1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2013 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.
51 @c man begin COPYRIGHT
52 Copyright @copyright{} 1988-2013 Free Software Foundation, Inc.
54 Permission is granted to copy, distribute and/or modify this document
55 under the terms of the GNU Free Documentation License, Version 1.3 or
56 any later version published by the Free Software Foundation; with the
57 Invariant Sections being ``Free Software'' and ``Free Software Needs
58 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
59 and with the Back-Cover Texts as in (a) below.
61 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
62 this GNU Manual. Buying copies from GNU Press supports the FSF in
63 developing GNU and promoting software freedom.''
68 This file documents the @sc{gnu} debugger @value{GDBN}.
70 This is the @value{EDITION} Edition, of @cite{Debugging with
71 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
72 @ifset VERSION_PACKAGE
73 @value{VERSION_PACKAGE}
75 Version @value{GDBVN}.
81 @title Debugging with @value{GDBN}
82 @subtitle The @sc{gnu} Source-Level Debugger
84 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
85 @ifset VERSION_PACKAGE
87 @subtitle @value{VERSION_PACKAGE}
89 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
93 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
94 \hfill {\it Debugging with @value{GDBN}}\par
95 \hfill \TeX{}info \texinfoversion\par
99 @vskip 0pt plus 1filll
100 Published by the Free Software Foundation @*
101 51 Franklin Street, Fifth Floor,
102 Boston, MA 02110-1301, USA@*
103 ISBN 978-0-9831592-3-0 @*
110 @node Top, Summary, (dir), (dir)
112 @top Debugging with @value{GDBN}
114 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
116 This is the @value{EDITION} Edition, for @value{GDBN}
117 @ifset VERSION_PACKAGE
118 @value{VERSION_PACKAGE}
120 Version @value{GDBVN}.
122 Copyright (C) 1988-2013 Free Software Foundation, Inc.
124 This edition of the GDB manual is dedicated to the memory of Fred
125 Fish. Fred was a long-standing contributor to GDB and to Free
126 software in general. We will miss him.
129 * Summary:: Summary of @value{GDBN}
130 * Sample Session:: A sample @value{GDBN} session
132 * Invocation:: Getting in and out of @value{GDBN}
133 * Commands:: @value{GDBN} commands
134 * Running:: Running programs under @value{GDBN}
135 * Stopping:: Stopping and continuing
136 * Reverse Execution:: Running programs backward
137 * Process Record and Replay:: Recording inferior's execution and replaying it
138 * Stack:: Examining the stack
139 * Source:: Examining source files
140 * Data:: Examining data
141 * Optimized Code:: Debugging optimized code
142 * Macros:: Preprocessor Macros
143 * Tracepoints:: Debugging remote targets non-intrusively
144 * Overlays:: Debugging programs that use overlays
146 * Languages:: Using @value{GDBN} with different languages
148 * Symbols:: Examining the symbol table
149 * Altering:: Altering execution
150 * GDB Files:: @value{GDBN} files
151 * Targets:: Specifying a debugging target
152 * Remote Debugging:: Debugging remote programs
153 * Configurations:: Configuration-specific information
154 * Controlling GDB:: Controlling @value{GDBN}
155 * Extending GDB:: Extending @value{GDBN}
156 * Interpreters:: Command Interpreters
157 * TUI:: @value{GDBN} Text User Interface
158 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
159 * GDB/MI:: @value{GDBN}'s Machine Interface.
160 * Annotations:: @value{GDBN}'s annotation interface.
161 * JIT Interface:: Using the JIT debugging interface.
162 * In-Process Agent:: In-Process Agent
164 * GDB Bugs:: Reporting bugs in @value{GDBN}
166 @ifset SYSTEM_READLINE
167 * Command Line Editing: (rluserman). Command Line Editing
168 * Using History Interactively: (history). Using History Interactively
170 @ifclear SYSTEM_READLINE
171 * Command Line Editing:: Command Line Editing
172 * Using History Interactively:: Using History Interactively
174 * In Memoriam:: In Memoriam
175 * Formatting Documentation:: How to format and print @value{GDBN} documentation
176 * Installing GDB:: Installing GDB
177 * Maintenance Commands:: Maintenance Commands
178 * Remote Protocol:: GDB Remote Serial Protocol
179 * Agent Expressions:: The GDB Agent Expression Mechanism
180 * Target Descriptions:: How targets can describe themselves to
182 * Operating System Information:: Getting additional information from
184 * Trace File Format:: GDB trace file format
185 * Index Section Format:: .gdb_index section format
186 * Man Pages:: Manual pages
187 * Copying:: GNU General Public License says
188 how you can copy and share GDB
189 * GNU Free Documentation License:: The license for this documentation
190 * Concept Index:: Index of @value{GDBN} concepts
191 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
192 functions, and Python data types
200 @unnumbered Summary of @value{GDBN}
202 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
203 going on ``inside'' another program while it executes---or what another
204 program was doing at the moment it crashed.
206 @value{GDBN} can do four main kinds of things (plus other things in support of
207 these) to help you catch bugs in the act:
211 Start your program, specifying anything that might affect its behavior.
214 Make your program stop on specified conditions.
217 Examine what has happened, when your program has stopped.
220 Change things in your program, so you can experiment with correcting the
221 effects of one bug and go on to learn about another.
224 You can use @value{GDBN} to debug programs written in C and C@t{++}.
225 For more information, see @ref{Supported Languages,,Supported Languages}.
226 For more information, see @ref{C,,C and C++}.
228 Support for D is partial. For information on D, see
232 Support for Modula-2 is partial. For information on Modula-2, see
233 @ref{Modula-2,,Modula-2}.
235 Support for OpenCL C is partial. For information on OpenCL C, see
236 @ref{OpenCL C,,OpenCL C}.
239 Debugging Pascal programs which use sets, subranges, file variables, or
240 nested functions does not currently work. @value{GDBN} does not support
241 entering expressions, printing values, or similar features using Pascal
245 @value{GDBN} can be used to debug programs written in Fortran, although
246 it may be necessary to refer to some variables with a trailing
249 @value{GDBN} can be used to debug programs written in Objective-C,
250 using either the Apple/NeXT or the GNU Objective-C runtime.
253 * Free Software:: Freely redistributable software
254 * Free Documentation:: Free Software Needs Free Documentation
255 * Contributors:: Contributors to GDB
259 @unnumberedsec Free Software
261 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
262 General Public License
263 (GPL). The GPL gives you the freedom to copy or adapt a licensed
264 program---but every person getting a copy also gets with it the
265 freedom to modify that copy (which means that they must get access to
266 the source code), and the freedom to distribute further copies.
267 Typical software companies use copyrights to limit your freedoms; the
268 Free Software Foundation uses the GPL to preserve these freedoms.
270 Fundamentally, the General Public License is a license which says that
271 you have these freedoms and that you cannot take these freedoms away
274 @node Free Documentation
275 @unnumberedsec Free Software Needs Free Documentation
277 The biggest deficiency in the free software community today is not in
278 the software---it is the lack of good free documentation that we can
279 include with the free software. Many of our most important
280 programs do not come with free reference manuals and free introductory
281 texts. Documentation is an essential part of any software package;
282 when an important free software package does not come with a free
283 manual and a free tutorial, that is a major gap. We have many such
286 Consider Perl, for instance. The tutorial manuals that people
287 normally use are non-free. How did this come about? Because the
288 authors of those manuals published them with restrictive terms---no
289 copying, no modification, source files not available---which exclude
290 them from the free software world.
292 That wasn't the first time this sort of thing happened, and it was far
293 from the last. Many times we have heard a GNU user eagerly describe a
294 manual that he is writing, his intended contribution to the community,
295 only to learn that he had ruined everything by signing a publication
296 contract to make it non-free.
298 Free documentation, like free software, is a matter of freedom, not
299 price. The problem with the non-free manual is not that publishers
300 charge a price for printed copies---that in itself is fine. (The Free
301 Software Foundation sells printed copies of manuals, too.) The
302 problem is the restrictions on the use of the manual. Free manuals
303 are available in source code form, and give you permission to copy and
304 modify. Non-free manuals do not allow this.
306 The criteria of freedom for a free manual are roughly the same as for
307 free software. Redistribution (including the normal kinds of
308 commercial redistribution) must be permitted, so that the manual can
309 accompany every copy of the program, both on-line and on paper.
311 Permission for modification of the technical content is crucial too.
312 When people modify the software, adding or changing features, if they
313 are conscientious they will change the manual too---so they can
314 provide accurate and clear documentation for the modified program. A
315 manual that leaves you no choice but to write a new manual to document
316 a changed version of the program is not really available to our
319 Some kinds of limits on the way modification is handled are
320 acceptable. For example, requirements to preserve the original
321 author's copyright notice, the distribution terms, or the list of
322 authors, are ok. It is also no problem to require modified versions
323 to include notice that they were modified. Even entire sections that
324 may not be deleted or changed are acceptable, as long as they deal
325 with nontechnical topics (like this one). These kinds of restrictions
326 are acceptable because they don't obstruct the community's normal use
329 However, it must be possible to modify all the @emph{technical}
330 content of the manual, and then distribute the result in all the usual
331 media, through all the usual channels. Otherwise, the restrictions
332 obstruct the use of the manual, it is not free, and we need another
333 manual to replace it.
335 Please spread the word about this issue. Our community continues to
336 lose manuals to proprietary publishing. If we spread the word that
337 free software needs free reference manuals and free tutorials, perhaps
338 the next person who wants to contribute by writing documentation will
339 realize, before it is too late, that only free manuals contribute to
340 the free software community.
342 If you are writing documentation, please insist on publishing it under
343 the GNU Free Documentation License or another free documentation
344 license. Remember that this decision requires your approval---you
345 don't have to let the publisher decide. Some commercial publishers
346 will use a free license if you insist, but they will not propose the
347 option; it is up to you to raise the issue and say firmly that this is
348 what you want. If the publisher you are dealing with refuses, please
349 try other publishers. If you're not sure whether a proposed license
350 is free, write to @email{licensing@@gnu.org}.
352 You can encourage commercial publishers to sell more free, copylefted
353 manuals and tutorials by buying them, and particularly by buying
354 copies from the publishers that paid for their writing or for major
355 improvements. Meanwhile, try to avoid buying non-free documentation
356 at all. Check the distribution terms of a manual before you buy it,
357 and insist that whoever seeks your business must respect your freedom.
358 Check the history of the book, and try to reward the publishers that
359 have paid or pay the authors to work on it.
361 The Free Software Foundation maintains a list of free documentation
362 published by other publishers, at
363 @url{http://www.fsf.org/doc/other-free-books.html}.
366 @unnumberedsec Contributors to @value{GDBN}
368 Richard Stallman was the original author of @value{GDBN}, and of many
369 other @sc{gnu} programs. Many others have contributed to its
370 development. This section attempts to credit major contributors. One
371 of the virtues of free software is that everyone is free to contribute
372 to it; with regret, we cannot actually acknowledge everyone here. The
373 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
374 blow-by-blow account.
376 Changes much prior to version 2.0 are lost in the mists of time.
379 @emph{Plea:} Additions to this section are particularly welcome. If you
380 or your friends (or enemies, to be evenhanded) have been unfairly
381 omitted from this list, we would like to add your names!
384 So that they may not regard their many labors as thankless, we
385 particularly thank those who shepherded @value{GDBN} through major
387 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
388 Jim Blandy (release 4.18);
389 Jason Molenda (release 4.17);
390 Stan Shebs (release 4.14);
391 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
392 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
393 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
394 Jim Kingdon (releases 3.5, 3.4, and 3.3);
395 and Randy Smith (releases 3.2, 3.1, and 3.0).
397 Richard Stallman, assisted at various times by Peter TerMaat, Chris
398 Hanson, and Richard Mlynarik, handled releases through 2.8.
400 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
401 in @value{GDBN}, with significant additional contributions from Per
402 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
403 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
404 much general update work leading to release 3.0).
406 @value{GDBN} uses the BFD subroutine library to examine multiple
407 object-file formats; BFD was a joint project of David V.
408 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
410 David Johnson wrote the original COFF support; Pace Willison did
411 the original support for encapsulated COFF.
413 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
415 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
416 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
418 Jean-Daniel Fekete contributed Sun 386i support.
419 Chris Hanson improved the HP9000 support.
420 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
421 David Johnson contributed Encore Umax support.
422 Jyrki Kuoppala contributed Altos 3068 support.
423 Jeff Law contributed HP PA and SOM support.
424 Keith Packard contributed NS32K support.
425 Doug Rabson contributed Acorn Risc Machine support.
426 Bob Rusk contributed Harris Nighthawk CX-UX support.
427 Chris Smith contributed Convex support (and Fortran debugging).
428 Jonathan Stone contributed Pyramid support.
429 Michael Tiemann contributed SPARC support.
430 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
431 Pace Willison contributed Intel 386 support.
432 Jay Vosburgh contributed Symmetry support.
433 Marko Mlinar contributed OpenRISC 1000 support.
435 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
437 Rich Schaefer and Peter Schauer helped with support of SunOS shared
440 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
441 about several machine instruction sets.
443 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
444 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
445 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
446 and RDI targets, respectively.
448 Brian Fox is the author of the readline libraries providing
449 command-line editing and command history.
451 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
452 Modula-2 support, and contributed the Languages chapter of this manual.
454 Fred Fish wrote most of the support for Unix System Vr4.
455 He also enhanced the command-completion support to cover C@t{++} overloaded
458 Hitachi America (now Renesas America), Ltd. sponsored the support for
459 H8/300, H8/500, and Super-H processors.
461 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
463 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
466 Toshiba sponsored the support for the TX39 Mips processor.
468 Matsushita sponsored the support for the MN10200 and MN10300 processors.
470 Fujitsu sponsored the support for SPARClite and FR30 processors.
472 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
475 Michael Snyder added support for tracepoints.
477 Stu Grossman wrote gdbserver.
479 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
480 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
482 The following people at the Hewlett-Packard Company contributed
483 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
484 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
485 compiler, and the Text User Interface (nee Terminal User Interface):
486 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
487 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
488 provided HP-specific information in this manual.
490 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
491 Robert Hoehne made significant contributions to the DJGPP port.
493 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
494 development since 1991. Cygnus engineers who have worked on @value{GDBN}
495 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
496 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
497 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
498 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
499 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
500 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
501 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
502 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
503 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
504 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
505 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
506 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
507 Zuhn have made contributions both large and small.
509 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
510 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
512 Jim Blandy added support for preprocessor macros, while working for Red
515 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
516 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
517 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
518 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
519 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
520 with the migration of old architectures to this new framework.
522 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
523 unwinder framework, this consisting of a fresh new design featuring
524 frame IDs, independent frame sniffers, and the sentinel frame. Mark
525 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
526 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
527 trad unwinders. The architecture-specific changes, each involving a
528 complete rewrite of the architecture's frame code, were carried out by
529 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
530 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
531 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
532 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
535 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
536 Tensilica, Inc.@: contributed support for Xtensa processors. Others
537 who have worked on the Xtensa port of @value{GDBN} in the past include
538 Steve Tjiang, John Newlin, and Scott Foehner.
540 Michael Eager and staff of Xilinx, Inc., contributed support for the
541 Xilinx MicroBlaze architecture.
544 @chapter A Sample @value{GDBN} Session
546 You can use this manual at your leisure to read all about @value{GDBN}.
547 However, a handful of commands are enough to get started using the
548 debugger. This chapter illustrates those commands.
551 In this sample session, we emphasize user input like this: @b{input},
552 to make it easier to pick out from the surrounding output.
555 @c FIXME: this example may not be appropriate for some configs, where
556 @c FIXME...primary interest is in remote use.
558 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
559 processor) exhibits the following bug: sometimes, when we change its
560 quote strings from the default, the commands used to capture one macro
561 definition within another stop working. In the following short @code{m4}
562 session, we define a macro @code{foo} which expands to @code{0000}; we
563 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
564 same thing. However, when we change the open quote string to
565 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
566 procedure fails to define a new synonym @code{baz}:
575 @b{define(bar,defn(`foo'))}
579 @b{changequote(<QUOTE>,<UNQUOTE>)}
581 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
584 m4: End of input: 0: fatal error: EOF in string
588 Let us use @value{GDBN} to try to see what is going on.
591 $ @b{@value{GDBP} m4}
592 @c FIXME: this falsifies the exact text played out, to permit smallbook
593 @c FIXME... format to come out better.
594 @value{GDBN} is free software and you are welcome to distribute copies
595 of it under certain conditions; type "show copying" to see
597 There is absolutely no warranty for @value{GDBN}; type "show warranty"
600 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
605 @value{GDBN} reads only enough symbol data to know where to find the
606 rest when needed; as a result, the first prompt comes up very quickly.
607 We now tell @value{GDBN} to use a narrower display width than usual, so
608 that examples fit in this manual.
611 (@value{GDBP}) @b{set width 70}
615 We need to see how the @code{m4} built-in @code{changequote} works.
616 Having looked at the source, we know the relevant subroutine is
617 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
618 @code{break} command.
621 (@value{GDBP}) @b{break m4_changequote}
622 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
626 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
627 control; as long as control does not reach the @code{m4_changequote}
628 subroutine, the program runs as usual:
631 (@value{GDBP}) @b{run}
632 Starting program: /work/Editorial/gdb/gnu/m4/m4
640 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
641 suspends execution of @code{m4}, displaying information about the
642 context where it stops.
645 @b{changequote(<QUOTE>,<UNQUOTE>)}
647 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
649 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
653 Now we use the command @code{n} (@code{next}) to advance execution to
654 the next line of the current function.
658 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
663 @code{set_quotes} looks like a promising subroutine. We can go into it
664 by using the command @code{s} (@code{step}) instead of @code{next}.
665 @code{step} goes to the next line to be executed in @emph{any}
666 subroutine, so it steps into @code{set_quotes}.
670 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
672 530 if (lquote != def_lquote)
676 The display that shows the subroutine where @code{m4} is now
677 suspended (and its arguments) is called a stack frame display. It
678 shows a summary of the stack. We can use the @code{backtrace}
679 command (which can also be spelled @code{bt}), to see where we are
680 in the stack as a whole: the @code{backtrace} command displays a
681 stack frame for each active subroutine.
684 (@value{GDBP}) @b{bt}
685 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
687 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
689 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
690 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
692 #4 0x79dc in expand_input () at macro.c:40
693 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
697 We step through a few more lines to see what happens. The first two
698 times, we can use @samp{s}; the next two times we use @code{n} to avoid
699 falling into the @code{xstrdup} subroutine.
703 0x3b5c 532 if (rquote != def_rquote)
705 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
706 def_lquote : xstrdup(lq);
708 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
711 538 len_lquote = strlen(rquote);
715 The last line displayed looks a little odd; we can examine the variables
716 @code{lquote} and @code{rquote} to see if they are in fact the new left
717 and right quotes we specified. We use the command @code{p}
718 (@code{print}) to see their values.
721 (@value{GDBP}) @b{p lquote}
722 $1 = 0x35d40 "<QUOTE>"
723 (@value{GDBP}) @b{p rquote}
724 $2 = 0x35d50 "<UNQUOTE>"
728 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
729 To look at some context, we can display ten lines of source
730 surrounding the current line with the @code{l} (@code{list}) command.
736 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
738 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
741 538 len_lquote = strlen(rquote);
742 539 len_rquote = strlen(lquote);
749 Let us step past the two lines that set @code{len_lquote} and
750 @code{len_rquote}, and then examine the values of those variables.
754 539 len_rquote = strlen(lquote);
757 (@value{GDBP}) @b{p len_lquote}
759 (@value{GDBP}) @b{p len_rquote}
764 That certainly looks wrong, assuming @code{len_lquote} and
765 @code{len_rquote} are meant to be the lengths of @code{lquote} and
766 @code{rquote} respectively. We can set them to better values using
767 the @code{p} command, since it can print the value of
768 any expression---and that expression can include subroutine calls and
772 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
774 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
779 Is that enough to fix the problem of using the new quotes with the
780 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
781 executing with the @code{c} (@code{continue}) command, and then try the
782 example that caused trouble initially:
788 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
795 Success! The new quotes now work just as well as the default ones. The
796 problem seems to have been just the two typos defining the wrong
797 lengths. We allow @code{m4} exit by giving it an EOF as input:
801 Program exited normally.
805 The message @samp{Program exited normally.} is from @value{GDBN}; it
806 indicates @code{m4} has finished executing. We can end our @value{GDBN}
807 session with the @value{GDBN} @code{quit} command.
810 (@value{GDBP}) @b{quit}
814 @chapter Getting In and Out of @value{GDBN}
816 This chapter discusses how to start @value{GDBN}, and how to get out of it.
820 type @samp{@value{GDBP}} to start @value{GDBN}.
822 type @kbd{quit} or @kbd{Ctrl-d} to exit.
826 * Invoking GDB:: How to start @value{GDBN}
827 * Quitting GDB:: How to quit @value{GDBN}
828 * Shell Commands:: How to use shell commands inside @value{GDBN}
829 * Logging Output:: How to log @value{GDBN}'s output to a file
833 @section Invoking @value{GDBN}
835 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
836 @value{GDBN} reads commands from the terminal until you tell it to exit.
838 You can also run @code{@value{GDBP}} with a variety of arguments and options,
839 to specify more of your debugging environment at the outset.
841 The command-line options described here are designed
842 to cover a variety of situations; in some environments, some of these
843 options may effectively be unavailable.
845 The most usual way to start @value{GDBN} is with one argument,
846 specifying an executable program:
849 @value{GDBP} @var{program}
853 You can also start with both an executable program and a core file
857 @value{GDBP} @var{program} @var{core}
860 You can, instead, specify a process ID as a second argument, if you want
861 to debug a running process:
864 @value{GDBP} @var{program} 1234
868 would attach @value{GDBN} to process @code{1234} (unless you also have a file
869 named @file{1234}; @value{GDBN} does check for a core file first).
871 Taking advantage of the second command-line argument requires a fairly
872 complete operating system; when you use @value{GDBN} as a remote
873 debugger attached to a bare board, there may not be any notion of
874 ``process'', and there is often no way to get a core dump. @value{GDBN}
875 will warn you if it is unable to attach or to read core dumps.
877 You can optionally have @code{@value{GDBP}} pass any arguments after the
878 executable file to the inferior using @code{--args}. This option stops
881 @value{GDBP} --args gcc -O2 -c foo.c
883 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
884 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
886 You can run @code{@value{GDBP}} without printing the front material, which describes
887 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
894 You can further control how @value{GDBN} starts up by using command-line
895 options. @value{GDBN} itself can remind you of the options available.
905 to display all available options and briefly describe their use
906 (@samp{@value{GDBP} -h} is a shorter equivalent).
908 All options and command line arguments you give are processed
909 in sequential order. The order makes a difference when the
910 @samp{-x} option is used.
914 * File Options:: Choosing files
915 * Mode Options:: Choosing modes
916 * Startup:: What @value{GDBN} does during startup
920 @subsection Choosing Files
922 When @value{GDBN} starts, it reads any arguments other than options as
923 specifying an executable file and core file (or process ID). This is
924 the same as if the arguments were specified by the @samp{-se} and
925 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
926 first argument that does not have an associated option flag as
927 equivalent to the @samp{-se} option followed by that argument; and the
928 second argument that does not have an associated option flag, if any, as
929 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
930 If the second argument begins with a decimal digit, @value{GDBN} will
931 first attempt to attach to it as a process, and if that fails, attempt
932 to open it as a corefile. If you have a corefile whose name begins with
933 a digit, you can prevent @value{GDBN} from treating it as a pid by
934 prefixing it with @file{./}, e.g.@: @file{./12345}.
936 If @value{GDBN} has not been configured to included core file support,
937 such as for most embedded targets, then it will complain about a second
938 argument and ignore it.
940 Many options have both long and short forms; both are shown in the
941 following list. @value{GDBN} also recognizes the long forms if you truncate
942 them, so long as enough of the option is present to be unambiguous.
943 (If you prefer, you can flag option arguments with @samp{--} rather
944 than @samp{-}, though we illustrate the more usual convention.)
946 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
947 @c way, both those who look for -foo and --foo in the index, will find
951 @item -symbols @var{file}
953 @cindex @code{--symbols}
955 Read symbol table from file @var{file}.
957 @item -exec @var{file}
959 @cindex @code{--exec}
961 Use file @var{file} as the executable file to execute when appropriate,
962 and for examining pure data in conjunction with a core dump.
966 Read symbol table from file @var{file} and use it as the executable
969 @item -core @var{file}
971 @cindex @code{--core}
973 Use file @var{file} as a core dump to examine.
975 @item -pid @var{number}
976 @itemx -p @var{number}
979 Connect to process ID @var{number}, as with the @code{attach} command.
981 @item -command @var{file}
983 @cindex @code{--command}
985 Execute commands from file @var{file}. The contents of this file is
986 evaluated exactly as the @code{source} command would.
987 @xref{Command Files,, Command files}.
989 @item -eval-command @var{command}
990 @itemx -ex @var{command}
991 @cindex @code{--eval-command}
993 Execute a single @value{GDBN} command.
995 This option may be used multiple times to call multiple commands. It may
996 also be interleaved with @samp{-command} as required.
999 @value{GDBP} -ex 'target sim' -ex 'load' \
1000 -x setbreakpoints -ex 'run' a.out
1003 @item -init-command @var{file}
1004 @itemx -ix @var{file}
1005 @cindex @code{--init-command}
1007 Execute commands from file @var{file} before loading the inferior (but
1008 after loading gdbinit files).
1011 @item -init-eval-command @var{command}
1012 @itemx -iex @var{command}
1013 @cindex @code{--init-eval-command}
1015 Execute a single @value{GDBN} command before loading the inferior (but
1016 after loading gdbinit files).
1019 @item -directory @var{directory}
1020 @itemx -d @var{directory}
1021 @cindex @code{--directory}
1023 Add @var{directory} to the path to search for source and script files.
1027 @cindex @code{--readnow}
1029 Read each symbol file's entire symbol table immediately, rather than
1030 the default, which is to read it incrementally as it is needed.
1031 This makes startup slower, but makes future operations faster.
1036 @subsection Choosing Modes
1038 You can run @value{GDBN} in various alternative modes---for example, in
1039 batch mode or quiet mode.
1047 Do not execute commands found in any initialization file.
1048 There are three init files, loaded in the following order:
1051 @item @file{system.gdbinit}
1052 This is the system-wide init file.
1053 Its location is specified with the @code{--with-system-gdbinit}
1054 configure option (@pxref{System-wide configuration}).
1055 It is loaded first when @value{GDBN} starts, before command line options
1056 have been processed.
1057 @item @file{~/.gdbinit}
1058 This is the init file in your home directory.
1059 It is loaded next, after @file{system.gdbinit}, and before
1060 command options have been processed.
1061 @item @file{./.gdbinit}
1062 This is the init file in the current directory.
1063 It is loaded last, after command line options other than @code{-x} and
1064 @code{-ex} have been processed. Command line options @code{-x} and
1065 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1068 For further documentation on startup processing, @xref{Startup}.
1069 For documentation on how to write command files,
1070 @xref{Command Files,,Command Files}.
1075 Do not execute commands found in @file{~/.gdbinit}, the init file
1076 in your home directory.
1082 @cindex @code{--quiet}
1083 @cindex @code{--silent}
1085 ``Quiet''. Do not print the introductory and copyright messages. These
1086 messages are also suppressed in batch mode.
1089 @cindex @code{--batch}
1090 Run in batch mode. Exit with status @code{0} after processing all the
1091 command files specified with @samp{-x} (and all commands from
1092 initialization files, if not inhibited with @samp{-n}). Exit with
1093 nonzero status if an error occurs in executing the @value{GDBN} commands
1094 in the command files. Batch mode also disables pagination, sets unlimited
1095 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1096 off} were in effect (@pxref{Messages/Warnings}).
1098 Batch mode may be useful for running @value{GDBN} as a filter, for
1099 example to download and run a program on another computer; in order to
1100 make this more useful, the message
1103 Program exited normally.
1107 (which is ordinarily issued whenever a program running under
1108 @value{GDBN} control terminates) is not issued when running in batch
1112 @cindex @code{--batch-silent}
1113 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1114 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1115 unaffected). This is much quieter than @samp{-silent} and would be useless
1116 for an interactive session.
