dynamic varobj within the selected
30593 update range (as set by @code{-var-set-update-range}), then they will
30594 be listed in this attribute.
30597 @subsubheading Example
30604 -var-update --all-values var1
30605 ^done,changelist=[@{name="var1",value="3",in_scope="true",
30606 type_changed="false"@}]
30610 @subheading The @code{-var-set-frozen} Command
30611 @findex -var-set-frozen
30612 @anchor{-var-set-frozen}
30614 @subsubheading Synopsis
30617 -var-set-frozen @var{name} @var{flag}
30620 Set the frozenness flag on the variable object @var{name}. The
30621 @var{flag} parameter should be either @samp{1} to make the variable
30622 frozen or @samp{0} to make it unfrozen. If a variable object is
30623 frozen, then neither itself, nor any of its children, are
30624 implicitly updated by @code{-var-update} of
30625 a parent variable or by @code{-var-update *}. Only
30626 @code{-var-update} of the variable itself will update its value and
30627 values of its children. After a variable object is unfrozen, it is
30628 implicitly updated by all subsequent @code{-var-update} operations.
30629 Unfreezing a variable does not update it, only subsequent
30630 @code{-var-update} does.
30632 @subsubheading Example
30636 -var-set-frozen V 1
30641 @subheading The @code{-var-set-update-range} command
30642 @findex -var-set-update-range
30643 @anchor{-var-set-update-range}
30645 @subsubheading Synopsis
30648 -var-set-update-range @var{name} @var{from} @var{to}
30651 Set the range of children to be returned by future invocations of
30652 @code{-var-update}.
30654 @var{from} and @var{to} indicate the range of children to report. If
30655 @var{from} or @var{to} is less than zero, the range is reset and all
30656 children will be reported. Otherwise, children starting at @var{from}
30657 (zero-based) and up to and excluding @var{to} will be reported.
30659 @subsubheading Example
30663 -var-set-update-range V 1 2
30667 @subheading The @code{-var-set-visualizer} command
30668 @findex -var-set-visualizer
30669 @anchor{-var-set-visualizer}
30671 @subsubheading Synopsis
30674 -var-set-visualizer @var{name} @var{visualizer}
30677 Set a visualizer for the variable object @var{name}.
30679 @var{visualizer} is the visualizer to use. The special value
30680 @samp{None} means to disable any visualizer in use.
30682 If not @samp{None}, @var{visualizer} must be a Python expression.
30683 This expression must evaluate to a callable object which accepts a
30684 single argument. @value{GDBN} will call this object with the value of
30685 the varobj @var{name} as an argument (this is done so that the same
30686 Python pretty-printing code can be used for both the CLI and MI).
30687 When called, this object must return an object which conforms to the
30688 pretty-printing interface (@pxref{Pretty Printing API}).
30690 The pre-defined function @code{gdb.default_visualizer} may be used to
30691 select a visualizer by following the built-in process
30692 (@pxref{Selecting Pretty-Printers}). This is done automatically when
30693 a varobj is created, and so ordinarily is not needed.
30695 This feature is only available if Python support is enabled. The MI
30696 command @code{-list-features} (@pxref{GDB/MI Support Commands})
30697 can be used to check this.
30699 @subsubheading Example
30701 Resetting the visualizer:
30705 -var-set-visualizer V None
30709 Reselecting the default (type-based) visualizer:
30713 -var-set-visualizer V gdb.default_visualizer
30717 Suppose @code{SomeClass} is a visualizer class. A lambda expression
30718 can be used to instantiate this class for a varobj:
30722 -var-set-visualizer V "lambda val: SomeClass()"
30726 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30727 @node GDB/MI Data Manipulation
30728 @section @sc{gdb/mi} Data Manipulation
30730 @cindex data manipulation, in @sc{gdb/mi}
30731 @cindex @sc{gdb/mi}, data manipulation
30732 This section describes the @sc{gdb/mi} commands that manipulate data:
30733 examine memory and registers, evaluate expressions, etc.
30735 For details about what an addressable memory unit is,
30736 @pxref{addressable memory unit}.
30738 @c REMOVED FROM THE INTERFACE.
30739 @c @subheading -data-assign
30740 @c Change the value of a program variable. Plenty of side effects.
30741 @c @subsubheading GDB Command
30743 @c @subsubheading Example
30746 @subheading The @code{-data-disassemble} Command
30747 @findex -data-disassemble
30749 @subsubheading Synopsis
30753 [ -s @var{start-addr} -e @var{end-addr} ]
30754 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
30762 @item @var{start-addr}
30763 is the beginning address (or @code{$pc})
30764 @item @var{end-addr}
30766 @item @var{filename}
30767 is the name of the file to disassemble
30768 @item @var{linenum}
30769 is the line number to disassemble around
30771 is the number of disassembly lines to be produced. If it is -1,
30772 the whole function will be disassembled, in case no @var{end-addr} is
30773 specified. If @var{end-addr} is specified as a non-zero value, and
30774 @var{lines} is lower than the number of disassembly lines between
30775 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
30776 displayed; if @var{lines} is higher than the number of lines between
30777 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
30782 @item 0 disassembly only
30783 @item 1 mixed source and disassembly (deprecated)
30784 @item 2 disassembly with raw opcodes
30785 @item 3 mixed source and disassembly with raw opcodes (deprecated)
30786 @item 4 mixed source and disassembly
30787 @item 5 mixed source and disassembly with raw opcodes
30790 Modes 1 and 3 are deprecated. The output is ``source centric''
30791 which hasn't proved useful in practice.
30792 @xref{Machine Code}, for a discussion of the difference between
30793 @code{/m} and @code{/s} output of the @code{disassemble} command.
30796 @subsubheading Result
30798 The result of the @code{-data-disassemble} command will be a list named
30799 @samp{asm_insns}, the contents of this list depend on the @var{mode}
30800 used with the @code{-data-disassemble} command.
30802 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
30807 The address at which this instruction was disassembled.
30810 The name of the function this instruction is within.
30813 The decimal offset in bytes from the start of @samp{func-name}.
30816 The text disassembly for this @samp{address}.
30819 This field is only present for modes 2, 3 and 5. This contains the raw opcode
30820 bytes for the @samp{inst} field.
30824 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
30825 @samp{src_and_asm_line}, each of which has the following fields:
30829 The line number within @samp{file}.
30832 The file name from the compilation unit. This might be an absolute
30833 file name or a relative file name depending on the compile command
30837 Absolute file name of @samp{file}. It is converted to a canonical form
30838 using the source file search path
30839 (@pxref{Source Path, ,Specifying Source Directories})
30840 and after resolving all the symbolic links.
30842 If the source file is not found this field will contain the path as
30843 present in the debug information.
30845 @item line_asm_insn
30846 This is a list of tuples containing the disassembly for @samp{line} in
30847 @samp{file}. The fields of each tuple are the same as for
30848 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
30849 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
30854 Note that whatever included in the @samp{inst} field, is not
30855 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
30858 @subsubheading @value{GDBN} Command
30860 The corresponding @value{GDBN} command is @samp{disassemble}.
30862 @subsubheading Example
30864 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
30868 -data-disassemble -s $pc -e "$pc + 20" -- 0
30871 @{address="0x000107c0",func-name="main",offset="4",
30872 inst="mov 2, %o0"@},
30873 @{address="0x000107c4",func-name="main",offset="8",
30874 inst="sethi %hi(0x11800), %o2"@},
30875 @{address="0x000107c8",func-name="main",offset="12",
30876 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
30877 @{address="0x000107cc",func-name="main",offset="16",
30878 inst="sethi %hi(0x11800), %o2"@},
30879 @{address="0x000107d0",func-name="main",offset="20",
30880 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
30884 Disassemble the whole @code{main} function. Line 32 is part of
30888 -data-disassemble -f basics.c -l 32 -- 0
30890 @{address="0x000107bc",func-name="main",offset="0",
30891 inst="save %sp, -112, %sp"@},
30892 @{address="0x000107c0",func-name="main",offset="4",
30893 inst="mov 2, %o0"@},
30894 @{address="0x000107c4",func-name="main",offset="8",
30895 inst="sethi %hi(0x11800), %o2"@},
30897 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
30898 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
30902 Disassemble 3 instructions from the start of @code{main}:
30906 -data-disassemble -f basics.c -l 32 -n 3 -- 0
30908 @{address="0x000107bc",func-name="main",offset="0",
30909 inst="save %sp, -112, %sp"@},
30910 @{address="0x000107c0",func-name="main",offset="4",
30911 inst="mov 2, %o0"@},
30912 @{address="0x000107c4",func-name="main",offset="8",
30913 inst="sethi %hi(0x11800), %o2"@}]
30917 Disassemble 3 instructions from the start of @code{main} in mixed mode:
30921 -data-disassemble -f basics.c -l 32 -n 3 -- 1
30923 src_and_asm_line=@{line="31",
30924 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
30925 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
30926 line_asm_insn=[@{address="0x000107bc",
30927 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
30928 src_and_asm_line=@{line="32",
30929 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
30930 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
30931 line_asm_insn=[@{address="0x000107c0",
30932 func-name="main",offset="4",inst="mov 2, %o0"@},
30933 @{address="0x000107c4",func-name="main",offset="8",
30934 inst="sethi %hi(0x11800), %o2"@}]@}]
30939 @subheading The @code{-data-evaluate-expression} Command
30940 @findex -data-evaluate-expression
30942 @subsubheading Synopsis
30945 -data-evaluate-expression @var{expr}
30948 Evaluate @var{expr} as an expression. The expression could contain an
30949 inferior function call. The function call will execute synchronously.
30950 If the expression contains spaces, it must be enclosed in double quotes.
30952 @subsubheading @value{GDBN} Command
30954 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
30955 @samp{call}. In @code{gdbtk} only, there's a corresponding
30956 @samp{gdb_eval} command.
30958 @subsubheading Example
30960 In the following example, the numbers that precede the commands are the
30961 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
30962 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
30966 211-data-evaluate-expression A
30969 311-data-evaluate-expression &A
30970 311^done,value="0xefffeb7c"
30972 411-data-evaluate-expression A+3
30975 511-data-evaluate-expression "A + 3"
30981 @subheading The @code{-data-list-changed-registers} Command
30982 @findex -data-list-changed-registers
30984 @subsubheading Synopsis
30987 -data-list-changed-registers
30990 Display a list of the registers that have changed.
30992 @subsubheading @value{GDBN} Command
30994 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
30995 has the corresponding command @samp{gdb_changed_register_list}.
30997 @subsubheading Example
30999 On a PPC MBX board:
31007 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
31008 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
31011 -data-list-changed-registers
31012 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
31013 "10","11","13","14","15","16","17","18","19","20","21","22","23",
31014 "24","25","26","27","28","30","31","64","65","66","67","69"]
31019 @subheading The @code{-data-list-register-names} Command
31020 @findex -data-list-register-names
31022 @subsubheading Synopsis
31025 -data-list-register-names [ ( @var{regno} )+ ]
31028 Show a list of register names for the current target. If no arguments
31029 are given, it shows a list of the names of all the registers. If
31030 integer numbers are given as arguments, it will print a list of the
31031 names of the registers corresponding to the arguments. To ensure
31032 consistency between a register name and its number, the output list may
31033 include empty register names.
31035 @subsubheading @value{GDBN} Command
31037 @value{GDBN} does not have a command which corresponds to
31038 @samp{-data-list-register-names}. In @code{gdbtk} there is a
31039 corresponding command @samp{gdb_regnames}.
31041 @subsubheading Example
31043 For the PPC MBX board:
31046 -data-list-register-names
31047 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
31048 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
31049 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
31050 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
31051 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
31052 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
31053 "", "pc","ps","cr","lr","ctr","xer"]
31055 -data-list-register-names 1 2 3
31056 ^done,register-names=["r1","r2","r3"]
31060 @subheading The @code{-data-list-register-values} Command
31061 @findex -data-list-register-values
31063 @subsubheading Synopsis
31066 -data-list-register-values
31067 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
31070 Display the registers' contents. The format according to which the
31071 registers' contents are to be returned is given by @var{fmt}, followed
31072 by an optional list of numbers specifying the registers to display. A
31073 missing list of numbers indicates that the contents of all the
31074 registers must be returned. The @code{--skip-unavailable} option
31075 indicates that only the available registers are to be returned.
31077 Allowed formats for @var{fmt} are:
31094 @subsubheading @value{GDBN} Command
31096 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
31097 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
31099 @subsubheading Example
31101 For a PPC MBX board (note: line breaks are for readability only, they
31102 don't appear in the actual output):
31106 -data-list-register-values r 64 65
31107 ^done,register-values=[@{number="64",value="0xfe00a300"@},
31108 @{number="65",value="0x00029002"@}]
31110 -data-list-register-values x
31111 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
31112 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
31113 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
31114 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
31115 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
31116 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
31117 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
31118 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
31119 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
31120 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
31121 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
31122 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
31123 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
31124 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
31125 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
31126 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
31127 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
31128 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
31129 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
31130 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
31131 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
31132 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
31133 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
31134 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
31135 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
31136 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
31137 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
31138 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
31139 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
31140 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
31141 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
31142 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
31143 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
31144 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
31145 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
31146 @{number="69",value="0x20002b03"@}]
31151 @subheading The @code{-data-read-memory} Command
31152 @findex -data-read-memory
31154 This command is deprecated, use @code{-data-read-memory-bytes} instead.
31156 @subsubheading Synopsis
31159 -data-read-memory [ -o @var{byte-offset} ]
31160 @var{address} @var{word-format} @var{word-size}
31161 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
31168 @item @var{address}
31169 An expression specifying the address of the first memory word to be
31170 read. Complex expressions containing embedded white space should be
31171 quoted using the C convention.
31173 @item @var{word-format}
31174 The format to be used to print the memory words. The notation is the
31175 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
31178 @item @var{word-size}
31179 The size of each memory word in bytes.
31181 @item @var{nr-rows}
31182 The number of rows in the output table.
31184 @item @var{nr-cols}
31185 The number of columns in the output table.
31188 If present, indicates that each row should include an @sc{ascii} dump. The
31189 value of @var{aschar} is used as a padding character when a byte is not a
31190 member of the printable @sc{ascii} character set (printable @sc{ascii}
31191 characters are those whose code is between 32 and 126, inclusively).
31193 @item @var{byte-offset}
31194 An offset to add to the @var{address} before fetching memory.
31197 This command displays memory contents as a table of @var{nr-rows} by
31198 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
31199 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
31200 (returned as @samp{total-bytes}). Should less than the requested number
31201 of bytes be returned by the target, the missing words are identified
31202 using @samp{N/A}. The number of bytes read from the target is returned
31203 in @samp{nr-bytes} and the starting address used to read memory in
31206 The address of the next/previous row or page is available in
31207 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
31210 @subsubheading @value{GDBN} Command
31212 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
31213 @samp{gdb_get_mem} memory read command.
31215 @subsubheading Example
31217 Read six bytes of memory starting at @code{bytes+6} but then offset by
31218 @code{-6} bytes. Format as three rows of two columns. One byte per
31219 word. Display each word in hex.
31223 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
31224 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
31225 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
31226 prev-page="0x0000138a",memory=[
31227 @{addr="0x00001390",data=["0x00","0x01"]@},
31228 @{addr="0x00001392",data=["0x02","0x03"]@},
31229 @{addr="0x00001394",data=["0x04","0x05"]@}]
31233 Read two bytes of memory starting at address @code{shorts + 64} and
31234 display as a single word formatted in decimal.
31238 5-data-read-memory shorts+64 d 2 1 1
31239 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
31240 next-row="0x00001512",prev-row="0x0000150e",
31241 next-page="0x00001512",prev-page="0x0000150e",memory=[
31242 @{addr="0x00001510",data=["128"]@}]
31246 Read thirty two bytes of memory starting at @code{bytes+16} and format
31247 as eight rows of four columns. Include a string encoding with @samp{x}
31248 used as the non-printable character.
31252 4-data-read-memory bytes+16 x 1 8 4 x
31253 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
31254 next-row="0x000013c0",prev-row="0x0000139c",
31255 next-page="0x000013c0",prev-page="0x00001380",memory=[
31256 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
31257 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
31258 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
31259 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
31260 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
31261 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
31262 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
31263 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
31267 @subheading The @code{-data-read-memory-bytes} Command
31268 @findex -data-read-memory-bytes
31270 @subsubheading Synopsis
31273 -data-read-memory-bytes [ -o @var{offset} ]
31274 @var{address} @var{count}
31281 @item @var{address}
31282 An expression specifying the address of the first addressable memory unit
31283 to be read. Complex expressions containing embedded white space should be
31284 quoted using the C convention.
31287 The number of addressable memory units to read. This should be an integer
31291 The offset relative to @var{address} at which to start reading. This
31292 should be an integer literal. This option is provided so that a frontend
31293 is not required to first evaluate address and then perform address
31294 arithmetics itself.
31298 This command attempts to read all accessible memory regions in the
31299 specified range. First, all regions marked as unreadable in the memory
31300 map (if one is defined) will be skipped. @xref{Memory Region
31301 Attributes}. Second, @value{GDBN} will attempt to read the remaining
31302 regions. For each one, if reading full region results in an errors,
31303 @value{GDBN} will try to read a subset of the region.
31305 In general, every single memory unit in the region may be readable or not,
31306 and the only way to read every readable unit is to try a read at
31307 every address, which is not practical. Therefore, @value{GDBN} will
31308 attempt to read all accessible memory units at either beginning or the end
31309 of the region, using a binary division scheme. This heuristic works
31310 well for reading accross a memory map boundary. Note that if a region
31311 has a readable range that is neither at the beginning or the end,
31312 @value{GDBN} will not read it.
31314 The result record (@pxref{GDB/MI Result Records}) that is output of
31315 the command includes a field named @samp{memory} whose content is a
31316 list of tuples. Each tuple represent a successfully read memory block
31317 and has the following fields:
31321 The start address of the memory block, as hexadecimal literal.
31324 The end address of the memory block, as hexadecimal literal.
31327 The offset of the memory block, as hexadecimal literal, relative to
31328 the start address passed to @code{-data-read-memory-bytes}.
31331 The contents of the memory block, in hex.
31337 @subsubheading @value{GDBN} Command
31339 The corresponding @value{GDBN} command is @samp{x}.
31341 @subsubheading Example
31345 -data-read-memory-bytes &a 10
31346 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
31348 contents="01000000020000000300"@}]
31353 @subheading The @code{-data-write-memory-bytes} Command
31354 @findex -data-write-memory-bytes
31356 @subsubheading Synopsis
31359 -data-write-memory-bytes @var{address} @var{contents}
31360 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
31367 @item @var{address}
31368 An expression specifying the address of the first addressable memory unit
31369 to be written. Complex expressions containing embedded white space should
31370 be quoted using the C convention.
31372 @item @var{contents}
31373 The hex-encoded data to write. It is an error if @var{contents} does
31374 not represent an integral number of addressable memory units.
31377 Optional argument indicating the number of addressable memory units to be
31378 written. If @var{count} is greater than @var{contents}' length,
31379 @value{GDBN} will repeatedly write @var{contents} until it fills
31380 @var{count} memory units.
31384 @subsubheading @value{GDBN} Command
31386 There's no corresponding @value{GDBN} command.
31388 @subsubheading Example
31392 -data-write-memory-bytes &a "aabbccdd"
31399 -data-write-memory-bytes &a "aabbccdd" 16e
31404 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31405 @node GDB/MI Tracepoint Commands
31406 @section @sc{gdb/mi} Tracepoint Commands
31408 The commands defined in this section implement MI support for
31409 tracepoints. For detailed introduction, see @ref{Tracepoints}.
31411 @subheading The @code{-trace-find} Command
31412 @findex -trace-find
31414 @subsubheading Synopsis
31417 -trace-find @var{mode} [@var{parameters}@dots{}]
31420 Find a trace frame using criteria defined by @var{mode} and
31421 @var{parameters}. The following table lists permissible
31422 modes and their parameters. For details of operation, see @ref{tfind}.
31427 No parameters are required. Stops examining trace frames.
31430 An integer is required as parameter. Selects tracepoint frame with
31433 @item tracepoint-number
31434 An integer is required as parameter. Finds next
31435 trace frame that corresponds to tracepoint with the specified number.
31438 An address is required as parameter. Finds
31439 next trace frame that corresponds to any tracepoint at the specified
31442 @item pc-inside-range
31443 Two addresses are required as parameters. Finds next trace
31444 frame that corresponds to a tracepoint at an address inside the
31445 specified range. Both bounds are considered to be inside the range.
31447 @item pc-outside-range
31448 Two addresses are required as parameters. Finds
31449 next trace frame that corresponds to a tracepoint at an address outside
31450 the specified range. Both bounds are considered to be inside the range.
31453 Line specification is required as parameter. @xref{Specify Location}.
31454 Finds next trace frame that corresponds to a tracepoint at
31455 the specified location.
31459 If @samp{none} was passed as @var{mode}, the response does not
31460 have fields. Otherwise, the response may have the following fields:
31464 This field has either @samp{0} or @samp{1} as the value, depending
31465 on whether a matching tracepoint was found.
31468 The index of the found traceframe. This field is present iff
31469 the @samp{found} field has value of @samp{1}.
31472 The index of the found tracepoint. This field is present iff
31473 the @samp{found} field has value of @samp{1}.
31476 The information about the frame corresponding to the found trace
31477 frame. This field is present only if a trace frame was found.
31478 @xref{GDB/MI Frame Information}, for description of this field.
31482 @subsubheading @value{GDBN} Command
31484 The corresponding @value{GDBN} command is @samp{tfind}.
31486 @subheading -trace-define-variable
31487 @findex -trace-define-variable
31489 @subsubheading Synopsis
31492 -trace-define-variable @var{name} [ @var{value} ]
31495 Create trace variable @var{name} if it does not exist. If
31496 @var{value} is specified, sets the initial value of the specified
31497 trace variable to that value. Note that the @var{name} should start
31498 with the @samp{$} character.
31500 @subsubheading @value{GDBN} Command
31502 The corresponding @value{GDBN} command is @samp{tvariable}.
31504 @subheading The @code{-trace-frame-collected} Command
31505 @findex -trace-frame-collected
31507 @subsubheading Synopsis
31510 -trace-frame-collected
31511 [--var-print-values @var{var_pval}]
31512 [--comp-print-values @var{comp_pval}]
31513 [--registers-format @var{regformat}]
31514 [--memory-contents]
31517 This command returns the set of collected objects, register names,
31518 trace state variable names, memory ranges and computed expressions
31519 that have been collected at a particular trace frame. The optional
31520 parameters to the command affect the output format in different ways.
31521 See the output description table below for more details.
31523 The reported names can be used in the normal manner to create
31524 varobjs and inspect the objects themselves. The items returned by
31525 this command are categorized so that it is clear which is a variable,
31526 which is a register, which is a trace state variable, which is a
31527 memory range and which is a computed expression.
31529 For instance, if the actions were
31531 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
31532 collect *(int*)0xaf02bef0@@40
31536 the object collected in its entirety would be @code{myVar}. The
31537 object @code{myArray} would be partially collected, because only the
31538 element at index @code{myIndex} would be collected. The remaining
31539 objects would be computed expressions.
31541 An example output would be:
31545 -trace-frame-collected
31547 explicit-variables=[@{name="myVar",value="1"@}],
31548 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
31549 @{name="myObj.field",value="0"@},
31550 @{name="myPtr->field",value="1"@},
31551 @{name="myCount + 2",value="3"@},
31552 @{name="$tvar1 + 1",value="43970027"@}],
31553 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
31554 @{number="1",value="0x0"@},
31555 @{number="2",value="0x4"@},
31557 @{number="125",value="0x0"@}],
31558 tvars=[@{name="$tvar1",current="43970026"@}],
31559 memory=[@{address="0x0000000000602264",length="4"@},
31560 @{address="0x0000000000615bc0",length="4"@}]
31567 @item explicit-variables
31568 The set of objects that have been collected in their entirety (as
31569 opposed to collecting just a few elements of an array or a few struct
31570 members). For each object, its name and value are printed.
31571 The @code{--var-print-values} option affects how or whether the value
31572 field is output. If @var{var_pval} is 0, then print only the names;
31573 if it is 1, print also their values; and if it is 2, print the name,
31574 type and value for simple data types, and the name and type for
31575 arrays, structures and unions.
31577 @item computed-expressions
31578 The set of computed expressions that have been collected at the
31579 current trace frame. The @code{--comp-print-values} option affects
31580 this set like the @code{--var-print-values} option affects the
31581 @code{explicit-variables} set. See above.
31584 The registers that have been collected at the current trace frame.
31585 For each register collected, the name and current value are returned.
31586 The value is formatted according to the @code{--registers-format}
31587 option. See the @command{-data-list-register-values} command for a
31588 list of the allowed formats. The default is @samp{x}.
31591 The trace state variables that have been collected at the current
31592 trace frame. For each trace state variable collected, the name and
31593 current value are returned.
31596 The set of memory ranges that have been collected at the current trace
31597 frame. Its content is a list of tuples. Each tuple represents a
31598 collected memory range and has the following fields:
31602 The start address of the memory range, as hexadecimal literal.
31605 The length of the memory range, as decimal literal.
31608 The contents of the memory block, in hex. This field is only present
31609 if the @code{--memory-contents} option is specified.
31615 @subsubheading @value{GDBN} Command
31617 There is no corresponding @value{GDBN} command.
31619 @subsubheading Example
31621 @subheading -trace-list-variables
31622 @findex -trace-list-variables
31624 @subsubheading Synopsis
31627 -trace-list-variables
31630 Return a table of all defined trace variables. Each element of the
31631 table has the following fields:
31635 The name of the trace variable. This field is always present.
31638 The initial value. This is a 64-bit signed integer. This
31639 field is always present.
31642 The value the trace variable has at the moment. This is a 64-bit
31643 signed integer. This field is absent iff current value is
31644 not defined, for example if the trace was never run, or is
31649 @subsubheading @value{GDBN} Command
31651 The corresponding @value{GDBN} command is @samp{tvariables}.
31653 @subsubheading Example
31657 -trace-list-variables
31658 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
31659 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
31660 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
31661 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
31662 body=[variable=@{name="$trace_timestamp",initial="0"@}
31663 variable=@{name="$foo",initial="10",current="15"@}]@}
31667 @subheading -trace-save
31668 @findex -trace-save
31670 @subsubheading Synopsis
31673 -trace-save [ -r ] [ -ctf ] @var{filename}
31676 Saves the collected trace data to @var{filename}. Without the
31677 @samp{-r} option, the data is downloaded from the target and saved
31678 in a local file. With the @samp{-r} option the target is asked
31679 to perform the save.
31681 By default, this command will save the trace in the tfile format. You can
31682 supply the optional @samp{-ctf} argument to save it the CTF format. See
31683 @ref{Trace Files} for more information about CTF.
31685 @subsubheading @value{GDBN} Command
31687 The corresponding @value{GDBN} command is @samp{tsave}.
31690 @subheading -trace-start
31691 @findex -trace-start
31693 @subsubheading Synopsis
31699 Starts a tracing experiment. The result of this command does not
31702 @subsubheading @value{GDBN} Command
31704 The corresponding @value{GDBN} command is @samp{tstart}.
31706 @subheading -trace-status
31707 @findex -trace-status
31709 @subsubheading Synopsis
31715 Obtains the status of a tracing experiment. The result may include
31716 the following fields:
31721 May have a value of either @samp{0}, when no tracing operations are
31722 supported, @samp{1}, when all tracing operations are supported, or
31723 @samp{file} when examining trace file. In the latter case, examining
31724 of trace frame is possible but new tracing experiement cannot be
31725 started. This field is always present.
31728 May have a value of either @samp{0} or @samp{1} depending on whether
31729 tracing experiement is in progress on target. This field is present
31730 if @samp{supported} field is not @samp{0}.
31733 Report the reason why the tracing was stopped last time. This field
31734 may be absent iff tracing was never stopped on target yet. The
31735 value of @samp{request} means the tracing was stopped as result of
31736 the @code{-trace-stop} command. The value of @samp{overflow} means
31737 the tracing buffer is full. The value of @samp{disconnection} means
31738 tracing was automatically stopped when @value{GDBN} has disconnected.
31739 The value of @samp{passcount} means tracing was stopped when a
31740 tracepoint was passed a maximal number of times for that tracepoint.
31741 This field is present if @samp{supported} field is not @samp{0}.
31743 @item stopping-tracepoint
31744 The number of tracepoint whose passcount as exceeded. This field is
31745 present iff the @samp{stop-reason} field has the value of
31749 @itemx frames-created
31750 The @samp{frames} field is a count of the total number of trace frames
31751 in the trace buffer, while @samp{frames-created} is the total created
31752 during the run, including ones that were discarded, such as when a
31753 circular trace buffer filled up. Both fields are optional.
31757 These fields tell the current size of the tracing buffer and the
31758 remaining space. These fields are optional.
31761 The value of the circular trace buffer flag. @code{1} means that the
31762 trace buffer is circular and old trace frames will be discarded if
31763 necessary to make room, @code{0} means that the trace buffer is linear
31767 The value of the disconnected tracing flag. @code{1} means that
31768 tracing will continue after @value{GDBN} disconnects, @code{0} means
31769 that the trace run will stop.
31772 The filename of the trace file being examined. This field is
31773 optional, and only present when examining a trace file.
31777 @subsubheading @value{GDBN} Command
31779 The corresponding @value{GDBN} command is @samp{tstatus}.
31781 @subheading -trace-stop
31782 @findex -trace-stop
31784 @subsubheading Synopsis
31790 Stops a tracing experiment. The result of this command has the same
31791 fields as @code{-trace-status}, except that the @samp{supported} and
31792 @samp{running} fields are not output.
31794 @subsubheading @value{GDBN} Command
31796 The corresponding @value{GDBN} command is @samp{tstop}.
31799 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31800 @node GDB/MI Symbol Query
31801 @section @sc{gdb/mi} Symbol Query Commands
31805 @subheading The @code{-symbol-info-address} Command
31806 @findex -symbol-info-address
31808 @subsubheading Synopsis
31811 -symbol-info-address @var{symbol}
31814 Describe where @var{symbol} is stored.
31816 @subsubheading @value{GDBN} Command
31818 The corresponding @value{GDBN} command is @samp{info address}.
31820 @subsubheading Example
31824 @subheading The @code{-symbol-info-file} Command
31825 @findex -symbol-info-file
31827 @subsubheading Synopsis
31833 Show the file for the symbol.
31835 @subsubheading @value{GDBN} Command
31837 There's no equivalent @value{GDBN} command. @code{gdbtk} has
31838 @samp{gdb_find_file}.
31840 @subsubheading Example
31844 @subheading The @code{-symbol-info-function} Command
31845 @findex -symbol-info-function
31847 @subsubheading Synopsis
31850 -symbol-info-function
31853 Show which function the symbol lives in.
31855 @subsubheading @value{GDBN} Command
31857 @samp{gdb_get_function} in @code{gdbtk}.
31859 @subsubheading Example
31863 @subheading The @code{-symbol-info-line} Command
31864 @findex -symbol-info-line
31866 @subsubheading Synopsis
31872 Show the core addresses of the code for a source line.
31874 @subsubheading @value{GDBN} Command
31876 The corresponding @value{GDBN} command is @samp{info line}.
31877 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
31879 @subsubheading Example
31883 @subheading The @code{-symbol-info-symbol} Command
31884 @findex -symbol-info-symbol
31886 @subsubheading Synopsis
31889 -symbol-info-symbol @var{addr}
31892 Describe what symbol is at location @var{addr}.
31894 @subsubheading @value{GDBN} Command
31896 The corresponding @value{GDBN} command is @samp{info symbol}.
31898 @subsubheading Example
31902 @subheading The @code{-symbol-list-functions} Command
31903 @findex -symbol-list-functions
31905 @subsubheading Synopsis
31908 -symbol-list-functions
31911 List the functions in the executable.
31913 @subsubheading @value{GDBN} Command
31915 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
31916 @samp{gdb_search} in @code{gdbtk}.
31918 @subsubheading Example
31923 @subheading The @code{-symbol-list-lines} Command
31924 @findex -symbol-list-lines
31926 @subsubheading Synopsis
31929 -symbol-list-lines @var{filename}
31932 Print the list of lines that contain code and their associated program
31933 addresses for the given source filename. The entries are sorted in
31934 ascending PC order.
31936 @subsubheading @value{GDBN} Command
31938 There is no corresponding @value{GDBN} command.
31940 @subsubheading Example
31943 -symbol-list-lines basics.c
31944 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
31950 @subheading The @code{-symbol-list-types} Command
31951 @findex -symbol-list-types
31953 @subsubheading Synopsis
31959 List all the type names.
31961 @subsubheading @value{GDBN} Command
31963 The corresponding commands are @samp{info types} in @value{GDBN},
31964 @samp{gdb_search} in @code{gdbtk}.
31966 @subsubheading Example
31970 @subheading The @code{-symbol-list-variables} Command
31971 @findex -symbol-list-variables
31973 @subsubheading Synopsis
31976 -symbol-list-variables
31979 List all the global and static variable names.
31981 @subsubheading @value{GDBN} Command
31983 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
31985 @subsubheading Example
31989 @subheading The @code{-symbol-locate} Command
31990 @findex -symbol-locate
31992 @subsubheading Synopsis
31998 @subsubheading @value{GDBN} Command
32000 @samp{gdb_loc} in @code{gdbtk}.
32002 @subsubheading Example
32006 @subheading The @code{-symbol-type} Command
32007 @findex -symbol-type
32009 @subsubheading Synopsis
32012 -symbol-type @var{variable}
32015 Show type of @var{variable}.
32017 @subsubheading @value{GDBN} Command
32019 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
32020 @samp{gdb_obj_variable}.
32022 @subsubheading Example
32027 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32028 @node GDB/MI File Commands
32029 @section @sc{gdb/mi} File Commands
32031 This section describes the GDB/MI commands to specify executable file names
32032 and to read in and obtain symbol table information.
32034 @subheading The @code{-file-exec-and-symbols} Command
32035 @findex -file-exec-and-symbols
32037 @subsubheading Synopsis
32040 -file-exec-and-symbols @var{file}
32043 Specify the executable file to be debugged. This file is the one from
32044 which the symbol table is also read. If no file is specified, the
32045 command clears the executable and symbol information. If breakpoints
32046 are set when using this command with no arguments, @value{GDBN} will produce
32047 error messages. Otherwise, no output is produced, except a completion
32050 @subsubheading @value{GDBN} Command
32052 The corresponding @value{GDBN} command is @samp{file}.
32054 @subsubheading Example
32058 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32064 @subheading The @code{-file-exec-file} Command
32065 @findex -file-exec-file
32067 @subsubheading Synopsis
32070 -file-exec-file @var{file}
32073 Specify the executable file to be debugged. Unlike
32074 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
32075 from this file. If used without argument, @value{GDBN} clears the information
32076 about the executable file. No output is produced, except a completion
32079 @subsubheading @value{GDBN} Command
32081 The corresponding @value{GDBN} command is @samp{exec-file}.
32083 @subsubheading Example
32087 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32094 @subheading The @code{-file-list-exec-sections} Command
32095 @findex -file-list-exec-sections
32097 @subsubheading Synopsis
32100 -file-list-exec-sections
32103 List the sections of the current executable file.
32105 @subsubheading @value{GDBN} Command
32107 The @value{GDBN} command @samp{info file} shows, among the rest, the same
32108 information as this command. @code{gdbtk} has a corresponding command
32109 @samp{gdb_load_info}.
32111 @subsubheading Example
32116 @subheading The @code{-file-list-exec-source-file} Command
32117 @findex -file-list-exec-source-file
32119 @subsubheading Synopsis
32122 -file-list-exec-source-file
32125 List the line number, the current source file, and the absolute path
32126 to the current source file for the current executable. The macro
32127 information field has a value of @samp{1} or @samp{0} depending on
32128 whether or not the file includes preprocessor macro information.
32130 @subsubheading @value{GDBN} Command
32132 The @value{GDBN} equivalent is @samp{info source}
32134 @subsubheading Example
32138 123-file-list-exec-source-file
32139 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
32144 @subheading The @code{-file-list-exec-source-files} Command
32145 @findex -file-list-exec-source-files
32147 @subsubheading Synopsis
32150 -file-list-exec-source-files
32153 List the source files for the current executable.
32155 It will always output both the filename and fullname (absolute file
32156 name) of a source file.
32158 @subsubheading @value{GDBN} Command
32160 The @value{GDBN} equivalent is @samp{info sources}.
32161 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
32163 @subsubheading Example
32166 -file-list-exec-source-files
32168 @{file=foo.c,fullname=/home/foo.c@},
32169 @{file=/home/bar.c,fullname=/home/bar.c@},
32170 @{file=gdb_could_not_find_fullpath.c@}]
32174 @subheading The @code{-file-list-shared-libraries} Command
32175 @findex -file-list-shared-libraries
32177 @subsubheading Synopsis
32180 -file-list-shared-libraries [ @var{regexp} ]
32183 List the shared libraries in the program.
32184 With a regular expression @var{regexp}, only those libraries whose
32185 names match @var{regexp} are listed.
32187 @subsubheading @value{GDBN} Command
32189 The corresponding @value{GDBN} command is @samp{info shared}. The fields
32190 have a similar meaning to the @code{=library-loaded} notification.
32191 The @code{ranges} field specifies the multiple segments belonging to this
32192 library. Each range has the following fields:
32196 The address defining the inclusive lower bound of the segment.
32198 The address defining the exclusive upper bound of the segment.
32201 @subsubheading Example
32204 -file-list-exec-source-files
32205 ^done,shared-libraries=[
32206 @{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"@}]@},
32207 @{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"@}]@}]
32213 @subheading The @code{-file-list-symbol-files} Command
32214 @findex -file-list-symbol-files
32216 @subsubheading Synopsis
32219 -file-list-symbol-files
32224 @subsubheading @value{GDBN} Command
32226 The corresponding @value{GDBN} command is @samp{info file} (part of it).
32228 @subsubheading Example
32233 @subheading The @code{-file-symbol-file} Command
32234 @findex -file-symbol-file
32236 @subsubheading Synopsis
32239 -file-symbol-file @var{file}
32242 Read symbol table info from the specified @var{file} argument. When
32243 used without arguments, clears @value{GDBN}'s symbol table info. No output is
32244 produced, except for a completion notification.
32246 @subsubheading @value{GDBN} Command
32248 The corresponding @value{GDBN} command is @samp{symbol-file}.
32250 @subsubheading Example
32254 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32260 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32261 @node GDB/MI Memory Overlay Commands
32262 @section @sc{gdb/mi} Memory Overlay Commands
32264 The memory overlay commands are not implemented.
32266 @c @subheading -overlay-auto
32268 @c @subheading -overlay-list-mapping-state
32270 @c @subheading -overlay-list-overlays
32272 @c @subheading -overlay-map
32274 @c @subheading -overlay-off
32276 @c @subheading -overlay-on
32278 @c @subheading -overlay-unmap
32280 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32281 @node GDB/MI Signal Handling Commands
32282 @section @sc{gdb/mi} Signal Handling Commands
32284 Signal handling commands are not implemented.
32286 @c @subheading -signal-handle
32288 @c @subheading -signal-list-handle-actions
32290 @c @subheading -signal-list-signal-types
32294 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32295 @node GDB/MI Target Manipulation
32296 @section @sc{gdb/mi} Target Manipulation Commands
32299 @subheading The @code{-target-attach} Command
32300 @findex -target-attach
32302 @subsubheading Synopsis
32305 -target-attach @var{pid} | @var{gid} | @var{file}
32308 Attach to a process @var{pid} or a file @var{file} outside of
32309 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
32310 group, the id previously returned by
32311 @samp{-list-thread-groups --available} must be used.
32313 @subsubheading @value{GDBN} Command
32315 The corresponding @value{GDBN} command is @samp{attach}.
32317 @subsubheading Example
32321 =thread-created,id="1"
32322 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
32328 @subheading The @code{-target-compare-sections} Command
32329 @findex -target-compare-sections
32331 @subsubheading Synopsis
32334 -target-compare-sections [ @var{section} ]
32337 Compare data of section @var{section} on target to the exec file.
32338 Without the argument, all sections are compared.
32340 @subsubheading @value{GDBN} Command
32342 The @value{GDBN} equivalent is @samp{compare-sections}.
32344 @subsubheading Example
32349 @subheading The @code{-target-detach} Command
32350 @findex -target-detach
32352 @subsubheading Synopsis
32355 -target-detach [ @var{pid} | @var{gid} ]
32358 Detach from the remote target which normally resumes its execution.
32359 If either @var{pid} or @var{gid} is specified, detaches from either
32360 the specified process, or specified thread group. There's no output.
32362 @subsubheading @value{GDBN} Command
32364 The corresponding @value{GDBN} command is @samp{detach}.
32366 @subsubheading Example
32376 @subheading The @code{-target-disconnect} Command
32377 @findex -target-disconnect
32379 @subsubheading Synopsis
32385 Disconnect from the remote target. There's no output and the target is
32386 generally not resumed.
32388 @subsubheading @value{GDBN} Command
32390 The corresponding @value{GDBN} command is @samp{disconnect}.
32392 @subsubheading Example
32402 @subheading The @code{-target-download} Command
32403 @findex -target-download
32405 @subsubheading Synopsis
32411 Loads the executable onto the remote target.
32412 It prints out an update message every half second, which includes the fields:
32416 The name of the section.
32418 The size of what has been sent so far for that section.
32420 The size of the section.
32422 The total size of what was sent so far (the current and the previous sections).
32424 The size of the overall executable to download.
32428 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
32429 @sc{gdb/mi} Output Syntax}).
32431 In addition, it prints the name and size of the sections, as they are
32432 downloaded. These messages include the following fields:
32436 The name of the section.
32438 The size of the section.
32440 The size of the overall executable to download.
32444 At the end, a summary is printed.
32446 @subsubheading @value{GDBN} Command
32448 The corresponding @value{GDBN} command is @samp{load}.
32450 @subsubheading Example
32452 Note: each status message appears on a single line. Here the messages
32453 have been broken down so that they can fit onto a page.
