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
8436 @itemx info line @var{location}
8437 Print the starting and ending addresses of the compiled code for
8438 source line @var{location}. You can specify source lines in any of
8439 the ways documented in @ref{Specify Location}. With no @var{location}
8440 information about the current source line is printed.
8443 For example, we can use @code{info line} to discover the location of
8444 the object code for the first line of function
8445 @code{m4_changequote}:
8448 (@value{GDBP}) info line m4_changequote
8449 Line 895 of "builtin.c" starts at pc 0x634c <m4_changequote> and \
8450 ends at 0x6350 <m4_changequote+4>.
8454 @cindex code address and its source line
8455 We can also inquire (using @code{*@var{addr}} as the form for
8456 @var{location}) what source line covers a particular address:
8458 (@value{GDBP}) info line *0x63ff
8459 Line 926 of "builtin.c" starts at pc 0x63e4 <m4_changequote+152> and \
8460 ends at 0x6404 <m4_changequote+184>.
8463 @cindex @code{$_} and @code{info line}
8464 @cindex @code{x} command, default address
8465 @kindex x@r{(examine), and} info line
8466 After @code{info line}, the default address for the @code{x} command
8467 is changed to the starting address of the line, so that @samp{x/i} is
8468 sufficient to begin examining the machine code (@pxref{Memory,
8469 ,Examining Memory}). Also, this address is saved as the value of the
8470 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
8473 @cindex info line, repeated calls
8474 After @code{info line}, using @code{info line} again without
8475 specifying a location will display information about the next source
8480 @cindex assembly instructions
8481 @cindex instructions, assembly
8482 @cindex machine instructions
8483 @cindex listing machine instructions
8485 @itemx disassemble /m
8486 @itemx disassemble /s
8487 @itemx disassemble /r
8488 This specialized command dumps a range of memory as machine
8489 instructions. It can also print mixed source+disassembly by specifying
8490 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
8491 as well as in symbolic form by specifying the @code{/r} modifier.
8492 The default memory range is the function surrounding the
8493 program counter of the selected frame. A single argument to this
8494 command is a program counter value; @value{GDBN} dumps the function
8495 surrounding this value. When two arguments are given, they should
8496 be separated by a comma, possibly surrounded by whitespace. The
8497 arguments specify a range of addresses to dump, in one of two forms:
8500 @item @var{start},@var{end}
8501 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8502 @item @var{start},+@var{length}
8503 the addresses from @var{start} (inclusive) to
8504 @code{@var{start}+@var{length}} (exclusive).
8508 When 2 arguments are specified, the name of the function is also
8509 printed (since there could be several functions in the given range).
8511 The argument(s) can be any expression yielding a numeric value, such as
8512 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8514 If the range of memory being disassembled contains current program counter,
8515 the instruction at that location is shown with a @code{=>} marker.
8518 The following example shows the disassembly of a range of addresses of
8519 HP PA-RISC 2.0 code:
8522 (@value{GDBP}) disas 0x32c4, 0x32e4
8523 Dump of assembler code from 0x32c4 to 0x32e4:
8524 0x32c4 <main+204>: addil 0,dp
8525 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8526 0x32cc <main+212>: ldil 0x3000,r31
8527 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8528 0x32d4 <main+220>: ldo 0(r31),rp
8529 0x32d8 <main+224>: addil -0x800,dp
8530 0x32dc <main+228>: ldo 0x588(r1),r26
8531 0x32e0 <main+232>: ldil 0x3000,r31
8532 End of assembler dump.
8535 Here is an example showing mixed source+assembly for Intel x86
8536 with @code{/m} or @code{/s}, when the program is stopped just after
8537 function prologue in a non-optimized function with no inline code.
8540 (@value{GDBP}) disas /m main
8541 Dump of assembler code for function main:
8543 0x08048330 <+0>: push %ebp
8544 0x08048331 <+1>: mov %esp,%ebp
8545 0x08048333 <+3>: sub $0x8,%esp
8546 0x08048336 <+6>: and $0xfffffff0,%esp
8547 0x08048339 <+9>: sub $0x10,%esp
8549 6 printf ("Hello.\n");
8550 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8551 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8555 0x08048348 <+24>: mov $0x0,%eax
8556 0x0804834d <+29>: leave
8557 0x0804834e <+30>: ret
8559 End of assembler dump.
8562 The @code{/m} option is deprecated as its output is not useful when
8563 there is either inlined code or re-ordered code.
8564 The @code{/s} option is the preferred choice.
8565 Here is an example for AMD x86-64 showing the difference between
8566 @code{/m} output and @code{/s} output.
8567 This example has one inline function defined in a header file,
8568 and the code is compiled with @samp{-O2} optimization.
8569 Note how the @code{/m} output is missing the disassembly of
8570 several instructions that are present in the @code{/s} output.
8600 (@value{GDBP}) disas /m main
8601 Dump of assembler code for function main:
8605 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8606 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8610 0x000000000040041d <+29>: xor %eax,%eax
8611 0x000000000040041f <+31>: retq
8612 0x0000000000400420 <+32>: add %eax,%eax
8613 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8615 End of assembler dump.
8616 (@value{GDBP}) disas /s main
8617 Dump of assembler code for function main:
8621 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8625 0x0000000000400406 <+6>: test %eax,%eax
8626 0x0000000000400408 <+8>: js 0x400420 <main+32>
8631 0x000000000040040a <+10>: lea 0xa(%rax),%edx
8632 0x000000000040040d <+13>: test %eax,%eax
8633 0x000000000040040f <+15>: mov $0x1,%eax
8634 0x0000000000400414 <+20>: cmovne %edx,%eax
8638 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8642 0x000000000040041d <+29>: xor %eax,%eax
8643 0x000000000040041f <+31>: retq
8647 0x0000000000400420 <+32>: add %eax,%eax
8648 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8649 End of assembler dump.
8652 Here is another example showing raw instructions in hex for AMD x86-64,
8655 (gdb) disas /r 0x400281,+10
8656 Dump of assembler code from 0x400281 to 0x40028b:
8657 0x0000000000400281: 38 36 cmp %dh,(%rsi)
8658 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
8659 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
8660 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
8661 End of assembler dump.
8664 Addresses cannot be specified as a location (@pxref{Specify Location}).
8665 So, for example, if you want to disassemble function @code{bar}
8666 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
8667 and not @samp{disassemble foo.c:bar}.
8669 Some architectures have more than one commonly-used set of instruction
8670 mnemonics or other syntax.
8672 For programs that were dynamically linked and use shared libraries,
8673 instructions that call functions or branch to locations in the shared
8674 libraries might show a seemingly bogus location---it's actually a
8675 location of the relocation table. On some architectures, @value{GDBN}
8676 might be able to resolve these to actual function names.
8679 @kindex set disassembler-options
8680 @cindex disassembler options
8681 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
8682 This command controls the passing of target specific information to
8683 the disassembler. For a list of valid options, please refer to the
8684 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
8685 manual and/or the output of @kbd{objdump --help}
8686 (@pxref{objdump,,objdump,binutils.info,The GNU Binary Utilities}).
8687 The default value is the empty string.
8689 If it is necessary to specify more than one disassembler option, then
8690 multiple options can be placed together into a comma separated list.
8691 Currently this command is only supported on targets ARM, PowerPC
8694 @kindex show disassembler-options
8695 @item show disassembler-options
8696 Show the current setting of the disassembler options.
8700 @kindex set disassembly-flavor
8701 @cindex Intel disassembly flavor
8702 @cindex AT&T disassembly flavor
8703 @item set disassembly-flavor @var{instruction-set}
8704 Select the instruction set to use when disassembling the
8705 program via the @code{disassemble} or @code{x/i} commands.
8707 Currently this command is only defined for the Intel x86 family. You
8708 can set @var{instruction-set} to either @code{intel} or @code{att}.
8709 The default is @code{att}, the AT&T flavor used by default by Unix
8710 assemblers for x86-based targets.
8712 @kindex show disassembly-flavor
8713 @item show disassembly-flavor
8714 Show the current setting of the disassembly flavor.
8718 @kindex set disassemble-next-line
8719 @kindex show disassemble-next-line
8720 @item set disassemble-next-line
8721 @itemx show disassemble-next-line
8722 Control whether or not @value{GDBN} will disassemble the next source
8723 line or instruction when execution stops. If ON, @value{GDBN} will
8724 display disassembly of the next source line when execution of the
8725 program being debugged stops. This is @emph{in addition} to
8726 displaying the source line itself, which @value{GDBN} always does if
8727 possible. If the next source line cannot be displayed for some reason
8728 (e.g., if @value{GDBN} cannot find the source file, or there's no line
8729 info in the debug info), @value{GDBN} will display disassembly of the
8730 next @emph{instruction} instead of showing the next source line. If
8731 AUTO, @value{GDBN} will display disassembly of next instruction only
8732 if the source line cannot be displayed. This setting causes
8733 @value{GDBN} to display some feedback when you step through a function
8734 with no line info or whose source file is unavailable. The default is
8735 OFF, which means never display the disassembly of the next line or
8741 @chapter Examining Data
8743 @cindex printing data
8744 @cindex examining data
8747 The usual way to examine data in your program is with the @code{print}
8748 command (abbreviated @code{p}), or its synonym @code{inspect}. It
8749 evaluates and prints the value of an expression of the language your
8750 program is written in (@pxref{Languages, ,Using @value{GDBN} with
8751 Different Languages}). It may also print the expression using a
8752 Python-based pretty-printer (@pxref{Pretty Printing}).
8755 @item print @var{expr}
8756 @itemx print /@var{f} @var{expr}
8757 @var{expr} is an expression (in the source language). By default the
8758 value of @var{expr} is printed in a format appropriate to its data type;
8759 you can choose a different format by specifying @samp{/@var{f}}, where
8760 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
8764 @itemx print /@var{f}
8765 @cindex reprint the last value
8766 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
8767 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
8768 conveniently inspect the same value in an alternative format.
8771 A more low-level way of examining data is with the @code{x} command.
8772 It examines data in memory at a specified address and prints it in a
8773 specified format. @xref{Memory, ,Examining Memory}.
8775 If you are interested in information about types, or about how the
8776 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
8777 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
8780 @cindex exploring hierarchical data structures
8782 Another way of examining values of expressions and type information is
8783 through the Python extension command @code{explore} (available only if
8784 the @value{GDBN} build is configured with @code{--with-python}). It
8785 offers an interactive way to start at the highest level (or, the most
8786 abstract level) of the data type of an expression (or, the data type
8787 itself) and explore all the way down to leaf scalar values/fields
8788 embedded in the higher level data types.
8791 @item explore @var{arg}
8792 @var{arg} is either an expression (in the source language), or a type
8793 visible in the current context of the program being debugged.
8796 The working of the @code{explore} command can be illustrated with an
8797 example. If a data type @code{struct ComplexStruct} is defined in your
8807 struct ComplexStruct
8809 struct SimpleStruct *ss_p;
8815 followed by variable declarations as
8818 struct SimpleStruct ss = @{ 10, 1.11 @};
8819 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8823 then, the value of the variable @code{cs} can be explored using the
8824 @code{explore} command as follows.
8828 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8829 the following fields:
8831 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8832 arr = <Enter 1 to explore this field of type `int [10]'>
8834 Enter the field number of choice:
8838 Since the fields of @code{cs} are not scalar values, you are being
8839 prompted to chose the field you want to explore. Let's say you choose
8840 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8841 pointer, you will be asked if it is pointing to a single value. From
8842 the declaration of @code{cs} above, it is indeed pointing to a single
8843 value, hence you enter @code{y}. If you enter @code{n}, then you will
8844 be asked if it were pointing to an array of values, in which case this
8845 field will be explored as if it were an array.
8848 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8849 Continue exploring it as a pointer to a single value [y/n]: y
8850 The value of `*(cs.ss_p)' is a struct/class of type `struct
8851 SimpleStruct' with the following fields:
8853 i = 10 .. (Value of type `int')
8854 d = 1.1100000000000001 .. (Value of type `double')
8856 Press enter to return to parent value:
8860 If the field @code{arr} of @code{cs} was chosen for exploration by
8861 entering @code{1} earlier, then since it is as array, you will be
8862 prompted to enter the index of the element in the array that you want
8866 `cs.arr' is an array of `int'.
8867 Enter the index of the element you want to explore in `cs.arr': 5
8869 `(cs.arr)[5]' is a scalar value of type `int'.
8873 Press enter to return to parent value:
8876 In general, at any stage of exploration, you can go deeper towards the
8877 leaf values by responding to the prompts appropriately, or hit the
8878 return key to return to the enclosing data structure (the @i{higher}
8879 level data structure).
8881 Similar to exploring values, you can use the @code{explore} command to
8882 explore types. Instead of specifying a value (which is typically a
8883 variable name or an expression valid in the current context of the
8884 program being debugged), you specify a type name. If you consider the
8885 same example as above, your can explore the type
8886 @code{struct ComplexStruct} by passing the argument
8887 @code{struct ComplexStruct} to the @code{explore} command.
8890 (gdb) explore struct ComplexStruct
8894 By responding to the prompts appropriately in the subsequent interactive
8895 session, you can explore the type @code{struct ComplexStruct} in a
8896 manner similar to how the value @code{cs} was explored in the above
8899 The @code{explore} command also has two sub-commands,
8900 @code{explore value} and @code{explore type}. The former sub-command is
8901 a way to explicitly specify that value exploration of the argument is
8902 being invoked, while the latter is a way to explicitly specify that type
8903 exploration of the argument is being invoked.
8906 @item explore value @var{expr}
8907 @cindex explore value
8908 This sub-command of @code{explore} explores the value of the
8909 expression @var{expr} (if @var{expr} is an expression valid in the
8910 current context of the program being debugged). The behavior of this
8911 command is identical to that of the behavior of the @code{explore}
8912 command being passed the argument @var{expr}.
8914 @item explore type @var{arg}
8915 @cindex explore type
8916 This sub-command of @code{explore} explores the type of @var{arg} (if
8917 @var{arg} is a type visible in the current context of program being
8918 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8919 is an expression valid in the current context of the program being
8920 debugged). If @var{arg} is a type, then the behavior of this command is
8921 identical to that of the @code{explore} command being passed the
8922 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8923 this command will be identical to that of the @code{explore} command
8924 being passed the type of @var{arg} as the argument.
8928 * Expressions:: Expressions
8929 * Ambiguous Expressions:: Ambiguous Expressions
8930 * Variables:: Program variables
8931 * Arrays:: Artificial arrays
8932 * Output Formats:: Output formats
8933 * Memory:: Examining memory
8934 * Auto Display:: Automatic display
8935 * Print Settings:: Print settings
8936 * Pretty Printing:: Python pretty printing
8937 * Value History:: Value history
8938 * Convenience Vars:: Convenience variables
8939 * Convenience Funs:: Convenience functions
8940 * Registers:: Registers
8941 * Floating Point Hardware:: Floating point hardware
8942 * Vector Unit:: Vector Unit
8943 * OS Information:: Auxiliary data provided by operating system
8944 * Memory Region Attributes:: Memory region attributes
8945 * Dump/Restore Files:: Copy between memory and a file
8946 * Core File Generation:: Cause a program dump its core
8947 * Character Sets:: Debugging programs that use a different
8948 character set than GDB does
8949 * Caching Target Data:: Data caching for targets
8950 * Searching Memory:: Searching memory for a sequence of bytes
8951 * Value Sizes:: Managing memory allocated for values
8955 @section Expressions
8958 @code{print} and many other @value{GDBN} commands accept an expression and
8959 compute its value. Any kind of constant, variable or operator defined
8960 by the programming language you are using is valid in an expression in
8961 @value{GDBN}. This includes conditional expressions, function calls,
8962 casts, and string constants. It also includes preprocessor macros, if
8963 you compiled your program to include this information; see
8966 @cindex arrays in expressions
8967 @value{GDBN} supports array constants in expressions input by
8968 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8969 you can use the command @code{print @{1, 2, 3@}} to create an array
8970 of three integers. If you pass an array to a function or assign it
8971 to a program variable, @value{GDBN} copies the array to memory that
8972 is @code{malloc}ed in the target program.
8974 Because C is so widespread, most of the expressions shown in examples in
8975 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8976 Languages}, for information on how to use expressions in other
8979 In this section, we discuss operators that you can use in @value{GDBN}
8980 expressions regardless of your programming language.
8982 @cindex casts, in expressions
8983 Casts are supported in all languages, not just in C, because it is so
8984 useful to cast a number into a pointer in order to examine a structure
8985 at that address in memory.
8986 @c FIXME: casts supported---Mod2 true?
8988 @value{GDBN} supports these operators, in addition to those common
8989 to programming languages:
8993 @samp{@@} is a binary operator for treating parts of memory as arrays.
8994 @xref{Arrays, ,Artificial Arrays}, for more information.
8997 @samp{::} allows you to specify a variable in terms of the file or
8998 function where it is defined. @xref{Variables, ,Program Variables}.
9000 @cindex @{@var{type}@}
9001 @cindex type casting memory
9002 @cindex memory, viewing as typed object
9003 @cindex casts, to view memory
9004 @item @{@var{type}@} @var{addr}
9005 Refers to an object of type @var{type} stored at address @var{addr} in
9006 memory. The address @var{addr} may be any expression whose value is
9007 an integer or pointer (but parentheses are required around binary
9008 operators, just as in a cast). This construct is allowed regardless
9009 of what kind of data is normally supposed to reside at @var{addr}.
9012 @node Ambiguous Expressions
9013 @section Ambiguous Expressions
9014 @cindex ambiguous expressions
9016 Expressions can sometimes contain some ambiguous elements. For instance,
9017 some programming languages (notably Ada, C@t{++} and Objective-C) permit
9018 a single function name to be defined several times, for application in
9019 different contexts. This is called @dfn{overloading}. Another example
9020 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
9021 templates and is typically instantiated several times, resulting in
9022 the same function name being defined in different contexts.
9024 In some cases and depending on the language, it is possible to adjust
9025 the expression to remove the ambiguity. For instance in C@t{++}, you
9026 can specify the signature of the function you want to break on, as in
9027 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
9028 qualified name of your function often makes the expression unambiguous
9031 When an ambiguity that needs to be resolved is detected, the debugger
9032 has the capability to display a menu of numbered choices for each
9033 possibility, and then waits for the selection with the prompt @samp{>}.
9034 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
9035 aborts the current command. If the command in which the expression was
9036 used allows more than one choice to be selected, the next option in the
9037 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
9040 For example, the following session excerpt shows an attempt to set a
9041 breakpoint at the overloaded symbol @code{String::after}.
9042 We choose three particular definitions of that function name:
9044 @c FIXME! This is likely to change to show arg type lists, at least
9047 (@value{GDBP}) b String::after
9050 [2] file:String.cc; line number:867
9051 [3] file:String.cc; line number:860
9052 [4] file:String.cc; line number:875
9053 [5] file:String.cc; line number:853
9054 [6] file:String.cc; line number:846
9055 [7] file:String.cc; line number:735
9057 Breakpoint 1 at 0xb26c: file String.cc, line 867.
9058 Breakpoint 2 at 0xb344: file String.cc, line 875.
9059 Breakpoint 3 at 0xafcc: file String.cc, line 846.
9060 Multiple breakpoints were set.
9061 Use the "delete" command to delete unwanted
9068 @kindex set multiple-symbols
9069 @item set multiple-symbols @var{mode}
9070 @cindex multiple-symbols menu
9072 This option allows you to adjust the debugger behavior when an expression
9075 By default, @var{mode} is set to @code{all}. If the command with which
9076 the expression is used allows more than one choice, then @value{GDBN}
9077 automatically selects all possible choices. For instance, inserting
9078 a breakpoint on a function using an ambiguous name results in a breakpoint
9079 inserted on each possible match. However, if a unique choice must be made,
9080 then @value{GDBN} uses the menu to help you disambiguate the expression.
9081 For instance, printing the address of an overloaded function will result
9082 in the use of the menu.
9084 When @var{mode} is set to @code{ask}, the debugger always uses the menu
9085 when an ambiguity is detected.
9087 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
9088 an error due to the ambiguity and the command is aborted.
9090 @kindex show multiple-symbols
9091 @item show multiple-symbols
9092 Show the current value of the @code{multiple-symbols} setting.
9096 @section Program Variables
9098 The most common kind of expression to use is the name of a variable
9101 Variables in expressions are understood in the selected stack frame
9102 (@pxref{Selection, ,Selecting a Frame}); they must be either:
9106 global (or file-static)
9113 visible according to the scope rules of the
9114 programming language from the point of execution in that frame
9117 @noindent This means that in the function
9132 you can examine and use the variable @code{a} whenever your program is
9133 executing within the function @code{foo}, but you can only use or
9134 examine the variable @code{b} while your program is executing inside
9135 the block where @code{b} is declared.
9137 @cindex variable name conflict
9138 There is an exception: you can refer to a variable or function whose
9139 scope is a single source file even if the current execution point is not
9140 in this file. But it is possible to have more than one such variable or
9141 function with the same name (in different source files). If that
9142 happens, referring to that name has unpredictable effects. If you wish,
9143 you can specify a static variable in a particular function or file by
9144 using the colon-colon (@code{::}) notation:
9146 @cindex colon-colon, context for variables/functions
9148 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
9149 @cindex @code{::}, context for variables/functions
9152 @var{file}::@var{variable}
9153 @var{function}::@var{variable}
9157 Here @var{file} or @var{function} is the name of the context for the
9158 static @var{variable}. In the case of file names, you can use quotes to
9159 make sure @value{GDBN} parses the file name as a single word---for example,
9160 to print a global value of @code{x} defined in @file{f2.c}:
9163 (@value{GDBP}) p 'f2.c'::x
9166 The @code{::} notation is normally used for referring to
9167 static variables, since you typically disambiguate uses of local variables
9168 in functions by selecting the appropriate frame and using the
9169 simple name of the variable. However, you may also use this notation
9170 to refer to local variables in frames enclosing the selected frame:
9179 process (a); /* Stop here */
9190 For example, if there is a breakpoint at the commented line,
9191 here is what you might see
9192 when the program stops after executing the call @code{bar(0)}:
9197 (@value{GDBP}) p bar::a
9200 #2 0x080483d0 in foo (a=5) at foobar.c:12
9203 (@value{GDBP}) p bar::a
9207 @cindex C@t{++} scope resolution
9208 These uses of @samp{::} are very rarely in conflict with the very
9209 similar use of the same notation in C@t{++}. When they are in
9210 conflict, the C@t{++} meaning takes precedence; however, this can be
9211 overridden by quoting the file or function name with single quotes.
9213 For example, suppose the program is stopped in a method of a class
9214 that has a field named @code{includefile}, and there is also an
9215 include file named @file{includefile} that defines a variable,
9219 (@value{GDBP}) p includefile
9221 (@value{GDBP}) p includefile::some_global
9222 A syntax error in expression, near `'.
9223 (@value{GDBP}) p 'includefile'::some_global
9227 @cindex wrong values
9228 @cindex variable values, wrong
9229 @cindex function entry/exit, wrong values of variables
9230 @cindex optimized code, wrong values of variables
9232 @emph{Warning:} Occasionally, a local variable may appear to have the
9233 wrong value at certain points in a function---just after entry to a new
9234 scope, and just before exit.
9236 You may see this problem when you are stepping by machine instructions.
9237 This is because, on most machines, it takes more than one instruction to
9238 set up a stack frame (including local variable definitions); if you are
9239 stepping by machine instructions, variables may appear to have the wrong
9240 values until the stack frame is completely built. On exit, it usually
9241 also takes more than one machine instruction to destroy a stack frame;
9242 after you begin stepping through that group of instructions, local
9243 variable definitions may be gone.
9245 This may also happen when the compiler does significant optimizations.
9246 To be sure of always seeing accurate values, turn off all optimization
9249 @cindex ``No symbol "foo" in current context''
9250 Another possible effect of compiler optimizations is to optimize
9251 unused variables out of existence, or assign variables to registers (as
9252 opposed to memory addresses). Depending on the support for such cases
9253 offered by the debug info format used by the compiler, @value{GDBN}
9254 might not be able to display values for such local variables. If that
9255 happens, @value{GDBN} will print a message like this:
9258 No symbol "foo" in current context.
9261 To solve such problems, either recompile without optimizations, or use a
9262 different debug info format, if the compiler supports several such
9263 formats. @xref{Compilation}, for more information on choosing compiler
9264 options. @xref{C, ,C and C@t{++}}, for more information about debug
9265 info formats that are best suited to C@t{++} programs.
9267 If you ask to print an object whose contents are unknown to
9268 @value{GDBN}, e.g., because its data type is not completely specified
9269 by the debug information, @value{GDBN} will say @samp{<incomplete
9270 type>}. @xref{Symbols, incomplete type}, for more about this.
9272 @cindex no debug info variables
9273 If you try to examine or use the value of a (global) variable for
9274 which @value{GDBN} has no type information, e.g., because the program
9275 includes no debug information, @value{GDBN} displays an error message.
9276 @xref{Symbols, unknown type}, for more about unknown types. If you
9277 cast the variable to its declared type, @value{GDBN} gets the
9278 variable's value using the cast-to type as the variable's type. For
9279 example, in a C program:
9282 (@value{GDBP}) p var
9283 'var' has unknown type; cast it to its declared type
9284 (@value{GDBP}) p (float) var
9288 If you append @kbd{@@entry} string to a function parameter name you get its
9289 value at the time the function got called. If the value is not available an
9290 error message is printed. Entry values are available only with some compilers.
9291 Entry values are normally also printed at the function parameter list according
9292 to @ref{set print entry-values}.
9295 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
9301 (gdb) print i@@entry
9305 Strings are identified as arrays of @code{char} values without specified
9306 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
9307 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
9308 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
9309 defines literal string type @code{"char"} as @code{char} without a sign.
9314 signed char var1[] = "A";
9317 You get during debugging
9322 $2 = @{65 'A', 0 '\0'@}
9326 @section Artificial Arrays
9328 @cindex artificial array
9330 @kindex @@@r{, referencing memory as an array}
9331 It is often useful to print out several successive objects of the
9332 same type in memory; a section of an array, or an array of
9333 dynamically determined size for which only a pointer exists in the
9336 You can do this by referring to a contiguous span of memory as an
9337 @dfn{artificial array}, using the binary operator @samp{@@}. The left
9338 operand of @samp{@@} should be the first element of the desired array
9339 and be an individual object. The right operand should be the desired length
9340 of the array. The result is an array value whose elements are all of
9341 the type of the left argument. The first element is actually the left
9342 argument; the second element comes from bytes of memory immediately
9343 following those that hold the first element, and so on. Here is an
9344 example. If a program says
9347 int *array = (int *) malloc (len * sizeof (int));
9351 you can print the contents of @code{array} with
9357 The left operand of @samp{@@} must reside in memory. Array values made
9358 with @samp{@@} in this way behave just like other arrays in terms of
9359 subscripting, and are coerced to pointers when used in expressions.
9360 Artificial arrays most often appear in expressions via the value history
9361 (@pxref{Value History, ,Value History}), after printing one out.
9363 Another way to create an artificial array is to use a cast.
9364 This re-interprets a value as if it were an array.
9365 The value need not be in memory:
9367 (@value{GDBP}) p/x (short[2])0x12345678
9368 $1 = @{0x1234, 0x5678@}
9371 As a convenience, if you leave the array length out (as in
9372 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
9373 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
9375 (@value{GDBP}) p/x (short[])0x12345678
9376 $2 = @{0x1234, 0x5678@}
9379 Sometimes the artificial array mechanism is not quite enough; in
9380 moderately complex data structures, the elements of interest may not
9381 actually be adjacent---for example, if you are interested in the values
9382 of pointers in an array. One useful work-around in this situation is
9383 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
9384 Variables}) as a counter in an expression that prints the first
9385 interesting value, and then repeat that expression via @key{RET}. For
9386 instance, suppose you have an array @code{dtab} of pointers to
9387 structures, and you are interested in the values of a field @code{fv}
9388 in each structure. Here is an example of what you might type:
9398 @node Output Formats
9399 @section Output Formats
9401 @cindex formatted output
9402 @cindex output formats
9403 By default, @value{GDBN} prints a value according to its data type. Sometimes
9404 this is not what you want. For example, you might want to print a number
9405 in hex, or a pointer in decimal. Or you might want to view data in memory
9406 at a certain address as a character string or as an instruction. To do
9407 these things, specify an @dfn{output format} when you print a value.
9409 The simplest use of output formats is to say how to print a value
9410 already computed. This is done by starting the arguments of the
9411 @code{print} command with a slash and a format letter. The format
9412 letters supported are:
9416 Regard the bits of the value as an integer, and print the integer in
9420 Print as integer in signed decimal.
9423 Print as integer in unsigned decimal.
9426 Print as integer in octal.
9429 Print as integer in binary. The letter @samp{t} stands for ``two''.
9430 @footnote{@samp{b} cannot be used because these format letters are also
9431 used with the @code{x} command, where @samp{b} stands for ``byte'';
9432 see @ref{Memory,,Examining Memory}.}
9435 @cindex unknown address, locating
9436 @cindex locate address
9437 Print as an address, both absolute in hexadecimal and as an offset from
9438 the nearest preceding symbol. You can use this format used to discover
9439 where (in what function) an unknown address is located:
9442 (@value{GDBP}) p/a 0x54320
9443 $3 = 0x54320 <_initialize_vx+396>
9447 The command @code{info symbol 0x54320} yields similar results.
9448 @xref{Symbols, info symbol}.
9451 Regard as an integer and print it as a character constant. This
9452 prints both the numerical value and its character representation. The
9453 character representation is replaced with the octal escape @samp{\nnn}
9454 for characters outside the 7-bit @sc{ascii} range.
9456 Without this format, @value{GDBN} displays @code{char},
9457 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
9458 constants. Single-byte members of vectors are displayed as integer
9462 Regard the bits of the value as a floating point number and print
9463 using typical floating point syntax.
9466 @cindex printing strings
9467 @cindex printing byte arrays
9468 Regard as a string, if possible. With this format, pointers to single-byte
9469 data are displayed as null-terminated strings and arrays of single-byte data
9470 are displayed as fixed-length strings. Other values are displayed in their
9473 Without this format, @value{GDBN} displays pointers to and arrays of
9474 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
9475 strings. Single-byte members of a vector are displayed as an integer
9479 Like @samp{x} formatting, the value is treated as an integer and
9480 printed as hexadecimal, but leading zeros are printed to pad the value
9481 to the size of the integer type.
9484 @cindex raw printing
9485 Print using the @samp{raw} formatting. By default, @value{GDBN} will
9486 use a Python-based pretty-printer, if one is available (@pxref{Pretty
9487 Printing}). This typically results in a higher-level display of the
9488 value's contents. The @samp{r} format bypasses any Python
9489 pretty-printer which might exist.
9492 For example, to print the program counter in hex (@pxref{Registers}), type
9499 Note that no space is required before the slash; this is because command
9500 names in @value{GDBN} cannot contain a slash.
9502 To reprint the last value in the value history with a different format,
9503 you can use the @code{print} command with just a format and no
9504 expression. For example, @samp{p/x} reprints the last value in hex.
9507 @section Examining Memory
9509 You can use the command @code{x} (for ``examine'') to examine memory in
9510 any of several formats, independently of your program's data types.
9512 @cindex examining memory
9514 @kindex x @r{(examine memory)}
9515 @item x/@var{nfu} @var{addr}
9518 Use the @code{x} command to examine memory.
9521 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
9522 much memory to display and how to format it; @var{addr} is an
9523 expression giving the address where you want to start displaying memory.
9524 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
9525 Several commands set convenient defaults for @var{addr}.
9528 @item @var{n}, the repeat count
9529 The repeat count is a decimal integer; the default is 1. It specifies
9530 how much memory (counting by units @var{u}) to display. If a negative
9531 number is specified, memory is examined backward from @var{addr}.
9532 @c This really is **decimal**; unaffected by 'set radix' as of GDB
9535 @item @var{f}, the display format
9536 The display format is one of the formats used by @code{print}
9537 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
9538 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
9539 The default is @samp{x} (hexadecimal) initially. The default changes
9540 each time you use either @code{x} or @code{print}.
9542 @item @var{u}, the unit size
9543 The unit size is any of
9549 Halfwords (two bytes).
9551 Words (four bytes). This is the initial default.
9553 Giant words (eight bytes).
9556 Each time you specify a unit size with @code{x}, that size becomes the
9557 default unit the next time you use @code{x}. For the @samp{i} format,
9558 the unit size is ignored and is normally not written. For the @samp{s} format,
9559 the unit size defaults to @samp{b}, unless it is explicitly given.
9560 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
9561 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
9562 Note that the results depend on the programming language of the
9563 current compilation unit. If the language is C, the @samp{s}
9564 modifier will use the UTF-16 encoding while @samp{w} will use
9565 UTF-32. The encoding is set by the programming language and cannot
9568 @item @var{addr}, starting display address
9569 @var{addr} is the address where you want @value{GDBN} to begin displaying
9570 memory. The expression need not have a pointer value (though it may);
9571 it is always interpreted as an integer address of a byte of memory.
9572 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
9573 @var{addr} is usually just after the last address examined---but several
9574 other commands also set the default address: @code{info breakpoints} (to
9575 the address of the last breakpoint listed), @code{info line} (to the
9576 starting address of a line), and @code{print} (if you use it to display
9577 a value from memory).
9580 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
9581 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
9582 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
9583 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
9584 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
9586 You can also specify a negative repeat count to examine memory backward
9587 from the given address. For example, @samp{x/-3uh 0x54320} prints three
9588 halfwords (@code{h}) at @code{0x54314}, @code{0x54328}, and @code{0x5431c}.
9590 Since the letters indicating unit sizes are all distinct from the
9591 letters specifying output formats, you do not have to remember whether
9592 unit size or format comes first; either order works. The output
9593 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
9594 (However, the count @var{n} must come first; @samp{wx4} does not work.)
9596 Even though the unit size @var{u} is ignored for the formats @samp{s}
9597 and @samp{i}, you might still want to use a count @var{n}; for example,
9598 @samp{3i} specifies that you want to see three machine instructions,
9599 including any operands. For convenience, especially when used with
9600 the @code{display} command, the @samp{i} format also prints branch delay
9601 slot instructions, if any, beyond the count specified, which immediately
9602 follow the last instruction that is within the count. The command
9603 @code{disassemble} gives an alternative way of inspecting machine
9604 instructions; see @ref{Machine Code,,Source and Machine Code}.
9606 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
9607 the command displays null-terminated strings or instructions before the given
9608 address as many as the absolute value of the given number. For the @samp{i}
9609 format, we use line number information in the debug info to accurately locate
9610 instruction boundaries while disassembling backward. If line info is not
9611 available, the command stops examining memory with an error message.
9613 All the defaults for the arguments to @code{x} are designed to make it
9614 easy to continue scanning memory with minimal specifications each time
9615 you use @code{x}. For example, after you have inspected three machine
9616 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
9617 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
9618 the repeat count @var{n} is used again; the other arguments default as
9619 for successive uses of @code{x}.
9621 When examining machine instructions, the instruction at current program
9622 counter is shown with a @code{=>} marker. For example:
9625 (@value{GDBP}) x/5i $pc-6
9626 0x804837f <main+11>: mov %esp,%ebp
9627 0x8048381 <main+13>: push %ecx
9628 0x8048382 <main+14>: sub $0x4,%esp
9629 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
9630 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
9633 @cindex @code{$_}, @code{$__}, and value history
9634 The addresses and contents printed by the @code{x} command are not saved
9635 in the value history because there is often too much of them and they
9636 would get in the way. Instead, @value{GDBN} makes these values available for
9637 subsequent use in expressions as values of the convenience variables
9638 @code{$_} and @code{$__}. After an @code{x} command, the last address
9639 examined is available for use in expressions in the convenience variable
9640 @code{$_}. The contents of that address, as examined, are available in
9641 the convenience variable @code{$__}.
9643 If the @code{x} command has a repeat count, the address and contents saved
9644 are from the last memory unit printed; this is not the same as the last
9645 address printed if several units were printed on the last line of output.
9647 @anchor{addressable memory unit}
9648 @cindex addressable memory unit
9649 Most targets have an addressable memory unit size of 8 bits. This means
9650 that to each memory address are associated 8 bits of data. Some
9651 targets, however, have other addressable memory unit sizes.
9652 Within @value{GDBN} and this document, the term
9653 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
9654 when explicitly referring to a chunk of data of that size. The word
9655 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
9656 the addressable memory unit size of the target. For most systems,
9657 addressable memory unit is a synonym of byte.
9659 @cindex remote memory comparison
9660 @cindex target memory comparison
9661 @cindex verify remote memory image
9662 @cindex verify target memory image
9663 When you are debugging a program running on a remote target machine
9664 (@pxref{Remote Debugging}), you may wish to verify the program's image
9665 in the remote machine's memory against the executable file you
9666 downloaded to the target. Or, on any target, you may want to check
9667 whether the program has corrupted its own read-only sections. The
9668 @code{compare-sections} command is provided for such situations.
9671 @kindex compare-sections
9672 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
9673 Compare the data of a loadable section @var{section-name} in the
9674 executable file of the program being debugged with the same section in
9675 the target machine's memory, and report any mismatches. With no
9676 arguments, compares all loadable sections. With an argument of
9677 @code{-r}, compares all loadable read-only sections.
9679 Note: for remote targets, this command can be accelerated if the
9680 target supports computing the CRC checksum of a block of memory
9681 (@pxref{qCRC packet}).
9685 @section Automatic Display
9686 @cindex automatic display
9687 @cindex display of expressions
9689 If you find that you want to print the value of an expression frequently
9690 (to see how it changes), you might want to add it to the @dfn{automatic
9691 display list} so that @value{GDBN} prints its value each time your program stops.
9692 Each expression added to the list is given a number to identify it;
9693 to remove an expression from the list, you specify that number.
9694 The automatic display looks like this:
9698 3: bar[5] = (struct hack *) 0x3804
9702 This display shows item numbers, expressions and their current values. As with
9703 displays you request manually using @code{x} or @code{print}, you can
9704 specify the output format you prefer; in fact, @code{display} decides
9705 whether to use @code{print} or @code{x} depending your format
9706 specification---it uses @code{x} if you specify either the @samp{i}
9707 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
9711 @item display @var{expr}
9712 Add the expression @var{expr} to the list of expressions to display
9713 each time your program stops. @xref{Expressions, ,Expressions}.
9715 @code{display} does not repeat if you press @key{RET} again after using it.
9717 @item display/@var{fmt} @var{expr}
9718 For @var{fmt} specifying only a display format and not a size or
9719 count, add the expression @var{expr} to the auto-display list but
9720 arrange to display it each time in the specified format @var{fmt}.
9721 @xref{Output Formats,,Output Formats}.
9723 @item display/@var{fmt} @var{addr}
9724 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
9725 number of units, add the expression @var{addr} as a memory address to
9726 be examined each time your program stops. Examining means in effect
9727 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
9730 For example, @samp{display/i $pc} can be helpful, to see the machine
9731 instruction about to be executed each time execution stops (@samp{$pc}
9732 is a common name for the program counter; @pxref{Registers, ,Registers}).
9735 @kindex delete display
9737 @item undisplay @var{dnums}@dots{}
9738 @itemx delete display @var{dnums}@dots{}
9739 Remove items from the list of expressions to display. Specify the
9740 numbers of the displays that you want affected with the command
9741 argument @var{dnums}. It can be a single display number, one of the
9742 numbers shown in the first field of the @samp{info display} display;
9743 or it could be a range of display numbers, as in @code{2-4}.
9745 @code{undisplay} does not repeat if you press @key{RET} after using it.
9746 (Otherwise you would just get the error @samp{No display number @dots{}}.)
9748 @kindex disable display
9749 @item disable display @var{dnums}@dots{}
9750 Disable the display of item numbers @var{dnums}. A disabled display
9751 item is not printed automatically, but is not forgotten. It may be
9752 enabled again later. Specify the numbers of the displays that you
9753 want affected with the command argument @var{dnums}. It can be a
9754 single display number, one of the numbers shown in the first field of
9755 the @samp{info display} display; or it could be a range of display
9756 numbers, as in @code{2-4}.
9758 @kindex enable display
9759 @item enable display @var{dnums}@dots{}
9760 Enable display of item numbers @var{dnums}. It becomes effective once
9761 again in auto display of its expression, until you specify otherwise.
9762 Specify the numbers of the displays that you want affected with the
9763 command argument @var{dnums}. It can be a single display number, one
9764 of the numbers shown in the first field of the @samp{info display}
9765 display; or it could be a range of display numbers, as in @code{2-4}.
9768 Display the current values of the expressions on the list, just as is
9769 done when your program stops.
9771 @kindex info display
9773 Print the list of expressions previously set up to display
9774 automatically, each one with its item number, but without showing the
9775 values. This includes disabled expressions, which are marked as such.
9776 It also includes expressions which would not be displayed right now
9777 because they refer to automatic variables not currently available.
9780 @cindex display disabled out of scope
9781 If a display expression refers to local variables, then it does not make
9782 sense outside the lexical context for which it was set up. Such an
9783 expression is disabled when execution enters a context where one of its
9784 variables is not defined. For example, if you give the command
9785 @code{display last_char} while inside a function with an argument
9786 @code{last_char}, @value{GDBN} displays this argument while your program
9787 continues to stop inside that function. When it stops elsewhere---where
9788 there is no variable @code{last_char}---the display is disabled
9789 automatically. The next time your program stops where @code{last_char}
9790 is meaningful, you can enable the display expression once again.
9792 @node Print Settings
9793 @section Print Settings
9795 @cindex format options
9796 @cindex print settings
9797 @value{GDBN} provides the following ways to control how arrays, structures,
9798 and symbols are printed.
9801 These settings are useful for debugging programs in any language:
9805 @item set print address
9806 @itemx set print address on
9807 @cindex print/don't print memory addresses
9808 @value{GDBN} prints memory addresses showing the location of stack
9809 traces, structure values, pointer values, breakpoints, and so forth,
9810 even when it also displays the contents of those addresses. The default
9811 is @code{on}. For example, this is what a stack frame display looks like with
9812 @code{set print address on}:
9817 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
9819 530 if (lquote != def_lquote)
9823 @item set print address off
9824 Do not print addresses when displaying their contents. For example,
9825 this is the same stack frame displayed with @code{set print address off}:
9829 (@value{GDBP}) set print addr off
9831 #0 set_quotes (lq="<<", rq=">>") at input.c:530
9832 530 if (lquote != def_lquote)
9836 You can use @samp{set print address off} to eliminate all machine
9837 dependent displays from the @value{GDBN} interface. For example, with
9838 @code{print address off}, you should get the same text for backtraces on
9839 all machines---whether or not they involve pointer arguments.
9842 @item show print address
9843 Show whether or not addresses are to be printed.
9846 When @value{GDBN} prints a symbolic address, it normally prints the
9847 closest earlier symbol plus an offset. If that symbol does not uniquely
9848 identify the address (for example, it is a name whose scope is a single
9849 source file), you may need to clarify. One way to do this is with
9850 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9851 you can set @value{GDBN} to print the source file and line number when
9852 it prints a symbolic address:
9855 @item set print symbol-filename on
9856 @cindex source file and line of a symbol
9857 @cindex symbol, source file and line
9858 Tell @value{GDBN} to print the source file name and line number of a
9859 symbol in the symbolic form of an address.
9861 @item set print symbol-filename off
9862 Do not print source file name and line number of a symbol. This is the
9865 @item show print symbol-filename
9866 Show whether or not @value{GDBN} will print the source file name and
9867 line number of a symbol in the symbolic form of an address.
9870 Another situation where it is helpful to show symbol filenames and line
9871 numbers is when disassembling code; @value{GDBN} shows you the line
9872 number and source file that corresponds to each instruction.
9874 Also, you may wish to see the symbolic form only if the address being
9875 printed is reasonably close to the closest earlier symbol:
9878 @item set print max-symbolic-offset @var{max-offset}
9879 @itemx set print max-symbolic-offset unlimited
9880 @cindex maximum value for offset of closest symbol
9881 Tell @value{GDBN} to only display the symbolic form of an address if the
9882 offset between the closest earlier symbol and the address is less than
9883 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9884 to always print the symbolic form of an address if any symbol precedes
9885 it. Zero is equivalent to @code{unlimited}.
9887 @item show print max-symbolic-offset
9888 Ask how large the maximum offset is that @value{GDBN} prints in a
9892 @cindex wild pointer, interpreting
9893 @cindex pointer, finding referent
9894 If you have a pointer and you are not sure where it points, try
9895 @samp{set print symbol-filename on}. Then you can determine the name
9896 and source file location of the variable where it points, using
9897 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9898 For example, here @value{GDBN} shows that a variable @code{ptt} points
9899 at another variable @code{t}, defined in @file{hi2.c}:
9902 (@value{GDBP}) set print symbol-filename on
9903 (@value{GDBP}) p/a ptt
9904 $4 = 0xe008 <t in hi2.c>
9908 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9909 does not show the symbol name and filename of the referent, even with
9910 the appropriate @code{set print} options turned on.
9913 You can also enable @samp{/a}-like formatting all the time using
9914 @samp{set print symbol on}:
9917 @item set print symbol on
9918 Tell @value{GDBN} to print the symbol corresponding to an address, if
9921 @item set print symbol off
9922 Tell @value{GDBN} not to print the symbol corresponding to an
9923 address. In this mode, @value{GDBN} will still print the symbol
9924 corresponding to pointers to functions. This is the default.
9926 @item show print symbol
9927 Show whether @value{GDBN} will display the symbol corresponding to an
9931 Other settings control how different kinds of objects are printed:
9934 @item set print array
9935 @itemx set print array on
9936 @cindex pretty print arrays
9937 Pretty print arrays. This format is more convenient to read,
9938 but uses more space. The default is off.
9940 @item set print array off
9941 Return to compressed format for arrays.
9943 @item show print array
9944 Show whether compressed or pretty format is selected for displaying
9947 @cindex print array indexes
9948 @item set print array-indexes
9949 @itemx set print array-indexes on
9950 Print the index of each element when displaying arrays. May be more
9951 convenient to locate a given element in the array or quickly find the
9952 index of a given element in that printed array. The default is off.
9954 @item set print array-indexes off
9955 Stop printing element indexes when displaying arrays.
9957 @item show print array-indexes
9958 Show whether the index of each element is printed when displaying
9961 @item set print elements @var{number-of-elements}
9962 @itemx set print elements unlimited
9963 @cindex number of array elements to print
9964 @cindex limit on number of printed array elements
9965 Set a limit on how many elements of an array @value{GDBN} will print.
9966 If @value{GDBN} is printing a large array, it stops printing after it has
9967 printed the number of elements set by the @code{set print elements} command.
9968 This limit also applies to the display of strings.
9969 When @value{GDBN} starts, this limit is set to 200.
9970 Setting @var{number-of-elements} to @code{unlimited} or zero means
9971 that the number of elements to print is unlimited.
9973 @item show print elements
9974 Display the number of elements of a large array that @value{GDBN} will print.
9975 If the number is 0, then the printing is unlimited.
9977 @item set print frame-arguments @var{value}
9978 @kindex set print frame-arguments
9979 @cindex printing frame argument values
9980 @cindex print all frame argument values
9981 @cindex print frame argument values for scalars only
9982 @cindex do not print frame argument values
9983 This command allows to control how the values of arguments are printed
9984 when the debugger prints a frame (@pxref{Frames}). The possible
9989 The values of all arguments are printed.
9992 Print the value of an argument only if it is a scalar. The value of more
9993 complex arguments such as arrays, structures, unions, etc, is replaced
9994 by @code{@dots{}}. This is the default. Here is an example where
9995 only scalar arguments are shown:
9998 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
10003 None of the argument values are printed. Instead, the value of each argument
10004 is replaced by @code{@dots{}}. In this case, the example above now becomes:
10007 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
10012 By default, only scalar arguments are printed. This command can be used
10013 to configure the debugger to print the value of all arguments, regardless
10014 of their type. However, it is often advantageous to not print the value
10015 of more complex parameters. For instance, it reduces the amount of
10016 information printed in each frame, making the backtrace more readable.
10017 Also, it improves performance when displaying Ada frames, because
10018 the computation of large arguments can sometimes be CPU-intensive,
10019 especially in large applications. Setting @code{print frame-arguments}
10020 to @code{scalars} (the default) or @code{none} avoids this computation,
10021 thus speeding up the display of each Ada frame.
10023 @item show print frame-arguments
10024 Show how the value of arguments should be displayed when printing a frame.
10026 @item set print raw frame-arguments on
10027 Print frame arguments in raw, non pretty-printed, form.
10029 @item set print raw frame-arguments off
10030 Print frame arguments in pretty-printed form, if there is a pretty-printer
10031 for the value (@pxref{Pretty Printing}),
10032 otherwise print the value in raw form.
10033 This is the default.
10035 @item show print raw frame-arguments
10036 Show whether to print frame arguments in raw form.
10038 @anchor{set print entry-values}
10039 @item set print entry-values @var{value}
10040 @kindex set print entry-values
10041 Set printing of frame argument values at function entry. In some cases
10042 @value{GDBN} can determine the value of function argument which was passed by
10043 the function caller, even if the value was modified inside the called function
10044 and therefore is different. With optimized code, the current value could be
10045 unavailable, but the entry value may still be known.
10047 The default value is @code{default} (see below for its description). Older
10048 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
10049 this feature will behave in the @code{default} setting the same way as with the
10052 This functionality is currently supported only by DWARF 2 debugging format and
10053 the compiler has to produce @samp{DW_TAG_call_site} tags. With
10054 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10057 The @var{value} parameter can be one of the following:
10061 Print only actual parameter values, never print values from function entry
10065 #0 different (val=6)
10066 #0 lost (val=<optimized out>)
10068 #0 invalid (val=<optimized out>)
10072 Print only parameter values from function entry point. The actual parameter
10073 values are never printed.
10075 #0 equal (val@@entry=5)
10076 #0 different (val@@entry=5)
10077 #0 lost (val@@entry=5)
10078 #0 born (val@@entry=<optimized out>)
10079 #0 invalid (val@@entry=<optimized out>)
10083 Print only parameter values from function entry point. If value from function
10084 entry point is not known while the actual value is known, print the actual
10085 value for such parameter.
10087 #0 equal (val@@entry=5)
10088 #0 different (val@@entry=5)
10089 #0 lost (val@@entry=5)
10091 #0 invalid (val@@entry=<optimized out>)
10095 Print actual parameter values. If actual parameter value is not known while
10096 value from function entry point is known, print the entry point value for such
10100 #0 different (val=6)
10101 #0 lost (val@@entry=5)
10103 #0 invalid (val=<optimized out>)
10107 Always print both the actual parameter value and its value from function entry
10108 point, even if values of one or both are not available due to compiler
10111 #0 equal (val=5, val@@entry=5)
10112 #0 different (val=6, val@@entry=5)
10113 #0 lost (val=<optimized out>, val@@entry=5)
10114 #0 born (val=10, val@@entry=<optimized out>)
10115 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
10119 Print the actual parameter value if it is known and also its value from
10120 function entry point if it is known. If neither is known, print for the actual
10121 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
10122 values are known and identical, print the shortened
10123 @code{param=param@@entry=VALUE} notation.
10125 #0 equal (val=val@@entry=5)
10126 #0 different (val=6, val@@entry=5)
10127 #0 lost (val@@entry=5)
10129 #0 invalid (val=<optimized out>)
10133 Always print the actual parameter value. Print also its value from function
10134 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
10135 if both values are known and identical, print the shortened
10136 @code{param=param@@entry=VALUE} notation.
10138 #0 equal (val=val@@entry=5)
10139 #0 different (val=6, val@@entry=5)
10140 #0 lost (val=<optimized out>, val@@entry=5)
10142 #0 invalid (val=<optimized out>)
10146 For analysis messages on possible failures of frame argument values at function
10147 entry resolution see @ref{set debug entry-values}.
10149 @item show print entry-values
10150 Show the method being used for printing of frame argument values at function
10153 @item set print repeats @var{number-of-repeats}
10154 @itemx set print repeats unlimited
10155 @cindex repeated array elements
10156 Set the threshold for suppressing display of repeated array
10157 elements. When the number of consecutive identical elements of an
10158 array exceeds the threshold, @value{GDBN} prints the string
10159 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
10160 identical repetitions, instead of displaying the identical elements
10161 themselves. Setting the threshold to @code{unlimited} or zero will
10162 cause all elements to be individually printed. The default threshold
10165 @item show print repeats
10166 Display the current threshold for printing repeated identical
10169 @item set print null-stop
10170 @cindex @sc{null} elements in arrays
10171 Cause @value{GDBN} to stop printing the characters of an array when the first
10172 @sc{null} is encountered. This is useful when large arrays actually
10173 contain only short strings.
10174 The default is off.
10176 @item show print null-stop
10177 Show whether @value{GDBN} stops printing an array on the first
10178 @sc{null} character.
10180 @item set print pretty on
10181 @cindex print structures in indented form
10182 @cindex indentation in structure display
10183 Cause @value{GDBN} to print structures in an indented format with one member
10184 per line, like this:
10199 @item set print pretty off
10200 Cause @value{GDBN} to print structures in a compact format, like this:
10204 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
10205 meat = 0x54 "Pork"@}
10210 This is the default format.
10212 @item show print pretty
10213 Show which format @value{GDBN} is using to print structures.
10215 @item set print sevenbit-strings on
10216 @cindex eight-bit characters in strings
10217 @cindex octal escapes in strings
10218 Print using only seven-bit characters; if this option is set,
10219 @value{GDBN} displays any eight-bit characters (in strings or
10220 character values) using the notation @code{\}@var{nnn}. This setting is
10221 best if you are working in English (@sc{ascii}) and you use the
10222 high-order bit of characters as a marker or ``meta'' bit.
10224 @item set print sevenbit-strings off
10225 Print full eight-bit characters. This allows the use of more
10226 international character sets, and is the default.
10228 @item show print sevenbit-strings
10229 Show whether or not @value{GDBN} is printing only seven-bit characters.
10231 @item set print union on
10232 @cindex unions in structures, printing
10233 Tell @value{GDBN} to print unions which are contained in structures
10234 and other unions. This is the default setting.
10236 @item set print union off
10237 Tell @value{GDBN} not to print unions which are contained in
10238 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
10241 @item show print union
10242 Ask @value{GDBN} whether or not it will print unions which are contained in
10243 structures and other unions.
10245 For example, given the declarations
10248 typedef enum @{Tree, Bug@} Species;
10249 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
10250 typedef enum @{Caterpillar, Cocoon, Butterfly@}
10261 struct thing foo = @{Tree, @{Acorn@}@};
10265 with @code{set print union on} in effect @samp{p foo} would print
10268 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
10272 and with @code{set print union off} in effect it would print
10275 $1 = @{it = Tree, form = @{...@}@}
10279 @code{set print union} affects programs written in C-like languages
10285 These settings are of interest when debugging C@t{++} programs:
10288 @cindex demangling C@t{++} names
10289 @item set print demangle
10290 @itemx set print demangle on
10291 Print C@t{++} names in their source form rather than in the encoded
10292 (``mangled'') form passed to the assembler and linker for type-safe
10293 linkage. The default is on.
10295 @item show print demangle
10296 Show whether C@t{++} names are printed in mangled or demangled form.
10298 @item set print asm-demangle
10299 @itemx set print asm-demangle on
10300 Print C@t{++} names in their source form rather than their mangled form, even
10301 in assembler code printouts such as instruction disassemblies.
10302 The default is off.
10304 @item show print asm-demangle
10305 Show whether C@t{++} names in assembly listings are printed in mangled
10308 @cindex C@t{++} symbol decoding style
10309 @cindex symbol decoding style, C@t{++}
10310 @kindex set demangle-style
10311 @item set demangle-style @var{style}
10312 Choose among several encoding schemes used by different compilers to
10313 represent C@t{++} names. The choices for @var{style} are currently:
10317 Allow @value{GDBN} to choose a decoding style by inspecting your program.
10318 This is the default.
10321 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
10324 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
10327 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
10330 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
10331 @strong{Warning:} this setting alone is not sufficient to allow
10332 debugging @code{cfront}-generated executables. @value{GDBN} would
10333 require further enhancement to permit that.
10336 If you omit @var{style}, you will see a list of possible formats.
10338 @item show demangle-style
10339 Display the encoding style currently in use for decoding C@t{++} symbols.
10341 @item set print object
10342 @itemx set print object on
10343 @cindex derived type of an object, printing
10344 @cindex display derived types
10345 When displaying a pointer to an object, identify the @emph{actual}
10346 (derived) type of the object rather than the @emph{declared} type, using
10347 the virtual function table. Note that the virtual function table is
10348 required---this feature can only work for objects that have run-time
10349 type identification; a single virtual method in the object's declared
10350 type is sufficient. Note that this setting is also taken into account when
10351 working with variable objects via MI (@pxref{GDB/MI}).
10353 @item set print object off
10354 Display only the declared type of objects, without reference to the
10355 virtual function table. This is the default setting.
10357 @item show print object
10358 Show whether actual, or declared, object types are displayed.
10360 @item set print static-members
10361 @itemx set print static-members on
10362 @cindex static members of C@t{++} objects
10363 Print static members when displaying a C@t{++} object. The default is on.
10365 @item set print static-members off
10366 Do not print static members when displaying a C@t{++} object.
10368 @item show print static-members
10369 Show whether C@t{++} static members are printed or not.
10371 @item set print pascal_static-members
10372 @itemx set print pascal_static-members on
10373 @cindex static members of Pascal objects
10374 @cindex Pascal objects, static members display
10375 Print static members when displaying a Pascal object. The default is on.
10377 @item set print pascal_static-members off
10378 Do not print static members when displaying a Pascal object.
10380 @item show print pascal_static-members
10381 Show whether Pascal static members are printed or not.
10383 @c These don't work with HP ANSI C++ yet.
10384 @item set print vtbl
10385 @itemx set print vtbl on
10386 @cindex pretty print C@t{++} virtual function tables
10387 @cindex virtual functions (C@t{++}) display
10388 @cindex VTBL display
10389 Pretty print C@t{++} virtual function tables. The default is off.
10390 (The @code{vtbl} commands do not work on programs compiled with the HP
10391 ANSI C@t{++} compiler (@code{aCC}).)
10393 @item set print vtbl off
10394 Do not pretty print C@t{++} virtual function tables.
10396 @item show print vtbl
10397 Show whether C@t{++} virtual function tables are pretty printed, or not.
10400 @node Pretty Printing
10401 @section Pretty Printing
10403 @value{GDBN} provides a mechanism to allow pretty-printing of values using
10404 Python code. It greatly simplifies the display of complex objects. This
10405 mechanism works for both MI and the CLI.
10408 * Pretty-Printer Introduction:: Introduction to pretty-printers
10409 * Pretty-Printer Example:: An example pretty-printer
10410 * Pretty-Printer Commands:: Pretty-printer commands
10413 @node Pretty-Printer Introduction
10414 @subsection Pretty-Printer Introduction
10416 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
10417 registered for the value. If there is then @value{GDBN} invokes the
10418 pretty-printer to print the value. Otherwise the value is printed normally.
10420 Pretty-printers are normally named. This makes them easy to manage.
10421 The @samp{info pretty-printer} command will list all the installed
10422 pretty-printers with their names.
10423 If a pretty-printer can handle multiple data types, then its
10424 @dfn{subprinters} are the printers for the individual data types.
10425 Each such subprinter has its own name.
10426 The format of the name is @var{printer-name};@var{subprinter-name}.
10428 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
10429 Typically they are automatically loaded and registered when the corresponding
10430 debug information is loaded, thus making them available without having to
10431 do anything special.
10433 There are three places where a pretty-printer can be registered.
10437 Pretty-printers registered globally are available when debugging
10441 Pretty-printers registered with a program space are available only
10442 when debugging that program.
10443 @xref{Progspaces In Python}, for more details on program spaces in Python.
10446 Pretty-printers registered with an objfile are loaded and unloaded
10447 with the corresponding objfile (e.g., shared library).
10448 @xref{Objfiles In Python}, for more details on objfiles in Python.
10451 @xref{Selecting Pretty-Printers}, for further information on how
10452 pretty-printers are selected,
10454 @xref{Writing a Pretty-Printer}, for implementing pretty printers
10457 @node Pretty-Printer Example
10458 @subsection Pretty-Printer Example
10460 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
10463 (@value{GDBP}) print s
10465 static npos = 4294967295,
10467 <std::allocator<char>> = @{
10468 <__gnu_cxx::new_allocator<char>> = @{
10469 <No data fields>@}, <No data fields>
10471 members of std::basic_string<char, std::char_traits<char>,
10472 std::allocator<char> >::_Alloc_hider:
10473 _M_p = 0x804a014 "abcd"
10478 With a pretty-printer for @code{std::string} only the contents are printed:
10481 (@value{GDBP}) print s
10485 @node Pretty-Printer Commands
10486 @subsection Pretty-Printer Commands
10487 @cindex pretty-printer commands
10490 @kindex info pretty-printer
10491 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10492 Print the list of installed pretty-printers.
10493 This includes disabled pretty-printers, which are marked as such.
10495 @var{object-regexp} is a regular expression matching the objects
10496 whose pretty-printers to list.
10497 Objects can be @code{global}, the program space's file
10498 (@pxref{Progspaces In Python}),
10499 and the object files within that program space (@pxref{Objfiles In Python}).
10500 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
10501 looks up a printer from these three objects.
10503 @var{name-regexp} is a regular expression matching the name of the printers
10506 @kindex disable pretty-printer
10507 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10508 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10509 A disabled pretty-printer is not forgotten, it may be enabled again later.
10511 @kindex enable pretty-printer
10512 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10513 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10518 Suppose we have three pretty-printers installed: one from library1.so
10519 named @code{foo} that prints objects of type @code{foo}, and
10520 another from library2.so named @code{bar} that prints two types of objects,
10521 @code{bar1} and @code{bar2}.
10524 (gdb) info pretty-printer
10531 (gdb) info pretty-printer library2
10536 (gdb) disable pretty-printer library1
10538 2 of 3 printers enabled
10539 (gdb) info pretty-printer
10546 (gdb) disable pretty-printer library2 bar:bar1
10548 1 of 3 printers enabled
10549 (gdb) info pretty-printer library2
10556 (gdb) disable pretty-printer library2 bar
10558 0 of 3 printers enabled
10559 (gdb) info pretty-printer library2
10568 Note that for @code{bar} the entire printer can be disabled,
10569 as can each individual subprinter.
10571 @node Value History
10572 @section Value History
10574 @cindex value history
10575 @cindex history of values printed by @value{GDBN}
10576 Values printed by the @code{print} command are saved in the @value{GDBN}
10577 @dfn{value history}. This allows you to refer to them in other expressions.
10578 Values are kept until the symbol table is re-read or discarded
10579 (for example with the @code{file} or @code{symbol-file} commands).
10580 When the symbol table changes, the value history is discarded,
10581 since the values may contain pointers back to the types defined in the
10586 @cindex history number
10587 The values printed are given @dfn{history numbers} by which you can
10588 refer to them. These are successive integers starting with one.
10589 @code{print} shows you the history number assigned to a value by
10590 printing @samp{$@var{num} = } before the value; here @var{num} is the
10593 To refer to any previous value, use @samp{$} followed by the value's
10594 history number. The way @code{print} labels its output is designed to
10595 remind you of this. Just @code{$} refers to the most recent value in
10596 the history, and @code{$$} refers to the value before that.
10597 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
10598 is the value just prior to @code{$$}, @code{$$1} is equivalent to
10599 @code{$$}, and @code{$$0} is equivalent to @code{$}.
10601 For example, suppose you have just printed a pointer to a structure and
10602 want to see the contents of the structure. It suffices to type
10608 If you have a chain of structures where the component @code{next} points
10609 to the next one, you can print the contents of the next one with this:
10616 You can print successive links in the chain by repeating this
10617 command---which you can do by just typing @key{RET}.
10619 Note that the history records values, not expressions. If the value of
10620 @code{x} is 4 and you type these commands:
10628 then the value recorded in the value history by the @code{print} command
10629 remains 4 even though the value of @code{x} has changed.
10632 @kindex show values
10634 Print the last ten values in the value history, with their item numbers.
10635 This is like @samp{p@ $$9} repeated ten times, except that @code{show
10636 values} does not change the history.
10638 @item show values @var{n}
10639 Print ten history values centered on history item number @var{n}.
10641 @item show values +
10642 Print ten history values just after the values last printed. If no more
10643 values are available, @code{show values +} produces no display.
10646 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
10647 same effect as @samp{show values +}.
10649 @node Convenience Vars
10650 @section Convenience Variables
10652 @cindex convenience variables
10653 @cindex user-defined variables
10654 @value{GDBN} provides @dfn{convenience variables} that you can use within
10655 @value{GDBN} to hold on to a value and refer to it later. These variables
10656 exist entirely within @value{GDBN}; they are not part of your program, and
10657 setting a convenience variable has no direct effect on further execution
10658 of your program. That is why you can use them freely.
10660 Convenience variables are prefixed with @samp{$}. Any name preceded by
10661 @samp{$} can be used for a convenience variable, unless it is one of
10662 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
10663 (Value history references, in contrast, are @emph{numbers} preceded
10664 by @samp{$}. @xref{Value History, ,Value History}.)
10666 You can save a value in a convenience variable with an assignment
10667 expression, just as you would set a variable in your program.
10671 set $foo = *object_ptr
10675 would save in @code{$foo} the value contained in the object pointed to by
10678 Using a convenience variable for the first time creates it, but its
10679 value is @code{void} until you assign a new value. You can alter the
10680 value with another assignment at any time.
10682 Convenience variables have no fixed types. You can assign a convenience
10683 variable any type of value, including structures and arrays, even if
10684 that variable already has a value of a different type. The convenience
10685 variable, when used as an expression, has the type of its current value.
10688 @kindex show convenience
10689 @cindex show all user variables and functions
10690 @item show convenience
10691 Print a list of convenience variables used so far, and their values,
10692 as well as a list of the convenience functions.
10693 Abbreviated @code{show conv}.
10695 @kindex init-if-undefined
10696 @cindex convenience variables, initializing
10697 @item init-if-undefined $@var{variable} = @var{expression}
10698 Set a convenience variable if it has not already been set. This is useful
10699 for user-defined commands that keep some state. It is similar, in concept,
10700 to using local static variables with initializers in C (except that
10701 convenience variables are global). It can also be used to allow users to
10702 override default values used in a command script.
10704 If the variable is already defined then the expression is not evaluated so
10705 any side-effects do not occur.
10708 One of the ways to use a convenience variable is as a counter to be
10709 incremented or a pointer to be advanced. For example, to print
10710 a field from successive elements of an array of structures:
10714 print bar[$i++]->contents
10718 Repeat that command by typing @key{RET}.
10720 Some convenience variables are created automatically by @value{GDBN} and given
10721 values likely to be useful.
10724 @vindex $_@r{, convenience variable}
10726 The variable @code{$_} is automatically set by the @code{x} command to
10727 the last address examined (@pxref{Memory, ,Examining Memory}). Other
10728 commands which provide a default address for @code{x} to examine also
10729 set @code{$_} to that address; these commands include @code{info line}
10730 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
10731 except when set by the @code{x} command, in which case it is a pointer
10732 to the type of @code{$__}.
10734 @vindex $__@r{, convenience variable}
10736 The variable @code{$__} is automatically set by the @code{x} command
10737 to the value found in the last address examined. Its type is chosen
10738 to match the format in which the data was printed.
10741 @vindex $_exitcode@r{, convenience variable}
10742 When the program being debugged terminates normally, @value{GDBN}
10743 automatically sets this variable to the exit code of the program, and
10744 resets @code{$_exitsignal} to @code{void}.
10747 @vindex $_exitsignal@r{, convenience variable}
10748 When the program being debugged dies due to an uncaught signal,
10749 @value{GDBN} automatically sets this variable to that signal's number,
10750 and resets @code{$_exitcode} to @code{void}.
10752 To distinguish between whether the program being debugged has exited
10753 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
10754 @code{$_exitsignal} is not @code{void}), the convenience function
10755 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
10756 Functions}). For example, considering the following source code:
10759 #include <signal.h>
10762 main (int argc, char *argv[])
10769 A valid way of telling whether the program being debugged has exited
10770 or signalled would be:
10773 (@value{GDBP}) define has_exited_or_signalled
10774 Type commands for definition of ``has_exited_or_signalled''.
10775 End with a line saying just ``end''.
10776 >if $_isvoid ($_exitsignal)
10777 >echo The program has exited\n
10779 >echo The program has signalled\n
10785 Program terminated with signal SIGALRM, Alarm clock.
10786 The program no longer exists.
10787 (@value{GDBP}) has_exited_or_signalled
10788 The program has signalled
10791 As can be seen, @value{GDBN} correctly informs that the program being
10792 debugged has signalled, since it calls @code{raise} and raises a
10793 @code{SIGALRM} signal. If the program being debugged had not called
10794 @code{raise}, then @value{GDBN} would report a normal exit:
10797 (@value{GDBP}) has_exited_or_signalled
10798 The program has exited
10802 The variable @code{$_exception} is set to the exception object being
10803 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
10806 @itemx $_probe_arg0@dots{}$_probe_arg11
10807 Arguments to a static probe. @xref{Static Probe Points}.
10810 @vindex $_sdata@r{, inspect, convenience variable}
10811 The variable @code{$_sdata} contains extra collected static tracepoint
10812 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
10813 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
10814 if extra static tracepoint data has not been collected.
10817 @vindex $_siginfo@r{, convenience variable}
10818 The variable @code{$_siginfo} contains extra signal information
10819 (@pxref{extra signal information}). Note that @code{$_siginfo}
10820 could be empty, if the application has not yet received any signals.
10821 For example, it will be empty before you execute the @code{run} command.
10824 @vindex $_tlb@r{, convenience variable}
10825 The variable @code{$_tlb} is automatically set when debugging
10826 applications running on MS-Windows in native mode or connected to
10827 gdbserver that supports the @code{qGetTIBAddr} request.
10828 @xref{General Query Packets}.
10829 This variable contains the address of the thread information block.
10832 The number of the current inferior. @xref{Inferiors and
10833 Programs, ,Debugging Multiple Inferiors and Programs}.
10836 The thread number of the current thread. @xref{thread numbers}.
10839 The global number of the current thread. @xref{global thread numbers}.
10843 @node Convenience Funs
10844 @section Convenience Functions
10846 @cindex convenience functions
10847 @value{GDBN} also supplies some @dfn{convenience functions}. These
10848 have a syntax similar to convenience variables. A convenience
10849 function can be used in an expression just like an ordinary function;
10850 however, a convenience function is implemented internally to
10853 These functions do not require @value{GDBN} to be configured with
10854 @code{Python} support, which means that they are always available.
10858 @item $_isvoid (@var{expr})
10859 @findex $_isvoid@r{, convenience function}
10860 Return one if the expression @var{expr} is @code{void}. Otherwise it
10863 A @code{void} expression is an expression where the type of the result
10864 is @code{void}. For example, you can examine a convenience variable
10865 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10869 (@value{GDBP}) print $_exitcode
10871 (@value{GDBP}) print $_isvoid ($_exitcode)
10874 Starting program: ./a.out
10875 [Inferior 1 (process 29572) exited normally]
10876 (@value{GDBP}) print $_exitcode
10878 (@value{GDBP}) print $_isvoid ($_exitcode)
10882 In the example above, we used @code{$_isvoid} to check whether
10883 @code{$_exitcode} is @code{void} before and after the execution of the
10884 program being debugged. Before the execution there is no exit code to
10885 be examined, therefore @code{$_exitcode} is @code{void}. After the
10886 execution the program being debugged returned zero, therefore
10887 @code{$_exitcode} is zero, which means that it is not @code{void}
10890 The @code{void} expression can also be a call of a function from the
10891 program being debugged. For example, given the following function:
10900 The result of calling it inside @value{GDBN} is @code{void}:
10903 (@value{GDBP}) print foo ()
10905 (@value{GDBP}) print $_isvoid (foo ())
10907 (@value{GDBP}) set $v = foo ()
10908 (@value{GDBP}) print $v
10910 (@value{GDBP}) print $_isvoid ($v)
10916 These functions require @value{GDBN} to be configured with
10917 @code{Python} support.
10921 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10922 @findex $_memeq@r{, convenience function}
10923 Returns one if the @var{length} bytes at the addresses given by
10924 @var{buf1} and @var{buf2} are equal.
10925 Otherwise it returns zero.
10927 @item $_regex(@var{str}, @var{regex})
10928 @findex $_regex@r{, convenience function}
10929 Returns one if the string @var{str} matches the regular expression
10930 @var{regex}. Otherwise it returns zero.
10931 The syntax of the regular expression is that specified by @code{Python}'s
10932 regular expression support.
10934 @item $_streq(@var{str1}, @var{str2})
10935 @findex $_streq@r{, convenience function}
10936 Returns one if the strings @var{str1} and @var{str2} are equal.
10937 Otherwise it returns zero.
10939 @item $_strlen(@var{str})
10940 @findex $_strlen@r{, convenience function}
10941 Returns the length of string @var{str}.
10943 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10944 @findex $_caller_is@r{, convenience function}
10945 Returns one if the calling function's name is equal to @var{name}.
10946 Otherwise it returns zero.
10948 If the optional argument @var{number_of_frames} is provided,
10949 it is the number of frames up in the stack to look.
10957 at testsuite/gdb.python/py-caller-is.c:21
10958 #1 0x00000000004005a0 in middle_func ()
10959 at testsuite/gdb.python/py-caller-is.c:27
10960 #2 0x00000000004005ab in top_func ()
10961 at testsuite/gdb.python/py-caller-is.c:33
10962 #3 0x00000000004005b6 in main ()
10963 at testsuite/gdb.python/py-caller-is.c:39
10964 (gdb) print $_caller_is ("middle_func")
10966 (gdb) print $_caller_is ("top_func", 2)
10970 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10971 @findex $_caller_matches@r{, convenience function}
10972 Returns one if the calling function's name matches the regular expression
10973 @var{regexp}. Otherwise it returns zero.
10975 If the optional argument @var{number_of_frames} is provided,
10976 it is the number of frames up in the stack to look.
10979 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10980 @findex $_any_caller_is@r{, convenience function}
10981 Returns one if any calling function's name is equal to @var{name}.
10982 Otherwise it returns zero.
10984 If the optional argument @var{number_of_frames} is provided,
10985 it is the number of frames up in the stack to look.
10988 This function differs from @code{$_caller_is} in that this function
10989 checks all stack frames from the immediate caller to the frame specified
10990 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
10991 frame specified by @var{number_of_frames}.
10993 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10994 @findex $_any_caller_matches@r{, convenience function}
10995 Returns one if any calling function's name matches the regular expression
10996 @var{regexp}. Otherwise it returns zero.
10998 If the optional argument @var{number_of_frames} is provided,
10999 it is the number of frames up in the stack to look.
11002 This function differs from @code{$_caller_matches} in that this function
11003 checks all stack frames from the immediate caller to the frame specified
11004 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
11005 frame specified by @var{number_of_frames}.
11007 @item $_as_string(@var{value})
11008 @findex $_as_string@r{, convenience function}
11009 Return the string representation of @var{value}.
11011 This function is useful to obtain the textual label (enumerator) of an
11012 enumeration value. For example, assuming the variable @var{node} is of
11013 an enumerated type:
11016 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
11017 Visiting node of type NODE_INTEGER
11022 @value{GDBN} provides the ability to list and get help on
11023 convenience functions.
11026 @item help function
11027 @kindex help function
11028 @cindex show all convenience functions
11029 Print a list of all convenience functions.
11036 You can refer to machine register contents, in expressions, as variables
11037 with names starting with @samp{$}. The names of registers are different
11038 for each machine; use @code{info registers} to see the names used on
11042 @kindex info registers
11043 @item info registers
11044 Print the names and values of all registers except floating-point
11045 and vector registers (in the selected stack frame).
11047 @kindex info all-registers
11048 @cindex floating point registers
11049 @item info all-registers
11050 Print the names and values of all registers, including floating-point
11051 and vector registers (in the selected stack frame).
11053 @item info registers @var{reggroup} @dots{}
11054 Print the name and value of the registers in each of the specified
11055 @var{reggroup}s. The @var{reggoup} can be any of those returned by
11056 @code{maint print reggroups} (@pxref{Maintenance Commands}).
11058 @item info registers @var{regname} @dots{}
11059 Print the @dfn{relativized} value of each specified register @var{regname}.
11060 As discussed in detail below, register values are normally relative to
11061 the selected stack frame. The @var{regname} may be any register name valid on
11062 the machine you are using, with or without the initial @samp{$}.
11065 @anchor{standard registers}
11066 @cindex stack pointer register
11067 @cindex program counter register
11068 @cindex process status register
11069 @cindex frame pointer register
11070 @cindex standard registers
11071 @value{GDBN} has four ``standard'' register names that are available (in
11072 expressions) on most machines---whenever they do not conflict with an
11073 architecture's canonical mnemonics for registers. The register names
11074 @code{$pc} and @code{$sp} are used for the program counter register and
11075 the stack pointer. @code{$fp} is used for a register that contains a
11076 pointer to the current stack frame, and @code{$ps} is used for a
11077 register that contains the processor status. For example,
11078 you could print the program counter in hex with
11085 or print the instruction to be executed next with
11092 or add four to the stack pointer@footnote{This is a way of removing
11093 one word from the stack, on machines where stacks grow downward in
11094 memory (most machines, nowadays). This assumes that the innermost
11095 stack frame is selected; setting @code{$sp} is not allowed when other
11096 stack frames are selected. To pop entire frames off the stack,
11097 regardless of machine architecture, use @code{return};
11098 see @ref{Returning, ,Returning from a Function}.} with
11104 Whenever possible, these four standard register names are available on
11105 your machine even though the machine has different canonical mnemonics,
11106 so long as there is no conflict. The @code{info registers} command
11107 shows the canonical names. For example, on the SPARC, @code{info
11108 registers} displays the processor status register as @code{$psr} but you
11109 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
11110 is an alias for the @sc{eflags} register.
11112 @value{GDBN} always considers the contents of an ordinary register as an
11113 integer when the register is examined in this way. Some machines have
11114 special registers which can hold nothing but floating point; these
11115 registers are considered to have floating point values. There is no way
11116 to refer to the contents of an ordinary register as floating point value
11117 (although you can @emph{print} it as a floating point value with
11118 @samp{print/f $@var{regname}}).
11120 Some registers have distinct ``raw'' and ``virtual'' data formats. This
11121 means that the data format in which the register contents are saved by
11122 the operating system is not the same one that your program normally
11123 sees. For example, the registers of the 68881 floating point
11124 coprocessor are always saved in ``extended'' (raw) format, but all C
11125 programs expect to work with ``double'' (virtual) format. In such
11126 cases, @value{GDBN} normally works with the virtual format only (the format
11127 that makes sense for your program), but the @code{info registers} command
11128 prints the data in both formats.
11130 @cindex SSE registers (x86)
11131 @cindex MMX registers (x86)
11132 Some machines have special registers whose contents can be interpreted
11133 in several different ways. For example, modern x86-based machines
11134 have SSE and MMX registers that can hold several values packed
11135 together in several different formats. @value{GDBN} refers to such
11136 registers in @code{struct} notation:
11139 (@value{GDBP}) print $xmm1
11141 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
11142 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
11143 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
11144 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
11145 v4_int32 = @{0, 20657912, 11, 13@},
11146 v2_int64 = @{88725056443645952, 55834574859@},
11147 uint128 = 0x0000000d0000000b013b36f800000000
11152 To set values of such registers, you need to tell @value{GDBN} which
11153 view of the register you wish to change, as if you were assigning
11154 value to a @code{struct} member:
11157 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
11160 Normally, register values are relative to the selected stack frame
11161 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
11162 value that the register would contain if all stack frames farther in
11163 were exited and their saved registers restored. In order to see the
11164 true contents of hardware registers, you must select the innermost
11165 frame (with @samp{frame 0}).
11167 @cindex caller-saved registers
11168 @cindex call-clobbered registers
11169 @cindex volatile registers
11170 @cindex <not saved> values
11171 Usually ABIs reserve some registers as not needed to be saved by the
11172 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
11173 registers). It may therefore not be possible for @value{GDBN} to know
11174 the value a register had before the call (in other words, in the outer
11175 frame), if the register value has since been changed by the callee.
11176 @value{GDBN} tries to deduce where the inner frame saved
11177 (``callee-saved'') registers, from the debug info, unwind info, or the
11178 machine code generated by your compiler. If some register is not
11179 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
11180 its own knowledge of the ABI, or because the debug/unwind info
11181 explicitly says the register's value is undefined), @value{GDBN}
11182 displays @w{@samp{<not saved>}} as the register's value. With targets
11183 that @value{GDBN} has no knowledge of the register saving convention,
11184 if a register was not saved by the callee, then its value and location
11185 in the outer frame are assumed to be the same of the inner frame.
11186 This is usually harmless, because if the register is call-clobbered,
11187 the caller either does not care what is in the register after the
11188 call, or has code to restore the value that it does care about. Note,
11189 however, that if you change such a register in the outer frame, you
11190 may also be affecting the inner frame. Also, the more ``outer'' the
11191 frame is you're looking at, the more likely a call-clobbered
11192 register's value is to be wrong, in the sense that it doesn't actually
11193 represent the value the register had just before the call.
11195 @node Floating Point Hardware
11196 @section Floating Point Hardware
11197 @cindex floating point
11199 Depending on the configuration, @value{GDBN} may be able to give
11200 you more information about the status of the floating point hardware.
11205 Display hardware-dependent information about the floating
11206 point unit. The exact contents and layout vary depending on the
11207 floating point chip. Currently, @samp{info float} is supported on
11208 the ARM and x86 machines.
11212 @section Vector Unit
11213 @cindex vector unit
11215 Depending on the configuration, @value{GDBN} may be able to give you
11216 more information about the status of the vector unit.
11219 @kindex info vector
11221 Display information about the vector unit. The exact contents and
11222 layout vary depending on the hardware.
11225 @node OS Information
11226 @section Operating System Auxiliary Information
11227 @cindex OS information
11229 @value{GDBN} provides interfaces to useful OS facilities that can help
11230 you debug your program.
11232 @cindex auxiliary vector
11233 @cindex vector, auxiliary
11234 Some operating systems supply an @dfn{auxiliary vector} to programs at
11235 startup. This is akin to the arguments and environment that you
11236 specify for a program, but contains a system-dependent variety of
11237 binary values that tell system libraries important details about the
11238 hardware, operating system, and process. Each value's purpose is
11239 identified by an integer tag; the meanings are well-known but system-specific.
11240 Depending on the configuration and operating system facilities,
11241 @value{GDBN} may be able to show you this information. For remote
11242 targets, this functionality may further depend on the remote stub's
11243 support of the @samp{qXfer:auxv:read} packet, see
11244 @ref{qXfer auxiliary vector read}.
11249 Display the auxiliary vector of the inferior, which can be either a
11250 live process or a core dump file. @value{GDBN} prints each tag value
11251 numerically, and also shows names and text descriptions for recognized
11252 tags. Some values in the vector are numbers, some bit masks, and some
11253 pointers to strings or other data. @value{GDBN} displays each value in the
11254 most appropriate form for a recognized tag, and in hexadecimal for
11255 an unrecognized tag.
11258 On some targets, @value{GDBN} can access operating system-specific
11259 information and show it to you. The types of information available
11260 will differ depending on the type of operating system running on the
11261 target. The mechanism used to fetch the data is described in
11262 @ref{Operating System Information}. For remote targets, this
11263 functionality depends on the remote stub's support of the
11264 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
11268 @item info os @var{infotype}
11270 Display OS information of the requested type.
11272 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
11274 @anchor{linux info os infotypes}
11276 @kindex info os cpus
11278 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
11279 the available fields from /proc/cpuinfo. For each supported architecture
11280 different fields are available. Two common entries are processor which gives
11281 CPU number and bogomips; a system constant that is calculated during
11282 kernel initialization.
11284 @kindex info os files
11286 Display the list of open file descriptors on the target. For each
11287 file descriptor, @value{GDBN} prints the identifier of the process
11288 owning the descriptor, the command of the owning process, the value
11289 of the descriptor, and the target of the descriptor.
11291 @kindex info os modules
11293 Display the list of all loaded kernel modules on the target. For each
11294 module, @value{GDBN} prints the module name, the size of the module in
11295 bytes, the number of times the module is used, the dependencies of the
11296 module, the status of the module, and the address of the loaded module
11299 @kindex info os msg
11301 Display the list of all System V message queues on the target. For each
11302 message queue, @value{GDBN} prints the message queue key, the message
11303 queue identifier, the access permissions, the current number of bytes
11304 on the queue, the current number of messages on the queue, the processes
11305 that last sent and received a message on the queue, the user and group
11306 of the owner and creator of the message queue, the times at which a
11307 message was last sent and received on the queue, and the time at which
11308 the message queue was last changed.
11310 @kindex info os processes
11312 Display the list of processes on the target. For each process,
11313 @value{GDBN} prints the process identifier, the name of the user, the
11314 command corresponding to the process, and the list of processor cores
11315 that the process is currently running on. (To understand what these
11316 properties mean, for this and the following info types, please consult
11317 the general @sc{gnu}/Linux documentation.)
11319 @kindex info os procgroups
11321 Display the list of process groups on the target. For each process,
11322 @value{GDBN} prints the identifier of the process group that it belongs
11323 to, the command corresponding to the process group leader, the process
11324 identifier, and the command line of the process. The list is sorted
11325 first by the process group identifier, then by the process identifier,
11326 so that processes belonging to the same process group are grouped together
11327 and the process group leader is listed first.
11329 @kindex info os semaphores
11331 Display the list of all System V semaphore sets on the target. For each
11332 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
11333 set identifier, the access permissions, the number of semaphores in the
11334 set, the user and group of the owner and creator of the semaphore set,
11335 and the times at which the semaphore set was operated upon and changed.
11337 @kindex info os shm
11339 Display the list of all System V shared-memory regions on the target.
11340 For each shared-memory region, @value{GDBN} prints the region key,
11341 the shared-memory identifier, the access permissions, the size of the
11342 region, the process that created the region, the process that last
11343 attached to or detached from the region, the current number of live
11344 attaches to the region, and the times at which the region was last
11345 attached to, detach from, and changed.
11347 @kindex info os sockets
11349 Display the list of Internet-domain sockets on the target. For each
11350 socket, @value{GDBN} prints the address and port of the local and
11351 remote endpoints, the current state of the connection, the creator of
11352 the socket, the IP address family of the socket, and the type of the
11355 @kindex info os threads
11357 Display the list of threads running on the target. For each thread,
11358 @value{GDBN} prints the identifier of the process that the thread
11359 belongs to, the command of the process, the thread identifier, and the
11360 processor core that it is currently running on. The main thread of a
11361 process is not listed.
11365 If @var{infotype} is omitted, then list the possible values for
11366 @var{infotype} and the kind of OS information available for each
11367 @var{infotype}. If the target does not return a list of possible
11368 types, this command will report an error.
11371 @node Memory Region Attributes
11372 @section Memory Region Attributes
11373 @cindex memory region attributes
11375 @dfn{Memory region attributes} allow you to describe special handling
11376 required by regions of your target's memory. @value{GDBN} uses
11377 attributes to determine whether to allow certain types of memory
11378 accesses; whether to use specific width accesses; and whether to cache
11379 target memory. By default the description of memory regions is
11380 fetched from the target (if the current target supports this), but the
11381 user can override the fetched regions.
11383 Defined memory regions can be individually enabled and disabled. When a
11384 memory region is disabled, @value{GDBN} uses the default attributes when
11385 accessing memory in that region. Similarly, if no memory regions have
11386 been defined, @value{GDBN} uses the default attributes when accessing
11389 When a memory region is defined, it is given a number to identify it;
11390 to enable, disable, or remove a memory region, you specify that number.
11394 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
11395 Define a memory region bounded by @var{lower} and @var{upper} with
11396 attributes @var{attributes}@dots{}, and add it to the list of regions
11397 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
11398 case: it is treated as the target's maximum memory address.
11399 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
11402 Discard any user changes to the memory regions and use target-supplied
11403 regions, if available, or no regions if the target does not support.
11406 @item delete mem @var{nums}@dots{}
11407 Remove memory regions @var{nums}@dots{} from the list of regions
11408 monitored by @value{GDBN}.
11410 @kindex disable mem
11411 @item disable mem @var{nums}@dots{}
11412 Disable monitoring of memory regions @var{nums}@dots{}.
11413 A disabled memory region is not forgotten.
11414 It may be enabled again later.
11417 @item enable mem @var{nums}@dots{}
11418 Enable monitoring of memory regions @var{nums}@dots{}.
11422 Print a table of all defined memory regions, with the following columns
11426 @item Memory Region Number
11427 @item Enabled or Disabled.
11428 Enabled memory regions are marked with @samp{y}.
11429 Disabled memory regions are marked with @samp{n}.
11432 The address defining the inclusive lower bound of the memory region.
11435 The address defining the exclusive upper bound of the memory region.
11438 The list of attributes set for this memory region.
11443 @subsection Attributes
11445 @subsubsection Memory Access Mode
11446 The access mode attributes set whether @value{GDBN} may make read or
11447 write accesses to a memory region.
11449 While these attributes prevent @value{GDBN} from performing invalid
11450 memory accesses, they do nothing to prevent the target system, I/O DMA,
11451 etc.@: from accessing memory.
11455 Memory is read only.
11457 Memory is write only.
11459 Memory is read/write. This is the default.
11462 @subsubsection Memory Access Size
11463 The access size attribute tells @value{GDBN} to use specific sized
11464 accesses in the memory region. Often memory mapped device registers
11465 require specific sized accesses. If no access size attribute is
11466 specified, @value{GDBN} may use accesses of any size.
11470 Use 8 bit memory accesses.
11472 Use 16 bit memory accesses.
11474 Use 32 bit memory accesses.
11476 Use 64 bit memory accesses.
11479 @c @subsubsection Hardware/Software Breakpoints
11480 @c The hardware/software breakpoint attributes set whether @value{GDBN}
11481 @c will use hardware or software breakpoints for the internal breakpoints
11482 @c used by the step, next, finish, until, etc. commands.
11486 @c Always use hardware breakpoints
11487 @c @item swbreak (default)
11490 @subsubsection Data Cache
11491 The data cache attributes set whether @value{GDBN} will cache target
11492 memory. While this generally improves performance by reducing debug
11493 protocol overhead, it can lead to incorrect results because @value{GDBN}
11494 does not know about volatile variables or memory mapped device
11499 Enable @value{GDBN} to cache target memory.
11501 Disable @value{GDBN} from caching target memory. This is the default.
11504 @subsection Memory Access Checking
11505 @value{GDBN} can be instructed to refuse accesses to memory that is
11506 not explicitly described. This can be useful if accessing such
11507 regions has undesired effects for a specific target, or to provide
11508 better error checking. The following commands control this behaviour.
11511 @kindex set mem inaccessible-by-default
11512 @item set mem inaccessible-by-default [on|off]
11513 If @code{on} is specified, make @value{GDBN} treat memory not
11514 explicitly described by the memory ranges as non-existent and refuse accesses
11515 to such memory. The checks are only performed if there's at least one
11516 memory range defined. If @code{off} is specified, make @value{GDBN}
11517 treat the memory not explicitly described by the memory ranges as RAM.
11518 The default value is @code{on}.
11519 @kindex show mem inaccessible-by-default
11520 @item show mem inaccessible-by-default
11521 Show the current handling of accesses to unknown memory.
11525 @c @subsubsection Memory Write Verification
11526 @c The memory write verification attributes set whether @value{GDBN}
11527 @c will re-reads data after each write to verify the write was successful.
11531 @c @item noverify (default)
11534 @node Dump/Restore Files
11535 @section Copy Between Memory and a File
11536 @cindex dump/restore files
11537 @cindex append data to a file
11538 @cindex dump data to a file
11539 @cindex restore data from a file
11541 You can use the commands @code{dump}, @code{append}, and
11542 @code{restore} to copy data between target memory and a file. The
11543 @code{dump} and @code{append} commands write data to a file, and the
11544 @code{restore} command reads data from a file back into the inferior's
11545 memory. Files may be in binary, Motorola S-record, Intel hex,
11546 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
11547 append to binary files, and cannot read from Verilog Hex files.
11552 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11553 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
11554 Dump the contents of memory from @var{start_addr} to @var{end_addr},
11555 or the value of @var{expr}, to @var{filename} in the given format.
11557 The @var{format} parameter may be any one of:
11564 Motorola S-record format.
11566 Tektronix Hex format.
11568 Verilog Hex format.
11571 @value{GDBN} uses the same definitions of these formats as the
11572 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
11573 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
11577 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11578 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
11579 Append the contents of memory from @var{start_addr} to @var{end_addr},
11580 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
11581 (@value{GDBN} can only append data to files in raw binary form.)
11584 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
11585 Restore the contents of file @var{filename} into memory. The
11586 @code{restore} command can automatically recognize any known @sc{bfd}
11587 file format, except for raw binary. To restore a raw binary file you
11588 must specify the optional keyword @code{binary} after the filename.
11590 If @var{bias} is non-zero, its value will be added to the addresses
11591 contained in the file. Binary files always start at address zero, so
11592 they will be restored at address @var{bias}. Other bfd files have
11593 a built-in location; they will be restored at offset @var{bias}
11594 from that location.
11596 If @var{start} and/or @var{end} are non-zero, then only data between
11597 file offset @var{start} and file offset @var{end} will be restored.
11598 These offsets are relative to the addresses in the file, before
11599 the @var{bias} argument is applied.
11603 @node Core File Generation
11604 @section How to Produce a Core File from Your Program
11605 @cindex dump core from inferior
11607 A @dfn{core file} or @dfn{core dump} is a file that records the memory
11608 image of a running process and its process status (register values
11609 etc.). Its primary use is post-mortem debugging of a program that
11610 crashed while it ran outside a debugger. A program that crashes
11611 automatically produces a core file, unless this feature is disabled by
11612 the user. @xref{Files}, for information on invoking @value{GDBN} in
11613 the post-mortem debugging mode.
11615 Occasionally, you may wish to produce a core file of the program you
11616 are debugging in order to preserve a snapshot of its state.
11617 @value{GDBN} has a special command for that.
11621 @kindex generate-core-file
11622 @item generate-core-file [@var{file}]
11623 @itemx gcore [@var{file}]
11624 Produce a core dump of the inferior process. The optional argument
11625 @var{file} specifies the file name where to put the core dump. If not
11626 specified, the file name defaults to @file{core.@var{pid}}, where
11627 @var{pid} is the inferior process ID.
11629 Note that this command is implemented only for some systems (as of
11630 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
11632 On @sc{gnu}/Linux, this command can take into account the value of the
11633 file @file{/proc/@var{pid}/coredump_filter} when generating the core
11634 dump (@pxref{set use-coredump-filter}), and by default honors the
11635 @code{VM_DONTDUMP} flag for mappings where it is present in the file
11636 @file{/proc/@var{pid}/smaps} (@pxref{set dump-excluded-mappings}).
11638 @kindex set use-coredump-filter
11639 @anchor{set use-coredump-filter}
11640 @item set use-coredump-filter on
11641 @itemx set use-coredump-filter off
11642 Enable or disable the use of the file
11643 @file{/proc/@var{pid}/coredump_filter} when generating core dump
11644 files. This file is used by the Linux kernel to decide what types of
11645 memory mappings will be dumped or ignored when generating a core dump
11646 file. @var{pid} is the process ID of a currently running process.
11648 To make use of this feature, you have to write in the
11649 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
11650 which is a bit mask representing the memory mapping types. If a bit
11651 is set in the bit mask, then the memory mappings of the corresponding
11652 types will be dumped; otherwise, they will be ignored. This
11653 configuration is inherited by child processes. For more information
11654 about the bits that can be set in the
11655 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
11656 manpage of @code{core(5)}.
11658 By default, this option is @code{on}. If this option is turned
11659 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
11660 and instead uses the same default value as the Linux kernel in order
11661 to decide which pages will be dumped in the core dump file. This
11662 value is currently @code{0x33}, which means that bits @code{0}
11663 (anonymous private mappings), @code{1} (anonymous shared mappings),
11664 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
11665 This will cause these memory mappings to be dumped automatically.
11667 @kindex set dump-excluded-mappings
11668 @anchor{set dump-excluded-mappings}
11669 @item set dump-excluded-mappings on
11670 @itemx set dump-excluded-mappings off
11671 If @code{on} is specified, @value{GDBN} will dump memory mappings
11672 marked with the @code{VM_DONTDUMP} flag. This flag is represented in
11673 the file @file{/proc/@var{pid}/smaps} with the acronym @code{dd}.
11675 The default value is @code{off}.
11678 @node Character Sets
11679 @section Character Sets
11680 @cindex character sets
11682 @cindex translating between character sets
11683 @cindex host character set
11684 @cindex target character set
11686 If the program you are debugging uses a different character set to
11687 represent characters and strings than the one @value{GDBN} uses itself,
11688 @value{GDBN} can automatically translate between the character sets for
11689 you. The character set @value{GDBN} uses we call the @dfn{host
11690 character set}; the one the inferior program uses we call the
11691 @dfn{target character set}.
11693 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
11694 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
11695 remote protocol (@pxref{Remote Debugging}) to debug a program
11696 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
11697 then the host character set is Latin-1, and the target character set is
11698 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
11699 target-charset EBCDIC-US}, then @value{GDBN} translates between
11700 @sc{ebcdic} and Latin 1 as you print character or string values, or use
11701 character and string literals in expressions.
11703 @value{GDBN} has no way to automatically recognize which character set
11704 the inferior program uses; you must tell it, using the @code{set
11705 target-charset} command, described below.
11707 Here are the commands for controlling @value{GDBN}'s character set
11711 @item set target-charset @var{charset}
11712 @kindex set target-charset
11713 Set the current target character set to @var{charset}. To display the
11714 list of supported target character sets, type
11715 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
11717 @item set host-charset @var{charset}
11718 @kindex set host-charset
11719 Set the current host character set to @var{charset}.
11721 By default, @value{GDBN} uses a host character set appropriate to the
11722 system it is running on; you can override that default using the
11723 @code{set host-charset} command. On some systems, @value{GDBN} cannot
11724 automatically determine the appropriate host character set. In this
11725 case, @value{GDBN} uses @samp{UTF-8}.
11727 @value{GDBN} can only use certain character sets as its host character
11728 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
11729 @value{GDBN} will list the host character sets it supports.
11731 @item set charset @var{charset}
11732 @kindex set charset
11733 Set the current host and target character sets to @var{charset}. As
11734 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
11735 @value{GDBN} will list the names of the character sets that can be used
11736 for both host and target.
11739 @kindex show charset
11740 Show the names of the current host and target character sets.
11742 @item show host-charset
11743 @kindex show host-charset
11744 Show the name of the current host character set.
11746 @item show target-charset
11747 @kindex show target-charset
11748 Show the name of the current target character set.
11750 @item set target-wide-charset @var{charset}
11751 @kindex set target-wide-charset
11752 Set the current target's wide character set to @var{charset}. This is
11753 the character set used by the target's @code{wchar_t} type. To
11754 display the list of supported wide character sets, type
11755 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
11757 @item show target-wide-charset
11758 @kindex show target-wide-charset
11759 Show the name of the current target's wide character set.
11762 Here is an example of @value{GDBN}'s character set support in action.
11763 Assume that the following source code has been placed in the file
11764 @file{charset-test.c}:
11770 = @{72, 101, 108, 108, 111, 44, 32, 119,
11771 111, 114, 108, 100, 33, 10, 0@};
11772 char ibm1047_hello[]
11773 = @{200, 133, 147, 147, 150, 107, 64, 166,
11774 150, 153, 147, 132, 90, 37, 0@};
11778 printf ("Hello, world!\n");
11782 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
11783 containing the string @samp{Hello, world!} followed by a newline,
11784 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
11786 We compile the program, and invoke the debugger on it:
11789 $ gcc -g charset-test.c -o charset-test
11790 $ gdb -nw charset-test
11791 GNU gdb 2001-12-19-cvs
11792 Copyright 2001 Free Software Foundation, Inc.
11797 We can use the @code{show charset} command to see what character sets
11798 @value{GDBN} is currently using to interpret and display characters and
11802 (@value{GDBP}) show charset
11803 The current host and target character set is `ISO-8859-1'.
11807 For the sake of printing this manual, let's use @sc{ascii} as our
11808 initial character set:
11810 (@value{GDBP}) set charset ASCII
11811 (@value{GDBP}) show charset
11812 The current host and target character set is `ASCII'.
11816 Let's assume that @sc{ascii} is indeed the correct character set for our
11817 host system --- in other words, let's assume that if @value{GDBN} prints
11818 characters using the @sc{ascii} character set, our terminal will display
11819 them properly. Since our current target character set is also
11820 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
11823 (@value{GDBP}) print ascii_hello
11824 $1 = 0x401698 "Hello, world!\n"
11825 (@value{GDBP}) print ascii_hello[0]
11830 @value{GDBN} uses the target character set for character and string
11831 literals you use in expressions:
11834 (@value{GDBP}) print '+'
11839 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
11842 @value{GDBN} relies on the user to tell it which character set the
11843 target program uses. If we print @code{ibm1047_hello} while our target
11844 character set is still @sc{ascii}, we get jibberish:
11847 (@value{GDBP}) print ibm1047_hello
11848 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
11849 (@value{GDBP}) print ibm1047_hello[0]
11854 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
11855 @value{GDBN} tells us the character sets it supports:
11858 (@value{GDBP}) set target-charset
11859 ASCII EBCDIC-US IBM1047 ISO-8859-1
11860 (@value{GDBP}) set target-charset
11863 We can select @sc{ibm1047} as our target character set, and examine the
11864 program's strings again. Now the @sc{ascii} string is wrong, but
11865 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
11866 target character set, @sc{ibm1047}, to the host character set,
11867 @sc{ascii}, and they display correctly:
11870 (@value{GDBP}) set target-charset IBM1047
11871 (@value{GDBP}) show charset
11872 The current host character set is `ASCII'.
11873 The current target character set is `IBM1047'.
11874 (@value{GDBP}) print ascii_hello
11875 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
11876 (@value{GDBP}) print ascii_hello[0]
11878 (@value{GDBP}) print ibm1047_hello
11879 $8 = 0x4016a8 "Hello, world!\n"
11880 (@value{GDBP}) print ibm1047_hello[0]
11885 As above, @value{GDBN} uses the target character set for character and
11886 string literals you use in expressions:
11889 (@value{GDBP}) print '+'
11894 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
11897 @node Caching Target Data
11898 @section Caching Data of Targets
11899 @cindex caching data of targets
11901 @value{GDBN} caches data exchanged between the debugger and a target.
11902 Each cache is associated with the address space of the inferior.
11903 @xref{Inferiors and Programs}, about inferior and address space.
11904 Such caching generally improves performance in remote debugging
11905 (@pxref{Remote Debugging}), because it reduces the overhead of the
11906 remote protocol by bundling memory reads and writes into large chunks.
11907 Unfortunately, simply caching everything would lead to incorrect results,
11908 since @value{GDBN} does not necessarily know anything about volatile
11909 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
11910 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
11912 Therefore, by default, @value{GDBN} only caches data
11913 known to be on the stack@footnote{In non-stop mode, it is moderately
11914 rare for a running thread to modify the stack of a stopped thread
11915 in a way that would interfere with a backtrace, and caching of
11916 stack reads provides a significant speed up of remote backtraces.} or
11917 in the code segment.
11918 Other regions of memory can be explicitly marked as
11919 cacheable; @pxref{Memory Region Attributes}.
11922 @kindex set remotecache
11923 @item set remotecache on
11924 @itemx set remotecache off
11925 This option no longer does anything; it exists for compatibility
11928 @kindex show remotecache
11929 @item show remotecache
11930 Show the current state of the obsolete remotecache flag.
11932 @kindex set stack-cache
11933 @item set stack-cache on
11934 @itemx set stack-cache off
11935 Enable or disable caching of stack accesses. When @code{on}, use
11936 caching. By default, this option is @code{on}.
11938 @kindex show stack-cache
11939 @item show stack-cache
11940 Show the current state of data caching for memory accesses.
11942 @kindex set code-cache
11943 @item set code-cache on
11944 @itemx set code-cache off
11945 Enable or disable caching of code segment accesses. When @code{on},
11946 use caching. By default, this option is @code{on}. This improves
11947 performance of disassembly in remote debugging.
11949 @kindex show code-cache
11950 @item show code-cache
11951 Show the current state of target memory cache for code segment
11954 @kindex info dcache
11955 @item info dcache @r{[}line@r{]}
11956 Print the information about the performance of data cache of the
11957 current inferior's address space. The information displayed
11958 includes the dcache width and depth, and for each cache line, its
11959 number, address, and how many times it was referenced. This
11960 command is useful for debugging the data cache operation.
11962 If a line number is specified, the contents of that line will be
11965 @item set dcache size @var{size}
11966 @cindex dcache size
11967 @kindex set dcache size
11968 Set maximum number of entries in dcache (dcache depth above).
11970 @item set dcache line-size @var{line-size}
11971 @cindex dcache line-size
11972 @kindex set dcache line-size
11973 Set number of bytes each dcache entry caches (dcache width above).
11974 Must be a power of 2.
11976 @item show dcache size
11977 @kindex show dcache size
11978 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
11980 @item show dcache line-size
11981 @kindex show dcache line-size
11982 Show default size of dcache lines.
11986 @node Searching Memory
11987 @section Search Memory
11988 @cindex searching memory
11990 Memory can be searched for a particular sequence of bytes with the
11991 @code{find} command.
11995 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11996 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11997 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
11998 etc. The search begins at address @var{start_addr} and continues for either
11999 @var{len} bytes or through to @var{end_addr} inclusive.
12002 @var{s} and @var{n} are optional parameters.
12003 They may be specified in either order, apart or together.
12006 @item @var{s}, search query size
12007 The size of each search query value.
12013 halfwords (two bytes)
12017 giant words (eight bytes)
12020 All values are interpreted in the current language.
12021 This means, for example, that if the current source language is C/C@t{++}
12022 then searching for the string ``hello'' includes the trailing '\0'.
12023 The null terminator can be removed from searching by using casts,
12024 e.g.: @samp{@{char[5]@}"hello"}.
12026 If the value size is not specified, it is taken from the
12027 value's type in the current language.
12028 This is useful when one wants to specify the search
12029 pattern as a mixture of types.
12030 Note that this means, for example, that in the case of C-like languages
12031 a search for an untyped 0x42 will search for @samp{(int) 0x42}
12032 which is typically four bytes.
12034 @item @var{n}, maximum number of finds
12035 The maximum number of matches to print. The default is to print all finds.
12038 You can use strings as search values. Quote them with double-quotes
12040 The string value is copied into the search pattern byte by byte,
12041 regardless of the endianness of the target and the size specification.
12043 The address of each match found is printed as well as a count of the
12044 number of matches found.
12046 The address of the last value found is stored in convenience variable
12048 A count of the number of matches is stored in @samp{$numfound}.
12050 For example, if stopped at the @code{printf} in this function:
12056 static char hello[] = "hello-hello";
12057 static struct @{ char c; short s; int i; @}
12058 __attribute__ ((packed)) mixed
12059 = @{ 'c', 0x1234, 0x87654321 @};
12060 printf ("%s\n", hello);
12065 you get during debugging:
12068 (gdb) find &hello[0], +sizeof(hello), "hello"
12069 0x804956d <hello.1620+6>
12071 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
12072 0x8049567 <hello.1620>
12073 0x804956d <hello.1620+6>
12075 (gdb) find &hello[0], +sizeof(hello), @{char[5]@}"hello"
12076 0x8049567 <hello.1620>
12077 0x804956d <hello.1620+6>
12079 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
12080 0x8049567 <hello.1620>
12082 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
12083 0x8049560 <mixed.1625>
12085 (gdb) print $numfound
12088 $2 = (void *) 0x8049560
12092 @section Value Sizes
12094 Whenever @value{GDBN} prints a value memory will be allocated within
12095 @value{GDBN} to hold the contents of the value. It is possible in
12096 some languages with dynamic typing systems, that an invalid program
12097 may indicate a value that is incorrectly large, this in turn may cause
12098 @value{GDBN} to try and allocate an overly large ammount of memory.
12101 @kindex set max-value-size
12102 @item set max-value-size @var{bytes}
12103 @itemx set max-value-size unlimited
12104 Set the maximum size of memory that @value{GDBN} will allocate for the
12105 contents of a value to @var{bytes}, trying to display a value that
12106 requires more memory than that will result in an error.
12108 Setting this variable does not effect values that have already been
12109 allocated within @value{GDBN}, only future allocations.
12111 There's a minimum size that @code{max-value-size} can be set to in
12112 order that @value{GDBN} can still operate correctly, this minimum is
12113 currently 16 bytes.
12115 The limit applies to the results of some subexpressions as well as to
12116 complete expressions. For example, an expression denoting a simple
12117 integer component, such as @code{x.y.z}, may fail if the size of
12118 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
12119 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
12120 @var{A} is an array variable with non-constant size, will generally
12121 succeed regardless of the bounds on @var{A}, as long as the component
12122 size is less than @var{bytes}.
12124 The default value of @code{max-value-size} is currently 64k.
12126 @kindex show max-value-size
12127 @item show max-value-size
12128 Show the maximum size of memory, in bytes, that @value{GDBN} will
12129 allocate for the contents of a value.
12132 @node Optimized Code
12133 @chapter Debugging Optimized Code
12134 @cindex optimized code, debugging
12135 @cindex debugging optimized code
12137 Almost all compilers support optimization. With optimization
12138 disabled, the compiler generates assembly code that corresponds
12139 directly to your source code, in a simplistic way. As the compiler
12140 applies more powerful optimizations, the generated assembly code
12141 diverges from your original source code. With help from debugging
12142 information generated by the compiler, @value{GDBN} can map from
12143 the running program back to constructs from your original source.
12145 @value{GDBN} is more accurate with optimization disabled. If you
12146 can recompile without optimization, it is easier to follow the
12147 progress of your program during debugging. But, there are many cases
12148 where you may need to debug an optimized version.
12150 When you debug a program compiled with @samp{-g -O}, remember that the
12151 optimizer has rearranged your code; the debugger shows you what is
12152 really there. Do not be too surprised when the execution path does not
12153 exactly match your source file! An extreme example: if you define a
12154 variable, but never use it, @value{GDBN} never sees that
12155 variable---because the compiler optimizes it out of existence.
12157 Some things do not work as well with @samp{-g -O} as with just
12158 @samp{-g}, particularly on machines with instruction scheduling. If in
12159 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
12160 please report it to us as a bug (including a test case!).
12161 @xref{Variables}, for more information about debugging optimized code.
12164 * Inline Functions:: How @value{GDBN} presents inlining
12165 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
12168 @node Inline Functions
12169 @section Inline Functions
12170 @cindex inline functions, debugging
12172 @dfn{Inlining} is an optimization that inserts a copy of the function
12173 body directly at each call site, instead of jumping to a shared
12174 routine. @value{GDBN} displays inlined functions just like
12175 non-inlined functions. They appear in backtraces. You can view their
12176 arguments and local variables, step into them with @code{step}, skip
12177 them with @code{next}, and escape from them with @code{finish}.
12178 You can check whether a function was inlined by using the
12179 @code{info frame} command.
12181 For @value{GDBN} to support inlined functions, the compiler must
12182 record information about inlining in the debug information ---
12183 @value{NGCC} using the @sc{dwarf 2} format does this, and several
12184 other compilers do also. @value{GDBN} only supports inlined functions
12185 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
12186 do not emit two required attributes (@samp{DW_AT_call_file} and
12187 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
12188 function calls with earlier versions of @value{NGCC}. It instead
12189 displays the arguments and local variables of inlined functions as
12190 local variables in the caller.
12192 The body of an inlined function is directly included at its call site;
12193 unlike a non-inlined function, there are no instructions devoted to
12194 the call. @value{GDBN} still pretends that the call site and the
12195 start of the inlined function are different instructions. Stepping to
12196 the call site shows the call site, and then stepping again shows
12197 the first line of the inlined function, even though no additional
12198 instructions are executed.
12200 This makes source-level debugging much clearer; you can see both the
12201 context of the call and then the effect of the call. Only stepping by
12202 a single instruction using @code{stepi} or @code{nexti} does not do
12203 this; single instruction steps always show the inlined body.
12205 There are some ways that @value{GDBN} does not pretend that inlined
12206 function calls are the same as normal calls:
12210 Setting breakpoints at the call site of an inlined function may not
12211 work, because the call site does not contain any code. @value{GDBN}
12212 may incorrectly move the breakpoint to the next line of the enclosing
12213 function, after the call. This limitation will be removed in a future
12214 version of @value{GDBN}; until then, set a breakpoint on an earlier line
12215 or inside the inlined function instead.
12218 @value{GDBN} cannot locate the return value of inlined calls after
12219 using the @code{finish} command. This is a limitation of compiler-generated
12220 debugging information; after @code{finish}, you can step to the next line
12221 and print a variable where your program stored the return value.
12225 @node Tail Call Frames
12226 @section Tail Call Frames
12227 @cindex tail call frames, debugging
12229 Function @code{B} can call function @code{C} in its very last statement. In
12230 unoptimized compilation the call of @code{C} is immediately followed by return
12231 instruction at the end of @code{B} code. Optimizing compiler may replace the
12232 call and return in function @code{B} into one jump to function @code{C}
12233 instead. Such use of a jump instruction is called @dfn{tail call}.
12235 During execution of function @code{C}, there will be no indication in the
12236 function call stack frames that it was tail-called from @code{B}. If function
12237 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
12238 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
12239 some cases @value{GDBN} can determine that @code{C} was tail-called from
12240 @code{B}, and it will then create fictitious call frame for that, with the
12241 return address set up as if @code{B} called @code{C} normally.
12243 This functionality is currently supported only by DWARF 2 debugging format and
12244 the compiler has to produce @samp{DW_TAG_call_site} tags. With
12245 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
12248 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
12249 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
12253 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
12255 Stack level 1, frame at 0x7fffffffda30:
12256 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
12257 tail call frame, caller of frame at 0x7fffffffda30
12258 source language c++.
12259 Arglist at unknown address.
12260 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
12263 The detection of all the possible code path executions can find them ambiguous.
12264 There is no execution history stored (possible @ref{Reverse Execution} is never
12265 used for this purpose) and the last known caller could have reached the known
12266 callee by multiple different jump sequences. In such case @value{GDBN} still
12267 tries to show at least all the unambiguous top tail callers and all the
12268 unambiguous bottom tail calees, if any.
12271 @anchor{set debug entry-values}
12272 @item set debug entry-values
12273 @kindex set debug entry-values
12274 When set to on, enables printing of analysis messages for both frame argument
12275 values at function entry and tail calls. It will show all the possible valid
12276 tail calls code paths it has considered. It will also print the intersection
12277 of them with the final unambiguous (possibly partial or even empty) code path
12280 @item show debug entry-values
12281 @kindex show debug entry-values
12282 Show the current state of analysis messages printing for both frame argument
12283 values at function entry and tail calls.
12286 The analysis messages for tail calls can for example show why the virtual tail
12287 call frame for function @code{c} has not been recognized (due to the indirect
12288 reference by variable @code{x}):
12291 static void __attribute__((noinline, noclone)) c (void);
12292 void (*x) (void) = c;
12293 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12294 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
12295 int main (void) @{ x (); return 0; @}
12297 Breakpoint 1, DW_OP_entry_value resolving cannot find
12298 DW_TAG_call_site 0x40039a in main
12300 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12303 #1 0x000000000040039a in main () at t.c:5
12306 Another possibility is an ambiguous virtual tail call frames resolution:
12310 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
12311 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
12312 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
12313 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
12314 static void __attribute__((noinline, noclone)) b (void)
12315 @{ if (i) c (); else e (); @}
12316 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
12317 int main (void) @{ a (); return 0; @}
12319 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
12320 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
12321 tailcall: reduced: 0x4004d2(a) |
12324 #1 0x00000000004004d2 in a () at t.c:8
12325 #2 0x0000000000400395 in main () at t.c:9
12328 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
12329 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
12331 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
12332 @ifset HAVE_MAKEINFO_CLICK
12333 @set ARROW @click{}
12334 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
12335 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
12337 @ifclear HAVE_MAKEINFO_CLICK
12339 @set CALLSEQ1B @value{CALLSEQ1A}
12340 @set CALLSEQ2B @value{CALLSEQ2A}
12343 Frames #0 and #2 are real, #1 is a virtual tail call frame.
12344 The code can have possible execution paths @value{CALLSEQ1B} or
12345 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
12347 @code{initial:} state shows some random possible calling sequence @value{GDBN}
12348 has found. It then finds another possible calling sequcen - that one is
12349 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
12350 printed as the @code{reduced:} calling sequence. That one could have many
12351 futher @code{compare:} and @code{reduced:} statements as long as there remain
12352 any non-ambiguous sequence entries.
12354 For the frame of function @code{b} in both cases there are different possible
12355 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
12356 also ambigous. The only non-ambiguous frame is the one for function @code{a},
12357 therefore this one is displayed to the user while the ambiguous frames are
12360 There can be also reasons why printing of frame argument values at function
12365 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
12366 static void __attribute__((noinline, noclone)) a (int i);
12367 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
12368 static void __attribute__((noinline, noclone)) a (int i)
12369 @{ if (i) b (i - 1); else c (0); @}
12370 int main (void) @{ a (5); return 0; @}
12373 #0 c (i=i@@entry=0) at t.c:2
12374 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
12375 function "a" at 0x400420 can call itself via tail calls
12376 i=<optimized out>) at t.c:6
12377 #2 0x000000000040036e in main () at t.c:7
12380 @value{GDBN} cannot find out from the inferior state if and how many times did
12381 function @code{a} call itself (via function @code{b}) as these calls would be
12382 tail calls. Such tail calls would modify thue @code{i} variable, therefore
12383 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
12384 prints @code{<optimized out>} instead.
12387 @chapter C Preprocessor Macros
12389 Some languages, such as C and C@t{++}, provide a way to define and invoke
12390 ``preprocessor macros'' which expand into strings of tokens.
12391 @value{GDBN} can evaluate expressions containing macro invocations, show
12392 the result of macro expansion, and show a macro's definition, including
12393 where it was defined.
12395 You may need to compile your program specially to provide @value{GDBN}
12396 with information about preprocessor macros. Most compilers do not
12397 include macros in their debugging information, even when you compile
12398 with the @option{-g} flag. @xref{Compilation}.
12400 A program may define a macro at one point, remove that definition later,
12401 and then provide a different definition after that. Thus, at different
12402 points in the program, a macro may have different definitions, or have
12403 no definition at all. If there is a current stack frame, @value{GDBN}
12404 uses the macros in scope at that frame's source code line. Otherwise,
12405 @value{GDBN} uses the macros in scope at the current listing location;
12408 Whenever @value{GDBN} evaluates an expression, it always expands any
12409 macro invocations present in the expression. @value{GDBN} also provides
12410 the following commands for working with macros explicitly.
12414 @kindex macro expand
12415 @cindex macro expansion, showing the results of preprocessor
12416 @cindex preprocessor macro expansion, showing the results of
12417 @cindex expanding preprocessor macros
12418 @item macro expand @var{expression}
12419 @itemx macro exp @var{expression}
12420 Show the results of expanding all preprocessor macro invocations in
12421 @var{expression}. Since @value{GDBN} simply expands macros, but does
12422 not parse the result, @var{expression} need not be a valid expression;
12423 it can be any string of tokens.
12426 @item macro expand-once @var{expression}
12427 @itemx macro exp1 @var{expression}
12428 @cindex expand macro once
12429 @i{(This command is not yet implemented.)} Show the results of
12430 expanding those preprocessor macro invocations that appear explicitly in
12431 @var{expression}. Macro invocations appearing in that expansion are
12432 left unchanged. This command allows you to see the effect of a
12433 particular macro more clearly, without being confused by further
12434 expansions. Since @value{GDBN} simply expands macros, but does not
12435 parse the result, @var{expression} need not be a valid expression; it
12436 can be any string of tokens.
12439 @cindex macro definition, showing
12440 @cindex definition of a macro, showing
12441 @cindex macros, from debug info
12442 @item info macro [-a|-all] [--] @var{macro}
12443 Show the current definition or all definitions of the named @var{macro},
12444 and describe the source location or compiler command-line where that
12445 definition was established. The optional double dash is to signify the end of
12446 argument processing and the beginning of @var{macro} for non C-like macros where
12447 the macro may begin with a hyphen.
12449 @kindex info macros
12450 @item info macros @var{location}
12451 Show all macro definitions that are in effect at the location specified
12452 by @var{location}, and describe the source location or compiler
12453 command-line where those definitions were established.
12455 @kindex macro define
12456 @cindex user-defined macros
12457 @cindex defining macros interactively
12458 @cindex macros, user-defined
12459 @item macro define @var{macro} @var{replacement-list}
12460 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
12461 Introduce a definition for a preprocessor macro named @var{macro},
12462 invocations of which are replaced by the tokens given in
12463 @var{replacement-list}. The first form of this command defines an
12464 ``object-like'' macro, which takes no arguments; the second form
12465 defines a ``function-like'' macro, which takes the arguments given in
12468 A definition introduced by this command is in scope in every
12469 expression evaluated in @value{GDBN}, until it is removed with the
12470 @code{macro undef} command, described below. The definition overrides
12471 all definitions for @var{macro} present in the program being debugged,
12472 as well as any previous user-supplied definition.
12474 @kindex macro undef
12475 @item macro undef @var{macro}
12476 Remove any user-supplied definition for the macro named @var{macro}.
12477 This command only affects definitions provided with the @code{macro
12478 define} command, described above; it cannot remove definitions present
12479 in the program being debugged.
12483 List all the macros defined using the @code{macro define} command.
12486 @cindex macros, example of debugging with
12487 Here is a transcript showing the above commands in action. First, we
12488 show our source files:
12493 #include "sample.h"
12496 #define ADD(x) (M + x)
12501 printf ("Hello, world!\n");
12503 printf ("We're so creative.\n");
12505 printf ("Goodbye, world!\n");
12512 Now, we compile the program using the @sc{gnu} C compiler,
12513 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
12514 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
12515 and @option{-gdwarf-4}; we recommend always choosing the most recent
12516 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
12517 includes information about preprocessor macros in the debugging
12521 $ gcc -gdwarf-2 -g3 sample.c -o sample
12525 Now, we start @value{GDBN} on our sample program:
12529 GNU gdb 2002-05-06-cvs
12530 Copyright 2002 Free Software Foundation, Inc.
12531 GDB is free software, @dots{}
12535 We can expand macros and examine their definitions, even when the
12536 program is not running. @value{GDBN} uses the current listing position
12537 to decide which macro definitions are in scope:
12540 (@value{GDBP}) list main
12543 5 #define ADD(x) (M + x)
12548 10 printf ("Hello, world!\n");
12550 12 printf ("We're so creative.\n");
12551 (@value{GDBP}) info macro ADD
12552 Defined at /home/jimb/gdb/macros/play/sample.c:5
12553 #define ADD(x) (M + x)
12554 (@value{GDBP}) info macro Q
12555 Defined at /home/jimb/gdb/macros/play/sample.h:1
12556 included at /home/jimb/gdb/macros/play/sample.c:2
12558 (@value{GDBP}) macro expand ADD(1)
12559 expands to: (42 + 1)
12560 (@value{GDBP}) macro expand-once ADD(1)
12561 expands to: once (M + 1)
12565 In the example above, note that @code{macro expand-once} expands only
12566 the macro invocation explicit in the original text --- the invocation of
12567 @code{ADD} --- but does not expand the invocation of the macro @code{M},
12568 which was introduced by @code{ADD}.
12570 Once the program is running, @value{GDBN} uses the macro definitions in
12571 force at the source line of the current stack frame:
12574 (@value{GDBP}) break main
12575 Breakpoint 1 at 0x8048370: file sample.c, line 10.
12577 Starting program: /home/jimb/gdb/macros/play/sample
12579 Breakpoint 1, main () at sample.c:10
12580 10 printf ("Hello, world!\n");
12584 At line 10, the definition of the macro @code{N} at line 9 is in force:
12587 (@value{GDBP}) info macro N
12588 Defined at /home/jimb/gdb/macros/play/sample.c:9
12590 (@value{GDBP}) macro expand N Q M
12591 expands to: 28 < 42
12592 (@value{GDBP}) print N Q M
12597 As we step over directives that remove @code{N}'s definition, and then
12598 give it a new definition, @value{GDBN} finds the definition (or lack
12599 thereof) in force at each point:
12602 (@value{GDBP}) next
12604 12 printf ("We're so creative.\n");
12605 (@value{GDBP}) info macro N
12606 The symbol `N' has no definition as a C/C++ preprocessor macro
12607 at /home/jimb/gdb/macros/play/sample.c:12
12608 (@value{GDBP}) next
12610 14 printf ("Goodbye, world!\n");
12611 (@value{GDBP}) info macro N
12612 Defined at /home/jimb/gdb/macros/play/sample.c:13
12614 (@value{GDBP}) macro expand N Q M
12615 expands to: 1729 < 42
12616 (@value{GDBP}) print N Q M
12621 In addition to source files, macros can be defined on the compilation command
12622 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
12623 such a way, @value{GDBN} displays the location of their definition as line zero
12624 of the source file submitted to the compiler.