1118 This is particularly useful when using targets that give @samp{Loading section}
1119 messages, for example.
1121 Note that targets that give their output via @value{GDBN}, as opposed to
1122 writing directly to @code{stdout}, will also be made silent.
1124 @item -return-child-result
1125 @cindex @code{--return-child-result}
1126 The return code from @value{GDBN} will be the return code from the child
1127 process (the process being debugged), with the following exceptions:
1131 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1132 internal error. In this case the exit code is the same as it would have been
1133 without @samp{-return-child-result}.
1135 The user quits with an explicit value. E.g., @samp{quit 1}.
1137 The child process never runs, or is not allowed to terminate, in which case
1138 the exit code will be -1.
1141 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1142 when @value{GDBN} is being used as a remote program loader or simulator
1147 @cindex @code{--nowindows}
1149 ``No windows''. If @value{GDBN} comes with a graphical user interface
1150 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1151 interface. If no GUI is available, this option has no effect.
1155 @cindex @code{--windows}
1157 If @value{GDBN} includes a GUI, then this option requires it to be
1160 @item -cd @var{directory}
1162 Run @value{GDBN} using @var{directory} as its working directory,
1163 instead of the current directory.
1165 @item -data-directory @var{directory}
1166 @cindex @code{--data-directory}
1167 Run @value{GDBN} using @var{directory} as its data directory.
1168 The data directory is where @value{GDBN} searches for its
1169 auxiliary files. @xref{Data Files}.
1173 @cindex @code{--fullname}
1175 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1176 subprocess. It tells @value{GDBN} to output the full file name and line
1177 number in a standard, recognizable fashion each time a stack frame is
1178 displayed (which includes each time your program stops). This
1179 recognizable format looks like two @samp{\032} characters, followed by
1180 the file name, line number and character position separated by colons,
1181 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1182 @samp{\032} characters as a signal to display the source code for the
1185 @item -annotate @var{level}
1186 @cindex @code{--annotate}
1187 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1188 effect is identical to using @samp{set annotate @var{level}}
1189 (@pxref{Annotations}). The annotation @var{level} controls how much
1190 information @value{GDBN} prints together with its prompt, values of
1191 expressions, source lines, and other types of output. Level 0 is the
1192 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1193 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1194 that control @value{GDBN}, and level 2 has been deprecated.
1196 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1200 @cindex @code{--args}
1201 Change interpretation of command line so that arguments following the
1202 executable file are passed as command line arguments to the inferior.
1203 This option stops option processing.
1205 @item -baud @var{bps}
1207 @cindex @code{--baud}
1209 Set the line speed (baud rate or bits per second) of any serial
1210 interface used by @value{GDBN} for remote debugging.
1212 @item -l @var{timeout}
1214 Set the timeout (in seconds) of any communication used by @value{GDBN}
1215 for remote debugging.
1217 @item -tty @var{device}
1218 @itemx -t @var{device}
1219 @cindex @code{--tty}
1221 Run using @var{device} for your program's standard input and output.
1222 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1224 @c resolve the situation of these eventually
1226 @cindex @code{--tui}
1227 Activate the @dfn{Text User Interface} when starting. The Text User
1228 Interface manages several text windows on the terminal, showing
1229 source, assembly, registers and @value{GDBN} command outputs
1230 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1231 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1232 Using @value{GDBN} under @sc{gnu} Emacs}).
1235 @c @cindex @code{--xdb}
1236 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1237 @c For information, see the file @file{xdb_trans.html}, which is usually
1238 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1241 @item -interpreter @var{interp}
1242 @cindex @code{--interpreter}
1243 Use the interpreter @var{interp} for interface with the controlling
1244 program or device. This option is meant to be set by programs which
1245 communicate with @value{GDBN} using it as a back end.
1246 @xref{Interpreters, , Command Interpreters}.
1248 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1249 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1250 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1251 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1252 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1253 @sc{gdb/mi} interfaces are no longer supported.
1256 @cindex @code{--write}
1257 Open the executable and core files for both reading and writing. This
1258 is equivalent to the @samp{set write on} command inside @value{GDBN}
1262 @cindex @code{--statistics}
1263 This option causes @value{GDBN} to print statistics about time and
1264 memory usage after it completes each command and returns to the prompt.
1267 @cindex @code{--version}
1268 This option causes @value{GDBN} to print its version number and
1269 no-warranty blurb, and exit.
1271 @item -configuration
1272 @cindex @code{--configuration}
1273 This option causes @value{GDBN} to print details about its build-time
1274 configuration parameters, and then exit. These details can be
1275 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1280 @subsection What @value{GDBN} Does During Startup
1281 @cindex @value{GDBN} startup
1283 Here's the description of what @value{GDBN} does during session startup:
1287 Sets up the command interpreter as specified by the command line
1288 (@pxref{Mode Options, interpreter}).
1292 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1293 used when building @value{GDBN}; @pxref{System-wide configuration,
1294 ,System-wide configuration and settings}) and executes all the commands in
1297 @anchor{Home Directory Init File}
1299 Reads the init file (if any) in your home directory@footnote{On
1300 DOS/Windows systems, the home directory is the one pointed to by the
1301 @code{HOME} environment variable.} and executes all the commands in
1304 @anchor{Option -init-eval-command}
1306 Executes commands and command files specified by the @samp{-iex} and
1307 @samp{-ix} options in their specified order. Usually you should use the
1308 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1309 settings before @value{GDBN} init files get executed and before inferior
1313 Processes command line options and operands.
1315 @anchor{Init File in the Current Directory during Startup}
1317 Reads and executes the commands from init file (if any) in the current
1318 working directory as long as @samp{set auto-load local-gdbinit} is set to
1319 @samp{on} (@pxref{Init File in the Current Directory}).
1320 This is only done if the current directory is
1321 different from your home directory. Thus, you can have more than one
1322 init file, one generic in your home directory, and another, specific
1323 to the program you are debugging, in the directory where you invoke
1327 If the command line specified a program to debug, or a process to
1328 attach to, or a core file, @value{GDBN} loads any auto-loaded
1329 scripts provided for the program or for its loaded shared libraries.
1330 @xref{Auto-loading}.
1332 If you wish to disable the auto-loading during startup,
1333 you must do something like the following:
1336 $ gdb -iex "set auto-load python-scripts off" myprogram
1339 Option @samp{-ex} does not work because the auto-loading is then turned
1343 Executes commands and command files specified by the @samp{-ex} and
1344 @samp{-x} options in their specified order. @xref{Command Files}, for
1345 more details about @value{GDBN} command files.
1348 Reads the command history recorded in the @dfn{history file}.
1349 @xref{Command History}, for more details about the command history and the
1350 files where @value{GDBN} records it.
1353 Init files use the same syntax as @dfn{command files} (@pxref{Command
1354 Files}) and are processed by @value{GDBN} in the same way. The init
1355 file in your home directory can set options (such as @samp{set
1356 complaints}) that affect subsequent processing of command line options
1357 and operands. Init files are not executed if you use the @samp{-nx}
1358 option (@pxref{Mode Options, ,Choosing Modes}).
1360 To display the list of init files loaded by gdb at startup, you
1361 can use @kbd{gdb --help}.
1363 @cindex init file name
1364 @cindex @file{.gdbinit}
1365 @cindex @file{gdb.ini}
1366 The @value{GDBN} init files are normally called @file{.gdbinit}.
1367 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1368 the limitations of file names imposed by DOS filesystems. The Windows
1369 port of @value{GDBN} uses the standard name, but if it finds a
1370 @file{gdb.ini} file in your home directory, it warns you about that
1371 and suggests to rename the file to the standard name.
1375 @section Quitting @value{GDBN}
1376 @cindex exiting @value{GDBN}
1377 @cindex leaving @value{GDBN}
1380 @kindex quit @r{[}@var{expression}@r{]}
1381 @kindex q @r{(@code{quit})}
1382 @item quit @r{[}@var{expression}@r{]}
1384 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1385 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1386 do not supply @var{expression}, @value{GDBN} will terminate normally;
1387 otherwise it will terminate using the result of @var{expression} as the
1392 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1393 terminates the action of any @value{GDBN} command that is in progress and
1394 returns to @value{GDBN} command level. It is safe to type the interrupt
1395 character at any time because @value{GDBN} does not allow it to take effect
1396 until a time when it is safe.
1398 If you have been using @value{GDBN} to control an attached process or
1399 device, you can release it with the @code{detach} command
1400 (@pxref{Attach, ,Debugging an Already-running Process}).
1402 @node Shell Commands
1403 @section Shell Commands
1405 If you need to execute occasional shell commands during your
1406 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1407 just use the @code{shell} command.
1412 @cindex shell escape
1413 @item shell @var{command-string}
1414 @itemx !@var{command-string}
1415 Invoke a standard shell to execute @var{command-string}.
1416 Note that no space is needed between @code{!} and @var{command-string}.
1417 If it exists, the environment variable @code{SHELL} determines which
1418 shell to run. Otherwise @value{GDBN} uses the default shell
1419 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1422 The utility @code{make} is often needed in development environments.
1423 You do not have to use the @code{shell} command for this purpose in
1428 @cindex calling make
1429 @item make @var{make-args}
1430 Execute the @code{make} program with the specified
1431 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1434 @node Logging Output
1435 @section Logging Output
1436 @cindex logging @value{GDBN} output
1437 @cindex save @value{GDBN} output to a file
1439 You may want to save the output of @value{GDBN} commands to a file.
1440 There are several commands to control @value{GDBN}'s logging.
1444 @item set logging on
1446 @item set logging off
1448 @cindex logging file name
1449 @item set logging file @var{file}
1450 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1451 @item set logging overwrite [on|off]
1452 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1453 you want @code{set logging on} to overwrite the logfile instead.
1454 @item set logging redirect [on|off]
1455 By default, @value{GDBN} output will go to both the terminal and the logfile.
1456 Set @code{redirect} if you want output to go only to the log file.
1457 @kindex show logging
1459 Show the current values of the logging settings.
1463 @chapter @value{GDBN} Commands
1465 You can abbreviate a @value{GDBN} command to the first few letters of the command
1466 name, if that abbreviation is unambiguous; and you can repeat certain
1467 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1468 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1469 show you the alternatives available, if there is more than one possibility).
1472 * Command Syntax:: How to give commands to @value{GDBN}
1473 * Completion:: Command completion
1474 * Help:: How to ask @value{GDBN} for help
1477 @node Command Syntax
1478 @section Command Syntax
1480 A @value{GDBN} command is a single line of input. There is no limit on
1481 how long it can be. It starts with a command name, which is followed by
1482 arguments whose meaning depends on the command name. For example, the
1483 command @code{step} accepts an argument which is the number of times to
1484 step, as in @samp{step 5}. You can also use the @code{step} command
1485 with no arguments. Some commands do not allow any arguments.
1487 @cindex abbreviation
1488 @value{GDBN} command names may always be truncated if that abbreviation is
1489 unambiguous. Other possible command abbreviations are listed in the
1490 documentation for individual commands. In some cases, even ambiguous
1491 abbreviations are allowed; for example, @code{s} is specially defined as
1492 equivalent to @code{step} even though there are other commands whose
1493 names start with @code{s}. You can test abbreviations by using them as
1494 arguments to the @code{help} command.
1496 @cindex repeating commands
1497 @kindex RET @r{(repeat last command)}
1498 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1499 repeat the previous command. Certain commands (for example, @code{run})
1500 will not repeat this way; these are commands whose unintentional
1501 repetition might cause trouble and which you are unlikely to want to
1502 repeat. User-defined commands can disable this feature; see
1503 @ref{Define, dont-repeat}.
1505 The @code{list} and @code{x} commands, when you repeat them with
1506 @key{RET}, construct new arguments rather than repeating
1507 exactly as typed. This permits easy scanning of source or memory.
1509 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1510 output, in a way similar to the common utility @code{more}
1511 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1512 @key{RET} too many in this situation, @value{GDBN} disables command
1513 repetition after any command that generates this sort of display.
1515 @kindex # @r{(a comment)}
1517 Any text from a @kbd{#} to the end of the line is a comment; it does
1518 nothing. This is useful mainly in command files (@pxref{Command
1519 Files,,Command Files}).
1521 @cindex repeating command sequences
1522 @kindex Ctrl-o @r{(operate-and-get-next)}
1523 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1524 commands. This command accepts the current line, like @key{RET}, and
1525 then fetches the next line relative to the current line from the history
1529 @section Command Completion
1532 @cindex word completion
1533 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1534 only one possibility; it can also show you what the valid possibilities
1535 are for the next word in a command, at any time. This works for @value{GDBN}
1536 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1538 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1539 of a word. If there is only one possibility, @value{GDBN} fills in the
1540 word, and waits for you to finish the command (or press @key{RET} to
1541 enter it). For example, if you type
1543 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1544 @c complete accuracy in these examples; space introduced for clarity.
1545 @c If texinfo enhancements make it unnecessary, it would be nice to
1546 @c replace " @key" by "@key" in the following...
1548 (@value{GDBP}) info bre @key{TAB}
1552 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1553 the only @code{info} subcommand beginning with @samp{bre}:
1556 (@value{GDBP}) info breakpoints
1560 You can either press @key{RET} at this point, to run the @code{info
1561 breakpoints} command, or backspace and enter something else, if
1562 @samp{breakpoints} does not look like the command you expected. (If you
1563 were sure you wanted @code{info breakpoints} in the first place, you
1564 might as well just type @key{RET} immediately after @samp{info bre},
1565 to exploit command abbreviations rather than command completion).
1567 If there is more than one possibility for the next word when you press
1568 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1569 characters and try again, or just press @key{TAB} a second time;
1570 @value{GDBN} displays all the possible completions for that word. For
1571 example, you might want to set a breakpoint on a subroutine whose name
1572 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1573 just sounds the bell. Typing @key{TAB} again displays all the
1574 function names in your program that begin with those characters, for
1578 (@value{GDBP}) b make_ @key{TAB}
1579 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1580 make_a_section_from_file make_environ
1581 make_abs_section make_function_type
1582 make_blockvector make_pointer_type
1583 make_cleanup make_reference_type
1584 make_command make_symbol_completion_list
1585 (@value{GDBP}) b make_
1589 After displaying the available possibilities, @value{GDBN} copies your
1590 partial input (@samp{b make_} in the example) so you can finish the
1593 If you just want to see the list of alternatives in the first place, you
1594 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1595 means @kbd{@key{META} ?}. You can type this either by holding down a
1596 key designated as the @key{META} shift on your keyboard (if there is
1597 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1599 @cindex quotes in commands
1600 @cindex completion of quoted strings
1601 Sometimes the string you need, while logically a ``word'', may contain
1602 parentheses or other characters that @value{GDBN} normally excludes from
1603 its notion of a word. To permit word completion to work in this
1604 situation, you may enclose words in @code{'} (single quote marks) in
1605 @value{GDBN} commands.
1607 The most likely situation where you might need this is in typing the
1608 name of a C@t{++} function. This is because C@t{++} allows function
1609 overloading (multiple definitions of the same function, distinguished
1610 by argument type). For example, when you want to set a breakpoint you
1611 may need to distinguish whether you mean the version of @code{name}
1612 that takes an @code{int} parameter, @code{name(int)}, or the version
1613 that takes a @code{float} parameter, @code{name(float)}. To use the
1614 word-completion facilities in this situation, type a single quote
1615 @code{'} at the beginning of the function name. This alerts
1616 @value{GDBN} that it may need to consider more information than usual
1617 when you press @key{TAB} or @kbd{M-?} to request word completion:
1620 (@value{GDBP}) b 'bubble( @kbd{M-?}
1621 bubble(double,double) bubble(int,int)
1622 (@value{GDBP}) b 'bubble(
1625 In some cases, @value{GDBN} can tell that completing a name requires using
1626 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1627 completing as much as it can) if you do not type the quote in the first
1631 (@value{GDBP}) b bub @key{TAB}
1632 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1633 (@value{GDBP}) b 'bubble(
1637 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1638 you have not yet started typing the argument list when you ask for
1639 completion on an overloaded symbol.
1641 For more information about overloaded functions, see @ref{C Plus Plus
1642 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1643 overload-resolution off} to disable overload resolution;
1644 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1646 @cindex completion of structure field names
1647 @cindex structure field name completion
1648 @cindex completion of union field names
1649 @cindex union field name completion
1650 When completing in an expression which looks up a field in a
1651 structure, @value{GDBN} also tries@footnote{The completer can be
1652 confused by certain kinds of invalid expressions. Also, it only
1653 examines the static type of the expression, not the dynamic type.} to
1654 limit completions to the field names available in the type of the
1658 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1659 magic to_fputs to_rewind
1660 to_data to_isatty to_write
1661 to_delete to_put to_write_async_safe
1666 This is because the @code{gdb_stdout} is a variable of the type
1667 @code{struct ui_file} that is defined in @value{GDBN} sources as
1674 ui_file_flush_ftype *to_flush;
1675 ui_file_write_ftype *to_write;
1676 ui_file_write_async_safe_ftype *to_write_async_safe;
1677 ui_file_fputs_ftype *to_fputs;
1678 ui_file_read_ftype *to_read;
1679 ui_file_delete_ftype *to_delete;
1680 ui_file_isatty_ftype *to_isatty;
1681 ui_file_rewind_ftype *to_rewind;
1682 ui_file_put_ftype *to_put;
1689 @section Getting Help
1690 @cindex online documentation
1693 You can always ask @value{GDBN} itself for information on its commands,
1694 using the command @code{help}.
1697 @kindex h @r{(@code{help})}
1700 You can use @code{help} (abbreviated @code{h}) with no arguments to
1701 display a short list of named classes of commands:
1705 List of classes of commands:
1707 aliases -- Aliases of other commands
1708 breakpoints -- Making program stop at certain points
1709 data -- Examining data
1710 files -- Specifying and examining files
1711 internals -- Maintenance commands
1712 obscure -- Obscure features
1713 running -- Running the program
1714 stack -- Examining the stack
1715 status -- Status inquiries
1716 support -- Support facilities
1717 tracepoints -- Tracing of program execution without
1718 stopping the program
1719 user-defined -- User-defined commands
1721 Type "help" followed by a class name for a list of
1722 commands in that class.
1723 Type "help" followed by command name for full
1725 Command name abbreviations are allowed if unambiguous.
1728 @c the above line break eliminates huge line overfull...
1730 @item help @var{class}
1731 Using one of the general help classes as an argument, you can get a
1732 list of the individual commands in that class. For example, here is the
1733 help display for the class @code{status}:
1736 (@value{GDBP}) help status
1741 @c Line break in "show" line falsifies real output, but needed
1742 @c to fit in smallbook page size.
1743 info -- Generic command for showing things
1744 about the program being debugged
1745 show -- Generic command for showing things
1748 Type "help" followed by command name for full
1750 Command name abbreviations are allowed if unambiguous.
1754 @item help @var{command}
1755 With a command name as @code{help} argument, @value{GDBN} displays a
1756 short paragraph on how to use that command.
1759 @item apropos @var{args}
1760 The @code{apropos} command searches through all of the @value{GDBN}
1761 commands, and their documentation, for the regular expression specified in
1762 @var{args}. It prints out all matches found. For example:
1773 alias -- Define a new command that is an alias of an existing command
1774 aliases -- Aliases of other commands
1775 d -- Delete some breakpoints or auto-display expressions
1776 del -- Delete some breakpoints or auto-display expressions
1777 delete -- Delete some breakpoints or auto-display expressions
1782 @item complete @var{args}
1783 The @code{complete @var{args}} command lists all the possible completions
1784 for the beginning of a command. Use @var{args} to specify the beginning of the
1785 command you want completed. For example:
1791 @noindent results in:
1802 @noindent This is intended for use by @sc{gnu} Emacs.
1805 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1806 and @code{show} to inquire about the state of your program, or the state
1807 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1808 manual introduces each of them in the appropriate context. The listings
1809 under @code{info} and under @code{show} in the Command, Variable, and
1810 Function Index point to all the sub-commands. @xref{Command and Variable
1816 @kindex i @r{(@code{info})}
1818 This command (abbreviated @code{i}) is for describing the state of your
1819 program. For example, you can show the arguments passed to a function
1820 with @code{info args}, list the registers currently in use with @code{info
1821 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1822 You can get a complete list of the @code{info} sub-commands with
1823 @w{@code{help info}}.
1827 You can assign the result of an expression to an environment variable with
1828 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1829 @code{set prompt $}.
1833 In contrast to @code{info}, @code{show} is for describing the state of
1834 @value{GDBN} itself.
1835 You can change most of the things you can @code{show}, by using the
1836 related command @code{set}; for example, you can control what number
1837 system is used for displays with @code{set radix}, or simply inquire
1838 which is currently in use with @code{show radix}.
1841 To display all the settable parameters and their current
1842 values, you can use @code{show} with no arguments; you may also use
1843 @code{info set}. Both commands produce the same display.
1844 @c FIXME: "info set" violates the rule that "info" is for state of
1845 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1846 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1850 Here are several miscellaneous @code{show} subcommands, all of which are
1851 exceptional in lacking corresponding @code{set} commands:
1854 @kindex show version
1855 @cindex @value{GDBN} version number
1857 Show what version of @value{GDBN} is running. You should include this
1858 information in @value{GDBN} bug-reports. If multiple versions of
1859 @value{GDBN} are in use at your site, you may need to determine which
1860 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1861 commands are introduced, and old ones may wither away. Also, many
1862 system vendors ship variant versions of @value{GDBN}, and there are
1863 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1864 The version number is the same as the one announced when you start
1867 @kindex show copying
1868 @kindex info copying
1869 @cindex display @value{GDBN} copyright
1872 Display information about permission for copying @value{GDBN}.
1874 @kindex show warranty
1875 @kindex info warranty
1877 @itemx info warranty
1878 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1879 if your version of @value{GDBN} comes with one.
1881 @kindex show configuration
1882 @item show configuration
1883 Display detailed information about the way @value{GDBN} was configured
1884 when it was built. This displays the optional arguments passed to the
1885 @file{configure} script and also configuration parameters detected
1886 automatically by @command{configure}. When reporting a @value{GDBN}
1887 bug (@pxref{GDB Bugs}), it is important to include this information in
1893 @chapter Running Programs Under @value{GDBN}
1895 When you run a program under @value{GDBN}, you must first generate
1896 debugging information when you compile it.
1898 You may start @value{GDBN} with its arguments, if any, in an environment
1899 of your choice. If you are doing native debugging, you may redirect
1900 your program's input and output, debug an already running process, or
1901 kill a child process.
1904 * Compilation:: Compiling for debugging
1905 * Starting:: Starting your program
1906 * Arguments:: Your program's arguments
1907 * Environment:: Your program's environment
1909 * Working Directory:: Your program's working directory
1910 * Input/Output:: Your program's input and output
1911 * Attach:: Debugging an already-running process
1912 * Kill Process:: Killing the child process
1914 * Inferiors and Programs:: Debugging multiple inferiors and programs
1915 * Threads:: Debugging programs with multiple threads
1916 * Forks:: Debugging forks
1917 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1921 @section Compiling for Debugging
1923 In order to debug a program effectively, you need to generate
1924 debugging information when you compile it. This debugging information
1925 is stored in the object file; it describes the data type of each
1926 variable or function and the correspondence between source line numbers
1927 and addresses in the executable code.
1929 To request debugging information, specify the @samp{-g} option when you run
1932 Programs that are to be shipped to your customers are compiled with
1933 optimizations, using the @samp{-O} compiler option. However, some
1934 compilers are unable to handle the @samp{-g} and @samp{-O} options
1935 together. Using those compilers, you cannot generate optimized
1936 executables containing debugging information.
1938 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1939 without @samp{-O}, making it possible to debug optimized code. We
1940 recommend that you @emph{always} use @samp{-g} whenever you compile a
1941 program. You may think your program is correct, but there is no sense
1942 in pushing your luck. For more information, see @ref{Optimized Code}.
1944 Older versions of the @sc{gnu} C compiler permitted a variant option
1945 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1946 format; if your @sc{gnu} C compiler has this option, do not use it.
1948 @value{GDBN} knows about preprocessor macros and can show you their
1949 expansion (@pxref{Macros}). Most compilers do not include information
1950 about preprocessor macros in the debugging information if you specify
1951 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1952 the @sc{gnu} C compiler, provides macro information if you are using
1953 the DWARF debugging format, and specify the option @option{-g3}.
1955 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1956 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1957 information on @value{NGCC} options affecting debug information.
1959 You will have the best debugging experience if you use the latest
1960 version of the DWARF debugging format that your compiler supports.
1961 DWARF is currently the most expressive and best supported debugging
1962 format in @value{GDBN}.
1966 @section Starting your Program
1972 @kindex r @r{(@code{run})}
1975 Use the @code{run} command to start your program under @value{GDBN}.
1976 You must first specify the program name (except on VxWorks) with an
1977 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1978 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1979 (@pxref{Files, ,Commands to Specify Files}).
1983 If you are running your program in an execution environment that
1984 supports processes, @code{run} creates an inferior process and makes
1985 that process run your program. In some environments without processes,
1986 @code{run} jumps to the start of your program. Other targets,
1987 like @samp{remote}, are always running. If you get an error
1988 message like this one:
1991 The "remote" target does not support "run".
1992 Try "help target" or "continue".
1996 then use @code{continue} to run your program. You may need @code{load}
1997 first (@pxref{load}).
1999 The execution of a program is affected by certain information it
2000 receives from its superior. @value{GDBN} provides ways to specify this
2001 information, which you must do @emph{before} starting your program. (You
2002 can change it after starting your program, but such changes only affect
2003 your program the next time you start it.) This information may be
2004 divided into four categories:
2007 @item The @emph{arguments.}
2008 Specify the arguments to give your program as the arguments of the
2009 @code{run} command. If a shell is available on your target, the shell
2010 is used to pass the arguments, so that you may use normal conventions
2011 (such as wildcard expansion or variable substitution) in describing
2013 In Unix systems, you can control which shell is used with the
2014 @code{SHELL} environment variable.
2015 @xref{Arguments, ,Your Program's Arguments}.
2017 @item The @emph{environment.}
2018 Your program normally inherits its environment from @value{GDBN}, but you can
2019 use the @value{GDBN} commands @code{set environment} and @code{unset
2020 environment} to change parts of the environment that affect
2021 your program. @xref{Environment, ,Your Program's Environment}.
2023 @item The @emph{working directory.}
2024 Your program inherits its working directory from @value{GDBN}. You can set
2025 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2026 @xref{Working Directory, ,Your Program's Working Directory}.
2028 @item The @emph{standard input and output.}
2029 Your program normally uses the same device for standard input and
2030 standard output as @value{GDBN} is using. You can redirect input and output
2031 in the @code{run} command line, or you can use the @code{tty} command to
2032 set a different device for your program.
2033 @xref{Input/Output, ,Your Program's Input and Output}.
2036 @emph{Warning:} While input and output redirection work, you cannot use
2037 pipes to pass the output of the program you are debugging to another
2038 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2042 When you issue the @code{run} command, your program begins to execute
2043 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2044 of how to arrange for your program to stop. Once your program has
2045 stopped, you may call functions in your program, using the @code{print}
2046 or @code{call} commands. @xref{Data, ,Examining Data}.
2048 If the modification time of your symbol file has changed since the last
2049 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2050 table, and reads it again. When it does this, @value{GDBN} tries to retain
2051 your current breakpoints.
2056 @cindex run to main procedure
2057 The name of the main procedure can vary from language to language.
2058 With C or C@t{++}, the main procedure name is always @code{main}, but
2059 other languages such as Ada do not require a specific name for their
2060 main procedure. The debugger provides a convenient way to start the
2061 execution of the program and to stop at the beginning of the main
2062 procedure, depending on the language used.
2064 The @samp{start} command does the equivalent of setting a temporary
2065 breakpoint at the beginning of the main procedure and then invoking
2066 the @samp{run} command.