32458 +download,@{section=".text",section-size="6668",total-size="9880"@}
32459 +download,@{section=".text",section-sent="512",section-size="6668",
32460 total-sent="512",total-size="9880"@}
32461 +download,@{section=".text",section-sent="1024",section-size="6668",
32462 total-sent="1024",total-size="9880"@}
32463 +download,@{section=".text",section-sent="1536",section-size="6668",
32464 total-sent="1536",total-size="9880"@}
32465 +download,@{section=".text",section-sent="2048",section-size="6668",
32466 total-sent="2048",total-size="9880"@}
32467 +download,@{section=".text",section-sent="2560",section-size="6668",
32468 total-sent="2560",total-size="9880"@}
32469 +download,@{section=".text",section-sent="3072",section-size="6668",
32470 total-sent="3072",total-size="9880"@}
32471 +download,@{section=".text",section-sent="3584",section-size="6668",
32472 total-sent="3584",total-size="9880"@}
32473 +download,@{section=".text",section-sent="4096",section-size="6668",
32474 total-sent="4096",total-size="9880"@}
32475 +download,@{section=".text",section-sent="4608",section-size="6668",
32476 total-sent="4608",total-size="9880"@}
32477 +download,@{section=".text",section-sent="5120",section-size="6668",
32478 total-sent="5120",total-size="9880"@}
32479 +download,@{section=".text",section-sent="5632",section-size="6668",
32480 total-sent="5632",total-size="9880"@}
32481 +download,@{section=".text",section-sent="6144",section-size="6668",
32482 total-sent="6144",total-size="9880"@}
32483 +download,@{section=".text",section-sent="6656",section-size="6668",
32484 total-sent="6656",total-size="9880"@}
32485 +download,@{section=".init",section-size="28",total-size="9880"@}
32486 +download,@{section=".fini",section-size="28",total-size="9880"@}
32487 +download,@{section=".data",section-size="3156",total-size="9880"@}
32488 +download,@{section=".data",section-sent="512",section-size="3156",
32489 total-sent="7236",total-size="9880"@}
32490 +download,@{section=".data",section-sent="1024",section-size="3156",
32491 total-sent="7748",total-size="9880"@}
32492 +download,@{section=".data",section-sent="1536",section-size="3156",
32493 total-sent="8260",total-size="9880"@}
32494 +download,@{section=".data",section-sent="2048",section-size="3156",
32495 total-sent="8772",total-size="9880"@}
32496 +download,@{section=".data",section-sent="2560",section-size="3156",
32497 total-sent="9284",total-size="9880"@}
32498 +download,@{section=".data",section-sent="3072",section-size="3156",
32499 total-sent="9796",total-size="9880"@}
32500 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
32507 @subheading The @code{-target-exec-status} Command
32508 @findex -target-exec-status
32510 @subsubheading Synopsis
32513 -target-exec-status
32516 Provide information on the state of the target (whether it is running or
32517 not, for instance).
32519 @subsubheading @value{GDBN} Command
32521 There's no equivalent @value{GDBN} command.
32523 @subsubheading Example
32527 @subheading The @code{-target-list-available-targets} Command
32528 @findex -target-list-available-targets
32530 @subsubheading Synopsis
32533 -target-list-available-targets
32536 List the possible targets to connect to.
32538 @subsubheading @value{GDBN} Command
32540 The corresponding @value{GDBN} command is @samp{help target}.
32542 @subsubheading Example
32546 @subheading The @code{-target-list-current-targets} Command
32547 @findex -target-list-current-targets
32549 @subsubheading Synopsis
32552 -target-list-current-targets
32555 Describe the current target.
32557 @subsubheading @value{GDBN} Command
32559 The corresponding information is printed by @samp{info file} (among
32562 @subsubheading Example
32566 @subheading The @code{-target-list-parameters} Command
32567 @findex -target-list-parameters
32569 @subsubheading Synopsis
32572 -target-list-parameters
32578 @subsubheading @value{GDBN} Command
32582 @subsubheading Example
32585 @subheading The @code{-target-flash-erase} Command
32586 @findex -target-flash-erase
32588 @subsubheading Synopsis
32591 -target-flash-erase
32594 Erases all known flash memory regions on the target.
32596 The corresponding @value{GDBN} command is @samp{flash-erase}.
32598 The output is a list of flash regions that have been erased, with starting
32599 addresses and memory region sizes.
32603 -target-flash-erase
32604 ^done,erased-regions=@{address="0x0",size="0x40000"@}
32608 @subheading The @code{-target-select} Command
32609 @findex -target-select
32611 @subsubheading Synopsis
32614 -target-select @var{type} @var{parameters @dots{}}
32617 Connect @value{GDBN} to the remote target. This command takes two args:
32621 The type of target, for instance @samp{remote}, etc.
32622 @item @var{parameters}
32623 Device names, host names and the like. @xref{Target Commands, ,
32624 Commands for Managing Targets}, for more details.
32627 The output is a connection notification, followed by the address at
32628 which the target program is, in the following form:
32631 ^connected,addr="@var{address}",func="@var{function name}",
32632 args=[@var{arg list}]
32635 @subsubheading @value{GDBN} Command
32637 The corresponding @value{GDBN} command is @samp{target}.
32639 @subsubheading Example
32643 -target-select remote /dev/ttya
32644 ^connected,addr="0xfe00a300",func="??",args=[]
32648 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32649 @node GDB/MI File Transfer Commands
32650 @section @sc{gdb/mi} File Transfer Commands
32653 @subheading The @code{-target-file-put} Command
32654 @findex -target-file-put
32656 @subsubheading Synopsis
32659 -target-file-put @var{hostfile} @var{targetfile}
32662 Copy file @var{hostfile} from the host system (the machine running
32663 @value{GDBN}) to @var{targetfile} on the target system.
32665 @subsubheading @value{GDBN} Command
32667 The corresponding @value{GDBN} command is @samp{remote put}.
32669 @subsubheading Example
32673 -target-file-put localfile remotefile
32679 @subheading The @code{-target-file-get} Command
32680 @findex -target-file-get
32682 @subsubheading Synopsis
32685 -target-file-get @var{targetfile} @var{hostfile}
32688 Copy file @var{targetfile} from the target system to @var{hostfile}
32689 on the host system.
32691 @subsubheading @value{GDBN} Command
32693 The corresponding @value{GDBN} command is @samp{remote get}.
32695 @subsubheading Example
32699 -target-file-get remotefile localfile
32705 @subheading The @code{-target-file-delete} Command
32706 @findex -target-file-delete
32708 @subsubheading Synopsis
32711 -target-file-delete @var{targetfile}
32714 Delete @var{targetfile} from the target system.
32716 @subsubheading @value{GDBN} Command
32718 The corresponding @value{GDBN} command is @samp{remote delete}.
32720 @subsubheading Example
32724 -target-file-delete remotefile
32730 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32731 @node GDB/MI Ada Exceptions Commands
32732 @section Ada Exceptions @sc{gdb/mi} Commands
32734 @subheading The @code{-info-ada-exceptions} Command
32735 @findex -info-ada-exceptions
32737 @subsubheading Synopsis
32740 -info-ada-exceptions [ @var{regexp}]
32743 List all Ada exceptions defined within the program being debugged.
32744 With a regular expression @var{regexp}, only those exceptions whose
32745 names match @var{regexp} are listed.
32747 @subsubheading @value{GDBN} Command
32749 The corresponding @value{GDBN} command is @samp{info exceptions}.
32751 @subsubheading Result
32753 The result is a table of Ada exceptions. The following columns are
32754 defined for each exception:
32758 The name of the exception.
32761 The address of the exception.
32765 @subsubheading Example
32768 -info-ada-exceptions aint
32769 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
32770 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
32771 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
32772 body=[@{name="constraint_error",address="0x0000000000613da0"@},
32773 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
32776 @subheading Catching Ada Exceptions
32778 The commands describing how to ask @value{GDBN} to stop when a program
32779 raises an exception are described at @ref{Ada Exception GDB/MI
32780 Catchpoint Commands}.
32783 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32784 @node GDB/MI Support Commands
32785 @section @sc{gdb/mi} Support Commands
32787 Since new commands and features get regularly added to @sc{gdb/mi},
32788 some commands are available to help front-ends query the debugger
32789 about support for these capabilities. Similarly, it is also possible
32790 to query @value{GDBN} about target support of certain features.
32792 @subheading The @code{-info-gdb-mi-command} Command
32793 @cindex @code{-info-gdb-mi-command}
32794 @findex -info-gdb-mi-command
32796 @subsubheading Synopsis
32799 -info-gdb-mi-command @var{cmd_name}
32802 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
32804 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
32805 is technically not part of the command name (@pxref{GDB/MI Input
32806 Syntax}), and thus should be omitted in @var{cmd_name}. However,
32807 for ease of use, this command also accepts the form with the leading
32810 @subsubheading @value{GDBN} Command
32812 There is no corresponding @value{GDBN} command.
32814 @subsubheading Result
32816 The result is a tuple. There is currently only one field:
32820 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
32821 @code{"false"} otherwise.
32825 @subsubheading Example
32827 Here is an example where the @sc{gdb/mi} command does not exist:
32830 -info-gdb-mi-command unsupported-command
32831 ^done,command=@{exists="false"@}
32835 And here is an example where the @sc{gdb/mi} command is known
32839 -info-gdb-mi-command symbol-list-lines
32840 ^done,command=@{exists="true"@}
32843 @subheading The @code{-list-features} Command
32844 @findex -list-features
32845 @cindex supported @sc{gdb/mi} features, list
32847 Returns a list of particular features of the MI protocol that
32848 this version of gdb implements. A feature can be a command,
32849 or a new field in an output of some command, or even an
32850 important bugfix. While a frontend can sometimes detect presence
32851 of a feature at runtime, it is easier to perform detection at debugger
32854 The command returns a list of strings, with each string naming an
32855 available feature. Each returned string is just a name, it does not
32856 have any internal structure. The list of possible feature names
32862 (gdb) -list-features
32863 ^done,result=["feature1","feature2"]
32866 The current list of features is:
32869 @item frozen-varobjs
32870 Indicates support for the @code{-var-set-frozen} command, as well
32871 as possible presense of the @code{frozen} field in the output
32872 of @code{-varobj-create}.
32873 @item pending-breakpoints
32874 Indicates support for the @option{-f} option to the @code{-break-insert}
32877 Indicates Python scripting support, Python-based
32878 pretty-printing commands, and possible presence of the
32879 @samp{display_hint} field in the output of @code{-var-list-children}
32881 Indicates support for the @code{-thread-info} command.
32882 @item data-read-memory-bytes
32883 Indicates support for the @code{-data-read-memory-bytes} and the
32884 @code{-data-write-memory-bytes} commands.
32885 @item breakpoint-notifications
32886 Indicates that changes to breakpoints and breakpoints created via the
32887 CLI will be announced via async records.
32888 @item ada-task-info
32889 Indicates support for the @code{-ada-task-info} command.
32890 @item language-option
32891 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
32892 option (@pxref{Context management}).
32893 @item info-gdb-mi-command
32894 Indicates support for the @code{-info-gdb-mi-command} command.
32895 @item undefined-command-error-code
32896 Indicates support for the "undefined-command" error code in error result
32897 records, produced when trying to execute an undefined @sc{gdb/mi} command
32898 (@pxref{GDB/MI Result Records}).
32899 @item exec-run-start-option
32900 Indicates that the @code{-exec-run} command supports the @option{--start}
32901 option (@pxref{GDB/MI Program Execution}).
32904 @subheading The @code{-list-target-features} Command
32905 @findex -list-target-features
32907 Returns a list of particular features that are supported by the
32908 target. Those features affect the permitted MI commands, but
32909 unlike the features reported by the @code{-list-features} command, the
32910 features depend on which target GDB is using at the moment. Whenever
32911 a target can change, due to commands such as @code{-target-select},
32912 @code{-target-attach} or @code{-exec-run}, the list of target features
32913 may change, and the frontend should obtain it again.
32917 (gdb) -list-target-features
32918 ^done,result=["async"]
32921 The current list of features is:
32925 Indicates that the target is capable of asynchronous command
32926 execution, which means that @value{GDBN} will accept further commands
32927 while the target is running.
32930 Indicates that the target is capable of reverse execution.
32931 @xref{Reverse Execution}, for more information.
32935 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32936 @node GDB/MI Miscellaneous Commands
32937 @section Miscellaneous @sc{gdb/mi} Commands
32939 @c @subheading -gdb-complete
32941 @subheading The @code{-gdb-exit} Command
32944 @subsubheading Synopsis
32950 Exit @value{GDBN} immediately.
32952 @subsubheading @value{GDBN} Command
32954 Approximately corresponds to @samp{quit}.
32956 @subsubheading Example
32966 @subheading The @code{-exec-abort} Command
32967 @findex -exec-abort
32969 @subsubheading Synopsis
32975 Kill the inferior running program.
32977 @subsubheading @value{GDBN} Command
32979 The corresponding @value{GDBN} command is @samp{kill}.
32981 @subsubheading Example
32986 @subheading The @code{-gdb-set} Command
32989 @subsubheading Synopsis
32995 Set an internal @value{GDBN} variable.
32996 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
32998 @subsubheading @value{GDBN} Command
33000 The corresponding @value{GDBN} command is @samp{set}.
33002 @subsubheading Example
33012 @subheading The @code{-gdb-show} Command
33015 @subsubheading Synopsis
33021 Show the current value of a @value{GDBN} variable.
33023 @subsubheading @value{GDBN} Command
33025 The corresponding @value{GDBN} command is @samp{show}.
33027 @subsubheading Example
33036 @c @subheading -gdb-source
33039 @subheading The @code{-gdb-version} Command
33040 @findex -gdb-version
33042 @subsubheading Synopsis
33048 Show version information for @value{GDBN}. Used mostly in testing.
33050 @subsubheading @value{GDBN} Command
33052 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
33053 default shows this information when you start an interactive session.
33055 @subsubheading Example
33057 @c This example modifies the actual output from GDB to avoid overfull
33063 ~Copyright 2000 Free Software Foundation, Inc.
33064 ~GDB is free software, covered by the GNU General Public License, and
33065 ~you are welcome to change it and/or distribute copies of it under
33066 ~ certain conditions.
33067 ~Type "show copying" to see the conditions.
33068 ~There is absolutely no warranty for GDB. Type "show warranty" for
33070 ~This GDB was configured as
33071 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
33076 @subheading The @code{-list-thread-groups} Command
33077 @findex -list-thread-groups
33079 @subheading Synopsis
33082 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
33085 Lists thread groups (@pxref{Thread groups}). When a single thread
33086 group is passed as the argument, lists the children of that group.
33087 When several thread group are passed, lists information about those
33088 thread groups. Without any parameters, lists information about all
33089 top-level thread groups.
33091 Normally, thread groups that are being debugged are reported.
33092 With the @samp{--available} option, @value{GDBN} reports thread groups
33093 available on the target.
33095 The output of this command may have either a @samp{threads} result or
33096 a @samp{groups} result. The @samp{thread} result has a list of tuples
33097 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
33098 Information}). The @samp{groups} result has a list of tuples as value,
33099 each tuple describing a thread group. If top-level groups are
33100 requested (that is, no parameter is passed), or when several groups
33101 are passed, the output always has a @samp{groups} result. The format
33102 of the @samp{group} result is described below.
33104 To reduce the number of roundtrips it's possible to list thread groups
33105 together with their children, by passing the @samp{--recurse} option
33106 and the recursion depth. Presently, only recursion depth of 1 is
33107 permitted. If this option is present, then every reported thread group
33108 will also include its children, either as @samp{group} or
33109 @samp{threads} field.
33111 In general, any combination of option and parameters is permitted, with
33112 the following caveats:
33116 When a single thread group is passed, the output will typically
33117 be the @samp{threads} result. Because threads may not contain
33118 anything, the @samp{recurse} option will be ignored.
33121 When the @samp{--available} option is passed, limited information may
33122 be available. In particular, the list of threads of a process might
33123 be inaccessible. Further, specifying specific thread groups might
33124 not give any performance advantage over listing all thread groups.
33125 The frontend should assume that @samp{-list-thread-groups --available}
33126 is always an expensive operation and cache the results.
33130 The @samp{groups} result is a list of tuples, where each tuple may
33131 have the following fields:
33135 Identifier of the thread group. This field is always present.
33136 The identifier is an opaque string; frontends should not try to
33137 convert it to an integer, even though it might look like one.
33140 The type of the thread group. At present, only @samp{process} is a
33144 The target-specific process identifier. This field is only present
33145 for thread groups of type @samp{process} and only if the process exists.
33148 The exit code of this group's last exited thread, formatted in octal.
33149 This field is only present for thread groups of type @samp{process} and
33150 only if the process is not running.
33153 The number of children this thread group has. This field may be
33154 absent for an available thread group.
33157 This field has a list of tuples as value, each tuple describing a
33158 thread. It may be present if the @samp{--recurse} option is
33159 specified, and it's actually possible to obtain the threads.
33162 This field is a list of integers, each identifying a core that one
33163 thread of the group is running on. This field may be absent if
33164 such information is not available.
33167 The name of the executable file that corresponds to this thread group.
33168 The field is only present for thread groups of type @samp{process},
33169 and only if there is a corresponding executable file.
33173 @subheading Example
33177 -list-thread-groups
33178 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
33179 -list-thread-groups 17
33180 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
33181 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
33182 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
33183 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
33184 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
33185 -list-thread-groups --available
33186 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
33187 -list-thread-groups --available --recurse 1
33188 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33189 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33190 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
33191 -list-thread-groups --available --recurse 1 17 18
33192 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33193 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33194 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
33197 @subheading The @code{-info-os} Command
33200 @subsubheading Synopsis
33203 -info-os [ @var{type} ]
33206 If no argument is supplied, the command returns a table of available
33207 operating-system-specific information types. If one of these types is
33208 supplied as an argument @var{type}, then the command returns a table
33209 of data of that type.
33211 The types of information available depend on the target operating
33214 @subsubheading @value{GDBN} Command
33216 The corresponding @value{GDBN} command is @samp{info os}.
33218 @subsubheading Example
33220 When run on a @sc{gnu}/Linux system, the output will look something
33226 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
33227 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
33228 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
33229 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
33230 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
33232 item=@{col0="files",col1="Listing of all file descriptors",
33233 col2="File descriptors"@},
33234 item=@{col0="modules",col1="Listing of all loaded kernel modules",
33235 col2="Kernel modules"@},
33236 item=@{col0="msg",col1="Listing of all message queues",
33237 col2="Message queues"@},
33238 item=@{col0="processes",col1="Listing of all processes",
33239 col2="Processes"@},
33240 item=@{col0="procgroups",col1="Listing of all process groups",
33241 col2="Process groups"@},
33242 item=@{col0="semaphores",col1="Listing of all semaphores",
33243 col2="Semaphores"@},
33244 item=@{col0="shm",col1="Listing of all shared-memory regions",
33245 col2="Shared-memory regions"@},
33246 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
33248 item=@{col0="threads",col1="Listing of all threads",
33252 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
33253 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
33254 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
33255 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
33256 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
33257 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
33258 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
33259 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
33261 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
33262 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
33266 (Note that the MI output here includes a @code{"Title"} column that
33267 does not appear in command-line @code{info os}; this column is useful
33268 for MI clients that want to enumerate the types of data, such as in a
33269 popup menu, but is needless clutter on the command line, and
33270 @code{info os} omits it.)
33272 @subheading The @code{-add-inferior} Command
33273 @findex -add-inferior
33275 @subheading Synopsis
33281 Creates a new inferior (@pxref{Inferiors and Programs}). The created
33282 inferior is not associated with any executable. Such association may
33283 be established with the @samp{-file-exec-and-symbols} command
33284 (@pxref{GDB/MI File Commands}). The command response has a single
33285 field, @samp{inferior}, whose value is the identifier of the
33286 thread group corresponding to the new inferior.
33288 @subheading Example
33293 ^done,inferior="i3"
33296 @subheading The @code{-interpreter-exec} Command
33297 @findex -interpreter-exec
33299 @subheading Synopsis
33302 -interpreter-exec @var{interpreter} @var{command}
33304 @anchor{-interpreter-exec}
33306 Execute the specified @var{command} in the given @var{interpreter}.
33308 @subheading @value{GDBN} Command
33310 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
33312 @subheading Example
33316 -interpreter-exec console "break main"
33317 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
33318 &"During symbol reading, bad structure-type format.\n"
33319 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
33324 @subheading The @code{-inferior-tty-set} Command
33325 @findex -inferior-tty-set
33327 @subheading Synopsis
33330 -inferior-tty-set /dev/pts/1
33333 Set terminal for future runs of the program being debugged.
33335 @subheading @value{GDBN} Command
33337 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
33339 @subheading Example
33343 -inferior-tty-set /dev/pts/1
33348 @subheading The @code{-inferior-tty-show} Command
33349 @findex -inferior-tty-show
33351 @subheading Synopsis
33357 Show terminal for future runs of program being debugged.
33359 @subheading @value{GDBN} Command
33361 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
33363 @subheading Example
33367 -inferior-tty-set /dev/pts/1
33371 ^done,inferior_tty_terminal="/dev/pts/1"
33375 @subheading The @code{-enable-timings} Command
33376 @findex -enable-timings
33378 @subheading Synopsis
33381 -enable-timings [yes | no]
33384 Toggle the printing of the wallclock, user and system times for an MI
33385 command as a field in its output. This command is to help frontend
33386 developers optimize the performance of their code. No argument is
33387 equivalent to @samp{yes}.
33389 @subheading @value{GDBN} Command
33393 @subheading Example
33401 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
33402 addr="0x080484ed",func="main",file="myprog.c",
33403 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
33405 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
33413 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
33414 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
33415 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
33416 fullname="/home/nickrob/myprog.c",line="73"@}
33421 @chapter @value{GDBN} Annotations
33423 This chapter describes annotations in @value{GDBN}. Annotations were
33424 designed to interface @value{GDBN} to graphical user interfaces or other
33425 similar programs which want to interact with @value{GDBN} at a
33426 relatively high level.
33428 The annotation mechanism has largely been superseded by @sc{gdb/mi}
33432 This is Edition @value{EDITION}, @value{DATE}.
33436 * Annotations Overview:: What annotations are; the general syntax.
33437 * Server Prefix:: Issuing a command without affecting user state.
33438 * Prompting:: Annotations marking @value{GDBN}'s need for input.
33439 * Errors:: Annotations for error messages.
33440 * Invalidation:: Some annotations describe things now invalid.
33441 * Annotations for Running::
33442 Whether the program is running, how it stopped, etc.
33443 * Source Annotations:: Annotations describing source code.
33446 @node Annotations Overview
33447 @section What is an Annotation?
33448 @cindex annotations
33450 Annotations start with a newline character, two @samp{control-z}
33451 characters, and the name of the annotation. If there is no additional
33452 information associated with this annotation, the name of the annotation
33453 is followed immediately by a newline. If there is additional
33454 information, the name of the annotation is followed by a space, the
33455 additional information, and a newline. The additional information
33456 cannot contain newline characters.
33458 Any output not beginning with a newline and two @samp{control-z}
33459 characters denotes literal output from @value{GDBN}. Currently there is
33460 no need for @value{GDBN} to output a newline followed by two
33461 @samp{control-z} characters, but if there was such a need, the
33462 annotations could be extended with an @samp{escape} annotation which
33463 means those three characters as output.
33465 The annotation @var{level}, which is specified using the
33466 @option{--annotate} command line option (@pxref{Mode Options}), controls
33467 how much information @value{GDBN} prints together with its prompt,
33468 values of expressions, source lines, and other types of output. Level 0
33469 is for no annotations, level 1 is for use when @value{GDBN} is run as a
33470 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
33471 for programs that control @value{GDBN}, and level 2 annotations have
33472 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
33473 Interface, annotate, GDB's Obsolete Annotations}).
33476 @kindex set annotate
33477 @item set annotate @var{level}
33478 The @value{GDBN} command @code{set annotate} sets the level of
33479 annotations to the specified @var{level}.
33481 @item show annotate
33482 @kindex show annotate
33483 Show the current annotation level.
33486 This chapter describes level 3 annotations.
33488 A simple example of starting up @value{GDBN} with annotations is:
33491 $ @kbd{gdb --annotate=3}
33493 Copyright 2003 Free Software Foundation, Inc.
33494 GDB is free software, covered by the GNU General Public License,
33495 and you are welcome to change it and/or distribute copies of it
33496 under certain conditions.
33497 Type "show copying" to see the conditions.
33498 There is absolutely no warranty for GDB. Type "show warranty"
33500 This GDB was configured as "i386-pc-linux-gnu"
33511 Here @samp{quit} is input to @value{GDBN}; the rest is output from
33512 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
33513 denotes a @samp{control-z} character) are annotations; the rest is
33514 output from @value{GDBN}.
33516 @node Server Prefix
33517 @section The Server Prefix
33518 @cindex server prefix
33520 If you prefix a command with @samp{server } then it will not affect
33521 the command history, nor will it affect @value{GDBN}'s notion of which
33522 command to repeat if @key{RET} is pressed on a line by itself. This
33523 means that commands can be run behind a user's back by a front-end in
33524 a transparent manner.
33526 The @code{server } prefix does not affect the recording of values into
33527 the value history; to print a value without recording it into the
33528 value history, use the @code{output} command instead of the
33529 @code{print} command.
33531 Using this prefix also disables confirmation requests
33532 (@pxref{confirmation requests}).
33535 @section Annotation for @value{GDBN} Input
33537 @cindex annotations for prompts
33538 When @value{GDBN} prompts for input, it annotates this fact so it is possible
33539 to know when to send output, when the output from a given command is
33542 Different kinds of input each have a different @dfn{input type}. Each
33543 input type has three annotations: a @code{pre-} annotation, which
33544 denotes the beginning of any prompt which is being output, a plain
33545 annotation, which denotes the end of the prompt, and then a @code{post-}
33546 annotation which denotes the end of any echo which may (or may not) be
33547 associated with the input. For example, the @code{prompt} input type
33548 features the following annotations:
33556 The input types are
33559 @findex pre-prompt annotation
33560 @findex prompt annotation
33561 @findex post-prompt annotation
33563 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
33565 @findex pre-commands annotation
33566 @findex commands annotation
33567 @findex post-commands annotation
33569 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
33570 command. The annotations are repeated for each command which is input.
33572 @findex pre-overload-choice annotation
33573 @findex overload-choice annotation
33574 @findex post-overload-choice annotation
33575 @item overload-choice
33576 When @value{GDBN} wants the user to select between various overloaded functions.
33578 @findex pre-query annotation
33579 @findex query annotation
33580 @findex post-query annotation
33582 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
33584 @findex pre-prompt-for-continue annotation
33585 @findex prompt-for-continue annotation
33586 @findex post-prompt-for-continue annotation
33587 @item prompt-for-continue
33588 When @value{GDBN} is asking the user to press return to continue. Note: Don't
33589 expect this to work well; instead use @code{set height 0} to disable
33590 prompting. This is because the counting of lines is buggy in the
33591 presence of annotations.
33596 @cindex annotations for errors, warnings and interrupts
33598 @findex quit annotation
33603 This annotation occurs right before @value{GDBN} responds to an interrupt.
33605 @findex error annotation
33610 This annotation occurs right before @value{GDBN} responds to an error.
33612 Quit and error annotations indicate that any annotations which @value{GDBN} was
33613 in the middle of may end abruptly. For example, if a
33614 @code{value-history-begin} annotation is followed by a @code{error}, one
33615 cannot expect to receive the matching @code{value-history-end}. One
33616 cannot expect not to receive it either, however; an error annotation
33617 does not necessarily mean that @value{GDBN} is immediately returning all the way
33620 @findex error-begin annotation
33621 A quit or error annotation may be preceded by
33627 Any output between that and the quit or error annotation is the error
33630 Warning messages are not yet annotated.
33631 @c If we want to change that, need to fix warning(), type_error(),
33632 @c range_error(), and possibly other places.
33635 @section Invalidation Notices
33637 @cindex annotations for invalidation messages
33638 The following annotations say that certain pieces of state may have
33642 @findex frames-invalid annotation
33643 @item ^Z^Zframes-invalid
33645 The frames (for example, output from the @code{backtrace} command) may
33648 @findex breakpoints-invalid annotation
33649 @item ^Z^Zbreakpoints-invalid
33651 The breakpoints may have changed. For example, the user just added or
33652 deleted a breakpoint.
33655 @node Annotations for Running
33656 @section Running the Program
33657 @cindex annotations for running programs
33659 @findex starting annotation
33660 @findex stopping annotation
33661 When the program starts executing due to a @value{GDBN} command such as
33662 @code{step} or @code{continue},
33668 is output. When the program stops,
33674 is output. Before the @code{stopped} annotation, a variety of
33675 annotations describe how the program stopped.
33678 @findex exited annotation
33679 @item ^Z^Zexited @var{exit-status}
33680 The program exited, and @var{exit-status} is the exit status (zero for
33681 successful exit, otherwise nonzero).
33683 @findex signalled annotation
33684 @findex signal-name annotation
33685 @findex signal-name-end annotation
33686 @findex signal-string annotation
33687 @findex signal-string-end annotation
33688 @item ^Z^Zsignalled
33689 The program exited with a signal. After the @code{^Z^Zsignalled}, the
33690 annotation continues:
33696 ^Z^Zsignal-name-end
33700 ^Z^Zsignal-string-end
33705 where @var{name} is the name of the signal, such as @code{SIGILL} or
33706 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
33707 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
33708 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
33709 user's benefit and have no particular format.
33711 @findex signal annotation
33713 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
33714 just saying that the program received the signal, not that it was
33715 terminated with it.
33717 @findex breakpoint annotation
33718 @item ^Z^Zbreakpoint @var{number}
33719 The program hit breakpoint number @var{number}.
33721 @findex watchpoint annotation
33722 @item ^Z^Zwatchpoint @var{number}
33723 The program hit watchpoint number @var{number}.
33726 @node Source Annotations
33727 @section Displaying Source
33728 @cindex annotations for source display
33730 @findex source annotation
33731 The following annotation is used instead of displaying source code:
33734 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
33737 where @var{filename} is an absolute file name indicating which source
33738 file, @var{line} is the line number within that file (where 1 is the
33739 first line in the file), @var{character} is the character position
33740 within the file (where 0 is the first character in the file) (for most
33741 debug formats this will necessarily point to the beginning of a line),
33742 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
33743 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
33744 @var{addr} is the address in the target program associated with the
33745 source which is being displayed. The @var{addr} is in the form @samp{0x}
33746 followed by one or more lowercase hex digits (note that this does not
33747 depend on the language).
33749 @node JIT Interface
33750 @chapter JIT Compilation Interface
33751 @cindex just-in-time compilation
33752 @cindex JIT compilation interface
33754 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
33755 interface. A JIT compiler is a program or library that generates native
33756 executable code at runtime and executes it, usually in order to achieve good
33757 performance while maintaining platform independence.
33759 Programs that use JIT compilation are normally difficult to debug because
33760 portions of their code are generated at runtime, instead of being loaded from
33761 object files, which is where @value{GDBN} normally finds the program's symbols
33762 and debug information. In order to debug programs that use JIT compilation,
33763 @value{GDBN} has an interface that allows the program to register in-memory
33764 symbol files with @value{GDBN} at runtime.
33766 If you are using @value{GDBN} to debug a program that uses this interface, then
33767 it should work transparently so long as you have not stripped the binary. If
33768 you are developing a JIT compiler, then the interface is documented in the rest
33769 of this chapter. At this time, the only known client of this interface is the
33772 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
33773 JIT compiler communicates with @value{GDBN} by writing data into a global
33774 variable and calling a fuction at a well-known symbol. When @value{GDBN}
33775 attaches, it reads a linked list of symbol files from the global variable to
33776 find existing code, and puts a breakpoint in the function so that it can find
33777 out about additional code.
33780 * Declarations:: Relevant C struct declarations
33781 * Registering Code:: Steps to register code
33782 * Unregistering Code:: Steps to unregister code
33783 * Custom Debug Info:: Emit debug information in a custom format
33787 @section JIT Declarations
33789 These are the relevant struct declarations that a C program should include to
33790 implement the interface:
33800 struct jit_code_entry
33802 struct jit_code_entry *next_entry;
33803 struct jit_code_entry *prev_entry;
33804 const char *symfile_addr;
33805 uint64_t symfile_size;
33808 struct jit_descriptor
33811 /* This type should be jit_actions_t, but we use uint32_t
33812 to be explicit about the bitwidth. */
33813 uint32_t action_flag;
33814 struct jit_code_entry *relevant_entry;
33815 struct jit_code_entry *first_entry;
33818 /* GDB puts a breakpoint in this function. */
33819 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
33821 /* Make sure to specify the version statically, because the
33822 debugger may check the version before we can set it. */
33823 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
33826 If the JIT is multi-threaded, then it is important that the JIT synchronize any
33827 modifications to this global data properly, which can easily be done by putting
33828 a global mutex around modifications to these structures.
33830 @node Registering Code
33831 @section Registering Code
33833 To register code with @value{GDBN}, the JIT should follow this protocol:
33837 Generate an object file in memory with symbols and other desired debug
33838 information. The file must include the virtual addresses of the sections.
33841 Create a code entry for the file, which gives the start and size of the symbol
33845 Add it to the linked list in the JIT descriptor.
33848 Point the relevant_entry field of the descriptor at the entry.
33851 Set @code{action_flag} to @code{JIT_REGISTER} and call
33852 @code{__jit_debug_register_code}.
33855 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
33856 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
33857 new code. However, the linked list must still be maintained in order to allow
33858 @value{GDBN} to attach to a running process and still find the symbol files.
33860 @node Unregistering Code
33861 @section Unregistering Code
33863 If code is freed, then the JIT should use the following protocol:
33867 Remove the code entry corresponding to the code from the linked list.
33870 Point the @code{relevant_entry} field of the descriptor at the code entry.
33873 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
33874 @code{__jit_debug_register_code}.
33877 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
33878 and the JIT will leak the memory used for the associated symbol files.
33880 @node Custom Debug Info
33881 @section Custom Debug Info
33882 @cindex custom JIT debug info
33883 @cindex JIT debug info reader
33885 Generating debug information in platform-native file formats (like ELF
33886 or COFF) may be an overkill for JIT compilers; especially if all the
33887 debug info is used for is displaying a meaningful backtrace. The
33888 issue can be resolved by having the JIT writers decide on a debug info
33889 format and also provide a reader that parses the debug info generated
33890 by the JIT compiler. This section gives a brief overview on writing
33891 such a parser. More specific details can be found in the source file
33892 @file{gdb/jit-reader.in}, which is also installed as a header at
33893 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
33895 The reader is implemented as a shared object (so this functionality is
33896 not available on platforms which don't allow loading shared objects at
33897 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
33898 @code{jit-reader-unload} are provided, to be used to load and unload
33899 the readers from a preconfigured directory. Once loaded, the shared
33900 object is used the parse the debug information emitted by the JIT
33904 * Using JIT Debug Info Readers:: How to use supplied readers correctly
33905 * Writing JIT Debug Info Readers:: Creating a debug-info reader
33908 @node Using JIT Debug Info Readers
33909 @subsection Using JIT Debug Info Readers
33910 @kindex jit-reader-load
33911 @kindex jit-reader-unload
33913 Readers can be loaded and unloaded using the @code{jit-reader-load}
33914 and @code{jit-reader-unload} commands.
33917 @item jit-reader-load @var{reader}
33918 Load the JIT reader named @var{reader}, which is a shared
33919 object specified as either an absolute or a relative file name. In
33920 the latter case, @value{GDBN} will try to load the reader from a
33921 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
33922 system (here @var{libdir} is the system library directory, often
33923 @file{/usr/local/lib}).
33925 Only one reader can be active at a time; trying to load a second
33926 reader when one is already loaded will result in @value{GDBN}
33927 reporting an error. A new JIT reader can be loaded by first unloading
33928 the current one using @code{jit-reader-unload} and then invoking
33929 @code{jit-reader-load}.
33931 @item jit-reader-unload
33932 Unload the currently loaded JIT reader.
33936 @node Writing JIT Debug Info Readers
33937 @subsection Writing JIT Debug Info Readers
33938 @cindex writing JIT debug info readers
33940 As mentioned, a reader is essentially a shared object conforming to a
33941 certain ABI. This ABI is described in @file{jit-reader.h}.
33943 @file{jit-reader.h} defines the structures, macros and functions
33944 required to write a reader. It is installed (along with
33945 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
33946 the system include directory.
33948 Readers need to be released under a GPL compatible license. A reader
33949 can be declared as released under such a license by placing the macro
33950 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
33952 The entry point for readers is the symbol @code{gdb_init_reader},
33953 which is expected to be a function with the prototype
33955 @findex gdb_init_reader
33957 extern struct gdb_reader_funcs *gdb_init_reader (void);
33960 @cindex @code{struct gdb_reader_funcs}
33962 @code{struct gdb_reader_funcs} contains a set of pointers to callback
33963 functions. These functions are executed to read the debug info
33964 generated by the JIT compiler (@code{read}), to unwind stack frames
33965 (@code{unwind}) and to create canonical frame IDs
33966 (@code{get_Frame_id}). It also has a callback that is called when the
33967 reader is being unloaded (@code{destroy}). The struct looks like this
33970 struct gdb_reader_funcs
33972 /* Must be set to GDB_READER_INTERFACE_VERSION. */
33973 int reader_version;
33975 /* For use by the reader. */
33978 gdb_read_debug_info *read;
33979 gdb_unwind_frame *unwind;
33980 gdb_get_frame_id *get_frame_id;
33981 gdb_destroy_reader *destroy;
33985 @cindex @code{struct gdb_symbol_callbacks}
33986 @cindex @code{struct gdb_unwind_callbacks}
33988 The callbacks are provided with another set of callbacks by
33989 @value{GDBN} to do their job. For @code{read}, these callbacks are
33990 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
33991 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
33992 @code{struct gdb_symbol_callbacks} has callbacks to create new object
33993 files and new symbol tables inside those object files. @code{struct
33994 gdb_unwind_callbacks} has callbacks to read registers off the current
33995 frame and to write out the values of the registers in the previous
33996 frame. Both have a callback (@code{target_read}) to read bytes off the
33997 target's address space.
33999 @node In-Process Agent
34000 @chapter In-Process Agent
34001 @cindex debugging agent
34002 The traditional debugging model is conceptually low-speed, but works fine,
34003 because most bugs can be reproduced in debugging-mode execution. However,
34004 as multi-core or many-core processors are becoming mainstream, and
34005 multi-threaded programs become more and more popular, there should be more
34006 and more bugs that only manifest themselves at normal-mode execution, for
34007 example, thread races, because debugger's interference with the program's
34008 timing may conceal the bugs. On the other hand, in some applications,
34009 it is not feasible for the debugger to interrupt the program's execution
34010 long enough for the developer to learn anything helpful about its behavior.
34011 If the program's correctness depends on its real-time behavior, delays
34012 introduced by a debugger might cause the program to fail, even when the
34013 code itself is correct. It is useful to be able to observe the program's
34014 behavior without interrupting it.
34016 Therefore, traditional debugging model is too intrusive to reproduce
34017 some bugs. In order to reduce the interference with the program, we can
34018 reduce the number of operations performed by debugger. The
34019 @dfn{In-Process Agent}, a shared library, is running within the same
34020 process with inferior, and is able to perform some debugging operations
34021 itself. As a result, debugger is only involved when necessary, and
34022 performance of debugging can be improved accordingly. Note that
34023 interference with program can be reduced but can't be removed completely,
34024 because the in-process agent will still stop or slow down the program.
34026 The in-process agent can interpret and execute Agent Expressions
34027 (@pxref{Agent Expressions}) during performing debugging operations. The
34028 agent expressions can be used for different purposes, such as collecting
34029 data in tracepoints, and condition evaluation in breakpoints.
34031 @anchor{Control Agent}
34032 You can control whether the in-process agent is used as an aid for
34033 debugging with the following commands:
34036 @kindex set agent on
34038 Causes the in-process agent to perform some operations on behalf of the
34039 debugger. Just which operations requested by the user will be done
34040 by the in-process agent depends on the its capabilities. For example,
34041 if you request to evaluate breakpoint conditions in the in-process agent,
34042 and the in-process agent has such capability as well, then breakpoint
34043 conditions will be evaluated in the in-process agent.
34045 @kindex set agent off
34046 @item set agent off
34047 Disables execution of debugging operations by the in-process agent. All
34048 of the operations will be performed by @value{GDBN}.
34052 Display the current setting of execution of debugging operations by
34053 the in-process agent.
34057 * In-Process Agent Protocol::
34060 @node In-Process Agent Protocol
34061 @section In-Process Agent Protocol
34062 @cindex in-process agent protocol
34064 The in-process agent is able to communicate with both @value{GDBN} and
34065 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
34066 used for communications between @value{GDBN} or GDBserver and the IPA.
34067 In general, @value{GDBN} or GDBserver sends commands
34068 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
34069 in-process agent replies back with the return result of the command, or
34070 some other information. The data sent to in-process agent is composed
34071 of primitive data types, such as 4-byte or 8-byte type, and composite
34072 types, which are called objects (@pxref{IPA Protocol Objects}).
34075 * IPA Protocol Objects::
34076 * IPA Protocol Commands::
34079 @node IPA Protocol Objects
34080 @subsection IPA Protocol Objects
34081 @cindex ipa protocol objects
34083 The commands sent to and results received from agent may contain some
34084 complex data types called @dfn{objects}.
34086 The in-process agent is running on the same machine with @value{GDBN}
34087 or GDBserver, so it doesn't have to handle as much differences between
34088 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
34089 However, there are still some differences of two ends in two processes:
34093 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
34094 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
34096 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
34097 GDBserver is compiled with one, and in-process agent is compiled with
34101 Here are the IPA Protocol Objects:
34105 agent expression object. It represents an agent expression
34106 (@pxref{Agent Expressions}).
34107 @anchor{agent expression object}
34109 tracepoint action object. It represents a tracepoint action
34110 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
34111 memory, static trace data and to evaluate expression.
34112 @anchor{tracepoint action object}
34114 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
34115 @anchor{tracepoint object}
34119 The following table describes important attributes of each IPA protocol
34122 @multitable @columnfractions .30 .20 .50
34123 @headitem Name @tab Size @tab Description
34124 @item @emph{agent expression object} @tab @tab
34125 @item length @tab 4 @tab length of bytes code
34126 @item byte code @tab @var{length} @tab contents of byte code
34127 @item @emph{tracepoint action for collecting memory} @tab @tab
34128 @item 'M' @tab 1 @tab type of tracepoint action
34129 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
34130 address of the lowest byte to collect, otherwise @var{addr} is the offset
34131 of @var{basereg} for memory collecting.
34132 @item len @tab 8 @tab length of memory for collecting
34133 @item basereg @tab 4 @tab the register number containing the starting
34134 memory address for collecting.
34135 @item @emph{tracepoint action for collecting registers} @tab @tab
34136 @item 'R' @tab 1 @tab type of tracepoint action
34137 @item @emph{tracepoint action for collecting static trace data} @tab @tab
34138 @item 'L' @tab 1 @tab type of tracepoint action
34139 @item @emph{tracepoint action for expression evaluation} @tab @tab
34140 @item 'X' @tab 1 @tab type of tracepoint action
34141 @item agent expression @tab length of @tab @ref{agent expression object}
34142 @item @emph{tracepoint object} @tab @tab
34143 @item number @tab 4 @tab number of tracepoint
34144 @item address @tab 8 @tab address of tracepoint inserted on
34145 @item type @tab 4 @tab type of tracepoint
34146 @item enabled @tab 1 @tab enable or disable of tracepoint
34147 @item step_count @tab 8 @tab step
34148 @item pass_count @tab 8 @tab pass
34149 @item numactions @tab 4 @tab number of tracepoint actions
34150 @item hit count @tab 8 @tab hit count
34151 @item trace frame usage @tab 8 @tab trace frame usage
34152 @item compiled_cond @tab 8 @tab compiled condition
34153 @item orig_size @tab 8 @tab orig size
34154 @item condition @tab 4 if condition is NULL otherwise length of
34155 @ref{agent expression object}
34156 @tab zero if condition is NULL, otherwise is
34157 @ref{agent expression object}
34158 @item actions @tab variable
34159 @tab numactions number of @ref{tracepoint action object}
34162 @node IPA Protocol Commands
34163 @subsection IPA Protocol Commands
34164 @cindex ipa protocol commands
34166 The spaces in each command are delimiters to ease reading this commands
34167 specification. They don't exist in real commands.