12627 (@value{GDBP}) info macro __STDC__
12628 Defined at /home/jimb/gdb/macros/play/sample.c:0
12635 @chapter Tracepoints
12636 @c This chapter is based on the documentation written by Michael
12637 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
12639 @cindex tracepoints
12640 In some applications, it is not feasible for the debugger to interrupt
12641 the program's execution long enough for the developer to learn
12642 anything helpful about its behavior. If the program's correctness
12643 depends on its real-time behavior, delays introduced by a debugger
12644 might cause the program to change its behavior drastically, or perhaps
12645 fail, even when the code itself is correct. It is useful to be able
12646 to observe the program's behavior without interrupting it.
12648 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
12649 specify locations in the program, called @dfn{tracepoints}, and
12650 arbitrary expressions to evaluate when those tracepoints are reached.
12651 Later, using the @code{tfind} command, you can examine the values
12652 those expressions had when the program hit the tracepoints. The
12653 expressions may also denote objects in memory---structures or arrays,
12654 for example---whose values @value{GDBN} should record; while visiting
12655 a particular tracepoint, you may inspect those objects as if they were
12656 in memory at that moment. However, because @value{GDBN} records these
12657 values without interacting with you, it can do so quickly and
12658 unobtrusively, hopefully not disturbing the program's behavior.
12660 The tracepoint facility is currently available only for remote
12661 targets. @xref{Targets}. In addition, your remote target must know
12662 how to collect trace data. This functionality is implemented in the
12663 remote stub; however, none of the stubs distributed with @value{GDBN}
12664 support tracepoints as of this writing. The format of the remote
12665 packets used to implement tracepoints are described in @ref{Tracepoint
12668 It is also possible to get trace data from a file, in a manner reminiscent
12669 of corefiles; you specify the filename, and use @code{tfind} to search
12670 through the file. @xref{Trace Files}, for more details.
12672 This chapter describes the tracepoint commands and features.
12675 * Set Tracepoints::
12676 * Analyze Collected Data::
12677 * Tracepoint Variables::
12681 @node Set Tracepoints
12682 @section Commands to Set Tracepoints
12684 Before running such a @dfn{trace experiment}, an arbitrary number of
12685 tracepoints can be set. A tracepoint is actually a special type of
12686 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
12687 standard breakpoint commands. For instance, as with breakpoints,
12688 tracepoint numbers are successive integers starting from one, and many
12689 of the commands associated with tracepoints take the tracepoint number
12690 as their argument, to identify which tracepoint to work on.
12692 For each tracepoint, you can specify, in advance, some arbitrary set
12693 of data that you want the target to collect in the trace buffer when
12694 it hits that tracepoint. The collected data can include registers,
12695 local variables, or global data. Later, you can use @value{GDBN}
12696 commands to examine the values these data had at the time the
12697 tracepoint was hit.
12699 Tracepoints do not support every breakpoint feature. Ignore counts on
12700 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
12701 commands when they are hit. Tracepoints may not be thread-specific
12704 @cindex fast tracepoints
12705 Some targets may support @dfn{fast tracepoints}, which are inserted in
12706 a different way (such as with a jump instead of a trap), that is
12707 faster but possibly restricted in where they may be installed.
12709 @cindex static tracepoints
12710 @cindex markers, static tracepoints
12711 @cindex probing markers, static tracepoints
12712 Regular and fast tracepoints are dynamic tracing facilities, meaning
12713 that they can be used to insert tracepoints at (almost) any location
12714 in the target. Some targets may also support controlling @dfn{static
12715 tracepoints} from @value{GDBN}. With static tracing, a set of
12716 instrumentation points, also known as @dfn{markers}, are embedded in
12717 the target program, and can be activated or deactivated by name or
12718 address. These are usually placed at locations which facilitate
12719 investigating what the target is actually doing. @value{GDBN}'s
12720 support for static tracing includes being able to list instrumentation
12721 points, and attach them with @value{GDBN} defined high level
12722 tracepoints that expose the whole range of convenience of
12723 @value{GDBN}'s tracepoints support. Namely, support for collecting
12724 registers values and values of global or local (to the instrumentation
12725 point) variables; tracepoint conditions and trace state variables.
12726 The act of installing a @value{GDBN} static tracepoint on an
12727 instrumentation point, or marker, is referred to as @dfn{probing} a
12728 static tracepoint marker.
12730 @code{gdbserver} supports tracepoints on some target systems.
12731 @xref{Server,,Tracepoints support in @code{gdbserver}}.
12733 This section describes commands to set tracepoints and associated
12734 conditions and actions.
12737 * Create and Delete Tracepoints::
12738 * Enable and Disable Tracepoints::
12739 * Tracepoint Passcounts::
12740 * Tracepoint Conditions::
12741 * Trace State Variables::
12742 * Tracepoint Actions::
12743 * Listing Tracepoints::
12744 * Listing Static Tracepoint Markers::
12745 * Starting and Stopping Trace Experiments::
12746 * Tracepoint Restrictions::
12749 @node Create and Delete Tracepoints
12750 @subsection Create and Delete Tracepoints
12753 @cindex set tracepoint
12755 @item trace @var{location}
12756 The @code{trace} command is very similar to the @code{break} command.
12757 Its argument @var{location} can be any valid location.
12758 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
12759 which is a point in the target program where the debugger will briefly stop,
12760 collect some data, and then allow the program to continue. Setting a tracepoint
12761 or changing its actions takes effect immediately if the remote stub
12762 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
12764 If remote stub doesn't support the @samp{InstallInTrace} feature, all
12765 these changes don't take effect until the next @code{tstart}
12766 command, and once a trace experiment is running, further changes will
12767 not have any effect until the next trace experiment starts. In addition,
12768 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
12769 address is not yet resolved. (This is similar to pending breakpoints.)
12770 Pending tracepoints are not downloaded to the target and not installed
12771 until they are resolved. The resolution of pending tracepoints requires
12772 @value{GDBN} support---when debugging with the remote target, and
12773 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
12774 tracing}), pending tracepoints can not be resolved (and downloaded to
12775 the remote stub) while @value{GDBN} is disconnected.
12777 Here are some examples of using the @code{trace} command:
12780 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
12782 (@value{GDBP}) @b{trace +2} // 2 lines forward
12784 (@value{GDBP}) @b{trace my_function} // first source line of function
12786 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
12788 (@value{GDBP}) @b{trace *0x2117c4} // an address
12792 You can abbreviate @code{trace} as @code{tr}.
12794 @item trace @var{location} if @var{cond}
12795 Set a tracepoint with condition @var{cond}; evaluate the expression
12796 @var{cond} each time the tracepoint is reached, and collect data only
12797 if the value is nonzero---that is, if @var{cond} evaluates as true.
12798 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
12799 information on tracepoint conditions.
12801 @item ftrace @var{location} [ if @var{cond} ]
12802 @cindex set fast tracepoint
12803 @cindex fast tracepoints, setting
12805 The @code{ftrace} command sets a fast tracepoint. For targets that
12806 support them, fast tracepoints will use a more efficient but possibly
12807 less general technique to trigger data collection, such as a jump
12808 instruction instead of a trap, or some sort of hardware support. It
12809 may not be possible to create a fast tracepoint at the desired
12810 location, in which case the command will exit with an explanatory
12813 @value{GDBN} handles arguments to @code{ftrace} exactly as for
12816 On 32-bit x86-architecture systems, fast tracepoints normally need to
12817 be placed at an instruction that is 5 bytes or longer, but can be
12818 placed at 4-byte instructions if the low 64K of memory of the target
12819 program is available to install trampolines. Some Unix-type systems,
12820 such as @sc{gnu}/Linux, exclude low addresses from the program's
12821 address space; but for instance with the Linux kernel it is possible
12822 to let @value{GDBN} use this area by doing a @command{sysctl} command
12823 to set the @code{mmap_min_addr} kernel parameter, as in
12826 sudo sysctl -w vm.mmap_min_addr=32768
12830 which sets the low address to 32K, which leaves plenty of room for
12831 trampolines. The minimum address should be set to a page boundary.
12833 @item strace @var{location} [ if @var{cond} ]
12834 @cindex set static tracepoint
12835 @cindex static tracepoints, setting
12836 @cindex probe static tracepoint marker
12838 The @code{strace} command sets a static tracepoint. For targets that
12839 support it, setting a static tracepoint probes a static
12840 instrumentation point, or marker, found at @var{location}. It may not
12841 be possible to set a static tracepoint at the desired location, in
12842 which case the command will exit with an explanatory message.
12844 @value{GDBN} handles arguments to @code{strace} exactly as for
12845 @code{trace}, with the addition that the user can also specify
12846 @code{-m @var{marker}} as @var{location}. This probes the marker
12847 identified by the @var{marker} string identifier. This identifier
12848 depends on the static tracepoint backend library your program is
12849 using. You can find all the marker identifiers in the @samp{ID} field
12850 of the @code{info static-tracepoint-markers} command output.
12851 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
12852 Markers}. For example, in the following small program using the UST
12858 trace_mark(ust, bar33, "str %s", "FOOBAZ");
12863 the marker id is composed of joining the first two arguments to the
12864 @code{trace_mark} call with a slash, which translates to:
12867 (@value{GDBP}) info static-tracepoint-markers
12868 Cnt Enb ID Address What
12869 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
12875 so you may probe the marker above with:
12878 (@value{GDBP}) strace -m ust/bar33
12881 Static tracepoints accept an extra collect action --- @code{collect
12882 $_sdata}. This collects arbitrary user data passed in the probe point
12883 call to the tracing library. In the UST example above, you'll see
12884 that the third argument to @code{trace_mark} is a printf-like format
12885 string. The user data is then the result of running that formating
12886 string against the following arguments. Note that @code{info
12887 static-tracepoint-markers} command output lists that format string in
12888 the @samp{Data:} field.
12890 You can inspect this data when analyzing the trace buffer, by printing
12891 the $_sdata variable like any other variable available to
12892 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
12895 @cindex last tracepoint number
12896 @cindex recent tracepoint number
12897 @cindex tracepoint number
12898 The convenience variable @code{$tpnum} records the tracepoint number
12899 of the most recently set tracepoint.
12901 @kindex delete tracepoint
12902 @cindex tracepoint deletion
12903 @item delete tracepoint @r{[}@var{num}@r{]}
12904 Permanently delete one or more tracepoints. With no argument, the
12905 default is to delete all tracepoints. Note that the regular
12906 @code{delete} command can remove tracepoints also.
12911 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
12913 (@value{GDBP}) @b{delete trace} // remove all tracepoints
12917 You can abbreviate this command as @code{del tr}.
12920 @node Enable and Disable Tracepoints
12921 @subsection Enable and Disable Tracepoints
12923 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
12926 @kindex disable tracepoint
12927 @item disable tracepoint @r{[}@var{num}@r{]}
12928 Disable tracepoint @var{num}, or all tracepoints if no argument
12929 @var{num} is given. A disabled tracepoint will have no effect during
12930 a trace experiment, but it is not forgotten. You can re-enable
12931 a disabled tracepoint using the @code{enable tracepoint} command.
12932 If the command is issued during a trace experiment and the debug target
12933 has support for disabling tracepoints during a trace experiment, then the
12934 change will be effective immediately. Otherwise, it will be applied to the
12935 next trace experiment.
12937 @kindex enable tracepoint
12938 @item enable tracepoint @r{[}@var{num}@r{]}
12939 Enable tracepoint @var{num}, or all tracepoints. If this command is
12940 issued during a trace experiment and the debug target supports enabling
12941 tracepoints during a trace experiment, then the enabled tracepoints will
12942 become effective immediately. Otherwise, they will become effective the
12943 next time a trace experiment is run.
12946 @node Tracepoint Passcounts
12947 @subsection Tracepoint Passcounts
12951 @cindex tracepoint pass count
12952 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
12953 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
12954 automatically stop a trace experiment. If a tracepoint's passcount is
12955 @var{n}, then the trace experiment will be automatically stopped on
12956 the @var{n}'th time that tracepoint is hit. If the tracepoint number
12957 @var{num} is not specified, the @code{passcount} command sets the
12958 passcount of the most recently defined tracepoint. If no passcount is
12959 given, the trace experiment will run until stopped explicitly by the
12965 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
12966 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
12968 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
12969 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
12970 (@value{GDBP}) @b{trace foo}
12971 (@value{GDBP}) @b{pass 3}
12972 (@value{GDBP}) @b{trace bar}
12973 (@value{GDBP}) @b{pass 2}
12974 (@value{GDBP}) @b{trace baz}
12975 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
12976 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
12977 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
12978 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
12982 @node Tracepoint Conditions
12983 @subsection Tracepoint Conditions
12984 @cindex conditional tracepoints
12985 @cindex tracepoint conditions
12987 The simplest sort of tracepoint collects data every time your program
12988 reaches a specified place. You can also specify a @dfn{condition} for
12989 a tracepoint. A condition is just a Boolean expression in your
12990 programming language (@pxref{Expressions, ,Expressions}). A
12991 tracepoint with a condition evaluates the expression each time your
12992 program reaches it, and data collection happens only if the condition
12995 Tracepoint conditions can be specified when a tracepoint is set, by
12996 using @samp{if} in the arguments to the @code{trace} command.
12997 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
12998 also be set or changed at any time with the @code{condition} command,
12999 just as with breakpoints.
13001 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
13002 the conditional expression itself. Instead, @value{GDBN} encodes the
13003 expression into an agent expression (@pxref{Agent Expressions})
13004 suitable for execution on the target, independently of @value{GDBN}.
13005 Global variables become raw memory locations, locals become stack
13006 accesses, and so forth.
13008 For instance, suppose you have a function that is usually called
13009 frequently, but should not be called after an error has occurred. You
13010 could use the following tracepoint command to collect data about calls
13011 of that function that happen while the error code is propagating
13012 through the program; an unconditional tracepoint could end up
13013 collecting thousands of useless trace frames that you would have to
13017 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
13020 @node Trace State Variables
13021 @subsection Trace State Variables
13022 @cindex trace state variables
13024 A @dfn{trace state variable} is a special type of variable that is
13025 created and managed by target-side code. The syntax is the same as
13026 that for GDB's convenience variables (a string prefixed with ``$''),
13027 but they are stored on the target. They must be created explicitly,
13028 using a @code{tvariable} command. They are always 64-bit signed
13031 Trace state variables are remembered by @value{GDBN}, and downloaded
13032 to the target along with tracepoint information when the trace
13033 experiment starts. There are no intrinsic limits on the number of
13034 trace state variables, beyond memory limitations of the target.
13036 @cindex convenience variables, and trace state variables
13037 Although trace state variables are managed by the target, you can use
13038 them in print commands and expressions as if they were convenience
13039 variables; @value{GDBN} will get the current value from the target
13040 while the trace experiment is running. Trace state variables share
13041 the same namespace as other ``$'' variables, which means that you
13042 cannot have trace state variables with names like @code{$23} or
13043 @code{$pc}, nor can you have a trace state variable and a convenience
13044 variable with the same name.
13048 @item tvariable $@var{name} [ = @var{expression} ]
13050 The @code{tvariable} command creates a new trace state variable named
13051 @code{$@var{name}}, and optionally gives it an initial value of
13052 @var{expression}. The @var{expression} is evaluated when this command is
13053 entered; the result will be converted to an integer if possible,
13054 otherwise @value{GDBN} will report an error. A subsequent
13055 @code{tvariable} command specifying the same name does not create a
13056 variable, but instead assigns the supplied initial value to the
13057 existing variable of that name, overwriting any previous initial
13058 value. The default initial value is 0.
13060 @item info tvariables
13061 @kindex info tvariables
13062 List all the trace state variables along with their initial values.
13063 Their current values may also be displayed, if the trace experiment is
13066 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
13067 @kindex delete tvariable
13068 Delete the given trace state variables, or all of them if no arguments
13073 @node Tracepoint Actions
13074 @subsection Tracepoint Action Lists
13078 @cindex tracepoint actions
13079 @item actions @r{[}@var{num}@r{]}
13080 This command will prompt for a list of actions to be taken when the
13081 tracepoint is hit. If the tracepoint number @var{num} is not
13082 specified, this command sets the actions for the one that was most
13083 recently defined (so that you can define a tracepoint and then say
13084 @code{actions} without bothering about its number). You specify the
13085 actions themselves on the following lines, one action at a time, and
13086 terminate the actions list with a line containing just @code{end}. So
13087 far, the only defined actions are @code{collect}, @code{teval}, and
13088 @code{while-stepping}.
13090 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
13091 Commands, ,Breakpoint Command Lists}), except that only the defined
13092 actions are allowed; any other @value{GDBN} command is rejected.
13094 @cindex remove actions from a tracepoint
13095 To remove all actions from a tracepoint, type @samp{actions @var{num}}
13096 and follow it immediately with @samp{end}.
13099 (@value{GDBP}) @b{collect @var{data}} // collect some data
13101 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
13103 (@value{GDBP}) @b{end} // signals the end of actions.
13106 In the following example, the action list begins with @code{collect}
13107 commands indicating the things to be collected when the tracepoint is
13108 hit. Then, in order to single-step and collect additional data
13109 following the tracepoint, a @code{while-stepping} command is used,
13110 followed by the list of things to be collected after each step in a
13111 sequence of single steps. The @code{while-stepping} command is
13112 terminated by its own separate @code{end} command. Lastly, the action
13113 list is terminated by an @code{end} command.
13116 (@value{GDBP}) @b{trace foo}
13117 (@value{GDBP}) @b{actions}
13118 Enter actions for tracepoint 1, one per line:
13121 > while-stepping 12
13122 > collect $pc, arr[i]
13127 @kindex collect @r{(tracepoints)}
13128 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
13129 Collect values of the given expressions when the tracepoint is hit.
13130 This command accepts a comma-separated list of any valid expressions.
13131 In addition to global, static, or local variables, the following
13132 special arguments are supported:
13136 Collect all registers.
13139 Collect all function arguments.
13142 Collect all local variables.
13145 Collect the return address. This is helpful if you want to see more
13148 @emph{Note:} The return address location can not always be reliably
13149 determined up front, and the wrong address / registers may end up
13150 collected instead. On some architectures the reliability is higher
13151 for tracepoints at function entry, while on others it's the opposite.
13152 When this happens, backtracing will stop because the return address is
13153 found unavailable (unless another collect rule happened to match it).
13156 Collects the number of arguments from the static probe at which the
13157 tracepoint is located.
13158 @xref{Static Probe Points}.
13160 @item $_probe_arg@var{n}
13161 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
13162 from the static probe at which the tracepoint is located.
13163 @xref{Static Probe Points}.
13166 @vindex $_sdata@r{, collect}
13167 Collect static tracepoint marker specific data. Only available for
13168 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
13169 Lists}. On the UST static tracepoints library backend, an
13170 instrumentation point resembles a @code{printf} function call. The
13171 tracing library is able to collect user specified data formatted to a
13172 character string using the format provided by the programmer that
13173 instrumented the program. Other backends have similar mechanisms.
13174 Here's an example of a UST marker call:
13177 const char master_name[] = "$your_name";
13178 trace_mark(channel1, marker1, "hello %s", master_name)
13181 In this case, collecting @code{$_sdata} collects the string
13182 @samp{hello $yourname}. When analyzing the trace buffer, you can
13183 inspect @samp{$_sdata} like any other variable available to
13187 You can give several consecutive @code{collect} commands, each one
13188 with a single argument, or one @code{collect} command with several
13189 arguments separated by commas; the effect is the same.
13191 The optional @var{mods} changes the usual handling of the arguments.
13192 @code{s} requests that pointers to chars be handled as strings, in
13193 particular collecting the contents of the memory being pointed at, up
13194 to the first zero. The upper bound is by default the value of the
13195 @code{print elements} variable; if @code{s} is followed by a decimal
13196 number, that is the upper bound instead. So for instance
13197 @samp{collect/s25 mystr} collects as many as 25 characters at
13200 The command @code{info scope} (@pxref{Symbols, info scope}) is
13201 particularly useful for figuring out what data to collect.
13203 @kindex teval @r{(tracepoints)}
13204 @item teval @var{expr1}, @var{expr2}, @dots{}
13205 Evaluate the given expressions when the tracepoint is hit. This
13206 command accepts a comma-separated list of expressions. The results
13207 are discarded, so this is mainly useful for assigning values to trace
13208 state variables (@pxref{Trace State Variables}) without adding those
13209 values to the trace buffer, as would be the case if the @code{collect}
13212 @kindex while-stepping @r{(tracepoints)}
13213 @item while-stepping @var{n}
13214 Perform @var{n} single-step instruction traces after the tracepoint,
13215 collecting new data after each step. The @code{while-stepping}
13216 command is followed by the list of what to collect while stepping
13217 (followed by its own @code{end} command):
13220 > while-stepping 12
13221 > collect $regs, myglobal
13227 Note that @code{$pc} is not automatically collected by
13228 @code{while-stepping}; you need to explicitly collect that register if
13229 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
13232 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
13233 @kindex set default-collect
13234 @cindex default collection action
13235 This variable is a list of expressions to collect at each tracepoint
13236 hit. It is effectively an additional @code{collect} action prepended
13237 to every tracepoint action list. The expressions are parsed
13238 individually for each tracepoint, so for instance a variable named
13239 @code{xyz} may be interpreted as a global for one tracepoint, and a
13240 local for another, as appropriate to the tracepoint's location.
13242 @item show default-collect
13243 @kindex show default-collect
13244 Show the list of expressions that are collected by default at each
13249 @node Listing Tracepoints
13250 @subsection Listing Tracepoints
13253 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
13254 @kindex info tp @r{[}@var{n}@dots{}@r{]}
13255 @cindex information about tracepoints
13256 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
13257 Display information about the tracepoint @var{num}. If you don't
13258 specify a tracepoint number, displays information about all the
13259 tracepoints defined so far. The format is similar to that used for
13260 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
13261 command, simply restricting itself to tracepoints.
13263 A tracepoint's listing may include additional information specific to
13268 its passcount as given by the @code{passcount @var{n}} command
13271 the state about installed on target of each location
13275 (@value{GDBP}) @b{info trace}
13276 Num Type Disp Enb Address What
13277 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
13279 collect globfoo, $regs
13284 2 tracepoint keep y <MULTIPLE>
13286 2.1 y 0x0804859c in func4 at change-loc.h:35
13287 installed on target
13288 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
13289 installed on target
13290 2.3 y <PENDING> set_tracepoint
13291 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
13292 not installed on target
13297 This command can be abbreviated @code{info tp}.
13300 @node Listing Static Tracepoint Markers
13301 @subsection Listing Static Tracepoint Markers
13304 @kindex info static-tracepoint-markers
13305 @cindex information about static tracepoint markers
13306 @item info static-tracepoint-markers
13307 Display information about all static tracepoint markers defined in the
13310 For each marker, the following columns are printed:
13314 An incrementing counter, output to help readability. This is not a
13317 The marker ID, as reported by the target.
13318 @item Enabled or Disabled
13319 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
13320 that are not enabled.
13322 Where the marker is in your program, as a memory address.
13324 Where the marker is in the source for your program, as a file and line
13325 number. If the debug information included in the program does not
13326 allow @value{GDBN} to locate the source of the marker, this column
13327 will be left blank.
13331 In addition, the following information may be printed for each marker:
13335 User data passed to the tracing library by the marker call. In the
13336 UST backend, this is the format string passed as argument to the
13338 @item Static tracepoints probing the marker
13339 The list of static tracepoints attached to the marker.
13343 (@value{GDBP}) info static-tracepoint-markers
13344 Cnt ID Enb Address What
13345 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
13346 Data: number1 %d number2 %d
13347 Probed by static tracepoints: #2
13348 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
13354 @node Starting and Stopping Trace Experiments
13355 @subsection Starting and Stopping Trace Experiments
13358 @kindex tstart [ @var{notes} ]
13359 @cindex start a new trace experiment
13360 @cindex collected data discarded
13362 This command starts the trace experiment, and begins collecting data.
13363 It has the side effect of discarding all the data collected in the
13364 trace buffer during the previous trace experiment. If any arguments
13365 are supplied, they are taken as a note and stored with the trace
13366 experiment's state. The notes may be arbitrary text, and are
13367 especially useful with disconnected tracing in a multi-user context;
13368 the notes can explain what the trace is doing, supply user contact
13369 information, and so forth.
13371 @kindex tstop [ @var{notes} ]
13372 @cindex stop a running trace experiment
13374 This command stops the trace experiment. If any arguments are
13375 supplied, they are recorded with the experiment as a note. This is
13376 useful if you are stopping a trace started by someone else, for
13377 instance if the trace is interfering with the system's behavior and
13378 needs to be stopped quickly.
13380 @strong{Note}: a trace experiment and data collection may stop
13381 automatically if any tracepoint's passcount is reached
13382 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
13385 @cindex status of trace data collection
13386 @cindex trace experiment, status of
13388 This command displays the status of the current trace data
13392 Here is an example of the commands we described so far:
13395 (@value{GDBP}) @b{trace gdb_c_test}
13396 (@value{GDBP}) @b{actions}
13397 Enter actions for tracepoint #1, one per line.
13398 > collect $regs,$locals,$args
13399 > while-stepping 11
13403 (@value{GDBP}) @b{tstart}
13404 [time passes @dots{}]
13405 (@value{GDBP}) @b{tstop}
13408 @anchor{disconnected tracing}
13409 @cindex disconnected tracing
13410 You can choose to continue running the trace experiment even if
13411 @value{GDBN} disconnects from the target, voluntarily or
13412 involuntarily. For commands such as @code{detach}, the debugger will
13413 ask what you want to do with the trace. But for unexpected
13414 terminations (@value{GDBN} crash, network outage), it would be
13415 unfortunate to lose hard-won trace data, so the variable
13416 @code{disconnected-tracing} lets you decide whether the trace should
13417 continue running without @value{GDBN}.
13420 @item set disconnected-tracing on
13421 @itemx set disconnected-tracing off
13422 @kindex set disconnected-tracing
13423 Choose whether a tracing run should continue to run if @value{GDBN}
13424 has disconnected from the target. Note that @code{detach} or
13425 @code{quit} will ask you directly what to do about a running trace no
13426 matter what this variable's setting, so the variable is mainly useful
13427 for handling unexpected situations, such as loss of the network.
13429 @item show disconnected-tracing
13430 @kindex show disconnected-tracing
13431 Show the current choice for disconnected tracing.
13435 When you reconnect to the target, the trace experiment may or may not
13436 still be running; it might have filled the trace buffer in the
13437 meantime, or stopped for one of the other reasons. If it is running,
13438 it will continue after reconnection.
13440 Upon reconnection, the target will upload information about the
13441 tracepoints in effect. @value{GDBN} will then compare that
13442 information to the set of tracepoints currently defined, and attempt
13443 to match them up, allowing for the possibility that the numbers may
13444 have changed due to creation and deletion in the meantime. If one of
13445 the target's tracepoints does not match any in @value{GDBN}, the
13446 debugger will create a new tracepoint, so that you have a number with
13447 which to specify that tracepoint. This matching-up process is
13448 necessarily heuristic, and it may result in useless tracepoints being
13449 created; you may simply delete them if they are of no use.
13451 @cindex circular trace buffer
13452 If your target agent supports a @dfn{circular trace buffer}, then you
13453 can run a trace experiment indefinitely without filling the trace
13454 buffer; when space runs out, the agent deletes already-collected trace
13455 frames, oldest first, until there is enough room to continue
13456 collecting. This is especially useful if your tracepoints are being
13457 hit too often, and your trace gets terminated prematurely because the
13458 buffer is full. To ask for a circular trace buffer, simply set
13459 @samp{circular-trace-buffer} to on. You can set this at any time,
13460 including during tracing; if the agent can do it, it will change
13461 buffer handling on the fly, otherwise it will not take effect until
13465 @item set circular-trace-buffer on
13466 @itemx set circular-trace-buffer off
13467 @kindex set circular-trace-buffer
13468 Choose whether a tracing run should use a linear or circular buffer
13469 for trace data. A linear buffer will not lose any trace data, but may
13470 fill up prematurely, while a circular buffer will discard old trace
13471 data, but it will have always room for the latest tracepoint hits.
13473 @item show circular-trace-buffer
13474 @kindex show circular-trace-buffer
13475 Show the current choice for the trace buffer. Note that this may not
13476 match the agent's current buffer handling, nor is it guaranteed to
13477 match the setting that might have been in effect during a past run,
13478 for instance if you are looking at frames from a trace file.
13483 @item set trace-buffer-size @var{n}
13484 @itemx set trace-buffer-size unlimited
13485 @kindex set trace-buffer-size
13486 Request that the target use a trace buffer of @var{n} bytes. Not all
13487 targets will honor the request; they may have a compiled-in size for
13488 the trace buffer, or some other limitation. Set to a value of
13489 @code{unlimited} or @code{-1} to let the target use whatever size it
13490 likes. This is also the default.
13492 @item show trace-buffer-size
13493 @kindex show trace-buffer-size
13494 Show the current requested size for the trace buffer. Note that this
13495 will only match the actual size if the target supports size-setting,
13496 and was able to handle the requested size. For instance, if the
13497 target can only change buffer size between runs, this variable will
13498 not reflect the change until the next run starts. Use @code{tstatus}
13499 to get a report of the actual buffer size.
13503 @item set trace-user @var{text}
13504 @kindex set trace-user
13506 @item show trace-user
13507 @kindex show trace-user
13509 @item set trace-notes @var{text}
13510 @kindex set trace-notes
13511 Set the trace run's notes.
13513 @item show trace-notes
13514 @kindex show trace-notes
13515 Show the trace run's notes.
13517 @item set trace-stop-notes @var{text}
13518 @kindex set trace-stop-notes
13519 Set the trace run's stop notes. The handling of the note is as for
13520 @code{tstop} arguments; the set command is convenient way to fix a
13521 stop note that is mistaken or incomplete.
13523 @item show trace-stop-notes
13524 @kindex show trace-stop-notes
13525 Show the trace run's stop notes.
13529 @node Tracepoint Restrictions
13530 @subsection Tracepoint Restrictions
13532 @cindex tracepoint restrictions
13533 There are a number of restrictions on the use of tracepoints. As
13534 described above, tracepoint data gathering occurs on the target
13535 without interaction from @value{GDBN}. Thus the full capabilities of
13536 the debugger are not available during data gathering, and then at data
13537 examination time, you will be limited by only having what was
13538 collected. The following items describe some common problems, but it
13539 is not exhaustive, and you may run into additional difficulties not
13545 Tracepoint expressions are intended to gather objects (lvalues). Thus
13546 the full flexibility of GDB's expression evaluator is not available.
13547 You cannot call functions, cast objects to aggregate types, access
13548 convenience variables or modify values (except by assignment to trace
13549 state variables). Some language features may implicitly call
13550 functions (for instance Objective-C fields with accessors), and therefore
13551 cannot be collected either.
13554 Collection of local variables, either individually or in bulk with
13555 @code{$locals} or @code{$args}, during @code{while-stepping} may
13556 behave erratically. The stepping action may enter a new scope (for
13557 instance by stepping into a function), or the location of the variable
13558 may change (for instance it is loaded into a register). The
13559 tracepoint data recorded uses the location information for the
13560 variables that is correct for the tracepoint location. When the
13561 tracepoint is created, it is not possible, in general, to determine
13562 where the steps of a @code{while-stepping} sequence will advance the
13563 program---particularly if a conditional branch is stepped.
13566 Collection of an incompletely-initialized or partially-destroyed object
13567 may result in something that @value{GDBN} cannot display, or displays
13568 in a misleading way.
13571 When @value{GDBN} displays a pointer to character it automatically
13572 dereferences the pointer to also display characters of the string
13573 being pointed to. However, collecting the pointer during tracing does
13574 not automatically collect the string. You need to explicitly
13575 dereference the pointer and provide size information if you want to
13576 collect not only the pointer, but the memory pointed to. For example,
13577 @code{*ptr@@50} can be used to collect the 50 element array pointed to
13581 It is not possible to collect a complete stack backtrace at a
13582 tracepoint. Instead, you may collect the registers and a few hundred
13583 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
13584 (adjust to use the name of the actual stack pointer register on your
13585 target architecture, and the amount of stack you wish to capture).
13586 Then the @code{backtrace} command will show a partial backtrace when
13587 using a trace frame. The number of stack frames that can be examined
13588 depends on the sizes of the frames in the collected stack. Note that
13589 if you ask for a block so large that it goes past the bottom of the
13590 stack, the target agent may report an error trying to read from an
13594 If you do not collect registers at a tracepoint, @value{GDBN} can
13595 infer that the value of @code{$pc} must be the same as the address of
13596 the tracepoint and use that when you are looking at a trace frame
13597 for that tracepoint. However, this cannot work if the tracepoint has
13598 multiple locations (for instance if it was set in a function that was
13599 inlined), or if it has a @code{while-stepping} loop. In those cases
13600 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
13605 @node Analyze Collected Data
13606 @section Using the Collected Data
13608 After the tracepoint experiment ends, you use @value{GDBN} commands
13609 for examining the trace data. The basic idea is that each tracepoint
13610 collects a trace @dfn{snapshot} every time it is hit and another
13611 snapshot every time it single-steps. All these snapshots are
13612 consecutively numbered from zero and go into a buffer, and you can
13613 examine them later. The way you examine them is to @dfn{focus} on a
13614 specific trace snapshot. When the remote stub is focused on a trace
13615 snapshot, it will respond to all @value{GDBN} requests for memory and
13616 registers by reading from the buffer which belongs to that snapshot,
13617 rather than from @emph{real} memory or registers of the program being
13618 debugged. This means that @strong{all} @value{GDBN} commands
13619 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
13620 behave as if we were currently debugging the program state as it was
13621 when the tracepoint occurred. Any requests for data that are not in
13622 the buffer will fail.
13625 * tfind:: How to select a trace snapshot
13626 * tdump:: How to display all data for a snapshot
13627 * save tracepoints:: How to save tracepoints for a future run
13631 @subsection @code{tfind @var{n}}
13634 @cindex select trace snapshot
13635 @cindex find trace snapshot
13636 The basic command for selecting a trace snapshot from the buffer is
13637 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
13638 counting from zero. If no argument @var{n} is given, the next
13639 snapshot is selected.
13641 Here are the various forms of using the @code{tfind} command.
13645 Find the first snapshot in the buffer. This is a synonym for
13646 @code{tfind 0} (since 0 is the number of the first snapshot).
13649 Stop debugging trace snapshots, resume @emph{live} debugging.
13652 Same as @samp{tfind none}.
13655 No argument means find the next trace snapshot or find the first
13656 one if no trace snapshot is selected.
13659 Find the previous trace snapshot before the current one. This permits
13660 retracing earlier steps.
13662 @item tfind tracepoint @var{num}
13663 Find the next snapshot associated with tracepoint @var{num}. Search
13664 proceeds forward from the last examined trace snapshot. If no
13665 argument @var{num} is given, it means find the next snapshot collected
13666 for the same tracepoint as the current snapshot.
13668 @item tfind pc @var{addr}
13669 Find the next snapshot associated with the value @var{addr} of the
13670 program counter. Search proceeds forward from the last examined trace
13671 snapshot. If no argument @var{addr} is given, it means find the next
13672 snapshot with the same value of PC as the current snapshot.
13674 @item tfind outside @var{addr1}, @var{addr2}
13675 Find the next snapshot whose PC is outside the given range of
13676 addresses (exclusive).
13678 @item tfind range @var{addr1}, @var{addr2}
13679 Find the next snapshot whose PC is between @var{addr1} and
13680 @var{addr2} (inclusive).
13682 @item tfind line @r{[}@var{file}:@r{]}@var{n}
13683 Find the next snapshot associated with the source line @var{n}. If
13684 the optional argument @var{file} is given, refer to line @var{n} in
13685 that source file. Search proceeds forward from the last examined
13686 trace snapshot. If no argument @var{n} is given, it means find the
13687 next line other than the one currently being examined; thus saying
13688 @code{tfind line} repeatedly can appear to have the same effect as
13689 stepping from line to line in a @emph{live} debugging session.
13692 The default arguments for the @code{tfind} commands are specifically
13693 designed to make it easy to scan through the trace buffer. For
13694 instance, @code{tfind} with no argument selects the next trace
13695 snapshot, and @code{tfind -} with no argument selects the previous
13696 trace snapshot. So, by giving one @code{tfind} command, and then
13697 simply hitting @key{RET} repeatedly you can examine all the trace
13698 snapshots in order. Or, by saying @code{tfind -} and then hitting
13699 @key{RET} repeatedly you can examine the snapshots in reverse order.
13700 The @code{tfind line} command with no argument selects the snapshot
13701 for the next source line executed. The @code{tfind pc} command with
13702 no argument selects the next snapshot with the same program counter
13703 (PC) as the current frame. The @code{tfind tracepoint} command with
13704 no argument selects the next trace snapshot collected by the same
13705 tracepoint as the current one.
13707 In addition to letting you scan through the trace buffer manually,
13708 these commands make it easy to construct @value{GDBN} scripts that
13709 scan through the trace buffer and print out whatever collected data
13710 you are interested in. Thus, if we want to examine the PC, FP, and SP
13711 registers from each trace frame in the buffer, we can say this:
13714 (@value{GDBP}) @b{tfind start}
13715 (@value{GDBP}) @b{while ($trace_frame != -1)}
13716 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
13717 $trace_frame, $pc, $sp, $fp
13721 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
13722 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
13723 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
13724 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
13725 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
13726 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
13727 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
13728 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
13729 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
13730 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
13731 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
13734 Or, if we want to examine the variable @code{X} at each source line in
13738 (@value{GDBP}) @b{tfind start}
13739 (@value{GDBP}) @b{while ($trace_frame != -1)}
13740 > printf "Frame %d, X == %d\n", $trace_frame, X
13750 @subsection @code{tdump}
13752 @cindex dump all data collected at tracepoint
13753 @cindex tracepoint data, display
13755 This command takes no arguments. It prints all the data collected at
13756 the current trace snapshot.
13759 (@value{GDBP}) @b{trace 444}
13760 (@value{GDBP}) @b{actions}
13761 Enter actions for tracepoint #2, one per line:
13762 > collect $regs, $locals, $args, gdb_long_test
13765 (@value{GDBP}) @b{tstart}
13767 (@value{GDBP}) @b{tfind line 444}
13768 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
13770 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
13772 (@value{GDBP}) @b{tdump}
13773 Data collected at tracepoint 2, trace frame 1:
13774 d0 0xc4aa0085 -995491707
13778 d4 0x71aea3d 119204413
13781 d7 0x380035 3670069
13782 a0 0x19e24a 1696330
13783 a1 0x3000668 50333288
13785 a3 0x322000 3284992
13786 a4 0x3000698 50333336
13787 a5 0x1ad3cc 1758156
13788 fp 0x30bf3c 0x30bf3c
13789 sp 0x30bf34 0x30bf34
13791 pc 0x20b2c8 0x20b2c8
13795 p = 0x20e5b4 "gdb-test"
13802 gdb_long_test = 17 '\021'
13807 @code{tdump} works by scanning the tracepoint's current collection
13808 actions and printing the value of each expression listed. So
13809 @code{tdump} can fail, if after a run, you change the tracepoint's
13810 actions to mention variables that were not collected during the run.
13812 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
13813 uses the collected value of @code{$pc} to distinguish between trace
13814 frames that were collected at the tracepoint hit, and frames that were
13815 collected while stepping. This allows it to correctly choose whether
13816 to display the basic list of collections, or the collections from the
13817 body of the while-stepping loop. However, if @code{$pc} was not collected,
13818 then @code{tdump} will always attempt to dump using the basic collection
13819 list, and may fail if a while-stepping frame does not include all the
13820 same data that is collected at the tracepoint hit.
13821 @c This is getting pretty arcane, example would be good.
13823 @node save tracepoints
13824 @subsection @code{save tracepoints @var{filename}}
13825 @kindex save tracepoints
13826 @kindex save-tracepoints
13827 @cindex save tracepoints for future sessions
13829 This command saves all current tracepoint definitions together with
13830 their actions and passcounts, into a file @file{@var{filename}}
13831 suitable for use in a later debugging session. To read the saved
13832 tracepoint definitions, use the @code{source} command (@pxref{Command
13833 Files}). The @w{@code{save-tracepoints}} command is a deprecated
13834 alias for @w{@code{save tracepoints}}
13836 @node Tracepoint Variables
13837 @section Convenience Variables for Tracepoints
13838 @cindex tracepoint variables
13839 @cindex convenience variables for tracepoints
13842 @vindex $trace_frame
13843 @item (int) $trace_frame
13844 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
13845 snapshot is selected.
13847 @vindex $tracepoint
13848 @item (int) $tracepoint
13849 The tracepoint for the current trace snapshot.
13851 @vindex $trace_line
13852 @item (int) $trace_line
13853 The line number for the current trace snapshot.
13855 @vindex $trace_file
13856 @item (char []) $trace_file
13857 The source file for the current trace snapshot.
13859 @vindex $trace_func
13860 @item (char []) $trace_func
13861 The name of the function containing @code{$tracepoint}.
13864 Note: @code{$trace_file} is not suitable for use in @code{printf},
13865 use @code{output} instead.
13867 Here's a simple example of using these convenience variables for
13868 stepping through all the trace snapshots and printing some of their
13869 data. Note that these are not the same as trace state variables,
13870 which are managed by the target.
13873 (@value{GDBP}) @b{tfind start}
13875 (@value{GDBP}) @b{while $trace_frame != -1}
13876 > output $trace_file
13877 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
13883 @section Using Trace Files
13884 @cindex trace files
13886 In some situations, the target running a trace experiment may no
13887 longer be available; perhaps it crashed, or the hardware was needed
13888 for a different activity. To handle these cases, you can arrange to
13889 dump the trace data into a file, and later use that file as a source
13890 of trace data, via the @code{target tfile} command.
13895 @item tsave [ -r ] @var{filename}
13896 @itemx tsave [-ctf] @var{dirname}
13897 Save the trace data to @var{filename}. By default, this command
13898 assumes that @var{filename} refers to the host filesystem, so if
13899 necessary @value{GDBN} will copy raw trace data up from the target and
13900 then save it. If the target supports it, you can also supply the
13901 optional argument @code{-r} (``remote'') to direct the target to save
13902 the data directly into @var{filename} in its own filesystem, which may be
13903 more efficient if the trace buffer is very large. (Note, however, that
13904 @code{target tfile} can only read from files accessible to the host.)
13905 By default, this command will save trace frame in tfile format.
13906 You can supply the optional argument @code{-ctf} to save data in CTF
13907 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
13908 that can be shared by multiple debugging and tracing tools. Please go to
13909 @indicateurl{http://www.efficios.com/ctf} to get more information.
13911 @kindex target tfile
13915 @item target tfile @var{filename}
13916 @itemx target ctf @var{dirname}
13917 Use the file named @var{filename} or directory named @var{dirname} as
13918 a source of trace data. Commands that examine data work as they do with
13919 a live target, but it is not possible to run any new trace experiments.
13920 @code{tstatus} will report the state of the trace run at the moment
13921 the data was saved, as well as the current trace frame you are examining.
13922 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
13926 (@value{GDBP}) target ctf ctf.ctf
13927 (@value{GDBP}) tfind
13928 Found trace frame 0, tracepoint 2
13929 39 ++a; /* set tracepoint 1 here */
13930 (@value{GDBP}) tdump
13931 Data collected at tracepoint 2, trace frame 0:
13935 c = @{"123", "456", "789", "123", "456", "789"@}
13936 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
13944 @chapter Debugging Programs That Use Overlays
13947 If your program is too large to fit completely in your target system's
13948 memory, you can sometimes use @dfn{overlays} to work around this
13949 problem. @value{GDBN} provides some support for debugging programs that
13953 * How Overlays Work:: A general explanation of overlays.
13954 * Overlay Commands:: Managing overlays in @value{GDBN}.
13955 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
13956 mapped by asking the inferior.
13957 * Overlay Sample Program:: A sample program using overlays.
13960 @node How Overlays Work
13961 @section How Overlays Work
13962 @cindex mapped overlays
13963 @cindex unmapped overlays
13964 @cindex load address, overlay's
13965 @cindex mapped address
13966 @cindex overlay area
13968 Suppose you have a computer whose instruction address space is only 64
13969 kilobytes long, but which has much more memory which can be accessed by
13970 other means: special instructions, segment registers, or memory
13971 management hardware, for example. Suppose further that you want to
13972 adapt a program which is larger than 64 kilobytes to run on this system.
13974 One solution is to identify modules of your program which are relatively
13975 independent, and need not call each other directly; call these modules
13976 @dfn{overlays}. Separate the overlays from the main program, and place
13977 their machine code in the larger memory. Place your main program in
13978 instruction memory, but leave at least enough space there to hold the
13979 largest overlay as well.
13981 Now, to call a function located in an overlay, you must first copy that
13982 overlay's machine code from the large memory into the space set aside
13983 for it in the instruction memory, and then jump to its entry point
13986 @c NB: In the below the mapped area's size is greater or equal to the
13987 @c size of all overlays. This is intentional to remind the developer
13988 @c that overlays don't necessarily need to be the same size.
13992 Data Instruction Larger
13993 Address Space Address Space Address Space
13994 +-----------+ +-----------+ +-----------+
13996 +-----------+ +-----------+ +-----------+<-- overlay 1
13997 | program | | main | .----| overlay 1 | load address
13998 | variables | | program | | +-----------+
13999 | and heap | | | | | |
14000 +-----------+ | | | +-----------+<-- overlay 2
14001 | | +-----------+ | | | load address
14002 +-----------+ | | | .-| overlay 2 |
14004 mapped --->+-----------+ | | +-----------+
14005 address | | | | | |
14006 | overlay | <-' | | |
14007 | area | <---' +-----------+<-- overlay 3
14008 | | <---. | | load address
14009 +-----------+ `--| overlay 3 |
14016 @anchor{A code overlay}A code overlay
14020 The diagram (@pxref{A code overlay}) shows a system with separate data
14021 and instruction address spaces. To map an overlay, the program copies
14022 its code from the larger address space to the instruction address space.
14023 Since the overlays shown here all use the same mapped address, only one
14024 may be mapped at a time. For a system with a single address space for
14025 data and instructions, the diagram would be similar, except that the
14026 program variables and heap would share an address space with the main
14027 program and the overlay area.
14029 An overlay loaded into instruction memory and ready for use is called a
14030 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
14031 instruction memory. An overlay not present (or only partially present)
14032 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
14033 is its address in the larger memory. The mapped address is also called
14034 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
14035 called the @dfn{load memory address}, or @dfn{LMA}.
14037 Unfortunately, overlays are not a completely transparent way to adapt a
14038 program to limited instruction memory. They introduce a new set of
14039 global constraints you must keep in mind as you design your program:
14044 Before calling or returning to a function in an overlay, your program
14045 must make sure that overlay is actually mapped. Otherwise, the call or
14046 return will transfer control to the right address, but in the wrong
14047 overlay, and your program will probably crash.
14050 If the process of mapping an overlay is expensive on your system, you
14051 will need to choose your overlays carefully to minimize their effect on
14052 your program's performance.
14055 The executable file you load onto your system must contain each
14056 overlay's instructions, appearing at the overlay's load address, not its
14057 mapped address. However, each overlay's instructions must be relocated
14058 and its symbols defined as if the overlay were at its mapped address.
14059 You can use GNU linker scripts to specify different load and relocation
14060 addresses for pieces of your program; see @ref{Overlay Description,,,
14061 ld.info, Using ld: the GNU linker}.
14064 The procedure for loading executable files onto your system must be able
14065 to load their contents into the larger address space as well as the
14066 instruction and data spaces.
14070 The overlay system described above is rather simple, and could be
14071 improved in many ways:
14076 If your system has suitable bank switch registers or memory management
14077 hardware, you could use those facilities to make an overlay's load area
14078 contents simply appear at their mapped address in instruction space.
14079 This would probably be faster than copying the overlay to its mapped
14080 area in the usual way.
14083 If your overlays are small enough, you could set aside more than one
14084 overlay area, and have more than one overlay mapped at a time.
14087 You can use overlays to manage data, as well as instructions. In
14088 general, data overlays are even less transparent to your design than
14089 code overlays: whereas code overlays only require care when you call or
14090 return to functions, data overlays require care every time you access
14091 the data. Also, if you change the contents of a data overlay, you
14092 must copy its contents back out to its load address before you can copy a
14093 different data overlay into the same mapped area.
14098 @node Overlay Commands
14099 @section Overlay Commands
14101 To use @value{GDBN}'s overlay support, each overlay in your program must
14102 correspond to a separate section of the executable file. The section's
14103 virtual memory address and load memory address must be the overlay's
14104 mapped and load addresses. Identifying overlays with sections allows
14105 @value{GDBN} to determine the appropriate address of a function or
14106 variable, depending on whether the overlay is mapped or not.
14108 @value{GDBN}'s overlay commands all start with the word @code{overlay};
14109 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
14114 Disable @value{GDBN}'s overlay support. When overlay support is
14115 disabled, @value{GDBN} assumes that all functions and variables are
14116 always present at their mapped addresses. By default, @value{GDBN}'s
14117 overlay support is disabled.
14119 @item overlay manual
14120 @cindex manual overlay debugging
14121 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
14122 relies on you to tell it which overlays are mapped, and which are not,
14123 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
14124 commands described below.
14126 @item overlay map-overlay @var{overlay}
14127 @itemx overlay map @var{overlay}
14128 @cindex map an overlay
14129 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
14130 be the name of the object file section containing the overlay. When an
14131 overlay is mapped, @value{GDBN} assumes it can find the overlay's
14132 functions and variables at their mapped addresses. @value{GDBN} assumes
14133 that any other overlays whose mapped ranges overlap that of
14134 @var{overlay} are now unmapped.
14136 @item overlay unmap-overlay @var{overlay}
14137 @itemx overlay unmap @var{overlay}
14138 @cindex unmap an overlay
14139 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
14140 must be the name of the object file section containing the overlay.
14141 When an overlay is unmapped, @value{GDBN} assumes it can find the
14142 overlay's functions and variables at their load addresses.
14145 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
14146 consults a data structure the overlay manager maintains in the inferior
14147 to see which overlays are mapped. For details, see @ref{Automatic
14148 Overlay Debugging}.
14150 @item overlay load-target
14151 @itemx overlay load
14152 @cindex reloading the overlay table
14153 Re-read the overlay table from the inferior. Normally, @value{GDBN}
14154 re-reads the table @value{GDBN} automatically each time the inferior
14155 stops, so this command should only be necessary if you have changed the
14156 overlay mapping yourself using @value{GDBN}. This command is only
14157 useful when using automatic overlay debugging.
14159 @item overlay list-overlays
14160 @itemx overlay list
14161 @cindex listing mapped overlays
14162 Display a list of the overlays currently mapped, along with their mapped
14163 addresses, load addresses, and sizes.
14167 Normally, when @value{GDBN} prints a code address, it includes the name
14168 of the function the address falls in:
14171 (@value{GDBP}) print main
14172 $3 = @{int ()@} 0x11a0 <main>
14175 When overlay debugging is enabled, @value{GDBN} recognizes code in
14176 unmapped overlays, and prints the names of unmapped functions with
14177 asterisks around them. For example, if @code{foo} is a function in an
14178 unmapped overlay, @value{GDBN} prints it this way:
14181 (@value{GDBP}) overlay list
14182 No sections are mapped.
14183 (@value{GDBP}) print foo
14184 $5 = @{int (int)@} 0x100000 <*foo*>
14187 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
14191 (@value{GDBP}) overlay list
14192 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
14193 mapped at 0x1016 - 0x104a
14194 (@value{GDBP}) print foo
14195 $6 = @{int (int)@} 0x1016 <foo>
14198 When overlay debugging is enabled, @value{GDBN} can find the correct
14199 address for functions and variables in an overlay, whether or not the
14200 overlay is mapped. This allows most @value{GDBN} commands, like
14201 @code{break} and @code{disassemble}, to work normally, even on unmapped
14202 code. However, @value{GDBN}'s breakpoint support has some limitations:
14206 @cindex breakpoints in overlays
14207 @cindex overlays, setting breakpoints in
14208 You can set breakpoints in functions in unmapped overlays, as long as
14209 @value{GDBN} can write to the overlay at its load address.
14211 @value{GDBN} can not set hardware or simulator-based breakpoints in
14212 unmapped overlays. However, if you set a breakpoint at the end of your
14213 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
14214 you are using manual overlay management), @value{GDBN} will re-set its
14215 breakpoints properly.
14219 @node Automatic Overlay Debugging
14220 @section Automatic Overlay Debugging
14221 @cindex automatic overlay debugging
14223 @value{GDBN} can automatically track which overlays are mapped and which
14224 are not, given some simple co-operation from the overlay manager in the
14225 inferior. If you enable automatic overlay debugging with the
14226 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
14227 looks in the inferior's memory for certain variables describing the
14228 current state of the overlays.
14230 Here are the variables your overlay manager must define to support
14231 @value{GDBN}'s automatic overlay debugging:
14235 @item @code{_ovly_table}:
14236 This variable must be an array of the following structures:
14241 /* The overlay's mapped address. */
14244 /* The size of the overlay, in bytes. */
14245 unsigned long size;
14247 /* The overlay's load address. */
14250 /* Non-zero if the overlay is currently mapped;
14252 unsigned long mapped;
14256 @item @code{_novlys}:
14257 This variable must be a four-byte signed integer, holding the total
14258 number of elements in @code{_ovly_table}.
14262 To decide whether a particular overlay is mapped or not, @value{GDBN}
14263 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
14264 @code{lma} members equal the VMA and LMA of the overlay's section in the
14265 executable file. When @value{GDBN} finds a matching entry, it consults
14266 the entry's @code{mapped} member to determine whether the overlay is
14269 In addition, your overlay manager may define a function called
14270 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
14271 will silently set a breakpoint there. If the overlay manager then
14272 calls this function whenever it has changed the overlay table, this
14273 will enable @value{GDBN} to accurately keep track of which overlays
14274 are in program memory, and update any breakpoints that may be set
14275 in overlays. This will allow breakpoints to work even if the
14276 overlays are kept in ROM or other non-writable memory while they
14277 are not being executed.
14279 @node Overlay Sample Program
14280 @section Overlay Sample Program
14281 @cindex overlay example program
14283 When linking a program which uses overlays, you must place the overlays
14284 at their load addresses, while relocating them to run at their mapped
14285 addresses. To do this, you must write a linker script (@pxref{Overlay
14286 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
14287 since linker scripts are specific to a particular host system, target
14288 architecture, and target memory layout, this manual cannot provide
14289 portable sample code demonstrating @value{GDBN}'s overlay support.
14291 However, the @value{GDBN} source distribution does contain an overlaid
14292 program, with linker scripts for a few systems, as part of its test
14293 suite. The program consists of the following files from
14294 @file{gdb/testsuite/gdb.base}:
14298 The main program file.
14300 A simple overlay manager, used by @file{overlays.c}.
14305 Overlay modules, loaded and used by @file{overlays.c}.
14308 Linker scripts for linking the test program on the @code{d10v-elf}
14309 and @code{m32r-elf} targets.
14312 You can build the test program using the @code{d10v-elf} GCC
14313 cross-compiler like this:
14316 $ d10v-elf-gcc -g -c overlays.c
14317 $ d10v-elf-gcc -g -c ovlymgr.c
14318 $ d10v-elf-gcc -g -c foo.c
14319 $ d10v-elf-gcc -g -c bar.c
14320 $ d10v-elf-gcc -g -c baz.c
14321 $ d10v-elf-gcc -g -c grbx.c
14322 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
14323 baz.o grbx.o -Wl,-Td10v.ld -o overlays
14326 The build process is identical for any other architecture, except that
14327 you must substitute the appropriate compiler and linker script for the
14328 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
14332 @chapter Using @value{GDBN} with Different Languages
14335 Although programming languages generally have common aspects, they are
14336 rarely expressed in the same manner. For instance, in ANSI C,
14337 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
14338 Modula-2, it is accomplished by @code{p^}. Values can also be
14339 represented (and displayed) differently. Hex numbers in C appear as
14340 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
14342 @cindex working language
14343 Language-specific information is built into @value{GDBN} for some languages,
14344 allowing you to express operations like the above in your program's
14345 native language, and allowing @value{GDBN} to output values in a manner
14346 consistent with the syntax of your program's native language. The
14347 language you use to build expressions is called the @dfn{working
14351 * Setting:: Switching between source languages
14352 * Show:: Displaying the language
14353 * Checks:: Type and range checks
14354 * Supported Languages:: Supported languages
14355 * Unsupported Languages:: Unsupported languages
14359 @section Switching Between Source Languages
14361 There are two ways to control the working language---either have @value{GDBN}
14362 set it automatically, or select it manually yourself. You can use the
14363 @code{set language} command for either purpose. On startup, @value{GDBN}
14364 defaults to setting the language automatically. The working language is
14365 used to determine how expressions you type are interpreted, how values
14368 In addition to the working language, every source file that
14369 @value{GDBN} knows about has its own working language. For some object
14370 file formats, the compiler might indicate which language a particular
14371 source file is in. However, most of the time @value{GDBN} infers the
14372 language from the name of the file. The language of a source file
14373 controls whether C@t{++} names are demangled---this way @code{backtrace} can
14374 show each frame appropriately for its own language. There is no way to
14375 set the language of a source file from within @value{GDBN}, but you can
14376 set the language associated with a filename extension. @xref{Show, ,
14377 Displaying the Language}.
14379 This is most commonly a problem when you use a program, such
14380 as @code{cfront} or @code{f2c}, that generates C but is written in
14381 another language. In that case, make the
14382 program use @code{#line} directives in its C output; that way
14383 @value{GDBN} will know the correct language of the source code of the original
14384 program, and will display that source code, not the generated C code.
14387 * Filenames:: Filename extensions and languages.
14388 * Manually:: Setting the working language manually
14389 * Automatically:: Having @value{GDBN} infer the source language
14393 @subsection List of Filename Extensions and Languages
14395 If a source file name ends in one of the following extensions, then
14396 @value{GDBN} infers that its language is the one indicated.
14414 C@t{++} source file
14420 Objective-C source file
14424 Fortran source file
14427 Modula-2 source file
14431 Assembler source file. This actually behaves almost like C, but
14432 @value{GDBN} does not skip over function prologues when stepping.
14435 In addition, you may set the language associated with a filename
14436 extension. @xref{Show, , Displaying the Language}.
14439 @subsection Setting the Working Language
14441 If you allow @value{GDBN} to set the language automatically,
14442 expressions are interpreted the same way in your debugging session and
14445 @kindex set language
14446 If you wish, you may set the language manually. To do this, issue the
14447 command @samp{set language @var{lang}}, where @var{lang} is the name of
14448 a language, such as
14449 @code{c} or @code{modula-2}.
14450 For a list of the supported languages, type @samp{set language}.
14452 Setting the language manually prevents @value{GDBN} from updating the working
14453 language automatically. This can lead to confusion if you try
14454 to debug a program when the working language is not the same as the
14455 source language, when an expression is acceptable to both
14456 languages---but means different things. For instance, if the current
14457 source file were written in C, and @value{GDBN} was parsing Modula-2, a
14465 might not have the effect you intended. In C, this means to add
14466 @code{b} and @code{c} and place the result in @code{a}. The result
14467 printed would be the value of @code{a}. In Modula-2, this means to compare
14468 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
14470 @node Automatically
14471 @subsection Having @value{GDBN} Infer the Source Language
14473 To have @value{GDBN} set the working language automatically, use
14474 @samp{set language local} or @samp{set language auto}. @value{GDBN}
14475 then infers the working language. That is, when your program stops in a
14476 frame (usually by encountering a breakpoint), @value{GDBN} sets the
14477 working language to the language recorded for the function in that
14478 frame. If the language for a frame is unknown (that is, if the function
14479 or block corresponding to the frame was defined in a source file that
14480 does not have a recognized extension), the current working language is
14481 not changed, and @value{GDBN} issues a warning.
14483 This may not seem necessary for most programs, which are written
14484 entirely in one source language. However, program modules and libraries
14485 written in one source language can be used by a main program written in
14486 a different source language. Using @samp{set language auto} in this
14487 case frees you from having to set the working language manually.
14490 @section Displaying the Language
14492 The following commands help you find out which language is the
14493 working language, and also what language source files were written in.
14496 @item show language
14497 @anchor{show language}
14498 @kindex show language
14499 Display the current working language. This is the
14500 language you can use with commands such as @code{print} to
14501 build and compute expressions that may involve variables in your program.
14504 @kindex info frame@r{, show the source language}
14505 Display the source language for this frame. This language becomes the
14506 working language if you use an identifier from this frame.
14507 @xref{Frame Info, ,Information about a Frame}, to identify the other
14508 information listed here.
14511 @kindex info source@r{, show the source language}
14512 Display the source language of this source file.
14513 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
14514 information listed here.
14517 In unusual circumstances, you may have source files with extensions
14518 not in the standard list. You can then set the extension associated
14519 with a language explicitly:
14522 @item set extension-language @var{ext} @var{language}
14523 @kindex set extension-language
14524 Tell @value{GDBN} that source files with extension @var{ext} are to be
14525 assumed as written in the source language @var{language}.
14527 @item info extensions
14528 @kindex info extensions
14529 List all the filename extensions and the associated languages.
14533 @section Type and Range Checking
14535 Some languages are designed to guard you against making seemingly common
14536 errors through a series of compile- and run-time checks. These include
14537 checking the type of arguments to functions and operators and making
14538 sure mathematical overflows are caught at run time. Checks such as
14539 these help to ensure a program's correctness once it has been compiled
14540 by eliminating type mismatches and providing active checks for range
14541 errors when your program is running.
14543 By default @value{GDBN} checks for these errors according to the
14544 rules of the current source language. Although @value{GDBN} does not check
14545 the statements in your program, it can check expressions entered directly
14546 into @value{GDBN} for evaluation via the @code{print} command, for example.
14549 * Type Checking:: An overview of type checking
14550 * Range Checking:: An overview of range checking
14553 @cindex type checking
14554 @cindex checks, type
14555 @node Type Checking
14556 @subsection An Overview of Type Checking
14558 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
14559 arguments to operators and functions have to be of the correct type,
14560 otherwise an error occurs. These checks prevent type mismatch
14561 errors from ever causing any run-time problems. For example,
14564 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
14566 (@value{GDBP}) print obj.my_method (0)
14569 (@value{GDBP}) print obj.my_method (0x1234)
14570 Cannot resolve method klass::my_method to any overloaded instance
14573 The second example fails because in C@t{++} the integer constant
14574 @samp{0x1234} is not type-compatible with the pointer parameter type.
14576 For the expressions you use in @value{GDBN} commands, you can tell
14577 @value{GDBN} to not enforce strict type checking or
14578 to treat any mismatches as errors and abandon the expression;
14579 When type checking is disabled, @value{GDBN} successfully evaluates
14580 expressions like the second example above.
14582 Even if type checking is off, there may be other reasons
14583 related to type that prevent @value{GDBN} from evaluating an expression.
14584 For instance, @value{GDBN} does not know how to add an @code{int} and
14585 a @code{struct foo}. These particular type errors have nothing to do
14586 with the language in use and usually arise from expressions which make
14587 little sense to evaluate anyway.
14589 @value{GDBN} provides some additional commands for controlling type checking:
14591 @kindex set check type
14592 @kindex show check type
14594 @item set check type on
14595 @itemx set check type off
14596 Set strict type checking on or off. If any type mismatches occur in
14597 evaluating an expression while type checking is on, @value{GDBN} prints a
14598 message and aborts evaluation of the expression.
14600 @item show check type
14601 Show the current setting of type checking and whether @value{GDBN}
14602 is enforcing strict type checking rules.
14605 @cindex range checking
14606 @cindex checks, range
14607 @node Range Checking
14608 @subsection An Overview of Range Checking
14610 In some languages (such as Modula-2), it is an error to exceed the
14611 bounds of a type; this is enforced with run-time checks. Such range
14612 checking is meant to ensure program correctness by making sure
14613 computations do not overflow, or indices on an array element access do
14614 not exceed the bounds of the array.
14616 For expressions you use in @value{GDBN} commands, you can tell
14617 @value{GDBN} to treat range errors in one of three ways: ignore them,
14618 always treat them as errors and abandon the expression, or issue
14619 warnings but evaluate the expression anyway.
14621 A range error can result from numerical overflow, from exceeding an
14622 array index bound, or when you type a constant that is not a member
14623 of any type. Some languages, however, do not treat overflows as an
14624 error. In many implementations of C, mathematical overflow causes the
14625 result to ``wrap around'' to lower values---for example, if @var{m} is
14626 the largest integer value, and @var{s} is the smallest, then
14629 @var{m} + 1 @result{} @var{s}
14632 This, too, is specific to individual languages, and in some cases
14633 specific to individual compilers or machines. @xref{Supported Languages, ,
14634 Supported Languages}, for further details on specific languages.
14636 @value{GDBN} provides some additional commands for controlling the range checker:
14638 @kindex set check range
14639 @kindex show check range
14641 @item set check range auto
14642 Set range checking on or off based on the current working language.
14643 @xref{Supported Languages, ,Supported Languages}, for the default settings for
14646 @item set check range on
14647 @itemx set check range off
14648 Set range checking on or off, overriding the default setting for the
14649 current working language. A warning is issued if the setting does not
14650 match the language default. If a range error occurs and range checking is on,
14651 then a message is printed and evaluation of the expression is aborted.
14653 @item set check range warn
14654 Output messages when the @value{GDBN} range checker detects a range error,
14655 but attempt to evaluate the expression anyway. Evaluating the
14656 expression may still be impossible for other reasons, such as accessing
14657 memory that the process does not own (a typical example from many Unix
14661 Show the current setting of the range checker, and whether or not it is
14662 being set automatically by @value{GDBN}.
14665 @node Supported Languages
14666 @section Supported Languages
14668 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
14669 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
14670 @c This is false ...
14671 Some @value{GDBN} features may be used in expressions regardless of the
14672 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
14673 and the @samp{@{type@}addr} construct (@pxref{Expressions,
14674 ,Expressions}) can be used with the constructs of any supported
14677 The following sections detail to what degree each source language is
14678 supported by @value{GDBN}. These sections are not meant to be language
14679 tutorials or references, but serve only as a reference guide to what the
14680 @value{GDBN} expression parser accepts, and what input and output
14681 formats should look like for different languages. There are many good
14682 books written on each of these languages; please look to these for a
14683 language reference or tutorial.
14686 * C:: C and C@t{++}
14689 * Objective-C:: Objective-C
14690 * OpenCL C:: OpenCL C
14691 * Fortran:: Fortran
14694 * Modula-2:: Modula-2
14699 @subsection C and C@t{++}
14701 @cindex C and C@t{++}
14702 @cindex expressions in C or C@t{++}
14704 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
14705 to both languages. Whenever this is the case, we discuss those languages
14709 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
14710 @cindex @sc{gnu} C@t{++}
14711 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
14712 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
14713 effectively, you must compile your C@t{++} programs with a supported
14714 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
14715 compiler (@code{aCC}).
14718 * C Operators:: C and C@t{++} operators
14719 * C Constants:: C and C@t{++} constants
14720 * C Plus Plus Expressions:: C@t{++} expressions
14721 * C Defaults:: Default settings for C and C@t{++}
14722 * C Checks:: C and C@t{++} type and range checks
14723 * Debugging C:: @value{GDBN} and C
14724 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
14725 * Decimal Floating Point:: Numbers in Decimal Floating Point format
14729 @subsubsection C and C@t{++} Operators
14731 @cindex C and C@t{++} operators
14733 Operators must be defined on values of specific types. For instance,
14734 @code{+} is defined on numbers, but not on structures. Operators are
14735 often defined on groups of types.
14737 For the purposes of C and C@t{++}, the following definitions hold:
14742 @emph{Integral types} include @code{int} with any of its storage-class
14743 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
14746 @emph{Floating-point types} include @code{float}, @code{double}, and
14747 @code{long double} (if supported by the target platform).
14750 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
14753 @emph{Scalar types} include all of the above.
14758 The following operators are supported. They are listed here
14759 in order of increasing precedence:
14763 The comma or sequencing operator. Expressions in a comma-separated list
14764 are evaluated from left to right, with the result of the entire
14765 expression being the last expression evaluated.
14768 Assignment. The value of an assignment expression is the value
14769 assigned. Defined on scalar types.
14772 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
14773 and translated to @w{@code{@var{a} = @var{a op b}}}.
14774 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
14775 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
14776 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
14779 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
14780 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
14781 should be of an integral type.
14784 Logical @sc{or}. Defined on integral types.
14787 Logical @sc{and}. Defined on integral types.
14790 Bitwise @sc{or}. Defined on integral types.
14793 Bitwise exclusive-@sc{or}. Defined on integral types.
14796 Bitwise @sc{and}. Defined on integral types.
14799 Equality and inequality. Defined on scalar types. The value of these
14800 expressions is 0 for false and non-zero for true.
14802 @item <@r{, }>@r{, }<=@r{, }>=
14803 Less than, greater than, less than or equal, greater than or equal.
14804 Defined on scalar types. The value of these expressions is 0 for false
14805 and non-zero for true.
14808 left shift, and right shift. Defined on integral types.
14811 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14814 Addition and subtraction. Defined on integral types, floating-point types and
14817 @item *@r{, }/@r{, }%
14818 Multiplication, division, and modulus. Multiplication and division are
14819 defined on integral and floating-point types. Modulus is defined on
14823 Increment and decrement. When appearing before a variable, the
14824 operation is performed before the variable is used in an expression;
14825 when appearing after it, the variable's value is used before the
14826 operation takes place.
14829 Pointer dereferencing. Defined on pointer types. Same precedence as
14833 Address operator. Defined on variables. Same precedence as @code{++}.
14835 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
14836 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
14837 to examine the address
14838 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
14842 Negative. Defined on integral and floating-point types. Same
14843 precedence as @code{++}.
14846 Logical negation. Defined on integral types. Same precedence as
14850 Bitwise complement operator. Defined on integral types. Same precedence as
14855 Structure member, and pointer-to-structure member. For convenience,
14856 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
14857 pointer based on the stored type information.
14858 Defined on @code{struct} and @code{union} data.
14861 Dereferences of pointers to members.
14864 Array indexing. @code{@var{a}[@var{i}]} is defined as
14865 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
14868 Function parameter list. Same precedence as @code{->}.
14871 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
14872 and @code{class} types.
14875 Doubled colons also represent the @value{GDBN} scope operator
14876 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
14880 If an operator is redefined in the user code, @value{GDBN} usually
14881 attempts to invoke the redefined version instead of using the operator's
14882 predefined meaning.
14885 @subsubsection C and C@t{++} Constants
14887 @cindex C and C@t{++} constants
14889 @value{GDBN} allows you to express the constants of C and C@t{++} in the
14894 Integer constants are a sequence of digits. Octal constants are
14895 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
14896 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
14897 @samp{l}, specifying that the constant should be treated as a
14901 Floating point constants are a sequence of digits, followed by a decimal
14902 point, followed by a sequence of digits, and optionally followed by an
14903 exponent. An exponent is of the form:
14904 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
14905 sequence of digits. The @samp{+} is optional for positive exponents.
14906 A floating-point constant may also end with a letter @samp{f} or
14907 @samp{F}, specifying that the constant should be treated as being of
14908 the @code{float} (as opposed to the default @code{double}) type; or with
14909 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
14913 Enumerated constants consist of enumerated identifiers, or their
14914 integral equivalents.
14917 Character constants are a single character surrounded by single quotes
14918 (@code{'}), or a number---the ordinal value of the corresponding character
14919 (usually its @sc{ascii} value). Within quotes, the single character may
14920 be represented by a letter or by @dfn{escape sequences}, which are of
14921 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
14922 of the character's ordinal value; or of the form @samp{\@var{x}}, where
14923 @samp{@var{x}} is a predefined special character---for example,
14924 @samp{\n} for newline.
14926 Wide character constants can be written by prefixing a character
14927 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
14928 form of @samp{x}. The target wide character set is used when
14929 computing the value of this constant (@pxref{Character Sets}).
14932 String constants are a sequence of character constants surrounded by
14933 double quotes (@code{"}). Any valid character constant (as described
14934 above) may appear. Double quotes within the string must be preceded by
14935 a backslash, so for instance @samp{"a\"b'c"} is a string of five
14938 Wide string constants can be written by prefixing a string constant
14939 with @samp{L}, as in C. The target wide character set is used when
14940 computing the value of this constant (@pxref{Character Sets}).
14943 Pointer constants are an integral value. You can also write pointers
14944 to constants using the C operator @samp{&}.
14947 Array constants are comma-separated lists surrounded by braces @samp{@{}
14948 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
14949 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
14950 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
14953 @node C Plus Plus Expressions
14954 @subsubsection C@t{++} Expressions
14956 @cindex expressions in C@t{++}
14957 @value{GDBN} expression handling can interpret most C@t{++} expressions.
14959 @cindex debugging C@t{++} programs
14960 @cindex C@t{++} compilers
14961 @cindex debug formats and C@t{++}
14962 @cindex @value{NGCC} and C@t{++}
14964 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
14965 the proper compiler and the proper debug format. Currently,
14966 @value{GDBN} works best when debugging C@t{++} code that is compiled
14967 with the most recent version of @value{NGCC} possible. The DWARF
14968 debugging format is preferred; @value{NGCC} defaults to this on most
14969 popular platforms. Other compilers and/or debug formats are likely to
14970 work badly or not at all when using @value{GDBN} to debug C@t{++}
14971 code. @xref{Compilation}.
14976 @cindex member functions
14978 Member function calls are allowed; you can use expressions like
14981 count = aml->GetOriginal(x, y)
14984 @vindex this@r{, inside C@t{++} member functions}
14985 @cindex namespace in C@t{++}
14987 While a member function is active (in the selected stack frame), your
14988 expressions have the same namespace available as the member function;
14989 that is, @value{GDBN} allows implicit references to the class instance
14990 pointer @code{this} following the same rules as C@t{++}. @code{using}
14991 declarations in the current scope are also respected by @value{GDBN}.
14993 @cindex call overloaded functions
14994 @cindex overloaded functions, calling
14995 @cindex type conversions in C@t{++}
14997 You can call overloaded functions; @value{GDBN} resolves the function
14998 call to the right definition, with some restrictions. @value{GDBN} does not
14999 perform overload resolution involving user-defined type conversions,
15000 calls to constructors, or instantiations of templates that do not exist
15001 in the program. It also cannot handle ellipsis argument lists or
15004 It does perform integral conversions and promotions, floating-point
15005 promotions, arithmetic conversions, pointer conversions, conversions of
15006 class objects to base classes, and standard conversions such as those of
15007 functions or arrays to pointers; it requires an exact match on the
15008 number of function arguments.
15010 Overload resolution is always performed, unless you have specified
15011 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
15012 ,@value{GDBN} Features for C@t{++}}.
15014 You must specify @code{set overload-resolution off} in order to use an
15015 explicit function signature to call an overloaded function, as in
15017 p 'foo(char,int)'('x', 13)
15020 The @value{GDBN} command-completion facility can simplify this;
15021 see @ref{Completion, ,Command Completion}.
15023 @cindex reference declarations
15025 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
15026 references; you can use them in expressions just as you do in C@t{++}
15027 source---they are automatically dereferenced.
15029 In the parameter list shown when @value{GDBN} displays a frame, the values of
15030 reference variables are not displayed (unlike other variables); this
15031 avoids clutter, since references are often used for large structures.
15032 The @emph{address} of a reference variable is always shown, unless
15033 you have specified @samp{set print address off}.
15036 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
15037 expressions can use it just as expressions in your program do. Since
15038 one scope may be defined in another, you can use @code{::} repeatedly if
15039 necessary, for example in an expression like
15040 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
15041 resolving name scope by reference to source files, in both C and C@t{++}
15042 debugging (@pxref{Variables, ,Program Variables}).
15045 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
15050 @subsubsection C and C@t{++} Defaults
15052 @cindex C and C@t{++} defaults
15054 If you allow @value{GDBN} to set range checking automatically, it
15055 defaults to @code{off} whenever the working language changes to
15056 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
15057 selects the working language.
15059 If you allow @value{GDBN} to set the language automatically, it
15060 recognizes source files whose names end with @file{.c}, @file{.C}, or
15061 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
15062 these files, it sets the working language to C or C@t{++}.
15063 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
15064 for further details.
15067 @subsubsection C and C@t{++} Type and Range Checks
15069 @cindex C and C@t{++} checks
15071 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
15072 checking is used. However, if you turn type checking off, @value{GDBN}
15073 will allow certain non-standard conversions, such as promoting integer
15074 constants to pointers.
15076 Range checking, if turned on, is done on mathematical operations. Array
15077 indices are not checked, since they are often used to index a pointer
15078 that is not itself an array.
15081 @subsubsection @value{GDBN} and C
15083 The @code{set print union} and @code{show print union} commands apply to
15084 the @code{union} type. When set to @samp{on}, any @code{union} that is
15085 inside a @code{struct} or @code{class} is also printed. Otherwise, it
15086 appears as @samp{@{...@}}.
15088 The @code{@@} operator aids in the debugging of dynamic arrays, formed
15089 with pointers and a memory allocation function. @xref{Expressions,
15092 @node Debugging C Plus Plus
15093 @subsubsection @value{GDBN} Features for C@t{++}
15095 @cindex commands for C@t{++}
15097 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
15098 designed specifically for use with C@t{++}. Here is a summary:
15101 @cindex break in overloaded functions
15102 @item @r{breakpoint menus}
15103 When you want a breakpoint in a function whose name is overloaded,
15104 @value{GDBN} has the capability to display a menu of possible breakpoint
15105 locations to help you specify which function definition you want.
15106 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
15108 @cindex overloading in C@t{++}
15109 @item rbreak @var{regex}
15110 Setting breakpoints using regular expressions is helpful for setting
15111 breakpoints on overloaded functions that are not members of any special
15113 @xref{Set Breaks, ,Setting Breakpoints}.
15115 @cindex C@t{++} exception handling
15117 @itemx catch rethrow
15119 Debug C@t{++} exception handling using these commands. @xref{Set
15120 Catchpoints, , Setting Catchpoints}.
15122 @cindex inheritance
15123 @item ptype @var{typename}
15124 Print inheritance relationships as well as other information for type
15126 @xref{Symbols, ,Examining the Symbol Table}.
15128 @item info vtbl @var{expression}.
15129 The @code{info vtbl} command can be used to display the virtual
15130 method tables of the object computed by @var{expression}. This shows
15131 one entry per virtual table; there may be multiple virtual tables when
15132 multiple inheritance is in use.
15134 @cindex C@t{++} demangling
15135 @item demangle @var{name}
15136 Demangle @var{name}.
15137 @xref{Symbols}, for a more complete description of the @code{demangle} command.
15139 @cindex C@t{++} symbol display
15140 @item set print demangle
15141 @itemx show print demangle
15142 @itemx set print asm-demangle
15143 @itemx show print asm-demangle
15144 Control whether C@t{++} symbols display in their source form, both when
15145 displaying code as C@t{++} source and when displaying disassemblies.
15146 @xref{Print Settings, ,Print Settings}.
15148 @item set print object
15149 @itemx show print object
15150 Choose whether to print derived (actual) or declared types of objects.
15151 @xref{Print Settings, ,Print Settings}.
15153 @item set print vtbl
15154 @itemx show print vtbl
15155 Control the format for printing virtual function tables.
15156 @xref{Print Settings, ,Print Settings}.
15157 (The @code{vtbl} commands do not work on programs compiled with the HP
15158 ANSI C@t{++} compiler (@code{aCC}).)
15160 @kindex set overload-resolution
15161 @cindex overloaded functions, overload resolution
15162 @item set overload-resolution on
15163 Enable overload resolution for C@t{++} expression evaluation. The default
15164 is on. For overloaded functions, @value{GDBN} evaluates the arguments
15165 and searches for a function whose signature matches the argument types,
15166 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
15167 Expressions, ,C@t{++} Expressions}, for details).
15168 If it cannot find a match, it emits a message.
15170 @item set overload-resolution off
15171 Disable overload resolution for C@t{++} expression evaluation. For
15172 overloaded functions that are not class member functions, @value{GDBN}
15173 chooses the first function of the specified name that it finds in the
15174 symbol table, whether or not its arguments are of the correct type. For
15175 overloaded functions that are class member functions, @value{GDBN}
15176 searches for a function whose signature @emph{exactly} matches the
15179 @kindex show overload-resolution
15180 @item show overload-resolution
15181 Show the current setting of overload resolution.
15183 @item @r{Overloaded symbol names}
15184 You can specify a particular definition of an overloaded symbol, using
15185 the same notation that is used to declare such symbols in C@t{++}: type
15186 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
15187 also use the @value{GDBN} command-line word completion facilities to list the
15188 available choices, or to finish the type list for you.
15189 @xref{Completion,, Command Completion}, for details on how to do this.
15191 @item @r{Breakpoints in functions with ABI tags}
15193 The GNU C@t{++} compiler introduced the notion of ABI ``tags'', which
15194 correspond to changes in the ABI of a type, function, or variable that
15195 would not otherwise be reflected in a mangled name. See
15196 @url{https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/}
15199 The ABI tags are visible in C@t{++} demangled names. For example, a
15200 function that returns a std::string:
15203 std::string function(int);
15207 when compiled for the C++11 ABI is marked with the @code{cxx11} ABI
15208 tag, and @value{GDBN} displays the symbol like this:
15211 function[abi:cxx11](int)
15214 You can set a breakpoint on such functions simply as if they had no
15218 (gdb) b function(int)
15219 Breakpoint 2 at 0x40060d: file main.cc, line 10.
15220 (gdb) info breakpoints
15221 Num Type Disp Enb Address What
15222 1 breakpoint keep y 0x0040060d in function[abi:cxx11](int)
15226 On the rare occasion you need to disambiguate between different ABI
15227 tags, you can do so by simply including the ABI tag in the function
15231 (@value{GDBP}) b ambiguous[abi:other_tag](int)
15235 @node Decimal Floating Point
15236 @subsubsection Decimal Floating Point format
15237 @cindex decimal floating point format
15239 @value{GDBN} can examine, set and perform computations with numbers in
15240 decimal floating point format, which in the C language correspond to the
15241 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
15242 specified by the extension to support decimal floating-point arithmetic.
15244 There are two encodings in use, depending on the architecture: BID (Binary
15245 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
15246 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
15249 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
15250 to manipulate decimal floating point numbers, it is not possible to convert
15251 (using a cast, for example) integers wider than 32-bit to decimal float.
15253 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
15254 point computations, error checking in decimal float operations ignores
15255 underflow, overflow and divide by zero exceptions.
15257 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
15258 to inspect @code{_Decimal128} values stored in floating point registers.
15259 See @ref{PowerPC,,PowerPC} for more details.
15265 @value{GDBN} can be used to debug programs written in D and compiled with
15266 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
15267 specific feature --- dynamic arrays.
15272 @cindex Go (programming language)
15273 @value{GDBN} can be used to debug programs written in Go and compiled with
15274 @file{gccgo} or @file{6g} compilers.
15276 Here is a summary of the Go-specific features and restrictions:
15279 @cindex current Go package
15280 @item The current Go package
15281 The name of the current package does not need to be specified when
15282 specifying global variables and functions.
15284 For example, given the program:
15288 var myglob = "Shall we?"
15294 When stopped inside @code{main} either of these work:
15298 (gdb) p main.myglob
15301 @cindex builtin Go types
15302 @item Builtin Go types
15303 The @code{string} type is recognized by @value{GDBN} and is printed
15306 @cindex builtin Go functions
15307 @item Builtin Go functions
15308 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
15309 function and handles it internally.
15311 @cindex restrictions on Go expressions
15312 @item Restrictions on Go expressions
15313 All Go operators are supported except @code{&^}.
15314 The Go @code{_} ``blank identifier'' is not supported.
15315 Automatic dereferencing of pointers is not supported.
15319 @subsection Objective-C
15321 @cindex Objective-C
15322 This section provides information about some commands and command
15323 options that are useful for debugging Objective-C code. See also
15324 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
15325 few more commands specific to Objective-C support.
15328 * Method Names in Commands::
15329 * The Print Command with Objective-C::
15332 @node Method Names in Commands
15333 @subsubsection Method Names in Commands
15335 The following commands have been extended to accept Objective-C method
15336 names as line specifications:
15338 @kindex clear@r{, and Objective-C}
15339 @kindex break@r{, and Objective-C}
15340 @kindex info line@r{, and Objective-C}
15341 @kindex jump@r{, and Objective-C}
15342 @kindex list@r{, and Objective-C}
15346 @item @code{info line}
15351 A fully qualified Objective-C method name is specified as
15354 -[@var{Class} @var{methodName}]
15357 where the minus sign is used to indicate an instance method and a
15358 plus sign (not shown) is used to indicate a class method. The class
15359 name @var{Class} and method name @var{methodName} are enclosed in
15360 brackets, similar to the way messages are specified in Objective-C
15361 source code. For example, to set a breakpoint at the @code{create}
15362 instance method of class @code{Fruit} in the program currently being
15366 break -[Fruit create]
15369 To list ten program lines around the @code{initialize} class method,
15373 list +[NSText initialize]
15376 In the current version of @value{GDBN}, the plus or minus sign is
15377 required. In future versions of @value{GDBN}, the plus or minus
15378 sign will be optional, but you can use it to narrow the search. It
15379 is also possible to specify just a method name:
15385 You must specify the complete method name, including any colons. If
15386 your program's source files contain more than one @code{create} method,
15387 you'll be presented with a numbered list of classes that implement that
15388 method. Indicate your choice by number, or type @samp{0} to exit if
15391 As another example, to clear a breakpoint established at the
15392 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
15395 clear -[NSWindow makeKeyAndOrderFront:]
15398 @node The Print Command with Objective-C
15399 @subsubsection The Print Command With Objective-C
15400 @cindex Objective-C, print objects
15401 @kindex print-object
15402 @kindex po @r{(@code{print-object})}
15404 The print command has also been extended to accept methods. For example:
15407 print -[@var{object} hash]
15410 @cindex print an Objective-C object description
15411 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
15413 will tell @value{GDBN} to send the @code{hash} message to @var{object}
15414 and print the result. Also, an additional command has been added,
15415 @code{print-object} or @code{po} for short, which is meant to print
15416 the description of an object. However, this command may only work
15417 with certain Objective-C libraries that have a particular hook
15418 function, @code{_NSPrintForDebugger}, defined.
15421 @subsection OpenCL C
15424 This section provides information about @value{GDBN}s OpenCL C support.
15427 * OpenCL C Datatypes::
15428 * OpenCL C Expressions::
15429 * OpenCL C Operators::
15432 @node OpenCL C Datatypes
15433 @subsubsection OpenCL C Datatypes
15435 @cindex OpenCL C Datatypes
15436 @value{GDBN} supports the builtin scalar and vector datatypes specified
15437 by OpenCL 1.1. In addition the half- and double-precision floating point
15438 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
15439 extensions are also known to @value{GDBN}.
15441 @node OpenCL C Expressions
15442 @subsubsection OpenCL C Expressions
15444 @cindex OpenCL C Expressions
15445 @value{GDBN} supports accesses to vector components including the access as
15446 lvalue where possible. Since OpenCL C is based on C99 most C expressions
15447 supported by @value{GDBN} can be used as well.
15449 @node OpenCL C Operators
15450 @subsubsection OpenCL C Operators
15452 @cindex OpenCL C Operators
15453 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
15457 @subsection Fortran
15458 @cindex Fortran-specific support in @value{GDBN}
15460 @value{GDBN} can be used to debug programs written in Fortran, but it
15461 currently supports only the features of Fortran 77 language.
15463 @cindex trailing underscore, in Fortran symbols
15464 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
15465 among them) append an underscore to the names of variables and
15466 functions. When you debug programs compiled by those compilers, you
15467 will need to refer to variables and functions with a trailing
15471 * Fortran Operators:: Fortran operators and expressions
15472 * Fortran Defaults:: Default settings for Fortran
15473 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
15476 @node Fortran Operators
15477 @subsubsection Fortran Operators and Expressions
15479 @cindex Fortran operators and expressions
15481 Operators must be defined on values of specific types. For instance,
15482 @code{+} is defined on numbers, but not on characters or other non-
15483 arithmetic types. Operators are often defined on groups of types.
15487 The exponentiation operator. It raises the first operand to the power
15491 The range operator. Normally used in the form of array(low:high) to
15492 represent a section of array.
15495 The access component operator. Normally used to access elements in derived
15496 types. Also suitable for unions. As unions aren't part of regular Fortran,
15497 this can only happen when accessing a register that uses a gdbarch-defined
15501 @node Fortran Defaults
15502 @subsubsection Fortran Defaults
15504 @cindex Fortran Defaults
15506 Fortran symbols are usually case-insensitive, so @value{GDBN} by
15507 default uses case-insensitive matches for Fortran symbols. You can
15508 change that with the @samp{set case-insensitive} command, see
15509 @ref{Symbols}, for the details.
15511 @node Special Fortran Commands
15512 @subsubsection Special Fortran Commands
15514 @cindex Special Fortran commands
15516 @value{GDBN} has some commands to support Fortran-specific features,
15517 such as displaying common blocks.
15520 @cindex @code{COMMON} blocks, Fortran
15521 @kindex info common
15522 @item info common @r{[}@var{common-name}@r{]}
15523 This command prints the values contained in the Fortran @code{COMMON}
15524 block whose name is @var{common-name}. With no argument, the names of
15525 all @code{COMMON} blocks visible at the current program location are
15532 @cindex Pascal support in @value{GDBN}, limitations
15533 Debugging Pascal programs which use sets, subranges, file variables, or
15534 nested functions does not currently work. @value{GDBN} does not support
15535 entering expressions, printing values, or similar features using Pascal
15538 The Pascal-specific command @code{set print pascal_static-members}
15539 controls whether static members of Pascal objects are displayed.
15540 @xref{Print Settings, pascal_static-members}.
15545 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
15546 Programming Language}. Type- and value-printing, and expression
15547 parsing, are reasonably complete. However, there are a few
15548 peculiarities and holes to be aware of.
15552 Linespecs (@pxref{Specify Location}) are never relative to the current
15553 crate. Instead, they act as if there were a global namespace of
15554 crates, somewhat similar to the way @code{extern crate} behaves.
15556 That is, if @value{GDBN} is stopped at a breakpoint in a function in
15557 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
15558 to set a breakpoint in a function named @samp{f} in a crate named
15561 As a consequence of this approach, linespecs also cannot refer to
15562 items using @samp{self::} or @samp{super::}.
15565 Because @value{GDBN} implements Rust name-lookup semantics in
15566 expressions, it will sometimes prepend the current crate to a name.
15567 For example, if @value{GDBN} is stopped at a breakpoint in the crate
15568 @samp{K}, then @code{print ::x::y} will try to find the symbol
15571 However, since it is useful to be able to refer to other crates when
15572 debugging, @value{GDBN} provides the @code{extern} extension to
15573 circumvent this. To use the extension, just put @code{extern} before
15574 a path expression to refer to the otherwise unavailable ``global''
15577 In the above example, if you wanted to refer to the symbol @samp{y} in
15578 the crate @samp{x}, you would use @code{print extern x::y}.
15581 The Rust expression evaluator does not support ``statement-like''
15582 expressions such as @code{if} or @code{match}, or lambda expressions.
15585 Tuple expressions are not implemented.
15588 The Rust expression evaluator does not currently implement the
15589 @code{Drop} trait. Objects that may be created by the evaluator will
15590 never be destroyed.
15593 @value{GDBN} does not implement type inference for generics. In order
15594 to call generic functions or otherwise refer to generic items, you
15595 will have to specify the type parameters manually.
15598 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
15599 cases this does not cause any problems. However, in an expression
15600 context, completing a generic function name will give syntactically
15601 invalid results. This happens because Rust requires the @samp{::}
15602 operator between the function name and its generic arguments. For
15603 example, @value{GDBN} might provide a completion like
15604 @code{crate::f<u32>}, where the parser would require
15605 @code{crate::f::<u32>}.
15608 As of this writing, the Rust compiler (version 1.8) has a few holes in
15609 the debugging information it generates. These holes prevent certain
15610 features from being implemented by @value{GDBN}:
15614 Method calls cannot be made via traits.
15617 Operator overloading is not implemented.
15620 When debugging in a monomorphized function, you cannot use the generic
15624 The type @code{Self} is not available.
15627 @code{use} statements are not available, so some names may not be
15628 available in the crate.
15633 @subsection Modula-2
15635 @cindex Modula-2, @value{GDBN} support
15637 The extensions made to @value{GDBN} to support Modula-2 only support
15638 output from the @sc{gnu} Modula-2 compiler (which is currently being
15639 developed). Other Modula-2 compilers are not currently supported, and
15640 attempting to debug executables produced by them is most likely
15641 to give an error as @value{GDBN} reads in the executable's symbol
15644 @cindex expressions in Modula-2
15646 * M2 Operators:: Built-in operators
15647 * Built-In Func/Proc:: Built-in functions and procedures
15648 * M2 Constants:: Modula-2 constants
15649 * M2 Types:: Modula-2 types
15650 * M2 Defaults:: Default settings for Modula-2
15651 * Deviations:: Deviations from standard Modula-2
15652 * M2 Checks:: Modula-2 type and range checks
15653 * M2 Scope:: The scope operators @code{::} and @code{.}
15654 * GDB/M2:: @value{GDBN} and Modula-2
15658 @subsubsection Operators
15659 @cindex Modula-2 operators
15661 Operators must be defined on values of specific types. For instance,
15662 @code{+} is defined on numbers, but not on structures. Operators are
15663 often defined on groups of types. For the purposes of Modula-2, the
15664 following definitions hold:
15669 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
15673 @emph{Character types} consist of @code{CHAR} and its subranges.
15676 @emph{Floating-point types} consist of @code{REAL}.
15679 @emph{Pointer types} consist of anything declared as @code{POINTER TO
15683 @emph{Scalar types} consist of all of the above.
15686 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
15689 @emph{Boolean types} consist of @code{BOOLEAN}.
15693 The following operators are supported, and appear in order of
15694 increasing precedence:
15698 Function argument or array index separator.
15701 Assignment. The value of @var{var} @code{:=} @var{value} is
15705 Less than, greater than on integral, floating-point, or enumerated
15709 Less than or equal to, greater than or equal to
15710 on integral, floating-point and enumerated types, or set inclusion on
15711 set types. Same precedence as @code{<}.
15713 @item =@r{, }<>@r{, }#
15714 Equality and two ways of expressing inequality, valid on scalar types.
15715 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
15716 available for inequality, since @code{#} conflicts with the script
15720 Set membership. Defined on set types and the types of their members.
15721 Same precedence as @code{<}.
15724 Boolean disjunction. Defined on boolean types.
15727 Boolean conjunction. Defined on boolean types.
15730 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15733 Addition and subtraction on integral and floating-point types, or union
15734 and difference on set types.
15737 Multiplication on integral and floating-point types, or set intersection
15741 Division on floating-point types, or symmetric set difference on set
15742 types. Same precedence as @code{*}.
15745 Integer division and remainder. Defined on integral types. Same
15746 precedence as @code{*}.
15749 Negative. Defined on @code{INTEGER} and @code{REAL} data.
15752 Pointer dereferencing. Defined on pointer types.
15755 Boolean negation. Defined on boolean types. Same precedence as
15759 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
15760 precedence as @code{^}.
15763 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
15766 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
15770 @value{GDBN} and Modula-2 scope operators.
15774 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
15775 treats the use of the operator @code{IN}, or the use of operators
15776 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
15777 @code{<=}, and @code{>=} on sets as an error.
15781 @node Built-In Func/Proc
15782 @subsubsection Built-in Functions and Procedures
15783 @cindex Modula-2 built-ins
15785 Modula-2 also makes available several built-in procedures and functions.
15786 In describing these, the following metavariables are used:
15791 represents an @code{ARRAY} variable.
15794 represents a @code{CHAR} constant or variable.
15797 represents a variable or constant of integral type.
15800 represents an identifier that belongs to a set. Generally used in the
15801 same function with the metavariable @var{s}. The type of @var{s} should
15802 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
15805 represents a variable or constant of integral or floating-point type.
15808 represents a variable or constant of floating-point type.
15814 represents a variable.
15817 represents a variable or constant of one of many types. See the
15818 explanation of the function for details.
15821 All Modula-2 built-in procedures also return a result, described below.
15825 Returns the absolute value of @var{n}.
15828 If @var{c} is a lower case letter, it returns its upper case
15829 equivalent, otherwise it returns its argument.
15832 Returns the character whose ordinal value is @var{i}.
15835 Decrements the value in the variable @var{v} by one. Returns the new value.
15837 @item DEC(@var{v},@var{i})
15838 Decrements the value in the variable @var{v} by @var{i}. Returns the
15841 @item EXCL(@var{m},@var{s})
15842 Removes the element @var{m} from the set @var{s}. Returns the new
15845 @item FLOAT(@var{i})
15846 Returns the floating point equivalent of the integer @var{i}.
15848 @item HIGH(@var{a})
15849 Returns the index of the last member of @var{a}.
15852 Increments the value in the variable @var{v} by one. Returns the new value.
15854 @item INC(@var{v},@var{i})
15855 Increments the value in the variable @var{v} by @var{i}. Returns the
15858 @item INCL(@var{m},@var{s})
15859 Adds the element @var{m} to the set @var{s} if it is not already
15860 there. Returns the new set.
15863 Returns the maximum value of the type @var{t}.
15866 Returns the minimum value of the type @var{t}.
15869 Returns boolean TRUE if @var{i} is an odd number.
15872 Returns the ordinal value of its argument. For example, the ordinal
15873 value of a character is its @sc{ascii} value (on machines supporting
15874 the @sc{ascii} character set). The argument @var{x} must be of an
15875 ordered type, which include integral, character and enumerated types.
15877 @item SIZE(@var{x})
15878 Returns the size of its argument. The argument @var{x} can be a
15879 variable or a type.
15881 @item TRUNC(@var{r})
15882 Returns the integral part of @var{r}.
15884 @item TSIZE(@var{x})
15885 Returns the size of its argument. The argument @var{x} can be a
15886 variable or a type.
15888 @item VAL(@var{t},@var{i})
15889 Returns the member of the type @var{t} whose ordinal value is @var{i}.
15893 @emph{Warning:} Sets and their operations are not yet supported, so
15894 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
15898 @cindex Modula-2 constants
15900 @subsubsection Constants
15902 @value{GDBN} allows you to express the constants of Modula-2 in the following
15908 Integer constants are simply a sequence of digits. When used in an
15909 expression, a constant is interpreted to be type-compatible with the
15910 rest of the expression. Hexadecimal integers are specified by a
15911 trailing @samp{H}, and octal integers by a trailing @samp{B}.
15914 Floating point constants appear as a sequence of digits, followed by a
15915 decimal point and another sequence of digits. An optional exponent can
15916 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
15917 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
15918 digits of the floating point constant must be valid decimal (base 10)
15922 Character constants consist of a single character enclosed by a pair of
15923 like quotes, either single (@code{'}) or double (@code{"}). They may
15924 also be expressed by their ordinal value (their @sc{ascii} value, usually)
15925 followed by a @samp{C}.
15928 String constants consist of a sequence of characters enclosed by a
15929 pair of like quotes, either single (@code{'}) or double (@code{"}).
15930 Escape sequences in the style of C are also allowed. @xref{C
15931 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
15935 Enumerated constants consist of an enumerated identifier.
15938 Boolean constants consist of the identifiers @code{TRUE} and
15942 Pointer constants consist of integral values only.
15945 Set constants are not yet supported.
15949 @subsubsection Modula-2 Types
15950 @cindex Modula-2 types
15952 Currently @value{GDBN} can print the following data types in Modula-2
15953 syntax: array types, record types, set types, pointer types, procedure
15954 types, enumerated types, subrange types and base types. You can also
15955 print the contents of variables declared using these type.
15956 This section gives a number of simple source code examples together with
15957 sample @value{GDBN} sessions.
15959 The first example contains the following section of code:
15968 and you can request @value{GDBN} to interrogate the type and value of
15969 @code{r} and @code{s}.
15972 (@value{GDBP}) print s
15974 (@value{GDBP}) ptype s
15976 (@value{GDBP}) print r
15978 (@value{GDBP}) ptype r
15983 Likewise if your source code declares @code{s} as:
15987 s: SET ['A'..'Z'] ;
15991 then you may query the type of @code{s} by:
15994 (@value{GDBP}) ptype s
15995 type = SET ['A'..'Z']
15999 Note that at present you cannot interactively manipulate set
16000 expressions using the debugger.
16002 The following example shows how you might declare an array in Modula-2
16003 and how you can interact with @value{GDBN} to print its type and contents:
16007 s: ARRAY [-10..10] OF CHAR ;
16011 (@value{GDBP}) ptype s
16012 ARRAY [-10..10] OF CHAR
16015 Note that the array handling is not yet complete and although the type
16016 is printed correctly, expression handling still assumes that all
16017 arrays have a lower bound of zero and not @code{-10} as in the example
16020 Here are some more type related Modula-2 examples:
16024 colour = (blue, red, yellow, green) ;
16025 t = [blue..yellow] ;
16033 The @value{GDBN} interaction shows how you can query the data type
16034 and value of a variable.
16037 (@value{GDBP}) print s
16039 (@value{GDBP}) ptype t
16040 type = [blue..yellow]
16044 In this example a Modula-2 array is declared and its contents
16045 displayed. Observe that the contents are written in the same way as
16046 their @code{C} counterparts.
16050 s: ARRAY [1..5] OF CARDINAL ;
16056 (@value{GDBP}) print s
16057 $1 = @{1, 0, 0, 0, 0@}
16058 (@value{GDBP}) ptype s
16059 type = ARRAY [1..5] OF CARDINAL
16062 The Modula-2 language interface to @value{GDBN} also understands
16063 pointer types as shown in this example:
16067 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
16074 and you can request that @value{GDBN} describes the type of @code{s}.
16077 (@value{GDBP}) ptype s
16078 type = POINTER TO ARRAY [1..5] OF CARDINAL
16081 @value{GDBN} handles compound types as we can see in this example.
16082 Here we combine array types, record types, pointer types and subrange
16093 myarray = ARRAY myrange OF CARDINAL ;
16094 myrange = [-2..2] ;
16096 s: POINTER TO ARRAY myrange OF foo ;
16100 and you can ask @value{GDBN} to describe the type of @code{s} as shown
16104 (@value{GDBP}) ptype s
16105 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
16108 f3 : ARRAY [-2..2] OF CARDINAL;
16113 @subsubsection Modula-2 Defaults
16114 @cindex Modula-2 defaults
16116 If type and range checking are set automatically by @value{GDBN}, they
16117 both default to @code{on} whenever the working language changes to
16118 Modula-2. This happens regardless of whether you or @value{GDBN}
16119 selected the working language.
16121 If you allow @value{GDBN} to set the language automatically, then entering
16122 code compiled from a file whose name ends with @file{.mod} sets the
16123 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
16124 Infer the Source Language}, for further details.
16127 @subsubsection Deviations from Standard Modula-2
16128 @cindex Modula-2, deviations from
16130 A few changes have been made to make Modula-2 programs easier to debug.
16131 This is done primarily via loosening its type strictness:
16135 Unlike in standard Modula-2, pointer constants can be formed by
16136 integers. This allows you to modify pointer variables during
16137 debugging. (In standard Modula-2, the actual address contained in a
16138 pointer variable is hidden from you; it can only be modified
16139 through direct assignment to another pointer variable or expression that
16140 returned a pointer.)
16143 C escape sequences can be used in strings and characters to represent
16144 non-printable characters. @value{GDBN} prints out strings with these
16145 escape sequences embedded. Single non-printable characters are
16146 printed using the @samp{CHR(@var{nnn})} format.
16149 The assignment operator (@code{:=}) returns the value of its right-hand
16153 All built-in procedures both modify @emph{and} return their argument.
16157 @subsubsection Modula-2 Type and Range Checks
16158 @cindex Modula-2 checks
16161 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
16164 @c FIXME remove warning when type/range checks added
16166 @value{GDBN} considers two Modula-2 variables type equivalent if:
16170 They are of types that have been declared equivalent via a @code{TYPE
16171 @var{t1} = @var{t2}} statement
16174 They have been declared on the same line. (Note: This is true of the
16175 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
16178 As long as type checking is enabled, any attempt to combine variables
16179 whose types are not equivalent is an error.
16181 Range checking is done on all mathematical operations, assignment, array
16182 index bounds, and all built-in functions and procedures.
16185 @subsubsection The Scope Operators @code{::} and @code{.}
16187 @cindex @code{.}, Modula-2 scope operator
16188 @cindex colon, doubled as scope operator
16190 @vindex colon-colon@r{, in Modula-2}
16191 @c Info cannot handle :: but TeX can.
16194 @vindex ::@r{, in Modula-2}
16197 There are a few subtle differences between the Modula-2 scope operator
16198 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
16203 @var{module} . @var{id}
16204 @var{scope} :: @var{id}
16208 where @var{scope} is the name of a module or a procedure,
16209 @var{module} the name of a module, and @var{id} is any declared
16210 identifier within your program, except another module.
16212 Using the @code{::} operator makes @value{GDBN} search the scope
16213 specified by @var{scope} for the identifier @var{id}. If it is not
16214 found in the specified scope, then @value{GDBN} searches all scopes
16215 enclosing the one specified by @var{scope}.
16217 Using the @code{.} operator makes @value{GDBN} search the current scope for
16218 the identifier specified by @var{id} that was imported from the
16219 definition module specified by @var{module}. With this operator, it is
16220 an error if the identifier @var{id} was not imported from definition
16221 module @var{module}, or if @var{id} is not an identifier in
16225 @subsubsection @value{GDBN} and Modula-2
16227 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
16228 Five subcommands of @code{set print} and @code{show print} apply
16229 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
16230 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
16231 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
16232 analogue in Modula-2.
16234 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
16235 with any language, is not useful with Modula-2. Its
16236 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
16237 created in Modula-2 as they can in C or C@t{++}. However, because an
16238 address can be specified by an integral constant, the construct
16239 @samp{@{@var{type}@}@var{adrexp}} is still useful.
16241 @cindex @code{#} in Modula-2
16242 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
16243 interpreted as the beginning of a comment. Use @code{<>} instead.
16249 The extensions made to @value{GDBN} for Ada only support
16250 output from the @sc{gnu} Ada (GNAT) compiler.
16251 Other Ada compilers are not currently supported, and
16252 attempting to debug executables produced by them is most likely
16256 @cindex expressions in Ada
16258 * Ada Mode Intro:: General remarks on the Ada syntax
16259 and semantics supported by Ada mode
16261 * Omissions from Ada:: Restrictions on the Ada expression syntax.
16262 * Additions to Ada:: Extensions of the Ada expression syntax.
16263 * Overloading support for Ada:: Support for expressions involving overloaded
16265 * Stopping Before Main Program:: Debugging the program during elaboration.
16266 * Ada Exceptions:: Ada Exceptions
16267 * Ada Tasks:: Listing and setting breakpoints in tasks.
16268 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
16269 * Ravenscar Profile:: Tasking Support when using the Ravenscar
16271 * Ada Glitches:: Known peculiarities of Ada mode.
16274 @node Ada Mode Intro
16275 @subsubsection Introduction
16276 @cindex Ada mode, general
16278 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
16279 syntax, with some extensions.
16280 The philosophy behind the design of this subset is
16284 That @value{GDBN} should provide basic literals and access to operations for
16285 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
16286 leaving more sophisticated computations to subprograms written into the
16287 program (which therefore may be called from @value{GDBN}).
16290 That type safety and strict adherence to Ada language restrictions
16291 are not particularly important to the @value{GDBN} user.
16294 That brevity is important to the @value{GDBN} user.
16297 Thus, for brevity, the debugger acts as if all names declared in
16298 user-written packages are directly visible, even if they are not visible
16299 according to Ada rules, thus making it unnecessary to fully qualify most
16300 names with their packages, regardless of context. Where this causes
16301 ambiguity, @value{GDBN} asks the user's intent.
16303 The debugger will start in Ada mode if it detects an Ada main program.
16304 As for other languages, it will enter Ada mode when stopped in a program that
16305 was translated from an Ada source file.
16307 While in Ada mode, you may use `@t{--}' for comments. This is useful
16308 mostly for documenting command files. The standard @value{GDBN} comment
16309 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
16310 middle (to allow based literals).
16312 @node Omissions from Ada
16313 @subsubsection Omissions from Ada
16314 @cindex Ada, omissions from
16316 Here are the notable omissions from the subset:
16320 Only a subset of the attributes are supported:
16324 @t{'First}, @t{'Last}, and @t{'Length}
16325 on array objects (not on types and subtypes).
16328 @t{'Min} and @t{'Max}.
16331 @t{'Pos} and @t{'Val}.
16337 @t{'Range} on array objects (not subtypes), but only as the right
16338 operand of the membership (@code{in}) operator.
16341 @t{'Access}, @t{'Unchecked_Access}, and
16342 @t{'Unrestricted_Access} (a GNAT extension).
16350 @code{Characters.Latin_1} are not available and
16351 concatenation is not implemented. Thus, escape characters in strings are
16352 not currently available.
16355 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
16356 equality of representations. They will generally work correctly
16357 for strings and arrays whose elements have integer or enumeration types.
16358 They may not work correctly for arrays whose element
16359 types have user-defined equality, for arrays of real values
16360 (in particular, IEEE-conformant floating point, because of negative
16361 zeroes and NaNs), and for arrays whose elements contain unused bits with
16362 indeterminate values.
16365 The other component-by-component array operations (@code{and}, @code{or},
16366 @code{xor}, @code{not}, and relational tests other than equality)
16367 are not implemented.
16370 @cindex array aggregates (Ada)
16371 @cindex record aggregates (Ada)
16372 @cindex aggregates (Ada)
16373 There is limited support for array and record aggregates. They are
16374 permitted only on the right sides of assignments, as in these examples:
16377 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
16378 (@value{GDBP}) set An_Array := (1, others => 0)
16379 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
16380 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
16381 (@value{GDBP}) set A_Record := (1, "Peter", True);
16382 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
16386 discriminant's value by assigning an aggregate has an
16387 undefined effect if that discriminant is used within the record.
16388 However, you can first modify discriminants by directly assigning to
16389 them (which normally would not be allowed in Ada), and then performing an
16390 aggregate assignment. For example, given a variable @code{A_Rec}
16391 declared to have a type such as:
16394 type Rec (Len : Small_Integer := 0) is record
16396 Vals : IntArray (1 .. Len);
16400 you can assign a value with a different size of @code{Vals} with two
16404 (@value{GDBP}) set A_Rec.Len := 4
16405 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
16408 As this example also illustrates, @value{GDBN} is very loose about the usual
16409 rules concerning aggregates. You may leave out some of the
16410 components of an array or record aggregate (such as the @code{Len}
16411 component in the assignment to @code{A_Rec} above); they will retain their
16412 original values upon assignment. You may freely use dynamic values as
16413 indices in component associations. You may even use overlapping or
16414 redundant component associations, although which component values are
16415 assigned in such cases is not defined.
16418 Calls to dispatching subprograms are not implemented.
16421 The overloading algorithm is much more limited (i.e., less selective)
16422 than that of real Ada. It makes only limited use of the context in
16423 which a subexpression appears to resolve its meaning, and it is much
16424 looser in its rules for allowing type matches. As a result, some
16425 function calls will be ambiguous, and the user will be asked to choose
16426 the proper resolution.
16429 The @code{new} operator is not implemented.
16432 Entry calls are not implemented.
16435 Aside from printing, arithmetic operations on the native VAX floating-point
16436 formats are not supported.
16439 It is not possible to slice a packed array.
16442 The names @code{True} and @code{False}, when not part of a qualified name,
16443 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
16445 Should your program
16446 redefine these names in a package or procedure (at best a dubious practice),
16447 you will have to use fully qualified names to access their new definitions.
16450 @node Additions to Ada
16451 @subsubsection Additions to Ada
16452 @cindex Ada, deviations from
16454 As it does for other languages, @value{GDBN} makes certain generic
16455 extensions to Ada (@pxref{Expressions}):
16459 If the expression @var{E} is a variable residing in memory (typically
16460 a local variable or array element) and @var{N} is a positive integer,
16461 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
16462 @var{N}-1 adjacent variables following it in memory as an array. In
16463 Ada, this operator is generally not necessary, since its prime use is
16464 in displaying parts of an array, and slicing will usually do this in
16465 Ada. However, there are occasional uses when debugging programs in
16466 which certain debugging information has been optimized away.
16469 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
16470 appears in function or file @var{B}.'' When @var{B} is a file name,
16471 you must typically surround it in single quotes.
16474 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
16475 @var{type} that appears at address @var{addr}.''
16478 A name starting with @samp{$} is a convenience variable
16479 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
16482 In addition, @value{GDBN} provides a few other shortcuts and outright
16483 additions specific to Ada:
16487 The assignment statement is allowed as an expression, returning
16488 its right-hand operand as its value. Thus, you may enter
16491 (@value{GDBP}) set x := y + 3
16492 (@value{GDBP}) print A(tmp := y + 1)
16496 The semicolon is allowed as an ``operator,'' returning as its value
16497 the value of its right-hand operand.
16498 This allows, for example,
16499 complex conditional breaks:
16502 (@value{GDBP}) break f
16503 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
16507 Rather than use catenation and symbolic character names to introduce special
16508 characters into strings, one may instead use a special bracket notation,
16509 which is also used to print strings. A sequence of characters of the form
16510 @samp{["@var{XX}"]} within a string or character literal denotes the
16511 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
16512 sequence of characters @samp{["""]} also denotes a single quotation mark
16513 in strings. For example,
16515 "One line.["0a"]Next line.["0a"]"
16518 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
16522 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
16523 @t{'Max} is optional (and is ignored in any case). For example, it is valid
16527 (@value{GDBP}) print 'max(x, y)
16531 When printing arrays, @value{GDBN} uses positional notation when the
16532 array has a lower bound of 1, and uses a modified named notation otherwise.
16533 For example, a one-dimensional array of three integers with a lower bound
16534 of 3 might print as
16541 That is, in contrast to valid Ada, only the first component has a @code{=>}
16545 You may abbreviate attributes in expressions with any unique,
16546 multi-character subsequence of
16547 their names (an exact match gets preference).
16548 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
16549 in place of @t{a'length}.
16552 @cindex quoting Ada internal identifiers
16553 Since Ada is case-insensitive, the debugger normally maps identifiers you type
16554 to lower case. The GNAT compiler uses upper-case characters for
16555 some of its internal identifiers, which are normally of no interest to users.
16556 For the rare occasions when you actually have to look at them,
16557 enclose them in angle brackets to avoid the lower-case mapping.
16560 (@value{GDBP}) print <JMPBUF_SAVE>[0]
16564 Printing an object of class-wide type or dereferencing an
16565 access-to-class-wide value will display all the components of the object's
16566 specific type (as indicated by its run-time tag). Likewise, component
16567 selection on such a value will operate on the specific type of the
16572 @node Overloading support for Ada
16573 @subsubsection Overloading support for Ada
16574 @cindex overloading, Ada
16576 The debugger supports limited overloading. Given a subprogram call in which
16577 the function symbol has multiple definitions, it will use the number of
16578 actual parameters and some information about their types to attempt to narrow
16579 the set of definitions. It also makes very limited use of context, preferring
16580 procedures to functions in the context of the @code{call} command, and
16581 functions to procedures elsewhere.
16583 If, after narrowing, the set of matching definitions still contains more than
16584 one definition, @value{GDBN} will display a menu to query which one it should
16588 (@value{GDBP}) print f(1)
16589 Multiple matches for f
16591 [1] foo.f (integer) return boolean at foo.adb:23
16592 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
16596 In this case, just select one menu entry either to cancel expression evaluation
16597 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
16598 instance (type the corresponding number and press @key{RET}).
16600 Here are a couple of commands to customize @value{GDBN}'s behavior in this
16605 @kindex set ada print-signatures
16606 @item set ada print-signatures
16607 Control whether parameter types and return types are displayed in overloads
16608 selection menus. It is @code{on} by default.
16609 @xref{Overloading support for Ada}.
16611 @kindex show ada print-signatures
16612 @item show ada print-signatures
16613 Show the current setting for displaying parameter types and return types in
16614 overloads selection menu.
16615 @xref{Overloading support for Ada}.
16619 @node Stopping Before Main Program
16620 @subsubsection Stopping at the Very Beginning
16622 @cindex breakpointing Ada elaboration code
16623 It is sometimes necessary to debug the program during elaboration, and
16624 before reaching the main procedure.
16625 As defined in the Ada Reference
16626 Manual, the elaboration code is invoked from a procedure called
16627 @code{adainit}. To run your program up to the beginning of
16628 elaboration, simply use the following two commands:
16629 @code{tbreak adainit} and @code{run}.
16631 @node Ada Exceptions
16632 @subsubsection Ada Exceptions
16634 A command is provided to list all Ada exceptions:
16637 @kindex info exceptions
16638 @item info exceptions
16639 @itemx info exceptions @var{regexp}
16640 The @code{info exceptions} command allows you to list all Ada exceptions
16641 defined within the program being debugged, as well as their addresses.
16642 With a regular expression, @var{regexp}, as argument, only those exceptions
16643 whose names match @var{regexp} are listed.
16646 Below is a small example, showing how the command can be used, first
16647 without argument, and next with a regular expression passed as an
16651 (@value{GDBP}) info exceptions
16652 All defined Ada exceptions:
16653 constraint_error: 0x613da0
16654 program_error: 0x613d20
16655 storage_error: 0x613ce0
16656 tasking_error: 0x613ca0
16657 const.aint_global_e: 0x613b00
16658 (@value{GDBP}) info exceptions const.aint
16659 All Ada exceptions matching regular expression "const.aint":
16660 constraint_error: 0x613da0
16661 const.aint_global_e: 0x613b00
16664 It is also possible to ask @value{GDBN} to stop your program's execution
16665 when an exception is raised. For more details, see @ref{Set Catchpoints}.
16668 @subsubsection Extensions for Ada Tasks
16669 @cindex Ada, tasking
16671 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
16672 @value{GDBN} provides the following task-related commands:
16677 This command shows a list of current Ada tasks, as in the following example:
16684 (@value{GDBP}) info tasks
16685 ID TID P-ID Pri State Name
16686 1 8088000 0 15 Child Activation Wait main_task
16687 2 80a4000 1 15 Accept Statement b
16688 3 809a800 1 15 Child Activation Wait a
16689 * 4 80ae800 3 15 Runnable c
16694 In this listing, the asterisk before the last task indicates it to be the
16695 task currently being inspected.
16699 Represents @value{GDBN}'s internal task number.
16705 The parent's task ID (@value{GDBN}'s internal task number).
16708 The base priority of the task.
16711 Current state of the task.
16715 The task has been created but has not been activated. It cannot be
16719 The task is not blocked for any reason known to Ada. (It may be waiting
16720 for a mutex, though.) It is conceptually "executing" in normal mode.
16723 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
16724 that were waiting on terminate alternatives have been awakened and have
16725 terminated themselves.
16727 @item Child Activation Wait
16728 The task is waiting for created tasks to complete activation.
16730 @item Accept Statement
16731 The task is waiting on an accept or selective wait statement.
16733 @item Waiting on entry call
16734 The task is waiting on an entry call.
16736 @item Async Select Wait
16737 The task is waiting to start the abortable part of an asynchronous
16741 The task is waiting on a select statement with only a delay
16744 @item Child Termination Wait
16745 The task is sleeping having completed a master within itself, and is
16746 waiting for the tasks dependent on that master to become terminated or
16747 waiting on a terminate Phase.
16749 @item Wait Child in Term Alt
16750 The task is sleeping waiting for tasks on terminate alternatives to
16751 finish terminating.
16753 @item Accepting RV with @var{taskno}
16754 The task is accepting a rendez-vous with the task @var{taskno}.
16758 Name of the task in the program.
16762 @kindex info task @var{taskno}
16763 @item info task @var{taskno}
16764 This command shows detailled informations on the specified task, as in
16765 the following example:
16770 (@value{GDBP}) info tasks
16771 ID TID P-ID Pri State Name
16772 1 8077880 0 15 Child Activation Wait main_task
16773 * 2 807c468 1 15 Runnable task_1
16774 (@value{GDBP}) info task 2
16775 Ada Task: 0x807c468
16778 Parent: 1 (main_task)
16784 @kindex task@r{ (Ada)}
16785 @cindex current Ada task ID
16786 This command prints the ID of the current task.
16792 (@value{GDBP}) info tasks
16793 ID TID P-ID Pri State Name
16794 1 8077870 0 15 Child Activation Wait main_task
16795 * 2 807c458 1 15 Runnable t
16796 (@value{GDBP}) task
16797 [Current task is 2]
16800 @item task @var{taskno}
16801 @cindex Ada task switching
16802 This command is like the @code{thread @var{thread-id}}
16803 command (@pxref{Threads}). It switches the context of debugging
16804 from the current task to the given task.
16810 (@value{GDBP}) info tasks
16811 ID TID P-ID Pri State Name
16812 1 8077870 0 15 Child Activation Wait main_task
16813 * 2 807c458 1 15 Runnable t
16814 (@value{GDBP}) task 1
16815 [Switching to task 1]
16816 #0 0x8067726 in pthread_cond_wait ()
16818 #0 0x8067726 in pthread_cond_wait ()
16819 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
16820 #2 0x805cb63 in system.task_primitives.operations.sleep ()
16821 #3 0x806153e in system.tasking.stages.activate_tasks ()
16822 #4 0x804aacc in un () at un.adb:5
16825 @item break @var{location} task @var{taskno}
16826 @itemx break @var{location} task @var{taskno} if @dots{}
16827 @cindex breakpoints and tasks, in Ada
16828 @cindex task breakpoints, in Ada
16829 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
16830 These commands are like the @code{break @dots{} thread @dots{}}
16831 command (@pxref{Thread Stops}). The
16832 @var{location} argument specifies source lines, as described
16833 in @ref{Specify Location}.
16835 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
16836 to specify that you only want @value{GDBN} to stop the program when a
16837 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
16838 numeric task identifiers assigned by @value{GDBN}, shown in the first
16839 column of the @samp{info tasks} display.
16841 If you do not specify @samp{task @var{taskno}} when you set a
16842 breakpoint, the breakpoint applies to @emph{all} tasks of your
16845 You can use the @code{task} qualifier on conditional breakpoints as
16846 well; in this case, place @samp{task @var{taskno}} before the
16847 breakpoint condition (before the @code{if}).
16855 (@value{GDBP}) info tasks
16856 ID TID P-ID Pri State Name
16857 1 140022020 0 15 Child Activation Wait main_task
16858 2 140045060 1 15 Accept/Select Wait t2
16859 3 140044840 1 15 Runnable t1
16860 * 4 140056040 1 15 Runnable t3
16861 (@value{GDBP}) b 15 task 2
16862 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
16863 (@value{GDBP}) cont
16868 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
16870 (@value{GDBP}) info tasks
16871 ID TID P-ID Pri State Name
16872 1 140022020 0 15 Child Activation Wait main_task
16873 * 2 140045060 1 15 Runnable t2
16874 3 140044840 1 15 Runnable t1
16875 4 140056040 1 15 Delay Sleep t3
16879 @node Ada Tasks and Core Files
16880 @subsubsection Tasking Support when Debugging Core Files
16881 @cindex Ada tasking and core file debugging
16883 When inspecting a core file, as opposed to debugging a live program,
16884 tasking support may be limited or even unavailable, depending on
16885 the platform being used.
16886 For instance, on x86-linux, the list of tasks is available, but task
16887 switching is not supported.
16889 On certain platforms, the debugger needs to perform some
16890 memory writes in order to provide Ada tasking support. When inspecting
16891 a core file, this means that the core file must be opened with read-write
16892 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
16893 Under these circumstances, you should make a backup copy of the core
16894 file before inspecting it with @value{GDBN}.