2068 @cindex elaboration phase
2069 Some programs contain an @dfn{elaboration} phase where some startup code is
2070 executed before the main procedure is called. This depends on the
2071 languages used to write your program. In C@t{++}, for instance,
2072 constructors for static and global objects are executed before
2073 @code{main} is called. It is therefore possible that the debugger stops
2074 before reaching the main procedure. However, the temporary breakpoint
2075 will remain to halt execution.
2077 Specify the arguments to give to your program as arguments to the
2078 @samp{start} command. These arguments will be given verbatim to the
2079 underlying @samp{run} command. Note that the same arguments will be
2080 reused if no argument is provided during subsequent calls to
2081 @samp{start} or @samp{run}.
2083 It is sometimes necessary to debug the program during elaboration. In
2084 these cases, using the @code{start} command would stop the execution of
2085 your program too late, as the program would have already completed the
2086 elaboration phase. Under these circumstances, insert breakpoints in your
2087 elaboration code before running your program.
2089 @kindex set exec-wrapper
2090 @item set exec-wrapper @var{wrapper}
2091 @itemx show exec-wrapper
2092 @itemx unset exec-wrapper
2093 When @samp{exec-wrapper} is set, the specified wrapper is used to
2094 launch programs for debugging. @value{GDBN} starts your program
2095 with a shell command of the form @kbd{exec @var{wrapper}
2096 @var{program}}. Quoting is added to @var{program} and its
2097 arguments, but not to @var{wrapper}, so you should add quotes if
2098 appropriate for your shell. The wrapper runs until it executes
2099 your program, and then @value{GDBN} takes control.
2101 You can use any program that eventually calls @code{execve} with
2102 its arguments as a wrapper. Several standard Unix utilities do
2103 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2104 with @code{exec "$@@"} will also work.
2106 For example, you can use @code{env} to pass an environment variable to
2107 the debugged program, without setting the variable in your shell's
2111 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2115 This command is available when debugging locally on most targets, excluding
2116 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2118 @kindex set disable-randomization
2119 @item set disable-randomization
2120 @itemx set disable-randomization on
2121 This option (enabled by default in @value{GDBN}) will turn off the native
2122 randomization of the virtual address space of the started program. This option
2123 is useful for multiple debugging sessions to make the execution better
2124 reproducible and memory addresses reusable across debugging sessions.
2126 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2127 On @sc{gnu}/Linux you can get the same behavior using
2130 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2133 @item set disable-randomization off
2134 Leave the behavior of the started executable unchanged. Some bugs rear their
2135 ugly heads only when the program is loaded at certain addresses. If your bug
2136 disappears when you run the program under @value{GDBN}, that might be because
2137 @value{GDBN} by default disables the address randomization on platforms, such
2138 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2139 disable-randomization off} to try to reproduce such elusive bugs.
2141 On targets where it is available, virtual address space randomization
2142 protects the programs against certain kinds of security attacks. In these
2143 cases the attacker needs to know the exact location of a concrete executable
2144 code. Randomizing its location makes it impossible to inject jumps misusing
2145 a code at its expected addresses.
2147 Prelinking shared libraries provides a startup performance advantage but it
2148 makes addresses in these libraries predictable for privileged processes by
2149 having just unprivileged access at the target system. Reading the shared
2150 library binary gives enough information for assembling the malicious code
2151 misusing it. Still even a prelinked shared library can get loaded at a new
2152 random address just requiring the regular relocation process during the
2153 startup. Shared libraries not already prelinked are always loaded at
2154 a randomly chosen address.
2156 Position independent executables (PIE) contain position independent code
2157 similar to the shared libraries and therefore such executables get loaded at
2158 a randomly chosen address upon startup. PIE executables always load even
2159 already prelinked shared libraries at a random address. You can build such
2160 executable using @command{gcc -fPIE -pie}.
2162 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2163 (as long as the randomization is enabled).
2165 @item show disable-randomization
2166 Show the current setting of the explicit disable of the native randomization of
2167 the virtual address space of the started program.
2172 @section Your Program's Arguments
2174 @cindex arguments (to your program)
2175 The arguments to your program can be specified by the arguments of the
2177 They are passed to a shell, which expands wildcard characters and
2178 performs redirection of I/O, and thence to your program. Your
2179 @code{SHELL} environment variable (if it exists) specifies what shell
2180 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2181 the default shell (@file{/bin/sh} on Unix).
2183 On non-Unix systems, the program is usually invoked directly by
2184 @value{GDBN}, which emulates I/O redirection via the appropriate system
2185 calls, and the wildcard characters are expanded by the startup code of
2186 the program, not by the shell.
2188 @code{run} with no arguments uses the same arguments used by the previous
2189 @code{run}, or those set by the @code{set args} command.
2194 Specify the arguments to be used the next time your program is run. If
2195 @code{set args} has no arguments, @code{run} executes your program
2196 with no arguments. Once you have run your program with arguments,
2197 using @code{set args} before the next @code{run} is the only way to run
2198 it again without arguments.
2202 Show the arguments to give your program when it is started.
2206 @section Your Program's Environment
2208 @cindex environment (of your program)
2209 The @dfn{environment} consists of a set of environment variables and
2210 their values. Environment variables conventionally record such things as
2211 your user name, your home directory, your terminal type, and your search
2212 path for programs to run. Usually you set up environment variables with
2213 the shell and they are inherited by all the other programs you run. When
2214 debugging, it can be useful to try running your program with a modified
2215 environment without having to start @value{GDBN} over again.
2219 @item path @var{directory}
2220 Add @var{directory} to the front of the @code{PATH} environment variable
2221 (the search path for executables) that will be passed to your program.
2222 The value of @code{PATH} used by @value{GDBN} does not change.
2223 You may specify several directory names, separated by whitespace or by a
2224 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2225 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2226 is moved to the front, so it is searched sooner.
2228 You can use the string @samp{$cwd} to refer to whatever is the current
2229 working directory at the time @value{GDBN} searches the path. If you
2230 use @samp{.} instead, it refers to the directory where you executed the
2231 @code{path} command. @value{GDBN} replaces @samp{.} in the
2232 @var{directory} argument (with the current path) before adding
2233 @var{directory} to the search path.
2234 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2235 @c document that, since repeating it would be a no-op.
2239 Display the list of search paths for executables (the @code{PATH}
2240 environment variable).
2242 @kindex show environment
2243 @item show environment @r{[}@var{varname}@r{]}
2244 Print the value of environment variable @var{varname} to be given to
2245 your program when it starts. If you do not supply @var{varname},
2246 print the names and values of all environment variables to be given to
2247 your program. You can abbreviate @code{environment} as @code{env}.
2249 @kindex set environment
2250 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2251 Set environment variable @var{varname} to @var{value}. The value
2252 changes for your program only, not for @value{GDBN} itself. @var{value} may
2253 be any string; the values of environment variables are just strings, and
2254 any interpretation is supplied by your program itself. The @var{value}
2255 parameter is optional; if it is eliminated, the variable is set to a
2257 @c "any string" here does not include leading, trailing
2258 @c blanks. Gnu asks: does anyone care?
2260 For example, this command:
2267 tells the debugged program, when subsequently run, that its user is named
2268 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2269 are not actually required.)
2271 @kindex unset environment
2272 @item unset environment @var{varname}
2273 Remove variable @var{varname} from the environment to be passed to your
2274 program. This is different from @samp{set env @var{varname} =};
2275 @code{unset environment} removes the variable from the environment,
2276 rather than assigning it an empty value.
2279 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2281 by your @code{SHELL} environment variable if it exists (or
2282 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2283 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2284 @file{.bashrc} for BASH---any variables you set in that file affect
2285 your program. You may wish to move setting of environment variables to
2286 files that are only run when you sign on, such as @file{.login} or
2289 @node Working Directory
2290 @section Your Program's Working Directory
2292 @cindex working directory (of your program)
2293 Each time you start your program with @code{run}, it inherits its
2294 working directory from the current working directory of @value{GDBN}.
2295 The @value{GDBN} working directory is initially whatever it inherited
2296 from its parent process (typically the shell), but you can specify a new
2297 working directory in @value{GDBN} with the @code{cd} command.
2299 The @value{GDBN} working directory also serves as a default for the commands
2300 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2305 @cindex change working directory
2306 @item cd @r{[}@var{directory}@r{]}
2307 Set the @value{GDBN} working directory to @var{directory}. If not
2308 given, @var{directory} uses @file{'~'}.
2312 Print the @value{GDBN} working directory.
2315 It is generally impossible to find the current working directory of
2316 the process being debugged (since a program can change its directory
2317 during its run). If you work on a system where @value{GDBN} is
2318 configured with the @file{/proc} support, you can use the @code{info
2319 proc} command (@pxref{SVR4 Process Information}) to find out the
2320 current working directory of the debuggee.
2323 @section Your Program's Input and Output
2328 By default, the program you run under @value{GDBN} does input and output to
2329 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2330 to its own terminal modes to interact with you, but it records the terminal
2331 modes your program was using and switches back to them when you continue
2332 running your program.
2335 @kindex info terminal
2337 Displays information recorded by @value{GDBN} about the terminal modes your
2341 You can redirect your program's input and/or output using shell
2342 redirection with the @code{run} command. For example,
2349 starts your program, diverting its output to the file @file{outfile}.
2352 @cindex controlling terminal
2353 Another way to specify where your program should do input and output is
2354 with the @code{tty} command. This command accepts a file name as
2355 argument, and causes this file to be the default for future @code{run}
2356 commands. It also resets the controlling terminal for the child
2357 process, for future @code{run} commands. For example,
2364 directs that processes started with subsequent @code{run} commands
2365 default to do input and output on the terminal @file{/dev/ttyb} and have
2366 that as their controlling terminal.
2368 An explicit redirection in @code{run} overrides the @code{tty} command's
2369 effect on the input/output device, but not its effect on the controlling
2372 When you use the @code{tty} command or redirect input in the @code{run}
2373 command, only the input @emph{for your program} is affected. The input
2374 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2375 for @code{set inferior-tty}.
2377 @cindex inferior tty
2378 @cindex set inferior controlling terminal
2379 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2380 display the name of the terminal that will be used for future runs of your
2384 @item set inferior-tty /dev/ttyb
2385 @kindex set inferior-tty
2386 Set the tty for the program being debugged to /dev/ttyb.
2388 @item show inferior-tty
2389 @kindex show inferior-tty
2390 Show the current tty for the program being debugged.
2394 @section Debugging an Already-running Process
2399 @item attach @var{process-id}
2400 This command attaches to a running process---one that was started
2401 outside @value{GDBN}. (@code{info files} shows your active
2402 targets.) The command takes as argument a process ID. The usual way to
2403 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2404 or with the @samp{jobs -l} shell command.
2406 @code{attach} does not repeat if you press @key{RET} a second time after
2407 executing the command.
2410 To use @code{attach}, your program must be running in an environment
2411 which supports processes; for example, @code{attach} does not work for
2412 programs on bare-board targets that lack an operating system. You must
2413 also have permission to send the process a signal.
2415 When you use @code{attach}, the debugger finds the program running in
2416 the process first by looking in the current working directory, then (if
2417 the program is not found) by using the source file search path
2418 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2419 the @code{file} command to load the program. @xref{Files, ,Commands to
2422 The first thing @value{GDBN} does after arranging to debug the specified
2423 process is to stop it. You can examine and modify an attached process
2424 with all the @value{GDBN} commands that are ordinarily available when
2425 you start processes with @code{run}. You can insert breakpoints; you
2426 can step and continue; you can modify storage. If you would rather the
2427 process continue running, you may use the @code{continue} command after
2428 attaching @value{GDBN} to the process.
2433 When you have finished debugging the attached process, you can use the
2434 @code{detach} command to release it from @value{GDBN} control. Detaching
2435 the process continues its execution. After the @code{detach} command,
2436 that process and @value{GDBN} become completely independent once more, and you
2437 are ready to @code{attach} another process or start one with @code{run}.
2438 @code{detach} does not repeat if you press @key{RET} again after
2439 executing the command.
2442 If you exit @value{GDBN} while you have an attached process, you detach
2443 that process. If you use the @code{run} command, you kill that process.
2444 By default, @value{GDBN} asks for confirmation if you try to do either of these
2445 things; you can control whether or not you need to confirm by using the
2446 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2450 @section Killing the Child Process
2455 Kill the child process in which your program is running under @value{GDBN}.
2458 This command is useful if you wish to debug a core dump instead of a
2459 running process. @value{GDBN} ignores any core dump file while your program
2462 On some operating systems, a program cannot be executed outside @value{GDBN}
2463 while you have breakpoints set on it inside @value{GDBN}. You can use the
2464 @code{kill} command in this situation to permit running your program
2465 outside the debugger.
2467 The @code{kill} command is also useful if you wish to recompile and
2468 relink your program, since on many systems it is impossible to modify an
2469 executable file while it is running in a process. In this case, when you
2470 next type @code{run}, @value{GDBN} notices that the file has changed, and
2471 reads the symbol table again (while trying to preserve your current
2472 breakpoint settings).
2474 @node Inferiors and Programs
2475 @section Debugging Multiple Inferiors and Programs
2477 @value{GDBN} lets you run and debug multiple programs in a single
2478 session. In addition, @value{GDBN} on some systems may let you run
2479 several programs simultaneously (otherwise you have to exit from one
2480 before starting another). In the most general case, you can have
2481 multiple threads of execution in each of multiple processes, launched
2482 from multiple executables.
2485 @value{GDBN} represents the state of each program execution with an
2486 object called an @dfn{inferior}. An inferior typically corresponds to
2487 a process, but is more general and applies also to targets that do not
2488 have processes. Inferiors may be created before a process runs, and
2489 may be retained after a process exits. Inferiors have unique
2490 identifiers that are different from process ids. Usually each
2491 inferior will also have its own distinct address space, although some
2492 embedded targets may have several inferiors running in different parts
2493 of a single address space. Each inferior may in turn have multiple
2494 threads running in it.
2496 To find out what inferiors exist at any moment, use @w{@code{info
2500 @kindex info inferiors
2501 @item info inferiors
2502 Print a list of all inferiors currently being managed by @value{GDBN}.
2504 @value{GDBN} displays for each inferior (in this order):
2508 the inferior number assigned by @value{GDBN}
2511 the target system's inferior identifier
2514 the name of the executable the inferior is running.
2519 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2520 indicates the current inferior.
2524 @c end table here to get a little more width for example
2527 (@value{GDBP}) info inferiors
2528 Num Description Executable
2529 2 process 2307 hello
2530 * 1 process 3401 goodbye
2533 To switch focus between inferiors, use the @code{inferior} command:
2536 @kindex inferior @var{infno}
2537 @item inferior @var{infno}
2538 Make inferior number @var{infno} the current inferior. The argument
2539 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2540 in the first field of the @samp{info inferiors} display.
2544 You can get multiple executables into a debugging session via the
2545 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2546 systems @value{GDBN} can add inferiors to the debug session
2547 automatically by following calls to @code{fork} and @code{exec}. To
2548 remove inferiors from the debugging session use the
2549 @w{@code{remove-inferiors}} command.
2552 @kindex add-inferior
2553 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2554 Adds @var{n} inferiors to be run using @var{executable} as the
2555 executable. @var{n} defaults to 1. If no executable is specified,
2556 the inferiors begins empty, with no program. You can still assign or
2557 change the program assigned to the inferior at any time by using the
2558 @code{file} command with the executable name as its argument.
2560 @kindex clone-inferior
2561 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2562 Adds @var{n} inferiors ready to execute the same program as inferior
2563 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2564 number of the current inferior. This is a convenient command when you
2565 want to run another instance of the inferior you are debugging.
2568 (@value{GDBP}) info inferiors
2569 Num Description Executable
2570 * 1 process 29964 helloworld
2571 (@value{GDBP}) clone-inferior
2574 (@value{GDBP}) info inferiors
2575 Num Description Executable
2577 * 1 process 29964 helloworld
2580 You can now simply switch focus to inferior 2 and run it.
2582 @kindex remove-inferiors
2583 @item remove-inferiors @var{infno}@dots{}
2584 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2585 possible to remove an inferior that is running with this command. For
2586 those, use the @code{kill} or @code{detach} command first.
2590 To quit debugging one of the running inferiors that is not the current
2591 inferior, you can either detach from it by using the @w{@code{detach
2592 inferior}} command (allowing it to run independently), or kill it
2593 using the @w{@code{kill inferiors}} command:
2596 @kindex detach inferiors @var{infno}@dots{}
2597 @item detach inferior @var{infno}@dots{}
2598 Detach from the inferior or inferiors identified by @value{GDBN}
2599 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2600 still stays on the list of inferiors shown by @code{info inferiors},
2601 but its Description will show @samp{<null>}.
2603 @kindex kill inferiors @var{infno}@dots{}
2604 @item kill inferiors @var{infno}@dots{}
2605 Kill the inferior or inferiors identified by @value{GDBN} inferior
2606 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2607 stays on the list of inferiors shown by @code{info inferiors}, but its
2608 Description will show @samp{<null>}.
2611 After the successful completion of a command such as @code{detach},
2612 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2613 a normal process exit, the inferior is still valid and listed with
2614 @code{info inferiors}, ready to be restarted.
2617 To be notified when inferiors are started or exit under @value{GDBN}'s
2618 control use @w{@code{set print inferior-events}}:
2621 @kindex set print inferior-events
2622 @cindex print messages on inferior start and exit
2623 @item set print inferior-events
2624 @itemx set print inferior-events on
2625 @itemx set print inferior-events off
2626 The @code{set print inferior-events} command allows you to enable or
2627 disable printing of messages when @value{GDBN} notices that new
2628 inferiors have started or that inferiors have exited or have been
2629 detached. By default, these messages will not be printed.
2631 @kindex show print inferior-events
2632 @item show print inferior-events
2633 Show whether messages will be printed when @value{GDBN} detects that
2634 inferiors have started, exited or have been detached.
2637 Many commands will work the same with multiple programs as with a
2638 single program: e.g., @code{print myglobal} will simply display the
2639 value of @code{myglobal} in the current inferior.
2642 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2643 get more info about the relationship of inferiors, programs, address
2644 spaces in a debug session. You can do that with the @w{@code{maint
2645 info program-spaces}} command.
2648 @kindex maint info program-spaces
2649 @item maint info program-spaces
2650 Print a list of all program spaces currently being managed by
2653 @value{GDBN} displays for each program space (in this order):
2657 the program space number assigned by @value{GDBN}
2660 the name of the executable loaded into the program space, with e.g.,
2661 the @code{file} command.
2666 An asterisk @samp{*} preceding the @value{GDBN} program space number
2667 indicates the current program space.
2669 In addition, below each program space line, @value{GDBN} prints extra
2670 information that isn't suitable to display in tabular form. For
2671 example, the list of inferiors bound to the program space.
2674 (@value{GDBP}) maint info program-spaces
2677 Bound inferiors: ID 1 (process 21561)
2681 Here we can see that no inferior is running the program @code{hello},
2682 while @code{process 21561} is running the program @code{goodbye}. On
2683 some targets, it is possible that multiple inferiors are bound to the
2684 same program space. The most common example is that of debugging both
2685 the parent and child processes of a @code{vfork} call. For example,
2688 (@value{GDBP}) maint info program-spaces
2691 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2694 Here, both inferior 2 and inferior 1 are running in the same program
2695 space as a result of inferior 1 having executed a @code{vfork} call.
2699 @section Debugging Programs with Multiple Threads
2701 @cindex threads of execution
2702 @cindex multiple threads
2703 @cindex switching threads
2704 In some operating systems, such as HP-UX and Solaris, a single program
2705 may have more than one @dfn{thread} of execution. The precise semantics
2706 of threads differ from one operating system to another, but in general
2707 the threads of a single program are akin to multiple processes---except
2708 that they share one address space (that is, they can all examine and
2709 modify the same variables). On the other hand, each thread has its own
2710 registers and execution stack, and perhaps private memory.
2712 @value{GDBN} provides these facilities for debugging multi-thread
2716 @item automatic notification of new threads
2717 @item @samp{thread @var{threadno}}, a command to switch among threads
2718 @item @samp{info threads}, a command to inquire about existing threads
2719 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2720 a command to apply a command to a list of threads
2721 @item thread-specific breakpoints
2722 @item @samp{set print thread-events}, which controls printing of
2723 messages on thread start and exit.
2724 @item @samp{set libthread-db-search-path @var{path}}, which lets
2725 the user specify which @code{libthread_db} to use if the default choice
2726 isn't compatible with the program.
2730 @emph{Warning:} These facilities are not yet available on every
2731 @value{GDBN} configuration where the operating system supports threads.
2732 If your @value{GDBN} does not support threads, these commands have no
2733 effect. For example, a system without thread support shows no output
2734 from @samp{info threads}, and always rejects the @code{thread} command,
2738 (@value{GDBP}) info threads
2739 (@value{GDBP}) thread 1
2740 Thread ID 1 not known. Use the "info threads" command to
2741 see the IDs of currently known threads.
2743 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2744 @c doesn't support threads"?
2747 @cindex focus of debugging
2748 @cindex current thread
2749 The @value{GDBN} thread debugging facility allows you to observe all
2750 threads while your program runs---but whenever @value{GDBN} takes
2751 control, one thread in particular is always the focus of debugging.
2752 This thread is called the @dfn{current thread}. Debugging commands show
2753 program information from the perspective of the current thread.
2755 @cindex @code{New} @var{systag} message
2756 @cindex thread identifier (system)
2757 @c FIXME-implementors!! It would be more helpful if the [New...] message
2758 @c included GDB's numeric thread handle, so you could just go to that
2759 @c thread without first checking `info threads'.
2760 Whenever @value{GDBN} detects a new thread in your program, it displays
2761 the target system's identification for the thread with a message in the
2762 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2763 whose form varies depending on the particular system. For example, on
2764 @sc{gnu}/Linux, you might see
2767 [New Thread 0x41e02940 (LWP 25582)]
2771 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2772 the @var{systag} is simply something like @samp{process 368}, with no
2775 @c FIXME!! (1) Does the [New...] message appear even for the very first
2776 @c thread of a program, or does it only appear for the
2777 @c second---i.e.@: when it becomes obvious we have a multithread
2779 @c (2) *Is* there necessarily a first thread always? Or do some
2780 @c multithread systems permit starting a program with multiple
2781 @c threads ab initio?
2783 @cindex thread number
2784 @cindex thread identifier (GDB)
2785 For debugging purposes, @value{GDBN} associates its own thread
2786 number---always a single integer---with each thread in your program.
2789 @kindex info threads
2790 @item info threads @r{[}@var{id}@dots{}@r{]}
2791 Display a summary of all threads currently in your program. Optional
2792 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2793 means to print information only about the specified thread or threads.
2794 @value{GDBN} displays for each thread (in this order):
2798 the thread number assigned by @value{GDBN}
2801 the target system's thread identifier (@var{systag})
2804 the thread's name, if one is known. A thread can either be named by
2805 the user (see @code{thread name}, below), or, in some cases, by the
2809 the current stack frame summary for that thread
2813 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2814 indicates the current thread.
2818 @c end table here to get a little more width for example
2821 (@value{GDBP}) info threads
2823 3 process 35 thread 27 0x34e5 in sigpause ()
2824 2 process 35 thread 23 0x34e5 in sigpause ()
2825 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2829 On Solaris, you can display more information about user threads with a
2830 Solaris-specific command:
2833 @item maint info sol-threads
2834 @kindex maint info sol-threads
2835 @cindex thread info (Solaris)
2836 Display info on Solaris user threads.
2840 @kindex thread @var{threadno}
2841 @item thread @var{threadno}
2842 Make thread number @var{threadno} the current thread. The command
2843 argument @var{threadno} is the internal @value{GDBN} thread number, as
2844 shown in the first field of the @samp{info threads} display.
2845 @value{GDBN} responds by displaying the system identifier of the thread
2846 you selected, and its current stack frame summary:
2849 (@value{GDBP}) thread 2
2850 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2851 #0 some_function (ignore=0x0) at example.c:8
2852 8 printf ("hello\n");
2856 As with the @samp{[New @dots{}]} message, the form of the text after
2857 @samp{Switching to} depends on your system's conventions for identifying
2860 @vindex $_thread@r{, convenience variable}
2861 The debugger convenience variable @samp{$_thread} contains the number
2862 of the current thread. You may find this useful in writing breakpoint
2863 conditional expressions, command scripts, and so forth. See
2864 @xref{Convenience Vars,, Convenience Variables}, for general
2865 information on convenience variables.
2867 @kindex thread apply
2868 @cindex apply command to several threads
2869 @item thread apply [@var{threadno} | all] @var{command}
2870 The @code{thread apply} command allows you to apply the named
2871 @var{command} to one or more threads. Specify the numbers of the
2872 threads that you want affected with the command argument
2873 @var{threadno}. It can be a single thread number, one of the numbers
2874 shown in the first field of the @samp{info threads} display; or it
2875 could be a range of thread numbers, as in @code{2-4}. To apply a
2876 command to all threads, type @kbd{thread apply all @var{command}}.
2879 @cindex name a thread
2880 @item thread name [@var{name}]
2881 This command assigns a name to the current thread. If no argument is
2882 given, any existing user-specified name is removed. The thread name
2883 appears in the @samp{info threads} display.
2885 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2886 determine the name of the thread as given by the OS. On these
2887 systems, a name specified with @samp{thread name} will override the
2888 system-give name, and removing the user-specified name will cause
2889 @value{GDBN} to once again display the system-specified name.
2892 @cindex search for a thread
2893 @item thread find [@var{regexp}]
2894 Search for and display thread ids whose name or @var{systag}
2895 matches the supplied regular expression.
2897 As well as being the complement to the @samp{thread name} command,
2898 this command also allows you to identify a thread by its target
2899 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2903 (@value{GDBN}) thread find 26688
2904 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2905 (@value{GDBN}) info thread 4
2907 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2910 @kindex set print thread-events
2911 @cindex print messages on thread start and exit
2912 @item set print thread-events
2913 @itemx set print thread-events on
2914 @itemx set print thread-events off
2915 The @code{set print thread-events} command allows you to enable or
2916 disable printing of messages when @value{GDBN} notices that new threads have
2917 started or that threads have exited. By default, these messages will
2918 be printed if detection of these events is supported by the target.
2919 Note that these messages cannot be disabled on all targets.
2921 @kindex show print thread-events
2922 @item show print thread-events
2923 Show whether messages will be printed when @value{GDBN} detects that threads
2924 have started and exited.
2927 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2928 more information about how @value{GDBN} behaves when you stop and start
2929 programs with multiple threads.
2931 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2932 watchpoints in programs with multiple threads.
2934 @anchor{set libthread-db-search-path}
2936 @kindex set libthread-db-search-path
2937 @cindex search path for @code{libthread_db}
2938 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2939 If this variable is set, @var{path} is a colon-separated list of
2940 directories @value{GDBN} will use to search for @code{libthread_db}.
2941 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2942 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
2943 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
2946 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2947 @code{libthread_db} library to obtain information about threads in the
2948 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2949 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
2950 specific thread debugging library loading is enabled
2951 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
2953 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
2954 refers to the default system directories that are
2955 normally searched for loading shared libraries. The @samp{$sdir} entry
2956 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
2957 (@pxref{libthread_db.so.1 file}).
2959 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
2960 refers to the directory from which @code{libpthread}
2961 was loaded in the inferior process.
2963 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2964 @value{GDBN} attempts to initialize it with the current inferior process.
2965 If this initialization fails (which could happen because of a version
2966 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2967 will unload @code{libthread_db}, and continue with the next directory.
2968 If none of @code{libthread_db} libraries initialize successfully,
2969 @value{GDBN} will issue a warning and thread debugging will be disabled.
2971 Setting @code{libthread-db-search-path} is currently implemented
2972 only on some platforms.