34171 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
34172 Installs a new fast tracepoint described by @var{tracepoint_object}
34173 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
34174 head of @dfn{jumppad}, which is used to jump to data collection routine
34179 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
34180 @var{target_address} is address of tracepoint in the inferior.
34181 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
34182 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
34183 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
34184 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
34191 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
34192 is about to kill inferiors.
34200 @item probe_marker_at:@var{address}
34201 Asks in-process agent to probe the marker at @var{address}.
34208 @item unprobe_marker_at:@var{address}
34209 Asks in-process agent to unprobe the marker at @var{address}.
34213 @chapter Reporting Bugs in @value{GDBN}
34214 @cindex bugs in @value{GDBN}
34215 @cindex reporting bugs in @value{GDBN}
34217 Your bug reports play an essential role in making @value{GDBN} reliable.
34219 Reporting a bug may help you by bringing a solution to your problem, or it
34220 may not. But in any case the principal function of a bug report is to help
34221 the entire community by making the next version of @value{GDBN} work better. Bug
34222 reports are your contribution to the maintenance of @value{GDBN}.
34224 In order for a bug report to serve its purpose, you must include the
34225 information that enables us to fix the bug.
34228 * Bug Criteria:: Have you found a bug?
34229 * Bug Reporting:: How to report bugs
34233 @section Have You Found a Bug?
34234 @cindex bug criteria
34236 If you are not sure whether you have found a bug, here are some guidelines:
34239 @cindex fatal signal
34240 @cindex debugger crash
34241 @cindex crash of debugger
34243 If the debugger gets a fatal signal, for any input whatever, that is a
34244 @value{GDBN} bug. Reliable debuggers never crash.
34246 @cindex error on valid input
34248 If @value{GDBN} produces an error message for valid input, that is a
34249 bug. (Note that if you're cross debugging, the problem may also be
34250 somewhere in the connection to the target.)
34252 @cindex invalid input
34254 If @value{GDBN} does not produce an error message for invalid input,
34255 that is a bug. However, you should note that your idea of
34256 ``invalid input'' might be our idea of ``an extension'' or ``support
34257 for traditional practice''.
34260 If you are an experienced user of debugging tools, your suggestions
34261 for improvement of @value{GDBN} are welcome in any case.
34264 @node Bug Reporting
34265 @section How to Report Bugs
34266 @cindex bug reports
34267 @cindex @value{GDBN} bugs, reporting
34269 A number of companies and individuals offer support for @sc{gnu} products.
34270 If you obtained @value{GDBN} from a support organization, we recommend you
34271 contact that organization first.
34273 You can find contact information for many support companies and
34274 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
34276 @c should add a web page ref...
34279 @ifset BUGURL_DEFAULT
34280 In any event, we also recommend that you submit bug reports for
34281 @value{GDBN}. The preferred method is to submit them directly using
34282 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
34283 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
34286 @strong{Do not send bug reports to @samp{info-gdb}, or to
34287 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
34288 not want to receive bug reports. Those that do have arranged to receive
34291 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
34292 serves as a repeater. The mailing list and the newsgroup carry exactly
34293 the same messages. Often people think of posting bug reports to the
34294 newsgroup instead of mailing them. This appears to work, but it has one
34295 problem which can be crucial: a newsgroup posting often lacks a mail
34296 path back to the sender. Thus, if we need to ask for more information,
34297 we may be unable to reach you. For this reason, it is better to send
34298 bug reports to the mailing list.
34300 @ifclear BUGURL_DEFAULT
34301 In any event, we also recommend that you submit bug reports for
34302 @value{GDBN} to @value{BUGURL}.
34306 The fundamental principle of reporting bugs usefully is this:
34307 @strong{report all the facts}. If you are not sure whether to state a
34308 fact or leave it out, state it!
34310 Often people omit facts because they think they know what causes the
34311 problem and assume that some details do not matter. Thus, you might
34312 assume that the name of the variable you use in an example does not matter.
34313 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
34314 stray memory reference which happens to fetch from the location where that
34315 name is stored in memory; perhaps, if the name were different, the contents
34316 of that location would fool the debugger into doing the right thing despite
34317 the bug. Play it safe and give a specific, complete example. That is the
34318 easiest thing for you to do, and the most helpful.
34320 Keep in mind that the purpose of a bug report is to enable us to fix the
34321 bug. It may be that the bug has been reported previously, but neither
34322 you nor we can know that unless your bug report is complete and
34325 Sometimes people give a few sketchy facts and ask, ``Does this ring a
34326 bell?'' Those bug reports are useless, and we urge everyone to
34327 @emph{refuse to respond to them} except to chide the sender to report
34330 To enable us to fix the bug, you should include all these things:
34334 The version of @value{GDBN}. @value{GDBN} announces it if you start
34335 with no arguments; you can also print it at any time using @code{show
34338 Without this, we will not know whether there is any point in looking for
34339 the bug in the current version of @value{GDBN}.
34342 The type of machine you are using, and the operating system name and
34346 The details of the @value{GDBN} build-time configuration.
34347 @value{GDBN} shows these details if you invoke it with the
34348 @option{--configuration} command-line option, or if you type
34349 @code{show configuration} at @value{GDBN}'s prompt.
34352 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
34353 ``@value{GCC}--2.8.1''.
34356 What compiler (and its version) was used to compile the program you are
34357 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
34358 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
34359 to get this information; for other compilers, see the documentation for
34363 The command arguments you gave the compiler to compile your example and
34364 observe the bug. For example, did you use @samp{-O}? To guarantee
34365 you will not omit something important, list them all. A copy of the
34366 Makefile (or the output from make) is sufficient.
34368 If we were to try to guess the arguments, we would probably guess wrong
34369 and then we might not encounter the bug.
34372 A complete input script, and all necessary source files, that will
34376 A description of what behavior you observe that you believe is
34377 incorrect. For example, ``It gets a fatal signal.''
34379 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
34380 will certainly notice it. But if the bug is incorrect output, we might
34381 not notice unless it is glaringly wrong. You might as well not give us
34382 a chance to make a mistake.
34384 Even if the problem you experience is a fatal signal, you should still
34385 say so explicitly. Suppose something strange is going on, such as, your
34386 copy of @value{GDBN} is out of synch, or you have encountered a bug in
34387 the C library on your system. (This has happened!) Your copy might
34388 crash and ours would not. If you told us to expect a crash, then when
34389 ours fails to crash, we would know that the bug was not happening for
34390 us. If you had not told us to expect a crash, then we would not be able
34391 to draw any conclusion from our observations.
34394 @cindex recording a session script
34395 To collect all this information, you can use a session recording program
34396 such as @command{script}, which is available on many Unix systems.
34397 Just run your @value{GDBN} session inside @command{script} and then
34398 include the @file{typescript} file with your bug report.
34400 Another way to record a @value{GDBN} session is to run @value{GDBN}
34401 inside Emacs and then save the entire buffer to a file.
34404 If you wish to suggest changes to the @value{GDBN} source, send us context
34405 diffs. If you even discuss something in the @value{GDBN} source, refer to
34406 it by context, not by line number.
34408 The line numbers in our development sources will not match those in your
34409 sources. Your line numbers would convey no useful information to us.
34413 Here are some things that are not necessary:
34417 A description of the envelope of the bug.
34419 Often people who encounter a bug spend a lot of time investigating
34420 which changes to the input file will make the bug go away and which
34421 changes will not affect it.
34423 This is often time consuming and not very useful, because the way we
34424 will find the bug is by running a single example under the debugger
34425 with breakpoints, not by pure deduction from a series of examples.
34426 We recommend that you save your time for something else.
34428 Of course, if you can find a simpler example to report @emph{instead}
34429 of the original one, that is a convenience for us. Errors in the
34430 output will be easier to spot, running under the debugger will take
34431 less time, and so on.
34433 However, simplification is not vital; if you do not want to do this,
34434 report the bug anyway and send us the entire test case you used.
34437 A patch for the bug.
34439 A patch for the bug does help us if it is a good one. But do not omit
34440 the necessary information, such as the test case, on the assumption that
34441 a patch is all we need. We might see problems with your patch and decide
34442 to fix the problem another way, or we might not understand it at all.
34444 Sometimes with a program as complicated as @value{GDBN} it is very hard to
34445 construct an example that will make the program follow a certain path
34446 through the code. If you do not send us the example, we will not be able
34447 to construct one, so we will not be able to verify that the bug is fixed.
34449 And if we cannot understand what bug you are trying to fix, or why your
34450 patch should be an improvement, we will not install it. A test case will
34451 help us to understand.
34454 A guess about what the bug is or what it depends on.
34456 Such guesses are usually wrong. Even we cannot guess right about such
34457 things without first using the debugger to find the facts.
34460 @c The readline documentation is distributed with the readline code
34461 @c and consists of the two following files:
34464 @c Use -I with makeinfo to point to the appropriate directory,
34465 @c environment var TEXINPUTS with TeX.
34466 @ifclear SYSTEM_READLINE
34467 @include rluser.texi
34468 @include hsuser.texi
34472 @appendix In Memoriam
34474 The @value{GDBN} project mourns the loss of the following long-time
34479 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
34480 to Free Software in general. Outside of @value{GDBN}, he was known in
34481 the Amiga world for his series of Fish Disks, and the GeekGadget project.
34483 @item Michael Snyder
34484 Michael was one of the Global Maintainers of the @value{GDBN} project,
34485 with contributions recorded as early as 1996, until 2011. In addition
34486 to his day to day participation, he was a large driving force behind
34487 adding Reverse Debugging to @value{GDBN}.
34490 Beyond their technical contributions to the project, they were also
34491 enjoyable members of the Free Software Community. We will miss them.
34493 @node Formatting Documentation
34494 @appendix Formatting Documentation
34496 @cindex @value{GDBN} reference card
34497 @cindex reference card
34498 The @value{GDBN} 4 release includes an already-formatted reference card, ready
34499 for printing with PostScript or Ghostscript, in the @file{gdb}
34500 subdirectory of the main source directory@footnote{In
34501 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
34502 release.}. If you can use PostScript or Ghostscript with your printer,
34503 you can print the reference card immediately with @file{refcard.ps}.
34505 The release also includes the source for the reference card. You
34506 can format it, using @TeX{}, by typing:
34512 The @value{GDBN} reference card is designed to print in @dfn{landscape}
34513 mode on US ``letter'' size paper;
34514 that is, on a sheet 11 inches wide by 8.5 inches
34515 high. You will need to specify this form of printing as an option to
34516 your @sc{dvi} output program.
34518 @cindex documentation
34520 All the documentation for @value{GDBN} comes as part of the machine-readable
34521 distribution. The documentation is written in Texinfo format, which is
34522 a documentation system that uses a single source file to produce both
34523 on-line information and a printed manual. You can use one of the Info
34524 formatting commands to create the on-line version of the documentation
34525 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
34527 @value{GDBN} includes an already formatted copy of the on-line Info
34528 version of this manual in the @file{gdb} subdirectory. The main Info
34529 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
34530 subordinate files matching @samp{gdb.info*} in the same directory. If
34531 necessary, you can print out these files, or read them with any editor;
34532 but they are easier to read using the @code{info} subsystem in @sc{gnu}
34533 Emacs or the standalone @code{info} program, available as part of the
34534 @sc{gnu} Texinfo distribution.
34536 If you want to format these Info files yourself, you need one of the
34537 Info formatting programs, such as @code{texinfo-format-buffer} or
34540 If you have @code{makeinfo} installed, and are in the top level
34541 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
34542 version @value{GDBVN}), you can make the Info file by typing:
34549 If you want to typeset and print copies of this manual, you need @TeX{},
34550 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
34551 Texinfo definitions file.
34553 @TeX{} is a typesetting program; it does not print files directly, but
34554 produces output files called @sc{dvi} files. To print a typeset
34555 document, you need a program to print @sc{dvi} files. If your system
34556 has @TeX{} installed, chances are it has such a program. The precise
34557 command to use depends on your system; @kbd{lpr -d} is common; another
34558 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
34559 require a file name without any extension or a @samp{.dvi} extension.
34561 @TeX{} also requires a macro definitions file called
34562 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
34563 written in Texinfo format. On its own, @TeX{} cannot either read or
34564 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
34565 and is located in the @file{gdb-@var{version-number}/texinfo}
34568 If you have @TeX{} and a @sc{dvi} printer program installed, you can
34569 typeset and print this manual. First switch to the @file{gdb}
34570 subdirectory of the main source directory (for example, to
34571 @file{gdb-@value{GDBVN}/gdb}) and type:
34577 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
34579 @node Installing GDB
34580 @appendix Installing @value{GDBN}
34581 @cindex installation
34584 * Requirements:: Requirements for building @value{GDBN}
34585 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
34586 * Separate Objdir:: Compiling @value{GDBN} in another directory
34587 * Config Names:: Specifying names for hosts and targets
34588 * Configure Options:: Summary of options for configure
34589 * System-wide configuration:: Having a system-wide init file
34593 @section Requirements for Building @value{GDBN}
34594 @cindex building @value{GDBN}, requirements for
34596 Building @value{GDBN} requires various tools and packages to be available.
34597 Other packages will be used only if they are found.
34599 @heading Tools/Packages Necessary for Building @value{GDBN}
34601 @item ISO C90 compiler
34602 @value{GDBN} is written in ISO C90. It should be buildable with any
34603 working C90 compiler, e.g.@: GCC.
34607 @heading Tools/Packages Optional for Building @value{GDBN}
34611 @value{GDBN} can use the Expat XML parsing library. This library may be
34612 included with your operating system distribution; if it is not, you
34613 can get the latest version from @url{http://expat.sourceforge.net}.
34614 The @file{configure} script will search for this library in several
34615 standard locations; if it is installed in an unusual path, you can
34616 use the @option{--with-libexpat-prefix} option to specify its location.
34622 Remote protocol memory maps (@pxref{Memory Map Format})
34624 Target descriptions (@pxref{Target Descriptions})
34626 Remote shared library lists (@xref{Library List Format},
34627 or alternatively @pxref{Library List Format for SVR4 Targets})
34629 MS-Windows shared libraries (@pxref{Shared Libraries})
34631 Traceframe info (@pxref{Traceframe Info Format})
34633 Branch trace (@pxref{Branch Trace Format},
34634 @pxref{Branch Trace Configuration Format})
34639 @value{GDBN} can use the GNU MPFR multiple-precision floating-point
34640 library. This library may be included with your operating system
34641 distribution; if it is not, you can get the latest version from
34642 @url{http://www.mpfr.org}. The @file{configure} script will search
34643 for this library in several standard locations; if it is installed
34644 in an unusual path, you can use the @option{--with-libmpfr-prefix}
34645 option to specify its location.
34647 GNU MPFR is used to emulate target floating-point arithmetic during
34648 expression evaluation when the target uses different floating-point
34649 formats than the host. If GNU MPFR it is not available, @value{GDBN}
34650 will fall back to using host floating-point arithmetic.
34653 @cindex compressed debug sections
34654 @value{GDBN} will use the @samp{zlib} library, if available, to read
34655 compressed debug sections. Some linkers, such as GNU gold, are capable
34656 of producing binaries with compressed debug sections. If @value{GDBN}
34657 is compiled with @samp{zlib}, it will be able to read the debug
34658 information in such binaries.
34660 The @samp{zlib} library is likely included with your operating system
34661 distribution; if it is not, you can get the latest version from
34662 @url{http://zlib.net}.
34665 @value{GDBN}'s features related to character sets (@pxref{Character
34666 Sets}) require a functioning @code{iconv} implementation. If you are
34667 on a GNU system, then this is provided by the GNU C Library. Some
34668 other systems also provide a working @code{iconv}.
34670 If @value{GDBN} is using the @code{iconv} program which is installed
34671 in a non-standard place, you will need to tell @value{GDBN} where to find it.
34672 This is done with @option{--with-iconv-bin} which specifies the
34673 directory that contains the @code{iconv} program.
34675 On systems without @code{iconv}, you can install GNU Libiconv. If you
34676 have previously installed Libiconv, you can use the
34677 @option{--with-libiconv-prefix} option to configure.
34679 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
34680 arrange to build Libiconv if a directory named @file{libiconv} appears
34681 in the top-most source directory. If Libiconv is built this way, and
34682 if the operating system does not provide a suitable @code{iconv}
34683 implementation, then the just-built library will automatically be used
34684 by @value{GDBN}. One easy way to set this up is to download GNU
34685 Libiconv, unpack it, and then rename the directory holding the
34686 Libiconv source code to @samp{libiconv}.
34689 @node Running Configure
34690 @section Invoking the @value{GDBN} @file{configure} Script
34691 @cindex configuring @value{GDBN}
34692 @value{GDBN} comes with a @file{configure} script that automates the process
34693 of preparing @value{GDBN} for installation; you can then use @code{make} to
34694 build the @code{gdb} program.
34696 @c irrelevant in info file; it's as current as the code it lives with.
34697 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
34698 look at the @file{README} file in the sources; we may have improved the
34699 installation procedures since publishing this manual.}
34702 The @value{GDBN} distribution includes all the source code you need for
34703 @value{GDBN} in a single directory, whose name is usually composed by
34704 appending the version number to @samp{gdb}.
34706 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
34707 @file{gdb-@value{GDBVN}} directory. That directory contains:
34710 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
34711 script for configuring @value{GDBN} and all its supporting libraries
34713 @item gdb-@value{GDBVN}/gdb
34714 the source specific to @value{GDBN} itself
34716 @item gdb-@value{GDBVN}/bfd
34717 source for the Binary File Descriptor library
34719 @item gdb-@value{GDBVN}/include
34720 @sc{gnu} include files
34722 @item gdb-@value{GDBVN}/libiberty
34723 source for the @samp{-liberty} free software library
34725 @item gdb-@value{GDBVN}/opcodes
34726 source for the library of opcode tables and disassemblers
34728 @item gdb-@value{GDBVN}/readline
34729 source for the @sc{gnu} command-line interface
34731 @item gdb-@value{GDBVN}/glob
34732 source for the @sc{gnu} filename pattern-matching subroutine
34734 @item gdb-@value{GDBVN}/mmalloc
34735 source for the @sc{gnu} memory-mapped malloc package
34738 The simplest way to configure and build @value{GDBN} is to run @file{configure}
34739 from the @file{gdb-@var{version-number}} source directory, which in
34740 this example is the @file{gdb-@value{GDBVN}} directory.
34742 First switch to the @file{gdb-@var{version-number}} source directory
34743 if you are not already in it; then run @file{configure}. Pass the
34744 identifier for the platform on which @value{GDBN} will run as an
34750 cd gdb-@value{GDBVN}
34751 ./configure @var{host}
34756 where @var{host} is an identifier such as @samp{sun4} or
34757 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
34758 (You can often leave off @var{host}; @file{configure} tries to guess the
34759 correct value by examining your system.)
34761 Running @samp{configure @var{host}} and then running @code{make} builds the
34762 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
34763 libraries, then @code{gdb} itself. The configured source files, and the
34764 binaries, are left in the corresponding source directories.
34767 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
34768 system does not recognize this automatically when you run a different
34769 shell, you may need to run @code{sh} on it explicitly:
34772 sh configure @var{host}
34775 If you run @file{configure} from a directory that contains source
34776 directories for multiple libraries or programs, such as the
34777 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
34779 creates configuration files for every directory level underneath (unless
34780 you tell it not to, with the @samp{--norecursion} option).
34782 You should run the @file{configure} script from the top directory in the
34783 source tree, the @file{gdb-@var{version-number}} directory. If you run
34784 @file{configure} from one of the subdirectories, you will configure only
34785 that subdirectory. That is usually not what you want. In particular,
34786 if you run the first @file{configure} from the @file{gdb} subdirectory
34787 of the @file{gdb-@var{version-number}} directory, you will omit the
34788 configuration of @file{bfd}, @file{readline}, and other sibling
34789 directories of the @file{gdb} subdirectory. This leads to build errors
34790 about missing include files such as @file{bfd/bfd.h}.
34792 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
34793 However, you should make sure that the shell on your path (named by
34794 the @samp{SHELL} environment variable) is publicly readable. Remember
34795 that @value{GDBN} uses the shell to start your program---some systems refuse to
34796 let @value{GDBN} debug child processes whose programs are not readable.
34798 @node Separate Objdir
34799 @section Compiling @value{GDBN} in Another Directory
34801 If you want to run @value{GDBN} versions for several host or target machines,
34802 you need a different @code{gdb} compiled for each combination of
34803 host and target. @file{configure} is designed to make this easy by
34804 allowing you to generate each configuration in a separate subdirectory,
34805 rather than in the source directory. If your @code{make} program
34806 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
34807 @code{make} in each of these directories builds the @code{gdb}
34808 program specified there.
34810 To build @code{gdb} in a separate directory, run @file{configure}
34811 with the @samp{--srcdir} option to specify where to find the source.
34812 (You also need to specify a path to find @file{configure}
34813 itself from your working directory. If the path to @file{configure}
34814 would be the same as the argument to @samp{--srcdir}, you can leave out
34815 the @samp{--srcdir} option; it is assumed.)
34817 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
34818 separate directory for a Sun 4 like this:
34822 cd gdb-@value{GDBVN}
34825 ../gdb-@value{GDBVN}/configure sun4
34830 When @file{configure} builds a configuration using a remote source
34831 directory, it creates a tree for the binaries with the same structure
34832 (and using the same names) as the tree under the source directory. In
34833 the example, you'd find the Sun 4 library @file{libiberty.a} in the
34834 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
34835 @file{gdb-sun4/gdb}.
34837 Make sure that your path to the @file{configure} script has just one
34838 instance of @file{gdb} in it. If your path to @file{configure} looks
34839 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
34840 one subdirectory of @value{GDBN}, not the whole package. This leads to
34841 build errors about missing include files such as @file{bfd/bfd.h}.
34843 One popular reason to build several @value{GDBN} configurations in separate
34844 directories is to configure @value{GDBN} for cross-compiling (where
34845 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
34846 programs that run on another machine---the @dfn{target}).
34847 You specify a cross-debugging target by
34848 giving the @samp{--target=@var{target}} option to @file{configure}.
34850 When you run @code{make} to build a program or library, you must run
34851 it in a configured directory---whatever directory you were in when you
34852 called @file{configure} (or one of its subdirectories).
34854 The @code{Makefile} that @file{configure} generates in each source
34855 directory also runs recursively. If you type @code{make} in a source
34856 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
34857 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
34858 will build all the required libraries, and then build GDB.
34860 When you have multiple hosts or targets configured in separate
34861 directories, you can run @code{make} on them in parallel (for example,
34862 if they are NFS-mounted on each of the hosts); they will not interfere
34866 @section Specifying Names for Hosts and Targets
34868 The specifications used for hosts and targets in the @file{configure}
34869 script are based on a three-part naming scheme, but some short predefined
34870 aliases are also supported. The full naming scheme encodes three pieces
34871 of information in the following pattern:
34874 @var{architecture}-@var{vendor}-@var{os}
34877 For example, you can use the alias @code{sun4} as a @var{host} argument,
34878 or as the value for @var{target} in a @code{--target=@var{target}}
34879 option. The equivalent full name is @samp{sparc-sun-sunos4}.
34881 The @file{configure} script accompanying @value{GDBN} does not provide
34882 any query facility to list all supported host and target names or
34883 aliases. @file{configure} calls the Bourne shell script
34884 @code{config.sub} to map abbreviations to full names; you can read the
34885 script, if you wish, or you can use it to test your guesses on
34886 abbreviations---for example:
34889 % sh config.sub i386-linux
34891 % sh config.sub alpha-linux
34892 alpha-unknown-linux-gnu
34893 % sh config.sub hp9k700
34895 % sh config.sub sun4
34896 sparc-sun-sunos4.1.1
34897 % sh config.sub sun3
34898 m68k-sun-sunos4.1.1
34899 % sh config.sub i986v
34900 Invalid configuration `i986v': machine `i986v' not recognized
34904 @code{config.sub} is also distributed in the @value{GDBN} source
34905 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
34907 @node Configure Options
34908 @section @file{configure} Options
34910 Here is a summary of the @file{configure} options and arguments that
34911 are most often useful for building @value{GDBN}. @file{configure} also has
34912 several other options not listed here. @inforef{What Configure
34913 Does,,configure.info}, for a full explanation of @file{configure}.
34916 configure @r{[}--help@r{]}
34917 @r{[}--prefix=@var{dir}@r{]}
34918 @r{[}--exec-prefix=@var{dir}@r{]}
34919 @r{[}--srcdir=@var{dirname}@r{]}
34920 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
34921 @r{[}--target=@var{target}@r{]}
34926 You may introduce options with a single @samp{-} rather than
34927 @samp{--} if you prefer; but you may abbreviate option names if you use
34932 Display a quick summary of how to invoke @file{configure}.
34934 @item --prefix=@var{dir}
34935 Configure the source to install programs and files under directory
34938 @item --exec-prefix=@var{dir}
34939 Configure the source to install programs under directory
34942 @c avoid splitting the warning from the explanation:
34944 @item --srcdir=@var{dirname}
34945 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
34946 @code{make} that implements the @code{VPATH} feature.}@*
34947 Use this option to make configurations in directories separate from the
34948 @value{GDBN} source directories. Among other things, you can use this to
34949 build (or maintain) several configurations simultaneously, in separate
34950 directories. @file{configure} writes configuration-specific files in
34951 the current directory, but arranges for them to use the source in the
34952 directory @var{dirname}. @file{configure} creates directories under
34953 the working directory in parallel to the source directories below
34956 @item --norecursion
34957 Configure only the directory level where @file{configure} is executed; do not
34958 propagate configuration to subdirectories.
34960 @item --target=@var{target}
34961 Configure @value{GDBN} for cross-debugging programs running on the specified
34962 @var{target}. Without this option, @value{GDBN} is configured to debug
34963 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
34965 There is no convenient way to generate a list of all available targets.
34967 @item @var{host} @dots{}
34968 Configure @value{GDBN} to run on the specified @var{host}.
34970 There is no convenient way to generate a list of all available hosts.
34973 There are many other options available as well, but they are generally
34974 needed for special purposes only.
34976 @node System-wide configuration
34977 @section System-wide configuration and settings
34978 @cindex system-wide init file
34980 @value{GDBN} can be configured to have a system-wide init file;
34981 this file will be read and executed at startup (@pxref{Startup, , What
34982 @value{GDBN} does during startup}).
34984 Here is the corresponding configure option:
34987 @item --with-system-gdbinit=@var{file}
34988 Specify that the default location of the system-wide init file is
34992 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
34993 it may be subject to relocation. Two possible cases:
34997 If the default location of this init file contains @file{$prefix},
34998 it will be subject to relocation. Suppose that the configure options
34999 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
35000 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
35001 init file is looked for as @file{$install/etc/gdbinit} instead of
35002 @file{$prefix/etc/gdbinit}.
35005 By contrast, if the default location does not contain the prefix,
35006 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
35007 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
35008 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
35009 wherever @value{GDBN} is installed.
35012 If the configured location of the system-wide init file (as given by the
35013 @option{--with-system-gdbinit} option at configure time) is in the
35014 data-directory (as specified by @option{--with-gdb-datadir} at configure
35015 time) or in one of its subdirectories, then @value{GDBN} will look for the
35016 system-wide init file in the directory specified by the
35017 @option{--data-directory} command-line option.
35018 Note that the system-wide init file is only read once, during @value{GDBN}
35019 initialization. If the data-directory is changed after @value{GDBN} has
35020 started with the @code{set data-directory} command, the file will not be
35024 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
35027 @node System-wide Configuration Scripts
35028 @subsection Installed System-wide Configuration Scripts
35029 @cindex system-wide configuration scripts
35031 The @file{system-gdbinit} directory, located inside the data-directory
35032 (as specified by @option{--with-gdb-datadir} at configure time) contains
35033 a number of scripts which can be used as system-wide init files. To
35034 automatically source those scripts at startup, @value{GDBN} should be
35035 configured with @option{--with-system-gdbinit}. Otherwise, any user
35036 should be able to source them by hand as needed.
35038 The following scripts are currently available:
35041 @item @file{elinos.py}
35043 @cindex ELinOS system-wide configuration script
35044 This script is useful when debugging a program on an ELinOS target.
35045 It takes advantage of the environment variables defined in a standard
35046 ELinOS environment in order to determine the location of the system
35047 shared libraries, and then sets the @samp{solib-absolute-prefix}
35048 and @samp{solib-search-path} variables appropriately.
35050 @item @file{wrs-linux.py}
35051 @pindex wrs-linux.py
35052 @cindex Wind River Linux system-wide configuration script
35053 This script is useful when debugging a program on a target running
35054 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
35055 the host-side sysroot used by the target system.
35059 @node Maintenance Commands
35060 @appendix Maintenance Commands
35061 @cindex maintenance commands
35062 @cindex internal commands
35064 In addition to commands intended for @value{GDBN} users, @value{GDBN}
35065 includes a number of commands intended for @value{GDBN} developers,
35066 that are not documented elsewhere in this manual. These commands are
35067 provided here for reference. (For commands that turn on debugging
35068 messages, see @ref{Debugging Output}.)
35071 @kindex maint agent
35072 @kindex maint agent-eval
35073 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
35074 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
35075 Translate the given @var{expression} into remote agent bytecodes.
35076 This command is useful for debugging the Agent Expression mechanism
35077 (@pxref{Agent Expressions}). The @samp{agent} version produces an
35078 expression useful for data collection, such as by tracepoints, while
35079 @samp{maint agent-eval} produces an expression that evaluates directly
35080 to a result. For instance, a collection expression for @code{globa +
35081 globb} will include bytecodes to record four bytes of memory at each
35082 of the addresses of @code{globa} and @code{globb}, while discarding
35083 the result of the addition, while an evaluation expression will do the
35084 addition and return the sum.
35085 If @code{-at} is given, generate remote agent bytecode for @var{location}.
35086 If not, generate remote agent bytecode for current frame PC address.
35088 @kindex maint agent-printf
35089 @item maint agent-printf @var{format},@var{expr},...
35090 Translate the given format string and list of argument expressions
35091 into remote agent bytecodes and display them as a disassembled list.
35092 This command is useful for debugging the agent version of dynamic
35093 printf (@pxref{Dynamic Printf}).
35095 @kindex maint info breakpoints
35096 @item @anchor{maint info breakpoints}maint info breakpoints
35097 Using the same format as @samp{info breakpoints}, display both the
35098 breakpoints you've set explicitly, and those @value{GDBN} is using for
35099 internal purposes. Internal breakpoints are shown with negative
35100 breakpoint numbers. The type column identifies what kind of breakpoint
35105 Normal, explicitly set breakpoint.
35108 Normal, explicitly set watchpoint.
35111 Internal breakpoint, used to handle correctly stepping through
35112 @code{longjmp} calls.
35114 @item longjmp resume
35115 Internal breakpoint at the target of a @code{longjmp}.
35118 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
35121 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
35124 Shared library events.
35128 @kindex maint info btrace
35129 @item maint info btrace
35130 Pint information about raw branch tracing data.
35132 @kindex maint btrace packet-history
35133 @item maint btrace packet-history
35134 Print the raw branch trace packets that are used to compute the
35135 execution history for the @samp{record btrace} command. Both the
35136 information and the format in which it is printed depend on the btrace
35141 For the BTS recording format, print a list of blocks of sequential
35142 code. For each block, the following information is printed:
35146 Newer blocks have higher numbers. The oldest block has number zero.
35147 @item Lowest @samp{PC}
35148 @item Highest @samp{PC}
35152 For the Intel Processor Trace recording format, print a list of
35153 Intel Processor Trace packets. For each packet, the following
35154 information is printed:
35157 @item Packet number
35158 Newer packets have higher numbers. The oldest packet has number zero.
35160 The packet's offset in the trace stream.
35161 @item Packet opcode and payload
35165 @kindex maint btrace clear-packet-history
35166 @item maint btrace clear-packet-history
35167 Discards the cached packet history printed by the @samp{maint btrace
35168 packet-history} command. The history will be computed again when
35171 @kindex maint btrace clear
35172 @item maint btrace clear
35173 Discard the branch trace data. The data will be fetched anew and the
35174 branch trace will be recomputed when needed.
35176 This implicitly truncates the branch trace to a single branch trace
35177 buffer. When updating branch trace incrementally, the branch trace
35178 available to @value{GDBN} may be bigger than a single branch trace
35181 @kindex maint set btrace pt skip-pad
35182 @item maint set btrace pt skip-pad
35183 @kindex maint show btrace pt skip-pad
35184 @item maint show btrace pt skip-pad
35185 Control whether @value{GDBN} will skip PAD packets when computing the
35188 @kindex set displaced-stepping
35189 @kindex show displaced-stepping
35190 @cindex displaced stepping support
35191 @cindex out-of-line single-stepping
35192 @item set displaced-stepping
35193 @itemx show displaced-stepping
35194 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
35195 if the target supports it. Displaced stepping is a way to single-step
35196 over breakpoints without removing them from the inferior, by executing
35197 an out-of-line copy of the instruction that was originally at the
35198 breakpoint location. It is also known as out-of-line single-stepping.
35201 @item set displaced-stepping on
35202 If the target architecture supports it, @value{GDBN} will use
35203 displaced stepping to step over breakpoints.
35205 @item set displaced-stepping off
35206 @value{GDBN} will not use displaced stepping to step over breakpoints,
35207 even if such is supported by the target architecture.
35209 @cindex non-stop mode, and @samp{set displaced-stepping}
35210 @item set displaced-stepping auto
35211 This is the default mode. @value{GDBN} will use displaced stepping
35212 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
35213 architecture supports displaced stepping.
35216 @kindex maint check-psymtabs
35217 @item maint check-psymtabs
35218 Check the consistency of currently expanded psymtabs versus symtabs.
35219 Use this to check, for example, whether a symbol is in one but not the other.
35221 @kindex maint check-symtabs
35222 @item maint check-symtabs
35223 Check the consistency of currently expanded symtabs.
35225 @kindex maint expand-symtabs
35226 @item maint expand-symtabs [@var{regexp}]
35227 Expand symbol tables.
35228 If @var{regexp} is specified, only expand symbol tables for file
35229 names matching @var{regexp}.
35231 @kindex maint set catch-demangler-crashes
35232 @kindex maint show catch-demangler-crashes
35233 @cindex demangler crashes
35234 @item maint set catch-demangler-crashes [on|off]
35235 @itemx maint show catch-demangler-crashes
35236 Control whether @value{GDBN} should attempt to catch crashes in the
35237 symbol name demangler. The default is to attempt to catch crashes.
35238 If enabled, the first time a crash is caught, a core file is created,
35239 the offending symbol is displayed and the user is presented with the
35240 option to terminate the current session.
35242 @kindex maint cplus first_component
35243 @item maint cplus first_component @var{name}
35244 Print the first C@t{++} class/namespace component of @var{name}.
35246 @kindex maint cplus namespace
35247 @item maint cplus namespace
35248 Print the list of possible C@t{++} namespaces.
35250 @kindex maint deprecate
35251 @kindex maint undeprecate
35252 @cindex deprecated commands
35253 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
35254 @itemx maint undeprecate @var{command}
35255 Deprecate or undeprecate the named @var{command}. Deprecated commands
35256 cause @value{GDBN} to issue a warning when you use them. The optional
35257 argument @var{replacement} says which newer command should be used in
35258 favor of the deprecated one; if it is given, @value{GDBN} will mention
35259 the replacement as part of the warning.
35261 @kindex maint dump-me
35262 @item maint dump-me
35263 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
35264 Cause a fatal signal in the debugger and force it to dump its core.
35265 This is supported only on systems which support aborting a program
35266 with the @code{SIGQUIT} signal.
35268 @kindex maint internal-error
35269 @kindex maint internal-warning
35270 @kindex maint demangler-warning
35271 @cindex demangler crashes
35272 @item maint internal-error @r{[}@var{message-text}@r{]}
35273 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
35274 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
35276 Cause @value{GDBN} to call the internal function @code{internal_error},
35277 @code{internal_warning} or @code{demangler_warning} and hence behave
35278 as though an internal problem has been detected. In addition to
35279 reporting the internal problem, these functions give the user the
35280 opportunity to either quit @value{GDBN} or (for @code{internal_error}
35281 and @code{internal_warning}) create a core file of the current
35282 @value{GDBN} session.
35284 These commands take an optional parameter @var{message-text} that is
35285 used as the text of the error or warning message.
35287 Here's an example of using @code{internal-error}:
35290 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
35291 @dots{}/maint.c:121: internal-error: testing, 1, 2
35292 A problem internal to GDB has been detected. Further
35293 debugging may prove unreliable.
35294 Quit this debugging session? (y or n) @kbd{n}
35295 Create a core file? (y or n) @kbd{n}
35299 @cindex @value{GDBN} internal error
35300 @cindex internal errors, control of @value{GDBN} behavior
35301 @cindex demangler crashes
35303 @kindex maint set internal-error
35304 @kindex maint show internal-error
35305 @kindex maint set internal-warning
35306 @kindex maint show internal-warning
35307 @kindex maint set demangler-warning
35308 @kindex maint show demangler-warning
35309 @item maint set internal-error @var{action} [ask|yes|no]
35310 @itemx maint show internal-error @var{action}
35311 @itemx maint set internal-warning @var{action} [ask|yes|no]
35312 @itemx maint show internal-warning @var{action}
35313 @itemx maint set demangler-warning @var{action} [ask|yes|no]
35314 @itemx maint show demangler-warning @var{action}
35315 When @value{GDBN} reports an internal problem (error or warning) it
35316 gives the user the opportunity to both quit @value{GDBN} and create a
35317 core file of the current @value{GDBN} session. These commands let you
35318 override the default behaviour for each particular @var{action},
35319 described in the table below.
35323 You can specify that @value{GDBN} should always (yes) or never (no)
35324 quit. The default is to ask the user what to do.
35327 You can specify that @value{GDBN} should always (yes) or never (no)
35328 create a core file. The default is to ask the user what to do. Note
35329 that there is no @code{corefile} option for @code{demangler-warning}:
35330 demangler warnings always create a core file and this cannot be
35334 @kindex maint packet
35335 @item maint packet @var{text}
35336 If @value{GDBN} is talking to an inferior via the serial protocol,
35337 then this command sends the string @var{text} to the inferior, and
35338 displays the response packet. @value{GDBN} supplies the initial
35339 @samp{$} character, the terminating @samp{#} character, and the
35342 @kindex maint print architecture
35343 @item maint print architecture @r{[}@var{file}@r{]}
35344 Print the entire architecture configuration. The optional argument
35345 @var{file} names the file where the output goes.
35347 @kindex maint print c-tdesc @r{[}@var{file}@r{]}
35348 @item maint print c-tdesc
35349 Print the target description (@pxref{Target Descriptions}) as
35350 a C source file. By default, the target description is for the current
35351 target, but if the optional argument @var{file} is provided, that file
35352 is used to produce the description. The @var{file} should be an XML
35353 document, of the form described in @ref{Target Description Format}.
35354 The created source file is built into @value{GDBN} when @value{GDBN} is
35355 built again. This command is used by developers after they add or
35356 modify XML target descriptions.
35358 @kindex maint check xml-descriptions
35359 @item maint check xml-descriptions @var{dir}
35360 Check that the target descriptions dynamically created by @value{GDBN}
35361 equal the descriptions created from XML files found in @var{dir}.
35363 @kindex maint print dummy-frames
35364 @item maint print dummy-frames
35365 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
35368 (@value{GDBP}) @kbd{b add}
35370 (@value{GDBP}) @kbd{print add(2,3)}
35371 Breakpoint 2, add (a=2, b=3) at @dots{}
35373 The program being debugged stopped while in a function called from GDB.
35375 (@value{GDBP}) @kbd{maint print dummy-frames}
35376 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
35380 Takes an optional file parameter.
35382 @kindex maint print registers
35383 @kindex maint print raw-registers
35384 @kindex maint print cooked-registers
35385 @kindex maint print register-groups
35386 @kindex maint print remote-registers
35387 @item maint print registers @r{[}@var{file}@r{]}
35388 @itemx maint print raw-registers @r{[}@var{file}@r{]}
35389 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
35390 @itemx maint print register-groups @r{[}@var{file}@r{]}
35391 @itemx maint print remote-registers @r{[}@var{file}@r{]}
35392 Print @value{GDBN}'s internal register data structures.
35394 The command @code{maint print raw-registers} includes the contents of
35395 the raw register cache; the command @code{maint print
35396 cooked-registers} includes the (cooked) value of all registers,
35397 including registers which aren't available on the target nor visible
35398 to user; the command @code{maint print register-groups} includes the
35399 groups that each register is a member of; and the command @code{maint
35400 print remote-registers} includes the remote target's register numbers
35401 and offsets in the `G' packets.
35403 These commands take an optional parameter, a file name to which to
35404 write the information.
35406 @kindex maint print reggroups
35407 @item maint print reggroups @r{[}@var{file}@r{]}
35408 Print @value{GDBN}'s internal register group data structures. The
35409 optional argument @var{file} tells to what file to write the
35412 The register groups info looks like this:
35415 (@value{GDBP}) @kbd{maint print reggroups}
35428 This command forces @value{GDBN} to flush its internal register cache.
35430 @kindex maint print objfiles
35431 @cindex info for known object files
35432 @item maint print objfiles @r{[}@var{regexp}@r{]}
35433 Print a dump of all known object files.
35434 If @var{regexp} is specified, only print object files whose names
35435 match @var{regexp}. For each object file, this command prints its name,
35436 address in memory, and all of its psymtabs and symtabs.
35438 @kindex maint print user-registers
35439 @cindex user registers
35440 @item maint print user-registers
35441 List all currently available @dfn{user registers}. User registers
35442 typically provide alternate names for actual hardware registers. They
35443 include the four ``standard'' registers @code{$fp}, @code{$pc},
35444 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
35445 registers can be used in expressions in the same way as the canonical
35446 register names, but only the latter are listed by the @code{info
35447 registers} and @code{maint print registers} commands.
35449 @kindex maint print section-scripts
35450 @cindex info for known .debug_gdb_scripts-loaded scripts
35451 @item maint print section-scripts [@var{regexp}]
35452 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
35453 If @var{regexp} is specified, only print scripts loaded by object files
35454 matching @var{regexp}.
35455 For each script, this command prints its name as specified in the objfile,
35456 and the full path if known.
35457 @xref{dotdebug_gdb_scripts section}.
35459 @kindex maint print statistics
35460 @cindex bcache statistics
35461 @item maint print statistics
35462 This command prints, for each object file in the program, various data
35463 about that object file followed by the byte cache (@dfn{bcache})
35464 statistics for the object file. The objfile data includes the number
35465 of minimal, partial, full, and stabs symbols, the number of types
35466 defined by the objfile, the number of as yet unexpanded psym tables,
35467 the number of line tables and string tables, and the amount of memory
35468 used by the various tables. The bcache statistics include the counts,
35469 sizes, and counts of duplicates of all and unique objects, max,
35470 average, and median entry size, total memory used and its overhead and
35471 savings, and various measures of the hash table size and chain
35474 @kindex maint print target-stack
35475 @cindex target stack description
35476 @item maint print target-stack
35477 A @dfn{target} is an interface between the debugger and a particular
35478 kind of file or process. Targets can be stacked in @dfn{strata},
35479 so that more than one target can potentially respond to a request.
35480 In particular, memory accesses will walk down the stack of targets
35481 until they find a target that is interested in handling that particular
35484 This command prints a short description of each layer that was pushed on
35485 the @dfn{target stack}, starting from the top layer down to the bottom one.