16896 @node Ravenscar Profile
16897 @subsubsection Tasking Support when using the Ravenscar Profile
16898 @cindex Ravenscar Profile
16900 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
16901 specifically designed for systems with safety-critical real-time
16905 @kindex set ravenscar task-switching on
16906 @cindex task switching with program using Ravenscar Profile
16907 @item set ravenscar task-switching on
16908 Allows task switching when debugging a program that uses the Ravenscar
16909 Profile. This is the default.
16911 @kindex set ravenscar task-switching off
16912 @item set ravenscar task-switching off
16913 Turn off task switching when debugging a program that uses the Ravenscar
16914 Profile. This is mostly intended to disable the code that adds support
16915 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
16916 the Ravenscar runtime is preventing @value{GDBN} from working properly.
16917 To be effective, this command should be run before the program is started.
16919 @kindex show ravenscar task-switching
16920 @item show ravenscar task-switching
16921 Show whether it is possible to switch from task to task in a program
16922 using the Ravenscar Profile.
16927 @subsubsection Known Peculiarities of Ada Mode
16928 @cindex Ada, problems
16930 Besides the omissions listed previously (@pxref{Omissions from Ada}),
16931 we know of several problems with and limitations of Ada mode in
16933 some of which will be fixed with planned future releases of the debugger
16934 and the GNU Ada compiler.
16938 Static constants that the compiler chooses not to materialize as objects in
16939 storage are invisible to the debugger.
16942 Named parameter associations in function argument lists are ignored (the
16943 argument lists are treated as positional).
16946 Many useful library packages are currently invisible to the debugger.
16949 Fixed-point arithmetic, conversions, input, and output is carried out using
16950 floating-point arithmetic, and may give results that only approximate those on
16954 The GNAT compiler never generates the prefix @code{Standard} for any of
16955 the standard symbols defined by the Ada language. @value{GDBN} knows about
16956 this: it will strip the prefix from names when you use it, and will never
16957 look for a name you have so qualified among local symbols, nor match against
16958 symbols in other packages or subprograms. If you have
16959 defined entities anywhere in your program other than parameters and
16960 local variables whose simple names match names in @code{Standard},
16961 GNAT's lack of qualification here can cause confusion. When this happens,
16962 you can usually resolve the confusion
16963 by qualifying the problematic names with package
16964 @code{Standard} explicitly.
16967 Older versions of the compiler sometimes generate erroneous debugging
16968 information, resulting in the debugger incorrectly printing the value
16969 of affected entities. In some cases, the debugger is able to work
16970 around an issue automatically. In other cases, the debugger is able
16971 to work around the issue, but the work-around has to be specifically
16974 @kindex set ada trust-PAD-over-XVS
16975 @kindex show ada trust-PAD-over-XVS
16978 @item set ada trust-PAD-over-XVS on
16979 Configure GDB to strictly follow the GNAT encoding when computing the
16980 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
16981 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
16982 a complete description of the encoding used by the GNAT compiler).
16983 This is the default.
16985 @item set ada trust-PAD-over-XVS off
16986 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
16987 sometimes prints the wrong value for certain entities, changing @code{ada
16988 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
16989 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
16990 @code{off}, but this incurs a slight performance penalty, so it is
16991 recommended to leave this setting to @code{on} unless necessary.
16995 @cindex GNAT descriptive types
16996 @cindex GNAT encoding
16997 Internally, the debugger also relies on the compiler following a number
16998 of conventions known as the @samp{GNAT Encoding}, all documented in
16999 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
17000 how the debugging information should be generated for certain types.
17001 In particular, this convention makes use of @dfn{descriptive types},
17002 which are artificial types generated purely to help the debugger.
17004 These encodings were defined at a time when the debugging information
17005 format used was not powerful enough to describe some of the more complex
17006 types available in Ada. Since DWARF allows us to express nearly all
17007 Ada features, the long-term goal is to slowly replace these descriptive
17008 types by their pure DWARF equivalent. To facilitate that transition,
17009 a new maintenance option is available to force the debugger to ignore
17010 those descriptive types. It allows the user to quickly evaluate how
17011 well @value{GDBN} works without them.
17015 @kindex maint ada set ignore-descriptive-types
17016 @item maintenance ada set ignore-descriptive-types [on|off]
17017 Control whether the debugger should ignore descriptive types.
17018 The default is not to ignore descriptives types (@code{off}).
17020 @kindex maint ada show ignore-descriptive-types
17021 @item maintenance ada show ignore-descriptive-types
17022 Show if descriptive types are ignored by @value{GDBN}.
17026 @node Unsupported Languages
17027 @section Unsupported Languages
17029 @cindex unsupported languages
17030 @cindex minimal language
17031 In addition to the other fully-supported programming languages,
17032 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
17033 It does not represent a real programming language, but provides a set
17034 of capabilities close to what the C or assembly languages provide.
17035 This should allow most simple operations to be performed while debugging
17036 an application that uses a language currently not supported by @value{GDBN}.
17038 If the language is set to @code{auto}, @value{GDBN} will automatically
17039 select this language if the current frame corresponds to an unsupported
17043 @chapter Examining the Symbol Table
17045 The commands described in this chapter allow you to inquire about the
17046 symbols (names of variables, functions and types) defined in your
17047 program. This information is inherent in the text of your program and
17048 does not change as your program executes. @value{GDBN} finds it in your
17049 program's symbol table, in the file indicated when you started @value{GDBN}
17050 (@pxref{File Options, ,Choosing Files}), or by one of the
17051 file-management commands (@pxref{Files, ,Commands to Specify Files}).
17053 @cindex symbol names
17054 @cindex names of symbols
17055 @cindex quoting names
17056 @anchor{quoting names}
17057 Occasionally, you may need to refer to symbols that contain unusual
17058 characters, which @value{GDBN} ordinarily treats as word delimiters. The
17059 most frequent case is in referring to static variables in other
17060 source files (@pxref{Variables,,Program Variables}). File names
17061 are recorded in object files as debugging symbols, but @value{GDBN} would
17062 ordinarily parse a typical file name, like @file{foo.c}, as the three words
17063 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
17064 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
17071 looks up the value of @code{x} in the scope of the file @file{foo.c}.
17074 @cindex case-insensitive symbol names
17075 @cindex case sensitivity in symbol names
17076 @kindex set case-sensitive
17077 @item set case-sensitive on
17078 @itemx set case-sensitive off
17079 @itemx set case-sensitive auto
17080 Normally, when @value{GDBN} looks up symbols, it matches their names
17081 with case sensitivity determined by the current source language.
17082 Occasionally, you may wish to control that. The command @code{set
17083 case-sensitive} lets you do that by specifying @code{on} for
17084 case-sensitive matches or @code{off} for case-insensitive ones. If
17085 you specify @code{auto}, case sensitivity is reset to the default
17086 suitable for the source language. The default is case-sensitive
17087 matches for all languages except for Fortran, for which the default is
17088 case-insensitive matches.
17090 @kindex show case-sensitive
17091 @item show case-sensitive
17092 This command shows the current setting of case sensitivity for symbols
17095 @kindex set print type methods
17096 @item set print type methods
17097 @itemx set print type methods on
17098 @itemx set print type methods off
17099 Normally, when @value{GDBN} prints a class, it displays any methods
17100 declared in that class. You can control this behavior either by
17101 passing the appropriate flag to @code{ptype}, or using @command{set
17102 print type methods}. Specifying @code{on} will cause @value{GDBN} to
17103 display the methods; this is the default. Specifying @code{off} will
17104 cause @value{GDBN} to omit the methods.
17106 @kindex show print type methods
17107 @item show print type methods
17108 This command shows the current setting of method display when printing
17111 @kindex set print type nested-type-limit
17112 @item set print type nested-type-limit @var{limit}
17113 @itemx set print type nested-type-limit unlimited
17114 Set the limit of displayed nested types that the type printer will
17115 show. A @var{limit} of @code{unlimited} or @code{-1} will show all
17116 nested definitions. By default, the type printer will not show any nested
17117 types defined in classes.
17119 @kindex show print type nested-type-limit
17120 @item show print type nested-type-limit
17121 This command shows the current display limit of nested types when
17124 @kindex set print type typedefs
17125 @item set print type typedefs
17126 @itemx set print type typedefs on
17127 @itemx set print type typedefs off
17129 Normally, when @value{GDBN} prints a class, it displays any typedefs
17130 defined in that class. You can control this behavior either by
17131 passing the appropriate flag to @code{ptype}, or using @command{set
17132 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
17133 display the typedef definitions; this is the default. Specifying
17134 @code{off} will cause @value{GDBN} to omit the typedef definitions.
17135 Note that this controls whether the typedef definition itself is
17136 printed, not whether typedef names are substituted when printing other
17139 @kindex show print type typedefs
17140 @item show print type typedefs
17141 This command shows the current setting of typedef display when
17144 @kindex info address
17145 @cindex address of a symbol
17146 @item info address @var{symbol}
17147 Describe where the data for @var{symbol} is stored. For a register
17148 variable, this says which register it is kept in. For a non-register
17149 local variable, this prints the stack-frame offset at which the variable
17152 Note the contrast with @samp{print &@var{symbol}}, which does not work
17153 at all for a register variable, and for a stack local variable prints
17154 the exact address of the current instantiation of the variable.
17156 @kindex info symbol
17157 @cindex symbol from address
17158 @cindex closest symbol and offset for an address
17159 @item info symbol @var{addr}
17160 Print the name of a symbol which is stored at the address @var{addr}.
17161 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
17162 nearest symbol and an offset from it:
17165 (@value{GDBP}) info symbol 0x54320
17166 _initialize_vx + 396 in section .text
17170 This is the opposite of the @code{info address} command. You can use
17171 it to find out the name of a variable or a function given its address.
17173 For dynamically linked executables, the name of executable or shared
17174 library containing the symbol is also printed:
17177 (@value{GDBP}) info symbol 0x400225
17178 _start + 5 in section .text of /tmp/a.out
17179 (@value{GDBP}) info symbol 0x2aaaac2811cf
17180 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
17185 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
17186 Demangle @var{name}.
17187 If @var{language} is provided it is the name of the language to demangle
17188 @var{name} in. Otherwise @var{name} is demangled in the current language.
17190 The @samp{--} option specifies the end of options,
17191 and is useful when @var{name} begins with a dash.
17193 The parameter @code{demangle-style} specifies how to interpret the kind
17194 of mangling used. @xref{Print Settings}.
17197 @item whatis[/@var{flags}] [@var{arg}]
17198 Print the data type of @var{arg}, which can be either an expression
17199 or a name of a data type. With no argument, print the data type of
17200 @code{$}, the last value in the value history.
17202 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
17203 is not actually evaluated, and any side-effecting operations (such as
17204 assignments or function calls) inside it do not take place.
17206 If @var{arg} is a variable or an expression, @code{whatis} prints its
17207 literal type as it is used in the source code. If the type was
17208 defined using a @code{typedef}, @code{whatis} will @emph{not} print
17209 the data type underlying the @code{typedef}. If the type of the
17210 variable or the expression is a compound data type, such as
17211 @code{struct} or @code{class}, @code{whatis} never prints their
17212 fields or methods. It just prints the @code{struct}/@code{class}
17213 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
17214 such a compound data type, use @code{ptype}.
17216 If @var{arg} is a type name that was defined using @code{typedef},
17217 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
17218 Unrolling means that @code{whatis} will show the underlying type used
17219 in the @code{typedef} declaration of @var{arg}. However, if that
17220 underlying type is also a @code{typedef}, @code{whatis} will not
17223 For C code, the type names may also have the form @samp{class
17224 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
17225 @var{union-tag}} or @samp{enum @var{enum-tag}}.
17227 @var{flags} can be used to modify how the type is displayed.
17228 Available flags are:
17232 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
17233 parameters and typedefs defined in a class when printing the class'
17234 members. The @code{/r} flag disables this.
17237 Do not print methods defined in the class.
17240 Print methods defined in the class. This is the default, but the flag
17241 exists in case you change the default with @command{set print type methods}.
17244 Do not print typedefs defined in the class. Note that this controls
17245 whether the typedef definition itself is printed, not whether typedef
17246 names are substituted when printing other types.
17249 Print typedefs defined in the class. This is the default, but the flag
17250 exists in case you change the default with @command{set print type typedefs}.
17253 Print the offsets and sizes of fields in a struct, similar to what the
17254 @command{pahole} tool does. This option implies the @code{/tm} flags.
17256 For example, given the following declarations:
17292 Issuing a @kbd{ptype /o struct tuv} command would print:
17295 (@value{GDBP}) ptype /o struct tuv
17296 /* offset | size */ type = struct tuv @{
17297 /* 0 | 4 */ int a1;
17298 /* XXX 4-byte hole */
17299 /* 8 | 8 */ char *a2;
17300 /* 16 | 4 */ int a3;
17302 /* total size (bytes): 24 */
17306 Notice the format of the first column of comments. There, you can
17307 find two parts separated by the @samp{|} character: the @emph{offset},
17308 which indicates where the field is located inside the struct, in
17309 bytes, and the @emph{size} of the field. Another interesting line is
17310 the marker of a @emph{hole} in the struct, indicating that it may be
17311 possible to pack the struct and make it use less space by reorganizing
17314 It is also possible to print offsets inside an union:
17317 (@value{GDBP}) ptype /o union qwe
17318 /* offset | size */ type = union qwe @{
17319 /* 24 */ struct tuv @{
17320 /* 0 | 4 */ int a1;
17321 /* XXX 4-byte hole */
17322 /* 8 | 8 */ char *a2;
17323 /* 16 | 4 */ int a3;
17325 /* total size (bytes): 24 */
17327 /* 40 */ struct xyz @{
17328 /* 0 | 4 */ int f1;
17329 /* 4 | 1 */ char f2;
17330 /* XXX 3-byte hole */
17331 /* 8 | 8 */ void *f3;
17332 /* 16 | 24 */ struct tuv @{
17333 /* 16 | 4 */ int a1;
17334 /* XXX 4-byte hole */
17335 /* 24 | 8 */ char *a2;
17336 /* 32 | 4 */ int a3;
17338 /* total size (bytes): 24 */
17341 /* total size (bytes): 40 */
17344 /* total size (bytes): 40 */
17348 In this case, since @code{struct tuv} and @code{struct xyz} occupy the
17349 same space (because we are dealing with an union), the offset is not
17350 printed for them. However, you can still examine the offset of each
17351 of these structures' fields.
17353 Another useful scenario is printing the offsets of a struct containing
17357 (@value{GDBP}) ptype /o struct tyu
17358 /* offset | size */ type = struct tyu @{
17359 /* 0:31 | 4 */ int a1 : 1;
17360 /* 0:28 | 4 */ int a2 : 3;
17361 /* 0: 5 | 4 */ int a3 : 23;
17362 /* 3: 3 | 1 */ signed char a4 : 2;
17363 /* XXX 3-bit hole */
17364 /* XXX 4-byte hole */
17365 /* 8 | 8 */ int64_t a5;
17366 /* 16:27 | 4 */ int a6 : 5;
17367 /* 16:56 | 8 */ int64_t a7 : 3;
17369 /* total size (bytes): 24 */
17373 Note how the offset information is now extended to also include how
17374 many bits are left to be used in each bitfield.
17378 @item ptype[/@var{flags}] [@var{arg}]
17379 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
17380 detailed description of the type, instead of just the name of the type.
17381 @xref{Expressions, ,Expressions}.
17383 Contrary to @code{whatis}, @code{ptype} always unrolls any
17384 @code{typedef}s in its argument declaration, whether the argument is
17385 a variable, expression, or a data type. This means that @code{ptype}
17386 of a variable or an expression will not print literally its type as
17387 present in the source code---use @code{whatis} for that. @code{typedef}s at
17388 the pointer or reference targets are also unrolled. Only @code{typedef}s of
17389 fields, methods and inner @code{class typedef}s of @code{struct}s,
17390 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
17392 For example, for this variable declaration:
17395 typedef double real_t;
17396 struct complex @{ real_t real; double imag; @};
17397 typedef struct complex complex_t;
17399 real_t *real_pointer_var;
17403 the two commands give this output:
17407 (@value{GDBP}) whatis var
17409 (@value{GDBP}) ptype var
17410 type = struct complex @{
17414 (@value{GDBP}) whatis complex_t
17415 type = struct complex
17416 (@value{GDBP}) whatis struct complex
17417 type = struct complex
17418 (@value{GDBP}) ptype struct complex
17419 type = struct complex @{
17423 (@value{GDBP}) whatis real_pointer_var
17425 (@value{GDBP}) ptype real_pointer_var
17431 As with @code{whatis}, using @code{ptype} without an argument refers to
17432 the type of @code{$}, the last value in the value history.
17434 @cindex incomplete type
17435 Sometimes, programs use opaque data types or incomplete specifications
17436 of complex data structure. If the debug information included in the
17437 program does not allow @value{GDBN} to display a full declaration of
17438 the data type, it will say @samp{<incomplete type>}. For example,
17439 given these declarations:
17443 struct foo *fooptr;
17447 but no definition for @code{struct foo} itself, @value{GDBN} will say:
17450 (@value{GDBP}) ptype foo
17451 $1 = <incomplete type>
17455 ``Incomplete type'' is C terminology for data types that are not
17456 completely specified.
17458 @cindex unknown type
17459 Othertimes, information about a variable's type is completely absent
17460 from the debug information included in the program. This most often
17461 happens when the program or library where the variable is defined
17462 includes no debug information at all. @value{GDBN} knows the variable
17463 exists from inspecting the linker/loader symbol table (e.g., the ELF
17464 dynamic symbol table), but such symbols do not contain type
17465 information. Inspecting the type of a (global) variable for which
17466 @value{GDBN} has no type information shows:
17469 (@value{GDBP}) ptype var
17470 type = <data variable, no debug info>
17473 @xref{Variables, no debug info variables}, for how to print the values
17477 @item info types @var{regexp}
17479 Print a brief description of all types whose names match the regular
17480 expression @var{regexp} (or all types in your program, if you supply
17481 no argument). Each complete typename is matched as though it were a
17482 complete line; thus, @samp{i type value} gives information on all
17483 types in your program whose names include the string @code{value}, but
17484 @samp{i type ^value$} gives information only on types whose complete
17485 name is @code{value}.
17487 This command differs from @code{ptype} in two ways: first, like
17488 @code{whatis}, it does not print a detailed description; second, it
17489 lists all source files where a type is defined.
17491 @kindex info type-printers
17492 @item info type-printers
17493 Versions of @value{GDBN} that ship with Python scripting enabled may
17494 have ``type printers'' available. When using @command{ptype} or
17495 @command{whatis}, these printers are consulted when the name of a type
17496 is needed. @xref{Type Printing API}, for more information on writing
17499 @code{info type-printers} displays all the available type printers.
17501 @kindex enable type-printer
17502 @kindex disable type-printer
17503 @item enable type-printer @var{name}@dots{}
17504 @item disable type-printer @var{name}@dots{}
17505 These commands can be used to enable or disable type printers.
17508 @cindex local variables
17509 @item info scope @var{location}
17510 List all the variables local to a particular scope. This command
17511 accepts a @var{location} argument---a function name, a source line, or
17512 an address preceded by a @samp{*}, and prints all the variables local
17513 to the scope defined by that location. (@xref{Specify Location}, for
17514 details about supported forms of @var{location}.) For example:
17517 (@value{GDBP}) @b{info scope command_line_handler}
17518 Scope for command_line_handler:
17519 Symbol rl is an argument at stack/frame offset 8, length 4.
17520 Symbol linebuffer is in static storage at address 0x150a18, length 4.
17521 Symbol linelength is in static storage at address 0x150a1c, length 4.
17522 Symbol p is a local variable in register $esi, length 4.
17523 Symbol p1 is a local variable in register $ebx, length 4.
17524 Symbol nline is a local variable in register $edx, length 4.
17525 Symbol repeat is a local variable at frame offset -8, length 4.
17529 This command is especially useful for determining what data to collect
17530 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
17533 @kindex info source
17535 Show information about the current source file---that is, the source file for
17536 the function containing the current point of execution:
17539 the name of the source file, and the directory containing it,
17541 the directory it was compiled in,
17543 its length, in lines,
17545 which programming language it is written in,
17547 if the debug information provides it, the program that compiled the file
17548 (which may include, e.g., the compiler version and command line arguments),
17550 whether the executable includes debugging information for that file, and
17551 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
17553 whether the debugging information includes information about
17554 preprocessor macros.
17558 @kindex info sources
17560 Print the names of all source files in your program for which there is
17561 debugging information, organized into two lists: files whose symbols
17562 have already been read, and files whose symbols will be read when needed.
17564 @kindex info functions
17565 @item info functions
17566 Print the names and data types of all defined functions.
17568 @item info functions @var{regexp}
17569 Print the names and data types of all defined functions
17570 whose names contain a match for regular expression @var{regexp}.
17571 Thus, @samp{info fun step} finds all functions whose names
17572 include @code{step}; @samp{info fun ^step} finds those whose names
17573 start with @code{step}. If a function name contains characters
17574 that conflict with the regular expression language (e.g.@:
17575 @samp{operator*()}), they may be quoted with a backslash.
17577 @kindex info variables
17578 @item info variables
17579 Print the names and data types of all variables that are defined
17580 outside of functions (i.e.@: excluding local variables).
17582 @item info variables @var{regexp}
17583 Print the names and data types of all variables (except for local
17584 variables) whose names contain a match for regular expression
17587 @kindex info classes
17588 @cindex Objective-C, classes and selectors
17590 @itemx info classes @var{regexp}
17591 Display all Objective-C classes in your program, or
17592 (with the @var{regexp} argument) all those matching a particular regular
17595 @kindex info selectors
17596 @item info selectors
17597 @itemx info selectors @var{regexp}
17598 Display all Objective-C selectors in your program, or
17599 (with the @var{regexp} argument) all those matching a particular regular
17603 This was never implemented.
17604 @kindex info methods
17606 @itemx info methods @var{regexp}
17607 The @code{info methods} command permits the user to examine all defined
17608 methods within C@t{++} program, or (with the @var{regexp} argument) a
17609 specific set of methods found in the various C@t{++} classes. Many
17610 C@t{++} classes provide a large number of methods. Thus, the output
17611 from the @code{ptype} command can be overwhelming and hard to use. The
17612 @code{info-methods} command filters the methods, printing only those
17613 which match the regular-expression @var{regexp}.
17616 @cindex opaque data types
17617 @kindex set opaque-type-resolution
17618 @item set opaque-type-resolution on
17619 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
17620 declared as a pointer to a @code{struct}, @code{class}, or
17621 @code{union}---for example, @code{struct MyType *}---that is used in one
17622 source file although the full declaration of @code{struct MyType} is in
17623 another source file. The default is on.
17625 A change in the setting of this subcommand will not take effect until
17626 the next time symbols for a file are loaded.
17628 @item set opaque-type-resolution off
17629 Tell @value{GDBN} not to resolve opaque types. In this case, the type
17630 is printed as follows:
17632 @{<no data fields>@}
17635 @kindex show opaque-type-resolution
17636 @item show opaque-type-resolution
17637 Show whether opaque types are resolved or not.
17639 @kindex set print symbol-loading
17640 @cindex print messages when symbols are loaded
17641 @item set print symbol-loading
17642 @itemx set print symbol-loading full
17643 @itemx set print symbol-loading brief
17644 @itemx set print symbol-loading off
17645 The @code{set print symbol-loading} command allows you to control the
17646 printing of messages when @value{GDBN} loads symbol information.
17647 By default a message is printed for the executable and one for each
17648 shared library, and normally this is what you want. However, when
17649 debugging apps with large numbers of shared libraries these messages
17651 When set to @code{brief} a message is printed for each executable,
17652 and when @value{GDBN} loads a collection of shared libraries at once
17653 it will only print one message regardless of the number of shared
17654 libraries. When set to @code{off} no messages are printed.
17656 @kindex show print symbol-loading
17657 @item show print symbol-loading
17658 Show whether messages will be printed when a @value{GDBN} command
17659 entered from the keyboard causes symbol information to be loaded.
17661 @kindex maint print symbols
17662 @cindex symbol dump
17663 @kindex maint print psymbols
17664 @cindex partial symbol dump
17665 @kindex maint print msymbols
17666 @cindex minimal symbol dump
17667 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
17668 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17669 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17670 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17671 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17672 Write a dump of debugging symbol data into the file @var{filename} or
17673 the terminal if @var{filename} is unspecified.
17674 If @code{-objfile @var{objfile}} is specified, only dump symbols for
17676 If @code{-pc @var{address}} is specified, only dump symbols for the file
17677 with code at that address. Note that @var{address} may be a symbol like
17679 If @code{-source @var{source}} is specified, only dump symbols for that
17682 These commands are used to debug the @value{GDBN} symbol-reading code.
17683 These commands do not modify internal @value{GDBN} state, therefore
17684 @samp{maint print symbols} will only print symbols for already expanded symbol
17686 You can use the command @code{info sources} to find out which files these are.
17687 If you use @samp{maint print psymbols} instead, the dump shows information
17688 about symbols that @value{GDBN} only knows partially---that is, symbols
17689 defined in files that @value{GDBN} has skimmed, but not yet read completely.
17690 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
17693 @xref{Files, ,Commands to Specify Files}, for a discussion of how
17694 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
17696 @kindex maint info symtabs
17697 @kindex maint info psymtabs
17698 @cindex listing @value{GDBN}'s internal symbol tables
17699 @cindex symbol tables, listing @value{GDBN}'s internal
17700 @cindex full symbol tables, listing @value{GDBN}'s internal
17701 @cindex partial symbol tables, listing @value{GDBN}'s internal
17702 @item maint info symtabs @r{[} @var{regexp} @r{]}
17703 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
17705 List the @code{struct symtab} or @code{struct partial_symtab}
17706 structures whose names match @var{regexp}. If @var{regexp} is not
17707 given, list them all. The output includes expressions which you can
17708 copy into a @value{GDBN} debugging this one to examine a particular
17709 structure in more detail. For example:
17712 (@value{GDBP}) maint info psymtabs dwarf2read
17713 @{ objfile /home/gnu/build/gdb/gdb
17714 ((struct objfile *) 0x82e69d0)
17715 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
17716 ((struct partial_symtab *) 0x8474b10)
17719 text addresses 0x814d3c8 -- 0x8158074
17720 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
17721 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
17722 dependencies (none)
17725 (@value{GDBP}) maint info symtabs
17729 We see that there is one partial symbol table whose filename contains
17730 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
17731 and we see that @value{GDBN} has not read in any symtabs yet at all.
17732 If we set a breakpoint on a function, that will cause @value{GDBN} to
17733 read the symtab for the compilation unit containing that function:
17736 (@value{GDBP}) break dwarf2_psymtab_to_symtab
17737 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
17739 (@value{GDBP}) maint info symtabs
17740 @{ objfile /home/gnu/build/gdb/gdb
17741 ((struct objfile *) 0x82e69d0)
17742 @{ symtab /home/gnu/src/gdb/dwarf2read.c
17743 ((struct symtab *) 0x86c1f38)
17746 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
17747 linetable ((struct linetable *) 0x8370fa0)
17748 debugformat DWARF 2
17754 @kindex maint info line-table
17755 @cindex listing @value{GDBN}'s internal line tables
17756 @cindex line tables, listing @value{GDBN}'s internal
17757 @item maint info line-table @r{[} @var{regexp} @r{]}
17759 List the @code{struct linetable} from all @code{struct symtab}
17760 instances whose name matches @var{regexp}. If @var{regexp} is not
17761 given, list the @code{struct linetable} from all @code{struct symtab}.
17763 @kindex maint set symbol-cache-size
17764 @cindex symbol cache size
17765 @item maint set symbol-cache-size @var{size}
17766 Set the size of the symbol cache to @var{size}.
17767 The default size is intended to be good enough for debugging
17768 most applications. This option exists to allow for experimenting
17769 with different sizes.
17771 @kindex maint show symbol-cache-size
17772 @item maint show symbol-cache-size
17773 Show the size of the symbol cache.
17775 @kindex maint print symbol-cache
17776 @cindex symbol cache, printing its contents
17777 @item maint print symbol-cache
17778 Print the contents of the symbol cache.
17779 This is useful when debugging symbol cache issues.
17781 @kindex maint print symbol-cache-statistics
17782 @cindex symbol cache, printing usage statistics
17783 @item maint print symbol-cache-statistics
17784 Print symbol cache usage statistics.
17785 This helps determine how well the cache is being utilized.
17787 @kindex maint flush-symbol-cache
17788 @cindex symbol cache, flushing
17789 @item maint flush-symbol-cache
17790 Flush the contents of the symbol cache, all entries are removed.
17791 This command is useful when debugging the symbol cache.
17792 It is also useful when collecting performance data.
17797 @chapter Altering Execution
17799 Once you think you have found an error in your program, you might want to
17800 find out for certain whether correcting the apparent error would lead to
17801 correct results in the rest of the run. You can find the answer by
17802 experiment, using the @value{GDBN} features for altering execution of the
17805 For example, you can store new values into variables or memory
17806 locations, give your program a signal, restart it at a different
17807 address, or even return prematurely from a function.
17810 * Assignment:: Assignment to variables
17811 * Jumping:: Continuing at a different address
17812 * Signaling:: Giving your program a signal
17813 * Returning:: Returning from a function
17814 * Calling:: Calling your program's functions
17815 * Patching:: Patching your program
17816 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
17820 @section Assignment to Variables
17823 @cindex setting variables
17824 To alter the value of a variable, evaluate an assignment expression.
17825 @xref{Expressions, ,Expressions}. For example,
17832 stores the value 4 into the variable @code{x}, and then prints the
17833 value of the assignment expression (which is 4).
17834 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
17835 information on operators in supported languages.
17837 @kindex set variable
17838 @cindex variables, setting
17839 If you are not interested in seeing the value of the assignment, use the
17840 @code{set} command instead of the @code{print} command. @code{set} is
17841 really the same as @code{print} except that the expression's value is
17842 not printed and is not put in the value history (@pxref{Value History,
17843 ,Value History}). The expression is evaluated only for its effects.
17845 If the beginning of the argument string of the @code{set} command
17846 appears identical to a @code{set} subcommand, use the @code{set
17847 variable} command instead of just @code{set}. This command is identical
17848 to @code{set} except for its lack of subcommands. For example, if your
17849 program has a variable @code{width}, you get an error if you try to set
17850 a new value with just @samp{set width=13}, because @value{GDBN} has the
17851 command @code{set width}:
17854 (@value{GDBP}) whatis width
17856 (@value{GDBP}) p width
17858 (@value{GDBP}) set width=47
17859 Invalid syntax in expression.
17863 The invalid expression, of course, is @samp{=47}. In
17864 order to actually set the program's variable @code{width}, use
17867 (@value{GDBP}) set var width=47
17870 Because the @code{set} command has many subcommands that can conflict
17871 with the names of program variables, it is a good idea to use the
17872 @code{set variable} command instead of just @code{set}. For example, if
17873 your program has a variable @code{g}, you run into problems if you try
17874 to set a new value with just @samp{set g=4}, because @value{GDBN} has
17875 the command @code{set gnutarget}, abbreviated @code{set g}:
17879 (@value{GDBP}) whatis g
17883 (@value{GDBP}) set g=4
17887 The program being debugged has been started already.
17888 Start it from the beginning? (y or n) y
17889 Starting program: /home/smith/cc_progs/a.out
17890 "/home/smith/cc_progs/a.out": can't open to read symbols:
17891 Invalid bfd target.
17892 (@value{GDBP}) show g
17893 The current BFD target is "=4".
17898 The program variable @code{g} did not change, and you silently set the
17899 @code{gnutarget} to an invalid value. In order to set the variable
17903 (@value{GDBP}) set var g=4
17906 @value{GDBN} allows more implicit conversions in assignments than C; you can
17907 freely store an integer value into a pointer variable or vice versa,
17908 and you can convert any structure to any other structure that is the
17909 same length or shorter.
17910 @comment FIXME: how do structs align/pad in these conversions?
17911 @comment /doc@cygnus.com 18dec1990
17913 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
17914 construct to generate a value of specified type at a specified address
17915 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
17916 to memory location @code{0x83040} as an integer (which implies a certain size
17917 and representation in memory), and
17920 set @{int@}0x83040 = 4
17924 stores the value 4 into that memory location.
17927 @section Continuing at a Different Address
17929 Ordinarily, when you continue your program, you do so at the place where
17930 it stopped, with the @code{continue} command. You can instead continue at
17931 an address of your own choosing, with the following commands:
17935 @kindex j @r{(@code{jump})}
17936 @item jump @var{location}
17937 @itemx j @var{location}
17938 Resume execution at @var{location}. Execution stops again immediately
17939 if there is a breakpoint there. @xref{Specify Location}, for a description
17940 of the different forms of @var{location}. It is common
17941 practice to use the @code{tbreak} command in conjunction with
17942 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
17944 The @code{jump} command does not change the current stack frame, or
17945 the stack pointer, or the contents of any memory location or any
17946 register other than the program counter. If @var{location} is in
17947 a different function from the one currently executing, the results may
17948 be bizarre if the two functions expect different patterns of arguments or
17949 of local variables. For this reason, the @code{jump} command requests
17950 confirmation if the specified line is not in the function currently
17951 executing. However, even bizarre results are predictable if you are
17952 well acquainted with the machine-language code of your program.
17955 On many systems, you can get much the same effect as the @code{jump}
17956 command by storing a new value into the register @code{$pc}. The
17957 difference is that this does not start your program running; it only
17958 changes the address of where it @emph{will} run when you continue. For
17966 makes the next @code{continue} command or stepping command execute at
17967 address @code{0x485}, rather than at the address where your program stopped.
17968 @xref{Continuing and Stepping, ,Continuing and Stepping}.
17970 The most common occasion to use the @code{jump} command is to back
17971 up---perhaps with more breakpoints set---over a portion of a program
17972 that has already executed, in order to examine its execution in more
17977 @section Giving your Program a Signal
17978 @cindex deliver a signal to a program
17982 @item signal @var{signal}
17983 Resume execution where your program is stopped, but immediately give it the
17984 signal @var{signal}. The @var{signal} can be the name or the number of a
17985 signal. For example, on many systems @code{signal 2} and @code{signal
17986 SIGINT} are both ways of sending an interrupt signal.
17988 Alternatively, if @var{signal} is zero, continue execution without
17989 giving a signal. This is useful when your program stopped on account of
17990 a signal and would ordinarily see the signal when resumed with the
17991 @code{continue} command; @samp{signal 0} causes it to resume without a
17994 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
17995 delivered to the currently selected thread, not the thread that last
17996 reported a stop. This includes the situation where a thread was
17997 stopped due to a signal. So if you want to continue execution
17998 suppressing the signal that stopped a thread, you should select that
17999 same thread before issuing the @samp{signal 0} command. If you issue
18000 the @samp{signal 0} command with another thread as the selected one,
18001 @value{GDBN} detects that and asks for confirmation.
18003 Invoking the @code{signal} command is not the same as invoking the
18004 @code{kill} utility from the shell. Sending a signal with @code{kill}
18005 causes @value{GDBN} to decide what to do with the signal depending on
18006 the signal handling tables (@pxref{Signals}). The @code{signal} command
18007 passes the signal directly to your program.
18009 @code{signal} does not repeat when you press @key{RET} a second time
18010 after executing the command.
18012 @kindex queue-signal
18013 @item queue-signal @var{signal}
18014 Queue @var{signal} to be delivered immediately to the current thread
18015 when execution of the thread resumes. The @var{signal} can be the name or
18016 the number of a signal. For example, on many systems @code{signal 2} and
18017 @code{signal SIGINT} are both ways of sending an interrupt signal.
18018 The handling of the signal must be set to pass the signal to the program,
18019 otherwise @value{GDBN} will report an error.
18020 You can control the handling of signals from @value{GDBN} with the
18021 @code{handle} command (@pxref{Signals}).
18023 Alternatively, if @var{signal} is zero, any currently queued signal
18024 for the current thread is discarded and when execution resumes no signal
18025 will be delivered. This is useful when your program stopped on account
18026 of a signal and would ordinarily see the signal when resumed with the
18027 @code{continue} command.
18029 This command differs from the @code{signal} command in that the signal
18030 is just queued, execution is not resumed. And @code{queue-signal} cannot
18031 be used to pass a signal whose handling state has been set to @code{nopass}
18036 @xref{stepping into signal handlers}, for information on how stepping
18037 commands behave when the thread has a signal queued.
18040 @section Returning from a Function
18043 @cindex returning from a function
18046 @itemx return @var{expression}
18047 You can cancel execution of a function call with the @code{return}
18048 command. If you give an
18049 @var{expression} argument, its value is used as the function's return
18053 When you use @code{return}, @value{GDBN} discards the selected stack frame
18054 (and all frames within it). You can think of this as making the
18055 discarded frame return prematurely. If you wish to specify a value to
18056 be returned, give that value as the argument to @code{return}.
18058 This pops the selected stack frame (@pxref{Selection, ,Selecting a
18059 Frame}), and any other frames inside of it, leaving its caller as the
18060 innermost remaining frame. That frame becomes selected. The
18061 specified value is stored in the registers used for returning values
18064 The @code{return} command does not resume execution; it leaves the
18065 program stopped in the state that would exist if the function had just
18066 returned. In contrast, the @code{finish} command (@pxref{Continuing
18067 and Stepping, ,Continuing and Stepping}) resumes execution until the
18068 selected stack frame returns naturally.
18070 @value{GDBN} needs to know how the @var{expression} argument should be set for
18071 the inferior. The concrete registers assignment depends on the OS ABI and the
18072 type being returned by the selected stack frame. For example it is common for
18073 OS ABI to return floating point values in FPU registers while integer values in
18074 CPU registers. Still some ABIs return even floating point values in CPU
18075 registers. Larger integer widths (such as @code{long long int}) also have
18076 specific placement rules. @value{GDBN} already knows the OS ABI from its
18077 current target so it needs to find out also the type being returned to make the
18078 assignment into the right register(s).
18080 Normally, the selected stack frame has debug info. @value{GDBN} will always
18081 use the debug info instead of the implicit type of @var{expression} when the
18082 debug info is available. For example, if you type @kbd{return -1}, and the
18083 function in the current stack frame is declared to return a @code{long long
18084 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
18085 into a @code{long long int}:
18088 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
18090 (@value{GDBP}) return -1
18091 Make func return now? (y or n) y
18092 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
18093 43 printf ("result=%lld\n", func ());
18097 However, if the selected stack frame does not have a debug info, e.g., if the
18098 function was compiled without debug info, @value{GDBN} has to find out the type
18099 to return from user. Specifying a different type by mistake may set the value
18100 in different inferior registers than the caller code expects. For example,
18101 typing @kbd{return -1} with its implicit type @code{int} would set only a part
18102 of a @code{long long int} result for a debug info less function (on 32-bit
18103 architectures). Therefore the user is required to specify the return type by
18104 an appropriate cast explicitly:
18107 Breakpoint 2, 0x0040050b in func ()
18108 (@value{GDBP}) return -1
18109 Return value type not available for selected stack frame.
18110 Please use an explicit cast of the value to return.
18111 (@value{GDBP}) return (long long int) -1
18112 Make selected stack frame return now? (y or n) y
18113 #0 0x00400526 in main ()
18118 @section Calling Program Functions
18121 @cindex calling functions
18122 @cindex inferior functions, calling
18123 @item print @var{expr}
18124 Evaluate the expression @var{expr} and display the resulting value.
18125 The expression may include calls to functions in the program being
18129 @item call @var{expr}
18130 Evaluate the expression @var{expr} without displaying @code{void}
18133 You can use this variant of the @code{print} command if you want to
18134 execute a function from your program that does not return anything
18135 (a.k.a.@: @dfn{a void function}), but without cluttering the output
18136 with @code{void} returned values that @value{GDBN} will otherwise
18137 print. If the result is not void, it is printed and saved in the
18141 It is possible for the function you call via the @code{print} or
18142 @code{call} command to generate a signal (e.g., if there's a bug in
18143 the function, or if you passed it incorrect arguments). What happens
18144 in that case is controlled by the @code{set unwindonsignal} command.
18146 Similarly, with a C@t{++} program it is possible for the function you
18147 call via the @code{print} or @code{call} command to generate an
18148 exception that is not handled due to the constraints of the dummy
18149 frame. In this case, any exception that is raised in the frame, but has
18150 an out-of-frame exception handler will not be found. GDB builds a
18151 dummy-frame for the inferior function call, and the unwinder cannot
18152 seek for exception handlers outside of this dummy-frame. What happens
18153 in that case is controlled by the
18154 @code{set unwind-on-terminating-exception} command.
18157 @item set unwindonsignal
18158 @kindex set unwindonsignal
18159 @cindex unwind stack in called functions
18160 @cindex call dummy stack unwinding
18161 Set unwinding of the stack if a signal is received while in a function
18162 that @value{GDBN} called in the program being debugged. If set to on,
18163 @value{GDBN} unwinds the stack it created for the call and restores
18164 the context to what it was before the call. If set to off (the
18165 default), @value{GDBN} stops in the frame where the signal was
18168 @item show unwindonsignal
18169 @kindex show unwindonsignal
18170 Show the current setting of stack unwinding in the functions called by
18173 @item set unwind-on-terminating-exception
18174 @kindex set unwind-on-terminating-exception
18175 @cindex unwind stack in called functions with unhandled exceptions
18176 @cindex call dummy stack unwinding on unhandled exception.
18177 Set unwinding of the stack if a C@t{++} exception is raised, but left
18178 unhandled while in a function that @value{GDBN} called in the program being
18179 debugged. If set to on (the default), @value{GDBN} unwinds the stack
18180 it created for the call and restores the context to what it was before
18181 the call. If set to off, @value{GDBN} the exception is delivered to
18182 the default C@t{++} exception handler and the inferior terminated.
18184 @item show unwind-on-terminating-exception
18185 @kindex show unwind-on-terminating-exception
18186 Show the current setting of stack unwinding in the functions called by
18191 @subsection Calling functions with no debug info
18193 @cindex no debug info functions
18194 Sometimes, a function you wish to call is missing debug information.
18195 In such case, @value{GDBN} does not know the type of the function,
18196 including the types of the function's parameters. To avoid calling
18197 the inferior function incorrectly, which could result in the called
18198 function functioning erroneously and even crash, @value{GDBN} refuses
18199 to call the function unless you tell it the type of the function.
18201 For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
18202 to do that. The simplest is to cast the call to the function's
18203 declared return type. For example:
18206 (@value{GDBP}) p getenv ("PATH")
18207 'getenv' has unknown return type; cast the call to its declared return type
18208 (@value{GDBP}) p (char *) getenv ("PATH")
18209 $1 = 0x7fffffffe7ba "/usr/local/bin:/"...
18212 Casting the return type of a no-debug function is equivalent to
18213 casting the function to a pointer to a prototyped function that has a
18214 prototype that matches the types of the passed-in arguments, and
18215 calling that. I.e., the call above is equivalent to:
18218 (@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
18222 and given this prototyped C or C++ function with float parameters:
18225 float multiply (float v1, float v2) @{ return v1 * v2; @}
18229 these calls are equivalent:
18232 (@value{GDBP}) p (float) multiply (2.0f, 3.0f)
18233 (@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
18236 If the function you wish to call is declared as unprototyped (i.e.@:
18237 old K&R style), you must use the cast-to-function-pointer syntax, so
18238 that @value{GDBN} knows that it needs to apply default argument
18239 promotions (promote float arguments to double). @xref{ABI, float
18240 promotion}. For example, given this unprototyped C function with
18241 float parameters, and no debug info:
18245 multiply_noproto (v1, v2)
18253 you call it like this:
18256 (@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
18260 @section Patching Programs
18262 @cindex patching binaries
18263 @cindex writing into executables
18264 @cindex writing into corefiles
18266 By default, @value{GDBN} opens the file containing your program's
18267 executable code (or the corefile) read-only. This prevents accidental
18268 alterations to machine code; but it also prevents you from intentionally
18269 patching your program's binary.
18271 If you'd like to be able to patch the binary, you can specify that
18272 explicitly with the @code{set write} command. For example, you might
18273 want to turn on internal debugging flags, or even to make emergency
18279 @itemx set write off
18280 If you specify @samp{set write on}, @value{GDBN} opens executable and
18281 core files for both reading and writing; if you specify @kbd{set write
18282 off} (the default), @value{GDBN} opens them read-only.
18284 If you have already loaded a file, you must load it again (using the
18285 @code{exec-file} or @code{core-file} command) after changing @code{set
18286 write}, for your new setting to take effect.
18290 Display whether executable files and core files are opened for writing
18291 as well as reading.
18294 @node Compiling and Injecting Code
18295 @section Compiling and injecting code in @value{GDBN}
18296 @cindex injecting code
18297 @cindex writing into executables
18298 @cindex compiling code
18300 @value{GDBN} supports on-demand compilation and code injection into
18301 programs running under @value{GDBN}. GCC 5.0 or higher built with
18302 @file{libcc1.so} must be installed for this functionality to be enabled.
18303 This functionality is implemented with the following commands.
18306 @kindex compile code
18307 @item compile code @var{source-code}
18308 @itemx compile code -raw @var{--} @var{source-code}
18309 Compile @var{source-code} with the compiler language found as the current
18310 language in @value{GDBN} (@pxref{Languages}). If compilation and
18311 injection is not supported with the current language specified in
18312 @value{GDBN}, or the compiler does not support this feature, an error
18313 message will be printed. If @var{source-code} compiles and links
18314 successfully, @value{GDBN} will load the object-code emitted,
18315 and execute it within the context of the currently selected inferior.
18316 It is important to note that the compiled code is executed immediately.
18317 After execution, the compiled code is removed from @value{GDBN} and any
18318 new types or variables you have defined will be deleted.
18320 The command allows you to specify @var{source-code} in two ways.
18321 The simplest method is to provide a single line of code to the command.
18325 compile code printf ("hello world\n");
18328 If you specify options on the command line as well as source code, they
18329 may conflict. The @samp{--} delimiter can be used to separate options
18330 from actual source code. E.g.:
18333 compile code -r -- printf ("hello world\n");
18336 Alternatively you can enter source code as multiple lines of text. To
18337 enter this mode, invoke the @samp{compile code} command without any text
18338 following the command. This will start the multiple-line editor and
18339 allow you to type as many lines of source code as required. When you
18340 have completed typing, enter @samp{end} on its own line to exit the
18345 >printf ("hello\n");
18346 >printf ("world\n");
18350 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
18351 provided @var{source-code} in a callable scope. In this case, you must
18352 specify the entry point of the code by defining a function named
18353 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
18354 inferior. Using @samp{-raw} option may be needed for example when
18355 @var{source-code} requires @samp{#include} lines which may conflict with
18356 inferior symbols otherwise.
18358 @kindex compile file
18359 @item compile file @var{filename}
18360 @itemx compile file -raw @var{filename}
18361 Like @code{compile code}, but take the source code from @var{filename}.
18364 compile file /home/user/example.c
18369 @item compile print @var{expr}
18370 @itemx compile print /@var{f} @var{expr}
18371 Compile and execute @var{expr} with the compiler language found as the
18372 current language in @value{GDBN} (@pxref{Languages}). By default the
18373 value of @var{expr} is printed in a format appropriate to its data type;
18374 you can choose a different format by specifying @samp{/@var{f}}, where
18375 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
18378 @item compile print
18379 @itemx compile print /@var{f}
18380 @cindex reprint the last value
18381 Alternatively you can enter the expression (source code producing it) as
18382 multiple lines of text. To enter this mode, invoke the @samp{compile print}
18383 command without any text following the command. This will start the
18384 multiple-line editor.
18388 The process of compiling and injecting the code can be inspected using:
18391 @anchor{set debug compile}
18392 @item set debug compile
18393 @cindex compile command debugging info
18394 Turns on or off display of @value{GDBN} process of compiling and
18395 injecting the code. The default is off.
18397 @item show debug compile
18398 Displays the current state of displaying @value{GDBN} process of
18399 compiling and injecting the code.
18402 @subsection Compilation options for the @code{compile} command
18404 @value{GDBN} needs to specify the right compilation options for the code
18405 to be injected, in part to make its ABI compatible with the inferior
18406 and in part to make the injected code compatible with @value{GDBN}'s
18410 The options used, in increasing precedence:
18413 @item target architecture and OS options (@code{gdbarch})
18414 These options depend on target processor type and target operating
18415 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
18416 (@code{-m64}) compilation option.
18418 @item compilation options recorded in the target
18419 @value{NGCC} (since version 4.7) stores the options used for compilation
18420 into @code{DW_AT_producer} part of DWARF debugging information according
18421 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
18422 explicitly specify @code{-g} during inferior compilation otherwise
18423 @value{NGCC} produces no DWARF. This feature is only relevant for
18424 platforms where @code{-g} produces DWARF by default, otherwise one may
18425 try to enforce DWARF by using @code{-gdwarf-4}.
18427 @item compilation options set by @code{set compile-args}
18431 You can override compilation options using the following command:
18434 @item set compile-args
18435 @cindex compile command options override
18436 Set compilation options used for compiling and injecting code with the
18437 @code{compile} commands. These options override any conflicting ones
18438 from the target architecture and/or options stored during inferior
18441 @item show compile-args
18442 Displays the current state of compilation options override.
18443 This does not show all the options actually used during compilation,
18444 use @ref{set debug compile} for that.
18447 @subsection Caveats when using the @code{compile} command
18449 There are a few caveats to keep in mind when using the @code{compile}
18450 command. As the caveats are different per language, the table below
18451 highlights specific issues on a per language basis.
18454 @item C code examples and caveats
18455 When the language in @value{GDBN} is set to @samp{C}, the compiler will
18456 attempt to compile the source code with a @samp{C} compiler. The source
18457 code provided to the @code{compile} command will have much the same
18458 access to variables and types as it normally would if it were part of
18459 the program currently being debugged in @value{GDBN}.
18461 Below is a sample program that forms the basis of the examples that
18462 follow. This program has been compiled and loaded into @value{GDBN},
18463 much like any other normal debugging session.
18466 void function1 (void)
18469 printf ("function 1\n");
18472 void function2 (void)
18487 For the purposes of the examples in this section, the program above has
18488 been compiled, loaded into @value{GDBN}, stopped at the function
18489 @code{main}, and @value{GDBN} is awaiting input from the user.
18491 To access variables and types for any program in @value{GDBN}, the
18492 program must be compiled and packaged with debug information. The
18493 @code{compile} command is not an exception to this rule. Without debug
18494 information, you can still use the @code{compile} command, but you will
18495 be very limited in what variables and types you can access.
18497 So with that in mind, the example above has been compiled with debug
18498 information enabled. The @code{compile} command will have access to
18499 all variables and types (except those that may have been optimized
18500 out). Currently, as @value{GDBN} has stopped the program in the
18501 @code{main} function, the @code{compile} command would have access to
18502 the variable @code{k}. You could invoke the @code{compile} command
18503 and type some source code to set the value of @code{k}. You can also
18504 read it, or do anything with that variable you would normally do in
18505 @code{C}. Be aware that changes to inferior variables in the
18506 @code{compile} command are persistent. In the following example:
18509 compile code k = 3;
18513 the variable @code{k} is now 3. It will retain that value until
18514 something else in the example program changes it, or another
18515 @code{compile} command changes it.
18517 Normal scope and access rules apply to source code compiled and
18518 injected by the @code{compile} command. In the example, the variables
18519 @code{j} and @code{k} are not accessible yet, because the program is
18520 currently stopped in the @code{main} function, where these variables
18521 are not in scope. Therefore, the following command
18524 compile code j = 3;
18528 will result in a compilation error message.
18530 Once the program is continued, execution will bring these variables in
18531 scope, and they will become accessible; then the code you specify via
18532 the @code{compile} command will be able to access them.
18534 You can create variables and types with the @code{compile} command as
18535 part of your source code. Variables and types that are created as part
18536 of the @code{compile} command are not visible to the rest of the program for
18537 the duration of its run. This example is valid:
18540 compile code int ff = 5; printf ("ff is %d\n", ff);
18543 However, if you were to type the following into @value{GDBN} after that
18544 command has completed:
18547 compile code printf ("ff is %d\n'', ff);
18551 a compiler error would be raised as the variable @code{ff} no longer
18552 exists. Object code generated and injected by the @code{compile}
18553 command is removed when its execution ends. Caution is advised
18554 when assigning to program variables values of variables created by the
18555 code submitted to the @code{compile} command. This example is valid:
18558 compile code int ff = 5; k = ff;
18561 The value of the variable @code{ff} is assigned to @code{k}. The variable
18562 @code{k} does not require the existence of @code{ff} to maintain the value
18563 it has been assigned. However, pointers require particular care in
18564 assignment. If the source code compiled with the @code{compile} command
18565 changed the address of a pointer in the example program, perhaps to a
18566 variable created in the @code{compile} command, that pointer would point
18567 to an invalid location when the command exits. The following example
18568 would likely cause issues with your debugged program:
18571 compile code int ff = 5; p = &ff;
18574 In this example, @code{p} would point to @code{ff} when the
18575 @code{compile} command is executing the source code provided to it.
18576 However, as variables in the (example) program persist with their
18577 assigned values, the variable @code{p} would point to an invalid
18578 location when the command exists. A general rule should be followed
18579 in that you should either assign @code{NULL} to any assigned pointers,
18580 or restore a valid location to the pointer before the command exits.
18582 Similar caution must be exercised with any structs, unions, and typedefs
18583 defined in @code{compile} command. Types defined in the @code{compile}
18584 command will no longer be available in the next @code{compile} command.
18585 Therefore, if you cast a variable to a type defined in the
18586 @code{compile} command, care must be taken to ensure that any future
18587 need to resolve the type can be achieved.
18590 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
18591 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
18592 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
18593 Compilation failed.
18594 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
18598 Variables that have been optimized away by the compiler are not
18599 accessible to the code submitted to the @code{compile} command.
18600 Access to those variables will generate a compiler error which @value{GDBN}
18601 will print to the console.
18604 @subsection Compiler search for the @code{compile} command
18606 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
18607 which may not be obvious for remote targets of different architecture
18608 than where @value{GDBN} is running. Environment variable @code{PATH} on
18609 @value{GDBN} host is searched for @value{NGCC} binary matching the
18610 target architecture and operating system. This search can be overriden
18611 by @code{set compile-gcc} @value{GDBN} command below. @code{PATH} is
18612 taken from shell that executed @value{GDBN}, it is not the value set by
18613 @value{GDBN} command @code{set environment}). @xref{Environment}.
18616 Specifically @code{PATH} is searched for binaries matching regular expression
18617 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
18618 debugged. @var{arch} is processor name --- multiarch is supported, so for
18619 example both @code{i386} and @code{x86_64} targets look for pattern
18620 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
18621 for pattern @code{s390x?}. @var{os} is currently supported only for
18622 pattern @code{linux(-gnu)?}.
18624 On Posix hosts the compiler driver @value{GDBN} needs to find also
18625 shared library @file{libcc1.so} from the compiler. It is searched in
18626 default shared library search path (overridable with usual environment
18627 variable @code{LD_LIBRARY_PATH}), unrelated to @code{PATH} or @code{set
18628 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
18629 according to the installation of the found compiler --- as possibly
18630 specified by the @code{set compile-gcc} command.
18633 @item set compile-gcc
18634 @cindex compile command driver filename override
18635 Set compilation command used for compiling and injecting code with the
18636 @code{compile} commands. If this option is not set (it is set to
18637 an empty string), the search described above will occur --- that is the
18640 @item show compile-gcc
18641 Displays the current compile command @value{NGCC} driver filename.
18642 If set, it is the main command @command{gcc}, found usually for example
18643 under name @file{x86_64-linux-gnu-gcc}.
18647 @chapter @value{GDBN} Files
18649 @value{GDBN} needs to know the file name of the program to be debugged,
18650 both in order to read its symbol table and in order to start your
18651 program. To debug a core dump of a previous run, you must also tell
18652 @value{GDBN} the name of the core dump file.
18655 * Files:: Commands to specify files
18656 * File Caching:: Information about @value{GDBN}'s file caching
18657 * Separate Debug Files:: Debugging information in separate files
18658 * MiniDebugInfo:: Debugging information in a special section
18659 * Index Files:: Index files speed up GDB
18660 * Symbol Errors:: Errors reading symbol files
18661 * Data Files:: GDB data files
18665 @section Commands to Specify Files
18667 @cindex symbol table
18668 @cindex core dump file
18670 You may want to specify executable and core dump file names. The usual
18671 way to do this is at start-up time, using the arguments to
18672 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
18673 Out of @value{GDBN}}).
18675 Occasionally it is necessary to change to a different file during a
18676 @value{GDBN} session. Or you may run @value{GDBN} and forget to
18677 specify a file you want to use. Or you are debugging a remote target
18678 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
18679 Program}). In these situations the @value{GDBN} commands to specify
18680 new files are useful.
18683 @cindex executable file
18685 @item file @var{filename}
18686 Use @var{filename} as the program to be debugged. It is read for its
18687 symbols and for the contents of pure memory. It is also the program
18688 executed when you use the @code{run} command. If you do not specify a
18689 directory and the file is not found in the @value{GDBN} working directory,
18690 @value{GDBN} uses the environment variable @code{PATH} as a list of
18691 directories to search, just as the shell does when looking for a program
18692 to run. You can change the value of this variable, for both @value{GDBN}
18693 and your program, using the @code{path} command.
18695 @cindex unlinked object files
18696 @cindex patching object files
18697 You can load unlinked object @file{.o} files into @value{GDBN} using
18698 the @code{file} command. You will not be able to ``run'' an object
18699 file, but you can disassemble functions and inspect variables. Also,
18700 if the underlying BFD functionality supports it, you could use
18701 @kbd{gdb -write} to patch object files using this technique. Note
18702 that @value{GDBN} can neither interpret nor modify relocations in this
18703 case, so branches and some initialized variables will appear to go to
18704 the wrong place. But this feature is still handy from time to time.
18707 @code{file} with no argument makes @value{GDBN} discard any information it
18708 has on both executable file and the symbol table.
18711 @item exec-file @r{[} @var{filename} @r{]}
18712 Specify that the program to be run (but not the symbol table) is found
18713 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
18714 if necessary to locate your program. Omitting @var{filename} means to
18715 discard information on the executable file.
18717 @kindex symbol-file
18718 @item symbol-file @r{[} @var{filename} @r{]}
18719 Read symbol table information from file @var{filename}. @code{PATH} is
18720 searched when necessary. Use the @code{file} command to get both symbol
18721 table and program to run from the same file.
18723 @code{symbol-file} with no argument clears out @value{GDBN} information on your
18724 program's symbol table.
18726 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
18727 some breakpoints and auto-display expressions. This is because they may
18728 contain pointers to the internal data recording symbols and data types,
18729 which are part of the old symbol table data being discarded inside
18732 @code{symbol-file} does not repeat if you press @key{RET} again after
18735 When @value{GDBN} is configured for a particular environment, it
18736 understands debugging information in whatever format is the standard
18737 generated for that environment; you may use either a @sc{gnu} compiler, or
18738 other compilers that adhere to the local conventions.
18739 Best results are usually obtained from @sc{gnu} compilers; for example,
18740 using @code{@value{NGCC}} you can generate debugging information for
18743 For most kinds of object files, with the exception of old SVR3 systems
18744 using COFF, the @code{symbol-file} command does not normally read the
18745 symbol table in full right away. Instead, it scans the symbol table
18746 quickly to find which source files and which symbols are present. The
18747 details are read later, one source file at a time, as they are needed.
18749 The purpose of this two-stage reading strategy is to make @value{GDBN}
18750 start up faster. For the most part, it is invisible except for
18751 occasional pauses while the symbol table details for a particular source
18752 file are being read. (The @code{set verbose} command can turn these
18753 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
18754 Warnings and Messages}.)
18756 We have not implemented the two-stage strategy for COFF yet. When the
18757 symbol table is stored in COFF format, @code{symbol-file} reads the
18758 symbol table data in full right away. Note that ``stabs-in-COFF''
18759 still does the two-stage strategy, since the debug info is actually
18763 @cindex reading symbols immediately
18764 @cindex symbols, reading immediately
18765 @item symbol-file @r{[} -readnow @r{]} @var{filename}
18766 @itemx file @r{[} -readnow @r{]} @var{filename}
18767 You can override the @value{GDBN} two-stage strategy for reading symbol
18768 tables by using the @samp{-readnow} option with any of the commands that
18769 load symbol table information, if you want to be sure @value{GDBN} has the
18770 entire symbol table available.
18772 @cindex @code{-readnever}, option for symbol-file command
18773 @cindex never read symbols
18774 @cindex symbols, never read
18775 @item symbol-file @r{[} -readnever @r{]} @var{filename}
18776 @itemx file @r{[} -readnever @r{]} @var{filename}
18777 You can instruct @value{GDBN} to never read the symbolic information
18778 contained in @var{filename} by using the @samp{-readnever} option.
18779 @xref{--readnever}.
18781 @c FIXME: for now no mention of directories, since this seems to be in
18782 @c flux. 13mar1992 status is that in theory GDB would look either in
18783 @c current dir or in same dir as myprog; but issues like competing
18784 @c GDB's, or clutter in system dirs, mean that in practice right now
18785 @c only current dir is used. FFish says maybe a special GDB hierarchy
18786 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
18790 @item core-file @r{[}@var{filename}@r{]}
18792 Specify the whereabouts of a core dump file to be used as the ``contents
18793 of memory''. Traditionally, core files contain only some parts of the
18794 address space of the process that generated them; @value{GDBN} can access the
18795 executable file itself for other parts.
18797 @code{core-file} with no argument specifies that no core file is
18800 Note that the core file is ignored when your program is actually running
18801 under @value{GDBN}. So, if you have been running your program and you
18802 wish to debug a core file instead, you must kill the subprocess in which
18803 the program is running. To do this, use the @code{kill} command
18804 (@pxref{Kill Process, ,Killing the Child Process}).
18806 @kindex add-symbol-file
18807 @cindex dynamic linking
18808 @item add-symbol-file @var{filename} @var{address}
18809 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{|} -readnever @r{]}
18810 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
18811 The @code{add-symbol-file} command reads additional symbol table
18812 information from the file @var{filename}. You would use this command
18813 when @var{filename} has been dynamically loaded (by some other means)
18814 into the program that is running. The @var{address} should give the memory
18815 address at which the file has been loaded; @value{GDBN} cannot figure
18816 this out for itself. You can additionally specify an arbitrary number
18817 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
18818 section name and base address for that section. You can specify any
18819 @var{address} as an expression.
18821 The symbol table of the file @var{filename} is added to the symbol table
18822 originally read with the @code{symbol-file} command. You can use the
18823 @code{add-symbol-file} command any number of times; the new symbol data
18824 thus read is kept in addition to the old.
18826 Changes can be reverted using the command @code{remove-symbol-file}.
18828 @cindex relocatable object files, reading symbols from
18829 @cindex object files, relocatable, reading symbols from
18830 @cindex reading symbols from relocatable object files
18831 @cindex symbols, reading from relocatable object files
18832 @cindex @file{.o} files, reading symbols from
18833 Although @var{filename} is typically a shared library file, an
18834 executable file, or some other object file which has been fully
18835 relocated for loading into a process, you can also load symbolic
18836 information from relocatable @file{.o} files, as long as:
18840 the file's symbolic information refers only to linker symbols defined in
18841 that file, not to symbols defined by other object files,
18843 every section the file's symbolic information refers to has actually
18844 been loaded into the inferior, as it appears in the file, and
18846 you can determine the address at which every section was loaded, and
18847 provide these to the @code{add-symbol-file} command.
18851 Some embedded operating systems, like Sun Chorus and VxWorks, can load
18852 relocatable files into an already running program; such systems
18853 typically make the requirements above easy to meet. However, it's
18854 important to recognize that many native systems use complex link
18855 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
18856 assembly, for example) that make the requirements difficult to meet. In
18857 general, one cannot assume that using @code{add-symbol-file} to read a
18858 relocatable object file's symbolic information will have the same effect
18859 as linking the relocatable object file into the program in the normal
18862 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
18864 @kindex remove-symbol-file
18865 @item remove-symbol-file @var{filename}
18866 @item remove-symbol-file -a @var{address}
18867 Remove a symbol file added via the @code{add-symbol-file} command. The
18868 file to remove can be identified by its @var{filename} or by an @var{address}
18869 that lies within the boundaries of this symbol file in memory. Example:
18872 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
18873 add symbol table from file "/home/user/gdb/mylib.so" at
18874 .text_addr = 0x7ffff7ff9480
18876 Reading symbols from /home/user/gdb/mylib.so...done.
18877 (gdb) remove-symbol-file -a 0x7ffff7ff9480
18878 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
18883 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
18885 @kindex add-symbol-file-from-memory
18886 @cindex @code{syscall DSO}
18887 @cindex load symbols from memory
18888 @item add-symbol-file-from-memory @var{address}
18889 Load symbols from the given @var{address} in a dynamically loaded
18890 object file whose image is mapped directly into the inferior's memory.
18891 For example, the Linux kernel maps a @code{syscall DSO} into each
18892 process's address space; this DSO provides kernel-specific code for
18893 some system calls. The argument can be any expression whose
18894 evaluation yields the address of the file's shared object file header.
18895 For this command to work, you must have used @code{symbol-file} or
18896 @code{exec-file} commands in advance.
18899 @item section @var{section} @var{addr}
18900 The @code{section} command changes the base address of the named
18901 @var{section} of the exec file to @var{addr}. This can be used if the
18902 exec file does not contain section addresses, (such as in the
18903 @code{a.out} format), or when the addresses specified in the file
18904 itself are wrong. Each section must be changed separately. The
18905 @code{info files} command, described below, lists all the sections and
18909 @kindex info target
18912 @code{info files} and @code{info target} are synonymous; both print the
18913 current target (@pxref{Targets, ,Specifying a Debugging Target}),
18914 including the names of the executable and core dump files currently in
18915 use by @value{GDBN}, and the files from which symbols were loaded. The
18916 command @code{help target} lists all possible targets rather than
18919 @kindex maint info sections
18920 @item maint info sections
18921 Another command that can give you extra information about program sections
18922 is @code{maint info sections}. In addition to the section information
18923 displayed by @code{info files}, this command displays the flags and file
18924 offset of each section in the executable and core dump files. In addition,
18925 @code{maint info sections} provides the following command options (which
18926 may be arbitrarily combined):
18930 Display sections for all loaded object files, including shared libraries.
18931 @item @var{sections}
18932 Display info only for named @var{sections}.
18933 @item @var{section-flags}
18934 Display info only for sections for which @var{section-flags} are true.
18935 The section flags that @value{GDBN} currently knows about are:
18938 Section will have space allocated in the process when loaded.
18939 Set for all sections except those containing debug information.
18941 Section will be loaded from the file into the child process memory.
18942 Set for pre-initialized code and data, clear for @code{.bss} sections.
18944 Section needs to be relocated before loading.
18946 Section cannot be modified by the child process.
18948 Section contains executable code only.
18950 Section contains data only (no executable code).
18952 Section will reside in ROM.
18954 Section contains data for constructor/destructor lists.
18956 Section is not empty.
18958 An instruction to the linker to not output the section.
18959 @item COFF_SHARED_LIBRARY
18960 A notification to the linker that the section contains
18961 COFF shared library information.
18963 Section contains common symbols.
18966 @kindex set trust-readonly-sections
18967 @cindex read-only sections
18968 @item set trust-readonly-sections on
18969 Tell @value{GDBN} that readonly sections in your object file
18970 really are read-only (i.e.@: that their contents will not change).
18971 In that case, @value{GDBN} can fetch values from these sections
18972 out of the object file, rather than from the target program.
18973 For some targets (notably embedded ones), this can be a significant
18974 enhancement to debugging performance.
18976 The default is off.
18978 @item set trust-readonly-sections off
18979 Tell @value{GDBN} not to trust readonly sections. This means that
18980 the contents of the section might change while the program is running,
18981 and must therefore be fetched from the target when needed.
18983 @item show trust-readonly-sections
18984 Show the current setting of trusting readonly sections.
18987 All file-specifying commands allow both absolute and relative file names
18988 as arguments. @value{GDBN} always converts the file name to an absolute file
18989 name and remembers it that way.
18991 @cindex shared libraries
18992 @anchor{Shared Libraries}
18993 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
18994 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
18995 DSBT (TIC6X) shared libraries.
18997 On MS-Windows @value{GDBN} must be linked with the Expat library to support
18998 shared libraries. @xref{Expat}.
19000 @value{GDBN} automatically loads symbol definitions from shared libraries
19001 when you use the @code{run} command, or when you examine a core file.
19002 (Before you issue the @code{run} command, @value{GDBN} does not understand
19003 references to a function in a shared library, however---unless you are
19004 debugging a core file).
19006 @c FIXME: some @value{GDBN} release may permit some refs to undef
19007 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
19008 @c FIXME...lib; check this from time to time when updating manual
19010 There are times, however, when you may wish to not automatically load
19011 symbol definitions from shared libraries, such as when they are
19012 particularly large or there are many of them.
19014 To control the automatic loading of shared library symbols, use the
19018 @kindex set auto-solib-add
19019 @item set auto-solib-add @var{mode}
19020 If @var{mode} is @code{on}, symbols from all shared object libraries
19021 will be loaded automatically when the inferior begins execution, you
19022 attach to an independently started inferior, or when the dynamic linker
19023 informs @value{GDBN} that a new library has been loaded. If @var{mode}
19024 is @code{off}, symbols must be loaded manually, using the
19025 @code{sharedlibrary} command. The default value is @code{on}.
19027 @cindex memory used for symbol tables
19028 If your program uses lots of shared libraries with debug info that
19029 takes large amounts of memory, you can decrease the @value{GDBN}
19030 memory footprint by preventing it from automatically loading the
19031 symbols from shared libraries. To that end, type @kbd{set
19032 auto-solib-add off} before running the inferior, then load each
19033 library whose debug symbols you do need with @kbd{sharedlibrary
19034 @var{regexp}}, where @var{regexp} is a regular expression that matches
19035 the libraries whose symbols you want to be loaded.
19037 @kindex show auto-solib-add
19038 @item show auto-solib-add
19039 Display the current autoloading mode.
19042 @cindex load shared library
19043 To explicitly load shared library symbols, use the @code{sharedlibrary}
19047 @kindex info sharedlibrary
19049 @item info share @var{regex}
19050 @itemx info sharedlibrary @var{regex}
19051 Print the names of the shared libraries which are currently loaded
19052 that match @var{regex}. If @var{regex} is omitted then print
19053 all shared libraries that are loaded.
19056 @item info dll @var{regex}
19057 This is an alias of @code{info sharedlibrary}.
19059 @kindex sharedlibrary
19061 @item sharedlibrary @var{regex}
19062 @itemx share @var{regex}
19063 Load shared object library symbols for files matching a
19064 Unix regular expression.
19065 As with files loaded automatically, it only loads shared libraries
19066 required by your program for a core file or after typing @code{run}. If
19067 @var{regex} is omitted all shared libraries required by your program are
19070 @item nosharedlibrary
19071 @kindex nosharedlibrary
19072 @cindex unload symbols from shared libraries
19073 Unload all shared object library symbols. This discards all symbols
19074 that have been loaded from all shared libraries. Symbols from shared
19075 libraries that were loaded by explicit user requests are not
19079 Sometimes you may wish that @value{GDBN} stops and gives you control
19080 when any of shared library events happen. The best way to do this is
19081 to use @code{catch load} and @code{catch unload} (@pxref{Set
19084 @value{GDBN} also supports the the @code{set stop-on-solib-events}
19085 command for this. This command exists for historical reasons. It is
19086 less useful than setting a catchpoint, because it does not allow for
19087 conditions or commands as a catchpoint does.
19090 @item set stop-on-solib-events
19091 @kindex set stop-on-solib-events
19092 This command controls whether @value{GDBN} should give you control
19093 when the dynamic linker notifies it about some shared library event.
19094 The most common event of interest is loading or unloading of a new
19097 @item show stop-on-solib-events
19098 @kindex show stop-on-solib-events
19099 Show whether @value{GDBN} stops and gives you control when shared
19100 library events happen.
19103 Shared libraries are also supported in many cross or remote debugging
19104 configurations. @value{GDBN} needs to have access to the target's libraries;
19105 this can be accomplished either by providing copies of the libraries
19106 on the host system, or by asking @value{GDBN} to automatically retrieve the
19107 libraries from the target. If copies of the target libraries are
19108 provided, they need to be the same as the target libraries, although the
19109 copies on the target can be stripped as long as the copies on the host are
19112 @cindex where to look for shared libraries
19113 For remote debugging, you need to tell @value{GDBN} where the target
19114 libraries are, so that it can load the correct copies---otherwise, it
19115 may try to load the host's libraries. @value{GDBN} has two variables
19116 to specify the search directories for target libraries.
19119 @cindex prefix for executable and shared library file names
19120 @cindex system root, alternate
19121 @kindex set solib-absolute-prefix
19122 @kindex set sysroot
19123 @item set sysroot @var{path}
19124 Use @var{path} as the system root for the program being debugged. Any
19125 absolute shared library paths will be prefixed with @var{path}; many
19126 runtime loaders store the absolute paths to the shared library in the
19127 target program's memory. When starting processes remotely, and when
19128 attaching to already-running processes (local or remote), their
19129 executable filenames will be prefixed with @var{path} if reported to
19130 @value{GDBN} as absolute by the operating system. If you use
19131 @code{set sysroot} to find executables and shared libraries, they need
19132 to be laid out in the same way that they are on the target, with
19133 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
19136 If @var{path} starts with the sequence @file{target:} and the target
19137 system is remote then @value{GDBN} will retrieve the target binaries
19138 from the remote system. This is only supported when using a remote
19139 target that supports the @code{remote get} command (@pxref{File
19140 Transfer,,Sending files to a remote system}). The part of @var{path}
19141 following the initial @file{target:} (if present) is used as system
19142 root prefix on the remote file system. If @var{path} starts with the
19143 sequence @file{remote:} this is converted to the sequence
19144 @file{target:} by @code{set sysroot}@footnote{Historically the
19145 functionality to retrieve binaries from the remote system was
19146 provided by prefixing @var{path} with @file{remote:}}. If you want
19147 to specify a local system root using a directory that happens to be
19148 named @file{target:} or @file{remote:}, you need to use some
19149 equivalent variant of the name like @file{./target:}.
19151 For targets with an MS-DOS based filesystem, such as MS-Windows and
19152 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
19153 absolute file name with @var{path}. But first, on Unix hosts,
19154 @value{GDBN} converts all backslash directory separators into forward
19155 slashes, because the backslash is not a directory separator on Unix:
19158 c:\foo\bar.dll @result{} c:/foo/bar.dll
19161 Then, @value{GDBN} attempts prefixing the target file name with
19162 @var{path}, and looks for the resulting file name in the host file
19166 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
19169 If that does not find the binary, @value{GDBN} tries removing
19170 the @samp{:} character from the drive spec, both for convenience, and,
19171 for the case of the host file system not supporting file names with
19175 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
19178 This makes it possible to have a system root that mirrors a target
19179 with more than one drive. E.g., you may want to setup your local
19180 copies of the target system shared libraries like so (note @samp{c} vs
19184 @file{/path/to/sysroot/c/sys/bin/foo.dll}
19185 @file{/path/to/sysroot/c/sys/bin/bar.dll}
19186 @file{/path/to/sysroot/z/sys/bin/bar.dll}
19190 and point the system root at @file{/path/to/sysroot}, so that
19191 @value{GDBN} can find the correct copies of both
19192 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
19194 If that still does not find the binary, @value{GDBN} tries
19195 removing the whole drive spec from the target file name:
19198 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
19201 This last lookup makes it possible to not care about the drive name,
19202 if you don't want or need to.
19204 The @code{set solib-absolute-prefix} command is an alias for @code{set
19207 @cindex default system root
19208 @cindex @samp{--with-sysroot}
19209 You can set the default system root by using the configure-time
19210 @samp{--with-sysroot} option. If the system root is inside
19211 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19212 @samp{--exec-prefix}), then the default system root will be updated
19213 automatically if the installed @value{GDBN} is moved to a new
19216 @kindex show sysroot
19218 Display the current executable and shared library prefix.
19220 @kindex set solib-search-path
19221 @item set solib-search-path @var{path}
19222 If this variable is set, @var{path} is a colon-separated list of
19223 directories to search for shared libraries. @samp{solib-search-path}
19224 is used after @samp{sysroot} fails to locate the library, or if the
19225 path to the library is relative instead of absolute. If you want to
19226 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
19227 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
19228 finding your host's libraries. @samp{sysroot} is preferred; setting
19229 it to a nonexistent directory may interfere with automatic loading
19230 of shared library symbols.
19232 @kindex show solib-search-path
19233 @item show solib-search-path
19234 Display the current shared library search path.
19236 @cindex DOS file-name semantics of file names.
19237 @kindex set target-file-system-kind (unix|dos-based|auto)
19238 @kindex show target-file-system-kind
19239 @item set target-file-system-kind @var{kind}
19240 Set assumed file system kind for target reported file names.
19242 Shared library file names as reported by the target system may not
19243 make sense as is on the system @value{GDBN} is running on. For
19244 example, when remote debugging a target that has MS-DOS based file
19245 system semantics, from a Unix host, the target may be reporting to
19246 @value{GDBN} a list of loaded shared libraries with file names such as
19247 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
19248 drive letters, so the @samp{c:\} prefix is not normally understood as
19249 indicating an absolute file name, and neither is the backslash
19250 normally considered a directory separator character. In that case,
19251 the native file system would interpret this whole absolute file name
19252 as a relative file name with no directory components. This would make
19253 it impossible to point @value{GDBN} at a copy of the remote target's
19254 shared libraries on the host using @code{set sysroot}, and impractical
19255 with @code{set solib-search-path}. Setting
19256 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
19257 to interpret such file names similarly to how the target would, and to
19258 map them to file names valid on @value{GDBN}'s native file system
19259 semantics. The value of @var{kind} can be @code{"auto"}, in addition
19260 to one of the supported file system kinds. In that case, @value{GDBN}
19261 tries to determine the appropriate file system variant based on the
19262 current target's operating system (@pxref{ABI, ,Configuring the
19263 Current ABI}). The supported file system settings are:
19267 Instruct @value{GDBN} to assume the target file system is of Unix
19268 kind. Only file names starting the forward slash (@samp{/}) character
19269 are considered absolute, and the directory separator character is also
19273 Instruct @value{GDBN} to assume the target file system is DOS based.
19274 File names starting with either a forward slash, or a drive letter
19275 followed by a colon (e.g., @samp{c:}), are considered absolute, and
19276 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
19277 considered directory separators.
19280 Instruct @value{GDBN} to use the file system kind associated with the
19281 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
19282 This is the default.
19286 @cindex file name canonicalization
19287 @cindex base name differences
19288 When processing file names provided by the user, @value{GDBN}
19289 frequently needs to compare them to the file names recorded in the
19290 program's debug info. Normally, @value{GDBN} compares just the
19291 @dfn{base names} of the files as strings, which is reasonably fast
19292 even for very large programs. (The base name of a file is the last
19293 portion of its name, after stripping all the leading directories.)
19294 This shortcut in comparison is based upon the assumption that files
19295 cannot have more than one base name. This is usually true, but
19296 references to files that use symlinks or similar filesystem
19297 facilities violate that assumption. If your program records files
19298 using such facilities, or if you provide file names to @value{GDBN}
19299 using symlinks etc., you can set @code{basenames-may-differ} to
19300 @code{true} to instruct @value{GDBN} to completely canonicalize each
19301 pair of file names it needs to compare. This will make file-name
19302 comparisons accurate, but at a price of a significant slowdown.
19305 @item set basenames-may-differ
19306 @kindex set basenames-may-differ
19307 Set whether a source file may have multiple base names.
19309 @item show basenames-may-differ
19310 @kindex show basenames-may-differ
19311 Show whether a source file may have multiple base names.
19315 @section File Caching
19316 @cindex caching of opened files
19317 @cindex caching of bfd objects
19319 To speed up file loading, and reduce memory usage, @value{GDBN} will
19320 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
19321 BFD, bfd, The Binary File Descriptor Library}. The following commands
19322 allow visibility and control of the caching behavior.
19325 @kindex maint info bfds
19326 @item maint info bfds
19327 This prints information about each @code{bfd} object that is known to
19330 @kindex maint set bfd-sharing
19331 @kindex maint show bfd-sharing
19332 @kindex bfd caching
19333 @item maint set bfd-sharing
19334 @item maint show bfd-sharing
19335 Control whether @code{bfd} objects can be shared. When sharing is
19336 enabled @value{GDBN} reuses already open @code{bfd} objects rather
19337 than reopening the same file. Turning sharing off does not cause
19338 already shared @code{bfd} objects to be unshared, but all future files
19339 that are opened will create a new @code{bfd} object. Similarly,
19340 re-enabling sharing does not cause multiple existing @code{bfd}
19341 objects to be collapsed into a single shared @code{bfd} object.
19343 @kindex set debug bfd-cache @var{level}
19344 @kindex bfd caching
19345 @item set debug bfd-cache @var{level}
19346 Turns on debugging of the bfd cache, setting the level to @var{level}.
19348 @kindex show debug bfd-cache
19349 @kindex bfd caching
19350 @item show debug bfd-cache
19351 Show the current debugging level of the bfd cache.
19354 @node Separate Debug Files
19355 @section Debugging Information in Separate Files
19356 @cindex separate debugging information files
19357 @cindex debugging information in separate files
19358 @cindex @file{.debug} subdirectories
19359 @cindex debugging information directory, global
19360 @cindex global debugging information directories
19361 @cindex build ID, and separate debugging files
19362 @cindex @file{.build-id} directory
19364 @value{GDBN} allows you to put a program's debugging information in a
19365 file separate from the executable itself, in a way that allows
19366 @value{GDBN} to find and load the debugging information automatically.
19367 Since debugging information can be very large---sometimes larger
19368 than the executable code itself---some systems distribute debugging
19369 information for their executables in separate files, which users can
19370 install only when they need to debug a problem.
19372 @value{GDBN} supports two ways of specifying the separate debug info
19377 The executable contains a @dfn{debug link} that specifies the name of
19378 the separate debug info file. The separate debug file's name is
19379 usually @file{@var{executable}.debug}, where @var{executable} is the
19380 name of the corresponding executable file without leading directories
19381 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
19382 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
19383 checksum for the debug file, which @value{GDBN} uses to validate that
19384 the executable and the debug file came from the same build.
19387 The executable contains a @dfn{build ID}, a unique bit string that is
19388 also present in the corresponding debug info file. (This is supported
19389 only on some operating systems, when using the ELF or PE file formats
19390 for binary files and the @sc{gnu} Binutils.) For more details about
19391 this feature, see the description of the @option{--build-id}
19392 command-line option in @ref{Options, , Command Line Options, ld.info,
19393 The GNU Linker}. The debug info file's name is not specified
19394 explicitly by the build ID, but can be computed from the build ID, see
19398 Depending on the way the debug info file is specified, @value{GDBN}
19399 uses two different methods of looking for the debug file:
19403 For the ``debug link'' method, @value{GDBN} looks up the named file in
19404 the directory of the executable file, then in a subdirectory of that
19405 directory named @file{.debug}, and finally under each one of the global debug
19406 directories, in a subdirectory whose name is identical to the leading
19407 directories of the executable's absolute file name.
19410 For the ``build ID'' method, @value{GDBN} looks in the
19411 @file{.build-id} subdirectory of each one of the global debug directories for
19412 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
19413 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
19414 are the rest of the bit string. (Real build ID strings are 32 or more
19415 hex characters, not 10.)
19418 So, for example, suppose you ask @value{GDBN} to debug
19419 @file{/usr/bin/ls}, which has a debug link that specifies the
19420 file @file{ls.debug}, and a build ID whose value in hex is
19421 @code{abcdef1234}. If the list of the global debug directories includes
19422 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
19423 debug information files, in the indicated order:
19427 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
19429 @file{/usr/bin/ls.debug}
19431 @file{/usr/bin/.debug/ls.debug}
19433 @file{/usr/lib/debug/usr/bin/ls.debug}.
19436 @anchor{debug-file-directory}
19437 Global debugging info directories default to what is set by @value{GDBN}
19438 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
19439 you can also set the global debugging info directories, and view the list
19440 @value{GDBN} is currently using.
19444 @kindex set debug-file-directory
19445 @item set debug-file-directory @var{directories}
19446 Set the directories which @value{GDBN} searches for separate debugging
19447 information files to @var{directory}. Multiple path components can be set
19448 concatenating them by a path separator.
19450 @kindex show debug-file-directory
19451 @item show debug-file-directory
19452 Show the directories @value{GDBN} searches for separate debugging
19457 @cindex @code{.gnu_debuglink} sections
19458 @cindex debug link sections
19459 A debug link is a special section of the executable file named
19460 @code{.gnu_debuglink}. The section must contain:
19464 A filename, with any leading directory components removed, followed by
19467 zero to three bytes of padding, as needed to reach the next four-byte
19468 boundary within the section, and
19470 a four-byte CRC checksum, stored in the same endianness used for the
19471 executable file itself. The checksum is computed on the debugging
19472 information file's full contents by the function given below, passing
19473 zero as the @var{crc} argument.
19476 Any executable file format can carry a debug link, as long as it can
19477 contain a section named @code{.gnu_debuglink} with the contents
19480 @cindex @code{.note.gnu.build-id} sections
19481 @cindex build ID sections
19482 The build ID is a special section in the executable file (and in other
19483 ELF binary files that @value{GDBN} may consider). This section is
19484 often named @code{.note.gnu.build-id}, but that name is not mandatory.
19485 It contains unique identification for the built files---the ID remains
19486 the same across multiple builds of the same build tree. The default
19487 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
19488 content for the build ID string. The same section with an identical
19489 value is present in the original built binary with symbols, in its
19490 stripped variant, and in the separate debugging information file.
19492 The debugging information file itself should be an ordinary
19493 executable, containing a full set of linker symbols, sections, and
19494 debugging information. The sections of the debugging information file
19495 should have the same names, addresses, and sizes as the original file,
19496 but they need not contain any data---much like a @code{.bss} section
19497 in an ordinary executable.
19499 The @sc{gnu} binary utilities (Binutils) package includes the
19500 @samp{objcopy} utility that can produce
19501 the separated executable / debugging information file pairs using the
19502 following commands:
19505 @kbd{objcopy --only-keep-debug foo foo.debug}
19510 These commands remove the debugging
19511 information from the executable file @file{foo} and place it in the file
19512 @file{foo.debug}. You can use the first, second or both methods to link the
19517 The debug link method needs the following additional command to also leave
19518 behind a debug link in @file{foo}:
19521 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
19524 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
19525 a version of the @code{strip} command such that the command @kbd{strip foo -f
19526 foo.debug} has the same functionality as the two @code{objcopy} commands and
19527 the @code{ln -s} command above, together.
19530 Build ID gets embedded into the main executable using @code{ld --build-id} or
19531 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
19532 compatibility fixes for debug files separation are present in @sc{gnu} binary
19533 utilities (Binutils) package since version 2.18.
19538 @cindex CRC algorithm definition
19539 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
19540 IEEE 802.3 using the polynomial:
19542 @c TexInfo requires naked braces for multi-digit exponents for Tex
19543 @c output, but this causes HTML output to barf. HTML has to be set using
19544 @c raw commands. So we end up having to specify this equation in 2
19549 <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>
19550 + <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
19556 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
19557 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
19561 The function is computed byte at a time, taking the least
19562 significant bit of each byte first. The initial pattern
19563 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
19564 the final result is inverted to ensure trailing zeros also affect the
19567 @emph{Note:} This is the same CRC polynomial as used in handling the
19568 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
19569 However in the case of the Remote Serial Protocol, the CRC is computed
19570 @emph{most} significant bit first, and the result is not inverted, so
19571 trailing zeros have no effect on the CRC value.
19573 To complete the description, we show below the code of the function
19574 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
19575 initially supplied @code{crc} argument means that an initial call to
19576 this function passing in zero will start computing the CRC using
19579 @kindex gnu_debuglink_crc32
19582 gnu_debuglink_crc32 (unsigned long crc,
19583 unsigned char *buf, size_t len)
19585 static const unsigned long crc32_table[256] =
19587 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
19588 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
19589 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
19590 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
19591 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
19592 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
19593 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
19594 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
19595 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
19596 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
19597 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
19598 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
19599 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
19600 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
19601 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
19602 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
19603 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
19604 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
19605 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
19606 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
19607 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
19608 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
19609 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
19610 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
19611 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
19612 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
19613 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
19614 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
19615 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
19616 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
19617 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
19618 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
19619 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
19620 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
19621 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
19622 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
19623 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
19624 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
19625 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
19626 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
19627 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
19628 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
19629 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
19630 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
19631 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
19632 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
19633 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
19634 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
19635 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
19636 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
19637 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
19640 unsigned char *end;
19642 crc = ~crc & 0xffffffff;
19643 for (end = buf + len; buf < end; ++buf)
19644 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
19645 return ~crc & 0xffffffff;
19650 This computation does not apply to the ``build ID'' method.
19652 @node MiniDebugInfo
19653 @section Debugging information in a special section
19654 @cindex separate debug sections
19655 @cindex @samp{.gnu_debugdata} section
19657 Some systems ship pre-built executables and libraries that have a
19658 special @samp{.gnu_debugdata} section. This feature is called
19659 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
19660 is used to supply extra symbols for backtraces.
19662 The intent of this section is to provide extra minimal debugging
19663 information for use in simple backtraces. It is not intended to be a
19664 replacement for full separate debugging information (@pxref{Separate
19665 Debug Files}). The example below shows the intended use; however,
19666 @value{GDBN} does not currently put restrictions on what sort of
19667 debugging information might be included in the section.
19669 @value{GDBN} has support for this extension. If the section exists,
19670 then it is used provided that no other source of debugging information
19671 can be found, and that @value{GDBN} was configured with LZMA support.
19673 This section can be easily created using @command{objcopy} and other
19674 standard utilities:
19677 # Extract the dynamic symbols from the main binary, there is no need
19678 # to also have these in the normal symbol table.
19679 nm -D @var{binary} --format=posix --defined-only \
19680 | awk '@{ print $1 @}' | sort > dynsyms
19682 # Extract all the text (i.e. function) symbols from the debuginfo.
19683 # (Note that we actually also accept "D" symbols, for the benefit
19684 # of platforms like PowerPC64 that use function descriptors.)
19685 nm @var{binary} --format=posix --defined-only \
19686 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
19689 # Keep all the function symbols not already in the dynamic symbol
19691 comm -13 dynsyms funcsyms > keep_symbols
19693 # Separate full debug info into debug binary.
19694 objcopy --only-keep-debug @var{binary} debug
19696 # Copy the full debuginfo, keeping only a minimal set of symbols and
19697 # removing some unnecessary sections.
19698 objcopy -S --remove-section .gdb_index --remove-section .comment \
19699 --keep-symbols=keep_symbols debug mini_debuginfo
19701 # Drop the full debug info from the original binary.
19702 strip --strip-all -R .comment @var{binary}
19704 # Inject the compressed data into the .gnu_debugdata section of the
19707 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
19711 @section Index Files Speed Up @value{GDBN}
19712 @cindex index files
19713 @cindex @samp{.gdb_index} section
19715 When @value{GDBN} finds a symbol file, it scans the symbols in the
19716 file in order to construct an internal symbol table. This lets most
19717 @value{GDBN} operations work quickly---at the cost of a delay early
19718 on. For large programs, this delay can be quite lengthy, so
19719 @value{GDBN} provides a way to build an index, which speeds up
19722 For convenience, @value{GDBN} comes with a program,
19723 @command{gdb-add-index}, which can be used to add the index to a
19724 symbol file. It takes the symbol file as its only argument:
19727 $ gdb-add-index symfile
19730 @xref{gdb-add-index}.
19732 It is also possible to do the work manually. Here is what
19733 @command{gdb-add-index} does behind the curtains.
19735 The index is stored as a section in the symbol file. @value{GDBN} can
19736 write the index to a file, then you can put it into the symbol file
19737 using @command{objcopy}.
19739 To create an index file, use the @code{save gdb-index} command:
19742 @item save gdb-index [-dwarf-5] @var{directory}
19743 @kindex save gdb-index
19744 Create index files for all symbol files currently known by
19745 @value{GDBN}. For each known @var{symbol-file}, this command by
19746 default creates it produces a single file
19747 @file{@var{symbol-file}.gdb-index}. If you invoke this command with
19748 the @option{-dwarf-5} option, it produces 2 files:
19749 @file{@var{symbol-file}.debug_names} and
19750 @file{@var{symbol-file}.debug_str}. The files are created in the
19751 given @var{directory}.
19754 Once you have created an index file you can merge it into your symbol
19755 file, here named @file{symfile}, using @command{objcopy}:
19758 $ objcopy --add-section .gdb_index=symfile.gdb-index \
19759 --set-section-flags .gdb_index=readonly symfile symfile
19762 Or for @code{-dwarf-5}:
19765 $ objcopy --dump-section .debug_str=symfile.debug_str.new symfile
19766 $ cat symfile.debug_str >>symfile.debug_str.new
19767 $ objcopy --add-section .debug_names=symfile.gdb-index \
19768 --set-section-flags .debug_names=readonly \
19769 --update-section .debug_str=symfile.debug_str.new symfile symfile
19772 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
19773 sections that have been deprecated. Usually they are deprecated because
19774 they are missing a new feature or have performance issues.
19775 To tell @value{GDBN} to use a deprecated index section anyway
19776 specify @code{set use-deprecated-index-sections on}.
19777 The default is @code{off}.
19778 This can speed up startup, but may result in some functionality being lost.
19779 @xref{Index Section Format}.
19781 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
19782 must be done before gdb reads the file. The following will not work:
19785 $ gdb -ex "set use-deprecated-index-sections on" <program>
19788 Instead you must do, for example,
19791 $ gdb -iex "set use-deprecated-index-sections on" <program>
19794 There are currently some limitation on indices. They only work when
19795 for DWARF debugging information, not stabs. And, they do not
19796 currently work for programs using Ada.
19798 @node Symbol Errors
19799 @section Errors Reading Symbol Files
19801 While reading a symbol file, @value{GDBN} occasionally encounters problems,
19802 such as symbol types it does not recognize, or known bugs in compiler
19803 output. By default, @value{GDBN} does not notify you of such problems, since
19804 they are relatively common and primarily of interest to people
19805 debugging compilers. If you are interested in seeing information
19806 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
19807 only one message about each such type of problem, no matter how many
19808 times the problem occurs; or you can ask @value{GDBN} to print more messages,
19809 to see how many times the problems occur, with the @code{set
19810 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
19813 The messages currently printed, and their meanings, include:
19816 @item inner block not inside outer block in @var{symbol}
19818 The symbol information shows where symbol scopes begin and end
19819 (such as at the start of a function or a block of statements). This
19820 error indicates that an inner scope block is not fully contained
19821 in its outer scope blocks.
19823 @value{GDBN} circumvents the problem by treating the inner block as if it had
19824 the same scope as the outer block. In the error message, @var{symbol}
19825 may be shown as ``@code{(don't know)}'' if the outer block is not a
19828 @item block at @var{address} out of order
19830 The symbol information for symbol scope blocks should occur in
19831 order of increasing addresses. This error indicates that it does not
19834 @value{GDBN} does not circumvent this problem, and has trouble
19835 locating symbols in the source file whose symbols it is reading. (You
19836 can often determine what source file is affected by specifying
19837 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
19840 @item bad block start address patched
19842 The symbol information for a symbol scope block has a start address
19843 smaller than the address of the preceding source line. This is known
19844 to occur in the SunOS 4.1.1 (and earlier) C compiler.
19846 @value{GDBN} circumvents the problem by treating the symbol scope block as
19847 starting on the previous source line.
19849 @item bad string table offset in symbol @var{n}
19852 Symbol number @var{n} contains a pointer into the string table which is
19853 larger than the size of the string table.
19855 @value{GDBN} circumvents the problem by considering the symbol to have the
19856 name @code{foo}, which may cause other problems if many symbols end up
19859 @item unknown symbol type @code{0x@var{nn}}
19861 The symbol information contains new data types that @value{GDBN} does
19862 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
19863 uncomprehended information, in hexadecimal.
19865 @value{GDBN} circumvents the error by ignoring this symbol information.
19866 This usually allows you to debug your program, though certain symbols
19867 are not accessible. If you encounter such a problem and feel like
19868 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
19869 on @code{complain}, then go up to the function @code{read_dbx_symtab}
19870 and examine @code{*bufp} to see the symbol.
19872 @item stub type has NULL name
19874 @value{GDBN} could not find the full definition for a struct or class.
19876 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
19877 The symbol information for a C@t{++} member function is missing some
19878 information that recent versions of the compiler should have output for
19881 @item info mismatch between compiler and debugger
19883 @value{GDBN} could not parse a type specification output by the compiler.
19888 @section GDB Data Files
19890 @cindex prefix for data files
19891 @value{GDBN} will sometimes read an auxiliary data file. These files
19892 are kept in a directory known as the @dfn{data directory}.
19894 You can set the data directory's name, and view the name @value{GDBN}
19895 is currently using.
19898 @kindex set data-directory
19899 @item set data-directory @var{directory}
19900 Set the directory which @value{GDBN} searches for auxiliary data files
19901 to @var{directory}.
19903 @kindex show data-directory
19904 @item show data-directory
19905 Show the directory @value{GDBN} searches for auxiliary data files.
19908 @cindex default data directory
19909 @cindex @samp{--with-gdb-datadir}
19910 You can set the default data directory by using the configure-time
19911 @samp{--with-gdb-datadir} option. If the data directory is inside
19912 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19913 @samp{--exec-prefix}), then the default data directory will be updated
19914 automatically if the installed @value{GDBN} is moved to a new
19917 The data directory may also be specified with the
19918 @code{--data-directory} command line option.
19919 @xref{Mode Options}.
19922 @chapter Specifying a Debugging Target
19924 @cindex debugging target
19925 A @dfn{target} is the execution environment occupied by your program.
19927 Often, @value{GDBN} runs in the same host environment as your program;
19928 in that case, the debugging target is specified as a side effect when
19929 you use the @code{file} or @code{core} commands. When you need more
19930 flexibility---for example, running @value{GDBN} on a physically separate
19931 host, or controlling a standalone system over a serial port or a
19932 realtime system over a TCP/IP connection---you can use the @code{target}
19933 command to specify one of the target types configured for @value{GDBN}
19934 (@pxref{Target Commands, ,Commands for Managing Targets}).
19936 @cindex target architecture
19937 It is possible to build @value{GDBN} for several different @dfn{target
19938 architectures}. When @value{GDBN} is built like that, you can choose
19939 one of the available architectures with the @kbd{set architecture}
19943 @kindex set architecture
19944 @kindex show architecture
19945 @item set architecture @var{arch}
19946 This command sets the current target architecture to @var{arch}. The
19947 value of @var{arch} can be @code{"auto"}, in addition to one of the
19948 supported architectures.
19950 @item show architecture
19951 Show the current target architecture.
19953 @item set processor
19955 @kindex set processor
19956 @kindex show processor
19957 These are alias commands for, respectively, @code{set architecture}
19958 and @code{show architecture}.
19962 * Active Targets:: Active targets
19963 * Target Commands:: Commands for managing targets
19964 * Byte Order:: Choosing target byte order
19967 @node Active Targets
19968 @section Active Targets
19970 @cindex stacking targets
19971 @cindex active targets
19972 @cindex multiple targets
19974 There are multiple classes of targets such as: processes, executable files or
19975 recording sessions. Core files belong to the process class, making core file
19976 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
19977 on multiple active targets, one in each class. This allows you to (for
19978 example) start a process and inspect its activity, while still having access to
19979 the executable file after the process finishes. Or if you start process
19980 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
19981 presented a virtual layer of the recording target, while the process target
19982 remains stopped at the chronologically last point of the process execution.
19984 Use the @code{core-file} and @code{exec-file} commands to select a new core
19985 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
19986 specify as a target a process that is already running, use the @code{attach}
19987 command (@pxref{Attach, ,Debugging an Already-running Process}).
19989 @node Target Commands
19990 @section Commands for Managing Targets
19993 @item target @var{type} @var{parameters}
19994 Connects the @value{GDBN} host environment to a target machine or
19995 process. A target is typically a protocol for talking to debugging
19996 facilities. You use the argument @var{type} to specify the type or
19997 protocol of the target machine.
19999 Further @var{parameters} are interpreted by the target protocol, but
20000 typically include things like device names or host names to connect
20001 with, process numbers, and baud rates.
20003 The @code{target} command does not repeat if you press @key{RET} again
20004 after executing the command.
20006 @kindex help target
20008 Displays the names of all targets available. To display targets
20009 currently selected, use either @code{info target} or @code{info files}
20010 (@pxref{Files, ,Commands to Specify Files}).
20012 @item help target @var{name}
20013 Describe a particular target, including any parameters necessary to
20016 @kindex set gnutarget
20017 @item set gnutarget @var{args}
20018 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
20019 knows whether it is reading an @dfn{executable},
20020 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
20021 with the @code{set gnutarget} command. Unlike most @code{target} commands,
20022 with @code{gnutarget} the @code{target} refers to a program, not a machine.
20025 @emph{Warning:} To specify a file format with @code{set gnutarget},
20026 you must know the actual BFD name.
20030 @xref{Files, , Commands to Specify Files}.
20032 @kindex show gnutarget
20033 @item show gnutarget
20034 Use the @code{show gnutarget} command to display what file format
20035 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
20036 @value{GDBN} will determine the file format for each file automatically,
20037 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
20040 @cindex common targets
20041 Here are some common targets (available, or not, depending on the GDB
20046 @item target exec @var{program}
20047 @cindex executable file target
20048 An executable file. @samp{target exec @var{program}} is the same as
20049 @samp{exec-file @var{program}}.
20051 @item target core @var{filename}
20052 @cindex core dump file target
20053 A core dump file. @samp{target core @var{filename}} is the same as
20054 @samp{core-file @var{filename}}.
20056 @item target remote @var{medium}
20057 @cindex remote target
20058 A remote system connected to @value{GDBN} via a serial line or network
20059 connection. This command tells @value{GDBN} to use its own remote
20060 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
20062 For example, if you have a board connected to @file{/dev/ttya} on the
20063 machine running @value{GDBN}, you could say:
20066 target remote /dev/ttya
20069 @code{target remote} supports the @code{load} command. This is only
20070 useful if you have some other way of getting the stub to the target
20071 system, and you can put it somewhere in memory where it won't get
20072 clobbered by the download.
20074 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20075 @cindex built-in simulator target
20076 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
20084 works; however, you cannot assume that a specific memory map, device
20085 drivers, or even basic I/O is available, although some simulators do
20086 provide these. For info about any processor-specific simulator details,
20087 see the appropriate section in @ref{Embedded Processors, ,Embedded
20090 @item target native
20091 @cindex native target
20092 Setup for local/native process debugging. Useful to make the
20093 @code{run} command spawn native processes (likewise @code{attach},
20094 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
20095 (@pxref{set auto-connect-native-target}).
20099 Different targets are available on different configurations of @value{GDBN};
20100 your configuration may have more or fewer targets.
20102 Many remote targets require you to download the executable's code once
20103 you've successfully established a connection. You may wish to control
20104 various aspects of this process.
20109 @kindex set hash@r{, for remote monitors}
20110 @cindex hash mark while downloading
20111 This command controls whether a hash mark @samp{#} is displayed while
20112 downloading a file to the remote monitor. If on, a hash mark is
20113 displayed after each S-record is successfully downloaded to the
20117 @kindex show hash@r{, for remote monitors}
20118 Show the current status of displaying the hash mark.
20120 @item set debug monitor
20121 @kindex set debug monitor
20122 @cindex display remote monitor communications
20123 Enable or disable display of communications messages between
20124 @value{GDBN} and the remote monitor.
20126 @item show debug monitor
20127 @kindex show debug monitor
20128 Show the current status of displaying communications between
20129 @value{GDBN} and the remote monitor.
20134 @kindex load @var{filename} @var{offset}
20135 @item load @var{filename} @var{offset}
20137 Depending on what remote debugging facilities are configured into
20138 @value{GDBN}, the @code{load} command may be available. Where it exists, it
20139 is meant to make @var{filename} (an executable) available for debugging
20140 on the remote system---by downloading, or dynamic linking, for example.
20141 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
20142 the @code{add-symbol-file} command.
20144 If your @value{GDBN} does not have a @code{load} command, attempting to
20145 execute it gets the error message ``@code{You can't do that when your
20146 target is @dots{}}''
20148 The file is loaded at whatever address is specified in the executable.
20149 For some object file formats, you can specify the load address when you
20150 link the program; for other formats, like a.out, the object file format
20151 specifies a fixed address.
20152 @c FIXME! This would be a good place for an xref to the GNU linker doc.
20154 It is also possible to tell @value{GDBN} to load the executable file at a
20155 specific offset described by the optional argument @var{offset}. When
20156 @var{offset} is provided, @var{filename} must also be provided.
20158 Depending on the remote side capabilities, @value{GDBN} may be able to
20159 load programs into flash memory.
20161 @code{load} does not repeat if you press @key{RET} again after using it.
20166 @kindex flash-erase
20168 @anchor{flash-erase}
20170 Erases all known flash memory regions on the target.
20175 @section Choosing Target Byte Order
20177 @cindex choosing target byte order
20178 @cindex target byte order
20180 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
20181 offer the ability to run either big-endian or little-endian byte
20182 orders. Usually the executable or symbol will include a bit to
20183 designate the endian-ness, and you will not need to worry about
20184 which to use. However, you may still find it useful to adjust
20185 @value{GDBN}'s idea of processor endian-ness manually.
20189 @item set endian big
20190 Instruct @value{GDBN} to assume the target is big-endian.
20192 @item set endian little
20193 Instruct @value{GDBN} to assume the target is little-endian.
20195 @item set endian auto
20196 Instruct @value{GDBN} to use the byte order associated with the
20200 Display @value{GDBN}'s current idea of the target byte order.
20204 Note that these commands merely adjust interpretation of symbolic
20205 data on the host, and that they have absolutely no effect on the
20209 @node Remote Debugging
20210 @chapter Debugging Remote Programs
20211 @cindex remote debugging
20213 If you are trying to debug a program running on a machine that cannot run
20214 @value{GDBN} in the usual way, it is often useful to use remote debugging.
20215 For example, you might use remote debugging on an operating system kernel,
20216 or on a small system which does not have a general purpose operating system
20217 powerful enough to run a full-featured debugger.
20219 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
20220 to make this work with particular debugging targets. In addition,
20221 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
20222 but not specific to any particular target system) which you can use if you
20223 write the remote stubs---the code that runs on the remote system to
20224 communicate with @value{GDBN}.
20226 Other remote targets may be available in your
20227 configuration of @value{GDBN}; use @code{help target} to list them.
20230 * Connecting:: Connecting to a remote target
20231 * File Transfer:: Sending files to a remote system
20232 * Server:: Using the gdbserver program
20233 * Remote Configuration:: Remote configuration
20234 * Remote Stub:: Implementing a remote stub
20238 @section Connecting to a Remote Target
20239 @cindex remote debugging, connecting
20240 @cindex @code{gdbserver}, connecting
20241 @cindex remote debugging, types of connections
20242 @cindex @code{gdbserver}, types of connections
20243 @cindex @code{gdbserver}, @code{target remote} mode
20244 @cindex @code{gdbserver}, @code{target extended-remote} mode
20246 This section describes how to connect to a remote target, including the
20247 types of connections and their differences, how to set up executable and
20248 symbol files on the host and target, and the commands used for
20249 connecting to and disconnecting from the remote target.
20251 @subsection Types of Remote Connections
20253 @value{GDBN} supports two types of remote connections, @code{target remote}
20254 mode and @code{target extended-remote} mode. Note that many remote targets
20255 support only @code{target remote} mode. There are several major
20256 differences between the two types of connections, enumerated here:
20260 @cindex remote debugging, detach and program exit
20261 @item Result of detach or program exit
20262 @strong{With target remote mode:} When the debugged program exits or you
20263 detach from it, @value{GDBN} disconnects from the target. When using
20264 @code{gdbserver}, @code{gdbserver} will exit.
20266 @strong{With target extended-remote mode:} When the debugged program exits or
20267 you detach from it, @value{GDBN} remains connected to the target, even
20268 though no program is running. You can rerun the program, attach to a
20269 running program, or use @code{monitor} commands specific to the target.
20271 When using @code{gdbserver} in this case, it does not exit unless it was
20272 invoked using the @option{--once} option. If the @option{--once} option
20273 was not used, you can ask @code{gdbserver} to exit using the
20274 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
20276 @item Specifying the program to debug
20277 For both connection types you use the @code{file} command to specify the
20278 program on the host system. If you are using @code{gdbserver} there are
20279 some differences in how to specify the location of the program on the
20282 @strong{With target remote mode:} You must either specify the program to debug
20283 on the @code{gdbserver} command line or use the @option{--attach} option
20284 (@pxref{Attaching to a program,,Attaching to a Running Program}).
20286 @cindex @option{--multi}, @code{gdbserver} option
20287 @strong{With target extended-remote mode:} You may specify the program to debug
20288 on the @code{gdbserver} command line, or you can load the program or attach
20289 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
20291 @anchor{--multi Option in Types of Remote Connnections}
20292 You can start @code{gdbserver} without supplying an initial command to run
20293 or process ID to attach. To do this, use the @option{--multi} command line
20294 option. Then you can connect using @code{target extended-remote} and start
20295 the program you want to debug (see below for details on using the
20296 @code{run} command in this scenario). Note that the conditions under which
20297 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
20298 (@code{target remote} or @code{target extended-remote}). The
20299 @option{--multi} option to @code{gdbserver} has no influence on that.
20301 @item The @code{run} command
20302 @strong{With target remote mode:} The @code{run} command is not
20303 supported. Once a connection has been established, you can use all
20304 the usual @value{GDBN} commands to examine and change data. The
20305 remote program is already running, so you can use commands like
20306 @kbd{step} and @kbd{continue}.
20308 @strong{With target extended-remote mode:} The @code{run} command is
20309 supported. The @code{run} command uses the value set by
20310 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
20311 the program to run. Command line arguments are supported, except for
20312 wildcard expansion and I/O redirection (@pxref{Arguments}).
20314 If you specify the program to debug on the command line, then the
20315 @code{run} command is not required to start execution, and you can
20316 resume using commands like @kbd{step} and @kbd{continue} as with
20317 @code{target remote} mode.
20319 @anchor{Attaching in Types of Remote Connections}
20321 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
20322 not supported. To attach to a running program using @code{gdbserver}, you
20323 must use the @option{--attach} option (@pxref{Running gdbserver}).
20325 @strong{With target extended-remote mode:} To attach to a running program,
20326 you may use the @code{attach} command after the connection has been
20327 established. If you are using @code{gdbserver}, you may also invoke
20328 @code{gdbserver} using the @option{--attach} option
20329 (@pxref{Running gdbserver}).
20333 @anchor{Host and target files}
20334 @subsection Host and Target Files
20335 @cindex remote debugging, symbol files
20336 @cindex symbol files, remote debugging
20338 @value{GDBN}, running on the host, needs access to symbol and debugging
20339 information for your program running on the target. This requires
20340 access to an unstripped copy of your program, and possibly any associated
20341 symbol files. Note that this section applies equally to both @code{target
20342 remote} mode and @code{target extended-remote} mode.
20344 Some remote targets (@pxref{qXfer executable filename read}, and
20345 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
20346 the same connection used to communicate with @value{GDBN}. With such a
20347 target, if the remote program is unstripped, the only command you need is
20348 @code{target remote} (or @code{target extended-remote}).
20350 If the remote program is stripped, or the target does not support remote
20351 program file access, start up @value{GDBN} using the name of the local
20352 unstripped copy of your program as the first argument, or use the
20353 @code{file} command. Use @code{set sysroot} to specify the location (on
20354 the host) of target libraries (unless your @value{GDBN} was compiled with
20355 the correct sysroot using @code{--with-sysroot}). Alternatively, you
20356 may use @code{set solib-search-path} to specify how @value{GDBN} locates
20359 The symbol file and target libraries must exactly match the executable
20360 and libraries on the target, with one exception: the files on the host
20361 system should not be stripped, even if the files on the target system
20362 are. Mismatched or missing files will lead to confusing results
20363 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
20364 files may also prevent @code{gdbserver} from debugging multi-threaded
20367 @subsection Remote Connection Commands
20368 @cindex remote connection commands
20369 @value{GDBN} can communicate with the target over a serial line, or
20370 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
20371 each case, @value{GDBN} uses the same protocol for debugging your
20372 program; only the medium carrying the debugging packets varies. The
20373 @code{target remote} and @code{target extended-remote} commands
20374 establish a connection to the target. Both commands accept the same
20375 arguments, which indicate the medium to use:
20379 @item target remote @var{serial-device}
20380 @itemx target extended-remote @var{serial-device}
20381 @cindex serial line, @code{target remote}
20382 Use @var{serial-device} to communicate with the target. For example,
20383 to use a serial line connected to the device named @file{/dev/ttyb}:
20386 target remote /dev/ttyb
20389 If you're using a serial line, you may want to give @value{GDBN} the
20390 @samp{--baud} option, or use the @code{set serial baud} command
20391 (@pxref{Remote Configuration, set serial baud}) before the
20392 @code{target} command.
20394 @item target remote @code{@var{host}:@var{port}}
20395 @itemx target remote @code{tcp:@var{host}:@var{port}}
20396 @itemx target extended-remote @code{@var{host}:@var{port}}
20397 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
20398 @cindex @acronym{TCP} port, @code{target remote}
20399 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
20400 The @var{host} may be either a host name or a numeric @acronym{IP}
20401 address; @var{port} must be a decimal number. The @var{host} could be
20402 the target machine itself, if it is directly connected to the net, or
20403 it might be a terminal server which in turn has a serial line to the
20406 For example, to connect to port 2828 on a terminal server named
20410 target remote manyfarms:2828
20413 If your remote target is actually running on the same machine as your
20414 debugger session (e.g.@: a simulator for your target running on the
20415 same host), you can omit the hostname. For example, to connect to
20416 port 1234 on your local machine:
20419 target remote :1234
20423 Note that the colon is still required here.
20425 @item target remote @code{udp:@var{host}:@var{port}}
20426 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
20427 @cindex @acronym{UDP} port, @code{target remote}
20428 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
20429 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
20432 target remote udp:manyfarms:2828
20435 When using a @acronym{UDP} connection for remote debugging, you should
20436 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
20437 can silently drop packets on busy or unreliable networks, which will
20438 cause havoc with your debugging session.
20440 @item target remote | @var{command}
20441 @itemx target extended-remote | @var{command}
20442 @cindex pipe, @code{target remote} to
20443 Run @var{command} in the background and communicate with it using a
20444 pipe. The @var{command} is a shell command, to be parsed and expanded
20445 by the system's command shell, @code{/bin/sh}; it should expect remote
20446 protocol packets on its standard input, and send replies on its
20447 standard output. You could use this to run a stand-alone simulator
20448 that speaks the remote debugging protocol, to make net connections
20449 using programs like @code{ssh}, or for other similar tricks.
20451 If @var{command} closes its standard output (perhaps by exiting),
20452 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
20453 program has already exited, this will have no effect.)
20457 @cindex interrupting remote programs
20458 @cindex remote programs, interrupting
20459 Whenever @value{GDBN} is waiting for the remote program, if you type the
20460 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
20461 program. This may or may not succeed, depending in part on the hardware
20462 and the serial drivers the remote system uses. If you type the
20463 interrupt character once again, @value{GDBN} displays this prompt:
20466 Interrupted while waiting for the program.
20467 Give up (and stop debugging it)? (y or n)
20470 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
20471 the remote debugging session. (If you decide you want to try again later,
20472 you can use @kbd{target remote} again to connect once more.) If you type
20473 @kbd{n}, @value{GDBN} goes back to waiting.
20475 In @code{target extended-remote} mode, typing @kbd{n} will leave
20476 @value{GDBN} connected to the target.
20479 @kindex detach (remote)
20481 When you have finished debugging the remote program, you can use the
20482 @code{detach} command to release it from @value{GDBN} control.
20483 Detaching from the target normally resumes its execution, but the results
20484 will depend on your particular remote stub. After the @code{detach}
20485 command in @code{target remote} mode, @value{GDBN} is free to connect to
20486 another target. In @code{target extended-remote} mode, @value{GDBN} is
20487 still connected to the target.
20491 The @code{disconnect} command closes the connection to the target, and
20492 the target is generally not resumed. It will wait for @value{GDBN}
20493 (this instance or another one) to connect and continue debugging. After
20494 the @code{disconnect} command, @value{GDBN} is again free to connect to
20497 @cindex send command to remote monitor
20498 @cindex extend @value{GDBN} for remote targets
20499 @cindex add new commands for external monitor
20501 @item monitor @var{cmd}
20502 This command allows you to send arbitrary commands directly to the
20503 remote monitor. Since @value{GDBN} doesn't care about the commands it
20504 sends like this, this command is the way to extend @value{GDBN}---you
20505 can add new commands that only the external monitor will understand
20509 @node File Transfer
20510 @section Sending files to a remote system
20511 @cindex remote target, file transfer
20512 @cindex file transfer
20513 @cindex sending files to remote systems
20515 Some remote targets offer the ability to transfer files over the same
20516 connection used to communicate with @value{GDBN}. This is convenient
20517 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
20518 running @code{gdbserver} over a network interface. For other targets,
20519 e.g.@: embedded devices with only a single serial port, this may be
20520 the only way to upload or download files.
20522 Not all remote targets support these commands.
20526 @item remote put @var{hostfile} @var{targetfile}
20527 Copy file @var{hostfile} from the host system (the machine running
20528 @value{GDBN}) to @var{targetfile} on the target system.
20531 @item remote get @var{targetfile} @var{hostfile}
20532 Copy file @var{targetfile} from the target system to @var{hostfile}
20533 on the host system.
20535 @kindex remote delete
20536 @item remote delete @var{targetfile}
20537 Delete @var{targetfile} from the target system.
20542 @section Using the @code{gdbserver} Program
20545 @cindex remote connection without stubs
20546 @code{gdbserver} is a control program for Unix-like systems, which
20547 allows you to connect your program with a remote @value{GDBN} via
20548 @code{target remote} or @code{target extended-remote}---but without
20549 linking in the usual debugging stub.
20551 @code{gdbserver} is not a complete replacement for the debugging stubs,
20552 because it requires essentially the same operating-system facilities
20553 that @value{GDBN} itself does. In fact, a system that can run
20554 @code{gdbserver} to connect to a remote @value{GDBN} could also run
20555 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
20556 because it is a much smaller program than @value{GDBN} itself. It is
20557 also easier to port than all of @value{GDBN}, so you may be able to get
20558 started more quickly on a new system by using @code{gdbserver}.
20559 Finally, if you develop code for real-time systems, you may find that
20560 the tradeoffs involved in real-time operation make it more convenient to
20561 do as much development work as possible on another system, for example
20562 by cross-compiling. You can use @code{gdbserver} to make a similar
20563 choice for debugging.
20565 @value{GDBN} and @code{gdbserver} communicate via either a serial line
20566 or a TCP connection, using the standard @value{GDBN} remote serial
20570 @emph{Warning:} @code{gdbserver} does not have any built-in security.
20571 Do not run @code{gdbserver} connected to any public network; a
20572 @value{GDBN} connection to @code{gdbserver} provides access to the
20573 target system with the same privileges as the user running
20577 @anchor{Running gdbserver}
20578 @subsection Running @code{gdbserver}
20579 @cindex arguments, to @code{gdbserver}
20580 @cindex @code{gdbserver}, command-line arguments
20582 Run @code{gdbserver} on the target system. You need a copy of the
20583 program you want to debug, including any libraries it requires.
20584 @code{gdbserver} does not need your program's symbol table, so you can
20585 strip the program if necessary to save space. @value{GDBN} on the host
20586 system does all the symbol handling.
20588 To use the server, you must tell it how to communicate with @value{GDBN};
20589 the name of your program; and the arguments for your program. The usual
20593 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
20596 @var{comm} is either a device name (to use a serial line), or a TCP
20597 hostname and portnumber, or @code{-} or @code{stdio} to use
20598 stdin/stdout of @code{gdbserver}.
20599 For example, to debug Emacs with the argument
20600 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
20604 target> gdbserver /dev/com1 emacs foo.txt
20607 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
20610 To use a TCP connection instead of a serial line:
20613 target> gdbserver host:2345 emacs foo.txt
20616 The only difference from the previous example is the first argument,
20617 specifying that you are communicating with the host @value{GDBN} via
20618 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
20619 expect a TCP connection from machine @samp{host} to local TCP port 2345.
20620 (Currently, the @samp{host} part is ignored.) You can choose any number
20621 you want for the port number as long as it does not conflict with any
20622 TCP ports already in use on the target system (for example, @code{23} is
20623 reserved for @code{telnet}).@footnote{If you choose a port number that
20624 conflicts with another service, @code{gdbserver} prints an error message
20625 and exits.} You must use the same port number with the host @value{GDBN}
20626 @code{target remote} command.
20628 The @code{stdio} connection is useful when starting @code{gdbserver}
20632 (gdb) target remote | ssh -T hostname gdbserver - hello
20635 The @samp{-T} option to ssh is provided because we don't need a remote pty,
20636 and we don't want escape-character handling. Ssh does this by default when
20637 a command is provided, the flag is provided to make it explicit.
20638 You could elide it if you want to.
20640 Programs started with stdio-connected gdbserver have @file{/dev/null} for
20641 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
20642 display through a pipe connected to gdbserver.
20643 Both @code{stdout} and @code{stderr} use the same pipe.
20645 @anchor{Attaching to a program}
20646 @subsubsection Attaching to a Running Program
20647 @cindex attach to a program, @code{gdbserver}
20648 @cindex @option{--attach}, @code{gdbserver} option
20650 On some targets, @code{gdbserver} can also attach to running programs.
20651 This is accomplished via the @code{--attach} argument. The syntax is:
20654 target> gdbserver --attach @var{comm} @var{pid}
20657 @var{pid} is the process ID of a currently running process. It isn't
20658 necessary to point @code{gdbserver} at a binary for the running process.
20660 In @code{target extended-remote} mode, you can also attach using the
20661 @value{GDBN} attach command
20662 (@pxref{Attaching in Types of Remote Connections}).
20665 You can debug processes by name instead of process ID if your target has the
20666 @code{pidof} utility:
20669 target> gdbserver --attach @var{comm} `pidof @var{program}`
20672 In case more than one copy of @var{program} is running, or @var{program}
20673 has multiple threads, most versions of @code{pidof} support the
20674 @code{-s} option to only return the first process ID.
20676 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
20678 This section applies only when @code{gdbserver} is run to listen on a TCP
20681 @code{gdbserver} normally terminates after all of its debugged processes have
20682 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
20683 extended-remote}, @code{gdbserver} stays running even with no processes left.
20684 @value{GDBN} normally terminates the spawned debugged process on its exit,
20685 which normally also terminates @code{gdbserver} in the @kbd{target remote}
20686 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
20687 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
20688 stays running even in the @kbd{target remote} mode.
20690 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
20691 Such reconnecting is useful for features like @ref{disconnected tracing}. For
20692 completeness, at most one @value{GDBN} can be connected at a time.
20694 @cindex @option{--once}, @code{gdbserver} option
20695 By default, @code{gdbserver} keeps the listening TCP port open, so that
20696 subsequent connections are possible. However, if you start @code{gdbserver}
20697 with the @option{--once} option, it will stop listening for any further
20698 connection attempts after connecting to the first @value{GDBN} session. This
20699 means no further connections to @code{gdbserver} will be possible after the
20700 first one. It also means @code{gdbserver} will terminate after the first
20701 connection with remote @value{GDBN} has closed, even for unexpectedly closed
20702 connections and even in the @kbd{target extended-remote} mode. The
20703 @option{--once} option allows reusing the same port number for connecting to
20704 multiple instances of @code{gdbserver} running on the same host, since each
20705 instance closes its port after the first connection.
20707 @anchor{Other Command-Line Arguments for gdbserver}
20708 @subsubsection Other Command-Line Arguments for @code{gdbserver}
20710 You can use the @option{--multi} option to start @code{gdbserver} without
20711 specifying a program to debug or a process to attach to. Then you can
20712 attach in @code{target extended-remote} mode and run or attach to a
20713 program. For more information,
20714 @pxref{--multi Option in Types of Remote Connnections}.