2974 @kindex show libthread-db-search-path
2975 @item show libthread-db-search-path
2976 Display current libthread_db search path.
2978 @kindex set debug libthread-db
2979 @kindex show debug libthread-db
2980 @cindex debugging @code{libthread_db}
2981 @item set debug libthread-db
2982 @itemx show debug libthread-db
2983 Turns on or off display of @code{libthread_db}-related events.
2984 Use @code{1} to enable, @code{0} to disable.
2988 @section Debugging Forks
2990 @cindex fork, debugging programs which call
2991 @cindex multiple processes
2992 @cindex processes, multiple
2993 On most systems, @value{GDBN} has no special support for debugging
2994 programs which create additional processes using the @code{fork}
2995 function. When a program forks, @value{GDBN} will continue to debug the
2996 parent process and the child process will run unimpeded. If you have
2997 set a breakpoint in any code which the child then executes, the child
2998 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2999 will cause it to terminate.
3001 However, if you want to debug the child process there is a workaround
3002 which isn't too painful. Put a call to @code{sleep} in the code which
3003 the child process executes after the fork. It may be useful to sleep
3004 only if a certain environment variable is set, or a certain file exists,
3005 so that the delay need not occur when you don't want to run @value{GDBN}
3006 on the child. While the child is sleeping, use the @code{ps} program to
3007 get its process ID. Then tell @value{GDBN} (a new invocation of
3008 @value{GDBN} if you are also debugging the parent process) to attach to
3009 the child process (@pxref{Attach}). From that point on you can debug
3010 the child process just like any other process which you attached to.
3012 On some systems, @value{GDBN} provides support for debugging programs that
3013 create additional processes using the @code{fork} or @code{vfork} functions.
3014 Currently, the only platforms with this feature are HP-UX (11.x and later
3015 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
3017 By default, when a program forks, @value{GDBN} will continue to debug
3018 the parent process and the child process will run unimpeded.
3020 If you want to follow the child process instead of the parent process,
3021 use the command @w{@code{set follow-fork-mode}}.
3024 @kindex set follow-fork-mode
3025 @item set follow-fork-mode @var{mode}
3026 Set the debugger response to a program call of @code{fork} or
3027 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3028 process. The @var{mode} argument can be:
3032 The original process is debugged after a fork. The child process runs
3033 unimpeded. This is the default.
3036 The new process is debugged after a fork. The parent process runs
3041 @kindex show follow-fork-mode
3042 @item show follow-fork-mode
3043 Display the current debugger response to a @code{fork} or @code{vfork} call.
3046 @cindex debugging multiple processes
3047 On Linux, if you want to debug both the parent and child processes, use the
3048 command @w{@code{set detach-on-fork}}.
3051 @kindex set detach-on-fork
3052 @item set detach-on-fork @var{mode}
3053 Tells gdb whether to detach one of the processes after a fork, or
3054 retain debugger control over them both.
3058 The child process (or parent process, depending on the value of
3059 @code{follow-fork-mode}) will be detached and allowed to run
3060 independently. This is the default.
3063 Both processes will be held under the control of @value{GDBN}.
3064 One process (child or parent, depending on the value of
3065 @code{follow-fork-mode}) is debugged as usual, while the other
3070 @kindex show detach-on-fork
3071 @item show detach-on-fork
3072 Show whether detach-on-fork mode is on/off.
3075 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3076 will retain control of all forked processes (including nested forks).
3077 You can list the forked processes under the control of @value{GDBN} by
3078 using the @w{@code{info inferiors}} command, and switch from one fork
3079 to another by using the @code{inferior} command (@pxref{Inferiors and
3080 Programs, ,Debugging Multiple Inferiors and Programs}).
3082 To quit debugging one of the forked processes, you can either detach
3083 from it by using the @w{@code{detach inferiors}} command (allowing it
3084 to run independently), or kill it using the @w{@code{kill inferiors}}
3085 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3088 If you ask to debug a child process and a @code{vfork} is followed by an
3089 @code{exec}, @value{GDBN} executes the new target up to the first
3090 breakpoint in the new target. If you have a breakpoint set on
3091 @code{main} in your original program, the breakpoint will also be set on
3092 the child process's @code{main}.
3094 On some systems, when a child process is spawned by @code{vfork}, you
3095 cannot debug the child or parent until an @code{exec} call completes.
3097 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3098 call executes, the new target restarts. To restart the parent
3099 process, use the @code{file} command with the parent executable name
3100 as its argument. By default, after an @code{exec} call executes,
3101 @value{GDBN} discards the symbols of the previous executable image.
3102 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3106 @kindex set follow-exec-mode
3107 @item set follow-exec-mode @var{mode}
3109 Set debugger response to a program call of @code{exec}. An
3110 @code{exec} call replaces the program image of a process.
3112 @code{follow-exec-mode} can be:
3116 @value{GDBN} creates a new inferior and rebinds the process to this
3117 new inferior. The program the process was running before the
3118 @code{exec} call can be restarted afterwards by restarting the
3124 (@value{GDBP}) info inferiors
3126 Id Description Executable
3129 process 12020 is executing new program: prog2
3130 Program exited normally.
3131 (@value{GDBP}) info inferiors
3132 Id Description Executable
3138 @value{GDBN} keeps the process bound to the same inferior. The new
3139 executable image replaces the previous executable loaded in the
3140 inferior. Restarting the inferior after the @code{exec} call, with
3141 e.g., the @code{run} command, restarts the executable the process was
3142 running after the @code{exec} call. This is the default mode.
3147 (@value{GDBP}) info inferiors
3148 Id Description Executable
3151 process 12020 is executing new program: prog2
3152 Program exited normally.
3153 (@value{GDBP}) info inferiors
3154 Id Description Executable
3161 You can use the @code{catch} command to make @value{GDBN} stop whenever
3162 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3163 Catchpoints, ,Setting Catchpoints}.
3165 @node Checkpoint/Restart
3166 @section Setting a @emph{Bookmark} to Return to Later
3171 @cindex snapshot of a process
3172 @cindex rewind program state
3174 On certain operating systems@footnote{Currently, only
3175 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3176 program's state, called a @dfn{checkpoint}, and come back to it
3179 Returning to a checkpoint effectively undoes everything that has
3180 happened in the program since the @code{checkpoint} was saved. This
3181 includes changes in memory, registers, and even (within some limits)
3182 system state. Effectively, it is like going back in time to the
3183 moment when the checkpoint was saved.
3185 Thus, if you're stepping thru a program and you think you're
3186 getting close to the point where things go wrong, you can save
3187 a checkpoint. Then, if you accidentally go too far and miss
3188 the critical statement, instead of having to restart your program
3189 from the beginning, you can just go back to the checkpoint and
3190 start again from there.
3192 This can be especially useful if it takes a lot of time or
3193 steps to reach the point where you think the bug occurs.
3195 To use the @code{checkpoint}/@code{restart} method of debugging:
3200 Save a snapshot of the debugged program's current execution state.
3201 The @code{checkpoint} command takes no arguments, but each checkpoint
3202 is assigned a small integer id, similar to a breakpoint id.
3204 @kindex info checkpoints
3205 @item info checkpoints
3206 List the checkpoints that have been saved in the current debugging
3207 session. For each checkpoint, the following information will be
3214 @item Source line, or label
3217 @kindex restart @var{checkpoint-id}
3218 @item restart @var{checkpoint-id}
3219 Restore the program state that was saved as checkpoint number
3220 @var{checkpoint-id}. All program variables, registers, stack frames
3221 etc.@: will be returned to the values that they had when the checkpoint
3222 was saved. In essence, gdb will ``wind back the clock'' to the point
3223 in time when the checkpoint was saved.
3225 Note that breakpoints, @value{GDBN} variables, command history etc.
3226 are not affected by restoring a checkpoint. In general, a checkpoint
3227 only restores things that reside in the program being debugged, not in
3230 @kindex delete checkpoint @var{checkpoint-id}
3231 @item delete checkpoint @var{checkpoint-id}
3232 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3236 Returning to a previously saved checkpoint will restore the user state
3237 of the program being debugged, plus a significant subset of the system
3238 (OS) state, including file pointers. It won't ``un-write'' data from
3239 a file, but it will rewind the file pointer to the previous location,
3240 so that the previously written data can be overwritten. For files
3241 opened in read mode, the pointer will also be restored so that the
3242 previously read data can be read again.
3244 Of course, characters that have been sent to a printer (or other
3245 external device) cannot be ``snatched back'', and characters received
3246 from eg.@: a serial device can be removed from internal program buffers,
3247 but they cannot be ``pushed back'' into the serial pipeline, ready to
3248 be received again. Similarly, the actual contents of files that have
3249 been changed cannot be restored (at this time).
3251 However, within those constraints, you actually can ``rewind'' your
3252 program to a previously saved point in time, and begin debugging it
3253 again --- and you can change the course of events so as to debug a
3254 different execution path this time.
3256 @cindex checkpoints and process id
3257 Finally, there is one bit of internal program state that will be
3258 different when you return to a checkpoint --- the program's process
3259 id. Each checkpoint will have a unique process id (or @var{pid}),
3260 and each will be different from the program's original @var{pid}.
3261 If your program has saved a local copy of its process id, this could
3262 potentially pose a problem.
3264 @subsection A Non-obvious Benefit of Using Checkpoints
3266 On some systems such as @sc{gnu}/Linux, address space randomization
3267 is performed on new processes for security reasons. This makes it
3268 difficult or impossible to set a breakpoint, or watchpoint, on an
3269 absolute address if you have to restart the program, since the
3270 absolute location of a symbol will change from one execution to the
3273 A checkpoint, however, is an @emph{identical} copy of a process.
3274 Therefore if you create a checkpoint at (eg.@:) the start of main,
3275 and simply return to that checkpoint instead of restarting the
3276 process, you can avoid the effects of address randomization and
3277 your symbols will all stay in the same place.
3280 @chapter Stopping and Continuing
3282 The principal purposes of using a debugger are so that you can stop your
3283 program before it terminates; or so that, if your program runs into
3284 trouble, you can investigate and find out why.
3286 Inside @value{GDBN}, your program may stop for any of several reasons,
3287 such as a signal, a breakpoint, or reaching a new line after a
3288 @value{GDBN} command such as @code{step}. You may then examine and
3289 change variables, set new breakpoints or remove old ones, and then
3290 continue execution. Usually, the messages shown by @value{GDBN} provide
3291 ample explanation of the status of your program---but you can also
3292 explicitly request this information at any time.
3295 @kindex info program
3297 Display information about the status of your program: whether it is
3298 running or not, what process it is, and why it stopped.
3302 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3303 * Continuing and Stepping:: Resuming execution
3304 * Skipping Over Functions and Files::
3305 Skipping over functions and files
3307 * Thread Stops:: Stopping and starting multi-thread programs
3311 @section Breakpoints, Watchpoints, and Catchpoints
3314 A @dfn{breakpoint} makes your program stop whenever a certain point in
3315 the program is reached. For each breakpoint, you can add conditions to
3316 control in finer detail whether your program stops. You can set
3317 breakpoints with the @code{break} command and its variants (@pxref{Set
3318 Breaks, ,Setting Breakpoints}), to specify the place where your program
3319 should stop by line number, function name or exact address in the
3322 On some systems, you can set breakpoints in shared libraries before
3323 the executable is run. There is a minor limitation on HP-UX systems:
3324 you must wait until the executable is run in order to set breakpoints
3325 in shared library routines that are not called directly by the program
3326 (for example, routines that are arguments in a @code{pthread_create}
3330 @cindex data breakpoints
3331 @cindex memory tracing
3332 @cindex breakpoint on memory address
3333 @cindex breakpoint on variable modification
3334 A @dfn{watchpoint} is a special breakpoint that stops your program
3335 when the value of an expression changes. The expression may be a value
3336 of a variable, or it could involve values of one or more variables
3337 combined by operators, such as @samp{a + b}. This is sometimes called
3338 @dfn{data breakpoints}. You must use a different command to set
3339 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3340 from that, you can manage a watchpoint like any other breakpoint: you
3341 enable, disable, and delete both breakpoints and watchpoints using the
3344 You can arrange to have values from your program displayed automatically
3345 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3349 @cindex breakpoint on events
3350 A @dfn{catchpoint} is another special breakpoint that stops your program
3351 when a certain kind of event occurs, such as the throwing of a C@t{++}
3352 exception or the loading of a library. As with watchpoints, you use a
3353 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3354 Catchpoints}), but aside from that, you can manage a catchpoint like any
3355 other breakpoint. (To stop when your program receives a signal, use the
3356 @code{handle} command; see @ref{Signals, ,Signals}.)
3358 @cindex breakpoint numbers
3359 @cindex numbers for breakpoints
3360 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3361 catchpoint when you create it; these numbers are successive integers
3362 starting with one. In many of the commands for controlling various
3363 features of breakpoints you use the breakpoint number to say which
3364 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3365 @dfn{disabled}; if disabled, it has no effect on your program until you
3368 @cindex breakpoint ranges
3369 @cindex ranges of breakpoints
3370 Some @value{GDBN} commands accept a range of breakpoints on which to
3371 operate. A breakpoint range is either a single breakpoint number, like
3372 @samp{5}, or two such numbers, in increasing order, separated by a
3373 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3374 all breakpoints in that range are operated on.
3377 * Set Breaks:: Setting breakpoints
3378 * Set Watchpoints:: Setting watchpoints
3379 * Set Catchpoints:: Setting catchpoints
3380 * Delete Breaks:: Deleting breakpoints
3381 * Disabling:: Disabling breakpoints
3382 * Conditions:: Break conditions
3383 * Break Commands:: Breakpoint command lists
3384 * Dynamic Printf:: Dynamic printf
3385 * Save Breakpoints:: How to save breakpoints in a file
3386 * Static Probe Points:: Listing static probe points
3387 * Error in Breakpoints:: ``Cannot insert breakpoints''
3388 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3392 @subsection Setting Breakpoints
3394 @c FIXME LMB what does GDB do if no code on line of breakpt?
3395 @c consider in particular declaration with/without initialization.
3397 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3400 @kindex b @r{(@code{break})}
3401 @vindex $bpnum@r{, convenience variable}
3402 @cindex latest breakpoint
3403 Breakpoints are set with the @code{break} command (abbreviated
3404 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3405 number of the breakpoint you've set most recently; see @ref{Convenience
3406 Vars,, Convenience Variables}, for a discussion of what you can do with
3407 convenience variables.
3410 @item break @var{location}
3411 Set a breakpoint at the given @var{location}, which can specify a
3412 function name, a line number, or an address of an instruction.
3413 (@xref{Specify Location}, for a list of all the possible ways to
3414 specify a @var{location}.) The breakpoint will stop your program just
3415 before it executes any of the code in the specified @var{location}.
3417 When using source languages that permit overloading of symbols, such as
3418 C@t{++}, a function name may refer to more than one possible place to break.
3419 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3422 It is also possible to insert a breakpoint that will stop the program
3423 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3424 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3427 When called without any arguments, @code{break} sets a breakpoint at
3428 the next instruction to be executed in the selected stack frame
3429 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3430 innermost, this makes your program stop as soon as control
3431 returns to that frame. This is similar to the effect of a
3432 @code{finish} command in the frame inside the selected frame---except
3433 that @code{finish} does not leave an active breakpoint. If you use
3434 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3435 the next time it reaches the current location; this may be useful
3438 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3439 least one instruction has been executed. If it did not do this, you
3440 would be unable to proceed past a breakpoint without first disabling the
3441 breakpoint. This rule applies whether or not the breakpoint already
3442 existed when your program stopped.
3444 @item break @dots{} if @var{cond}
3445 Set a breakpoint with condition @var{cond}; evaluate the expression
3446 @var{cond} each time the breakpoint is reached, and stop only if the
3447 value is nonzero---that is, if @var{cond} evaluates as true.
3448 @samp{@dots{}} stands for one of the possible arguments described
3449 above (or no argument) specifying where to break. @xref{Conditions,
3450 ,Break Conditions}, for more information on breakpoint conditions.
3453 @item tbreak @var{args}
3454 Set a breakpoint enabled only for one stop. @var{args} are the
3455 same as for the @code{break} command, and the breakpoint is set in the same
3456 way, but the breakpoint is automatically deleted after the first time your
3457 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3460 @cindex hardware breakpoints
3461 @item hbreak @var{args}
3462 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3463 @code{break} command and the breakpoint is set in the same way, but the
3464 breakpoint requires hardware support and some target hardware may not
3465 have this support. The main purpose of this is EPROM/ROM code
3466 debugging, so you can set a breakpoint at an instruction without
3467 changing the instruction. This can be used with the new trap-generation
3468 provided by SPARClite DSU and most x86-based targets. These targets
3469 will generate traps when a program accesses some data or instruction
3470 address that is assigned to the debug registers. However the hardware
3471 breakpoint registers can take a limited number of breakpoints. For
3472 example, on the DSU, only two data breakpoints can be set at a time, and
3473 @value{GDBN} will reject this command if more than two are used. Delete
3474 or disable unused hardware breakpoints before setting new ones
3475 (@pxref{Disabling, ,Disabling Breakpoints}).
3476 @xref{Conditions, ,Break Conditions}.
3477 For remote targets, you can restrict the number of hardware
3478 breakpoints @value{GDBN} will use, see @ref{set remote
3479 hardware-breakpoint-limit}.
3482 @item thbreak @var{args}
3483 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3484 are the same as for the @code{hbreak} command and the breakpoint is set in
3485 the same way. However, like the @code{tbreak} command,
3486 the breakpoint is automatically deleted after the
3487 first time your program stops there. Also, like the @code{hbreak}
3488 command, the breakpoint requires hardware support and some target hardware
3489 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3490 See also @ref{Conditions, ,Break Conditions}.
3493 @cindex regular expression
3494 @cindex breakpoints at functions matching a regexp
3495 @cindex set breakpoints in many functions
3496 @item rbreak @var{regex}
3497 Set breakpoints on all functions matching the regular expression
3498 @var{regex}. This command sets an unconditional breakpoint on all
3499 matches, printing a list of all breakpoints it set. Once these
3500 breakpoints are set, they are treated just like the breakpoints set with
3501 the @code{break} command. You can delete them, disable them, or make
3502 them conditional the same way as any other breakpoint.
3504 The syntax of the regular expression is the standard one used with tools
3505 like @file{grep}. Note that this is different from the syntax used by
3506 shells, so for instance @code{foo*} matches all functions that include
3507 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3508 @code{.*} leading and trailing the regular expression you supply, so to
3509 match only functions that begin with @code{foo}, use @code{^foo}.
3511 @cindex non-member C@t{++} functions, set breakpoint in
3512 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3513 breakpoints on overloaded functions that are not members of any special
3516 @cindex set breakpoints on all functions
3517 The @code{rbreak} command can be used to set breakpoints in
3518 @strong{all} the functions in a program, like this:
3521 (@value{GDBP}) rbreak .
3524 @item rbreak @var{file}:@var{regex}
3525 If @code{rbreak} is called with a filename qualification, it limits
3526 the search for functions matching the given regular expression to the
3527 specified @var{file}. This can be used, for example, to set breakpoints on
3528 every function in a given file:
3531 (@value{GDBP}) rbreak file.c:.
3534 The colon separating the filename qualifier from the regex may
3535 optionally be surrounded by spaces.
3537 @kindex info breakpoints
3538 @cindex @code{$_} and @code{info breakpoints}
3539 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3540 @itemx info break @r{[}@var{n}@dots{}@r{]}
3541 Print a table of all breakpoints, watchpoints, and catchpoints set and
3542 not deleted. Optional argument @var{n} means print information only
3543 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3544 For each breakpoint, following columns are printed:
3547 @item Breakpoint Numbers
3549 Breakpoint, watchpoint, or catchpoint.
3551 Whether the breakpoint is marked to be disabled or deleted when hit.
3552 @item Enabled or Disabled
3553 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3554 that are not enabled.
3556 Where the breakpoint is in your program, as a memory address. For a
3557 pending breakpoint whose address is not yet known, this field will
3558 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3559 library that has the symbol or line referred by breakpoint is loaded.
3560 See below for details. A breakpoint with several locations will
3561 have @samp{<MULTIPLE>} in this field---see below for details.
3563 Where the breakpoint is in the source for your program, as a file and
3564 line number. For a pending breakpoint, the original string passed to
3565 the breakpoint command will be listed as it cannot be resolved until
3566 the appropriate shared library is loaded in the future.
3570 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3571 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3572 @value{GDBN} on the host's side. If it is ``target'', then the condition
3573 is evaluated by the target. The @code{info break} command shows
3574 the condition on the line following the affected breakpoint, together with
3575 its condition evaluation mode in between parentheses.
3577 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3578 allowed to have a condition specified for it. The condition is not parsed for
3579 validity until a shared library is loaded that allows the pending
3580 breakpoint to resolve to a valid location.
3583 @code{info break} with a breakpoint
3584 number @var{n} as argument lists only that breakpoint. The
3585 convenience variable @code{$_} and the default examining-address for
3586 the @code{x} command are set to the address of the last breakpoint
3587 listed (@pxref{Memory, ,Examining Memory}).
3590 @code{info break} displays a count of the number of times the breakpoint
3591 has been hit. This is especially useful in conjunction with the
3592 @code{ignore} command. You can ignore a large number of breakpoint
3593 hits, look at the breakpoint info to see how many times the breakpoint
3594 was hit, and then run again, ignoring one less than that number. This
3595 will get you quickly to the last hit of that breakpoint.
3598 For a breakpoints with an enable count (xref) greater than 1,
3599 @code{info break} also displays that count.
3603 @value{GDBN} allows you to set any number of breakpoints at the same place in
3604 your program. There is nothing silly or meaningless about this. When
3605 the breakpoints are conditional, this is even useful
3606 (@pxref{Conditions, ,Break Conditions}).
3608 @cindex multiple locations, breakpoints
3609 @cindex breakpoints, multiple locations
3610 It is possible that a breakpoint corresponds to several locations
3611 in your program. Examples of this situation are:
3615 Multiple functions in the program may have the same name.
3618 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3619 instances of the function body, used in different cases.
3622 For a C@t{++} template function, a given line in the function can
3623 correspond to any number of instantiations.
3626 For an inlined function, a given source line can correspond to
3627 several places where that function is inlined.
3630 In all those cases, @value{GDBN} will insert a breakpoint at all
3631 the relevant locations.
3633 A breakpoint with multiple locations is displayed in the breakpoint
3634 table using several rows---one header row, followed by one row for
3635 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3636 address column. The rows for individual locations contain the actual
3637 addresses for locations, and show the functions to which those
3638 locations belong. The number column for a location is of the form
3639 @var{breakpoint-number}.@var{location-number}.
3644 Num Type Disp Enb Address What
3645 1 breakpoint keep y <MULTIPLE>
3647 breakpoint already hit 1 time
3648 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3649 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3652 Each location can be individually enabled or disabled by passing
3653 @var{breakpoint-number}.@var{location-number} as argument to the
3654 @code{enable} and @code{disable} commands. Note that you cannot
3655 delete the individual locations from the list, you can only delete the
3656 entire list of locations that belong to their parent breakpoint (with
3657 the @kbd{delete @var{num}} command, where @var{num} is the number of
3658 the parent breakpoint, 1 in the above example). Disabling or enabling
3659 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3660 that belong to that breakpoint.
3662 @cindex pending breakpoints
3663 It's quite common to have a breakpoint inside a shared library.
3664 Shared libraries can be loaded and unloaded explicitly,
3665 and possibly repeatedly, as the program is executed. To support
3666 this use case, @value{GDBN} updates breakpoint locations whenever
3667 any shared library is loaded or unloaded. Typically, you would
3668 set a breakpoint in a shared library at the beginning of your
3669 debugging session, when the library is not loaded, and when the
3670 symbols from the library are not available. When you try to set
3671 breakpoint, @value{GDBN} will ask you if you want to set
3672 a so called @dfn{pending breakpoint}---breakpoint whose address
3673 is not yet resolved.
3675 After the program is run, whenever a new shared library is loaded,
3676 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3677 shared library contains the symbol or line referred to by some
3678 pending breakpoint, that breakpoint is resolved and becomes an
3679 ordinary breakpoint. When a library is unloaded, all breakpoints
3680 that refer to its symbols or source lines become pending again.
3682 This logic works for breakpoints with multiple locations, too. For
3683 example, if you have a breakpoint in a C@t{++} template function, and
3684 a newly loaded shared library has an instantiation of that template,
3685 a new location is added to the list of locations for the breakpoint.
3687 Except for having unresolved address, pending breakpoints do not
3688 differ from regular breakpoints. You can set conditions or commands,
3689 enable and disable them and perform other breakpoint operations.
3691 @value{GDBN} provides some additional commands for controlling what
3692 happens when the @samp{break} command cannot resolve breakpoint
3693 address specification to an address:
3695 @kindex set breakpoint pending
3696 @kindex show breakpoint pending
3698 @item set breakpoint pending auto
3699 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3700 location, it queries you whether a pending breakpoint should be created.
3702 @item set breakpoint pending on
3703 This indicates that an unrecognized breakpoint location should automatically
3704 result in a pending breakpoint being created.
3706 @item set breakpoint pending off
3707 This indicates that pending breakpoints are not to be created. Any
3708 unrecognized breakpoint location results in an error. This setting does
3709 not affect any pending breakpoints previously created.
3711 @item show breakpoint pending
3712 Show the current behavior setting for creating pending breakpoints.
3715 The settings above only affect the @code{break} command and its
3716 variants. Once breakpoint is set, it will be automatically updated
3717 as shared libraries are loaded and unloaded.
3719 @cindex automatic hardware breakpoints
3720 For some targets, @value{GDBN} can automatically decide if hardware or
3721 software breakpoints should be used, depending on whether the
3722 breakpoint address is read-only or read-write. This applies to
3723 breakpoints set with the @code{break} command as well as to internal
3724 breakpoints set by commands like @code{next} and @code{finish}. For
3725 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3728 You can control this automatic behaviour with the following commands::
3730 @kindex set breakpoint auto-hw
3731 @kindex show breakpoint auto-hw
3733 @item set breakpoint auto-hw on
3734 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3735 will try to use the target memory map to decide if software or hardware
3736 breakpoint must be used.
3738 @item set breakpoint auto-hw off
3739 This indicates @value{GDBN} should not automatically select breakpoint
3740 type. If the target provides a memory map, @value{GDBN} will warn when
3741 trying to set software breakpoint at a read-only address.
3744 @value{GDBN} normally implements breakpoints by replacing the program code
3745 at the breakpoint address with a special instruction, which, when
3746 executed, given control to the debugger. By default, the program
3747 code is so modified only when the program is resumed. As soon as
3748 the program stops, @value{GDBN} restores the original instructions. This
3749 behaviour guards against leaving breakpoints inserted in the
3750 target should gdb abrubptly disconnect. However, with slow remote
3751 targets, inserting and removing breakpoint can reduce the performance.
3752 This behavior can be controlled with the following commands::
3754 @kindex set breakpoint always-inserted
3755 @kindex show breakpoint always-inserted
3757 @item set breakpoint always-inserted off
3758 All breakpoints, including newly added by the user, are inserted in
3759 the target only when the target is resumed. All breakpoints are
3760 removed from the target when it stops.
3762 @item set breakpoint always-inserted on
3763 Causes all breakpoints to be inserted in the target at all times. If
3764 the user adds a new breakpoint, or changes an existing breakpoint, the
3765 breakpoints in the target are updated immediately. A breakpoint is
3766 removed from the target only when breakpoint itself is removed.
3768 @cindex non-stop mode, and @code{breakpoint always-inserted}
3769 @item set breakpoint always-inserted auto
3770 This is the default mode. If @value{GDBN} is controlling the inferior
3771 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3772 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3773 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3774 @code{breakpoint always-inserted} mode is off.
3777 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3778 when a breakpoint breaks. If the condition is true, then the process being
3779 debugged stops, otherwise the process is resumed.
3781 If the target supports evaluating conditions on its end, @value{GDBN} may
3782 download the breakpoint, together with its conditions, to it.
3784 This feature can be controlled via the following commands:
3786 @kindex set breakpoint condition-evaluation
3787 @kindex show breakpoint condition-evaluation
3789 @item set breakpoint condition-evaluation host
3790 This option commands @value{GDBN} to evaluate the breakpoint
3791 conditions on the host's side. Unconditional breakpoints are sent to
3792 the target which in turn receives the triggers and reports them back to GDB
3793 for condition evaluation. This is the standard evaluation mode.