35487 @kindex maint print type
35488 @cindex type chain of a data type
35489 @item maint print type @var{expr}
35490 Print the type chain for a type specified by @var{expr}. The argument
35491 can be either a type name or a symbol. If it is a symbol, the type of
35492 that symbol is described. The type chain produced by this command is
35493 a recursive definition of the data type as stored in @value{GDBN}'s
35494 data structures, including its flags and contained types.
35496 @kindex maint selftest
35498 @item maint selftest @r{[}@var{filter}@r{]}
35499 Run any self tests that were compiled in to @value{GDBN}. This will
35500 print a message showing how many tests were run, and how many failed.
35501 If a @var{filter} is passed, only the tests with @var{filter} in their
35504 @kindex "maint info selftests"
35506 @item maint info selftests
35507 List the selftests compiled in to @value{GDBN}.
35509 @kindex maint set dwarf always-disassemble
35510 @kindex maint show dwarf always-disassemble
35511 @item maint set dwarf always-disassemble
35512 @item maint show dwarf always-disassemble
35513 Control the behavior of @code{info address} when using DWARF debugging
35516 The default is @code{off}, which means that @value{GDBN} should try to
35517 describe a variable's location in an easily readable format. When
35518 @code{on}, @value{GDBN} will instead display the DWARF location
35519 expression in an assembly-like format. Note that some locations are
35520 too complex for @value{GDBN} to describe simply; in this case you will
35521 always see the disassembly form.
35523 Here is an example of the resulting disassembly:
35526 (gdb) info addr argc
35527 Symbol "argc" is a complex DWARF expression:
35531 For more information on these expressions, see
35532 @uref{http://www.dwarfstd.org/, the DWARF standard}.
35534 @kindex maint set dwarf max-cache-age
35535 @kindex maint show dwarf max-cache-age
35536 @item maint set dwarf max-cache-age
35537 @itemx maint show dwarf max-cache-age
35538 Control the DWARF compilation unit cache.
35540 @cindex DWARF compilation units cache
35541 In object files with inter-compilation-unit references, such as those
35542 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
35543 reader needs to frequently refer to previously read compilation units.
35544 This setting controls how long a compilation unit will remain in the
35545 cache if it is not referenced. A higher limit means that cached
35546 compilation units will be stored in memory longer, and more total
35547 memory will be used. Setting it to zero disables caching, which will
35548 slow down @value{GDBN} startup, but reduce memory consumption.
35550 @kindex maint set profile
35551 @kindex maint show profile
35552 @cindex profiling GDB
35553 @item maint set profile
35554 @itemx maint show profile
35555 Control profiling of @value{GDBN}.
35557 Profiling will be disabled until you use the @samp{maint set profile}
35558 command to enable it. When you enable profiling, the system will begin
35559 collecting timing and execution count data; when you disable profiling or
35560 exit @value{GDBN}, the results will be written to a log file. Remember that
35561 if you use profiling, @value{GDBN} will overwrite the profiling log file
35562 (often called @file{gmon.out}). If you have a record of important profiling
35563 data in a @file{gmon.out} file, be sure to move it to a safe location.
35565 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
35566 compiled with the @samp{-pg} compiler option.
35568 @kindex maint set show-debug-regs
35569 @kindex maint show show-debug-regs
35570 @cindex hardware debug registers
35571 @item maint set show-debug-regs
35572 @itemx maint show show-debug-regs
35573 Control whether to show variables that mirror the hardware debug
35574 registers. Use @code{on} to enable, @code{off} to disable. If
35575 enabled, the debug registers values are shown when @value{GDBN} inserts or
35576 removes a hardware breakpoint or watchpoint, and when the inferior
35577 triggers a hardware-assisted breakpoint or watchpoint.
35579 @kindex maint set show-all-tib
35580 @kindex maint show show-all-tib
35581 @item maint set show-all-tib
35582 @itemx maint show show-all-tib
35583 Control whether to show all non zero areas within a 1k block starting
35584 at thread local base, when using the @samp{info w32 thread-information-block}
35587 @kindex maint set target-async
35588 @kindex maint show target-async
35589 @item maint set target-async
35590 @itemx maint show target-async
35591 This controls whether @value{GDBN} targets operate in synchronous or
35592 asynchronous mode (@pxref{Background Execution}). Normally the
35593 default is asynchronous, if it is available; but this can be changed
35594 to more easily debug problems occurring only in synchronous mode.
35596 @kindex maint set target-non-stop @var{mode} [on|off|auto]
35597 @kindex maint show target-non-stop
35598 @item maint set target-non-stop
35599 @itemx maint show target-non-stop
35601 This controls whether @value{GDBN} targets always operate in non-stop
35602 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
35603 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
35604 if supported by the target.
35607 @item maint set target-non-stop auto
35608 This is the default mode. @value{GDBN} controls the target in
35609 non-stop mode if the target supports it.
35611 @item maint set target-non-stop on
35612 @value{GDBN} controls the target in non-stop mode even if the target
35613 does not indicate support.
35615 @item maint set target-non-stop off
35616 @value{GDBN} does not control the target in non-stop mode even if the
35617 target supports it.
35620 @kindex maint set per-command
35621 @kindex maint show per-command
35622 @item maint set per-command
35623 @itemx maint show per-command
35624 @cindex resources used by commands
35626 @value{GDBN} can display the resources used by each command.
35627 This is useful in debugging performance problems.
35630 @item maint set per-command space [on|off]
35631 @itemx maint show per-command space
35632 Enable or disable the printing of the memory used by GDB for each command.
35633 If enabled, @value{GDBN} will display how much memory each command
35634 took, following the command's own output.
35635 This can also be requested by invoking @value{GDBN} with the
35636 @option{--statistics} command-line switch (@pxref{Mode Options}).
35638 @item maint set per-command time [on|off]
35639 @itemx maint show per-command time
35640 Enable or disable the printing of the execution time of @value{GDBN}
35642 If enabled, @value{GDBN} will display how much time it
35643 took to execute each command, following the command's own output.
35644 Both CPU time and wallclock time are printed.
35645 Printing both is useful when trying to determine whether the cost is
35646 CPU or, e.g., disk/network latency.
35647 Note that the CPU time printed is for @value{GDBN} only, it does not include
35648 the execution time of the inferior because there's no mechanism currently
35649 to compute how much time was spent by @value{GDBN} and how much time was
35650 spent by the program been debugged.
35651 This can also be requested by invoking @value{GDBN} with the
35652 @option{--statistics} command-line switch (@pxref{Mode Options}).
35654 @item maint set per-command symtab [on|off]
35655 @itemx maint show per-command symtab
35656 Enable or disable the printing of basic symbol table statistics
35658 If enabled, @value{GDBN} will display the following information:
35662 number of symbol tables
35664 number of primary symbol tables
35666 number of blocks in the blockvector
35670 @kindex maint space
35671 @cindex memory used by commands
35672 @item maint space @var{value}
35673 An alias for @code{maint set per-command space}.
35674 A non-zero value enables it, zero disables it.
35677 @cindex time of command execution
35678 @item maint time @var{value}
35679 An alias for @code{maint set per-command time}.
35680 A non-zero value enables it, zero disables it.
35682 @kindex maint translate-address
35683 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
35684 Find the symbol stored at the location specified by the address
35685 @var{addr} and an optional section name @var{section}. If found,
35686 @value{GDBN} prints the name of the closest symbol and an offset from
35687 the symbol's location to the specified address. This is similar to
35688 the @code{info address} command (@pxref{Symbols}), except that this
35689 command also allows to find symbols in other sections.
35691 If section was not specified, the section in which the symbol was found
35692 is also printed. For dynamically linked executables, the name of
35693 executable or shared library containing the symbol is printed as well.
35697 The following command is useful for non-interactive invocations of
35698 @value{GDBN}, such as in the test suite.
35701 @item set watchdog @var{nsec}
35702 @kindex set watchdog
35703 @cindex watchdog timer
35704 @cindex timeout for commands
35705 Set the maximum number of seconds @value{GDBN} will wait for the
35706 target operation to finish. If this time expires, @value{GDBN}
35707 reports and error and the command is aborted.
35709 @item show watchdog
35710 Show the current setting of the target wait timeout.
35713 @node Remote Protocol
35714 @appendix @value{GDBN} Remote Serial Protocol
35719 * Stop Reply Packets::
35720 * General Query Packets::
35721 * Architecture-Specific Protocol Details::
35722 * Tracepoint Packets::
35723 * Host I/O Packets::
35725 * Notification Packets::
35726 * Remote Non-Stop::
35727 * Packet Acknowledgment::
35729 * File-I/O Remote Protocol Extension::
35730 * Library List Format::
35731 * Library List Format for SVR4 Targets::
35732 * Memory Map Format::
35733 * Thread List Format::
35734 * Traceframe Info Format::
35735 * Branch Trace Format::
35736 * Branch Trace Configuration Format::
35742 There may be occasions when you need to know something about the
35743 protocol---for example, if there is only one serial port to your target
35744 machine, you might want your program to do something special if it
35745 recognizes a packet meant for @value{GDBN}.
35747 In the examples below, @samp{->} and @samp{<-} are used to indicate
35748 transmitted and received data, respectively.
35750 @cindex protocol, @value{GDBN} remote serial
35751 @cindex serial protocol, @value{GDBN} remote
35752 @cindex remote serial protocol
35753 All @value{GDBN} commands and responses (other than acknowledgments
35754 and notifications, see @ref{Notification Packets}) are sent as a
35755 @var{packet}. A @var{packet} is introduced with the character
35756 @samp{$}, the actual @var{packet-data}, and the terminating character
35757 @samp{#} followed by a two-digit @var{checksum}:
35760 @code{$}@var{packet-data}@code{#}@var{checksum}
35764 @cindex checksum, for @value{GDBN} remote
35766 The two-digit @var{checksum} is computed as the modulo 256 sum of all
35767 characters between the leading @samp{$} and the trailing @samp{#} (an
35768 eight bit unsigned checksum).
35770 Implementors should note that prior to @value{GDBN} 5.0 the protocol
35771 specification also included an optional two-digit @var{sequence-id}:
35774 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
35777 @cindex sequence-id, for @value{GDBN} remote
35779 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
35780 has never output @var{sequence-id}s. Stubs that handle packets added
35781 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
35783 When either the host or the target machine receives a packet, the first
35784 response expected is an acknowledgment: either @samp{+} (to indicate
35785 the package was received correctly) or @samp{-} (to request
35789 -> @code{$}@var{packet-data}@code{#}@var{checksum}
35794 The @samp{+}/@samp{-} acknowledgments can be disabled
35795 once a connection is established.
35796 @xref{Packet Acknowledgment}, for details.
35798 The host (@value{GDBN}) sends @var{command}s, and the target (the
35799 debugging stub incorporated in your program) sends a @var{response}. In
35800 the case of step and continue @var{command}s, the response is only sent
35801 when the operation has completed, and the target has again stopped all
35802 threads in all attached processes. This is the default all-stop mode
35803 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
35804 execution mode; see @ref{Remote Non-Stop}, for details.
35806 @var{packet-data} consists of a sequence of characters with the
35807 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
35810 @cindex remote protocol, field separator
35811 Fields within the packet should be separated using @samp{,} @samp{;} or
35812 @samp{:}. Except where otherwise noted all numbers are represented in
35813 @sc{hex} with leading zeros suppressed.
35815 Implementors should note that prior to @value{GDBN} 5.0, the character
35816 @samp{:} could not appear as the third character in a packet (as it
35817 would potentially conflict with the @var{sequence-id}).
35819 @cindex remote protocol, binary data
35820 @anchor{Binary Data}
35821 Binary data in most packets is encoded either as two hexadecimal
35822 digits per byte of binary data. This allowed the traditional remote
35823 protocol to work over connections which were only seven-bit clean.
35824 Some packets designed more recently assume an eight-bit clean
35825 connection, and use a more efficient encoding to send and receive
35828 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
35829 as an escape character. Any escaped byte is transmitted as the escape
35830 character followed by the original character XORed with @code{0x20}.
35831 For example, the byte @code{0x7d} would be transmitted as the two
35832 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
35833 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
35834 @samp{@}}) must always be escaped. Responses sent by the stub
35835 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
35836 is not interpreted as the start of a run-length encoded sequence
35839 Response @var{data} can be run-length encoded to save space.
35840 Run-length encoding replaces runs of identical characters with one
35841 instance of the repeated character, followed by a @samp{*} and a
35842 repeat count. The repeat count is itself sent encoded, to avoid
35843 binary characters in @var{data}: a value of @var{n} is sent as
35844 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
35845 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
35846 code 32) for a repeat count of 3. (This is because run-length
35847 encoding starts to win for counts 3 or more.) Thus, for example,
35848 @samp{0* } is a run-length encoding of ``0000'': the space character
35849 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
35852 The printable characters @samp{#} and @samp{$} or with a numeric value
35853 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
35854 seven repeats (@samp{$}) can be expanded using a repeat count of only
35855 five (@samp{"}). For example, @samp{00000000} can be encoded as
35858 The error response returned for some packets includes a two character
35859 error number. That number is not well defined.
35861 @cindex empty response, for unsupported packets
35862 For any @var{command} not supported by the stub, an empty response
35863 (@samp{$#00}) should be returned. That way it is possible to extend the
35864 protocol. A newer @value{GDBN} can tell if a packet is supported based
35867 At a minimum, a stub is required to support the @samp{g} and @samp{G}
35868 commands for register access, and the @samp{m} and @samp{M} commands
35869 for memory access. Stubs that only control single-threaded targets
35870 can implement run control with the @samp{c} (continue), and @samp{s}
35871 (step) commands. Stubs that support multi-threading targets should
35872 support the @samp{vCont} command. All other commands are optional.
35877 The following table provides a complete list of all currently defined
35878 @var{command}s and their corresponding response @var{data}.
35879 @xref{File-I/O Remote Protocol Extension}, for details about the File
35880 I/O extension of the remote protocol.
35882 Each packet's description has a template showing the packet's overall
35883 syntax, followed by an explanation of the packet's meaning. We
35884 include spaces in some of the templates for clarity; these are not
35885 part of the packet's syntax. No @value{GDBN} packet uses spaces to
35886 separate its components. For example, a template like @samp{foo
35887 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
35888 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
35889 @var{baz}. @value{GDBN} does not transmit a space character between the
35890 @samp{foo} and the @var{bar}, or between the @var{bar} and the
35893 @cindex @var{thread-id}, in remote protocol
35894 @anchor{thread-id syntax}
35895 Several packets and replies include a @var{thread-id} field to identify
35896 a thread. Normally these are positive numbers with a target-specific
35897 interpretation, formatted as big-endian hex strings. A @var{thread-id}
35898 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
35901 In addition, the remote protocol supports a multiprocess feature in
35902 which the @var{thread-id} syntax is extended to optionally include both
35903 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
35904 The @var{pid} (process) and @var{tid} (thread) components each have the
35905 format described above: a positive number with target-specific
35906 interpretation formatted as a big-endian hex string, literal @samp{-1}
35907 to indicate all processes or threads (respectively), or @samp{0} to
35908 indicate an arbitrary process or thread. Specifying just a process, as
35909 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
35910 error to specify all processes but a specific thread, such as
35911 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
35912 for those packets and replies explicitly documented to include a process
35913 ID, rather than a @var{thread-id}.
35915 The multiprocess @var{thread-id} syntax extensions are only used if both
35916 @value{GDBN} and the stub report support for the @samp{multiprocess}
35917 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
35920 Note that all packet forms beginning with an upper- or lower-case
35921 letter, other than those described here, are reserved for future use.
35923 Here are the packet descriptions.
35928 @cindex @samp{!} packet
35929 @anchor{extended mode}
35930 Enable extended mode. In extended mode, the remote server is made
35931 persistent. The @samp{R} packet is used to restart the program being
35937 The remote target both supports and has enabled extended mode.
35941 @cindex @samp{?} packet
35943 Indicate the reason the target halted. The reply is the same as for
35944 step and continue. This packet has a special interpretation when the
35945 target is in non-stop mode; see @ref{Remote Non-Stop}.
35948 @xref{Stop Reply Packets}, for the reply specifications.
35950 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
35951 @cindex @samp{A} packet
35952 Initialized @code{argv[]} array passed into program. @var{arglen}
35953 specifies the number of bytes in the hex encoded byte stream
35954 @var{arg}. See @code{gdbserver} for more details.
35959 The arguments were set.
35965 @cindex @samp{b} packet
35966 (Don't use this packet; its behavior is not well-defined.)
35967 Change the serial line speed to @var{baud}.
35969 JTC: @emph{When does the transport layer state change? When it's
35970 received, or after the ACK is transmitted. In either case, there are
35971 problems if the command or the acknowledgment packet is dropped.}
35973 Stan: @emph{If people really wanted to add something like this, and get
35974 it working for the first time, they ought to modify ser-unix.c to send
35975 some kind of out-of-band message to a specially-setup stub and have the
35976 switch happen "in between" packets, so that from remote protocol's point
35977 of view, nothing actually happened.}
35979 @item B @var{addr},@var{mode}
35980 @cindex @samp{B} packet
35981 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
35982 breakpoint at @var{addr}.
35984 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
35985 (@pxref{insert breakpoint or watchpoint packet}).
35987 @cindex @samp{bc} packet
35990 Backward continue. Execute the target system in reverse. No parameter.
35991 @xref{Reverse Execution}, for more information.
35994 @xref{Stop Reply Packets}, for the reply specifications.
35996 @cindex @samp{bs} packet
35999 Backward single step. Execute one instruction in reverse. No parameter.
36000 @xref{Reverse Execution}, for more information.
36003 @xref{Stop Reply Packets}, for the reply specifications.
36005 @item c @r{[}@var{addr}@r{]}
36006 @cindex @samp{c} packet
36007 Continue at @var{addr}, which is the address to resume. If @var{addr}
36008 is omitted, resume at current address.
36010 This packet is deprecated for multi-threading support. @xref{vCont
36014 @xref{Stop Reply Packets}, for the reply specifications.
36016 @item C @var{sig}@r{[};@var{addr}@r{]}
36017 @cindex @samp{C} packet
36018 Continue with signal @var{sig} (hex signal number). If
36019 @samp{;@var{addr}} is omitted, resume at same address.
36021 This packet is deprecated for multi-threading support. @xref{vCont
36025 @xref{Stop Reply Packets}, for the reply specifications.
36028 @cindex @samp{d} packet
36031 Don't use this packet; instead, define a general set packet
36032 (@pxref{General Query Packets}).
36036 @cindex @samp{D} packet
36037 The first form of the packet is used to detach @value{GDBN} from the
36038 remote system. It is sent to the remote target
36039 before @value{GDBN} disconnects via the @code{detach} command.
36041 The second form, including a process ID, is used when multiprocess
36042 protocol extensions are enabled (@pxref{multiprocess extensions}), to
36043 detach only a specific process. The @var{pid} is specified as a
36044 big-endian hex string.
36054 @item F @var{RC},@var{EE},@var{CF};@var{XX}
36055 @cindex @samp{F} packet
36056 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
36057 This is part of the File-I/O protocol extension. @xref{File-I/O
36058 Remote Protocol Extension}, for the specification.
36061 @anchor{read registers packet}
36062 @cindex @samp{g} packet
36063 Read general registers.
36067 @item @var{XX@dots{}}
36068 Each byte of register data is described by two hex digits. The bytes
36069 with the register are transmitted in target byte order. The size of
36070 each register and their position within the @samp{g} packet are
36071 determined by the @value{GDBN} internal gdbarch functions
36072 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
36074 When reading registers from a trace frame (@pxref{Analyze Collected
36075 Data,,Using the Collected Data}), the stub may also return a string of
36076 literal @samp{x}'s in place of the register data digits, to indicate
36077 that the corresponding register has not been collected, thus its value
36078 is unavailable. For example, for an architecture with 4 registers of
36079 4 bytes each, the following reply indicates to @value{GDBN} that
36080 registers 0 and 2 have not been collected, while registers 1 and 3
36081 have been collected, and both have zero value:
36085 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
36092 @item G @var{XX@dots{}}
36093 @cindex @samp{G} packet
36094 Write general registers. @xref{read registers packet}, for a
36095 description of the @var{XX@dots{}} data.
36105 @item H @var{op} @var{thread-id}
36106 @cindex @samp{H} packet
36107 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
36108 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
36109 should be @samp{c} for step and continue operations (note that this
36110 is deprecated, supporting the @samp{vCont} command is a better
36111 option), and @samp{g} for other operations. The thread designator
36112 @var{thread-id} has the format and interpretation described in
36113 @ref{thread-id syntax}.
36124 @c 'H': How restrictive (or permissive) is the thread model. If a
36125 @c thread is selected and stopped, are other threads allowed
36126 @c to continue to execute? As I mentioned above, I think the
36127 @c semantics of each command when a thread is selected must be
36128 @c described. For example:
36130 @c 'g': If the stub supports threads and a specific thread is
36131 @c selected, returns the register block from that thread;
36132 @c otherwise returns current registers.
36134 @c 'G' If the stub supports threads and a specific thread is
36135 @c selected, sets the registers of the register block of
36136 @c that thread; otherwise sets current registers.
36138 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
36139 @anchor{cycle step packet}
36140 @cindex @samp{i} packet
36141 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
36142 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
36143 step starting at that address.
36146 @cindex @samp{I} packet
36147 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
36151 @cindex @samp{k} packet
36154 The exact effect of this packet is not specified.
36156 For a bare-metal target, it may power cycle or reset the target
36157 system. For that reason, the @samp{k} packet has no reply.
36159 For a single-process target, it may kill that process if possible.
36161 A multiple-process target may choose to kill just one process, or all
36162 that are under @value{GDBN}'s control. For more precise control, use
36163 the vKill packet (@pxref{vKill packet}).
36165 If the target system immediately closes the connection in response to
36166 @samp{k}, @value{GDBN} does not consider the lack of packet
36167 acknowledgment to be an error, and assumes the kill was successful.
36169 If connected using @kbd{target extended-remote}, and the target does
36170 not close the connection in response to a kill request, @value{GDBN}
36171 probes the target state as if a new connection was opened
36172 (@pxref{? packet}).
36174 @item m @var{addr},@var{length}
36175 @cindex @samp{m} packet
36176 Read @var{length} addressable memory units starting at address @var{addr}
36177 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
36178 any particular boundary.
36180 The stub need not use any particular size or alignment when gathering
36181 data from memory for the response; even if @var{addr} is word-aligned
36182 and @var{length} is a multiple of the word size, the stub is free to
36183 use byte accesses, or not. For this reason, this packet may not be
36184 suitable for accessing memory-mapped I/O devices.
36185 @cindex alignment of remote memory accesses
36186 @cindex size of remote memory accesses
36187 @cindex memory, alignment and size of remote accesses
36191 @item @var{XX@dots{}}
36192 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
36193 The reply may contain fewer addressable memory units than requested if the
36194 server was able to read only part of the region of memory.
36199 @item M @var{addr},@var{length}:@var{XX@dots{}}
36200 @cindex @samp{M} packet
36201 Write @var{length} addressable memory units starting at address @var{addr}
36202 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
36203 byte is transmitted as a two-digit hexadecimal number.
36210 for an error (this includes the case where only part of the data was
36215 @cindex @samp{p} packet
36216 Read the value of register @var{n}; @var{n} is in hex.
36217 @xref{read registers packet}, for a description of how the returned
36218 register value is encoded.
36222 @item @var{XX@dots{}}
36223 the register's value
36227 Indicating an unrecognized @var{query}.
36230 @item P @var{n@dots{}}=@var{r@dots{}}
36231 @anchor{write register packet}
36232 @cindex @samp{P} packet
36233 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
36234 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
36235 digits for each byte in the register (target byte order).
36245 @item q @var{name} @var{params}@dots{}
36246 @itemx Q @var{name} @var{params}@dots{}
36247 @cindex @samp{q} packet
36248 @cindex @samp{Q} packet
36249 General query (@samp{q}) and set (@samp{Q}). These packets are
36250 described fully in @ref{General Query Packets}.
36253 @cindex @samp{r} packet
36254 Reset the entire system.
36256 Don't use this packet; use the @samp{R} packet instead.
36259 @cindex @samp{R} packet
36260 Restart the program being debugged. The @var{XX}, while needed, is ignored.
36261 This packet is only available in extended mode (@pxref{extended mode}).
36263 The @samp{R} packet has no reply.
36265 @item s @r{[}@var{addr}@r{]}
36266 @cindex @samp{s} packet
36267 Single step, resuming at @var{addr}. If
36268 @var{addr} is omitted, resume at same address.
36270 This packet is deprecated for multi-threading support. @xref{vCont
36274 @xref{Stop Reply Packets}, for the reply specifications.
36276 @item S @var{sig}@r{[};@var{addr}@r{]}
36277 @anchor{step with signal packet}
36278 @cindex @samp{S} packet
36279 Step with signal. This is analogous to the @samp{C} packet, but
36280 requests a single-step, rather than a normal resumption of execution.
36282 This packet is deprecated for multi-threading support. @xref{vCont
36286 @xref{Stop Reply Packets}, for the reply specifications.
36288 @item t @var{addr}:@var{PP},@var{MM}
36289 @cindex @samp{t} packet
36290 Search backwards starting at address @var{addr} for a match with pattern
36291 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
36292 There must be at least 3 digits in @var{addr}.
36294 @item T @var{thread-id}
36295 @cindex @samp{T} packet
36296 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
36301 thread is still alive
36307 Packets starting with @samp{v} are identified by a multi-letter name,
36308 up to the first @samp{;} or @samp{?} (or the end of the packet).
36310 @item vAttach;@var{pid}
36311 @cindex @samp{vAttach} packet
36312 Attach to a new process with the specified process ID @var{pid}.
36313 The process ID is a
36314 hexadecimal integer identifying the process. In all-stop mode, all
36315 threads in the attached process are stopped; in non-stop mode, it may be
36316 attached without being stopped if that is supported by the target.
36318 @c In non-stop mode, on a successful vAttach, the stub should set the
36319 @c current thread to a thread of the newly-attached process. After
36320 @c attaching, GDB queries for the attached process's thread ID with qC.
36321 @c Also note that, from a user perspective, whether or not the
36322 @c target is stopped on attach in non-stop mode depends on whether you
36323 @c use the foreground or background version of the attach command, not
36324 @c on what vAttach does; GDB does the right thing with respect to either
36325 @c stopping or restarting threads.
36327 This packet is only available in extended mode (@pxref{extended mode}).
36333 @item @r{Any stop packet}
36334 for success in all-stop mode (@pxref{Stop Reply Packets})
36336 for success in non-stop mode (@pxref{Remote Non-Stop})
36339 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
36340 @cindex @samp{vCont} packet
36341 @anchor{vCont packet}
36342 Resume the inferior, specifying different actions for each thread.
36344 For each inferior thread, the leftmost action with a matching
36345 @var{thread-id} is applied. Threads that don't match any action
36346 remain in their current state. Thread IDs are specified using the
36347 syntax described in @ref{thread-id syntax}. If multiprocess
36348 extensions (@pxref{multiprocess extensions}) are supported, actions
36349 can be specified to match all threads in a process by using the
36350 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
36351 @var{thread-id} matches all threads. Specifying no actions is an
36354 Currently supported actions are:
36360 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
36364 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
36367 @item r @var{start},@var{end}
36368 Step once, and then keep stepping as long as the thread stops at
36369 addresses between @var{start} (inclusive) and @var{end} (exclusive).
36370 The remote stub reports a stop reply when either the thread goes out
36371 of the range or is stopped due to an unrelated reason, such as hitting
36372 a breakpoint. @xref{range stepping}.
36374 If the range is empty (@var{start} == @var{end}), then the action
36375 becomes equivalent to the @samp{s} action. In other words,
36376 single-step once, and report the stop (even if the stepped instruction
36377 jumps to @var{start}).
36379 (A stop reply may be sent at any point even if the PC is still within
36380 the stepping range; for example, it is valid to implement this packet
36381 in a degenerate way as a single instruction step operation.)
36385 The optional argument @var{addr} normally associated with the
36386 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
36387 not supported in @samp{vCont}.
36389 The @samp{t} action is only relevant in non-stop mode
36390 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
36391 A stop reply should be generated for any affected thread not already stopped.
36392 When a thread is stopped by means of a @samp{t} action,
36393 the corresponding stop reply should indicate that the thread has stopped with
36394 signal @samp{0}, regardless of whether the target uses some other signal
36395 as an implementation detail.
36397 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
36398 @samp{r} actions for threads that are already running. Conversely,
36399 the server must ignore @samp{t} actions for threads that are already
36402 @emph{Note:} In non-stop mode, a thread is considered running until
36403 @value{GDBN} acknowleges an asynchronous stop notification for it with
36404 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
36406 The stub must support @samp{vCont} if it reports support for
36407 multiprocess extensions (@pxref{multiprocess extensions}).
36410 @xref{Stop Reply Packets}, for the reply specifications.
36413 @cindex @samp{vCont?} packet
36414 Request a list of actions supported by the @samp{vCont} packet.
36418 @item vCont@r{[};@var{action}@dots{}@r{]}
36419 The @samp{vCont} packet is supported. Each @var{action} is a supported
36420 command in the @samp{vCont} packet.
36422 The @samp{vCont} packet is not supported.
36425 @anchor{vCtrlC packet}
36427 @cindex @samp{vCtrlC} packet
36428 Interrupt remote target as if a control-C was pressed on the remote
36429 terminal. This is the equivalent to reacting to the @code{^C}
36430 (@samp{\003}, the control-C character) character in all-stop mode
36431 while the target is running, except this works in non-stop mode.
36432 @xref{interrupting remote targets}, for more info on the all-stop
36443 @item vFile:@var{operation}:@var{parameter}@dots{}
36444 @cindex @samp{vFile} packet
36445 Perform a file operation on the target system. For details,
36446 see @ref{Host I/O Packets}.
36448 @item vFlashErase:@var{addr},@var{length}
36449 @cindex @samp{vFlashErase} packet
36450 Direct the stub to erase @var{length} bytes of flash starting at
36451 @var{addr}. The region may enclose any number of flash blocks, but
36452 its start and end must fall on block boundaries, as indicated by the
36453 flash block size appearing in the memory map (@pxref{Memory Map
36454 Format}). @value{GDBN} groups flash memory programming operations
36455 together, and sends a @samp{vFlashDone} request after each group; the
36456 stub is allowed to delay erase operation until the @samp{vFlashDone}
36457 packet is received.
36467 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
36468 @cindex @samp{vFlashWrite} packet
36469 Direct the stub to write data to flash address @var{addr}. The data
36470 is passed in binary form using the same encoding as for the @samp{X}
36471 packet (@pxref{Binary Data}). The memory ranges specified by
36472 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
36473 not overlap, and must appear in order of increasing addresses
36474 (although @samp{vFlashErase} packets for higher addresses may already
36475 have been received; the ordering is guaranteed only between
36476 @samp{vFlashWrite} packets). If a packet writes to an address that was
36477 neither erased by a preceding @samp{vFlashErase} packet nor by some other
36478 target-specific method, the results are unpredictable.
36486 for vFlashWrite addressing non-flash memory
36492 @cindex @samp{vFlashDone} packet
36493 Indicate to the stub that flash programming operation is finished.
36494 The stub is permitted to delay or batch the effects of a group of
36495 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
36496 @samp{vFlashDone} packet is received. The contents of the affected
36497 regions of flash memory are unpredictable until the @samp{vFlashDone}
36498 request is completed.
36500 @item vKill;@var{pid}
36501 @cindex @samp{vKill} packet
36502 @anchor{vKill packet}
36503 Kill the process with the specified process ID @var{pid}, which is a
36504 hexadecimal integer identifying the process. This packet is used in
36505 preference to @samp{k} when multiprocess protocol extensions are
36506 supported; see @ref{multiprocess extensions}.
36516 @item vMustReplyEmpty
36517 @cindex @samp{vMustReplyEmpty} packet
36518 The correct reply to an unknown @samp{v} packet is to return the empty
36519 string, however, some older versions of @command{gdbserver} would
36520 incorrectly return @samp{OK} for unknown @samp{v} packets.
36522 The @samp{vMustReplyEmpty} is used as a feature test to check how
36523 @command{gdbserver} handles unknown packets, it is important that this
36524 packet be handled in the same way as other unknown @samp{v} packets.
36525 If this packet is handled differently to other unknown @samp{v}
36526 packets then it is possile that @value{GDBN} may run into problems in
36527 other areas, specifically around use of @samp{vFile:setfs:}.
36529 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
36530 @cindex @samp{vRun} packet
36531 Run the program @var{filename}, passing it each @var{argument} on its
36532 command line. The file and arguments are hex-encoded strings. If
36533 @var{filename} is an empty string, the stub may use a default program
36534 (e.g.@: the last program run). The program is created in the stopped
36537 @c FIXME: What about non-stop mode?
36539 This packet is only available in extended mode (@pxref{extended mode}).
36545 @item @r{Any stop packet}
36546 for success (@pxref{Stop Reply Packets})
36550 @cindex @samp{vStopped} packet
36551 @xref{Notification Packets}.
36553 @item X @var{addr},@var{length}:@var{XX@dots{}}
36555 @cindex @samp{X} packet
36556 Write data to memory, where the data is transmitted in binary.
36557 Memory is specified by its address @var{addr} and number of addressable memory
36558 units @var{length} (@pxref{addressable memory unit});
36559 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
36569 @item z @var{type},@var{addr},@var{kind}
36570 @itemx Z @var{type},@var{addr},@var{kind}
36571 @anchor{insert breakpoint or watchpoint packet}
36572 @cindex @samp{z} packet
36573 @cindex @samp{Z} packets
36574 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
36575 watchpoint starting at address @var{address} of kind @var{kind}.
36577 Each breakpoint and watchpoint packet @var{type} is documented
36580 @emph{Implementation notes: A remote target shall return an empty string
36581 for an unrecognized breakpoint or watchpoint packet @var{type}. A
36582 remote target shall support either both or neither of a given
36583 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
36584 avoid potential problems with duplicate packets, the operations should
36585 be implemented in an idempotent way.}
36587 @item z0,@var{addr},@var{kind}
36588 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
36589 @cindex @samp{z0} packet
36590 @cindex @samp{Z0} packet
36591 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
36592 @var{addr} of type @var{kind}.
36594 A software breakpoint is implemented by replacing the instruction at
36595 @var{addr} with a software breakpoint or trap instruction. The
36596 @var{kind} is target-specific and typically indicates the size of the
36597 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
36598 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
36599 architectures have additional meanings for @var{kind}
36600 (@pxref{Architecture-Specific Protocol Details}); if no
36601 architecture-specific value is being used, it should be @samp{0}.
36602 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
36603 conditional expressions in bytecode form that should be evaluated on
36604 the target's side. These are the conditions that should be taken into
36605 consideration when deciding if the breakpoint trigger should be
36606 reported back to @value{GDBN}.
36608 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
36609 for how to best report a software breakpoint event to @value{GDBN}.
36611 The @var{cond_list} parameter is comprised of a series of expressions,
36612 concatenated without separators. Each expression has the following form:
36616 @item X @var{len},@var{expr}
36617 @var{len} is the length of the bytecode expression and @var{expr} is the
36618 actual conditional expression in bytecode form.
36622 The optional @var{cmd_list} parameter introduces commands that may be
36623 run on the target, rather than being reported back to @value{GDBN}.
36624 The parameter starts with a numeric flag @var{persist}; if the flag is
36625 nonzero, then the breakpoint may remain active and the commands
36626 continue to be run even when @value{GDBN} disconnects from the target.
36627 Following this flag is a series of expressions concatenated with no
36628 separators. Each expression has the following form:
36632 @item X @var{len},@var{expr}
36633 @var{len} is the length of the bytecode expression and @var{expr} is the
36634 actual commands expression in bytecode form.
36638 @emph{Implementation note: It is possible for a target to copy or move
36639 code that contains software breakpoints (e.g., when implementing
36640 overlays). The behavior of this packet, in the presence of such a
36641 target, is not defined.}
36653 @item z1,@var{addr},@var{kind}
36654 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
36655 @cindex @samp{z1} packet
36656 @cindex @samp{Z1} packet
36657 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
36658 address @var{addr}.
36660 A hardware breakpoint is implemented using a mechanism that is not
36661 dependent on being able to modify the target's memory. The
36662 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
36663 same meaning as in @samp{Z0} packets.
36665 @emph{Implementation note: A hardware breakpoint is not affected by code
36678 @item z2,@var{addr},@var{kind}
36679 @itemx Z2,@var{addr},@var{kind}
36680 @cindex @samp{z2} packet
36681 @cindex @samp{Z2} packet
36682 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
36683 The number of bytes to watch is specified by @var{kind}.
36695 @item z3,@var{addr},@var{kind}
36696 @itemx Z3,@var{addr},@var{kind}
36697 @cindex @samp{z3} packet
36698 @cindex @samp{Z3} packet
36699 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
36700 The number of bytes to watch is specified by @var{kind}.
36712 @item z4,@var{addr},@var{kind}
36713 @itemx Z4,@var{addr},@var{kind}
36714 @cindex @samp{z4} packet
36715 @cindex @samp{Z4} packet
36716 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
36717 The number of bytes to watch is specified by @var{kind}.
36731 @node Stop Reply Packets
36732 @section Stop Reply Packets
36733 @cindex stop reply packets
36735 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
36736 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
36737 receive any of the below as a reply. Except for @samp{?}
36738 and @samp{vStopped}, that reply is only returned
36739 when the target halts. In the below the exact meaning of @dfn{signal
36740 number} is defined by the header @file{include/gdb/signals.h} in the
36741 @value{GDBN} source code.
36743 In non-stop mode, the server will simply reply @samp{OK} to commands
36744 such as @samp{vCont}; any stop will be the subject of a future
36745 notification. @xref{Remote Non-Stop}.
36747 As in the description of request packets, we include spaces in the
36748 reply templates for clarity; these are not part of the reply packet's
36749 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
36755 The program received signal number @var{AA} (a two-digit hexadecimal
36756 number). This is equivalent to a @samp{T} response with no
36757 @var{n}:@var{r} pairs.
36759 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
36760 @cindex @samp{T} packet reply
36761 The program received signal number @var{AA} (a two-digit hexadecimal
36762 number). This is equivalent to an @samp{S} response, except that the
36763 @samp{@var{n}:@var{r}} pairs can carry values of important registers
36764 and other information directly in the stop reply packet, reducing
36765 round-trip latency. Single-step and breakpoint traps are reported
36766 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
36770 If @var{n} is a hexadecimal number, it is a register number, and the
36771 corresponding @var{r} gives that register's value. The data @var{r} is a
36772 series of bytes in target byte order, with each byte given by a
36773 two-digit hex number.
36776 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
36777 the stopped thread, as specified in @ref{thread-id syntax}.
36780 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
36781 the core on which the stop event was detected.
36784 If @var{n} is a recognized @dfn{stop reason}, it describes a more
36785 specific event that stopped the target. The currently defined stop
36786 reasons are listed below. The @var{aa} should be @samp{05}, the trap
36787 signal. At most one stop reason should be present.
36790 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
36791 and go on to the next; this allows us to extend the protocol in the
36795 The currently defined stop reasons are:
36801 The packet indicates a watchpoint hit, and @var{r} is the data address, in
36804 @item syscall_entry
36805 @itemx syscall_return
36806 The packet indicates a syscall entry or return, and @var{r} is the
36807 syscall number, in hex.
36809 @cindex shared library events, remote reply
36811 The packet indicates that the loaded libraries have changed.
36812 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
36813 list of loaded libraries. The @var{r} part is ignored.
36815 @cindex replay log events, remote reply
36817 The packet indicates that the target cannot continue replaying
36818 logged execution events, because it has reached the end (or the
36819 beginning when executing backward) of the log. The value of @var{r}
36820 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
36821 for more information.
36824 @anchor{swbreak stop reason}
36825 The packet indicates a software breakpoint instruction was executed,
36826 irrespective of whether it was @value{GDBN} that planted the
36827 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
36828 part must be left empty.
36830 On some architectures, such as x86, at the architecture level, when a
36831 breakpoint instruction executes the program counter points at the
36832 breakpoint address plus an offset. On such targets, the stub is
36833 responsible for adjusting the PC to point back at the breakpoint
36836 This packet should not be sent by default; older @value{GDBN} versions
36837 did not support it. @value{GDBN} requests it, by supplying an
36838 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36839 remote stub must also supply the appropriate @samp{qSupported} feature
36840 indicating support.
36842 This packet is required for correct non-stop mode operation.
36845 The packet indicates the target stopped for a hardware breakpoint.
36846 The @var{r} part must be left empty.
36848 The same remarks about @samp{qSupported} and non-stop mode above
36851 @cindex fork events, remote reply
36853 The packet indicates that @code{fork} was called, and @var{r}
36854 is the thread ID of the new child process. Refer to
36855 @ref{thread-id syntax} for the format of the @var{thread-id}
36856 field. This packet is only applicable to targets that support
36859 This packet should not be sent by default; older @value{GDBN} versions
36860 did not support it. @value{GDBN} requests it, by supplying an
36861 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36862 remote stub must also supply the appropriate @samp{qSupported} feature
36863 indicating support.
36865 @cindex vfork events, remote reply
36867 The packet indicates that @code{vfork} was called, and @var{r}
36868 is the thread ID of the new child process. Refer to
36869 @ref{thread-id syntax} for the format of the @var{thread-id}
36870 field. This packet is only applicable to targets that support
36873 This packet should not be sent by default; older @value{GDBN} versions
36874 did not support it. @value{GDBN} requests it, by supplying an
36875 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36876 remote stub must also supply the appropriate @samp{qSupported} feature
36877 indicating support.
36879 @cindex vforkdone events, remote reply
36881 The packet indicates that a child process created by a vfork
36882 has either called @code{exec} or terminated, so that the
36883 address spaces of the parent and child process are no longer
36884 shared. The @var{r} part is ignored. This packet is only
36885 applicable to targets that support vforkdone events.
36887 This packet should not be sent by default; older @value{GDBN} versions
36888 did not support it. @value{GDBN} requests it, by supplying an
36889 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36890 remote stub must also supply the appropriate @samp{qSupported} feature
36891 indicating support.
36893 @cindex exec events, remote reply
36895 The packet indicates that @code{execve} was called, and @var{r}
36896 is the absolute pathname of the file that was executed, in hex.
36897 This packet is only applicable to targets that support exec events.
36899 This packet should not be sent by default; older @value{GDBN} versions
36900 did not support it. @value{GDBN} requests it, by supplying an
36901 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36902 remote stub must also supply the appropriate @samp{qSupported} feature
36903 indicating support.
36905 @cindex thread create event, remote reply
36906 @anchor{thread create event}
36908 The packet indicates that the thread was just created. The new thread
36909 is stopped until @value{GDBN} sets it running with a resumption packet
36910 (@pxref{vCont packet}). This packet should not be sent by default;
36911 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
36912 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
36913 @var{r} part is ignored.
36918 @itemx W @var{AA} ; process:@var{pid}
36919 The process exited, and @var{AA} is the exit status. This is only
36920 applicable to certain targets.