20716 @cindex @option{--debug}, @code{gdbserver} option
20717 The @option{--debug} option tells @code{gdbserver} to display extra
20718 status information about the debugging process.
20719 @cindex @option{--remote-debug}, @code{gdbserver} option
20720 The @option{--remote-debug} option tells @code{gdbserver} to display
20721 remote protocol debug output. These options are intended for
20722 @code{gdbserver} development and for bug reports to the developers.
20724 @cindex @option{--debug-format}, @code{gdbserver} option
20725 The @option{--debug-format=option1[,option2,...]} option tells
20726 @code{gdbserver} to include additional information in each output.
20727 Possible options are:
20731 Turn off all extra information in debugging output.
20733 Turn on all extra information in debugging output.
20735 Include a timestamp in each line of debugging output.
20738 Options are processed in order. Thus, for example, if @option{none}
20739 appears last then no additional information is added to debugging output.
20741 @cindex @option{--wrapper}, @code{gdbserver} option
20742 The @option{--wrapper} option specifies a wrapper to launch programs
20743 for debugging. The option should be followed by the name of the
20744 wrapper, then any command-line arguments to pass to the wrapper, then
20745 @kbd{--} indicating the end of the wrapper arguments.
20747 @code{gdbserver} runs the specified wrapper program with a combined
20748 command line including the wrapper arguments, then the name of the
20749 program to debug, then any arguments to the program. The wrapper
20750 runs until it executes your program, and then @value{GDBN} gains control.
20752 You can use any program that eventually calls @code{execve} with
20753 its arguments as a wrapper. Several standard Unix utilities do
20754 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
20755 with @code{exec "$@@"} will also work.
20757 For example, you can use @code{env} to pass an environment variable to
20758 the debugged program, without setting the variable in @code{gdbserver}'s
20762 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
20765 @cindex @option{--selftest}
20766 The @option{--selftest} option runs the self tests in @code{gdbserver}:
20769 $ gdbserver --selftest
20770 Ran 2 unit tests, 0 failed
20773 These tests are disabled in release.
20774 @subsection Connecting to @code{gdbserver}
20776 The basic procedure for connecting to the remote target is:
20780 Run @value{GDBN} on the host system.
20783 Make sure you have the necessary symbol files
20784 (@pxref{Host and target files}).
20785 Load symbols for your application using the @code{file} command before you
20786 connect. Use @code{set sysroot} to locate target libraries (unless your
20787 @value{GDBN} was compiled with the correct sysroot using
20788 @code{--with-sysroot}).
20791 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
20792 For TCP connections, you must start up @code{gdbserver} prior to using
20793 the @code{target} command. Otherwise you may get an error whose
20794 text depends on the host system, but which usually looks something like
20795 @samp{Connection refused}. Don't use the @code{load}
20796 command in @value{GDBN} when using @code{target remote} mode, since the
20797 program is already on the target.
20801 @anchor{Monitor Commands for gdbserver}
20802 @subsection Monitor Commands for @code{gdbserver}
20803 @cindex monitor commands, for @code{gdbserver}
20805 During a @value{GDBN} session using @code{gdbserver}, you can use the
20806 @code{monitor} command to send special requests to @code{gdbserver}.
20807 Here are the available commands.
20811 List the available monitor commands.
20813 @item monitor set debug 0
20814 @itemx monitor set debug 1
20815 Disable or enable general debugging messages.
20817 @item monitor set remote-debug 0
20818 @itemx monitor set remote-debug 1
20819 Disable or enable specific debugging messages associated with the remote
20820 protocol (@pxref{Remote Protocol}).
20822 @item monitor set debug-format option1@r{[},option2,...@r{]}
20823 Specify additional text to add to debugging messages.
20824 Possible options are:
20828 Turn off all extra information in debugging output.
20830 Turn on all extra information in debugging output.
20832 Include a timestamp in each line of debugging output.
20835 Options are processed in order. Thus, for example, if @option{none}
20836 appears last then no additional information is added to debugging output.
20838 @item monitor set libthread-db-search-path [PATH]
20839 @cindex gdbserver, search path for @code{libthread_db}
20840 When this command is issued, @var{path} is a colon-separated list of
20841 directories to search for @code{libthread_db} (@pxref{Threads,,set
20842 libthread-db-search-path}). If you omit @var{path},
20843 @samp{libthread-db-search-path} will be reset to its default value.
20845 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
20846 not supported in @code{gdbserver}.
20849 Tell gdbserver to exit immediately. This command should be followed by
20850 @code{disconnect} to close the debugging session. @code{gdbserver} will
20851 detach from any attached processes and kill any processes it created.
20852 Use @code{monitor exit} to terminate @code{gdbserver} at the end
20853 of a multi-process mode debug session.
20857 @subsection Tracepoints support in @code{gdbserver}
20858 @cindex tracepoints support in @code{gdbserver}
20860 On some targets, @code{gdbserver} supports tracepoints, fast
20861 tracepoints and static tracepoints.
20863 For fast or static tracepoints to work, a special library called the
20864 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
20865 This library is built and distributed as an integral part of
20866 @code{gdbserver}. In addition, support for static tracepoints
20867 requires building the in-process agent library with static tracepoints
20868 support. At present, the UST (LTTng Userspace Tracer,
20869 @url{http://lttng.org/ust}) tracing engine is supported. This support
20870 is automatically available if UST development headers are found in the
20871 standard include path when @code{gdbserver} is built, or if
20872 @code{gdbserver} was explicitly configured using @option{--with-ust}
20873 to point at such headers. You can explicitly disable the support
20874 using @option{--with-ust=no}.
20876 There are several ways to load the in-process agent in your program:
20879 @item Specifying it as dependency at link time
20881 You can link your program dynamically with the in-process agent
20882 library. On most systems, this is accomplished by adding
20883 @code{-linproctrace} to the link command.
20885 @item Using the system's preloading mechanisms
20887 You can force loading the in-process agent at startup time by using
20888 your system's support for preloading shared libraries. Many Unixes
20889 support the concept of preloading user defined libraries. In most
20890 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
20891 in the environment. See also the description of @code{gdbserver}'s
20892 @option{--wrapper} command line option.
20894 @item Using @value{GDBN} to force loading the agent at run time
20896 On some systems, you can force the inferior to load a shared library,
20897 by calling a dynamic loader function in the inferior that takes care
20898 of dynamically looking up and loading a shared library. On most Unix
20899 systems, the function is @code{dlopen}. You'll use the @code{call}
20900 command for that. For example:
20903 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
20906 Note that on most Unix systems, for the @code{dlopen} function to be
20907 available, the program needs to be linked with @code{-ldl}.
20910 On systems that have a userspace dynamic loader, like most Unix
20911 systems, when you connect to @code{gdbserver} using @code{target
20912 remote}, you'll find that the program is stopped at the dynamic
20913 loader's entry point, and no shared library has been loaded in the
20914 program's address space yet, including the in-process agent. In that
20915 case, before being able to use any of the fast or static tracepoints
20916 features, you need to let the loader run and load the shared
20917 libraries. The simplest way to do that is to run the program to the
20918 main procedure. E.g., if debugging a C or C@t{++} program, start
20919 @code{gdbserver} like so:
20922 $ gdbserver :9999 myprogram
20925 Start GDB and connect to @code{gdbserver} like so, and run to main:
20929 (@value{GDBP}) target remote myhost:9999
20930 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
20931 (@value{GDBP}) b main
20932 (@value{GDBP}) continue
20935 The in-process tracing agent library should now be loaded into the
20936 process; you can confirm it with the @code{info sharedlibrary}
20937 command, which will list @file{libinproctrace.so} as loaded in the
20938 process. You are now ready to install fast tracepoints, list static
20939 tracepoint markers, probe static tracepoints markers, and start
20942 @node Remote Configuration
20943 @section Remote Configuration
20946 @kindex show remote
20947 This section documents the configuration options available when
20948 debugging remote programs. For the options related to the File I/O
20949 extensions of the remote protocol, see @ref{system,
20950 system-call-allowed}.
20953 @item set remoteaddresssize @var{bits}
20954 @cindex address size for remote targets
20955 @cindex bits in remote address
20956 Set the maximum size of address in a memory packet to the specified
20957 number of bits. @value{GDBN} will mask off the address bits above
20958 that number, when it passes addresses to the remote target. The
20959 default value is the number of bits in the target's address.
20961 @item show remoteaddresssize
20962 Show the current value of remote address size in bits.
20964 @item set serial baud @var{n}
20965 @cindex baud rate for remote targets
20966 Set the baud rate for the remote serial I/O to @var{n} baud. The
20967 value is used to set the speed of the serial port used for debugging
20970 @item show serial baud
20971 Show the current speed of the remote connection.
20973 @item set serial parity @var{parity}
20974 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
20975 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
20977 @item show serial parity
20978 Show the current parity of the serial port.
20980 @item set remotebreak
20981 @cindex interrupt remote programs
20982 @cindex BREAK signal instead of Ctrl-C
20983 @anchor{set remotebreak}
20984 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
20985 when you type @kbd{Ctrl-c} to interrupt the program running
20986 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
20987 character instead. The default is off, since most remote systems
20988 expect to see @samp{Ctrl-C} as the interrupt signal.
20990 @item show remotebreak
20991 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
20992 interrupt the remote program.
20994 @item set remoteflow on
20995 @itemx set remoteflow off
20996 @kindex set remoteflow
20997 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
20998 on the serial port used to communicate to the remote target.
21000 @item show remoteflow
21001 @kindex show remoteflow
21002 Show the current setting of hardware flow control.
21004 @item set remotelogbase @var{base}
21005 Set the base (a.k.a.@: radix) of logging serial protocol
21006 communications to @var{base}. Supported values of @var{base} are:
21007 @code{ascii}, @code{octal}, and @code{hex}. The default is
21010 @item show remotelogbase
21011 Show the current setting of the radix for logging remote serial
21014 @item set remotelogfile @var{file}
21015 @cindex record serial communications on file
21016 Record remote serial communications on the named @var{file}. The
21017 default is not to record at all.
21019 @item show remotelogfile.
21020 Show the current setting of the file name on which to record the
21021 serial communications.
21023 @item set remotetimeout @var{num}
21024 @cindex timeout for serial communications
21025 @cindex remote timeout
21026 Set the timeout limit to wait for the remote target to respond to
21027 @var{num} seconds. The default is 2 seconds.
21029 @item show remotetimeout
21030 Show the current number of seconds to wait for the remote target
21033 @cindex limit hardware breakpoints and watchpoints
21034 @cindex remote target, limit break- and watchpoints
21035 @anchor{set remote hardware-watchpoint-limit}
21036 @anchor{set remote hardware-breakpoint-limit}
21037 @item set remote hardware-watchpoint-limit @var{limit}
21038 @itemx set remote hardware-breakpoint-limit @var{limit}
21039 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
21040 watchpoints. A limit of -1, the default, is treated as unlimited.
21042 @cindex limit hardware watchpoints length
21043 @cindex remote target, limit watchpoints length
21044 @anchor{set remote hardware-watchpoint-length-limit}
21045 @item set remote hardware-watchpoint-length-limit @var{limit}
21046 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
21047 a remote hardware watchpoint. A limit of -1, the default, is treated
21050 @item show remote hardware-watchpoint-length-limit
21051 Show the current limit (in bytes) of the maximum length of
21052 a remote hardware watchpoint.
21054 @item set remote exec-file @var{filename}
21055 @itemx show remote exec-file
21056 @anchor{set remote exec-file}
21057 @cindex executable file, for remote target
21058 Select the file used for @code{run} with @code{target
21059 extended-remote}. This should be set to a filename valid on the
21060 target system. If it is not set, the target will use a default
21061 filename (e.g.@: the last program run).
21063 @item set remote interrupt-sequence
21064 @cindex interrupt remote programs
21065 @cindex select Ctrl-C, BREAK or BREAK-g
21066 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
21067 @samp{BREAK-g} as the
21068 sequence to the remote target in order to interrupt the execution.
21069 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
21070 is high level of serial line for some certain time.
21071 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
21072 It is @code{BREAK} signal followed by character @code{g}.
21074 @item show interrupt-sequence
21075 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
21076 is sent by @value{GDBN} to interrupt the remote program.
21077 @code{BREAK-g} is BREAK signal followed by @code{g} and
21078 also known as Magic SysRq g.
21080 @item set remote interrupt-on-connect
21081 @cindex send interrupt-sequence on start
21082 Specify whether interrupt-sequence is sent to remote target when
21083 @value{GDBN} connects to it. This is mostly needed when you debug
21084 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
21085 which is known as Magic SysRq g in order to connect @value{GDBN}.
21087 @item show interrupt-on-connect
21088 Show whether interrupt-sequence is sent
21089 to remote target when @value{GDBN} connects to it.
21093 @item set tcp auto-retry on
21094 @cindex auto-retry, for remote TCP target
21095 Enable auto-retry for remote TCP connections. This is useful if the remote
21096 debugging agent is launched in parallel with @value{GDBN}; there is a race
21097 condition because the agent may not become ready to accept the connection
21098 before @value{GDBN} attempts to connect. When auto-retry is
21099 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
21100 to establish the connection using the timeout specified by
21101 @code{set tcp connect-timeout}.
21103 @item set tcp auto-retry off
21104 Do not auto-retry failed TCP connections.
21106 @item show tcp auto-retry
21107 Show the current auto-retry setting.
21109 @item set tcp connect-timeout @var{seconds}
21110 @itemx set tcp connect-timeout unlimited
21111 @cindex connection timeout, for remote TCP target
21112 @cindex timeout, for remote target connection
21113 Set the timeout for establishing a TCP connection to the remote target to
21114 @var{seconds}. The timeout affects both polling to retry failed connections
21115 (enabled by @code{set tcp auto-retry on}) and waiting for connections
21116 that are merely slow to complete, and represents an approximate cumulative
21117 value. If @var{seconds} is @code{unlimited}, there is no timeout and
21118 @value{GDBN} will keep attempting to establish a connection forever,
21119 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
21121 @item show tcp connect-timeout
21122 Show the current connection timeout setting.
21125 @cindex remote packets, enabling and disabling
21126 The @value{GDBN} remote protocol autodetects the packets supported by
21127 your debugging stub. If you need to override the autodetection, you
21128 can use these commands to enable or disable individual packets. Each
21129 packet can be set to @samp{on} (the remote target supports this
21130 packet), @samp{off} (the remote target does not support this packet),
21131 or @samp{auto} (detect remote target support for this packet). They
21132 all default to @samp{auto}. For more information about each packet,
21133 see @ref{Remote Protocol}.
21135 During normal use, you should not have to use any of these commands.
21136 If you do, that may be a bug in your remote debugging stub, or a bug
21137 in @value{GDBN}. You may want to report the problem to the
21138 @value{GDBN} developers.
21140 For each packet @var{name}, the command to enable or disable the
21141 packet is @code{set remote @var{name}-packet}. The available settings
21144 @multitable @columnfractions 0.28 0.32 0.25
21147 @tab Related Features
21149 @item @code{fetch-register}
21151 @tab @code{info registers}
21153 @item @code{set-register}
21157 @item @code{binary-download}
21159 @tab @code{load}, @code{set}
21161 @item @code{read-aux-vector}
21162 @tab @code{qXfer:auxv:read}
21163 @tab @code{info auxv}
21165 @item @code{symbol-lookup}
21166 @tab @code{qSymbol}
21167 @tab Detecting multiple threads
21169 @item @code{attach}
21170 @tab @code{vAttach}
21173 @item @code{verbose-resume}
21175 @tab Stepping or resuming multiple threads
21181 @item @code{software-breakpoint}
21185 @item @code{hardware-breakpoint}
21189 @item @code{write-watchpoint}
21193 @item @code{read-watchpoint}
21197 @item @code{access-watchpoint}
21201 @item @code{pid-to-exec-file}
21202 @tab @code{qXfer:exec-file:read}
21203 @tab @code{attach}, @code{run}
21205 @item @code{target-features}
21206 @tab @code{qXfer:features:read}
21207 @tab @code{set architecture}
21209 @item @code{library-info}
21210 @tab @code{qXfer:libraries:read}
21211 @tab @code{info sharedlibrary}
21213 @item @code{memory-map}
21214 @tab @code{qXfer:memory-map:read}
21215 @tab @code{info mem}
21217 @item @code{read-sdata-object}
21218 @tab @code{qXfer:sdata:read}
21219 @tab @code{print $_sdata}
21221 @item @code{read-spu-object}
21222 @tab @code{qXfer:spu:read}
21223 @tab @code{info spu}
21225 @item @code{write-spu-object}
21226 @tab @code{qXfer:spu:write}
21227 @tab @code{info spu}
21229 @item @code{read-siginfo-object}
21230 @tab @code{qXfer:siginfo:read}
21231 @tab @code{print $_siginfo}
21233 @item @code{write-siginfo-object}
21234 @tab @code{qXfer:siginfo:write}
21235 @tab @code{set $_siginfo}
21237 @item @code{threads}
21238 @tab @code{qXfer:threads:read}
21239 @tab @code{info threads}
21241 @item @code{get-thread-local-@*storage-address}
21242 @tab @code{qGetTLSAddr}
21243 @tab Displaying @code{__thread} variables
21245 @item @code{get-thread-information-block-address}
21246 @tab @code{qGetTIBAddr}
21247 @tab Display MS-Windows Thread Information Block.
21249 @item @code{search-memory}
21250 @tab @code{qSearch:memory}
21253 @item @code{supported-packets}
21254 @tab @code{qSupported}
21255 @tab Remote communications parameters
21257 @item @code{catch-syscalls}
21258 @tab @code{QCatchSyscalls}
21259 @tab @code{catch syscall}
21261 @item @code{pass-signals}
21262 @tab @code{QPassSignals}
21263 @tab @code{handle @var{signal}}
21265 @item @code{program-signals}
21266 @tab @code{QProgramSignals}
21267 @tab @code{handle @var{signal}}
21269 @item @code{hostio-close-packet}
21270 @tab @code{vFile:close}
21271 @tab @code{remote get}, @code{remote put}
21273 @item @code{hostio-open-packet}
21274 @tab @code{vFile:open}
21275 @tab @code{remote get}, @code{remote put}
21277 @item @code{hostio-pread-packet}
21278 @tab @code{vFile:pread}
21279 @tab @code{remote get}, @code{remote put}
21281 @item @code{hostio-pwrite-packet}
21282 @tab @code{vFile:pwrite}
21283 @tab @code{remote get}, @code{remote put}
21285 @item @code{hostio-unlink-packet}
21286 @tab @code{vFile:unlink}
21287 @tab @code{remote delete}
21289 @item @code{hostio-readlink-packet}
21290 @tab @code{vFile:readlink}
21293 @item @code{hostio-fstat-packet}
21294 @tab @code{vFile:fstat}
21297 @item @code{hostio-setfs-packet}
21298 @tab @code{vFile:setfs}
21301 @item @code{noack-packet}
21302 @tab @code{QStartNoAckMode}
21303 @tab Packet acknowledgment
21305 @item @code{osdata}
21306 @tab @code{qXfer:osdata:read}
21307 @tab @code{info os}
21309 @item @code{query-attached}
21310 @tab @code{qAttached}
21311 @tab Querying remote process attach state.
21313 @item @code{trace-buffer-size}
21314 @tab @code{QTBuffer:size}
21315 @tab @code{set trace-buffer-size}
21317 @item @code{trace-status}
21318 @tab @code{qTStatus}
21319 @tab @code{tstatus}
21321 @item @code{traceframe-info}
21322 @tab @code{qXfer:traceframe-info:read}
21323 @tab Traceframe info
21325 @item @code{install-in-trace}
21326 @tab @code{InstallInTrace}
21327 @tab Install tracepoint in tracing
21329 @item @code{disable-randomization}
21330 @tab @code{QDisableRandomization}
21331 @tab @code{set disable-randomization}
21333 @item @code{startup-with-shell}
21334 @tab @code{QStartupWithShell}
21335 @tab @code{set startup-with-shell}
21337 @item @code{environment-hex-encoded}
21338 @tab @code{QEnvironmentHexEncoded}
21339 @tab @code{set environment}
21341 @item @code{environment-unset}
21342 @tab @code{QEnvironmentUnset}
21343 @tab @code{unset environment}
21345 @item @code{environment-reset}
21346 @tab @code{QEnvironmentReset}
21347 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
21349 @item @code{set-working-dir}
21350 @tab @code{QSetWorkingDir}
21351 @tab @code{set cwd}
21353 @item @code{conditional-breakpoints-packet}
21354 @tab @code{Z0 and Z1}
21355 @tab @code{Support for target-side breakpoint condition evaluation}
21357 @item @code{multiprocess-extensions}
21358 @tab @code{multiprocess extensions}
21359 @tab Debug multiple processes and remote process PID awareness
21361 @item @code{swbreak-feature}
21362 @tab @code{swbreak stop reason}
21365 @item @code{hwbreak-feature}
21366 @tab @code{hwbreak stop reason}
21369 @item @code{fork-event-feature}
21370 @tab @code{fork stop reason}
21373 @item @code{vfork-event-feature}
21374 @tab @code{vfork stop reason}
21377 @item @code{exec-event-feature}
21378 @tab @code{exec stop reason}
21381 @item @code{thread-events}
21382 @tab @code{QThreadEvents}
21383 @tab Tracking thread lifetime.
21385 @item @code{no-resumed-stop-reply}
21386 @tab @code{no resumed thread left stop reply}
21387 @tab Tracking thread lifetime.
21392 @section Implementing a Remote Stub
21394 @cindex debugging stub, example
21395 @cindex remote stub, example
21396 @cindex stub example, remote debugging
21397 The stub files provided with @value{GDBN} implement the target side of the
21398 communication protocol, and the @value{GDBN} side is implemented in the
21399 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
21400 these subroutines to communicate, and ignore the details. (If you're
21401 implementing your own stub file, you can still ignore the details: start
21402 with one of the existing stub files. @file{sparc-stub.c} is the best
21403 organized, and therefore the easiest to read.)
21405 @cindex remote serial debugging, overview
21406 To debug a program running on another machine (the debugging
21407 @dfn{target} machine), you must first arrange for all the usual
21408 prerequisites for the program to run by itself. For example, for a C
21413 A startup routine to set up the C runtime environment; these usually
21414 have a name like @file{crt0}. The startup routine may be supplied by
21415 your hardware supplier, or you may have to write your own.
21418 A C subroutine library to support your program's
21419 subroutine calls, notably managing input and output.
21422 A way of getting your program to the other machine---for example, a
21423 download program. These are often supplied by the hardware
21424 manufacturer, but you may have to write your own from hardware
21428 The next step is to arrange for your program to use a serial port to
21429 communicate with the machine where @value{GDBN} is running (the @dfn{host}
21430 machine). In general terms, the scheme looks like this:
21434 @value{GDBN} already understands how to use this protocol; when everything
21435 else is set up, you can simply use the @samp{target remote} command
21436 (@pxref{Targets,,Specifying a Debugging Target}).
21438 @item On the target,
21439 you must link with your program a few special-purpose subroutines that
21440 implement the @value{GDBN} remote serial protocol. The file containing these
21441 subroutines is called a @dfn{debugging stub}.
21443 On certain remote targets, you can use an auxiliary program
21444 @code{gdbserver} instead of linking a stub into your program.
21445 @xref{Server,,Using the @code{gdbserver} Program}, for details.
21448 The debugging stub is specific to the architecture of the remote
21449 machine; for example, use @file{sparc-stub.c} to debug programs on
21452 @cindex remote serial stub list
21453 These working remote stubs are distributed with @value{GDBN}:
21458 @cindex @file{i386-stub.c}
21461 For Intel 386 and compatible architectures.
21464 @cindex @file{m68k-stub.c}
21465 @cindex Motorola 680x0
21467 For Motorola 680x0 architectures.
21470 @cindex @file{sh-stub.c}
21473 For Renesas SH architectures.
21476 @cindex @file{sparc-stub.c}
21478 For @sc{sparc} architectures.
21480 @item sparcl-stub.c
21481 @cindex @file{sparcl-stub.c}
21484 For Fujitsu @sc{sparclite} architectures.
21488 The @file{README} file in the @value{GDBN} distribution may list other
21489 recently added stubs.
21492 * Stub Contents:: What the stub can do for you
21493 * Bootstrapping:: What you must do for the stub
21494 * Debug Session:: Putting it all together
21497 @node Stub Contents
21498 @subsection What the Stub Can Do for You
21500 @cindex remote serial stub
21501 The debugging stub for your architecture supplies these three
21505 @item set_debug_traps
21506 @findex set_debug_traps
21507 @cindex remote serial stub, initialization
21508 This routine arranges for @code{handle_exception} to run when your
21509 program stops. You must call this subroutine explicitly in your
21510 program's startup code.
21512 @item handle_exception
21513 @findex handle_exception
21514 @cindex remote serial stub, main routine
21515 This is the central workhorse, but your program never calls it
21516 explicitly---the setup code arranges for @code{handle_exception} to
21517 run when a trap is triggered.
21519 @code{handle_exception} takes control when your program stops during
21520 execution (for example, on a breakpoint), and mediates communications
21521 with @value{GDBN} on the host machine. This is where the communications
21522 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
21523 representative on the target machine. It begins by sending summary
21524 information on the state of your program, then continues to execute,
21525 retrieving and transmitting any information @value{GDBN} needs, until you
21526 execute a @value{GDBN} command that makes your program resume; at that point,
21527 @code{handle_exception} returns control to your own code on the target
21531 @cindex @code{breakpoint} subroutine, remote
21532 Use this auxiliary subroutine to make your program contain a
21533 breakpoint. Depending on the particular situation, this may be the only
21534 way for @value{GDBN} to get control. For instance, if your target
21535 machine has some sort of interrupt button, you won't need to call this;
21536 pressing the interrupt button transfers control to
21537 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
21538 simply receiving characters on the serial port may also trigger a trap;
21539 again, in that situation, you don't need to call @code{breakpoint} from
21540 your own program---simply running @samp{target remote} from the host
21541 @value{GDBN} session gets control.
21543 Call @code{breakpoint} if none of these is true, or if you simply want
21544 to make certain your program stops at a predetermined point for the
21545 start of your debugging session.
21548 @node Bootstrapping
21549 @subsection What You Must Do for the Stub
21551 @cindex remote stub, support routines
21552 The debugging stubs that come with @value{GDBN} are set up for a particular
21553 chip architecture, but they have no information about the rest of your
21554 debugging target machine.
21556 First of all you need to tell the stub how to communicate with the
21560 @item int getDebugChar()
21561 @findex getDebugChar
21562 Write this subroutine to read a single character from the serial port.
21563 It may be identical to @code{getchar} for your target system; a
21564 different name is used to allow you to distinguish the two if you wish.
21566 @item void putDebugChar(int)
21567 @findex putDebugChar
21568 Write this subroutine to write a single character to the serial port.
21569 It may be identical to @code{putchar} for your target system; a
21570 different name is used to allow you to distinguish the two if you wish.
21573 @cindex control C, and remote debugging
21574 @cindex interrupting remote targets
21575 If you want @value{GDBN} to be able to stop your program while it is
21576 running, you need to use an interrupt-driven serial driver, and arrange
21577 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
21578 character). That is the character which @value{GDBN} uses to tell the
21579 remote system to stop.
21581 Getting the debugging target to return the proper status to @value{GDBN}
21582 probably requires changes to the standard stub; one quick and dirty way
21583 is to just execute a breakpoint instruction (the ``dirty'' part is that
21584 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
21586 Other routines you need to supply are:
21589 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
21590 @findex exceptionHandler
21591 Write this function to install @var{exception_address} in the exception
21592 handling tables. You need to do this because the stub does not have any
21593 way of knowing what the exception handling tables on your target system
21594 are like (for example, the processor's table might be in @sc{rom},
21595 containing entries which point to a table in @sc{ram}).
21596 The @var{exception_number} specifies the exception which should be changed;
21597 its meaning is architecture-dependent (for example, different numbers
21598 might represent divide by zero, misaligned access, etc). When this
21599 exception occurs, control should be transferred directly to
21600 @var{exception_address}, and the processor state (stack, registers,
21601 and so on) should be just as it is when a processor exception occurs. So if
21602 you want to use a jump instruction to reach @var{exception_address}, it
21603 should be a simple jump, not a jump to subroutine.
21605 For the 386, @var{exception_address} should be installed as an interrupt
21606 gate so that interrupts are masked while the handler runs. The gate
21607 should be at privilege level 0 (the most privileged level). The
21608 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
21609 help from @code{exceptionHandler}.
21611 @item void flush_i_cache()
21612 @findex flush_i_cache
21613 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
21614 instruction cache, if any, on your target machine. If there is no
21615 instruction cache, this subroutine may be a no-op.
21617 On target machines that have instruction caches, @value{GDBN} requires this
21618 function to make certain that the state of your program is stable.
21622 You must also make sure this library routine is available:
21625 @item void *memset(void *, int, int)
21627 This is the standard library function @code{memset} that sets an area of
21628 memory to a known value. If you have one of the free versions of
21629 @code{libc.a}, @code{memset} can be found there; otherwise, you must
21630 either obtain it from your hardware manufacturer, or write your own.
21633 If you do not use the GNU C compiler, you may need other standard
21634 library subroutines as well; this varies from one stub to another,
21635 but in general the stubs are likely to use any of the common library
21636 subroutines which @code{@value{NGCC}} generates as inline code.
21639 @node Debug Session
21640 @subsection Putting it All Together
21642 @cindex remote serial debugging summary
21643 In summary, when your program is ready to debug, you must follow these
21648 Make sure you have defined the supporting low-level routines
21649 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
21651 @code{getDebugChar}, @code{putDebugChar},
21652 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
21656 Insert these lines in your program's startup code, before the main
21657 procedure is called:
21664 On some machines, when a breakpoint trap is raised, the hardware
21665 automatically makes the PC point to the instruction after the
21666 breakpoint. If your machine doesn't do that, you may need to adjust
21667 @code{handle_exception} to arrange for it to return to the instruction
21668 after the breakpoint on this first invocation, so that your program
21669 doesn't keep hitting the initial breakpoint instead of making
21673 For the 680x0 stub only, you need to provide a variable called
21674 @code{exceptionHook}. Normally you just use:
21677 void (*exceptionHook)() = 0;
21681 but if before calling @code{set_debug_traps}, you set it to point to a
21682 function in your program, that function is called when
21683 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
21684 error). The function indicated by @code{exceptionHook} is called with
21685 one parameter: an @code{int} which is the exception number.
21688 Compile and link together: your program, the @value{GDBN} debugging stub for
21689 your target architecture, and the supporting subroutines.
21692 Make sure you have a serial connection between your target machine and
21693 the @value{GDBN} host, and identify the serial port on the host.
21696 @c The "remote" target now provides a `load' command, so we should
21697 @c document that. FIXME.
21698 Download your program to your target machine (or get it there by
21699 whatever means the manufacturer provides), and start it.
21702 Start @value{GDBN} on the host, and connect to the target
21703 (@pxref{Connecting,,Connecting to a Remote Target}).
21707 @node Configurations
21708 @chapter Configuration-Specific Information
21710 While nearly all @value{GDBN} commands are available for all native and
21711 cross versions of the debugger, there are some exceptions. This chapter
21712 describes things that are only available in certain configurations.
21714 There are three major categories of configurations: native
21715 configurations, where the host and target are the same, embedded
21716 operating system configurations, which are usually the same for several
21717 different processor architectures, and bare embedded processors, which
21718 are quite different from each other.
21723 * Embedded Processors::
21730 This section describes details specific to particular native
21734 * BSD libkvm Interface:: Debugging BSD kernel memory images
21735 * Process Information:: Process information
21736 * DJGPP Native:: Features specific to the DJGPP port
21737 * Cygwin Native:: Features specific to the Cygwin port
21738 * Hurd Native:: Features specific to @sc{gnu} Hurd
21739 * Darwin:: Features specific to Darwin
21742 @node BSD libkvm Interface
21743 @subsection BSD libkvm Interface
21746 @cindex kernel memory image
21747 @cindex kernel crash dump
21749 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
21750 interface that provides a uniform interface for accessing kernel virtual
21751 memory images, including live systems and crash dumps. @value{GDBN}
21752 uses this interface to allow you to debug live kernels and kernel crash
21753 dumps on many native BSD configurations. This is implemented as a
21754 special @code{kvm} debugging target. For debugging a live system, load
21755 the currently running kernel into @value{GDBN} and connect to the
21759 (@value{GDBP}) @b{target kvm}
21762 For debugging crash dumps, provide the file name of the crash dump as an
21766 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
21769 Once connected to the @code{kvm} target, the following commands are
21775 Set current context from the @dfn{Process Control Block} (PCB) address.
21778 Set current context from proc address. This command isn't available on
21779 modern FreeBSD systems.
21782 @node Process Information
21783 @subsection Process Information
21785 @cindex examine process image
21786 @cindex process info via @file{/proc}
21788 Some operating systems provide interfaces to fetch additional
21789 information about running processes beyond memory and per-thread
21790 register state. If @value{GDBN} is configured for an operating system
21791 with a supported interface, the command @code{info proc} is available
21792 to report information about the process running your program, or about
21793 any process running on your system.
21795 One supported interface is a facility called @samp{/proc} that can be
21796 used to examine the image of a running process using file-system
21797 subroutines. This facility is supported on @sc{gnu}/Linux and Solaris
21800 On FreeBSD systems, system control nodes are used to query process
21803 In addition, some systems may provide additional process information
21804 in core files. Note that a core file may include a subset of the
21805 information available from a live process. Process information is
21806 currently avaiable from cores created on @sc{gnu}/Linux and FreeBSD
21813 @itemx info proc @var{process-id}
21814 Summarize available information about any running process. If a
21815 process ID is specified by @var{process-id}, display information about
21816 that process; otherwise display information about the program being
21817 debugged. The summary includes the debugged process ID, the command
21818 line used to invoke it, its current working directory, and its
21819 executable file's absolute file name.
21821 On some systems, @var{process-id} can be of the form
21822 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
21823 within a process. If the optional @var{pid} part is missing, it means
21824 a thread from the process being debugged (the leading @samp{/} still
21825 needs to be present, or else @value{GDBN} will interpret the number as
21826 a process ID rather than a thread ID).
21828 @item info proc cmdline
21829 @cindex info proc cmdline
21830 Show the original command line of the process. This command is
21831 supported on @sc{gnu}/Linux and FreeBSD.
21833 @item info proc cwd
21834 @cindex info proc cwd
21835 Show the current working directory of the process. This command is
21836 supported on @sc{gnu}/Linux and FreeBSD.
21838 @item info proc exe
21839 @cindex info proc exe
21840 Show the name of executable of the process. This command is supported
21841 on @sc{gnu}/Linux and FreeBSD.
21843 @item info proc mappings
21844 @cindex memory address space mappings
21845 Report the memory address space ranges accessible in the program. On
21846 Solaris and FreeBSD systems, each memory range includes information on
21847 whether the process has read, write, or execute access rights to each
21848 range. On @sc{gnu}/Linux and FreeBSD systems, each memory range
21849 includes the object file which is mapped to that range.
21851 @item info proc stat
21852 @itemx info proc status
21853 @cindex process detailed status information
21854 Show additional process-related information, including the user ID and
21855 group ID; virtual memory usage; the signals that are pending, blocked,
21856 and ignored; its TTY; its consumption of system and user time; its
21857 stack size; its @samp{nice} value; etc. These commands are supported
21858 on @sc{gnu}/Linux and FreeBSD.
21860 For @sc{gnu}/Linux systems, see the @samp{proc} man page for more
21861 information (type @kbd{man 5 proc} from your shell prompt).
21863 For FreeBSD systems, @code{info proc stat} is an alias for @code{info
21866 @item info proc all
21867 Show all the information about the process described under all of the
21868 above @code{info proc} subcommands.
21871 @comment These sub-options of 'info proc' were not included when
21872 @comment procfs.c was re-written. Keep their descriptions around
21873 @comment against the day when someone finds the time to put them back in.
21874 @kindex info proc times
21875 @item info proc times
21876 Starting time, user CPU time, and system CPU time for your program and
21879 @kindex info proc id
21881 Report on the process IDs related to your program: its own process ID,
21882 the ID of its parent, the process group ID, and the session ID.
21885 @item set procfs-trace
21886 @kindex set procfs-trace
21887 @cindex @code{procfs} API calls
21888 This command enables and disables tracing of @code{procfs} API calls.
21890 @item show procfs-trace
21891 @kindex show procfs-trace
21892 Show the current state of @code{procfs} API call tracing.
21894 @item set procfs-file @var{file}
21895 @kindex set procfs-file
21896 Tell @value{GDBN} to write @code{procfs} API trace to the named
21897 @var{file}. @value{GDBN} appends the trace info to the previous
21898 contents of the file. The default is to display the trace on the
21901 @item show procfs-file
21902 @kindex show procfs-file
21903 Show the file to which @code{procfs} API trace is written.
21905 @item proc-trace-entry
21906 @itemx proc-trace-exit
21907 @itemx proc-untrace-entry
21908 @itemx proc-untrace-exit
21909 @kindex proc-trace-entry
21910 @kindex proc-trace-exit
21911 @kindex proc-untrace-entry
21912 @kindex proc-untrace-exit
21913 These commands enable and disable tracing of entries into and exits
21914 from the @code{syscall} interface.
21917 @kindex info pidlist
21918 @cindex process list, QNX Neutrino
21919 For QNX Neutrino only, this command displays the list of all the
21920 processes and all the threads within each process.
21923 @kindex info meminfo
21924 @cindex mapinfo list, QNX Neutrino
21925 For QNX Neutrino only, this command displays the list of all mapinfos.
21929 @subsection Features for Debugging @sc{djgpp} Programs
21930 @cindex @sc{djgpp} debugging
21931 @cindex native @sc{djgpp} debugging
21932 @cindex MS-DOS-specific commands
21935 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
21936 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
21937 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
21938 top of real-mode DOS systems and their emulations.
21940 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
21941 defines a few commands specific to the @sc{djgpp} port. This
21942 subsection describes those commands.
21947 This is a prefix of @sc{djgpp}-specific commands which print
21948 information about the target system and important OS structures.
21951 @cindex MS-DOS system info
21952 @cindex free memory information (MS-DOS)
21953 @item info dos sysinfo
21954 This command displays assorted information about the underlying
21955 platform: the CPU type and features, the OS version and flavor, the
21956 DPMI version, and the available conventional and DPMI memory.
21961 @cindex segment descriptor tables
21962 @cindex descriptor tables display
21964 @itemx info dos ldt
21965 @itemx info dos idt
21966 These 3 commands display entries from, respectively, Global, Local,
21967 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
21968 tables are data structures which store a descriptor for each segment
21969 that is currently in use. The segment's selector is an index into a
21970 descriptor table; the table entry for that index holds the
21971 descriptor's base address and limit, and its attributes and access
21974 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
21975 segment (used for both data and the stack), and a DOS segment (which
21976 allows access to DOS/BIOS data structures and absolute addresses in
21977 conventional memory). However, the DPMI host will usually define
21978 additional segments in order to support the DPMI environment.
21980 @cindex garbled pointers
21981 These commands allow to display entries from the descriptor tables.
21982 Without an argument, all entries from the specified table are
21983 displayed. An argument, which should be an integer expression, means
21984 display a single entry whose index is given by the argument. For
21985 example, here's a convenient way to display information about the
21986 debugged program's data segment:
21989 @exdent @code{(@value{GDBP}) info dos ldt $ds}
21990 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
21994 This comes in handy when you want to see whether a pointer is outside
21995 the data segment's limit (i.e.@: @dfn{garbled}).
21997 @cindex page tables display (MS-DOS)
21999 @itemx info dos pte
22000 These two commands display entries from, respectively, the Page
22001 Directory and the Page Tables. Page Directories and Page Tables are
22002 data structures which control how virtual memory addresses are mapped
22003 into physical addresses. A Page Table includes an entry for every
22004 page of memory that is mapped into the program's address space; there
22005 may be several Page Tables, each one holding up to 4096 entries. A
22006 Page Directory has up to 4096 entries, one each for every Page Table
22007 that is currently in use.
22009 Without an argument, @kbd{info dos pde} displays the entire Page
22010 Directory, and @kbd{info dos pte} displays all the entries in all of
22011 the Page Tables. An argument, an integer expression, given to the
22012 @kbd{info dos pde} command means display only that entry from the Page
22013 Directory table. An argument given to the @kbd{info dos pte} command
22014 means display entries from a single Page Table, the one pointed to by
22015 the specified entry in the Page Directory.
22017 @cindex direct memory access (DMA) on MS-DOS
22018 These commands are useful when your program uses @dfn{DMA} (Direct
22019 Memory Access), which needs physical addresses to program the DMA
22022 These commands are supported only with some DPMI servers.
22024 @cindex physical address from linear address
22025 @item info dos address-pte @var{addr}
22026 This command displays the Page Table entry for a specified linear
22027 address. The argument @var{addr} is a linear address which should
22028 already have the appropriate segment's base address added to it,
22029 because this command accepts addresses which may belong to @emph{any}
22030 segment. For example, here's how to display the Page Table entry for
22031 the page where a variable @code{i} is stored:
22034 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
22035 @exdent @code{Page Table entry for address 0x11a00d30:}
22036 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
22040 This says that @code{i} is stored at offset @code{0xd30} from the page
22041 whose physical base address is @code{0x02698000}, and shows all the
22042 attributes of that page.
22044 Note that you must cast the addresses of variables to a @code{char *},
22045 since otherwise the value of @code{__djgpp_base_address}, the base
22046 address of all variables and functions in a @sc{djgpp} program, will
22047 be added using the rules of C pointer arithmetics: if @code{i} is
22048 declared an @code{int}, @value{GDBN} will add 4 times the value of
22049 @code{__djgpp_base_address} to the address of @code{i}.
22051 Here's another example, it displays the Page Table entry for the
22055 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
22056 @exdent @code{Page Table entry for address 0x29110:}
22057 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
22061 (The @code{+ 3} offset is because the transfer buffer's address is the
22062 3rd member of the @code{_go32_info_block} structure.) The output
22063 clearly shows that this DPMI server maps the addresses in conventional
22064 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
22065 linear (@code{0x29110}) addresses are identical.
22067 This command is supported only with some DPMI servers.
22070 @cindex DOS serial data link, remote debugging
22071 In addition to native debugging, the DJGPP port supports remote
22072 debugging via a serial data link. The following commands are specific
22073 to remote serial debugging in the DJGPP port of @value{GDBN}.
22076 @kindex set com1base
22077 @kindex set com1irq
22078 @kindex set com2base
22079 @kindex set com2irq
22080 @kindex set com3base
22081 @kindex set com3irq
22082 @kindex set com4base
22083 @kindex set com4irq
22084 @item set com1base @var{addr}
22085 This command sets the base I/O port address of the @file{COM1} serial
22088 @item set com1irq @var{irq}
22089 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
22090 for the @file{COM1} serial port.
22092 There are similar commands @samp{set com2base}, @samp{set com3irq},
22093 etc.@: for setting the port address and the @code{IRQ} lines for the
22096 @kindex show com1base
22097 @kindex show com1irq
22098 @kindex show com2base
22099 @kindex show com2irq
22100 @kindex show com3base
22101 @kindex show com3irq
22102 @kindex show com4base
22103 @kindex show com4irq
22104 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
22105 display the current settings of the base address and the @code{IRQ}
22106 lines used by the COM ports.
22109 @kindex info serial
22110 @cindex DOS serial port status
22111 This command prints the status of the 4 DOS serial ports. For each
22112 port, it prints whether it's active or not, its I/O base address and
22113 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
22114 counts of various errors encountered so far.
22118 @node Cygwin Native
22119 @subsection Features for Debugging MS Windows PE Executables
22120 @cindex MS Windows debugging
22121 @cindex native Cygwin debugging
22122 @cindex Cygwin-specific commands
22124 @value{GDBN} supports native debugging of MS Windows programs, including
22125 DLLs with and without symbolic debugging information.
22127 @cindex Ctrl-BREAK, MS-Windows
22128 @cindex interrupt debuggee on MS-Windows
22129 MS-Windows programs that call @code{SetConsoleMode} to switch off the
22130 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
22131 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
22132 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
22133 sequence, which can be used to interrupt the debuggee even if it
22136 There are various additional Cygwin-specific commands, described in
22137 this section. Working with DLLs that have no debugging symbols is
22138 described in @ref{Non-debug DLL Symbols}.
22143 This is a prefix of MS Windows-specific commands which print
22144 information about the target system and important OS structures.
22146 @item info w32 selector
22147 This command displays information returned by
22148 the Win32 API @code{GetThreadSelectorEntry} function.
22149 It takes an optional argument that is evaluated to
22150 a long value to give the information about this given selector.
22151 Without argument, this command displays information
22152 about the six segment registers.
22154 @item info w32 thread-information-block
22155 This command displays thread specific information stored in the
22156 Thread Information Block (readable on the X86 CPU family using @code{$fs}
22157 selector for 32-bit programs and @code{$gs} for 64-bit programs).
22159 @kindex signal-event
22160 @item signal-event @var{id}
22161 This command signals an event with user-provided @var{id}. Used to resume
22162 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
22164 To use it, create or edit the following keys in
22165 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
22166 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
22167 (for x86_64 versions):
22171 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
22172 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
22173 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
22175 The first @code{%ld} will be replaced by the process ID of the
22176 crashing process, the second @code{%ld} will be replaced by the ID of
22177 the event that blocks the crashing process, waiting for @value{GDBN}
22181 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
22182 make the system run debugger specified by the Debugger key
22183 automatically, @code{0} will cause a dialog box with ``OK'' and
22184 ``Cancel'' buttons to appear, which allows the user to either
22185 terminate the crashing process (OK) or debug it (Cancel).
22188 @kindex set cygwin-exceptions
22189 @cindex debugging the Cygwin DLL
22190 @cindex Cygwin DLL, debugging
22191 @item set cygwin-exceptions @var{mode}
22192 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
22193 happen inside the Cygwin DLL. If @var{mode} is @code{off},
22194 @value{GDBN} will delay recognition of exceptions, and may ignore some
22195 exceptions which seem to be caused by internal Cygwin DLL
22196 ``bookkeeping''. This option is meant primarily for debugging the
22197 Cygwin DLL itself; the default value is @code{off} to avoid annoying
22198 @value{GDBN} users with false @code{SIGSEGV} signals.
22200 @kindex show cygwin-exceptions
22201 @item show cygwin-exceptions
22202 Displays whether @value{GDBN} will break on exceptions that happen
22203 inside the Cygwin DLL itself.
22205 @kindex set new-console
22206 @item set new-console @var{mode}
22207 If @var{mode} is @code{on} the debuggee will
22208 be started in a new console on next start.
22209 If @var{mode} is @code{off}, the debuggee will
22210 be started in the same console as the debugger.
22212 @kindex show new-console
22213 @item show new-console
22214 Displays whether a new console is used
22215 when the debuggee is started.
22217 @kindex set new-group
22218 @item set new-group @var{mode}
22219 This boolean value controls whether the debuggee should
22220 start a new group or stay in the same group as the debugger.
22221 This affects the way the Windows OS handles
22224 @kindex show new-group
22225 @item show new-group
22226 Displays current value of new-group boolean.
22228 @kindex set debugevents
22229 @item set debugevents
22230 This boolean value adds debug output concerning kernel events related
22231 to the debuggee seen by the debugger. This includes events that
22232 signal thread and process creation and exit, DLL loading and
22233 unloading, console interrupts, and debugging messages produced by the
22234 Windows @code{OutputDebugString} API call.
22236 @kindex set debugexec
22237 @item set debugexec
22238 This boolean value adds debug output concerning execute events
22239 (such as resume thread) seen by the debugger.
22241 @kindex set debugexceptions
22242 @item set debugexceptions
22243 This boolean value adds debug output concerning exceptions in the
22244 debuggee seen by the debugger.
22246 @kindex set debugmemory
22247 @item set debugmemory
22248 This boolean value adds debug output concerning debuggee memory reads
22249 and writes by the debugger.
22253 This boolean values specifies whether the debuggee is called
22254 via a shell or directly (default value is on).
22258 Displays if the debuggee will be started with a shell.
22263 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
22266 @node Non-debug DLL Symbols
22267 @subsubsection Support for DLLs without Debugging Symbols
22268 @cindex DLLs with no debugging symbols
22269 @cindex Minimal symbols and DLLs
22271 Very often on windows, some of the DLLs that your program relies on do
22272 not include symbolic debugging information (for example,
22273 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
22274 symbols in a DLL, it relies on the minimal amount of symbolic
22275 information contained in the DLL's export table. This section
22276 describes working with such symbols, known internally to @value{GDBN} as
22277 ``minimal symbols''.
22279 Note that before the debugged program has started execution, no DLLs
22280 will have been loaded. The easiest way around this problem is simply to
22281 start the program --- either by setting a breakpoint or letting the
22282 program run once to completion.
22284 @subsubsection DLL Name Prefixes
22286 In keeping with the naming conventions used by the Microsoft debugging
22287 tools, DLL export symbols are made available with a prefix based on the
22288 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
22289 also entered into the symbol table, so @code{CreateFileA} is often
22290 sufficient. In some cases there will be name clashes within a program
22291 (particularly if the executable itself includes full debugging symbols)
22292 necessitating the use of the fully qualified name when referring to the
22293 contents of the DLL. Use single-quotes around the name to avoid the
22294 exclamation mark (``!'') being interpreted as a language operator.
22296 Note that the internal name of the DLL may be all upper-case, even
22297 though the file name of the DLL is lower-case, or vice-versa. Since
22298 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
22299 some confusion. If in doubt, try the @code{info functions} and
22300 @code{info variables} commands or even @code{maint print msymbols}
22301 (@pxref{Symbols}). Here's an example:
22304 (@value{GDBP}) info function CreateFileA
22305 All functions matching regular expression "CreateFileA":
22307 Non-debugging symbols:
22308 0x77e885f4 CreateFileA
22309 0x77e885f4 KERNEL32!CreateFileA
22313 (@value{GDBP}) info function !
22314 All functions matching regular expression "!":
22316 Non-debugging symbols:
22317 0x6100114c cygwin1!__assert
22318 0x61004034 cygwin1!_dll_crt0@@0
22319 0x61004240 cygwin1!dll_crt0(per_process *)
22323 @subsubsection Working with Minimal Symbols
22325 Symbols extracted from a DLL's export table do not contain very much
22326 type information. All that @value{GDBN} can do is guess whether a symbol
22327 refers to a function or variable depending on the linker section that
22328 contains the symbol. Also note that the actual contents of the memory
22329 contained in a DLL are not available unless the program is running. This
22330 means that you cannot examine the contents of a variable or disassemble
22331 a function within a DLL without a running program.
22333 Variables are generally treated as pointers and dereferenced
22334 automatically. For this reason, it is often necessary to prefix a
22335 variable name with the address-of operator (``&'') and provide explicit
22336 type information in the command. Here's an example of the type of
22340 (@value{GDBP}) print 'cygwin1!__argv'
22341 'cygwin1!__argv' has unknown type; cast it to its declared type
22345 (@value{GDBP}) x 'cygwin1!__argv'
22346 'cygwin1!__argv' has unknown type; cast it to its declared type
22349 And two possible solutions:
22352 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
22353 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
22357 (@value{GDBP}) x/2x &'cygwin1!__argv'
22358 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
22359 (@value{GDBP}) x/x 0x10021608
22360 0x10021608: 0x0022fd98
22361 (@value{GDBP}) x/s 0x0022fd98
22362 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
22365 Setting a break point within a DLL is possible even before the program
22366 starts execution. However, under these circumstances, @value{GDBN} can't
22367 examine the initial instructions of the function in order to skip the
22368 function's frame set-up code. You can work around this by using ``*&''
22369 to set the breakpoint at a raw memory address:
22372 (@value{GDBP}) break *&'python22!PyOS_Readline'
22373 Breakpoint 1 at 0x1e04eff0
22376 The author of these extensions is not entirely convinced that setting a
22377 break point within a shared DLL like @file{kernel32.dll} is completely
22381 @subsection Commands Specific to @sc{gnu} Hurd Systems
22382 @cindex @sc{gnu} Hurd debugging
22384 This subsection describes @value{GDBN} commands specific to the
22385 @sc{gnu} Hurd native debugging.
22390 @kindex set signals@r{, Hurd command}
22391 @kindex set sigs@r{, Hurd command}
22392 This command toggles the state of inferior signal interception by
22393 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
22394 affected by this command. @code{sigs} is a shorthand alias for
22399 @kindex show signals@r{, Hurd command}
22400 @kindex show sigs@r{, Hurd command}
22401 Show the current state of intercepting inferior's signals.
22403 @item set signal-thread
22404 @itemx set sigthread
22405 @kindex set signal-thread
22406 @kindex set sigthread
22407 This command tells @value{GDBN} which thread is the @code{libc} signal
22408 thread. That thread is run when a signal is delivered to a running
22409 process. @code{set sigthread} is the shorthand alias of @code{set
22412 @item show signal-thread
22413 @itemx show sigthread
22414 @kindex show signal-thread
22415 @kindex show sigthread
22416 These two commands show which thread will run when the inferior is
22417 delivered a signal.
22420 @kindex set stopped@r{, Hurd command}
22421 This commands tells @value{GDBN} that the inferior process is stopped,
22422 as with the @code{SIGSTOP} signal. The stopped process can be
22423 continued by delivering a signal to it.
22426 @kindex show stopped@r{, Hurd command}
22427 This command shows whether @value{GDBN} thinks the debuggee is
22430 @item set exceptions
22431 @kindex set exceptions@r{, Hurd command}
22432 Use this command to turn off trapping of exceptions in the inferior.
22433 When exception trapping is off, neither breakpoints nor
22434 single-stepping will work. To restore the default, set exception
22437 @item show exceptions
22438 @kindex show exceptions@r{, Hurd command}
22439 Show the current state of trapping exceptions in the inferior.
22441 @item set task pause
22442 @kindex set task@r{, Hurd commands}
22443 @cindex task attributes (@sc{gnu} Hurd)
22444 @cindex pause current task (@sc{gnu} Hurd)
22445 This command toggles task suspension when @value{GDBN} has control.
22446 Setting it to on takes effect immediately, and the task is suspended
22447 whenever @value{GDBN} gets control. Setting it to off will take
22448 effect the next time the inferior is continued. If this option is set
22449 to off, you can use @code{set thread default pause on} or @code{set
22450 thread pause on} (see below) to pause individual threads.
22452 @item show task pause
22453 @kindex show task@r{, Hurd commands}
22454 Show the current state of task suspension.
22456 @item set task detach-suspend-count
22457 @cindex task suspend count
22458 @cindex detach from task, @sc{gnu} Hurd
22459 This command sets the suspend count the task will be left with when
22460 @value{GDBN} detaches from it.
22462 @item show task detach-suspend-count
22463 Show the suspend count the task will be left with when detaching.
22465 @item set task exception-port
22466 @itemx set task excp
22467 @cindex task exception port, @sc{gnu} Hurd
22468 This command sets the task exception port to which @value{GDBN} will
22469 forward exceptions. The argument should be the value of the @dfn{send
22470 rights} of the task. @code{set task excp} is a shorthand alias.
22472 @item set noninvasive
22473 @cindex noninvasive task options
22474 This command switches @value{GDBN} to a mode that is the least
22475 invasive as far as interfering with the inferior is concerned. This
22476 is the same as using @code{set task pause}, @code{set exceptions}, and
22477 @code{set signals} to values opposite to the defaults.
22479 @item info send-rights
22480 @itemx info receive-rights
22481 @itemx info port-rights
22482 @itemx info port-sets
22483 @itemx info dead-names
22486 @cindex send rights, @sc{gnu} Hurd
22487 @cindex receive rights, @sc{gnu} Hurd
22488 @cindex port rights, @sc{gnu} Hurd
22489 @cindex port sets, @sc{gnu} Hurd
22490 @cindex dead names, @sc{gnu} Hurd
22491 These commands display information about, respectively, send rights,
22492 receive rights, port rights, port sets, and dead names of a task.
22493 There are also shorthand aliases: @code{info ports} for @code{info
22494 port-rights} and @code{info psets} for @code{info port-sets}.
22496 @item set thread pause
22497 @kindex set thread@r{, Hurd command}
22498 @cindex thread properties, @sc{gnu} Hurd
22499 @cindex pause current thread (@sc{gnu} Hurd)
22500 This command toggles current thread suspension when @value{GDBN} has
22501 control. Setting it to on takes effect immediately, and the current
22502 thread is suspended whenever @value{GDBN} gets control. Setting it to
22503 off will take effect the next time the inferior is continued.
22504 Normally, this command has no effect, since when @value{GDBN} has
22505 control, the whole task is suspended. However, if you used @code{set
22506 task pause off} (see above), this command comes in handy to suspend
22507 only the current thread.
22509 @item show thread pause
22510 @kindex show thread@r{, Hurd command}
22511 This command shows the state of current thread suspension.
22513 @item set thread run
22514 This command sets whether the current thread is allowed to run.
22516 @item show thread run
22517 Show whether the current thread is allowed to run.
22519 @item set thread detach-suspend-count
22520 @cindex thread suspend count, @sc{gnu} Hurd
22521 @cindex detach from thread, @sc{gnu} Hurd
22522 This command sets the suspend count @value{GDBN} will leave on a
22523 thread when detaching. This number is relative to the suspend count
22524 found by @value{GDBN} when it notices the thread; use @code{set thread
22525 takeover-suspend-count} to force it to an absolute value.
22527 @item show thread detach-suspend-count
22528 Show the suspend count @value{GDBN} will leave on the thread when
22531 @item set thread exception-port
22532 @itemx set thread excp
22533 Set the thread exception port to which to forward exceptions. This
22534 overrides the port set by @code{set task exception-port} (see above).
22535 @code{set thread excp} is the shorthand alias.
22537 @item set thread takeover-suspend-count
22538 Normally, @value{GDBN}'s thread suspend counts are relative to the
22539 value @value{GDBN} finds when it notices each thread. This command
22540 changes the suspend counts to be absolute instead.
22542 @item set thread default
22543 @itemx show thread default
22544 @cindex thread default settings, @sc{gnu} Hurd
22545 Each of the above @code{set thread} commands has a @code{set thread
22546 default} counterpart (e.g., @code{set thread default pause}, @code{set
22547 thread default exception-port}, etc.). The @code{thread default}
22548 variety of commands sets the default thread properties for all
22549 threads; you can then change the properties of individual threads with
22550 the non-default commands.
22557 @value{GDBN} provides the following commands specific to the Darwin target:
22560 @item set debug darwin @var{num}
22561 @kindex set debug darwin
22562 When set to a non zero value, enables debugging messages specific to
22563 the Darwin support. Higher values produce more verbose output.
22565 @item show debug darwin
22566 @kindex show debug darwin
22567 Show the current state of Darwin messages.
22569 @item set debug mach-o @var{num}
22570 @kindex set debug mach-o
22571 When set to a non zero value, enables debugging messages while
22572 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
22573 file format used on Darwin for object and executable files.) Higher
22574 values produce more verbose output. This is a command to diagnose
22575 problems internal to @value{GDBN} and should not be needed in normal
22578 @item show debug mach-o
22579 @kindex show debug mach-o
22580 Show the current state of Mach-O file messages.
22582 @item set mach-exceptions on
22583 @itemx set mach-exceptions off
22584 @kindex set mach-exceptions
22585 On Darwin, faults are first reported as a Mach exception and are then
22586 mapped to a Posix signal. Use this command to turn on trapping of
22587 Mach exceptions in the inferior. This might be sometimes useful to
22588 better understand the cause of a fault. The default is off.
22590 @item show mach-exceptions
22591 @kindex show mach-exceptions
22592 Show the current state of exceptions trapping.
22597 @section Embedded Operating Systems
22599 This section describes configurations involving the debugging of
22600 embedded operating systems that are available for several different
22603 @value{GDBN} includes the ability to debug programs running on
22604 various real-time operating systems.
22606 @node Embedded Processors
22607 @section Embedded Processors
22609 This section goes into details specific to particular embedded
22612 @cindex send command to simulator
22613 Whenever a specific embedded processor has a simulator, @value{GDBN}
22614 allows to send an arbitrary command to the simulator.
22617 @item sim @var{command}
22618 @kindex sim@r{, a command}
22619 Send an arbitrary @var{command} string to the simulator. Consult the
22620 documentation for the specific simulator in use for information about
22621 acceptable commands.
22626 * ARC:: Synopsys ARC
22628 * M68K:: Motorola M68K
22629 * MicroBlaze:: Xilinx MicroBlaze
22630 * MIPS Embedded:: MIPS Embedded
22631 * OpenRISC 1000:: OpenRISC 1000 (or1k)
22632 * PowerPC Embedded:: PowerPC Embedded
22635 * Super-H:: Renesas Super-H
22639 @subsection Synopsys ARC
22640 @cindex Synopsys ARC
22641 @cindex ARC specific commands
22647 @value{GDBN} provides the following ARC-specific commands:
22650 @item set debug arc
22651 @kindex set debug arc
22652 Control the level of ARC specific debug messages. Use 0 for no messages (the
22653 default), 1 for debug messages, and 2 for even more debug messages.
22655 @item show debug arc
22656 @kindex show debug arc
22657 Show the level of ARC specific debugging in operation.
22659 @item maint print arc arc-instruction @var{address}
22660 @kindex maint print arc arc-instruction
22661 Print internal disassembler information about instruction at a given address.
22668 @value{GDBN} provides the following ARM-specific commands:
22671 @item set arm disassembler
22673 This commands selects from a list of disassembly styles. The
22674 @code{"std"} style is the standard style.
22676 @item show arm disassembler
22678 Show the current disassembly style.
22680 @item set arm apcs32
22681 @cindex ARM 32-bit mode
22682 This command toggles ARM operation mode between 32-bit and 26-bit.
22684 @item show arm apcs32
22685 Display the current usage of the ARM 32-bit mode.
22687 @item set arm fpu @var{fputype}
22688 This command sets the ARM floating-point unit (FPU) type. The
22689 argument @var{fputype} can be one of these:
22693 Determine the FPU type by querying the OS ABI.
22695 Software FPU, with mixed-endian doubles on little-endian ARM
22698 GCC-compiled FPA co-processor.
22700 Software FPU with pure-endian doubles.
22706 Show the current type of the FPU.
22709 This command forces @value{GDBN} to use the specified ABI.
22712 Show the currently used ABI.
22714 @item set arm fallback-mode (arm|thumb|auto)
22715 @value{GDBN} uses the symbol table, when available, to determine
22716 whether instructions are ARM or Thumb. This command controls
22717 @value{GDBN}'s default behavior when the symbol table is not
22718 available. The default is @samp{auto}, which causes @value{GDBN} to
22719 use the current execution mode (from the @code{T} bit in the @code{CPSR}
22722 @item show arm fallback-mode
22723 Show the current fallback instruction mode.
22725 @item set arm force-mode (arm|thumb|auto)
22726 This command overrides use of the symbol table to determine whether
22727 instructions are ARM or Thumb. The default is @samp{auto}, which
22728 causes @value{GDBN} to use the symbol table and then the setting
22729 of @samp{set arm fallback-mode}.
22731 @item show arm force-mode
22732 Show the current forced instruction mode.
22734 @item set debug arm
22735 Toggle whether to display ARM-specific debugging messages from the ARM
22736 target support subsystem.
22738 @item show debug arm
22739 Show whether ARM-specific debugging messages are enabled.
22743 @item target sim @r{[}@var{simargs}@r{]} @dots{}
22744 The @value{GDBN} ARM simulator accepts the following optional arguments.
22747 @item --swi-support=@var{type}
22748 Tell the simulator which SWI interfaces to support. The argument
22749 @var{type} may be a comma separated list of the following values.
22750 The default value is @code{all}.
22765 The Motorola m68k configuration includes ColdFire support.
22768 @subsection MicroBlaze
22769 @cindex Xilinx MicroBlaze
22770 @cindex XMD, Xilinx Microprocessor Debugger
22772 The MicroBlaze is a soft-core processor supported on various Xilinx
22773 FPGAs, such as Spartan or Virtex series. Boards with these processors
22774 usually have JTAG ports which connect to a host system running the Xilinx
22775 Embedded Development Kit (EDK) or Software Development Kit (SDK).
22776 This host system is used to download the configuration bitstream to
22777 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
22778 communicates with the target board using the JTAG interface and
22779 presents a @code{gdbserver} interface to the board. By default
22780 @code{xmd} uses port @code{1234}. (While it is possible to change
22781 this default port, it requires the use of undocumented @code{xmd}
22782 commands. Contact Xilinx support if you need to do this.)
22784 Use these GDB commands to connect to the MicroBlaze target processor.
22787 @item target remote :1234
22788 Use this command to connect to the target if you are running @value{GDBN}
22789 on the same system as @code{xmd}.
22791 @item target remote @var{xmd-host}:1234
22792 Use this command to connect to the target if it is connected to @code{xmd}
22793 running on a different system named @var{xmd-host}.
22796 Use this command to download a program to the MicroBlaze target.
22798 @item set debug microblaze @var{n}
22799 Enable MicroBlaze-specific debugging messages if non-zero.
22801 @item show debug microblaze @var{n}
22802 Show MicroBlaze-specific debugging level.
22805 @node MIPS Embedded
22806 @subsection @acronym{MIPS} Embedded
22809 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
22812 @item set mipsfpu double
22813 @itemx set mipsfpu single
22814 @itemx set mipsfpu none
22815 @itemx set mipsfpu auto
22816 @itemx show mipsfpu
22817 @kindex set mipsfpu
22818 @kindex show mipsfpu
22819 @cindex @acronym{MIPS} remote floating point
22820 @cindex floating point, @acronym{MIPS} remote
22821 If your target board does not support the @acronym{MIPS} floating point
22822 coprocessor, you should use the command @samp{set mipsfpu none} (if you
22823 need this, you may wish to put the command in your @value{GDBN} init
22824 file). This tells @value{GDBN} how to find the return value of
22825 functions which return floating point values. It also allows
22826 @value{GDBN} to avoid saving the floating point registers when calling
22827 functions on the board. If you are using a floating point coprocessor
22828 with only single precision floating point support, as on the @sc{r4650}
22829 processor, use the command @samp{set mipsfpu single}. The default
22830 double precision floating point coprocessor may be selected using
22831 @samp{set mipsfpu double}.
22833 In previous versions the only choices were double precision or no
22834 floating point, so @samp{set mipsfpu on} will select double precision
22835 and @samp{set mipsfpu off} will select no floating point.
22837 As usual, you can inquire about the @code{mipsfpu} variable with
22838 @samp{show mipsfpu}.
22841 @node OpenRISC 1000
22842 @subsection OpenRISC 1000
22843 @cindex OpenRISC 1000
22846 The OpenRISC 1000 provides a free RISC instruction set architecture. It is
22847 mainly provided as a soft-core which can run on Xilinx, Altera and other
22850 @value{GDBN} for OpenRISC supports the below commands when connecting to
22858 Runs the builtin CPU simulator which can run very basic
22859 programs but does not support most hardware functions like MMU.
22860 For more complex use cases the user is advised to run an external
22861 target, and connect using @samp{target remote}.
22863 Example: @code{target sim}
22865 @item set debug or1k
22866 Toggle whether to display OpenRISC-specific debugging messages from the
22867 OpenRISC target support subsystem.
22869 @item show debug or1k
22870 Show whether OpenRISC-specific debugging messages are enabled.
22873 @node PowerPC Embedded
22874 @subsection PowerPC Embedded
22876 @cindex DVC register
22877 @value{GDBN} supports using the DVC (Data Value Compare) register to
22878 implement in hardware simple hardware watchpoint conditions of the form:
22881 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
22882 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
22885 The DVC register will be automatically used when @value{GDBN} detects
22886 such pattern in a condition expression, and the created watchpoint uses one
22887 debug register (either the @code{exact-watchpoints} option is on and the
22888 variable is scalar, or the variable has a length of one byte). This feature
22889 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
22892 When running on PowerPC embedded processors, @value{GDBN} automatically uses
22893 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
22894 in which case watchpoints using only one debug register are created when
22895 watching variables of scalar types.
22897 You can create an artificial array to watch an arbitrary memory
22898 region using one of the following commands (@pxref{Expressions}):
22901 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
22902 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
22905 PowerPC embedded processors support masked watchpoints. See the discussion
22906 about the @code{mask} argument in @ref{Set Watchpoints}.
22908 @cindex ranged breakpoint
22909 PowerPC embedded processors support hardware accelerated
22910 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
22911 the inferior whenever it executes an instruction at any address within
22912 the range it specifies. To set a ranged breakpoint in @value{GDBN},
22913 use the @code{break-range} command.
22915 @value{GDBN} provides the following PowerPC-specific commands:
22918 @kindex break-range
22919 @item break-range @var{start-location}, @var{end-location}
22920 Set a breakpoint for an address range given by
22921 @var{start-location} and @var{end-location}, which can specify a function name,
22922 a line number, an offset of lines from the current line or from the start
22923 location, or an address of an instruction (see @ref{Specify Location},
22924 for a list of all the possible ways to specify a @var{location}.)
22925 The breakpoint will stop execution of the inferior whenever it
22926 executes an instruction at any address within the specified range,
22927 (including @var{start-location} and @var{end-location}.)
22929 @kindex set powerpc
22930 @item set powerpc soft-float
22931 @itemx show powerpc soft-float
22932 Force @value{GDBN} to use (or not use) a software floating point calling
22933 convention. By default, @value{GDBN} selects the calling convention based
22934 on the selected architecture and the provided executable file.
22936 @item set powerpc vector-abi
22937 @itemx show powerpc vector-abi
22938 Force @value{GDBN} to use the specified calling convention for vector
22939 arguments and return values. The valid options are @samp{auto};
22940 @samp{generic}, to avoid vector registers even if they are present;
22941 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
22942 registers. By default, @value{GDBN} selects the calling convention
22943 based on the selected architecture and the provided executable file.
22945 @item set powerpc exact-watchpoints
22946 @itemx show powerpc exact-watchpoints
22947 Allow @value{GDBN} to use only one debug register when watching a variable
22948 of scalar type, thus assuming that the variable is accessed through the
22949 address of its first byte.
22954 @subsection Atmel AVR
22957 When configured for debugging the Atmel AVR, @value{GDBN} supports the
22958 following AVR-specific commands:
22961 @item info io_registers
22962 @kindex info io_registers@r{, AVR}
22963 @cindex I/O registers (Atmel AVR)
22964 This command displays information about the AVR I/O registers. For
22965 each register, @value{GDBN} prints its number and value.
22972 When configured for debugging CRIS, @value{GDBN} provides the
22973 following CRIS-specific commands:
22976 @item set cris-version @var{ver}
22977 @cindex CRIS version
22978 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
22979 The CRIS version affects register names and sizes. This command is useful in
22980 case autodetection of the CRIS version fails.
22982 @item show cris-version
22983 Show the current CRIS version.
22985 @item set cris-dwarf2-cfi
22986 @cindex DWARF-2 CFI and CRIS
22987 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
22988 Change to @samp{off} when using @code{gcc-cris} whose version is below
22991 @item show cris-dwarf2-cfi
22992 Show the current state of using DWARF-2 CFI.
22994 @item set cris-mode @var{mode}
22996 Set the current CRIS mode to @var{mode}. It should only be changed when
22997 debugging in guru mode, in which case it should be set to
22998 @samp{guru} (the default is @samp{normal}).
23000 @item show cris-mode
23001 Show the current CRIS mode.
23005 @subsection Renesas Super-H
23008 For the Renesas Super-H processor, @value{GDBN} provides these
23012 @item set sh calling-convention @var{convention}
23013 @kindex set sh calling-convention
23014 Set the calling-convention used when calling functions from @value{GDBN}.
23015 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
23016 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
23017 convention. If the DWARF-2 information of the called function specifies
23018 that the function follows the Renesas calling convention, the function
23019 is called using the Renesas calling convention. If the calling convention
23020 is set to @samp{renesas}, the Renesas calling convention is always used,
23021 regardless of the DWARF-2 information. This can be used to override the
23022 default of @samp{gcc} if debug information is missing, or the compiler
23023 does not emit the DWARF-2 calling convention entry for a function.
23025 @item show sh calling-convention
23026 @kindex show sh calling-convention
23027 Show the current calling convention setting.
23032 @node Architectures
23033 @section Architectures
23035 This section describes characteristics of architectures that affect
23036 all uses of @value{GDBN} with the architecture, both native and cross.
23043 * HPPA:: HP PA architecture
23044 * SPU:: Cell Broadband Engine SPU architecture
23051 @subsection AArch64
23052 @cindex AArch64 support
23054 When @value{GDBN} is debugging the AArch64 architecture, it provides the
23055 following special commands:
23058 @item set debug aarch64
23059 @kindex set debug aarch64
23060 This command determines whether AArch64 architecture-specific debugging
23061 messages are to be displayed.
23063 @item show debug aarch64
23064 Show whether AArch64 debugging messages are displayed.
23069 @subsection x86 Architecture-specific Issues
23072 @item set struct-convention @var{mode}
23073 @kindex set struct-convention
23074 @cindex struct return convention
23075 @cindex struct/union returned in registers
23076 Set the convention used by the inferior to return @code{struct}s and
23077 @code{union}s from functions to @var{mode}. Possible values of
23078 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
23079 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
23080 are returned on the stack, while @code{"reg"} means that a
23081 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
23082 be returned in a register.
23084 @item show struct-convention
23085 @kindex show struct-convention
23086 Show the current setting of the convention to return @code{struct}s
23091 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
23092 @cindex Intel Memory Protection Extensions (MPX).
23094 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
23095 @footnote{The register named with capital letters represent the architecture
23096 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
23097 which are the lower bound and upper bound. Bounds are effective addresses or
23098 memory locations. The upper bounds are architecturally represented in 1's
23099 complement form. A bound having lower bound = 0, and upper bound = 0
23100 (1's complement of all bits set) will allow access to the entire address space.
23102 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
23103 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
23104 display the upper bound performing the complement of one operation on the
23105 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
23106 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
23107 can also be noted that the upper bounds are inclusive.
23109 As an example, assume that the register BND0 holds bounds for a pointer having
23110 access allowed for the range between 0x32 and 0x71. The values present on
23111 bnd0raw and bnd registers are presented as follows:
23114 bnd0raw = @{0x32, 0xffffffff8e@}
23115 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
23118 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
23119 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
23120 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
23121 Python, the display includes the memory size, in bits, accessible to
23124 Bounds can also be stored in bounds tables, which are stored in
23125 application memory. These tables store bounds for pointers by specifying
23126 the bounds pointer's value along with its bounds. Evaluating and changing
23127 bounds located in bound tables is therefore interesting while investigating
23128 bugs on MPX context. @value{GDBN} provides commands for this purpose:
23131 @item show mpx bound @var{pointer}
23132 @kindex show mpx bound
23133 Display bounds of the given @var{pointer}.
23135 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
23136 @kindex set mpx bound
23137 Set the bounds of a pointer in the bound table.
23138 This command takes three parameters: @var{pointer} is the pointers
23139 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
23140 for lower and upper bounds respectively.
23143 When you call an inferior function on an Intel MPX enabled program,
23144 GDB sets the inferior's bound registers to the init (disabled) state
23145 before calling the function. As a consequence, bounds checks for the
23146 pointer arguments passed to the function will always pass.
23148 This is necessary because when you call an inferior function, the
23149 program is usually in the middle of the execution of other function.
23150 Since at that point bound registers are in an arbitrary state, not
23151 clearing them would lead to random bound violations in the called
23154 You can still examine the influence of the bound registers on the
23155 execution of the called function by stopping the execution of the
23156 called function at its prologue, setting bound registers, and
23157 continuing the execution. For example:
23161 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
23162 $ print upper (a, b, c, d, 1)
23163 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
23165 @{lbound = 0x0, ubound = ffffffff@} : size -1
23168 At this last step the value of bnd0 can be changed for investigation of bound
23169 violations caused along the execution of the call. In order to know how to
23170 set the bound registers or bound table for the call consult the ABI.
23175 See the following section.
23178 @subsection @acronym{MIPS}
23180 @cindex stack on Alpha
23181 @cindex stack on @acronym{MIPS}
23182 @cindex Alpha stack
23183 @cindex @acronym{MIPS} stack
23184 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
23185 sometimes requires @value{GDBN} to search backward in the object code to
23186 find the beginning of a function.
23188 @cindex response time, @acronym{MIPS} debugging
23189 To improve response time (especially for embedded applications, where
23190 @value{GDBN} may be restricted to a slow serial line for this search)
23191 you may want to limit the size of this search, using one of these
23195 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
23196 @item set heuristic-fence-post @var{limit}
23197 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
23198 search for the beginning of a function. A value of @var{0} (the
23199 default) means there is no limit. However, except for @var{0}, the
23200 larger the limit the more bytes @code{heuristic-fence-post} must search
23201 and therefore the longer it takes to run. You should only need to use
23202 this command when debugging a stripped executable.
23204 @item show heuristic-fence-post
23205 Display the current limit.
23209 These commands are available @emph{only} when @value{GDBN} is configured
23210 for debugging programs on Alpha or @acronym{MIPS} processors.
23212 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
23216 @item set mips abi @var{arg}
23217 @kindex set mips abi
23218 @cindex set ABI for @acronym{MIPS}
23219 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
23220 values of @var{arg} are:
23224 The default ABI associated with the current binary (this is the
23234 @item show mips abi
23235 @kindex show mips abi
23236 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
23238 @item set mips compression @var{arg}
23239 @kindex set mips compression
23240 @cindex code compression, @acronym{MIPS}
23241 Tell @value{GDBN} which @acronym{MIPS} compressed
23242 @acronym{ISA, Instruction Set Architecture} encoding is used by the
23243 inferior. @value{GDBN} uses this for code disassembly and other
23244 internal interpretation purposes. This setting is only referred to
23245 when no executable has been associated with the debugging session or
23246 the executable does not provide information about the encoding it uses.
23247 Otherwise this setting is automatically updated from information
23248 provided by the executable.
23250 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
23251 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
23252 executables containing @acronym{MIPS16} code frequently are not
23253 identified as such.
23255 This setting is ``sticky''; that is, it retains its value across
23256 debugging sessions until reset either explicitly with this command or
23257 implicitly from an executable.
23259 The compiler and/or assembler typically add symbol table annotations to
23260 identify functions compiled for the @acronym{MIPS16} or
23261 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
23262 are present, @value{GDBN} uses them in preference to the global
23263 compressed @acronym{ISA} encoding setting.
23265 @item show mips compression
23266 @kindex show mips compression
23267 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
23268 @value{GDBN} to debug the inferior.
23271 @itemx show mipsfpu
23272 @xref{MIPS Embedded, set mipsfpu}.
23274 @item set mips mask-address @var{arg}
23275 @kindex set mips mask-address
23276 @cindex @acronym{MIPS} addresses, masking
23277 This command determines whether the most-significant 32 bits of 64-bit
23278 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
23279 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
23280 setting, which lets @value{GDBN} determine the correct value.
23282 @item show mips mask-address
23283 @kindex show mips mask-address
23284 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
23287 @item set remote-mips64-transfers-32bit-regs
23288 @kindex set remote-mips64-transfers-32bit-regs
23289 This command controls compatibility with 64-bit @acronym{MIPS} targets that
23290 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
23291 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
23292 and 64 bits for other registers, set this option to @samp{on}.
23294 @item show remote-mips64-transfers-32bit-regs
23295 @kindex show remote-mips64-transfers-32bit-regs
23296 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
23298 @item set debug mips
23299 @kindex set debug mips
23300 This command turns on and off debugging messages for the @acronym{MIPS}-specific
23301 target code in @value{GDBN}.
23303 @item show debug mips
23304 @kindex show debug mips
23305 Show the current setting of @acronym{MIPS} debugging messages.
23311 @cindex HPPA support
23313 When @value{GDBN} is debugging the HP PA architecture, it provides the
23314 following special commands:
23317 @item set debug hppa
23318 @kindex set debug hppa
23319 This command determines whether HPPA architecture-specific debugging
23320 messages are to be displayed.
23322 @item show debug hppa
23323 Show whether HPPA debugging messages are displayed.
23325 @item maint print unwind @var{address}
23326 @kindex maint print unwind@r{, HPPA}
23327 This command displays the contents of the unwind table entry at the
23328 given @var{address}.
23334 @subsection Cell Broadband Engine SPU architecture
23335 @cindex Cell Broadband Engine
23338 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
23339 it provides the following special commands:
23342 @item info spu event
23344 Display SPU event facility status. Shows current event mask
23345 and pending event status.
23347 @item info spu signal
23348 Display SPU signal notification facility status. Shows pending
23349 signal-control word and signal notification mode of both signal
23350 notification channels.
23352 @item info spu mailbox
23353 Display SPU mailbox facility status. Shows all pending entries,
23354 in order of processing, in each of the SPU Write Outbound,
23355 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
23358 Display MFC DMA status. Shows all pending commands in the MFC
23359 DMA queue. For each entry, opcode, tag, class IDs, effective
23360 and local store addresses and transfer size are shown.
23362 @item info spu proxydma
23363 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
23364 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
23365 and local store addresses and transfer size are shown.
23369 When @value{GDBN} is debugging a combined PowerPC/SPU application
23370 on the Cell Broadband Engine, it provides in addition the following
23374 @item set spu stop-on-load @var{arg}
23376 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
23377 will give control to the user when a new SPE thread enters its @code{main}
23378 function. The default is @code{off}.
23380 @item show spu stop-on-load
23382 Show whether to stop for new SPE threads.
23384 @item set spu auto-flush-cache @var{arg}
23385 Set whether to automatically flush the software-managed cache. When set to
23386 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
23387 cache to be flushed whenever SPE execution stops. This provides a consistent
23388 view of PowerPC memory that is accessed via the cache. If an application
23389 does not use the software-managed cache, this option has no effect.
23391 @item show spu auto-flush-cache
23392 Show whether to automatically flush the software-managed cache.
23397 @subsection PowerPC
23398 @cindex PowerPC architecture
23400 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
23401 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
23402 numbers stored in the floating point registers. These values must be stored
23403 in two consecutive registers, always starting at an even register like
23404 @code{f0} or @code{f2}.
23406 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
23407 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
23408 @code{f2} and @code{f3} for @code{$dl1} and so on.
23410 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
23411 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
23414 @subsection Nios II
23415 @cindex Nios II architecture
23417 When @value{GDBN} is debugging the Nios II architecture,
23418 it provides the following special commands:
23422 @item set debug nios2
23423 @kindex set debug nios2
23424 This command turns on and off debugging messages for the Nios II
23425 target code in @value{GDBN}.
23427 @item show debug nios2
23428 @kindex show debug nios2
23429 Show the current setting of Nios II debugging messages.
23433 @subsection Sparc64
23434 @cindex Sparc64 support
23435 @cindex Application Data Integrity
23436 @subsubsection ADI Support
23438 The M7 processor supports an Application Data Integrity (ADI) feature that
23439 detects invalid data accesses. When software allocates memory and enables
23440 ADI on the allocated memory, it chooses a 4-bit version number, sets the
23441 version in the upper 4 bits of the 64-bit pointer to that data, and stores
23442 the 4-bit version in every cacheline of that data. Hardware saves the latter
23443 in spare bits in the cache and memory hierarchy. On each load and store,
23444 the processor compares the upper 4 VA (virtual address) bits to the
23445 cacheline's version. If there is a mismatch, the processor generates a
23446 version mismatch trap which can be either precise or disrupting. The trap
23447 is an error condition which the kernel delivers to the process as a SIGSEGV
23450 Note that only 64-bit applications can use ADI and need to be built with
23453 Values of the ADI version tags, which are in granularity of a
23454 cacheline (64 bytes), can be viewed or modified.
23458 @kindex adi examine
23459 @item adi (examine | x) [ / @var{n} ] @var{addr}
23461 The @code{adi examine} command displays the value of one ADI version tag per
23464 @var{n} is a decimal integer specifying the number in bytes; the default
23465 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
23466 block size, to display.
23468 @var{addr} is the address in user address space where you want @value{GDBN}
23469 to begin displaying the ADI version tags.
23471 Below is an example of displaying ADI versions of variable "shmaddr".
23474 (@value{GDBP}) adi x/100 shmaddr
23475 0xfff800010002c000: 0 0
23479 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
23481 The @code{adi assign} command is used to assign new ADI version tag
23484 @var{n} is a decimal integer specifying the number in bytes;
23485 the default is 1. It specifies how much ADI version information, at the
23486 ratio of 1:ADI block size, to modify.
23488 @var{addr} is the address in user address space where you want @value{GDBN}
23489 to begin modifying the ADI version tags.
23491 @var{tag} is the new ADI version tag.
23493 For example, do the following to modify then verify ADI versions of
23494 variable "shmaddr":
23497 (@value{GDBP}) adi a/100 shmaddr = 7
23498 (@value{GDBP}) adi x/100 shmaddr
23499 0xfff800010002c000: 7 7
23504 @node Controlling GDB
23505 @chapter Controlling @value{GDBN}
23507 You can alter the way @value{GDBN} interacts with you by using the
23508 @code{set} command. For commands controlling how @value{GDBN} displays
23509 data, see @ref{Print Settings, ,Print Settings}. Other settings are
23514 * Editing:: Command editing
23515 * Command History:: Command history
23516 * Screen Size:: Screen size
23517 * Numbers:: Numbers
23518 * ABI:: Configuring the current ABI
23519 * Auto-loading:: Automatically loading associated files
23520 * Messages/Warnings:: Optional warnings and messages
23521 * Debugging Output:: Optional messages about internal happenings
23522 * Other Misc Settings:: Other Miscellaneous Settings
23530 @value{GDBN} indicates its readiness to read a command by printing a string
23531 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
23532 can change the prompt string with the @code{set prompt} command. For
23533 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
23534 the prompt in one of the @value{GDBN} sessions so that you can always tell
23535 which one you are talking to.
23537 @emph{Note:} @code{set prompt} does not add a space for you after the
23538 prompt you set. This allows you to set a prompt which ends in a space
23539 or a prompt that does not.
23543 @item set prompt @var{newprompt}
23544 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
23546 @kindex show prompt
23548 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
23551 Versions of @value{GDBN} that ship with Python scripting enabled have
23552 prompt extensions. The commands for interacting with these extensions
23556 @kindex set extended-prompt
23557 @item set extended-prompt @var{prompt}
23558 Set an extended prompt that allows for substitutions.
23559 @xref{gdb.prompt}, for a list of escape sequences that can be used for
23560 substitution. Any escape sequences specified as part of the prompt
23561 string are replaced with the corresponding strings each time the prompt
23567 set extended-prompt Current working directory: \w (gdb)
23570 Note that when an extended-prompt is set, it takes control of the
23571 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
23573 @kindex show extended-prompt
23574 @item show extended-prompt
23575 Prints the extended prompt. Any escape sequences specified as part of
23576 the prompt string with @code{set extended-prompt}, are replaced with the
23577 corresponding strings each time the prompt is displayed.
23581 @section Command Editing
23583 @cindex command line editing
23585 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
23586 @sc{gnu} library provides consistent behavior for programs which provide a
23587 command line interface to the user. Advantages are @sc{gnu} Emacs-style
23588 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
23589 substitution, and a storage and recall of command history across
23590 debugging sessions.
23592 You may control the behavior of command line editing in @value{GDBN} with the
23593 command @code{set}.
23596 @kindex set editing
23599 @itemx set editing on
23600 Enable command line editing (enabled by default).
23602 @item set editing off
23603 Disable command line editing.
23605 @kindex show editing
23607 Show whether command line editing is enabled.
23610 @ifset SYSTEM_READLINE
23611 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
23613 @ifclear SYSTEM_READLINE
23614 @xref{Command Line Editing},
23616 for more details about the Readline
23617 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
23618 encouraged to read that chapter.
23620 @node Command History
23621 @section Command History
23622 @cindex command history
23624 @value{GDBN} can keep track of the commands you type during your
23625 debugging sessions, so that you can be certain of precisely what
23626 happened. Use these commands to manage the @value{GDBN} command
23629 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
23630 package, to provide the history facility.
23631 @ifset SYSTEM_READLINE
23632 @xref{Using History Interactively, , , history, GNU History Library},
23634 @ifclear SYSTEM_READLINE
23635 @xref{Using History Interactively},
23637 for the detailed description of the History library.
23639 To issue a command to @value{GDBN} without affecting certain aspects of
23640 the state which is seen by users, prefix it with @samp{server }
23641 (@pxref{Server Prefix}). This
23642 means that this command will not affect the command history, nor will it
23643 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
23644 pressed on a line by itself.
23646 @cindex @code{server}, command prefix
23647 The server prefix does not affect the recording of values into the value
23648 history; to print a value without recording it into the value history,
23649 use the @code{output} command instead of the @code{print} command.
23651 Here is the description of @value{GDBN} commands related to command
23655 @cindex history substitution
23656 @cindex history file
23657 @kindex set history filename
23658 @cindex @env{GDBHISTFILE}, environment variable
23659 @item set history filename @var{fname}
23660 Set the name of the @value{GDBN} command history file to @var{fname}.
23661 This is the file where @value{GDBN} reads an initial command history
23662 list, and where it writes the command history from this session when it
23663 exits. You can access this list through history expansion or through
23664 the history command editing characters listed below. This file defaults
23665 to the value of the environment variable @code{GDBHISTFILE}, or to
23666 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
23669 @cindex save command history
23670 @kindex set history save
23671 @item set history save
23672 @itemx set history save on
23673 Record command history in a file, whose name may be specified with the
23674 @code{set history filename} command. By default, this option is disabled.
23676 @item set history save off
23677 Stop recording command history in a file.
23679 @cindex history size
23680 @kindex set history size
23681 @cindex @env{GDBHISTSIZE}, environment variable
23682 @item set history size @var{size}
23683 @itemx set history size unlimited
23684 Set the number of commands which @value{GDBN} keeps in its history list.
23685 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
23686 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
23687 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
23688 either a negative number or the empty string, then the number of commands
23689 @value{GDBN} keeps in the history list is unlimited.
23691 @cindex remove duplicate history
23692 @kindex set history remove-duplicates
23693 @item set history remove-duplicates @var{count}
23694 @itemx set history remove-duplicates unlimited
23695 Control the removal of duplicate history entries in the command history list.
23696 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
23697 history entries and remove the first entry that is a duplicate of the current
23698 entry being added to the command history list. If @var{count} is
23699 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
23700 removal of duplicate history entries is disabled.
23702 Only history entries added during the current session are considered for
23703 removal. This option is set to 0 by default.
23707 History expansion assigns special meaning to the character @kbd{!}.
23708 @ifset SYSTEM_READLINE
23709 @xref{Event Designators, , , history, GNU History Library},
23711 @ifclear SYSTEM_READLINE
23712 @xref{Event Designators},
23716 @cindex history expansion, turn on/off
23717 Since @kbd{!} is also the logical not operator in C, history expansion
23718 is off by default. If you decide to enable history expansion with the
23719 @code{set history expansion on} command, you may sometimes need to
23720 follow @kbd{!} (when it is used as logical not, in an expression) with
23721 a space or a tab to prevent it from being expanded. The readline
23722 history facilities do not attempt substitution on the strings
23723 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
23725 The commands to control history expansion are:
23728 @item set history expansion on
23729 @itemx set history expansion
23730 @kindex set history expansion
23731 Enable history expansion. History expansion is off by default.
23733 @item set history expansion off
23734 Disable history expansion.
23737 @kindex show history
23739 @itemx show history filename
23740 @itemx show history save
23741 @itemx show history size
23742 @itemx show history expansion
23743 These commands display the state of the @value{GDBN} history parameters.
23744 @code{show history} by itself displays all four states.
23749 @kindex show commands
23750 @cindex show last commands
23751 @cindex display command history
23752 @item show commands
23753 Display the last ten commands in the command history.
23755 @item show commands @var{n}
23756 Print ten commands centered on command number @var{n}.
23758 @item show commands +
23759 Print ten commands just after the commands last printed.
23763 @section Screen Size
23764 @cindex size of screen
23765 @cindex screen size
23768 @cindex pauses in output
23770 Certain commands to @value{GDBN} may produce large amounts of
23771 information output to the screen. To help you read all of it,
23772 @value{GDBN} pauses and asks you for input at the end of each page of
23773 output. Type @key{RET} when you want to continue the output, or @kbd{q}
23774 to discard the remaining output. Also, the screen width setting
23775 determines when to wrap lines of output. Depending on what is being
23776 printed, @value{GDBN} tries to break the line at a readable place,
23777 rather than simply letting it overflow onto the following line.
23779 Normally @value{GDBN} knows the size of the screen from the terminal
23780 driver software. For example, on Unix @value{GDBN} uses the termcap data base
23781 together with the value of the @code{TERM} environment variable and the
23782 @code{stty rows} and @code{stty cols} settings. If this is not correct,
23783 you can override it with the @code{set height} and @code{set
23790 @kindex show height
23791 @item set height @var{lpp}
23792 @itemx set height unlimited
23794 @itemx set width @var{cpl}
23795 @itemx set width unlimited
23797 These @code{set} commands specify a screen height of @var{lpp} lines and
23798 a screen width of @var{cpl} characters. The associated @code{show}
23799 commands display the current settings.
23801 If you specify a height of either @code{unlimited} or zero lines,
23802 @value{GDBN} does not pause during output no matter how long the
23803 output is. This is useful if output is to a file or to an editor
23806 Likewise, you can specify @samp{set width unlimited} or @samp{set
23807 width 0} to prevent @value{GDBN} from wrapping its output.
23809 @item set pagination on
23810 @itemx set pagination off
23811 @kindex set pagination
23812 Turn the output pagination on or off; the default is on. Turning
23813 pagination off is the alternative to @code{set height unlimited}. Note that
23814 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
23815 Options, -batch}) also automatically disables pagination.
23817 @item show pagination
23818 @kindex show pagination
23819 Show the current pagination mode.
23824 @cindex number representation
23825 @cindex entering numbers
23827 You can always enter numbers in octal, decimal, or hexadecimal in
23828 @value{GDBN} by the usual conventions: octal numbers begin with
23829 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
23830 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
23831 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
23832 10; likewise, the default display for numbers---when no particular
23833 format is specified---is base 10. You can change the default base for
23834 both input and output with the commands described below.
23837 @kindex set input-radix
23838 @item set input-radix @var{base}
23839 Set the default base for numeric input. Supported choices
23840 for @var{base} are decimal 8, 10, or 16. The base must itself be
23841 specified either unambiguously or using the current input radix; for
23845 set input-radix 012
23846 set input-radix 10.
23847 set input-radix 0xa
23851 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
23852 leaves the input radix unchanged, no matter what it was, since
23853 @samp{10}, being without any leading or trailing signs of its base, is
23854 interpreted in the current radix. Thus, if the current radix is 16,
23855 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
23858 @kindex set output-radix
23859 @item set output-radix @var{base}
23860 Set the default base for numeric display. Supported choices
23861 for @var{base} are decimal 8, 10, or 16. The base must itself be
23862 specified either unambiguously or using the current input radix.
23864 @kindex show input-radix
23865 @item show input-radix
23866 Display the current default base for numeric input.
23868 @kindex show output-radix
23869 @item show output-radix
23870 Display the current default base for numeric display.
23872 @item set radix @r{[}@var{base}@r{]}
23876 These commands set and show the default base for both input and output
23877 of numbers. @code{set radix} sets the radix of input and output to
23878 the same base; without an argument, it resets the radix back to its
23879 default value of 10.
23884 @section Configuring the Current ABI
23886 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
23887 application automatically. However, sometimes you need to override its
23888 conclusions. Use these commands to manage @value{GDBN}'s view of the
23894 @cindex Newlib OS ABI and its influence on the longjmp handling
23896 One @value{GDBN} configuration can debug binaries for multiple operating
23897 system targets, either via remote debugging or native emulation.
23898 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
23899 but you can override its conclusion using the @code{set osabi} command.
23900 One example where this is useful is in debugging of binaries which use
23901 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
23902 not have the same identifying marks that the standard C library for your
23905 When @value{GDBN} is debugging the AArch64 architecture, it provides a
23906 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
23907 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
23908 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
23912 Show the OS ABI currently in use.
23915 With no argument, show the list of registered available OS ABI's.
23917 @item set osabi @var{abi}
23918 Set the current OS ABI to @var{abi}.
23921 @cindex float promotion
23923 Generally, the way that an argument of type @code{float} is passed to a
23924 function depends on whether the function is prototyped. For a prototyped
23925 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
23926 according to the architecture's convention for @code{float}. For unprototyped
23927 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
23928 @code{double} and then passed.
23930 Unfortunately, some forms of debug information do not reliably indicate whether
23931 a function is prototyped. If @value{GDBN} calls a function that is not marked
23932 as prototyped, it consults @kbd{set coerce-float-to-double}.
23935 @kindex set coerce-float-to-double
23936 @item set coerce-float-to-double
23937 @itemx set coerce-float-to-double on
23938 Arguments of type @code{float} will be promoted to @code{double} when passed
23939 to an unprototyped function. This is the default setting.
23941 @item set coerce-float-to-double off
23942 Arguments of type @code{float} will be passed directly to unprototyped
23945 @kindex show coerce-float-to-double
23946 @item show coerce-float-to-double
23947 Show the current setting of promoting @code{float} to @code{double}.
23951 @kindex show cp-abi
23952 @value{GDBN} needs to know the ABI used for your program's C@t{++}
23953 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
23954 used to build your application. @value{GDBN} only fully supports
23955 programs with a single C@t{++} ABI; if your program contains code using
23956 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
23957 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
23958 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
23959 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
23960 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
23961 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
23966 Show the C@t{++} ABI currently in use.
23969 With no argument, show the list of supported C@t{++} ABI's.
23971 @item set cp-abi @var{abi}
23972 @itemx set cp-abi auto
23973 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
23977 @section Automatically loading associated files
23978 @cindex auto-loading
23980 @value{GDBN} sometimes reads files with commands and settings automatically,
23981 without being explicitly told so by the user. We call this feature
23982 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
23983 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
23984 results or introduce security risks (e.g., if the file comes from untrusted
23988 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
23989 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
23991 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
23992 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
23995 There are various kinds of files @value{GDBN} can automatically load.
23996 In addition to these files, @value{GDBN} supports auto-loading code written
23997 in various extension languages. @xref{Auto-loading extensions}.
23999 Note that loading of these associated files (including the local @file{.gdbinit}
24000 file) requires accordingly configured @code{auto-load safe-path}
24001 (@pxref{Auto-loading safe path}).
24003 For these reasons, @value{GDBN} includes commands and options to let you
24004 control when to auto-load files and which files should be auto-loaded.
24007 @anchor{set auto-load off}
24008 @kindex set auto-load off
24009 @item set auto-load off
24010 Globally disable loading of all auto-loaded files.
24011 You may want to use this command with the @samp{-iex} option
24012 (@pxref{Option -init-eval-command}) such as:
24014 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
24017 Be aware that system init file (@pxref{System-wide configuration})
24018 and init files from your home directory (@pxref{Home Directory Init File})
24019 still get read (as they come from generally trusted directories).
24020 To prevent @value{GDBN} from auto-loading even those init files, use the
24021 @option{-nx} option (@pxref{Mode Options}), in addition to
24022 @code{set auto-load no}.
24024 @anchor{show auto-load}
24025 @kindex show auto-load
24026 @item show auto-load
24027 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
24031 (gdb) show auto-load
24032 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
24033 libthread-db: Auto-loading of inferior specific libthread_db is on.
24034 local-gdbinit: Auto-loading of .gdbinit script from current directory
24036 python-scripts: Auto-loading of Python scripts is on.
24037 safe-path: List of directories from which it is safe to auto-load files
24038 is $debugdir:$datadir/auto-load.
24039 scripts-directory: List of directories from which to load auto-loaded scripts
24040 is $debugdir:$datadir/auto-load.
24043 @anchor{info auto-load}
24044 @kindex info auto-load
24045 @item info auto-load
24046 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
24050 (gdb) info auto-load
24053 Yes /home/user/gdb/gdb-gdb.gdb
24054 libthread-db: No auto-loaded libthread-db.
24055 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
24059 Yes /home/user/gdb/gdb-gdb.py
24063 These are @value{GDBN} control commands for the auto-loading:
24065 @multitable @columnfractions .5 .5
24066 @item @xref{set auto-load off}.
24067 @tab Disable auto-loading globally.
24068 @item @xref{show auto-load}.
24069 @tab Show setting of all kinds of files.
24070 @item @xref{info auto-load}.
24071 @tab Show state of all kinds of files.
24072 @item @xref{set auto-load gdb-scripts}.
24073 @tab Control for @value{GDBN} command scripts.
24074 @item @xref{show auto-load gdb-scripts}.
24075 @tab Show setting of @value{GDBN} command scripts.
24076 @item @xref{info auto-load gdb-scripts}.
24077 @tab Show state of @value{GDBN} command scripts.
24078 @item @xref{set auto-load python-scripts}.
24079 @tab Control for @value{GDBN} Python scripts.
24080 @item @xref{show auto-load python-scripts}.
24081 @tab Show setting of @value{GDBN} Python scripts.
24082 @item @xref{info auto-load python-scripts}.
24083 @tab Show state of @value{GDBN} Python scripts.
24084 @item @xref{set auto-load guile-scripts}.
24085 @tab Control for @value{GDBN} Guile scripts.
24086 @item @xref{show auto-load guile-scripts}.
24087 @tab Show setting of @value{GDBN} Guile scripts.
24088 @item @xref{info auto-load guile-scripts}.
24089 @tab Show state of @value{GDBN} Guile scripts.
24090 @item @xref{set auto-load scripts-directory}.
24091 @tab Control for @value{GDBN} auto-loaded scripts location.
24092 @item @xref{show auto-load scripts-directory}.
24093 @tab Show @value{GDBN} auto-loaded scripts location.
24094 @item @xref{add-auto-load-scripts-directory}.
24095 @tab Add directory for auto-loaded scripts location list.
24096 @item @xref{set auto-load local-gdbinit}.
24097 @tab Control for init file in the current directory.
24098 @item @xref{show auto-load local-gdbinit}.
24099 @tab Show setting of init file in the current directory.
24100 @item @xref{info auto-load local-gdbinit}.
24101 @tab Show state of init file in the current directory.
24102 @item @xref{set auto-load libthread-db}.
24103 @tab Control for thread debugging library.
24104 @item @xref{show auto-load libthread-db}.
24105 @tab Show setting of thread debugging library.
24106 @item @xref{info auto-load libthread-db}.
24107 @tab Show state of thread debugging library.
24108 @item @xref{set auto-load safe-path}.
24109 @tab Control directories trusted for automatic loading.
24110 @item @xref{show auto-load safe-path}.
24111 @tab Show directories trusted for automatic loading.
24112 @item @xref{add-auto-load-safe-path}.
24113 @tab Add directory trusted for automatic loading.
24116 @node Init File in the Current Directory
24117 @subsection Automatically loading init file in the current directory
24118 @cindex auto-loading init file in the current directory
24120 By default, @value{GDBN} reads and executes the canned sequences of commands
24121 from init file (if any) in the current working directory,
24122 see @ref{Init File in the Current Directory during Startup}.
24124 Note that loading of this local @file{.gdbinit} file also requires accordingly
24125 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24128 @anchor{set auto-load local-gdbinit}
24129 @kindex set auto-load local-gdbinit
24130 @item set auto-load local-gdbinit [on|off]
24131 Enable or disable the auto-loading of canned sequences of commands
24132 (@pxref{Sequences}) found in init file in the current directory.
24134 @anchor{show auto-load local-gdbinit}
24135 @kindex show auto-load local-gdbinit
24136 @item show auto-load local-gdbinit
24137 Show whether auto-loading of canned sequences of commands from init file in the
24138 current directory is enabled or disabled.
24140 @anchor{info auto-load local-gdbinit}
24141 @kindex info auto-load local-gdbinit
24142 @item info auto-load local-gdbinit
24143 Print whether canned sequences of commands from init file in the
24144 current directory have been auto-loaded.
24147 @node libthread_db.so.1 file
24148 @subsection Automatically loading thread debugging library
24149 @cindex auto-loading libthread_db.so.1
24151 This feature is currently present only on @sc{gnu}/Linux native hosts.
24153 @value{GDBN} reads in some cases thread debugging library from places specific
24154 to the inferior (@pxref{set libthread-db-search-path}).
24156 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
24157 without checking this @samp{set auto-load libthread-db} switch as system
24158 libraries have to be trusted in general. In all other cases of
24159 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
24160 auto-load libthread-db} is enabled before trying to open such thread debugging
24163 Note that loading of this debugging library also requires accordingly configured
24164 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24167 @anchor{set auto-load libthread-db}
24168 @kindex set auto-load libthread-db
24169 @item set auto-load libthread-db [on|off]
24170 Enable or disable the auto-loading of inferior specific thread debugging library.
24172 @anchor{show auto-load libthread-db}
24173 @kindex show auto-load libthread-db
24174 @item show auto-load libthread-db
24175 Show whether auto-loading of inferior specific thread debugging library is
24176 enabled or disabled.
24178 @anchor{info auto-load libthread-db}
24179 @kindex info auto-load libthread-db
24180 @item info auto-load libthread-db
24181 Print the list of all loaded inferior specific thread debugging libraries and
24182 for each such library print list of inferior @var{pid}s using it.
24185 @node Auto-loading safe path
24186 @subsection Security restriction for auto-loading
24187 @cindex auto-loading safe-path
24189 As the files of inferior can come from untrusted source (such as submitted by
24190 an application user) @value{GDBN} does not always load any files automatically.
24191 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
24192 directories trusted for loading files not explicitly requested by user.
24193 Each directory can also be a shell wildcard pattern.
24195 If the path is not set properly you will see a warning and the file will not
24200 Reading symbols from /home/user/gdb/gdb...done.
24201 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
24202 declined by your `auto-load safe-path' set
24203 to "$debugdir:$datadir/auto-load".
24204 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
24205 declined by your `auto-load safe-path' set
24206 to "$debugdir:$datadir/auto-load".
24210 To instruct @value{GDBN} to go ahead and use the init files anyway,
24211 invoke @value{GDBN} like this:
24214 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
24217 The list of trusted directories is controlled by the following commands:
24220 @anchor{set auto-load safe-path}
24221 @kindex set auto-load safe-path
24222 @item set auto-load safe-path @r{[}@var{directories}@r{]}
24223 Set the list of directories (and their subdirectories) trusted for automatic
24224 loading and execution of scripts. You can also enter a specific trusted file.
24225 Each directory can also be a shell wildcard pattern; wildcards do not match
24226 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
24227 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
24228 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
24229 its default value as specified during @value{GDBN} compilation.
24231 The list of directories uses path separator (@samp{:} on GNU and Unix
24232 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
24233 to the @env{PATH} environment variable.
24235 @anchor{show auto-load safe-path}
24236 @kindex show auto-load safe-path
24237 @item show auto-load safe-path
24238 Show the list of directories trusted for automatic loading and execution of
24241 @anchor{add-auto-load-safe-path}
24242 @kindex add-auto-load-safe-path
24243 @item add-auto-load-safe-path
24244 Add an entry (or list of entries) to the list of directories trusted for
24245 automatic loading and execution of scripts. Multiple entries may be delimited
24246 by the host platform path separator in use.
24249 This variable defaults to what @code{--with-auto-load-dir} has been configured
24250 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
24251 substitution applies the same as for @ref{set auto-load scripts-directory}.
24252 The default @code{set auto-load safe-path} value can be also overriden by
24253 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
24255 Setting this variable to @file{/} disables this security protection,
24256 corresponding @value{GDBN} configuration option is
24257 @option{--without-auto-load-safe-path}.
24258 This variable is supposed to be set to the system directories writable by the
24259 system superuser only. Users can add their source directories in init files in
24260 their home directories (@pxref{Home Directory Init File}). See also deprecated
24261 init file in the current directory
24262 (@pxref{Init File in the Current Directory during Startup}).
24264 To force @value{GDBN} to load the files it declined to load in the previous
24265 example, you could use one of the following ways:
24268 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
24269 Specify this trusted directory (or a file) as additional component of the list.
24270 You have to specify also any existing directories displayed by
24271 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
24273 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
24274 Specify this directory as in the previous case but just for a single
24275 @value{GDBN} session.
24277 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
24278 Disable auto-loading safety for a single @value{GDBN} session.
24279 This assumes all the files you debug during this @value{GDBN} session will come
24280 from trusted sources.
24282 @item @kbd{./configure --without-auto-load-safe-path}
24283 During compilation of @value{GDBN} you may disable any auto-loading safety.
24284 This assumes all the files you will ever debug with this @value{GDBN} come from
24288 On the other hand you can also explicitly forbid automatic files loading which
24289 also suppresses any such warning messages:
24292 @item @kbd{gdb -iex "set auto-load no" @dots{}}
24293 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
24295 @item @file{~/.gdbinit}: @samp{set auto-load no}
24296 Disable auto-loading globally for the user
24297 (@pxref{Home Directory Init File}). While it is improbable, you could also
24298 use system init file instead (@pxref{System-wide configuration}).
24301 This setting applies to the file names as entered by user. If no entry matches
24302 @value{GDBN} tries as a last resort to also resolve all the file names into
24303 their canonical form (typically resolving symbolic links) and compare the
24304 entries again. @value{GDBN} already canonicalizes most of the filenames on its
24305 own before starting the comparison so a canonical form of directories is
24306 recommended to be entered.
24308 @node Auto-loading verbose mode
24309 @subsection Displaying files tried for auto-load
24310 @cindex auto-loading verbose mode
24312 For better visibility of all the file locations where you can place scripts to
24313 be auto-loaded with inferior --- or to protect yourself against accidental
24314 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
24315 all the files attempted to be loaded. Both existing and non-existing files may
24318 For example the list of directories from which it is safe to auto-load files
24319 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
24320 may not be too obvious while setting it up.
24323 (gdb) set debug auto-load on
24324 (gdb) file ~/src/t/true
24325 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
24326 for objfile "/tmp/true".
24327 auto-load: Updating directories of "/usr:/opt".
24328 auto-load: Using directory "/usr".
24329 auto-load: Using directory "/opt".
24330 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
24331 by your `auto-load safe-path' set to "/usr:/opt".
24335 @anchor{set debug auto-load}
24336 @kindex set debug auto-load
24337 @item set debug auto-load [on|off]
24338 Set whether to print the filenames attempted to be auto-loaded.
24340 @anchor{show debug auto-load}
24341 @kindex show debug auto-load
24342 @item show debug auto-load
24343 Show whether printing of the filenames attempted to be auto-loaded is turned
24347 @node Messages/Warnings
24348 @section Optional Warnings and Messages
24350 @cindex verbose operation
24351 @cindex optional warnings
24352 By default, @value{GDBN} is silent about its inner workings. If you are
24353 running on a slow machine, you may want to use the @code{set verbose}
24354 command. This makes @value{GDBN} tell you when it does a lengthy
24355 internal operation, so you will not think it has crashed.
24357 Currently, the messages controlled by @code{set verbose} are those
24358 which announce that the symbol table for a source file is being read;
24359 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
24362 @kindex set verbose
24363 @item set verbose on
24364 Enables @value{GDBN} output of certain informational messages.
24366 @item set verbose off
24367 Disables @value{GDBN} output of certain informational messages.
24369 @kindex show verbose
24371 Displays whether @code{set verbose} is on or off.
24374 By default, if @value{GDBN} encounters bugs in the symbol table of an
24375 object file, it is silent; but if you are debugging a compiler, you may
24376 find this information useful (@pxref{Symbol Errors, ,Errors Reading
24381 @kindex set complaints
24382 @item set complaints @var{limit}
24383 Permits @value{GDBN} to output @var{limit} complaints about each type of
24384 unusual symbols before becoming silent about the problem. Set
24385 @var{limit} to zero to suppress all complaints; set it to a large number
24386 to prevent complaints from being suppressed.
24388 @kindex show complaints
24389 @item show complaints
24390 Displays how many symbol complaints @value{GDBN} is permitted to produce.
24394 @anchor{confirmation requests}
24395 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
24396 lot of stupid questions to confirm certain commands. For example, if
24397 you try to run a program which is already running:
24401 The program being debugged has been started already.
24402 Start it from the beginning? (y or n)
24405 If you are willing to unflinchingly face the consequences of your own
24406 commands, you can disable this ``feature'':
24410 @kindex set confirm
24412 @cindex confirmation
24413 @cindex stupid questions
24414 @item set confirm off
24415 Disables confirmation requests. Note that running @value{GDBN} with
24416 the @option{--batch} option (@pxref{Mode Options, -batch}) also
24417 automatically disables confirmation requests.
24419 @item set confirm on
24420 Enables confirmation requests (the default).
24422 @kindex show confirm
24424 Displays state of confirmation requests.
24428 @cindex command tracing
24429 If you need to debug user-defined commands or sourced files you may find it
24430 useful to enable @dfn{command tracing}. In this mode each command will be
24431 printed as it is executed, prefixed with one or more @samp{+} symbols, the
24432 quantity denoting the call depth of each command.
24435 @kindex set trace-commands
24436 @cindex command scripts, debugging
24437 @item set trace-commands on
24438 Enable command tracing.
24439 @item set trace-commands off
24440 Disable command tracing.
24441 @item show trace-commands
24442 Display the current state of command tracing.
24445 @node Debugging Output
24446 @section Optional Messages about Internal Happenings
24447 @cindex optional debugging messages
24449 @value{GDBN} has commands that enable optional debugging messages from
24450 various @value{GDBN} subsystems; normally these commands are of
24451 interest to @value{GDBN} maintainers, or when reporting a bug. This
24452 section documents those commands.
24455 @kindex set exec-done-display
24456 @item set exec-done-display
24457 Turns on or off the notification of asynchronous commands'
24458 completion. When on, @value{GDBN} will print a message when an
24459 asynchronous command finishes its execution. The default is off.
24460 @kindex show exec-done-display
24461 @item show exec-done-display
24462 Displays the current setting of asynchronous command completion
24465 @cindex ARM AArch64
24466 @item set debug aarch64
24467 Turns on or off display of debugging messages related to ARM AArch64.
24468 The default is off.
24470 @item show debug aarch64
24471 Displays the current state of displaying debugging messages related to
24473 @cindex gdbarch debugging info
24474 @cindex architecture debugging info
24475 @item set debug arch
24476 Turns on or off display of gdbarch debugging info. The default is off
24477 @item show debug arch
24478 Displays the current state of displaying gdbarch debugging info.
24479 @item set debug aix-solib
24480 @cindex AIX shared library debugging
24481 Control display of debugging messages from the AIX shared library
24482 support module. The default is off.
24483 @item show debug aix-thread
24484 Show the current state of displaying AIX shared library debugging messages.
24485 @item set debug aix-thread
24486 @cindex AIX threads
24487 Display debugging messages about inner workings of the AIX thread
24489 @item show debug aix-thread
24490 Show the current state of AIX thread debugging info display.
24491 @item set debug check-physname
24493 Check the results of the ``physname'' computation. When reading DWARF
24494 debugging information for C@t{++}, @value{GDBN} attempts to compute
24495 each entity's name. @value{GDBN} can do this computation in two
24496 different ways, depending on exactly what information is present.
24497 When enabled, this setting causes @value{GDBN} to compute the names
24498 both ways and display any discrepancies.
24499 @item show debug check-physname
24500 Show the current state of ``physname'' checking.
24501 @item set debug coff-pe-read
24502 @cindex COFF/PE exported symbols
24503 Control display of debugging messages related to reading of COFF/PE
24504 exported symbols. The default is off.
24505 @item show debug coff-pe-read
24506 Displays the current state of displaying debugging messages related to
24507 reading of COFF/PE exported symbols.
24508 @item set debug dwarf-die
24510 Dump DWARF DIEs after they are read in.
24511 The value is the number of nesting levels to print.
24512 A value of zero turns off the display.
24513 @item show debug dwarf-die
24514 Show the current state of DWARF DIE debugging.
24515 @item set debug dwarf-line
24516 @cindex DWARF Line Tables
24517 Turns on or off display of debugging messages related to reading
24518 DWARF line tables. The default is 0 (off).
24519 A value of 1 provides basic information.
24520 A value greater than 1 provides more verbose information.
24521 @item show debug dwarf-line
24522 Show the current state of DWARF line table debugging.
24523 @item set debug dwarf-read
24524 @cindex DWARF Reading
24525 Turns on or off display of debugging messages related to reading
24526 DWARF debug info. The default is 0 (off).
24527 A value of 1 provides basic information.
24528 A value greater than 1 provides more verbose information.
24529 @item show debug dwarf-read
24530 Show the current state of DWARF reader debugging.
24531 @item set debug displaced
24532 @cindex displaced stepping debugging info
24533 Turns on or off display of @value{GDBN} debugging info for the
24534 displaced stepping support. The default is off.
24535 @item show debug displaced
24536 Displays the current state of displaying @value{GDBN} debugging info
24537 related to displaced stepping.
24538 @item set debug event
24539 @cindex event debugging info
24540 Turns on or off display of @value{GDBN} event debugging info. The
24542 @item show debug event
24543 Displays the current state of displaying @value{GDBN} event debugging
24545 @item set debug expression
24546 @cindex expression debugging info
24547 Turns on or off display of debugging info about @value{GDBN}
24548 expression parsing. The default is off.
24549 @item show debug expression
24550 Displays the current state of displaying debugging info about
24551 @value{GDBN} expression parsing.
24552 @item set debug fbsd-lwp
24553 @cindex FreeBSD LWP debug messages
24554 Turns on or off debugging messages from the FreeBSD LWP debug support.
24555 @item show debug fbsd-lwp
24556 Show the current state of FreeBSD LWP debugging messages.
24557 @item set debug fbsd-nat
24558 @cindex FreeBSD native target debug messages
24559 Turns on or off debugging messages from the FreeBSD native target.
24560 @item show debug fbsd-nat
24561 Show the current state of FreeBSD native target debugging messages.
24562 @item set debug frame
24563 @cindex frame debugging info
24564 Turns on or off display of @value{GDBN} frame debugging info. The
24566 @item show debug frame
24567 Displays the current state of displaying @value{GDBN} frame debugging
24569 @item set debug gnu-nat
24570 @cindex @sc{gnu}/Hurd debug messages
24571 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
24572 @item show debug gnu-nat
24573 Show the current state of @sc{gnu}/Hurd debugging messages.
24574 @item set debug infrun
24575 @cindex inferior debugging info
24576 Turns on or off display of @value{GDBN} debugging info for running the inferior.
24577 The default is off. @file{infrun.c} contains GDB's runtime state machine used
24578 for implementing operations such as single-stepping the inferior.
24579 @item show debug infrun
24580 Displays the current state of @value{GDBN} inferior debugging.
24581 @item set debug jit
24582 @cindex just-in-time compilation, debugging messages
24583 Turn on or off debugging messages from JIT debug support.
24584 @item show debug jit
24585 Displays the current state of @value{GDBN} JIT debugging.
24586 @item set debug lin-lwp
24587 @cindex @sc{gnu}/Linux LWP debug messages
24588 @cindex Linux lightweight processes
24589 Turn on or off debugging messages from the Linux LWP debug support.
24590 @item show debug lin-lwp
24591 Show the current state of Linux LWP debugging messages.
24592 @item set debug linux-namespaces
24593 @cindex @sc{gnu}/Linux namespaces debug messages
24594 Turn on or off debugging messages from the Linux namespaces debug support.
24595 @item show debug linux-namespaces
24596 Show the current state of Linux namespaces debugging messages.
24597 @item set debug mach-o
24598 @cindex Mach-O symbols processing
24599 Control display of debugging messages related to Mach-O symbols
24600 processing. The default is off.
24601 @item show debug mach-o
24602 Displays the current state of displaying debugging messages related to
24603 reading of COFF/PE exported symbols.
24604 @item set debug notification
24605 @cindex remote async notification debugging info
24606 Turn on or off debugging messages about remote async notification.
24607 The default is off.
24608 @item show debug notification
24609 Displays the current state of remote async notification debugging messages.
24610 @item set debug observer
24611 @cindex observer debugging info
24612 Turns on or off display of @value{GDBN} observer debugging. This
24613 includes info such as the notification of observable events.
24614 @item show debug observer
24615 Displays the current state of observer debugging.
24616 @item set debug overload
24617 @cindex C@t{++} overload debugging info
24618 Turns on or off display of @value{GDBN} C@t{++} overload debugging
24619 info. This includes info such as ranking of functions, etc. The default
24621 @item show debug overload
24622 Displays the current state of displaying @value{GDBN} C@t{++} overload
24624 @cindex expression parser, debugging info
24625 @cindex debug expression parser
24626 @item set debug parser
24627 Turns on or off the display of expression parser debugging output.
24628 Internally, this sets the @code{yydebug} variable in the expression
24629 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
24630 details. The default is off.
24631 @item show debug parser
24632 Show the current state of expression parser debugging.
24633 @cindex packets, reporting on stdout
24634 @cindex serial connections, debugging
24635 @cindex debug remote protocol
24636 @cindex remote protocol debugging
24637 @cindex display remote packets
24638 @item set debug remote
24639 Turns on or off display of reports on all packets sent back and forth across
24640 the serial line to the remote machine. The info is printed on the
24641 @value{GDBN} standard output stream. The default is off.
24642 @item show debug remote
24643 Displays the state of display of remote packets.
24645 @item set debug separate-debug-file
24646 Turns on or off display of debug output about separate debug file search.
24647 @item show debug separate-debug-file
24648 Displays the state of separate debug file search debug output.
24650 @item set debug serial
24651 Turns on or off display of @value{GDBN} serial debugging info. The
24653 @item show debug serial
24654 Displays the current state of displaying @value{GDBN} serial debugging
24656 @item set debug solib-frv
24657 @cindex FR-V shared-library debugging
24658 Turn on or off debugging messages for FR-V shared-library code.
24659 @item show debug solib-frv
24660 Display the current state of FR-V shared-library code debugging
24662 @item set debug symbol-lookup
24663 @cindex symbol lookup
24664 Turns on or off display of debugging messages related to symbol lookup.
24665 The default is 0 (off).
24666 A value of 1 provides basic information.
24667 A value greater than 1 provides more verbose information.
24668 @item show debug symbol-lookup
24669 Show the current state of symbol lookup debugging messages.
24670 @item set debug symfile
24671 @cindex symbol file functions
24672 Turns on or off display of debugging messages related to symbol file functions.
24673 The default is off. @xref{Files}.
24674 @item show debug symfile
24675 Show the current state of symbol file debugging messages.
24676 @item set debug symtab-create
24677 @cindex symbol table creation
24678 Turns on or off display of debugging messages related to symbol table creation.
24679 The default is 0 (off).
24680 A value of 1 provides basic information.
24681 A value greater than 1 provides more verbose information.
24682 @item show debug symtab-create
24683 Show the current state of symbol table creation debugging.
24684 @item set debug target
24685 @cindex target debugging info
24686 Turns on or off display of @value{GDBN} target debugging info. This info
24687 includes what is going on at the target level of GDB, as it happens. The
24688 default is 0. Set it to 1 to track events, and to 2 to also track the
24689 value of large memory transfers.
24690 @item show debug target
24691 Displays the current state of displaying @value{GDBN} target debugging
24693 @item set debug timestamp
24694 @cindex timestampping debugging info
24695 Turns on or off display of timestamps with @value{GDBN} debugging info.
24696 When enabled, seconds and microseconds are displayed before each debugging
24698 @item show debug timestamp
24699 Displays the current state of displaying timestamps with @value{GDBN}
24701 @item set debug varobj
24702 @cindex variable object debugging info
24703 Turns on or off display of @value{GDBN} variable object debugging
24704 info. The default is off.
24705 @item show debug varobj
24706 Displays the current state of displaying @value{GDBN} variable object
24708 @item set debug xml
24709 @cindex XML parser debugging
24710 Turn on or off debugging messages for built-in XML parsers.
24711 @item show debug xml
24712 Displays the current state of XML debugging messages.
24715 @node Other Misc Settings
24716 @section Other Miscellaneous Settings
24717 @cindex miscellaneous settings
24720 @kindex set interactive-mode
24721 @item set interactive-mode
24722 If @code{on}, forces @value{GDBN} to assume that GDB was started
24723 in a terminal. In practice, this means that @value{GDBN} should wait
24724 for the user to answer queries generated by commands entered at
24725 the command prompt. If @code{off}, forces @value{GDBN} to operate
24726 in the opposite mode, and it uses the default answers to all queries.
24727 If @code{auto} (the default), @value{GDBN} tries to determine whether
24728 its standard input is a terminal, and works in interactive-mode if it
24729 is, non-interactively otherwise.