3795 @item set breakpoint condition-evaluation target
3796 This option commands @value{GDBN} to download breakpoint conditions
3797 to the target at the moment of their insertion. The target
3798 is responsible for evaluating the conditional expression and reporting
3799 breakpoint stop events back to @value{GDBN} whenever the condition
3800 is true. Due to limitations of target-side evaluation, some conditions
3801 cannot be evaluated there, e.g., conditions that depend on local data
3802 that is only known to the host. Examples include
3803 conditional expressions involving convenience variables, complex types
3804 that cannot be handled by the agent expression parser and expressions
3805 that are too long to be sent over to the target, specially when the
3806 target is a remote system. In these cases, the conditions will be
3807 evaluated by @value{GDBN}.
3809 @item set breakpoint condition-evaluation auto
3810 This is the default mode. If the target supports evaluating breakpoint
3811 conditions on its end, @value{GDBN} will download breakpoint conditions to
3812 the target (limitations mentioned previously apply). If the target does
3813 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3814 to evaluating all these conditions on the host's side.
3818 @cindex negative breakpoint numbers
3819 @cindex internal @value{GDBN} breakpoints
3820 @value{GDBN} itself sometimes sets breakpoints in your program for
3821 special purposes, such as proper handling of @code{longjmp} (in C
3822 programs). These internal breakpoints are assigned negative numbers,
3823 starting with @code{-1}; @samp{info breakpoints} does not display them.
3824 You can see these breakpoints with the @value{GDBN} maintenance command
3825 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3828 @node Set Watchpoints
3829 @subsection Setting Watchpoints
3831 @cindex setting watchpoints
3832 You can use a watchpoint to stop execution whenever the value of an
3833 expression changes, without having to predict a particular place where
3834 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3835 The expression may be as simple as the value of a single variable, or
3836 as complex as many variables combined by operators. Examples include:
3840 A reference to the value of a single variable.
3843 An address cast to an appropriate data type. For example,
3844 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3845 address (assuming an @code{int} occupies 4 bytes).
3848 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3849 expression can use any operators valid in the program's native
3850 language (@pxref{Languages}).
3853 You can set a watchpoint on an expression even if the expression can
3854 not be evaluated yet. For instance, you can set a watchpoint on
3855 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3856 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3857 the expression produces a valid value. If the expression becomes
3858 valid in some other way than changing a variable (e.g.@: if the memory
3859 pointed to by @samp{*global_ptr} becomes readable as the result of a
3860 @code{malloc} call), @value{GDBN} may not stop until the next time
3861 the expression changes.
3863 @cindex software watchpoints
3864 @cindex hardware watchpoints
3865 Depending on your system, watchpoints may be implemented in software or
3866 hardware. @value{GDBN} does software watchpointing by single-stepping your
3867 program and testing the variable's value each time, which is hundreds of
3868 times slower than normal execution. (But this may still be worth it, to
3869 catch errors where you have no clue what part of your program is the
3872 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3873 x86-based targets, @value{GDBN} includes support for hardware
3874 watchpoints, which do not slow down the running of your program.
3878 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3879 Set a watchpoint for an expression. @value{GDBN} will break when the
3880 expression @var{expr} is written into by the program and its value
3881 changes. The simplest (and the most popular) use of this command is
3882 to watch the value of a single variable:
3885 (@value{GDBP}) watch foo
3888 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3889 argument, @value{GDBN} breaks only when the thread identified by
3890 @var{threadnum} changes the value of @var{expr}. If any other threads
3891 change the value of @var{expr}, @value{GDBN} will not break. Note
3892 that watchpoints restricted to a single thread in this way only work
3893 with Hardware Watchpoints.
3895 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3896 (see below). The @code{-location} argument tells @value{GDBN} to
3897 instead watch the memory referred to by @var{expr}. In this case,
3898 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3899 and watch the memory at that address. The type of the result is used
3900 to determine the size of the watched memory. If the expression's
3901 result does not have an address, then @value{GDBN} will print an
3904 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3905 of masked watchpoints, if the current architecture supports this
3906 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3907 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3908 to an address to watch. The mask specifies that some bits of an address
3909 (the bits which are reset in the mask) should be ignored when matching
3910 the address accessed by the inferior against the watchpoint address.
3911 Thus, a masked watchpoint watches many addresses simultaneously---those
3912 addresses whose unmasked bits are identical to the unmasked bits in the
3913 watchpoint address. The @code{mask} argument implies @code{-location}.
3917 (@value{GDBP}) watch foo mask 0xffff00ff
3918 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3922 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3923 Set a watchpoint that will break when the value of @var{expr} is read
3927 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3928 Set a watchpoint that will break when @var{expr} is either read from
3929 or written into by the program.
3931 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3932 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3933 This command prints a list of watchpoints, using the same format as
3934 @code{info break} (@pxref{Set Breaks}).
3937 If you watch for a change in a numerically entered address you need to
3938 dereference it, as the address itself is just a constant number which will
3939 never change. @value{GDBN} refuses to create a watchpoint that watches
3940 a never-changing value:
3943 (@value{GDBP}) watch 0x600850
3944 Cannot watch constant value 0x600850.
3945 (@value{GDBP}) watch *(int *) 0x600850
3946 Watchpoint 1: *(int *) 6293584
3949 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3950 watchpoints execute very quickly, and the debugger reports a change in
3951 value at the exact instruction where the change occurs. If @value{GDBN}
3952 cannot set a hardware watchpoint, it sets a software watchpoint, which
3953 executes more slowly and reports the change in value at the next
3954 @emph{statement}, not the instruction, after the change occurs.
3956 @cindex use only software watchpoints
3957 You can force @value{GDBN} to use only software watchpoints with the
3958 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3959 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3960 the underlying system supports them. (Note that hardware-assisted
3961 watchpoints that were set @emph{before} setting
3962 @code{can-use-hw-watchpoints} to zero will still use the hardware
3963 mechanism of watching expression values.)
3966 @item set can-use-hw-watchpoints
3967 @kindex set can-use-hw-watchpoints
3968 Set whether or not to use hardware watchpoints.
3970 @item show can-use-hw-watchpoints
3971 @kindex show can-use-hw-watchpoints
3972 Show the current mode of using hardware watchpoints.
3975 For remote targets, you can restrict the number of hardware
3976 watchpoints @value{GDBN} will use, see @ref{set remote
3977 hardware-breakpoint-limit}.
3979 When you issue the @code{watch} command, @value{GDBN} reports
3982 Hardware watchpoint @var{num}: @var{expr}
3986 if it was able to set a hardware watchpoint.
3988 Currently, the @code{awatch} and @code{rwatch} commands can only set
3989 hardware watchpoints, because accesses to data that don't change the
3990 value of the watched expression cannot be detected without examining
3991 every instruction as it is being executed, and @value{GDBN} does not do
3992 that currently. If @value{GDBN} finds that it is unable to set a
3993 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3994 will print a message like this:
3997 Expression cannot be implemented with read/access watchpoint.
4000 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4001 data type of the watched expression is wider than what a hardware
4002 watchpoint on the target machine can handle. For example, some systems
4003 can only watch regions that are up to 4 bytes wide; on such systems you
4004 cannot set hardware watchpoints for an expression that yields a
4005 double-precision floating-point number (which is typically 8 bytes
4006 wide). As a work-around, it might be possible to break the large region
4007 into a series of smaller ones and watch them with separate watchpoints.
4009 If you set too many hardware watchpoints, @value{GDBN} might be unable
4010 to insert all of them when you resume the execution of your program.
4011 Since the precise number of active watchpoints is unknown until such
4012 time as the program is about to be resumed, @value{GDBN} might not be
4013 able to warn you about this when you set the watchpoints, and the
4014 warning will be printed only when the program is resumed:
4017 Hardware watchpoint @var{num}: Could not insert watchpoint
4021 If this happens, delete or disable some of the watchpoints.
4023 Watching complex expressions that reference many variables can also
4024 exhaust the resources available for hardware-assisted watchpoints.
4025 That's because @value{GDBN} needs to watch every variable in the
4026 expression with separately allocated resources.
4028 If you call a function interactively using @code{print} or @code{call},
4029 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4030 kind of breakpoint or the call completes.
4032 @value{GDBN} automatically deletes watchpoints that watch local
4033 (automatic) variables, or expressions that involve such variables, when
4034 they go out of scope, that is, when the execution leaves the block in
4035 which these variables were defined. In particular, when the program
4036 being debugged terminates, @emph{all} local variables go out of scope,
4037 and so only watchpoints that watch global variables remain set. If you
4038 rerun the program, you will need to set all such watchpoints again. One
4039 way of doing that would be to set a code breakpoint at the entry to the
4040 @code{main} function and when it breaks, set all the watchpoints.
4042 @cindex watchpoints and threads
4043 @cindex threads and watchpoints
4044 In multi-threaded programs, watchpoints will detect changes to the
4045 watched expression from every thread.
4048 @emph{Warning:} In multi-threaded programs, software watchpoints
4049 have only limited usefulness. If @value{GDBN} creates a software
4050 watchpoint, it can only watch the value of an expression @emph{in a
4051 single thread}. If you are confident that the expression can only
4052 change due to the current thread's activity (and if you are also
4053 confident that no other thread can become current), then you can use
4054 software watchpoints as usual. However, @value{GDBN} may not notice
4055 when a non-current thread's activity changes the expression. (Hardware
4056 watchpoints, in contrast, watch an expression in all threads.)
4059 @xref{set remote hardware-watchpoint-limit}.
4061 @node Set Catchpoints
4062 @subsection Setting Catchpoints
4063 @cindex catchpoints, setting
4064 @cindex exception handlers
4065 @cindex event handling
4067 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4068 kinds of program events, such as C@t{++} exceptions or the loading of a
4069 shared library. Use the @code{catch} command to set a catchpoint.
4073 @item catch @var{event}
4074 Stop when @var{event} occurs. @var{event} can be any of the following:
4077 @cindex stop on C@t{++} exceptions
4078 The throwing of a C@t{++} exception.
4081 The catching of a C@t{++} exception.
4084 @cindex Ada exception catching
4085 @cindex catch Ada exceptions
4086 An Ada exception being raised. If an exception name is specified
4087 at the end of the command (eg @code{catch exception Program_Error}),
4088 the debugger will stop only when this specific exception is raised.
4089 Otherwise, the debugger stops execution when any Ada exception is raised.
4091 When inserting an exception catchpoint on a user-defined exception whose
4092 name is identical to one of the exceptions defined by the language, the
4093 fully qualified name must be used as the exception name. Otherwise,
4094 @value{GDBN} will assume that it should stop on the pre-defined exception
4095 rather than the user-defined one. For instance, assuming an exception
4096 called @code{Constraint_Error} is defined in package @code{Pck}, then
4097 the command to use to catch such exceptions is @kbd{catch exception
4098 Pck.Constraint_Error}.
4100 @item exception unhandled
4101 An exception that was raised but is not handled by the program.
4104 A failed Ada assertion.
4107 @cindex break on fork/exec
4108 A call to @code{exec}. This is currently only available for HP-UX
4112 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4113 @cindex break on a system call.
4114 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4115 syscall is a mechanism for application programs to request a service
4116 from the operating system (OS) or one of the OS system services.
4117 @value{GDBN} can catch some or all of the syscalls issued by the
4118 debuggee, and show the related information for each syscall. If no
4119 argument is specified, calls to and returns from all system calls
4122 @var{name} can be any system call name that is valid for the
4123 underlying OS. Just what syscalls are valid depends on the OS. On
4124 GNU and Unix systems, you can find the full list of valid syscall
4125 names on @file{/usr/include/asm/unistd.h}.
4127 @c For MS-Windows, the syscall names and the corresponding numbers
4128 @c can be found, e.g., on this URL:
4129 @c http://www.metasploit.com/users/opcode/syscalls.html
4130 @c but we don't support Windows syscalls yet.
4132 Normally, @value{GDBN} knows in advance which syscalls are valid for
4133 each OS, so you can use the @value{GDBN} command-line completion
4134 facilities (@pxref{Completion,, command completion}) to list the
4137 You may also specify the system call numerically. A syscall's
4138 number is the value passed to the OS's syscall dispatcher to
4139 identify the requested service. When you specify the syscall by its
4140 name, @value{GDBN} uses its database of syscalls to convert the name
4141 into the corresponding numeric code, but using the number directly
4142 may be useful if @value{GDBN}'s database does not have the complete
4143 list of syscalls on your system (e.g., because @value{GDBN} lags
4144 behind the OS upgrades).
4146 The example below illustrates how this command works if you don't provide
4150 (@value{GDBP}) catch syscall
4151 Catchpoint 1 (syscall)
4153 Starting program: /tmp/catch-syscall
4155 Catchpoint 1 (call to syscall 'close'), \
4156 0xffffe424 in __kernel_vsyscall ()
4160 Catchpoint 1 (returned from syscall 'close'), \
4161 0xffffe424 in __kernel_vsyscall ()
4165 Here is an example of catching a system call by name:
4168 (@value{GDBP}) catch syscall chroot
4169 Catchpoint 1 (syscall 'chroot' [61])
4171 Starting program: /tmp/catch-syscall
4173 Catchpoint 1 (call to syscall 'chroot'), \
4174 0xffffe424 in __kernel_vsyscall ()
4178 Catchpoint 1 (returned from syscall 'chroot'), \
4179 0xffffe424 in __kernel_vsyscall ()
4183 An example of specifying a system call numerically. In the case
4184 below, the syscall number has a corresponding entry in the XML
4185 file, so @value{GDBN} finds its name and prints it:
4188 (@value{GDBP}) catch syscall 252
4189 Catchpoint 1 (syscall(s) 'exit_group')
4191 Starting program: /tmp/catch-syscall
4193 Catchpoint 1 (call to syscall 'exit_group'), \
4194 0xffffe424 in __kernel_vsyscall ()
4198 Program exited normally.
4202 However, there can be situations when there is no corresponding name
4203 in XML file for that syscall number. In this case, @value{GDBN} prints
4204 a warning message saying that it was not able to find the syscall name,
4205 but the catchpoint will be set anyway. See the example below:
4208 (@value{GDBP}) catch syscall 764
4209 warning: The number '764' does not represent a known syscall.
4210 Catchpoint 2 (syscall 764)
4214 If you configure @value{GDBN} using the @samp{--without-expat} option,
4215 it will not be able to display syscall names. Also, if your
4216 architecture does not have an XML file describing its system calls,
4217 you will not be able to see the syscall names. It is important to
4218 notice that these two features are used for accessing the syscall
4219 name database. In either case, you will see a warning like this:
4222 (@value{GDBP}) catch syscall
4223 warning: Could not open "syscalls/i386-linux.xml"
4224 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4225 GDB will not be able to display syscall names.
4226 Catchpoint 1 (syscall)
4230 Of course, the file name will change depending on your architecture and system.
4232 Still using the example above, you can also try to catch a syscall by its
4233 number. In this case, you would see something like:
4236 (@value{GDBP}) catch syscall 252
4237 Catchpoint 1 (syscall(s) 252)
4240 Again, in this case @value{GDBN} would not be able to display syscall's names.
4243 A call to @code{fork}. This is currently only available for HP-UX
4247 A call to @code{vfork}. This is currently only available for HP-UX
4250 @item load @r{[}regexp@r{]}
4251 @itemx unload @r{[}regexp@r{]}
4252 The loading or unloading of a shared library. If @var{regexp} is
4253 given, then the catchpoint will stop only if the regular expression
4254 matches one of the affected libraries.
4256 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4257 The delivery of a signal.
4259 With no arguments, this catchpoint will catch any signal that is not
4260 used internally by @value{GDBN}, specifically, all signals except
4261 @samp{SIGTRAP} and @samp{SIGINT}.
4263 With the argument @samp{all}, all signals, including those used by
4264 @value{GDBN}, will be caught. This argument cannot be used with other
4267 Otherwise, the arguments are a list of signal names as given to
4268 @code{handle} (@pxref{Signals}). Only signals specified in this list
4271 One reason that @code{catch signal} can be more useful than
4272 @code{handle} is that you can attach commands and conditions to the
4275 When a signal is caught by a catchpoint, the signal's @code{stop} and
4276 @code{print} settings, as specified by @code{handle}, are ignored.
4277 However, whether the signal is still delivered to the inferior depends
4278 on the @code{pass} setting; this can be changed in the catchpoint's
4283 @item tcatch @var{event}
4284 Set a catchpoint that is enabled only for one stop. The catchpoint is
4285 automatically deleted after the first time the event is caught.
4289 Use the @code{info break} command to list the current catchpoints.
4291 There are currently some limitations to C@t{++} exception handling
4292 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4296 If you call a function interactively, @value{GDBN} normally returns
4297 control to you when the function has finished executing. If the call
4298 raises an exception, however, the call may bypass the mechanism that
4299 returns control to you and cause your program either to abort or to
4300 simply continue running until it hits a breakpoint, catches a signal
4301 that @value{GDBN} is listening for, or exits. This is the case even if
4302 you set a catchpoint for the exception; catchpoints on exceptions are
4303 disabled within interactive calls.
4306 You cannot raise an exception interactively.
4309 You cannot install an exception handler interactively.
4312 @cindex raise exceptions
4313 Sometimes @code{catch} is not the best way to debug exception handling:
4314 if you need to know exactly where an exception is raised, it is better to
4315 stop @emph{before} the exception handler is called, since that way you
4316 can see the stack before any unwinding takes place. If you set a
4317 breakpoint in an exception handler instead, it may not be easy to find
4318 out where the exception was raised.
4320 To stop just before an exception handler is called, you need some
4321 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4322 raised by calling a library function named @code{__raise_exception}
4323 which has the following ANSI C interface:
4326 /* @var{addr} is where the exception identifier is stored.
4327 @var{id} is the exception identifier. */
4328 void __raise_exception (void **addr, void *id);
4332 To make the debugger catch all exceptions before any stack
4333 unwinding takes place, set a breakpoint on @code{__raise_exception}
4334 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4336 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4337 that depends on the value of @var{id}, you can stop your program when
4338 a specific exception is raised. You can use multiple conditional
4339 breakpoints to stop your program when any of a number of exceptions are
4344 @subsection Deleting Breakpoints
4346 @cindex clearing breakpoints, watchpoints, catchpoints
4347 @cindex deleting breakpoints, watchpoints, catchpoints
4348 It is often necessary to eliminate a breakpoint, watchpoint, or
4349 catchpoint once it has done its job and you no longer want your program
4350 to stop there. This is called @dfn{deleting} the breakpoint. A
4351 breakpoint that has been deleted no longer exists; it is forgotten.
4353 With the @code{clear} command you can delete breakpoints according to
4354 where they are in your program. With the @code{delete} command you can
4355 delete individual breakpoints, watchpoints, or catchpoints by specifying
4356 their breakpoint numbers.
4358 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4359 automatically ignores breakpoints on the first instruction to be executed
4360 when you continue execution without changing the execution address.
4365 Delete any breakpoints at the next instruction to be executed in the
4366 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4367 the innermost frame is selected, this is a good way to delete a
4368 breakpoint where your program just stopped.
4370 @item clear @var{location}
4371 Delete any breakpoints set at the specified @var{location}.
4372 @xref{Specify Location}, for the various forms of @var{location}; the
4373 most useful ones are listed below:
4376 @item clear @var{function}
4377 @itemx clear @var{filename}:@var{function}
4378 Delete any breakpoints set at entry to the named @var{function}.
4380 @item clear @var{linenum}
4381 @itemx clear @var{filename}:@var{linenum}
4382 Delete any breakpoints set at or within the code of the specified
4383 @var{linenum} of the specified @var{filename}.
4386 @cindex delete breakpoints
4388 @kindex d @r{(@code{delete})}
4389 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4390 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4391 ranges specified as arguments. If no argument is specified, delete all
4392 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4393 confirm off}). You can abbreviate this command as @code{d}.
4397 @subsection Disabling Breakpoints
4399 @cindex enable/disable a breakpoint
4400 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4401 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4402 it had been deleted, but remembers the information on the breakpoint so
4403 that you can @dfn{enable} it again later.
4405 You disable and enable breakpoints, watchpoints, and catchpoints with
4406 the @code{enable} and @code{disable} commands, optionally specifying
4407 one or more breakpoint numbers as arguments. Use @code{info break} to
4408 print a list of all breakpoints, watchpoints, and catchpoints if you
4409 do not know which numbers to use.
4411 Disabling and enabling a breakpoint that has multiple locations
4412 affects all of its locations.
4414 A breakpoint, watchpoint, or catchpoint can have any of several
4415 different states of enablement:
4419 Enabled. The breakpoint stops your program. A breakpoint set
4420 with the @code{break} command starts out in this state.
4422 Disabled. The breakpoint has no effect on your program.
4424 Enabled once. The breakpoint stops your program, but then becomes
4427 Enabled for a count. The breakpoint stops your program for the next
4428 N times, then becomes disabled.
4430 Enabled for deletion. The breakpoint stops your program, but
4431 immediately after it does so it is deleted permanently. A breakpoint
4432 set with the @code{tbreak} command starts out in this state.
4435 You can use the following commands to enable or disable breakpoints,
4436 watchpoints, and catchpoints:
4440 @kindex dis @r{(@code{disable})}
4441 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4442 Disable the specified breakpoints---or all breakpoints, if none are
4443 listed. A disabled breakpoint has no effect but is not forgotten. All
4444 options such as ignore-counts, conditions and commands are remembered in
4445 case the breakpoint is enabled again later. You may abbreviate
4446 @code{disable} as @code{dis}.
4449 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4450 Enable the specified breakpoints (or all defined breakpoints). They
4451 become effective once again in stopping your program.
4453 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4454 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4455 of these breakpoints immediately after stopping your program.
4457 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4458 Enable the specified breakpoints temporarily. @value{GDBN} records
4459 @var{count} with each of the specified breakpoints, and decrements a
4460 breakpoint's count when it is hit. When any count reaches 0,
4461 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4462 count (@pxref{Conditions, ,Break Conditions}), that will be
4463 decremented to 0 before @var{count} is affected.
4465 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4466 Enable the specified breakpoints to work once, then die. @value{GDBN}
4467 deletes any of these breakpoints as soon as your program stops there.
4468 Breakpoints set by the @code{tbreak} command start out in this state.
4471 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4472 @c confusing: tbreak is also initially enabled.
4473 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4474 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4475 subsequently, they become disabled or enabled only when you use one of
4476 the commands above. (The command @code{until} can set and delete a
4477 breakpoint of its own, but it does not change the state of your other
4478 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4482 @subsection Break Conditions
4483 @cindex conditional breakpoints
4484 @cindex breakpoint conditions
4486 @c FIXME what is scope of break condition expr? Context where wanted?
4487 @c in particular for a watchpoint?
4488 The simplest sort of breakpoint breaks every time your program reaches a
4489 specified place. You can also specify a @dfn{condition} for a
4490 breakpoint. A condition is just a Boolean expression in your
4491 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4492 a condition evaluates the expression each time your program reaches it,
4493 and your program stops only if the condition is @emph{true}.
4495 This is the converse of using assertions for program validation; in that
4496 situation, you want to stop when the assertion is violated---that is,
4497 when the condition is false. In C, if you want to test an assertion expressed
4498 by the condition @var{assert}, you should set the condition
4499 @samp{! @var{assert}} on the appropriate breakpoint.
4501 Conditions are also accepted for watchpoints; you may not need them,
4502 since a watchpoint is inspecting the value of an expression anyhow---but
4503 it might be simpler, say, to just set a watchpoint on a variable name,
4504 and specify a condition that tests whether the new value is an interesting
4507 Break conditions can have side effects, and may even call functions in
4508 your program. This can be useful, for example, to activate functions
4509 that log program progress, or to use your own print functions to
4510 format special data structures. The effects are completely predictable
4511 unless there is another enabled breakpoint at the same address. (In
4512 that case, @value{GDBN} might see the other breakpoint first and stop your
4513 program without checking the condition of this one.) Note that
4514 breakpoint commands are usually more convenient and flexible than break
4516 purpose of performing side effects when a breakpoint is reached
4517 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4519 Breakpoint conditions can also be evaluated on the target's side if
4520 the target supports it. Instead of evaluating the conditions locally,
4521 @value{GDBN} encodes the expression into an agent expression
4522 (@pxref{Agent Expressions}) suitable for execution on the target,
4523 independently of @value{GDBN}. Global variables become raw memory
4524 locations, locals become stack accesses, and so forth.
4526 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4527 when its condition evaluates to true. This mechanism may provide faster
4528 response times depending on the performance characteristics of the target
4529 since it does not need to keep @value{GDBN} informed about
4530 every breakpoint trigger, even those with false conditions.
4532 Break conditions can be specified when a breakpoint is set, by using
4533 @samp{if} in the arguments to the @code{break} command. @xref{Set
4534 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4535 with the @code{condition} command.
4537 You can also use the @code{if} keyword with the @code{watch} command.
4538 The @code{catch} command does not recognize the @code{if} keyword;
4539 @code{condition} is the only way to impose a further condition on a
4544 @item condition @var{bnum} @var{expression}
4545 Specify @var{expression} as the break condition for breakpoint,
4546 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4547 breakpoint @var{bnum} stops your program only if the value of
4548 @var{expression} is true (nonzero, in C). When you use
4549 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4550 syntactic correctness, and to determine whether symbols in it have
4551 referents in the context of your breakpoint. If @var{expression} uses
4552 symbols not referenced in the context of the breakpoint, @value{GDBN}
4553 prints an error message:
4556 No symbol "foo" in current context.
4561 not actually evaluate @var{expression} at the time the @code{condition}
4562 command (or a command that sets a breakpoint with a condition, like
4563 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4565 @item condition @var{bnum}
4566 Remove the condition from breakpoint number @var{bnum}. It becomes
4567 an ordinary unconditional breakpoint.
4570 @cindex ignore count (of breakpoint)
4571 A special case of a breakpoint condition is to stop only when the
4572 breakpoint has been reached a certain number of times. This is so
4573 useful that there is a special way to do it, using the @dfn{ignore
4574 count} of the breakpoint. Every breakpoint has an ignore count, which
4575 is an integer. Most of the time, the ignore count is zero, and
4576 therefore has no effect. But if your program reaches a breakpoint whose
4577 ignore count is positive, then instead of stopping, it just decrements
4578 the ignore count by one and continues. As a result, if the ignore count
4579 value is @var{n}, the breakpoint does not stop the next @var{n} times
4580 your program reaches it.
4584 @item ignore @var{bnum} @var{count}
4585 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4586 The next @var{count} times the breakpoint is reached, your program's
4587 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4590 To make the breakpoint stop the next time it is reached, specify
4593 When you use @code{continue} to resume execution of your program from a
4594 breakpoint, you can specify an ignore count directly as an argument to
4595 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4596 Stepping,,Continuing and Stepping}.
4598 If a breakpoint has a positive ignore count and a condition, the
4599 condition is not checked. Once the ignore count reaches zero,
4600 @value{GDBN} resumes checking the condition.
4602 You could achieve the effect of the ignore count with a condition such
4603 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4604 is decremented each time. @xref{Convenience Vars, ,Convenience
4608 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4611 @node Break Commands
4612 @subsection Breakpoint Command Lists
4614 @cindex breakpoint commands
4615 You can give any breakpoint (or watchpoint or catchpoint) a series of
4616 commands to execute when your program stops due to that breakpoint. For
4617 example, you might want to print the values of certain expressions, or
4618 enable other breakpoints.
4622 @kindex end@r{ (breakpoint commands)}
4623 @item commands @r{[}@var{range}@dots{}@r{]}
4624 @itemx @dots{} @var{command-list} @dots{}
4626 Specify a list of commands for the given breakpoints. The commands
4627 themselves appear on the following lines. Type a line containing just
4628 @code{end} to terminate the commands.
4630 To remove all commands from a breakpoint, type @code{commands} and
4631 follow it immediately with @code{end}; that is, give no commands.
4633 With no argument, @code{commands} refers to the last breakpoint,
4634 watchpoint, or catchpoint set (not to the breakpoint most recently
4635 encountered). If the most recent breakpoints were set with a single
4636 command, then the @code{commands} will apply to all the breakpoints
4637 set by that command. This applies to breakpoints set by
4638 @code{rbreak}, and also applies when a single @code{break} command
4639 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4643 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4644 disabled within a @var{command-list}.