36922 The second form of the response, including the process ID of the
36923 exited process, can be used only when @value{GDBN} has reported
36924 support for multiprocess protocol extensions; see @ref{multiprocess
36925 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
36929 @itemx X @var{AA} ; process:@var{pid}
36930 The process terminated with signal @var{AA}.
36932 The second form of the response, including the process ID of the
36933 terminated process, can be used only when @value{GDBN} has reported
36934 support for multiprocess protocol extensions; see @ref{multiprocess
36935 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
36938 @anchor{thread exit event}
36939 @cindex thread exit event, remote reply
36940 @item w @var{AA} ; @var{tid}
36942 The thread exited, and @var{AA} is the exit status. This response
36943 should not be sent by default; @value{GDBN} requests it with the
36944 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
36945 @var{AA} is formatted as a big-endian hex string.
36948 There are no resumed threads left in the target. In other words, even
36949 though the process is alive, the last resumed thread has exited. For
36950 example, say the target process has two threads: thread 1 and thread
36951 2. The client leaves thread 1 stopped, and resumes thread 2, which
36952 subsequently exits. At this point, even though the process is still
36953 alive, and thus no @samp{W} stop reply is sent, no thread is actually
36954 executing either. The @samp{N} stop reply thus informs the client
36955 that it can stop waiting for stop replies. This packet should not be
36956 sent by default; older @value{GDBN} versions did not support it.
36957 @value{GDBN} requests it, by supplying an appropriate
36958 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
36959 also supply the appropriate @samp{qSupported} feature indicating
36962 @item O @var{XX}@dots{}
36963 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
36964 written as the program's console output. This can happen at any time
36965 while the program is running and the debugger should continue to wait
36966 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
36968 @item F @var{call-id},@var{parameter}@dots{}
36969 @var{call-id} is the identifier which says which host system call should
36970 be called. This is just the name of the function. Translation into the
36971 correct system call is only applicable as it's defined in @value{GDBN}.
36972 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
36975 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
36976 this very system call.
36978 The target replies with this packet when it expects @value{GDBN} to
36979 call a host system call on behalf of the target. @value{GDBN} replies
36980 with an appropriate @samp{F} packet and keeps up waiting for the next
36981 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
36982 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
36983 Protocol Extension}, for more details.
36987 @node General Query Packets
36988 @section General Query Packets
36989 @cindex remote query requests
36991 Packets starting with @samp{q} are @dfn{general query packets};
36992 packets starting with @samp{Q} are @dfn{general set packets}. General
36993 query and set packets are a semi-unified form for retrieving and
36994 sending information to and from the stub.
36996 The initial letter of a query or set packet is followed by a name
36997 indicating what sort of thing the packet applies to. For example,
36998 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
36999 definitions with the stub. These packet names follow some
37004 The name must not contain commas, colons or semicolons.
37006 Most @value{GDBN} query and set packets have a leading upper case
37009 The names of custom vendor packets should use a company prefix, in
37010 lower case, followed by a period. For example, packets designed at
37011 the Acme Corporation might begin with @samp{qacme.foo} (for querying
37012 foos) or @samp{Qacme.bar} (for setting bars).
37015 The name of a query or set packet should be separated from any
37016 parameters by a @samp{:}; the parameters themselves should be
37017 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
37018 full packet name, and check for a separator or the end of the packet,
37019 in case two packet names share a common prefix. New packets should not begin
37020 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
37021 packets predate these conventions, and have arguments without any terminator
37022 for the packet name; we suspect they are in widespread use in places that
37023 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
37024 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
37027 Like the descriptions of the other packets, each description here
37028 has a template showing the packet's overall syntax, followed by an
37029 explanation of the packet's meaning. We include spaces in some of the
37030 templates for clarity; these are not part of the packet's syntax. No
37031 @value{GDBN} packet uses spaces to separate its components.
37033 Here are the currently defined query and set packets:
37039 Turn on or off the agent as a helper to perform some debugging operations
37040 delegated from @value{GDBN} (@pxref{Control Agent}).
37042 @item QAllow:@var{op}:@var{val}@dots{}
37043 @cindex @samp{QAllow} packet
37044 Specify which operations @value{GDBN} expects to request of the
37045 target, as a semicolon-separated list of operation name and value
37046 pairs. Possible values for @var{op} include @samp{WriteReg},
37047 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
37048 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
37049 indicating that @value{GDBN} will not request the operation, or 1,
37050 indicating that it may. (The target can then use this to set up its
37051 own internals optimally, for instance if the debugger never expects to
37052 insert breakpoints, it may not need to install its own trap handler.)
37055 @cindex current thread, remote request
37056 @cindex @samp{qC} packet
37057 Return the current thread ID.
37061 @item QC @var{thread-id}
37062 Where @var{thread-id} is a thread ID as documented in
37063 @ref{thread-id syntax}.
37064 @item @r{(anything else)}
37065 Any other reply implies the old thread ID.
37068 @item qCRC:@var{addr},@var{length}
37069 @cindex CRC of memory block, remote request
37070 @cindex @samp{qCRC} packet
37071 @anchor{qCRC packet}
37072 Compute the CRC checksum of a block of memory using CRC-32 defined in
37073 IEEE 802.3. The CRC is computed byte at a time, taking the most
37074 significant bit of each byte first. The initial pattern code
37075 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
37077 @emph{Note:} This is the same CRC used in validating separate debug
37078 files (@pxref{Separate Debug Files, , Debugging Information in Separate
37079 Files}). However the algorithm is slightly different. When validating
37080 separate debug files, the CRC is computed taking the @emph{least}
37081 significant bit of each byte first, and the final result is inverted to
37082 detect trailing zeros.
37087 An error (such as memory fault)
37088 @item C @var{crc32}
37089 The specified memory region's checksum is @var{crc32}.
37092 @item QDisableRandomization:@var{value}
37093 @cindex disable address space randomization, remote request
37094 @cindex @samp{QDisableRandomization} packet
37095 Some target operating systems will randomize the virtual address space
37096 of the inferior process as a security feature, but provide a feature
37097 to disable such randomization, e.g.@: to allow for a more deterministic
37098 debugging experience. On such systems, this packet with a @var{value}
37099 of 1 directs the target to disable address space randomization for
37100 processes subsequently started via @samp{vRun} packets, while a packet
37101 with a @var{value} of 0 tells the target to enable address space
37104 This packet is only available in extended mode (@pxref{extended mode}).
37109 The request succeeded.
37112 An error occurred. The error number @var{nn} is given as hex digits.
37115 An empty reply indicates that @samp{QDisableRandomization} is not supported
37119 This packet is not probed by default; the remote stub must request it,
37120 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37121 This should only be done on targets that actually support disabling
37122 address space randomization.
37124 @item QStartupWithShell:@var{value}
37125 @cindex startup with shell, remote request
37126 @cindex @samp{QStartupWithShell} packet
37127 On UNIX-like targets, it is possible to start the inferior using a
37128 shell program. This is the default behavior on both @value{GDBN} and
37129 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
37130 used to inform @command{gdbserver} whether it should start the
37131 inferior using a shell or not.
37133 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
37134 to start the inferior. If @var{value} is @samp{1},
37135 @command{gdbserver} will use a shell to start the inferior. All other
37136 values are considered an error.
37138 This packet is only available in extended mode (@pxref{extended
37144 The request succeeded.
37147 An error occurred. The error number @var{nn} is given as hex digits.
37150 This packet is not probed by default; the remote stub must request it,
37151 by supplying an appropriate @samp{qSupported} response
37152 (@pxref{qSupported}). This should only be done on targets that
37153 actually support starting the inferior using a shell.
37155 Use of this packet is controlled by the @code{set startup-with-shell}
37156 command; @pxref{set startup-with-shell}.
37158 @item QEnvironmentHexEncoded:@var{hex-value}
37159 @anchor{QEnvironmentHexEncoded}
37160 @cindex set environment variable, remote request
37161 @cindex @samp{QEnvironmentHexEncoded} packet
37162 On UNIX-like targets, it is possible to set environment variables that
37163 will be passed to the inferior during the startup process. This
37164 packet is used to inform @command{gdbserver} of an environment
37165 variable that has been defined by the user on @value{GDBN} (@pxref{set
37168 The packet is composed by @var{hex-value}, an hex encoded
37169 representation of the @var{name=value} format representing an
37170 environment variable. The name of the environment variable is
37171 represented by @var{name}, and the value to be assigned to the
37172 environment variable is represented by @var{value}. If the variable
37173 has no value (i.e., the value is @code{null}), then @var{value} will
37176 This packet is only available in extended mode (@pxref{extended
37182 The request succeeded.
37185 This packet is not probed by default; the remote stub must request it,
37186 by supplying an appropriate @samp{qSupported} response
37187 (@pxref{qSupported}). This should only be done on targets that
37188 actually support passing environment variables to the starting
37191 This packet is related to the @code{set environment} command;
37192 @pxref{set environment}.
37194 @item QEnvironmentUnset:@var{hex-value}
37195 @anchor{QEnvironmentUnset}
37196 @cindex unset environment variable, remote request
37197 @cindex @samp{QEnvironmentUnset} packet
37198 On UNIX-like targets, it is possible to unset environment variables
37199 before starting the inferior in the remote target. This packet is
37200 used to inform @command{gdbserver} of an environment variable that has
37201 been unset by the user on @value{GDBN} (@pxref{unset environment}).
37203 The packet is composed by @var{hex-value}, an hex encoded
37204 representation of the name of the environment variable to be unset.
37206 This packet is only available in extended mode (@pxref{extended
37212 The request succeeded.
37215 This packet is not probed by default; the remote stub must request it,
37216 by supplying an appropriate @samp{qSupported} response
37217 (@pxref{qSupported}). This should only be done on targets that
37218 actually support passing environment variables to the starting
37221 This packet is related to the @code{unset environment} command;
37222 @pxref{unset environment}.
37224 @item QEnvironmentReset
37225 @anchor{QEnvironmentReset}
37226 @cindex reset environment, remote request
37227 @cindex @samp{QEnvironmentReset} packet
37228 On UNIX-like targets, this packet is used to reset the state of
37229 environment variables in the remote target before starting the
37230 inferior. In this context, reset means unsetting all environment
37231 variables that were previously set by the user (i.e., were not
37232 initially present in the environment). It is sent to
37233 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
37234 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
37235 (@pxref{QEnvironmentUnset}) packets.
37237 This packet is only available in extended mode (@pxref{extended
37243 The request succeeded.
37246 This packet is not probed by default; the remote stub must request it,
37247 by supplying an appropriate @samp{qSupported} response
37248 (@pxref{qSupported}). This should only be done on targets that
37249 actually support passing environment variables to the starting
37252 @item QSetWorkingDir:@r{[}@var{directory}@r{]}
37253 @anchor{QSetWorkingDir packet}
37254 @cindex set working directory, remote request
37255 @cindex @samp{QSetWorkingDir} packet
37256 This packet is used to inform the remote server of the intended
37257 current working directory for programs that are going to be executed.
37259 The packet is composed by @var{directory}, an hex encoded
37260 representation of the directory that the remote inferior will use as
37261 its current working directory. If @var{directory} is an empty string,
37262 the remote server should reset the inferior's current working
37263 directory to its original, empty value.
37265 This packet is only available in extended mode (@pxref{extended
37271 The request succeeded.
37275 @itemx qsThreadInfo
37276 @cindex list active threads, remote request
37277 @cindex @samp{qfThreadInfo} packet
37278 @cindex @samp{qsThreadInfo} packet
37279 Obtain a list of all active thread IDs from the target (OS). Since there
37280 may be too many active threads to fit into one reply packet, this query
37281 works iteratively: it may require more than one query/reply sequence to
37282 obtain the entire list of threads. The first query of the sequence will
37283 be the @samp{qfThreadInfo} query; subsequent queries in the
37284 sequence will be the @samp{qsThreadInfo} query.
37286 NOTE: This packet replaces the @samp{qL} query (see below).
37290 @item m @var{thread-id}
37292 @item m @var{thread-id},@var{thread-id}@dots{}
37293 a comma-separated list of thread IDs
37295 (lower case letter @samp{L}) denotes end of list.
37298 In response to each query, the target will reply with a list of one or
37299 more thread IDs, separated by commas.
37300 @value{GDBN} will respond to each reply with a request for more thread
37301 ids (using the @samp{qs} form of the query), until the target responds
37302 with @samp{l} (lower-case ell, for @dfn{last}).
37303 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
37306 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
37307 initial connection with the remote target, and the very first thread ID
37308 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
37309 message. Therefore, the stub should ensure that the first thread ID in
37310 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
37312 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
37313 @cindex get thread-local storage address, remote request
37314 @cindex @samp{qGetTLSAddr} packet
37315 Fetch the address associated with thread local storage specified
37316 by @var{thread-id}, @var{offset}, and @var{lm}.
37318 @var{thread-id} is the thread ID associated with the
37319 thread for which to fetch the TLS address. @xref{thread-id syntax}.
37321 @var{offset} is the (big endian, hex encoded) offset associated with the
37322 thread local variable. (This offset is obtained from the debug
37323 information associated with the variable.)
37325 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
37326 load module associated with the thread local storage. For example,
37327 a @sc{gnu}/Linux system will pass the link map address of the shared
37328 object associated with the thread local storage under consideration.
37329 Other operating environments may choose to represent the load module
37330 differently, so the precise meaning of this parameter will vary.
37334 @item @var{XX}@dots{}
37335 Hex encoded (big endian) bytes representing the address of the thread
37336 local storage requested.
37339 An error occurred. The error number @var{nn} is given as hex digits.
37342 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
37345 @item qGetTIBAddr:@var{thread-id}
37346 @cindex get thread information block address
37347 @cindex @samp{qGetTIBAddr} packet
37348 Fetch address of the Windows OS specific Thread Information Block.
37350 @var{thread-id} is the thread ID associated with the thread.
37354 @item @var{XX}@dots{}
37355 Hex encoded (big endian) bytes representing the linear address of the
37356 thread information block.
37359 An error occured. This means that either the thread was not found, or the
37360 address could not be retrieved.
37363 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
37366 @item qL @var{startflag} @var{threadcount} @var{nextthread}
37367 Obtain thread information from RTOS. Where: @var{startflag} (one hex
37368 digit) is one to indicate the first query and zero to indicate a
37369 subsequent query; @var{threadcount} (two hex digits) is the maximum
37370 number of threads the response packet can contain; and @var{nextthread}
37371 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
37372 returned in the response as @var{argthread}.
37374 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
37378 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
37379 Where: @var{count} (two hex digits) is the number of threads being
37380 returned; @var{done} (one hex digit) is zero to indicate more threads
37381 and one indicates no further threads; @var{argthreadid} (eight hex
37382 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
37383 is a sequence of thread IDs, @var{threadid} (eight hex
37384 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
37388 @cindex section offsets, remote request
37389 @cindex @samp{qOffsets} packet
37390 Get section offsets that the target used when relocating the downloaded
37395 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
37396 Relocate the @code{Text} section by @var{xxx} from its original address.
37397 Relocate the @code{Data} section by @var{yyy} from its original address.
37398 If the object file format provides segment information (e.g.@: @sc{elf}
37399 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
37400 segments by the supplied offsets.
37402 @emph{Note: while a @code{Bss} offset may be included in the response,
37403 @value{GDBN} ignores this and instead applies the @code{Data} offset
37404 to the @code{Bss} section.}
37406 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
37407 Relocate the first segment of the object file, which conventionally
37408 contains program code, to a starting address of @var{xxx}. If
37409 @samp{DataSeg} is specified, relocate the second segment, which
37410 conventionally contains modifiable data, to a starting address of
37411 @var{yyy}. @value{GDBN} will report an error if the object file
37412 does not contain segment information, or does not contain at least
37413 as many segments as mentioned in the reply. Extra segments are
37414 kept at fixed offsets relative to the last relocated segment.
37417 @item qP @var{mode} @var{thread-id}
37418 @cindex thread information, remote request
37419 @cindex @samp{qP} packet
37420 Returns information on @var{thread-id}. Where: @var{mode} is a hex
37421 encoded 32 bit mode; @var{thread-id} is a thread ID
37422 (@pxref{thread-id syntax}).
37424 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
37427 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
37431 @cindex non-stop mode, remote request
37432 @cindex @samp{QNonStop} packet
37434 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
37435 @xref{Remote Non-Stop}, for more information.
37440 The request succeeded.
37443 An error occurred. The error number @var{nn} is given as hex digits.
37446 An empty reply indicates that @samp{QNonStop} is not supported by
37450 This packet is not probed by default; the remote stub must request it,
37451 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37452 Use of this packet is controlled by the @code{set non-stop} command;
37453 @pxref{Non-Stop Mode}.
37455 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
37456 @itemx QCatchSyscalls:0
37457 @cindex catch syscalls from inferior, remote request
37458 @cindex @samp{QCatchSyscalls} packet
37459 @anchor{QCatchSyscalls}
37460 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
37461 catching syscalls from the inferior process.
37463 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
37464 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
37465 is listed, every system call should be reported.
37467 Note that if a syscall not in the list is reported, @value{GDBN} will
37468 still filter the event according to its own list from all corresponding
37469 @code{catch syscall} commands. However, it is more efficient to only
37470 report the requested syscalls.
37472 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
37473 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
37475 If the inferior process execs, the state of @samp{QCatchSyscalls} is
37476 kept for the new process too. On targets where exec may affect syscall
37477 numbers, for example with exec between 32 and 64-bit processes, the
37478 client should send a new packet with the new syscall list.
37483 The request succeeded.
37486 An error occurred. @var{nn} are hex digits.
37489 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
37493 Use of this packet is controlled by the @code{set remote catch-syscalls}
37494 command (@pxref{Remote Configuration, set remote catch-syscalls}).
37495 This packet is not probed by default; the remote stub must request it,
37496 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37498 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37499 @cindex pass signals to inferior, remote request
37500 @cindex @samp{QPassSignals} packet
37501 @anchor{QPassSignals}
37502 Each listed @var{signal} should be passed directly to the inferior process.
37503 Signals are numbered identically to continue packets and stop replies
37504 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37505 strictly greater than the previous item. These signals do not need to stop
37506 the inferior, or be reported to @value{GDBN}. All other signals should be
37507 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
37508 combine; any earlier @samp{QPassSignals} list is completely replaced by the
37509 new list. This packet improves performance when using @samp{handle
37510 @var{signal} nostop noprint pass}.
37515 The request succeeded.
37518 An error occurred. The error number @var{nn} is given as hex digits.
37521 An empty reply indicates that @samp{QPassSignals} is not supported by
37525 Use of this packet is controlled by the @code{set remote pass-signals}
37526 command (@pxref{Remote Configuration, set remote pass-signals}).
37527 This packet is not probed by default; the remote stub must request it,
37528 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37530 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37531 @cindex signals the inferior may see, remote request
37532 @cindex @samp{QProgramSignals} packet
37533 @anchor{QProgramSignals}
37534 Each listed @var{signal} may be delivered to the inferior process.
37535 Others should be silently discarded.
37537 In some cases, the remote stub may need to decide whether to deliver a
37538 signal to the program or not without @value{GDBN} involvement. One
37539 example of that is while detaching --- the program's threads may have
37540 stopped for signals that haven't yet had a chance of being reported to
37541 @value{GDBN}, and so the remote stub can use the signal list specified
37542 by this packet to know whether to deliver or ignore those pending
37545 This does not influence whether to deliver a signal as requested by a
37546 resumption packet (@pxref{vCont packet}).
37548 Signals are numbered identically to continue packets and stop replies
37549 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37550 strictly greater than the previous item. Multiple
37551 @samp{QProgramSignals} packets do not combine; any earlier
37552 @samp{QProgramSignals} list is completely replaced by the new list.
37557 The request succeeded.
37560 An error occurred. The error number @var{nn} is given as hex digits.
37563 An empty reply indicates that @samp{QProgramSignals} is not supported
37567 Use of this packet is controlled by the @code{set remote program-signals}
37568 command (@pxref{Remote Configuration, set remote program-signals}).
37569 This packet is not probed by default; the remote stub must request it,
37570 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37572 @anchor{QThreadEvents}
37573 @item QThreadEvents:1
37574 @itemx QThreadEvents:0
37575 @cindex thread create/exit events, remote request
37576 @cindex @samp{QThreadEvents} packet
37578 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
37579 reporting of thread create and exit events. @xref{thread create
37580 event}, for the reply specifications. For example, this is used in
37581 non-stop mode when @value{GDBN} stops a set of threads and
37582 synchronously waits for the their corresponding stop replies. Without
37583 exit events, if one of the threads exits, @value{GDBN} would hang
37584 forever not knowing that it should no longer expect a stop for that
37585 same thread. @value{GDBN} does not enable this feature unless the
37586 stub reports that it supports it by including @samp{QThreadEvents+} in
37587 its @samp{qSupported} reply.
37592 The request succeeded.
37595 An error occurred. The error number @var{nn} is given as hex digits.
37598 An empty reply indicates that @samp{QThreadEvents} is not supported by
37602 Use of this packet is controlled by the @code{set remote thread-events}
37603 command (@pxref{Remote Configuration, set remote thread-events}).
37605 @item qRcmd,@var{command}
37606 @cindex execute remote command, remote request
37607 @cindex @samp{qRcmd} packet
37608 @var{command} (hex encoded) is passed to the local interpreter for
37609 execution. Invalid commands should be reported using the output
37610 string. Before the final result packet, the target may also respond
37611 with a number of intermediate @samp{O@var{output}} console output
37612 packets. @emph{Implementors should note that providing access to a
37613 stubs's interpreter may have security implications}.
37618 A command response with no output.
37620 A command response with the hex encoded output string @var{OUTPUT}.
37622 Indicate a badly formed request.
37624 An empty reply indicates that @samp{qRcmd} is not recognized.
37627 (Note that the @code{qRcmd} packet's name is separated from the
37628 command by a @samp{,}, not a @samp{:}, contrary to the naming
37629 conventions above. Please don't use this packet as a model for new
37632 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
37633 @cindex searching memory, in remote debugging
37635 @cindex @samp{qSearch:memory} packet
37637 @cindex @samp{qSearch memory} packet
37638 @anchor{qSearch memory}
37639 Search @var{length} bytes at @var{address} for @var{search-pattern}.
37640 Both @var{address} and @var{length} are encoded in hex;
37641 @var{search-pattern} is a sequence of bytes, also hex encoded.
37646 The pattern was not found.
37648 The pattern was found at @var{address}.
37650 A badly formed request or an error was encountered while searching memory.
37652 An empty reply indicates that @samp{qSearch:memory} is not recognized.
37655 @item QStartNoAckMode
37656 @cindex @samp{QStartNoAckMode} packet
37657 @anchor{QStartNoAckMode}
37658 Request that the remote stub disable the normal @samp{+}/@samp{-}
37659 protocol acknowledgments (@pxref{Packet Acknowledgment}).
37664 The stub has switched to no-acknowledgment mode.
37665 @value{GDBN} acknowledges this reponse,
37666 but neither the stub nor @value{GDBN} shall send or expect further
37667 @samp{+}/@samp{-} acknowledgments in the current connection.
37669 An empty reply indicates that the stub does not support no-acknowledgment mode.
37672 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
37673 @cindex supported packets, remote query
37674 @cindex features of the remote protocol
37675 @cindex @samp{qSupported} packet
37676 @anchor{qSupported}
37677 Tell the remote stub about features supported by @value{GDBN}, and
37678 query the stub for features it supports. This packet allows
37679 @value{GDBN} and the remote stub to take advantage of each others'
37680 features. @samp{qSupported} also consolidates multiple feature probes
37681 at startup, to improve @value{GDBN} performance---a single larger
37682 packet performs better than multiple smaller probe packets on
37683 high-latency links. Some features may enable behavior which must not
37684 be on by default, e.g.@: because it would confuse older clients or
37685 stubs. Other features may describe packets which could be
37686 automatically probed for, but are not. These features must be
37687 reported before @value{GDBN} will use them. This ``default
37688 unsupported'' behavior is not appropriate for all packets, but it
37689 helps to keep the initial connection time under control with new
37690 versions of @value{GDBN} which support increasing numbers of packets.
37694 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
37695 The stub supports or does not support each returned @var{stubfeature},
37696 depending on the form of each @var{stubfeature} (see below for the
37699 An empty reply indicates that @samp{qSupported} is not recognized,
37700 or that no features needed to be reported to @value{GDBN}.
37703 The allowed forms for each feature (either a @var{gdbfeature} in the
37704 @samp{qSupported} packet, or a @var{stubfeature} in the response)
37708 @item @var{name}=@var{value}
37709 The remote protocol feature @var{name} is supported, and associated
37710 with the specified @var{value}. The format of @var{value} depends
37711 on the feature, but it must not include a semicolon.
37713 The remote protocol feature @var{name} is supported, and does not
37714 need an associated value.
37716 The remote protocol feature @var{name} is not supported.
37718 The remote protocol feature @var{name} may be supported, and
37719 @value{GDBN} should auto-detect support in some other way when it is
37720 needed. This form will not be used for @var{gdbfeature} notifications,
37721 but may be used for @var{stubfeature} responses.
37724 Whenever the stub receives a @samp{qSupported} request, the
37725 supplied set of @value{GDBN} features should override any previous
37726 request. This allows @value{GDBN} to put the stub in a known
37727 state, even if the stub had previously been communicating with
37728 a different version of @value{GDBN}.
37730 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
37735 This feature indicates whether @value{GDBN} supports multiprocess
37736 extensions to the remote protocol. @value{GDBN} does not use such
37737 extensions unless the stub also reports that it supports them by
37738 including @samp{multiprocess+} in its @samp{qSupported} reply.
37739 @xref{multiprocess extensions}, for details.
37742 This feature indicates that @value{GDBN} supports the XML target
37743 description. If the stub sees @samp{xmlRegisters=} with target
37744 specific strings separated by a comma, it will report register
37748 This feature indicates whether @value{GDBN} supports the
37749 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
37750 instruction reply packet}).
37753 This feature indicates whether @value{GDBN} supports the swbreak stop
37754 reason in stop replies. @xref{swbreak stop reason}, for details.
37757 This feature indicates whether @value{GDBN} supports the hwbreak stop
37758 reason in stop replies. @xref{swbreak stop reason}, for details.
37761 This feature indicates whether @value{GDBN} supports fork event
37762 extensions to the remote protocol. @value{GDBN} does not use such
37763 extensions unless the stub also reports that it supports them by
37764 including @samp{fork-events+} in its @samp{qSupported} reply.
37767 This feature indicates whether @value{GDBN} supports vfork event
37768 extensions to the remote protocol. @value{GDBN} does not use such
37769 extensions unless the stub also reports that it supports them by
37770 including @samp{vfork-events+} in its @samp{qSupported} reply.
37773 This feature indicates whether @value{GDBN} supports exec event
37774 extensions to the remote protocol. @value{GDBN} does not use such
37775 extensions unless the stub also reports that it supports them by
37776 including @samp{exec-events+} in its @samp{qSupported} reply.
37778 @item vContSupported
37779 This feature indicates whether @value{GDBN} wants to know the
37780 supported actions in the reply to @samp{vCont?} packet.
37783 Stubs should ignore any unknown values for
37784 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
37785 packet supports receiving packets of unlimited length (earlier
37786 versions of @value{GDBN} may reject overly long responses). Additional values
37787 for @var{gdbfeature} may be defined in the future to let the stub take
37788 advantage of new features in @value{GDBN}, e.g.@: incompatible
37789 improvements in the remote protocol---the @samp{multiprocess} feature is
37790 an example of such a feature. The stub's reply should be independent
37791 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
37792 describes all the features it supports, and then the stub replies with
37793 all the features it supports.
37795 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
37796 responses, as long as each response uses one of the standard forms.
37798 Some features are flags. A stub which supports a flag feature
37799 should respond with a @samp{+} form response. Other features
37800 require values, and the stub should respond with an @samp{=}
37803 Each feature has a default value, which @value{GDBN} will use if
37804 @samp{qSupported} is not available or if the feature is not mentioned
37805 in the @samp{qSupported} response. The default values are fixed; a
37806 stub is free to omit any feature responses that match the defaults.
37808 Not all features can be probed, but for those which can, the probing
37809 mechanism is useful: in some cases, a stub's internal
37810 architecture may not allow the protocol layer to know some information
37811 about the underlying target in advance. This is especially common in
37812 stubs which may be configured for multiple targets.
37814 These are the currently defined stub features and their properties:
37816 @multitable @columnfractions 0.35 0.2 0.12 0.2
37817 @c NOTE: The first row should be @headitem, but we do not yet require
37818 @c a new enough version of Texinfo (4.7) to use @headitem.
37820 @tab Value Required
37824 @item @samp{PacketSize}
37829 @item @samp{qXfer:auxv:read}
37834 @item @samp{qXfer:btrace:read}
37839 @item @samp{qXfer:btrace-conf:read}
37844 @item @samp{qXfer:exec-file:read}
37849 @item @samp{qXfer:features:read}
37854 @item @samp{qXfer:libraries:read}
37859 @item @samp{qXfer:libraries-svr4:read}
37864 @item @samp{augmented-libraries-svr4-read}
37869 @item @samp{qXfer:memory-map:read}
37874 @item @samp{qXfer:sdata:read}
37879 @item @samp{qXfer:spu:read}
37884 @item @samp{qXfer:spu:write}
37889 @item @samp{qXfer:siginfo:read}
37894 @item @samp{qXfer:siginfo:write}
37899 @item @samp{qXfer:threads:read}
37904 @item @samp{qXfer:traceframe-info:read}
37909 @item @samp{qXfer:uib:read}
37914 @item @samp{qXfer:fdpic:read}
37919 @item @samp{Qbtrace:off}
37924 @item @samp{Qbtrace:bts}
37929 @item @samp{Qbtrace:pt}
37934 @item @samp{Qbtrace-conf:bts:size}
37939 @item @samp{Qbtrace-conf:pt:size}
37944 @item @samp{QNonStop}
37949 @item @samp{QCatchSyscalls}
37954 @item @samp{QPassSignals}
37959 @item @samp{QStartNoAckMode}
37964 @item @samp{multiprocess}
37969 @item @samp{ConditionalBreakpoints}
37974 @item @samp{ConditionalTracepoints}
37979 @item @samp{ReverseContinue}
37984 @item @samp{ReverseStep}
37989 @item @samp{TracepointSource}
37994 @item @samp{QAgent}
37999 @item @samp{QAllow}
38004 @item @samp{QDisableRandomization}
38009 @item @samp{EnableDisableTracepoints}
38014 @item @samp{QTBuffer:size}
38019 @item @samp{tracenz}
38024 @item @samp{BreakpointCommands}
38029 @item @samp{swbreak}
38034 @item @samp{hwbreak}
38039 @item @samp{fork-events}
38044 @item @samp{vfork-events}
38049 @item @samp{exec-events}
38054 @item @samp{QThreadEvents}
38059 @item @samp{no-resumed}
38066 These are the currently defined stub features, in more detail:
38069 @cindex packet size, remote protocol
38070 @item PacketSize=@var{bytes}
38071 The remote stub can accept packets up to at least @var{bytes} in
38072 length. @value{GDBN} will send packets up to this size for bulk
38073 transfers, and will never send larger packets. This is a limit on the
38074 data characters in the packet, including the frame and checksum.
38075 There is no trailing NUL byte in a remote protocol packet; if the stub
38076 stores packets in a NUL-terminated format, it should allow an extra
38077 byte in its buffer for the NUL. If this stub feature is not supported,
38078 @value{GDBN} guesses based on the size of the @samp{g} packet response.
38080 @item qXfer:auxv:read
38081 The remote stub understands the @samp{qXfer:auxv:read} packet
38082 (@pxref{qXfer auxiliary vector read}).
38084 @item qXfer:btrace:read
38085 The remote stub understands the @samp{qXfer:btrace:read}
38086 packet (@pxref{qXfer btrace read}).
38088 @item qXfer:btrace-conf:read
38089 The remote stub understands the @samp{qXfer:btrace-conf:read}
38090 packet (@pxref{qXfer btrace-conf read}).
38092 @item qXfer:exec-file:read
38093 The remote stub understands the @samp{qXfer:exec-file:read} packet
38094 (@pxref{qXfer executable filename read}).
38096 @item qXfer:features:read
38097 The remote stub understands the @samp{qXfer:features:read} packet
38098 (@pxref{qXfer target description read}).
38100 @item qXfer:libraries:read
38101 The remote stub understands the @samp{qXfer:libraries:read} packet
38102 (@pxref{qXfer library list read}).
38104 @item qXfer:libraries-svr4:read
38105 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
38106 (@pxref{qXfer svr4 library list read}).
38108 @item augmented-libraries-svr4-read
38109 The remote stub understands the augmented form of the
38110 @samp{qXfer:libraries-svr4:read} packet
38111 (@pxref{qXfer svr4 library list read}).
38113 @item qXfer:memory-map:read
38114 The remote stub understands the @samp{qXfer:memory-map:read} packet
38115 (@pxref{qXfer memory map read}).
38117 @item qXfer:sdata:read
38118 The remote stub understands the @samp{qXfer:sdata:read} packet
38119 (@pxref{qXfer sdata read}).
38121 @item qXfer:spu:read
38122 The remote stub understands the @samp{qXfer:spu:read} packet
38123 (@pxref{qXfer spu read}).
38125 @item qXfer:spu:write
38126 The remote stub understands the @samp{qXfer:spu:write} packet
38127 (@pxref{qXfer spu write}).
38129 @item qXfer:siginfo:read
38130 The remote stub understands the @samp{qXfer:siginfo:read} packet
38131 (@pxref{qXfer siginfo read}).
38133 @item qXfer:siginfo:write
38134 The remote stub understands the @samp{qXfer:siginfo:write} packet
38135 (@pxref{qXfer siginfo write}).
38137 @item qXfer:threads:read
38138 The remote stub understands the @samp{qXfer:threads:read} packet
38139 (@pxref{qXfer threads read}).
38141 @item qXfer:traceframe-info:read
38142 The remote stub understands the @samp{qXfer:traceframe-info:read}
38143 packet (@pxref{qXfer traceframe info read}).
38145 @item qXfer:uib:read
38146 The remote stub understands the @samp{qXfer:uib:read}
38147 packet (@pxref{qXfer unwind info block}).
38149 @item qXfer:fdpic:read
38150 The remote stub understands the @samp{qXfer:fdpic:read}
38151 packet (@pxref{qXfer fdpic loadmap read}).
38154 The remote stub understands the @samp{QNonStop} packet
38155 (@pxref{QNonStop}).
38157 @item QCatchSyscalls
38158 The remote stub understands the @samp{QCatchSyscalls} packet
38159 (@pxref{QCatchSyscalls}).
38162 The remote stub understands the @samp{QPassSignals} packet
38163 (@pxref{QPassSignals}).
38165 @item QStartNoAckMode
38166 The remote stub understands the @samp{QStartNoAckMode} packet and
38167 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
38170 @anchor{multiprocess extensions}
38171 @cindex multiprocess extensions, in remote protocol
38172 The remote stub understands the multiprocess extensions to the remote
38173 protocol syntax. The multiprocess extensions affect the syntax of
38174 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
38175 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
38176 replies. Note that reporting this feature indicates support for the
38177 syntactic extensions only, not that the stub necessarily supports
38178 debugging of more than one process at a time. The stub must not use
38179 multiprocess extensions in packet replies unless @value{GDBN} has also
38180 indicated it supports them in its @samp{qSupported} request.
38182 @item qXfer:osdata:read
38183 The remote stub understands the @samp{qXfer:osdata:read} packet
38184 ((@pxref{qXfer osdata read}).
38186 @item ConditionalBreakpoints
38187 The target accepts and implements evaluation of conditional expressions
38188 defined for breakpoints. The target will only report breakpoint triggers
38189 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
38191 @item ConditionalTracepoints
38192 The remote stub accepts and implements conditional expressions defined
38193 for tracepoints (@pxref{Tracepoint Conditions}).
38195 @item ReverseContinue
38196 The remote stub accepts and implements the reverse continue packet
38200 The remote stub accepts and implements the reverse step packet
38203 @item TracepointSource
38204 The remote stub understands the @samp{QTDPsrc} packet that supplies
38205 the source form of tracepoint definitions.
38208 The remote stub understands the @samp{QAgent} packet.
38211 The remote stub understands the @samp{QAllow} packet.
38213 @item QDisableRandomization
38214 The remote stub understands the @samp{QDisableRandomization} packet.
38216 @item StaticTracepoint
38217 @cindex static tracepoints, in remote protocol
38218 The remote stub supports static tracepoints.
38220 @item InstallInTrace
38221 @anchor{install tracepoint in tracing}
38222 The remote stub supports installing tracepoint in tracing.
38224 @item EnableDisableTracepoints
38225 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
38226 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
38227 to be enabled and disabled while a trace experiment is running.
38229 @item QTBuffer:size
38230 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
38231 packet that allows to change the size of the trace buffer.
38234 @cindex string tracing, in remote protocol
38235 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
38236 See @ref{Bytecode Descriptions} for details about the bytecode.
38238 @item BreakpointCommands
38239 @cindex breakpoint commands, in remote protocol
38240 The remote stub supports running a breakpoint's command list itself,
38241 rather than reporting the hit to @value{GDBN}.
38244 The remote stub understands the @samp{Qbtrace:off} packet.
38247 The remote stub understands the @samp{Qbtrace:bts} packet.
38250 The remote stub understands the @samp{Qbtrace:pt} packet.
38252 @item Qbtrace-conf:bts:size
38253 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
38255 @item Qbtrace-conf:pt:size
38256 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
38259 The remote stub reports the @samp{swbreak} stop reason for memory
38263 The remote stub reports the @samp{hwbreak} stop reason for hardware
38267 The remote stub reports the @samp{fork} stop reason for fork events.
38270 The remote stub reports the @samp{vfork} stop reason for vfork events
38271 and vforkdone events.
38274 The remote stub reports the @samp{exec} stop reason for exec events.
38276 @item vContSupported
38277 The remote stub reports the supported actions in the reply to
38278 @samp{vCont?} packet.
38280 @item QThreadEvents
38281 The remote stub understands the @samp{QThreadEvents} packet.
38284 The remote stub reports the @samp{N} stop reply.
38289 @cindex symbol lookup, remote request
38290 @cindex @samp{qSymbol} packet
38291 Notify the target that @value{GDBN} is prepared to serve symbol lookup
38292 requests. Accept requests from the target for the values of symbols.
38297 The target does not need to look up any (more) symbols.
38298 @item qSymbol:@var{sym_name}
38299 The target requests the value of symbol @var{sym_name} (hex encoded).
38300 @value{GDBN} may provide the value by using the
38301 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
38305 @item qSymbol:@var{sym_value}:@var{sym_name}
38306 Set the value of @var{sym_name} to @var{sym_value}.
38308 @var{sym_name} (hex encoded) is the name of a symbol whose value the
38309 target has previously requested.
38311 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
38312 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
38318 The target does not need to look up any (more) symbols.
38319 @item qSymbol:@var{sym_name}
38320 The target requests the value of a new symbol @var{sym_name} (hex
38321 encoded). @value{GDBN} will continue to supply the values of symbols
38322 (if available), until the target ceases to request them.
38327 @itemx QTDisconnected
38334 @itemx qTMinFTPILen
38336 @xref{Tracepoint Packets}.
38338 @item qThreadExtraInfo,@var{thread-id}
38339 @cindex thread attributes info, remote request
38340 @cindex @samp{qThreadExtraInfo} packet
38341 Obtain from the target OS a printable string description of thread
38342 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
38343 for the forms of @var{thread-id}. This
38344 string may contain anything that the target OS thinks is interesting
38345 for @value{GDBN} to tell the user about the thread. The string is
38346 displayed in @value{GDBN}'s @code{info threads} display. Some
38347 examples of possible thread extra info strings are @samp{Runnable}, or
38348 @samp{Blocked on Mutex}.
38352 @item @var{XX}@dots{}
38353 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
38354 comprising the printable string containing the extra information about
38355 the thread's attributes.
38358 (Note that the @code{qThreadExtraInfo} packet's name is separated from
38359 the command by a @samp{,}, not a @samp{:}, contrary to the naming
38360 conventions above. Please don't use this packet as a model for new
38379 @xref{Tracepoint Packets}.
38381 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
38382 @cindex read special object, remote request
38383 @cindex @samp{qXfer} packet
38384 @anchor{qXfer read}
38385 Read uninterpreted bytes from the target's special data area
38386 identified by the keyword @var{object}. Request @var{length} bytes
38387 starting at @var{offset} bytes into the data. The content and
38388 encoding of @var{annex} is specific to @var{object}; it can supply
38389 additional details about what data to access.
38394 Data @var{data} (@pxref{Binary Data}) has been read from the
38395 target. There may be more data at a higher address (although
38396 it is permitted to return @samp{m} even for the last valid
38397 block of data, as long as at least one byte of data was read).
38398 It is possible for @var{data} to have fewer bytes than the @var{length} in the
38402 Data @var{data} (@pxref{Binary Data}) has been read from the target.
38403 There is no more data to be read. It is possible for @var{data} to
38404 have fewer bytes than the @var{length} in the request.
38407 The @var{offset} in the request is at the end of the data.
38408 There is no more data to be read.
38411 The request was malformed, or @var{annex} was invalid.
38414 The offset was invalid, or there was an error encountered reading 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 recognized by
38419 the stub, or that the object does not support reading.
38422 Here are the specific requests of this form defined so far. All the
38423 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
38424 formats, listed above.
38427 @item qXfer:auxv:read::@var{offset},@var{length}
38428 @anchor{qXfer auxiliary vector read}
38429 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
38430 auxiliary vector}. Note @var{annex} must be empty.
38432 This packet is not probed by default; the remote stub must request it,
38433 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38435 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
38436 @anchor{qXfer btrace read}
38438 Return a description of the current branch trace.
38439 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
38440 packet may have one of the following values:
38444 Returns all available branch trace.
38447 Returns all available branch trace if the branch trace changed since
38448 the last read request.
38451 Returns the new branch trace since the last read request. Adds a new
38452 block to the end of the trace that begins at zero and ends at the source
38453 location of the first branch in the trace buffer. This extra block is
38454 used to stitch traces together.
38456 If the trace buffer overflowed, returns an error indicating the overflow.
38459 This packet is not probed by default; the remote stub must request it
38460 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38462 @item qXfer:btrace-conf:read::@var{offset},@var{length}
38463 @anchor{qXfer btrace-conf read}
38465 Return a description of the current branch trace configuration.
38466 @xref{Branch Trace Configuration Format}.
38468 This packet is not probed by default; the remote stub must request it
38469 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38471 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
38472 @anchor{qXfer executable filename read}
38473 Return the full absolute name of the file that was executed to create
38474 a process running on the remote system. The annex specifies the
38475 numeric process ID of the process to query, encoded as a hexadecimal
38476 number. If the annex part is empty the remote stub should return the
38477 filename corresponding to the currently executing process.
38479 This packet is not probed by default; the remote stub must request it,
38480 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38482 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
38483 @anchor{qXfer target description read}
38484 Access the @dfn{target description}. @xref{Target Descriptions}. The
38485 annex specifies which XML document to access. The main description is
38486 always loaded from the @samp{target.xml} annex.
38488 This packet is not probed by default; the remote stub must request it,
38489 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38491 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
38492 @anchor{qXfer library list read}
38493 Access the target's list of loaded libraries. @xref{Library List Format}.
38494 The annex part of the generic @samp{qXfer} packet must be empty
38495 (@pxref{qXfer read}).