24731 In the vast majority of cases, the debugger should be able to guess
24732 correctly which mode should be used. But this setting can be useful
24733 in certain specific cases, such as running a MinGW @value{GDBN}
24734 inside a cygwin window.
24736 @kindex show interactive-mode
24737 @item show interactive-mode
24738 Displays whether the debugger is operating in interactive mode or not.
24741 @node Extending GDB
24742 @chapter Extending @value{GDBN}
24743 @cindex extending GDB
24745 @value{GDBN} provides several mechanisms for extension.
24746 @value{GDBN} also provides the ability to automatically load
24747 extensions when it reads a file for debugging. This allows the
24748 user to automatically customize @value{GDBN} for the program
24752 * Sequences:: Canned Sequences of @value{GDBN} Commands
24753 * Python:: Extending @value{GDBN} using Python
24754 * Guile:: Extending @value{GDBN} using Guile
24755 * Auto-loading extensions:: Automatically loading extensions
24756 * Multiple Extension Languages:: Working with multiple extension languages
24757 * Aliases:: Creating new spellings of existing commands
24760 To facilitate the use of extension languages, @value{GDBN} is capable
24761 of evaluating the contents of a file. When doing so, @value{GDBN}
24762 can recognize which extension language is being used by looking at
24763 the filename extension. Files with an unrecognized filename extension
24764 are always treated as a @value{GDBN} Command Files.
24765 @xref{Command Files,, Command files}.
24767 You can control how @value{GDBN} evaluates these files with the following
24771 @kindex set script-extension
24772 @kindex show script-extension
24773 @item set script-extension off
24774 All scripts are always evaluated as @value{GDBN} Command Files.
24776 @item set script-extension soft
24777 The debugger determines the scripting language based on filename
24778 extension. If this scripting language is supported, @value{GDBN}
24779 evaluates the script using that language. Otherwise, it evaluates
24780 the file as a @value{GDBN} Command File.
24782 @item set script-extension strict
24783 The debugger determines the scripting language based on filename
24784 extension, and evaluates the script using that language. If the
24785 language is not supported, then the evaluation fails.
24787 @item show script-extension
24788 Display the current value of the @code{script-extension} option.
24793 @section Canned Sequences of Commands
24795 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
24796 Command Lists}), @value{GDBN} provides two ways to store sequences of
24797 commands for execution as a unit: user-defined commands and command
24801 * Define:: How to define your own commands
24802 * Hooks:: Hooks for user-defined commands
24803 * Command Files:: How to write scripts of commands to be stored in a file
24804 * Output:: Commands for controlled output
24805 * Auto-loading sequences:: Controlling auto-loaded command files
24809 @subsection User-defined Commands
24811 @cindex user-defined command
24812 @cindex arguments, to user-defined commands
24813 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
24814 which you assign a new name as a command. This is done with the
24815 @code{define} command. User commands may accept an unlimited number of arguments
24816 separated by whitespace. Arguments are accessed within the user command
24817 via @code{$arg0@dots{}$argN}. A trivial example:
24821 print $arg0 + $arg1 + $arg2
24826 To execute the command use:
24833 This defines the command @code{adder}, which prints the sum of
24834 its three arguments. Note the arguments are text substitutions, so they may
24835 reference variables, use complex expressions, or even perform inferior
24838 @cindex argument count in user-defined commands
24839 @cindex how many arguments (user-defined commands)
24840 In addition, @code{$argc} may be used to find out how many arguments have
24846 print $arg0 + $arg1
24849 print $arg0 + $arg1 + $arg2
24854 Combining with the @code{eval} command (@pxref{eval}) makes it easier
24855 to process a variable number of arguments:
24862 eval "set $sum = $sum + $arg%d", $i
24872 @item define @var{commandname}
24873 Define a command named @var{commandname}. If there is already a command
24874 by that name, you are asked to confirm that you want to redefine it.
24875 The argument @var{commandname} may be a bare command name consisting of letters,
24876 numbers, dashes, and underscores. It may also start with any predefined
24877 prefix command. For example, @samp{define target my-target} creates
24878 a user-defined @samp{target my-target} command.
24880 The definition of the command is made up of other @value{GDBN} command lines,
24881 which are given following the @code{define} command. The end of these
24882 commands is marked by a line containing @code{end}.
24885 @kindex end@r{ (user-defined commands)}
24886 @item document @var{commandname}
24887 Document the user-defined command @var{commandname}, so that it can be
24888 accessed by @code{help}. The command @var{commandname} must already be
24889 defined. This command reads lines of documentation just as @code{define}
24890 reads the lines of the command definition, ending with @code{end}.
24891 After the @code{document} command is finished, @code{help} on command
24892 @var{commandname} displays the documentation you have written.
24894 You may use the @code{document} command again to change the
24895 documentation of a command. Redefining the command with @code{define}
24896 does not change the documentation.
24898 @kindex dont-repeat
24899 @cindex don't repeat command
24901 Used inside a user-defined command, this tells @value{GDBN} that this
24902 command should not be repeated when the user hits @key{RET}
24903 (@pxref{Command Syntax, repeat last command}).
24905 @kindex help user-defined
24906 @item help user-defined
24907 List all user-defined commands and all python commands defined in class
24908 COMAND_USER. The first line of the documentation or docstring is
24913 @itemx show user @var{commandname}
24914 Display the @value{GDBN} commands used to define @var{commandname} (but
24915 not its documentation). If no @var{commandname} is given, display the
24916 definitions for all user-defined commands.
24917 This does not work for user-defined python commands.
24919 @cindex infinite recursion in user-defined commands
24920 @kindex show max-user-call-depth
24921 @kindex set max-user-call-depth
24922 @item show max-user-call-depth
24923 @itemx set max-user-call-depth
24924 The value of @code{max-user-call-depth} controls how many recursion
24925 levels are allowed in user-defined commands before @value{GDBN} suspects an
24926 infinite recursion and aborts the command.
24927 This does not apply to user-defined python commands.
24930 In addition to the above commands, user-defined commands frequently
24931 use control flow commands, described in @ref{Command Files}.
24933 When user-defined commands are executed, the
24934 commands of the definition are not printed. An error in any command
24935 stops execution of the user-defined command.
24937 If used interactively, commands that would ask for confirmation proceed
24938 without asking when used inside a user-defined command. Many @value{GDBN}
24939 commands that normally print messages to say what they are doing omit the
24940 messages when used in a user-defined command.
24943 @subsection User-defined Command Hooks
24944 @cindex command hooks
24945 @cindex hooks, for commands
24946 @cindex hooks, pre-command
24949 You may define @dfn{hooks}, which are a special kind of user-defined
24950 command. Whenever you run the command @samp{foo}, if the user-defined
24951 command @samp{hook-foo} exists, it is executed (with no arguments)
24952 before that command.
24954 @cindex hooks, post-command
24956 A hook may also be defined which is run after the command you executed.
24957 Whenever you run the command @samp{foo}, if the user-defined command
24958 @samp{hookpost-foo} exists, it is executed (with no arguments) after
24959 that command. Post-execution hooks may exist simultaneously with
24960 pre-execution hooks, for the same command.
24962 It is valid for a hook to call the command which it hooks. If this
24963 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
24965 @c It would be nice if hookpost could be passed a parameter indicating
24966 @c if the command it hooks executed properly or not. FIXME!
24968 @kindex stop@r{, a pseudo-command}
24969 In addition, a pseudo-command, @samp{stop} exists. Defining
24970 (@samp{hook-stop}) makes the associated commands execute every time
24971 execution stops in your program: before breakpoint commands are run,
24972 displays are printed, or the stack frame is printed.
24974 For example, to ignore @code{SIGALRM} signals while
24975 single-stepping, but treat them normally during normal execution,
24980 handle SIGALRM nopass
24984 handle SIGALRM pass
24987 define hook-continue
24988 handle SIGALRM pass
24992 As a further example, to hook at the beginning and end of the @code{echo}
24993 command, and to add extra text to the beginning and end of the message,
25001 define hookpost-echo
25005 (@value{GDBP}) echo Hello World
25006 <<<---Hello World--->>>
25011 You can define a hook for any single-word command in @value{GDBN}, but
25012 not for command aliases; you should define a hook for the basic command
25013 name, e.g.@: @code{backtrace} rather than @code{bt}.
25014 @c FIXME! So how does Joe User discover whether a command is an alias
25016 You can hook a multi-word command by adding @code{hook-} or
25017 @code{hookpost-} to the last word of the command, e.g.@:
25018 @samp{define target hook-remote} to add a hook to @samp{target remote}.
25020 If an error occurs during the execution of your hook, execution of
25021 @value{GDBN} commands stops and @value{GDBN} issues a prompt
25022 (before the command that you actually typed had a chance to run).
25024 If you try to define a hook which does not match any known command, you
25025 get a warning from the @code{define} command.
25027 @node Command Files
25028 @subsection Command Files
25030 @cindex command files
25031 @cindex scripting commands
25032 A command file for @value{GDBN} is a text file made of lines that are
25033 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
25034 also be included. An empty line in a command file does nothing; it
25035 does not mean to repeat the last command, as it would from the
25038 You can request the execution of a command file with the @code{source}
25039 command. Note that the @code{source} command is also used to evaluate
25040 scripts that are not Command Files. The exact behavior can be configured
25041 using the @code{script-extension} setting.
25042 @xref{Extending GDB,, Extending GDB}.
25046 @cindex execute commands from a file
25047 @item source [-s] [-v] @var{filename}
25048 Execute the command file @var{filename}.
25051 The lines in a command file are generally executed sequentially,
25052 unless the order of execution is changed by one of the
25053 @emph{flow-control commands} described below. The commands are not
25054 printed as they are executed. An error in any command terminates
25055 execution of the command file and control is returned to the console.
25057 @value{GDBN} first searches for @var{filename} in the current directory.
25058 If the file is not found there, and @var{filename} does not specify a
25059 directory, then @value{GDBN} also looks for the file on the source search path
25060 (specified with the @samp{directory} command);
25061 except that @file{$cdir} is not searched because the compilation directory
25062 is not relevant to scripts.
25064 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
25065 on the search path even if @var{filename} specifies a directory.
25066 The search is done by appending @var{filename} to each element of the
25067 search path. So, for example, if @var{filename} is @file{mylib/myscript}
25068 and the search path contains @file{/home/user} then @value{GDBN} will
25069 look for the script @file{/home/user/mylib/myscript}.
25070 The search is also done if @var{filename} is an absolute path.
25071 For example, if @var{filename} is @file{/tmp/myscript} and
25072 the search path contains @file{/home/user} then @value{GDBN} will
25073 look for the script @file{/home/user/tmp/myscript}.
25074 For DOS-like systems, if @var{filename} contains a drive specification,
25075 it is stripped before concatenation. For example, if @var{filename} is
25076 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
25077 will look for the script @file{c:/tmp/myscript}.
25079 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
25080 each command as it is executed. The option must be given before
25081 @var{filename}, and is interpreted as part of the filename anywhere else.
25083 Commands that would ask for confirmation if used interactively proceed
25084 without asking when used in a command file. Many @value{GDBN} commands that
25085 normally print messages to say what they are doing omit the messages
25086 when called from command files.
25088 @value{GDBN} also accepts command input from standard input. In this
25089 mode, normal output goes to standard output and error output goes to
25090 standard error. Errors in a command file supplied on standard input do
25091 not terminate execution of the command file---execution continues with
25095 gdb < cmds > log 2>&1
25098 (The syntax above will vary depending on the shell used.) This example
25099 will execute commands from the file @file{cmds}. All output and errors
25100 would be directed to @file{log}.
25102 Since commands stored on command files tend to be more general than
25103 commands typed interactively, they frequently need to deal with
25104 complicated situations, such as different or unexpected values of
25105 variables and symbols, changes in how the program being debugged is
25106 built, etc. @value{GDBN} provides a set of flow-control commands to
25107 deal with these complexities. Using these commands, you can write
25108 complex scripts that loop over data structures, execute commands
25109 conditionally, etc.
25116 This command allows to include in your script conditionally executed
25117 commands. The @code{if} command takes a single argument, which is an
25118 expression to evaluate. It is followed by a series of commands that
25119 are executed only if the expression is true (its value is nonzero).
25120 There can then optionally be an @code{else} line, followed by a series
25121 of commands that are only executed if the expression was false. The
25122 end of the list is marked by a line containing @code{end}.
25126 This command allows to write loops. Its syntax is similar to
25127 @code{if}: the command takes a single argument, which is an expression
25128 to evaluate, and must be followed by the commands to execute, one per
25129 line, terminated by an @code{end}. These commands are called the
25130 @dfn{body} of the loop. The commands in the body of @code{while} are
25131 executed repeatedly as long as the expression evaluates to true.
25135 This command exits the @code{while} loop in whose body it is included.
25136 Execution of the script continues after that @code{while}s @code{end}
25139 @kindex loop_continue
25140 @item loop_continue
25141 This command skips the execution of the rest of the body of commands
25142 in the @code{while} loop in whose body it is included. Execution
25143 branches to the beginning of the @code{while} loop, where it evaluates
25144 the controlling expression.
25146 @kindex end@r{ (if/else/while commands)}
25148 Terminate the block of commands that are the body of @code{if},
25149 @code{else}, or @code{while} flow-control commands.
25154 @subsection Commands for Controlled Output
25156 During the execution of a command file or a user-defined command, normal
25157 @value{GDBN} output is suppressed; the only output that appears is what is
25158 explicitly printed by the commands in the definition. This section
25159 describes three commands useful for generating exactly the output you
25164 @item echo @var{text}
25165 @c I do not consider backslash-space a standard C escape sequence
25166 @c because it is not in ANSI.
25167 Print @var{text}. Nonprinting characters can be included in
25168 @var{text} using C escape sequences, such as @samp{\n} to print a
25169 newline. @strong{No newline is printed unless you specify one.}
25170 In addition to the standard C escape sequences, a backslash followed
25171 by a space stands for a space. This is useful for displaying a
25172 string with spaces at the beginning or the end, since leading and
25173 trailing spaces are otherwise trimmed from all arguments.
25174 To print @samp{@w{ }and foo =@w{ }}, use the command
25175 @samp{echo \@w{ }and foo = \@w{ }}.
25177 A backslash at the end of @var{text} can be used, as in C, to continue
25178 the command onto subsequent lines. For example,
25181 echo This is some text\n\
25182 which is continued\n\
25183 onto several lines.\n
25186 produces the same output as
25189 echo This is some text\n
25190 echo which is continued\n
25191 echo onto several lines.\n
25195 @item output @var{expression}
25196 Print the value of @var{expression} and nothing but that value: no
25197 newlines, no @samp{$@var{nn} = }. The value is not entered in the
25198 value history either. @xref{Expressions, ,Expressions}, for more information
25201 @item output/@var{fmt} @var{expression}
25202 Print the value of @var{expression} in format @var{fmt}. You can use
25203 the same formats as for @code{print}. @xref{Output Formats,,Output
25204 Formats}, for more information.
25207 @item printf @var{template}, @var{expressions}@dots{}
25208 Print the values of one or more @var{expressions} under the control of
25209 the string @var{template}. To print several values, make
25210 @var{expressions} be a comma-separated list of individual expressions,
25211 which may be either numbers or pointers. Their values are printed as
25212 specified by @var{template}, exactly as a C program would do by
25213 executing the code below:
25216 printf (@var{template}, @var{expressions}@dots{});
25219 As in @code{C} @code{printf}, ordinary characters in @var{template}
25220 are printed verbatim, while @dfn{conversion specification} introduced
25221 by the @samp{%} character cause subsequent @var{expressions} to be
25222 evaluated, their values converted and formatted according to type and
25223 style information encoded in the conversion specifications, and then
25226 For example, you can print two values in hex like this:
25229 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
25232 @code{printf} supports all the standard @code{C} conversion
25233 specifications, including the flags and modifiers between the @samp{%}
25234 character and the conversion letter, with the following exceptions:
25238 The argument-ordering modifiers, such as @samp{2$}, are not supported.
25241 The modifier @samp{*} is not supported for specifying precision or
25245 The @samp{'} flag (for separation of digits into groups according to
25246 @code{LC_NUMERIC'}) is not supported.
25249 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
25253 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
25256 The conversion letters @samp{a} and @samp{A} are not supported.
25260 Note that the @samp{ll} type modifier is supported only if the
25261 underlying @code{C} implementation used to build @value{GDBN} supports
25262 the @code{long long int} type, and the @samp{L} type modifier is
25263 supported only if @code{long double} type is available.
25265 As in @code{C}, @code{printf} supports simple backslash-escape
25266 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
25267 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
25268 single character. Octal and hexadecimal escape sequences are not
25271 Additionally, @code{printf} supports conversion specifications for DFP
25272 (@dfn{Decimal Floating Point}) types using the following length modifiers
25273 together with a floating point specifier.
25278 @samp{H} for printing @code{Decimal32} types.
25281 @samp{D} for printing @code{Decimal64} types.
25284 @samp{DD} for printing @code{Decimal128} types.
25287 If the underlying @code{C} implementation used to build @value{GDBN} has
25288 support for the three length modifiers for DFP types, other modifiers
25289 such as width and precision will also be available for @value{GDBN} to use.
25291 In case there is no such @code{C} support, no additional modifiers will be
25292 available and the value will be printed in the standard way.
25294 Here's an example of printing DFP types using the above conversion letters:
25296 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
25301 @item eval @var{template}, @var{expressions}@dots{}
25302 Convert the values of one or more @var{expressions} under the control of
25303 the string @var{template} to a command line, and call it.
25307 @node Auto-loading sequences
25308 @subsection Controlling auto-loading native @value{GDBN} scripts
25309 @cindex native script auto-loading
25311 When a new object file is read (for example, due to the @code{file}
25312 command, or because the inferior has loaded a shared library),
25313 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
25314 @xref{Auto-loading extensions}.
25316 Auto-loading can be enabled or disabled,
25317 and the list of auto-loaded scripts can be printed.
25320 @anchor{set auto-load gdb-scripts}
25321 @kindex set auto-load gdb-scripts
25322 @item set auto-load gdb-scripts [on|off]
25323 Enable or disable the auto-loading of canned sequences of commands scripts.
25325 @anchor{show auto-load gdb-scripts}
25326 @kindex show auto-load gdb-scripts
25327 @item show auto-load gdb-scripts
25328 Show whether auto-loading of canned sequences of commands scripts is enabled or
25331 @anchor{info auto-load gdb-scripts}
25332 @kindex info auto-load gdb-scripts
25333 @cindex print list of auto-loaded canned sequences of commands scripts
25334 @item info auto-load gdb-scripts [@var{regexp}]
25335 Print the list of all canned sequences of commands scripts that @value{GDBN}
25339 If @var{regexp} is supplied only canned sequences of commands scripts with
25340 matching names are printed.
25342 @c Python docs live in a separate file.
25343 @include python.texi
25345 @c Guile docs live in a separate file.
25346 @include guile.texi
25348 @node Auto-loading extensions
25349 @section Auto-loading extensions
25350 @cindex auto-loading extensions
25352 @value{GDBN} provides two mechanisms for automatically loading extensions
25353 when a new object file is read (for example, due to the @code{file}
25354 command, or because the inferior has loaded a shared library):
25355 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
25356 section of modern file formats like ELF.
25359 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
25360 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
25361 * Which flavor to choose?::
25364 The auto-loading feature is useful for supplying application-specific
25365 debugging commands and features.
25367 Auto-loading can be enabled or disabled,
25368 and the list of auto-loaded scripts can be printed.
25369 See the @samp{auto-loading} section of each extension language
25370 for more information.
25371 For @value{GDBN} command files see @ref{Auto-loading sequences}.
25372 For Python files see @ref{Python Auto-loading}.
25374 Note that loading of this script file also requires accordingly configured
25375 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25377 @node objfile-gdbdotext file
25378 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
25379 @cindex @file{@var{objfile}-gdb.gdb}
25380 @cindex @file{@var{objfile}-gdb.py}
25381 @cindex @file{@var{objfile}-gdb.scm}
25383 When a new object file is read, @value{GDBN} looks for a file named
25384 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
25385 where @var{objfile} is the object file's name and
25386 where @var{ext} is the file extension for the extension language:
25389 @item @file{@var{objfile}-gdb.gdb}
25390 GDB's own command language
25391 @item @file{@var{objfile}-gdb.py}
25393 @item @file{@var{objfile}-gdb.scm}
25397 @var{script-name} is formed by ensuring that the file name of @var{objfile}
25398 is absolute, following all symlinks, and resolving @code{.} and @code{..}
25399 components, and appending the @file{-gdb.@var{ext}} suffix.
25400 If this file exists and is readable, @value{GDBN} will evaluate it as a
25401 script in the specified extension language.
25403 If this file does not exist, then @value{GDBN} will look for
25404 @var{script-name} file in all of the directories as specified below.
25406 Note that loading of these files requires an accordingly configured
25407 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25409 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
25410 scripts normally according to its @file{.exe} filename. But if no scripts are
25411 found @value{GDBN} also tries script filenames matching the object file without
25412 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
25413 is attempted on any platform. This makes the script filenames compatible
25414 between Unix and MS-Windows hosts.
25417 @anchor{set auto-load scripts-directory}
25418 @kindex set auto-load scripts-directory
25419 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
25420 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
25421 may be delimited by the host platform path separator in use
25422 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
25424 Each entry here needs to be covered also by the security setting
25425 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
25427 @anchor{with-auto-load-dir}
25428 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
25429 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
25430 configuration option @option{--with-auto-load-dir}.
25432 Any reference to @file{$debugdir} will get replaced by
25433 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
25434 reference to @file{$datadir} will get replaced by @var{data-directory} which is
25435 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
25436 @file{$datadir} must be placed as a directory component --- either alone or
25437 delimited by @file{/} or @file{\} directory separators, depending on the host
25440 The list of directories uses path separator (@samp{:} on GNU and Unix
25441 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
25442 to the @env{PATH} environment variable.
25444 @anchor{show auto-load scripts-directory}
25445 @kindex show auto-load scripts-directory
25446 @item show auto-load scripts-directory
25447 Show @value{GDBN} auto-loaded scripts location.
25449 @anchor{add-auto-load-scripts-directory}
25450 @kindex add-auto-load-scripts-directory
25451 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
25452 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
25453 Multiple entries may be delimited by the host platform path separator in use.
25456 @value{GDBN} does not track which files it has already auto-loaded this way.
25457 @value{GDBN} will load the associated script every time the corresponding
25458 @var{objfile} is opened.
25459 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
25460 is evaluated more than once.
25462 @node dotdebug_gdb_scripts section
25463 @subsection The @code{.debug_gdb_scripts} section
25464 @cindex @code{.debug_gdb_scripts} section
25466 For systems using file formats like ELF and COFF,
25467 when @value{GDBN} loads a new object file
25468 it will look for a special section named @code{.debug_gdb_scripts}.
25469 If this section exists, its contents is a list of null-terminated entries
25470 specifying scripts to load. Each entry begins with a non-null prefix byte that
25471 specifies the kind of entry, typically the extension language and whether the
25472 script is in a file or inlined in @code{.debug_gdb_scripts}.
25474 The following entries are supported:
25477 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
25478 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
25479 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
25480 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
25483 @subsubsection Script File Entries
25485 If the entry specifies a file, @value{GDBN} will look for the file first
25486 in the current directory and then along the source search path
25487 (@pxref{Source Path, ,Specifying Source Directories}),
25488 except that @file{$cdir} is not searched, since the compilation
25489 directory is not relevant to scripts.
25491 File entries can be placed in section @code{.debug_gdb_scripts} with,
25492 for example, this GCC macro for Python scripts.
25495 /* Note: The "MS" section flags are to remove duplicates. */
25496 #define DEFINE_GDB_PY_SCRIPT(script_name) \
25498 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
25499 .byte 1 /* Python */\n\
25500 .asciz \"" script_name "\"\n\
25506 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
25507 Then one can reference the macro in a header or source file like this:
25510 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
25513 The script name may include directories if desired.
25515 Note that loading of this script file also requires accordingly configured
25516 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25518 If the macro invocation is put in a header, any application or library
25519 using this header will get a reference to the specified script,
25520 and with the use of @code{"MS"} attributes on the section, the linker
25521 will remove duplicates.
25523 @subsubsection Script Text Entries
25525 Script text entries allow to put the executable script in the entry
25526 itself instead of loading it from a file.
25527 The first line of the entry, everything after the prefix byte and up to
25528 the first newline (@code{0xa}) character, is the script name, and must not
25529 contain any kind of space character, e.g., spaces or tabs.
25530 The rest of the entry, up to the trailing null byte, is the script to
25531 execute in the specified language. The name needs to be unique among
25532 all script names, as @value{GDBN} executes each script only once based
25535 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
25539 #include "symcat.h"
25540 #include "gdb/section-scripts.h"
25542 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
25543 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
25544 ".ascii \"gdb.inlined-script\\n\"\n"
25545 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
25546 ".ascii \" def __init__ (self):\\n\"\n"
25547 ".ascii \" super (test_cmd, self).__init__ ("
25548 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
25549 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
25550 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
25551 ".ascii \"test_cmd ()\\n\"\n"
25557 Loading of inlined scripts requires a properly configured
25558 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25559 The path to specify in @code{auto-load safe-path} is the path of the file
25560 containing the @code{.debug_gdb_scripts} section.
25562 @node Which flavor to choose?
25563 @subsection Which flavor to choose?
25565 Given the multiple ways of auto-loading extensions, it might not always
25566 be clear which one to choose. This section provides some guidance.
25569 Benefits of the @file{-gdb.@var{ext}} way:
25573 Can be used with file formats that don't support multiple sections.
25576 Ease of finding scripts for public libraries.
25578 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
25579 in the source search path.
25580 For publicly installed libraries, e.g., @file{libstdc++}, there typically
25581 isn't a source directory in which to find the script.
25584 Doesn't require source code additions.
25588 Benefits of the @code{.debug_gdb_scripts} way:
25592 Works with static linking.
25594 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
25595 trigger their loading. When an application is statically linked the only
25596 objfile available is the executable, and it is cumbersome to attach all the
25597 scripts from all the input libraries to the executable's
25598 @file{-gdb.@var{ext}} script.
25601 Works with classes that are entirely inlined.
25603 Some classes can be entirely inlined, and thus there may not be an associated
25604 shared library to attach a @file{-gdb.@var{ext}} script to.
25607 Scripts needn't be copied out of the source tree.
25609 In some circumstances, apps can be built out of large collections of internal
25610 libraries, and the build infrastructure necessary to install the
25611 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
25612 cumbersome. It may be easier to specify the scripts in the
25613 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
25614 top of the source tree to the source search path.
25617 @node Multiple Extension Languages
25618 @section Multiple Extension Languages
25620 The Guile and Python extension languages do not share any state,
25621 and generally do not interfere with each other.
25622 There are some things to be aware of, however.
25624 @subsection Python comes first
25626 Python was @value{GDBN}'s first extension language, and to avoid breaking
25627 existing behaviour Python comes first. This is generally solved by the
25628 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
25629 extension languages, and when it makes a call to an extension language,
25630 (say to pretty-print a value), it tries each in turn until an extension
25631 language indicates it has performed the request (e.g., has returned the
25632 pretty-printed form of a value).
25633 This extends to errors while performing such requests: If an error happens
25634 while, for example, trying to pretty-print an object then the error is
25635 reported and any following extension languages are not tried.
25638 @section Creating new spellings of existing commands
25639 @cindex aliases for commands
25641 It is often useful to define alternate spellings of existing commands.
25642 For example, if a new @value{GDBN} command defined in Python has
25643 a long name to type, it is handy to have an abbreviated version of it
25644 that involves less typing.
25646 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
25647 of the @samp{step} command even though it is otherwise an ambiguous
25648 abbreviation of other commands like @samp{set} and @samp{show}.
25650 Aliases are also used to provide shortened or more common versions
25651 of multi-word commands. For example, @value{GDBN} provides the
25652 @samp{tty} alias of the @samp{set inferior-tty} command.
25654 You can define a new alias with the @samp{alias} command.
25659 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
25663 @var{ALIAS} specifies the name of the new alias.
25664 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
25667 @var{COMMAND} specifies the name of an existing command
25668 that is being aliased.
25670 The @samp{-a} option specifies that the new alias is an abbreviation
25671 of the command. Abbreviations are not shown in command
25672 lists displayed by the @samp{help} command.
25674 The @samp{--} option specifies the end of options,
25675 and is useful when @var{ALIAS} begins with a dash.
25677 Here is a simple example showing how to make an abbreviation
25678 of a command so that there is less to type.
25679 Suppose you were tired of typing @samp{disas}, the current
25680 shortest unambiguous abbreviation of the @samp{disassemble} command
25681 and you wanted an even shorter version named @samp{di}.
25682 The following will accomplish this.
25685 (gdb) alias -a di = disas
25688 Note that aliases are different from user-defined commands.
25689 With a user-defined command, you also need to write documentation
25690 for it with the @samp{document} command.
25691 An alias automatically picks up the documentation of the existing command.
25693 Here is an example where we make @samp{elms} an abbreviation of
25694 @samp{elements} in the @samp{set print elements} command.
25695 This is to show that you can make an abbreviation of any part
25699 (gdb) alias -a set print elms = set print elements
25700 (gdb) alias -a show print elms = show print elements
25701 (gdb) set p elms 20
25703 Limit on string chars or array elements to print is 200.
25706 Note that if you are defining an alias of a @samp{set} command,
25707 and you want to have an alias for the corresponding @samp{show}
25708 command, then you need to define the latter separately.
25710 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
25711 @var{ALIAS}, just as they are normally.
25714 (gdb) alias -a set pr elms = set p ele
25717 Finally, here is an example showing the creation of a one word
25718 alias for a more complex command.
25719 This creates alias @samp{spe} of the command @samp{set print elements}.
25722 (gdb) alias spe = set print elements
25727 @chapter Command Interpreters
25728 @cindex command interpreters
25730 @value{GDBN} supports multiple command interpreters, and some command
25731 infrastructure to allow users or user interface writers to switch
25732 between interpreters or run commands in other interpreters.
25734 @value{GDBN} currently supports two command interpreters, the console
25735 interpreter (sometimes called the command-line interpreter or @sc{cli})
25736 and the machine interface interpreter (or @sc{gdb/mi}). This manual
25737 describes both of these interfaces in great detail.
25739 By default, @value{GDBN} will start with the console interpreter.
25740 However, the user may choose to start @value{GDBN} with another
25741 interpreter by specifying the @option{-i} or @option{--interpreter}
25742 startup options. Defined interpreters include:
25746 @cindex console interpreter
25747 The traditional console or command-line interpreter. This is the most often
25748 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
25749 @value{GDBN} will use this interpreter.
25752 @cindex mi interpreter
25753 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
25754 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
25755 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
25759 @cindex mi2 interpreter
25760 The current @sc{gdb/mi} interface.
25763 @cindex mi1 interpreter
25764 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
25768 @cindex invoke another interpreter
25770 @kindex interpreter-exec
25771 You may execute commands in any interpreter from the current
25772 interpreter using the appropriate command. If you are running the
25773 console interpreter, simply use the @code{interpreter-exec} command:
25776 interpreter-exec mi "-data-list-register-names"
25779 @sc{gdb/mi} has a similar command, although it is only available in versions of
25780 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
25782 Note that @code{interpreter-exec} only changes the interpreter for the
25783 duration of the specified command. It does not change the interpreter
25786 @cindex start a new independent interpreter
25788 Although you may only choose a single interpreter at startup, it is
25789 possible to run an independent interpreter on a specified input/output
25790 device (usually a tty).
25792 For example, consider a debugger GUI or IDE that wants to provide a
25793 @value{GDBN} console view. It may do so by embedding a terminal
25794 emulator widget in its GUI, starting @value{GDBN} in the traditional
25795 command-line mode with stdin/stdout/stderr redirected to that
25796 terminal, and then creating an MI interpreter running on a specified
25797 input/output device. The console interpreter created by @value{GDBN}
25798 at startup handles commands the user types in the terminal widget,
25799 while the GUI controls and synchronizes state with @value{GDBN} using
25800 the separate MI interpreter.
25802 To start a new secondary @dfn{user interface} running MI, use the
25803 @code{new-ui} command:
25806 @cindex new user interface
25808 new-ui @var{interpreter} @var{tty}
25811 The @var{interpreter} parameter specifies the interpreter to run.
25812 This accepts the same values as the @code{interpreter-exec} command.
25813 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
25814 @var{tty} parameter specifies the name of the bidirectional file the
25815 interpreter uses for input/output, usually the name of a
25816 pseudoterminal slave on Unix systems. For example:
25819 (@value{GDBP}) new-ui mi /dev/pts/9
25823 runs an MI interpreter on @file{/dev/pts/9}.
25826 @chapter @value{GDBN} Text User Interface
25828 @cindex Text User Interface
25831 * TUI Overview:: TUI overview
25832 * TUI Keys:: TUI key bindings
25833 * TUI Single Key Mode:: TUI single key mode
25834 * TUI Commands:: TUI-specific commands
25835 * TUI Configuration:: TUI configuration variables
25838 The @value{GDBN} Text User Interface (TUI) is a terminal
25839 interface which uses the @code{curses} library to show the source
25840 file, the assembly output, the program registers and @value{GDBN}
25841 commands in separate text windows. The TUI mode is supported only
25842 on platforms where a suitable version of the @code{curses} library
25845 The TUI mode is enabled by default when you invoke @value{GDBN} as
25846 @samp{@value{GDBP} -tui}.
25847 You can also switch in and out of TUI mode while @value{GDBN} runs by
25848 using various TUI commands and key bindings, such as @command{tui
25849 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
25850 @ref{TUI Keys, ,TUI Key Bindings}.
25853 @section TUI Overview
25855 In TUI mode, @value{GDBN} can display several text windows:
25859 This window is the @value{GDBN} command window with the @value{GDBN}
25860 prompt and the @value{GDBN} output. The @value{GDBN} input is still
25861 managed using readline.
25864 The source window shows the source file of the program. The current
25865 line and active breakpoints are displayed in this window.
25868 The assembly window shows the disassembly output of the program.
25871 This window shows the processor registers. Registers are highlighted
25872 when their values change.
25875 The source and assembly windows show the current program position
25876 by highlighting the current line and marking it with a @samp{>} marker.
25877 Breakpoints are indicated with two markers. The first marker
25878 indicates the breakpoint type:
25882 Breakpoint which was hit at least once.
25885 Breakpoint which was never hit.
25888 Hardware breakpoint which was hit at least once.
25891 Hardware breakpoint which was never hit.
25894 The second marker indicates whether the breakpoint is enabled or not:
25898 Breakpoint is enabled.
25901 Breakpoint is disabled.
25904 The source, assembly and register windows are updated when the current
25905 thread changes, when the frame changes, or when the program counter
25908 These windows are not all visible at the same time. The command
25909 window is always visible. The others can be arranged in several
25920 source and assembly,
25923 source and registers, or
25926 assembly and registers.
25929 A status line above the command window shows the following information:
25933 Indicates the current @value{GDBN} target.
25934 (@pxref{Targets, ,Specifying a Debugging Target}).
25937 Gives the current process or thread number.
25938 When no process is being debugged, this field is set to @code{No process}.
25941 Gives the current function name for the selected frame.
25942 The name is demangled if demangling is turned on (@pxref{Print Settings}).
25943 When there is no symbol corresponding to the current program counter,
25944 the string @code{??} is displayed.
25947 Indicates the current line number for the selected frame.
25948 When the current line number is not known, the string @code{??} is displayed.
25951 Indicates the current program counter address.
25955 @section TUI Key Bindings
25956 @cindex TUI key bindings
25958 The TUI installs several key bindings in the readline keymaps
25959 @ifset SYSTEM_READLINE
25960 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
25962 @ifclear SYSTEM_READLINE
25963 (@pxref{Command Line Editing}).
25965 The following key bindings are installed for both TUI mode and the
25966 @value{GDBN} standard mode.
25975 Enter or leave the TUI mode. When leaving the TUI mode,
25976 the curses window management stops and @value{GDBN} operates using
25977 its standard mode, writing on the terminal directly. When reentering
25978 the TUI mode, control is given back to the curses windows.
25979 The screen is then refreshed.
25983 Use a TUI layout with only one window. The layout will
25984 either be @samp{source} or @samp{assembly}. When the TUI mode
25985 is not active, it will switch to the TUI mode.
25987 Think of this key binding as the Emacs @kbd{C-x 1} binding.
25991 Use a TUI layout with at least two windows. When the current
25992 layout already has two windows, the next layout with two windows is used.
25993 When a new layout is chosen, one window will always be common to the
25994 previous layout and the new one.
25996 Think of it as the Emacs @kbd{C-x 2} binding.
26000 Change the active window. The TUI associates several key bindings
26001 (like scrolling and arrow keys) with the active window. This command
26002 gives the focus to the next TUI window.
26004 Think of it as the Emacs @kbd{C-x o} binding.
26008 Switch in and out of the TUI SingleKey mode that binds single
26009 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
26012 The following key bindings only work in the TUI mode:
26017 Scroll the active window one page up.
26021 Scroll the active window one page down.
26025 Scroll the active window one line up.
26029 Scroll the active window one line down.
26033 Scroll the active window one column left.
26037 Scroll the active window one column right.
26041 Refresh the screen.
26044 Because the arrow keys scroll the active window in the TUI mode, they
26045 are not available for their normal use by readline unless the command
26046 window has the focus. When another window is active, you must use
26047 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
26048 and @kbd{C-f} to control the command window.
26050 @node TUI Single Key Mode
26051 @section TUI Single Key Mode
26052 @cindex TUI single key mode
26054 The TUI also provides a @dfn{SingleKey} mode, which binds several
26055 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
26056 switch into this mode, where the following key bindings are used:
26059 @kindex c @r{(SingleKey TUI key)}
26063 @kindex d @r{(SingleKey TUI key)}
26067 @kindex f @r{(SingleKey TUI key)}
26071 @kindex n @r{(SingleKey TUI key)}
26075 @kindex o @r{(SingleKey TUI key)}
26077 nexti. The shortcut letter @samp{o} stands for ``step Over''.
26079 @kindex q @r{(SingleKey TUI key)}
26081 exit the SingleKey mode.
26083 @kindex r @r{(SingleKey TUI key)}
26087 @kindex s @r{(SingleKey TUI key)}
26091 @kindex i @r{(SingleKey TUI key)}
26093 stepi. The shortcut letter @samp{i} stands for ``step Into''.
26095 @kindex u @r{(SingleKey TUI key)}
26099 @kindex v @r{(SingleKey TUI key)}
26103 @kindex w @r{(SingleKey TUI key)}
26108 Other keys temporarily switch to the @value{GDBN} command prompt.
26109 The key that was pressed is inserted in the editing buffer so that
26110 it is possible to type most @value{GDBN} commands without interaction
26111 with the TUI SingleKey mode. Once the command is entered the TUI
26112 SingleKey mode is restored. The only way to permanently leave
26113 this mode is by typing @kbd{q} or @kbd{C-x s}.
26117 @section TUI-specific Commands
26118 @cindex TUI commands
26120 The TUI has specific commands to control the text windows.
26121 These commands are always available, even when @value{GDBN} is not in
26122 the TUI mode. When @value{GDBN} is in the standard mode, most
26123 of these commands will automatically switch to the TUI mode.
26125 Note that if @value{GDBN}'s @code{stdout} is not connected to a
26126 terminal, or @value{GDBN} has been started with the machine interface
26127 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
26128 these commands will fail with an error, because it would not be
26129 possible or desirable to enable curses window management.
26134 Activate TUI mode. The last active TUI window layout will be used if
26135 TUI mode has prevsiouly been used in the current debugging session,
26136 otherwise a default layout is used.
26139 @kindex tui disable
26140 Disable TUI mode, returning to the console interpreter.
26144 List and give the size of all displayed windows.
26146 @item layout @var{name}
26148 Changes which TUI windows are displayed. In each layout the command
26149 window is always displayed, the @var{name} parameter controls which
26150 additional windows are displayed, and can be any of the following:
26154 Display the next layout.
26157 Display the previous layout.
26160 Display the source and command windows.
26163 Display the assembly and command windows.
26166 Display the source, assembly, and command windows.
26169 When in @code{src} layout display the register, source, and command
26170 windows. When in @code{asm} or @code{split} layout display the
26171 register, assembler, and command windows.
26174 @item focus @var{name}
26176 Changes which TUI window is currently active for scrolling. The
26177 @var{name} parameter can be any of the following:
26181 Make the next window active for scrolling.
26184 Make the previous window active for scrolling.
26187 Make the source window active for scrolling.
26190 Make the assembly window active for scrolling.
26193 Make the register window active for scrolling.
26196 Make the command window active for scrolling.
26201 Refresh the screen. This is similar to typing @kbd{C-L}.
26203 @item tui reg @var{group}
26205 Changes the register group displayed in the tui register window to
26206 @var{group}. If the register window is not currently displayed this
26207 command will cause the register window to be displayed. The list of
26208 register groups, as well as their order is target specific. The
26209 following groups are available on most targets:
26212 Repeatedly selecting this group will cause the display to cycle
26213 through all of the available register groups.
26216 Repeatedly selecting this group will cause the display to cycle
26217 through all of the available register groups in the reverse order to
26221 Display the general registers.
26223 Display the floating point registers.
26225 Display the system registers.
26227 Display the vector registers.
26229 Display all registers.
26234 Update the source window and the current execution point.
26236 @item winheight @var{name} +@var{count}
26237 @itemx winheight @var{name} -@var{count}
26239 Change the height of the window @var{name} by @var{count}
26240 lines. Positive counts increase the height, while negative counts
26241 decrease it. The @var{name} parameter can be one of @code{src} (the
26242 source window), @code{cmd} (the command window), @code{asm} (the
26243 disassembly window), or @code{regs} (the register display window).
26245 @item tabset @var{nchars}
26247 Set the width of tab stops to be @var{nchars} characters. This
26248 setting affects the display of TAB characters in the source and
26252 @node TUI Configuration
26253 @section TUI Configuration Variables
26254 @cindex TUI configuration variables
26256 Several configuration variables control the appearance of TUI windows.
26259 @item set tui border-kind @var{kind}
26260 @kindex set tui border-kind
26261 Select the border appearance for the source, assembly and register windows.
26262 The possible values are the following:
26265 Use a space character to draw the border.
26268 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
26271 Use the Alternate Character Set to draw the border. The border is
26272 drawn using character line graphics if the terminal supports them.
26275 @item set tui border-mode @var{mode}
26276 @kindex set tui border-mode
26277 @itemx set tui active-border-mode @var{mode}
26278 @kindex set tui active-border-mode
26279 Select the display attributes for the borders of the inactive windows
26280 or the active window. The @var{mode} can be one of the following:
26283 Use normal attributes to display the border.
26289 Use reverse video mode.
26292 Use half bright mode.
26294 @item half-standout
26295 Use half bright and standout mode.
26298 Use extra bright or bold mode.
26300 @item bold-standout
26301 Use extra bright or bold and standout mode.
26306 @chapter Using @value{GDBN} under @sc{gnu} Emacs
26309 @cindex @sc{gnu} Emacs
26310 A special interface allows you to use @sc{gnu} Emacs to view (and
26311 edit) the source files for the program you are debugging with
26314 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
26315 executable file you want to debug as an argument. This command starts
26316 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
26317 created Emacs buffer.
26318 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
26320 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
26325 All ``terminal'' input and output goes through an Emacs buffer, called
26328 This applies both to @value{GDBN} commands and their output, and to the input
26329 and output done by the program you are debugging.
26331 This is useful because it means that you can copy the text of previous
26332 commands and input them again; you can even use parts of the output
26335 All the facilities of Emacs' Shell mode are available for interacting
26336 with your program. In particular, you can send signals the usual
26337 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
26341 @value{GDBN} displays source code through Emacs.
26343 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
26344 source file for that frame and puts an arrow (@samp{=>}) at the
26345 left margin of the current line. Emacs uses a separate buffer for
26346 source display, and splits the screen to show both your @value{GDBN} session
26349 Explicit @value{GDBN} @code{list} or search commands still produce output as
26350 usual, but you probably have no reason to use them from Emacs.
26353 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
26354 a graphical mode, enabled by default, which provides further buffers
26355 that can control the execution and describe the state of your program.
26356 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
26358 If you specify an absolute file name when prompted for the @kbd{M-x
26359 gdb} argument, then Emacs sets your current working directory to where
26360 your program resides. If you only specify the file name, then Emacs
26361 sets your current working directory to the directory associated
26362 with the previous buffer. In this case, @value{GDBN} may find your
26363 program by searching your environment's @code{PATH} variable, but on
26364 some operating systems it might not find the source. So, although the
26365 @value{GDBN} input and output session proceeds normally, the auxiliary
26366 buffer does not display the current source and line of execution.
26368 The initial working directory of @value{GDBN} is printed on the top
26369 line of the GUD buffer and this serves as a default for the commands
26370 that specify files for @value{GDBN} to operate on. @xref{Files,
26371 ,Commands to Specify Files}.
26373 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
26374 need to call @value{GDBN} by a different name (for example, if you
26375 keep several configurations around, with different names) you can
26376 customize the Emacs variable @code{gud-gdb-command-name} to run the
26379 In the GUD buffer, you can use these special Emacs commands in
26380 addition to the standard Shell mode commands:
26384 Describe the features of Emacs' GUD Mode.
26387 Execute to another source line, like the @value{GDBN} @code{step} command; also
26388 update the display window to show the current file and location.
26391 Execute to next source line in this function, skipping all function
26392 calls, like the @value{GDBN} @code{next} command. Then update the display window
26393 to show the current file and location.
26396 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
26397 display window accordingly.
26400 Execute until exit from the selected stack frame, like the @value{GDBN}
26401 @code{finish} command.
26404 Continue execution of your program, like the @value{GDBN} @code{continue}
26408 Go up the number of frames indicated by the numeric argument
26409 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
26410 like the @value{GDBN} @code{up} command.
26413 Go down the number of frames indicated by the numeric argument, like the
26414 @value{GDBN} @code{down} command.
26417 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
26418 tells @value{GDBN} to set a breakpoint on the source line point is on.
26420 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
26421 separate frame which shows a backtrace when the GUD buffer is current.
26422 Move point to any frame in the stack and type @key{RET} to make it
26423 become the current frame and display the associated source in the
26424 source buffer. Alternatively, click @kbd{Mouse-2} to make the
26425 selected frame become the current one. In graphical mode, the
26426 speedbar displays watch expressions.
26428 If you accidentally delete the source-display buffer, an easy way to get
26429 it back is to type the command @code{f} in the @value{GDBN} buffer, to
26430 request a frame display; when you run under Emacs, this recreates
26431 the source buffer if necessary to show you the context of the current
26434 The source files displayed in Emacs are in ordinary Emacs buffers
26435 which are visiting the source files in the usual way. You can edit
26436 the files with these buffers if you wish; but keep in mind that @value{GDBN}
26437 communicates with Emacs in terms of line numbers. If you add or
26438 delete lines from the text, the line numbers that @value{GDBN} knows cease
26439 to correspond properly with the code.
26441 A more detailed description of Emacs' interaction with @value{GDBN} is
26442 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
26446 @chapter The @sc{gdb/mi} Interface
26448 @unnumberedsec Function and Purpose
26450 @cindex @sc{gdb/mi}, its purpose
26451 @sc{gdb/mi} is a line based machine oriented text interface to
26452 @value{GDBN} and is activated by specifying using the
26453 @option{--interpreter} command line option (@pxref{Mode Options}). It
26454 is specifically intended to support the development of systems which
26455 use the debugger as just one small component of a larger system.
26457 This chapter is a specification of the @sc{gdb/mi} interface. It is written
26458 in the form of a reference manual.
26460 Note that @sc{gdb/mi} is still under construction, so some of the
26461 features described below are incomplete and subject to change
26462 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
26464 @unnumberedsec Notation and Terminology
26466 @cindex notational conventions, for @sc{gdb/mi}
26467 This chapter uses the following notation:
26471 @code{|} separates two alternatives.
26474 @code{[ @var{something} ]} indicates that @var{something} is optional:
26475 it may or may not be given.
26478 @code{( @var{group} )*} means that @var{group} inside the parentheses
26479 may repeat zero or more times.
26482 @code{( @var{group} )+} means that @var{group} inside the parentheses
26483 may repeat one or more times.
26486 @code{"@var{string}"} means a literal @var{string}.
26490 @heading Dependencies
26494 * GDB/MI General Design::
26495 * GDB/MI Command Syntax::
26496 * GDB/MI Compatibility with CLI::
26497 * GDB/MI Development and Front Ends::
26498 * GDB/MI Output Records::
26499 * GDB/MI Simple Examples::
26500 * GDB/MI Command Description Format::
26501 * GDB/MI Breakpoint Commands::
26502 * GDB/MI Catchpoint Commands::
26503 * GDB/MI Program Context::
26504 * GDB/MI Thread Commands::
26505 * GDB/MI Ada Tasking Commands::
26506 * GDB/MI Program Execution::
26507 * GDB/MI Stack Manipulation::
26508 * GDB/MI Variable Objects::
26509 * GDB/MI Data Manipulation::
26510 * GDB/MI Tracepoint Commands::
26511 * GDB/MI Symbol Query::
26512 * GDB/MI File Commands::
26514 * GDB/MI Kod Commands::
26515 * GDB/MI Memory Overlay Commands::
26516 * GDB/MI Signal Handling Commands::
26518 * GDB/MI Target Manipulation::
26519 * GDB/MI File Transfer Commands::
26520 * GDB/MI Ada Exceptions Commands::
26521 * GDB/MI Support Commands::
26522 * GDB/MI Miscellaneous Commands::
26525 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26526 @node GDB/MI General Design
26527 @section @sc{gdb/mi} General Design
26528 @cindex GDB/MI General Design
26530 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
26531 parts---commands sent to @value{GDBN}, responses to those commands
26532 and notifications. Each command results in exactly one response,
26533 indicating either successful completion of the command, or an error.
26534 For the commands that do not resume the target, the response contains the
26535 requested information. For the commands that resume the target, the
26536 response only indicates whether the target was successfully resumed.
26537 Notifications is the mechanism for reporting changes in the state of the
26538 target, or in @value{GDBN} state, that cannot conveniently be associated with
26539 a command and reported as part of that command response.
26541 The important examples of notifications are:
26545 Exec notifications. These are used to report changes in
26546 target state---when a target is resumed, or stopped. It would not
26547 be feasible to include this information in response of resuming
26548 commands, because one resume commands can result in multiple events in
26549 different threads. Also, quite some time may pass before any event
26550 happens in the target, while a frontend needs to know whether the resuming
26551 command itself was successfully executed.
26554 Console output, and status notifications. Console output
26555 notifications are used to report output of CLI commands, as well as
26556 diagnostics for other commands. Status notifications are used to
26557 report the progress of a long-running operation. Naturally, including
26558 this information in command response would mean no output is produced
26559 until the command is finished, which is undesirable.
26562 General notifications. Commands may have various side effects on
26563 the @value{GDBN} or target state beyond their official purpose. For example,
26564 a command may change the selected thread. Although such changes can
26565 be included in command response, using notification allows for more
26566 orthogonal frontend design.
26570 There's no guarantee that whenever an MI command reports an error,
26571 @value{GDBN} or the target are in any specific state, and especially,
26572 the state is not reverted to the state before the MI command was
26573 processed. Therefore, whenever an MI command results in an error,
26574 we recommend that the frontend refreshes all the information shown in
26575 the user interface.
26579 * Context management::
26580 * Asynchronous and non-stop modes::
26584 @node Context management
26585 @subsection Context management
26587 @subsubsection Threads and Frames
26589 In most cases when @value{GDBN} accesses the target, this access is
26590 done in context of a specific thread and frame (@pxref{Frames}).
26591 Often, even when accessing global data, the target requires that a thread
26592 be specified. The CLI interface maintains the selected thread and frame,
26593 and supplies them to target on each command. This is convenient,
26594 because a command line user would not want to specify that information
26595 explicitly on each command, and because user interacts with
26596 @value{GDBN} via a single terminal, so no confusion is possible as
26597 to what thread and frame are the current ones.
26599 In the case of MI, the concept of selected thread and frame is less
26600 useful. First, a frontend can easily remember this information
26601 itself. Second, a graphical frontend can have more than one window,
26602 each one used for debugging a different thread, and the frontend might
26603 want to access additional threads for internal purposes. This
26604 increases the risk that by relying on implicitly selected thread, the
26605 frontend may be operating on a wrong one. Therefore, each MI command
26606 should explicitly specify which thread and frame to operate on. To
26607 make it possible, each MI command accepts the @samp{--thread} and
26608 @samp{--frame} options, the value to each is @value{GDBN} global
26609 identifier for thread and frame to operate on.
26611 Usually, each top-level window in a frontend allows the user to select
26612 a thread and a frame, and remembers the user selection for further
26613 operations. However, in some cases @value{GDBN} may suggest that the
26614 current thread or frame be changed. For example, when stopping on a
26615 breakpoint it is reasonable to switch to the thread where breakpoint is
26616 hit. For another example, if the user issues the CLI @samp{thread} or
26617 @samp{frame} commands via the frontend, it is desirable to change the
26618 frontend's selection to the one specified by user. @value{GDBN}
26619 communicates the suggestion to change current thread and frame using the
26620 @samp{=thread-selected} notification.
26622 Note that historically, MI shares the selected thread with CLI, so
26623 frontends used the @code{-thread-select} to execute commands in the
26624 right context. However, getting this to work right is cumbersome. The
26625 simplest way is for frontend to emit @code{-thread-select} command
26626 before every command. This doubles the number of commands that need
26627 to be sent. The alternative approach is to suppress @code{-thread-select}
26628 if the selected thread in @value{GDBN} is supposed to be identical to the
26629 thread the frontend wants to operate on. However, getting this
26630 optimization right can be tricky. In particular, if the frontend
26631 sends several commands to @value{GDBN}, and one of the commands changes the
26632 selected thread, then the behaviour of subsequent commands will
26633 change. So, a frontend should either wait for response from such
26634 problematic commands, or explicitly add @code{-thread-select} for
26635 all subsequent commands. No frontend is known to do this exactly
26636 right, so it is suggested to just always pass the @samp{--thread} and
26637 @samp{--frame} options.
26639 @subsubsection Language
26641 The execution of several commands depends on which language is selected.
26642 By default, the current language (@pxref{show language}) is used.
26643 But for commands known to be language-sensitive, it is recommended
26644 to use the @samp{--language} option. This option takes one argument,
26645 which is the name of the language to use while executing the command.
26649 -data-evaluate-expression --language c "sizeof (void*)"
26654 The valid language names are the same names accepted by the
26655 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
26656 @samp{local} or @samp{unknown}.
26658 @node Asynchronous and non-stop modes
26659 @subsection Asynchronous command execution and non-stop mode
26661 On some targets, @value{GDBN} is capable of processing MI commands
26662 even while the target is running. This is called @dfn{asynchronous
26663 command execution} (@pxref{Background Execution}). The frontend may
26664 specify a preferrence for asynchronous execution using the
26665 @code{-gdb-set mi-async 1} command, which should be emitted before
26666 either running the executable or attaching to the target. After the
26667 frontend has started the executable or attached to the target, it can
26668 find if asynchronous execution is enabled using the
26669 @code{-list-target-features} command.
26672 @item -gdb-set mi-async on
26673 @item -gdb-set mi-async off
26674 Set whether MI is in asynchronous mode.
26676 When @code{off}, which is the default, MI execution commands (e.g.,
26677 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
26678 for the program to stop before processing further commands.
26680 When @code{on}, MI execution commands are background execution
26681 commands (e.g., @code{-exec-continue} becomes the equivalent of the
26682 @code{c&} CLI command), and so @value{GDBN} is capable of processing
26683 MI commands even while the target is running.
26685 @item -gdb-show mi-async
26686 Show whether MI asynchronous mode is enabled.
26689 Note: In @value{GDBN} version 7.7 and earlier, this option was called
26690 @code{target-async} instead of @code{mi-async}, and it had the effect
26691 of both putting MI in asynchronous mode and making CLI background
26692 commands possible. CLI background commands are now always possible
26693 ``out of the box'' if the target supports them. The old spelling is
26694 kept as a deprecated alias for backwards compatibility.
26696 Even if @value{GDBN} can accept a command while target is running,
26697 many commands that access the target do not work when the target is
26698 running. Therefore, asynchronous command execution is most useful
26699 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
26700 it is possible to examine the state of one thread, while other threads
26703 When a given thread is running, MI commands that try to access the
26704 target in the context of that thread may not work, or may work only on
26705 some targets. In particular, commands that try to operate on thread's
26706 stack will not work, on any target. Commands that read memory, or
26707 modify breakpoints, may work or not work, depending on the target. Note
26708 that even commands that operate on global state, such as @code{print},
26709 @code{set}, and breakpoint commands, still access the target in the
26710 context of a specific thread, so frontend should try to find a
26711 stopped thread and perform the operation on that thread (using the
26712 @samp{--thread} option).
26714 Which commands will work in the context of a running thread is
26715 highly target dependent. However, the two commands
26716 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
26717 to find the state of a thread, will always work.
26719 @node Thread groups
26720 @subsection Thread groups
26721 @value{GDBN} may be used to debug several processes at the same time.
26722 On some platfroms, @value{GDBN} may support debugging of several
26723 hardware systems, each one having several cores with several different
26724 processes running on each core. This section describes the MI
26725 mechanism to support such debugging scenarios.
26727 The key observation is that regardless of the structure of the
26728 target, MI can have a global list of threads, because most commands that
26729 accept the @samp{--thread} option do not need to know what process that
26730 thread belongs to. Therefore, it is not necessary to introduce
26731 neither additional @samp{--process} option, nor an notion of the
26732 current process in the MI interface. The only strictly new feature
26733 that is required is the ability to find how the threads are grouped
26736 To allow the user to discover such grouping, and to support arbitrary
26737 hierarchy of machines/cores/processes, MI introduces the concept of a
26738 @dfn{thread group}. Thread group is a collection of threads and other
26739 thread groups. A thread group always has a string identifier, a type,
26740 and may have additional attributes specific to the type. A new
26741 command, @code{-list-thread-groups}, returns the list of top-level
26742 thread groups, which correspond to processes that @value{GDBN} is
26743 debugging at the moment. By passing an identifier of a thread group
26744 to the @code{-list-thread-groups} command, it is possible to obtain
26745 the members of specific thread group.
26747 To allow the user to easily discover processes, and other objects, he
26748 wishes to debug, a concept of @dfn{available thread group} is
26749 introduced. Available thread group is an thread group that
26750 @value{GDBN} is not debugging, but that can be attached to, using the
26751 @code{-target-attach} command. The list of available top-level thread
26752 groups can be obtained using @samp{-list-thread-groups --available}.
26753 In general, the content of a thread group may be only retrieved only
26754 after attaching to that thread group.
26756 Thread groups are related to inferiors (@pxref{Inferiors and
26757 Programs}). Each inferior corresponds to a thread group of a special
26758 type @samp{process}, and some additional operations are permitted on
26759 such thread groups.
26761 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26762 @node GDB/MI Command Syntax
26763 @section @sc{gdb/mi} Command Syntax
26766 * GDB/MI Input Syntax::
26767 * GDB/MI Output Syntax::
26770 @node GDB/MI Input Syntax
26771 @subsection @sc{gdb/mi} Input Syntax
26773 @cindex input syntax for @sc{gdb/mi}
26774 @cindex @sc{gdb/mi}, input syntax
26776 @item @var{command} @expansion{}
26777 @code{@var{cli-command} | @var{mi-command}}
26779 @item @var{cli-command} @expansion{}
26780 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
26781 @var{cli-command} is any existing @value{GDBN} CLI command.
26783 @item @var{mi-command} @expansion{}
26784 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
26785 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
26787 @item @var{token} @expansion{}
26788 "any sequence of digits"
26790 @item @var{option} @expansion{}
26791 @code{"-" @var{parameter} [ " " @var{parameter} ]}
26793 @item @var{parameter} @expansion{}
26794 @code{@var{non-blank-sequence} | @var{c-string}}
26796 @item @var{operation} @expansion{}
26797 @emph{any of the operations described in this chapter}
26799 @item @var{non-blank-sequence} @expansion{}
26800 @emph{anything, provided it doesn't contain special characters such as
26801 "-", @var{nl}, """ and of course " "}
26803 @item @var{c-string} @expansion{}
26804 @code{""" @var{seven-bit-iso-c-string-content} """}
26806 @item @var{nl} @expansion{}
26815 The CLI commands are still handled by the @sc{mi} interpreter; their
26816 output is described below.
26819 The @code{@var{token}}, when present, is passed back when the command
26823 Some @sc{mi} commands accept optional arguments as part of the parameter
26824 list. Each option is identified by a leading @samp{-} (dash) and may be
26825 followed by an optional argument parameter. Options occur first in the
26826 parameter list and can be delimited from normal parameters using
26827 @samp{--} (this is useful when some parameters begin with a dash).
26834 We want easy access to the existing CLI syntax (for debugging).
26837 We want it to be easy to spot a @sc{mi} operation.
26840 @node GDB/MI Output Syntax
26841 @subsection @sc{gdb/mi} Output Syntax
26843 @cindex output syntax of @sc{gdb/mi}
26844 @cindex @sc{gdb/mi}, output syntax
26845 The output from @sc{gdb/mi} consists of zero or more out-of-band records
26846 followed, optionally, by a single result record. This result record
26847 is for the most recent command. The sequence of output records is
26848 terminated by @samp{(gdb)}.
26850 If an input command was prefixed with a @code{@var{token}} then the
26851 corresponding output for that command will also be prefixed by that same
26855 @item @var{output} @expansion{}
26856 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
26858 @item @var{result-record} @expansion{}
26859 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
26861 @item @var{out-of-band-record} @expansion{}
26862 @code{@var{async-record} | @var{stream-record}}
26864 @item @var{async-record} @expansion{}
26865 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
26867 @item @var{exec-async-output} @expansion{}
26868 @code{[ @var{token} ] "*" @var{async-output nl}}
26870 @item @var{status-async-output} @expansion{}
26871 @code{[ @var{token} ] "+" @var{async-output nl}}
26873 @item @var{notify-async-output} @expansion{}
26874 @code{[ @var{token} ] "=" @var{async-output nl}}
26876 @item @var{async-output} @expansion{}
26877 @code{@var{async-class} ( "," @var{result} )*}
26879 @item @var{result-class} @expansion{}
26880 @code{"done" | "running" | "connected" | "error" | "exit"}
26882 @item @var{async-class} @expansion{}
26883 @code{"stopped" | @var{others}} (where @var{others} will be added
26884 depending on the needs---this is still in development).
26886 @item @var{result} @expansion{}
26887 @code{ @var{variable} "=" @var{value}}
26889 @item @var{variable} @expansion{}
26890 @code{ @var{string} }
26892 @item @var{value} @expansion{}
26893 @code{ @var{const} | @var{tuple} | @var{list} }
26895 @item @var{const} @expansion{}
26896 @code{@var{c-string}}
26898 @item @var{tuple} @expansion{}
26899 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
26901 @item @var{list} @expansion{}
26902 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
26903 @var{result} ( "," @var{result} )* "]" }
26905 @item @var{stream-record} @expansion{}
26906 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
26908 @item @var{console-stream-output} @expansion{}
26909 @code{"~" @var{c-string nl}}
26911 @item @var{target-stream-output} @expansion{}
26912 @code{"@@" @var{c-string nl}}
26914 @item @var{log-stream-output} @expansion{}
26915 @code{"&" @var{c-string nl}}
26917 @item @var{nl} @expansion{}
26920 @item @var{token} @expansion{}
26921 @emph{any sequence of digits}.
26929 All output sequences end in a single line containing a period.
26932 The @code{@var{token}} is from the corresponding request. Note that
26933 for all async output, while the token is allowed by the grammar and
26934 may be output by future versions of @value{GDBN} for select async
26935 output messages, it is generally omitted. Frontends should treat
26936 all async output as reporting general changes in the state of the
26937 target and there should be no need to associate async output to any
26941 @cindex status output in @sc{gdb/mi}
26942 @var{status-async-output} contains on-going status information about the
26943 progress of a slow operation. It can be discarded. All status output is
26944 prefixed by @samp{+}.
26947 @cindex async output in @sc{gdb/mi}
26948 @var{exec-async-output} contains asynchronous state change on the target
26949 (stopped, started, disappeared). All async output is prefixed by
26953 @cindex notify output in @sc{gdb/mi}
26954 @var{notify-async-output} contains supplementary information that the
26955 client should handle (e.g., a new breakpoint information). All notify
26956 output is prefixed by @samp{=}.
26959 @cindex console output in @sc{gdb/mi}
26960 @var{console-stream-output} is output that should be displayed as is in the
26961 console. It is the textual response to a CLI command. All the console
26962 output is prefixed by @samp{~}.
26965 @cindex target output in @sc{gdb/mi}
26966 @var{target-stream-output} is the output produced by the target program.
26967 All the target output is prefixed by @samp{@@}.
26970 @cindex log output in @sc{gdb/mi}
26971 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
26972 instance messages that should be displayed as part of an error log. All
26973 the log output is prefixed by @samp{&}.
26976 @cindex list output in @sc{gdb/mi}
26977 New @sc{gdb/mi} commands should only output @var{lists} containing
26983 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
26984 details about the various output records.
26986 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26987 @node GDB/MI Compatibility with CLI
26988 @section @sc{gdb/mi} Compatibility with CLI
26990 @cindex compatibility, @sc{gdb/mi} and CLI
26991 @cindex @sc{gdb/mi}, compatibility with CLI
26993 For the developers convenience CLI commands can be entered directly,
26994 but there may be some unexpected behaviour. For example, commands
26995 that query the user will behave as if the user replied yes, breakpoint
26996 command lists are not executed and some CLI commands, such as
26997 @code{if}, @code{when} and @code{define}, prompt for further input with
26998 @samp{>}, which is not valid MI output.
27000 This feature may be removed at some stage in the future and it is
27001 recommended that front ends use the @code{-interpreter-exec} command
27002 (@pxref{-interpreter-exec}).
27004 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27005 @node GDB/MI Development and Front Ends
27006 @section @sc{gdb/mi} Development and Front Ends
27007 @cindex @sc{gdb/mi} development
27009 The application which takes the MI output and presents the state of the
27010 program being debugged to the user is called a @dfn{front end}.
27012 Although @sc{gdb/mi} is still incomplete, it is currently being used
27013 by a variety of front ends to @value{GDBN}. This makes it difficult
27014 to introduce new functionality without breaking existing usage. This
27015 section tries to minimize the problems by describing how the protocol
27018 Some changes in MI need not break a carefully designed front end, and
27019 for these the MI version will remain unchanged. The following is a
27020 list of changes that may occur within one level, so front ends should
27021 parse MI output in a way that can handle them:
27025 New MI commands may be added.
27028 New fields may be added to the output of any MI command.
27031 The range of values for fields with specified values, e.g.,
27032 @code{in_scope} (@pxref{-var-update}) may be extended.
27034 @c The format of field's content e.g type prefix, may change so parse it
27035 @c at your own risk. Yes, in general?
27037 @c The order of fields may change? Shouldn't really matter but it might
27038 @c resolve inconsistencies.
27041 If the changes are likely to break front ends, the MI version level
27042 will be increased by one. This will allow the front end to parse the
27043 output according to the MI version. Apart from mi0, new versions of
27044 @value{GDBN} will not support old versions of MI and it will be the
27045 responsibility of the front end to work with the new one.
27047 @c Starting with mi3, add a new command -mi-version that prints the MI
27050 The best way to avoid unexpected changes in MI that might break your front
27051 end is to make your project known to @value{GDBN} developers and
27052 follow development on @email{gdb@@sourceware.org} and
27053 @email{gdb-patches@@sourceware.org}.
27054 @cindex mailing lists
27056 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27057 @node GDB/MI Output Records
27058 @section @sc{gdb/mi} Output Records
27061 * GDB/MI Result Records::
27062 * GDB/MI Stream Records::
27063 * GDB/MI Async Records::
27064 * GDB/MI Breakpoint Information::
27065 * GDB/MI Frame Information::
27066 * GDB/MI Thread Information::
27067 * GDB/MI Ada Exception Information::
27070 @node GDB/MI Result Records
27071 @subsection @sc{gdb/mi} Result Records
27073 @cindex result records in @sc{gdb/mi}
27074 @cindex @sc{gdb/mi}, result records
27075 In addition to a number of out-of-band notifications, the response to a
27076 @sc{gdb/mi} command includes one of the following result indications:
27080 @item "^done" [ "," @var{results} ]
27081 The synchronous operation was successful, @code{@var{results}} are the return
27086 This result record is equivalent to @samp{^done}. Historically, it
27087 was output instead of @samp{^done} if the command has resumed the
27088 target. This behaviour is maintained for backward compatibility, but
27089 all frontends should treat @samp{^done} and @samp{^running}
27090 identically and rely on the @samp{*running} output record to determine
27091 which threads are resumed.
27095 @value{GDBN} has connected to a remote target.
27097 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
27099 The operation failed. The @code{msg=@var{c-string}} variable contains
27100 the corresponding error message.
27102 If present, the @code{code=@var{c-string}} variable provides an error
27103 code on which consumers can rely on to detect the corresponding
27104 error condition. At present, only one error code is defined:
27107 @item "undefined-command"
27108 Indicates that the command causing the error does not exist.
27113 @value{GDBN} has terminated.
27117 @node GDB/MI Stream Records
27118 @subsection @sc{gdb/mi} Stream Records
27120 @cindex @sc{gdb/mi}, stream records
27121 @cindex stream records in @sc{gdb/mi}
27122 @value{GDBN} internally maintains a number of output streams: the console, the
27123 target, and the log. The output intended for each of these streams is
27124 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
27126 Each stream record begins with a unique @dfn{prefix character} which
27127 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
27128 Syntax}). In addition to the prefix, each stream record contains a
27129 @code{@var{string-output}}. This is either raw text (with an implicit new
27130 line) or a quoted C string (which does not contain an implicit newline).
27133 @item "~" @var{string-output}
27134 The console output stream contains text that should be displayed in the
27135 CLI console window. It contains the textual responses to CLI commands.
27137 @item "@@" @var{string-output}
27138 The target output stream contains any textual output from the running
27139 target. This is only present when GDB's event loop is truly
27140 asynchronous, which is currently only the case for remote targets.
27142 @item "&" @var{string-output}
27143 The log stream contains debugging messages being produced by @value{GDBN}'s
27147 @node GDB/MI Async Records
27148 @subsection @sc{gdb/mi} Async Records
27150 @cindex async records in @sc{gdb/mi}
27151 @cindex @sc{gdb/mi}, async records
27152 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
27153 additional changes that have occurred. Those changes can either be a
27154 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
27155 target activity (e.g., target stopped).
27157 The following is the list of possible async records:
27161 @item *running,thread-id="@var{thread}"
27162 The target is now running. The @var{thread} field can be the global
27163 thread ID of the the thread that is now running, and it can be
27164 @samp{all} if all threads are running. The frontend should assume
27165 that no interaction with a running thread is possible after this
27166 notification is produced. The frontend should not assume that this
27167 notification is output only once for any command. @value{GDBN} may
27168 emit this notification several times, either for different threads,
27169 because it cannot resume all threads together, or even for a single
27170 thread, if the thread must be stepped though some code before letting
27173 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
27174 The target has stopped. The @var{reason} field can have one of the
27178 @item breakpoint-hit
27179 A breakpoint was reached.
27180 @item watchpoint-trigger
27181 A watchpoint was triggered.
27182 @item read-watchpoint-trigger
27183 A read watchpoint was triggered.
27184 @item access-watchpoint-trigger
27185 An access watchpoint was triggered.
27186 @item function-finished
27187 An -exec-finish or similar CLI command was accomplished.
27188 @item location-reached
27189 An -exec-until or similar CLI command was accomplished.
27190 @item watchpoint-scope
27191 A watchpoint has gone out of scope.
27192 @item end-stepping-range
27193 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
27194 similar CLI command was accomplished.
27195 @item exited-signalled
27196 The inferior exited because of a signal.
27198 The inferior exited.
27199 @item exited-normally
27200 The inferior exited normally.
27201 @item signal-received
27202 A signal was received by the inferior.
27204 The inferior has stopped due to a library being loaded or unloaded.
27205 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
27206 set or when a @code{catch load} or @code{catch unload} catchpoint is
27207 in use (@pxref{Set Catchpoints}).
27209 The inferior has forked. This is reported when @code{catch fork}
27210 (@pxref{Set Catchpoints}) has been used.
27212 The inferior has vforked. This is reported in when @code{catch vfork}
27213 (@pxref{Set Catchpoints}) has been used.
27214 @item syscall-entry
27215 The inferior entered a system call. This is reported when @code{catch
27216 syscall} (@pxref{Set Catchpoints}) has been used.
27217 @item syscall-return
27218 The inferior returned from a system call. This is reported when
27219 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
27221 The inferior called @code{exec}. This is reported when @code{catch exec}
27222 (@pxref{Set Catchpoints}) has been used.
27225 The @var{id} field identifies the global thread ID of the thread
27226 that directly caused the stop -- for example by hitting a breakpoint.
27227 Depending on whether all-stop
27228 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
27229 stop all threads, or only the thread that directly triggered the stop.
27230 If all threads are stopped, the @var{stopped} field will have the
27231 value of @code{"all"}. Otherwise, the value of the @var{stopped}
27232 field will be a list of thread identifiers. Presently, this list will
27233 always include a single thread, but frontend should be prepared to see
27234 several threads in the list. The @var{core} field reports the
27235 processor core on which the stop event has happened. This field may be absent
27236 if such information is not available.
27238 @item =thread-group-added,id="@var{id}"
27239 @itemx =thread-group-removed,id="@var{id}"
27240 A thread group was either added or removed. The @var{id} field
27241 contains the @value{GDBN} identifier of the thread group. When a thread
27242 group is added, it generally might not be associated with a running
27243 process. When a thread group is removed, its id becomes invalid and
27244 cannot be used in any way.
27246 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
27247 A thread group became associated with a running program,
27248 either because the program was just started or the thread group
27249 was attached to a program. The @var{id} field contains the
27250 @value{GDBN} identifier of the thread group. The @var{pid} field
27251 contains process identifier, specific to the operating system.
27253 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
27254 A thread group is no longer associated with a running program,
27255 either because the program has exited, or because it was detached
27256 from. The @var{id} field contains the @value{GDBN} identifier of the
27257 thread group. The @var{code} field is the exit code of the inferior; it exists
27258 only when the inferior exited with some code.
27260 @item =thread-created,id="@var{id}",group-id="@var{gid}"
27261 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
27262 A thread either was created, or has exited. The @var{id} field
27263 contains the global @value{GDBN} identifier of the thread. The @var{gid}
27264 field identifies the thread group this thread belongs to.
27266 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
27267 Informs that the selected thread or frame were changed. This notification
27268 is not emitted as result of the @code{-thread-select} or
27269 @code{-stack-select-frame} commands, but is emitted whenever an MI command
27270 that is not documented to change the selected thread and frame actually
27271 changes them. In particular, invoking, directly or indirectly
27272 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
27273 will generate this notification. Changing the thread or frame from another
27274 user interface (see @ref{Interpreters}) will also generate this notification.
27276 The @var{frame} field is only present if the newly selected thread is
27277 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
27279 We suggest that in response to this notification, front ends
27280 highlight the selected thread and cause subsequent commands to apply to
27283 @item =library-loaded,...
27284 Reports that a new library file was loaded by the program. This
27285 notification has 5 fields---@var{id}, @var{target-name},
27286 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
27287 opaque identifier of the library. For remote debugging case,
27288 @var{target-name} and @var{host-name} fields give the name of the
27289 library file on the target, and on the host respectively. For native
27290 debugging, both those fields have the same value. The
27291 @var{symbols-loaded} field is emitted only for backward compatibility
27292 and should not be relied on to convey any useful information. The
27293 @var{thread-group} field, if present, specifies the id of the thread
27294 group in whose context the library was loaded. If the field is
27295 absent, it means the library was loaded in the context of all present
27296 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
27299 @item =library-unloaded,...
27300 Reports that a library was unloaded by the program. This notification
27301 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
27302 the same meaning as for the @code{=library-loaded} notification.
27303 The @var{thread-group} field, if present, specifies the id of the
27304 thread group in whose context the library was unloaded. If the field is
27305 absent, it means the library was unloaded in the context of all present
27308 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
27309 @itemx =traceframe-changed,end
27310 Reports that the trace frame was changed and its new number is
27311 @var{tfnum}. The number of the tracepoint associated with this trace
27312 frame is @var{tpnum}.
27314 @item =tsv-created,name=@var{name},initial=@var{initial}
27315 Reports that the new trace state variable @var{name} is created with
27316 initial value @var{initial}.
27318 @item =tsv-deleted,name=@var{name}
27319 @itemx =tsv-deleted
27320 Reports that the trace state variable @var{name} is deleted or all
27321 trace state variables are deleted.
27323 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
27324 Reports that the trace state variable @var{name} is modified with
27325 the initial value @var{initial}. The current value @var{current} of
27326 trace state variable is optional and is reported if the current
27327 value of trace state variable is known.
27329 @item =breakpoint-created,bkpt=@{...@}
27330 @itemx =breakpoint-modified,bkpt=@{...@}
27331 @itemx =breakpoint-deleted,id=@var{number}
27332 Reports that a breakpoint was created, modified, or deleted,
27333 respectively. Only user-visible breakpoints are reported to the MI
27336 The @var{bkpt} argument is of the same form as returned by the various
27337 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
27338 @var{number} is the ordinal number of the breakpoint.
27340 Note that if a breakpoint is emitted in the result record of a
27341 command, then it will not also be emitted in an async record.
27343 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
27344 @itemx =record-stopped,thread-group="@var{id}"
27345 Execution log recording was either started or stopped on an
27346 inferior. The @var{id} is the @value{GDBN} identifier of the thread
27347 group corresponding to the affected inferior.
27349 The @var{method} field indicates the method used to record execution. If the
27350 method in use supports multiple recording formats, @var{format} will be present
27351 and contain the currently used format. @xref{Process Record and Replay},
27352 for existing method and format values.
27354 @item =cmd-param-changed,param=@var{param},value=@var{value}
27355 Reports that a parameter of the command @code{set @var{param}} is
27356 changed to @var{value}. In the multi-word @code{set} command,
27357 the @var{param} is the whole parameter list to @code{set} command.
27358 For example, In command @code{set check type on}, @var{param}
27359 is @code{check type} and @var{value} is @code{on}.
27361 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
27362 Reports that bytes from @var{addr} to @var{data} + @var{len} were
27363 written in an inferior. The @var{id} is the identifier of the
27364 thread group corresponding to the affected inferior. The optional
27365 @code{type="code"} part is reported if the memory written to holds
27369 @node GDB/MI Breakpoint Information
27370 @subsection @sc{gdb/mi} Breakpoint Information
27372 When @value{GDBN} reports information about a breakpoint, a
27373 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
27378 The breakpoint number. For a breakpoint that represents one location
27379 of a multi-location breakpoint, this will be a dotted pair, like
27383 The type of the breakpoint. For ordinary breakpoints this will be
27384 @samp{breakpoint}, but many values are possible.
27387 If the type of the breakpoint is @samp{catchpoint}, then this
27388 indicates the exact type of catchpoint.
27391 This is the breakpoint disposition---either @samp{del}, meaning that
27392 the breakpoint will be deleted at the next stop, or @samp{keep},
27393 meaning that the breakpoint will not be deleted.
27396 This indicates whether the breakpoint is enabled, in which case the
27397 value is @samp{y}, or disabled, in which case the value is @samp{n}.
27398 Note that this is not the same as the field @code{enable}.
27401 The address of the breakpoint. This may be a hexidecimal number,
27402 giving the address; or the string @samp{<PENDING>}, for a pending
27403 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
27404 multiple locations. This field will not be present if no address can
27405 be determined. For example, a watchpoint does not have an address.
27408 If known, the function in which the breakpoint appears.
27409 If not known, this field is not present.
27412 The name of the source file which contains this function, if known.
27413 If not known, this field is not present.
27416 The full file name of the source file which contains this function, if
27417 known. If not known, this field is not present.
27420 The line number at which this breakpoint appears, if known.
27421 If not known, this field is not present.
27424 If the source file is not known, this field may be provided. If
27425 provided, this holds the address of the breakpoint, possibly followed
27429 If this breakpoint is pending, this field is present and holds the
27430 text used to set the breakpoint, as entered by the user.
27433 Where this breakpoint's condition is evaluated, either @samp{host} or
27437 If this is a thread-specific breakpoint, then this identifies the
27438 thread in which the breakpoint can trigger.
27441 If this breakpoint is restricted to a particular Ada task, then this
27442 field will hold the task identifier.
27445 If the breakpoint is conditional, this is the condition expression.
27448 The ignore count of the breakpoint.
27451 The enable count of the breakpoint.
27453 @item traceframe-usage
27456 @item static-tracepoint-marker-string-id
27457 For a static tracepoint, the name of the static tracepoint marker.
27460 For a masked watchpoint, this is the mask.
27463 A tracepoint's pass count.
27465 @item original-location
27466 The location of the breakpoint as originally specified by the user.
27467 This field is optional.
27470 The number of times the breakpoint has been hit.
27473 This field is only given for tracepoints. This is either @samp{y},
27474 meaning that the tracepoint is installed, or @samp{n}, meaning that it
27478 Some extra data, the exact contents of which are type-dependent.
27482 For example, here is what the output of @code{-break-insert}
27483 (@pxref{GDB/MI Breakpoint Commands}) might be:
27486 -> -break-insert main
27487 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27488 enabled="y",addr="0x08048564",func="main",file="myprog.c",
27489 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
27494 @node GDB/MI Frame Information
27495 @subsection @sc{gdb/mi} Frame Information
27497 Response from many MI commands includes an information about stack
27498 frame. This information is a tuple that may have the following
27503 The level of the stack frame. The innermost frame has the level of
27504 zero. This field is always present.
27507 The name of the function corresponding to the frame. This field may
27508 be absent if @value{GDBN} is unable to determine the function name.
27511 The code address for the frame. This field is always present.
27514 The name of the source files that correspond to the frame's code
27515 address. This field may be absent.
27518 The source line corresponding to the frames' code address. This field
27522 The name of the binary file (either executable or shared library) the
27523 corresponds to the frame's code address. This field may be absent.
27527 @node GDB/MI Thread Information
27528 @subsection @sc{gdb/mi} Thread Information
27530 Whenever @value{GDBN} has to report an information about a thread, it
27531 uses a tuple with the following fields. The fields are always present unless
27536 The global numeric id assigned to the thread by @value{GDBN}.
27539 The target-specific string identifying the thread.
27542 Additional information about the thread provided by the target.
27543 It is supposed to be human-readable and not interpreted by the
27544 frontend. This field is optional.
27547 The name of the thread. If the user specified a name using the
27548 @code{thread name} command, then this name is given. Otherwise, if
27549 @value{GDBN} can extract the thread name from the target, then that
27550 name is given. If @value{GDBN} cannot find the thread name, then this
27554 The execution state of the thread, either @samp{stopped} or @samp{running},
27555 depending on whether the thread is presently running.
27558 The stack frame currently executing in the thread. This field is only present
27559 if the thread is stopped. Its format is documented in
27560 @ref{GDB/MI Frame Information}.
27563 The value of this field is an integer number of the processor core the
27564 thread was last seen on. This field is optional.
27567 @node GDB/MI Ada Exception Information
27568 @subsection @sc{gdb/mi} Ada Exception Information
27570 Whenever a @code{*stopped} record is emitted because the program
27571 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
27572 @value{GDBN} provides the name of the exception that was raised via
27573 the @code{exception-name} field. Also, for exceptions that were raised
27574 with an exception message, @value{GDBN} provides that message via
27575 the @code{exception-message} field.
27577 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27578 @node GDB/MI Simple Examples
27579 @section Simple Examples of @sc{gdb/mi} Interaction
27580 @cindex @sc{gdb/mi}, simple examples
27582 This subsection presents several simple examples of interaction using
27583 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
27584 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
27585 the output received from @sc{gdb/mi}.
27587 Note the line breaks shown in the examples are here only for
27588 readability, they don't appear in the real output.
27590 @subheading Setting a Breakpoint
27592 Setting a breakpoint generates synchronous output which contains detailed
27593 information of the breakpoint.
27596 -> -break-insert main
27597 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27598 enabled="y",addr="0x08048564",func="main",file="myprog.c",
27599 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
27604 @subheading Program Execution
27606 Program execution generates asynchronous records and MI gives the
27607 reason that execution stopped.
27613 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
27614 frame=@{addr="0x08048564",func="main",
27615 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
27616 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
27621 <- *stopped,reason="exited-normally"
27625 @subheading Quitting @value{GDBN}
27627 Quitting @value{GDBN} just prints the result class @samp{^exit}.
27635 Please note that @samp{^exit} is printed immediately, but it might
27636 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
27637 performs necessary cleanups, including killing programs being debugged
27638 or disconnecting from debug hardware, so the frontend should wait till
27639 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
27640 fails to exit in reasonable time.
27642 @subheading A Bad Command
27644 Here's what happens if you pass a non-existent command:
27648 <- ^error,msg="Undefined MI command: rubbish"
27653 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27654 @node GDB/MI Command Description Format
27655 @section @sc{gdb/mi} Command Description Format
27657 The remaining sections describe blocks of commands. Each block of
27658 commands is laid out in a fashion similar to this section.
27660 @subheading Motivation
27662 The motivation for this collection of commands.
27664 @subheading Introduction
27666 A brief introduction to this collection of commands as a whole.
27668 @subheading Commands
27670 For each command in the block, the following is described:
27672 @subsubheading Synopsis
27675 -command @var{args}@dots{}
27678 @subsubheading Result
27680 @subsubheading @value{GDBN} Command
27682 The corresponding @value{GDBN} CLI command(s), if any.
27684 @subsubheading Example
27686 Example(s) formatted for readability. Some of the described commands have
27687 not been implemented yet and these are labeled N.A.@: (not available).
27690 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27691 @node GDB/MI Breakpoint Commands
27692 @section @sc{gdb/mi} Breakpoint Commands
27694 @cindex breakpoint commands for @sc{gdb/mi}
27695 @cindex @sc{gdb/mi}, breakpoint commands
27696 This section documents @sc{gdb/mi} commands for manipulating
27699 @subheading The @code{-break-after} Command
27700 @findex -break-after
27702 @subsubheading Synopsis
27705 -break-after @var{number} @var{count}
27708 The breakpoint number @var{number} is not in effect until it has been
27709 hit @var{count} times. To see how this is reflected in the output of
27710 the @samp{-break-list} command, see the description of the
27711 @samp{-break-list} command below.
27713 @subsubheading @value{GDBN} Command
27715 The corresponding @value{GDBN} command is @samp{ignore}.
27717 @subsubheading Example
27722 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27723 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27724 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
27732 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27733 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27734 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27735 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27736 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27737 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27738 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27739 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27740 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27741 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
27746 @subheading The @code{-break-catch} Command
27747 @findex -break-catch
27750 @subheading The @code{-break-commands} Command
27751 @findex -break-commands
27753 @subsubheading Synopsis
27756 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
27759 Specifies the CLI commands that should be executed when breakpoint
27760 @var{number} is hit. The parameters @var{command1} to @var{commandN}
27761 are the commands. If no command is specified, any previously-set
27762 commands are cleared. @xref{Break Commands}. Typical use of this
27763 functionality is tracing a program, that is, printing of values of
27764 some variables whenever breakpoint is hit and then continuing.
27766 @subsubheading @value{GDBN} Command
27768 The corresponding @value{GDBN} command is @samp{commands}.
27770 @subsubheading Example
27775 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27776 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27777 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
27780 -break-commands 1 "print v" "continue"
27785 @subheading The @code{-break-condition} Command
27786 @findex -break-condition
27788 @subsubheading Synopsis
27791 -break-condition @var{number} @var{expr}
27794 Breakpoint @var{number} will stop the program only if the condition in
27795 @var{expr} is true. The condition becomes part of the
27796 @samp{-break-list} output (see the description of the @samp{-break-list}
27799 @subsubheading @value{GDBN} Command
27801 The corresponding @value{GDBN} command is @samp{condition}.
27803 @subsubheading Example
27807 -break-condition 1 1
27811 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27812 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27813 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27814 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27815 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27816 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27817 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27818 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27819 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27820 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
27824 @subheading The @code{-break-delete} Command
27825 @findex -break-delete
27827 @subsubheading Synopsis
27830 -break-delete ( @var{breakpoint} )+
27833 Delete the breakpoint(s) whose number(s) are specified in the argument
27834 list. This is obviously reflected in the breakpoint list.
27836 @subsubheading @value{GDBN} Command
27838 The corresponding @value{GDBN} command is @samp{delete}.
27840 @subsubheading Example
27848 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27849 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27850 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27851 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27852 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27853 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27854 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27859 @subheading The @code{-break-disable} Command
27860 @findex -break-disable
27862 @subsubheading Synopsis
27865 -break-disable ( @var{breakpoint} )+
27868 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
27869 break list is now set to @samp{n} for the named @var{breakpoint}(s).
27871 @subsubheading @value{GDBN} Command
27873 The corresponding @value{GDBN} command is @samp{disable}.
27875 @subsubheading Example
27883 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27884 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27885 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27886 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27887 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27888 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27889 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27890 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
27891 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27892 line="5",thread-groups=["i1"],times="0"@}]@}
27896 @subheading The @code{-break-enable} Command
27897 @findex -break-enable
27899 @subsubheading Synopsis
27902 -break-enable ( @var{breakpoint} )+
27905 Enable (previously disabled) @var{breakpoint}(s).
27907 @subsubheading @value{GDBN} Command
27909 The corresponding @value{GDBN} command is @samp{enable}.
27911 @subsubheading Example
27919 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27920 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27921 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27922 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27923 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27924 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27925 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27926 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27927 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27928 line="5",thread-groups=["i1"],times="0"@}]@}
27932 @subheading The @code{-break-info} Command
27933 @findex -break-info
27935 @subsubheading Synopsis
27938 -break-info @var{breakpoint}
27942 Get information about a single breakpoint.
27944 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
27945 Information}, for details on the format of each breakpoint in the
27948 @subsubheading @value{GDBN} Command
27950 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
27952 @subsubheading Example
27955 @subheading The @code{-break-insert} Command
27956 @findex -break-insert
27957 @anchor{-break-insert}
27959 @subsubheading Synopsis
27962 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
27963 [ -c @var{condition} ] [ -i @var{ignore-count} ]
27964 [ -p @var{thread-id} ] [ @var{location} ]
27968 If specified, @var{location}, can be one of:
27971 @item linespec location
27972 A linespec location. @xref{Linespec Locations}.
27974 @item explicit location
27975 An explicit location. @sc{gdb/mi} explicit locations are
27976 analogous to the CLI's explicit locations using the option names
27977 listed below. @xref{Explicit Locations}.
27980 @item --source @var{filename}
27981 The source file name of the location. This option requires the use
27982 of either @samp{--function} or @samp{--line}.
27984 @item --function @var{function}
27985 The name of a function or method.
27987 @item --label @var{label}
27988 The name of a label.
27990 @item --line @var{lineoffset}
27991 An absolute or relative line offset from the start of the location.
27994 @item address location
27995 An address location, *@var{address}. @xref{Address Locations}.
27999 The possible optional parameters of this command are:
28003 Insert a temporary breakpoint.
28005 Insert a hardware breakpoint.
28007 If @var{location} cannot be parsed (for example if it
28008 refers to unknown files or functions), create a pending
28009 breakpoint. Without this flag, @value{GDBN} will report
28010 an error, and won't create a breakpoint, if @var{location}
28013 Create a disabled breakpoint.
28015 Create a tracepoint. @xref{Tracepoints}. When this parameter
28016 is used together with @samp{-h}, a fast tracepoint is created.
28017 @item -c @var{condition}
28018 Make the breakpoint conditional on @var{condition}.
28019 @item -i @var{ignore-count}
28020 Initialize the @var{ignore-count}.
28021 @item -p @var{thread-id}
28022 Restrict the breakpoint to the thread with the specified global
28026 @subsubheading Result
28028 @xref{GDB/MI Breakpoint Information}, for details on the format of the
28029 resulting breakpoint.
28031 Note: this format is open to change.
28032 @c An out-of-band breakpoint instead of part of the result?
28034 @subsubheading @value{GDBN} Command
28036 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
28037 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
28039 @subsubheading Example
28044 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
28045 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
28048 -break-insert -t foo
28049 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
28050 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
28054 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28055 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28056 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28057 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28058 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28059 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28060 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28061 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28062 addr="0x0001072c", func="main",file="recursive2.c",
28063 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
28065 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
28066 addr="0x00010774",func="foo",file="recursive2.c",
28067 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28070 @c -break-insert -r foo.*
28071 @c ~int foo(int, int);
28072 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
28073 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28078 @subheading The @code{-dprintf-insert} Command
28079 @findex -dprintf-insert
28081 @subsubheading Synopsis
28084 -dprintf-insert [ -t ] [ -f ] [ -d ]
28085 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28086 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
28091 If supplied, @var{location} may be specified the same way as for
28092 the @code{-break-insert} command. @xref{-break-insert}.
28094 The possible optional parameters of this command are:
28098 Insert a temporary breakpoint.
28100 If @var{location} cannot be parsed (for example, if it
28101 refers to unknown files or functions), create a pending
28102 breakpoint. Without this flag, @value{GDBN} will report
28103 an error, and won't create a breakpoint, if @var{location}
28106 Create a disabled breakpoint.
28107 @item -c @var{condition}
28108 Make the breakpoint conditional on @var{condition}.
28109 @item -i @var{ignore-count}
28110 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
28111 to @var{ignore-count}.
28112 @item -p @var{thread-id}
28113 Restrict the breakpoint to the thread with the specified global
28117 @subsubheading Result
28119 @xref{GDB/MI Breakpoint Information}, for details on the format of the
28120 resulting breakpoint.
28122 @c An out-of-band breakpoint instead of part of the result?
28124 @subsubheading @value{GDBN} Command
28126 The corresponding @value{GDBN} command is @samp{dprintf}.
28128 @subsubheading Example
28132 4-dprintf-insert foo "At foo entry\n"
28133 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
28134 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
28135 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
28136 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
28137 original-location="foo"@}
28139 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
28140 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
28141 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
28142 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
28143 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
28144 original-location="mi-dprintf.c:26"@}
28148 @subheading The @code{-break-list} Command
28149 @findex -break-list
28151 @subsubheading Synopsis
28157 Displays the list of inserted breakpoints, showing the following fields:
28161 number of the breakpoint
28163 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
28165 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
28168 is the breakpoint enabled or no: @samp{y} or @samp{n}
28170 memory location at which the breakpoint is set
28172 logical location of the breakpoint, expressed by function name, file
28174 @item Thread-groups
28175 list of thread groups to which this breakpoint applies
28177 number of times the breakpoint has been hit
28180 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
28181 @code{body} field is an empty list.
28183 @subsubheading @value{GDBN} Command
28185 The corresponding @value{GDBN} command is @samp{info break}.
28187 @subsubheading Example
28192 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28193 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28194 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28195 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28196 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28197 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28198 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28199 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28200 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
28202 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28203 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
28204 line="13",thread-groups=["i1"],times="0"@}]@}
28208 Here's an example of the result when there are no breakpoints:
28213 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28214 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28215 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28216 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28217 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28218 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28219 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28224 @subheading The @code{-break-passcount} Command
28225 @findex -break-passcount
28227 @subsubheading Synopsis
28230 -break-passcount @var{tracepoint-number} @var{passcount}
28233 Set the passcount for tracepoint @var{tracepoint-number} to
28234 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
28235 is not a tracepoint, error is emitted. This corresponds to CLI
28236 command @samp{passcount}.
28238 @subheading The @code{-break-watch} Command
28239 @findex -break-watch
28241 @subsubheading Synopsis
28244 -break-watch [ -a | -r ]
28247 Create a watchpoint. With the @samp{-a} option it will create an
28248 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
28249 read from or on a write to the memory location. With the @samp{-r}
28250 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
28251 trigger only when the memory location is accessed for reading. Without
28252 either of the options, the watchpoint created is a regular watchpoint,
28253 i.e., it will trigger when the memory location is accessed for writing.
28254 @xref{Set Watchpoints, , Setting Watchpoints}.
28256 Note that @samp{-break-list} will report a single list of watchpoints and
28257 breakpoints inserted.
28259 @subsubheading @value{GDBN} Command
28261 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
28264 @subsubheading Example
28266 Setting a watchpoint on a variable in the @code{main} function:
28271 ^done,wpt=@{number="2",exp="x"@}
28276 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
28277 value=@{old="-268439212",new="55"@},
28278 frame=@{func="main",args=[],file="recursive2.c",
28279 fullname="/home/foo/bar/recursive2.c",line="5"@}
28283 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
28284 the program execution twice: first for the variable changing value, then
28285 for the watchpoint going out of scope.
28290 ^done,wpt=@{number="5",exp="C"@}
28295 *stopped,reason="watchpoint-trigger",
28296 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
28297 frame=@{func="callee4",args=[],
28298 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28299 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28304 *stopped,reason="watchpoint-scope",wpnum="5",
28305 frame=@{func="callee3",args=[@{name="strarg",
28306 value="0x11940 \"A string argument.\""@}],
28307 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28308 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28312 Listing breakpoints and watchpoints, at different points in the program
28313 execution. Note that once the watchpoint goes out of scope, it is
28319 ^done,wpt=@{number="2",exp="C"@}
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="0"@}]@}
28340 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
28341 value=@{old="-276895068",new="3"@},
28342 frame=@{func="callee4",args=[],
28343 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28344 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28347 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28348 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28349 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28350 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28351 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28352 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28353 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28354 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28355 addr="0x00010734",func="callee4",
28356 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28357 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
28359 bkpt=@{number="2",type="watchpoint",disp="keep",
28360 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
28364 ^done,reason="watchpoint-scope",wpnum="2",
28365 frame=@{func="callee3",args=[@{name="strarg",
28366 value="0x11940 \"A string argument.\""@}],
28367 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28368 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28371 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28372 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28373 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28374 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28375 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28376 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28377 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28378 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28379 addr="0x00010734",func="callee4",
28380 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28381 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
28382 thread-groups=["i1"],times="1"@}]@}
28387 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28388 @node GDB/MI Catchpoint Commands
28389 @section @sc{gdb/mi} Catchpoint Commands
28391 This section documents @sc{gdb/mi} commands for manipulating
28395 * Shared Library GDB/MI Catchpoint Commands::
28396 * Ada Exception GDB/MI Catchpoint Commands::
28399 @node Shared Library GDB/MI Catchpoint Commands
28400 @subsection Shared Library @sc{gdb/mi} Catchpoints
28402 @subheading The @code{-catch-load} Command
28403 @findex -catch-load
28405 @subsubheading Synopsis
28408 -catch-load [ -t ] [ -d ] @var{regexp}
28411 Add a catchpoint for library load events. If the @samp{-t} option is used,
28412 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
28413 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
28414 in a disabled state. The @samp{regexp} argument is a regular
28415 expression used to match the name of the loaded library.
28418 @subsubheading @value{GDBN} Command
28420 The corresponding @value{GDBN} command is @samp{catch load}.
28422 @subsubheading Example
28425 -catch-load -t foo.so
28426 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
28427 what="load of library matching foo.so",catch-type="load",times="0"@}
28432 @subheading The @code{-catch-unload} Command
28433 @findex -catch-unload
28435 @subsubheading Synopsis
28438 -catch-unload [ -t ] [ -d ] @var{regexp}
28441 Add a catchpoint for library unload events. If the @samp{-t} option is
28442 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
28443 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
28444 created in a disabled state. The @samp{regexp} argument is a regular
28445 expression used to match the name of the unloaded library.
28447 @subsubheading @value{GDBN} Command
28449 The corresponding @value{GDBN} command is @samp{catch unload}.
28451 @subsubheading Example
28454 -catch-unload -d bar.so
28455 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
28456 what="load of library matching bar.so",catch-type="unload",times="0"@}
28460 @node Ada Exception GDB/MI Catchpoint Commands
28461 @subsection Ada Exception @sc{gdb/mi} Catchpoints
28463 The following @sc{gdb/mi} commands can be used to create catchpoints
28464 that stop the execution when Ada exceptions are being raised.
28466 @subheading The @code{-catch-assert} Command
28467 @findex -catch-assert
28469 @subsubheading Synopsis
28472 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
28475 Add a catchpoint for failed Ada assertions.
28477 The possible optional parameters for this command are:
28480 @item -c @var{condition}
28481 Make the catchpoint conditional on @var{condition}.
28483 Create a disabled catchpoint.
28485 Create a temporary catchpoint.
28488 @subsubheading @value{GDBN} Command
28490 The corresponding @value{GDBN} command is @samp{catch assert}.
28492 @subsubheading Example
28496 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
28497 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
28498 thread-groups=["i1"],times="0",
28499 original-location="__gnat_debug_raise_assert_failure"@}
28503 @subheading The @code{-catch-exception} Command
28504 @findex -catch-exception
28506 @subsubheading Synopsis
28509 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
28513 Add a catchpoint stopping when Ada exceptions are raised.
28514 By default, the command stops the program when any Ada exception
28515 gets raised. But it is also possible, by using some of the
28516 optional parameters described below, to create more selective
28519 The possible optional parameters for this command are:
28522 @item -c @var{condition}
28523 Make the catchpoint conditional on @var{condition}.
28525 Create a disabled catchpoint.
28526 @item -e @var{exception-name}
28527 Only stop when @var{exception-name} is raised. This option cannot
28528 be used combined with @samp{-u}.
28530 Create a temporary catchpoint.
28532 Stop only when an unhandled exception gets raised. This option
28533 cannot be used combined with @samp{-e}.
28536 @subsubheading @value{GDBN} Command
28538 The corresponding @value{GDBN} commands are @samp{catch exception}
28539 and @samp{catch exception unhandled}.
28541 @subsubheading Example
28544 -catch-exception -e Program_Error
28545 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
28546 enabled="y",addr="0x0000000000404874",
28547 what="`Program_Error' Ada exception", thread-groups=["i1"],
28548 times="0",original-location="__gnat_debug_raise_exception"@}
28552 @subheading The @code{-catch-handlers} Command
28553 @findex -catch-handlers
28555 @subsubheading Synopsis
28558 -catch-handlers [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
28562 Add a catchpoint stopping when Ada exceptions are handled.
28563 By default, the command stops the program when any Ada exception
28564 gets handled. But it is also possible, by using some of the
28565 optional parameters described below, to create more selective
28568 The possible optional parameters for this command are:
28571 @item -c @var{condition}
28572 Make the catchpoint conditional on @var{condition}.
28574 Create a disabled catchpoint.
28575 @item -e @var{exception-name}
28576 Only stop when @var{exception-name} is handled.
28578 Create a temporary catchpoint.
28581 @subsubheading @value{GDBN} Command
28583 The corresponding @value{GDBN} command is @samp{catch handlers}.
28585 @subsubheading Example
28588 -catch-handlers -e Constraint_Error
28589 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
28590 enabled="y",addr="0x0000000000402f68",
28591 what="`Constraint_Error' Ada exception handlers",thread-groups=["i1"],
28592 times="0",original-location="__gnat_begin_handler"@}
28596 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28597 @node GDB/MI Program Context
28598 @section @sc{gdb/mi} Program Context
28600 @subheading The @code{-exec-arguments} Command
28601 @findex -exec-arguments
28604 @subsubheading Synopsis
28607 -exec-arguments @var{args}
28610 Set the inferior program arguments, to be used in the next
28613 @subsubheading @value{GDBN} Command
28615 The corresponding @value{GDBN} command is @samp{set args}.
28617 @subsubheading Example
28621 -exec-arguments -v word
28628 @subheading The @code{-exec-show-arguments} Command
28629 @findex -exec-show-arguments
28631 @subsubheading Synopsis
28634 -exec-show-arguments
28637 Print the arguments of the program.
28639 @subsubheading @value{GDBN} Command
28641 The corresponding @value{GDBN} command is @samp{show args}.
28643 @subsubheading Example
28648 @subheading The @code{-environment-cd} Command
28649 @findex -environment-cd
28651 @subsubheading Synopsis
28654 -environment-cd @var{pathdir}
28657 Set @value{GDBN}'s working directory.
28659 @subsubheading @value{GDBN} Command
28661 The corresponding @value{GDBN} command is @samp{cd}.
28663 @subsubheading Example
28667 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
28673 @subheading The @code{-environment-directory} Command
28674 @findex -environment-directory
28676 @subsubheading Synopsis
28679 -environment-directory [ -r ] [ @var{pathdir} ]+
28682 Add directories @var{pathdir} to beginning of search path for source files.
28683 If the @samp{-r} option is used, the search path is reset to the default
28684 search path. If directories @var{pathdir} are supplied in addition to the
28685 @samp{-r} option, the search path is first reset and then addition
28687 Multiple directories may be specified, separated by blanks. Specifying
28688 multiple directories in a single command
28689 results in the directories added to the beginning of the
28690 search path in the same order they were presented in the command.
28691 If blanks are needed as
28692 part of a directory name, double-quotes should be used around
28693 the name. In the command output, the path will show up separated
28694 by the system directory-separator character. The directory-separator
28695 character must not be used
28696 in any directory name.
28697 If no directories are specified, the current search path is displayed.
28699 @subsubheading @value{GDBN} Command
28701 The corresponding @value{GDBN} command is @samp{dir}.
28703 @subsubheading Example
28707 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
28708 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
28710 -environment-directory ""
28711 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
28713 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
28714 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
28716 -environment-directory -r
28717 ^done,source-path="$cdir:$cwd"
28722 @subheading The @code{-environment-path} Command
28723 @findex -environment-path
28725 @subsubheading Synopsis
28728 -environment-path [ -r ] [ @var{pathdir} ]+
28731 Add directories @var{pathdir} to beginning of search path for object files.
28732 If the @samp{-r} option is used, the search path is reset to the original
28733 search path that existed at gdb start-up. If directories @var{pathdir} are
28734 supplied in addition to the
28735 @samp{-r} option, the search path is first reset and then addition
28737 Multiple directories may be specified, separated by blanks. Specifying
28738 multiple directories in a single command
28739 results in the directories added to the beginning of the
28740 search path in the same order they were presented in the command.
28741 If blanks are needed as
28742 part of a directory name, double-quotes should be used around
28743 the name. In the command output, the path will show up separated
28744 by the system directory-separator character. The directory-separator
28745 character must not be used
28746 in any directory name.
28747 If no directories are specified, the current path is displayed.
28750 @subsubheading @value{GDBN} Command
28752 The corresponding @value{GDBN} command is @samp{path}.
28754 @subsubheading Example
28759 ^done,path="/usr/bin"
28761 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
28762 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
28764 -environment-path -r /usr/local/bin
28765 ^done,path="/usr/local/bin:/usr/bin"
28770 @subheading The @code{-environment-pwd} Command
28771 @findex -environment-pwd
28773 @subsubheading Synopsis
28779 Show the current working directory.
28781 @subsubheading @value{GDBN} Command
28783 The corresponding @value{GDBN} command is @samp{pwd}.
28785 @subsubheading Example
28790 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
28794 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28795 @node GDB/MI Thread Commands
28796 @section @sc{gdb/mi} Thread Commands
28799 @subheading The @code{-thread-info} Command
28800 @findex -thread-info
28802 @subsubheading Synopsis
28805 -thread-info [ @var{thread-id} ]
28808 Reports information about either a specific thread, if the
28809 @var{thread-id} parameter is present, or about all threads.
28810 @var{thread-id} is the thread's global thread ID. When printing
28811 information about all threads, also reports the global ID of the
28814 @subsubheading @value{GDBN} Command
28816 The @samp{info thread} command prints the same information
28819 @subsubheading Result
28821 The result contains the following attributes:
28825 A list of threads. The format of the elements of the list is described in
28826 @ref{GDB/MI Thread Information}.
28828 @item current-thread-id
28829 The global id of the currently selected thread. This field is omitted if there
28830 is no selected thread (for example, when the selected inferior is not running,
28831 and therefore has no threads) or if a @var{thread-id} argument was passed to
28836 @subsubheading Example
28841 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
28842 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
28843 args=[]@},state="running"@},
28844 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
28845 frame=@{level="0",addr="0x0804891f",func="foo",
28846 args=[@{name="i",value="10"@}],
28847 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
28848 state="running"@}],
28849 current-thread-id="1"
28853 @subheading The @code{-thread-list-ids} Command
28854 @findex -thread-list-ids
28856 @subsubheading Synopsis
28862 Produces a list of the currently known global @value{GDBN} thread ids.
28863 At the end of the list it also prints the total number of such
28866 This command is retained for historical reasons, the
28867 @code{-thread-info} command should be used instead.
28869 @subsubheading @value{GDBN} Command
28871 Part of @samp{info threads} supplies the same information.
28873 @subsubheading Example
28878 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28879 current-thread-id="1",number-of-threads="3"
28884 @subheading The @code{-thread-select} Command
28885 @findex -thread-select
28887 @subsubheading Synopsis
28890 -thread-select @var{thread-id}
28893 Make thread with global thread number @var{thread-id} the current
28894 thread. It prints the number of the new current thread, and the
28895 topmost frame for that thread.
28897 This command is deprecated in favor of explicitly using the
28898 @samp{--thread} option to each command.
28900 @subsubheading @value{GDBN} Command
28902 The corresponding @value{GDBN} command is @samp{thread}.
28904 @subsubheading Example
28911 *stopped,reason="end-stepping-range",thread-id="2",line="187",
28912 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
28916 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28917 number-of-threads="3"
28920 ^done,new-thread-id="3",
28921 frame=@{level="0",func="vprintf",
28922 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
28923 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
28927 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28928 @node GDB/MI Ada Tasking Commands
28929 @section @sc{gdb/mi} Ada Tasking Commands
28931 @subheading The @code{-ada-task-info} Command
28932 @findex -ada-task-info
28934 @subsubheading Synopsis
28937 -ada-task-info [ @var{task-id} ]
28940 Reports information about either a specific Ada task, if the
28941 @var{task-id} parameter is present, or about all Ada tasks.
28943 @subsubheading @value{GDBN} Command
28945 The @samp{info tasks} command prints the same information
28946 about all Ada tasks (@pxref{Ada Tasks}).
28948 @subsubheading Result
28950 The result is a table of Ada tasks. The following columns are
28951 defined for each Ada task:
28955 This field exists only for the current thread. It has the value @samp{*}.
28958 The identifier that @value{GDBN} uses to refer to the Ada task.
28961 The identifier that the target uses to refer to the Ada task.
28964 The global thread identifier of the thread corresponding to the Ada
28967 This field should always exist, as Ada tasks are always implemented
28968 on top of a thread. But if @value{GDBN} cannot find this corresponding
28969 thread for any reason, the field is omitted.
28972 This field exists only when the task was created by another task.
28973 In this case, it provides the ID of the parent task.
28976 The base priority of the task.
28979 The current state of the task. For a detailed description of the
28980 possible states, see @ref{Ada Tasks}.
28983 The name of the task.
28987 @subsubheading Example
28991 ^done,tasks=@{nr_rows="3",nr_cols="8",
28992 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
28993 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
28994 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
28995 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
28996 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
28997 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
28998 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
28999 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
29000 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
29001 state="Child Termination Wait",name="main_task"@}]@}
29005 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29006 @node GDB/MI Program Execution
29007 @section @sc{gdb/mi} Program Execution
29009 These are the asynchronous commands which generate the out-of-band
29010 record @samp{*stopped}. Currently @value{GDBN} only really executes
29011 asynchronously with remote targets and this interaction is mimicked in
29014 @subheading The @code{-exec-continue} Command
29015 @findex -exec-continue
29017 @subsubheading Synopsis
29020 -exec-continue [--reverse] [--all|--thread-group N]
29023 Resumes the execution of the inferior program, which will continue
29024 to execute until it reaches a debugger stop event. If the
29025 @samp{--reverse} option is specified, execution resumes in reverse until
29026 it reaches a stop event. Stop events may include
29029 breakpoints or watchpoints
29031 signals or exceptions
29033 the end of the process (or its beginning under @samp{--reverse})
29035 the end or beginning of a replay log if one is being used.
29037 In all-stop mode (@pxref{All-Stop
29038 Mode}), may resume only one thread, or all threads, depending on the
29039 value of the @samp{scheduler-locking} variable. If @samp{--all} is
29040 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
29041 ignored in all-stop mode. If the @samp{--thread-group} options is
29042 specified, then all threads in that thread group are resumed.
29044 @subsubheading @value{GDBN} Command
29046 The corresponding @value{GDBN} corresponding is @samp{continue}.
29048 @subsubheading Example
29055 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
29056 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
29062 @subheading The @code{-exec-finish} Command
29063 @findex -exec-finish
29065 @subsubheading Synopsis
29068 -exec-finish [--reverse]
29071 Resumes the execution of the inferior program until the current
29072 function is exited. Displays the results returned by the function.
29073 If the @samp{--reverse} option is specified, resumes the reverse
29074 execution of the inferior program until the point where current
29075 function was called.
29077 @subsubheading @value{GDBN} Command
29079 The corresponding @value{GDBN} command is @samp{finish}.
29081 @subsubheading Example
29083 Function returning @code{void}.
29090 *stopped,reason="function-finished",frame=@{func="main",args=[],
29091 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
29095 Function returning other than @code{void}. The name of the internal
29096 @value{GDBN} variable storing the result is printed, together with the
29103 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
29104 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
29105 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29106 gdb-result-var="$1",return-value="0"
29111 @subheading The @code{-exec-interrupt} Command
29112 @findex -exec-interrupt
29114 @subsubheading Synopsis
29117 -exec-interrupt [--all|--thread-group N]
29120 Interrupts the background execution of the target. Note how the token
29121 associated with the stop message is the one for the execution command
29122 that has been interrupted. The token for the interrupt itself only
29123 appears in the @samp{^done} output. If the user is trying to
29124 interrupt a non-running program, an error message will be printed.
29126 Note that when asynchronous execution is enabled, this command is
29127 asynchronous just like other execution commands. That is, first the
29128 @samp{^done} response will be printed, and the target stop will be
29129 reported after that using the @samp{*stopped} notification.
29131 In non-stop mode, only the context thread is interrupted by default.
29132 All threads (in all inferiors) will be interrupted if the
29133 @samp{--all} option is specified. If the @samp{--thread-group}
29134 option is specified, all threads in that group will be interrupted.
29136 @subsubheading @value{GDBN} Command
29138 The corresponding @value{GDBN} command is @samp{interrupt}.
29140 @subsubheading Example
29151 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
29152 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
29153 fullname="/home/foo/bar/try.c",line="13"@}
29158 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
29162 @subheading The @code{-exec-jump} Command
29165 @subsubheading Synopsis
29168 -exec-jump @var{location}
29171 Resumes execution of the inferior program at the location specified by
29172 parameter. @xref{Specify Location}, for a description of the
29173 different forms of @var{location}.
29175 @subsubheading @value{GDBN} Command
29177 The corresponding @value{GDBN} command is @samp{jump}.
29179 @subsubheading Example
29182 -exec-jump foo.c:10
29183 *running,thread-id="all"
29188 @subheading The @code{-exec-next} Command
29191 @subsubheading Synopsis
29194 -exec-next [--reverse]
29197 Resumes execution of the inferior program, stopping when the beginning
29198 of the next source line is reached.
29200 If the @samp{--reverse} option is specified, resumes reverse execution
29201 of the inferior program, stopping at the beginning of the previous
29202 source line. If you issue this command on the first line of a
29203 function, it will take you back to the caller of that function, to the
29204 source line where the function was called.
29207 @subsubheading @value{GDBN} Command
29209 The corresponding @value{GDBN} command is @samp{next}.
29211 @subsubheading Example
29217 *stopped,reason="end-stepping-range",line="8",file="hello.c"
29222 @subheading The @code{-exec-next-instruction} Command
29223 @findex -exec-next-instruction
29225 @subsubheading Synopsis
29228 -exec-next-instruction [--reverse]
29231 Executes one machine instruction. If the instruction is a function
29232 call, continues until the function returns. If the program stops at an
29233 instruction in the middle of a source line, the address will be
29236 If the @samp{--reverse} option is specified, resumes reverse execution
29237 of the inferior program, stopping at the previous instruction. If the
29238 previously executed instruction was a return from another function,
29239 it will continue to execute in reverse until the call to that function
29240 (from the current stack frame) is reached.
29242 @subsubheading @value{GDBN} Command
29244 The corresponding @value{GDBN} command is @samp{nexti}.
29246 @subsubheading Example
29250 -exec-next-instruction
29254 *stopped,reason="end-stepping-range",
29255 addr="0x000100d4",line="5",file="hello.c"
29260 @subheading The @code{-exec-return} Command
29261 @findex -exec-return
29263 @subsubheading Synopsis
29269 Makes current function return immediately. Doesn't execute the inferior.
29270 Displays the new current frame.
29272 @subsubheading @value{GDBN} Command
29274 The corresponding @value{GDBN} command is @samp{return}.
29276 @subsubheading Example
29280 200-break-insert callee4
29281 200^done,bkpt=@{number="1",addr="0x00010734",
29282 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29287 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29288 frame=@{func="callee4",args=[],
29289 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29290 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29296 111^done,frame=@{level="0",func="callee3",
29297 args=[@{name="strarg",
29298 value="0x11940 \"A string argument.\""@}],
29299 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29300 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29305 @subheading The @code{-exec-run} Command
29308 @subsubheading Synopsis
29311 -exec-run [ --all | --thread-group N ] [ --start ]
29314 Starts execution of the inferior from the beginning. The inferior
29315 executes until either a breakpoint is encountered or the program
29316 exits. In the latter case the output will include an exit code, if
29317 the program has exited exceptionally.
29319 When neither the @samp{--all} nor the @samp{--thread-group} option
29320 is specified, the current inferior is started. If the
29321 @samp{--thread-group} option is specified, it should refer to a thread
29322 group of type @samp{process}, and that thread group will be started.
29323 If the @samp{--all} option is specified, then all inferiors will be started.
29325 Using the @samp{--start} option instructs the debugger to stop
29326 the execution at the start of the inferior's main subprogram,
29327 following the same behavior as the @code{start} command
29328 (@pxref{Starting}).
29330 @subsubheading @value{GDBN} Command
29332 The corresponding @value{GDBN} command is @samp{run}.
29334 @subsubheading Examples
29339 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
29344 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29345 frame=@{func="main",args=[],file="recursive2.c",
29346 fullname="/home/foo/bar/recursive2.c",line="4"@}
29351 Program exited normally:
29359 *stopped,reason="exited-normally"
29364 Program exited exceptionally:
29372 *stopped,reason="exited",exit-code="01"
29376 Another way the program can terminate is if it receives a signal such as
29377 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
29381 *stopped,reason="exited-signalled",signal-name="SIGINT",
29382 signal-meaning="Interrupt"
29386 @c @subheading -exec-signal
29389 @subheading The @code{-exec-step} Command
29392 @subsubheading Synopsis
29395 -exec-step [--reverse]
29398 Resumes execution of the inferior program, stopping when the beginning
29399 of the next source line is reached, if the next source line is not a
29400 function call. If it is, stop at the first instruction of the called
29401 function. If the @samp{--reverse} option is specified, resumes reverse
29402 execution of the inferior program, stopping at the beginning of the
29403 previously executed source line.
29405 @subsubheading @value{GDBN} Command
29407 The corresponding @value{GDBN} command is @samp{step}.
29409 @subsubheading Example
29411 Stepping into a function:
29417 *stopped,reason="end-stepping-range",
29418 frame=@{func="foo",args=[@{name="a",value="10"@},
29419 @{name="b",value="0"@}],file="recursive2.c",
29420 fullname="/home/foo/bar/recursive2.c",line="11"@}
29430 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
29435 @subheading The @code{-exec-step-instruction} Command
29436 @findex -exec-step-instruction
29438 @subsubheading Synopsis
29441 -exec-step-instruction [--reverse]
29444 Resumes the inferior which executes one machine instruction. If the
29445 @samp{--reverse} option is specified, resumes reverse execution of the
29446 inferior program, stopping at the previously executed instruction.
29447 The output, once @value{GDBN} has stopped, will vary depending on
29448 whether we have stopped in the middle of a source line or not. In the
29449 former case, the address at which the program stopped will be printed
29452 @subsubheading @value{GDBN} Command
29454 The corresponding @value{GDBN} command is @samp{stepi}.
29456 @subsubheading Example
29460 -exec-step-instruction
29464 *stopped,reason="end-stepping-range",
29465 frame=@{func="foo",args=[],file="try.c",
29466 fullname="/home/foo/bar/try.c",line="10"@}
29468 -exec-step-instruction
29472 *stopped,reason="end-stepping-range",
29473 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
29474 fullname="/home/foo/bar/try.c",line="10"@}
29479 @subheading The @code{-exec-until} Command
29480 @findex -exec-until
29482 @subsubheading Synopsis
29485 -exec-until [ @var{location} ]
29488 Executes the inferior until the @var{location} specified in the
29489 argument is reached. If there is no argument, the inferior executes
29490 until a source line greater than the current one is reached. The
29491 reason for stopping in this case will be @samp{location-reached}.
29493 @subsubheading @value{GDBN} Command
29495 The corresponding @value{GDBN} command is @samp{until}.
29497 @subsubheading Example
29501 -exec-until recursive2.c:6
29505 *stopped,reason="location-reached",frame=@{func="main",args=[],
29506 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
29511 @subheading -file-clear
29512 Is this going away????
29515 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29516 @node GDB/MI Stack Manipulation
29517 @section @sc{gdb/mi} Stack Manipulation Commands
29519 @subheading The @code{-enable-frame-filters} Command
29520 @findex -enable-frame-filters
29523 -enable-frame-filters
29526 @value{GDBN} allows Python-based frame filters to affect the output of
29527 the MI commands relating to stack traces. As there is no way to
29528 implement this in a fully backward-compatible way, a front end must
29529 request that this functionality be enabled.
29531 Once enabled, this feature cannot be disabled.
29533 Note that if Python support has not been compiled into @value{GDBN},
29534 this command will still succeed (and do nothing).
29536 @subheading The @code{-stack-info-frame} Command
29537 @findex -stack-info-frame
29539 @subsubheading Synopsis
29545 Get info on the selected frame.
29547 @subsubheading @value{GDBN} Command
29549 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
29550 (without arguments).
29552 @subsubheading Example
29557 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
29558 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29559 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
29563 @subheading The @code{-stack-info-depth} Command
29564 @findex -stack-info-depth
29566 @subsubheading Synopsis
29569 -stack-info-depth [ @var{max-depth} ]
29572 Return the depth of the stack. If the integer argument @var{max-depth}
29573 is specified, do not count beyond @var{max-depth} frames.
29575 @subsubheading @value{GDBN} Command
29577 There's no equivalent @value{GDBN} command.
29579 @subsubheading Example
29581 For a stack with frame levels 0 through 11:
29588 -stack-info-depth 4
29591 -stack-info-depth 12
29594 -stack-info-depth 11
29597 -stack-info-depth 13
29602 @anchor{-stack-list-arguments}
29603 @subheading The @code{-stack-list-arguments} Command
29604 @findex -stack-list-arguments
29606 @subsubheading Synopsis
29609 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29610 [ @var{low-frame} @var{high-frame} ]
29613 Display a list of the arguments for the frames between @var{low-frame}
29614 and @var{high-frame} (inclusive). If @var{low-frame} and
29615 @var{high-frame} are not provided, list the arguments for the whole
29616 call stack. If the two arguments are equal, show the single frame
29617 at the corresponding level. It is an error if @var{low-frame} is
29618 larger than the actual number of frames. On the other hand,
29619 @var{high-frame} may be larger than the actual number of frames, in
29620 which case only existing frames will be returned.
29622 If @var{print-values} is 0 or @code{--no-values}, print only the names of
29623 the variables; if it is 1 or @code{--all-values}, print also their
29624 values; and if it is 2 or @code{--simple-values}, print the name,
29625 type and value for simple data types, and the name and type for arrays,
29626 structures and unions. If the option @code{--no-frame-filters} is
29627 supplied, then Python frame filters will not be executed.
29629 If the @code{--skip-unavailable} option is specified, arguments that
29630 are not available are not listed. Partially available arguments
29631 are still displayed, however.
29633 Use of this command to obtain arguments in a single frame is
29634 deprecated in favor of the @samp{-stack-list-variables} command.
29636 @subsubheading @value{GDBN} Command
29638 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
29639 @samp{gdb_get_args} command which partially overlaps with the
29640 functionality of @samp{-stack-list-arguments}.