4646 You can use breakpoint commands to start your program up again. Simply
4647 use the @code{continue} command, or @code{step}, or any other command
4648 that resumes execution.
4650 Any other commands in the command list, after a command that resumes
4651 execution, are ignored. This is because any time you resume execution
4652 (even with a simple @code{next} or @code{step}), you may encounter
4653 another breakpoint---which could have its own command list, leading to
4654 ambiguities about which list to execute.
4657 If the first command you specify in a command list is @code{silent}, the
4658 usual message about stopping at a breakpoint is not printed. This may
4659 be desirable for breakpoints that are to print a specific message and
4660 then continue. If none of the remaining commands print anything, you
4661 see no sign that the breakpoint was reached. @code{silent} is
4662 meaningful only at the beginning of a breakpoint command list.
4664 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4665 print precisely controlled output, and are often useful in silent
4666 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4668 For example, here is how you could use breakpoint commands to print the
4669 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4675 printf "x is %d\n",x
4680 One application for breakpoint commands is to compensate for one bug so
4681 you can test for another. Put a breakpoint just after the erroneous line
4682 of code, give it a condition to detect the case in which something
4683 erroneous has been done, and give it commands to assign correct values
4684 to any variables that need them. End with the @code{continue} command
4685 so that your program does not stop, and start with the @code{silent}
4686 command so that no output is produced. Here is an example:
4697 @node Dynamic Printf
4698 @subsection Dynamic Printf
4700 @cindex dynamic printf
4702 The dynamic printf command @code{dprintf} combines a breakpoint with
4703 formatted printing of your program's data to give you the effect of
4704 inserting @code{printf} calls into your program on-the-fly, without
4705 having to recompile it.
4707 In its most basic form, the output goes to the GDB console. However,
4708 you can set the variable @code{dprintf-style} for alternate handling.
4709 For instance, you can ask to format the output by calling your
4710 program's @code{printf} function. This has the advantage that the
4711 characters go to the program's output device, so they can recorded in
4712 redirects to files and so forth.
4714 If you are doing remote debugging with a stub or agent, you can also
4715 ask to have the printf handled by the remote agent. In addition to
4716 ensuring that the output goes to the remote program's device along
4717 with any other output the program might produce, you can also ask that
4718 the dprintf remain active even after disconnecting from the remote
4719 target. Using the stub/agent is also more efficient, as it can do
4720 everything without needing to communicate with @value{GDBN}.
4724 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4725 Whenever execution reaches @var{location}, print the values of one or
4726 more @var{expressions} under the control of the string @var{template}.
4727 To print several values, separate them with commas.
4729 @item set dprintf-style @var{style}
4730 Set the dprintf output to be handled in one of several different
4731 styles enumerated below. A change of style affects all existing
4732 dynamic printfs immediately. (If you need individual control over the
4733 print commands, simply define normal breakpoints with
4734 explicitly-supplied command lists.)
4737 @kindex dprintf-style gdb
4738 Handle the output using the @value{GDBN} @code{printf} command.
4741 @kindex dprintf-style call
4742 Handle the output by calling a function in your program (normally
4746 @kindex dprintf-style agent
4747 Have the remote debugging agent (such as @code{gdbserver}) handle
4748 the output itself. This style is only available for agents that
4749 support running commands on the target.
4751 @item set dprintf-function @var{function}
4752 Set the function to call if the dprintf style is @code{call}. By
4753 default its value is @code{printf}. You may set it to any expression.
4754 that @value{GDBN} can evaluate to a function, as per the @code{call}
4757 @item set dprintf-channel @var{channel}
4758 Set a ``channel'' for dprintf. If set to a non-empty value,
4759 @value{GDBN} will evaluate it as an expression and pass the result as
4760 a first argument to the @code{dprintf-function}, in the manner of
4761 @code{fprintf} and similar functions. Otherwise, the dprintf format
4762 string will be the first argument, in the manner of @code{printf}.
4764 As an example, if you wanted @code{dprintf} output to go to a logfile
4765 that is a standard I/O stream assigned to the variable @code{mylog},
4766 you could do the following:
4769 (gdb) set dprintf-style call
4770 (gdb) set dprintf-function fprintf
4771 (gdb) set dprintf-channel mylog
4772 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4773 Dprintf 1 at 0x123456: file main.c, line 25.
4775 1 dprintf keep y 0x00123456 in main at main.c:25
4776 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4781 Note that the @code{info break} displays the dynamic printf commands
4782 as normal breakpoint commands; you can thus easily see the effect of
4783 the variable settings.
4785 @item set disconnected-dprintf on
4786 @itemx set disconnected-dprintf off
4787 @kindex set disconnected-dprintf
4788 Choose whether @code{dprintf} commands should continue to run if
4789 @value{GDBN} has disconnected from the target. This only applies
4790 if the @code{dprintf-style} is @code{agent}.
4792 @item show disconnected-dprintf off
4793 @kindex show disconnected-dprintf
4794 Show the current choice for disconnected @code{dprintf}.
4798 @value{GDBN} does not check the validity of function and channel,
4799 relying on you to supply values that are meaningful for the contexts
4800 in which they are being used. For instance, the function and channel
4801 may be the values of local variables, but if that is the case, then
4802 all enabled dynamic prints must be at locations within the scope of
4803 those locals. If evaluation fails, @value{GDBN} will report an error.
4805 @node Save Breakpoints
4806 @subsection How to save breakpoints to a file
4808 To save breakpoint definitions to a file use the @w{@code{save
4809 breakpoints}} command.
4812 @kindex save breakpoints
4813 @cindex save breakpoints to a file for future sessions
4814 @item save breakpoints [@var{filename}]
4815 This command saves all current breakpoint definitions together with
4816 their commands and ignore counts, into a file @file{@var{filename}}
4817 suitable for use in a later debugging session. This includes all
4818 types of breakpoints (breakpoints, watchpoints, catchpoints,
4819 tracepoints). To read the saved breakpoint definitions, use the
4820 @code{source} command (@pxref{Command Files}). Note that watchpoints
4821 with expressions involving local variables may fail to be recreated
4822 because it may not be possible to access the context where the
4823 watchpoint is valid anymore. Because the saved breakpoint definitions
4824 are simply a sequence of @value{GDBN} commands that recreate the
4825 breakpoints, you can edit the file in your favorite editing program,
4826 and remove the breakpoint definitions you're not interested in, or
4827 that can no longer be recreated.
4830 @node Static Probe Points
4831 @subsection Static Probe Points
4833 @cindex static probe point, SystemTap
4834 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4835 for Statically Defined Tracing, and the probes are designed to have a tiny
4836 runtime code and data footprint, and no dynamic relocations. They are
4837 usable from assembly, C and C@t{++} languages. See
4838 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4839 for a good reference on how the @acronym{SDT} probes are implemented.
4841 Currently, @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4842 @acronym{SDT} probes are supported on ELF-compatible systems. See
4843 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4844 for more information on how to add @code{SystemTap} @acronym{SDT} probes
4845 in your applications.
4847 @cindex semaphores on static probe points
4848 Some probes have an associated semaphore variable; for instance, this
4849 happens automatically if you defined your probe using a DTrace-style
4850 @file{.d} file. If your probe has a semaphore, @value{GDBN} will
4851 automatically enable it when you specify a breakpoint using the
4852 @samp{-probe-stap} notation. But, if you put a breakpoint at a probe's
4853 location by some other method (e.g., @code{break file:line}), then
4854 @value{GDBN} will not automatically set the semaphore.
4856 You can examine the available static static probes using @code{info
4857 probes}, with optional arguments:
4861 @item info probes stap @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
4862 If given, @var{provider} is a regular expression used to match against provider
4863 names when selecting which probes to list. If omitted, probes by all
4864 probes from all providers are listed.
4866 If given, @var{name} is a regular expression to match against probe names
4867 when selecting which probes to list. If omitted, probe names are not
4868 considered when deciding whether to display them.
4870 If given, @var{objfile} is a regular expression used to select which
4871 object files (executable or shared libraries) to examine. If not
4872 given, all object files are considered.
4874 @item info probes all
4875 List the available static probes, from all types.
4878 @vindex $_probe_arg@r{, convenience variable}
4879 A probe may specify up to twelve arguments. These are available at the
4880 point at which the probe is defined---that is, when the current PC is
4881 at the probe's location. The arguments are available using the
4882 convenience variables (@pxref{Convenience Vars})
4883 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. Each probe argument is
4884 an integer of the appropriate size; types are not preserved. The
4885 convenience variable @code{$_probe_argc} holds the number of arguments
4886 at the current probe point.
4888 These variables are always available, but attempts to access them at
4889 any location other than a probe point will cause @value{GDBN} to give
4893 @c @ifclear BARETARGET
4894 @node Error in Breakpoints
4895 @subsection ``Cannot insert breakpoints''
4897 If you request too many active hardware-assisted breakpoints and
4898 watchpoints, you will see this error message:
4900 @c FIXME: the precise wording of this message may change; the relevant
4901 @c source change is not committed yet (Sep 3, 1999).
4903 Stopped; cannot insert breakpoints.
4904 You may have requested too many hardware breakpoints and watchpoints.
4908 This message is printed when you attempt to resume the program, since
4909 only then @value{GDBN} knows exactly how many hardware breakpoints and
4910 watchpoints it needs to insert.
4912 When this message is printed, you need to disable or remove some of the
4913 hardware-assisted breakpoints and watchpoints, and then continue.
4915 @node Breakpoint-related Warnings
4916 @subsection ``Breakpoint address adjusted...''
4917 @cindex breakpoint address adjusted
4919 Some processor architectures place constraints on the addresses at
4920 which breakpoints may be placed. For architectures thus constrained,
4921 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4922 with the constraints dictated by the architecture.
4924 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4925 a VLIW architecture in which a number of RISC-like instructions may be
4926 bundled together for parallel execution. The FR-V architecture
4927 constrains the location of a breakpoint instruction within such a
4928 bundle to the instruction with the lowest address. @value{GDBN}
4929 honors this constraint by adjusting a breakpoint's address to the
4930 first in the bundle.
4932 It is not uncommon for optimized code to have bundles which contain
4933 instructions from different source statements, thus it may happen that
4934 a breakpoint's address will be adjusted from one source statement to
4935 another. Since this adjustment may significantly alter @value{GDBN}'s
4936 breakpoint related behavior from what the user expects, a warning is
4937 printed when the breakpoint is first set and also when the breakpoint
4940 A warning like the one below is printed when setting a breakpoint
4941 that's been subject to address adjustment:
4944 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4947 Such warnings are printed both for user settable and @value{GDBN}'s
4948 internal breakpoints. If you see one of these warnings, you should
4949 verify that a breakpoint set at the adjusted address will have the
4950 desired affect. If not, the breakpoint in question may be removed and
4951 other breakpoints may be set which will have the desired behavior.
4952 E.g., it may be sufficient to place the breakpoint at a later
4953 instruction. A conditional breakpoint may also be useful in some
4954 cases to prevent the breakpoint from triggering too often.
4956 @value{GDBN} will also issue a warning when stopping at one of these
4957 adjusted breakpoints:
4960 warning: Breakpoint 1 address previously adjusted from 0x00010414
4964 When this warning is encountered, it may be too late to take remedial
4965 action except in cases where the breakpoint is hit earlier or more
4966 frequently than expected.
4968 @node Continuing and Stepping
4969 @section Continuing and Stepping
4973 @cindex resuming execution
4974 @dfn{Continuing} means resuming program execution until your program
4975 completes normally. In contrast, @dfn{stepping} means executing just
4976 one more ``step'' of your program, where ``step'' may mean either one
4977 line of source code, or one machine instruction (depending on what
4978 particular command you use). Either when continuing or when stepping,
4979 your program may stop even sooner, due to a breakpoint or a signal. (If
4980 it stops due to a signal, you may want to use @code{handle}, or use
4981 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4985 @kindex c @r{(@code{continue})}
4986 @kindex fg @r{(resume foreground execution)}
4987 @item continue @r{[}@var{ignore-count}@r{]}
4988 @itemx c @r{[}@var{ignore-count}@r{]}
4989 @itemx fg @r{[}@var{ignore-count}@r{]}
4990 Resume program execution, at the address where your program last stopped;
4991 any breakpoints set at that address are bypassed. The optional argument
4992 @var{ignore-count} allows you to specify a further number of times to
4993 ignore a breakpoint at this location; its effect is like that of
4994 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4996 The argument @var{ignore-count} is meaningful only when your program
4997 stopped due to a breakpoint. At other times, the argument to
4998 @code{continue} is ignored.
5000 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5001 debugged program is deemed to be the foreground program) are provided
5002 purely for convenience, and have exactly the same behavior as
5006 To resume execution at a different place, you can use @code{return}
5007 (@pxref{Returning, ,Returning from a Function}) to go back to the
5008 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5009 Different Address}) to go to an arbitrary location in your program.
5011 A typical technique for using stepping is to set a breakpoint
5012 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5013 beginning of the function or the section of your program where a problem
5014 is believed to lie, run your program until it stops at that breakpoint,
5015 and then step through the suspect area, examining the variables that are
5016 interesting, until you see the problem happen.
5020 @kindex s @r{(@code{step})}
5022 Continue running your program until control reaches a different source
5023 line, then stop it and return control to @value{GDBN}. This command is
5024 abbreviated @code{s}.
5027 @c "without debugging information" is imprecise; actually "without line
5028 @c numbers in the debugging information". (gcc -g1 has debugging info but
5029 @c not line numbers). But it seems complex to try to make that
5030 @c distinction here.
5031 @emph{Warning:} If you use the @code{step} command while control is
5032 within a function that was compiled without debugging information,
5033 execution proceeds until control reaches a function that does have
5034 debugging information. Likewise, it will not step into a function which
5035 is compiled without debugging information. To step through functions
5036 without debugging information, use the @code{stepi} command, described
5040 The @code{step} command only stops at the first instruction of a source
5041 line. This prevents the multiple stops that could otherwise occur in
5042 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5043 to stop if a function that has debugging information is called within
5044 the line. In other words, @code{step} @emph{steps inside} any functions
5045 called within the line.
5047 Also, the @code{step} command only enters a function if there is line
5048 number information for the function. Otherwise it acts like the
5049 @code{next} command. This avoids problems when using @code{cc -gl}
5050 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5051 was any debugging information about the routine.
5053 @item step @var{count}
5054 Continue running as in @code{step}, but do so @var{count} times. If a
5055 breakpoint is reached, or a signal not related to stepping occurs before
5056 @var{count} steps, stepping stops right away.
5059 @kindex n @r{(@code{next})}
5060 @item next @r{[}@var{count}@r{]}
5061 Continue to the next source line in the current (innermost) stack frame.
5062 This is similar to @code{step}, but function calls that appear within
5063 the line of code are executed without stopping. Execution stops when
5064 control reaches a different line of code at the original stack level
5065 that was executing when you gave the @code{next} command. This command
5066 is abbreviated @code{n}.
5068 An argument @var{count} is a repeat count, as for @code{step}.
5071 @c FIX ME!! Do we delete this, or is there a way it fits in with
5072 @c the following paragraph? --- Vctoria
5074 @c @code{next} within a function that lacks debugging information acts like
5075 @c @code{step}, but any function calls appearing within the code of the
5076 @c function are executed without stopping.
5078 The @code{next} command only stops at the first instruction of a
5079 source line. This prevents multiple stops that could otherwise occur in
5080 @code{switch} statements, @code{for} loops, etc.
5082 @kindex set step-mode
5084 @cindex functions without line info, and stepping
5085 @cindex stepping into functions with no line info
5086 @itemx set step-mode on
5087 The @code{set step-mode on} command causes the @code{step} command to
5088 stop at the first instruction of a function which contains no debug line
5089 information rather than stepping over it.
5091 This is useful in cases where you may be interested in inspecting the
5092 machine instructions of a function which has no symbolic info and do not
5093 want @value{GDBN} to automatically skip over this function.
5095 @item set step-mode off
5096 Causes the @code{step} command to step over any functions which contains no
5097 debug information. This is the default.
5099 @item show step-mode
5100 Show whether @value{GDBN} will stop in or step over functions without
5101 source line debug information.
5104 @kindex fin @r{(@code{finish})}
5106 Continue running until just after function in the selected stack frame
5107 returns. Print the returned value (if any). This command can be
5108 abbreviated as @code{fin}.
5110 Contrast this with the @code{return} command (@pxref{Returning,
5111 ,Returning from a Function}).
5114 @kindex u @r{(@code{until})}
5115 @cindex run until specified location
5118 Continue running until a source line past the current line, in the
5119 current stack frame, is reached. This command is used to avoid single
5120 stepping through a loop more than once. It is like the @code{next}
5121 command, except that when @code{until} encounters a jump, it
5122 automatically continues execution until the program counter is greater
5123 than the address of the jump.
5125 This means that when you reach the end of a loop after single stepping
5126 though it, @code{until} makes your program continue execution until it
5127 exits the loop. In contrast, a @code{next} command at the end of a loop
5128 simply steps back to the beginning of the loop, which forces you to step
5129 through the next iteration.
5131 @code{until} always stops your program if it attempts to exit the current
5134 @code{until} may produce somewhat counterintuitive results if the order
5135 of machine code does not match the order of the source lines. For
5136 example, in the following excerpt from a debugging session, the @code{f}
5137 (@code{frame}) command shows that execution is stopped at line
5138 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5142 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5144 (@value{GDBP}) until
5145 195 for ( ; argc > 0; NEXTARG) @{
5148 This happened because, for execution efficiency, the compiler had
5149 generated code for the loop closure test at the end, rather than the
5150 start, of the loop---even though the test in a C @code{for}-loop is
5151 written before the body of the loop. The @code{until} command appeared
5152 to step back to the beginning of the loop when it advanced to this
5153 expression; however, it has not really gone to an earlier
5154 statement---not in terms of the actual machine code.
5156 @code{until} with no argument works by means of single
5157 instruction stepping, and hence is slower than @code{until} with an
5160 @item until @var{location}
5161 @itemx u @var{location}
5162 Continue running your program until either the specified location is
5163 reached, or the current stack frame returns. @var{location} is any of
5164 the forms described in @ref{Specify Location}.
5165 This form of the command uses temporary breakpoints, and
5166 hence is quicker than @code{until} without an argument. The specified
5167 location is actually reached only if it is in the current frame. This
5168 implies that @code{until} can be used to skip over recursive function
5169 invocations. For instance in the code below, if the current location is
5170 line @code{96}, issuing @code{until 99} will execute the program up to
5171 line @code{99} in the same invocation of factorial, i.e., after the inner
5172 invocations have returned.
5175 94 int factorial (int value)
5177 96 if (value > 1) @{
5178 97 value *= factorial (value - 1);
5185 @kindex advance @var{location}
5186 @item advance @var{location}
5187 Continue running the program up to the given @var{location}. An argument is
5188 required, which should be of one of the forms described in
5189 @ref{Specify Location}.
5190 Execution will also stop upon exit from the current stack
5191 frame. This command is similar to @code{until}, but @code{advance} will
5192 not skip over recursive function calls, and the target location doesn't
5193 have to be in the same frame as the current one.
5197 @kindex si @r{(@code{stepi})}
5199 @itemx stepi @var{arg}
5201 Execute one machine instruction, then stop and return to the debugger.
5203 It is often useful to do @samp{display/i $pc} when stepping by machine
5204 instructions. This makes @value{GDBN} automatically display the next
5205 instruction to be executed, each time your program stops. @xref{Auto
5206 Display,, Automatic Display}.
5208 An argument is a repeat count, as in @code{step}.
5212 @kindex ni @r{(@code{nexti})}
5214 @itemx nexti @var{arg}
5216 Execute one machine instruction, but if it is a function call,
5217 proceed until the function returns.
5219 An argument is a repeat count, as in @code{next}.
5222 @node Skipping Over Functions and Files
5223 @section Skipping Over Functions and Files
5224 @cindex skipping over functions and files
5226 The program you are debugging may contain some functions which are
5227 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5228 skip a function or all functions in a file when stepping.
5230 For example, consider the following C function:
5241 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5242 are not interested in stepping through @code{boring}. If you run @code{step}
5243 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5244 step over both @code{foo} and @code{boring}!
5246 One solution is to @code{step} into @code{boring} and use the @code{finish}
5247 command to immediately exit it. But this can become tedious if @code{boring}
5248 is called from many places.
5250 A more flexible solution is to execute @kbd{skip boring}. This instructs
5251 @value{GDBN} never to step into @code{boring}. Now when you execute
5252 @code{step} at line 103, you'll step over @code{boring} and directly into
5255 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5256 example, @code{skip file boring.c}.
5259 @kindex skip function
5260 @item skip @r{[}@var{linespec}@r{]}
5261 @itemx skip function @r{[}@var{linespec}@r{]}
5262 After running this command, the function named by @var{linespec} or the
5263 function containing the line named by @var{linespec} will be skipped over when
5264 stepping. @xref{Specify Location}.
5266 If you do not specify @var{linespec}, the function you're currently debugging
5269 (If you have a function called @code{file} that you want to skip, use
5270 @kbd{skip function file}.)
5273 @item skip file @r{[}@var{filename}@r{]}
5274 After running this command, any function whose source lives in @var{filename}
5275 will be skipped over when stepping.
5277 If you do not specify @var{filename}, functions whose source lives in the file
5278 you're currently debugging will be skipped.
5281 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5282 These are the commands for managing your list of skips:
5286 @item info skip @r{[}@var{range}@r{]}
5287 Print details about the specified skip(s). If @var{range} is not specified,
5288 print a table with details about all functions and files marked for skipping.
5289 @code{info skip} prints the following information about each skip:
5293 A number identifying this skip.
5295 The type of this skip, either @samp{function} or @samp{file}.
5296 @item Enabled or Disabled
5297 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5299 For function skips, this column indicates the address in memory of the function
5300 being skipped. If you've set a function skip on a function which has not yet
5301 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5302 which has the function is loaded, @code{info skip} will show the function's
5305 For file skips, this field contains the filename being skipped. For functions
5306 skips, this field contains the function name and its line number in the file
5307 where it is defined.
5311 @item skip delete @r{[}@var{range}@r{]}
5312 Delete the specified skip(s). If @var{range} is not specified, delete all
5316 @item skip enable @r{[}@var{range}@r{]}
5317 Enable the specified skip(s). If @var{range} is not specified, enable all
5320 @kindex skip disable
5321 @item skip disable @r{[}@var{range}@r{]}
5322 Disable the specified skip(s). If @var{range} is not specified, disable all
5331 A signal is an asynchronous event that can happen in a program. The
5332 operating system defines the possible kinds of signals, and gives each
5333 kind a name and a number. For example, in Unix @code{SIGINT} is the
5334 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5335 @code{SIGSEGV} is the signal a program gets from referencing a place in
5336 memory far away from all the areas in use; @code{SIGALRM} occurs when
5337 the alarm clock timer goes off (which happens only if your program has
5338 requested an alarm).
5340 @cindex fatal signals
5341 Some signals, including @code{SIGALRM}, are a normal part of the
5342 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5343 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5344 program has not specified in advance some other way to handle the signal.
5345 @code{SIGINT} does not indicate an error in your program, but it is normally
5346 fatal so it can carry out the purpose of the interrupt: to kill the program.
5348 @value{GDBN} has the ability to detect any occurrence of a signal in your
5349 program. You can tell @value{GDBN} in advance what to do for each kind of
5352 @cindex handling signals
5353 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5354 @code{SIGALRM} be silently passed to your program
5355 (so as not to interfere with their role in the program's functioning)
5356 but to stop your program immediately whenever an error signal happens.
5357 You can change these settings with the @code{handle} command.
5360 @kindex info signals
5364 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5365 handle each one. You can use this to see the signal numbers of all
5366 the defined types of signals.
5368 @item info signals @var{sig}
5369 Similar, but print information only about the specified signal number.
5371 @code{info handle} is an alias for @code{info signals}.
5373 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5374 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5375 for details about this command.
5378 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5379 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5380 can be the number of a signal or its name (with or without the
5381 @samp{SIG} at the beginning); a list of signal numbers of the form
5382 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5383 known signals. Optional arguments @var{keywords}, described below,
5384 say what change to make.
5388 The keywords allowed by the @code{handle} command can be abbreviated.
5389 Their full names are:
5393 @value{GDBN} should not stop your program when this signal happens. It may
5394 still print a message telling you that the signal has come in.
5397 @value{GDBN} should stop your program when this signal happens. This implies
5398 the @code{print} keyword as well.
5401 @value{GDBN} should print a message when this signal happens.
5404 @value{GDBN} should not mention the occurrence of the signal at all. This
5405 implies the @code{nostop} keyword as well.
5409 @value{GDBN} should allow your program to see this signal; your program
5410 can handle the signal, or else it may terminate if the signal is fatal
5411 and not handled. @code{pass} and @code{noignore} are synonyms.
5415 @value{GDBN} should not allow your program to see this signal.
5416 @code{nopass} and @code{ignore} are synonyms.
5420 When a signal stops your program, the signal is not visible to the
5422 continue. Your program sees the signal then, if @code{pass} is in
5423 effect for the signal in question @emph{at that time}. In other words,
5424 after @value{GDBN} reports a signal, you can use the @code{handle}
5425 command with @code{pass} or @code{nopass} to control whether your
5426 program sees that signal when you continue.
5428 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5429 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5430 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5433 You can also use the @code{signal} command to prevent your program from
5434 seeing a signal, or cause it to see a signal it normally would not see,
5435 or to give it any signal at any time. For example, if your program stopped
5436 due to some sort of memory reference error, you might store correct
5437 values into the erroneous variables and continue, hoping to see more
5438 execution; but your program would probably terminate immediately as
5439 a result of the fatal signal once it saw the signal. To prevent this,
5440 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5443 @cindex extra signal information
5444 @anchor{extra signal information}
5446 On some targets, @value{GDBN} can inspect extra signal information
5447 associated with the intercepted signal, before it is actually
5448 delivered to the program being debugged. This information is exported
5449 by the convenience variable @code{$_siginfo}, and consists of data
5450 that is passed by the kernel to the signal handler at the time of the
5451 receipt of a signal. The data type of the information itself is
5452 target dependent. You can see the data type using the @code{ptype
5453 $_siginfo} command. On Unix systems, it typically corresponds to the
5454 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5457 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5458 referenced address that raised a segmentation fault.
5462 (@value{GDBP}) continue
5463 Program received signal SIGSEGV, Segmentation fault.
5464 0x0000000000400766 in main ()
5466 (@value{GDBP}) ptype $_siginfo
5473 struct @{...@} _kill;
5474 struct @{...@} _timer;
5476 struct @{...@} _sigchld;
5477 struct @{...@} _sigfault;
5478 struct @{...@} _sigpoll;
5481 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5485 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5486 $1 = (void *) 0x7ffff7ff7000
5490 Depending on target support, @code{$_siginfo} may also be writable.
5493 @section Stopping and Starting Multi-thread Programs
5495 @cindex stopped threads
5496 @cindex threads, stopped
5498 @cindex continuing threads
5499 @cindex threads, continuing
5501 @value{GDBN} supports debugging programs with multiple threads
5502 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5503 are two modes of controlling execution of your program within the
5504 debugger. In the default mode, referred to as @dfn{all-stop mode},
5505 when any thread in your program stops (for example, at a breakpoint
5506 or while being stepped), all other threads in the program are also stopped by
5507 @value{GDBN}. On some targets, @value{GDBN} also supports
5508 @dfn{non-stop mode}, in which other threads can continue to run freely while
5509 you examine the stopped thread in the debugger.
5512 * All-Stop Mode:: All threads stop when GDB takes control
5513 * Non-Stop Mode:: Other threads continue to execute
5514 * Background Execution:: Running your program asynchronously
5515 * Thread-Specific Breakpoints:: Controlling breakpoints
5516 * Interrupted System Calls:: GDB may interfere with system calls
5517 * Observer Mode:: GDB does not alter program behavior
5521 @subsection All-Stop Mode
5523 @cindex all-stop mode
5525 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5526 @emph{all} threads of execution stop, not just the current thread. This
5527 allows you to examine the overall state of the program, including
5528 switching between threads, without worrying that things may change
5531 Conversely, whenever you restart the program, @emph{all} threads start
5532 executing. @emph{This is true even when single-stepping} with commands
5533 like @code{step} or @code{next}.