38497 Targets which maintain a list of libraries in the program's memory do
38498 not need to implement this packet; it is designed for platforms where
38499 the operating system manages the list of loaded libraries.
38501 This packet is not probed by default; the remote stub must request it,
38502 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38504 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
38505 @anchor{qXfer svr4 library list read}
38506 Access the target's list of loaded libraries when the target is an SVR4
38507 platform. @xref{Library List Format for SVR4 Targets}. The annex part
38508 of the generic @samp{qXfer} packet must be empty unless the remote
38509 stub indicated it supports the augmented form of this packet
38510 by supplying an appropriate @samp{qSupported} response
38511 (@pxref{qXfer read}, @ref{qSupported}).
38513 This packet is optional for better performance on SVR4 targets.
38514 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
38516 This packet is not probed by default; the remote stub must request it,
38517 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38519 If the remote stub indicates it supports the augmented form of this
38520 packet then the annex part of the generic @samp{qXfer} packet may
38521 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
38522 arguments. The currently supported arguments are:
38525 @item start=@var{address}
38526 A hexadecimal number specifying the address of the @samp{struct
38527 link_map} to start reading the library list from. If unset or zero
38528 then the first @samp{struct link_map} in the library list will be
38529 chosen as the starting point.
38531 @item prev=@var{address}
38532 A hexadecimal number specifying the address of the @samp{struct
38533 link_map} immediately preceding the @samp{struct link_map}
38534 specified by the @samp{start} argument. If unset or zero then
38535 the remote stub will expect that no @samp{struct link_map}
38536 exists prior to the starting point.
38540 Arguments that are not understood by the remote stub will be silently
38543 @item qXfer:memory-map:read::@var{offset},@var{length}
38544 @anchor{qXfer memory map read}
38545 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
38546 annex part of the generic @samp{qXfer} packet must be empty
38547 (@pxref{qXfer read}).
38549 This packet is not probed by default; the remote stub must request it,
38550 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38552 @item qXfer:sdata:read::@var{offset},@var{length}
38553 @anchor{qXfer sdata read}
38555 Read contents of the extra collected static tracepoint marker
38556 information. The annex part of the generic @samp{qXfer} packet must
38557 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
38560 This packet is not probed by default; the remote stub must request it,
38561 by supplying an appropriate @samp{qSupported} response
38562 (@pxref{qSupported}).
38564 @item qXfer:siginfo:read::@var{offset},@var{length}
38565 @anchor{qXfer siginfo read}
38566 Read contents of the extra signal information on the target
38567 system. The annex part of the generic @samp{qXfer} packet must be
38568 empty (@pxref{qXfer read}).
38570 This packet is not probed by default; the remote stub must request it,
38571 by supplying an appropriate @samp{qSupported} response
38572 (@pxref{qSupported}).
38574 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
38575 @anchor{qXfer spu read}
38576 Read contents of an @code{spufs} file on the target system. The
38577 annex specifies which file to read; it must be of the form
38578 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
38579 in the target process, and @var{name} identifes the @code{spufs} file
38580 in that context to be accessed.
38582 This packet is not probed by default; the remote stub must request it,
38583 by supplying an appropriate @samp{qSupported} response
38584 (@pxref{qSupported}).
38586 @item qXfer:threads:read::@var{offset},@var{length}
38587 @anchor{qXfer threads read}
38588 Access the list of threads on target. @xref{Thread List Format}. The
38589 annex part of the generic @samp{qXfer} packet must be empty
38590 (@pxref{qXfer read}).
38592 This packet is not probed by default; the remote stub must request it,
38593 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38595 @item qXfer:traceframe-info:read::@var{offset},@var{length}
38596 @anchor{qXfer traceframe info read}
38598 Return a description of the current traceframe's contents.
38599 @xref{Traceframe Info Format}. The annex part of the generic
38600 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
38602 This packet is not probed by default; the remote stub must request it,
38603 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38605 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
38606 @anchor{qXfer unwind info block}
38608 Return the unwind information block for @var{pc}. This packet is used
38609 on OpenVMS/ia64 to ask the kernel unwind information.
38611 This packet is not probed by default.
38613 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
38614 @anchor{qXfer fdpic loadmap read}
38615 Read contents of @code{loadmap}s on the target system. The
38616 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
38617 executable @code{loadmap} or interpreter @code{loadmap} to read.
38619 This packet is not probed by default; the remote stub must request it,
38620 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38622 @item qXfer:osdata:read::@var{offset},@var{length}
38623 @anchor{qXfer osdata read}
38624 Access the target's @dfn{operating system information}.
38625 @xref{Operating System Information}.
38629 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
38630 @cindex write data into object, remote request
38631 @anchor{qXfer write}
38632 Write uninterpreted bytes into the target's special data area
38633 identified by the keyword @var{object}, starting at @var{offset} bytes
38634 into the data. The binary-encoded data (@pxref{Binary Data}) to be
38635 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
38636 is specific to @var{object}; it can supply additional details about what data
38642 @var{nn} (hex encoded) is the number of bytes written.
38643 This may be fewer bytes than supplied in the request.
38646 The request was malformed, or @var{annex} was invalid.
38649 The offset was invalid, or there was an error encountered writing the data.
38650 The @var{nn} part is a hex-encoded @code{errno} value.
38653 An empty reply indicates the @var{object} string was not
38654 recognized by the stub, or that the object does not support writing.
38657 Here are the specific requests of this form defined so far. All the
38658 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
38659 formats, listed above.
38662 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
38663 @anchor{qXfer siginfo write}
38664 Write @var{data} to the extra signal information on the target system.
38665 The annex part of the generic @samp{qXfer} packet must be
38666 empty (@pxref{qXfer write}).
38668 This packet is not probed by default; the remote stub must request it,
38669 by supplying an appropriate @samp{qSupported} response
38670 (@pxref{qSupported}).
38672 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
38673 @anchor{qXfer spu write}
38674 Write @var{data} to an @code{spufs} file on the target system. The
38675 annex specifies which file to write; it must be of the form
38676 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
38677 in the target process, and @var{name} identifes the @code{spufs} file
38678 in that context to be accessed.
38680 This packet is not probed by default; the remote stub must request it,
38681 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38684 @item qXfer:@var{object}:@var{operation}:@dots{}
38685 Requests of this form may be added in the future. When a stub does
38686 not recognize the @var{object} keyword, or its support for
38687 @var{object} does not recognize the @var{operation} keyword, the stub
38688 must respond with an empty packet.
38690 @item qAttached:@var{pid}
38691 @cindex query attached, remote request
38692 @cindex @samp{qAttached} packet
38693 Return an indication of whether the remote server attached to an
38694 existing process or created a new process. When the multiprocess
38695 protocol extensions are supported (@pxref{multiprocess extensions}),
38696 @var{pid} is an integer in hexadecimal format identifying the target
38697 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
38698 the query packet will be simplified as @samp{qAttached}.
38700 This query is used, for example, to know whether the remote process
38701 should be detached or killed when a @value{GDBN} session is ended with
38702 the @code{quit} command.
38707 The remote server attached to an existing process.
38709 The remote server created a new process.
38711 A badly formed request or an error was encountered.
38715 Enable branch tracing for the current thread using Branch Trace Store.
38720 Branch tracing has been enabled.
38722 A badly formed request or an error was encountered.
38726 Enable branch tracing for the current thread using Intel Processor Trace.
38731 Branch tracing has been enabled.
38733 A badly formed request or an error was encountered.
38737 Disable branch tracing for the current thread.
38742 Branch tracing has been disabled.
38744 A badly formed request or an error was encountered.
38747 @item Qbtrace-conf:bts:size=@var{value}
38748 Set the requested ring buffer size for new threads that use the
38749 btrace recording method in bts format.
38754 The ring buffer size has been set.
38756 A badly formed request or an error was encountered.
38759 @item Qbtrace-conf:pt:size=@var{value}
38760 Set the requested ring buffer size for new threads that use the
38761 btrace recording method in pt format.
38766 The ring buffer size has been set.
38768 A badly formed request or an error was encountered.
38773 @node Architecture-Specific Protocol Details
38774 @section Architecture-Specific Protocol Details
38776 This section describes how the remote protocol is applied to specific
38777 target architectures. Also see @ref{Standard Target Features}, for
38778 details of XML target descriptions for each architecture.
38781 * ARM-Specific Protocol Details::
38782 * MIPS-Specific Protocol Details::
38785 @node ARM-Specific Protocol Details
38786 @subsection @acronym{ARM}-specific Protocol Details
38789 * ARM Breakpoint Kinds::
38792 @node ARM Breakpoint Kinds
38793 @subsubsection @acronym{ARM} Breakpoint Kinds
38794 @cindex breakpoint kinds, @acronym{ARM}
38796 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38801 16-bit Thumb mode breakpoint.
38804 32-bit Thumb mode (Thumb-2) breakpoint.
38807 32-bit @acronym{ARM} mode breakpoint.
38811 @node MIPS-Specific Protocol Details
38812 @subsection @acronym{MIPS}-specific Protocol Details
38815 * MIPS Register packet Format::
38816 * MIPS Breakpoint Kinds::
38819 @node MIPS Register packet Format
38820 @subsubsection @acronym{MIPS} Register Packet Format
38821 @cindex register packet format, @acronym{MIPS}
38823 The following @code{g}/@code{G} packets have previously been defined.
38824 In the below, some thirty-two bit registers are transferred as
38825 sixty-four bits. Those registers should be zero/sign extended (which?)
38826 to fill the space allocated. Register bytes are transferred in target
38827 byte order. The two nibbles within a register byte are transferred
38828 most-significant -- least-significant.
38833 All registers are transferred as thirty-two bit quantities in the order:
38834 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
38835 registers; fsr; fir; fp.
38838 All registers are transferred as sixty-four bit quantities (including
38839 thirty-two bit registers such as @code{sr}). The ordering is the same
38844 @node MIPS Breakpoint Kinds
38845 @subsubsection @acronym{MIPS} Breakpoint Kinds
38846 @cindex breakpoint kinds, @acronym{MIPS}
38848 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38853 16-bit @acronym{MIPS16} mode breakpoint.
38856 16-bit @acronym{microMIPS} mode breakpoint.
38859 32-bit standard @acronym{MIPS} mode breakpoint.
38862 32-bit @acronym{microMIPS} mode breakpoint.
38866 @node Tracepoint Packets
38867 @section Tracepoint Packets
38868 @cindex tracepoint packets
38869 @cindex packets, tracepoint
38871 Here we describe the packets @value{GDBN} uses to implement
38872 tracepoints (@pxref{Tracepoints}).
38876 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
38877 @cindex @samp{QTDP} packet
38878 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
38879 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
38880 the tracepoint is disabled. The @var{step} gives the tracepoint's step
38881 count, and @var{pass} gives its pass count. If an @samp{F} is present,
38882 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
38883 the number of bytes that the target should copy elsewhere to make room
38884 for the tracepoint. If an @samp{X} is present, it introduces a
38885 tracepoint condition, which consists of a hexadecimal length, followed
38886 by a comma and hex-encoded bytes, in a manner similar to action
38887 encodings as described below. If the trailing @samp{-} is present,
38888 further @samp{QTDP} packets will follow to specify this tracepoint's
38894 The packet was understood and carried out.
38896 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38898 The packet was not recognized.
38901 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
38902 Define actions to be taken when a tracepoint is hit. The @var{n} and
38903 @var{addr} must be the same as in the initial @samp{QTDP} packet for
38904 this tracepoint. This packet may only be sent immediately after
38905 another @samp{QTDP} packet that ended with a @samp{-}. If the
38906 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
38907 specifying more actions for this tracepoint.
38909 In the series of action packets for a given tracepoint, at most one
38910 can have an @samp{S} before its first @var{action}. If such a packet
38911 is sent, it and the following packets define ``while-stepping''
38912 actions. Any prior packets define ordinary actions --- that is, those
38913 taken when the tracepoint is first hit. If no action packet has an
38914 @samp{S}, then all the packets in the series specify ordinary
38915 tracepoint actions.
38917 The @samp{@var{action}@dots{}} portion of the packet is a series of
38918 actions, concatenated without separators. Each action has one of the
38924 Collect the registers whose bits are set in @var{mask},
38925 a hexadecimal number whose @var{i}'th bit is set if register number
38926 @var{i} should be collected. (The least significant bit is numbered
38927 zero.) Note that @var{mask} may be any number of digits long; it may
38928 not fit in a 32-bit word.
38930 @item M @var{basereg},@var{offset},@var{len}
38931 Collect @var{len} bytes of memory starting at the address in register
38932 number @var{basereg}, plus @var{offset}. If @var{basereg} is
38933 @samp{-1}, then the range has a fixed address: @var{offset} is the
38934 address of the lowest byte to collect. The @var{basereg},
38935 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
38936 values (the @samp{-1} value for @var{basereg} is a special case).
38938 @item X @var{len},@var{expr}
38939 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
38940 it directs. The agent expression @var{expr} is as described in
38941 @ref{Agent Expressions}. Each byte of the expression is encoded as a
38942 two-digit hex number in the packet; @var{len} is the number of bytes
38943 in the expression (and thus one-half the number of hex digits in the
38948 Any number of actions may be packed together in a single @samp{QTDP}
38949 packet, as long as the packet does not exceed the maximum packet
38950 length (400 bytes, for many stubs). There may be only one @samp{R}
38951 action per tracepoint, and it must precede any @samp{M} or @samp{X}
38952 actions. Any registers referred to by @samp{M} and @samp{X} actions
38953 must be collected by a preceding @samp{R} action. (The
38954 ``while-stepping'' actions are treated as if they were attached to a
38955 separate tracepoint, as far as these restrictions are concerned.)
38960 The packet was understood and carried out.
38962 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38964 The packet was not recognized.
38967 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
38968 @cindex @samp{QTDPsrc} packet
38969 Specify a source string of tracepoint @var{n} at address @var{addr}.
38970 This is useful to get accurate reproduction of the tracepoints
38971 originally downloaded at the beginning of the trace run. The @var{type}
38972 is the name of the tracepoint part, such as @samp{cond} for the
38973 tracepoint's conditional expression (see below for a list of types), while
38974 @var{bytes} is the string, encoded in hexadecimal.
38976 @var{start} is the offset of the @var{bytes} within the overall source
38977 string, while @var{slen} is the total length of the source string.
38978 This is intended for handling source strings that are longer than will
38979 fit in a single packet.
38980 @c Add detailed example when this info is moved into a dedicated
38981 @c tracepoint descriptions section.
38983 The available string types are @samp{at} for the location,
38984 @samp{cond} for the conditional, and @samp{cmd} for an action command.
38985 @value{GDBN} sends a separate packet for each command in the action
38986 list, in the same order in which the commands are stored in the list.
38988 The target does not need to do anything with source strings except
38989 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
38992 Although this packet is optional, and @value{GDBN} will only send it
38993 if the target replies with @samp{TracepointSource} @xref{General
38994 Query Packets}, it makes both disconnected tracing and trace files
38995 much easier to use. Otherwise the user must be careful that the
38996 tracepoints in effect while looking at trace frames are identical to
38997 the ones in effect during the trace run; even a small discrepancy
38998 could cause @samp{tdump} not to work, or a particular trace frame not
39001 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
39002 @cindex define trace state variable, remote request
39003 @cindex @samp{QTDV} packet
39004 Create a new trace state variable, number @var{n}, with an initial
39005 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
39006 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
39007 the option of not using this packet for initial values of zero; the
39008 target should simply create the trace state variables as they are
39009 mentioned in expressions. The value @var{builtin} should be 1 (one)
39010 if the trace state variable is builtin and 0 (zero) if it is not builtin.
39011 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
39012 @samp{qTsV} packet had it set. The contents of @var{name} is the
39013 hex-encoded name (without the leading @samp{$}) of the trace state
39016 @item QTFrame:@var{n}
39017 @cindex @samp{QTFrame} packet
39018 Select the @var{n}'th tracepoint frame from the buffer, and use the
39019 register and memory contents recorded there to answer subsequent
39020 request packets from @value{GDBN}.
39022 A successful reply from the stub indicates that the stub has found the
39023 requested frame. The response is a series of parts, concatenated
39024 without separators, describing the frame we selected. Each part has
39025 one of the following forms:
39029 The selected frame is number @var{n} in the trace frame buffer;
39030 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
39031 was no frame matching the criteria in the request packet.
39034 The selected trace frame records a hit of tracepoint number @var{t};
39035 @var{t} is a hexadecimal number.
39039 @item QTFrame:pc:@var{addr}
39040 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
39041 currently selected frame whose PC is @var{addr};
39042 @var{addr} is a hexadecimal number.
39044 @item QTFrame:tdp:@var{t}
39045 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
39046 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
39047 is a hexadecimal number.
39049 @item QTFrame:range:@var{start}:@var{end}
39050 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
39051 currently selected frame whose PC is between @var{start} (inclusive)
39052 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
39055 @item QTFrame:outside:@var{start}:@var{end}
39056 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
39057 frame @emph{outside} the given range of addresses (exclusive).
39060 @cindex @samp{qTMinFTPILen} packet
39061 This packet requests the minimum length of instruction at which a fast
39062 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
39063 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
39064 it depends on the target system being able to create trampolines in
39065 the first 64K of memory, which might or might not be possible for that
39066 system. So the reply to this packet will be 4 if it is able to
39073 The minimum instruction length is currently unknown.
39075 The minimum instruction length is @var{length}, where @var{length}
39076 is a hexadecimal number greater or equal to 1. A reply
39077 of 1 means that a fast tracepoint may be placed on any instruction
39078 regardless of size.
39080 An error has occurred.
39082 An empty reply indicates that the request is not supported by the stub.
39086 @cindex @samp{QTStart} packet
39087 Begin the tracepoint experiment. Begin collecting data from
39088 tracepoint hits in the trace frame buffer. This packet supports the
39089 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
39090 instruction reply packet}).
39093 @cindex @samp{QTStop} packet
39094 End the tracepoint experiment. Stop collecting trace frames.
39096 @item QTEnable:@var{n}:@var{addr}
39098 @cindex @samp{QTEnable} packet
39099 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
39100 experiment. If the tracepoint was previously disabled, then collection
39101 of data from it will resume.
39103 @item QTDisable:@var{n}:@var{addr}
39105 @cindex @samp{QTDisable} packet
39106 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
39107 experiment. No more data will be collected from the tracepoint unless
39108 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
39111 @cindex @samp{QTinit} packet
39112 Clear the table of tracepoints, and empty the trace frame buffer.
39114 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
39115 @cindex @samp{QTro} packet
39116 Establish the given ranges of memory as ``transparent''. The stub
39117 will answer requests for these ranges from memory's current contents,
39118 if they were not collected as part of the tracepoint hit.
39120 @value{GDBN} uses this to mark read-only regions of memory, like those
39121 containing program code. Since these areas never change, they should
39122 still have the same contents they did when the tracepoint was hit, so
39123 there's no reason for the stub to refuse to provide their contents.
39125 @item QTDisconnected:@var{value}
39126 @cindex @samp{QTDisconnected} packet
39127 Set the choice to what to do with the tracing run when @value{GDBN}
39128 disconnects from the target. A @var{value} of 1 directs the target to
39129 continue the tracing run, while 0 tells the target to stop tracing if
39130 @value{GDBN} is no longer in the picture.
39133 @cindex @samp{qTStatus} packet
39134 Ask the stub if there is a trace experiment running right now.
39136 The reply has the form:
39140 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
39141 @var{running} is a single digit @code{1} if the trace is presently
39142 running, or @code{0} if not. It is followed by semicolon-separated
39143 optional fields that an agent may use to report additional status.
39147 If the trace is not running, the agent may report any of several
39148 explanations as one of the optional fields:
39153 No trace has been run yet.
39155 @item tstop[:@var{text}]:0
39156 The trace was stopped by a user-originated stop command. The optional
39157 @var{text} field is a user-supplied string supplied as part of the
39158 stop command (for instance, an explanation of why the trace was
39159 stopped manually). It is hex-encoded.
39162 The trace stopped because the trace buffer filled up.
39164 @item tdisconnected:0
39165 The trace stopped because @value{GDBN} disconnected from the target.
39167 @item tpasscount:@var{tpnum}
39168 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
39170 @item terror:@var{text}:@var{tpnum}
39171 The trace stopped because tracepoint @var{tpnum} had an error. The
39172 string @var{text} is available to describe the nature of the error
39173 (for instance, a divide by zero in the condition expression); it
39177 The trace stopped for some other reason.
39181 Additional optional fields supply statistical and other information.
39182 Although not required, they are extremely useful for users monitoring
39183 the progress of a trace run. If a trace has stopped, and these
39184 numbers are reported, they must reflect the state of the just-stopped
39189 @item tframes:@var{n}
39190 The number of trace frames in the buffer.
39192 @item tcreated:@var{n}
39193 The total number of trace frames created during the run. This may
39194 be larger than the trace frame count, if the buffer is circular.
39196 @item tsize:@var{n}
39197 The total size of the trace buffer, in bytes.
39199 @item tfree:@var{n}
39200 The number of bytes still unused in the buffer.
39202 @item circular:@var{n}
39203 The value of the circular trace buffer flag. @code{1} means that the
39204 trace buffer is circular and old trace frames will be discarded if
39205 necessary to make room, @code{0} means that the trace buffer is linear
39208 @item disconn:@var{n}
39209 The value of the disconnected tracing flag. @code{1} means that
39210 tracing will continue after @value{GDBN} disconnects, @code{0} means
39211 that the trace run will stop.
39215 @item qTP:@var{tp}:@var{addr}
39216 @cindex tracepoint status, remote request
39217 @cindex @samp{qTP} packet
39218 Ask the stub for the current state of tracepoint number @var{tp} at
39219 address @var{addr}.
39223 @item V@var{hits}:@var{usage}
39224 The tracepoint has been hit @var{hits} times so far during the trace
39225 run, and accounts for @var{usage} in the trace buffer. Note that
39226 @code{while-stepping} steps are not counted as separate hits, but the
39227 steps' space consumption is added into the usage number.
39231 @item qTV:@var{var}
39232 @cindex trace state variable value, remote request
39233 @cindex @samp{qTV} packet
39234 Ask the stub for the value of the trace state variable number @var{var}.
39239 The value of the variable is @var{value}. This will be the current
39240 value of the variable if the user is examining a running target, or a
39241 saved value if the variable was collected in the trace frame that the
39242 user is looking at. Note that multiple requests may result in
39243 different reply values, such as when requesting values while the
39244 program is running.
39247 The value of the variable is unknown. This would occur, for example,
39248 if the user is examining a trace frame in which the requested variable
39253 @cindex @samp{qTfP} packet
39255 @cindex @samp{qTsP} packet
39256 These packets request data about tracepoints that are being used by
39257 the target. @value{GDBN} sends @code{qTfP} to get the first piece
39258 of data, and multiple @code{qTsP} to get additional pieces. Replies
39259 to these packets generally take the form of the @code{QTDP} packets
39260 that define tracepoints. (FIXME add detailed syntax)
39263 @cindex @samp{qTfV} packet
39265 @cindex @samp{qTsV} packet
39266 These packets request data about trace state variables that are on the
39267 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
39268 and multiple @code{qTsV} to get additional variables. Replies to
39269 these packets follow the syntax of the @code{QTDV} packets that define
39270 trace state variables.
39276 @cindex @samp{qTfSTM} packet
39277 @cindex @samp{qTsSTM} packet
39278 These packets request data about static tracepoint markers that exist
39279 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
39280 first piece of data, and multiple @code{qTsSTM} to get additional
39281 pieces. Replies to these packets take the following form:
39285 @item m @var{address}:@var{id}:@var{extra}
39287 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
39288 a comma-separated list of markers
39290 (lower case letter @samp{L}) denotes end of list.
39292 An error occurred. The error number @var{nn} is given as hex digits.
39294 An empty reply indicates that the request is not supported by the
39298 The @var{address} is encoded in hex;
39299 @var{id} and @var{extra} are strings encoded in hex.
39301 In response to each query, the target will reply with a list of one or
39302 more markers, separated by commas. @value{GDBN} will respond to each
39303 reply with a request for more markers (using the @samp{qs} form of the
39304 query), until the target responds with @samp{l} (lower-case ell, for
39307 @item qTSTMat:@var{address}
39309 @cindex @samp{qTSTMat} packet
39310 This packets requests data about static tracepoint markers in the
39311 target program at @var{address}. Replies to this packet follow the
39312 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
39313 tracepoint markers.
39315 @item QTSave:@var{filename}
39316 @cindex @samp{QTSave} packet
39317 This packet directs the target to save trace data to the file name
39318 @var{filename} in the target's filesystem. The @var{filename} is encoded
39319 as a hex string; the interpretation of the file name (relative vs
39320 absolute, wild cards, etc) is up to the target.
39322 @item qTBuffer:@var{offset},@var{len}
39323 @cindex @samp{qTBuffer} packet
39324 Return up to @var{len} bytes of the current contents of trace buffer,
39325 starting at @var{offset}. The trace buffer is treated as if it were
39326 a contiguous collection of traceframes, as per the trace file format.
39327 The reply consists as many hex-encoded bytes as the target can deliver
39328 in a packet; it is not an error to return fewer than were asked for.
39329 A reply consisting of just @code{l} indicates that no bytes are
39332 @item QTBuffer:circular:@var{value}
39333 This packet directs the target to use a circular trace buffer if
39334 @var{value} is 1, or a linear buffer if the value is 0.
39336 @item QTBuffer:size:@var{size}
39337 @anchor{QTBuffer-size}
39338 @cindex @samp{QTBuffer size} packet
39339 This packet directs the target to make the trace buffer be of size
39340 @var{size} if possible. A value of @code{-1} tells the target to
39341 use whatever size it prefers.
39343 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
39344 @cindex @samp{QTNotes} packet
39345 This packet adds optional textual notes to the trace run. Allowable
39346 types include @code{user}, @code{notes}, and @code{tstop}, the
39347 @var{text} fields are arbitrary strings, hex-encoded.
39351 @subsection Relocate instruction reply packet
39352 When installing fast tracepoints in memory, the target may need to
39353 relocate the instruction currently at the tracepoint address to a
39354 different address in memory. For most instructions, a simple copy is
39355 enough, but, for example, call instructions that implicitly push the
39356 return address on the stack, and relative branches or other
39357 PC-relative instructions require offset adjustment, so that the effect
39358 of executing the instruction at a different address is the same as if
39359 it had executed in the original location.
39361 In response to several of the tracepoint packets, the target may also
39362 respond with a number of intermediate @samp{qRelocInsn} request
39363 packets before the final result packet, to have @value{GDBN} handle
39364 this relocation operation. If a packet supports this mechanism, its
39365 documentation will explicitly say so. See for example the above
39366 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
39367 format of the request is:
39370 @item qRelocInsn:@var{from};@var{to}
39372 This requests @value{GDBN} to copy instruction at address @var{from}
39373 to address @var{to}, possibly adjusted so that executing the
39374 instruction at @var{to} has the same effect as executing it at
39375 @var{from}. @value{GDBN} writes the adjusted instruction to target
39376 memory starting at @var{to}.
39381 @item qRelocInsn:@var{adjusted_size}
39382 Informs the stub the relocation is complete. The @var{adjusted_size} is
39383 the length in bytes of resulting relocated instruction sequence.
39385 A badly formed request was detected, or an error was encountered while
39386 relocating the instruction.
39389 @node Host I/O Packets
39390 @section Host I/O Packets
39391 @cindex Host I/O, remote protocol
39392 @cindex file transfer, remote protocol
39394 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
39395 operations on the far side of a remote link. For example, Host I/O is
39396 used to upload and download files to a remote target with its own
39397 filesystem. Host I/O uses the same constant values and data structure
39398 layout as the target-initiated File-I/O protocol. However, the
39399 Host I/O packets are structured differently. The target-initiated
39400 protocol relies on target memory to store parameters and buffers.
39401 Host I/O requests are initiated by @value{GDBN}, and the
39402 target's memory is not involved. @xref{File-I/O Remote Protocol
39403 Extension}, for more details on the target-initiated protocol.
39405 The Host I/O request packets all encode a single operation along with
39406 its arguments. They have this format:
39410 @item vFile:@var{operation}: @var{parameter}@dots{}
39411 @var{operation} is the name of the particular request; the target
39412 should compare the entire packet name up to the second colon when checking
39413 for a supported operation. The format of @var{parameter} depends on
39414 the operation. Numbers are always passed in hexadecimal. Negative
39415 numbers have an explicit minus sign (i.e.@: two's complement is not
39416 used). Strings (e.g.@: filenames) are encoded as a series of
39417 hexadecimal bytes. The last argument to a system call may be a
39418 buffer of escaped binary data (@pxref{Binary Data}).
39422 The valid responses to Host I/O packets are:
39426 @item F @var{result} [, @var{errno}] [; @var{attachment}]
39427 @var{result} is the integer value returned by this operation, usually
39428 non-negative for success and -1 for errors. If an error has occured,
39429 @var{errno} will be included in the result specifying a
39430 value defined by the File-I/O protocol (@pxref{Errno Values}). For
39431 operations which return data, @var{attachment} supplies the data as a
39432 binary buffer. Binary buffers in response packets are escaped in the
39433 normal way (@pxref{Binary Data}). See the individual packet
39434 documentation for the interpretation of @var{result} and
39438 An empty response indicates that this operation is not recognized.
39442 These are the supported Host I/O operations:
39445 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
39446 Open a file at @var{filename} and return a file descriptor for it, or
39447 return -1 if an error occurs. The @var{filename} is a string,
39448 @var{flags} is an integer indicating a mask of open flags
39449 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
39450 of mode bits to use if the file is created (@pxref{mode_t Values}).
39451 @xref{open}, for details of the open flags and mode values.
39453 @item vFile:close: @var{fd}
39454 Close the open file corresponding to @var{fd} and return 0, or
39455 -1 if an error occurs.
39457 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
39458 Read data from the open file corresponding to @var{fd}. Up to
39459 @var{count} bytes will be read from the file, starting at @var{offset}
39460 relative to the start of the file. The target may read fewer bytes;
39461 common reasons include packet size limits and an end-of-file
39462 condition. The number of bytes read is returned. Zero should only be
39463 returned for a successful read at the end of the file, or if
39464 @var{count} was zero.
39466 The data read should be returned as a binary attachment on success.
39467 If zero bytes were read, the response should include an empty binary
39468 attachment (i.e.@: a trailing semicolon). The return value is the
39469 number of target bytes read; the binary attachment may be longer if
39470 some characters were escaped.
39472 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
39473 Write @var{data} (a binary buffer) to the open file corresponding
39474 to @var{fd}. Start the write at @var{offset} from the start of the
39475 file. Unlike many @code{write} system calls, there is no
39476 separate @var{count} argument; the length of @var{data} in the
39477 packet is used. @samp{vFile:write} returns the number of bytes written,
39478 which may be shorter than the length of @var{data}, or -1 if an
39481 @item vFile:fstat: @var{fd}
39482 Get information about the open file corresponding to @var{fd}.
39483 On success the information is returned as a binary attachment
39484 and the return value is the size of this attachment in bytes.
39485 If an error occurs the return value is -1. The format of the
39486 returned binary attachment is as described in @ref{struct stat}.
39488 @item vFile:unlink: @var{filename}
39489 Delete the file at @var{filename} on the target. Return 0,
39490 or -1 if an error occurs. The @var{filename} is a string.
39492 @item vFile:readlink: @var{filename}
39493 Read value of symbolic link @var{filename} on the target. Return
39494 the number of bytes read, or -1 if an error occurs.
39496 The data read should be returned as a binary attachment on success.
39497 If zero bytes were read, the response should include an empty binary
39498 attachment (i.e.@: a trailing semicolon). The return value is the
39499 number of target bytes read; the binary attachment may be longer if
39500 some characters were escaped.
39502 @item vFile:setfs: @var{pid}
39503 Select the filesystem on which @code{vFile} operations with
39504 @var{filename} arguments will operate. This is required for
39505 @value{GDBN} to be able to access files on remote targets where
39506 the remote stub does not share a common filesystem with the
39509 If @var{pid} is nonzero, select the filesystem as seen by process
39510 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
39511 the remote stub. Return 0 on success, or -1 if an error occurs.
39512 If @code{vFile:setfs:} indicates success, the selected filesystem
39513 remains selected until the next successful @code{vFile:setfs:}
39519 @section Interrupts
39520 @cindex interrupts (remote protocol)
39521 @anchor{interrupting remote targets}
39523 In all-stop mode, when a program on the remote target is running,
39524 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
39525 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
39526 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
39528 The precise meaning of @code{BREAK} is defined by the transport
39529 mechanism and may, in fact, be undefined. @value{GDBN} does not
39530 currently define a @code{BREAK} mechanism for any of the network
39531 interfaces except for TCP, in which case @value{GDBN} sends the
39532 @code{telnet} BREAK sequence.
39534 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
39535 transport mechanisms. It is represented by sending the single byte
39536 @code{0x03} without any of the usual packet overhead described in
39537 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
39538 transmitted as part of a packet, it is considered to be packet data
39539 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
39540 (@pxref{X packet}), used for binary downloads, may include an unescaped
39541 @code{0x03} as part of its packet.
39543 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
39544 When Linux kernel receives this sequence from serial port,
39545 it stops execution and connects to gdb.
39547 In non-stop mode, because packet resumptions are asynchronous
39548 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
39549 command to the remote stub, even when the target is running. For that
39550 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
39551 packet}) with the usual packet framing instead of the single byte
39554 Stubs are not required to recognize these interrupt mechanisms and the
39555 precise meaning associated with receipt of the interrupt is
39556 implementation defined. If the target supports debugging of multiple
39557 threads and/or processes, it should attempt to interrupt all
39558 currently-executing threads and processes.
39559 If the stub is successful at interrupting the
39560 running program, it should send one of the stop
39561 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
39562 of successfully stopping the program in all-stop mode, and a stop reply
39563 for each stopped thread in non-stop mode.
39564 Interrupts received while the
39565 program is stopped are queued and the program will be interrupted when
39566 it is resumed next time.
39568 @node Notification Packets
39569 @section Notification Packets
39570 @cindex notification packets
39571 @cindex packets, notification
39573 The @value{GDBN} remote serial protocol includes @dfn{notifications},
39574 packets that require no acknowledgment. Both the GDB and the stub
39575 may send notifications (although the only notifications defined at
39576 present are sent by the stub). Notifications carry information
39577 without incurring the round-trip latency of an acknowledgment, and so
39578 are useful for low-impact communications where occasional packet loss
39581 A notification packet has the form @samp{% @var{data} #
39582 @var{checksum}}, where @var{data} is the content of the notification,
39583 and @var{checksum} is a checksum of @var{data}, computed and formatted
39584 as for ordinary @value{GDBN} packets. A notification's @var{data}
39585 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
39586 receiving a notification, the recipient sends no @samp{+} or @samp{-}
39587 to acknowledge the notification's receipt or to report its corruption.
39589 Every notification's @var{data} begins with a name, which contains no
39590 colon characters, followed by a colon character.
39592 Recipients should silently ignore corrupted notifications and
39593 notifications they do not understand. Recipients should restart
39594 timeout periods on receipt of a well-formed notification, whether or
39595 not they understand it.
39597 Senders should only send the notifications described here when this
39598 protocol description specifies that they are permitted. In the
39599 future, we may extend the protocol to permit existing notifications in
39600 new contexts; this rule helps older senders avoid confusing newer
39603 (Older versions of @value{GDBN} ignore bytes received until they see
39604 the @samp{$} byte that begins an ordinary packet, so new stubs may
39605 transmit notifications without fear of confusing older clients. There
39606 are no notifications defined for @value{GDBN} to send at the moment, but we
39607 assume that most older stubs would ignore them, as well.)
39609 Each notification is comprised of three parts:
39611 @item @var{name}:@var{event}
39612 The notification packet is sent by the side that initiates the
39613 exchange (currently, only the stub does that), with @var{event}
39614 carrying the specific information about the notification, and
39615 @var{name} specifying the name of the notification.
39617 The acknowledge sent by the other side, usually @value{GDBN}, to
39618 acknowledge the exchange and request the event.
39621 The purpose of an asynchronous notification mechanism is to report to
39622 @value{GDBN} that something interesting happened in the remote stub.
39624 The remote stub may send notification @var{name}:@var{event}
39625 at any time, but @value{GDBN} acknowledges the notification when
39626 appropriate. The notification event is pending before @value{GDBN}
39627 acknowledges. Only one notification at a time may be pending; if
39628 additional events occur before @value{GDBN} has acknowledged the
39629 previous notification, they must be queued by the stub for later
39630 synchronous transmission in response to @var{ack} packets from
39631 @value{GDBN}. Because the notification mechanism is unreliable,
39632 the stub is permitted to resend a notification if it believes
39633 @value{GDBN} may not have received it.
39635 Specifically, notifications may appear when @value{GDBN} is not
39636 otherwise reading input from the stub, or when @value{GDBN} is
39637 expecting to read a normal synchronous response or a
39638 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
39639 Notification packets are distinct from any other communication from
39640 the stub so there is no ambiguity.
39642 After receiving a notification, @value{GDBN} shall acknowledge it by
39643 sending a @var{ack} packet as a regular, synchronous request to the
39644 stub. Such acknowledgment is not required to happen immediately, as
39645 @value{GDBN} is permitted to send other, unrelated packets to the
39646 stub first, which the stub should process normally.
39648 Upon receiving a @var{ack} packet, if the stub has other queued
39649 events to report to @value{GDBN}, it shall respond by sending a
39650 normal @var{event}. @value{GDBN} shall then send another @var{ack}
39651 packet to solicit further responses; again, it is permitted to send
39652 other, unrelated packets as well which the stub should process
39655 If the stub receives a @var{ack} packet and there are no additional
39656 @var{event} to report, the stub shall return an @samp{OK} response.
39657 At this point, @value{GDBN} has finished processing a notification
39658 and the stub has completed sending any queued events. @value{GDBN}
39659 won't accept any new notifications until the final @samp{OK} is
39660 received . If further notification events occur, the stub shall send
39661 a new notification, @value{GDBN} shall accept the notification, and
39662 the process shall be repeated.
39664 The process of asynchronous notification can be illustrated by the
39667 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
39670 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
39672 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
39677 The following notifications are defined:
39678 @multitable @columnfractions 0.12 0.12 0.38 0.38
39687 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
39688 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
39689 for information on how these notifications are acknowledged by
39691 @tab Report an asynchronous stop event in non-stop mode.
39695 @node Remote Non-Stop
39696 @section Remote Protocol Support for Non-Stop Mode
39698 @value{GDBN}'s remote protocol supports non-stop debugging of
39699 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
39700 supports non-stop mode, it should report that to @value{GDBN} by including
39701 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
39703 @value{GDBN} typically sends a @samp{QNonStop} packet only when
39704 establishing a new connection with the stub. Entering non-stop mode
39705 does not alter the state of any currently-running threads, but targets
39706 must stop all threads in any already-attached processes when entering
39707 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
39708 probe the target state after a mode change.
39710 In non-stop mode, when an attached process encounters an event that
39711 would otherwise be reported with a stop reply, it uses the
39712 asynchronous notification mechanism (@pxref{Notification Packets}) to
39713 inform @value{GDBN}. In contrast to all-stop mode, where all threads
39714 in all processes are stopped when a stop reply is sent, in non-stop
39715 mode only the thread reporting the stop event is stopped. That is,
39716 when reporting a @samp{S} or @samp{T} response to indicate completion
39717 of a step operation, hitting a breakpoint, or a fault, only the
39718 affected thread is stopped; any other still-running threads continue
39719 to run. When reporting a @samp{W} or @samp{X} response, all running
39720 threads belonging to other attached processes continue to run.
39722 In non-stop mode, the target shall respond to the @samp{?} packet as
39723 follows. First, any incomplete stop reply notification/@samp{vStopped}
39724 sequence in progress is abandoned. The target must begin a new
39725 sequence reporting stop events for all stopped threads, whether or not
39726 it has previously reported those events to @value{GDBN}. The first
39727 stop reply is sent as a synchronous reply to the @samp{?} packet, and
39728 subsequent stop replies are sent as responses to @samp{vStopped} packets
39729 using the mechanism described above. The target must not send
39730 asynchronous stop reply notifications until the sequence is complete.
39731 If all threads are running when the target receives the @samp{?} packet,
39732 or if the target is not attached to any process, it shall respond
39735 If the stub supports non-stop mode, it should also support the
39736 @samp{swbreak} stop reason if software breakpoints are supported, and
39737 the @samp{hwbreak} stop reason if hardware breakpoints are supported
39738 (@pxref{swbreak stop reason}). This is because given the asynchronous
39739 nature of non-stop mode, between the time a thread hits a breakpoint
39740 and the time the event is finally processed by @value{GDBN}, the
39741 breakpoint may have already been removed from the target. Due to
39742 this, @value{GDBN} needs to be able to tell whether a trap stop was
39743 caused by a delayed breakpoint event, which should be ignored, as
39744 opposed to a random trap signal, which should be reported to the user.
39745 Note the @samp{swbreak} feature implies that the target is responsible
39746 for adjusting the PC when a software breakpoint triggers, if
39747 necessary, such as on the x86 architecture.
39749 @node Packet Acknowledgment
39750 @section Packet Acknowledgment
39752 @cindex acknowledgment, for @value{GDBN} remote
39753 @cindex packet acknowledgment, for @value{GDBN} remote
39754 By default, when either the host or the target machine receives a packet,
39755 the first response expected is an acknowledgment: either @samp{+} (to indicate
39756 the package was received correctly) or @samp{-} (to request retransmission).
39757 This mechanism allows the @value{GDBN} remote protocol to operate over
39758 unreliable transport mechanisms, such as a serial line.
39760 In cases where the transport mechanism is itself reliable (such as a pipe or
39761 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
39762 It may be desirable to disable them in that case to reduce communication
39763 overhead, or for other reasons. This can be accomplished by means of the
39764 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
39766 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
39767 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
39768 and response format still includes the normal checksum, as described in
39769 @ref{Overview}, but the checksum may be ignored by the receiver.
39771 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
39772 no-acknowledgment mode, it should report that to @value{GDBN}
39773 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
39774 @pxref{qSupported}.
39775 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
39776 disabled via the @code{set remote noack-packet off} command
39777 (@pxref{Remote Configuration}),
39778 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
39779 Only then may the stub actually turn off packet acknowledgments.
39780 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
39781 response, which can be safely ignored by the stub.
39783 Note that @code{set remote noack-packet} command only affects negotiation
39784 between @value{GDBN} and the stub when subsequent connections are made;
39785 it does not affect the protocol acknowledgment state for any current
39787 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
39788 new connection is established,
39789 there is also no protocol request to re-enable the acknowledgments
39790 for the current connection, once disabled.
39795 Example sequence of a target being re-started. Notice how the restart
39796 does not get any direct output:
39801 @emph{target restarts}
39804 <- @code{T001:1234123412341234}
39808 Example sequence of a target being stepped by a single instruction:
39811 -> @code{G1445@dots{}}
39816 <- @code{T001:1234123412341234}
39820 <- @code{1455@dots{}}
39824 @node File-I/O Remote Protocol Extension
39825 @section File-I/O Remote Protocol Extension
39826 @cindex File-I/O remote protocol extension
39829 * File-I/O Overview::
39830 * Protocol Basics::
39831 * The F Request Packet::
39832 * The F Reply Packet::
39833 * The Ctrl-C Message::
39835 * List of Supported Calls::
39836 * Protocol-specific Representation of Datatypes::
39838 * File-I/O Examples::
39841 @node File-I/O Overview
39842 @subsection File-I/O Overview
39843 @cindex file-i/o overview
39845 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
39846 target to use the host's file system and console I/O to perform various
39847 system calls. System calls on the target system are translated into a
39848 remote protocol packet to the host system, which then performs the needed
39849 actions and returns a response packet to the target system.