29642 @subsubheading Example
29649 frame=@{level="0",addr="0x00010734",func="callee4",
29650 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29651 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
29652 frame=@{level="1",addr="0x0001076c",func="callee3",
29653 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29654 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
29655 frame=@{level="2",addr="0x0001078c",func="callee2",
29656 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29657 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
29658 frame=@{level="3",addr="0x000107b4",func="callee1",
29659 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29660 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
29661 frame=@{level="4",addr="0x000107e0",func="main",
29662 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29663 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
29665 -stack-list-arguments 0
29668 frame=@{level="0",args=[]@},
29669 frame=@{level="1",args=[name="strarg"]@},
29670 frame=@{level="2",args=[name="intarg",name="strarg"]@},
29671 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
29672 frame=@{level="4",args=[]@}]
29674 -stack-list-arguments 1
29677 frame=@{level="0",args=[]@},
29679 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
29680 frame=@{level="2",args=[
29681 @{name="intarg",value="2"@},
29682 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
29683 @{frame=@{level="3",args=[
29684 @{name="intarg",value="2"@},
29685 @{name="strarg",value="0x11940 \"A string argument.\""@},
29686 @{name="fltarg",value="3.5"@}]@},
29687 frame=@{level="4",args=[]@}]
29689 -stack-list-arguments 0 2 2
29690 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
29692 -stack-list-arguments 1 2 2
29693 ^done,stack-args=[frame=@{level="2",
29694 args=[@{name="intarg",value="2"@},
29695 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
29699 @c @subheading -stack-list-exception-handlers
29702 @anchor{-stack-list-frames}
29703 @subheading The @code{-stack-list-frames} Command
29704 @findex -stack-list-frames
29706 @subsubheading Synopsis
29709 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
29712 List the frames currently on the stack. For each frame it displays the
29717 The frame number, 0 being the topmost frame, i.e., the innermost function.
29719 The @code{$pc} value for that frame.
29723 File name of the source file where the function lives.
29724 @item @var{fullname}
29725 The full file name of the source file where the function lives.
29727 Line number corresponding to the @code{$pc}.
29729 The shared library where this function is defined. This is only given
29730 if the frame's function is not known.
29733 If invoked without arguments, this command prints a backtrace for the
29734 whole stack. If given two integer arguments, it shows the frames whose
29735 levels are between the two arguments (inclusive). If the two arguments
29736 are equal, it shows the single frame at the corresponding level. It is
29737 an error if @var{low-frame} is larger than the actual number of
29738 frames. On the other hand, @var{high-frame} may be larger than the
29739 actual number of frames, in which case only existing frames will be
29740 returned. If the option @code{--no-frame-filters} is supplied, then
29741 Python frame filters will not be executed.
29743 @subsubheading @value{GDBN} Command
29745 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
29747 @subsubheading Example
29749 Full stack backtrace:
29755 [frame=@{level="0",addr="0x0001076c",func="foo",
29756 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
29757 frame=@{level="1",addr="0x000107a4",func="foo",
29758 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29759 frame=@{level="2",addr="0x000107a4",func="foo",
29760 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29761 frame=@{level="3",addr="0x000107a4",func="foo",
29762 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29763 frame=@{level="4",addr="0x000107a4",func="foo",
29764 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29765 frame=@{level="5",addr="0x000107a4",func="foo",
29766 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29767 frame=@{level="6",addr="0x000107a4",func="foo",
29768 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29769 frame=@{level="7",addr="0x000107a4",func="foo",
29770 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29771 frame=@{level="8",addr="0x000107a4",func="foo",
29772 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29773 frame=@{level="9",addr="0x000107a4",func="foo",
29774 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29775 frame=@{level="10",addr="0x000107a4",func="foo",
29776 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29777 frame=@{level="11",addr="0x00010738",func="main",
29778 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
29782 Show frames between @var{low_frame} and @var{high_frame}:
29786 -stack-list-frames 3 5
29788 [frame=@{level="3",addr="0x000107a4",func="foo",
29789 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29790 frame=@{level="4",addr="0x000107a4",func="foo",
29791 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29792 frame=@{level="5",addr="0x000107a4",func="foo",
29793 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29797 Show a single frame:
29801 -stack-list-frames 3 3
29803 [frame=@{level="3",addr="0x000107a4",func="foo",
29804 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29809 @subheading The @code{-stack-list-locals} Command
29810 @findex -stack-list-locals
29811 @anchor{-stack-list-locals}
29813 @subsubheading Synopsis
29816 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29819 Display the local variable names for the selected frame. If
29820 @var{print-values} is 0 or @code{--no-values}, print only the names of
29821 the variables; if it is 1 or @code{--all-values}, print also their
29822 values; and if it is 2 or @code{--simple-values}, print the name,
29823 type and value for simple data types, and the name and type for arrays,
29824 structures and unions. In this last case, a frontend can immediately
29825 display the value of simple data types and create variable objects for
29826 other data types when the user wishes to explore their values in
29827 more detail. If the option @code{--no-frame-filters} is supplied, then
29828 Python frame filters will not be executed.
29830 If the @code{--skip-unavailable} option is specified, local variables
29831 that are not available are not listed. Partially available local
29832 variables are still displayed, however.
29834 This command is deprecated in favor of the
29835 @samp{-stack-list-variables} command.
29837 @subsubheading @value{GDBN} Command
29839 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
29841 @subsubheading Example
29845 -stack-list-locals 0
29846 ^done,locals=[name="A",name="B",name="C"]
29848 -stack-list-locals --all-values
29849 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
29850 @{name="C",value="@{1, 2, 3@}"@}]
29851 -stack-list-locals --simple-values
29852 ^done,locals=[@{name="A",type="int",value="1"@},
29853 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
29857 @anchor{-stack-list-variables}
29858 @subheading The @code{-stack-list-variables} Command
29859 @findex -stack-list-variables
29861 @subsubheading Synopsis
29864 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29867 Display the names of local variables and function arguments for the selected frame. If
29868 @var{print-values} is 0 or @code{--no-values}, print only the names of
29869 the variables; if it is 1 or @code{--all-values}, print also their
29870 values; and if it is 2 or @code{--simple-values}, print the name,
29871 type and value for simple data types, and the name and type for arrays,
29872 structures and unions. If the option @code{--no-frame-filters} is
29873 supplied, then Python frame filters will not be executed.
29875 If the @code{--skip-unavailable} option is specified, local variables
29876 and arguments that are not available are not listed. Partially
29877 available arguments and local variables are still displayed, however.
29879 @subsubheading Example
29883 -stack-list-variables --thread 1 --frame 0 --all-values
29884 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
29889 @subheading The @code{-stack-select-frame} Command
29890 @findex -stack-select-frame
29892 @subsubheading Synopsis
29895 -stack-select-frame @var{framenum}
29898 Change the selected frame. Select a different frame @var{framenum} on
29901 This command in deprecated in favor of passing the @samp{--frame}
29902 option to every command.
29904 @subsubheading @value{GDBN} Command
29906 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
29907 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
29909 @subsubheading Example
29913 -stack-select-frame 2
29918 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29919 @node GDB/MI Variable Objects
29920 @section @sc{gdb/mi} Variable Objects
29924 @subheading Motivation for Variable Objects in @sc{gdb/mi}
29926 For the implementation of a variable debugger window (locals, watched
29927 expressions, etc.), we are proposing the adaptation of the existing code
29928 used by @code{Insight}.
29930 The two main reasons for that are:
29934 It has been proven in practice (it is already on its second generation).
29937 It will shorten development time (needless to say how important it is
29941 The original interface was designed to be used by Tcl code, so it was
29942 slightly changed so it could be used through @sc{gdb/mi}. This section
29943 describes the @sc{gdb/mi} operations that will be available and gives some
29944 hints about their use.
29946 @emph{Note}: In addition to the set of operations described here, we
29947 expect the @sc{gui} implementation of a variable window to require, at
29948 least, the following operations:
29951 @item @code{-gdb-show} @code{output-radix}
29952 @item @code{-stack-list-arguments}
29953 @item @code{-stack-list-locals}
29954 @item @code{-stack-select-frame}
29959 @subheading Introduction to Variable Objects
29961 @cindex variable objects in @sc{gdb/mi}
29963 Variable objects are "object-oriented" MI interface for examining and
29964 changing values of expressions. Unlike some other MI interfaces that
29965 work with expressions, variable objects are specifically designed for
29966 simple and efficient presentation in the frontend. A variable object
29967 is identified by string name. When a variable object is created, the
29968 frontend specifies the expression for that variable object. The
29969 expression can be a simple variable, or it can be an arbitrary complex
29970 expression, and can even involve CPU registers. After creating a
29971 variable object, the frontend can invoke other variable object
29972 operations---for example to obtain or change the value of a variable
29973 object, or to change display format.
29975 Variable objects have hierarchical tree structure. Any variable object
29976 that corresponds to a composite type, such as structure in C, has
29977 a number of child variable objects, for example corresponding to each
29978 element of a structure. A child variable object can itself have
29979 children, recursively. Recursion ends when we reach
29980 leaf variable objects, which always have built-in types. Child variable
29981 objects are created only by explicit request, so if a frontend
29982 is not interested in the children of a particular variable object, no
29983 child will be created.
29985 For a leaf variable object it is possible to obtain its value as a
29986 string, or set the value from a string. String value can be also
29987 obtained for a non-leaf variable object, but it's generally a string
29988 that only indicates the type of the object, and does not list its
29989 contents. Assignment to a non-leaf variable object is not allowed.
29991 A frontend does not need to read the values of all variable objects each time
29992 the program stops. Instead, MI provides an update command that lists all
29993 variable objects whose values has changed since the last update
29994 operation. This considerably reduces the amount of data that must
29995 be transferred to the frontend. As noted above, children variable
29996 objects are created on demand, and only leaf variable objects have a
29997 real value. As result, gdb will read target memory only for leaf
29998 variables that frontend has created.
30000 The automatic update is not always desirable. For example, a frontend
30001 might want to keep a value of some expression for future reference,
30002 and never update it. For another example, fetching memory is
30003 relatively slow for embedded targets, so a frontend might want
30004 to disable automatic update for the variables that are either not
30005 visible on the screen, or ``closed''. This is possible using so
30006 called ``frozen variable objects''. Such variable objects are never
30007 implicitly updated.
30009 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
30010 fixed variable object, the expression is parsed when the variable
30011 object is created, including associating identifiers to specific
30012 variables. The meaning of expression never changes. For a floating
30013 variable object the values of variables whose names appear in the
30014 expressions are re-evaluated every time in the context of the current
30015 frame. Consider this example:
30020 struct work_state state;
30027 If a fixed variable object for the @code{state} variable is created in
30028 this function, and we enter the recursive call, the variable
30029 object will report the value of @code{state} in the top-level
30030 @code{do_work} invocation. On the other hand, a floating variable
30031 object will report the value of @code{state} in the current frame.
30033 If an expression specified when creating a fixed variable object
30034 refers to a local variable, the variable object becomes bound to the
30035 thread and frame in which the variable object is created. When such
30036 variable object is updated, @value{GDBN} makes sure that the
30037 thread/frame combination the variable object is bound to still exists,
30038 and re-evaluates the variable object in context of that thread/frame.
30040 The following is the complete set of @sc{gdb/mi} operations defined to
30041 access this functionality:
30043 @multitable @columnfractions .4 .6
30044 @item @strong{Operation}
30045 @tab @strong{Description}
30047 @item @code{-enable-pretty-printing}
30048 @tab enable Python-based pretty-printing
30049 @item @code{-var-create}
30050 @tab create a variable object
30051 @item @code{-var-delete}
30052 @tab delete the variable object and/or its children
30053 @item @code{-var-set-format}
30054 @tab set the display format of this variable
30055 @item @code{-var-show-format}
30056 @tab show the display format of this variable
30057 @item @code{-var-info-num-children}
30058 @tab tells how many children this object has
30059 @item @code{-var-list-children}
30060 @tab return a list of the object's children
30061 @item @code{-var-info-type}
30062 @tab show the type of this variable object
30063 @item @code{-var-info-expression}
30064 @tab print parent-relative expression that this variable object represents
30065 @item @code{-var-info-path-expression}
30066 @tab print full expression that this variable object represents
30067 @item @code{-var-show-attributes}
30068 @tab is this variable editable? does it exist here?
30069 @item @code{-var-evaluate-expression}
30070 @tab get the value of this variable
30071 @item @code{-var-assign}
30072 @tab set the value of this variable
30073 @item @code{-var-update}
30074 @tab update the variable and its children
30075 @item @code{-var-set-frozen}
30076 @tab set frozeness attribute
30077 @item @code{-var-set-update-range}
30078 @tab set range of children to display on update
30081 In the next subsection we describe each operation in detail and suggest
30082 how it can be used.
30084 @subheading Description And Use of Operations on Variable Objects
30086 @subheading The @code{-enable-pretty-printing} Command
30087 @findex -enable-pretty-printing
30090 -enable-pretty-printing
30093 @value{GDBN} allows Python-based visualizers to affect the output of the
30094 MI variable object commands. However, because there was no way to
30095 implement this in a fully backward-compatible way, a front end must
30096 request that this functionality be enabled.
30098 Once enabled, this feature cannot be disabled.
30100 Note that if Python support has not been compiled into @value{GDBN},
30101 this command will still succeed (and do nothing).
30103 This feature is currently (as of @value{GDBN} 7.0) experimental, and
30104 may work differently in future versions of @value{GDBN}.
30106 @subheading The @code{-var-create} Command
30107 @findex -var-create
30109 @subsubheading Synopsis
30112 -var-create @{@var{name} | "-"@}
30113 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
30116 This operation creates a variable object, which allows the monitoring of
30117 a variable, the result of an expression, a memory cell or a CPU
30120 The @var{name} parameter is the string by which the object can be
30121 referenced. It must be unique. If @samp{-} is specified, the varobj
30122 system will generate a string ``varNNNNNN'' automatically. It will be
30123 unique provided that one does not specify @var{name} of that format.
30124 The command fails if a duplicate name is found.
30126 The frame under which the expression should be evaluated can be
30127 specified by @var{frame-addr}. A @samp{*} indicates that the current
30128 frame should be used. A @samp{@@} indicates that a floating variable
30129 object must be created.
30131 @var{expression} is any expression valid on the current language set (must not
30132 begin with a @samp{*}), or one of the following:
30136 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
30139 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
30142 @samp{$@var{regname}} --- a CPU register name
30145 @cindex dynamic varobj
30146 A varobj's contents may be provided by a Python-based pretty-printer. In this
30147 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
30148 have slightly different semantics in some cases. If the
30149 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
30150 will never create a dynamic varobj. This ensures backward
30151 compatibility for existing clients.
30153 @subsubheading Result
30155 This operation returns attributes of the newly-created varobj. These
30160 The name of the varobj.
30163 The number of children of the varobj. This number is not necessarily
30164 reliable for a dynamic varobj. Instead, you must examine the
30165 @samp{has_more} attribute.
30168 The varobj's scalar value. For a varobj whose type is some sort of
30169 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
30170 will not be interesting.
30173 The varobj's type. This is a string representation of the type, as
30174 would be printed by the @value{GDBN} CLI. If @samp{print object}
30175 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30176 @emph{actual} (derived) type of the object is shown rather than the
30177 @emph{declared} one.
30180 If a variable object is bound to a specific thread, then this is the
30181 thread's global identifier.
30184 For a dynamic varobj, this indicates whether there appear to be any
30185 children available. For a non-dynamic varobj, this will be 0.
30188 This attribute will be present and have the value @samp{1} if the
30189 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30190 then this attribute will not be present.
30193 A dynamic varobj can supply a display hint to the front end. The
30194 value comes directly from the Python pretty-printer object's
30195 @code{display_hint} method. @xref{Pretty Printing API}.
30198 Typical output will look like this:
30201 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
30202 has_more="@var{has_more}"
30206 @subheading The @code{-var-delete} Command
30207 @findex -var-delete
30209 @subsubheading Synopsis
30212 -var-delete [ -c ] @var{name}
30215 Deletes a previously created variable object and all of its children.
30216 With the @samp{-c} option, just deletes the children.
30218 Returns an error if the object @var{name} is not found.
30221 @subheading The @code{-var-set-format} Command
30222 @findex -var-set-format
30224 @subsubheading Synopsis
30227 -var-set-format @var{name} @var{format-spec}
30230 Sets the output format for the value of the object @var{name} to be
30233 @anchor{-var-set-format}
30234 The syntax for the @var{format-spec} is as follows:
30237 @var{format-spec} @expansion{}
30238 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
30241 The natural format is the default format choosen automatically
30242 based on the variable type (like decimal for an @code{int}, hex
30243 for pointers, etc.).
30245 The zero-hexadecimal format has a representation similar to hexadecimal
30246 but with padding zeroes to the left of the value. For example, a 32-bit
30247 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
30248 zero-hexadecimal format.
30250 For a variable with children, the format is set only on the
30251 variable itself, and the children are not affected.
30253 @subheading The @code{-var-show-format} Command
30254 @findex -var-show-format
30256 @subsubheading Synopsis
30259 -var-show-format @var{name}
30262 Returns the format used to display the value of the object @var{name}.
30265 @var{format} @expansion{}
30270 @subheading The @code{-var-info-num-children} Command
30271 @findex -var-info-num-children
30273 @subsubheading Synopsis
30276 -var-info-num-children @var{name}
30279 Returns the number of children of a variable object @var{name}:
30285 Note that this number is not completely reliable for a dynamic varobj.
30286 It will return the current number of children, but more children may
30290 @subheading The @code{-var-list-children} Command
30291 @findex -var-list-children
30293 @subsubheading Synopsis
30296 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
30298 @anchor{-var-list-children}
30300 Return a list of the children of the specified variable object and
30301 create variable objects for them, if they do not already exist. With
30302 a single argument or if @var{print-values} has a value of 0 or
30303 @code{--no-values}, print only the names of the variables; if
30304 @var{print-values} is 1 or @code{--all-values}, also print their
30305 values; and if it is 2 or @code{--simple-values} print the name and
30306 value for simple data types and just the name for arrays, structures
30309 @var{from} and @var{to}, if specified, indicate the range of children
30310 to report. If @var{from} or @var{to} is less than zero, the range is
30311 reset and all children will be reported. Otherwise, children starting
30312 at @var{from} (zero-based) and up to and excluding @var{to} will be
30315 If a child range is requested, it will only affect the current call to
30316 @code{-var-list-children}, but not future calls to @code{-var-update}.
30317 For this, you must instead use @code{-var-set-update-range}. The
30318 intent of this approach is to enable a front end to implement any
30319 update approach it likes; for example, scrolling a view may cause the
30320 front end to request more children with @code{-var-list-children}, and
30321 then the front end could call @code{-var-set-update-range} with a
30322 different range to ensure that future updates are restricted to just
30325 For each child the following results are returned:
30330 Name of the variable object created for this child.
30333 The expression to be shown to the user by the front end to designate this child.
30334 For example this may be the name of a structure member.
30336 For a dynamic varobj, this value cannot be used to form an
30337 expression. There is no way to do this at all with a dynamic varobj.
30339 For C/C@t{++} structures there are several pseudo children returned to
30340 designate access qualifiers. For these pseudo children @var{exp} is
30341 @samp{public}, @samp{private}, or @samp{protected}. In this case the
30342 type and value are not present.
30344 A dynamic varobj will not report the access qualifying
30345 pseudo-children, regardless of the language. This information is not
30346 available at all with a dynamic varobj.
30349 Number of children this child has. For a dynamic varobj, this will be
30353 The type of the child. If @samp{print object}
30354 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30355 @emph{actual} (derived) type of the object is shown rather than the
30356 @emph{declared} one.
30359 If values were requested, this is the value.
30362 If this variable object is associated with a thread, this is the
30363 thread's global thread id. Otherwise this result is not present.
30366 If the variable object is frozen, this variable will be present with a value of 1.
30369 A dynamic varobj can supply a display hint to the front end. The
30370 value comes directly from the Python pretty-printer object's
30371 @code{display_hint} method. @xref{Pretty Printing API}.
30374 This attribute will be present and have the value @samp{1} if the
30375 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30376 then this attribute will not be present.
30380 The result may have its own attributes:
30384 A dynamic varobj can supply a display hint to the front end. The
30385 value comes directly from the Python pretty-printer object's
30386 @code{display_hint} method. @xref{Pretty Printing API}.
30389 This is an integer attribute which is nonzero if there are children
30390 remaining after the end of the selected range.
30393 @subsubheading Example
30397 -var-list-children n
30398 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30399 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
30401 -var-list-children --all-values n
30402 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30403 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
30407 @subheading The @code{-var-info-type} Command
30408 @findex -var-info-type
30410 @subsubheading Synopsis
30413 -var-info-type @var{name}
30416 Returns the type of the specified variable @var{name}. The type is
30417 returned as a string in the same format as it is output by the
30421 type=@var{typename}
30425 @subheading The @code{-var-info-expression} Command
30426 @findex -var-info-expression
30428 @subsubheading Synopsis
30431 -var-info-expression @var{name}
30434 Returns a string that is suitable for presenting this
30435 variable object in user interface. The string is generally
30436 not valid expression in the current language, and cannot be evaluated.
30438 For example, if @code{a} is an array, and variable object
30439 @code{A} was created for @code{a}, then we'll get this output:
30442 (gdb) -var-info-expression A.1
30443 ^done,lang="C",exp="1"
30447 Here, the value of @code{lang} is the language name, which can be
30448 found in @ref{Supported Languages}.
30450 Note that the output of the @code{-var-list-children} command also
30451 includes those expressions, so the @code{-var-info-expression} command
30454 @subheading The @code{-var-info-path-expression} Command
30455 @findex -var-info-path-expression
30457 @subsubheading Synopsis
30460 -var-info-path-expression @var{name}
30463 Returns an expression that can be evaluated in the current
30464 context and will yield the same value that a variable object has.
30465 Compare this with the @code{-var-info-expression} command, which
30466 result can be used only for UI presentation. Typical use of
30467 the @code{-var-info-path-expression} command is creating a
30468 watchpoint from a variable object.
30470 This command is currently not valid for children of a dynamic varobj,
30471 and will give an error when invoked on one.
30473 For example, suppose @code{C} is a C@t{++} class, derived from class
30474 @code{Base}, and that the @code{Base} class has a member called
30475 @code{m_size}. Assume a variable @code{c} is has the type of
30476 @code{C} and a variable object @code{C} was created for variable
30477 @code{c}. Then, we'll get this output:
30479 (gdb) -var-info-path-expression C.Base.public.m_size
30480 ^done,path_expr=((Base)c).m_size)
30483 @subheading The @code{-var-show-attributes} Command
30484 @findex -var-show-attributes
30486 @subsubheading Synopsis
30489 -var-show-attributes @var{name}
30492 List attributes of the specified variable object @var{name}:
30495 status=@var{attr} [ ( ,@var{attr} )* ]
30499 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
30501 @subheading The @code{-var-evaluate-expression} Command
30502 @findex -var-evaluate-expression
30504 @subsubheading Synopsis
30507 -var-evaluate-expression [-f @var{format-spec}] @var{name}
30510 Evaluates the expression that is represented by the specified variable
30511 object and returns its value as a string. The format of the string
30512 can be specified with the @samp{-f} option. The possible values of
30513 this option are the same as for @code{-var-set-format}
30514 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
30515 the current display format will be used. The current display format
30516 can be changed using the @code{-var-set-format} command.
30522 Note that one must invoke @code{-var-list-children} for a variable
30523 before the value of a child variable can be evaluated.
30525 @subheading The @code{-var-assign} Command
30526 @findex -var-assign
30528 @subsubheading Synopsis
30531 -var-assign @var{name} @var{expression}
30534 Assigns the value of @var{expression} to the variable object specified
30535 by @var{name}. The object must be @samp{editable}. If the variable's
30536 value is altered by the assign, the variable will show up in any
30537 subsequent @code{-var-update} list.
30539 @subsubheading Example
30547 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
30551 @subheading The @code{-var-update} Command
30552 @findex -var-update
30554 @subsubheading Synopsis
30557 -var-update [@var{print-values}] @{@var{name} | "*"@}
30560 Reevaluate the expressions corresponding to the variable object
30561 @var{name} and all its direct and indirect children, and return the
30562 list of variable objects whose values have changed; @var{name} must
30563 be a root variable object. Here, ``changed'' means that the result of
30564 @code{-var-evaluate-expression} before and after the
30565 @code{-var-update} is different. If @samp{*} is used as the variable
30566 object names, all existing variable objects are updated, except
30567 for frozen ones (@pxref{-var-set-frozen}). The option
30568 @var{print-values} determines whether both names and values, or just
30569 names are printed. The possible values of this option are the same
30570 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
30571 recommended to use the @samp{--all-values} option, to reduce the
30572 number of MI commands needed on each program stop.
30574 With the @samp{*} parameter, if a variable object is bound to a
30575 currently running thread, it will not be updated, without any
30578 If @code{-var-set-update-range} was previously used on a varobj, then
30579 only the selected range of children will be reported.
30581 @code{-var-update} reports all the changed varobjs in a tuple named
30584 Each item in the change list is itself a tuple holding:
30588 The name of the varobj.
30591 If values were requested for this update, then this field will be
30592 present and will hold the value of the varobj.
30595 @anchor{-var-update}
30596 This field is a string which may take one of three values:
30600 The variable object's current value is valid.
30603 The variable object does not currently hold a valid value but it may
30604 hold one in the future if its associated expression comes back into
30608 The variable object no longer holds a valid value.
30609 This can occur when the executable file being debugged has changed,
30610 either through recompilation or by using the @value{GDBN} @code{file}
30611 command. The front end should normally choose to delete these variable
30615 In the future new values may be added to this list so the front should
30616 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
30619 This is only present if the varobj is still valid. If the type
30620 changed, then this will be the string @samp{true}; otherwise it will
30623 When a varobj's type changes, its children are also likely to have
30624 become incorrect. Therefore, the varobj's children are automatically
30625 deleted when this attribute is @samp{true}. Also, the varobj's update
30626 range, when set using the @code{-var-set-update-range} command, is
30630 If the varobj's type changed, then this field will be present and will
30633 @item new_num_children
30634 For a dynamic varobj, if the number of children changed, or if the
30635 type changed, this will be the new number of children.
30637 The @samp{numchild} field in other varobj responses is generally not
30638 valid for a dynamic varobj -- it will show the number of children that
30639 @value{GDBN} knows about, but because dynamic varobjs lazily
30640 instantiate their children, this will not reflect the number of
30641 children which may be available.
30643 The @samp{new_num_children} attribute only reports changes to the
30644 number of children known by @value{GDBN}. This is the only way to
30645 detect whether an update has removed children (which necessarily can
30646 only happen at the end of the update range).
30649 The display hint, if any.
30652 This is an integer value, which will be 1 if there are more children
30653 available outside the varobj's update range.
30656 This attribute will be present and have the value @samp{1} if the
30657 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30658 then this attribute will not be present.
30661 If new children were added to a dynamic varobj within the selected
30662 update range (as set by @code{-var-set-update-range}), then they will
30663 be listed in this attribute.
30666 @subsubheading Example
30673 -var-update --all-values var1
30674 ^done,changelist=[@{name="var1",value="3",in_scope="true",
30675 type_changed="false"@}]
30679 @subheading The @code{-var-set-frozen} Command
30680 @findex -var-set-frozen
30681 @anchor{-var-set-frozen}
30683 @subsubheading Synopsis
30686 -var-set-frozen @var{name} @var{flag}
30689 Set the frozenness flag on the variable object @var{name}. The
30690 @var{flag} parameter should be either @samp{1} to make the variable
30691 frozen or @samp{0} to make it unfrozen. If a variable object is
30692 frozen, then neither itself, nor any of its children, are
30693 implicitly updated by @code{-var-update} of
30694 a parent variable or by @code{-var-update *}. Only
30695 @code{-var-update} of the variable itself will update its value and
30696 values of its children. After a variable object is unfrozen, it is
30697 implicitly updated by all subsequent @code{-var-update} operations.
30698 Unfreezing a variable does not update it, only subsequent
30699 @code{-var-update} does.
30701 @subsubheading Example
30705 -var-set-frozen V 1
30710 @subheading The @code{-var-set-update-range} command
30711 @findex -var-set-update-range
30712 @anchor{-var-set-update-range}
30714 @subsubheading Synopsis
30717 -var-set-update-range @var{name} @var{from} @var{to}
30720 Set the range of children to be returned by future invocations of
30721 @code{-var-update}.
30723 @var{from} and @var{to} indicate the range of children to report. If
30724 @var{from} or @var{to} is less than zero, the range is reset and all
30725 children will be reported. Otherwise, children starting at @var{from}
30726 (zero-based) and up to and excluding @var{to} will be reported.
30728 @subsubheading Example
30732 -var-set-update-range V 1 2
30736 @subheading The @code{-var-set-visualizer} command
30737 @findex -var-set-visualizer
30738 @anchor{-var-set-visualizer}
30740 @subsubheading Synopsis
30743 -var-set-visualizer @var{name} @var{visualizer}
30746 Set a visualizer for the variable object @var{name}.
30748 @var{visualizer} is the visualizer to use. The special value
30749 @samp{None} means to disable any visualizer in use.
30751 If not @samp{None}, @var{visualizer} must be a Python expression.
30752 This expression must evaluate to a callable object which accepts a
30753 single argument. @value{GDBN} will call this object with the value of
30754 the varobj @var{name} as an argument (this is done so that the same
30755 Python pretty-printing code can be used for both the CLI and MI).
30756 When called, this object must return an object which conforms to the
30757 pretty-printing interface (@pxref{Pretty Printing API}).
30759 The pre-defined function @code{gdb.default_visualizer} may be used to
30760 select a visualizer by following the built-in process
30761 (@pxref{Selecting Pretty-Printers}). This is done automatically when
30762 a varobj is created, and so ordinarily is not needed.
30764 This feature is only available if Python support is enabled. The MI
30765 command @code{-list-features} (@pxref{GDB/MI Support Commands})
30766 can be used to check this.
30768 @subsubheading Example
30770 Resetting the visualizer:
30774 -var-set-visualizer V None
30778 Reselecting the default (type-based) visualizer:
30782 -var-set-visualizer V gdb.default_visualizer
30786 Suppose @code{SomeClass} is a visualizer class. A lambda expression
30787 can be used to instantiate this class for a varobj:
30791 -var-set-visualizer V "lambda val: SomeClass()"
30795 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30796 @node GDB/MI Data Manipulation
30797 @section @sc{gdb/mi} Data Manipulation
30799 @cindex data manipulation, in @sc{gdb/mi}
30800 @cindex @sc{gdb/mi}, data manipulation
30801 This section describes the @sc{gdb/mi} commands that manipulate data:
30802 examine memory and registers, evaluate expressions, etc.
30804 For details about what an addressable memory unit is,
30805 @pxref{addressable memory unit}.
30807 @c REMOVED FROM THE INTERFACE.
30808 @c @subheading -data-assign
30809 @c Change the value of a program variable. Plenty of side effects.
30810 @c @subsubheading GDB Command
30812 @c @subsubheading Example
30815 @subheading The @code{-data-disassemble} Command
30816 @findex -data-disassemble
30818 @subsubheading Synopsis
30822 [ -s @var{start-addr} -e @var{end-addr} ]
30823 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
30831 @item @var{start-addr}
30832 is the beginning address (or @code{$pc})
30833 @item @var{end-addr}
30835 @item @var{filename}
30836 is the name of the file to disassemble
30837 @item @var{linenum}
30838 is the line number to disassemble around
30840 is the number of disassembly lines to be produced. If it is -1,
30841 the whole function will be disassembled, in case no @var{end-addr} is
30842 specified. If @var{end-addr} is specified as a non-zero value, and
30843 @var{lines} is lower than the number of disassembly lines between
30844 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
30845 displayed; if @var{lines} is higher than the number of lines between
30846 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
30851 @item 0 disassembly only
30852 @item 1 mixed source and disassembly (deprecated)
30853 @item 2 disassembly with raw opcodes
30854 @item 3 mixed source and disassembly with raw opcodes (deprecated)
30855 @item 4 mixed source and disassembly
30856 @item 5 mixed source and disassembly with raw opcodes
30859 Modes 1 and 3 are deprecated. The output is ``source centric''
30860 which hasn't proved useful in practice.
30861 @xref{Machine Code}, for a discussion of the difference between
30862 @code{/m} and @code{/s} output of the @code{disassemble} command.
30865 @subsubheading Result
30867 The result of the @code{-data-disassemble} command will be a list named
30868 @samp{asm_insns}, the contents of this list depend on the @var{mode}
30869 used with the @code{-data-disassemble} command.
30871 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
30876 The address at which this instruction was disassembled.
30879 The name of the function this instruction is within.
30882 The decimal offset in bytes from the start of @samp{func-name}.
30885 The text disassembly for this @samp{address}.
30888 This field is only present for modes 2, 3 and 5. This contains the raw opcode
30889 bytes for the @samp{inst} field.
30893 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
30894 @samp{src_and_asm_line}, each of which has the following fields:
30898 The line number within @samp{file}.
30901 The file name from the compilation unit. This might be an absolute
30902 file name or a relative file name depending on the compile command
30906 Absolute file name of @samp{file}. It is converted to a canonical form
30907 using the source file search path
30908 (@pxref{Source Path, ,Specifying Source Directories})
30909 and after resolving all the symbolic links.
30911 If the source file is not found this field will contain the path as
30912 present in the debug information.
30914 @item line_asm_insn
30915 This is a list of tuples containing the disassembly for @samp{line} in
30916 @samp{file}. The fields of each tuple are the same as for
30917 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
30918 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
30923 Note that whatever included in the @samp{inst} field, is not
30924 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
30927 @subsubheading @value{GDBN} Command
30929 The corresponding @value{GDBN} command is @samp{disassemble}.
30931 @subsubheading Example
30933 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
30937 -data-disassemble -s $pc -e "$pc + 20" -- 0
30940 @{address="0x000107c0",func-name="main",offset="4",
30941 inst="mov 2, %o0"@},
30942 @{address="0x000107c4",func-name="main",offset="8",
30943 inst="sethi %hi(0x11800), %o2"@},
30944 @{address="0x000107c8",func-name="main",offset="12",
30945 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
30946 @{address="0x000107cc",func-name="main",offset="16",
30947 inst="sethi %hi(0x11800), %o2"@},
30948 @{address="0x000107d0",func-name="main",offset="20",
30949 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
30953 Disassemble the whole @code{main} function. Line 32 is part of
30957 -data-disassemble -f basics.c -l 32 -- 0
30959 @{address="0x000107bc",func-name="main",offset="0",
30960 inst="save %sp, -112, %sp"@},
30961 @{address="0x000107c0",func-name="main",offset="4",
30962 inst="mov 2, %o0"@},
30963 @{address="0x000107c4",func-name="main",offset="8",
30964 inst="sethi %hi(0x11800), %o2"@},
30966 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
30967 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
30971 Disassemble 3 instructions from the start of @code{main}:
30975 -data-disassemble -f basics.c -l 32 -n 3 -- 0
30977 @{address="0x000107bc",func-name="main",offset="0",
30978 inst="save %sp, -112, %sp"@},
30979 @{address="0x000107c0",func-name="main",offset="4",
30980 inst="mov 2, %o0"@},
30981 @{address="0x000107c4",func-name="main",offset="8",
30982 inst="sethi %hi(0x11800), %o2"@}]
30986 Disassemble 3 instructions from the start of @code{main} in mixed mode:
30990 -data-disassemble -f basics.c -l 32 -n 3 -- 1
30992 src_and_asm_line=@{line="31",
30993 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
30994 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
30995 line_asm_insn=[@{address="0x000107bc",
30996 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
30997 src_and_asm_line=@{line="32",
30998 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
30999 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31000 line_asm_insn=[@{address="0x000107c0",
31001 func-name="main",offset="4",inst="mov 2, %o0"@},
31002 @{address="0x000107c4",func-name="main",offset="8",
31003 inst="sethi %hi(0x11800), %o2"@}]@}]
31008 @subheading The @code{-data-evaluate-expression} Command
31009 @findex -data-evaluate-expression
31011 @subsubheading Synopsis
31014 -data-evaluate-expression @var{expr}
31017 Evaluate @var{expr} as an expression. The expression could contain an
31018 inferior function call. The function call will execute synchronously.
31019 If the expression contains spaces, it must be enclosed in double quotes.
31021 @subsubheading @value{GDBN} Command
31023 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
31024 @samp{call}. In @code{gdbtk} only, there's a corresponding
31025 @samp{gdb_eval} command.
31027 @subsubheading Example
31029 In the following example, the numbers that precede the commands are the
31030 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
31031 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
31035 211-data-evaluate-expression A
31038 311-data-evaluate-expression &A
31039 311^done,value="0xefffeb7c"
31041 411-data-evaluate-expression A+3
31044 511-data-evaluate-expression "A + 3"
31050 @subheading The @code{-data-list-changed-registers} Command
31051 @findex -data-list-changed-registers
31053 @subsubheading Synopsis
31056 -data-list-changed-registers
31059 Display a list of the registers that have changed.
31061 @subsubheading @value{GDBN} Command
31063 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
31064 has the corresponding command @samp{gdb_changed_register_list}.
31066 @subsubheading Example
31068 On a PPC MBX board:
31076 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
31077 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
31080 -data-list-changed-registers
31081 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
31082 "10","11","13","14","15","16","17","18","19","20","21","22","23",
31083 "24","25","26","27","28","30","31","64","65","66","67","69"]
31088 @subheading The @code{-data-list-register-names} Command
31089 @findex -data-list-register-names
31091 @subsubheading Synopsis
31094 -data-list-register-names [ ( @var{regno} )+ ]
31097 Show a list of register names for the current target. If no arguments
31098 are given, it shows a list of the names of all the registers. If
31099 integer numbers are given as arguments, it will print a list of the
31100 names of the registers corresponding to the arguments. To ensure
31101 consistency between a register name and its number, the output list may
31102 include empty register names.
31104 @subsubheading @value{GDBN} Command
31106 @value{GDBN} does not have a command which corresponds to
31107 @samp{-data-list-register-names}. In @code{gdbtk} there is a
31108 corresponding command @samp{gdb_regnames}.
31110 @subsubheading Example
31112 For the PPC MBX board:
31115 -data-list-register-names
31116 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
31117 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
31118 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
31119 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
31120 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
31121 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
31122 "", "pc","ps","cr","lr","ctr","xer"]
31124 -data-list-register-names 1 2 3
31125 ^done,register-names=["r1","r2","r3"]
31129 @subheading The @code{-data-list-register-values} Command
31130 @findex -data-list-register-values
31132 @subsubheading Synopsis
31135 -data-list-register-values
31136 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
31139 Display the registers' contents. The format according to which the
31140 registers' contents are to be returned is given by @var{fmt}, followed
31141 by an optional list of numbers specifying the registers to display. A
31142 missing list of numbers indicates that the contents of all the
31143 registers must be returned. The @code{--skip-unavailable} option
31144 indicates that only the available registers are to be returned.
31146 Allowed formats for @var{fmt} are:
31163 @subsubheading @value{GDBN} Command
31165 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
31166 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
31168 @subsubheading Example
31170 For a PPC MBX board (note: line breaks are for readability only, they
31171 don't appear in the actual output):
31175 -data-list-register-values r 64 65
31176 ^done,register-values=[@{number="64",value="0xfe00a300"@},
31177 @{number="65",value="0x00029002"@}]
31179 -data-list-register-values x
31180 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
31181 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
31182 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
31183 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
31184 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
31185 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
31186 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
31187 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
31188 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
31189 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
31190 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
31191 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
31192 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
31193 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
31194 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
31195 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
31196 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
31197 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
31198 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
31199 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
31200 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
31201 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
31202 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
31203 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
31204 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
31205 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
31206 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
31207 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
31208 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
31209 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
31210 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
31211 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
31212 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
31213 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
31214 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
31215 @{number="69",value="0x20002b03"@}]
31220 @subheading The @code{-data-read-memory} Command
31221 @findex -data-read-memory
31223 This command is deprecated, use @code{-data-read-memory-bytes} instead.
31225 @subsubheading Synopsis
31228 -data-read-memory [ -o @var{byte-offset} ]
31229 @var{address} @var{word-format} @var{word-size}
31230 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
31237 @item @var{address}
31238 An expression specifying the address of the first memory word to be
31239 read. Complex expressions containing embedded white space should be
31240 quoted using the C convention.
31242 @item @var{word-format}
31243 The format to be used to print the memory words. The notation is the
31244 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
31247 @item @var{word-size}
31248 The size of each memory word in bytes.
31250 @item @var{nr-rows}
31251 The number of rows in the output table.
31253 @item @var{nr-cols}
31254 The number of columns in the output table.
31257 If present, indicates that each row should include an @sc{ascii} dump. The
31258 value of @var{aschar} is used as a padding character when a byte is not a
31259 member of the printable @sc{ascii} character set (printable @sc{ascii}
31260 characters are those whose code is between 32 and 126, inclusively).
31262 @item @var{byte-offset}
31263 An offset to add to the @var{address} before fetching memory.
31266 This command displays memory contents as a table of @var{nr-rows} by
31267 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
31268 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
31269 (returned as @samp{total-bytes}). Should less than the requested number
31270 of bytes be returned by the target, the missing words are identified
31271 using @samp{N/A}. The number of bytes read from the target is returned
31272 in @samp{nr-bytes} and the starting address used to read memory in
31275 The address of the next/previous row or page is available in
31276 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
31279 @subsubheading @value{GDBN} Command
31281 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
31282 @samp{gdb_get_mem} memory read command.
31284 @subsubheading Example
31286 Read six bytes of memory starting at @code{bytes+6} but then offset by
31287 @code{-6} bytes. Format as three rows of two columns. One byte per
31288 word. Display each word in hex.
31292 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
31293 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
31294 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
31295 prev-page="0x0000138a",memory=[
31296 @{addr="0x00001390",data=["0x00","0x01"]@},
31297 @{addr="0x00001392",data=["0x02","0x03"]@},
31298 @{addr="0x00001394",data=["0x04","0x05"]@}]
31302 Read two bytes of memory starting at address @code{shorts + 64} and
31303 display as a single word formatted in decimal.
31307 5-data-read-memory shorts+64 d 2 1 1
31308 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
31309 next-row="0x00001512",prev-row="0x0000150e",
31310 next-page="0x00001512",prev-page="0x0000150e",memory=[
31311 @{addr="0x00001510",data=["128"]@}]
31315 Read thirty two bytes of memory starting at @code{bytes+16} and format
31316 as eight rows of four columns. Include a string encoding with @samp{x}
31317 used as the non-printable character.
31321 4-data-read-memory bytes+16 x 1 8 4 x
31322 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
31323 next-row="0x000013c0",prev-row="0x0000139c",
31324 next-page="0x000013c0",prev-page="0x00001380",memory=[
31325 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
31326 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
31327 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
31328 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
31329 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
31330 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
31331 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
31332 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
31336 @subheading The @code{-data-read-memory-bytes} Command
31337 @findex -data-read-memory-bytes
31339 @subsubheading Synopsis
31342 -data-read-memory-bytes [ -o @var{offset} ]
31343 @var{address} @var{count}
31350 @item @var{address}
31351 An expression specifying the address of the first addressable memory unit
31352 to be read. Complex expressions containing embedded white space should be
31353 quoted using the C convention.
31356 The number of addressable memory units to read. This should be an integer
31360 The offset relative to @var{address} at which to start reading. This
31361 should be an integer literal. This option is provided so that a frontend
31362 is not required to first evaluate address and then perform address
31363 arithmetics itself.
31367 This command attempts to read all accessible memory regions in the
31368 specified range. First, all regions marked as unreadable in the memory
31369 map (if one is defined) will be skipped. @xref{Memory Region
31370 Attributes}. Second, @value{GDBN} will attempt to read the remaining
31371 regions. For each one, if reading full region results in an errors,
31372 @value{GDBN} will try to read a subset of the region.
31374 In general, every single memory unit in the region may be readable or not,
31375 and the only way to read every readable unit is to try a read at
31376 every address, which is not practical. Therefore, @value{GDBN} will
31377 attempt to read all accessible memory units at either beginning or the end
31378 of the region, using a binary division scheme. This heuristic works
31379 well for reading accross a memory map boundary. Note that if a region
31380 has a readable range that is neither at the beginning or the end,
31381 @value{GDBN} will not read it.
31383 The result record (@pxref{GDB/MI Result Records}) that is output of
31384 the command includes a field named @samp{memory} whose content is a
31385 list of tuples. Each tuple represent a successfully read memory block
31386 and has the following fields:
31390 The start address of the memory block, as hexadecimal literal.
31393 The end address of the memory block, as hexadecimal literal.
31396 The offset of the memory block, as hexadecimal literal, relative to
31397 the start address passed to @code{-data-read-memory-bytes}.
31400 The contents of the memory block, in hex.
31406 @subsubheading @value{GDBN} Command
31408 The corresponding @value{GDBN} command is @samp{x}.
31410 @subsubheading Example
31414 -data-read-memory-bytes &a 10
31415 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
31417 contents="01000000020000000300"@}]
31422 @subheading The @code{-data-write-memory-bytes} Command
31423 @findex -data-write-memory-bytes
31425 @subsubheading Synopsis
31428 -data-write-memory-bytes @var{address} @var{contents}
31429 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
31436 @item @var{address}
31437 An expression specifying the address of the first addressable memory unit
31438 to be written. Complex expressions containing embedded white space should
31439 be quoted using the C convention.
31441 @item @var{contents}
31442 The hex-encoded data to write. It is an error if @var{contents} does
31443 not represent an integral number of addressable memory units.
31446 Optional argument indicating the number of addressable memory units to be
31447 written. If @var{count} is greater than @var{contents}' length,
31448 @value{GDBN} will repeatedly write @var{contents} until it fills
31449 @var{count} memory units.
31453 @subsubheading @value{GDBN} Command
31455 There's no corresponding @value{GDBN} command.
31457 @subsubheading Example
31461 -data-write-memory-bytes &a "aabbccdd"
31468 -data-write-memory-bytes &a "aabbccdd" 16e
31473 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31474 @node GDB/MI Tracepoint Commands
31475 @section @sc{gdb/mi} Tracepoint Commands
31477 The commands defined in this section implement MI support for
31478 tracepoints. For detailed introduction, see @ref{Tracepoints}.
31480 @subheading The @code{-trace-find} Command
31481 @findex -trace-find
31483 @subsubheading Synopsis
31486 -trace-find @var{mode} [@var{parameters}@dots{}]
31489 Find a trace frame using criteria defined by @var{mode} and
31490 @var{parameters}. The following table lists permissible
31491 modes and their parameters. For details of operation, see @ref{tfind}.
31496 No parameters are required. Stops examining trace frames.
31499 An integer is required as parameter. Selects tracepoint frame with
31502 @item tracepoint-number
31503 An integer is required as parameter. Finds next
31504 trace frame that corresponds to tracepoint with the specified number.
31507 An address is required as parameter. Finds
31508 next trace frame that corresponds to any tracepoint at the specified
31511 @item pc-inside-range
31512 Two addresses are required as parameters. Finds next trace
31513 frame that corresponds to a tracepoint at an address inside the
31514 specified range. Both bounds are considered to be inside the range.
31516 @item pc-outside-range
31517 Two addresses are required as parameters. Finds
31518 next trace frame that corresponds to a tracepoint at an address outside
31519 the specified range. Both bounds are considered to be inside the range.
31522 Line specification is required as parameter. @xref{Specify Location}.
31523 Finds next trace frame that corresponds to a tracepoint at
31524 the specified location.
31528 If @samp{none} was passed as @var{mode}, the response does not
31529 have fields. Otherwise, the response may have the following fields:
31533 This field has either @samp{0} or @samp{1} as the value, depending
31534 on whether a matching tracepoint was found.
31537 The index of the found traceframe. This field is present iff
31538 the @samp{found} field has value of @samp{1}.
31541 The index of the found tracepoint. This field is present iff
31542 the @samp{found} field has value of @samp{1}.
31545 The information about the frame corresponding to the found trace
31546 frame. This field is present only if a trace frame was found.
31547 @xref{GDB/MI Frame Information}, for description of this field.
31551 @subsubheading @value{GDBN} Command
31553 The corresponding @value{GDBN} command is @samp{tfind}.
31555 @subheading -trace-define-variable
31556 @findex -trace-define-variable
31558 @subsubheading Synopsis
31561 -trace-define-variable @var{name} [ @var{value} ]
31564 Create trace variable @var{name} if it does not exist. If
31565 @var{value} is specified, sets the initial value of the specified
31566 trace variable to that value. Note that the @var{name} should start
31567 with the @samp{$} character.
31569 @subsubheading @value{GDBN} Command
31571 The corresponding @value{GDBN} command is @samp{tvariable}.
31573 @subheading The @code{-trace-frame-collected} Command
31574 @findex -trace-frame-collected
31576 @subsubheading Synopsis
31579 -trace-frame-collected
31580 [--var-print-values @var{var_pval}]
31581 [--comp-print-values @var{comp_pval}]
31582 [--registers-format @var{regformat}]
31583 [--memory-contents]
31586 This command returns the set of collected objects, register names,
31587 trace state variable names, memory ranges and computed expressions
31588 that have been collected at a particular trace frame. The optional
31589 parameters to the command affect the output format in different ways.
31590 See the output description table below for more details.
31592 The reported names can be used in the normal manner to create
31593 varobjs and inspect the objects themselves. The items returned by
31594 this command are categorized so that it is clear which is a variable,
31595 which is a register, which is a trace state variable, which is a
31596 memory range and which is a computed expression.
31598 For instance, if the actions were
31600 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
31601 collect *(int*)0xaf02bef0@@40
31605 the object collected in its entirety would be @code{myVar}. The
31606 object @code{myArray} would be partially collected, because only the
31607 element at index @code{myIndex} would be collected. The remaining
31608 objects would be computed expressions.
31610 An example output would be:
31614 -trace-frame-collected
31616 explicit-variables=[@{name="myVar",value="1"@}],
31617 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
31618 @{name="myObj.field",value="0"@},
31619 @{name="myPtr->field",value="1"@},
31620 @{name="myCount + 2",value="3"@},
31621 @{name="$tvar1 + 1",value="43970027"@}],
31622 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
31623 @{number="1",value="0x0"@},
31624 @{number="2",value="0x4"@},
31626 @{number="125",value="0x0"@}],
31627 tvars=[@{name="$tvar1",current="43970026"@}],
31628 memory=[@{address="0x0000000000602264",length="4"@},
31629 @{address="0x0000000000615bc0",length="4"@}]
31636 @item explicit-variables
31637 The set of objects that have been collected in their entirety (as
31638 opposed to collecting just a few elements of an array or a few struct
31639 members). For each object, its name and value are printed.
31640 The @code{--var-print-values} option affects how or whether the value
31641 field is output. If @var{var_pval} is 0, then print only the names;
31642 if it is 1, print also their values; and if it is 2, print the name,
31643 type and value for simple data types, and the name and type for
31644 arrays, structures and unions.
31646 @item computed-expressions
31647 The set of computed expressions that have been collected at the
31648 current trace frame. The @code{--comp-print-values} option affects
31649 this set like the @code{--var-print-values} option affects the
31650 @code{explicit-variables} set. See above.
31653 The registers that have been collected at the current trace frame.
31654 For each register collected, the name and current value are returned.
31655 The value is formatted according to the @code{--registers-format}
31656 option. See the @command{-data-list-register-values} command for a
31657 list of the allowed formats. The default is @samp{x}.
31660 The trace state variables that have been collected at the current
31661 trace frame. For each trace state variable collected, the name and
31662 current value are returned.
31665 The set of memory ranges that have been collected at the current trace
31666 frame. Its content is a list of tuples. Each tuple represents a
31667 collected memory range and has the following fields:
31671 The start address of the memory range, as hexadecimal literal.
31674 The length of the memory range, as decimal literal.
31677 The contents of the memory block, in hex. This field is only present
31678 if the @code{--memory-contents} option is specified.
31684 @subsubheading @value{GDBN} Command
31686 There is no corresponding @value{GDBN} command.
31688 @subsubheading Example
31690 @subheading -trace-list-variables
31691 @findex -trace-list-variables
31693 @subsubheading Synopsis
31696 -trace-list-variables
31699 Return a table of all defined trace variables. Each element of the
31700 table has the following fields:
31704 The name of the trace variable. This field is always present.
31707 The initial value. This is a 64-bit signed integer. This
31708 field is always present.
31711 The value the trace variable has at the moment. This is a 64-bit
31712 signed integer. This field is absent iff current value is
31713 not defined, for example if the trace was never run, or is
31718 @subsubheading @value{GDBN} Command
31720 The corresponding @value{GDBN} command is @samp{tvariables}.
31722 @subsubheading Example
31726 -trace-list-variables
31727 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
31728 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
31729 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
31730 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
31731 body=[variable=@{name="$trace_timestamp",initial="0"@}
31732 variable=@{name="$foo",initial="10",current="15"@}]@}
31736 @subheading -trace-save
31737 @findex -trace-save
31739 @subsubheading Synopsis
31742 -trace-save [ -r ] [ -ctf ] @var{filename}
31745 Saves the collected trace data to @var{filename}. Without the
31746 @samp{-r} option, the data is downloaded from the target and saved
31747 in a local file. With the @samp{-r} option the target is asked
31748 to perform the save.
31750 By default, this command will save the trace in the tfile format. You can
31751 supply the optional @samp{-ctf} argument to save it the CTF format. See
31752 @ref{Trace Files} for more information about CTF.
31754 @subsubheading @value{GDBN} Command
31756 The corresponding @value{GDBN} command is @samp{tsave}.
31759 @subheading -trace-start
31760 @findex -trace-start
31762 @subsubheading Synopsis
31768 Starts a tracing experiment. The result of this command does not
31771 @subsubheading @value{GDBN} Command
31773 The corresponding @value{GDBN} command is @samp{tstart}.
31775 @subheading -trace-status
31776 @findex -trace-status
31778 @subsubheading Synopsis
31784 Obtains the status of a tracing experiment. The result may include
31785 the following fields:
31790 May have a value of either @samp{0}, when no tracing operations are
31791 supported, @samp{1}, when all tracing operations are supported, or
31792 @samp{file} when examining trace file. In the latter case, examining
31793 of trace frame is possible but new tracing experiement cannot be
31794 started. This field is always present.
31797 May have a value of either @samp{0} or @samp{1} depending on whether
31798 tracing experiement is in progress on target. This field is present
31799 if @samp{supported} field is not @samp{0}.
31802 Report the reason why the tracing was stopped last time. This field
31803 may be absent iff tracing was never stopped on target yet. The
31804 value of @samp{request} means the tracing was stopped as result of
31805 the @code{-trace-stop} command. The value of @samp{overflow} means
31806 the tracing buffer is full. The value of @samp{disconnection} means
31807 tracing was automatically stopped when @value{GDBN} has disconnected.
31808 The value of @samp{passcount} means tracing was stopped when a
31809 tracepoint was passed a maximal number of times for that tracepoint.
31810 This field is present if @samp{supported} field is not @samp{0}.
31812 @item stopping-tracepoint
31813 The number of tracepoint whose passcount as exceeded. This field is
31814 present iff the @samp{stop-reason} field has the value of
31818 @itemx frames-created
31819 The @samp{frames} field is a count of the total number of trace frames
31820 in the trace buffer, while @samp{frames-created} is the total created
31821 during the run, including ones that were discarded, such as when a
31822 circular trace buffer filled up. Both fields are optional.
31826 These fields tell the current size of the tracing buffer and the
31827 remaining space. These fields are optional.
31830 The value of the circular trace buffer flag. @code{1} means that the
31831 trace buffer is circular and old trace frames will be discarded if
31832 necessary to make room, @code{0} means that the trace buffer is linear
31836 The value of the disconnected tracing flag. @code{1} means that
31837 tracing will continue after @value{GDBN} disconnects, @code{0} means
31838 that the trace run will stop.
31841 The filename of the trace file being examined. This field is
31842 optional, and only present when examining a trace file.
31846 @subsubheading @value{GDBN} Command
31848 The corresponding @value{GDBN} command is @samp{tstatus}.
31850 @subheading -trace-stop
31851 @findex -trace-stop
31853 @subsubheading Synopsis
31859 Stops a tracing experiment. The result of this command has the same
31860 fields as @code{-trace-status}, except that the @samp{supported} and
31861 @samp{running} fields are not output.
31863 @subsubheading @value{GDBN} Command
31865 The corresponding @value{GDBN} command is @samp{tstop}.
31868 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31869 @node GDB/MI Symbol Query
31870 @section @sc{gdb/mi} Symbol Query Commands
31874 @subheading The @code{-symbol-info-address} Command
31875 @findex -symbol-info-address
31877 @subsubheading Synopsis
31880 -symbol-info-address @var{symbol}
31883 Describe where @var{symbol} is stored.
31885 @subsubheading @value{GDBN} Command
31887 The corresponding @value{GDBN} command is @samp{info address}.
31889 @subsubheading Example
31893 @subheading The @code{-symbol-info-file} Command
31894 @findex -symbol-info-file
31896 @subsubheading Synopsis
31902 Show the file for the symbol.
31904 @subsubheading @value{GDBN} Command
31906 There's no equivalent @value{GDBN} command. @code{gdbtk} has
31907 @samp{gdb_find_file}.
31909 @subsubheading Example
31913 @subheading The @code{-symbol-info-function} Command
31914 @findex -symbol-info-function
31916 @subsubheading Synopsis
31919 -symbol-info-function
31922 Show which function the symbol lives in.
31924 @subsubheading @value{GDBN} Command
31926 @samp{gdb_get_function} in @code{gdbtk}.
31928 @subsubheading Example
31932 @subheading The @code{-symbol-info-line} Command
31933 @findex -symbol-info-line
31935 @subsubheading Synopsis
31941 Show the core addresses of the code for a source line.
31943 @subsubheading @value{GDBN} Command
31945 The corresponding @value{GDBN} command is @samp{info line}.
31946 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
31948 @subsubheading Example
31952 @subheading The @code{-symbol-info-symbol} Command
31953 @findex -symbol-info-symbol
31955 @subsubheading Synopsis
31958 -symbol-info-symbol @var{addr}
31961 Describe what symbol is at location @var{addr}.
31963 @subsubheading @value{GDBN} Command
31965 The corresponding @value{GDBN} command is @samp{info symbol}.
31967 @subsubheading Example
31971 @subheading The @code{-symbol-list-functions} Command
31972 @findex -symbol-list-functions
31974 @subsubheading Synopsis
31977 -symbol-list-functions
31980 List the functions in the executable.
31982 @subsubheading @value{GDBN} Command
31984 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
31985 @samp{gdb_search} in @code{gdbtk}.
31987 @subsubheading Example
31992 @subheading The @code{-symbol-list-lines} Command
31993 @findex -symbol-list-lines
31995 @subsubheading Synopsis
31998 -symbol-list-lines @var{filename}
32001 Print the list of lines that contain code and their associated program
32002 addresses for the given source filename. The entries are sorted in
32003 ascending PC order.
32005 @subsubheading @value{GDBN} Command
32007 There is no corresponding @value{GDBN} command.
32009 @subsubheading Example
32012 -symbol-list-lines basics.c
32013 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
32019 @subheading The @code{-symbol-list-types} Command
32020 @findex -symbol-list-types
32022 @subsubheading Synopsis
32028 List all the type names.
32030 @subsubheading @value{GDBN} Command
32032 The corresponding commands are @samp{info types} in @value{GDBN},
32033 @samp{gdb_search} in @code{gdbtk}.
32035 @subsubheading Example
32039 @subheading The @code{-symbol-list-variables} Command
32040 @findex -symbol-list-variables
32042 @subsubheading Synopsis
32045 -symbol-list-variables
32048 List all the global and static variable names.
32050 @subsubheading @value{GDBN} Command
32052 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
32054 @subsubheading Example
32058 @subheading The @code{-symbol-locate} Command
32059 @findex -symbol-locate
32061 @subsubheading Synopsis
32067 @subsubheading @value{GDBN} Command
32069 @samp{gdb_loc} in @code{gdbtk}.
32071 @subsubheading Example
32075 @subheading The @code{-symbol-type} Command
32076 @findex -symbol-type
32078 @subsubheading Synopsis
32081 -symbol-type @var{variable}
32084 Show type of @var{variable}.
32086 @subsubheading @value{GDBN} Command
32088 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
32089 @samp{gdb_obj_variable}.
32091 @subsubheading Example
32096 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32097 @node GDB/MI File Commands
32098 @section @sc{gdb/mi} File Commands
32100 This section describes the GDB/MI commands to specify executable file names
32101 and to read in and obtain symbol table information.
32103 @subheading The @code{-file-exec-and-symbols} Command
32104 @findex -file-exec-and-symbols
32106 @subsubheading Synopsis
32109 -file-exec-and-symbols @var{file}
32112 Specify the executable file to be debugged. This file is the one from
32113 which the symbol table is also read. If no file is specified, the
32114 command clears the executable and symbol information. If breakpoints
32115 are set when using this command with no arguments, @value{GDBN} will produce
32116 error messages. Otherwise, no output is produced, except a completion
32119 @subsubheading @value{GDBN} Command
32121 The corresponding @value{GDBN} command is @samp{file}.
32123 @subsubheading Example
32127 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32133 @subheading The @code{-file-exec-file} Command
32134 @findex -file-exec-file
32136 @subsubheading Synopsis
32139 -file-exec-file @var{file}
32142 Specify the executable file to be debugged. Unlike
32143 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
32144 from this file. If used without argument, @value{GDBN} clears the information
32145 about the executable file. No output is produced, except a completion
32148 @subsubheading @value{GDBN} Command
32150 The corresponding @value{GDBN} command is @samp{exec-file}.
32152 @subsubheading Example
32156 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32163 @subheading The @code{-file-list-exec-sections} Command
32164 @findex -file-list-exec-sections
32166 @subsubheading Synopsis
32169 -file-list-exec-sections
32172 List the sections of the current executable file.
32174 @subsubheading @value{GDBN} Command
32176 The @value{GDBN} command @samp{info file} shows, among the rest, the same
32177 information as this command. @code{gdbtk} has a corresponding command
32178 @samp{gdb_load_info}.
32180 @subsubheading Example
32185 @subheading The @code{-file-list-exec-source-file} Command
32186 @findex -file-list-exec-source-file
32188 @subsubheading Synopsis
32191 -file-list-exec-source-file
32194 List the line number, the current source file, and the absolute path
32195 to the current source file for the current executable. The macro
32196 information field has a value of @samp{1} or @samp{0} depending on
32197 whether or not the file includes preprocessor macro information.
32199 @subsubheading @value{GDBN} Command
32201 The @value{GDBN} equivalent is @samp{info source}
32203 @subsubheading Example
32207 123-file-list-exec-source-file
32208 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
32213 @subheading The @code{-file-list-exec-source-files} Command
32214 @findex -file-list-exec-source-files
32216 @subsubheading Synopsis
32219 -file-list-exec-source-files
32222 List the source files for the current executable.
32224 It will always output both the filename and fullname (absolute file
32225 name) of a source file.
32227 @subsubheading @value{GDBN} Command
32229 The @value{GDBN} equivalent is @samp{info sources}.
32230 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
32232 @subsubheading Example
32235 -file-list-exec-source-files
32237 @{file=foo.c,fullname=/home/foo.c@},
32238 @{file=/home/bar.c,fullname=/home/bar.c@},
32239 @{file=gdb_could_not_find_fullpath.c@}]
32243 @subheading The @code{-file-list-shared-libraries} Command
32244 @findex -file-list-shared-libraries
32246 @subsubheading Synopsis
32249 -file-list-shared-libraries [ @var{regexp} ]
32252 List the shared libraries in the program.
32253 With a regular expression @var{regexp}, only those libraries whose
32254 names match @var{regexp} are listed.
32256 @subsubheading @value{GDBN} Command
32258 The corresponding @value{GDBN} command is @samp{info shared}. The fields
32259 have a similar meaning to the @code{=library-loaded} notification.
32260 The @code{ranges} field specifies the multiple segments belonging to this
32261 library. Each range has the following fields:
32265 The address defining the inclusive lower bound of the segment.
32267 The address defining the exclusive upper bound of the segment.
32270 @subsubheading Example
32273 -file-list-exec-source-files
32274 ^done,shared-libraries=[
32275 @{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"@}]@},
32276 @{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"@}]@}]
32282 @subheading The @code{-file-list-symbol-files} Command
32283 @findex -file-list-symbol-files
32285 @subsubheading Synopsis
32288 -file-list-symbol-files
32293 @subsubheading @value{GDBN} Command
32295 The corresponding @value{GDBN} command is @samp{info file} (part of it).
32297 @subsubheading Example
32302 @subheading The @code{-file-symbol-file} Command
32303 @findex -file-symbol-file
32305 @subsubheading Synopsis
32308 -file-symbol-file @var{file}
32311 Read symbol table info from the specified @var{file} argument. When
32312 used without arguments, clears @value{GDBN}'s symbol table info. No output is
32313 produced, except for a completion notification.
32315 @subsubheading @value{GDBN} Command
32317 The corresponding @value{GDBN} command is @samp{symbol-file}.
32319 @subsubheading Example
32323 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32329 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32330 @node GDB/MI Memory Overlay Commands
32331 @section @sc{gdb/mi} Memory Overlay Commands
32333 The memory overlay commands are not implemented.
32335 @c @subheading -overlay-auto
32337 @c @subheading -overlay-list-mapping-state
32339 @c @subheading -overlay-list-overlays
32341 @c @subheading -overlay-map
32343 @c @subheading -overlay-off
32345 @c @subheading -overlay-on
32347 @c @subheading -overlay-unmap
32349 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32350 @node GDB/MI Signal Handling Commands
32351 @section @sc{gdb/mi} Signal Handling Commands
32353 Signal handling commands are not implemented.
32355 @c @subheading -signal-handle
32357 @c @subheading -signal-list-handle-actions
32359 @c @subheading -signal-list-signal-types
32363 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32364 @node GDB/MI Target Manipulation
32365 @section @sc{gdb/mi} Target Manipulation Commands
32368 @subheading The @code{-target-attach} Command
32369 @findex -target-attach
32371 @subsubheading Synopsis
32374 -target-attach @var{pid} | @var{gid} | @var{file}
32377 Attach to a process @var{pid} or a file @var{file} outside of
32378 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
32379 group, the id previously returned by
32380 @samp{-list-thread-groups --available} must be used.
32382 @subsubheading @value{GDBN} Command
32384 The corresponding @value{GDBN} command is @samp{attach}.
32386 @subsubheading Example
32390 =thread-created,id="1"
32391 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
32397 @subheading The @code{-target-compare-sections} Command
32398 @findex -target-compare-sections
32400 @subsubheading Synopsis
32403 -target-compare-sections [ @var{section} ]
32406 Compare data of section @var{section} on target to the exec file.
32407 Without the argument, all sections are compared.
32409 @subsubheading @value{GDBN} Command
32411 The @value{GDBN} equivalent is @samp{compare-sections}.
32413 @subsubheading Example
32418 @subheading The @code{-target-detach} Command
32419 @findex -target-detach
32421 @subsubheading Synopsis
32424 -target-detach [ @var{pid} | @var{gid} ]
32427 Detach from the remote target which normally resumes its execution.
32428 If either @var{pid} or @var{gid} is specified, detaches from either
32429 the specified process, or specified thread group. There's no output.
32431 @subsubheading @value{GDBN} Command
32433 The corresponding @value{GDBN} command is @samp{detach}.
32435 @subsubheading Example
32445 @subheading The @code{-target-disconnect} Command
32446 @findex -target-disconnect
32448 @subsubheading Synopsis
32454 Disconnect from the remote target. There's no output and the target is
32455 generally not resumed.
32457 @subsubheading @value{GDBN} Command
32459 The corresponding @value{GDBN} command is @samp{disconnect}.
32461 @subsubheading Example
32471 @subheading The @code{-target-download} Command
32472 @findex -target-download
32474 @subsubheading Synopsis
32480 Loads the executable onto the remote target.
32481 It prints out an update message every half second, which includes the fields:
32485 The name of the section.
32487 The size of what has been sent so far for that section.
32489 The size of the section.
32491 The total size of what was sent so far (the current and the previous sections).
32493 The size of the overall executable to download.
32497 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
32498 @sc{gdb/mi} Output Syntax}).
32500 In addition, it prints the name and size of the sections, as they are
32501 downloaded. These messages include the following fields:
32505 The name of the section.
32507 The size of the section.
32509 The size of the overall executable to download.
32513 At the end, a summary is printed.
32515 @subsubheading @value{GDBN} Command
32517 The corresponding @value{GDBN} command is @samp{load}.
32519 @subsubheading Example
32521 Note: each status message appears on a single line. Here the messages
32522 have been broken down so that they can fit onto a page.
32527 +download,@{section=".text",section-size="6668",total-size="9880"@}
32528 +download,@{section=".text",section-sent="512",section-size="6668",
32529 total-sent="512",total-size="9880"@}
32530 +download,@{section=".text",section-sent="1024",section-size="6668",
32531 total-sent="1024",total-size="9880"@}
32532 +download,@{section=".text",section-sent="1536",section-size="6668",
32533 total-sent="1536",total-size="9880"@}
32534 +download,@{section=".text",section-sent="2048",section-size="6668",
32535 total-sent="2048",total-size="9880"@}
32536 +download,@{section=".text",section-sent="2560",section-size="6668",
32537 total-sent="2560",total-size="9880"@}
32538 +download,@{section=".text",section-sent="3072",section-size="6668",
32539 total-sent="3072",total-size="9880"@}
32540 +download,@{section=".text",section-sent="3584",section-size="6668",
32541 total-sent="3584",total-size="9880"@}
32542 +download,@{section=".text",section-sent="4096",section-size="6668",
32543 total-sent="4096",total-size="9880"@}
32544 +download,@{section=".text",section-sent="4608",section-size="6668",
32545 total-sent="4608",total-size="9880"@}
32546 +download,@{section=".text",section-sent="5120",section-size="6668",
32547 total-sent="5120",total-size="9880"@}
32548 +download,@{section=".text",section-sent="5632",section-size="6668",
32549 total-sent="5632",total-size="9880"@}
32550 +download,@{section=".text",section-sent="6144",section-size="6668",
32551 total-sent="6144",total-size="9880"@}
32552 +download,@{section=".text",section-sent="6656",section-size="6668",
32553 total-sent="6656",total-size="9880"@}
32554 +download,@{section=".init",section-size="28",total-size="9880"@}
32555 +download,@{section=".fini",section-size="28",total-size="9880"@}
32556 +download,@{section=".data",section-size="3156",total-size="9880"@}
32557 +download,@{section=".data",section-sent="512",section-size="3156",
32558 total-sent="7236",total-size="9880"@}
32559 +download,@{section=".data",section-sent="1024",section-size="3156",
32560 total-sent="7748",total-size="9880"@}
32561 +download,@{section=".data",section-sent="1536",section-size="3156",
32562 total-sent="8260",total-size="9880"@}
32563 +download,@{section=".data",section-sent="2048",section-size="3156",
32564 total-sent="8772",total-size="9880"@}
32565 +download,@{section=".data",section-sent="2560",section-size="3156",
32566 total-sent="9284",total-size="9880"@}
32567 +download,@{section=".data",section-sent="3072",section-size="3156",
32568 total-sent="9796",total-size="9880"@}
32569 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
32576 @subheading The @code{-target-exec-status} Command
32577 @findex -target-exec-status
32579 @subsubheading Synopsis
32582 -target-exec-status
32585 Provide information on the state of the target (whether it is running or
32586 not, for instance).
32588 @subsubheading @value{GDBN} Command
32590 There's no equivalent @value{GDBN} command.
32592 @subsubheading Example
32596 @subheading The @code{-target-list-available-targets} Command
32597 @findex -target-list-available-targets
32599 @subsubheading Synopsis
32602 -target-list-available-targets
32605 List the possible targets to connect to.
32607 @subsubheading @value{GDBN} Command
32609 The corresponding @value{GDBN} command is @samp{help target}.
32611 @subsubheading Example
32615 @subheading The @code{-target-list-current-targets} Command
32616 @findex -target-list-current-targets
32618 @subsubheading Synopsis
32621 -target-list-current-targets
32624 Describe the current target.
32626 @subsubheading @value{GDBN} Command
32628 The corresponding information is printed by @samp{info file} (among
32631 @subsubheading Example
32635 @subheading The @code{-target-list-parameters} Command
32636 @findex -target-list-parameters
32638 @subsubheading Synopsis
32641 -target-list-parameters
32647 @subsubheading @value{GDBN} Command
32651 @subsubheading Example
32654 @subheading The @code{-target-flash-erase} Command
32655 @findex -target-flash-erase
32657 @subsubheading Synopsis
32660 -target-flash-erase
32663 Erases all known flash memory regions on the target.
32665 The corresponding @value{GDBN} command is @samp{flash-erase}.
32667 The output is a list of flash regions that have been erased, with starting
32668 addresses and memory region sizes.
32672 -target-flash-erase
32673 ^done,erased-regions=@{address="0x0",size="0x40000"@}
32677 @subheading The @code{-target-select} Command
32678 @findex -target-select
32680 @subsubheading Synopsis
32683 -target-select @var{type} @var{parameters @dots{}}
32686 Connect @value{GDBN} to the remote target. This command takes two args:
32690 The type of target, for instance @samp{remote}, etc.
32691 @item @var{parameters}
32692 Device names, host names and the like. @xref{Target Commands, ,
32693 Commands for Managing Targets}, for more details.
32696 The output is a connection notification, followed by the address at
32697 which the target program is, in the following form:
32700 ^connected,addr="@var{address}",func="@var{function name}",
32701 args=[@var{arg list}]
32704 @subsubheading @value{GDBN} Command
32706 The corresponding @value{GDBN} command is @samp{target}.
32708 @subsubheading Example
32712 -target-select remote /dev/ttya
32713 ^connected,addr="0xfe00a300",func="??",args=[]
32717 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32718 @node GDB/MI File Transfer Commands
32719 @section @sc{gdb/mi} File Transfer Commands
32722 @subheading The @code{-target-file-put} Command
32723 @findex -target-file-put
32725 @subsubheading Synopsis
32728 -target-file-put @var{hostfile} @var{targetfile}
32731 Copy file @var{hostfile} from the host system (the machine running
32732 @value{GDBN}) to @var{targetfile} on the target system.
32734 @subsubheading @value{GDBN} Command
32736 The corresponding @value{GDBN} command is @samp{remote put}.
32738 @subsubheading Example
32742 -target-file-put localfile remotefile
32748 @subheading The @code{-target-file-get} Command
32749 @findex -target-file-get
32751 @subsubheading Synopsis
32754 -target-file-get @var{targetfile} @var{hostfile}
32757 Copy file @var{targetfile} from the target system to @var{hostfile}
32758 on the host system.
32760 @subsubheading @value{GDBN} Command
32762 The corresponding @value{GDBN} command is @samp{remote get}.
32764 @subsubheading Example
32768 -target-file-get remotefile localfile
32774 @subheading The @code{-target-file-delete} Command
32775 @findex -target-file-delete
32777 @subsubheading Synopsis
32780 -target-file-delete @var{targetfile}
32783 Delete @var{targetfile} from the target system.
32785 @subsubheading @value{GDBN} Command
32787 The corresponding @value{GDBN} command is @samp{remote delete}.
32789 @subsubheading Example
32793 -target-file-delete remotefile
32799 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32800 @node GDB/MI Ada Exceptions Commands
32801 @section Ada Exceptions @sc{gdb/mi} Commands
32803 @subheading The @code{-info-ada-exceptions} Command
32804 @findex -info-ada-exceptions
32806 @subsubheading Synopsis
32809 -info-ada-exceptions [ @var{regexp}]
32812 List all Ada exceptions defined within the program being debugged.
32813 With a regular expression @var{regexp}, only those exceptions whose
32814 names match @var{regexp} are listed.
32816 @subsubheading @value{GDBN} Command
32818 The corresponding @value{GDBN} command is @samp{info exceptions}.
32820 @subsubheading Result
32822 The result is a table of Ada exceptions. The following columns are
32823 defined for each exception:
32827 The name of the exception.
32830 The address of the exception.
32834 @subsubheading Example
32837 -info-ada-exceptions aint
32838 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
32839 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
32840 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
32841 body=[@{name="constraint_error",address="0x0000000000613da0"@},
32842 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
32845 @subheading Catching Ada Exceptions
32847 The commands describing how to ask @value{GDBN} to stop when a program
32848 raises an exception are described at @ref{Ada Exception GDB/MI
32849 Catchpoint Commands}.
32852 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32853 @node GDB/MI Support Commands
32854 @section @sc{gdb/mi} Support Commands
32856 Since new commands and features get regularly added to @sc{gdb/mi},
32857 some commands are available to help front-ends query the debugger
32858 about support for these capabilities. Similarly, it is also possible
32859 to query @value{GDBN} about target support of certain features.
32861 @subheading The @code{-info-gdb-mi-command} Command
32862 @cindex @code{-info-gdb-mi-command}
32863 @findex -info-gdb-mi-command
32865 @subsubheading Synopsis
32868 -info-gdb-mi-command @var{cmd_name}
32871 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
32873 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
32874 is technically not part of the command name (@pxref{GDB/MI Input
32875 Syntax}), and thus should be omitted in @var{cmd_name}. However,
32876 for ease of use, this command also accepts the form with the leading
32879 @subsubheading @value{GDBN} Command
32881 There is no corresponding @value{GDBN} command.
32883 @subsubheading Result
32885 The result is a tuple. There is currently only one field:
32889 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
32890 @code{"false"} otherwise.
32894 @subsubheading Example
32896 Here is an example where the @sc{gdb/mi} command does not exist:
32899 -info-gdb-mi-command unsupported-command
32900 ^done,command=@{exists="false"@}
32904 And here is an example where the @sc{gdb/mi} command is known
32908 -info-gdb-mi-command symbol-list-lines
32909 ^done,command=@{exists="true"@}
32912 @subheading The @code{-list-features} Command
32913 @findex -list-features
32914 @cindex supported @sc{gdb/mi} features, list
32916 Returns a list of particular features of the MI protocol that
32917 this version of gdb implements. A feature can be a command,
32918 or a new field in an output of some command, or even an
32919 important bugfix. While a frontend can sometimes detect presence
32920 of a feature at runtime, it is easier to perform detection at debugger
32923 The command returns a list of strings, with each string naming an
32924 available feature. Each returned string is just a name, it does not
32925 have any internal structure. The list of possible feature names
32931 (gdb) -list-features
32932 ^done,result=["feature1","feature2"]
32935 The current list of features is:
32938 @item frozen-varobjs
32939 Indicates support for the @code{-var-set-frozen} command, as well
32940 as possible presense of the @code{frozen} field in the output
32941 of @code{-varobj-create}.
32942 @item pending-breakpoints
32943 Indicates support for the @option{-f} option to the @code{-break-insert}
32946 Indicates Python scripting support, Python-based
32947 pretty-printing commands, and possible presence of the
32948 @samp{display_hint} field in the output of @code{-var-list-children}
32950 Indicates support for the @code{-thread-info} command.
32951 @item data-read-memory-bytes
32952 Indicates support for the @code{-data-read-memory-bytes} and the
32953 @code{-data-write-memory-bytes} commands.
32954 @item breakpoint-notifications
32955 Indicates that changes to breakpoints and breakpoints created via the
32956 CLI will be announced via async records.
32957 @item ada-task-info
32958 Indicates support for the @code{-ada-task-info} command.
32959 @item language-option
32960 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
32961 option (@pxref{Context management}).
32962 @item info-gdb-mi-command
32963 Indicates support for the @code{-info-gdb-mi-command} command.
32964 @item undefined-command-error-code
32965 Indicates support for the "undefined-command" error code in error result
32966 records, produced when trying to execute an undefined @sc{gdb/mi} command
32967 (@pxref{GDB/MI Result Records}).
32968 @item exec-run-start-option
32969 Indicates that the @code{-exec-run} command supports the @option{--start}
32970 option (@pxref{GDB/MI Program Execution}).
32973 @subheading The @code{-list-target-features} Command
32974 @findex -list-target-features
32976 Returns a list of particular features that are supported by the
32977 target. Those features affect the permitted MI commands, but
32978 unlike the features reported by the @code{-list-features} command, the
32979 features depend on which target GDB is using at the moment. Whenever
32980 a target can change, due to commands such as @code{-target-select},
32981 @code{-target-attach} or @code{-exec-run}, the list of target features
32982 may change, and the frontend should obtain it again.
32986 (gdb) -list-target-features
32987 ^done,result=["async"]
32990 The current list of features is:
32994 Indicates that the target is capable of asynchronous command
32995 execution, which means that @value{GDBN} will accept further commands
32996 while the target is running.
32999 Indicates that the target is capable of reverse execution.
33000 @xref{Reverse Execution}, for more information.
33004 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33005 @node GDB/MI Miscellaneous Commands
33006 @section Miscellaneous @sc{gdb/mi} Commands
33008 @c @subheading -gdb-complete
33010 @subheading The @code{-gdb-exit} Command
33013 @subsubheading Synopsis
33019 Exit @value{GDBN} immediately.
33021 @subsubheading @value{GDBN} Command
33023 Approximately corresponds to @samp{quit}.
33025 @subsubheading Example
33035 @subheading The @code{-exec-abort} Command
33036 @findex -exec-abort
33038 @subsubheading Synopsis
33044 Kill the inferior running program.
33046 @subsubheading @value{GDBN} Command
33048 The corresponding @value{GDBN} command is @samp{kill}.
33050 @subsubheading Example
33055 @subheading The @code{-gdb-set} Command
33058 @subsubheading Synopsis
33064 Set an internal @value{GDBN} variable.
33065 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
33067 @subsubheading @value{GDBN} Command
33069 The corresponding @value{GDBN} command is @samp{set}.
33071 @subsubheading Example
33081 @subheading The @code{-gdb-show} Command
33084 @subsubheading Synopsis
33090 Show the current value of a @value{GDBN} variable.
33092 @subsubheading @value{GDBN} Command
33094 The corresponding @value{GDBN} command is @samp{show}.
33096 @subsubheading Example
33105 @c @subheading -gdb-source
33108 @subheading The @code{-gdb-version} Command
33109 @findex -gdb-version
33111 @subsubheading Synopsis
33117 Show version information for @value{GDBN}. Used mostly in testing.
33119 @subsubheading @value{GDBN} Command
33121 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
33122 default shows this information when you start an interactive session.
33124 @subsubheading Example
33126 @c This example modifies the actual output from GDB to avoid overfull
33132 ~Copyright 2000 Free Software Foundation, Inc.
33133 ~GDB is free software, covered by the GNU General Public License, and
33134 ~you are welcome to change it and/or distribute copies of it under
33135 ~ certain conditions.
33136 ~Type "show copying" to see the conditions.
33137 ~There is absolutely no warranty for GDB. Type "show warranty" for
33139 ~This GDB was configured as
33140 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
33145 @subheading The @code{-list-thread-groups} Command
33146 @findex -list-thread-groups
33148 @subheading Synopsis
33151 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
33154 Lists thread groups (@pxref{Thread groups}). When a single thread
33155 group is passed as the argument, lists the children of that group.
33156 When several thread group are passed, lists information about those
33157 thread groups. Without any parameters, lists information about all
33158 top-level thread groups.
33160 Normally, thread groups that are being debugged are reported.
33161 With the @samp{--available} option, @value{GDBN} reports thread groups
33162 available on the target.
33164 The output of this command may have either a @samp{threads} result or
33165 a @samp{groups} result. The @samp{thread} result has a list of tuples
33166 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
33167 Information}). The @samp{groups} result has a list of tuples as value,
33168 each tuple describing a thread group. If top-level groups are
33169 requested (that is, no parameter is passed), or when several groups
33170 are passed, the output always has a @samp{groups} result. The format
33171 of the @samp{group} result is described below.
33173 To reduce the number of roundtrips it's possible to list thread groups
33174 together with their children, by passing the @samp{--recurse} option
33175 and the recursion depth. Presently, only recursion depth of 1 is
33176 permitted. If this option is present, then every reported thread group
33177 will also include its children, either as @samp{group} or
33178 @samp{threads} field.
33180 In general, any combination of option and parameters is permitted, with
33181 the following caveats:
33185 When a single thread group is passed, the output will typically
33186 be the @samp{threads} result. Because threads may not contain
33187 anything, the @samp{recurse} option will be ignored.
33190 When the @samp{--available} option is passed, limited information may
33191 be available. In particular, the list of threads of a process might
33192 be inaccessible. Further, specifying specific thread groups might
33193 not give any performance advantage over listing all thread groups.
33194 The frontend should assume that @samp{-list-thread-groups --available}
33195 is always an expensive operation and cache the results.
33199 The @samp{groups} result is a list of tuples, where each tuple may
33200 have the following fields:
33204 Identifier of the thread group. This field is always present.
33205 The identifier is an opaque string; frontends should not try to
33206 convert it to an integer, even though it might look like one.
33209 The type of the thread group. At present, only @samp{process} is a
33213 The target-specific process identifier. This field is only present
33214 for thread groups of type @samp{process} and only if the process exists.
33217 The exit code of this group's last exited thread, formatted in octal.
33218 This field is only present for thread groups of type @samp{process} and
33219 only if the process is not running.
33222 The number of children this thread group has. This field may be
33223 absent for an available thread group.
33226 This field has a list of tuples as value, each tuple describing a
33227 thread. It may be present if the @samp{--recurse} option is
33228 specified, and it's actually possible to obtain the threads.
33231 This field is a list of integers, each identifying a core that one
33232 thread of the group is running on. This field may be absent if
33233 such information is not available.
33236 The name of the executable file that corresponds to this thread group.
33237 The field is only present for thread groups of type @samp{process},
33238 and only if there is a corresponding executable file.
33242 @subheading Example
33246 -list-thread-groups
33247 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
33248 -list-thread-groups 17
33249 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
33250 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
33251 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
33252 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
33253 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
33254 -list-thread-groups --available
33255 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
33256 -list-thread-groups --available --recurse 1
33257 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33258 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33259 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
33260 -list-thread-groups --available --recurse 1 17 18
33261 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33262 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33263 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
33266 @subheading The @code{-info-os} Command
33269 @subsubheading Synopsis
33272 -info-os [ @var{type} ]
33275 If no argument is supplied, the command returns a table of available
33276 operating-system-specific information types. If one of these types is
33277 supplied as an argument @var{type}, then the command returns a table
33278 of data of that type.
33280 The types of information available depend on the target operating
33283 @subsubheading @value{GDBN} Command
33285 The corresponding @value{GDBN} command is @samp{info os}.
33287 @subsubheading Example
33289 When run on a @sc{gnu}/Linux system, the output will look something
33295 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
33296 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
33297 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
33298 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
33299 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
33301 item=@{col0="files",col1="Listing of all file descriptors",
33302 col2="File descriptors"@},
33303 item=@{col0="modules",col1="Listing of all loaded kernel modules",
33304 col2="Kernel modules"@},
33305 item=@{col0="msg",col1="Listing of all message queues",
33306 col2="Message queues"@},
33307 item=@{col0="processes",col1="Listing of all processes",
33308 col2="Processes"@},
33309 item=@{col0="procgroups",col1="Listing of all process groups",
33310 col2="Process groups"@},
33311 item=@{col0="semaphores",col1="Listing of all semaphores",
33312 col2="Semaphores"@},
33313 item=@{col0="shm",col1="Listing of all shared-memory regions",
33314 col2="Shared-memory regions"@},
33315 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
33317 item=@{col0="threads",col1="Listing of all threads",
33321 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
33322 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
33323 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
33324 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
33325 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
33326 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
33327 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
33328 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
33330 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
33331 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
33335 (Note that the MI output here includes a @code{"Title"} column that
33336 does not appear in command-line @code{info os}; this column is useful
33337 for MI clients that want to enumerate the types of data, such as in a
33338 popup menu, but is needless clutter on the command line, and
33339 @code{info os} omits it.)
33341 @subheading The @code{-add-inferior} Command
33342 @findex -add-inferior
33344 @subheading Synopsis
33350 Creates a new inferior (@pxref{Inferiors and Programs}). The created
33351 inferior is not associated with any executable. Such association may
33352 be established with the @samp{-file-exec-and-symbols} command
33353 (@pxref{GDB/MI File Commands}). The command response has a single
33354 field, @samp{inferior}, whose value is the identifier of the
33355 thread group corresponding to the new inferior.
33357 @subheading Example
33362 ^done,inferior="i3"
33365 @subheading The @code{-interpreter-exec} Command
33366 @findex -interpreter-exec
33368 @subheading Synopsis
33371 -interpreter-exec @var{interpreter} @var{command}
33373 @anchor{-interpreter-exec}
33375 Execute the specified @var{command} in the given @var{interpreter}.
33377 @subheading @value{GDBN} Command
33379 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
33381 @subheading Example
33385 -interpreter-exec console "break main"
33386 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
33387 &"During symbol reading, bad structure-type format.\n"
33388 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
33393 @subheading The @code{-inferior-tty-set} Command
33394 @findex -inferior-tty-set
33396 @subheading Synopsis
33399 -inferior-tty-set /dev/pts/1
33402 Set terminal for future runs of the program being debugged.
33404 @subheading @value{GDBN} Command
33406 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
33408 @subheading Example
33412 -inferior-tty-set /dev/pts/1
33417 @subheading The @code{-inferior-tty-show} Command
33418 @findex -inferior-tty-show
33420 @subheading Synopsis
33426 Show terminal for future runs of program being debugged.
33428 @subheading @value{GDBN} Command
33430 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
33432 @subheading Example
33436 -inferior-tty-set /dev/pts/1
33440 ^done,inferior_tty_terminal="/dev/pts/1"
33444 @subheading The @code{-enable-timings} Command
33445 @findex -enable-timings
33447 @subheading Synopsis
33450 -enable-timings [yes | no]
33453 Toggle the printing of the wallclock, user and system times for an MI
33454 command as a field in its output. This command is to help frontend
33455 developers optimize the performance of their code. No argument is
33456 equivalent to @samp{yes}.
33458 @subheading @value{GDBN} Command
33462 @subheading Example
33470 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
33471 addr="0x080484ed",func="main",file="myprog.c",
33472 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
33474 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
33482 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
33483 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
33484 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
33485 fullname="/home/nickrob/myprog.c",line="73"@}
33490 @chapter @value{GDBN} Annotations
33492 This chapter describes annotations in @value{GDBN}. Annotations were
33493 designed to interface @value{GDBN} to graphical user interfaces or other
33494 similar programs which want to interact with @value{GDBN} at a
33495 relatively high level.
33497 The annotation mechanism has largely been superseded by @sc{gdb/mi}
33501 This is Edition @value{EDITION}, @value{DATE}.
33505 * Annotations Overview:: What annotations are; the general syntax.
33506 * Server Prefix:: Issuing a command without affecting user state.
33507 * Prompting:: Annotations marking @value{GDBN}'s need for input.
33508 * Errors:: Annotations for error messages.
33509 * Invalidation:: Some annotations describe things now invalid.
33510 * Annotations for Running::
33511 Whether the program is running, how it stopped, etc.
33512 * Source Annotations:: Annotations describing source code.
33515 @node Annotations Overview
33516 @section What is an Annotation?
33517 @cindex annotations
33519 Annotations start with a newline character, two @samp{control-z}
33520 characters, and the name of the annotation. If there is no additional
33521 information associated with this annotation, the name of the annotation
33522 is followed immediately by a newline. If there is additional
33523 information, the name of the annotation is followed by a space, the
33524 additional information, and a newline. The additional information
33525 cannot contain newline characters.
33527 Any output not beginning with a newline and two @samp{control-z}
33528 characters denotes literal output from @value{GDBN}. Currently there is
33529 no need for @value{GDBN} to output a newline followed by two
33530 @samp{control-z} characters, but if there was such a need, the
33531 annotations could be extended with an @samp{escape} annotation which
33532 means those three characters as output.
33534 The annotation @var{level}, which is specified using the
33535 @option{--annotate} command line option (@pxref{Mode Options}), controls
33536 how much information @value{GDBN} prints together with its prompt,
33537 values of expressions, source lines, and other types of output. Level 0
33538 is for no annotations, level 1 is for use when @value{GDBN} is run as a
33539 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
33540 for programs that control @value{GDBN}, and level 2 annotations have
33541 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
33542 Interface, annotate, GDB's Obsolete Annotations}).
33545 @kindex set annotate
33546 @item set annotate @var{level}
33547 The @value{GDBN} command @code{set annotate} sets the level of
33548 annotations to the specified @var{level}.
33550 @item show annotate
33551 @kindex show annotate
33552 Show the current annotation level.
33555 This chapter describes level 3 annotations.
33557 A simple example of starting up @value{GDBN} with annotations is:
33560 $ @kbd{gdb --annotate=3}
33562 Copyright 2003 Free Software Foundation, Inc.
33563 GDB is free software, covered by the GNU General Public License,
33564 and you are welcome to change it and/or distribute copies of it
33565 under certain conditions.
33566 Type "show copying" to see the conditions.
33567 There is absolutely no warranty for GDB. Type "show warranty"
33569 This GDB was configured as "i386-pc-linux-gnu"
33580 Here @samp{quit} is input to @value{GDBN}; the rest is output from
33581 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
33582 denotes a @samp{control-z} character) are annotations; the rest is
33583 output from @value{GDBN}.
33585 @node Server Prefix
33586 @section The Server Prefix
33587 @cindex server prefix
33589 If you prefix a command with @samp{server } then it will not affect
33590 the command history, nor will it affect @value{GDBN}'s notion of which
33591 command to repeat if @key{RET} is pressed on a line by itself. This
33592 means that commands can be run behind a user's back by a front-end in
33593 a transparent manner.
33595 The @code{server } prefix does not affect the recording of values into
33596 the value history; to print a value without recording it into the
33597 value history, use the @code{output} command instead of the
33598 @code{print} command.
33600 Using this prefix also disables confirmation requests
33601 (@pxref{confirmation requests}).
33604 @section Annotation for @value{GDBN} Input
33606 @cindex annotations for prompts
33607 When @value{GDBN} prompts for input, it annotates this fact so it is possible
33608 to know when to send output, when the output from a given command is
33611 Different kinds of input each have a different @dfn{input type}. Each
33612 input type has three annotations: a @code{pre-} annotation, which
33613 denotes the beginning of any prompt which is being output, a plain
33614 annotation, which denotes the end of the prompt, and then a @code{post-}
33615 annotation which denotes the end of any echo which may (or may not) be
33616 associated with the input. For example, the @code{prompt} input type
33617 features the following annotations:
33625 The input types are
33628 @findex pre-prompt annotation
33629 @findex prompt annotation
33630 @findex post-prompt annotation
33632 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
33634 @findex pre-commands annotation
33635 @findex commands annotation
33636 @findex post-commands annotation
33638 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
33639 command. The annotations are repeated for each command which is input.
33641 @findex pre-overload-choice annotation
33642 @findex overload-choice annotation
33643 @findex post-overload-choice annotation
33644 @item overload-choice
33645 When @value{GDBN} wants the user to select between various overloaded functions.
33647 @findex pre-query annotation
33648 @findex query annotation
33649 @findex post-query annotation
33651 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
33653 @findex pre-prompt-for-continue annotation
33654 @findex prompt-for-continue annotation
33655 @findex post-prompt-for-continue annotation
33656 @item prompt-for-continue
33657 When @value{GDBN} is asking the user to press return to continue. Note: Don't
33658 expect this to work well; instead use @code{set height 0} to disable
33659 prompting. This is because the counting of lines is buggy in the
33660 presence of annotations.
33665 @cindex annotations for errors, warnings and interrupts
33667 @findex quit annotation
33672 This annotation occurs right before @value{GDBN} responds to an interrupt.
33674 @findex error annotation
33679 This annotation occurs right before @value{GDBN} responds to an error.
33681 Quit and error annotations indicate that any annotations which @value{GDBN} was
33682 in the middle of may end abruptly. For example, if a
33683 @code{value-history-begin} annotation is followed by a @code{error}, one
33684 cannot expect to receive the matching @code{value-history-end}. One
33685 cannot expect not to receive it either, however; an error annotation
33686 does not necessarily mean that @value{GDBN} is immediately returning all the way
33689 @findex error-begin annotation
33690 A quit or error annotation may be preceded by
33696 Any output between that and the quit or error annotation is the error
33699 Warning messages are not yet annotated.
33700 @c If we want to change that, need to fix warning(), type_error(),
33701 @c range_error(), and possibly other places.
33704 @section Invalidation Notices
33706 @cindex annotations for invalidation messages
33707 The following annotations say that certain pieces of state may have
33711 @findex frames-invalid annotation
33712 @item ^Z^Zframes-invalid
33714 The frames (for example, output from the @code{backtrace} command) may
33717 @findex breakpoints-invalid annotation
33718 @item ^Z^Zbreakpoints-invalid
33720 The breakpoints may have changed. For example, the user just added or
33721 deleted a breakpoint.
33724 @node Annotations for Running
33725 @section Running the Program
33726 @cindex annotations for running programs
33728 @findex starting annotation
33729 @findex stopping annotation
33730 When the program starts executing due to a @value{GDBN} command such as
33731 @code{step} or @code{continue},
33737 is output. When the program stops,
33743 is output. Before the @code{stopped} annotation, a variety of
33744 annotations describe how the program stopped.
33747 @findex exited annotation
33748 @item ^Z^Zexited @var{exit-status}
33749 The program exited, and @var{exit-status} is the exit status (zero for
33750 successful exit, otherwise nonzero).
33752 @findex signalled annotation
33753 @findex signal-name annotation
33754 @findex signal-name-end annotation
33755 @findex signal-string annotation
33756 @findex signal-string-end annotation
33757 @item ^Z^Zsignalled
33758 The program exited with a signal. After the @code{^Z^Zsignalled}, the
33759 annotation continues:
33765 ^Z^Zsignal-name-end
33769 ^Z^Zsignal-string-end
33774 where @var{name} is the name of the signal, such as @code{SIGILL} or
33775 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
33776 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
33777 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
33778 user's benefit and have no particular format.
33780 @findex signal annotation
33782 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
33783 just saying that the program received the signal, not that it was
33784 terminated with it.
33786 @findex breakpoint annotation
33787 @item ^Z^Zbreakpoint @var{number}
33788 The program hit breakpoint number @var{number}.
33790 @findex watchpoint annotation
33791 @item ^Z^Zwatchpoint @var{number}
33792 The program hit watchpoint number @var{number}.
33795 @node Source Annotations
33796 @section Displaying Source
33797 @cindex annotations for source display
33799 @findex source annotation
33800 The following annotation is used instead of displaying source code:
33803 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
33806 where @var{filename} is an absolute file name indicating which source
33807 file, @var{line} is the line number within that file (where 1 is the
33808 first line in the file), @var{character} is the character position
33809 within the file (where 0 is the first character in the file) (for most
33810 debug formats this will necessarily point to the beginning of a line),
33811 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
33812 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
33813 @var{addr} is the address in the target program associated with the
33814 source which is being displayed. The @var{addr} is in the form @samp{0x}
33815 followed by one or more lowercase hex digits (note that this does not
33816 depend on the language).
33818 @node JIT Interface
33819 @chapter JIT Compilation Interface
33820 @cindex just-in-time compilation
33821 @cindex JIT compilation interface
33823 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
33824 interface. A JIT compiler is a program or library that generates native
33825 executable code at runtime and executes it, usually in order to achieve good
33826 performance while maintaining platform independence.
33828 Programs that use JIT compilation are normally difficult to debug because
33829 portions of their code are generated at runtime, instead of being loaded from
33830 object files, which is where @value{GDBN} normally finds the program's symbols
33831 and debug information. In order to debug programs that use JIT compilation,
33832 @value{GDBN} has an interface that allows the program to register in-memory
33833 symbol files with @value{GDBN} at runtime.
33835 If you are using @value{GDBN} to debug a program that uses this interface, then
33836 it should work transparently so long as you have not stripped the binary. If
33837 you are developing a JIT compiler, then the interface is documented in the rest
33838 of this chapter. At this time, the only known client of this interface is the
33841 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
33842 JIT compiler communicates with @value{GDBN} by writing data into a global
33843 variable and calling a fuction at a well-known symbol. When @value{GDBN}
33844 attaches, it reads a linked list of symbol files from the global variable to
33845 find existing code, and puts a breakpoint in the function so that it can find
33846 out about additional code.
33849 * Declarations:: Relevant C struct declarations
33850 * Registering Code:: Steps to register code
33851 * Unregistering Code:: Steps to unregister code
33852 * Custom Debug Info:: Emit debug information in a custom format
33856 @section JIT Declarations
33858 These are the relevant struct declarations that a C program should include to
33859 implement the interface:
33869 struct jit_code_entry
33871 struct jit_code_entry *next_entry;
33872 struct jit_code_entry *prev_entry;
33873 const char *symfile_addr;
33874 uint64_t symfile_size;
33877 struct jit_descriptor
33880 /* This type should be jit_actions_t, but we use uint32_t
33881 to be explicit about the bitwidth. */
33882 uint32_t action_flag;
33883 struct jit_code_entry *relevant_entry;
33884 struct jit_code_entry *first_entry;
33887 /* GDB puts a breakpoint in this function. */
33888 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
33890 /* Make sure to specify the version statically, because the
33891 debugger may check the version before we can set it. */
33892 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
33895 If the JIT is multi-threaded, then it is important that the JIT synchronize any
33896 modifications to this global data properly, which can easily be done by putting
33897 a global mutex around modifications to these structures.
33899 @node Registering Code
33900 @section Registering Code
33902 To register code with @value{GDBN}, the JIT should follow this protocol:
33906 Generate an object file in memory with symbols and other desired debug
33907 information. The file must include the virtual addresses of the sections.
33910 Create a code entry for the file, which gives the start and size of the symbol
33914 Add it to the linked list in the JIT descriptor.
33917 Point the relevant_entry field of the descriptor at the entry.
33920 Set @code{action_flag} to @code{JIT_REGISTER} and call
33921 @code{__jit_debug_register_code}.
33924 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
33925 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
33926 new code. However, the linked list must still be maintained in order to allow
33927 @value{GDBN} to attach to a running process and still find the symbol files.
33929 @node Unregistering Code
33930 @section Unregistering Code
33932 If code is freed, then the JIT should use the following protocol:
33936 Remove the code entry corresponding to the code from the linked list.
33939 Point the @code{relevant_entry} field of the descriptor at the code entry.
33942 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
33943 @code{__jit_debug_register_code}.
33946 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
33947 and the JIT will leak the memory used for the associated symbol files.
33949 @node Custom Debug Info
33950 @section Custom Debug Info
33951 @cindex custom JIT debug info
33952 @cindex JIT debug info reader
33954 Generating debug information in platform-native file formats (like ELF
33955 or COFF) may be an overkill for JIT compilers; especially if all the
33956 debug info is used for is displaying a meaningful backtrace. The
33957 issue can be resolved by having the JIT writers decide on a debug info
33958 format and also provide a reader that parses the debug info generated
33959 by the JIT compiler. This section gives a brief overview on writing
33960 such a parser. More specific details can be found in the source file
33961 @file{gdb/jit-reader.in}, which is also installed as a header at
33962 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
33964 The reader is implemented as a shared object (so this functionality is
33965 not available on platforms which don't allow loading shared objects at
33966 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
33967 @code{jit-reader-unload} are provided, to be used to load and unload
33968 the readers from a preconfigured directory. Once loaded, the shared
33969 object is used the parse the debug information emitted by the JIT
33973 * Using JIT Debug Info Readers:: How to use supplied readers correctly
33974 * Writing JIT Debug Info Readers:: Creating a debug-info reader
33977 @node Using JIT Debug Info Readers
33978 @subsection Using JIT Debug Info Readers
33979 @kindex jit-reader-load
33980 @kindex jit-reader-unload
33982 Readers can be loaded and unloaded using the @code{jit-reader-load}
33983 and @code{jit-reader-unload} commands.
33986 @item jit-reader-load @var{reader}
33987 Load the JIT reader named @var{reader}, which is a shared
33988 object specified as either an absolute or a relative file name. In
33989 the latter case, @value{GDBN} will try to load the reader from a
33990 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
33991 system (here @var{libdir} is the system library directory, often
33992 @file{/usr/local/lib}).
33994 Only one reader can be active at a time; trying to load a second
33995 reader when one is already loaded will result in @value{GDBN}
33996 reporting an error. A new JIT reader can be loaded by first unloading
33997 the current one using @code{jit-reader-unload} and then invoking
33998 @code{jit-reader-load}.
34000 @item jit-reader-unload
34001 Unload the currently loaded JIT reader.
34005 @node Writing JIT Debug Info Readers
34006 @subsection Writing JIT Debug Info Readers
34007 @cindex writing JIT debug info readers
34009 As mentioned, a reader is essentially a shared object conforming to a
34010 certain ABI. This ABI is described in @file{jit-reader.h}.
34012 @file{jit-reader.h} defines the structures, macros and functions
34013 required to write a reader. It is installed (along with
34014 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
34015 the system include directory.
34017 Readers need to be released under a GPL compatible license. A reader
34018 can be declared as released under such a license by placing the macro
34019 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
34021 The entry point for readers is the symbol @code{gdb_init_reader},
34022 which is expected to be a function with the prototype
34024 @findex gdb_init_reader
34026 extern struct gdb_reader_funcs *gdb_init_reader (void);
34029 @cindex @code{struct gdb_reader_funcs}
34031 @code{struct gdb_reader_funcs} contains a set of pointers to callback
34032 functions. These functions are executed to read the debug info
34033 generated by the JIT compiler (@code{read}), to unwind stack frames
34034 (@code{unwind}) and to create canonical frame IDs
34035 (@code{get_Frame_id}). It also has a callback that is called when the
34036 reader is being unloaded (@code{destroy}). The struct looks like this
34039 struct gdb_reader_funcs
34041 /* Must be set to GDB_READER_INTERFACE_VERSION. */
34042 int reader_version;
34044 /* For use by the reader. */
34047 gdb_read_debug_info *read;
34048 gdb_unwind_frame *unwind;
34049 gdb_get_frame_id *get_frame_id;
34050 gdb_destroy_reader *destroy;
34054 @cindex @code{struct gdb_symbol_callbacks}
34055 @cindex @code{struct gdb_unwind_callbacks}
34057 The callbacks are provided with another set of callbacks by
34058 @value{GDBN} to do their job. For @code{read}, these callbacks are
34059 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
34060 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
34061 @code{struct gdb_symbol_callbacks} has callbacks to create new object
34062 files and new symbol tables inside those object files. @code{struct
34063 gdb_unwind_callbacks} has callbacks to read registers off the current
34064 frame and to write out the values of the registers in the previous
34065 frame. Both have a callback (@code{target_read}) to read bytes off the
34066 target's address space.
34068 @node In-Process Agent
34069 @chapter In-Process Agent
34070 @cindex debugging agent
34071 The traditional debugging model is conceptually low-speed, but works fine,
34072 because most bugs can be reproduced in debugging-mode execution. However,
34073 as multi-core or many-core processors are becoming mainstream, and
34074 multi-threaded programs become more and more popular, there should be more
34075 and more bugs that only manifest themselves at normal-mode execution, for
34076 example, thread races, because debugger's interference with the program's
34077 timing may conceal the bugs. On the other hand, in some applications,
34078 it is not feasible for the debugger to interrupt the program's execution
34079 long enough for the developer to learn anything helpful about its behavior.
34080 If the program's correctness depends on its real-time behavior, delays
34081 introduced by a debugger might cause the program to fail, even when the
34082 code itself is correct. It is useful to be able to observe the program's
34083 behavior without interrupting it.
34085 Therefore, traditional debugging model is too intrusive to reproduce
34086 some bugs. In order to reduce the interference with the program, we can
34087 reduce the number of operations performed by debugger. The
34088 @dfn{In-Process Agent}, a shared library, is running within the same
34089 process with inferior, and is able to perform some debugging operations
34090 itself. As a result, debugger is only involved when necessary, and
34091 performance of debugging can be improved accordingly. Note that
34092 interference with program can be reduced but can't be removed completely,
34093 because the in-process agent will still stop or slow down the program.
34095 The in-process agent can interpret and execute Agent Expressions
34096 (@pxref{Agent Expressions}) during performing debugging operations. The
34097 agent expressions can be used for different purposes, such as collecting
34098 data in tracepoints, and condition evaluation in breakpoints.
34100 @anchor{Control Agent}
34101 You can control whether the in-process agent is used as an aid for
34102 debugging with the following commands:
34105 @kindex set agent on
34107 Causes the in-process agent to perform some operations on behalf of the
34108 debugger. Just which operations requested by the user will be done
34109 by the in-process agent depends on the its capabilities. For example,
34110 if you request to evaluate breakpoint conditions in the in-process agent,
34111 and the in-process agent has such capability as well, then breakpoint
34112 conditions will be evaluated in the in-process agent.
34114 @kindex set agent off
34115 @item set agent off
34116 Disables execution of debugging operations by the in-process agent. All
34117 of the operations will be performed by @value{GDBN}.
34121 Display the current setting of execution of debugging operations by
34122 the in-process agent.
34126 * In-Process Agent Protocol::
34129 @node In-Process Agent Protocol
34130 @section In-Process Agent Protocol
34131 @cindex in-process agent protocol
34133 The in-process agent is able to communicate with both @value{GDBN} and
34134 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
34135 used for communications between @value{GDBN} or GDBserver and the IPA.
34136 In general, @value{GDBN} or GDBserver sends commands
34137 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
34138 in-process agent replies back with the return result of the command, or
34139 some other information. The data sent to in-process agent is composed
34140 of primitive data types, such as 4-byte or 8-byte type, and composite
34141 types, which are called objects (@pxref{IPA Protocol Objects}).
34144 * IPA Protocol Objects::
34145 * IPA Protocol Commands::
34148 @node IPA Protocol Objects
34149 @subsection IPA Protocol Objects
34150 @cindex ipa protocol objects
34152 The commands sent to and results received from agent may contain some
34153 complex data types called @dfn{objects}.
34155 The in-process agent is running on the same machine with @value{GDBN}
34156 or GDBserver, so it doesn't have to handle as much differences between
34157 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
34158 However, there are still some differences of two ends in two processes:
34162 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
34163 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
34165 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
34166 GDBserver is compiled with one, and in-process agent is compiled with
34170 Here are the IPA Protocol Objects:
34174 agent expression object. It represents an agent expression
34175 (@pxref{Agent Expressions}).
34176 @anchor{agent expression object}
34178 tracepoint action object. It represents a tracepoint action
34179 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
34180 memory, static trace data and to evaluate expression.
34181 @anchor{tracepoint action object}
34183 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
34184 @anchor{tracepoint object}
34188 The following table describes important attributes of each IPA protocol
34191 @multitable @columnfractions .30 .20 .50
34192 @headitem Name @tab Size @tab Description
34193 @item @emph{agent expression object} @tab @tab
34194 @item length @tab 4 @tab length of bytes code
34195 @item byte code @tab @var{length} @tab contents of byte code
34196 @item @emph{tracepoint action for collecting memory} @tab @tab
34197 @item 'M' @tab 1 @tab type of tracepoint action
34198 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
34199 address of the lowest byte to collect, otherwise @var{addr} is the offset
34200 of @var{basereg} for memory collecting.
34201 @item len @tab 8 @tab length of memory for collecting
34202 @item basereg @tab 4 @tab the register number containing the starting
34203 memory address for collecting.
34204 @item @emph{tracepoint action for collecting registers} @tab @tab
34205 @item 'R' @tab 1 @tab type of tracepoint action
34206 @item @emph{tracepoint action for collecting static trace data} @tab @tab
34207 @item 'L' @tab 1 @tab type of tracepoint action
34208 @item @emph{tracepoint action for expression evaluation} @tab @tab
34209 @item 'X' @tab 1 @tab type of tracepoint action
34210 @item agent expression @tab length of @tab @ref{agent expression object}
34211 @item @emph{tracepoint object} @tab @tab
34212 @item number @tab 4 @tab number of tracepoint
34213 @item address @tab 8 @tab address of tracepoint inserted on
34214 @item type @tab 4 @tab type of tracepoint
34215 @item enabled @tab 1 @tab enable or disable of tracepoint
34216 @item step_count @tab 8 @tab step
34217 @item pass_count @tab 8 @tab pass
34218 @item numactions @tab 4 @tab number of tracepoint actions
34219 @item hit count @tab 8 @tab hit count
34220 @item trace frame usage @tab 8 @tab trace frame usage
34221 @item compiled_cond @tab 8 @tab compiled condition
34222 @item orig_size @tab 8 @tab orig size
34223 @item condition @tab 4 if condition is NULL otherwise length of
34224 @ref{agent expression object}
34225 @tab zero if condition is NULL, otherwise is
34226 @ref{agent expression object}
34227 @item actions @tab variable
34228 @tab numactions number of @ref{tracepoint action object}
34231 @node IPA Protocol Commands
34232 @subsection IPA Protocol Commands
34233 @cindex ipa protocol commands
34235 The spaces in each command are delimiters to ease reading this commands
34236 specification. They don't exist in real commands.
34240 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
34241 Installs a new fast tracepoint described by @var{tracepoint_object}
34242 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
34243 head of @dfn{jumppad}, which is used to jump to data collection routine
34248 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
34249 @var{target_address} is address of tracepoint in the inferior.
34250 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
34251 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
34252 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
34253 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
34260 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
34261 is about to kill inferiors.
34269 @item probe_marker_at:@var{address}
34270 Asks in-process agent to probe the marker at @var{address}.
34277 @item unprobe_marker_at:@var{address}
34278 Asks in-process agent to unprobe the marker at @var{address}.
34282 @chapter Reporting Bugs in @value{GDBN}
34283 @cindex bugs in @value{GDBN}
34284 @cindex reporting bugs in @value{GDBN}
34286 Your bug reports play an essential role in making @value{GDBN} reliable.
34288 Reporting a bug may help you by bringing a solution to your problem, or it
34289 may not. But in any case the principal function of a bug report is to help
34290 the entire community by making the next version of @value{GDBN} work better. Bug
34291 reports are your contribution to the maintenance of @value{GDBN}.
34293 In order for a bug report to serve its purpose, you must include the
34294 information that enables us to fix the bug.
34297 * Bug Criteria:: Have you found a bug?
34298 * Bug Reporting:: How to report bugs
34302 @section Have You Found a Bug?
34303 @cindex bug criteria
34305 If you are not sure whether you have found a bug, here are some guidelines:
34308 @cindex fatal signal
34309 @cindex debugger crash
34310 @cindex crash of debugger
34312 If the debugger gets a fatal signal, for any input whatever, that is a
34313 @value{GDBN} bug. Reliable debuggers never crash.
34315 @cindex error on valid input
34317 If @value{GDBN} produces an error message for valid input, that is a
34318 bug. (Note that if you're cross debugging, the problem may also be
34319 somewhere in the connection to the target.)
34321 @cindex invalid input
34323 If @value{GDBN} does not produce an error message for invalid input,
34324 that is a bug. However, you should note that your idea of
34325 ``invalid input'' might be our idea of ``an extension'' or ``support
34326 for traditional practice''.
34329 If you are an experienced user of debugging tools, your suggestions
34330 for improvement of @value{GDBN} are welcome in any case.
34333 @node Bug Reporting
34334 @section How to Report Bugs
34335 @cindex bug reports
34336 @cindex @value{GDBN} bugs, reporting
34338 A number of companies and individuals offer support for @sc{gnu} products.
34339 If you obtained @value{GDBN} from a support organization, we recommend you
34340 contact that organization first.
34342 You can find contact information for many support companies and
34343 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
34345 @c should add a web page ref...
34348 @ifset BUGURL_DEFAULT
34349 In any event, we also recommend that you submit bug reports for
34350 @value{GDBN}. The preferred method is to submit them directly using
34351 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
34352 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
34355 @strong{Do not send bug reports to @samp{info-gdb}, or to
34356 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
34357 not want to receive bug reports. Those that do have arranged to receive
34360 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
34361 serves as a repeater. The mailing list and the newsgroup carry exactly
34362 the same messages. Often people think of posting bug reports to the
34363 newsgroup instead of mailing them. This appears to work, but it has one
34364 problem which can be crucial: a newsgroup posting often lacks a mail
34365 path back to the sender. Thus, if we need to ask for more information,
34366 we may be unable to reach you. For this reason, it is better to send
34367 bug reports to the mailing list.
34369 @ifclear BUGURL_DEFAULT
34370 In any event, we also recommend that you submit bug reports for
34371 @value{GDBN} to @value{BUGURL}.
34375 The fundamental principle of reporting bugs usefully is this:
34376 @strong{report all the facts}. If you are not sure whether to state a
34377 fact or leave it out, state it!
34379 Often people omit facts because they think they know what causes the
34380 problem and assume that some details do not matter. Thus, you might
34381 assume that the name of the variable you use in an example does not matter.
34382 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
34383 stray memory reference which happens to fetch from the location where that
34384 name is stored in memory; perhaps, if the name were different, the contents
34385 of that location would fool the debugger into doing the right thing despite
34386 the bug. Play it safe and give a specific, complete example. That is the
34387 easiest thing for you to do, and the most helpful.
34389 Keep in mind that the purpose of a bug report is to enable us to fix the
34390 bug. It may be that the bug has been reported previously, but neither
34391 you nor we can know that unless your bug report is complete and
34394 Sometimes people give a few sketchy facts and ask, ``Does this ring a
34395 bell?'' Those bug reports are useless, and we urge everyone to
34396 @emph{refuse to respond to them} except to chide the sender to report
34399 To enable us to fix the bug, you should include all these things:
34403 The version of @value{GDBN}. @value{GDBN} announces it if you start
34404 with no arguments; you can also print it at any time using @code{show
34407 Without this, we will not know whether there is any point in looking for
34408 the bug in the current version of @value{GDBN}.
34411 The type of machine you are using, and the operating system name and
34415 The details of the @value{GDBN} build-time configuration.
34416 @value{GDBN} shows these details if you invoke it with the
34417 @option{--configuration} command-line option, or if you type
34418 @code{show configuration} at @value{GDBN}'s prompt.
34421 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
34422 ``@value{GCC}--2.8.1''.
34425 What compiler (and its version) was used to compile the program you are
34426 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
34427 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
34428 to get this information; for other compilers, see the documentation for
34432 The command arguments you gave the compiler to compile your example and
34433 observe the bug. For example, did you use @samp{-O}? To guarantee
34434 you will not omit something important, list them all. A copy of the
34435 Makefile (or the output from make) is sufficient.
34437 If we were to try to guess the arguments, we would probably guess wrong
34438 and then we might not encounter the bug.
34441 A complete input script, and all necessary source files, that will
34445 A description of what behavior you observe that you believe is
34446 incorrect. For example, ``It gets a fatal signal.''
34448 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
34449 will certainly notice it. But if the bug is incorrect output, we might
34450 not notice unless it is glaringly wrong. You might as well not give us
34451 a chance to make a mistake.
34453 Even if the problem you experience is a fatal signal, you should still
34454 say so explicitly. Suppose something strange is going on, such as, your
34455 copy of @value{GDBN} is out of synch, or you have encountered a bug in
34456 the C library on your system. (This has happened!) Your copy might
34457 crash and ours would not. If you told us to expect a crash, then when
34458 ours fails to crash, we would know that the bug was not happening for
34459 us. If you had not told us to expect a crash, then we would not be able
34460 to draw any conclusion from our observations.
34463 @cindex recording a session script
34464 To collect all this information, you can use a session recording program
34465 such as @command{script}, which is available on many Unix systems.
34466 Just run your @value{GDBN} session inside @command{script} and then
34467 include the @file{typescript} file with your bug report.
34469 Another way to record a @value{GDBN} session is to run @value{GDBN}
34470 inside Emacs and then save the entire buffer to a file.
34473 If you wish to suggest changes to the @value{GDBN} source, send us context
34474 diffs. If you even discuss something in the @value{GDBN} source, refer to
34475 it by context, not by line number.
34477 The line numbers in our development sources will not match those in your
34478 sources. Your line numbers would convey no useful information to us.
34482 Here are some things that are not necessary:
34486 A description of the envelope of the bug.
34488 Often people who encounter a bug spend a lot of time investigating
34489 which changes to the input file will make the bug go away and which
34490 changes will not affect it.
34492 This is often time consuming and not very useful, because the way we
34493 will find the bug is by running a single example under the debugger
34494 with breakpoints, not by pure deduction from a series of examples.
34495 We recommend that you save your time for something else.
34497 Of course, if you can find a simpler example to report @emph{instead}
34498 of the original one, that is a convenience for us. Errors in the
34499 output will be easier to spot, running under the debugger will take
34500 less time, and so on.
34502 However, simplification is not vital; if you do not want to do this,
34503 report the bug anyway and send us the entire test case you used.
34506 A patch for the bug.
34508 A patch for the bug does help us if it is a good one. But do not omit
34509 the necessary information, such as the test case, on the assumption that
34510 a patch is all we need. We might see problems with your patch and decide
34511 to fix the problem another way, or we might not understand it at all.
34513 Sometimes with a program as complicated as @value{GDBN} it is very hard to
34514 construct an example that will make the program follow a certain path
34515 through the code. If you do not send us the example, we will not be able
34516 to construct one, so we will not be able to verify that the bug is fixed.
34518 And if we cannot understand what bug you are trying to fix, or why your
34519 patch should be an improvement, we will not install it. A test case will
34520 help us to understand.
34523 A guess about what the bug is or what it depends on.
34525 Such guesses are usually wrong. Even we cannot guess right about such
34526 things without first using the debugger to find the facts.
34529 @c The readline documentation is distributed with the readline code
34530 @c and consists of the two following files:
34533 @c Use -I with makeinfo to point to the appropriate directory,
34534 @c environment var TEXINPUTS with TeX.
34535 @ifclear SYSTEM_READLINE
34536 @include rluser.texi
34537 @include hsuser.texi
34541 @appendix In Memoriam
34543 The @value{GDBN} project mourns the loss of the following long-time
34548 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
34549 to Free Software in general. Outside of @value{GDBN}, he was known in
34550 the Amiga world for his series of Fish Disks, and the GeekGadget project.
34552 @item Michael Snyder
34553 Michael was one of the Global Maintainers of the @value{GDBN} project,
34554 with contributions recorded as early as 1996, until 2011. In addition
34555 to his day to day participation, he was a large driving force behind
34556 adding Reverse Debugging to @value{GDBN}.
34559 Beyond their technical contributions to the project, they were also
34560 enjoyable members of the Free Software Community. We will miss them.
34562 @node Formatting Documentation
34563 @appendix Formatting Documentation
34565 @cindex @value{GDBN} reference card
34566 @cindex reference card
34567 The @value{GDBN} 4 release includes an already-formatted reference card, ready
34568 for printing with PostScript or Ghostscript, in the @file{gdb}
34569 subdirectory of the main source directory@footnote{In
34570 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
34571 release.}. If you can use PostScript or Ghostscript with your printer,
34572 you can print the reference card immediately with @file{refcard.ps}.
34574 The release also includes the source for the reference card. You
34575 can format it, using @TeX{}, by typing:
34581 The @value{GDBN} reference card is designed to print in @dfn{landscape}
34582 mode on US ``letter'' size paper;
34583 that is, on a sheet 11 inches wide by 8.5 inches
34584 high. You will need to specify this form of printing as an option to
34585 your @sc{dvi} output program.
34587 @cindex documentation
34589 All the documentation for @value{GDBN} comes as part of the machine-readable
34590 distribution. The documentation is written in Texinfo format, which is
34591 a documentation system that uses a single source file to produce both
34592 on-line information and a printed manual. You can use one of the Info
34593 formatting commands to create the on-line version of the documentation
34594 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
34596 @value{GDBN} includes an already formatted copy of the on-line Info
34597 version of this manual in the @file{gdb} subdirectory. The main Info
34598 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
34599 subordinate files matching @samp{gdb.info*} in the same directory. If
34600 necessary, you can print out these files, or read them with any editor;
34601 but they are easier to read using the @code{info} subsystem in @sc{gnu}
34602 Emacs or the standalone @code{info} program, available as part of the
34603 @sc{gnu} Texinfo distribution.
34605 If you want to format these Info files yourself, you need one of the
34606 Info formatting programs, such as @code{texinfo-format-buffer} or
34609 If you have @code{makeinfo} installed, and are in the top level
34610 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
34611 version @value{GDBVN}), you can make the Info file by typing:
34618 If you want to typeset and print copies of this manual, you need @TeX{},
34619 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
34620 Texinfo definitions file.
34622 @TeX{} is a typesetting program; it does not print files directly, but
34623 produces output files called @sc{dvi} files. To print a typeset
34624 document, you need a program to print @sc{dvi} files. If your system
34625 has @TeX{} installed, chances are it has such a program. The precise
34626 command to use depends on your system; @kbd{lpr -d} is common; another
34627 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
34628 require a file name without any extension or a @samp{.dvi} extension.