5535 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5536 Since thread scheduling is up to your debugging target's operating
5537 system (not controlled by @value{GDBN}), other threads may
5538 execute more than one statement while the current thread completes a
5539 single step. Moreover, in general other threads stop in the middle of a
5540 statement, rather than at a clean statement boundary, when the program
5543 You might even find your program stopped in another thread after
5544 continuing or even single-stepping. This happens whenever some other
5545 thread runs into a breakpoint, a signal, or an exception before the
5546 first thread completes whatever you requested.
5548 @cindex automatic thread selection
5549 @cindex switching threads automatically
5550 @cindex threads, automatic switching
5551 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5552 signal, it automatically selects the thread where that breakpoint or
5553 signal happened. @value{GDBN} alerts you to the context switch with a
5554 message such as @samp{[Switching to Thread @var{n}]} to identify the
5557 On some OSes, you can modify @value{GDBN}'s default behavior by
5558 locking the OS scheduler to allow only a single thread to run.
5561 @item set scheduler-locking @var{mode}
5562 @cindex scheduler locking mode
5563 @cindex lock scheduler
5564 Set the scheduler locking mode. If it is @code{off}, then there is no
5565 locking and any thread may run at any time. If @code{on}, then only the
5566 current thread may run when the inferior is resumed. The @code{step}
5567 mode optimizes for single-stepping; it prevents other threads
5568 from preempting the current thread while you are stepping, so that
5569 the focus of debugging does not change unexpectedly.
5570 Other threads only rarely (or never) get a chance to run
5571 when you step. They are more likely to run when you @samp{next} over a
5572 function call, and they are completely free to run when you use commands
5573 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5574 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5575 the current thread away from the thread that you are debugging.
5577 @item show scheduler-locking
5578 Display the current scheduler locking mode.
5581 @cindex resume threads of multiple processes simultaneously
5582 By default, when you issue one of the execution commands such as
5583 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5584 threads of the current inferior to run. For example, if @value{GDBN}
5585 is attached to two inferiors, each with two threads, the
5586 @code{continue} command resumes only the two threads of the current
5587 inferior. This is useful, for example, when you debug a program that
5588 forks and you want to hold the parent stopped (so that, for instance,
5589 it doesn't run to exit), while you debug the child. In other
5590 situations, you may not be interested in inspecting the current state
5591 of any of the processes @value{GDBN} is attached to, and you may want
5592 to resume them all until some breakpoint is hit. In the latter case,
5593 you can instruct @value{GDBN} to allow all threads of all the
5594 inferiors to run with the @w{@code{set schedule-multiple}} command.
5597 @kindex set schedule-multiple
5598 @item set schedule-multiple
5599 Set the mode for allowing threads of multiple processes to be resumed
5600 when an execution command is issued. When @code{on}, all threads of
5601 all processes are allowed to run. When @code{off}, only the threads
5602 of the current process are resumed. The default is @code{off}. The
5603 @code{scheduler-locking} mode takes precedence when set to @code{on},
5604 or while you are stepping and set to @code{step}.
5606 @item show schedule-multiple
5607 Display the current mode for resuming the execution of threads of
5612 @subsection Non-Stop Mode
5614 @cindex non-stop mode
5616 @c This section is really only a place-holder, and needs to be expanded
5617 @c with more details.
5619 For some multi-threaded targets, @value{GDBN} supports an optional
5620 mode of operation in which you can examine stopped program threads in
5621 the debugger while other threads continue to execute freely. This
5622 minimizes intrusion when debugging live systems, such as programs
5623 where some threads have real-time constraints or must continue to
5624 respond to external events. This is referred to as @dfn{non-stop} mode.
5626 In non-stop mode, when a thread stops to report a debugging event,
5627 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5628 threads as well, in contrast to the all-stop mode behavior. Additionally,
5629 execution commands such as @code{continue} and @code{step} apply by default
5630 only to the current thread in non-stop mode, rather than all threads as
5631 in all-stop mode. This allows you to control threads explicitly in
5632 ways that are not possible in all-stop mode --- for example, stepping
5633 one thread while allowing others to run freely, stepping
5634 one thread while holding all others stopped, or stepping several threads
5635 independently and simultaneously.
5637 To enter non-stop mode, use this sequence of commands before you run
5638 or attach to your program:
5641 # Enable the async interface.
5644 # If using the CLI, pagination breaks non-stop.
5647 # Finally, turn it on!
5651 You can use these commands to manipulate the non-stop mode setting:
5654 @kindex set non-stop
5655 @item set non-stop on
5656 Enable selection of non-stop mode.
5657 @item set non-stop off
5658 Disable selection of non-stop mode.
5659 @kindex show non-stop
5661 Show the current non-stop enablement setting.
5664 Note these commands only reflect whether non-stop mode is enabled,
5665 not whether the currently-executing program is being run in non-stop mode.
5666 In particular, the @code{set non-stop} preference is only consulted when
5667 @value{GDBN} starts or connects to the target program, and it is generally
5668 not possible to switch modes once debugging has started. Furthermore,
5669 since not all targets support non-stop mode, even when you have enabled
5670 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5673 In non-stop mode, all execution commands apply only to the current thread
5674 by default. That is, @code{continue} only continues one thread.
5675 To continue all threads, issue @code{continue -a} or @code{c -a}.
5677 You can use @value{GDBN}'s background execution commands
5678 (@pxref{Background Execution}) to run some threads in the background
5679 while you continue to examine or step others from @value{GDBN}.
5680 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5681 always executed asynchronously in non-stop mode.
5683 Suspending execution is done with the @code{interrupt} command when
5684 running in the background, or @kbd{Ctrl-c} during foreground execution.
5685 In all-stop mode, this stops the whole process;
5686 but in non-stop mode the interrupt applies only to the current thread.
5687 To stop the whole program, use @code{interrupt -a}.
5689 Other execution commands do not currently support the @code{-a} option.
5691 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5692 that thread current, as it does in all-stop mode. This is because the
5693 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5694 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5695 changed to a different thread just as you entered a command to operate on the
5696 previously current thread.
5698 @node Background Execution
5699 @subsection Background Execution
5701 @cindex foreground execution
5702 @cindex background execution
5703 @cindex asynchronous execution
5704 @cindex execution, foreground, background and asynchronous
5706 @value{GDBN}'s execution commands have two variants: the normal
5707 foreground (synchronous) behavior, and a background
5708 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5709 the program to report that some thread has stopped before prompting for
5710 another command. In background execution, @value{GDBN} immediately gives
5711 a command prompt so that you can issue other commands while your program runs.
5713 You need to explicitly enable asynchronous mode before you can use
5714 background execution commands. You can use these commands to
5715 manipulate the asynchronous mode setting:
5718 @kindex set target-async
5719 @item set target-async on
5720 Enable asynchronous mode.
5721 @item set target-async off
5722 Disable asynchronous mode.
5723 @kindex show target-async
5724 @item show target-async
5725 Show the current target-async setting.
5728 If the target doesn't support async mode, @value{GDBN} issues an error
5729 message if you attempt to use the background execution commands.
5731 To specify background execution, add a @code{&} to the command. For example,
5732 the background form of the @code{continue} command is @code{continue&}, or
5733 just @code{c&}. The execution commands that accept background execution
5739 @xref{Starting, , Starting your Program}.
5743 @xref{Attach, , Debugging an Already-running Process}.
5747 @xref{Continuing and Stepping, step}.
5751 @xref{Continuing and Stepping, stepi}.
5755 @xref{Continuing and Stepping, next}.
5759 @xref{Continuing and Stepping, nexti}.
5763 @xref{Continuing and Stepping, continue}.
5767 @xref{Continuing and Stepping, finish}.
5771 @xref{Continuing and Stepping, until}.
5775 Background execution is especially useful in conjunction with non-stop
5776 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5777 However, you can also use these commands in the normal all-stop mode with
5778 the restriction that you cannot issue another execution command until the
5779 previous one finishes. Examples of commands that are valid in all-stop
5780 mode while the program is running include @code{help} and @code{info break}.
5782 You can interrupt your program while it is running in the background by
5783 using the @code{interrupt} command.
5790 Suspend execution of the running program. In all-stop mode,
5791 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5792 only the current thread. To stop the whole program in non-stop mode,
5793 use @code{interrupt -a}.
5796 @node Thread-Specific Breakpoints
5797 @subsection Thread-Specific Breakpoints
5799 When your program has multiple threads (@pxref{Threads,, Debugging
5800 Programs with Multiple Threads}), you can choose whether to set
5801 breakpoints on all threads, or on a particular thread.
5804 @cindex breakpoints and threads
5805 @cindex thread breakpoints
5806 @kindex break @dots{} thread @var{threadno}
5807 @item break @var{linespec} thread @var{threadno}
5808 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5809 @var{linespec} specifies source lines; there are several ways of
5810 writing them (@pxref{Specify Location}), but the effect is always to
5811 specify some source line.
5813 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5814 to specify that you only want @value{GDBN} to stop the program when a
5815 particular thread reaches this breakpoint. @var{threadno} is one of the
5816 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5817 column of the @samp{info threads} display.
5819 If you do not specify @samp{thread @var{threadno}} when you set a
5820 breakpoint, the breakpoint applies to @emph{all} threads of your
5823 You can use the @code{thread} qualifier on conditional breakpoints as
5824 well; in this case, place @samp{thread @var{threadno}} before or
5825 after the breakpoint condition, like this:
5828 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5833 @node Interrupted System Calls
5834 @subsection Interrupted System Calls
5836 @cindex thread breakpoints and system calls
5837 @cindex system calls and thread breakpoints
5838 @cindex premature return from system calls
5839 There is an unfortunate side effect when using @value{GDBN} to debug
5840 multi-threaded programs. If one thread stops for a
5841 breakpoint, or for some other reason, and another thread is blocked in a
5842 system call, then the system call may return prematurely. This is a
5843 consequence of the interaction between multiple threads and the signals
5844 that @value{GDBN} uses to implement breakpoints and other events that
5847 To handle this problem, your program should check the return value of
5848 each system call and react appropriately. This is good programming
5851 For example, do not write code like this:
5857 The call to @code{sleep} will return early if a different thread stops
5858 at a breakpoint or for some other reason.
5860 Instead, write this:
5865 unslept = sleep (unslept);
5868 A system call is allowed to return early, so the system is still
5869 conforming to its specification. But @value{GDBN} does cause your
5870 multi-threaded program to behave differently than it would without
5873 Also, @value{GDBN} uses internal breakpoints in the thread library to
5874 monitor certain events such as thread creation and thread destruction.
5875 When such an event happens, a system call in another thread may return
5876 prematurely, even though your program does not appear to stop.
5879 @subsection Observer Mode
5881 If you want to build on non-stop mode and observe program behavior
5882 without any chance of disruption by @value{GDBN}, you can set
5883 variables to disable all of the debugger's attempts to modify state,
5884 whether by writing memory, inserting breakpoints, etc. These operate
5885 at a low level, intercepting operations from all commands.
5887 When all of these are set to @code{off}, then @value{GDBN} is said to
5888 be @dfn{observer mode}. As a convenience, the variable
5889 @code{observer} can be set to disable these, plus enable non-stop
5892 Note that @value{GDBN} will not prevent you from making nonsensical
5893 combinations of these settings. For instance, if you have enabled
5894 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5895 then breakpoints that work by writing trap instructions into the code
5896 stream will still not be able to be placed.
5901 @item set observer on
5902 @itemx set observer off
5903 When set to @code{on}, this disables all the permission variables
5904 below (except for @code{insert-fast-tracepoints}), plus enables
5905 non-stop debugging. Setting this to @code{off} switches back to
5906 normal debugging, though remaining in non-stop mode.
5909 Show whether observer mode is on or off.
5911 @kindex may-write-registers
5912 @item set may-write-registers on
5913 @itemx set may-write-registers off
5914 This controls whether @value{GDBN} will attempt to alter the values of
5915 registers, such as with assignment expressions in @code{print}, or the
5916 @code{jump} command. It defaults to @code{on}.
5918 @item show may-write-registers
5919 Show the current permission to write registers.
5921 @kindex may-write-memory
5922 @item set may-write-memory on
5923 @itemx set may-write-memory off
5924 This controls whether @value{GDBN} will attempt to alter the contents
5925 of memory, such as with assignment expressions in @code{print}. It
5926 defaults to @code{on}.
5928 @item show may-write-memory
5929 Show the current permission to write memory.
5931 @kindex may-insert-breakpoints
5932 @item set may-insert-breakpoints on
5933 @itemx set may-insert-breakpoints off
5934 This controls whether @value{GDBN} will attempt to insert breakpoints.
5935 This affects all breakpoints, including internal breakpoints defined
5936 by @value{GDBN}. It defaults to @code{on}.
5938 @item show may-insert-breakpoints
5939 Show the current permission to insert breakpoints.
5941 @kindex may-insert-tracepoints
5942 @item set may-insert-tracepoints on
5943 @itemx set may-insert-tracepoints off
5944 This controls whether @value{GDBN} will attempt to insert (regular)
5945 tracepoints at the beginning of a tracing experiment. It affects only
5946 non-fast tracepoints, fast tracepoints being under the control of
5947 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5949 @item show may-insert-tracepoints
5950 Show the current permission to insert tracepoints.
5952 @kindex may-insert-fast-tracepoints
5953 @item set may-insert-fast-tracepoints on
5954 @itemx set may-insert-fast-tracepoints off
5955 This controls whether @value{GDBN} will attempt to insert fast
5956 tracepoints at the beginning of a tracing experiment. It affects only
5957 fast tracepoints, regular (non-fast) tracepoints being under the
5958 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5960 @item show may-insert-fast-tracepoints
5961 Show the current permission to insert fast tracepoints.
5963 @kindex may-interrupt
5964 @item set may-interrupt on
5965 @itemx set may-interrupt off
5966 This controls whether @value{GDBN} will attempt to interrupt or stop
5967 program execution. When this variable is @code{off}, the
5968 @code{interrupt} command will have no effect, nor will
5969 @kbd{Ctrl-c}. It defaults to @code{on}.
5971 @item show may-interrupt
5972 Show the current permission to interrupt or stop the program.
5976 @node Reverse Execution
5977 @chapter Running programs backward
5978 @cindex reverse execution
5979 @cindex running programs backward
5981 When you are debugging a program, it is not unusual to realize that
5982 you have gone too far, and some event of interest has already happened.
5983 If the target environment supports it, @value{GDBN} can allow you to
5984 ``rewind'' the program by running it backward.
5986 A target environment that supports reverse execution should be able
5987 to ``undo'' the changes in machine state that have taken place as the
5988 program was executing normally. Variables, registers etc.@: should
5989 revert to their previous values. Obviously this requires a great
5990 deal of sophistication on the part of the target environment; not
5991 all target environments can support reverse execution.
5993 When a program is executed in reverse, the instructions that
5994 have most recently been executed are ``un-executed'', in reverse
5995 order. The program counter runs backward, following the previous
5996 thread of execution in reverse. As each instruction is ``un-executed'',
5997 the values of memory and/or registers that were changed by that
5998 instruction are reverted to their previous states. After executing
5999 a piece of source code in reverse, all side effects of that code
6000 should be ``undone'', and all variables should be returned to their
6001 prior values@footnote{
6002 Note that some side effects are easier to undo than others. For instance,
6003 memory and registers are relatively easy, but device I/O is hard. Some
6004 targets may be able undo things like device I/O, and some may not.
6006 The contract between @value{GDBN} and the reverse executing target
6007 requires only that the target do something reasonable when
6008 @value{GDBN} tells it to execute backwards, and then report the
6009 results back to @value{GDBN}. Whatever the target reports back to
6010 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6011 assumes that the memory and registers that the target reports are in a
6012 consistant state, but @value{GDBN} accepts whatever it is given.
6015 If you are debugging in a target environment that supports
6016 reverse execution, @value{GDBN} provides the following commands.
6019 @kindex reverse-continue
6020 @kindex rc @r{(@code{reverse-continue})}
6021 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6022 @itemx rc @r{[}@var{ignore-count}@r{]}
6023 Beginning at the point where your program last stopped, start executing
6024 in reverse. Reverse execution will stop for breakpoints and synchronous
6025 exceptions (signals), just like normal execution. Behavior of
6026 asynchronous signals depends on the target environment.
6028 @kindex reverse-step
6029 @kindex rs @r{(@code{step})}
6030 @item reverse-step @r{[}@var{count}@r{]}
6031 Run the program backward until control reaches the start of a
6032 different source line; then stop it, and return control to @value{GDBN}.
6034 Like the @code{step} command, @code{reverse-step} will only stop
6035 at the beginning of a source line. It ``un-executes'' the previously
6036 executed source line. If the previous source line included calls to
6037 debuggable functions, @code{reverse-step} will step (backward) into
6038 the called function, stopping at the beginning of the @emph{last}
6039 statement in the called function (typically a return statement).
6041 Also, as with the @code{step} command, if non-debuggable functions are
6042 called, @code{reverse-step} will run thru them backward without stopping.
6044 @kindex reverse-stepi
6045 @kindex rsi @r{(@code{reverse-stepi})}
6046 @item reverse-stepi @r{[}@var{count}@r{]}
6047 Reverse-execute one machine instruction. Note that the instruction
6048 to be reverse-executed is @emph{not} the one pointed to by the program
6049 counter, but the instruction executed prior to that one. For instance,
6050 if the last instruction was a jump, @code{reverse-stepi} will take you
6051 back from the destination of the jump to the jump instruction itself.
6053 @kindex reverse-next
6054 @kindex rn @r{(@code{reverse-next})}
6055 @item reverse-next @r{[}@var{count}@r{]}
6056 Run backward to the beginning of the previous line executed in
6057 the current (innermost) stack frame. If the line contains function
6058 calls, they will be ``un-executed'' without stopping. Starting from
6059 the first line of a function, @code{reverse-next} will take you back
6060 to the caller of that function, @emph{before} the function was called,
6061 just as the normal @code{next} command would take you from the last
6062 line of a function back to its return to its caller
6063 @footnote{Unless the code is too heavily optimized.}.
6065 @kindex reverse-nexti
6066 @kindex rni @r{(@code{reverse-nexti})}
6067 @item reverse-nexti @r{[}@var{count}@r{]}
6068 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6069 in reverse, except that called functions are ``un-executed'' atomically.
6070 That is, if the previously executed instruction was a return from
6071 another function, @code{reverse-nexti} will continue to execute
6072 in reverse until the call to that function (from the current stack
6075 @kindex reverse-finish
6076 @item reverse-finish
6077 Just as the @code{finish} command takes you to the point where the
6078 current function returns, @code{reverse-finish} takes you to the point
6079 where it was called. Instead of ending up at the end of the current
6080 function invocation, you end up at the beginning.
6082 @kindex set exec-direction
6083 @item set exec-direction
6084 Set the direction of target execution.
6085 @item set exec-direction reverse
6086 @cindex execute forward or backward in time
6087 @value{GDBN} will perform all execution commands in reverse, until the
6088 exec-direction mode is changed to ``forward''. Affected commands include
6089 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6090 command cannot be used in reverse mode.
6091 @item set exec-direction forward
6092 @value{GDBN} will perform all execution commands in the normal fashion.
6093 This is the default.
6097 @node Process Record and Replay
6098 @chapter Recording Inferior's Execution and Replaying It
6099 @cindex process record and replay
6100 @cindex recording inferior's execution and replaying it
6102 On some platforms, @value{GDBN} provides a special @dfn{process record
6103 and replay} target that can record a log of the process execution, and
6104 replay it later with both forward and reverse execution commands.
6107 When this target is in use, if the execution log includes the record
6108 for the next instruction, @value{GDBN} will debug in @dfn{replay
6109 mode}. In the replay mode, the inferior does not really execute code
6110 instructions. Instead, all the events that normally happen during
6111 code execution are taken from the execution log. While code is not
6112 really executed in replay mode, the values of registers (including the
6113 program counter register) and the memory of the inferior are still
6114 changed as they normally would. Their contents are taken from the
6118 If the record for the next instruction is not in the execution log,
6119 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6120 inferior executes normally, and @value{GDBN} records the execution log
6123 The process record and replay target supports reverse execution
6124 (@pxref{Reverse Execution}), even if the platform on which the
6125 inferior runs does not. However, the reverse execution is limited in
6126 this case by the range of the instructions recorded in the execution
6127 log. In other words, reverse execution on platforms that don't
6128 support it directly can only be done in the replay mode.
6130 When debugging in the reverse direction, @value{GDBN} will work in
6131 replay mode as long as the execution log includes the record for the
6132 previous instruction; otherwise, it will work in record mode, if the
6133 platform supports reverse execution, or stop if not.
6135 For architecture environments that support process record and replay,
6136 @value{GDBN} provides the following commands:
6139 @kindex target record
6140 @kindex target record-full
6141 @kindex target record-btrace
6144 @kindex record btrace
6148 @item record @var{method}
6149 This command starts the process record and replay target. The
6150 recording method can be specified as parameter. Without a parameter
6151 the command uses the @code{full} recording method. The following
6152 recording methods are available:
6156 Full record/replay recording using @value{GDBN}'s software record and
6157 replay implementation. This method allows replaying and reverse
6161 Hardware-supported instruction recording. This method does not allow
6162 replaying and reverse execution.
6164 This recording method may not be available on all processors.
6167 The process record and replay target can only debug a process that is
6168 already running. Therefore, you need first to start the process with
6169 the @kbd{run} or @kbd{start} commands, and then start the recording
6170 with the @kbd{record @var{method}} command.
6172 Both @code{record @var{method}} and @code{rec @var{method}} are
6173 aliases of @code{target record-@var{method}}.
6175 @cindex displaced stepping, and process record and replay
6176 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6177 will be automatically disabled when process record and replay target
6178 is started. That's because the process record and replay target
6179 doesn't support displaced stepping.
6181 @cindex non-stop mode, and process record and replay
6182 @cindex asynchronous execution, and process record and replay
6183 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6184 the asynchronous execution mode (@pxref{Background Execution}), not
6185 all recording methods are available. The @code{full} recording method
6186 does not support these two modes.
6191 Stop the process record and replay target. When process record and
6192 replay target stops, the entire execution log will be deleted and the
6193 inferior will either be terminated, or will remain in its final state.
6195 When you stop the process record and replay target in record mode (at
6196 the end of the execution log), the inferior will be stopped at the
6197 next instruction that would have been recorded. In other words, if
6198 you record for a while and then stop recording, the inferior process
6199 will be left in the same state as if the recording never happened.
6201 On the other hand, if the process record and replay target is stopped
6202 while in replay mode (that is, not at the end of the execution log,
6203 but at some earlier point), the inferior process will become ``live''
6204 at that earlier state, and it will then be possible to continue the
6205 usual ``live'' debugging of the process from that state.
6207 When the inferior process exits, or @value{GDBN} detaches from it,
6208 process record and replay target will automatically stop itself.
6211 @item record save @var{filename}
6212 Save the execution log to a file @file{@var{filename}}.
6213 Default filename is @file{gdb_record.@var{process_id}}, where
6214 @var{process_id} is the process ID of the inferior.
6216 This command may not be available for all recording methods.
6218 @kindex record restore
6219 @item record restore @var{filename}
6220 Restore the execution log from a file @file{@var{filename}}.
6221 File must have been created with @code{record save}.
6223 @kindex set record full
6224 @item set record full insn-number-max @var{limit}
6225 @itemx set record full insn-number-max unlimited
6226 Set the limit of instructions to be recorded for the @code{full}
6227 recording method. Default value is 200000.
6229 If @var{limit} is a positive number, then @value{GDBN} will start
6230 deleting instructions from the log once the number of the record
6231 instructions becomes greater than @var{limit}. For every new recorded
6232 instruction, @value{GDBN} will delete the earliest recorded
6233 instruction to keep the number of recorded instructions at the limit.
6234 (Since deleting recorded instructions loses information, @value{GDBN}
6235 lets you control what happens when the limit is reached, by means of
6236 the @code{stop-at-limit} option, described below.)
6238 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6239 delete recorded instructions from the execution log. The number of
6240 recorded instructions is limited only by the available memory.
6242 @kindex show record full
6243 @item show record full insn-number-max
6244 Show the limit of instructions to be recorded with the @code{full}
6247 @item set record full stop-at-limit
6248 Control the behavior of the @code{full} recording method when the
6249 number of recorded instructions reaches the limit. If ON (the
6250 default), @value{GDBN} will stop when the limit is reached for the
6251 first time and ask you whether you want to stop the inferior or
6252 continue running it and recording the execution log. If you decide
6253 to continue recording, each new recorded instruction will cause the
6254 oldest one to be deleted.
6256 If this option is OFF, @value{GDBN} will automatically delete the
6257 oldest record to make room for each new one, without asking.
6259 @item show record full stop-at-limit
6260 Show the current setting of @code{stop-at-limit}.
6262 @item set record full memory-query
6263 Control the behavior when @value{GDBN} is unable to record memory
6264 changes caused by an instruction for the @code{full} recording method.
6265 If ON, @value{GDBN} will query whether to stop the inferior in that
6268 If this option is OFF (the default), @value{GDBN} will automatically
6269 ignore the effect of such instructions on memory. Later, when
6270 @value{GDBN} replays this execution log, it will mark the log of this
6271 instruction as not accessible, and it will not affect the replay
6274 @item show record full memory-query
6275 Show the current setting of @code{memory-query}.
6279 Show various statistics about the recording depending on the recording
6284 For the @code{full} recording method, it shows the state of process
6285 record and its in-memory execution log buffer, including:
6289 Whether in record mode or replay mode.
6291 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6293 Highest recorded instruction number.
6295 Current instruction about to be replayed (if in replay mode).
6297 Number of instructions contained in the execution log.
6299 Maximum number of instructions that may be contained in the execution log.
6303 For the @code{btrace} recording method, it shows the number of
6304 instructions that have been recorded and the number of blocks of
6305 sequential control-flow that is formed by the recorded instructions.
6308 @kindex record delete
6311 When record target runs in replay mode (``in the past''), delete the
6312 subsequent execution log and begin to record a new execution log starting
6313 from the current address. This means you will abandon the previously
6314 recorded ``future'' and begin recording a new ``future''.
6316 @kindex record instruction-history
6317 @kindex rec instruction-history
6318 @item record instruction-history
6319 Disassembles instructions from the recorded execution log. By
6320 default, ten instructions are disassembled. This can be changed using
6321 the @code{set record instruction-history-size} command. Instructions
6322 are printed in execution order. There are several ways to specify
6323 what part of the execution log to disassemble:
6326 @item record instruction-history @var{insn}
6327 Disassembles ten instructions starting from instruction number
6330 @item record instruction-history @var{insn}, +/-@var{n}
6331 Disassembles @var{n} instructions around instruction number
6332 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6333 @var{n} instructions after instruction number @var{insn}. If
6334 @var{n} is preceded with @code{-}, disassembles @var{n}
6335 instructions before instruction number @var{insn}.
6337 @item record instruction-history
6338 Disassembles ten more instructions after the last disassembly.
6340 @item record instruction-history -
6341 Disassembles ten more instructions before the last disassembly.
6343 @item record instruction-history @var{begin} @var{end}
6344 Disassembles instructions beginning with instruction number
6345 @var{begin} until instruction number @var{end}. The instruction
6346 number @var{end} is not included.
6349 This command may not be available for all recording methods.
6352 @item set record instruction-history-size @var{size}
6353 @itemx set record instruction-history-size unlimited
6354 Define how many instructions to disassemble in the @code{record
6355 instruction-history} command. The default value is 10.
6356 A @var{size} of @code{unlimited} means unlimited instructions.
6359 @item show record instruction-history-size
6360 Show how many instructions to disassemble in the @code{record
6361 instruction-history} command.