39850 This simulates file system operations even on targets that lack file systems.
39852 The protocol is defined to be independent of both the host and target systems.
39853 It uses its own internal representation of datatypes and values. Both
39854 @value{GDBN} and the target's @value{GDBN} stub are responsible for
39855 translating the system-dependent value representations into the internal
39856 protocol representations when data is transmitted.
39858 The communication is synchronous. A system call is possible only when
39859 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
39860 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
39861 the target is stopped to allow deterministic access to the target's
39862 memory. Therefore File-I/O is not interruptible by target signals. On
39863 the other hand, it is possible to interrupt File-I/O by a user interrupt
39864 (@samp{Ctrl-C}) within @value{GDBN}.
39866 The target's request to perform a host system call does not finish
39867 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
39868 after finishing the system call, the target returns to continuing the
39869 previous activity (continue, step). No additional continue or step
39870 request from @value{GDBN} is required.
39873 (@value{GDBP}) continue
39874 <- target requests 'system call X'
39875 target is stopped, @value{GDBN} executes system call
39876 -> @value{GDBN} returns result
39877 ... target continues, @value{GDBN} returns to wait for the target
39878 <- target hits breakpoint and sends a Txx packet
39881 The protocol only supports I/O on the console and to regular files on
39882 the host file system. Character or block special devices, pipes,
39883 named pipes, sockets or any other communication method on the host
39884 system are not supported by this protocol.
39886 File I/O is not supported in non-stop mode.
39888 @node Protocol Basics
39889 @subsection Protocol Basics
39890 @cindex protocol basics, file-i/o
39892 The File-I/O protocol uses the @code{F} packet as the request as well
39893 as reply packet. Since a File-I/O system call can only occur when
39894 @value{GDBN} is waiting for a response from the continuing or stepping target,
39895 the File-I/O request is a reply that @value{GDBN} has to expect as a result
39896 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
39897 This @code{F} packet contains all information needed to allow @value{GDBN}
39898 to call the appropriate host system call:
39902 A unique identifier for the requested system call.
39905 All parameters to the system call. Pointers are given as addresses
39906 in the target memory address space. Pointers to strings are given as
39907 pointer/length pair. Numerical values are given as they are.
39908 Numerical control flags are given in a protocol-specific representation.
39912 At this point, @value{GDBN} has to perform the following actions.
39916 If the parameters include pointer values to data needed as input to a
39917 system call, @value{GDBN} requests this data from the target with a
39918 standard @code{m} packet request. This additional communication has to be
39919 expected by the target implementation and is handled as any other @code{m}
39923 @value{GDBN} translates all value from protocol representation to host
39924 representation as needed. Datatypes are coerced into the host types.
39927 @value{GDBN} calls the system call.
39930 It then coerces datatypes back to protocol representation.
39933 If the system call is expected to return data in buffer space specified
39934 by pointer parameters to the call, the data is transmitted to the
39935 target using a @code{M} or @code{X} packet. This packet has to be expected
39936 by the target implementation and is handled as any other @code{M} or @code{X}
39941 Eventually @value{GDBN} replies with another @code{F} packet which contains all
39942 necessary information for the target to continue. This at least contains
39949 @code{errno}, if has been changed by the system call.
39956 After having done the needed type and value coercion, the target continues
39957 the latest continue or step action.
39959 @node The F Request Packet
39960 @subsection The @code{F} Request Packet
39961 @cindex file-i/o request packet
39962 @cindex @code{F} request packet
39964 The @code{F} request packet has the following format:
39967 @item F@var{call-id},@var{parameter@dots{}}
39969 @var{call-id} is the identifier to indicate the host system call to be called.
39970 This is just the name of the function.
39972 @var{parameter@dots{}} are the parameters to the system call.
39973 Parameters are hexadecimal integer values, either the actual values in case
39974 of scalar datatypes, pointers to target buffer space in case of compound
39975 datatypes and unspecified memory areas, or pointer/length pairs in case
39976 of string parameters. These are appended to the @var{call-id} as a
39977 comma-delimited list. All values are transmitted in ASCII
39978 string representation, pointer/length pairs separated by a slash.
39984 @node The F Reply Packet
39985 @subsection The @code{F} Reply Packet
39986 @cindex file-i/o reply packet
39987 @cindex @code{F} reply packet
39989 The @code{F} reply packet has the following format:
39993 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
39995 @var{retcode} is the return code of the system call as hexadecimal value.
39997 @var{errno} is the @code{errno} set by the call, in protocol-specific
39999 This parameter can be omitted if the call was successful.
40001 @var{Ctrl-C flag} is only sent if the user requested a break. In this
40002 case, @var{errno} must be sent as well, even if the call was successful.
40003 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
40010 or, if the call was interrupted before the host call has been performed:
40017 assuming 4 is the protocol-specific representation of @code{EINTR}.
40022 @node The Ctrl-C Message
40023 @subsection The @samp{Ctrl-C} Message
40024 @cindex ctrl-c message, in file-i/o protocol
40026 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
40027 reply packet (@pxref{The F Reply Packet}),
40028 the target should behave as if it had
40029 gotten a break message. The meaning for the target is ``system call
40030 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
40031 (as with a break message) and return to @value{GDBN} with a @code{T02}
40034 It's important for the target to know in which
40035 state the system call was interrupted. There are two possible cases:
40039 The system call hasn't been performed on the host yet.
40042 The system call on the host has been finished.
40046 These two states can be distinguished by the target by the value of the
40047 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
40048 call hasn't been performed. This is equivalent to the @code{EINTR} handling
40049 on POSIX systems. In any other case, the target may presume that the
40050 system call has been finished --- successfully or not --- and should behave
40051 as if the break message arrived right after the system call.
40053 @value{GDBN} must behave reliably. If the system call has not been called
40054 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
40055 @code{errno} in the packet. If the system call on the host has been finished
40056 before the user requests a break, the full action must be finished by
40057 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
40058 The @code{F} packet may only be sent when either nothing has happened
40059 or the full action has been completed.
40062 @subsection Console I/O
40063 @cindex console i/o as part of file-i/o
40065 By default and if not explicitly closed by the target system, the file
40066 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
40067 on the @value{GDBN} console is handled as any other file output operation
40068 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
40069 by @value{GDBN} so that after the target read request from file descriptor
40070 0 all following typing is buffered until either one of the following
40075 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
40077 system call is treated as finished.
40080 The user presses @key{RET}. This is treated as end of input with a trailing
40084 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
40085 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
40089 If the user has typed more characters than fit in the buffer given to
40090 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
40091 either another @code{read(0, @dots{})} is requested by the target, or debugging
40092 is stopped at the user's request.
40095 @node List of Supported Calls
40096 @subsection List of Supported Calls
40097 @cindex list of supported file-i/o calls
40114 @unnumberedsubsubsec open
40115 @cindex open, file-i/o system call
40120 int open(const char *pathname, int flags);
40121 int open(const char *pathname, int flags, mode_t mode);
40125 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
40128 @var{flags} is the bitwise @code{OR} of the following values:
40132 If the file does not exist it will be created. The host
40133 rules apply as far as file ownership and time stamps
40137 When used with @code{O_CREAT}, if the file already exists it is
40138 an error and open() fails.
40141 If the file already exists and the open mode allows
40142 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
40143 truncated to zero length.
40146 The file is opened in append mode.
40149 The file is opened for reading only.
40152 The file is opened for writing only.
40155 The file is opened for reading and writing.
40159 Other bits are silently ignored.
40163 @var{mode} is the bitwise @code{OR} of the following values:
40167 User has read permission.
40170 User has write permission.
40173 Group has read permission.
40176 Group has write permission.
40179 Others have read permission.
40182 Others have write permission.
40186 Other bits are silently ignored.
40189 @item Return value:
40190 @code{open} returns the new file descriptor or -1 if an error
40197 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
40200 @var{pathname} refers to a directory.
40203 The requested access is not allowed.
40206 @var{pathname} was too long.
40209 A directory component in @var{pathname} does not exist.
40212 @var{pathname} refers to a device, pipe, named pipe or socket.
40215 @var{pathname} refers to a file on a read-only filesystem and
40216 write access was requested.
40219 @var{pathname} is an invalid pointer value.
40222 No space on device to create the file.
40225 The process already has the maximum number of files open.
40228 The limit on the total number of files open on the system
40232 The call was interrupted by the user.
40238 @unnumberedsubsubsec close
40239 @cindex close, file-i/o system call
40248 @samp{Fclose,@var{fd}}
40250 @item Return value:
40251 @code{close} returns zero on success, or -1 if an error occurred.
40257 @var{fd} isn't a valid open file descriptor.
40260 The call was interrupted by the user.
40266 @unnumberedsubsubsec read
40267 @cindex read, file-i/o system call
40272 int read(int fd, void *buf, unsigned int count);
40276 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
40278 @item Return value:
40279 On success, the number of bytes read is returned.
40280 Zero indicates end of file. If count is zero, read
40281 returns zero as well. On error, -1 is returned.
40287 @var{fd} is not a valid file descriptor or is not open for
40291 @var{bufptr} is an invalid pointer value.
40294 The call was interrupted by the user.
40300 @unnumberedsubsubsec write
40301 @cindex write, file-i/o system call
40306 int write(int fd, const void *buf, unsigned int count);
40310 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
40312 @item Return value:
40313 On success, the number of bytes written are returned.
40314 Zero indicates nothing was written. On error, -1
40321 @var{fd} is not a valid file descriptor or is not open for
40325 @var{bufptr} is an invalid pointer value.
40328 An attempt was made to write a file that exceeds the
40329 host-specific maximum file size allowed.
40332 No space on device to write the data.
40335 The call was interrupted by the user.
40341 @unnumberedsubsubsec lseek
40342 @cindex lseek, file-i/o system call
40347 long lseek (int fd, long offset, int flag);
40351 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
40353 @var{flag} is one of:
40357 The offset is set to @var{offset} bytes.
40360 The offset is set to its current location plus @var{offset}
40364 The offset is set to the size of the file plus @var{offset}
40368 @item Return value:
40369 On success, the resulting unsigned offset in bytes from
40370 the beginning of the file is returned. Otherwise, a
40371 value of -1 is returned.
40377 @var{fd} is not a valid open file descriptor.
40380 @var{fd} is associated with the @value{GDBN} console.
40383 @var{flag} is not a proper value.
40386 The call was interrupted by the user.
40392 @unnumberedsubsubsec rename
40393 @cindex rename, file-i/o system call
40398 int rename(const char *oldpath, const char *newpath);
40402 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
40404 @item Return value:
40405 On success, zero is returned. On error, -1 is returned.
40411 @var{newpath} is an existing directory, but @var{oldpath} is not a
40415 @var{newpath} is a non-empty directory.
40418 @var{oldpath} or @var{newpath} is a directory that is in use by some
40422 An attempt was made to make a directory a subdirectory
40426 A component used as a directory in @var{oldpath} or new
40427 path is not a directory. Or @var{oldpath} is a directory
40428 and @var{newpath} exists but is not a directory.
40431 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
40434 No access to the file or the path of the file.
40438 @var{oldpath} or @var{newpath} was too long.
40441 A directory component in @var{oldpath} or @var{newpath} does not exist.
40444 The file is on a read-only filesystem.
40447 The device containing the file has no room for the new
40451 The call was interrupted by the user.
40457 @unnumberedsubsubsec unlink
40458 @cindex unlink, file-i/o system call
40463 int unlink(const char *pathname);
40467 @samp{Funlink,@var{pathnameptr}/@var{len}}
40469 @item Return value:
40470 On success, zero is returned. On error, -1 is returned.
40476 No access to the file or the path of the file.
40479 The system does not allow unlinking of directories.
40482 The file @var{pathname} cannot be unlinked because it's
40483 being used by another process.
40486 @var{pathnameptr} is an invalid pointer value.
40489 @var{pathname} was too long.
40492 A directory component in @var{pathname} does not exist.
40495 A component of the path is not a directory.
40498 The file is on a read-only filesystem.
40501 The call was interrupted by the user.
40507 @unnumberedsubsubsec stat/fstat
40508 @cindex fstat, file-i/o system call
40509 @cindex stat, file-i/o system call
40514 int stat(const char *pathname, struct stat *buf);
40515 int fstat(int fd, struct stat *buf);
40519 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
40520 @samp{Ffstat,@var{fd},@var{bufptr}}
40522 @item Return value:
40523 On success, zero is returned. On error, -1 is returned.
40529 @var{fd} is not a valid open file.
40532 A directory component in @var{pathname} does not exist or the
40533 path is an empty string.
40536 A component of the path is not a directory.
40539 @var{pathnameptr} is an invalid pointer value.
40542 No access to the file or the path of the file.
40545 @var{pathname} was too long.
40548 The call was interrupted by the user.
40554 @unnumberedsubsubsec gettimeofday
40555 @cindex gettimeofday, file-i/o system call
40560 int gettimeofday(struct timeval *tv, void *tz);
40564 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
40566 @item Return value:
40567 On success, 0 is returned, -1 otherwise.
40573 @var{tz} is a non-NULL pointer.
40576 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
40582 @unnumberedsubsubsec isatty
40583 @cindex isatty, file-i/o system call
40588 int isatty(int fd);
40592 @samp{Fisatty,@var{fd}}
40594 @item Return value:
40595 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
40601 The call was interrupted by the user.
40606 Note that the @code{isatty} call is treated as a special case: it returns
40607 1 to the target if the file descriptor is attached
40608 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
40609 would require implementing @code{ioctl} and would be more complex than
40614 @unnumberedsubsubsec system
40615 @cindex system, file-i/o system call
40620 int system(const char *command);
40624 @samp{Fsystem,@var{commandptr}/@var{len}}
40626 @item Return value:
40627 If @var{len} is zero, the return value indicates whether a shell is
40628 available. A zero return value indicates a shell is not available.
40629 For non-zero @var{len}, the value returned is -1 on error and the
40630 return status of the command otherwise. Only the exit status of the
40631 command is returned, which is extracted from the host's @code{system}
40632 return value by calling @code{WEXITSTATUS(retval)}. In case
40633 @file{/bin/sh} could not be executed, 127 is returned.
40639 The call was interrupted by the user.
40644 @value{GDBN} takes over the full task of calling the necessary host calls
40645 to perform the @code{system} call. The return value of @code{system} on
40646 the host is simplified before it's returned
40647 to the target. Any termination signal information from the child process
40648 is discarded, and the return value consists
40649 entirely of the exit status of the called command.
40651 Due to security concerns, the @code{system} call is by default refused
40652 by @value{GDBN}. The user has to allow this call explicitly with the
40653 @code{set remote system-call-allowed 1} command.
40656 @item set remote system-call-allowed
40657 @kindex set remote system-call-allowed
40658 Control whether to allow the @code{system} calls in the File I/O
40659 protocol for the remote target. The default is zero (disabled).
40661 @item show remote system-call-allowed
40662 @kindex show remote system-call-allowed
40663 Show whether the @code{system} calls are allowed in the File I/O
40667 @node Protocol-specific Representation of Datatypes
40668 @subsection Protocol-specific Representation of Datatypes
40669 @cindex protocol-specific representation of datatypes, in file-i/o protocol
40672 * Integral Datatypes::
40674 * Memory Transfer::
40679 @node Integral Datatypes
40680 @unnumberedsubsubsec Integral Datatypes
40681 @cindex integral datatypes, in file-i/o protocol
40683 The integral datatypes used in the system calls are @code{int},
40684 @code{unsigned int}, @code{long}, @code{unsigned long},
40685 @code{mode_t}, and @code{time_t}.
40687 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
40688 implemented as 32 bit values in this protocol.
40690 @code{long} and @code{unsigned long} are implemented as 64 bit types.
40692 @xref{Limits}, for corresponding MIN and MAX values (similar to those
40693 in @file{limits.h}) to allow range checking on host and target.
40695 @code{time_t} datatypes are defined as seconds since the Epoch.
40697 All integral datatypes transferred as part of a memory read or write of a
40698 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
40701 @node Pointer Values
40702 @unnumberedsubsubsec Pointer Values
40703 @cindex pointer values, in file-i/o protocol
40705 Pointers to target data are transmitted as they are. An exception
40706 is made for pointers to buffers for which the length isn't
40707 transmitted as part of the function call, namely strings. Strings
40708 are transmitted as a pointer/length pair, both as hex values, e.g.@:
40715 which is a pointer to data of length 18 bytes at position 0x1aaf.
40716 The length is defined as the full string length in bytes, including
40717 the trailing null byte. For example, the string @code{"hello world"}
40718 at address 0x123456 is transmitted as
40724 @node Memory Transfer
40725 @unnumberedsubsubsec Memory Transfer
40726 @cindex memory transfer, in file-i/o protocol
40728 Structured data which is transferred using a memory read or write (for
40729 example, a @code{struct stat}) is expected to be in a protocol-specific format
40730 with all scalar multibyte datatypes being big endian. Translation to
40731 this representation needs to be done both by the target before the @code{F}
40732 packet is sent, and by @value{GDBN} before
40733 it transfers memory to the target. Transferred pointers to structured
40734 data should point to the already-coerced data at any time.
40738 @unnumberedsubsubsec struct stat
40739 @cindex struct stat, in file-i/o protocol
40741 The buffer of type @code{struct stat} used by the target and @value{GDBN}
40742 is defined as follows:
40746 unsigned int st_dev; /* device */
40747 unsigned int st_ino; /* inode */
40748 mode_t st_mode; /* protection */
40749 unsigned int st_nlink; /* number of hard links */
40750 unsigned int st_uid; /* user ID of owner */
40751 unsigned int st_gid; /* group ID of owner */
40752 unsigned int st_rdev; /* device type (if inode device) */
40753 unsigned long st_size; /* total size, in bytes */
40754 unsigned long st_blksize; /* blocksize for filesystem I/O */
40755 unsigned long st_blocks; /* number of blocks allocated */
40756 time_t st_atime; /* time of last access */
40757 time_t st_mtime; /* time of last modification */
40758 time_t st_ctime; /* time of last change */
40762 The integral datatypes conform to the definitions given in the
40763 appropriate section (see @ref{Integral Datatypes}, for details) so this
40764 structure is of size 64 bytes.
40766 The values of several fields have a restricted meaning and/or
40772 A value of 0 represents a file, 1 the console.
40775 No valid meaning for the target. Transmitted unchanged.
40778 Valid mode bits are described in @ref{Constants}. Any other
40779 bits have currently no meaning for the target.
40784 No valid meaning for the target. Transmitted unchanged.
40789 These values have a host and file system dependent
40790 accuracy. Especially on Windows hosts, the file system may not
40791 support exact timing values.
40794 The target gets a @code{struct stat} of the above representation and is
40795 responsible for coercing it to the target representation before
40798 Note that due to size differences between the host, target, and protocol
40799 representations of @code{struct stat} members, these members could eventually
40800 get truncated on the target.
40802 @node struct timeval
40803 @unnumberedsubsubsec struct timeval
40804 @cindex struct timeval, in file-i/o protocol
40806 The buffer of type @code{struct timeval} used by the File-I/O protocol
40807 is defined as follows:
40811 time_t tv_sec; /* second */
40812 long tv_usec; /* microsecond */
40816 The integral datatypes conform to the definitions given in the
40817 appropriate section (see @ref{Integral Datatypes}, for details) so this
40818 structure is of size 8 bytes.
40821 @subsection Constants
40822 @cindex constants, in file-i/o protocol
40824 The following values are used for the constants inside of the
40825 protocol. @value{GDBN} and target are responsible for translating these
40826 values before and after the call as needed.
40837 @unnumberedsubsubsec Open Flags
40838 @cindex open flags, in file-i/o protocol
40840 All values are given in hexadecimal representation.
40852 @node mode_t Values
40853 @unnumberedsubsubsec mode_t Values
40854 @cindex mode_t values, in file-i/o protocol
40856 All values are given in octal representation.
40873 @unnumberedsubsubsec Errno Values
40874 @cindex errno values, in file-i/o protocol
40876 All values are given in decimal representation.
40901 @code{EUNKNOWN} is used as a fallback error value if a host system returns
40902 any error value not in the list of supported error numbers.
40905 @unnumberedsubsubsec Lseek Flags
40906 @cindex lseek flags, in file-i/o protocol
40915 @unnumberedsubsubsec Limits
40916 @cindex limits, in file-i/o protocol
40918 All values are given in decimal representation.
40921 INT_MIN -2147483648
40923 UINT_MAX 4294967295
40924 LONG_MIN -9223372036854775808
40925 LONG_MAX 9223372036854775807
40926 ULONG_MAX 18446744073709551615
40929 @node File-I/O Examples
40930 @subsection File-I/O Examples
40931 @cindex file-i/o examples
40933 Example sequence of a write call, file descriptor 3, buffer is at target
40934 address 0x1234, 6 bytes should be written:
40937 <- @code{Fwrite,3,1234,6}
40938 @emph{request memory read from target}
40941 @emph{return "6 bytes written"}
40945 Example sequence of a read call, file descriptor 3, buffer is at target
40946 address 0x1234, 6 bytes should be read:
40949 <- @code{Fread,3,1234,6}
40950 @emph{request memory write to target}
40951 -> @code{X1234,6:XXXXXX}
40952 @emph{return "6 bytes read"}
40956 Example sequence of a read call, call fails on the host due to invalid
40957 file descriptor (@code{EBADF}):
40960 <- @code{Fread,3,1234,6}
40964 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
40968 <- @code{Fread,3,1234,6}
40973 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
40977 <- @code{Fread,3,1234,6}
40978 -> @code{X1234,6:XXXXXX}
40982 @node Library List Format
40983 @section Library List Format
40984 @cindex library list format, remote protocol
40986 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
40987 same process as your application to manage libraries. In this case,
40988 @value{GDBN} can use the loader's symbol table and normal memory
40989 operations to maintain a list of shared libraries. On other
40990 platforms, the operating system manages loaded libraries.
40991 @value{GDBN} can not retrieve the list of currently loaded libraries
40992 through memory operations, so it uses the @samp{qXfer:libraries:read}
40993 packet (@pxref{qXfer library list read}) instead. The remote stub
40994 queries the target's operating system and reports which libraries
40997 The @samp{qXfer:libraries:read} packet returns an XML document which
40998 lists loaded libraries and their offsets. Each library has an
40999 associated name and one or more segment or section base addresses,
41000 which report where the library was loaded in memory.
41002 For the common case of libraries that are fully linked binaries, the
41003 library should have a list of segments. If the target supports
41004 dynamic linking of a relocatable object file, its library XML element
41005 should instead include a list of allocated sections. The segment or
41006 section bases are start addresses, not relocation offsets; they do not
41007 depend on the library's link-time base addresses.
41009 @value{GDBN} must be linked with the Expat library to support XML
41010 library lists. @xref{Expat}.
41012 A simple memory map, with one loaded library relocated by a single
41013 offset, looks like this:
41017 <library name="/lib/libc.so.6">
41018 <segment address="0x10000000"/>
41023 Another simple memory map, with one loaded library with three
41024 allocated sections (.text, .data, .bss), looks like this:
41028 <library name="sharedlib.o">
41029 <section address="0x10000000"/>
41030 <section address="0x20000000"/>
41031 <section address="0x30000000"/>
41036 The format of a library list is described by this DTD:
41039 <!-- library-list: Root element with versioning -->
41040 <!ELEMENT library-list (library)*>
41041 <!ATTLIST library-list version CDATA #FIXED "1.0">
41042 <!ELEMENT library (segment*, section*)>
41043 <!ATTLIST library name CDATA #REQUIRED>
41044 <!ELEMENT segment EMPTY>
41045 <!ATTLIST segment address CDATA #REQUIRED>
41046 <!ELEMENT section EMPTY>
41047 <!ATTLIST section address CDATA #REQUIRED>
41050 In addition, segments and section descriptors cannot be mixed within a
41051 single library element, and you must supply at least one segment or
41052 section for each library.
41054 @node Library List Format for SVR4 Targets
41055 @section Library List Format for SVR4 Targets
41056 @cindex library list format, remote protocol
41058 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
41059 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
41060 shared libraries. Still a special library list provided by this packet is
41061 more efficient for the @value{GDBN} remote protocol.
41063 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
41064 loaded libraries and their SVR4 linker parameters. For each library on SVR4
41065 target, the following parameters are reported:
41069 @code{name}, the absolute file name from the @code{l_name} field of
41070 @code{struct link_map}.
41072 @code{lm} with address of @code{struct link_map} used for TLS
41073 (Thread Local Storage) access.
41075 @code{l_addr}, the displacement as read from the field @code{l_addr} of
41076 @code{struct link_map}. For prelinked libraries this is not an absolute
41077 memory address. It is a displacement of absolute memory address against
41078 address the file was prelinked to during the library load.
41080 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
41083 Additionally the single @code{main-lm} attribute specifies address of
41084 @code{struct link_map} used for the main executable. This parameter is used
41085 for TLS access and its presence is optional.
41087 @value{GDBN} must be linked with the Expat library to support XML
41088 SVR4 library lists. @xref{Expat}.
41090 A simple memory map, with two loaded libraries (which do not use prelink),
41094 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
41095 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
41097 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
41099 </library-list-svr>
41102 The format of an SVR4 library list is described by this DTD:
41105 <!-- library-list-svr4: Root element with versioning -->
41106 <!ELEMENT library-list-svr4 (library)*>
41107 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
41108 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
41109 <!ELEMENT library EMPTY>
41110 <!ATTLIST library name CDATA #REQUIRED>
41111 <!ATTLIST library lm CDATA #REQUIRED>
41112 <!ATTLIST library l_addr CDATA #REQUIRED>
41113 <!ATTLIST library l_ld CDATA #REQUIRED>
41116 @node Memory Map Format
41117 @section Memory Map Format
41118 @cindex memory map format
41120 To be able to write into flash memory, @value{GDBN} needs to obtain a
41121 memory map from the target. This section describes the format of the
41124 The memory map is obtained using the @samp{qXfer:memory-map:read}
41125 (@pxref{qXfer memory map read}) packet and is an XML document that
41126 lists memory regions.
41128 @value{GDBN} must be linked with the Expat library to support XML
41129 memory maps. @xref{Expat}.
41131 The top-level structure of the document is shown below:
41134 <?xml version="1.0"?>
41135 <!DOCTYPE memory-map
41136 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
41137 "http://sourceware.org/gdb/gdb-memory-map.dtd">
41143 Each region can be either:
41148 A region of RAM starting at @var{addr} and extending for @var{length}
41152 <memory type="ram" start="@var{addr}" length="@var{length}"/>
41157 A region of read-only memory:
41160 <memory type="rom" start="@var{addr}" length="@var{length}"/>
41165 A region of flash memory, with erasure blocks @var{blocksize}
41169 <memory type="flash" start="@var{addr}" length="@var{length}">
41170 <property name="blocksize">@var{blocksize}</property>
41176 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
41177 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
41178 packets to write to addresses in such ranges.
41180 The formal DTD for memory map format is given below:
41183 <!-- ................................................... -->
41184 <!-- Memory Map XML DTD ................................ -->
41185 <!-- File: memory-map.dtd .............................. -->
41186 <!-- .................................... .............. -->
41187 <!-- memory-map.dtd -->
41188 <!-- memory-map: Root element with versioning -->
41189 <!ELEMENT memory-map (memory)*>
41190 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
41191 <!ELEMENT memory (property)*>
41192 <!-- memory: Specifies a memory region,
41193 and its type, or device. -->
41194 <!ATTLIST memory type (ram|rom|flash) #REQUIRED
41195 start CDATA #REQUIRED
41196 length CDATA #REQUIRED>
41197 <!-- property: Generic attribute tag -->
41198 <!ELEMENT property (#PCDATA | property)*>
41199 <!ATTLIST property name (blocksize) #REQUIRED>
41202 @node Thread List Format
41203 @section Thread List Format
41204 @cindex thread list format
41206 To efficiently update the list of threads and their attributes,
41207 @value{GDBN} issues the @samp{qXfer:threads:read} packet
41208 (@pxref{qXfer threads read}) and obtains the XML document with
41209 the following structure:
41212 <?xml version="1.0"?>
41214 <thread id="id" core="0" name="name">
41215 ... description ...
41220 Each @samp{thread} element must have the @samp{id} attribute that
41221 identifies the thread (@pxref{thread-id syntax}). The
41222 @samp{core} attribute, if present, specifies which processor core
41223 the thread was last executing on. The @samp{name} attribute, if
41224 present, specifies the human-readable name of the thread. The content
41225 of the of @samp{thread} element is interpreted as human-readable
41226 auxiliary information. The @samp{handle} attribute, if present,
41227 is a hex encoded representation of the thread handle.
41230 @node Traceframe Info Format
41231 @section Traceframe Info Format
41232 @cindex traceframe info format
41234 To be able to know which objects in the inferior can be examined when
41235 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
41236 memory ranges, registers and trace state variables that have been
41237 collected in a traceframe.
41239 This list is obtained using the @samp{qXfer:traceframe-info:read}
41240 (@pxref{qXfer traceframe info read}) packet and is an XML document.
41242 @value{GDBN} must be linked with the Expat library to support XML
41243 traceframe info discovery. @xref{Expat}.
41245 The top-level structure of the document is shown below:
41248 <?xml version="1.0"?>
41249 <!DOCTYPE traceframe-info
41250 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
41251 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
41257 Each traceframe block can be either:
41262 A region of collected memory starting at @var{addr} and extending for
41263 @var{length} bytes from there:
41266 <memory start="@var{addr}" length="@var{length}"/>
41270 A block indicating trace state variable numbered @var{number} has been
41274 <tvar id="@var{number}"/>
41279 The formal DTD for the traceframe info format is given below:
41282 <!ELEMENT traceframe-info (memory | tvar)* >
41283 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
41285 <!ELEMENT memory EMPTY>
41286 <!ATTLIST memory start CDATA #REQUIRED
41287 length CDATA #REQUIRED>
41289 <!ATTLIST tvar id CDATA #REQUIRED>
41292 @node Branch Trace Format
41293 @section Branch Trace Format
41294 @cindex branch trace format
41296 In order to display the branch trace of an inferior thread,
41297 @value{GDBN} needs to obtain the list of branches. This list is
41298 represented as list of sequential code blocks that are connected via
41299 branches. The code in each block has been executed sequentially.
41301 This list is obtained using the @samp{qXfer:btrace:read}
41302 (@pxref{qXfer btrace read}) packet and is an XML document.
41304 @value{GDBN} must be linked with the Expat library to support XML
41305 traceframe info discovery. @xref{Expat}.
41307 The top-level structure of the document is shown below:
41310 <?xml version="1.0"?>
41312 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
41313 "http://sourceware.org/gdb/gdb-btrace.dtd">
41322 A block of sequentially executed instructions starting at @var{begin}
41323 and ending at @var{end}:
41326 <block begin="@var{begin}" end="@var{end}"/>
41331 The formal DTD for the branch trace format is given below:
41334 <!ELEMENT btrace (block* | pt) >
41335 <!ATTLIST btrace version CDATA #FIXED "1.0">
41337 <!ELEMENT block EMPTY>
41338 <!ATTLIST block begin CDATA #REQUIRED
41339 end CDATA #REQUIRED>
41341 <!ELEMENT pt (pt-config?, raw?)>
41343 <!ELEMENT pt-config (cpu?)>
41345 <!ELEMENT cpu EMPTY>
41346 <!ATTLIST cpu vendor CDATA #REQUIRED
41347 family CDATA #REQUIRED
41348 model CDATA #REQUIRED
41349 stepping CDATA #REQUIRED>
41351 <!ELEMENT raw (#PCDATA)>
41354 @node Branch Trace Configuration Format
41355 @section Branch Trace Configuration Format
41356 @cindex branch trace configuration format
41358 For each inferior thread, @value{GDBN} can obtain the branch trace
41359 configuration using the @samp{qXfer:btrace-conf:read}
41360 (@pxref{qXfer btrace-conf read}) packet.
41362 The configuration describes the branch trace format and configuration
41363 settings for that format. The following information is described:
41367 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
41370 The size of the @acronym{BTS} ring buffer in bytes.
41373 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
41377 The size of the @acronym{Intel PT} ring buffer in bytes.
41381 @value{GDBN} must be linked with the Expat library to support XML
41382 branch trace configuration discovery. @xref{Expat}.
41384 The formal DTD for the branch trace configuration format is given below:
41387 <!ELEMENT btrace-conf (bts?, pt?)>
41388 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
41390 <!ELEMENT bts EMPTY>
41391 <!ATTLIST bts size CDATA #IMPLIED>
41393 <!ELEMENT pt EMPTY>
41394 <!ATTLIST pt size CDATA #IMPLIED>
41397 @include agentexpr.texi
41399 @node Target Descriptions
41400 @appendix Target Descriptions
41401 @cindex target descriptions
41403 One of the challenges of using @value{GDBN} to debug embedded systems
41404 is that there are so many minor variants of each processor
41405 architecture in use. It is common practice for vendors to start with
41406 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
41407 and then make changes to adapt it to a particular market niche. Some
41408 architectures have hundreds of variants, available from dozens of
41409 vendors. This leads to a number of problems:
41413 With so many different customized processors, it is difficult for
41414 the @value{GDBN} maintainers to keep up with the changes.
41416 Since individual variants may have short lifetimes or limited
41417 audiences, it may not be worthwhile to carry information about every
41418 variant in the @value{GDBN} source tree.
41420 When @value{GDBN} does support the architecture of the embedded system
41421 at hand, the task of finding the correct architecture name to give the
41422 @command{set architecture} command can be error-prone.
41425 To address these problems, the @value{GDBN} remote protocol allows a
41426 target system to not only identify itself to @value{GDBN}, but to
41427 actually describe its own features. This lets @value{GDBN} support
41428 processor variants it has never seen before --- to the extent that the
41429 descriptions are accurate, and that @value{GDBN} understands them.
41431 @value{GDBN} must be linked with the Expat library to support XML
41432 target descriptions. @xref{Expat}.
41435 * Retrieving Descriptions:: How descriptions are fetched from a target.
41436 * Target Description Format:: The contents of a target description.
41437 * Predefined Target Types:: Standard types available for target
41439 * Enum Target Types:: How to define enum target types.
41440 * Standard Target Features:: Features @value{GDBN} knows about.
41443 @node Retrieving Descriptions
41444 @section Retrieving Descriptions
41446 Target descriptions can be read from the target automatically, or
41447 specified by the user manually. The default behavior is to read the
41448 description from the target. @value{GDBN} retrieves it via the remote
41449 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
41450 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
41451 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
41452 XML document, of the form described in @ref{Target Description
41455 Alternatively, you can specify a file to read for the target description.
41456 If a file is set, the target will not be queried. The commands to
41457 specify a file are:
41460 @cindex set tdesc filename
41461 @item set tdesc filename @var{path}
41462 Read the target description from @var{path}.
41464 @cindex unset tdesc filename
41465 @item unset tdesc filename
41466 Do not read the XML target description from a file. @value{GDBN}
41467 will use the description supplied by the current target.
41469 @cindex show tdesc filename
41470 @item show tdesc filename
41471 Show the filename to read for a target description, if any.
41475 @node Target Description Format
41476 @section Target Description Format
41477 @cindex target descriptions, XML format
41479 A target description annex is an @uref{http://www.w3.org/XML/, XML}
41480 document which complies with the Document Type Definition provided in
41481 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
41482 means you can use generally available tools like @command{xmllint} to
41483 check that your feature descriptions are well-formed and valid.
41484 However, to help people unfamiliar with XML write descriptions for
41485 their targets, we also describe the grammar here.
41487 Target descriptions can identify the architecture of the remote target
41488 and (for some architectures) provide information about custom register
41489 sets. They can also identify the OS ABI of the remote target.
41490 @value{GDBN} can use this information to autoconfigure for your
41491 target, or to warn you if you connect to an unsupported target.
41493 Here is a simple target description:
41496 <target version="1.0">
41497 <architecture>i386:x86-64</architecture>
41502 This minimal description only says that the target uses
41503 the x86-64 architecture.
41505 A target description has the following overall form, with [ ] marking
41506 optional elements and @dots{} marking repeatable elements. The elements
41507 are explained further below.
41510 <?xml version="1.0"?>
41511 <!DOCTYPE target SYSTEM "gdb-target.dtd">
41512 <target version="1.0">
41513 @r{[}@var{architecture}@r{]}
41514 @r{[}@var{osabi}@r{]}
41515 @r{[}@var{compatible}@r{]}
41516 @r{[}@var{feature}@dots{}@r{]}
41521 The description is generally insensitive to whitespace and line
41522 breaks, under the usual common-sense rules. The XML version
41523 declaration and document type declaration can generally be omitted
41524 (@value{GDBN} does not require them), but specifying them may be
41525 useful for XML validation tools. The @samp{version} attribute for
41526 @samp{<target>} may also be omitted, but we recommend
41527 including it; if future versions of @value{GDBN} use an incompatible
41528 revision of @file{gdb-target.dtd}, they will detect and report
41529 the version mismatch.
41531 @subsection Inclusion
41532 @cindex target descriptions, inclusion
41535 @cindex <xi:include>
41538 It can sometimes be valuable to split a target description up into
41539 several different annexes, either for organizational purposes, or to
41540 share files between different possible target descriptions. You can
41541 divide a description into multiple files by replacing any element of
41542 the target description with an inclusion directive of the form:
41545 <xi:include href="@var{document}"/>
41549 When @value{GDBN} encounters an element of this form, it will retrieve
41550 the named XML @var{document}, and replace the inclusion directive with
41551 the contents of that document. If the current description was read
41552 using @samp{qXfer}, then so will be the included document;
41553 @var{document} will be interpreted as the name of an annex. If the
41554 current description was read from a file, @value{GDBN} will look for
41555 @var{document} as a file in the same directory where it found the
41556 original description.
41558 @subsection Architecture
41559 @cindex <architecture>
41561 An @samp{<architecture>} element has this form:
41564 <architecture>@var{arch}</architecture>
41567 @var{arch} is one of the architectures from the set accepted by
41568 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
41571 @cindex @code{<osabi>}
41573 This optional field was introduced in @value{GDBN} version 7.0.
41574 Previous versions of @value{GDBN} ignore it.
41576 An @samp{<osabi>} element has this form:
41579 <osabi>@var{abi-name}</osabi>
41582 @var{abi-name} is an OS ABI name from the same selection accepted by
41583 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
41585 @subsection Compatible Architecture
41586 @cindex @code{<compatible>}
41588 This optional field was introduced in @value{GDBN} version 7.0.
41589 Previous versions of @value{GDBN} ignore it.
41591 A @samp{<compatible>} element has this form:
41594 <compatible>@var{arch}</compatible>
41597 @var{arch} is one of the architectures from the set accepted by
41598 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
41600 A @samp{<compatible>} element is used to specify that the target
41601 is able to run binaries in some other than the main target architecture
41602 given by the @samp{<architecture>} element. For example, on the
41603 Cell Broadband Engine, the main architecture is @code{powerpc:common}
41604 or @code{powerpc:common64}, but the system is able to run binaries
41605 in the @code{spu} architecture as well. The way to describe this
41606 capability with @samp{<compatible>} is as follows:
41609 <architecture>powerpc:common</architecture>
41610 <compatible>spu</compatible>
41613 @subsection Features
41616 Each @samp{<feature>} describes some logical portion of the target
41617 system. Features are currently used to describe available CPU
41618 registers and the types of their contents. A @samp{<feature>} element
41622 <feature name="@var{name}">
41623 @r{[}@var{type}@dots{}@r{]}
41629 Each feature's name should be unique within the description. The name
41630 of a feature does not matter unless @value{GDBN} has some special
41631 knowledge of the contents of that feature; if it does, the feature
41632 should have its standard name. @xref{Standard Target Features}.
41636 Any register's value is a collection of bits which @value{GDBN} must
41637 interpret. The default interpretation is a two's complement integer,
41638 but other types can be requested by name in the register description.
41639 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
41640 Target Types}), and the description can define additional composite
41643 Each type element must have an @samp{id} attribute, which gives
41644 a unique (within the containing @samp{<feature>}) name to the type.
41645 Types must be defined before they are used.
41648 Some targets offer vector registers, which can be treated as arrays
41649 of scalar elements. These types are written as @samp{<vector>} elements,
41650 specifying the array element type, @var{type}, and the number of elements,
41654 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
41658 If a register's value is usefully viewed in multiple ways, define it
41659 with a union type containing the useful representations. The
41660 @samp{<union>} element contains one or more @samp{<field>} elements,
41661 each of which has a @var{name} and a @var{type}:
41664 <union id="@var{id}">
41665 <field name="@var{name}" type="@var{type}"/>
41672 If a register's value is composed from several separate values, define
41673 it with either a structure type or a flags type.
41674 A flags type may only contain bitfields.
41675 A structure type may either contain only bitfields or contain no bitfields.
41676 If the value contains only bitfields, its total size in bytes must be
41679 Non-bitfield values have a @var{name} and @var{type}.
41682 <struct id="@var{id}">
41683 <field name="@var{name}" type="@var{type}"/>
41688 Both @var{name} and @var{type} values are required.
41689 No implicit padding is added.
41691 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
41694 <struct id="@var{id}" size="@var{size}">
41695 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
41701 <flags id="@var{id}" size="@var{size}">
41702 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
41707 The @var{name} value is required.
41708 Bitfield values may be named with the empty string, @samp{""},
41709 in which case the field is ``filler'' and its value is not printed.
41710 Not all bits need to be specified, so ``filler'' fields are optional.
41712 The @var{start} and @var{end} values are required, and @var{type}
41714 The field's @var{start} must be less than or equal to its @var{end},
41715 and zero represents the least significant bit.
41717 The default value of @var{type} is @code{bool} for single bit fields,
41718 and an unsigned integer otherwise.
41720 Which to choose? Structures or flags?
41722 Registers defined with @samp{flags} have these advantages over
41723 defining them with @samp{struct}:
41727 Arithmetic may be performed on them as if they were integers.
41729 They are printed in a more readable fashion.
41732 Registers defined with @samp{struct} have one advantage over
41733 defining them with @samp{flags}:
41737 One can fetch individual fields like in @samp{C}.
41740 (gdb) print $my_struct_reg.field3
41746 @subsection Registers
41749 Each register is represented as an element with this form:
41752 <reg name="@var{name}"
41753 bitsize="@var{size}"
41754 @r{[}regnum="@var{num}"@r{]}
41755 @r{[}save-restore="@var{save-restore}"@r{]}
41756 @r{[}type="@var{type}"@r{]}
41757 @r{[}group="@var{group}"@r{]}/>
41761 The components are as follows:
41766 The register's name; it must be unique within the target description.
41769 The register's size, in bits.
41772 The register's number. If omitted, a register's number is one greater
41773 than that of the previous register (either in the current feature or in
41774 a preceding feature); the first register in the target description
41775 defaults to zero. This register number is used to read or write
41776 the register; e.g.@: it is used in the remote @code{p} and @code{P}
41777 packets, and registers appear in the @code{g} and @code{G} packets
41778 in order of increasing register number.