34630 @TeX{} also requires a macro definitions file called
34631 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
34632 written in Texinfo format. On its own, @TeX{} cannot either read or
34633 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
34634 and is located in the @file{gdb-@var{version-number}/texinfo}
34637 If you have @TeX{} and a @sc{dvi} printer program installed, you can
34638 typeset and print this manual. First switch to the @file{gdb}
34639 subdirectory of the main source directory (for example, to
34640 @file{gdb-@value{GDBVN}/gdb}) and type:
34646 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
34648 @node Installing GDB
34649 @appendix Installing @value{GDBN}
34650 @cindex installation
34653 * Requirements:: Requirements for building @value{GDBN}
34654 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
34655 * Separate Objdir:: Compiling @value{GDBN} in another directory
34656 * Config Names:: Specifying names for hosts and targets
34657 * Configure Options:: Summary of options for configure
34658 * System-wide configuration:: Having a system-wide init file
34662 @section Requirements for Building @value{GDBN}
34663 @cindex building @value{GDBN}, requirements for
34665 Building @value{GDBN} requires various tools and packages to be available.
34666 Other packages will be used only if they are found.
34668 @heading Tools/Packages Necessary for Building @value{GDBN}
34670 @item ISO C90 compiler
34671 @value{GDBN} is written in ISO C90. It should be buildable with any
34672 working C90 compiler, e.g.@: GCC.
34676 @heading Tools/Packages Optional for Building @value{GDBN}
34680 @value{GDBN} can use the Expat XML parsing library. This library may be
34681 included with your operating system distribution; if it is not, you
34682 can get the latest version from @url{http://expat.sourceforge.net}.
34683 The @file{configure} script will search for this library in several
34684 standard locations; if it is installed in an unusual path, you can
34685 use the @option{--with-libexpat-prefix} option to specify its location.
34691 Remote protocol memory maps (@pxref{Memory Map Format})
34693 Target descriptions (@pxref{Target Descriptions})
34695 Remote shared library lists (@xref{Library List Format},
34696 or alternatively @pxref{Library List Format for SVR4 Targets})
34698 MS-Windows shared libraries (@pxref{Shared Libraries})
34700 Traceframe info (@pxref{Traceframe Info Format})
34702 Branch trace (@pxref{Branch Trace Format},
34703 @pxref{Branch Trace Configuration Format})
34708 @value{GDBN} can use the GNU MPFR multiple-precision floating-point
34709 library. This library may be included with your operating system
34710 distribution; if it is not, you can get the latest version from
34711 @url{http://www.mpfr.org}. The @file{configure} script will search
34712 for this library in several standard locations; if it is installed
34713 in an unusual path, you can use the @option{--with-libmpfr-prefix}
34714 option to specify its location.
34716 GNU MPFR is used to emulate target floating-point arithmetic during
34717 expression evaluation when the target uses different floating-point
34718 formats than the host. If GNU MPFR it is not available, @value{GDBN}
34719 will fall back to using host floating-point arithmetic.
34722 @cindex compressed debug sections
34723 @value{GDBN} will use the @samp{zlib} library, if available, to read
34724 compressed debug sections. Some linkers, such as GNU gold, are capable
34725 of producing binaries with compressed debug sections. If @value{GDBN}
34726 is compiled with @samp{zlib}, it will be able to read the debug
34727 information in such binaries.
34729 The @samp{zlib} library is likely included with your operating system
34730 distribution; if it is not, you can get the latest version from
34731 @url{http://zlib.net}.
34734 @value{GDBN}'s features related to character sets (@pxref{Character
34735 Sets}) require a functioning @code{iconv} implementation. If you are
34736 on a GNU system, then this is provided by the GNU C Library. Some
34737 other systems also provide a working @code{iconv}.
34739 If @value{GDBN} is using the @code{iconv} program which is installed
34740 in a non-standard place, you will need to tell @value{GDBN} where to find it.
34741 This is done with @option{--with-iconv-bin} which specifies the
34742 directory that contains the @code{iconv} program.
34744 On systems without @code{iconv}, you can install GNU Libiconv. If you
34745 have previously installed Libiconv, you can use the
34746 @option{--with-libiconv-prefix} option to configure.
34748 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
34749 arrange to build Libiconv if a directory named @file{libiconv} appears
34750 in the top-most source directory. If Libiconv is built this way, and
34751 if the operating system does not provide a suitable @code{iconv}
34752 implementation, then the just-built library will automatically be used
34753 by @value{GDBN}. One easy way to set this up is to download GNU
34754 Libiconv, unpack it, and then rename the directory holding the
34755 Libiconv source code to @samp{libiconv}.
34758 @node Running Configure
34759 @section Invoking the @value{GDBN} @file{configure} Script
34760 @cindex configuring @value{GDBN}
34761 @value{GDBN} comes with a @file{configure} script that automates the process
34762 of preparing @value{GDBN} for installation; you can then use @code{make} to
34763 build the @code{gdb} program.
34765 @c irrelevant in info file; it's as current as the code it lives with.
34766 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
34767 look at the @file{README} file in the sources; we may have improved the
34768 installation procedures since publishing this manual.}
34771 The @value{GDBN} distribution includes all the source code you need for
34772 @value{GDBN} in a single directory, whose name is usually composed by
34773 appending the version number to @samp{gdb}.
34775 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
34776 @file{gdb-@value{GDBVN}} directory. That directory contains:
34779 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
34780 script for configuring @value{GDBN} and all its supporting libraries
34782 @item gdb-@value{GDBVN}/gdb
34783 the source specific to @value{GDBN} itself
34785 @item gdb-@value{GDBVN}/bfd
34786 source for the Binary File Descriptor library
34788 @item gdb-@value{GDBVN}/include
34789 @sc{gnu} include files
34791 @item gdb-@value{GDBVN}/libiberty
34792 source for the @samp{-liberty} free software library
34794 @item gdb-@value{GDBVN}/opcodes
34795 source for the library of opcode tables and disassemblers
34797 @item gdb-@value{GDBVN}/readline
34798 source for the @sc{gnu} command-line interface
34800 @item gdb-@value{GDBVN}/glob
34801 source for the @sc{gnu} filename pattern-matching subroutine
34803 @item gdb-@value{GDBVN}/mmalloc
34804 source for the @sc{gnu} memory-mapped malloc package
34807 The simplest way to configure and build @value{GDBN} is to run @file{configure}
34808 from the @file{gdb-@var{version-number}} source directory, which in
34809 this example is the @file{gdb-@value{GDBVN}} directory.
34811 First switch to the @file{gdb-@var{version-number}} source directory
34812 if you are not already in it; then run @file{configure}. Pass the
34813 identifier for the platform on which @value{GDBN} will run as an
34819 cd gdb-@value{GDBVN}
34820 ./configure @var{host}
34825 where @var{host} is an identifier such as @samp{sun4} or
34826 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
34827 (You can often leave off @var{host}; @file{configure} tries to guess the
34828 correct value by examining your system.)
34830 Running @samp{configure @var{host}} and then running @code{make} builds the
34831 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
34832 libraries, then @code{gdb} itself. The configured source files, and the
34833 binaries, are left in the corresponding source directories.
34836 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
34837 system does not recognize this automatically when you run a different
34838 shell, you may need to run @code{sh} on it explicitly:
34841 sh configure @var{host}
34844 If you run @file{configure} from a directory that contains source
34845 directories for multiple libraries or programs, such as the
34846 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
34848 creates configuration files for every directory level underneath (unless
34849 you tell it not to, with the @samp{--norecursion} option).
34851 You should run the @file{configure} script from the top directory in the
34852 source tree, the @file{gdb-@var{version-number}} directory. If you run
34853 @file{configure} from one of the subdirectories, you will configure only
34854 that subdirectory. That is usually not what you want. In particular,
34855 if you run the first @file{configure} from the @file{gdb} subdirectory
34856 of the @file{gdb-@var{version-number}} directory, you will omit the
34857 configuration of @file{bfd}, @file{readline}, and other sibling
34858 directories of the @file{gdb} subdirectory. This leads to build errors
34859 about missing include files such as @file{bfd/bfd.h}.
34861 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
34862 However, you should make sure that the shell on your path (named by
34863 the @samp{SHELL} environment variable) is publicly readable. Remember
34864 that @value{GDBN} uses the shell to start your program---some systems refuse to
34865 let @value{GDBN} debug child processes whose programs are not readable.
34867 @node Separate Objdir
34868 @section Compiling @value{GDBN} in Another Directory
34870 If you want to run @value{GDBN} versions for several host or target machines,
34871 you need a different @code{gdb} compiled for each combination of
34872 host and target. @file{configure} is designed to make this easy by
34873 allowing you to generate each configuration in a separate subdirectory,
34874 rather than in the source directory. If your @code{make} program
34875 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
34876 @code{make} in each of these directories builds the @code{gdb}
34877 program specified there.
34879 To build @code{gdb} in a separate directory, run @file{configure}
34880 with the @samp{--srcdir} option to specify where to find the source.
34881 (You also need to specify a path to find @file{configure}
34882 itself from your working directory. If the path to @file{configure}
34883 would be the same as the argument to @samp{--srcdir}, you can leave out
34884 the @samp{--srcdir} option; it is assumed.)
34886 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
34887 separate directory for a Sun 4 like this:
34891 cd gdb-@value{GDBVN}
34894 ../gdb-@value{GDBVN}/configure sun4
34899 When @file{configure} builds a configuration using a remote source
34900 directory, it creates a tree for the binaries with the same structure
34901 (and using the same names) as the tree under the source directory. In
34902 the example, you'd find the Sun 4 library @file{libiberty.a} in the
34903 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
34904 @file{gdb-sun4/gdb}.
34906 Make sure that your path to the @file{configure} script has just one
34907 instance of @file{gdb} in it. If your path to @file{configure} looks
34908 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
34909 one subdirectory of @value{GDBN}, not the whole package. This leads to
34910 build errors about missing include files such as @file{bfd/bfd.h}.
34912 One popular reason to build several @value{GDBN} configurations in separate
34913 directories is to configure @value{GDBN} for cross-compiling (where
34914 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
34915 programs that run on another machine---the @dfn{target}).
34916 You specify a cross-debugging target by
34917 giving the @samp{--target=@var{target}} option to @file{configure}.
34919 When you run @code{make} to build a program or library, you must run
34920 it in a configured directory---whatever directory you were in when you
34921 called @file{configure} (or one of its subdirectories).
34923 The @code{Makefile} that @file{configure} generates in each source
34924 directory also runs recursively. If you type @code{make} in a source
34925 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
34926 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
34927 will build all the required libraries, and then build GDB.
34929 When you have multiple hosts or targets configured in separate
34930 directories, you can run @code{make} on them in parallel (for example,
34931 if they are NFS-mounted on each of the hosts); they will not interfere
34935 @section Specifying Names for Hosts and Targets
34937 The specifications used for hosts and targets in the @file{configure}
34938 script are based on a three-part naming scheme, but some short predefined
34939 aliases are also supported. The full naming scheme encodes three pieces
34940 of information in the following pattern:
34943 @var{architecture}-@var{vendor}-@var{os}
34946 For example, you can use the alias @code{sun4} as a @var{host} argument,
34947 or as the value for @var{target} in a @code{--target=@var{target}}
34948 option. The equivalent full name is @samp{sparc-sun-sunos4}.
34950 The @file{configure} script accompanying @value{GDBN} does not provide
34951 any query facility to list all supported host and target names or
34952 aliases. @file{configure} calls the Bourne shell script
34953 @code{config.sub} to map abbreviations to full names; you can read the
34954 script, if you wish, or you can use it to test your guesses on
34955 abbreviations---for example:
34958 % sh config.sub i386-linux
34960 % sh config.sub alpha-linux
34961 alpha-unknown-linux-gnu
34962 % sh config.sub hp9k700
34964 % sh config.sub sun4
34965 sparc-sun-sunos4.1.1
34966 % sh config.sub sun3
34967 m68k-sun-sunos4.1.1
34968 % sh config.sub i986v
34969 Invalid configuration `i986v': machine `i986v' not recognized
34973 @code{config.sub} is also distributed in the @value{GDBN} source
34974 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
34976 @node Configure Options
34977 @section @file{configure} Options
34979 Here is a summary of the @file{configure} options and arguments that
34980 are most often useful for building @value{GDBN}. @file{configure} also has
34981 several other options not listed here. @inforef{What Configure
34982 Does,,configure.info}, for a full explanation of @file{configure}.
34985 configure @r{[}--help@r{]}
34986 @r{[}--prefix=@var{dir}@r{]}
34987 @r{[}--exec-prefix=@var{dir}@r{]}
34988 @r{[}--srcdir=@var{dirname}@r{]}
34989 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
34990 @r{[}--target=@var{target}@r{]}
34995 You may introduce options with a single @samp{-} rather than
34996 @samp{--} if you prefer; but you may abbreviate option names if you use
35001 Display a quick summary of how to invoke @file{configure}.
35003 @item --prefix=@var{dir}
35004 Configure the source to install programs and files under directory
35007 @item --exec-prefix=@var{dir}
35008 Configure the source to install programs under directory
35011 @c avoid splitting the warning from the explanation:
35013 @item --srcdir=@var{dirname}
35014 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
35015 @code{make} that implements the @code{VPATH} feature.}@*
35016 Use this option to make configurations in directories separate from the
35017 @value{GDBN} source directories. Among other things, you can use this to
35018 build (or maintain) several configurations simultaneously, in separate
35019 directories. @file{configure} writes configuration-specific files in
35020 the current directory, but arranges for them to use the source in the
35021 directory @var{dirname}. @file{configure} creates directories under
35022 the working directory in parallel to the source directories below
35025 @item --norecursion
35026 Configure only the directory level where @file{configure} is executed; do not
35027 propagate configuration to subdirectories.
35029 @item --target=@var{target}
35030 Configure @value{GDBN} for cross-debugging programs running on the specified
35031 @var{target}. Without this option, @value{GDBN} is configured to debug
35032 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
35034 There is no convenient way to generate a list of all available targets.
35036 @item @var{host} @dots{}
35037 Configure @value{GDBN} to run on the specified @var{host}.
35039 There is no convenient way to generate a list of all available hosts.
35042 There are many other options available as well, but they are generally
35043 needed for special purposes only.
35045 @node System-wide configuration
35046 @section System-wide configuration and settings
35047 @cindex system-wide init file
35049 @value{GDBN} can be configured to have a system-wide init file;
35050 this file will be read and executed at startup (@pxref{Startup, , What
35051 @value{GDBN} does during startup}).
35053 Here is the corresponding configure option:
35056 @item --with-system-gdbinit=@var{file}
35057 Specify that the default location of the system-wide init file is
35061 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
35062 it may be subject to relocation. Two possible cases:
35066 If the default location of this init file contains @file{$prefix},
35067 it will be subject to relocation. Suppose that the configure options
35068 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
35069 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
35070 init file is looked for as @file{$install/etc/gdbinit} instead of
35071 @file{$prefix/etc/gdbinit}.
35074 By contrast, if the default location does not contain the prefix,
35075 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
35076 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
35077 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
35078 wherever @value{GDBN} is installed.
35081 If the configured location of the system-wide init file (as given by the
35082 @option{--with-system-gdbinit} option at configure time) is in the
35083 data-directory (as specified by @option{--with-gdb-datadir} at configure
35084 time) or in one of its subdirectories, then @value{GDBN} will look for the
35085 system-wide init file in the directory specified by the
35086 @option{--data-directory} command-line option.
35087 Note that the system-wide init file is only read once, during @value{GDBN}
35088 initialization. If the data-directory is changed after @value{GDBN} has
35089 started with the @code{set data-directory} command, the file will not be
35093 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
35096 @node System-wide Configuration Scripts
35097 @subsection Installed System-wide Configuration Scripts
35098 @cindex system-wide configuration scripts
35100 The @file{system-gdbinit} directory, located inside the data-directory
35101 (as specified by @option{--with-gdb-datadir} at configure time) contains
35102 a number of scripts which can be used as system-wide init files. To
35103 automatically source those scripts at startup, @value{GDBN} should be
35104 configured with @option{--with-system-gdbinit}. Otherwise, any user
35105 should be able to source them by hand as needed.
35107 The following scripts are currently available:
35110 @item @file{elinos.py}
35112 @cindex ELinOS system-wide configuration script
35113 This script is useful when debugging a program on an ELinOS target.
35114 It takes advantage of the environment variables defined in a standard
35115 ELinOS environment in order to determine the location of the system
35116 shared libraries, and then sets the @samp{solib-absolute-prefix}
35117 and @samp{solib-search-path} variables appropriately.
35119 @item @file{wrs-linux.py}
35120 @pindex wrs-linux.py
35121 @cindex Wind River Linux system-wide configuration script
35122 This script is useful when debugging a program on a target running
35123 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
35124 the host-side sysroot used by the target system.
35128 @node Maintenance Commands
35129 @appendix Maintenance Commands
35130 @cindex maintenance commands
35131 @cindex internal commands
35133 In addition to commands intended for @value{GDBN} users, @value{GDBN}
35134 includes a number of commands intended for @value{GDBN} developers,
35135 that are not documented elsewhere in this manual. These commands are
35136 provided here for reference. (For commands that turn on debugging
35137 messages, see @ref{Debugging Output}.)
35140 @kindex maint agent
35141 @kindex maint agent-eval
35142 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
35143 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
35144 Translate the given @var{expression} into remote agent bytecodes.
35145 This command is useful for debugging the Agent Expression mechanism
35146 (@pxref{Agent Expressions}). The @samp{agent} version produces an
35147 expression useful for data collection, such as by tracepoints, while
35148 @samp{maint agent-eval} produces an expression that evaluates directly
35149 to a result. For instance, a collection expression for @code{globa +
35150 globb} will include bytecodes to record four bytes of memory at each
35151 of the addresses of @code{globa} and @code{globb}, while discarding
35152 the result of the addition, while an evaluation expression will do the
35153 addition and return the sum.
35154 If @code{-at} is given, generate remote agent bytecode for @var{location}.
35155 If not, generate remote agent bytecode for current frame PC address.
35157 @kindex maint agent-printf
35158 @item maint agent-printf @var{format},@var{expr},...
35159 Translate the given format string and list of argument expressions
35160 into remote agent bytecodes and display them as a disassembled list.
35161 This command is useful for debugging the agent version of dynamic
35162 printf (@pxref{Dynamic Printf}).
35164 @kindex maint info breakpoints
35165 @item @anchor{maint info breakpoints}maint info breakpoints
35166 Using the same format as @samp{info breakpoints}, display both the
35167 breakpoints you've set explicitly, and those @value{GDBN} is using for
35168 internal purposes. Internal breakpoints are shown with negative
35169 breakpoint numbers. The type column identifies what kind of breakpoint
35174 Normal, explicitly set breakpoint.
35177 Normal, explicitly set watchpoint.
35180 Internal breakpoint, used to handle correctly stepping through
35181 @code{longjmp} calls.
35183 @item longjmp resume
35184 Internal breakpoint at the target of a @code{longjmp}.
35187 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
35190 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
35193 Shared library events.
35197 @kindex maint info btrace
35198 @item maint info btrace
35199 Pint information about raw branch tracing data.
35201 @kindex maint btrace packet-history
35202 @item maint btrace packet-history
35203 Print the raw branch trace packets that are used to compute the
35204 execution history for the @samp{record btrace} command. Both the
35205 information and the format in which it is printed depend on the btrace
35210 For the BTS recording format, print a list of blocks of sequential
35211 code. For each block, the following information is printed:
35215 Newer blocks have higher numbers. The oldest block has number zero.
35216 @item Lowest @samp{PC}
35217 @item Highest @samp{PC}
35221 For the Intel Processor Trace recording format, print a list of
35222 Intel Processor Trace packets. For each packet, the following
35223 information is printed:
35226 @item Packet number
35227 Newer packets have higher numbers. The oldest packet has number zero.
35229 The packet's offset in the trace stream.
35230 @item Packet opcode and payload
35234 @kindex maint btrace clear-packet-history
35235 @item maint btrace clear-packet-history
35236 Discards the cached packet history printed by the @samp{maint btrace
35237 packet-history} command. The history will be computed again when
35240 @kindex maint btrace clear
35241 @item maint btrace clear
35242 Discard the branch trace data. The data will be fetched anew and the
35243 branch trace will be recomputed when needed.
35245 This implicitly truncates the branch trace to a single branch trace
35246 buffer. When updating branch trace incrementally, the branch trace
35247 available to @value{GDBN} may be bigger than a single branch trace
35250 @kindex maint set btrace pt skip-pad
35251 @item maint set btrace pt skip-pad
35252 @kindex maint show btrace pt skip-pad
35253 @item maint show btrace pt skip-pad
35254 Control whether @value{GDBN} will skip PAD packets when computing the
35257 @kindex set displaced-stepping
35258 @kindex show displaced-stepping
35259 @cindex displaced stepping support
35260 @cindex out-of-line single-stepping
35261 @item set displaced-stepping
35262 @itemx show displaced-stepping
35263 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
35264 if the target supports it. Displaced stepping is a way to single-step
35265 over breakpoints without removing them from the inferior, by executing
35266 an out-of-line copy of the instruction that was originally at the
35267 breakpoint location. It is also known as out-of-line single-stepping.
35270 @item set displaced-stepping on
35271 If the target architecture supports it, @value{GDBN} will use
35272 displaced stepping to step over breakpoints.
35274 @item set displaced-stepping off
35275 @value{GDBN} will not use displaced stepping to step over breakpoints,
35276 even if such is supported by the target architecture.
35278 @cindex non-stop mode, and @samp{set displaced-stepping}
35279 @item set displaced-stepping auto
35280 This is the default mode. @value{GDBN} will use displaced stepping
35281 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
35282 architecture supports displaced stepping.
35285 @kindex maint check-psymtabs
35286 @item maint check-psymtabs
35287 Check the consistency of currently expanded psymtabs versus symtabs.
35288 Use this to check, for example, whether a symbol is in one but not the other.
35290 @kindex maint check-symtabs
35291 @item maint check-symtabs
35292 Check the consistency of currently expanded symtabs.
35294 @kindex maint expand-symtabs
35295 @item maint expand-symtabs [@var{regexp}]
35296 Expand symbol tables.
35297 If @var{regexp} is specified, only expand symbol tables for file
35298 names matching @var{regexp}.
35300 @kindex maint set catch-demangler-crashes
35301 @kindex maint show catch-demangler-crashes
35302 @cindex demangler crashes
35303 @item maint set catch-demangler-crashes [on|off]
35304 @itemx maint show catch-demangler-crashes
35305 Control whether @value{GDBN} should attempt to catch crashes in the
35306 symbol name demangler. The default is to attempt to catch crashes.
35307 If enabled, the first time a crash is caught, a core file is created,
35308 the offending symbol is displayed and the user is presented with the
35309 option to terminate the current session.
35311 @kindex maint cplus first_component
35312 @item maint cplus first_component @var{name}
35313 Print the first C@t{++} class/namespace component of @var{name}.
35315 @kindex maint cplus namespace
35316 @item maint cplus namespace
35317 Print the list of possible C@t{++} namespaces.
35319 @kindex maint deprecate
35320 @kindex maint undeprecate
35321 @cindex deprecated commands
35322 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
35323 @itemx maint undeprecate @var{command}
35324 Deprecate or undeprecate the named @var{command}. Deprecated commands
35325 cause @value{GDBN} to issue a warning when you use them. The optional
35326 argument @var{replacement} says which newer command should be used in
35327 favor of the deprecated one; if it is given, @value{GDBN} will mention
35328 the replacement as part of the warning.
35330 @kindex maint dump-me
35331 @item maint dump-me
35332 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
35333 Cause a fatal signal in the debugger and force it to dump its core.
35334 This is supported only on systems which support aborting a program
35335 with the @code{SIGQUIT} signal.
35337 @kindex maint internal-error
35338 @kindex maint internal-warning
35339 @kindex maint demangler-warning
35340 @cindex demangler crashes
35341 @item maint internal-error @r{[}@var{message-text}@r{]}
35342 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
35343 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
35345 Cause @value{GDBN} to call the internal function @code{internal_error},
35346 @code{internal_warning} or @code{demangler_warning} and hence behave
35347 as though an internal problem has been detected. In addition to
35348 reporting the internal problem, these functions give the user the
35349 opportunity to either quit @value{GDBN} or (for @code{internal_error}
35350 and @code{internal_warning}) create a core file of the current
35351 @value{GDBN} session.
35353 These commands take an optional parameter @var{message-text} that is
35354 used as the text of the error or warning message.
35356 Here's an example of using @code{internal-error}:
35359 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
35360 @dots{}/maint.c:121: internal-error: testing, 1, 2
35361 A problem internal to GDB has been detected. Further
35362 debugging may prove unreliable.
35363 Quit this debugging session? (y or n) @kbd{n}
35364 Create a core file? (y or n) @kbd{n}
35368 @cindex @value{GDBN} internal error
35369 @cindex internal errors, control of @value{GDBN} behavior
35370 @cindex demangler crashes
35372 @kindex maint set internal-error
35373 @kindex maint show internal-error
35374 @kindex maint set internal-warning
35375 @kindex maint show internal-warning
35376 @kindex maint set demangler-warning
35377 @kindex maint show demangler-warning
35378 @item maint set internal-error @var{action} [ask|yes|no]
35379 @itemx maint show internal-error @var{action}
35380 @itemx maint set internal-warning @var{action} [ask|yes|no]
35381 @itemx maint show internal-warning @var{action}
35382 @itemx maint set demangler-warning @var{action} [ask|yes|no]
35383 @itemx maint show demangler-warning @var{action}
35384 When @value{GDBN} reports an internal problem (error or warning) it
35385 gives the user the opportunity to both quit @value{GDBN} and create a
35386 core file of the current @value{GDBN} session. These commands let you
35387 override the default behaviour for each particular @var{action},
35388 described in the table below.
35392 You can specify that @value{GDBN} should always (yes) or never (no)
35393 quit. The default is to ask the user what to do.
35396 You can specify that @value{GDBN} should always (yes) or never (no)
35397 create a core file. The default is to ask the user what to do. Note
35398 that there is no @code{corefile} option for @code{demangler-warning}:
35399 demangler warnings always create a core file and this cannot be
35403 @kindex maint packet
35404 @item maint packet @var{text}
35405 If @value{GDBN} is talking to an inferior via the serial protocol,
35406 then this command sends the string @var{text} to the inferior, and
35407 displays the response packet. @value{GDBN} supplies the initial
35408 @samp{$} character, the terminating @samp{#} character, and the
35411 @kindex maint print architecture
35412 @item maint print architecture @r{[}@var{file}@r{]}
35413 Print the entire architecture configuration. The optional argument
35414 @var{file} names the file where the output goes.
35416 @kindex maint print c-tdesc @r{[}@var{file}@r{]}
35417 @item maint print c-tdesc
35418 Print the target description (@pxref{Target Descriptions}) as
35419 a C source file. By default, the target description is for the current
35420 target, but if the optional argument @var{file} is provided, that file
35421 is used to produce the description. The @var{file} should be an XML
35422 document, of the form described in @ref{Target Description Format}.
35423 The created source file is built into @value{GDBN} when @value{GDBN} is
35424 built again. This command is used by developers after they add or
35425 modify XML target descriptions.
35427 @kindex maint check xml-descriptions
35428 @item maint check xml-descriptions @var{dir}
35429 Check that the target descriptions dynamically created by @value{GDBN}
35430 equal the descriptions created from XML files found in @var{dir}.
35432 @kindex maint print dummy-frames
35433 @item maint print dummy-frames
35434 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
35437 (@value{GDBP}) @kbd{b add}
35439 (@value{GDBP}) @kbd{print add(2,3)}
35440 Breakpoint 2, add (a=2, b=3) at @dots{}
35442 The program being debugged stopped while in a function called from GDB.
35444 (@value{GDBP}) @kbd{maint print dummy-frames}
35445 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
35449 Takes an optional file parameter.
35451 @kindex maint print registers
35452 @kindex maint print raw-registers
35453 @kindex maint print cooked-registers
35454 @kindex maint print register-groups
35455 @kindex maint print remote-registers
35456 @item maint print registers @r{[}@var{file}@r{]}
35457 @itemx maint print raw-registers @r{[}@var{file}@r{]}
35458 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
35459 @itemx maint print register-groups @r{[}@var{file}@r{]}
35460 @itemx maint print remote-registers @r{[}@var{file}@r{]}
35461 Print @value{GDBN}'s internal register data structures.
35463 The command @code{maint print raw-registers} includes the contents of
35464 the raw register cache; the command @code{maint print
35465 cooked-registers} includes the (cooked) value of all registers,
35466 including registers which aren't available on the target nor visible
35467 to user; the command @code{maint print register-groups} includes the
35468 groups that each register is a member of; and the command @code{maint
35469 print remote-registers} includes the remote target's register numbers
35470 and offsets in the `G' packets.
35472 These commands take an optional parameter, a file name to which to
35473 write the information.
35475 @kindex maint print reggroups
35476 @item maint print reggroups @r{[}@var{file}@r{]}
35477 Print @value{GDBN}'s internal register group data structures. The
35478 optional argument @var{file} tells to what file to write the
35481 The register groups info looks like this:
35484 (@value{GDBP}) @kbd{maint print reggroups}
35497 This command forces @value{GDBN} to flush its internal register cache.
35499 @kindex maint print objfiles
35500 @cindex info for known object files
35501 @item maint print objfiles @r{[}@var{regexp}@r{]}
35502 Print a dump of all known object files.
35503 If @var{regexp} is specified, only print object files whose names
35504 match @var{regexp}. For each object file, this command prints its name,
35505 address in memory, and all of its psymtabs and symtabs.
35507 @kindex maint print user-registers
35508 @cindex user registers
35509 @item maint print user-registers
35510 List all currently available @dfn{user registers}. User registers
35511 typically provide alternate names for actual hardware registers. They
35512 include the four ``standard'' registers @code{$fp}, @code{$pc},
35513 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
35514 registers can be used in expressions in the same way as the canonical
35515 register names, but only the latter are listed by the @code{info
35516 registers} and @code{maint print registers} commands.
35518 @kindex maint print section-scripts
35519 @cindex info for known .debug_gdb_scripts-loaded scripts
35520 @item maint print section-scripts [@var{regexp}]
35521 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
35522 If @var{regexp} is specified, only print scripts loaded by object files
35523 matching @var{regexp}.
35524 For each script, this command prints its name as specified in the objfile,
35525 and the full path if known.
35526 @xref{dotdebug_gdb_scripts section}.
35528 @kindex maint print statistics
35529 @cindex bcache statistics
35530 @item maint print statistics
35531 This command prints, for each object file in the program, various data
35532 about that object file followed by the byte cache (@dfn{bcache})
35533 statistics for the object file. The objfile data includes the number
35534 of minimal, partial, full, and stabs symbols, the number of types
35535 defined by the objfile, the number of as yet unexpanded psym tables,
35536 the number of line tables and string tables, and the amount of memory
35537 used by the various tables. The bcache statistics include the counts,
35538 sizes, and counts of duplicates of all and unique objects, max,
35539 average, and median entry size, total memory used and its overhead and
35540 savings, and various measures of the hash table size and chain
35543 @kindex maint print target-stack
35544 @cindex target stack description
35545 @item maint print target-stack
35546 A @dfn{target} is an interface between the debugger and a particular
35547 kind of file or process. Targets can be stacked in @dfn{strata},
35548 so that more than one target can potentially respond to a request.
35549 In particular, memory accesses will walk down the stack of targets
35550 until they find a target that is interested in handling that particular
35553 This command prints a short description of each layer that was pushed on
35554 the @dfn{target stack}, starting from the top layer down to the bottom one.
35556 @kindex maint print type
35557 @cindex type chain of a data type
35558 @item maint print type @var{expr}
35559 Print the type chain for a type specified by @var{expr}. The argument
35560 can be either a type name or a symbol. If it is a symbol, the type of
35561 that symbol is described. The type chain produced by this command is
35562 a recursive definition of the data type as stored in @value{GDBN}'s
35563 data structures, including its flags and contained types.
35565 @kindex maint selftest
35567 @item maint selftest @r{[}@var{filter}@r{]}
35568 Run any self tests that were compiled in to @value{GDBN}. This will
35569 print a message showing how many tests were run, and how many failed.
35570 If a @var{filter} is passed, only the tests with @var{filter} in their
35573 @kindex "maint info selftests"
35575 @item maint info selftests
35576 List the selftests compiled in to @value{GDBN}.
35578 @kindex maint set dwarf always-disassemble
35579 @kindex maint show dwarf always-disassemble
35580 @item maint set dwarf always-disassemble
35581 @item maint show dwarf always-disassemble
35582 Control the behavior of @code{info address} when using DWARF debugging
35585 The default is @code{off}, which means that @value{GDBN} should try to
35586 describe a variable's location in an easily readable format. When
35587 @code{on}, @value{GDBN} will instead display the DWARF location
35588 expression in an assembly-like format. Note that some locations are
35589 too complex for @value{GDBN} to describe simply; in this case you will
35590 always see the disassembly form.
35592 Here is an example of the resulting disassembly:
35595 (gdb) info addr argc
35596 Symbol "argc" is a complex DWARF expression:
35600 For more information on these expressions, see
35601 @uref{http://www.dwarfstd.org/, the DWARF standard}.
35603 @kindex maint set dwarf max-cache-age
35604 @kindex maint show dwarf max-cache-age
35605 @item maint set dwarf max-cache-age
35606 @itemx maint show dwarf max-cache-age
35607 Control the DWARF compilation unit cache.
35609 @cindex DWARF compilation units cache
35610 In object files with inter-compilation-unit references, such as those
35611 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
35612 reader needs to frequently refer to previously read compilation units.
35613 This setting controls how long a compilation unit will remain in the
35614 cache if it is not referenced. A higher limit means that cached
35615 compilation units will be stored in memory longer, and more total
35616 memory will be used. Setting it to zero disables caching, which will
35617 slow down @value{GDBN} startup, but reduce memory consumption.
35619 @kindex maint set profile
35620 @kindex maint show profile
35621 @cindex profiling GDB
35622 @item maint set profile
35623 @itemx maint show profile
35624 Control profiling of @value{GDBN}.
35626 Profiling will be disabled until you use the @samp{maint set profile}
35627 command to enable it. When you enable profiling, the system will begin
35628 collecting timing and execution count data; when you disable profiling or
35629 exit @value{GDBN}, the results will be written to a log file. Remember that
35630 if you use profiling, @value{GDBN} will overwrite the profiling log file
35631 (often called @file{gmon.out}). If you have a record of important profiling
35632 data in a @file{gmon.out} file, be sure to move it to a safe location.
35634 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
35635 compiled with the @samp{-pg} compiler option.
35637 @kindex maint set show-debug-regs
35638 @kindex maint show show-debug-regs
35639 @cindex hardware debug registers
35640 @item maint set show-debug-regs
35641 @itemx maint show show-debug-regs
35642 Control whether to show variables that mirror the hardware debug
35643 registers. Use @code{on} to enable, @code{off} to disable. If
35644 enabled, the debug registers values are shown when @value{GDBN} inserts or
35645 removes a hardware breakpoint or watchpoint, and when the inferior
35646 triggers a hardware-assisted breakpoint or watchpoint.
35648 @kindex maint set show-all-tib
35649 @kindex maint show show-all-tib
35650 @item maint set show-all-tib
35651 @itemx maint show show-all-tib
35652 Control whether to show all non zero areas within a 1k block starting
35653 at thread local base, when using the @samp{info w32 thread-information-block}
35656 @kindex maint set target-async
35657 @kindex maint show target-async
35658 @item maint set target-async
35659 @itemx maint show target-async
35660 This controls whether @value{GDBN} targets operate in synchronous or
35661 asynchronous mode (@pxref{Background Execution}). Normally the
35662 default is asynchronous, if it is available; but this can be changed
35663 to more easily debug problems occurring only in synchronous mode.
35665 @kindex maint set target-non-stop @var{mode} [on|off|auto]
35666 @kindex maint show target-non-stop
35667 @item maint set target-non-stop
35668 @itemx maint show target-non-stop
35670 This controls whether @value{GDBN} targets always operate in non-stop
35671 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
35672 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
35673 if supported by the target.
35676 @item maint set target-non-stop auto
35677 This is the default mode. @value{GDBN} controls the target in
35678 non-stop mode if the target supports it.
35680 @item maint set target-non-stop on
35681 @value{GDBN} controls the target in non-stop mode even if the target
35682 does not indicate support.
35684 @item maint set target-non-stop off
35685 @value{GDBN} does not control the target in non-stop mode even if the
35686 target supports it.
35689 @kindex maint set per-command
35690 @kindex maint show per-command
35691 @item maint set per-command
35692 @itemx maint show per-command
35693 @cindex resources used by commands
35695 @value{GDBN} can display the resources used by each command.
35696 This is useful in debugging performance problems.
35699 @item maint set per-command space [on|off]
35700 @itemx maint show per-command space
35701 Enable or disable the printing of the memory used by GDB for each command.
35702 If enabled, @value{GDBN} will display how much memory each command
35703 took, following the command's own output.
35704 This can also be requested by invoking @value{GDBN} with the
35705 @option{--statistics} command-line switch (@pxref{Mode Options}).
35707 @item maint set per-command time [on|off]
35708 @itemx maint show per-command time
35709 Enable or disable the printing of the execution time of @value{GDBN}
35711 If enabled, @value{GDBN} will display how much time it
35712 took to execute each command, following the command's own output.
35713 Both CPU time and wallclock time are printed.
35714 Printing both is useful when trying to determine whether the cost is
35715 CPU or, e.g., disk/network latency.
35716 Note that the CPU time printed is for @value{GDBN} only, it does not include
35717 the execution time of the inferior because there's no mechanism currently
35718 to compute how much time was spent by @value{GDBN} and how much time was
35719 spent by the program been debugged.
35720 This can also be requested by invoking @value{GDBN} with the
35721 @option{--statistics} command-line switch (@pxref{Mode Options}).
35723 @item maint set per-command symtab [on|off]
35724 @itemx maint show per-command symtab
35725 Enable or disable the printing of basic symbol table statistics
35727 If enabled, @value{GDBN} will display the following information:
35731 number of symbol tables
35733 number of primary symbol tables
35735 number of blocks in the blockvector
35739 @kindex maint space
35740 @cindex memory used by commands
35741 @item maint space @var{value}
35742 An alias for @code{maint set per-command space}.
35743 A non-zero value enables it, zero disables it.
35746 @cindex time of command execution
35747 @item maint time @var{value}
35748 An alias for @code{maint set per-command time}.
35749 A non-zero value enables it, zero disables it.
35751 @kindex maint translate-address
35752 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
35753 Find the symbol stored at the location specified by the address
35754 @var{addr} and an optional section name @var{section}. If found,
35755 @value{GDBN} prints the name of the closest symbol and an offset from
35756 the symbol's location to the specified address. This is similar to
35757 the @code{info address} command (@pxref{Symbols}), except that this
35758 command also allows to find symbols in other sections.
35760 If section was not specified, the section in which the symbol was found
35761 is also printed. For dynamically linked executables, the name of
35762 executable or shared library containing the symbol is printed as well.
35766 The following command is useful for non-interactive invocations of
35767 @value{GDBN}, such as in the test suite.
35770 @item set watchdog @var{nsec}
35771 @kindex set watchdog
35772 @cindex watchdog timer
35773 @cindex timeout for commands
35774 Set the maximum number of seconds @value{GDBN} will wait for the
35775 target operation to finish. If this time expires, @value{GDBN}
35776 reports and error and the command is aborted.
35778 @item show watchdog
35779 Show the current setting of the target wait timeout.
35782 @node Remote Protocol
35783 @appendix @value{GDBN} Remote Serial Protocol
35788 * Stop Reply Packets::
35789 * General Query Packets::
35790 * Architecture-Specific Protocol Details::
35791 * Tracepoint Packets::
35792 * Host I/O Packets::
35794 * Notification Packets::
35795 * Remote Non-Stop::
35796 * Packet Acknowledgment::
35798 * File-I/O Remote Protocol Extension::
35799 * Library List Format::
35800 * Library List Format for SVR4 Targets::
35801 * Memory Map Format::
35802 * Thread List Format::
35803 * Traceframe Info Format::
35804 * Branch Trace Format::
35805 * Branch Trace Configuration Format::
35811 There may be occasions when you need to know something about the
35812 protocol---for example, if there is only one serial port to your target
35813 machine, you might want your program to do something special if it
35814 recognizes a packet meant for @value{GDBN}.
35816 In the examples below, @samp{->} and @samp{<-} are used to indicate
35817 transmitted and received data, respectively.
35819 @cindex protocol, @value{GDBN} remote serial
35820 @cindex serial protocol, @value{GDBN} remote
35821 @cindex remote serial protocol
35822 All @value{GDBN} commands and responses (other than acknowledgments
35823 and notifications, see @ref{Notification Packets}) are sent as a
35824 @var{packet}. A @var{packet} is introduced with the character
35825 @samp{$}, the actual @var{packet-data}, and the terminating character
35826 @samp{#} followed by a two-digit @var{checksum}:
35829 @code{$}@var{packet-data}@code{#}@var{checksum}
35833 @cindex checksum, for @value{GDBN} remote
35835 The two-digit @var{checksum} is computed as the modulo 256 sum of all
35836 characters between the leading @samp{$} and the trailing @samp{#} (an
35837 eight bit unsigned checksum).
35839 Implementors should note that prior to @value{GDBN} 5.0 the protocol
35840 specification also included an optional two-digit @var{sequence-id}:
35843 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
35846 @cindex sequence-id, for @value{GDBN} remote
35848 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
35849 has never output @var{sequence-id}s. Stubs that handle packets added
35850 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
35852 When either the host or the target machine receives a packet, the first
35853 response expected is an acknowledgment: either @samp{+} (to indicate
35854 the package was received correctly) or @samp{-} (to request
35858 -> @code{$}@var{packet-data}@code{#}@var{checksum}
35863 The @samp{+}/@samp{-} acknowledgments can be disabled
35864 once a connection is established.
35865 @xref{Packet Acknowledgment}, for details.
35867 The host (@value{GDBN}) sends @var{command}s, and the target (the
35868 debugging stub incorporated in your program) sends a @var{response}. In
35869 the case of step and continue @var{command}s, the response is only sent
35870 when the operation has completed, and the target has again stopped all
35871 threads in all attached processes. This is the default all-stop mode
35872 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
35873 execution mode; see @ref{Remote Non-Stop}, for details.
35875 @var{packet-data} consists of a sequence of characters with the
35876 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
35879 @cindex remote protocol, field separator
35880 Fields within the packet should be separated using @samp{,} @samp{;} or
35881 @samp{:}. Except where otherwise noted all numbers are represented in
35882 @sc{hex} with leading zeros suppressed.
35884 Implementors should note that prior to @value{GDBN} 5.0, the character
35885 @samp{:} could not appear as the third character in a packet (as it
35886 would potentially conflict with the @var{sequence-id}).
35888 @cindex remote protocol, binary data
35889 @anchor{Binary Data}
35890 Binary data in most packets is encoded either as two hexadecimal
35891 digits per byte of binary data. This allowed the traditional remote
35892 protocol to work over connections which were only seven-bit clean.
35893 Some packets designed more recently assume an eight-bit clean
35894 connection, and use a more efficient encoding to send and receive
35897 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
35898 as an escape character. Any escaped byte is transmitted as the escape
35899 character followed by the original character XORed with @code{0x20}.
35900 For example, the byte @code{0x7d} would be transmitted as the two
35901 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
35902 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
35903 @samp{@}}) must always be escaped. Responses sent by the stub
35904 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
35905 is not interpreted as the start of a run-length encoded sequence
35908 Response @var{data} can be run-length encoded to save space.
35909 Run-length encoding replaces runs of identical characters with one
35910 instance of the repeated character, followed by a @samp{*} and a
35911 repeat count. The repeat count is itself sent encoded, to avoid
35912 binary characters in @var{data}: a value of @var{n} is sent as
35913 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
35914 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
35915 code 32) for a repeat count of 3. (This is because run-length
35916 encoding starts to win for counts 3 or more.) Thus, for example,
35917 @samp{0* } is a run-length encoding of ``0000'': the space character
35918 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
35921 The printable characters @samp{#} and @samp{$} or with a numeric value
35922 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
35923 seven repeats (@samp{$}) can be expanded using a repeat count of only
35924 five (@samp{"}). For example, @samp{00000000} can be encoded as
35927 The error response returned for some packets includes a two character
35928 error number. That number is not well defined.
35930 @cindex empty response, for unsupported packets
35931 For any @var{command} not supported by the stub, an empty response
35932 (@samp{$#00}) should be returned. That way it is possible to extend the
35933 protocol. A newer @value{GDBN} can tell if a packet is supported based
35936 At a minimum, a stub is required to support the @samp{g} and @samp{G}
35937 commands for register access, and the @samp{m} and @samp{M} commands
35938 for memory access. Stubs that only control single-threaded targets
35939 can implement run control with the @samp{c} (continue), and @samp{s}
35940 (step) commands. Stubs that support multi-threading targets should
35941 support the @samp{vCont} command. All other commands are optional.
35946 The following table provides a complete list of all currently defined
35947 @var{command}s and their corresponding response @var{data}.
35948 @xref{File-I/O Remote Protocol Extension}, for details about the File
35949 I/O extension of the remote protocol.
35951 Each packet's description has a template showing the packet's overall
35952 syntax, followed by an explanation of the packet's meaning. We
35953 include spaces in some of the templates for clarity; these are not
35954 part of the packet's syntax. No @value{GDBN} packet uses spaces to
35955 separate its components. For example, a template like @samp{foo
35956 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
35957 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
35958 @var{baz}. @value{GDBN} does not transmit a space character between the
35959 @samp{foo} and the @var{bar}, or between the @var{bar} and the
35962 @cindex @var{thread-id}, in remote protocol
35963 @anchor{thread-id syntax}
35964 Several packets and replies include a @var{thread-id} field to identify
35965 a thread. Normally these are positive numbers with a target-specific
35966 interpretation, formatted as big-endian hex strings. A @var{thread-id}
35967 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
35970 In addition, the remote protocol supports a multiprocess feature in
35971 which the @var{thread-id} syntax is extended to optionally include both
35972 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
35973 The @var{pid} (process) and @var{tid} (thread) components each have the
35974 format described above: a positive number with target-specific
35975 interpretation formatted as a big-endian hex string, literal @samp{-1}
35976 to indicate all processes or threads (respectively), or @samp{0} to
35977 indicate an arbitrary process or thread. Specifying just a process, as
35978 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
35979 error to specify all processes but a specific thread, such as
35980 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
35981 for those packets and replies explicitly documented to include a process
35982 ID, rather than a @var{thread-id}.
35984 The multiprocess @var{thread-id} syntax extensions are only used if both
35985 @value{GDBN} and the stub report support for the @samp{multiprocess}
35986 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
35989 Note that all packet forms beginning with an upper- or lower-case
35990 letter, other than those described here, are reserved for future use.
35992 Here are the packet descriptions.
35997 @cindex @samp{!} packet
35998 @anchor{extended mode}
35999 Enable extended mode. In extended mode, the remote server is made
36000 persistent. The @samp{R} packet is used to restart the program being
36006 The remote target both supports and has enabled extended mode.
36010 @cindex @samp{?} packet
36012 Indicate the reason the target halted. The reply is the same as for
36013 step and continue. This packet has a special interpretation when the
36014 target is in non-stop mode; see @ref{Remote Non-Stop}.
36017 @xref{Stop Reply Packets}, for the reply specifications.
36019 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
36020 @cindex @samp{A} packet
36021 Initialized @code{argv[]} array passed into program. @var{arglen}
36022 specifies the number of bytes in the hex encoded byte stream
36023 @var{arg}. See @code{gdbserver} for more details.
36028 The arguments were set.
36034 @cindex @samp{b} packet
36035 (Don't use this packet; its behavior is not well-defined.)
36036 Change the serial line speed to @var{baud}.
36038 JTC: @emph{When does the transport layer state change? When it's
36039 received, or after the ACK is transmitted. In either case, there are
36040 problems if the command or the acknowledgment packet is dropped.}
36042 Stan: @emph{If people really wanted to add something like this, and get
36043 it working for the first time, they ought to modify ser-unix.c to send
36044 some kind of out-of-band message to a specially-setup stub and have the
36045 switch happen "in between" packets, so that from remote protocol's point
36046 of view, nothing actually happened.}
36048 @item B @var{addr},@var{mode}
36049 @cindex @samp{B} packet
36050 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
36051 breakpoint at @var{addr}.
36053 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
36054 (@pxref{insert breakpoint or watchpoint packet}).
36056 @cindex @samp{bc} packet
36059 Backward continue. Execute the target system in reverse. No parameter.
36060 @xref{Reverse Execution}, for more information.
36063 @xref{Stop Reply Packets}, for the reply specifications.
36065 @cindex @samp{bs} packet
36068 Backward single step. Execute one instruction in reverse. No parameter.
36069 @xref{Reverse Execution}, for more information.
36072 @xref{Stop Reply Packets}, for the reply specifications.
36074 @item c @r{[}@var{addr}@r{]}
36075 @cindex @samp{c} packet
36076 Continue at @var{addr}, which is the address to resume. If @var{addr}
36077 is omitted, resume at current address.
36079 This packet is deprecated for multi-threading support. @xref{vCont
36083 @xref{Stop Reply Packets}, for the reply specifications.
36085 @item C @var{sig}@r{[};@var{addr}@r{]}
36086 @cindex @samp{C} packet
36087 Continue with signal @var{sig} (hex signal number). If
36088 @samp{;@var{addr}} is omitted, resume at same address.
36090 This packet is deprecated for multi-threading support. @xref{vCont
36094 @xref{Stop Reply Packets}, for the reply specifications.
36097 @cindex @samp{d} packet
36100 Don't use this packet; instead, define a general set packet
36101 (@pxref{General Query Packets}).
36105 @cindex @samp{D} packet
36106 The first form of the packet is used to detach @value{GDBN} from the
36107 remote system. It is sent to the remote target
36108 before @value{GDBN} disconnects via the @code{detach} command.
36110 The second form, including a process ID, is used when multiprocess
36111 protocol extensions are enabled (@pxref{multiprocess extensions}), to
36112 detach only a specific process. The @var{pid} is specified as a
36113 big-endian hex string.
36123 @item F @var{RC},@var{EE},@var{CF};@var{XX}
36124 @cindex @samp{F} packet
36125 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
36126 This is part of the File-I/O protocol extension. @xref{File-I/O
36127 Remote Protocol Extension}, for the specification.
36130 @anchor{read registers packet}
36131 @cindex @samp{g} packet
36132 Read general registers.
36136 @item @var{XX@dots{}}
36137 Each byte of register data is described by two hex digits. The bytes
36138 with the register are transmitted in target byte order. The size of
36139 each register and their position within the @samp{g} packet are
36140 determined by the @value{GDBN} internal gdbarch functions
36141 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
36143 When reading registers from a trace frame (@pxref{Analyze Collected
36144 Data,,Using the Collected Data}), the stub may also return a string of
36145 literal @samp{x}'s in place of the register data digits, to indicate
36146 that the corresponding register has not been collected, thus its value
36147 is unavailable. For example, for an architecture with 4 registers of
36148 4 bytes each, the following reply indicates to @value{GDBN} that
36149 registers 0 and 2 have not been collected, while registers 1 and 3
36150 have been collected, and both have zero value:
36154 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
36161 @item G @var{XX@dots{}}
36162 @cindex @samp{G} packet
36163 Write general registers. @xref{read registers packet}, for a
36164 description of the @var{XX@dots{}} data.
36174 @item H @var{op} @var{thread-id}
36175 @cindex @samp{H} packet
36176 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
36177 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
36178 should be @samp{c} for step and continue operations (note that this
36179 is deprecated, supporting the @samp{vCont} command is a better
36180 option), and @samp{g} for other operations. The thread designator
36181 @var{thread-id} has the format and interpretation described in
36182 @ref{thread-id syntax}.
36193 @c 'H': How restrictive (or permissive) is the thread model. If a
36194 @c thread is selected and stopped, are other threads allowed
36195 @c to continue to execute? As I mentioned above, I think the
36196 @c semantics of each command when a thread is selected must be
36197 @c described. For example:
36199 @c 'g': If the stub supports threads and a specific thread is
36200 @c selected, returns the register block from that thread;
36201 @c otherwise returns current registers.
36203 @c 'G' If the stub supports threads and a specific thread is
36204 @c selected, sets the registers of the register block of
36205 @c that thread; otherwise sets current registers.
36207 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
36208 @anchor{cycle step packet}
36209 @cindex @samp{i} packet
36210 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
36211 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
36212 step starting at that address.
36215 @cindex @samp{I} packet
36216 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
36220 @cindex @samp{k} packet
36223 The exact effect of this packet is not specified.
36225 For a bare-metal target, it may power cycle or reset the target
36226 system. For that reason, the @samp{k} packet has no reply.
36228 For a single-process target, it may kill that process if possible.
36230 A multiple-process target may choose to kill just one process, or all
36231 that are under @value{GDBN}'s control. For more precise control, use
36232 the vKill packet (@pxref{vKill packet}).
36234 If the target system immediately closes the connection in response to
36235 @samp{k}, @value{GDBN} does not consider the lack of packet
36236 acknowledgment to be an error, and assumes the kill was successful.
36238 If connected using @kbd{target extended-remote}, and the target does
36239 not close the connection in response to a kill request, @value{GDBN}
36240 probes the target state as if a new connection was opened
36241 (@pxref{? packet}).
36243 @item m @var{addr},@var{length}
36244 @cindex @samp{m} packet
36245 Read @var{length} addressable memory units starting at address @var{addr}
36246 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
36247 any particular boundary.
36249 The stub need not use any particular size or alignment when gathering
36250 data from memory for the response; even if @var{addr} is word-aligned
36251 and @var{length} is a multiple of the word size, the stub is free to
36252 use byte accesses, or not. For this reason, this packet may not be
36253 suitable for accessing memory-mapped I/O devices.
36254 @cindex alignment of remote memory accesses
36255 @cindex size of remote memory accesses
36256 @cindex memory, alignment and size of remote accesses
36260 @item @var{XX@dots{}}
36261 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
36262 The reply may contain fewer addressable memory units than requested if the
36263 server was able to read only part of the region of memory.
36268 @item M @var{addr},@var{length}:@var{XX@dots{}}
36269 @cindex @samp{M} packet
36270 Write @var{length} addressable memory units starting at address @var{addr}
36271 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
36272 byte is transmitted as a two-digit hexadecimal number.
36279 for an error (this includes the case where only part of the data was
36284 @cindex @samp{p} packet
36285 Read the value of register @var{n}; @var{n} is in hex.
36286 @xref{read registers packet}, for a description of how the returned
36287 register value is encoded.
36291 @item @var{XX@dots{}}
36292 the register's value
36296 Indicating an unrecognized @var{query}.
36299 @item P @var{n@dots{}}=@var{r@dots{}}
36300 @anchor{write register packet}
36301 @cindex @samp{P} packet
36302 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
36303 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
36304 digits for each byte in the register (target byte order).
36314 @item q @var{name} @var{params}@dots{}
36315 @itemx Q @var{name} @var{params}@dots{}
36316 @cindex @samp{q} packet
36317 @cindex @samp{Q} packet
36318 General query (@samp{q}) and set (@samp{Q}). These packets are
36319 described fully in @ref{General Query Packets}.
36322 @cindex @samp{r} packet
36323 Reset the entire system.
36325 Don't use this packet; use the @samp{R} packet instead.
36328 @cindex @samp{R} packet
36329 Restart the program being debugged. The @var{XX}, while needed, is ignored.
36330 This packet is only available in extended mode (@pxref{extended mode}).
36332 The @samp{R} packet has no reply.
36334 @item s @r{[}@var{addr}@r{]}
36335 @cindex @samp{s} packet
36336 Single step, resuming at @var{addr}. If
36337 @var{addr} is omitted, resume at same address.
36339 This packet is deprecated for multi-threading support. @xref{vCont
36343 @xref{Stop Reply Packets}, for the reply specifications.
36345 @item S @var{sig}@r{[};@var{addr}@r{]}
36346 @anchor{step with signal packet}
36347 @cindex @samp{S} packet
36348 Step with signal. This is analogous to the @samp{C} packet, but
36349 requests a single-step, rather than a normal resumption of execution.
36351 This packet is deprecated for multi-threading support. @xref{vCont
36355 @xref{Stop Reply Packets}, for the reply specifications.
36357 @item t @var{addr}:@var{PP},@var{MM}
36358 @cindex @samp{t} packet
36359 Search backwards starting at address @var{addr} for a match with pattern
36360 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
36361 There must be at least 3 digits in @var{addr}.
36363 @item T @var{thread-id}
36364 @cindex @samp{T} packet
36365 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
36370 thread is still alive
36376 Packets starting with @samp{v} are identified by a multi-letter name,
36377 up to the first @samp{;} or @samp{?} (or the end of the packet).
36379 @item vAttach;@var{pid}
36380 @cindex @samp{vAttach} packet
36381 Attach to a new process with the specified process ID @var{pid}.
36382 The process ID is a
36383 hexadecimal integer identifying the process. In all-stop mode, all
36384 threads in the attached process are stopped; in non-stop mode, it may be
36385 attached without being stopped if that is supported by the target.
36387 @c In non-stop mode, on a successful vAttach, the stub should set the
36388 @c current thread to a thread of the newly-attached process. After
36389 @c attaching, GDB queries for the attached process's thread ID with qC.
36390 @c Also note that, from a user perspective, whether or not the
36391 @c target is stopped on attach in non-stop mode depends on whether you
36392 @c use the foreground or background version of the attach command, not
36393 @c on what vAttach does; GDB does the right thing with respect to either
36394 @c stopping or restarting threads.
36396 This packet is only available in extended mode (@pxref{extended mode}).
36402 @item @r{Any stop packet}
36403 for success in all-stop mode (@pxref{Stop Reply Packets})
36405 for success in non-stop mode (@pxref{Remote Non-Stop})
36408 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
36409 @cindex @samp{vCont} packet
36410 @anchor{vCont packet}
36411 Resume the inferior, specifying different actions for each thread.
36413 For each inferior thread, the leftmost action with a matching
36414 @var{thread-id} is applied. Threads that don't match any action
36415 remain in their current state. Thread IDs are specified using the
36416 syntax described in @ref{thread-id syntax}. If multiprocess
36417 extensions (@pxref{multiprocess extensions}) are supported, actions
36418 can be specified to match all threads in a process by using the
36419 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
36420 @var{thread-id} matches all threads. Specifying no actions is an
36423 Currently supported actions are:
36429 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
36433 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
36436 @item r @var{start},@var{end}
36437 Step once, and then keep stepping as long as the thread stops at
36438 addresses between @var{start} (inclusive) and @var{end} (exclusive).
36439 The remote stub reports a stop reply when either the thread goes out
36440 of the range or is stopped due to an unrelated reason, such as hitting
36441 a breakpoint. @xref{range stepping}.
36443 If the range is empty (@var{start} == @var{end}), then the action
36444 becomes equivalent to the @samp{s} action. In other words,
36445 single-step once, and report the stop (even if the stepped instruction
36446 jumps to @var{start}).
36448 (A stop reply may be sent at any point even if the PC is still within
36449 the stepping range; for example, it is valid to implement this packet
36450 in a degenerate way as a single instruction step operation.)
36454 The optional argument @var{addr} normally associated with the
36455 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
36456 not supported in @samp{vCont}.
36458 The @samp{t} action is only relevant in non-stop mode
36459 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
36460 A stop reply should be generated for any affected thread not already stopped.
36461 When a thread is stopped by means of a @samp{t} action,
36462 the corresponding stop reply should indicate that the thread has stopped with
36463 signal @samp{0}, regardless of whether the target uses some other signal
36464 as an implementation detail.
36466 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
36467 @samp{r} actions for threads that are already running. Conversely,
36468 the server must ignore @samp{t} actions for threads that are already
36471 @emph{Note:} In non-stop mode, a thread is considered running until
36472 @value{GDBN} acknowleges an asynchronous stop notification for it with
36473 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
36475 The stub must support @samp{vCont} if it reports support for
36476 multiprocess extensions (@pxref{multiprocess extensions}).
36479 @xref{Stop Reply Packets}, for the reply specifications.
36482 @cindex @samp{vCont?} packet
36483 Request a list of actions supported by the @samp{vCont} packet.
36487 @item vCont@r{[};@var{action}@dots{}@r{]}
36488 The @samp{vCont} packet is supported. Each @var{action} is a supported
36489 command in the @samp{vCont} packet.
36491 The @samp{vCont} packet is not supported.
36494 @anchor{vCtrlC packet}
36496 @cindex @samp{vCtrlC} packet
36497 Interrupt remote target as if a control-C was pressed on the remote
36498 terminal. This is the equivalent to reacting to the @code{^C}
36499 (@samp{\003}, the control-C character) character in all-stop mode
36500 while the target is running, except this works in non-stop mode.
36501 @xref{interrupting remote targets}, for more info on the all-stop
36512 @item vFile:@var{operation}:@var{parameter}@dots{}
36513 @cindex @samp{vFile} packet
36514 Perform a file operation on the target system. For details,
36515 see @ref{Host I/O Packets}.
36517 @item vFlashErase:@var{addr},@var{length}
36518 @cindex @samp{vFlashErase} packet
36519 Direct the stub to erase @var{length} bytes of flash starting at
36520 @var{addr}. The region may enclose any number of flash blocks, but
36521 its start and end must fall on block boundaries, as indicated by the
36522 flash block size appearing in the memory map (@pxref{Memory Map
36523 Format}). @value{GDBN} groups flash memory programming operations
36524 together, and sends a @samp{vFlashDone} request after each group; the
36525 stub is allowed to delay erase operation until the @samp{vFlashDone}
36526 packet is received.
36536 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
36537 @cindex @samp{vFlashWrite} packet
36538 Direct the stub to write data to flash address @var{addr}. The data
36539 is passed in binary form using the same encoding as for the @samp{X}
36540 packet (@pxref{Binary Data}). The memory ranges specified by
36541 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
36542 not overlap, and must appear in order of increasing addresses
36543 (although @samp{vFlashErase} packets for higher addresses may already
36544 have been received; the ordering is guaranteed only between
36545 @samp{vFlashWrite} packets). If a packet writes to an address that was
36546 neither erased by a preceding @samp{vFlashErase} packet nor by some other
36547 target-specific method, the results are unpredictable.
36555 for vFlashWrite addressing non-flash memory
36561 @cindex @samp{vFlashDone} packet
36562 Indicate to the stub that flash programming operation is finished.
36563 The stub is permitted to delay or batch the effects of a group of
36564 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
36565 @samp{vFlashDone} packet is received. The contents of the affected
36566 regions of flash memory are unpredictable until the @samp{vFlashDone}
36567 request is completed.
36569 @item vKill;@var{pid}
36570 @cindex @samp{vKill} packet
36571 @anchor{vKill packet}
36572 Kill the process with the specified process ID @var{pid}, which is a
36573 hexadecimal integer identifying the process. This packet is used in
36574 preference to @samp{k} when multiprocess protocol extensions are
36575 supported; see @ref{multiprocess extensions}.
36585 @item vMustReplyEmpty
36586 @cindex @samp{vMustReplyEmpty} packet
36587 The correct reply to an unknown @samp{v} packet is to return the empty
36588 string, however, some older versions of @command{gdbserver} would
36589 incorrectly return @samp{OK} for unknown @samp{v} packets.
36591 The @samp{vMustReplyEmpty} is used as a feature test to check how
36592 @command{gdbserver} handles unknown packets, it is important that this
36593 packet be handled in the same way as other unknown @samp{v} packets.
36594 If this packet is handled differently to other unknown @samp{v}
36595 packets then it is possile that @value{GDBN} may run into problems in
36596 other areas, specifically around use of @samp{vFile:setfs:}.
36598 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
36599 @cindex @samp{vRun} packet
36600 Run the program @var{filename}, passing it each @var{argument} on its
36601 command line. The file and arguments are hex-encoded strings. If
36602 @var{filename} is an empty string, the stub may use a default program
36603 (e.g.@: the last program run). The program is created in the stopped
36606 @c FIXME: What about non-stop mode?
36608 This packet is only available in extended mode (@pxref{extended mode}).
36614 @item @r{Any stop packet}
36615 for success (@pxref{Stop Reply Packets})
36619 @cindex @samp{vStopped} packet
36620 @xref{Notification Packets}.
36622 @item X @var{addr},@var{length}:@var{XX@dots{}}
36624 @cindex @samp{X} packet
36625 Write data to memory, where the data is transmitted in binary.
36626 Memory is specified by its address @var{addr} and number of addressable memory
36627 units @var{length} (@pxref{addressable memory unit});
36628 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
36638 @item z @var{type},@var{addr},@var{kind}
36639 @itemx Z @var{type},@var{addr},@var{kind}
36640 @anchor{insert breakpoint or watchpoint packet}
36641 @cindex @samp{z} packet
36642 @cindex @samp{Z} packets
36643 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
36644 watchpoint starting at address @var{address} of kind @var{kind}.
36646 Each breakpoint and watchpoint packet @var{type} is documented
36649 @emph{Implementation notes: A remote target shall return an empty string
36650 for an unrecognized breakpoint or watchpoint packet @var{type}. A
36651 remote target shall support either both or neither of a given
36652 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
36653 avoid potential problems with duplicate packets, the operations should
36654 be implemented in an idempotent way.}
36656 @item z0,@var{addr},@var{kind}
36657 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
36658 @cindex @samp{z0} packet
36659 @cindex @samp{Z0} packet
36660 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
36661 @var{addr} of type @var{kind}.
36663 A software breakpoint is implemented by replacing the instruction at
36664 @var{addr} with a software breakpoint or trap instruction. The
36665 @var{kind} is target-specific and typically indicates the size of the
36666 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
36667 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
36668 architectures have additional meanings for @var{kind}
36669 (@pxref{Architecture-Specific Protocol Details}); if no
36670 architecture-specific value is being used, it should be @samp{0}.
36671 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
36672 conditional expressions in bytecode form that should be evaluated on
36673 the target's side. These are the conditions that should be taken into
36674 consideration when deciding if the breakpoint trigger should be
36675 reported back to @value{GDBN}.
36677 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
36678 for how to best report a software breakpoint event to @value{GDBN}.
36680 The @var{cond_list} parameter is comprised of a series of expressions,
36681 concatenated without separators. Each expression has the following form:
36685 @item X @var{len},@var{expr}
36686 @var{len} is the length of the bytecode expression and @var{expr} is the
36687 actual conditional expression in bytecode form.
36691 The optional @var{cmd_list} parameter introduces commands that may be
36692 run on the target, rather than being reported back to @value{GDBN}.
36693 The parameter starts with a numeric flag @var{persist}; if the flag is
36694 nonzero, then the breakpoint may remain active and the commands
36695 continue to be run even when @value{GDBN} disconnects from the target.
36696 Following this flag is a series of expressions concatenated with no
36697 separators. Each expression has the following form:
36701 @item X @var{len},@var{expr}
36702 @var{len} is the length of the bytecode expression and @var{expr} is the
36703 actual commands expression in bytecode form.
36707 @emph{Implementation note: It is possible for a target to copy or move
36708 code that contains software breakpoints (e.g., when implementing
36709 overlays). The behavior of this packet, in the presence of such a
36710 target, is not defined.}
36722 @item z1,@var{addr},@var{kind}
36723 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
36724 @cindex @samp{z1} packet
36725 @cindex @samp{Z1} packet
36726 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
36727 address @var{addr}.
36729 A hardware breakpoint is implemented using a mechanism that is not
36730 dependent on being able to modify the target's memory. The
36731 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
36732 same meaning as in @samp{Z0} packets.
36734 @emph{Implementation note: A hardware breakpoint is not affected by code
36747 @item z2,@var{addr},@var{kind}
36748 @itemx Z2,@var{addr},@var{kind}
36749 @cindex @samp{z2} packet
36750 @cindex @samp{Z2} packet
36751 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
36752 The number of bytes to watch is specified by @var{kind}.
36764 @item z3,@var{addr},@var{kind}
36765 @itemx Z3,@var{addr},@var{kind}
36766 @cindex @samp{z3} packet
36767 @cindex @samp{Z3} packet
36768 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
36769 The number of bytes to watch is specified by @var{kind}.
36781 @item z4,@var{addr},@var{kind}
36782 @itemx Z4,@var{addr},@var{kind}
36783 @cindex @samp{z4} packet
36784 @cindex @samp{Z4} packet
36785 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
36786 The number of bytes to watch is specified by @var{kind}.
36800 @node Stop Reply Packets
36801 @section Stop Reply Packets
36802 @cindex stop reply packets
36804 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
36805 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
36806 receive any of the below as a reply. Except for @samp{?}
36807 and @samp{vStopped}, that reply is only returned
36808 when the target halts. In the below the exact meaning of @dfn{signal
36809 number} is defined by the header @file{include/gdb/signals.h} in the
36810 @value{GDBN} source code.
36812 In non-stop mode, the server will simply reply @samp{OK} to commands
36813 such as @samp{vCont}; any stop will be the subject of a future
36814 notification. @xref{Remote Non-Stop}.
36816 As in the description of request packets, we include spaces in the
36817 reply templates for clarity; these are not part of the reply packet's
36818 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
36824 The program received signal number @var{AA} (a two-digit hexadecimal
36825 number). This is equivalent to a @samp{T} response with no
36826 @var{n}:@var{r} pairs.
36828 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
36829 @cindex @samp{T} packet reply
36830 The program received signal number @var{AA} (a two-digit hexadecimal
36831 number). This is equivalent to an @samp{S} response, except that the
36832 @samp{@var{n}:@var{r}} pairs can carry values of important registers
36833 and other information directly in the stop reply packet, reducing
36834 round-trip latency. Single-step and breakpoint traps are reported
36835 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
36839 If @var{n} is a hexadecimal number, it is a register number, and the
36840 corresponding @var{r} gives that register's value. The data @var{r} is a
36841 series of bytes in target byte order, with each byte given by a
36842 two-digit hex number.
36845 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
36846 the stopped thread, as specified in @ref{thread-id syntax}.
36849 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
36850 the core on which the stop event was detected.
36853 If @var{n} is a recognized @dfn{stop reason}, it describes a more
36854 specific event that stopped the target. The currently defined stop
36855 reasons are listed below. The @var{aa} should be @samp{05}, the trap
36856 signal. At most one stop reason should be present.
36859 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
36860 and go on to the next; this allows us to extend the protocol in the
36864 The currently defined stop reasons are:
36870 The packet indicates a watchpoint hit, and @var{r} is the data address, in
36873 @item syscall_entry
36874 @itemx syscall_return
36875 The packet indicates a syscall entry or return, and @var{r} is the
36876 syscall number, in hex.
36878 @cindex shared library events, remote reply
36880 The packet indicates that the loaded libraries have changed.
36881 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
36882 list of loaded libraries. The @var{r} part is ignored.
36884 @cindex replay log events, remote reply
36886 The packet indicates that the target cannot continue replaying
36887 logged execution events, because it has reached the end (or the
36888 beginning when executing backward) of the log. The value of @var{r}
36889 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
36890 for more information.
36893 @anchor{swbreak stop reason}
36894 The packet indicates a software breakpoint instruction was executed,
36895 irrespective of whether it was @value{GDBN} that planted the
36896 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
36897 part must be left empty.
36899 On some architectures, such as x86, at the architecture level, when a
36900 breakpoint instruction executes the program counter points at the
36901 breakpoint address plus an offset. On such targets, the stub is
36902 responsible for adjusting the PC to point back at the breakpoint
36905 This packet should not be sent by default; older @value{GDBN} versions
36906 did not support it. @value{GDBN} requests it, by supplying an
36907 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36908 remote stub must also supply the appropriate @samp{qSupported} feature
36909 indicating support.
36911 This packet is required for correct non-stop mode operation.
36914 The packet indicates the target stopped for a hardware breakpoint.
36915 The @var{r} part must be left empty.
36917 The same remarks about @samp{qSupported} and non-stop mode above
36920 @cindex fork events, remote reply
36922 The packet indicates that @code{fork} was called, and @var{r}
36923 is the thread ID of the new child process. Refer to
36924 @ref{thread-id syntax} for the format of the @var{thread-id}
36925 field. This packet is only applicable to targets that support
36928 This packet should not be sent by default; older @value{GDBN} versions
36929 did not support it. @value{GDBN} requests it, by supplying an
36930 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36931 remote stub must also supply the appropriate @samp{qSupported} feature
36932 indicating support.
36934 @cindex vfork events, remote reply
36936 The packet indicates that @code{vfork} was called, and @var{r}
36937 is the thread ID of the new child process. Refer to
36938 @ref{thread-id syntax} for the format of the @var{thread-id}
36939 field. This packet is only applicable to targets that support
36942 This packet should not be sent by default; older @value{GDBN} versions
36943 did not support it. @value{GDBN} requests it, by supplying an
36944 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36945 remote stub must also supply the appropriate @samp{qSupported} feature
36946 indicating support.
36948 @cindex vforkdone events, remote reply
36950 The packet indicates that a child process created by a vfork
36951 has either called @code{exec} or terminated, so that the
36952 address spaces of the parent and child process are no longer
36953 shared. The @var{r} part is ignored. This packet is only
36954 applicable to targets that support vforkdone events.
36956 This packet should not be sent by default; older @value{GDBN} versions
36957 did not support it. @value{GDBN} requests it, by supplying an
36958 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36959 remote stub must also supply the appropriate @samp{qSupported} feature
36960 indicating support.
36962 @cindex exec events, remote reply
36964 The packet indicates that @code{execve} was called, and @var{r}
36965 is the absolute pathname of the file that was executed, in hex.
36966 This packet is only applicable to targets that support exec events.
36968 This packet should not be sent by default; older @value{GDBN} versions
36969 did not support it. @value{GDBN} requests it, by supplying an
36970 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36971 remote stub must also supply the appropriate @samp{qSupported} feature
36972 indicating support.
36974 @cindex thread create event, remote reply
36975 @anchor{thread create event}
36977 The packet indicates that the thread was just created. The new thread
36978 is stopped until @value{GDBN} sets it running with a resumption packet
36979 (@pxref{vCont packet}). This packet should not be sent by default;
36980 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
36981 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
36982 @var{r} part is ignored.
36987 @itemx W @var{AA} ; process:@var{pid}
36988 The process exited, and @var{AA} is the exit status. This is only
36989 applicable to certain targets.
36991 The second form of the response, including the process ID of the
36992 exited process, can be used only when @value{GDBN} has reported
36993 support for multiprocess protocol extensions; see @ref{multiprocess
36994 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
36998 @itemx X @var{AA} ; process:@var{pid}
36999 The process terminated with signal @var{AA}.
37001 The second form of the response, including the process ID of the
37002 terminated process, can be used only when @value{GDBN} has reported
37003 support for multiprocess protocol extensions; see @ref{multiprocess
37004 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
37007 @anchor{thread exit event}
37008 @cindex thread exit event, remote reply
37009 @item w @var{AA} ; @var{tid}
37011 The thread exited, and @var{AA} is the exit status. This response
37012 should not be sent by default; @value{GDBN} requests it with the
37013 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
37014 @var{AA} is formatted as a big-endian hex string.
37017 There are no resumed threads left in the target. In other words, even
37018 though the process is alive, the last resumed thread has exited. For
37019 example, say the target process has two threads: thread 1 and thread
37020 2. The client leaves thread 1 stopped, and resumes thread 2, which
37021 subsequently exits. At this point, even though the process is still
37022 alive, and thus no @samp{W} stop reply is sent, no thread is actually
37023 executing either. The @samp{N} stop reply thus informs the client
37024 that it can stop waiting for stop replies. This packet should not be
37025 sent by default; older @value{GDBN} versions did not support it.
37026 @value{GDBN} requests it, by supplying an appropriate
37027 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
37028 also supply the appropriate @samp{qSupported} feature indicating
37031 @item O @var{XX}@dots{}
37032 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
37033 written as the program's console output. This can happen at any time
37034 while the program is running and the debugger should continue to wait
37035 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
37037 @item F @var{call-id},@var{parameter}@dots{}
37038 @var{call-id} is the identifier which says which host system call should
37039 be called. This is just the name of the function. Translation into the
37040 correct system call is only applicable as it's defined in @value{GDBN}.
37041 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
37044 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
37045 this very system call.
37047 The target replies with this packet when it expects @value{GDBN} to
37048 call a host system call on behalf of the target. @value{GDBN} replies
37049 with an appropriate @samp{F} packet and keeps up waiting for the next
37050 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
37051 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
37052 Protocol Extension}, for more details.
37056 @node General Query Packets
37057 @section General Query Packets
37058 @cindex remote query requests
37060 Packets starting with @samp{q} are @dfn{general query packets};
37061 packets starting with @samp{Q} are @dfn{general set packets}. General
37062 query and set packets are a semi-unified form for retrieving and
37063 sending information to and from the stub.
37065 The initial letter of a query or set packet is followed by a name
37066 indicating what sort of thing the packet applies to. For example,
37067 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
37068 definitions with the stub. These packet names follow some
37073 The name must not contain commas, colons or semicolons.
37075 Most @value{GDBN} query and set packets have a leading upper case
37078 The names of custom vendor packets should use a company prefix, in
37079 lower case, followed by a period. For example, packets designed at
37080 the Acme Corporation might begin with @samp{qacme.foo} (for querying
37081 foos) or @samp{Qacme.bar} (for setting bars).
37084 The name of a query or set packet should be separated from any
37085 parameters by a @samp{:}; the parameters themselves should be
37086 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
37087 full packet name, and check for a separator or the end of the packet,
37088 in case two packet names share a common prefix. New packets should not begin
37089 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
37090 packets predate these conventions, and have arguments without any terminator
37091 for the packet name; we suspect they are in widespread use in places that
37092 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
37093 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
37096 Like the descriptions of the other packets, each description here
37097 has a template showing the packet's overall syntax, followed by an
37098 explanation of the packet's meaning. We include spaces in some of the
37099 templates for clarity; these are not part of the packet's syntax. No
37100 @value{GDBN} packet uses spaces to separate its components.
37102 Here are the currently defined query and set packets:
37108 Turn on or off the agent as a helper to perform some debugging operations
37109 delegated from @value{GDBN} (@pxref{Control Agent}).
37111 @item QAllow:@var{op}:@var{val}@dots{}
37112 @cindex @samp{QAllow} packet
37113 Specify which operations @value{GDBN} expects to request of the
37114 target, as a semicolon-separated list of operation name and value
37115 pairs. Possible values for @var{op} include @samp{WriteReg},
37116 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
37117 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
37118 indicating that @value{GDBN} will not request the operation, or 1,
37119 indicating that it may. (The target can then use this to set up its
37120 own internals optimally, for instance if the debugger never expects to
37121 insert breakpoints, it may not need to install its own trap handler.)
37124 @cindex current thread, remote request
37125 @cindex @samp{qC} packet
37126 Return the current thread ID.
37130 @item QC @var{thread-id}
37131 Where @var{thread-id} is a thread ID as documented in
37132 @ref{thread-id syntax}.
37133 @item @r{(anything else)}
37134 Any other reply implies the old thread ID.
37137 @item qCRC:@var{addr},@var{length}
37138 @cindex CRC of memory block, remote request
37139 @cindex @samp{qCRC} packet
37140 @anchor{qCRC packet}
37141 Compute the CRC checksum of a block of memory using CRC-32 defined in
37142 IEEE 802.3. The CRC is computed byte at a time, taking the most
37143 significant bit of each byte first. The initial pattern code
37144 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
37146 @emph{Note:} This is the same CRC used in validating separate debug
37147 files (@pxref{Separate Debug Files, , Debugging Information in Separate
37148 Files}). However the algorithm is slightly different. When validating
37149 separate debug files, the CRC is computed taking the @emph{least}
37150 significant bit of each byte first, and the final result is inverted to
37151 detect trailing zeros.
37156 An error (such as memory fault)
37157 @item C @var{crc32}
37158 The specified memory region's checksum is @var{crc32}.
37161 @item QDisableRandomization:@var{value}
37162 @cindex disable address space randomization, remote request
37163 @cindex @samp{QDisableRandomization} packet
37164 Some target operating systems will randomize the virtual address space
37165 of the inferior process as a security feature, but provide a feature
37166 to disable such randomization, e.g.@: to allow for a more deterministic
37167 debugging experience. On such systems, this packet with a @var{value}
37168 of 1 directs the target to disable address space randomization for
37169 processes subsequently started via @samp{vRun} packets, while a packet
37170 with a @var{value} of 0 tells the target to enable address space
37173 This packet is only available in extended mode (@pxref{extended mode}).
37178 The request succeeded.
37181 An error occurred. The error number @var{nn} is given as hex digits.
37184 An empty reply indicates that @samp{QDisableRandomization} is not supported
37188 This packet is not probed by default; the remote stub must request it,
37189 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37190 This should only be done on targets that actually support disabling
37191 address space randomization.
37193 @item QStartupWithShell:@var{value}
37194 @cindex startup with shell, remote request
37195 @cindex @samp{QStartupWithShell} packet
37196 On UNIX-like targets, it is possible to start the inferior using a
37197 shell program. This is the default behavior on both @value{GDBN} and
37198 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
37199 used to inform @command{gdbserver} whether it should start the
37200 inferior using a shell or not.
37202 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
37203 to start the inferior. If @var{value} is @samp{1},
37204 @command{gdbserver} will use a shell to start the inferior. All other
37205 values are considered an error.
37207 This packet is only available in extended mode (@pxref{extended
37213 The request succeeded.
37216 An error occurred. The error number @var{nn} is given as hex digits.
37219 This packet is not probed by default; the remote stub must request it,
37220 by supplying an appropriate @samp{qSupported} response
37221 (@pxref{qSupported}). This should only be done on targets that
37222 actually support starting the inferior using a shell.
37224 Use of this packet is controlled by the @code{set startup-with-shell}
37225 command; @pxref{set startup-with-shell}.
37227 @item QEnvironmentHexEncoded:@var{hex-value}
37228 @anchor{QEnvironmentHexEncoded}
37229 @cindex set environment variable, remote request
37230 @cindex @samp{QEnvironmentHexEncoded} packet
37231 On UNIX-like targets, it is possible to set environment variables that
37232 will be passed to the inferior during the startup process. This
37233 packet is used to inform @command{gdbserver} of an environment
37234 variable that has been defined by the user on @value{GDBN} (@pxref{set
37237 The packet is composed by @var{hex-value}, an hex encoded
37238 representation of the @var{name=value} format representing an
37239 environment variable. The name of the environment variable is
37240 represented by @var{name}, and the value to be assigned to the
37241 environment variable is represented by @var{value}. If the variable
37242 has no value (i.e., the value is @code{null}), then @var{value} will
37245 This packet is only available in extended mode (@pxref{extended
37251 The request succeeded.
37254 This packet is not probed by default; the remote stub must request it,
37255 by supplying an appropriate @samp{qSupported} response
37256 (@pxref{qSupported}). This should only be done on targets that
37257 actually support passing environment variables to the starting
37260 This packet is related to the @code{set environment} command;
37261 @pxref{set environment}.
37263 @item QEnvironmentUnset:@var{hex-value}
37264 @anchor{QEnvironmentUnset}
37265 @cindex unset environment variable, remote request
37266 @cindex @samp{QEnvironmentUnset} packet
37267 On UNIX-like targets, it is possible to unset environment variables
37268 before starting the inferior in the remote target. This packet is
37269 used to inform @command{gdbserver} of an environment variable that has
37270 been unset by the user on @value{GDBN} (@pxref{unset environment}).
37272 The packet is composed by @var{hex-value}, an hex encoded
37273 representation of the name of the environment variable to be unset.
37275 This packet is only available in extended mode (@pxref{extended
37281 The request succeeded.
37284 This packet is not probed by default; the remote stub must request it,
37285 by supplying an appropriate @samp{qSupported} response
37286 (@pxref{qSupported}). This should only be done on targets that
37287 actually support passing environment variables to the starting
37290 This packet is related to the @code{unset environment} command;
37291 @pxref{unset environment}.
37293 @item QEnvironmentReset
37294 @anchor{QEnvironmentReset}
37295 @cindex reset environment, remote request
37296 @cindex @samp{QEnvironmentReset} packet
37297 On UNIX-like targets, this packet is used to reset the state of
37298 environment variables in the remote target before starting the
37299 inferior. In this context, reset means unsetting all environment
37300 variables that were previously set by the user (i.e., were not
37301 initially present in the environment). It is sent to
37302 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
37303 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
37304 (@pxref{QEnvironmentUnset}) packets.
37306 This packet is only available in extended mode (@pxref{extended
37312 The request succeeded.
37315 This packet is not probed by default; the remote stub must request it,
37316 by supplying an appropriate @samp{qSupported} response
37317 (@pxref{qSupported}). This should only be done on targets that
37318 actually support passing environment variables to the starting
37321 @item QSetWorkingDir:@r{[}@var{directory}@r{]}
37322 @anchor{QSetWorkingDir packet}
37323 @cindex set working directory, remote request
37324 @cindex @samp{QSetWorkingDir} packet
37325 This packet is used to inform the remote server of the intended
37326 current working directory for programs that are going to be executed.
37328 The packet is composed by @var{directory}, an hex encoded
37329 representation of the directory that the remote inferior will use as
37330 its current working directory. If @var{directory} is an empty string,
37331 the remote server should reset the inferior's current working
37332 directory to its original, empty value.
37334 This packet is only available in extended mode (@pxref{extended
37340 The request succeeded.
37344 @itemx qsThreadInfo
37345 @cindex list active threads, remote request
37346 @cindex @samp{qfThreadInfo} packet
37347 @cindex @samp{qsThreadInfo} packet
37348 Obtain a list of all active thread IDs from the target (OS). Since there
37349 may be too many active threads to fit into one reply packet, this query
37350 works iteratively: it may require more than one query/reply sequence to
37351 obtain the entire list of threads. The first query of the sequence will
37352 be the @samp{qfThreadInfo} query; subsequent queries in the
37353 sequence will be the @samp{qsThreadInfo} query.
37355 NOTE: This packet replaces the @samp{qL} query (see below).
37359 @item m @var{thread-id}
37361 @item m @var{thread-id},@var{thread-id}@dots{}
37362 a comma-separated list of thread IDs
37364 (lower case letter @samp{L}) denotes end of list.
37367 In response to each query, the target will reply with a list of one or
37368 more thread IDs, separated by commas.
37369 @value{GDBN} will respond to each reply with a request for more thread
37370 ids (using the @samp{qs} form of the query), until the target responds
37371 with @samp{l} (lower-case ell, for @dfn{last}).
37372 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
37375 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
37376 initial connection with the remote target, and the very first thread ID
37377 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
37378 message. Therefore, the stub should ensure that the first thread ID in
37379 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
37381 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
37382 @cindex get thread-local storage address, remote request
37383 @cindex @samp{qGetTLSAddr} packet
37384 Fetch the address associated with thread local storage specified
37385 by @var{thread-id}, @var{offset}, and @var{lm}.
37387 @var{thread-id} is the thread ID associated with the
37388 thread for which to fetch the TLS address. @xref{thread-id syntax}.
37390 @var{offset} is the (big endian, hex encoded) offset associated with the
37391 thread local variable. (This offset is obtained from the debug
37392 information associated with the variable.)
37394 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
37395 load module associated with the thread local storage. For example,
37396 a @sc{gnu}/Linux system will pass the link map address of the shared
37397 object associated with the thread local storage under consideration.
37398 Other operating environments may choose to represent the load module
37399 differently, so the precise meaning of this parameter will vary.
37403 @item @var{XX}@dots{}
37404 Hex encoded (big endian) bytes representing the address of the thread
37405 local storage requested.
37408 An error occurred. The error number @var{nn} is given as hex digits.
37411 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
37414 @item qGetTIBAddr:@var{thread-id}
37415 @cindex get thread information block address
37416 @cindex @samp{qGetTIBAddr} packet
37417 Fetch address of the Windows OS specific Thread Information Block.
37419 @var{thread-id} is the thread ID associated with the thread.
37423 @item @var{XX}@dots{}
37424 Hex encoded (big endian) bytes representing the linear address of the
37425 thread information block.
37428 An error occured. This means that either the thread was not found, or the
37429 address could not be retrieved.
37432 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
37435 @item qL @var{startflag} @var{threadcount} @var{nextthread}
37436 Obtain thread information from RTOS. Where: @var{startflag} (one hex
37437 digit) is one to indicate the first query and zero to indicate a
37438 subsequent query; @var{threadcount} (two hex digits) is the maximum
37439 number of threads the response packet can contain; and @var{nextthread}
37440 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
37441 returned in the response as @var{argthread}.
37443 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
37447 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
37448 Where: @var{count} (two hex digits) is the number of threads being
37449 returned; @var{done} (one hex digit) is zero to indicate more threads
37450 and one indicates no further threads; @var{argthreadid} (eight hex
37451 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
37452 is a sequence of thread IDs, @var{threadid} (eight hex
37453 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
37457 @cindex section offsets, remote request
37458 @cindex @samp{qOffsets} packet
37459 Get section offsets that the target used when relocating the downloaded
37464 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
37465 Relocate the @code{Text} section by @var{xxx} from its original address.
37466 Relocate the @code{Data} section by @var{yyy} from its original address.
37467 If the object file format provides segment information (e.g.@: @sc{elf}
37468 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
37469 segments by the supplied offsets.
37471 @emph{Note: while a @code{Bss} offset may be included in the response,
37472 @value{GDBN} ignores this and instead applies the @code{Data} offset
37473 to the @code{Bss} section.}
37475 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
37476 Relocate the first segment of the object file, which conventionally
37477 contains program code, to a starting address of @var{xxx}. If
37478 @samp{DataSeg} is specified, relocate the second segment, which
37479 conventionally contains modifiable data, to a starting address of
37480 @var{yyy}. @value{GDBN} will report an error if the object file
37481 does not contain segment information, or does not contain at least
37482 as many segments as mentioned in the reply. Extra segments are
37483 kept at fixed offsets relative to the last relocated segment.
37486 @item qP @var{mode} @var{thread-id}
37487 @cindex thread information, remote request
37488 @cindex @samp{qP} packet
37489 Returns information on @var{thread-id}. Where: @var{mode} is a hex
37490 encoded 32 bit mode; @var{thread-id} is a thread ID
37491 (@pxref{thread-id syntax}).
37493 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
37496 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
37500 @cindex non-stop mode, remote request
37501 @cindex @samp{QNonStop} packet
37503 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
37504 @xref{Remote Non-Stop}, for more information.
37509 The request succeeded.
37512 An error occurred. The error number @var{nn} is given as hex digits.
37515 An empty reply indicates that @samp{QNonStop} is not supported by
37519 This packet is not probed by default; the remote stub must request it,
37520 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37521 Use of this packet is controlled by the @code{set non-stop} command;
37522 @pxref{Non-Stop Mode}.
37524 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
37525 @itemx QCatchSyscalls:0
37526 @cindex catch syscalls from inferior, remote request
37527 @cindex @samp{QCatchSyscalls} packet
37528 @anchor{QCatchSyscalls}
37529 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
37530 catching syscalls from the inferior process.
37532 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
37533 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
37534 is listed, every system call should be reported.
37536 Note that if a syscall not in the list is reported, @value{GDBN} will
37537 still filter the event according to its own list from all corresponding
37538 @code{catch syscall} commands. However, it is more efficient to only
37539 report the requested syscalls.
37541 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
37542 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
37544 If the inferior process execs, the state of @samp{QCatchSyscalls} is
37545 kept for the new process too. On targets where exec may affect syscall
37546 numbers, for example with exec between 32 and 64-bit processes, the
37547 client should send a new packet with the new syscall list.
37552 The request succeeded.
37555 An error occurred. @var{nn} are hex digits.
37558 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
37562 Use of this packet is controlled by the @code{set remote catch-syscalls}
37563 command (@pxref{Remote Configuration, set remote catch-syscalls}).
37564 This packet is not probed by default; the remote stub must request it,
37565 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37567 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37568 @cindex pass signals to inferior, remote request
37569 @cindex @samp{QPassSignals} packet
37570 @anchor{QPassSignals}
37571 Each listed @var{signal} should be passed directly to the inferior process.
37572 Signals are numbered identically to continue packets and stop replies
37573 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37574 strictly greater than the previous item. These signals do not need to stop
37575 the inferior, or be reported to @value{GDBN}. All other signals should be
37576 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
37577 combine; any earlier @samp{QPassSignals} list is completely replaced by the
37578 new list. This packet improves performance when using @samp{handle
37579 @var{signal} nostop noprint pass}.
37584 The request succeeded.
37587 An error occurred. The error number @var{nn} is given as hex digits.
37590 An empty reply indicates that @samp{QPassSignals} is not supported by
37594 Use of this packet is controlled by the @code{set remote pass-signals}
37595 command (@pxref{Remote Configuration, set remote pass-signals}).
37596 This packet is not probed by default; the remote stub must request it,
37597 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37599 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37600 @cindex signals the inferior may see, remote request
37601 @cindex @samp{QProgramSignals} packet
37602 @anchor{QProgramSignals}
37603 Each listed @var{signal} may be delivered to the inferior process.
37604 Others should be silently discarded.
37606 In some cases, the remote stub may need to decide whether to deliver a
37607 signal to the program or not without @value{GDBN} involvement. One
37608 example of that is while detaching --- the program's threads may have
37609 stopped for signals that haven't yet had a chance of being reported to
37610 @value{GDBN}, and so the remote stub can use the signal list specified
37611 by this packet to know whether to deliver or ignore those pending
37614 This does not influence whether to deliver a signal as requested by a
37615 resumption packet (@pxref{vCont packet}).
37617 Signals are numbered identically to continue packets and stop replies
37618 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37619 strictly greater than the previous item. Multiple
37620 @samp{QProgramSignals} packets do not combine; any earlier
37621 @samp{QProgramSignals} list is completely replaced by the new list.
37626 The request succeeded.
37629 An error occurred. The error number @var{nn} is given as hex digits.
37632 An empty reply indicates that @samp{QProgramSignals} is not supported
37636 Use of this packet is controlled by the @code{set remote program-signals}
37637 command (@pxref{Remote Configuration, set remote program-signals}).
37638 This packet is not probed by default; the remote stub must request it,
37639 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37641 @anchor{QThreadEvents}
37642 @item QThreadEvents:1
37643 @itemx QThreadEvents:0
37644 @cindex thread create/exit events, remote request
37645 @cindex @samp{QThreadEvents} packet
37647 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
37648 reporting of thread create and exit events. @xref{thread create
37649 event}, for the reply specifications. For example, this is used in
37650 non-stop mode when @value{GDBN} stops a set of threads and
37651 synchronously waits for the their corresponding stop replies. Without
37652 exit events, if one of the threads exits, @value{GDBN} would hang
37653 forever not knowing that it should no longer expect a stop for that
37654 same thread. @value{GDBN} does not enable this feature unless the
37655 stub reports that it supports it by including @samp{QThreadEvents+} in
37656 its @samp{qSupported} reply.
37661 The request succeeded.
37664 An error occurred. The error number @var{nn} is given as hex digits.
37667 An empty reply indicates that @samp{QThreadEvents} is not supported by
37671 Use of this packet is controlled by the @code{set remote thread-events}
37672 command (@pxref{Remote Configuration, set remote thread-events}).
37674 @item qRcmd,@var{command}
37675 @cindex execute remote command, remote request
37676 @cindex @samp{qRcmd} packet
37677 @var{command} (hex encoded) is passed to the local interpreter for
37678 execution. Invalid commands should be reported using the output
37679 string. Before the final result packet, the target may also respond
37680 with a number of intermediate @samp{O@var{output}} console output
37681 packets. @emph{Implementors should note that providing access to a
37682 stubs's interpreter may have security implications}.
37687 A command response with no output.
37689 A command response with the hex encoded output string @var{OUTPUT}.
37691 Indicate a badly formed request.
37693 An empty reply indicates that @samp{qRcmd} is not recognized.
37696 (Note that the @code{qRcmd} packet's name is separated from the
37697 command by a @samp{,}, not a @samp{:}, contrary to the naming
37698 conventions above. Please don't use this packet as a model for new
37701 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
37702 @cindex searching memory, in remote debugging
37704 @cindex @samp{qSearch:memory} packet
37706 @cindex @samp{qSearch memory} packet
37707 @anchor{qSearch memory}
37708 Search @var{length} bytes at @var{address} for @var{search-pattern}.
37709 Both @var{address} and @var{length} are encoded in hex;
37710 @var{search-pattern} is a sequence of bytes, also hex encoded.
37715 The pattern was not found.
37717 The pattern was found at @var{address}.
37719 A badly formed request or an error was encountered while searching memory.
37721 An empty reply indicates that @samp{qSearch:memory} is not recognized.
37724 @item QStartNoAckMode
37725 @cindex @samp{QStartNoAckMode} packet
37726 @anchor{QStartNoAckMode}
37727 Request that the remote stub disable the normal @samp{+}/@samp{-}
37728 protocol acknowledgments (@pxref{Packet Acknowledgment}).
37733 The stub has switched to no-acknowledgment mode.
37734 @value{GDBN} acknowledges this reponse,
37735 but neither the stub nor @value{GDBN} shall send or expect further
37736 @samp{+}/@samp{-} acknowledgments in the current connection.
37738 An empty reply indicates that the stub does not support no-acknowledgment mode.
37741 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
37742 @cindex supported packets, remote query
37743 @cindex features of the remote protocol
37744 @cindex @samp{qSupported} packet
37745 @anchor{qSupported}
37746 Tell the remote stub about features supported by @value{GDBN}, and
37747 query the stub for features it supports. This packet allows
37748 @value{GDBN} and the remote stub to take advantage of each others'
37749 features. @samp{qSupported} also consolidates multiple feature probes
37750 at startup, to improve @value{GDBN} performance---a single larger
37751 packet performs better than multiple smaller probe packets on
37752 high-latency links. Some features may enable behavior which must not
37753 be on by default, e.g.@: because it would confuse older clients or
37754 stubs. Other features may describe packets which could be
37755 automatically probed for, but are not. These features must be
37756 reported before @value{GDBN} will use them. This ``default
37757 unsupported'' behavior is not appropriate for all packets, but it
37758 helps to keep the initial connection time under control with new
37759 versions of @value{GDBN} which support increasing numbers of packets.
37763 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
37764 The stub supports or does not support each returned @var{stubfeature},
37765 depending on the form of each @var{stubfeature} (see below for the
37768 An empty reply indicates that @samp{qSupported} is not recognized,
37769 or that no features needed to be reported to @value{GDBN}.
37772 The allowed forms for each feature (either a @var{gdbfeature} in the
37773 @samp{qSupported} packet, or a @var{stubfeature} in the response)
37777 @item @var{name}=@var{value}
37778 The remote protocol feature @var{name} is supported, and associated
37779 with the specified @var{value}. The format of @var{value} depends
37780 on the feature, but it must not include a semicolon.
37782 The remote protocol feature @var{name} is supported, and does not
37783 need an associated value.
37785 The remote protocol feature @var{name} is not supported.
37787 The remote protocol feature @var{name} may be supported, and
37788 @value{GDBN} should auto-detect support in some other way when it is
37789 needed. This form will not be used for @var{gdbfeature} notifications,
37790 but may be used for @var{stubfeature} responses.
37793 Whenever the stub receives a @samp{qSupported} request, the
37794 supplied set of @value{GDBN} features should override any previous
37795 request. This allows @value{GDBN} to put the stub in a known
37796 state, even if the stub had previously been communicating with
37797 a different version of @value{GDBN}.
37799 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
37804 This feature indicates whether @value{GDBN} supports multiprocess
37805 extensions to the remote protocol. @value{GDBN} does not use such
37806 extensions unless the stub also reports that it supports them by
37807 including @samp{multiprocess+} in its @samp{qSupported} reply.
37808 @xref{multiprocess extensions}, for details.
37811 This feature indicates that @value{GDBN} supports the XML target
37812 description. If the stub sees @samp{xmlRegisters=} with target
37813 specific strings separated by a comma, it will report register
37817 This feature indicates whether @value{GDBN} supports the
37818 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
37819 instruction reply packet}).
37822 This feature indicates whether @value{GDBN} supports the swbreak stop
37823 reason in stop replies. @xref{swbreak stop reason}, for details.
37826 This feature indicates whether @value{GDBN} supports the hwbreak stop
37827 reason in stop replies. @xref{swbreak stop reason}, for details.
37830 This feature indicates whether @value{GDBN} supports fork event
37831 extensions to the remote protocol. @value{GDBN} does not use such
37832 extensions unless the stub also reports that it supports them by
37833 including @samp{fork-events+} in its @samp{qSupported} reply.
37836 This feature indicates whether @value{GDBN} supports vfork event
37837 extensions to the remote protocol. @value{GDBN} does not use such
37838 extensions unless the stub also reports that it supports them by
37839 including @samp{vfork-events+} in its @samp{qSupported} reply.
37842 This feature indicates whether @value{GDBN} supports exec event
37843 extensions to the remote protocol. @value{GDBN} does not use such
37844 extensions unless the stub also reports that it supports them by
37845 including @samp{exec-events+} in its @samp{qSupported} reply.
37847 @item vContSupported
37848 This feature indicates whether @value{GDBN} wants to know the
37849 supported actions in the reply to @samp{vCont?} packet.
37852 Stubs should ignore any unknown values for
37853 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
37854 packet supports receiving packets of unlimited length (earlier
37855 versions of @value{GDBN} may reject overly long responses). Additional values
37856 for @var{gdbfeature} may be defined in the future to let the stub take
37857 advantage of new features in @value{GDBN}, e.g.@: incompatible
37858 improvements in the remote protocol---the @samp{multiprocess} feature is
37859 an example of such a feature. The stub's reply should be independent
37860 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
37861 describes all the features it supports, and then the stub replies with
37862 all the features it supports.
37864 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
37865 responses, as long as each response uses one of the standard forms.
37867 Some features are flags. A stub which supports a flag feature
37868 should respond with a @samp{+} form response. Other features
37869 require values, and the stub should respond with an @samp{=}
37872 Each feature has a default value, which @value{GDBN} will use if
37873 @samp{qSupported} is not available or if the feature is not mentioned
37874 in the @samp{qSupported} response. The default values are fixed; a
37875 stub is free to omit any feature responses that match the defaults.
37877 Not all features can be probed, but for those which can, the probing
37878 mechanism is useful: in some cases, a stub's internal
37879 architecture may not allow the protocol layer to know some information
37880 about the underlying target in advance. This is especially common in
37881 stubs which may be configured for multiple targets.
37883 These are the currently defined stub features and their properties:
37885 @multitable @columnfractions 0.35 0.2 0.12 0.2
37886 @c NOTE: The first row should be @headitem, but we do not yet require
37887 @c a new enough version of Texinfo (4.7) to use @headitem.
37889 @tab Value Required
37893 @item @samp{PacketSize}
37898 @item @samp{qXfer:auxv:read}
37903 @item @samp{qXfer:btrace:read}
37908 @item @samp{qXfer:btrace-conf:read}
37913 @item @samp{qXfer:exec-file:read}
37918 @item @samp{qXfer:features:read}
37923 @item @samp{qXfer:libraries:read}
37928 @item @samp{qXfer:libraries-svr4:read}
37933 @item @samp{augmented-libraries-svr4-read}
37938 @item @samp{qXfer:memory-map:read}
37943 @item @samp{qXfer:sdata:read}
37948 @item @samp{qXfer:spu:read}
37953 @item @samp{qXfer:spu:write}
37958 @item @samp{qXfer:siginfo:read}
37963 @item @samp{qXfer:siginfo:write}
37968 @item @samp{qXfer:threads:read}
37973 @item @samp{qXfer:traceframe-info:read}
37978 @item @samp{qXfer:uib:read}
37983 @item @samp{qXfer:fdpic:read}
37988 @item @samp{Qbtrace:off}
37993 @item @samp{Qbtrace:bts}
37998 @item @samp{Qbtrace:pt}
38003 @item @samp{Qbtrace-conf:bts:size}
38008 @item @samp{Qbtrace-conf:pt:size}
38013 @item @samp{QNonStop}
38018 @item @samp{QCatchSyscalls}
38023 @item @samp{QPassSignals}
38028 @item @samp{QStartNoAckMode}
38033 @item @samp{multiprocess}
38038 @item @samp{ConditionalBreakpoints}
38043 @item @samp{ConditionalTracepoints}
38048 @item @samp{ReverseContinue}
38053 @item @samp{ReverseStep}
38058 @item @samp{TracepointSource}
38063 @item @samp{QAgent}
38068 @item @samp{QAllow}
38073 @item @samp{QDisableRandomization}
38078 @item @samp{EnableDisableTracepoints}
38083 @item @samp{QTBuffer:size}
38088 @item @samp{tracenz}
38093 @item @samp{BreakpointCommands}
38098 @item @samp{swbreak}
38103 @item @samp{hwbreak}
38108 @item @samp{fork-events}
38113 @item @samp{vfork-events}
38118 @item @samp{exec-events}
38123 @item @samp{QThreadEvents}
38128 @item @samp{no-resumed}
38135 These are the currently defined stub features, in more detail:
38138 @cindex packet size, remote protocol
38139 @item PacketSize=@var{bytes}
38140 The remote stub can accept packets up to at least @var{bytes} in
38141 length. @value{GDBN} will send packets up to this size for bulk
38142 transfers, and will never send larger packets. This is a limit on the
38143 data characters in the packet, including the frame and checksum.
38144 There is no trailing NUL byte in a remote protocol packet; if the stub
38145 stores packets in a NUL-terminated format, it should allow an extra
38146 byte in its buffer for the NUL. If this stub feature is not supported,
38147 @value{GDBN} guesses based on the size of the @samp{g} packet response.
38149 @item qXfer:auxv:read
38150 The remote stub understands the @samp{qXfer:auxv:read} packet
38151 (@pxref{qXfer auxiliary vector read}).
38153 @item qXfer:btrace:read
38154 The remote stub understands the @samp{qXfer:btrace:read}
38155 packet (@pxref{qXfer btrace read}).
38157 @item qXfer:btrace-conf:read
38158 The remote stub understands the @samp{qXfer:btrace-conf:read}
38159 packet (@pxref{qXfer btrace-conf read}).
38161 @item qXfer:exec-file:read
38162 The remote stub understands the @samp{qXfer:exec-file:read} packet
38163 (@pxref{qXfer executable filename read}).
38165 @item qXfer:features:read
38166 The remote stub understands the @samp{qXfer:features:read} packet
38167 (@pxref{qXfer target description read}).
38169 @item qXfer:libraries:read
38170 The remote stub understands the @samp{qXfer:libraries:read} packet
38171 (@pxref{qXfer library list read}).
38173 @item qXfer:libraries-svr4:read
38174 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
38175 (@pxref{qXfer svr4 library list read}).
38177 @item augmented-libraries-svr4-read
38178 The remote stub understands the augmented form of the
38179 @samp{qXfer:libraries-svr4:read} packet
38180 (@pxref{qXfer svr4 library list read}).
38182 @item qXfer:memory-map:read
38183 The remote stub understands the @samp{qXfer:memory-map:read} packet
38184 (@pxref{qXfer memory map read}).
38186 @item qXfer:sdata:read
38187 The remote stub understands the @samp{qXfer:sdata:read} packet
38188 (@pxref{qXfer sdata read}).
38190 @item qXfer:spu:read
38191 The remote stub understands the @samp{qXfer:spu:read} packet
38192 (@pxref{qXfer spu read}).
38194 @item qXfer:spu:write
38195 The remote stub understands the @samp{qXfer:spu:write} packet
38196 (@pxref{qXfer spu write}).
38198 @item qXfer:siginfo:read
38199 The remote stub understands the @samp{qXfer:siginfo:read} packet
38200 (@pxref{qXfer siginfo read}).
38202 @item qXfer:siginfo:write
38203 The remote stub understands the @samp{qXfer:siginfo:write} packet
38204 (@pxref{qXfer siginfo write}).
38206 @item qXfer:threads:read
38207 The remote stub understands the @samp{qXfer:threads:read} packet
38208 (@pxref{qXfer threads read}).
38210 @item qXfer:traceframe-info:read
38211 The remote stub understands the @samp{qXfer:traceframe-info:read}
38212 packet (@pxref{qXfer traceframe info read}).
38214 @item qXfer:uib:read
38215 The remote stub understands the @samp{qXfer:uib:read}
38216 packet (@pxref{qXfer unwind info block}).
38218 @item qXfer:fdpic:read
38219 The remote stub understands the @samp{qXfer:fdpic:read}
38220 packet (@pxref{qXfer fdpic loadmap read}).
38223 The remote stub understands the @samp{QNonStop} packet
38224 (@pxref{QNonStop}).
38226 @item QCatchSyscalls
38227 The remote stub understands the @samp{QCatchSyscalls} packet
38228 (@pxref{QCatchSyscalls}).
38231 The remote stub understands the @samp{QPassSignals} packet
38232 (@pxref{QPassSignals}).
38234 @item QStartNoAckMode
38235 The remote stub understands the @samp{QStartNoAckMode} packet and
38236 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
38239 @anchor{multiprocess extensions}
38240 @cindex multiprocess extensions, in remote protocol
38241 The remote stub understands the multiprocess extensions to the remote
38242 protocol syntax. The multiprocess extensions affect the syntax of
38243 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
38244 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
38245 replies. Note that reporting this feature indicates support for the
38246 syntactic extensions only, not that the stub necessarily supports
38247 debugging of more than one process at a time. The stub must not use
38248 multiprocess extensions in packet replies unless @value{GDBN} has also
38249 indicated it supports them in its @samp{qSupported} request.
38251 @item qXfer:osdata:read
38252 The remote stub understands the @samp{qXfer:osdata:read} packet
38253 ((@pxref{qXfer osdata read}).
38255 @item ConditionalBreakpoints
38256 The target accepts and implements evaluation of conditional expressions
38257 defined for breakpoints. The target will only report breakpoint triggers
38258 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
38260 @item ConditionalTracepoints
38261 The remote stub accepts and implements conditional expressions defined
38262 for tracepoints (@pxref{Tracepoint Conditions}).
38264 @item ReverseContinue
38265 The remote stub accepts and implements the reverse continue packet
38269 The remote stub accepts and implements the reverse step packet
38272 @item TracepointSource
38273 The remote stub understands the @samp{QTDPsrc} packet that supplies
38274 the source form of tracepoint definitions.
38277 The remote stub understands the @samp{QAgent} packet.
38280 The remote stub understands the @samp{QAllow} packet.
38282 @item QDisableRandomization
38283 The remote stub understands the @samp{QDisableRandomization} packet.
38285 @item StaticTracepoint
38286 @cindex static tracepoints, in remote protocol
38287 The remote stub supports static tracepoints.
38289 @item InstallInTrace
38290 @anchor{install tracepoint in tracing}
38291 The remote stub supports installing tracepoint in tracing.
38293 @item EnableDisableTracepoints
38294 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
38295 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
38296 to be enabled and disabled while a trace experiment is running.
38298 @item QTBuffer:size
38299 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
38300 packet that allows to change the size of the trace buffer.
38303 @cindex string tracing, in remote protocol
38304 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
38305 See @ref{Bytecode Descriptions} for details about the bytecode.
38307 @item BreakpointCommands
38308 @cindex breakpoint commands, in remote protocol
38309 The remote stub supports running a breakpoint's command list itself,
38310 rather than reporting the hit to @value{GDBN}.
38313 The remote stub understands the @samp{Qbtrace:off} packet.
38316 The remote stub understands the @samp{Qbtrace:bts} packet.
38319 The remote stub understands the @samp{Qbtrace:pt} packet.
38321 @item Qbtrace-conf:bts:size
38322 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
38324 @item Qbtrace-conf:pt:size
38325 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
38328 The remote stub reports the @samp{swbreak} stop reason for memory
38332 The remote stub reports the @samp{hwbreak} stop reason for hardware
38336 The remote stub reports the @samp{fork} stop reason for fork events.
38339 The remote stub reports the @samp{vfork} stop reason for vfork events
38340 and vforkdone events.
38343 The remote stub reports the @samp{exec} stop reason for exec events.
38345 @item vContSupported
38346 The remote stub reports the supported actions in the reply to
38347 @samp{vCont?} packet.
38349 @item QThreadEvents
38350 The remote stub understands the @samp{QThreadEvents} packet.
38353 The remote stub reports the @samp{N} stop reply.
38358 @cindex symbol lookup, remote request
38359 @cindex @samp{qSymbol} packet
38360 Notify the target that @value{GDBN} is prepared to serve symbol lookup
38361 requests. Accept requests from the target for the values of symbols.
38366 The target does not need to look up any (more) symbols.
38367 @item qSymbol:@var{sym_name}
38368 The target requests the value of symbol @var{sym_name} (hex encoded).
38369 @value{GDBN} may provide the value by using the
38370 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
38374 @item qSymbol:@var{sym_value}:@var{sym_name}
38375 Set the value of @var{sym_name} to @var{sym_value}.
38377 @var{sym_name} (hex encoded) is the name of a symbol whose value the
38378 target has previously requested.
38380 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
38381 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
38387 The target does not need to look up any (more) symbols.
38388 @item qSymbol:@var{sym_name}
38389 The target requests the value of a new symbol @var{sym_name} (hex
38390 encoded). @value{GDBN} will continue to supply the values of symbols
38391 (if available), until the target ceases to request them.
38396 @itemx QTDisconnected
38403 @itemx qTMinFTPILen
38405 @xref{Tracepoint Packets}.
38407 @item qThreadExtraInfo,@var{thread-id}
38408 @cindex thread attributes info, remote request
38409 @cindex @samp{qThreadExtraInfo} packet
38410 Obtain from the target OS a printable string description of thread
38411 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
38412 for the forms of @var{thread-id}. This
38413 string may contain anything that the target OS thinks is interesting
38414 for @value{GDBN} to tell the user about the thread. The string is
38415 displayed in @value{GDBN}'s @code{info threads} display. Some
38416 examples of possible thread extra info strings are @samp{Runnable}, or
38417 @samp{Blocked on Mutex}.
38421 @item @var{XX}@dots{}
38422 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
38423 comprising the printable string containing the extra information about
38424 the thread's attributes.
38427 (Note that the @code{qThreadExtraInfo} packet's name is separated from
38428 the command by a @samp{,}, not a @samp{:}, contrary to the naming
38429 conventions above. Please don't use this packet as a model for new
38448 @xref{Tracepoint Packets}.
38450 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
38451 @cindex read special object, remote request
38452 @cindex @samp{qXfer} packet
38453 @anchor{qXfer read}
38454 Read uninterpreted bytes from the target's special data area
38455 identified by the keyword @var{object}. Request @var{length} bytes
38456 starting at @var{offset} bytes into the data. The content and
38457 encoding of @var{annex} is specific to @var{object}; it can supply
38458 additional details about what data to access.
38463 Data @var{data} (@pxref{Binary Data}) has been read from the
38464 target. There may be more data at a higher address (although
38465 it is permitted to return @samp{m} even for the last valid
38466 block of data, as long as at least one byte of data was read).
38467 It is possible for @var{data} to have fewer bytes than the @var{length} in the
38471 Data @var{data} (@pxref{Binary Data}) has been read from the target.
38472 There is no more data to be read. It is possible for @var{data} to
38473 have fewer bytes than the @var{length} in the request.
38476 The @var{offset} in the request is at the end of the data.
38477 There is no more data to be read.
38480 The request was malformed, or @var{annex} was invalid.
38483 The offset was invalid, or there was an error encountered reading the data.
38484 The @var{nn} part is a hex-encoded @code{errno} value.
38487 An empty reply indicates the @var{object} string was not recognized by
38488 the stub, or that the object does not support reading.
38491 Here are the specific requests of this form defined so far. All the
38492 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
38493 formats, listed above.
38496 @item qXfer:auxv:read::@var{offset},@var{length}
38497 @anchor{qXfer auxiliary vector read}
38498 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
38499 auxiliary vector}. Note @var{annex} must be empty.
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:btrace:read:@var{annex}:@var{offset},@var{length}
38505 @anchor{qXfer btrace read}
38507 Return a description of the current branch trace.
38508 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
38509 packet may have one of the following values:
38513 Returns all available branch trace.
38516 Returns all available branch trace if the branch trace changed since
38517 the last read request.
38520 Returns the new branch trace since the last read request. Adds a new
38521 block to the end of the trace that begins at zero and ends at the source
38522 location of the first branch in the trace buffer. This extra block is
38523 used to stitch traces together.
38525 If the trace buffer overflowed, returns an error indicating the overflow.
38528 This packet is not probed by default; the remote stub must request it
38529 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38531 @item qXfer:btrace-conf:read::@var{offset},@var{length}
38532 @anchor{qXfer btrace-conf read}
38534 Return a description of the current branch trace configuration.
38535 @xref{Branch Trace Configuration Format}.
38537 This packet is not probed by default; the remote stub must request it
38538 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38540 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
38541 @anchor{qXfer executable filename read}
38542 Return the full absolute name of the file that was executed to create
38543 a process running on the remote system. The annex specifies the
38544 numeric process ID of the process to query, encoded as a hexadecimal
38545 number. If the annex part is empty the remote stub should return the
38546 filename corresponding to the currently executing process.
38548 This packet is not probed by default; the remote stub must request it,
38549 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38551 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
38552 @anchor{qXfer target description read}
38553 Access the @dfn{target description}. @xref{Target Descriptions}. The
38554 annex specifies which XML document to access. The main description is
38555 always loaded from the @samp{target.xml} annex.
38557 This packet is not probed by default; the remote stub must request it,
38558 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38560 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
38561 @anchor{qXfer library list read}
38562 Access the target's list of loaded libraries. @xref{Library List Format}.
38563 The annex part of the generic @samp{qXfer} packet must be empty
38564 (@pxref{qXfer read}).
38566 Targets which maintain a list of libraries in the program's memory do
38567 not need to implement this packet; it is designed for platforms where
38568 the operating system manages the list of loaded libraries.
38570 This packet is not probed by default; the remote stub must request it,
38571 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38573 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
38574 @anchor{qXfer svr4 library list read}
38575 Access the target's list of loaded libraries when the target is an SVR4
38576 platform. @xref{Library List Format for SVR4 Targets}. The annex part
38577 of the generic @samp{qXfer} packet must be empty unless the remote
38578 stub indicated it supports the augmented form of this packet
38579 by supplying an appropriate @samp{qSupported} response
38580 (@pxref{qXfer read}, @ref{qSupported}).
38582 This packet is optional for better performance on SVR4 targets.
38583 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
38585 This packet is not probed by default; the remote stub must request it,
38586 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38588 If the remote stub indicates it supports the augmented form of this
38589 packet then the annex part of the generic @samp{qXfer} packet may
38590 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
38591 arguments. The currently supported arguments are:
38594 @item start=@var{address}
38595 A hexadecimal number specifying the address of the @samp{struct
38596 link_map} to start reading the library list from. If unset or zero
38597 then the first @samp{struct link_map} in the library list will be
38598 chosen as the starting point.
38600 @item prev=@var{address}
38601 A hexadecimal number specifying the address of the @samp{struct
38602 link_map} immediately preceding the @samp{struct link_map}
38603 specified by the @samp{start} argument. If unset or zero then
38604 the remote stub will expect that no @samp{struct link_map}
38605 exists prior to the starting point.
38609 Arguments that are not understood by the remote stub will be silently
38612 @item qXfer:memory-map:read::@var{offset},@var{length}
38613 @anchor{qXfer memory map read}
38614 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
38615 annex part of the generic @samp{qXfer} packet must be empty
38616 (@pxref{qXfer read}).
38618 This packet is not probed by default; the remote stub must request it,
38619 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38621 @item qXfer:sdata:read::@var{offset},@var{length}
38622 @anchor{qXfer sdata read}
38624 Read contents of the extra collected static tracepoint marker
38625 information. The annex part of the generic @samp{qXfer} packet must
38626 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
38629 This packet is not probed by default; the remote stub must request it,
38630 by supplying an appropriate @samp{qSupported} response
38631 (@pxref{qSupported}).
38633 @item qXfer:siginfo:read::@var{offset},@var{length}
38634 @anchor{qXfer siginfo read}
38635 Read contents of the extra signal information on the target
38636 system. The annex part of the generic @samp{qXfer} packet must be
38637 empty (@pxref{qXfer read}).
38639 This packet is not probed by default; the remote stub must request it,
38640 by supplying an appropriate @samp{qSupported} response
38641 (@pxref{qSupported}).
38643 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
38644 @anchor{qXfer spu read}
38645 Read contents of an @code{spufs} file on the target system. The
38646 annex specifies which file to read; it must be of the form
38647 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
38648 in the target process, and @var{name} identifes the @code{spufs} file
38649 in that context to be accessed.
38651 This packet is not probed by default; the remote stub must request it,
38652 by supplying an appropriate @samp{qSupported} response
38653 (@pxref{qSupported}).
38655 @item qXfer:threads:read::@var{offset},@var{length}
38656 @anchor{qXfer threads read}
38657 Access the list of threads on target. @xref{Thread List Format}. The
38658 annex part of the generic @samp{qXfer} packet must be empty
38659 (@pxref{qXfer read}).
38661 This packet is not probed by default; the remote stub must request it,
38662 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38664 @item qXfer:traceframe-info:read::@var{offset},@var{length}
38665 @anchor{qXfer traceframe info read}
38667 Return a description of the current traceframe's contents.
38668 @xref{Traceframe Info Format}. The annex part of the generic
38669 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
38671 This packet is not probed by default; the remote stub must request it,
38672 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38674 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
38675 @anchor{qXfer unwind info block}
38677 Return the unwind information block for @var{pc}. This packet is used
38678 on OpenVMS/ia64 to ask the kernel unwind information.
38680 This packet is not probed by default.
38682 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
38683 @anchor{qXfer fdpic loadmap read}
38684 Read contents of @code{loadmap}s on the target system. The
38685 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
38686 executable @code{loadmap} or interpreter @code{loadmap} to read.
38688 This packet is not probed by default; the remote stub must request it,
38689 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38691 @item qXfer:osdata:read::@var{offset},@var{length}
38692 @anchor{qXfer osdata read}
38693 Access the target's @dfn{operating system information}.
38694 @xref{Operating System Information}.
38698 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
38699 @cindex write data into object, remote request
38700 @anchor{qXfer write}
38701 Write uninterpreted bytes into the target's special data area
38702 identified by the keyword @var{object}, starting at @var{offset} bytes
38703 into the data. The binary-encoded data (@pxref{Binary Data}) to be
38704 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
38705 is specific to @var{object}; it can supply additional details about what data
38711 @var{nn} (hex encoded) is the number of bytes written.
38712 This may be fewer bytes than supplied in the request.
38715 The request was malformed, or @var{annex} was invalid.
38718 The offset was invalid, or there was an error encountered writing the data.
38719 The @var{nn} part is a hex-encoded @code{errno} value.
38722 An empty reply indicates the @var{object} string was not
38723 recognized by the stub, or that the object does not support writing.
38726 Here are the specific requests of this form defined so far. All the
38727 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
38728 formats, listed above.
38731 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
38732 @anchor{qXfer siginfo write}
38733 Write @var{data} to the extra signal information on the target system.
38734 The annex part of the generic @samp{qXfer} packet must be
38735 empty (@pxref{qXfer write}).
38737 This packet is not probed by default; the remote stub must request it,
38738 by supplying an appropriate @samp{qSupported} response
38739 (@pxref{qSupported}).
38741 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
38742 @anchor{qXfer spu write}
38743 Write @var{data} to an @code{spufs} file on the target system. The
38744 annex specifies which file to write; it must be of the form
38745 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
38746 in the target process, and @var{name} identifes the @code{spufs} file
38747 in that context to be accessed.
38749 This packet is not probed by default; the remote stub must request it,
38750 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38753 @item qXfer:@var{object}:@var{operation}:@dots{}
38754 Requests of this form may be added in the future. When a stub does
38755 not recognize the @var{object} keyword, or its support for
38756 @var{object} does not recognize the @var{operation} keyword, the stub
38757 must respond with an empty packet.
38759 @item qAttached:@var{pid}
38760 @cindex query attached, remote request
38761 @cindex @samp{qAttached} packet
38762 Return an indication of whether the remote server attached to an
38763 existing process or created a new process. When the multiprocess
38764 protocol extensions are supported (@pxref{multiprocess extensions}),
38765 @var{pid} is an integer in hexadecimal format identifying the target
38766 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
38767 the query packet will be simplified as @samp{qAttached}.