41781 Whether the register should be preserved across inferior function
41782 calls; this must be either @code{yes} or @code{no}. The default is
41783 @code{yes}, which is appropriate for most registers except for
41784 some system control registers; this is not related to the target's
41788 The type of the register. It may be a predefined type, a type
41789 defined in the current feature, or one of the special types @code{int}
41790 and @code{float}. @code{int} is an integer type of the correct size
41791 for @var{bitsize}, and @code{float} is a floating point type (in the
41792 architecture's normal floating point format) of the correct size for
41793 @var{bitsize}. The default is @code{int}.
41796 The register group to which this register belongs. It can be one of the
41797 standard register groups @code{general}, @code{float}, @code{vector} or an
41798 arbitrary string. Group names should be limited to alphanumeric characters.
41799 If a group name is made up of multiple words the words may be separated by
41800 hyphens; e.g.@: @code{special-group} or @code{ultra-special-group}. If no
41801 @var{group} is specified, @value{GDBN} will not display the register in
41802 @code{info registers}.
41806 @node Predefined Target Types
41807 @section Predefined Target Types
41808 @cindex target descriptions, predefined types
41810 Type definitions in the self-description can build up composite types
41811 from basic building blocks, but can not define fundamental types. Instead,
41812 standard identifiers are provided by @value{GDBN} for the fundamental
41813 types. The currently supported types are:
41818 Boolean type, occupying a single bit.
41825 Signed integer types holding the specified number of bits.
41832 Unsigned integer types holding the specified number of bits.
41836 Pointers to unspecified code and data. The program counter and
41837 any dedicated return address register may be marked as code
41838 pointers; printing a code pointer converts it into a symbolic
41839 address. The stack pointer and any dedicated address registers
41840 may be marked as data pointers.
41843 Single precision IEEE floating point.
41846 Double precision IEEE floating point.
41849 The 12-byte extended precision format used by ARM FPA registers.
41852 The 10-byte extended precision format used by x87 registers.
41855 32bit @sc{eflags} register used by x86.
41858 32bit @sc{mxcsr} register used by x86.
41862 @node Enum Target Types
41863 @section Enum Target Types
41864 @cindex target descriptions, enum types
41866 Enum target types are useful in @samp{struct} and @samp{flags}
41867 register descriptions. @xref{Target Description Format}.
41869 Enum types have a name, size and a list of name/value pairs.
41872 <enum id="@var{id}" size="@var{size}">
41873 <evalue name="@var{name}" value="@var{value}"/>
41878 Enums must be defined before they are used.
41881 <enum id="levels_type" size="4">
41882 <evalue name="low" value="0"/>
41883 <evalue name="high" value="1"/>
41885 <flags id="flags_type" size="4">
41886 <field name="X" start="0"/>
41887 <field name="LEVEL" start="1" end="1" type="levels_type"/>
41889 <reg name="flags" bitsize="32" type="flags_type"/>
41892 Given that description, a value of 3 for the @samp{flags} register
41893 would be printed as:
41896 (gdb) info register flags
41897 flags 0x3 [ X LEVEL=high ]
41900 @node Standard Target Features
41901 @section Standard Target Features
41902 @cindex target descriptions, standard features
41904 A target description must contain either no registers or all the
41905 target's registers. If the description contains no registers, then
41906 @value{GDBN} will assume a default register layout, selected based on
41907 the architecture. If the description contains any registers, the
41908 default layout will not be used; the standard registers must be
41909 described in the target description, in such a way that @value{GDBN}
41910 can recognize them.
41912 This is accomplished by giving specific names to feature elements
41913 which contain standard registers. @value{GDBN} will look for features
41914 with those names and verify that they contain the expected registers;
41915 if any known feature is missing required registers, or if any required
41916 feature is missing, @value{GDBN} will reject the target
41917 description. You can add additional registers to any of the
41918 standard features --- @value{GDBN} will display them just as if
41919 they were added to an unrecognized feature.
41921 This section lists the known features and their expected contents.
41922 Sample XML documents for these features are included in the
41923 @value{GDBN} source tree, in the directory @file{gdb/features}.
41925 Names recognized by @value{GDBN} should include the name of the
41926 company or organization which selected the name, and the overall
41927 architecture to which the feature applies; so e.g.@: the feature
41928 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
41930 The names of registers are not case sensitive for the purpose
41931 of recognizing standard features, but @value{GDBN} will only display
41932 registers using the capitalization used in the description.
41935 * AArch64 Features::
41939 * MicroBlaze Features::
41943 * Nios II Features::
41944 * OpenRISC 1000 Features::
41945 * PowerPC Features::
41946 * S/390 and System z Features::
41952 @node AArch64 Features
41953 @subsection AArch64 Features
41954 @cindex target descriptions, AArch64 features
41956 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
41957 targets. It should contain registers @samp{x0} through @samp{x30},
41958 @samp{sp}, @samp{pc}, and @samp{cpsr}.
41960 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
41961 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
41965 @subsection ARC Features
41966 @cindex target descriptions, ARC Features
41968 ARC processors are highly configurable, so even core registers and their number
41969 are not completely predetermined. In addition flags and PC registers which are
41970 important to @value{GDBN} are not ``core'' registers in ARC. It is required
41971 that one of the core registers features is present.
41972 @samp{org.gnu.gdb.arc.aux-minimal} feature is mandatory.
41974 The @samp{org.gnu.gdb.arc.core.v2} feature is required for ARC EM and ARC HS
41975 targets with a normal register file. It should contain registers @samp{r0}
41976 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
41977 @samp{lp_count} and @samp{pcl}. This feature may contain register @samp{ilink}
41978 and any of extension core registers @samp{r32} through @samp{r59/acch}.
41979 @samp{ilink} and extension core registers are not available to read/write, when
41980 debugging GNU/Linux applications, thus @samp{ilink} is made optional.
41982 The @samp{org.gnu.gdb.arc.core-reduced.v2} feature is required for ARC EM and
41983 ARC HS targets with a reduced register file. It should contain registers
41984 @samp{r0} through @samp{r3}, @samp{r10} through @samp{r15}, @samp{gp},
41985 @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink}, @samp{lp_count} and @samp{pcl}.
41986 This feature may contain register @samp{ilink} and any of extension core
41987 registers @samp{r32} through @samp{r59/acch}.
41989 The @samp{org.gnu.gdb.arc.core.arcompact} feature is required for ARCompact
41990 targets with a normal register file. It should contain registers @samp{r0}
41991 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
41992 @samp{lp_count} and @samp{pcl}. This feature may contain registers
41993 @samp{ilink1}, @samp{ilink2} and any of extension core registers @samp{r32}
41994 through @samp{r59/acch}. @samp{ilink1} and @samp{ilink2} and extension core
41995 registers are not available when debugging GNU/Linux applications. The only
41996 difference with @samp{org.gnu.gdb.arc.core.v2} feature is in the names of
41997 @samp{ilink1} and @samp{ilink2} registers and that @samp{r30} is mandatory in
41998 ARC v2, but @samp{ilink2} is optional on ARCompact.
42000 The @samp{org.gnu.gdb.arc.aux-minimal} feature is required for all ARC
42001 targets. It should contain registers @samp{pc} and @samp{status32}.
42004 @subsection ARM Features
42005 @cindex target descriptions, ARM features
42007 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
42009 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
42010 @samp{lr}, @samp{pc}, and @samp{cpsr}.
42012 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
42013 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
42014 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
42017 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
42018 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
42020 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
42021 it should contain at least registers @samp{wR0} through @samp{wR15} and
42022 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
42023 @samp{wCSSF}, and @samp{wCASF} registers are optional.
42025 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
42026 should contain at least registers @samp{d0} through @samp{d15}. If
42027 they are present, @samp{d16} through @samp{d31} should also be included.
42028 @value{GDBN} will synthesize the single-precision registers from
42029 halves of the double-precision registers.
42031 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
42032 need to contain registers; it instructs @value{GDBN} to display the
42033 VFP double-precision registers as vectors and to synthesize the
42034 quad-precision registers from pairs of double-precision registers.
42035 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
42036 be present and include 32 double-precision registers.
42038 @node i386 Features
42039 @subsection i386 Features
42040 @cindex target descriptions, i386 features
42042 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
42043 targets. It should describe the following registers:
42047 @samp{eax} through @samp{edi} plus @samp{eip} for i386
42049 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
42051 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
42052 @samp{fs}, @samp{gs}
42054 @samp{st0} through @samp{st7}
42056 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
42057 @samp{foseg}, @samp{fooff} and @samp{fop}
42060 The register sets may be different, depending on the target.
42062 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
42063 describe registers:
42067 @samp{xmm0} through @samp{xmm7} for i386
42069 @samp{xmm0} through @samp{xmm15} for amd64
42074 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
42075 @samp{org.gnu.gdb.i386.sse} feature. It should
42076 describe the upper 128 bits of @sc{ymm} registers:
42080 @samp{ymm0h} through @samp{ymm7h} for i386
42082 @samp{ymm0h} through @samp{ymm15h} for amd64
42085 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
42086 Memory Protection Extension (MPX). It should describe the following registers:
42090 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
42092 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
42095 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
42096 describe a single register, @samp{orig_eax}.
42098 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
42099 describe two system registers: @samp{fs_base} and @samp{gs_base}.
42101 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
42102 @samp{org.gnu.gdb.i386.avx} feature. It should
42103 describe additional @sc{xmm} registers:
42107 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
42110 It should describe the upper 128 bits of additional @sc{ymm} registers:
42114 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
42118 describe the upper 256 bits of @sc{zmm} registers:
42122 @samp{zmm0h} through @samp{zmm7h} for i386.
42124 @samp{zmm0h} through @samp{zmm15h} for amd64.
42128 describe the additional @sc{zmm} registers:
42132 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
42135 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
42136 describe a single register, @samp{pkru}. It is a 32-bit register
42137 valid for i386 and amd64.
42139 @node MicroBlaze Features
42140 @subsection MicroBlaze Features
42141 @cindex target descriptions, MicroBlaze features
42143 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
42144 targets. It should contain registers @samp{r0} through @samp{r31},
42145 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
42146 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
42147 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
42149 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
42150 If present, it should contain registers @samp{rshr} and @samp{rslr}
42152 @node MIPS Features
42153 @subsection @acronym{MIPS} Features
42154 @cindex target descriptions, @acronym{MIPS} features
42156 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
42157 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
42158 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
42161 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
42162 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
42163 registers. They may be 32-bit or 64-bit depending on the target.
42165 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
42166 it may be optional in a future version of @value{GDBN}. It should
42167 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
42168 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
42170 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
42171 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
42172 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
42173 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
42175 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
42176 contain a single register, @samp{restart}, which is used by the
42177 Linux kernel to control restartable syscalls.
42179 @node M68K Features
42180 @subsection M68K Features
42181 @cindex target descriptions, M68K features
42184 @item @samp{org.gnu.gdb.m68k.core}
42185 @itemx @samp{org.gnu.gdb.coldfire.core}
42186 @itemx @samp{org.gnu.gdb.fido.core}
42187 One of those features must be always present.
42188 The feature that is present determines which flavor of m68k is
42189 used. The feature that is present should contain registers
42190 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
42191 @samp{sp}, @samp{ps} and @samp{pc}.
42193 @item @samp{org.gnu.gdb.coldfire.fp}
42194 This feature is optional. If present, it should contain registers
42195 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
42199 @node NDS32 Features
42200 @subsection NDS32 Features
42201 @cindex target descriptions, NDS32 features
42203 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
42204 targets. It should contain at least registers @samp{r0} through
42205 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
42208 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
42209 it should contain 64-bit double-precision floating-point registers
42210 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
42211 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
42213 @emph{Note:} The first sixteen 64-bit double-precision floating-point
42214 registers are overlapped with the thirty-two 32-bit single-precision
42215 floating-point registers. The 32-bit single-precision registers, if
42216 not being listed explicitly, will be synthesized from halves of the
42217 overlapping 64-bit double-precision registers. Listing 32-bit
42218 single-precision registers explicitly is deprecated, and the
42219 support to it could be totally removed some day.
42221 @node Nios II Features
42222 @subsection Nios II Features
42223 @cindex target descriptions, Nios II features
42225 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
42226 targets. It should contain the 32 core registers (@samp{zero},
42227 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
42228 @samp{pc}, and the 16 control registers (@samp{status} through
42231 @node OpenRISC 1000 Features
42232 @subsection Openrisc 1000 Features
42233 @cindex target descriptions, OpenRISC 1000 features
42235 The @samp{org.gnu.gdb.or1k.group0} feature is required for OpenRISC 1000
42236 targets. It should contain the 32 general purpose registers (@samp{r0}
42237 through @samp{r31}), @samp{ppc}, @samp{npc} and @samp{sr}.
42239 @node PowerPC Features
42240 @subsection PowerPC Features
42241 @cindex target descriptions, PowerPC features
42243 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
42244 targets. It should contain registers @samp{r0} through @samp{r31},
42245 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
42246 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
42248 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
42249 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
42251 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
42252 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
42255 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
42256 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
42257 will combine these registers with the floating point registers
42258 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
42259 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
42260 through @samp{vs63}, the set of vector registers for POWER7.
42262 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
42263 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
42264 @samp{spefscr}. SPE targets should provide 32-bit registers in
42265 @samp{org.gnu.gdb.power.core} and provide the upper halves in
42266 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
42267 these to present registers @samp{ev0} through @samp{ev31} to the
42270 @node S/390 and System z Features
42271 @subsection S/390 and System z Features
42272 @cindex target descriptions, S/390 features
42273 @cindex target descriptions, System z features
42275 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
42276 System z targets. It should contain the PSW and the 16 general
42277 registers. In particular, System z targets should provide the 64-bit
42278 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
42279 S/390 targets should provide the 32-bit versions of these registers.
42280 A System z target that runs in 31-bit addressing mode should provide
42281 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
42282 register's upper halves @samp{r0h} through @samp{r15h}, and their
42283 lower halves @samp{r0l} through @samp{r15l}.
42285 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
42286 contain the 64-bit registers @samp{f0} through @samp{f15}, and
42289 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
42290 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
42292 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
42293 contain the register @samp{orig_r2}, which is 64-bit wide on System z
42294 targets and 32-bit otherwise. In addition, the feature may contain
42295 the @samp{last_break} register, whose width depends on the addressing
42296 mode, as well as the @samp{system_call} register, which is always
42299 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
42300 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
42301 @samp{atia}, and @samp{tr0} through @samp{tr15}.
42303 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
42304 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
42305 combined by @value{GDBN} with the floating point registers @samp{f0}
42306 through @samp{f15} to present the 128-bit wide vector registers
42307 @samp{v0} through @samp{v15}. In addition, this feature should
42308 contain the 128-bit wide vector registers @samp{v16} through
42311 The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
42312 the 64-bit wide guarded-storage-control registers @samp{gsd},
42313 @samp{gssm}, and @samp{gsepla}.
42315 The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
42316 the 64-bit wide guarded-storage broadcast control registers
42317 @samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
42319 @node Sparc Features
42320 @subsection Sparc Features
42321 @cindex target descriptions, sparc32 features
42322 @cindex target descriptions, sparc64 features
42323 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
42324 targets. It should describe the following registers:
42328 @samp{g0} through @samp{g7}
42330 @samp{o0} through @samp{o7}
42332 @samp{l0} through @samp{l7}
42334 @samp{i0} through @samp{i7}
42337 They may be 32-bit or 64-bit depending on the target.
42339 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
42340 targets. It should describe the following registers:
42344 @samp{f0} through @samp{f31}
42346 @samp{f32} through @samp{f62} for sparc64
42349 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
42350 targets. It should describe the following registers:
42354 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
42355 @samp{fsr}, and @samp{csr} for sparc32
42357 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
42361 @node TIC6x Features
42362 @subsection TMS320C6x Features
42363 @cindex target descriptions, TIC6x features
42364 @cindex target descriptions, TMS320C6x features
42365 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
42366 targets. It should contain registers @samp{A0} through @samp{A15},
42367 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
42369 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
42370 contain registers @samp{A16} through @samp{A31} and @samp{B16}
42371 through @samp{B31}.
42373 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
42374 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
42376 @node Operating System Information
42377 @appendix Operating System Information
42378 @cindex operating system information
42384 Users of @value{GDBN} often wish to obtain information about the state of
42385 the operating system running on the target---for example the list of
42386 processes, or the list of open files. This section describes the
42387 mechanism that makes it possible. This mechanism is similar to the
42388 target features mechanism (@pxref{Target Descriptions}), but focuses
42389 on a different aspect of target.
42391 Operating system information is retrived from the target via the
42392 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
42393 read}). The object name in the request should be @samp{osdata}, and
42394 the @var{annex} identifies the data to be fetched.
42397 @appendixsection Process list
42398 @cindex operating system information, process list
42400 When requesting the process list, the @var{annex} field in the
42401 @samp{qXfer} request should be @samp{processes}. The returned data is
42402 an XML document. The formal syntax of this document is defined in
42403 @file{gdb/features/osdata.dtd}.
42405 An example document is:
42408 <?xml version="1.0"?>
42409 <!DOCTYPE target SYSTEM "osdata.dtd">
42410 <osdata type="processes">
42412 <column name="pid">1</column>
42413 <column name="user">root</column>
42414 <column name="command">/sbin/init</column>
42415 <column name="cores">1,2,3</column>
42420 Each item should include a column whose name is @samp{pid}. The value
42421 of that column should identify the process on the target. The
42422 @samp{user} and @samp{command} columns are optional, and will be
42423 displayed by @value{GDBN}. The @samp{cores} column, if present,
42424 should contain a comma-separated list of cores that this process
42425 is running on. Target may provide additional columns,
42426 which @value{GDBN} currently ignores.
42428 @node Trace File Format
42429 @appendix Trace File Format
42430 @cindex trace file format
42432 The trace file comes in three parts: a header, a textual description
42433 section, and a trace frame section with binary data.
42435 The header has the form @code{\x7fTRACE0\n}. The first byte is
42436 @code{0x7f} so as to indicate that the file contains binary data,
42437 while the @code{0} is a version number that may have different values
42440 The description section consists of multiple lines of @sc{ascii} text
42441 separated by newline characters (@code{0xa}). The lines may include a
42442 variety of optional descriptive or context-setting information, such
42443 as tracepoint definitions or register set size. @value{GDBN} will
42444 ignore any line that it does not recognize. An empty line marks the end
42449 Specifies the size of a register block in bytes. This is equal to the
42450 size of a @code{g} packet payload in the remote protocol. @var{size}
42451 is an ascii decimal number. There should be only one such line in
42452 a single trace file.
42454 @item status @var{status}
42455 Trace status. @var{status} has the same format as a @code{qTStatus}
42456 remote packet reply. There should be only one such line in a single trace
42459 @item tp @var{payload}
42460 Tracepoint definition. The @var{payload} has the same format as
42461 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
42462 may take multiple lines of definition, corresponding to the multiple
42465 @item tsv @var{payload}
42466 Trace state variable definition. The @var{payload} has the same format as
42467 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
42468 may take multiple lines of definition, corresponding to the multiple
42471 @item tdesc @var{payload}
42472 Target description in XML format. The @var{payload} is a single line of
42473 the XML file. All such lines should be concatenated together to get
42474 the original XML file. This file is in the same format as @code{qXfer}
42475 @code{features} payload, and corresponds to the main @code{target.xml}
42476 file. Includes are not allowed.
42480 The trace frame section consists of a number of consecutive frames.
42481 Each frame begins with a two-byte tracepoint number, followed by a
42482 four-byte size giving the amount of data in the frame. The data in
42483 the frame consists of a number of blocks, each introduced by a
42484 character indicating its type (at least register, memory, and trace
42485 state variable). The data in this section is raw binary, not a
42486 hexadecimal or other encoding; its endianness matches the target's
42489 @c FIXME bi-arch may require endianness/arch info in description section
42492 @item R @var{bytes}
42493 Register block. The number and ordering of bytes matches that of a
42494 @code{g} packet in the remote protocol. Note that these are the
42495 actual bytes, in target order, not a hexadecimal encoding.
42497 @item M @var{address} @var{length} @var{bytes}...
42498 Memory block. This is a contiguous block of memory, at the 8-byte
42499 address @var{address}, with a 2-byte length @var{length}, followed by
42500 @var{length} bytes.
42502 @item V @var{number} @var{value}
42503 Trace state variable block. This records the 8-byte signed value
42504 @var{value} of trace state variable numbered @var{number}.
42508 Future enhancements of the trace file format may include additional types
42511 @node Index Section Format
42512 @appendix @code{.gdb_index} section format
42513 @cindex .gdb_index section format
42514 @cindex index section format
42516 This section documents the index section that is created by @code{save
42517 gdb-index} (@pxref{Index Files}). The index section is
42518 DWARF-specific; some knowledge of DWARF is assumed in this
42521 The mapped index file format is designed to be directly
42522 @code{mmap}able on any architecture. In most cases, a datum is
42523 represented using a little-endian 32-bit integer value, called an
42524 @code{offset_type}. Big endian machines must byte-swap the values
42525 before using them. Exceptions to this rule are noted. The data is
42526 laid out such that alignment is always respected.
42528 A mapped index consists of several areas, laid out in order.
42532 The file header. This is a sequence of values, of @code{offset_type}
42533 unless otherwise noted:
42537 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
42538 Version 4 uses a different hashing function from versions 5 and 6.
42539 Version 6 includes symbols for inlined functions, whereas versions 4
42540 and 5 do not. Version 7 adds attributes to the CU indices in the
42541 symbol table. Version 8 specifies that symbols from DWARF type units
42542 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
42543 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
42545 @value{GDBN} will only read version 4, 5, or 6 indices
42546 by specifying @code{set use-deprecated-index-sections on}.
42547 GDB has a workaround for potentially broken version 7 indices so it is
42548 currently not flagged as deprecated.
42551 The offset, from the start of the file, of the CU list.
42554 The offset, from the start of the file, of the types CU list. Note
42555 that this area can be empty, in which case this offset will be equal
42556 to the next offset.
42559 The offset, from the start of the file, of the address area.
42562 The offset, from the start of the file, of the symbol table.
42565 The offset, from the start of the file, of the constant pool.
42569 The CU list. This is a sequence of pairs of 64-bit little-endian
42570 values, sorted by the CU offset. The first element in each pair is
42571 the offset of a CU in the @code{.debug_info} section. The second
42572 element in each pair is the length of that CU. References to a CU
42573 elsewhere in the map are done using a CU index, which is just the
42574 0-based index into this table. Note that if there are type CUs, then
42575 conceptually CUs and type CUs form a single list for the purposes of
42579 The types CU list. This is a sequence of triplets of 64-bit
42580 little-endian values. In a triplet, the first value is the CU offset,
42581 the second value is the type offset in the CU, and the third value is
42582 the type signature. The types CU list is not sorted.
42585 The address area. The address area consists of a sequence of address
42586 entries. Each address entry has three elements:
42590 The low address. This is a 64-bit little-endian value.
42593 The high address. This is a 64-bit little-endian value. Like
42594 @code{DW_AT_high_pc}, the value is one byte beyond the end.
42597 The CU index. This is an @code{offset_type} value.
42601 The symbol table. This is an open-addressed hash table. The size of
42602 the hash table is always a power of 2.
42604 Each slot in the hash table consists of a pair of @code{offset_type}
42605 values. The first value is the offset of the symbol's name in the
42606 constant pool. The second value is the offset of the CU vector in the
42609 If both values are 0, then this slot in the hash table is empty. This
42610 is ok because while 0 is a valid constant pool index, it cannot be a
42611 valid index for both a string and a CU vector.
42613 The hash value for a table entry is computed by applying an
42614 iterative hash function to the symbol's name. Starting with an
42615 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
42616 the string is incorporated into the hash using the formula depending on the
42621 The formula is @code{r = r * 67 + c - 113}.
42623 @item Versions 5 to 7
42624 The formula is @code{r = r * 67 + tolower (c) - 113}.
42627 The terminating @samp{\0} is not incorporated into the hash.
42629 The step size used in the hash table is computed via
42630 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
42631 value, and @samp{size} is the size of the hash table. The step size
42632 is used to find the next candidate slot when handling a hash
42635 The names of C@t{++} symbols in the hash table are canonicalized. We
42636 don't currently have a simple description of the canonicalization
42637 algorithm; if you intend to create new index sections, you must read
42641 The constant pool. This is simply a bunch of bytes. It is organized
42642 so that alignment is correct: CU vectors are stored first, followed by
42645 A CU vector in the constant pool is a sequence of @code{offset_type}
42646 values. The first value is the number of CU indices in the vector.
42647 Each subsequent value is the index and symbol attributes of a CU in
42648 the CU list. This element in the hash table is used to indicate which
42649 CUs define the symbol and how the symbol is used.
42650 See below for the format of each CU index+attributes entry.
42652 A string in the constant pool is zero-terminated.
42655 Attributes were added to CU index values in @code{.gdb_index} version 7.
42656 If a symbol has multiple uses within a CU then there is one
42657 CU index+attributes value for each use.
42659 The format of each CU index+attributes entry is as follows
42665 This is the index of the CU in the CU list.
42667 These bits are reserved for future purposes and must be zero.
42669 The kind of the symbol in the CU.
42673 This value is reserved and should not be used.
42674 By reserving zero the full @code{offset_type} value is backwards compatible
42675 with previous versions of the index.
42677 The symbol is a type.
42679 The symbol is a variable or an enum value.
42681 The symbol is a function.
42683 Any other kind of symbol.
42685 These values are reserved.
42689 This bit is zero if the value is global and one if it is static.
42691 The determination of whether a symbol is global or static is complicated.
42692 The authorative reference is the file @file{dwarf2read.c} in
42693 @value{GDBN} sources.
42697 This pseudo-code describes the computation of a symbol's kind and
42698 global/static attributes in the index.
42701 is_external = get_attribute (die, DW_AT_external);
42702 language = get_attribute (cu_die, DW_AT_language);
42705 case DW_TAG_typedef:
42706 case DW_TAG_base_type:
42707 case DW_TAG_subrange_type:
42711 case DW_TAG_enumerator:
42713 is_static = language != CPLUS;
42715 case DW_TAG_subprogram:
42717 is_static = ! (is_external || language == ADA);
42719 case DW_TAG_constant:
42721 is_static = ! is_external;
42723 case DW_TAG_variable:
42725 is_static = ! is_external;
42727 case DW_TAG_namespace:
42731 case DW_TAG_class_type:
42732 case DW_TAG_interface_type:
42733 case DW_TAG_structure_type:
42734 case DW_TAG_union_type:
42735 case DW_TAG_enumeration_type:
42737 is_static = language != CPLUS;
42745 @appendix Manual pages
42749 * gdb man:: The GNU Debugger man page
42750 * gdbserver man:: Remote Server for the GNU Debugger man page
42751 * gcore man:: Generate a core file of a running program
42752 * gdbinit man:: gdbinit scripts
42758 @c man title gdb The GNU Debugger
42760 @c man begin SYNOPSIS gdb
42761 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
42762 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
42763 [@option{-b}@w{ }@var{bps}]
42764 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
42765 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
42766 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
42767 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
42768 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
42771 @c man begin DESCRIPTION gdb
42772 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
42773 going on ``inside'' another program while it executes -- or what another
42774 program was doing at the moment it crashed.
42776 @value{GDBN} can do four main kinds of things (plus other things in support of
42777 these) to help you catch bugs in the act:
42781 Start your program, specifying anything that might affect its behavior.
42784 Make your program stop on specified conditions.
42787 Examine what has happened, when your program has stopped.
42790 Change things in your program, so you can experiment with correcting the
42791 effects of one bug and go on to learn about another.
42794 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
42797 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
42798 commands from the terminal until you tell it to exit with the @value{GDBN}
42799 command @code{quit}. You can get online help from @value{GDBN} itself
42800 by using the command @code{help}.
42802 You can run @code{gdb} with no arguments or options; but the most
42803 usual way to start @value{GDBN} is with one argument or two, specifying an
42804 executable program as the argument:
42810 You can also start with both an executable program and a core file specified:
42816 You can, instead, specify a process ID as a second argument, if you want
42817 to debug a running process:
42825 would attach @value{GDBN} to process @code{1234} (unless you also have a file
42826 named @file{1234}; @value{GDBN} does check for a core file first).
42827 With option @option{-p} you can omit the @var{program} filename.
42829 Here are some of the most frequently needed @value{GDBN} commands:
42831 @c pod2man highlights the right hand side of the @item lines.
42833 @item break [@var{file}:]@var{function}
42834 Set a breakpoint at @var{function} (in @var{file}).
42836 @item run [@var{arglist}]
42837 Start your program (with @var{arglist}, if specified).
42840 Backtrace: display the program stack.
42842 @item print @var{expr}
42843 Display the value of an expression.
42846 Continue running your program (after stopping, e.g. at a breakpoint).
42849 Execute next program line (after stopping); step @emph{over} any
42850 function calls in the line.
42852 @item edit [@var{file}:]@var{function}
42853 look at the program line where it is presently stopped.
42855 @item list [@var{file}:]@var{function}
42856 type the text of the program in the vicinity of where it is presently stopped.
42859 Execute next program line (after stopping); step @emph{into} any
42860 function calls in the line.
42862 @item help [@var{name}]
42863 Show information about @value{GDBN} command @var{name}, or general information
42864 about using @value{GDBN}.
42867 Exit from @value{GDBN}.
42871 For full details on @value{GDBN},
42872 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42873 by Richard M. Stallman and Roland H. Pesch. The same text is available online
42874 as the @code{gdb} entry in the @code{info} program.
42878 @c man begin OPTIONS gdb
42879 Any arguments other than options specify an executable
42880 file and core file (or process ID); that is, the first argument
42881 encountered with no
42882 associated option flag is equivalent to a @option{-se} option, and the second,
42883 if any, is equivalent to a @option{-c} option if it's the name of a file.
42885 both long and short forms; both are shown here. The long forms are also
42886 recognized if you truncate them, so long as enough of the option is
42887 present to be unambiguous. (If you prefer, you can flag option
42888 arguments with @option{+} rather than @option{-}, though we illustrate the
42889 more usual convention.)
42891 All the options and command line arguments you give are processed
42892 in sequential order. The order makes a difference when the @option{-x}
42898 List all options, with brief explanations.
42900 @item -symbols=@var{file}
42901 @itemx -s @var{file}
42902 Read symbol table from file @var{file}.
42905 Enable writing into executable and core files.
42907 @item -exec=@var{file}
42908 @itemx -e @var{file}
42909 Use file @var{file} as the executable file to execute when
42910 appropriate, and for examining pure data in conjunction with a core
42913 @item -se=@var{file}
42914 Read symbol table from file @var{file} and use it as the executable
42917 @item -core=@var{file}
42918 @itemx -c @var{file}
42919 Use file @var{file} as a core dump to examine.
42921 @item -command=@var{file}
42922 @itemx -x @var{file}
42923 Execute @value{GDBN} commands from file @var{file}.
42925 @item -ex @var{command}
42926 Execute given @value{GDBN} @var{command}.
42928 @item -directory=@var{directory}
42929 @itemx -d @var{directory}
42930 Add @var{directory} to the path to search for source files.
42933 Do not execute commands from @file{~/.gdbinit}.
42937 Do not execute commands from any @file{.gdbinit} initialization files.
42941 ``Quiet''. Do not print the introductory and copyright messages. These
42942 messages are also suppressed in batch mode.
42945 Run in batch mode. Exit with status @code{0} after processing all the command
42946 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
42947 Exit with nonzero status if an error occurs in executing the @value{GDBN}
42948 commands in the command files.
42950 Batch mode may be useful for running @value{GDBN} as a filter, for example to
42951 download and run a program on another computer; in order to make this
42952 more useful, the message
42955 Program exited normally.
42959 (which is ordinarily issued whenever a program running under @value{GDBN} control
42960 terminates) is not issued when running in batch mode.
42962 @item -cd=@var{directory}
42963 Run @value{GDBN} using @var{directory} as its working directory,
42964 instead of the current directory.
42968 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
42969 @value{GDBN} to output the full file name and line number in a standard,
42970 recognizable fashion each time a stack frame is displayed (which
42971 includes each time the program stops). This recognizable format looks
42972 like two @samp{\032} characters, followed by the file name, line number
42973 and character position separated by colons, and a newline. The
42974 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
42975 characters as a signal to display the source code for the frame.
42978 Set the line speed (baud rate or bits per second) of any serial
42979 interface used by @value{GDBN} for remote debugging.
42981 @item -tty=@var{device}
42982 Run using @var{device} for your program's standard input and output.
42986 @c man begin SEEALSO gdb
42988 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42989 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42990 documentation are properly installed at your site, the command
42997 should give you access to the complete manual.
42999 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43000 Richard M. Stallman and Roland H. Pesch, July 1991.
43004 @node gdbserver man
43005 @heading gdbserver man
43007 @c man title gdbserver Remote Server for the GNU Debugger
43009 @c man begin SYNOPSIS gdbserver
43010 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
43012 gdbserver --attach @var{comm} @var{pid}
43014 gdbserver --multi @var{comm}
43018 @c man begin DESCRIPTION gdbserver
43019 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
43020 than the one which is running the program being debugged.
43023 @subheading Usage (server (target) side)
43026 Usage (server (target) side):
43029 First, you need to have a copy of the program you want to debug put onto
43030 the target system. The program can be stripped to save space if needed, as
43031 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
43032 the @value{GDBN} running on the host system.
43034 To use the server, you log on to the target system, and run the @command{gdbserver}
43035 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
43036 your program, and (c) its arguments. The general syntax is:
43039 target> gdbserver @var{comm} @var{program} [@var{args} ...]
43042 For example, using a serial port, you might say:
43046 @c @file would wrap it as F</dev/com1>.
43047 target> gdbserver /dev/com1 emacs foo.txt
43050 target> gdbserver @file{/dev/com1} emacs foo.txt
43054 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
43055 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
43056 waits patiently for the host @value{GDBN} to communicate with it.
43058 To use a TCP connection, you could say:
43061 target> gdbserver host:2345 emacs foo.txt
43064 This says pretty much the same thing as the last example, except that we are
43065 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
43066 that we are expecting to see a TCP connection from @code{host} to local TCP port
43067 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
43068 want for the port number as long as it does not conflict with any existing TCP
43069 ports on the target system. This same port number must be used in the host
43070 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
43071 you chose a port number that conflicts with another service, @command{gdbserver} will
43072 print an error message and exit.
43074 @command{gdbserver} can also attach to running programs.
43075 This is accomplished via the @option{--attach} argument. The syntax is:
43078 target> gdbserver --attach @var{comm} @var{pid}
43081 @var{pid} is the process ID of a currently running process. It isn't
43082 necessary to point @command{gdbserver} at a binary for the running process.
43084 To start @code{gdbserver} without supplying an initial command to run
43085 or process ID to attach, use the @option{--multi} command line option.
43086 In such case you should connect using @kbd{target extended-remote} to start
43087 the program you want to debug.
43090 target> gdbserver --multi @var{comm}
43094 @subheading Usage (host side)
43100 You need an unstripped copy of the target program on your host system, since
43101 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
43102 would, with the target program as the first argument. (You may need to use the
43103 @option{--baud} option if the serial line is running at anything except 9600 baud.)
43104 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
43105 new command you need to know about is @code{target remote}
43106 (or @code{target extended-remote}). Its argument is either
43107 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
43108 descriptor. For example:
43112 @c @file would wrap it as F</dev/ttyb>.
43113 (gdb) target remote /dev/ttyb
43116 (gdb) target remote @file{/dev/ttyb}
43121 communicates with the server via serial line @file{/dev/ttyb}, and:
43124 (gdb) target remote the-target:2345
43128 communicates via a TCP connection to port 2345 on host `the-target', where
43129 you previously started up @command{gdbserver} with the same port number. Note that for
43130 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
43131 command, otherwise you may get an error that looks something like
43132 `Connection refused'.
43134 @command{gdbserver} can also debug multiple inferiors at once,
43137 the @value{GDBN} manual in node @code{Inferiors and Programs}
43138 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
43141 @ref{Inferiors and Programs}.
43143 In such case use the @code{extended-remote} @value{GDBN} command variant:
43146 (gdb) target extended-remote the-target:2345
43149 The @command{gdbserver} option @option{--multi} may or may not be used in such
43153 @c man begin OPTIONS gdbserver
43154 There are three different modes for invoking @command{gdbserver}:
43159 Debug a specific program specified by its program name:
43162 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
43165 The @var{comm} parameter specifies how should the server communicate
43166 with @value{GDBN}; it is either a device name (to use a serial line),
43167 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
43168 stdin/stdout of @code{gdbserver}. Specify the name of the program to
43169 debug in @var{prog}. Any remaining arguments will be passed to the
43170 program verbatim. When the program exits, @value{GDBN} will close the
43171 connection, and @code{gdbserver} will exit.
43174 Debug a specific program by specifying the process ID of a running
43178 gdbserver --attach @var{comm} @var{pid}
43181 The @var{comm} parameter is as described above. Supply the process ID
43182 of a running program in @var{pid}; @value{GDBN} will do everything
43183 else. Like with the previous mode, when the process @var{pid} exits,
43184 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
43187 Multi-process mode -- debug more than one program/process:
43190 gdbserver --multi @var{comm}
43193 In this mode, @value{GDBN} can instruct @command{gdbserver} which
43194 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
43195 close the connection when a process being debugged exits, so you can
43196 debug several processes in the same session.
43199 In each of the modes you may specify these options:
43204 List all options, with brief explanations.
43207 This option causes @command{gdbserver} to print its version number and exit.
43210 @command{gdbserver} will attach to a running program. The syntax is:
43213 target> gdbserver --attach @var{comm} @var{pid}
43216 @var{pid} is the process ID of a currently running process. It isn't
43217 necessary to point @command{gdbserver} at a binary for the running process.
43220 To start @code{gdbserver} without supplying an initial command to run
43221 or process ID to attach, use this command line option.
43222 Then you can connect using @kbd{target extended-remote} and start
43223 the program you want to debug. The syntax is:
43226 target> gdbserver --multi @var{comm}
43230 Instruct @code{gdbserver} to display extra status information about the debugging
43232 This option is intended for @code{gdbserver} development and for bug reports to
43235 @item --remote-debug
43236 Instruct @code{gdbserver} to display remote protocol debug output.
43237 This option is intended for @code{gdbserver} development and for bug reports to
43240 @item --debug-format=option1@r{[},option2,...@r{]}
43241 Instruct @code{gdbserver} to include extra information in each line
43242 of debugging output.
43243 @xref{Other Command-Line Arguments for gdbserver}.
43246 Specify a wrapper to launch programs
43247 for debugging. The option should be followed by the name of the
43248 wrapper, then any command-line arguments to pass to the wrapper, then
43249 @kbd{--} indicating the end of the wrapper arguments.
43252 By default, @command{gdbserver} keeps the listening TCP port open, so that
43253 additional connections are possible. However, if you start @code{gdbserver}
43254 with the @option{--once} option, it will stop listening for any further
43255 connection attempts after connecting to the first @value{GDBN} session.
43257 @c --disable-packet is not documented for users.
43259 @c --disable-randomization and --no-disable-randomization are superseded by
43260 @c QDisableRandomization.
43265 @c man begin SEEALSO gdbserver
43267 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43268 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43269 documentation are properly installed at your site, the command
43275 should give you access to the complete manual.
43277 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43278 Richard M. Stallman and Roland H. Pesch, July 1991.
43285 @c man title gcore Generate a core file of a running program
43288 @c man begin SYNOPSIS gcore
43289 gcore [-a] [-o @var{filename}] @var{pid}
43293 @c man begin DESCRIPTION gcore
43294 Generate a core dump of a running program with process ID @var{pid}.
43295 Produced file is equivalent to a kernel produced core file as if the process
43296 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
43297 limit). Unlike after a crash, after @command{gcore} the program remains
43298 running without any change.
43301 @c man begin OPTIONS gcore
43304 Dump all memory mappings. The actual effect of this option depends on
43305 the Operating System. On @sc{gnu}/Linux, it will disable
43306 @code{use-coredump-filter} (@pxref{set use-coredump-filter}) and
43307 enable @code{dump-excluded-mappings} (@pxref{set
43308 dump-excluded-mappings}).
43310 @item -o @var{filename}
43311 The optional argument
43312 @var{filename} specifies the file name where to put the core dump.
43313 If not specified, the file name defaults to @file{core.@var{pid}},
43314 where @var{pid} is the running program process ID.
43318 @c man begin SEEALSO gcore
43320 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43321 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43322 documentation are properly installed at your site, the command
43329 should give you access to the complete manual.
43331 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43332 Richard M. Stallman and Roland H. Pesch, July 1991.
43339 @c man title gdbinit GDB initialization scripts
43342 @c man begin SYNOPSIS gdbinit
43343 @ifset SYSTEM_GDBINIT
43344 @value{SYSTEM_GDBINIT}
43353 @c man begin DESCRIPTION gdbinit
43354 These files contain @value{GDBN} commands to automatically execute during
43355 @value{GDBN} startup. The lines of contents are canned sequences of commands,
43358 the @value{GDBN} manual in node @code{Sequences}
43359 -- shell command @code{info -f gdb -n Sequences}.
43365 Please read more in
43367 the @value{GDBN} manual in node @code{Startup}
43368 -- shell command @code{info -f gdb -n Startup}.
43375 @ifset SYSTEM_GDBINIT
43376 @item @value{SYSTEM_GDBINIT}
43378 @ifclear SYSTEM_GDBINIT
43379 @item (not enabled with @code{--with-system-gdbinit} during compilation)
43381 System-wide initialization file. It is executed unless user specified
43382 @value{GDBN} option @code{-nx} or @code{-n}.
43385 the @value{GDBN} manual in node @code{System-wide configuration}
43386 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
43389 @ref{System-wide configuration}.
43393 User initialization file. It is executed unless user specified
43394 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
43397 Initialization file for current directory. It may need to be enabled with
43398 @value{GDBN} security command @code{set auto-load local-gdbinit}.
43401 the @value{GDBN} manual in node @code{Init File in the Current Directory}
43402 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
43405 @ref{Init File in the Current Directory}.
43410 @c man begin SEEALSO gdbinit
43412 gdb(1), @code{info -f gdb -n Startup}
43414 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43415 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43416 documentation are properly installed at your site, the command
43422 should give you access to the complete manual.
43424 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43425 Richard M. Stallman and Roland H. Pesch, July 1991.
43431 @node GNU Free Documentation License
43432 @appendix GNU Free Documentation License
43435 @node Concept Index
43436 @unnumbered Concept Index
43440 @node Command and Variable Index
43441 @unnumbered Command, Variable, and Function Index
43446 % I think something like @@colophon should be in texinfo. In the
43448 \long\def\colophon{\hbox to0pt{}\vfill
43449 \centerline{The body of this manual is set in}
43450 \centerline{\fontname\tenrm,}
43451 \centerline{with headings in {\bf\fontname\tenbf}}
43452 \centerline{and examples in {\tt\fontname\tentt}.}
43453 \centerline{{\it\fontname\tenit\/},}
43454 \centerline{{\bf\fontname\tenbf}, and}
43455 \centerline{{\sl\fontname\tensl\/}}
43456 \centerline{are used for emphasis.}\vfill}
43458 % Blame: doc@@cygnus.com, 1991.