38769 This query is used, for example, to know whether the remote process
38770 should be detached or killed when a @value{GDBN} session is ended with
38771 the @code{quit} command.
38776 The remote server attached to an existing process.
38778 The remote server created a new process.
38780 A badly formed request or an error was encountered.
38784 Enable branch tracing for the current thread using Branch Trace Store.
38789 Branch tracing has been enabled.
38791 A badly formed request or an error was encountered.
38795 Enable branch tracing for the current thread using Intel Processor Trace.
38800 Branch tracing has been enabled.
38802 A badly formed request or an error was encountered.
38806 Disable branch tracing for the current thread.
38811 Branch tracing has been disabled.
38813 A badly formed request or an error was encountered.
38816 @item Qbtrace-conf:bts:size=@var{value}
38817 Set the requested ring buffer size for new threads that use the
38818 btrace recording method in bts format.
38823 The ring buffer size has been set.
38825 A badly formed request or an error was encountered.
38828 @item Qbtrace-conf:pt:size=@var{value}
38829 Set the requested ring buffer size for new threads that use the
38830 btrace recording method in pt format.
38835 The ring buffer size has been set.
38837 A badly formed request or an error was encountered.
38842 @node Architecture-Specific Protocol Details
38843 @section Architecture-Specific Protocol Details
38845 This section describes how the remote protocol is applied to specific
38846 target architectures. Also see @ref{Standard Target Features}, for
38847 details of XML target descriptions for each architecture.
38850 * ARM-Specific Protocol Details::
38851 * MIPS-Specific Protocol Details::
38854 @node ARM-Specific Protocol Details
38855 @subsection @acronym{ARM}-specific Protocol Details
38858 * ARM Breakpoint Kinds::
38861 @node ARM Breakpoint Kinds
38862 @subsubsection @acronym{ARM} Breakpoint Kinds
38863 @cindex breakpoint kinds, @acronym{ARM}
38865 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38870 16-bit Thumb mode breakpoint.
38873 32-bit Thumb mode (Thumb-2) breakpoint.
38876 32-bit @acronym{ARM} mode breakpoint.
38880 @node MIPS-Specific Protocol Details
38881 @subsection @acronym{MIPS}-specific Protocol Details
38884 * MIPS Register packet Format::
38885 * MIPS Breakpoint Kinds::
38888 @node MIPS Register packet Format
38889 @subsubsection @acronym{MIPS} Register Packet Format
38890 @cindex register packet format, @acronym{MIPS}
38892 The following @code{g}/@code{G} packets have previously been defined.
38893 In the below, some thirty-two bit registers are transferred as
38894 sixty-four bits. Those registers should be zero/sign extended (which?)
38895 to fill the space allocated. Register bytes are transferred in target
38896 byte order. The two nibbles within a register byte are transferred
38897 most-significant -- least-significant.
38902 All registers are transferred as thirty-two bit quantities in the order:
38903 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
38904 registers; fsr; fir; fp.
38907 All registers are transferred as sixty-four bit quantities (including
38908 thirty-two bit registers such as @code{sr}). The ordering is the same
38913 @node MIPS Breakpoint Kinds
38914 @subsubsection @acronym{MIPS} Breakpoint Kinds
38915 @cindex breakpoint kinds, @acronym{MIPS}
38917 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38922 16-bit @acronym{MIPS16} mode breakpoint.
38925 16-bit @acronym{microMIPS} mode breakpoint.
38928 32-bit standard @acronym{MIPS} mode breakpoint.
38931 32-bit @acronym{microMIPS} mode breakpoint.
38935 @node Tracepoint Packets
38936 @section Tracepoint Packets
38937 @cindex tracepoint packets
38938 @cindex packets, tracepoint
38940 Here we describe the packets @value{GDBN} uses to implement
38941 tracepoints (@pxref{Tracepoints}).
38945 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
38946 @cindex @samp{QTDP} packet
38947 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
38948 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
38949 the tracepoint is disabled. The @var{step} gives the tracepoint's step
38950 count, and @var{pass} gives its pass count. If an @samp{F} is present,
38951 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
38952 the number of bytes that the target should copy elsewhere to make room
38953 for the tracepoint. If an @samp{X} is present, it introduces a
38954 tracepoint condition, which consists of a hexadecimal length, followed
38955 by a comma and hex-encoded bytes, in a manner similar to action
38956 encodings as described below. If the trailing @samp{-} is present,
38957 further @samp{QTDP} packets will follow to specify this tracepoint's
38963 The packet was understood and carried out.
38965 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38967 The packet was not recognized.
38970 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
38971 Define actions to be taken when a tracepoint is hit. The @var{n} and
38972 @var{addr} must be the same as in the initial @samp{QTDP} packet for
38973 this tracepoint. This packet may only be sent immediately after
38974 another @samp{QTDP} packet that ended with a @samp{-}. If the
38975 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
38976 specifying more actions for this tracepoint.
38978 In the series of action packets for a given tracepoint, at most one
38979 can have an @samp{S} before its first @var{action}. If such a packet
38980 is sent, it and the following packets define ``while-stepping''
38981 actions. Any prior packets define ordinary actions --- that is, those
38982 taken when the tracepoint is first hit. If no action packet has an
38983 @samp{S}, then all the packets in the series specify ordinary
38984 tracepoint actions.
38986 The @samp{@var{action}@dots{}} portion of the packet is a series of
38987 actions, concatenated without separators. Each action has one of the
38993 Collect the registers whose bits are set in @var{mask},
38994 a hexadecimal number whose @var{i}'th bit is set if register number
38995 @var{i} should be collected. (The least significant bit is numbered
38996 zero.) Note that @var{mask} may be any number of digits long; it may
38997 not fit in a 32-bit word.
38999 @item M @var{basereg},@var{offset},@var{len}
39000 Collect @var{len} bytes of memory starting at the address in register
39001 number @var{basereg}, plus @var{offset}. If @var{basereg} is
39002 @samp{-1}, then the range has a fixed address: @var{offset} is the
39003 address of the lowest byte to collect. The @var{basereg},
39004 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
39005 values (the @samp{-1} value for @var{basereg} is a special case).
39007 @item X @var{len},@var{expr}
39008 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
39009 it directs. The agent expression @var{expr} is as described in
39010 @ref{Agent Expressions}. Each byte of the expression is encoded as a
39011 two-digit hex number in the packet; @var{len} is the number of bytes
39012 in the expression (and thus one-half the number of hex digits in the
39017 Any number of actions may be packed together in a single @samp{QTDP}
39018 packet, as long as the packet does not exceed the maximum packet
39019 length (400 bytes, for many stubs). There may be only one @samp{R}
39020 action per tracepoint, and it must precede any @samp{M} or @samp{X}
39021 actions. Any registers referred to by @samp{M} and @samp{X} actions
39022 must be collected by a preceding @samp{R} action. (The
39023 ``while-stepping'' actions are treated as if they were attached to a
39024 separate tracepoint, as far as these restrictions are concerned.)
39029 The packet was understood and carried out.
39031 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
39033 The packet was not recognized.
39036 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
39037 @cindex @samp{QTDPsrc} packet
39038 Specify a source string of tracepoint @var{n} at address @var{addr}.
39039 This is useful to get accurate reproduction of the tracepoints
39040 originally downloaded at the beginning of the trace run. The @var{type}
39041 is the name of the tracepoint part, such as @samp{cond} for the
39042 tracepoint's conditional expression (see below for a list of types), while
39043 @var{bytes} is the string, encoded in hexadecimal.
39045 @var{start} is the offset of the @var{bytes} within the overall source
39046 string, while @var{slen} is the total length of the source string.
39047 This is intended for handling source strings that are longer than will
39048 fit in a single packet.
39049 @c Add detailed example when this info is moved into a dedicated
39050 @c tracepoint descriptions section.
39052 The available string types are @samp{at} for the location,
39053 @samp{cond} for the conditional, and @samp{cmd} for an action command.
39054 @value{GDBN} sends a separate packet for each command in the action
39055 list, in the same order in which the commands are stored in the list.
39057 The target does not need to do anything with source strings except
39058 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
39061 Although this packet is optional, and @value{GDBN} will only send it
39062 if the target replies with @samp{TracepointSource} @xref{General
39063 Query Packets}, it makes both disconnected tracing and trace files
39064 much easier to use. Otherwise the user must be careful that the
39065 tracepoints in effect while looking at trace frames are identical to
39066 the ones in effect during the trace run; even a small discrepancy
39067 could cause @samp{tdump} not to work, or a particular trace frame not
39070 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
39071 @cindex define trace state variable, remote request
39072 @cindex @samp{QTDV} packet
39073 Create a new trace state variable, number @var{n}, with an initial
39074 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
39075 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
39076 the option of not using this packet for initial values of zero; the
39077 target should simply create the trace state variables as they are
39078 mentioned in expressions. The value @var{builtin} should be 1 (one)
39079 if the trace state variable is builtin and 0 (zero) if it is not builtin.
39080 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
39081 @samp{qTsV} packet had it set. The contents of @var{name} is the
39082 hex-encoded name (without the leading @samp{$}) of the trace state
39085 @item QTFrame:@var{n}
39086 @cindex @samp{QTFrame} packet
39087 Select the @var{n}'th tracepoint frame from the buffer, and use the
39088 register and memory contents recorded there to answer subsequent
39089 request packets from @value{GDBN}.
39091 A successful reply from the stub indicates that the stub has found the
39092 requested frame. The response is a series of parts, concatenated
39093 without separators, describing the frame we selected. Each part has
39094 one of the following forms:
39098 The selected frame is number @var{n} in the trace frame buffer;
39099 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
39100 was no frame matching the criteria in the request packet.
39103 The selected trace frame records a hit of tracepoint number @var{t};
39104 @var{t} is a hexadecimal number.
39108 @item QTFrame:pc:@var{addr}
39109 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
39110 currently selected frame whose PC is @var{addr};
39111 @var{addr} is a hexadecimal number.
39113 @item QTFrame:tdp:@var{t}
39114 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
39115 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
39116 is a hexadecimal number.
39118 @item QTFrame:range:@var{start}:@var{end}
39119 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
39120 currently selected frame whose PC is between @var{start} (inclusive)
39121 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
39124 @item QTFrame:outside:@var{start}:@var{end}
39125 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
39126 frame @emph{outside} the given range of addresses (exclusive).
39129 @cindex @samp{qTMinFTPILen} packet
39130 This packet requests the minimum length of instruction at which a fast
39131 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
39132 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
39133 it depends on the target system being able to create trampolines in
39134 the first 64K of memory, which might or might not be possible for that
39135 system. So the reply to this packet will be 4 if it is able to
39142 The minimum instruction length is currently unknown.
39144 The minimum instruction length is @var{length}, where @var{length}
39145 is a hexadecimal number greater or equal to 1. A reply
39146 of 1 means that a fast tracepoint may be placed on any instruction
39147 regardless of size.
39149 An error has occurred.
39151 An empty reply indicates that the request is not supported by the stub.
39155 @cindex @samp{QTStart} packet
39156 Begin the tracepoint experiment. Begin collecting data from
39157 tracepoint hits in the trace frame buffer. This packet supports the
39158 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
39159 instruction reply packet}).
39162 @cindex @samp{QTStop} packet
39163 End the tracepoint experiment. Stop collecting trace frames.
39165 @item QTEnable:@var{n}:@var{addr}
39167 @cindex @samp{QTEnable} packet
39168 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
39169 experiment. If the tracepoint was previously disabled, then collection
39170 of data from it will resume.
39172 @item QTDisable:@var{n}:@var{addr}
39174 @cindex @samp{QTDisable} packet
39175 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
39176 experiment. No more data will be collected from the tracepoint unless
39177 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
39180 @cindex @samp{QTinit} packet
39181 Clear the table of tracepoints, and empty the trace frame buffer.
39183 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
39184 @cindex @samp{QTro} packet
39185 Establish the given ranges of memory as ``transparent''. The stub
39186 will answer requests for these ranges from memory's current contents,
39187 if they were not collected as part of the tracepoint hit.
39189 @value{GDBN} uses this to mark read-only regions of memory, like those
39190 containing program code. Since these areas never change, they should
39191 still have the same contents they did when the tracepoint was hit, so
39192 there's no reason for the stub to refuse to provide their contents.
39194 @item QTDisconnected:@var{value}
39195 @cindex @samp{QTDisconnected} packet
39196 Set the choice to what to do with the tracing run when @value{GDBN}
39197 disconnects from the target. A @var{value} of 1 directs the target to
39198 continue the tracing run, while 0 tells the target to stop tracing if
39199 @value{GDBN} is no longer in the picture.
39202 @cindex @samp{qTStatus} packet
39203 Ask the stub if there is a trace experiment running right now.
39205 The reply has the form:
39209 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
39210 @var{running} is a single digit @code{1} if the trace is presently
39211 running, or @code{0} if not. It is followed by semicolon-separated
39212 optional fields that an agent may use to report additional status.
39216 If the trace is not running, the agent may report any of several
39217 explanations as one of the optional fields:
39222 No trace has been run yet.
39224 @item tstop[:@var{text}]:0
39225 The trace was stopped by a user-originated stop command. The optional
39226 @var{text} field is a user-supplied string supplied as part of the
39227 stop command (for instance, an explanation of why the trace was
39228 stopped manually). It is hex-encoded.
39231 The trace stopped because the trace buffer filled up.
39233 @item tdisconnected:0
39234 The trace stopped because @value{GDBN} disconnected from the target.
39236 @item tpasscount:@var{tpnum}
39237 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
39239 @item terror:@var{text}:@var{tpnum}
39240 The trace stopped because tracepoint @var{tpnum} had an error. The
39241 string @var{text} is available to describe the nature of the error
39242 (for instance, a divide by zero in the condition expression); it
39246 The trace stopped for some other reason.
39250 Additional optional fields supply statistical and other information.
39251 Although not required, they are extremely useful for users monitoring
39252 the progress of a trace run. If a trace has stopped, and these
39253 numbers are reported, they must reflect the state of the just-stopped
39258 @item tframes:@var{n}
39259 The number of trace frames in the buffer.
39261 @item tcreated:@var{n}
39262 The total number of trace frames created during the run. This may
39263 be larger than the trace frame count, if the buffer is circular.
39265 @item tsize:@var{n}
39266 The total size of the trace buffer, in bytes.
39268 @item tfree:@var{n}
39269 The number of bytes still unused in the buffer.
39271 @item circular:@var{n}
39272 The value of the circular trace buffer flag. @code{1} means that the
39273 trace buffer is circular and old trace frames will be discarded if
39274 necessary to make room, @code{0} means that the trace buffer is linear
39277 @item disconn:@var{n}
39278 The value of the disconnected tracing flag. @code{1} means that
39279 tracing will continue after @value{GDBN} disconnects, @code{0} means
39280 that the trace run will stop.
39284 @item qTP:@var{tp}:@var{addr}
39285 @cindex tracepoint status, remote request
39286 @cindex @samp{qTP} packet
39287 Ask the stub for the current state of tracepoint number @var{tp} at
39288 address @var{addr}.
39292 @item V@var{hits}:@var{usage}
39293 The tracepoint has been hit @var{hits} times so far during the trace
39294 run, and accounts for @var{usage} in the trace buffer. Note that
39295 @code{while-stepping} steps are not counted as separate hits, but the
39296 steps' space consumption is added into the usage number.
39300 @item qTV:@var{var}
39301 @cindex trace state variable value, remote request
39302 @cindex @samp{qTV} packet
39303 Ask the stub for the value of the trace state variable number @var{var}.
39308 The value of the variable is @var{value}. This will be the current
39309 value of the variable if the user is examining a running target, or a
39310 saved value if the variable was collected in the trace frame that the
39311 user is looking at. Note that multiple requests may result in
39312 different reply values, such as when requesting values while the
39313 program is running.
39316 The value of the variable is unknown. This would occur, for example,
39317 if the user is examining a trace frame in which the requested variable
39322 @cindex @samp{qTfP} packet
39324 @cindex @samp{qTsP} packet
39325 These packets request data about tracepoints that are being used by
39326 the target. @value{GDBN} sends @code{qTfP} to get the first piece
39327 of data, and multiple @code{qTsP} to get additional pieces. Replies
39328 to these packets generally take the form of the @code{QTDP} packets
39329 that define tracepoints. (FIXME add detailed syntax)
39332 @cindex @samp{qTfV} packet
39334 @cindex @samp{qTsV} packet
39335 These packets request data about trace state variables that are on the
39336 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
39337 and multiple @code{qTsV} to get additional variables. Replies to
39338 these packets follow the syntax of the @code{QTDV} packets that define
39339 trace state variables.
39345 @cindex @samp{qTfSTM} packet
39346 @cindex @samp{qTsSTM} packet
39347 These packets request data about static tracepoint markers that exist
39348 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
39349 first piece of data, and multiple @code{qTsSTM} to get additional
39350 pieces. Replies to these packets take the following form:
39354 @item m @var{address}:@var{id}:@var{extra}
39356 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
39357 a comma-separated list of markers
39359 (lower case letter @samp{L}) denotes end of list.
39361 An error occurred. The error number @var{nn} is given as hex digits.
39363 An empty reply indicates that the request is not supported by the
39367 The @var{address} is encoded in hex;
39368 @var{id} and @var{extra} are strings encoded in hex.
39370 In response to each query, the target will reply with a list of one or
39371 more markers, separated by commas. @value{GDBN} will respond to each
39372 reply with a request for more markers (using the @samp{qs} form of the
39373 query), until the target responds with @samp{l} (lower-case ell, for
39376 @item qTSTMat:@var{address}
39378 @cindex @samp{qTSTMat} packet
39379 This packets requests data about static tracepoint markers in the
39380 target program at @var{address}. Replies to this packet follow the
39381 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
39382 tracepoint markers.
39384 @item QTSave:@var{filename}
39385 @cindex @samp{QTSave} packet
39386 This packet directs the target to save trace data to the file name
39387 @var{filename} in the target's filesystem. The @var{filename} is encoded
39388 as a hex string; the interpretation of the file name (relative vs
39389 absolute, wild cards, etc) is up to the target.
39391 @item qTBuffer:@var{offset},@var{len}
39392 @cindex @samp{qTBuffer} packet
39393 Return up to @var{len} bytes of the current contents of trace buffer,
39394 starting at @var{offset}. The trace buffer is treated as if it were
39395 a contiguous collection of traceframes, as per the trace file format.
39396 The reply consists as many hex-encoded bytes as the target can deliver
39397 in a packet; it is not an error to return fewer than were asked for.
39398 A reply consisting of just @code{l} indicates that no bytes are
39401 @item QTBuffer:circular:@var{value}
39402 This packet directs the target to use a circular trace buffer if
39403 @var{value} is 1, or a linear buffer if the value is 0.
39405 @item QTBuffer:size:@var{size}
39406 @anchor{QTBuffer-size}
39407 @cindex @samp{QTBuffer size} packet
39408 This packet directs the target to make the trace buffer be of size
39409 @var{size} if possible. A value of @code{-1} tells the target to
39410 use whatever size it prefers.
39412 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
39413 @cindex @samp{QTNotes} packet
39414 This packet adds optional textual notes to the trace run. Allowable
39415 types include @code{user}, @code{notes}, and @code{tstop}, the
39416 @var{text} fields are arbitrary strings, hex-encoded.
39420 @subsection Relocate instruction reply packet
39421 When installing fast tracepoints in memory, the target may need to
39422 relocate the instruction currently at the tracepoint address to a
39423 different address in memory. For most instructions, a simple copy is
39424 enough, but, for example, call instructions that implicitly push the
39425 return address on the stack, and relative branches or other
39426 PC-relative instructions require offset adjustment, so that the effect
39427 of executing the instruction at a different address is the same as if
39428 it had executed in the original location.
39430 In response to several of the tracepoint packets, the target may also
39431 respond with a number of intermediate @samp{qRelocInsn} request
39432 packets before the final result packet, to have @value{GDBN} handle
39433 this relocation operation. If a packet supports this mechanism, its
39434 documentation will explicitly say so. See for example the above
39435 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
39436 format of the request is:
39439 @item qRelocInsn:@var{from};@var{to}
39441 This requests @value{GDBN} to copy instruction at address @var{from}
39442 to address @var{to}, possibly adjusted so that executing the
39443 instruction at @var{to} has the same effect as executing it at
39444 @var{from}. @value{GDBN} writes the adjusted instruction to target
39445 memory starting at @var{to}.
39450 @item qRelocInsn:@var{adjusted_size}
39451 Informs the stub the relocation is complete. The @var{adjusted_size} is
39452 the length in bytes of resulting relocated instruction sequence.
39454 A badly formed request was detected, or an error was encountered while
39455 relocating the instruction.
39458 @node Host I/O Packets
39459 @section Host I/O Packets
39460 @cindex Host I/O, remote protocol
39461 @cindex file transfer, remote protocol
39463 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
39464 operations on the far side of a remote link. For example, Host I/O is
39465 used to upload and download files to a remote target with its own
39466 filesystem. Host I/O uses the same constant values and data structure
39467 layout as the target-initiated File-I/O protocol. However, the
39468 Host I/O packets are structured differently. The target-initiated
39469 protocol relies on target memory to store parameters and buffers.
39470 Host I/O requests are initiated by @value{GDBN}, and the
39471 target's memory is not involved. @xref{File-I/O Remote Protocol
39472 Extension}, for more details on the target-initiated protocol.
39474 The Host I/O request packets all encode a single operation along with
39475 its arguments. They have this format:
39479 @item vFile:@var{operation}: @var{parameter}@dots{}
39480 @var{operation} is the name of the particular request; the target
39481 should compare the entire packet name up to the second colon when checking
39482 for a supported operation. The format of @var{parameter} depends on
39483 the operation. Numbers are always passed in hexadecimal. Negative
39484 numbers have an explicit minus sign (i.e.@: two's complement is not
39485 used). Strings (e.g.@: filenames) are encoded as a series of
39486 hexadecimal bytes. The last argument to a system call may be a
39487 buffer of escaped binary data (@pxref{Binary Data}).
39491 The valid responses to Host I/O packets are:
39495 @item F @var{result} [, @var{errno}] [; @var{attachment}]
39496 @var{result} is the integer value returned by this operation, usually
39497 non-negative for success and -1 for errors. If an error has occured,
39498 @var{errno} will be included in the result specifying a
39499 value defined by the File-I/O protocol (@pxref{Errno Values}). For
39500 operations which return data, @var{attachment} supplies the data as a
39501 binary buffer. Binary buffers in response packets are escaped in the
39502 normal way (@pxref{Binary Data}). See the individual packet
39503 documentation for the interpretation of @var{result} and
39507 An empty response indicates that this operation is not recognized.
39511 These are the supported Host I/O operations:
39514 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
39515 Open a file at @var{filename} and return a file descriptor for it, or
39516 return -1 if an error occurs. The @var{filename} is a string,
39517 @var{flags} is an integer indicating a mask of open flags
39518 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
39519 of mode bits to use if the file is created (@pxref{mode_t Values}).
39520 @xref{open}, for details of the open flags and mode values.
39522 @item vFile:close: @var{fd}
39523 Close the open file corresponding to @var{fd} and return 0, or
39524 -1 if an error occurs.
39526 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
39527 Read data from the open file corresponding to @var{fd}. Up to
39528 @var{count} bytes will be read from the file, starting at @var{offset}
39529 relative to the start of the file. The target may read fewer bytes;
39530 common reasons include packet size limits and an end-of-file
39531 condition. The number of bytes read is returned. Zero should only be
39532 returned for a successful read at the end of the file, or if
39533 @var{count} was zero.
39535 The data read should be returned as a binary attachment on success.
39536 If zero bytes were read, the response should include an empty binary
39537 attachment (i.e.@: a trailing semicolon). The return value is the
39538 number of target bytes read; the binary attachment may be longer if
39539 some characters were escaped.
39541 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
39542 Write @var{data} (a binary buffer) to the open file corresponding
39543 to @var{fd}. Start the write at @var{offset} from the start of the
39544 file. Unlike many @code{write} system calls, there is no
39545 separate @var{count} argument; the length of @var{data} in the
39546 packet is used. @samp{vFile:write} returns the number of bytes written,
39547 which may be shorter than the length of @var{data}, or -1 if an
39550 @item vFile:fstat: @var{fd}
39551 Get information about the open file corresponding to @var{fd}.
39552 On success the information is returned as a binary attachment
39553 and the return value is the size of this attachment in bytes.
39554 If an error occurs the return value is -1. The format of the
39555 returned binary attachment is as described in @ref{struct stat}.
39557 @item vFile:unlink: @var{filename}
39558 Delete the file at @var{filename} on the target. Return 0,
39559 or -1 if an error occurs. The @var{filename} is a string.
39561 @item vFile:readlink: @var{filename}
39562 Read value of symbolic link @var{filename} on the target. Return
39563 the number of bytes read, or -1 if an error occurs.
39565 The data read should be returned as a binary attachment on success.
39566 If zero bytes were read, the response should include an empty binary
39567 attachment (i.e.@: a trailing semicolon). The return value is the
39568 number of target bytes read; the binary attachment may be longer if
39569 some characters were escaped.
39571 @item vFile:setfs: @var{pid}
39572 Select the filesystem on which @code{vFile} operations with
39573 @var{filename} arguments will operate. This is required for
39574 @value{GDBN} to be able to access files on remote targets where
39575 the remote stub does not share a common filesystem with the
39578 If @var{pid} is nonzero, select the filesystem as seen by process
39579 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
39580 the remote stub. Return 0 on success, or -1 if an error occurs.
39581 If @code{vFile:setfs:} indicates success, the selected filesystem
39582 remains selected until the next successful @code{vFile:setfs:}
39588 @section Interrupts
39589 @cindex interrupts (remote protocol)
39590 @anchor{interrupting remote targets}
39592 In all-stop mode, when a program on the remote target is running,
39593 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
39594 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
39595 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
39597 The precise meaning of @code{BREAK} is defined by the transport
39598 mechanism and may, in fact, be undefined. @value{GDBN} does not
39599 currently define a @code{BREAK} mechanism for any of the network
39600 interfaces except for TCP, in which case @value{GDBN} sends the
39601 @code{telnet} BREAK sequence.
39603 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
39604 transport mechanisms. It is represented by sending the single byte
39605 @code{0x03} without any of the usual packet overhead described in
39606 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
39607 transmitted as part of a packet, it is considered to be packet data
39608 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
39609 (@pxref{X packet}), used for binary downloads, may include an unescaped
39610 @code{0x03} as part of its packet.
39612 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
39613 When Linux kernel receives this sequence from serial port,
39614 it stops execution and connects to gdb.
39616 In non-stop mode, because packet resumptions are asynchronous
39617 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
39618 command to the remote stub, even when the target is running. For that
39619 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
39620 packet}) with the usual packet framing instead of the single byte
39623 Stubs are not required to recognize these interrupt mechanisms and the
39624 precise meaning associated with receipt of the interrupt is
39625 implementation defined. If the target supports debugging of multiple
39626 threads and/or processes, it should attempt to interrupt all
39627 currently-executing threads and processes.
39628 If the stub is successful at interrupting the
39629 running program, it should send one of the stop
39630 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
39631 of successfully stopping the program in all-stop mode, and a stop reply
39632 for each stopped thread in non-stop mode.
39633 Interrupts received while the
39634 program is stopped are queued and the program will be interrupted when
39635 it is resumed next time.
39637 @node Notification Packets
39638 @section Notification Packets
39639 @cindex notification packets
39640 @cindex packets, notification
39642 The @value{GDBN} remote serial protocol includes @dfn{notifications},
39643 packets that require no acknowledgment. Both the GDB and the stub
39644 may send notifications (although the only notifications defined at
39645 present are sent by the stub). Notifications carry information
39646 without incurring the round-trip latency of an acknowledgment, and so
39647 are useful for low-impact communications where occasional packet loss
39650 A notification packet has the form @samp{% @var{data} #
39651 @var{checksum}}, where @var{data} is the content of the notification,
39652 and @var{checksum} is a checksum of @var{data}, computed and formatted
39653 as for ordinary @value{GDBN} packets. A notification's @var{data}
39654 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
39655 receiving a notification, the recipient sends no @samp{+} or @samp{-}
39656 to acknowledge the notification's receipt or to report its corruption.
39658 Every notification's @var{data} begins with a name, which contains no
39659 colon characters, followed by a colon character.
39661 Recipients should silently ignore corrupted notifications and
39662 notifications they do not understand. Recipients should restart
39663 timeout periods on receipt of a well-formed notification, whether or
39664 not they understand it.
39666 Senders should only send the notifications described here when this
39667 protocol description specifies that they are permitted. In the
39668 future, we may extend the protocol to permit existing notifications in
39669 new contexts; this rule helps older senders avoid confusing newer
39672 (Older versions of @value{GDBN} ignore bytes received until they see
39673 the @samp{$} byte that begins an ordinary packet, so new stubs may
39674 transmit notifications without fear of confusing older clients. There
39675 are no notifications defined for @value{GDBN} to send at the moment, but we
39676 assume that most older stubs would ignore them, as well.)
39678 Each notification is comprised of three parts:
39680 @item @var{name}:@var{event}
39681 The notification packet is sent by the side that initiates the
39682 exchange (currently, only the stub does that), with @var{event}
39683 carrying the specific information about the notification, and
39684 @var{name} specifying the name of the notification.
39686 The acknowledge sent by the other side, usually @value{GDBN}, to
39687 acknowledge the exchange and request the event.
39690 The purpose of an asynchronous notification mechanism is to report to
39691 @value{GDBN} that something interesting happened in the remote stub.
39693 The remote stub may send notification @var{name}:@var{event}
39694 at any time, but @value{GDBN} acknowledges the notification when
39695 appropriate. The notification event is pending before @value{GDBN}
39696 acknowledges. Only one notification at a time may be pending; if
39697 additional events occur before @value{GDBN} has acknowledged the
39698 previous notification, they must be queued by the stub for later
39699 synchronous transmission in response to @var{ack} packets from
39700 @value{GDBN}. Because the notification mechanism is unreliable,
39701 the stub is permitted to resend a notification if it believes
39702 @value{GDBN} may not have received it.
39704 Specifically, notifications may appear when @value{GDBN} is not
39705 otherwise reading input from the stub, or when @value{GDBN} is
39706 expecting to read a normal synchronous response or a
39707 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
39708 Notification packets are distinct from any other communication from
39709 the stub so there is no ambiguity.
39711 After receiving a notification, @value{GDBN} shall acknowledge it by
39712 sending a @var{ack} packet as a regular, synchronous request to the
39713 stub. Such acknowledgment is not required to happen immediately, as
39714 @value{GDBN} is permitted to send other, unrelated packets to the
39715 stub first, which the stub should process normally.
39717 Upon receiving a @var{ack} packet, if the stub has other queued
39718 events to report to @value{GDBN}, it shall respond by sending a
39719 normal @var{event}. @value{GDBN} shall then send another @var{ack}
39720 packet to solicit further responses; again, it is permitted to send
39721 other, unrelated packets as well which the stub should process
39724 If the stub receives a @var{ack} packet and there are no additional
39725 @var{event} to report, the stub shall return an @samp{OK} response.
39726 At this point, @value{GDBN} has finished processing a notification
39727 and the stub has completed sending any queued events. @value{GDBN}
39728 won't accept any new notifications until the final @samp{OK} is
39729 received . If further notification events occur, the stub shall send
39730 a new notification, @value{GDBN} shall accept the notification, and
39731 the process shall be repeated.
39733 The process of asynchronous notification can be illustrated by the
39736 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
39739 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
39741 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
39746 The following notifications are defined:
39747 @multitable @columnfractions 0.12 0.12 0.38 0.38
39756 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
39757 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
39758 for information on how these notifications are acknowledged by
39760 @tab Report an asynchronous stop event in non-stop mode.
39764 @node Remote Non-Stop
39765 @section Remote Protocol Support for Non-Stop Mode
39767 @value{GDBN}'s remote protocol supports non-stop debugging of
39768 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
39769 supports non-stop mode, it should report that to @value{GDBN} by including
39770 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
39772 @value{GDBN} typically sends a @samp{QNonStop} packet only when
39773 establishing a new connection with the stub. Entering non-stop mode
39774 does not alter the state of any currently-running threads, but targets
39775 must stop all threads in any already-attached processes when entering
39776 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
39777 probe the target state after a mode change.
39779 In non-stop mode, when an attached process encounters an event that
39780 would otherwise be reported with a stop reply, it uses the
39781 asynchronous notification mechanism (@pxref{Notification Packets}) to
39782 inform @value{GDBN}. In contrast to all-stop mode, where all threads
39783 in all processes are stopped when a stop reply is sent, in non-stop
39784 mode only the thread reporting the stop event is stopped. That is,
39785 when reporting a @samp{S} or @samp{T} response to indicate completion
39786 of a step operation, hitting a breakpoint, or a fault, only the
39787 affected thread is stopped; any other still-running threads continue
39788 to run. When reporting a @samp{W} or @samp{X} response, all running
39789 threads belonging to other attached processes continue to run.
39791 In non-stop mode, the target shall respond to the @samp{?} packet as
39792 follows. First, any incomplete stop reply notification/@samp{vStopped}
39793 sequence in progress is abandoned. The target must begin a new
39794 sequence reporting stop events for all stopped threads, whether or not
39795 it has previously reported those events to @value{GDBN}. The first
39796 stop reply is sent as a synchronous reply to the @samp{?} packet, and
39797 subsequent stop replies are sent as responses to @samp{vStopped} packets
39798 using the mechanism described above. The target must not send
39799 asynchronous stop reply notifications until the sequence is complete.
39800 If all threads are running when the target receives the @samp{?} packet,
39801 or if the target is not attached to any process, it shall respond
39804 If the stub supports non-stop mode, it should also support the
39805 @samp{swbreak} stop reason if software breakpoints are supported, and
39806 the @samp{hwbreak} stop reason if hardware breakpoints are supported
39807 (@pxref{swbreak stop reason}). This is because given the asynchronous
39808 nature of non-stop mode, between the time a thread hits a breakpoint
39809 and the time the event is finally processed by @value{GDBN}, the
39810 breakpoint may have already been removed from the target. Due to
39811 this, @value{GDBN} needs to be able to tell whether a trap stop was
39812 caused by a delayed breakpoint event, which should be ignored, as
39813 opposed to a random trap signal, which should be reported to the user.
39814 Note the @samp{swbreak} feature implies that the target is responsible
39815 for adjusting the PC when a software breakpoint triggers, if
39816 necessary, such as on the x86 architecture.
39818 @node Packet Acknowledgment
39819 @section Packet Acknowledgment
39821 @cindex acknowledgment, for @value{GDBN} remote
39822 @cindex packet acknowledgment, for @value{GDBN} remote
39823 By default, when either the host or the target machine receives a packet,
39824 the first response expected is an acknowledgment: either @samp{+} (to indicate
39825 the package was received correctly) or @samp{-} (to request retransmission).
39826 This mechanism allows the @value{GDBN} remote protocol to operate over
39827 unreliable transport mechanisms, such as a serial line.
39829 In cases where the transport mechanism is itself reliable (such as a pipe or
39830 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
39831 It may be desirable to disable them in that case to reduce communication
39832 overhead, or for other reasons. This can be accomplished by means of the
39833 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
39835 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
39836 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
39837 and response format still includes the normal checksum, as described in
39838 @ref{Overview}, but the checksum may be ignored by the receiver.
39840 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
39841 no-acknowledgment mode, it should report that to @value{GDBN}
39842 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
39843 @pxref{qSupported}.
39844 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
39845 disabled via the @code{set remote noack-packet off} command
39846 (@pxref{Remote Configuration}),
39847 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
39848 Only then may the stub actually turn off packet acknowledgments.
39849 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
39850 response, which can be safely ignored by the stub.
39852 Note that @code{set remote noack-packet} command only affects negotiation
39853 between @value{GDBN} and the stub when subsequent connections are made;
39854 it does not affect the protocol acknowledgment state for any current
39856 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
39857 new connection is established,
39858 there is also no protocol request to re-enable the acknowledgments
39859 for the current connection, once disabled.
39864 Example sequence of a target being re-started. Notice how the restart
39865 does not get any direct output:
39870 @emph{target restarts}
39873 <- @code{T001:1234123412341234}
39877 Example sequence of a target being stepped by a single instruction:
39880 -> @code{G1445@dots{}}
39885 <- @code{T001:1234123412341234}
39889 <- @code{1455@dots{}}
39893 @node File-I/O Remote Protocol Extension
39894 @section File-I/O Remote Protocol Extension
39895 @cindex File-I/O remote protocol extension
39898 * File-I/O Overview::
39899 * Protocol Basics::
39900 * The F Request Packet::
39901 * The F Reply Packet::
39902 * The Ctrl-C Message::
39904 * List of Supported Calls::
39905 * Protocol-specific Representation of Datatypes::
39907 * File-I/O Examples::
39910 @node File-I/O Overview
39911 @subsection File-I/O Overview
39912 @cindex file-i/o overview
39914 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
39915 target to use the host's file system and console I/O to perform various
39916 system calls. System calls on the target system are translated into a
39917 remote protocol packet to the host system, which then performs the needed
39918 actions and returns a response packet to the target system.
39919 This simulates file system operations even on targets that lack file systems.
39921 The protocol is defined to be independent of both the host and target systems.
39922 It uses its own internal representation of datatypes and values. Both
39923 @value{GDBN} and the target's @value{GDBN} stub are responsible for
39924 translating the system-dependent value representations into the internal
39925 protocol representations when data is transmitted.
39927 The communication is synchronous. A system call is possible only when
39928 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
39929 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
39930 the target is stopped to allow deterministic access to the target's
39931 memory. Therefore File-I/O is not interruptible by target signals. On
39932 the other hand, it is possible to interrupt File-I/O by a user interrupt
39933 (@samp{Ctrl-C}) within @value{GDBN}.
39935 The target's request to perform a host system call does not finish
39936 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
39937 after finishing the system call, the target returns to continuing the
39938 previous activity (continue, step). No additional continue or step
39939 request from @value{GDBN} is required.
39942 (@value{GDBP}) continue
39943 <- target requests 'system call X'
39944 target is stopped, @value{GDBN} executes system call
39945 -> @value{GDBN} returns result
39946 ... target continues, @value{GDBN} returns to wait for the target
39947 <- target hits breakpoint and sends a Txx packet
39950 The protocol only supports I/O on the console and to regular files on
39951 the host file system. Character or block special devices, pipes,
39952 named pipes, sockets or any other communication method on the host
39953 system are not supported by this protocol.
39955 File I/O is not supported in non-stop mode.
39957 @node Protocol Basics
39958 @subsection Protocol Basics
39959 @cindex protocol basics, file-i/o
39961 The File-I/O protocol uses the @code{F} packet as the request as well
39962 as reply packet. Since a File-I/O system call can only occur when
39963 @value{GDBN} is waiting for a response from the continuing or stepping target,
39964 the File-I/O request is a reply that @value{GDBN} has to expect as a result
39965 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
39966 This @code{F} packet contains all information needed to allow @value{GDBN}
39967 to call the appropriate host system call:
39971 A unique identifier for the requested system call.
39974 All parameters to the system call. Pointers are given as addresses
39975 in the target memory address space. Pointers to strings are given as
39976 pointer/length pair. Numerical values are given as they are.
39977 Numerical control flags are given in a protocol-specific representation.
39981 At this point, @value{GDBN} has to perform the following actions.
39985 If the parameters include pointer values to data needed as input to a
39986 system call, @value{GDBN} requests this data from the target with a
39987 standard @code{m} packet request. This additional communication has to be
39988 expected by the target implementation and is handled as any other @code{m}
39992 @value{GDBN} translates all value from protocol representation to host
39993 representation as needed. Datatypes are coerced into the host types.
39996 @value{GDBN} calls the system call.
39999 It then coerces datatypes back to protocol representation.
40002 If the system call is expected to return data in buffer space specified
40003 by pointer parameters to the call, the data is transmitted to the
40004 target using a @code{M} or @code{X} packet. This packet has to be expected
40005 by the target implementation and is handled as any other @code{M} or @code{X}
40010 Eventually @value{GDBN} replies with another @code{F} packet which contains all
40011 necessary information for the target to continue. This at least contains
40018 @code{errno}, if has been changed by the system call.
40025 After having done the needed type and value coercion, the target continues
40026 the latest continue or step action.
40028 @node The F Request Packet
40029 @subsection The @code{F} Request Packet
40030 @cindex file-i/o request packet
40031 @cindex @code{F} request packet
40033 The @code{F} request packet has the following format:
40036 @item F@var{call-id},@var{parameter@dots{}}
40038 @var{call-id} is the identifier to indicate the host system call to be called.
40039 This is just the name of the function.
40041 @var{parameter@dots{}} are the parameters to the system call.
40042 Parameters are hexadecimal integer values, either the actual values in case
40043 of scalar datatypes, pointers to target buffer space in case of compound
40044 datatypes and unspecified memory areas, or pointer/length pairs in case
40045 of string parameters. These are appended to the @var{call-id} as a
40046 comma-delimited list. All values are transmitted in ASCII
40047 string representation, pointer/length pairs separated by a slash.
40053 @node The F Reply Packet
40054 @subsection The @code{F} Reply Packet
40055 @cindex file-i/o reply packet
40056 @cindex @code{F} reply packet
40058 The @code{F} reply packet has the following format:
40062 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
40064 @var{retcode} is the return code of the system call as hexadecimal value.
40066 @var{errno} is the @code{errno} set by the call, in protocol-specific
40068 This parameter can be omitted if the call was successful.
40070 @var{Ctrl-C flag} is only sent if the user requested a break. In this
40071 case, @var{errno} must be sent as well, even if the call was successful.
40072 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
40079 or, if the call was interrupted before the host call has been performed:
40086 assuming 4 is the protocol-specific representation of @code{EINTR}.
40091 @node The Ctrl-C Message
40092 @subsection The @samp{Ctrl-C} Message
40093 @cindex ctrl-c message, in file-i/o protocol
40095 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
40096 reply packet (@pxref{The F Reply Packet}),
40097 the target should behave as if it had
40098 gotten a break message. The meaning for the target is ``system call
40099 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
40100 (as with a break message) and return to @value{GDBN} with a @code{T02}
40103 It's important for the target to know in which
40104 state the system call was interrupted. There are two possible cases:
40108 The system call hasn't been performed on the host yet.
40111 The system call on the host has been finished.
40115 These two states can be distinguished by the target by the value of the
40116 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
40117 call hasn't been performed. This is equivalent to the @code{EINTR} handling
40118 on POSIX systems. In any other case, the target may presume that the
40119 system call has been finished --- successfully or not --- and should behave
40120 as if the break message arrived right after the system call.
40122 @value{GDBN} must behave reliably. If the system call has not been called
40123 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
40124 @code{errno} in the packet. If the system call on the host has been finished
40125 before the user requests a break, the full action must be finished by
40126 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
40127 The @code{F} packet may only be sent when either nothing has happened
40128 or the full action has been completed.
40131 @subsection Console I/O
40132 @cindex console i/o as part of file-i/o
40134 By default and if not explicitly closed by the target system, the file
40135 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
40136 on the @value{GDBN} console is handled as any other file output operation
40137 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
40138 by @value{GDBN} so that after the target read request from file descriptor
40139 0 all following typing is buffered until either one of the following
40144 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
40146 system call is treated as finished.
40149 The user presses @key{RET}. This is treated as end of input with a trailing
40153 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
40154 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
40158 If the user has typed more characters than fit in the buffer given to
40159 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
40160 either another @code{read(0, @dots{})} is requested by the target, or debugging
40161 is stopped at the user's request.
40164 @node List of Supported Calls
40165 @subsection List of Supported Calls
40166 @cindex list of supported file-i/o calls
40183 @unnumberedsubsubsec open
40184 @cindex open, file-i/o system call
40189 int open(const char *pathname, int flags);
40190 int open(const char *pathname, int flags, mode_t mode);
40194 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
40197 @var{flags} is the bitwise @code{OR} of the following values:
40201 If the file does not exist it will be created. The host
40202 rules apply as far as file ownership and time stamps
40206 When used with @code{O_CREAT}, if the file already exists it is
40207 an error and open() fails.
40210 If the file already exists and the open mode allows
40211 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
40212 truncated to zero length.
40215 The file is opened in append mode.
40218 The file is opened for reading only.
40221 The file is opened for writing only.
40224 The file is opened for reading and writing.
40228 Other bits are silently ignored.
40232 @var{mode} is the bitwise @code{OR} of the following values:
40236 User has read permission.
40239 User has write permission.
40242 Group has read permission.
40245 Group has write permission.
40248 Others have read permission.
40251 Others have write permission.
40255 Other bits are silently ignored.
40258 @item Return value:
40259 @code{open} returns the new file descriptor or -1 if an error
40266 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
40269 @var{pathname} refers to a directory.
40272 The requested access is not allowed.
40275 @var{pathname} was too long.
40278 A directory component in @var{pathname} does not exist.
40281 @var{pathname} refers to a device, pipe, named pipe or socket.
40284 @var{pathname} refers to a file on a read-only filesystem and
40285 write access was requested.
40288 @var{pathname} is an invalid pointer value.
40291 No space on device to create the file.
40294 The process already has the maximum number of files open.
40297 The limit on the total number of files open on the system
40301 The call was interrupted by the user.
40307 @unnumberedsubsubsec close
40308 @cindex close, file-i/o system call
40317 @samp{Fclose,@var{fd}}
40319 @item Return value:
40320 @code{close} returns zero on success, or -1 if an error occurred.
40326 @var{fd} isn't a valid open file descriptor.
40329 The call was interrupted by the user.
40335 @unnumberedsubsubsec read
40336 @cindex read, file-i/o system call
40341 int read(int fd, void *buf, unsigned int count);
40345 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
40347 @item Return value:
40348 On success, the number of bytes read is returned.
40349 Zero indicates end of file. If count is zero, read
40350 returns zero as well. On error, -1 is returned.
40356 @var{fd} is not a valid file descriptor or is not open for
40360 @var{bufptr} is an invalid pointer value.
40363 The call was interrupted by the user.
40369 @unnumberedsubsubsec write
40370 @cindex write, file-i/o system call
40375 int write(int fd, const void *buf, unsigned int count);
40379 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
40381 @item Return value:
40382 On success, the number of bytes written are returned.
40383 Zero indicates nothing was written. On error, -1
40390 @var{fd} is not a valid file descriptor or is not open for
40394 @var{bufptr} is an invalid pointer value.
40397 An attempt was made to write a file that exceeds the
40398 host-specific maximum file size allowed.
40401 No space on device to write the data.
40404 The call was interrupted by the user.
40410 @unnumberedsubsubsec lseek
40411 @cindex lseek, file-i/o system call
40416 long lseek (int fd, long offset, int flag);
40420 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
40422 @var{flag} is one of:
40426 The offset is set to @var{offset} bytes.
40429 The offset is set to its current location plus @var{offset}
40433 The offset is set to the size of the file plus @var{offset}
40437 @item Return value:
40438 On success, the resulting unsigned offset in bytes from
40439 the beginning of the file is returned. Otherwise, a
40440 value of -1 is returned.
40446 @var{fd} is not a valid open file descriptor.
40449 @var{fd} is associated with the @value{GDBN} console.
40452 @var{flag} is not a proper value.
40455 The call was interrupted by the user.
40461 @unnumberedsubsubsec rename
40462 @cindex rename, file-i/o system call
40467 int rename(const char *oldpath, const char *newpath);
40471 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
40473 @item Return value:
40474 On success, zero is returned. On error, -1 is returned.
40480 @var{newpath} is an existing directory, but @var{oldpath} is not a
40484 @var{newpath} is a non-empty directory.
40487 @var{oldpath} or @var{newpath} is a directory that is in use by some
40491 An attempt was made to make a directory a subdirectory
40495 A component used as a directory in @var{oldpath} or new
40496 path is not a directory. Or @var{oldpath} is a directory
40497 and @var{newpath} exists but is not a directory.
40500 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
40503 No access to the file or the path of the file.
40507 @var{oldpath} or @var{newpath} was too long.
40510 A directory component in @var{oldpath} or @var{newpath} does not exist.
40513 The file is on a read-only filesystem.
40516 The device containing the file has no room for the new
40520 The call was interrupted by the user.
40526 @unnumberedsubsubsec unlink
40527 @cindex unlink, file-i/o system call
40532 int unlink(const char *pathname);
40536 @samp{Funlink,@var{pathnameptr}/@var{len}}
40538 @item Return value:
40539 On success, zero is returned. On error, -1 is returned.
40545 No access to the file or the path of the file.
40548 The system does not allow unlinking of directories.
40551 The file @var{pathname} cannot be unlinked because it's
40552 being used by another process.
40555 @var{pathnameptr} is an invalid pointer value.
40558 @var{pathname} was too long.
40561 A directory component in @var{pathname} does not exist.
40564 A component of the path is not a directory.
40567 The file is on a read-only filesystem.
40570 The call was interrupted by the user.
40576 @unnumberedsubsubsec stat/fstat
40577 @cindex fstat, file-i/o system call
40578 @cindex stat, file-i/o system call
40583 int stat(const char *pathname, struct stat *buf);
40584 int fstat(int fd, struct stat *buf);
40588 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
40589 @samp{Ffstat,@var{fd},@var{bufptr}}
40591 @item Return value:
40592 On success, zero is returned. On error, -1 is returned.
40598 @var{fd} is not a valid open file.
40601 A directory component in @var{pathname} does not exist or the
40602 path is an empty string.
40605 A component of the path is not a directory.
40608 @var{pathnameptr} is an invalid pointer value.
40611 No access to the file or the path of the file.
40614 @var{pathname} was too long.
40617 The call was interrupted by the user.
40623 @unnumberedsubsubsec gettimeofday
40624 @cindex gettimeofday, file-i/o system call
40629 int gettimeofday(struct timeval *tv, void *tz);
40633 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
40635 @item Return value:
40636 On success, 0 is returned, -1 otherwise.
40642 @var{tz} is a non-NULL pointer.
40645 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
40651 @unnumberedsubsubsec isatty
40652 @cindex isatty, file-i/o system call
40657 int isatty(int fd);
40661 @samp{Fisatty,@var{fd}}
40663 @item Return value:
40664 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
40670 The call was interrupted by the user.
40675 Note that the @code{isatty} call is treated as a special case: it returns
40676 1 to the target if the file descriptor is attached
40677 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
40678 would require implementing @code{ioctl} and would be more complex than
40683 @unnumberedsubsubsec system
40684 @cindex system, file-i/o system call
40689 int system(const char *command);
40693 @samp{Fsystem,@var{commandptr}/@var{len}}
40695 @item Return value:
40696 If @var{len} is zero, the return value indicates whether a shell is
40697 available. A zero return value indicates a shell is not available.
40698 For non-zero @var{len}, the value returned is -1 on error and the
40699 return status of the command otherwise. Only the exit status of the
40700 command is returned, which is extracted from the host's @code{system}
40701 return value by calling @code{WEXITSTATUS(retval)}. In case
40702 @file{/bin/sh} could not be executed, 127 is returned.
40708 The call was interrupted by the user.
40713 @value{GDBN} takes over the full task of calling the necessary host calls
40714 to perform the @code{system} call. The return value of @code{system} on
40715 the host is simplified before it's returned
40716 to the target. Any termination signal information from the child process
40717 is discarded, and the return value consists
40718 entirely of the exit status of the called command.
40720 Due to security concerns, the @code{system} call is by default refused
40721 by @value{GDBN}. The user has to allow this call explicitly with the
40722 @code{set remote system-call-allowed 1} command.
40725 @item set remote system-call-allowed
40726 @kindex set remote system-call-allowed
40727 Control whether to allow the @code{system} calls in the File I/O
40728 protocol for the remote target. The default is zero (disabled).
40730 @item show remote system-call-allowed
40731 @kindex show remote system-call-allowed
40732 Show whether the @code{system} calls are allowed in the File I/O
40736 @node Protocol-specific Representation of Datatypes
40737 @subsection Protocol-specific Representation of Datatypes
40738 @cindex protocol-specific representation of datatypes, in file-i/o protocol
40741 * Integral Datatypes::
40743 * Memory Transfer::
40748 @node Integral Datatypes
40749 @unnumberedsubsubsec Integral Datatypes
40750 @cindex integral datatypes, in file-i/o protocol
40752 The integral datatypes used in the system calls are @code{int},
40753 @code{unsigned int}, @code{long}, @code{unsigned long},
40754 @code{mode_t}, and @code{time_t}.
40756 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
40757 implemented as 32 bit values in this protocol.
40759 @code{long} and @code{unsigned long} are implemented as 64 bit types.
40761 @xref{Limits}, for corresponding MIN and MAX values (similar to those
40762 in @file{limits.h}) to allow range checking on host and target.
40764 @code{time_t} datatypes are defined as seconds since the Epoch.
40766 All integral datatypes transferred as part of a memory read or write of a
40767 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
40770 @node Pointer Values
40771 @unnumberedsubsubsec Pointer Values
40772 @cindex pointer values, in file-i/o protocol
40774 Pointers to target data are transmitted as they are. An exception
40775 is made for pointers to buffers for which the length isn't
40776 transmitted as part of the function call, namely strings. Strings
40777 are transmitted as a pointer/length pair, both as hex values, e.g.@:
40784 which is a pointer to data of length 18 bytes at position 0x1aaf.
40785 The length is defined as the full string length in bytes, including
40786 the trailing null byte. For example, the string @code{"hello world"}
40787 at address 0x123456 is transmitted as
40793 @node Memory Transfer
40794 @unnumberedsubsubsec Memory Transfer
40795 @cindex memory transfer, in file-i/o protocol
40797 Structured data which is transferred using a memory read or write (for
40798 example, a @code{struct stat}) is expected to be in a protocol-specific format
40799 with all scalar multibyte datatypes being big endian. Translation to
40800 this representation needs to be done both by the target before the @code{F}
40801 packet is sent, and by @value{GDBN} before
40802 it transfers memory to the target. Transferred pointers to structured
40803 data should point to the already-coerced data at any time.
40807 @unnumberedsubsubsec struct stat
40808 @cindex struct stat, in file-i/o protocol
40810 The buffer of type @code{struct stat} used by the target and @value{GDBN}
40811 is defined as follows:
40815 unsigned int st_dev; /* device */
40816 unsigned int st_ino; /* inode */
40817 mode_t st_mode; /* protection */
40818 unsigned int st_nlink; /* number of hard links */
40819 unsigned int st_uid; /* user ID of owner */
40820 unsigned int st_gid; /* group ID of owner */
40821 unsigned int st_rdev; /* device type (if inode device) */
40822 unsigned long st_size; /* total size, in bytes */
40823 unsigned long st_blksize; /* blocksize for filesystem I/O */
40824 unsigned long st_blocks; /* number of blocks allocated */
40825 time_t st_atime; /* time of last access */
40826 time_t st_mtime; /* time of last modification */
40827 time_t st_ctime; /* time of last change */
40831 The integral datatypes conform to the definitions given in the
40832 appropriate section (see @ref{Integral Datatypes}, for details) so this
40833 structure is of size 64 bytes.
40835 The values of several fields have a restricted meaning and/or
40841 A value of 0 represents a file, 1 the console.
40844 No valid meaning for the target. Transmitted unchanged.
40847 Valid mode bits are described in @ref{Constants}. Any other
40848 bits have currently no meaning for the target.
40853 No valid meaning for the target. Transmitted unchanged.
40858 These values have a host and file system dependent
40859 accuracy. Especially on Windows hosts, the file system may not
40860 support exact timing values.
40863 The target gets a @code{struct stat} of the above representation and is
40864 responsible for coercing it to the target representation before
40867 Note that due to size differences between the host, target, and protocol
40868 representations of @code{struct stat} members, these members could eventually
40869 get truncated on the target.
40871 @node struct timeval
40872 @unnumberedsubsubsec struct timeval
40873 @cindex struct timeval, in file-i/o protocol
40875 The buffer of type @code{struct timeval} used by the File-I/O protocol
40876 is defined as follows:
40880 time_t tv_sec; /* second */
40881 long tv_usec; /* microsecond */
40885 The integral datatypes conform to the definitions given in the
40886 appropriate section (see @ref{Integral Datatypes}, for details) so this
40887 structure is of size 8 bytes.
40890 @subsection Constants
40891 @cindex constants, in file-i/o protocol
40893 The following values are used for the constants inside of the
40894 protocol. @value{GDBN} and target are responsible for translating these
40895 values before and after the call as needed.
40906 @unnumberedsubsubsec Open Flags
40907 @cindex open flags, in file-i/o protocol
40909 All values are given in hexadecimal representation.
40921 @node mode_t Values
40922 @unnumberedsubsubsec mode_t Values
40923 @cindex mode_t values, in file-i/o protocol
40925 All values are given in octal representation.
40942 @unnumberedsubsubsec Errno Values
40943 @cindex errno values, in file-i/o protocol
40945 All values are given in decimal representation.
40970 @code{EUNKNOWN} is used as a fallback error value if a host system returns
40971 any error value not in the list of supported error numbers.
40974 @unnumberedsubsubsec Lseek Flags
40975 @cindex lseek flags, in file-i/o protocol
40984 @unnumberedsubsubsec Limits
40985 @cindex limits, in file-i/o protocol
40987 All values are given in decimal representation.
40990 INT_MIN -2147483648
40992 UINT_MAX 4294967295
40993 LONG_MIN -9223372036854775808
40994 LONG_MAX 9223372036854775807
40995 ULONG_MAX 18446744073709551615
40998 @node File-I/O Examples
40999 @subsection File-I/O Examples
41000 @cindex file-i/o examples
41002 Example sequence of a write call, file descriptor 3, buffer is at target
41003 address 0x1234, 6 bytes should be written:
41006 <- @code{Fwrite,3,1234,6}
41007 @emph{request memory read from target}
41010 @emph{return "6 bytes written"}
41014 Example sequence of a read call, file descriptor 3, buffer is at target
41015 address 0x1234, 6 bytes should be read:
41018 <- @code{Fread,3,1234,6}
41019 @emph{request memory write to target}
41020 -> @code{X1234,6:XXXXXX}
41021 @emph{return "6 bytes read"}
41025 Example sequence of a read call, call fails on the host due to invalid
41026 file descriptor (@code{EBADF}):
41029 <- @code{Fread,3,1234,6}
41033 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
41037 <- @code{Fread,3,1234,6}
41042 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
41046 <- @code{Fread,3,1234,6}
41047 -> @code{X1234,6:XXXXXX}
41051 @node Library List Format
41052 @section Library List Format
41053 @cindex library list format, remote protocol
41055 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
41056 same process as your application to manage libraries. In this case,
41057 @value{GDBN} can use the loader's symbol table and normal memory
41058 operations to maintain a list of shared libraries. On other
41059 platforms, the operating system manages loaded libraries.
41060 @value{GDBN} can not retrieve the list of currently loaded libraries
41061 through memory operations, so it uses the @samp{qXfer:libraries:read}
41062 packet (@pxref{qXfer library list read}) instead. The remote stub
41063 queries the target's operating system and reports which libraries
41066 The @samp{qXfer:libraries:read} packet returns an XML document which
41067 lists loaded libraries and their offsets. Each library has an
41068 associated name and one or more segment or section base addresses,
41069 which report where the library was loaded in memory.
41071 For the common case of libraries that are fully linked binaries, the
41072 library should have a list of segments. If the target supports
41073 dynamic linking of a relocatable object file, its library XML element
41074 should instead include a list of allocated sections. The segment or
41075 section bases are start addresses, not relocation offsets; they do not
41076 depend on the library's link-time base addresses.
41078 @value{GDBN} must be linked with the Expat library to support XML
41079 library lists. @xref{Expat}.
41081 A simple memory map, with one loaded library relocated by a single
41082 offset, looks like this:
41086 <library name="/lib/libc.so.6">
41087 <segment address="0x10000000"/>
41092 Another simple memory map, with one loaded library with three
41093 allocated sections (.text, .data, .bss), looks like this:
41097 <library name="sharedlib.o">
41098 <section address="0x10000000"/>
41099 <section address="0x20000000"/>
41100 <section address="0x30000000"/>
41105 The format of a library list is described by this DTD:
41108 <!-- library-list: Root element with versioning -->
41109 <!ELEMENT library-list (library)*>
41110 <!ATTLIST library-list version CDATA #FIXED "1.0">
41111 <!ELEMENT library (segment*, section*)>
41112 <!ATTLIST library name CDATA #REQUIRED>
41113 <!ELEMENT segment EMPTY>
41114 <!ATTLIST segment address CDATA #REQUIRED>
41115 <!ELEMENT section EMPTY>
41116 <!ATTLIST section address CDATA #REQUIRED>
41119 In addition, segments and section descriptors cannot be mixed within a
41120 single library element, and you must supply at least one segment or
41121 section for each library.
41123 @node Library List Format for SVR4 Targets
41124 @section Library List Format for SVR4 Targets
41125 @cindex library list format, remote protocol
41127 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
41128 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
41129 shared libraries. Still a special library list provided by this packet is
41130 more efficient for the @value{GDBN} remote protocol.
41132 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
41133 loaded libraries and their SVR4 linker parameters. For each library on SVR4
41134 target, the following parameters are reported:
41138 @code{name}, the absolute file name from the @code{l_name} field of
41139 @code{struct link_map}.
41141 @code{lm} with address of @code{struct link_map} used for TLS
41142 (Thread Local Storage) access.
41144 @code{l_addr}, the displacement as read from the field @code{l_addr} of
41145 @code{struct link_map}. For prelinked libraries this is not an absolute
41146 memory address. It is a displacement of absolute memory address against
41147 address the file was prelinked to during the library load.
41149 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
41152 Additionally the single @code{main-lm} attribute specifies address of
41153 @code{struct link_map} used for the main executable. This parameter is used
41154 for TLS access and its presence is optional.
41156 @value{GDBN} must be linked with the Expat library to support XML
41157 SVR4 library lists. @xref{Expat}.
41159 A simple memory map, with two loaded libraries (which do not use prelink),
41163 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
41164 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
41166 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
41168 </library-list-svr>
41171 The format of an SVR4 library list is described by this DTD:
41174 <!-- library-list-svr4: Root element with versioning -->
41175 <!ELEMENT library-list-svr4 (library)*>
41176 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
41177 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
41178 <!ELEMENT library EMPTY>
41179 <!ATTLIST library name CDATA #REQUIRED>
41180 <!ATTLIST library lm CDATA #REQUIRED>
41181 <!ATTLIST library l_addr CDATA #REQUIRED>
41182 <!ATTLIST library l_ld CDATA #REQUIRED>
41185 @node Memory Map Format
41186 @section Memory Map Format
41187 @cindex memory map format
41189 To be able to write into flash memory, @value{GDBN} needs to obtain a
41190 memory map from the target. This section describes the format of the
41193 The memory map is obtained using the @samp{qXfer:memory-map:read}
41194 (@pxref{qXfer memory map read}) packet and is an XML document that
41195 lists memory regions.
41197 @value{GDBN} must be linked with the Expat library to support XML
41198 memory maps. @xref{Expat}.
41200 The top-level structure of the document is shown below:
41203 <?xml version="1.0"?>
41204 <!DOCTYPE memory-map
41205 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
41206 "http://sourceware.org/gdb/gdb-memory-map.dtd">
41212 Each region can be either:
41217 A region of RAM starting at @var{addr} and extending for @var{length}
41221 <memory type="ram" start="@var{addr}" length="@var{length}"/>
41226 A region of read-only memory:
41229 <memory type="rom" start="@var{addr}" length="@var{length}"/>
41234 A region of flash memory, with erasure blocks @var{blocksize}
41238 <memory type="flash" start="@var{addr}" length="@var{length}">
41239 <property name="blocksize">@var{blocksize}</property>
41245 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
41246 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
41247 packets to write to addresses in such ranges.
41249 The formal DTD for memory map format is given below:
41252 <!-- ................................................... -->
41253 <!-- Memory Map XML DTD ................................ -->
41254 <!-- File: memory-map.dtd .............................. -->
41255 <!-- .................................... .............. -->
41256 <!-- memory-map.dtd -->
41257 <!-- memory-map: Root element with versioning -->
41258 <!ELEMENT memory-map (memory)*>
41259 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
41260 <!ELEMENT memory (property)*>
41261 <!-- memory: Specifies a memory region,
41262 and its type, or device. -->
41263 <!ATTLIST memory type (ram|rom|flash) #REQUIRED
41264 start CDATA #REQUIRED
41265 length CDATA #REQUIRED>
41266 <!-- property: Generic attribute tag -->
41267 <!ELEMENT property (#PCDATA | property)*>
41268 <!ATTLIST property name (blocksize) #REQUIRED>
41271 @node Thread List Format
41272 @section Thread List Format
41273 @cindex thread list format
41275 To efficiently update the list of threads and their attributes,
41276 @value{GDBN} issues the @samp{qXfer:threads:read} packet
41277 (@pxref{qXfer threads read}) and obtains the XML document with
41278 the following structure:
41281 <?xml version="1.0"?>
41283 <thread id="id" core="0" name="name">
41284 ... description ...
41289 Each @samp{thread} element must have the @samp{id} attribute that
41290 identifies the thread (@pxref{thread-id syntax}). The
41291 @samp{core} attribute, if present, specifies which processor core
41292 the thread was last executing on. The @samp{name} attribute, if
41293 present, specifies the human-readable name of the thread. The content
41294 of the of @samp{thread} element is interpreted as human-readable
41295 auxiliary information. The @samp{handle} attribute, if present,
41296 is a hex encoded representation of the thread handle.
41299 @node Traceframe Info Format
41300 @section Traceframe Info Format
41301 @cindex traceframe info format
41303 To be able to know which objects in the inferior can be examined when
41304 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
41305 memory ranges, registers and trace state variables that have been
41306 collected in a traceframe.
41308 This list is obtained using the @samp{qXfer:traceframe-info:read}
41309 (@pxref{qXfer traceframe info read}) packet and is an XML document.
41311 @value{GDBN} must be linked with the Expat library to support XML
41312 traceframe info discovery. @xref{Expat}.
41314 The top-level structure of the document is shown below:
41317 <?xml version="1.0"?>
41318 <!DOCTYPE traceframe-info
41319 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
41320 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
41326 Each traceframe block can be either:
41331 A region of collected memory starting at @var{addr} and extending for
41332 @var{length} bytes from there:
41335 <memory start="@var{addr}" length="@var{length}"/>
41339 A block indicating trace state variable numbered @var{number} has been
41343 <tvar id="@var{number}"/>
41348 The formal DTD for the traceframe info format is given below:
41351 <!ELEMENT traceframe-info (memory | tvar)* >
41352 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
41354 <!ELEMENT memory EMPTY>
41355 <!ATTLIST memory start CDATA #REQUIRED
41356 length CDATA #REQUIRED>
41358 <!ATTLIST tvar id CDATA #REQUIRED>
41361 @node Branch Trace Format
41362 @section Branch Trace Format
41363 @cindex branch trace format
41365 In order to display the branch trace of an inferior thread,
41366 @value{GDBN} needs to obtain the list of branches. This list is
41367 represented as list of sequential code blocks that are connected via
41368 branches. The code in each block has been executed sequentially.
41370 This list is obtained using the @samp{qXfer:btrace:read}
41371 (@pxref{qXfer btrace read}) packet and is an XML document.
41373 @value{GDBN} must be linked with the Expat library to support XML
41374 traceframe info discovery. @xref{Expat}.
41376 The top-level structure of the document is shown below:
41379 <?xml version="1.0"?>
41381 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
41382 "http://sourceware.org/gdb/gdb-btrace.dtd">
41391 A block of sequentially executed instructions starting at @var{begin}
41392 and ending at @var{end}:
41395 <block begin="@var{begin}" end="@var{end}"/>
41400 The formal DTD for the branch trace format is given below:
41403 <!ELEMENT btrace (block* | pt) >
41404 <!ATTLIST btrace version CDATA #FIXED "1.0">
41406 <!ELEMENT block EMPTY>
41407 <!ATTLIST block begin CDATA #REQUIRED
41408 end CDATA #REQUIRED>
41410 <!ELEMENT pt (pt-config?, raw?)>
41412 <!ELEMENT pt-config (cpu?)>
41414 <!ELEMENT cpu EMPTY>
41415 <!ATTLIST cpu vendor CDATA #REQUIRED
41416 family CDATA #REQUIRED
41417 model CDATA #REQUIRED
41418 stepping CDATA #REQUIRED>
41420 <!ELEMENT raw (#PCDATA)>
41423 @node Branch Trace Configuration Format
41424 @section Branch Trace Configuration Format
41425 @cindex branch trace configuration format
41427 For each inferior thread, @value{GDBN} can obtain the branch trace
41428 configuration using the @samp{qXfer:btrace-conf:read}
41429 (@pxref{qXfer btrace-conf read}) packet.
41431 The configuration describes the branch trace format and configuration
41432 settings for that format. The following information is described:
41436 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
41439 The size of the @acronym{BTS} ring buffer in bytes.
41442 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
41446 The size of the @acronym{Intel PT} ring buffer in bytes.
41450 @value{GDBN} must be linked with the Expat library to support XML
41451 branch trace configuration discovery. @xref{Expat}.
41453 The formal DTD for the branch trace configuration format is given below:
41456 <!ELEMENT btrace-conf (bts?, pt?)>
41457 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
41459 <!ELEMENT bts EMPTY>
41460 <!ATTLIST bts size CDATA #IMPLIED>
41462 <!ELEMENT pt EMPTY>
41463 <!ATTLIST pt size CDATA #IMPLIED>
41466 @include agentexpr.texi
41468 @node Target Descriptions
41469 @appendix Target Descriptions
41470 @cindex target descriptions
41472 One of the challenges of using @value{GDBN} to debug embedded systems
41473 is that there are so many minor variants of each processor
41474 architecture in use. It is common practice for vendors to start with
41475 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
41476 and then make changes to adapt it to a particular market niche. Some
41477 architectures have hundreds of variants, available from dozens of
41478 vendors. This leads to a number of problems:
41482 With so many different customized processors, it is difficult for
41483 the @value{GDBN} maintainers to keep up with the changes.
41485 Since individual variants may have short lifetimes or limited
41486 audiences, it may not be worthwhile to carry information about every
41487 variant in the @value{GDBN} source tree.
41489 When @value{GDBN} does support the architecture of the embedded system
41490 at hand, the task of finding the correct architecture name to give the
41491 @command{set architecture} command can be error-prone.
41494 To address these problems, the @value{GDBN} remote protocol allows a
41495 target system to not only identify itself to @value{GDBN}, but to
41496 actually describe its own features. This lets @value{GDBN} support
41497 processor variants it has never seen before --- to the extent that the
41498 descriptions are accurate, and that @value{GDBN} understands them.
41500 @value{GDBN} must be linked with the Expat library to support XML
41501 target descriptions. @xref{Expat}.
41504 * Retrieving Descriptions:: How descriptions are fetched from a target.
41505 * Target Description Format:: The contents of a target description.
41506 * Predefined Target Types:: Standard types available for target
41508 * Enum Target Types:: How to define enum target types.
41509 * Standard Target Features:: Features @value{GDBN} knows about.
41512 @node Retrieving Descriptions
41513 @section Retrieving Descriptions
41515 Target descriptions can be read from the target automatically, or
41516 specified by the user manually. The default behavior is to read the
41517 description from the target. @value{GDBN} retrieves it via the remote
41518 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
41519 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
41520 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
41521 XML document, of the form described in @ref{Target Description
41524 Alternatively, you can specify a file to read for the target description.
41525 If a file is set, the target will not be queried. The commands to
41526 specify a file are:
41529 @cindex set tdesc filename
41530 @item set tdesc filename @var{path}
41531 Read the target description from @var{path}.
41533 @cindex unset tdesc filename
41534 @item unset tdesc filename
41535 Do not read the XML target description from a file. @value{GDBN}
41536 will use the description supplied by the current target.
41538 @cindex show tdesc filename
41539 @item show tdesc filename
41540 Show the filename to read for a target description, if any.
41544 @node Target Description Format
41545 @section Target Description Format
41546 @cindex target descriptions, XML format
41548 A target description annex is an @uref{http://www.w3.org/XML/, XML}
41549 document which complies with the Document Type Definition provided in
41550 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
41551 means you can use generally available tools like @command{xmllint} to
41552 check that your feature descriptions are well-formed and valid.
41553 However, to help people unfamiliar with XML write descriptions for
41554 their targets, we also describe the grammar here.
41556 Target descriptions can identify the architecture of the remote target
41557 and (for some architectures) provide information about custom register
41558 sets. They can also identify the OS ABI of the remote target.
41559 @value{GDBN} can use this information to autoconfigure for your
41560 target, or to warn you if you connect to an unsupported target.
41562 Here is a simple target description:
41565 <target version="1.0">
41566 <architecture>i386:x86-64</architecture>
41571 This minimal description only says that the target uses
41572 the x86-64 architecture.
41574 A target description has the following overall form, with [ ] marking
41575 optional elements and @dots{} marking repeatable elements. The elements
41576 are explained further below.
41579 <?xml version="1.0"?>
41580 <!DOCTYPE target SYSTEM "gdb-target.dtd">
41581 <target version="1.0">
41582 @r{[}@var{architecture}@r{]}
41583 @r{[}@var{osabi}@r{]}
41584 @r{[}@var{compatible}@r{]}
41585 @r{[}@var{feature}@dots{}@r{]}
41590 The description is generally insensitive to whitespace and line
41591 breaks, under the usual common-sense rules. The XML version
41592 declaration and document type declaration can generally be omitted
41593 (@value{GDBN} does not require them), but specifying them may be
41594 useful for XML validation tools. The @samp{version} attribute for
41595 @samp{<target>} may also be omitted, but we recommend
41596 including it; if future versions of @value{GDBN} use an incompatible
41597 revision of @file{gdb-target.dtd}, they will detect and report
41598 the version mismatch.
41600 @subsection Inclusion
41601 @cindex target descriptions, inclusion
41604 @cindex <xi:include>
41607 It can sometimes be valuable to split a target description up into
41608 several different annexes, either for organizational purposes, or to
41609 share files between different possible target descriptions. You can
41610 divide a description into multiple files by replacing any element of
41611 the target description with an inclusion directive of the form:
41614 <xi:include href="@var{document}"/>
41618 When @value{GDBN} encounters an element of this form, it will retrieve
41619 the named XML @var{document}, and replace the inclusion directive with
41620 the contents of that document. If the current description was read
41621 using @samp{qXfer}, then so will be the included document;
41622 @var{document} will be interpreted as the name of an annex. If the
41623 current description was read from a file, @value{GDBN} will look for
41624 @var{document} as a file in the same directory where it found the
41625 original description.
41627 @subsection Architecture
41628 @cindex <architecture>
41630 An @samp{<architecture>} element has this form:
41633 <architecture>@var{arch}</architecture>
41636 @var{arch} is one of the architectures from the set accepted by
41637 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
41640 @cindex @code{<osabi>}
41642 This optional field was introduced in @value{GDBN} version 7.0.
41643 Previous versions of @value{GDBN} ignore it.
41645 An @samp{<osabi>} element has this form:
41648 <osabi>@var{abi-name}</osabi>
41651 @var{abi-name} is an OS ABI name from the same selection accepted by
41652 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
41654 @subsection Compatible Architecture
41655 @cindex @code{<compatible>}
41657 This optional field was introduced in @value{GDBN} version 7.0.
41658 Previous versions of @value{GDBN} ignore it.
41660 A @samp{<compatible>} element has this form:
41663 <compatible>@var{arch}</compatible>
41666 @var{arch} is one of the architectures from the set accepted by
41667 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
41669 A @samp{<compatible>} element is used to specify that the target
41670 is able to run binaries in some other than the main target architecture
41671 given by the @samp{<architecture>} element. For example, on the
41672 Cell Broadband Engine, the main architecture is @code{powerpc:common}
41673 or @code{powerpc:common64}, but the system is able to run binaries
41674 in the @code{spu} architecture as well. The way to describe this
41675 capability with @samp{<compatible>} is as follows:
41678 <architecture>powerpc:common</architecture>
41679 <compatible>spu</compatible>
41682 @subsection Features
41685 Each @samp{<feature>} describes some logical portion of the target
41686 system. Features are currently used to describe available CPU
41687 registers and the types of their contents. A @samp{<feature>} element
41691 <feature name="@var{name}">
41692 @r{[}@var{type}@dots{}@r{]}
41698 Each feature's name should be unique within the description. The name
41699 of a feature does not matter unless @value{GDBN} has some special
41700 knowledge of the contents of that feature; if it does, the feature
41701 should have its standard name. @xref{Standard Target Features}.
41705 Any register's value is a collection of bits which @value{GDBN} must
41706 interpret. The default interpretation is a two's complement integer,
41707 but other types can be requested by name in the register description.
41708 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
41709 Target Types}), and the description can define additional composite
41712 Each type element must have an @samp{id} attribute, which gives
41713 a unique (within the containing @samp{<feature>}) name to the type.
41714 Types must be defined before they are used.
41717 Some targets offer vector registers, which can be treated as arrays
41718 of scalar elements. These types are written as @samp{<vector>} elements,
41719 specifying the array element type, @var{type}, and the number of elements,
41723 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
41727 If a register's value is usefully viewed in multiple ways, define it
41728 with a union type containing the useful representations. The
41729 @samp{<union>} element contains one or more @samp{<field>} elements,
41730 each of which has a @var{name} and a @var{type}:
41733 <union id="@var{id}">
41734 <field name="@var{name}" type="@var{type}"/>
41741 If a register's value is composed from several separate values, define
41742 it with either a structure type or a flags type.
41743 A flags type may only contain bitfields.
41744 A structure type may either contain only bitfields or contain no bitfields.
41745 If the value contains only bitfields, its total size in bytes must be
41748 Non-bitfield values have a @var{name} and @var{type}.
41751 <struct id="@var{id}">
41752 <field name="@var{name}" type="@var{type}"/>
41757 Both @var{name} and @var{type} values are required.
41758 No implicit padding is added.
41760 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
41763 <struct id="@var{id}" size="@var{size}">
41764 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
41770 <flags id="@var{id}" size="@var{size}">
41771 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
41776 The @var{name} value is required.
41777 Bitfield values may be named with the empty string, @samp{""},
41778 in which case the field is ``filler'' and its value is not printed.
41779 Not all bits need to be specified, so ``filler'' fields are optional.
41781 The @var{start} and @var{end} values are required, and @var{type}
41783 The field's @var{start} must be less than or equal to its @var{end},
41784 and zero represents the least significant bit.
41786 The default value of @var{type} is @code{bool} for single bit fields,
41787 and an unsigned integer otherwise.
41789 Which to choose? Structures or flags?
41791 Registers defined with @samp{flags} have these advantages over
41792 defining them with @samp{struct}:
41796 Arithmetic may be performed on them as if they were integers.
41798 They are printed in a more readable fashion.
41801 Registers defined with @samp{struct} have one advantage over
41802 defining them with @samp{flags}:
41806 One can fetch individual fields like in @samp{C}.
41809 (gdb) print $my_struct_reg.field3
41815 @subsection Registers
41818 Each register is represented as an element with this form:
41821 <reg name="@var{name}"
41822 bitsize="@var{size}"
41823 @r{[}regnum="@var{num}"@r{]}
41824 @r{[}save-restore="@var{save-restore}"@r{]}
41825 @r{[}type="@var{type}"@r{]}
41826 @r{[}group="@var{group}"@r{]}/>
41830 The components are as follows:
41835 The register's name; it must be unique within the target description.
41838 The register's size, in bits.
41841 The register's number. If omitted, a register's number is one greater
41842 than that of the previous register (either in the current feature or in
41843 a preceding feature); the first register in the target description
41844 defaults to zero. This register number is used to read or write
41845 the register; e.g.@: it is used in the remote @code{p} and @code{P}
41846 packets, and registers appear in the @code{g} and @code{G} packets
41847 in order of increasing register number.
41850 Whether the register should be preserved across inferior function
41851 calls; this must be either @code{yes} or @code{no}. The default is
41852 @code{yes}, which is appropriate for most registers except for
41853 some system control registers; this is not related to the target's
41857 The type of the register. It may be a predefined type, a type
41858 defined in the current feature, or one of the special types @code{int}
41859 and @code{float}. @code{int} is an integer type of the correct size
41860 for @var{bitsize}, and @code{float} is a floating point type (in the
41861 architecture's normal floating point format) of the correct size for
41862 @var{bitsize}. The default is @code{int}.
41865 The register group to which this register belongs. It can be one of the
41866 standard register groups @code{general}, @code{float}, @code{vector} or an
41867 arbitrary string. Group names should be limited to alphanumeric characters.
41868 If a group name is made up of multiple words the words may be separated by
41869 hyphens; e.g.@: @code{special-group} or @code{ultra-special-group}. If no
41870 @var{group} is specified, @value{GDBN} will not display the register in
41871 @code{info registers}.
41875 @node Predefined Target Types
41876 @section Predefined Target Types
41877 @cindex target descriptions, predefined types
41879 Type definitions in the self-description can build up composite types
41880 from basic building blocks, but can not define fundamental types. Instead,
41881 standard identifiers are provided by @value{GDBN} for the fundamental
41882 types. The currently supported types are:
41887 Boolean type, occupying a single bit.
41894 Signed integer types holding the specified number of bits.
41901 Unsigned integer types holding the specified number of bits.
41905 Pointers to unspecified code and data. The program counter and
41906 any dedicated return address register may be marked as code
41907 pointers; printing a code pointer converts it into a symbolic
41908 address. The stack pointer and any dedicated address registers
41909 may be marked as data pointers.
41912 Single precision IEEE floating point.
41915 Double precision IEEE floating point.
41918 The 12-byte extended precision format used by ARM FPA registers.
41921 The 10-byte extended precision format used by x87 registers.
41924 32bit @sc{eflags} register used by x86.
41927 32bit @sc{mxcsr} register used by x86.
41931 @node Enum Target Types
41932 @section Enum Target Types
41933 @cindex target descriptions, enum types
41935 Enum target types are useful in @samp{struct} and @samp{flags}
41936 register descriptions. @xref{Target Description Format}.
41938 Enum types have a name, size and a list of name/value pairs.
41941 <enum id="@var{id}" size="@var{size}">
41942 <evalue name="@var{name}" value="@var{value}"/>
41947 Enums must be defined before they are used.
41950 <enum id="levels_type" size="4">
41951 <evalue name="low" value="0"/>
41952 <evalue name="high" value="1"/>
41954 <flags id="flags_type" size="4">
41955 <field name="X" start="0"/>
41956 <field name="LEVEL" start="1" end="1" type="levels_type"/>
41958 <reg name="flags" bitsize="32" type="flags_type"/>
41961 Given that description, a value of 3 for the @samp{flags} register
41962 would be printed as:
41965 (gdb) info register flags
41966 flags 0x3 [ X LEVEL=high ]
41969 @node Standard Target Features
41970 @section Standard Target Features
41971 @cindex target descriptions, standard features
41973 A target description must contain either no registers or all the
41974 target's registers. If the description contains no registers, then
41975 @value{GDBN} will assume a default register layout, selected based on
41976 the architecture. If the description contains any registers, the
41977 default layout will not be used; the standard registers must be
41978 described in the target description, in such a way that @value{GDBN}
41979 can recognize them.
41981 This is accomplished by giving specific names to feature elements
41982 which contain standard registers. @value{GDBN} will look for features
41983 with those names and verify that they contain the expected registers;
41984 if any known feature is missing required registers, or if any required
41985 feature is missing, @value{GDBN} will reject the target
41986 description. You can add additional registers to any of the
41987 standard features --- @value{GDBN} will display them just as if
41988 they were added to an unrecognized feature.
41990 This section lists the known features and their expected contents.
41991 Sample XML documents for these features are included in the
41992 @value{GDBN} source tree, in the directory @file{gdb/features}.
41994 Names recognized by @value{GDBN} should include the name of the
41995 company or organization which selected the name, and the overall
41996 architecture to which the feature applies; so e.g.@: the feature
41997 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
41999 The names of registers are not case sensitive for the purpose
42000 of recognizing standard features, but @value{GDBN} will only display
42001 registers using the capitalization used in the description.
42004 * AArch64 Features::
42008 * MicroBlaze Features::
42012 * Nios II Features::
42013 * OpenRISC 1000 Features::
42014 * PowerPC Features::
42015 * S/390 and System z Features::
42021 @node AArch64 Features
42022 @subsection AArch64 Features
42023 @cindex target descriptions, AArch64 features
42025 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
42026 targets. It should contain registers @samp{x0} through @samp{x30},
42027 @samp{sp}, @samp{pc}, and @samp{cpsr}.
42029 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
42030 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
42034 @subsection ARC Features
42035 @cindex target descriptions, ARC Features
42037 ARC processors are highly configurable, so even core registers and their number
42038 are not completely predetermined. In addition flags and PC registers which are
42039 important to @value{GDBN} are not ``core'' registers in ARC. It is required
42040 that one of the core registers features is present.
42041 @samp{org.gnu.gdb.arc.aux-minimal} feature is mandatory.
42043 The @samp{org.gnu.gdb.arc.core.v2} feature is required for ARC EM and ARC HS
42044 targets with a normal register file. It should contain registers @samp{r0}
42045 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
42046 @samp{lp_count} and @samp{pcl}. This feature may contain register @samp{ilink}
42047 and any of extension core registers @samp{r32} through @samp{r59/acch}.
42048 @samp{ilink} and extension core registers are not available to read/write, when
42049 debugging GNU/Linux applications, thus @samp{ilink} is made optional.
42051 The @samp{org.gnu.gdb.arc.core-reduced.v2} feature is required for ARC EM and
42052 ARC HS targets with a reduced register file. It should contain registers
42053 @samp{r0} through @samp{r3}, @samp{r10} through @samp{r15}, @samp{gp},
42054 @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink}, @samp{lp_count} and @samp{pcl}.
42055 This feature may contain register @samp{ilink} and any of extension core
42056 registers @samp{r32} through @samp{r59/acch}.
42058 The @samp{org.gnu.gdb.arc.core.arcompact} feature is required for ARCompact
42059 targets with a normal register file. It should contain registers @samp{r0}
42060 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
42061 @samp{lp_count} and @samp{pcl}. This feature may contain registers
42062 @samp{ilink1}, @samp{ilink2} and any of extension core registers @samp{r32}
42063 through @samp{r59/acch}. @samp{ilink1} and @samp{ilink2} and extension core
42064 registers are not available when debugging GNU/Linux applications. The only
42065 difference with @samp{org.gnu.gdb.arc.core.v2} feature is in the names of
42066 @samp{ilink1} and @samp{ilink2} registers and that @samp{r30} is mandatory in
42067 ARC v2, but @samp{ilink2} is optional on ARCompact.
42069 The @samp{org.gnu.gdb.arc.aux-minimal} feature is required for all ARC
42070 targets. It should contain registers @samp{pc} and @samp{status32}.
42073 @subsection ARM Features
42074 @cindex target descriptions, ARM features
42076 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
42078 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
42079 @samp{lr}, @samp{pc}, and @samp{cpsr}.
42081 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
42082 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
42083 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
42086 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
42087 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
42089 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
42090 it should contain at least registers @samp{wR0} through @samp{wR15} and
42091 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
42092 @samp{wCSSF}, and @samp{wCASF} registers are optional.
42094 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
42095 should contain at least registers @samp{d0} through @samp{d15}. If
42096 they are present, @samp{d16} through @samp{d31} should also be included.
42097 @value{GDBN} will synthesize the single-precision registers from
42098 halves of the double-precision registers.
42100 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
42101 need to contain registers; it instructs @value{GDBN} to display the
42102 VFP double-precision registers as vectors and to synthesize the
42103 quad-precision registers from pairs of double-precision registers.
42104 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
42105 be present and include 32 double-precision registers.
42107 @node i386 Features
42108 @subsection i386 Features
42109 @cindex target descriptions, i386 features
42111 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
42112 targets. It should describe the following registers:
42116 @samp{eax} through @samp{edi} plus @samp{eip} for i386
42118 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
42120 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
42121 @samp{fs}, @samp{gs}
42123 @samp{st0} through @samp{st7}
42125 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
42126 @samp{foseg}, @samp{fooff} and @samp{fop}
42129 The register sets may be different, depending on the target.
42131 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
42132 describe registers:
42136 @samp{xmm0} through @samp{xmm7} for i386
42138 @samp{xmm0} through @samp{xmm15} for amd64
42143 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
42144 @samp{org.gnu.gdb.i386.sse} feature. It should
42145 describe the upper 128 bits of @sc{ymm} registers:
42149 @samp{ymm0h} through @samp{ymm7h} for i386
42151 @samp{ymm0h} through @samp{ymm15h} for amd64
42154 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
42155 Memory Protection Extension (MPX). It should describe the following registers:
42159 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
42161 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
42164 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
42165 describe a single register, @samp{orig_eax}.
42167 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
42168 describe two system registers: @samp{fs_base} and @samp{gs_base}.
42170 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
42171 @samp{org.gnu.gdb.i386.avx} feature. It should
42172 describe additional @sc{xmm} registers:
42176 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
42179 It should describe the upper 128 bits of additional @sc{ymm} registers:
42183 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
42187 describe the upper 256 bits of @sc{zmm} registers:
42191 @samp{zmm0h} through @samp{zmm7h} for i386.
42193 @samp{zmm0h} through @samp{zmm15h} for amd64.
42197 describe the additional @sc{zmm} registers:
42201 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
42204 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
42205 describe a single register, @samp{pkru}. It is a 32-bit register
42206 valid for i386 and amd64.
42208 @node MicroBlaze Features
42209 @subsection MicroBlaze Features
42210 @cindex target descriptions, MicroBlaze features
42212 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
42213 targets. It should contain registers @samp{r0} through @samp{r31},
42214 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
42215 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
42216 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
42218 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
42219 If present, it should contain registers @samp{rshr} and @samp{rslr}
42221 @node MIPS Features
42222 @subsection @acronym{MIPS} Features
42223 @cindex target descriptions, @acronym{MIPS} features
42225 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
42226 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
42227 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
42230 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
42231 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
42232 registers. They may be 32-bit or 64-bit depending on the target.
42234 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
42235 it may be optional in a future version of @value{GDBN}. It should
42236 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
42237 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
42239 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
42240 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
42241 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
42242 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
42244 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
42245 contain a single register, @samp{restart}, which is used by the
42246 Linux kernel to control restartable syscalls.
42248 @node M68K Features
42249 @subsection M68K Features
42250 @cindex target descriptions, M68K features
42253 @item @samp{org.gnu.gdb.m68k.core}
42254 @itemx @samp{org.gnu.gdb.coldfire.core}
42255 @itemx @samp{org.gnu.gdb.fido.core}
42256 One of those features must be always present.
42257 The feature that is present determines which flavor of m68k is
42258 used. The feature that is present should contain registers
42259 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
42260 @samp{sp}, @samp{ps} and @samp{pc}.
42262 @item @samp{org.gnu.gdb.coldfire.fp}
42263 This feature is optional. If present, it should contain registers
42264 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
42268 @node NDS32 Features
42269 @subsection NDS32 Features
42270 @cindex target descriptions, NDS32 features
42272 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
42273 targets. It should contain at least registers @samp{r0} through
42274 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
42277 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
42278 it should contain 64-bit double-precision floating-point registers
42279 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
42280 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
42282 @emph{Note:} The first sixteen 64-bit double-precision floating-point
42283 registers are overlapped with the thirty-two 32-bit single-precision
42284 floating-point registers. The 32-bit single-precision registers, if
42285 not being listed explicitly, will be synthesized from halves of the
42286 overlapping 64-bit double-precision registers. Listing 32-bit
42287 single-precision registers explicitly is deprecated, and the
42288 support to it could be totally removed some day.
42290 @node Nios II Features
42291 @subsection Nios II Features
42292 @cindex target descriptions, Nios II features
42294 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
42295 targets. It should contain the 32 core registers (@samp{zero},
42296 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
42297 @samp{pc}, and the 16 control registers (@samp{status} through
42300 @node OpenRISC 1000 Features
42301 @subsection Openrisc 1000 Features
42302 @cindex target descriptions, OpenRISC 1000 features
42304 The @samp{org.gnu.gdb.or1k.group0} feature is required for OpenRISC 1000
42305 targets. It should contain the 32 general purpose registers (@samp{r0}
42306 through @samp{r31}), @samp{ppc}, @samp{npc} and @samp{sr}.
42308 @node PowerPC Features
42309 @subsection PowerPC Features
42310 @cindex target descriptions, PowerPC features
42312 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
42313 targets. It should contain registers @samp{r0} through @samp{r31},
42314 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
42315 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
42317 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
42318 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
42320 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
42321 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
42324 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
42325 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
42326 will combine these registers with the floating point registers
42327 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
42328 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
42329 through @samp{vs63}, the set of vector registers for POWER7.
42331 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
42332 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
42333 @samp{spefscr}. SPE targets should provide 32-bit registers in
42334 @samp{org.gnu.gdb.power.core} and provide the upper halves in
42335 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
42336 these to present registers @samp{ev0} through @samp{ev31} to the
42339 @node S/390 and System z Features
42340 @subsection S/390 and System z Features
42341 @cindex target descriptions, S/390 features
42342 @cindex target descriptions, System z features
42344 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
42345 System z targets. It should contain the PSW and the 16 general
42346 registers. In particular, System z targets should provide the 64-bit
42347 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
42348 S/390 targets should provide the 32-bit versions of these registers.
42349 A System z target that runs in 31-bit addressing mode should provide
42350 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
42351 register's upper halves @samp{r0h} through @samp{r15h}, and their
42352 lower halves @samp{r0l} through @samp{r15l}.
42354 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
42355 contain the 64-bit registers @samp{f0} through @samp{f15}, and
42358 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
42359 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
42361 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
42362 contain the register @samp{orig_r2}, which is 64-bit wide on System z
42363 targets and 32-bit otherwise. In addition, the feature may contain
42364 the @samp{last_break} register, whose width depends on the addressing
42365 mode, as well as the @samp{system_call} register, which is always
42368 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
42369 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
42370 @samp{atia}, and @samp{tr0} through @samp{tr15}.
42372 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
42373 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
42374 combined by @value{GDBN} with the floating point registers @samp{f0}
42375 through @samp{f15} to present the 128-bit wide vector registers
42376 @samp{v0} through @samp{v15}. In addition, this feature should
42377 contain the 128-bit wide vector registers @samp{v16} through
42380 The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
42381 the 64-bit wide guarded-storage-control registers @samp{gsd},
42382 @samp{gssm}, and @samp{gsepla}.
42384 The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
42385 the 64-bit wide guarded-storage broadcast control registers
42386 @samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
42388 @node Sparc Features
42389 @subsection Sparc Features
42390 @cindex target descriptions, sparc32 features
42391 @cindex target descriptions, sparc64 features
42392 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
42393 targets. It should describe the following registers:
42397 @samp{g0} through @samp{g7}
42399 @samp{o0} through @samp{o7}
42401 @samp{l0} through @samp{l7}
42403 @samp{i0} through @samp{i7}
42406 They may be 32-bit or 64-bit depending on the target.
42408 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
42409 targets. It should describe the following registers:
42413 @samp{f0} through @samp{f31}
42415 @samp{f32} through @samp{f62} for sparc64
42418 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
42419 targets. It should describe the following registers:
42423 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
42424 @samp{fsr}, and @samp{csr} for sparc32
42426 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
42430 @node TIC6x Features
42431 @subsection TMS320C6x Features
42432 @cindex target descriptions, TIC6x features
42433 @cindex target descriptions, TMS320C6x features
42434 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
42435 targets. It should contain registers @samp{A0} through @samp{A15},
42436 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
42438 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
42439 contain registers @samp{A16} through @samp{A31} and @samp{B16}
42440 through @samp{B31}.
42442 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
42443 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
42445 @node Operating System Information
42446 @appendix Operating System Information
42447 @cindex operating system information
42453 Users of @value{GDBN} often wish to obtain information about the state of
42454 the operating system running on the target---for example the list of
42455 processes, or the list of open files. This section describes the
42456 mechanism that makes it possible. This mechanism is similar to the
42457 target features mechanism (@pxref{Target Descriptions}), but focuses
42458 on a different aspect of target.
42460 Operating system information is retrived from the target via the
42461 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
42462 read}). The object name in the request should be @samp{osdata}, and
42463 the @var{annex} identifies the data to be fetched.
42466 @appendixsection Process list
42467 @cindex operating system information, process list
42469 When requesting the process list, the @var{annex} field in the
42470 @samp{qXfer} request should be @samp{processes}. The returned data is
42471 an XML document. The formal syntax of this document is defined in
42472 @file{gdb/features/osdata.dtd}.
42474 An example document is:
42477 <?xml version="1.0"?>
42478 <!DOCTYPE target SYSTEM "osdata.dtd">
42479 <osdata type="processes">
42481 <column name="pid">1</column>
42482 <column name="user">root</column>
42483 <column name="command">/sbin/init</column>
42484 <column name="cores">1,2,3</column>
42489 Each item should include a column whose name is @samp{pid}. The value
42490 of that column should identify the process on the target. The
42491 @samp{user} and @samp{command} columns are optional, and will be
42492 displayed by @value{GDBN}. The @samp{cores} column, if present,
42493 should contain a comma-separated list of cores that this process
42494 is running on. Target may provide additional columns,
42495 which @value{GDBN} currently ignores.
42497 @node Trace File Format
42498 @appendix Trace File Format
42499 @cindex trace file format
42501 The trace file comes in three parts: a header, a textual description
42502 section, and a trace frame section with binary data.
42504 The header has the form @code{\x7fTRACE0\n}. The first byte is
42505 @code{0x7f} so as to indicate that the file contains binary data,
42506 while the @code{0} is a version number that may have different values
42509 The description section consists of multiple lines of @sc{ascii} text
42510 separated by newline characters (@code{0xa}). The lines may include a
42511 variety of optional descriptive or context-setting information, such
42512 as tracepoint definitions or register set size. @value{GDBN} will
42513 ignore any line that it does not recognize. An empty line marks the end
42518 Specifies the size of a register block in bytes. This is equal to the
42519 size of a @code{g} packet payload in the remote protocol. @var{size}
42520 is an ascii decimal number. There should be only one such line in
42521 a single trace file.
42523 @item status @var{status}
42524 Trace status. @var{status} has the same format as a @code{qTStatus}
42525 remote packet reply. There should be only one such line in a single trace
42528 @item tp @var{payload}
42529 Tracepoint definition. The @var{payload} has the same format as
42530 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
42531 may take multiple lines of definition, corresponding to the multiple
42534 @item tsv @var{payload}
42535 Trace state variable definition. The @var{payload} has the same format as
42536 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
42537 may take multiple lines of definition, corresponding to the multiple
42540 @item tdesc @var{payload}
42541 Target description in XML format. The @var{payload} is a single line of
42542 the XML file. All such lines should be concatenated together to get
42543 the original XML file. This file is in the same format as @code{qXfer}
42544 @code{features} payload, and corresponds to the main @code{target.xml}
42545 file. Includes are not allowed.
42549 The trace frame section consists of a number of consecutive frames.
42550 Each frame begins with a two-byte tracepoint number, followed by a
42551 four-byte size giving the amount of data in the frame. The data in
42552 the frame consists of a number of blocks, each introduced by a
42553 character indicating its type (at least register, memory, and trace
42554 state variable). The data in this section is raw binary, not a
42555 hexadecimal or other encoding; its endianness matches the target's
42558 @c FIXME bi-arch may require endianness/arch info in description section
42561 @item R @var{bytes}
42562 Register block. The number and ordering of bytes matches that of a
42563 @code{g} packet in the remote protocol. Note that these are the
42564 actual bytes, in target order, not a hexadecimal encoding.
42566 @item M @var{address} @var{length} @var{bytes}...
42567 Memory block. This is a contiguous block of memory, at the 8-byte
42568 address @var{address}, with a 2-byte length @var{length}, followed by
42569 @var{length} bytes.
42571 @item V @var{number} @var{value}
42572 Trace state variable block. This records the 8-byte signed value
42573 @var{value} of trace state variable numbered @var{number}.
42577 Future enhancements of the trace file format may include additional types
42580 @node Index Section Format
42581 @appendix @code{.gdb_index} section format
42582 @cindex .gdb_index section format
42583 @cindex index section format
42585 This section documents the index section that is created by @code{save
42586 gdb-index} (@pxref{Index Files}). The index section is
42587 DWARF-specific; some knowledge of DWARF is assumed in this
42590 The mapped index file format is designed to be directly
42591 @code{mmap}able on any architecture. In most cases, a datum is
42592 represented using a little-endian 32-bit integer value, called an
42593 @code{offset_type}. Big endian machines must byte-swap the values
42594 before using them. Exceptions to this rule are noted. The data is
42595 laid out such that alignment is always respected.
42597 A mapped index consists of several areas, laid out in order.
42601 The file header. This is a sequence of values, of @code{offset_type}
42602 unless otherwise noted:
42606 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
42607 Version 4 uses a different hashing function from versions 5 and 6.
42608 Version 6 includes symbols for inlined functions, whereas versions 4
42609 and 5 do not. Version 7 adds attributes to the CU indices in the
42610 symbol table. Version 8 specifies that symbols from DWARF type units
42611 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
42612 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
42614 @value{GDBN} will only read version 4, 5, or 6 indices
42615 by specifying @code{set use-deprecated-index-sections on}.
42616 GDB has a workaround for potentially broken version 7 indices so it is
42617 currently not flagged as deprecated.
42620 The offset, from the start of the file, of the CU list.
42623 The offset, from the start of the file, of the types CU list. Note
42624 that this area can be empty, in which case this offset will be equal
42625 to the next offset.
42628 The offset, from the start of the file, of the address area.
42631 The offset, from the start of the file, of the symbol table.
42634 The offset, from the start of the file, of the constant pool.
42638 The CU list. This is a sequence of pairs of 64-bit little-endian
42639 values, sorted by the CU offset. The first element in each pair is
42640 the offset of a CU in the @code{.debug_info} section. The second
42641 element in each pair is the length of that CU. References to a CU
42642 elsewhere in the map are done using a CU index, which is just the
42643 0-based index into this table. Note that if there are type CUs, then
42644 conceptually CUs and type CUs form a single list for the purposes of
42648 The types CU list. This is a sequence of triplets of 64-bit
42649 little-endian values. In a triplet, the first value is the CU offset,
42650 the second value is the type offset in the CU, and the third value is
42651 the type signature. The types CU list is not sorted.
42654 The address area. The address area consists of a sequence of address
42655 entries. Each address entry has three elements:
42659 The low address. This is a 64-bit little-endian value.
42662 The high address. This is a 64-bit little-endian value. Like
42663 @code{DW_AT_high_pc}, the value is one byte beyond the end.
42666 The CU index. This is an @code{offset_type} value.
42670 The symbol table. This is an open-addressed hash table. The size of
42671 the hash table is always a power of 2.
42673 Each slot in the hash table consists of a pair of @code{offset_type}
42674 values. The first value is the offset of the symbol's name in the
42675 constant pool. The second value is the offset of the CU vector in the
42678 If both values are 0, then this slot in the hash table is empty. This
42679 is ok because while 0 is a valid constant pool index, it cannot be a
42680 valid index for both a string and a CU vector.
42682 The hash value for a table entry is computed by applying an
42683 iterative hash function to the symbol's name. Starting with an
42684 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
42685 the string is incorporated into the hash using the formula depending on the
42690 The formula is @code{r = r * 67 + c - 113}.
42692 @item Versions 5 to 7
42693 The formula is @code{r = r * 67 + tolower (c) - 113}.
42696 The terminating @samp{\0} is not incorporated into the hash.
42698 The step size used in the hash table is computed via
42699 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
42700 value, and @samp{size} is the size of the hash table. The step size
42701 is used to find the next candidate slot when handling a hash
42704 The names of C@t{++} symbols in the hash table are canonicalized. We
42705 don't currently have a simple description of the canonicalization
42706 algorithm; if you intend to create new index sections, you must read
42710 The constant pool. This is simply a bunch of bytes. It is organized
42711 so that alignment is correct: CU vectors are stored first, followed by
42714 A CU vector in the constant pool is a sequence of @code{offset_type}
42715 values. The first value is the number of CU indices in the vector.
42716 Each subsequent value is the index and symbol attributes of a CU in
42717 the CU list. This element in the hash table is used to indicate which
42718 CUs define the symbol and how the symbol is used.
42719 See below for the format of each CU index+attributes entry.
42721 A string in the constant pool is zero-terminated.
42724 Attributes were added to CU index values in @code{.gdb_index} version 7.
42725 If a symbol has multiple uses within a CU then there is one
42726 CU index+attributes value for each use.
42728 The format of each CU index+attributes entry is as follows
42734 This is the index of the CU in the CU list.
42736 These bits are reserved for future purposes and must be zero.
42738 The kind of the symbol in the CU.
42742 This value is reserved and should not be used.
42743 By reserving zero the full @code{offset_type} value is backwards compatible
42744 with previous versions of the index.
42746 The symbol is a type.
42748 The symbol is a variable or an enum value.
42750 The symbol is a function.
42752 Any other kind of symbol.
42754 These values are reserved.
42758 This bit is zero if the value is global and one if it is static.
42760 The determination of whether a symbol is global or static is complicated.
42761 The authorative reference is the file @file{dwarf2read.c} in
42762 @value{GDBN} sources.
42766 This pseudo-code describes the computation of a symbol's kind and
42767 global/static attributes in the index.
42770 is_external = get_attribute (die, DW_AT_external);
42771 language = get_attribute (cu_die, DW_AT_language);
42774 case DW_TAG_typedef:
42775 case DW_TAG_base_type:
42776 case DW_TAG_subrange_type:
42780 case DW_TAG_enumerator:
42782 is_static = language != CPLUS;
42784 case DW_TAG_subprogram:
42786 is_static = ! (is_external || language == ADA);
42788 case DW_TAG_constant:
42790 is_static = ! is_external;
42792 case DW_TAG_variable:
42794 is_static = ! is_external;
42796 case DW_TAG_namespace:
42800 case DW_TAG_class_type:
42801 case DW_TAG_interface_type:
42802 case DW_TAG_structure_type:
42803 case DW_TAG_union_type:
42804 case DW_TAG_enumeration_type:
42806 is_static = language != CPLUS;
42814 @appendix Manual pages
42818 * gdb man:: The GNU Debugger man page
42819 * gdbserver man:: Remote Server for the GNU Debugger man page
42820 * gcore man:: Generate a core file of a running program
42821 * gdbinit man:: gdbinit scripts
42822 * gdb-add-index man:: Add index files to speed up GDB
42828 @c man title gdb The GNU Debugger
42830 @c man begin SYNOPSIS gdb
42831 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
42832 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
42833 [@option{-b}@w{ }@var{bps}]
42834 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
42835 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
42836 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
42837 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
42838 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
42841 @c man begin DESCRIPTION gdb
42842 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
42843 going on ``inside'' another program while it executes -- or what another
42844 program was doing at the moment it crashed.
42846 @value{GDBN} can do four main kinds of things (plus other things in support of
42847 these) to help you catch bugs in the act:
42851 Start your program, specifying anything that might affect its behavior.
42854 Make your program stop on specified conditions.
42857 Examine what has happened, when your program has stopped.
42860 Change things in your program, so you can experiment with correcting the
42861 effects of one bug and go on to learn about another.
42864 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
42867 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
42868 commands from the terminal until you tell it to exit with the @value{GDBN}
42869 command @code{quit}. You can get online help from @value{GDBN} itself
42870 by using the command @code{help}.
42872 You can run @code{gdb} with no arguments or options; but the most
42873 usual way to start @value{GDBN} is with one argument or two, specifying an
42874 executable program as the argument:
42880 You can also start with both an executable program and a core file specified:
42886 You can, instead, specify a process ID as a second argument, if you want
42887 to debug a running process:
42895 would attach @value{GDBN} to process @code{1234} (unless you also have a file
42896 named @file{1234}; @value{GDBN} does check for a core file first).
42897 With option @option{-p} you can omit the @var{program} filename.
42899 Here are some of the most frequently needed @value{GDBN} commands:
42901 @c pod2man highlights the right hand side of the @item lines.
42903 @item break [@var{file}:]@var{function}
42904 Set a breakpoint at @var{function} (in @var{file}).
42906 @item run [@var{arglist}]
42907 Start your program (with @var{arglist}, if specified).
42910 Backtrace: display the program stack.
42912 @item print @var{expr}
42913 Display the value of an expression.
42916 Continue running your program (after stopping, e.g. at a breakpoint).
42919 Execute next program line (after stopping); step @emph{over} any
42920 function calls in the line.
42922 @item edit [@var{file}:]@var{function}
42923 look at the program line where it is presently stopped.
42925 @item list [@var{file}:]@var{function}
42926 type the text of the program in the vicinity of where it is presently stopped.
42929 Execute next program line (after stopping); step @emph{into} any
42930 function calls in the line.
42932 @item help [@var{name}]
42933 Show information about @value{GDBN} command @var{name}, or general information
42934 about using @value{GDBN}.
42937 Exit from @value{GDBN}.
42941 For full details on @value{GDBN},
42942 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42943 by Richard M. Stallman and Roland H. Pesch. The same text is available online
42944 as the @code{gdb} entry in the @code{info} program.
42948 @c man begin OPTIONS gdb
42949 Any arguments other than options specify an executable
42950 file and core file (or process ID); that is, the first argument
42951 encountered with no
42952 associated option flag is equivalent to a @option{-se} option, and the second,
42953 if any, is equivalent to a @option{-c} option if it's the name of a file.
42955 both long and short forms; both are shown here. The long forms are also
42956 recognized if you truncate them, so long as enough of the option is
42957 present to be unambiguous. (If you prefer, you can flag option
42958 arguments with @option{+} rather than @option{-}, though we illustrate the
42959 more usual convention.)
42961 All the options and command line arguments you give are processed
42962 in sequential order. The order makes a difference when the @option{-x}
42968 List all options, with brief explanations.
42970 @item -symbols=@var{file}
42971 @itemx -s @var{file}
42972 Read symbol table from file @var{file}.
42975 Enable writing into executable and core files.
42977 @item -exec=@var{file}
42978 @itemx -e @var{file}
42979 Use file @var{file} as the executable file to execute when
42980 appropriate, and for examining pure data in conjunction with a core
42983 @item -se=@var{file}
42984 Read symbol table from file @var{file} and use it as the executable
42987 @item -core=@var{file}
42988 @itemx -c @var{file}
42989 Use file @var{file} as a core dump to examine.
42991 @item -command=@var{file}
42992 @itemx -x @var{file}
42993 Execute @value{GDBN} commands from file @var{file}.
42995 @item -ex @var{command}
42996 Execute given @value{GDBN} @var{command}.
42998 @item -directory=@var{directory}
42999 @itemx -d @var{directory}
43000 Add @var{directory} to the path to search for source files.
43003 Do not execute commands from @file{~/.gdbinit}.
43007 Do not execute commands from any @file{.gdbinit} initialization files.
43011 ``Quiet''. Do not print the introductory and copyright messages. These
43012 messages are also suppressed in batch mode.
43015 Run in batch mode. Exit with status @code{0} after processing all the command
43016 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
43017 Exit with nonzero status if an error occurs in executing the @value{GDBN}
43018 commands in the command files.
43020 Batch mode may be useful for running @value{GDBN} as a filter, for example to
43021 download and run a program on another computer; in order to make this
43022 more useful, the message
43025 Program exited normally.
43029 (which is ordinarily issued whenever a program running under @value{GDBN} control
43030 terminates) is not issued when running in batch mode.
43032 @item -cd=@var{directory}
43033 Run @value{GDBN} using @var{directory} as its working directory,
43034 instead of the current directory.
43038 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
43039 @value{GDBN} to output the full file name and line number in a standard,
43040 recognizable fashion each time a stack frame is displayed (which
43041 includes each time the program stops). This recognizable format looks
43042 like two @samp{\032} characters, followed by the file name, line number
43043 and character position separated by colons, and a newline. The
43044 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
43045 characters as a signal to display the source code for the frame.
43048 Set the line speed (baud rate or bits per second) of any serial
43049 interface used by @value{GDBN} for remote debugging.
43051 @item -tty=@var{device}
43052 Run using @var{device} for your program's standard input and output.
43056 @c man begin SEEALSO gdb
43058 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43059 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43060 documentation are properly installed at your site, the command
43067 should give you access to the complete manual.
43069 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43070 Richard M. Stallman and Roland H. Pesch, July 1991.
43074 @node gdbserver man
43075 @heading gdbserver man
43077 @c man title gdbserver Remote Server for the GNU Debugger
43079 @c man begin SYNOPSIS gdbserver
43080 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
43082 gdbserver --attach @var{comm} @var{pid}
43084 gdbserver --multi @var{comm}
43088 @c man begin DESCRIPTION gdbserver
43089 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
43090 than the one which is running the program being debugged.
43093 @subheading Usage (server (target) side)
43096 Usage (server (target) side):
43099 First, you need to have a copy of the program you want to debug put onto
43100 the target system. The program can be stripped to save space if needed, as
43101 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
43102 the @value{GDBN} running on the host system.
43104 To use the server, you log on to the target system, and run the @command{gdbserver}
43105 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
43106 your program, and (c) its arguments. The general syntax is:
43109 target> gdbserver @var{comm} @var{program} [@var{args} ...]
43112 For example, using a serial port, you might say:
43116 @c @file would wrap it as F</dev/com1>.
43117 target> gdbserver /dev/com1 emacs foo.txt
43120 target> gdbserver @file{/dev/com1} emacs foo.txt
43124 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
43125 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
43126 waits patiently for the host @value{GDBN} to communicate with it.
43128 To use a TCP connection, you could say:
43131 target> gdbserver host:2345 emacs foo.txt
43134 This says pretty much the same thing as the last example, except that we are
43135 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
43136 that we are expecting to see a TCP connection from @code{host} to local TCP port
43137 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
43138 want for the port number as long as it does not conflict with any existing TCP
43139 ports on the target system. This same port number must be used in the host
43140 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
43141 you chose a port number that conflicts with another service, @command{gdbserver} will
43142 print an error message and exit.
43144 @command{gdbserver} can also attach to running programs.
43145 This is accomplished via the @option{--attach} argument. The syntax is:
43148 target> gdbserver --attach @var{comm} @var{pid}
43151 @var{pid} is the process ID of a currently running process. It isn't
43152 necessary to point @command{gdbserver} at a binary for the running process.
43154 To start @code{gdbserver} without supplying an initial command to run
43155 or process ID to attach, use the @option{--multi} command line option.
43156 In such case you should connect using @kbd{target extended-remote} to start
43157 the program you want to debug.
43160 target> gdbserver --multi @var{comm}
43164 @subheading Usage (host side)
43170 You need an unstripped copy of the target program on your host system, since
43171 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
43172 would, with the target program as the first argument. (You may need to use the
43173 @option{--baud} option if the serial line is running at anything except 9600 baud.)
43174 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
43175 new command you need to know about is @code{target remote}
43176 (or @code{target extended-remote}). Its argument is either
43177 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
43178 descriptor. For example:
43182 @c @file would wrap it as F</dev/ttyb>.
43183 (gdb) target remote /dev/ttyb
43186 (gdb) target remote @file{/dev/ttyb}
43191 communicates with the server via serial line @file{/dev/ttyb}, and:
43194 (gdb) target remote the-target:2345
43198 communicates via a TCP connection to port 2345 on host `the-target', where
43199 you previously started up @command{gdbserver} with the same port number. Note that for
43200 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
43201 command, otherwise you may get an error that looks something like
43202 `Connection refused'.
43204 @command{gdbserver} can also debug multiple inferiors at once,
43207 the @value{GDBN} manual in node @code{Inferiors and Programs}
43208 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
43211 @ref{Inferiors and Programs}.
43213 In such case use the @code{extended-remote} @value{GDBN} command variant:
43216 (gdb) target extended-remote the-target:2345
43219 The @command{gdbserver} option @option{--multi} may or may not be used in such
43223 @c man begin OPTIONS gdbserver
43224 There are three different modes for invoking @command{gdbserver}:
43229 Debug a specific program specified by its program name:
43232 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
43235 The @var{comm} parameter specifies how should the server communicate
43236 with @value{GDBN}; it is either a device name (to use a serial line),
43237 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
43238 stdin/stdout of @code{gdbserver}. Specify the name of the program to
43239 debug in @var{prog}. Any remaining arguments will be passed to the
43240 program verbatim. When the program exits, @value{GDBN} will close the
43241 connection, and @code{gdbserver} will exit.
43244 Debug a specific program by specifying the process ID of a running
43248 gdbserver --attach @var{comm} @var{pid}
43251 The @var{comm} parameter is as described above. Supply the process ID
43252 of a running program in @var{pid}; @value{GDBN} will do everything
43253 else. Like with the previous mode, when the process @var{pid} exits,
43254 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
43257 Multi-process mode -- debug more than one program/process:
43260 gdbserver --multi @var{comm}
43263 In this mode, @value{GDBN} can instruct @command{gdbserver} which
43264 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
43265 close the connection when a process being debugged exits, so you can
43266 debug several processes in the same session.
43269 In each of the modes you may specify these options:
43274 List all options, with brief explanations.
43277 This option causes @command{gdbserver} to print its version number and exit.
43280 @command{gdbserver} will attach to a running program. The syntax is:
43283 target> gdbserver --attach @var{comm} @var{pid}
43286 @var{pid} is the process ID of a currently running process. It isn't
43287 necessary to point @command{gdbserver} at a binary for the running process.
43290 To start @code{gdbserver} without supplying an initial command to run
43291 or process ID to attach, use this command line option.
43292 Then you can connect using @kbd{target extended-remote} and start
43293 the program you want to debug. The syntax is:
43296 target> gdbserver --multi @var{comm}
43300 Instruct @code{gdbserver} to display extra status information about the debugging
43302 This option is intended for @code{gdbserver} development and for bug reports to
43305 @item --remote-debug
43306 Instruct @code{gdbserver} to display remote protocol debug output.
43307 This option is intended for @code{gdbserver} development and for bug reports to
43310 @item --debug-format=option1@r{[},option2,...@r{]}
43311 Instruct @code{gdbserver} to include extra information in each line
43312 of debugging output.
43313 @xref{Other Command-Line Arguments for gdbserver}.
43316 Specify a wrapper to launch programs
43317 for debugging. The option should be followed by the name of the
43318 wrapper, then any command-line arguments to pass to the wrapper, then
43319 @kbd{--} indicating the end of the wrapper arguments.
43322 By default, @command{gdbserver} keeps the listening TCP port open, so that
43323 additional connections are possible. However, if you start @code{gdbserver}
43324 with the @option{--once} option, it will stop listening for any further
43325 connection attempts after connecting to the first @value{GDBN} session.
43327 @c --disable-packet is not documented for users.
43329 @c --disable-randomization and --no-disable-randomization are superseded by
43330 @c QDisableRandomization.
43335 @c man begin SEEALSO gdbserver
43337 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43338 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43339 documentation are properly installed at your site, the command
43345 should give you access to the complete manual.
43347 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43348 Richard M. Stallman and Roland H. Pesch, July 1991.
43355 @c man title gcore Generate a core file of a running program
43358 @c man begin SYNOPSIS gcore
43359 gcore [-a] [-o @var{filename}] @var{pid}
43363 @c man begin DESCRIPTION gcore
43364 Generate a core dump of a running program with process ID @var{pid}.
43365 Produced file is equivalent to a kernel produced core file as if the process
43366 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
43367 limit). Unlike after a crash, after @command{gcore} the program remains
43368 running without any change.
43371 @c man begin OPTIONS gcore
43374 Dump all memory mappings. The actual effect of this option depends on
43375 the Operating System. On @sc{gnu}/Linux, it will disable
43376 @code{use-coredump-filter} (@pxref{set use-coredump-filter}) and
43377 enable @code{dump-excluded-mappings} (@pxref{set
43378 dump-excluded-mappings}).
43380 @item -o @var{filename}
43381 The optional argument
43382 @var{filename} specifies the file name where to put the core dump.
43383 If not specified, the file name defaults to @file{core.@var{pid}},
43384 where @var{pid} is the running program process ID.
43388 @c man begin SEEALSO gcore
43390 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43391 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43392 documentation are properly installed at your site, the command
43399 should give you access to the complete manual.
43401 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43402 Richard M. Stallman and Roland H. Pesch, July 1991.
43409 @c man title gdbinit GDB initialization scripts
43412 @c man begin SYNOPSIS gdbinit
43413 @ifset SYSTEM_GDBINIT
43414 @value{SYSTEM_GDBINIT}
43423 @c man begin DESCRIPTION gdbinit
43424 These files contain @value{GDBN} commands to automatically execute during
43425 @value{GDBN} startup. The lines of contents are canned sequences of commands,
43428 the @value{GDBN} manual in node @code{Sequences}
43429 -- shell command @code{info -f gdb -n Sequences}.
43435 Please read more in
43437 the @value{GDBN} manual in node @code{Startup}
43438 -- shell command @code{info -f gdb -n Startup}.
43445 @ifset SYSTEM_GDBINIT
43446 @item @value{SYSTEM_GDBINIT}
43448 @ifclear SYSTEM_GDBINIT
43449 @item (not enabled with @code{--with-system-gdbinit} during compilation)
43451 System-wide initialization file. It is executed unless user specified
43452 @value{GDBN} option @code{-nx} or @code{-n}.
43455 the @value{GDBN} manual in node @code{System-wide configuration}
43456 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
43459 @ref{System-wide configuration}.
43463 User initialization file. It is executed unless user specified
43464 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
43467 Initialization file for current directory. It may need to be enabled with
43468 @value{GDBN} security command @code{set auto-load local-gdbinit}.
43471 the @value{GDBN} manual in node @code{Init File in the Current Directory}
43472 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
43475 @ref{Init File in the Current Directory}.
43480 @c man begin SEEALSO gdbinit
43482 gdb(1), @code{info -f gdb -n Startup}
43484 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43485 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43486 documentation are properly installed at your site, the command
43492 should give you access to the complete manual.
43494 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43495 Richard M. Stallman and Roland H. Pesch, July 1991.
43499 @node gdb-add-index man
43500 @heading gdb-add-index
43501 @pindex gdb-add-index
43502 @anchor{gdb-add-index}
43504 @c man title gdb-add-index Add index files to speed up GDB
43506 @c man begin SYNOPSIS gdb-add-index
43507 gdb-add-index @var{filename}
43510 @c man begin DESCRIPTION gdb-add-index
43511 When @value{GDBN} finds a symbol file, it scans the symbols in the
43512 file in order to construct an internal symbol table. This lets most
43513 @value{GDBN} operations work quickly--at the cost of a delay early on.
43514 For large programs, this delay can be quite lengthy, so @value{GDBN}
43515 provides a way to build an index, which speeds up startup.
43517 To determine whether a file contains such an index, use the command
43518 @kbd{readelf -S filename}: the index is stored in a section named
43519 @code{.gdb_index}. The index file can only be produced on systems
43520 which use ELF binaries and DWARF debug information (i.e., sections
43521 named @code{.debug_*}).
43523 @command{gdb-add-index} uses @value{GDBN} and @command{objdump} found
43524 in the @env{PATH} environment variable. If you want to use different
43525 versions of these programs, you can specify them through the
43526 @env{GDB} and @env{OBJDUMP} environment variables.
43530 the @value{GDBN} manual in node @code{Index Files}
43531 -- shell command @kbd{info -f gdb -n "Index Files"}.
43538 @c man begin SEEALSO gdb-add-index
43540 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43541 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43542 documentation are properly installed at your site, the command
43548 should give you access to the complete manual.
43550 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43551 Richard M. Stallman and Roland H. Pesch, July 1991.
43557 @node GNU Free Documentation License
43558 @appendix GNU Free Documentation License
43561 @node Concept Index
43562 @unnumbered Concept Index
43566 @node Command and Variable Index
43567 @unnumbered Command, Variable, and Function Index
43572 % I think something like @@colophon should be in texinfo. In the
43574 \long\def\colophon{\hbox to0pt{}\vfill
43575 \centerline{The body of this manual is set in}
43576 \centerline{\fontname\tenrm,}
43577 \centerline{with headings in {\bf\fontname\tenbf}}
43578 \centerline{and examples in {\tt\fontname\tentt}.}
43579 \centerline{{\it\fontname\tenit\/},}
43580 \centerline{{\bf\fontname\tenbf}, and}
43581 \centerline{{\sl\fontname\tensl\/}}
43582 \centerline{are used for emphasis.}\vfill}
43584 % Blame: doc@@cygnus.com, 1991.