6363 @kindex record function-call-history
6364 @kindex rec function-call-history
6365 @item record function-call-history
6366 Prints the execution history at function granularity. It prints one
6367 line for each sequence of instructions that belong to the same
6368 function giving the name of that function, the source lines
6369 for this instruction sequence (if the @code{/l} modifier is
6370 specified), and the instructions numbers that form the sequence (if
6371 the @code{/i} modifier is specified).
6374 (@value{GDBP}) @b{list 1, 10}
6385 (@value{GDBP}) @b{record function-call-history /l}
6391 By default, ten lines are printed. This can be changed using the
6392 @code{set record function-call-history-size} command. Functions are
6393 printed in execution order. There are several ways to specify what
6397 @item record function-call-history @var{func}
6398 Prints ten functions starting from function number @var{func}.
6400 @item record function-call-history @var{func}, +/-@var{n}
6401 Prints @var{n} functions around function number @var{func}. If
6402 @var{n} is preceded with @code{+}, prints @var{n} functions after
6403 function number @var{func}. If @var{n} is preceded with @code{-},
6404 prints @var{n} functions before function number @var{func}.
6406 @item record function-call-history
6407 Prints ten more functions after the last ten-line print.
6409 @item record function-call-history -
6410 Prints ten more functions before the last ten-line print.
6412 @item record function-call-history @var{begin} @var{end}
6413 Prints functions beginning with function number @var{begin} until
6414 function number @var{end}. The function number @var{end} is not
6418 This command may not be available for all recording methods.
6420 @item set record function-call-history-size @var{size}
6421 @itemx set record function-call-history-size unlimited
6422 Define how many lines to print in the
6423 @code{record function-call-history} command. The default value is 10.
6424 A size of @code{unlimited} means unlimited lines.
6426 @item show record function-call-history-size
6427 Show how many lines to print in the
6428 @code{record function-call-history} command.
6433 @chapter Examining the Stack
6435 When your program has stopped, the first thing you need to know is where it
6436 stopped and how it got there.
6439 Each time your program performs a function call, information about the call
6441 That information includes the location of the call in your program,
6442 the arguments of the call,
6443 and the local variables of the function being called.
6444 The information is saved in a block of data called a @dfn{stack frame}.
6445 The stack frames are allocated in a region of memory called the @dfn{call
6448 When your program stops, the @value{GDBN} commands for examining the
6449 stack allow you to see all of this information.
6451 @cindex selected frame
6452 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6453 @value{GDBN} commands refer implicitly to the selected frame. In
6454 particular, whenever you ask @value{GDBN} for the value of a variable in
6455 your program, the value is found in the selected frame. There are
6456 special @value{GDBN} commands to select whichever frame you are
6457 interested in. @xref{Selection, ,Selecting a Frame}.
6459 When your program stops, @value{GDBN} automatically selects the
6460 currently executing frame and describes it briefly, similar to the
6461 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6464 * Frames:: Stack frames
6465 * Backtrace:: Backtraces
6466 * Selection:: Selecting a frame
6467 * Frame Info:: Information on a frame
6472 @section Stack Frames
6474 @cindex frame, definition
6476 The call stack is divided up into contiguous pieces called @dfn{stack
6477 frames}, or @dfn{frames} for short; each frame is the data associated
6478 with one call to one function. The frame contains the arguments given
6479 to the function, the function's local variables, and the address at
6480 which the function is executing.
6482 @cindex initial frame
6483 @cindex outermost frame
6484 @cindex innermost frame
6485 When your program is started, the stack has only one frame, that of the
6486 function @code{main}. This is called the @dfn{initial} frame or the
6487 @dfn{outermost} frame. Each time a function is called, a new frame is
6488 made. Each time a function returns, the frame for that function invocation
6489 is eliminated. If a function is recursive, there can be many frames for
6490 the same function. The frame for the function in which execution is
6491 actually occurring is called the @dfn{innermost} frame. This is the most
6492 recently created of all the stack frames that still exist.
6494 @cindex frame pointer
6495 Inside your program, stack frames are identified by their addresses. A
6496 stack frame consists of many bytes, each of which has its own address; each
6497 kind of computer has a convention for choosing one byte whose
6498 address serves as the address of the frame. Usually this address is kept
6499 in a register called the @dfn{frame pointer register}
6500 (@pxref{Registers, $fp}) while execution is going on in that frame.
6502 @cindex frame number
6503 @value{GDBN} assigns numbers to all existing stack frames, starting with
6504 zero for the innermost frame, one for the frame that called it,
6505 and so on upward. These numbers do not really exist in your program;
6506 they are assigned by @value{GDBN} to give you a way of designating stack
6507 frames in @value{GDBN} commands.
6509 @c The -fomit-frame-pointer below perennially causes hbox overflow
6510 @c underflow problems.
6511 @cindex frameless execution
6512 Some compilers provide a way to compile functions so that they operate
6513 without stack frames. (For example, the @value{NGCC} option
6515 @samp{-fomit-frame-pointer}
6517 generates functions without a frame.)
6518 This is occasionally done with heavily used library functions to save
6519 the frame setup time. @value{GDBN} has limited facilities for dealing
6520 with these function invocations. If the innermost function invocation
6521 has no stack frame, @value{GDBN} nevertheless regards it as though
6522 it had a separate frame, which is numbered zero as usual, allowing
6523 correct tracing of the function call chain. However, @value{GDBN} has
6524 no provision for frameless functions elsewhere in the stack.
6527 @kindex frame@r{, command}
6528 @cindex current stack frame
6529 @item frame @var{args}
6530 The @code{frame} command allows you to move from one stack frame to another,
6531 and to print the stack frame you select. @var{args} may be either the
6532 address of the frame or the stack frame number. Without an argument,
6533 @code{frame} prints the current stack frame.
6535 @kindex select-frame
6536 @cindex selecting frame silently
6538 The @code{select-frame} command allows you to move from one stack frame
6539 to another without printing the frame. This is the silent version of
6547 @cindex call stack traces
6548 A backtrace is a summary of how your program got where it is. It shows one
6549 line per frame, for many frames, starting with the currently executing
6550 frame (frame zero), followed by its caller (frame one), and on up the
6555 @kindex bt @r{(@code{backtrace})}
6558 Print a backtrace of the entire stack: one line per frame for all
6559 frames in the stack.
6561 You can stop the backtrace at any time by typing the system interrupt
6562 character, normally @kbd{Ctrl-c}.
6564 @item backtrace @var{n}
6566 Similar, but print only the innermost @var{n} frames.
6568 @item backtrace -@var{n}
6570 Similar, but print only the outermost @var{n} frames.
6572 @item backtrace full
6574 @itemx bt full @var{n}
6575 @itemx bt full -@var{n}
6576 Print the values of the local variables also. @var{n} specifies the
6577 number of frames to print, as described above.
6582 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6583 are additional aliases for @code{backtrace}.
6585 @cindex multiple threads, backtrace
6586 In a multi-threaded program, @value{GDBN} by default shows the
6587 backtrace only for the current thread. To display the backtrace for
6588 several or all of the threads, use the command @code{thread apply}
6589 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6590 apply all backtrace}, @value{GDBN} will display the backtrace for all
6591 the threads; this is handy when you debug a core dump of a
6592 multi-threaded program.
6594 Each line in the backtrace shows the frame number and the function name.
6595 The program counter value is also shown---unless you use @code{set
6596 print address off}. The backtrace also shows the source file name and
6597 line number, as well as the arguments to the function. The program
6598 counter value is omitted if it is at the beginning of the code for that
6601 Here is an example of a backtrace. It was made with the command
6602 @samp{bt 3}, so it shows the innermost three frames.
6606 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6608 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6609 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6611 (More stack frames follow...)
6616 The display for frame zero does not begin with a program counter
6617 value, indicating that your program has stopped at the beginning of the
6618 code for line @code{993} of @code{builtin.c}.
6621 The value of parameter @code{data} in frame 1 has been replaced by
6622 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6623 only if it is a scalar (integer, pointer, enumeration, etc). See command
6624 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6625 on how to configure the way function parameter values are printed.
6627 @cindex optimized out, in backtrace
6628 @cindex function call arguments, optimized out
6629 If your program was compiled with optimizations, some compilers will
6630 optimize away arguments passed to functions if those arguments are
6631 never used after the call. Such optimizations generate code that
6632 passes arguments through registers, but doesn't store those arguments
6633 in the stack frame. @value{GDBN} has no way of displaying such
6634 arguments in stack frames other than the innermost one. Here's what
6635 such a backtrace might look like:
6639 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6641 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6642 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6644 (More stack frames follow...)
6649 The values of arguments that were not saved in their stack frames are
6650 shown as @samp{<optimized out>}.
6652 If you need to display the values of such optimized-out arguments,
6653 either deduce that from other variables whose values depend on the one
6654 you are interested in, or recompile without optimizations.
6656 @cindex backtrace beyond @code{main} function
6657 @cindex program entry point
6658 @cindex startup code, and backtrace
6659 Most programs have a standard user entry point---a place where system
6660 libraries and startup code transition into user code. For C this is
6661 @code{main}@footnote{
6662 Note that embedded programs (the so-called ``free-standing''
6663 environment) are not required to have a @code{main} function as the
6664 entry point. They could even have multiple entry points.}.
6665 When @value{GDBN} finds the entry function in a backtrace
6666 it will terminate the backtrace, to avoid tracing into highly
6667 system-specific (and generally uninteresting) code.
6669 If you need to examine the startup code, or limit the number of levels
6670 in a backtrace, you can change this behavior:
6673 @item set backtrace past-main
6674 @itemx set backtrace past-main on
6675 @kindex set backtrace
6676 Backtraces will continue past the user entry point.
6678 @item set backtrace past-main off
6679 Backtraces will stop when they encounter the user entry point. This is the
6682 @item show backtrace past-main
6683 @kindex show backtrace
6684 Display the current user entry point backtrace policy.
6686 @item set backtrace past-entry
6687 @itemx set backtrace past-entry on
6688 Backtraces will continue past the internal entry point of an application.
6689 This entry point is encoded by the linker when the application is built,
6690 and is likely before the user entry point @code{main} (or equivalent) is called.
6692 @item set backtrace past-entry off
6693 Backtraces will stop when they encounter the internal entry point of an
6694 application. This is the default.
6696 @item show backtrace past-entry
6697 Display the current internal entry point backtrace policy.
6699 @item set backtrace limit @var{n}
6700 @itemx set backtrace limit 0
6701 @itemx set backtrace limit unlimited
6702 @cindex backtrace limit
6703 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
6704 or zero means unlimited levels.
6706 @item show backtrace limit
6707 Display the current limit on backtrace levels.
6710 You can control how file names are displayed.
6713 @item set filename-display
6714 @itemx set filename-display relative
6715 @cindex filename-display
6716 Display file names relative to the compilation directory. This is the default.
6718 @item set filename-display basename
6719 Display only basename of a filename.
6721 @item set filename-display absolute
6722 Display an absolute filename.
6724 @item show filename-display
6725 Show the current way to display filenames.
6729 @section Selecting a Frame
6731 Most commands for examining the stack and other data in your program work on
6732 whichever stack frame is selected at the moment. Here are the commands for
6733 selecting a stack frame; all of them finish by printing a brief description
6734 of the stack frame just selected.
6737 @kindex frame@r{, selecting}
6738 @kindex f @r{(@code{frame})}
6741 Select frame number @var{n}. Recall that frame zero is the innermost
6742 (currently executing) frame, frame one is the frame that called the
6743 innermost one, and so on. The highest-numbered frame is the one for
6746 @item frame @var{addr}
6748 Select the frame at address @var{addr}. This is useful mainly if the
6749 chaining of stack frames has been damaged by a bug, making it
6750 impossible for @value{GDBN} to assign numbers properly to all frames. In
6751 addition, this can be useful when your program has multiple stacks and
6752 switches between them.
6754 On the SPARC architecture, @code{frame} needs two addresses to
6755 select an arbitrary frame: a frame pointer and a stack pointer.
6757 On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack
6758 pointer and a program counter.
6760 On the 29k architecture, it needs three addresses: a register stack
6761 pointer, a program counter, and a memory stack pointer.
6765 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6766 advances toward the outermost frame, to higher frame numbers, to frames
6767 that have existed longer. @var{n} defaults to one.
6770 @kindex do @r{(@code{down})}
6772 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6773 advances toward the innermost frame, to lower frame numbers, to frames
6774 that were created more recently. @var{n} defaults to one. You may
6775 abbreviate @code{down} as @code{do}.
6778 All of these commands end by printing two lines of output describing the
6779 frame. The first line shows the frame number, the function name, the
6780 arguments, and the source file and line number of execution in that
6781 frame. The second line shows the text of that source line.
6789 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6791 10 read_input_file (argv[i]);
6795 After such a printout, the @code{list} command with no arguments
6796 prints ten lines centered on the point of execution in the frame.
6797 You can also edit the program at the point of execution with your favorite
6798 editing program by typing @code{edit}.
6799 @xref{List, ,Printing Source Lines},
6803 @kindex down-silently
6805 @item up-silently @var{n}
6806 @itemx down-silently @var{n}
6807 These two commands are variants of @code{up} and @code{down},
6808 respectively; they differ in that they do their work silently, without
6809 causing display of the new frame. They are intended primarily for use
6810 in @value{GDBN} command scripts, where the output might be unnecessary and
6815 @section Information About a Frame
6817 There are several other commands to print information about the selected
6823 When used without any argument, this command does not change which
6824 frame is selected, but prints a brief description of the currently
6825 selected stack frame. It can be abbreviated @code{f}. With an
6826 argument, this command is used to select a stack frame.
6827 @xref{Selection, ,Selecting a Frame}.
6830 @kindex info f @r{(@code{info frame})}
6833 This command prints a verbose description of the selected stack frame,
6838 the address of the frame
6840 the address of the next frame down (called by this frame)
6842 the address of the next frame up (caller of this frame)
6844 the language in which the source code corresponding to this frame is written
6846 the address of the frame's arguments
6848 the address of the frame's local variables
6850 the program counter saved in it (the address of execution in the caller frame)
6852 which registers were saved in the frame
6855 @noindent The verbose description is useful when
6856 something has gone wrong that has made the stack format fail to fit
6857 the usual conventions.
6859 @item info frame @var{addr}
6860 @itemx info f @var{addr}
6861 Print a verbose description of the frame at address @var{addr}, without
6862 selecting that frame. The selected frame remains unchanged by this
6863 command. This requires the same kind of address (more than one for some
6864 architectures) that you specify in the @code{frame} command.
6865 @xref{Selection, ,Selecting a Frame}.
6869 Print the arguments of the selected frame, each on a separate line.
6873 Print the local variables of the selected frame, each on a separate
6874 line. These are all variables (declared either static or automatic)
6875 accessible at the point of execution of the selected frame.
6881 @chapter Examining Source Files
6883 @value{GDBN} can print parts of your program's source, since the debugging
6884 information recorded in the program tells @value{GDBN} what source files were
6885 used to build it. When your program stops, @value{GDBN} spontaneously prints
6886 the line where it stopped. Likewise, when you select a stack frame
6887 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6888 execution in that frame has stopped. You can print other portions of
6889 source files by explicit command.
6891 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6892 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6893 @value{GDBN} under @sc{gnu} Emacs}.
6896 * List:: Printing source lines
6897 * Specify Location:: How to specify code locations
6898 * Edit:: Editing source files
6899 * Search:: Searching source files
6900 * Source Path:: Specifying source directories
6901 * Machine Code:: Source and machine code
6905 @section Printing Source Lines
6908 @kindex l @r{(@code{list})}
6909 To print lines from a source file, use the @code{list} command
6910 (abbreviated @code{l}). By default, ten lines are printed.
6911 There are several ways to specify what part of the file you want to
6912 print; see @ref{Specify Location}, for the full list.
6914 Here are the forms of the @code{list} command most commonly used:
6917 @item list @var{linenum}
6918 Print lines centered around line number @var{linenum} in the
6919 current source file.
6921 @item list @var{function}
6922 Print lines centered around the beginning of function
6926 Print more lines. If the last lines printed were printed with a
6927 @code{list} command, this prints lines following the last lines
6928 printed; however, if the last line printed was a solitary line printed
6929 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6930 Stack}), this prints lines centered around that line.
6933 Print lines just before the lines last printed.
6936 @cindex @code{list}, how many lines to display
6937 By default, @value{GDBN} prints ten source lines with any of these forms of
6938 the @code{list} command. You can change this using @code{set listsize}:
6941 @kindex set listsize
6942 @item set listsize @var{count}
6943 @itemx set listsize unlimited
6944 Make the @code{list} command display @var{count} source lines (unless
6945 the @code{list} argument explicitly specifies some other number).
6946 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
6948 @kindex show listsize
6950 Display the number of lines that @code{list} prints.
6953 Repeating a @code{list} command with @key{RET} discards the argument,
6954 so it is equivalent to typing just @code{list}. This is more useful
6955 than listing the same lines again. An exception is made for an
6956 argument of @samp{-}; that argument is preserved in repetition so that
6957 each repetition moves up in the source file.
6959 In general, the @code{list} command expects you to supply zero, one or two
6960 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6961 of writing them (@pxref{Specify Location}), but the effect is always
6962 to specify some source line.
6964 Here is a complete description of the possible arguments for @code{list}:
6967 @item list @var{linespec}
6968 Print lines centered around the line specified by @var{linespec}.
6970 @item list @var{first},@var{last}
6971 Print lines from @var{first} to @var{last}. Both arguments are
6972 linespecs. When a @code{list} command has two linespecs, and the
6973 source file of the second linespec is omitted, this refers to
6974 the same source file as the first linespec.
6976 @item list ,@var{last}
6977 Print lines ending with @var{last}.
6979 @item list @var{first},
6980 Print lines starting with @var{first}.
6983 Print lines just after the lines last printed.
6986 Print lines just before the lines last printed.
6989 As described in the preceding table.
6992 @node Specify Location
6993 @section Specifying a Location
6994 @cindex specifying location
6997 Several @value{GDBN} commands accept arguments that specify a location
6998 of your program's code. Since @value{GDBN} is a source-level
6999 debugger, a location usually specifies some line in the source code;
7000 for that reason, locations are also known as @dfn{linespecs}.
7002 Here are all the different ways of specifying a code location that
7003 @value{GDBN} understands:
7007 Specifies the line number @var{linenum} of the current source file.
7010 @itemx +@var{offset}
7011 Specifies the line @var{offset} lines before or after the @dfn{current
7012 line}. For the @code{list} command, the current line is the last one
7013 printed; for the breakpoint commands, this is the line at which
7014 execution stopped in the currently selected @dfn{stack frame}
7015 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7016 used as the second of the two linespecs in a @code{list} command,
7017 this specifies the line @var{offset} lines up or down from the first
7020 @item @var{filename}:@var{linenum}
7021 Specifies the line @var{linenum} in the source file @var{filename}.
7022 If @var{filename} is a relative file name, then it will match any
7023 source file name with the same trailing components. For example, if
7024 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7025 name of @file{/build/trunk/gcc/expr.c}, but not
7026 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7028 @item @var{function}
7029 Specifies the line that begins the body of the function @var{function}.
7030 For example, in C, this is the line with the open brace.
7032 @item @var{function}:@var{label}
7033 Specifies the line where @var{label} appears in @var{function}.
7035 @item @var{filename}:@var{function}
7036 Specifies the line that begins the body of the function @var{function}
7037 in the file @var{filename}. You only need the file name with a
7038 function name to avoid ambiguity when there are identically named
7039 functions in different source files.
7042 Specifies the line at which the label named @var{label} appears.
7043 @value{GDBN} searches for the label in the function corresponding to
7044 the currently selected stack frame. If there is no current selected
7045 stack frame (for instance, if the inferior is not running), then
7046 @value{GDBN} will not search for a label.
7048 @item *@var{address}
7049 Specifies the program address @var{address}. For line-oriented
7050 commands, such as @code{list} and @code{edit}, this specifies a source
7051 line that contains @var{address}. For @code{break} and other
7052 breakpoint oriented commands, this can be used to set breakpoints in
7053 parts of your program which do not have debugging information or
7056 Here @var{address} may be any expression valid in the current working
7057 language (@pxref{Languages, working language}) that specifies a code
7058 address. In addition, as a convenience, @value{GDBN} extends the
7059 semantics of expressions used in locations to cover the situations
7060 that frequently happen during debugging. Here are the various forms
7064 @item @var{expression}
7065 Any expression valid in the current working language.
7067 @item @var{funcaddr}
7068 An address of a function or procedure derived from its name. In C,
7069 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7070 simply the function's name @var{function} (and actually a special case
7071 of a valid expression). In Pascal and Modula-2, this is
7072 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7073 (although the Pascal form also works).
7075 This form specifies the address of the function's first instruction,
7076 before the stack frame and arguments have been set up.
7078 @item '@var{filename}'::@var{funcaddr}
7079 Like @var{funcaddr} above, but also specifies the name of the source
7080 file explicitly. This is useful if the name of the function does not
7081 specify the function unambiguously, e.g., if there are several
7082 functions with identical names in different source files.
7085 @cindex breakpoint at static probe point
7086 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7087 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7088 applications to embed static probes. @xref{Static Probe Points}, for more
7089 information on finding and using static probes. This form of linespec
7090 specifies the location of such a static probe.
7092 If @var{objfile} is given, only probes coming from that shared library
7093 or executable matching @var{objfile} as a regular expression are considered.
7094 If @var{provider} is given, then only probes from that provider are considered.
7095 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7096 each one of those probes.
7102 @section Editing Source Files
7103 @cindex editing source files
7106 @kindex e @r{(@code{edit})}
7107 To edit the lines in a source file, use the @code{edit} command.
7108 The editing program of your choice
7109 is invoked with the current line set to
7110 the active line in the program.
7111 Alternatively, there are several ways to specify what part of the file you
7112 want to print if you want to see other parts of the program:
7115 @item edit @var{location}
7116 Edit the source file specified by @code{location}. Editing starts at
7117 that @var{location}, e.g., at the specified source line of the
7118 specified file. @xref{Specify Location}, for all the possible forms
7119 of the @var{location} argument; here are the forms of the @code{edit}
7120 command most commonly used:
7123 @item edit @var{number}
7124 Edit the current source file with @var{number} as the active line number.
7126 @item edit @var{function}
7127 Edit the file containing @var{function} at the beginning of its definition.
7132 @subsection Choosing your Editor
7133 You can customize @value{GDBN} to use any editor you want
7135 The only restriction is that your editor (say @code{ex}), recognizes the
7136 following command-line syntax:
7138 ex +@var{number} file
7140 The optional numeric value +@var{number} specifies the number of the line in
7141 the file where to start editing.}.
7142 By default, it is @file{@value{EDITOR}}, but you can change this
7143 by setting the environment variable @code{EDITOR} before using
7144 @value{GDBN}. For example, to configure @value{GDBN} to use the
7145 @code{vi} editor, you could use these commands with the @code{sh} shell:
7151 or in the @code{csh} shell,
7153 setenv EDITOR /usr/bin/vi
7158 @section Searching Source Files
7159 @cindex searching source files
7161 There are two commands for searching through the current source file for a
7166 @kindex forward-search
7167 @kindex fo @r{(@code{forward-search})}
7168 @item forward-search @var{regexp}
7169 @itemx search @var{regexp}
7170 The command @samp{forward-search @var{regexp}} checks each line,
7171 starting with the one following the last line listed, for a match for
7172 @var{regexp}. It lists the line that is found. You can use the
7173 synonym @samp{search @var{regexp}} or abbreviate the command name as
7176 @kindex reverse-search
7177 @item reverse-search @var{regexp}
7178 The command @samp{reverse-search @var{regexp}} checks each line, starting
7179 with the one before the last line listed and going backward, for a match
7180 for @var{regexp}. It lists the line that is found. You can abbreviate
7181 this command as @code{rev}.
7185 @section Specifying Source Directories
7188 @cindex directories for source files
7189 Executable programs sometimes do not record the directories of the source
7190 files from which they were compiled, just the names. Even when they do,
7191 the directories could be moved between the compilation and your debugging
7192 session. @value{GDBN} has a list of directories to search for source files;
7193 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7194 it tries all the directories in the list, in the order they are present
7195 in the list, until it finds a file with the desired name.
7197 For example, suppose an executable references the file
7198 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7199 @file{/mnt/cross}. The file is first looked up literally; if this
7200 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7201 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7202 message is printed. @value{GDBN} does not look up the parts of the
7203 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7204 Likewise, the subdirectories of the source path are not searched: if
7205 the source path is @file{/mnt/cross}, and the binary refers to
7206 @file{foo.c}, @value{GDBN} would not find it under
7207 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7209 Plain file names, relative file names with leading directories, file
7210 names containing dots, etc.@: are all treated as described above; for
7211 instance, if the source path is @file{/mnt/cross}, and the source file
7212 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7213 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7214 that---@file{/mnt/cross/foo.c}.
7216 Note that the executable search path is @emph{not} used to locate the
7219 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7220 any information it has cached about where source files are found and where
7221 each line is in the file.
7225 When you start @value{GDBN}, its source path includes only @samp{cdir}
7226 and @samp{cwd}, in that order.
7227 To add other directories, use the @code{directory} command.
7229 The search path is used to find both program source files and @value{GDBN}
7230 script files (read using the @samp{-command} option and @samp{source} command).
7232 In addition to the source path, @value{GDBN} provides a set of commands
7233 that manage a list of source path substitution rules. A @dfn{substitution
7234 rule} specifies how to rewrite source directories stored in the program's
7235 debug information in case the sources were moved to a different
7236 directory between compilation and debugging. A rule is made of
7237 two strings, the first specifying what needs to be rewritten in
7238 the path, and the second specifying how it should be rewritten.
7239 In @ref{set substitute-path}, we name these two parts @var{from} and
7240 @var{to} respectively. @value{GDBN} does a simple string replacement
7241 of @var{from} with @var{to} at the start of the directory part of the
7242 source file name, and uses that result instead of the original file
7243 name to look up the sources.
7245 Using the previous example, suppose the @file{foo-1.0} tree has been
7246 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7247 @value{GDBN} to replace @file{/usr/src} in all source path names with
7248 @file{/mnt/cross}. The first lookup will then be
7249 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7250 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7251 substitution rule, use the @code{set substitute-path} command
7252 (@pxref{set substitute-path}).
7254 To avoid unexpected substitution results, a rule is applied only if the
7255 @var{from} part of the directory name ends at a directory separator.
7256 For instance, a rule substituting @file{/usr/source} into
7257 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7258 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7259 is applied only at the beginning of the directory name, this rule will
7260 not be applied to @file{/root/usr/source/baz.c} either.
7262 In many cases, you can achieve the same result using the @code{directory}
7263 command. However, @code{set substitute-path} can be more efficient in
7264 the case where the sources are organized in a complex tree with multiple
7265 subdirectories. With the @code{directory} command, you need to add each
7266 subdirectory of your project. If you moved the entire tree while
7267 preserving its internal organization, then @code{set substitute-path}
7268 allows you to direct the debugger to all the sources with one single
7271 @code{set substitute-path} is also more than just a shortcut command.
7272 The source path is only used if the file at the original location no
7273 longer exists. On the other hand, @code{set substitute-path} modifies
7274 the debugger behavior to look at the rewritten location instead. So, if
7275 for any reason a source file that is not relevant to your executable is
7276 located at the original location, a substitution rule is the only
7277 method available to point @value{GDBN} at the new location.
7279 @cindex @samp{--with-relocated-sources}
7280 @cindex default source path substitution
7281 You can configure a default source path substitution rule by
7282 configuring @value{GDBN} with the
7283 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7284 should be the name of a directory under @value{GDBN}'s configured
7285 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7286 directory names in debug information under @var{dir} will be adjusted
7287 automatically if the installed @value{GDBN} is moved to a new
7288 location. This is useful if @value{GDBN}, libraries or executables
7289 with debug information and corresponding source code are being moved
7293 @item directory @var{dirname} @dots{}
7294 @item dir @var{dirname} @dots{}
7295 Add directory @var{dirname} to the front of the source path. Several
7296 directory names may be given to this command, separated by @samp{:}
7297 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7298 part of absolute file names) or
7299 whitespace. You may specify a directory that is already in the source
7300 path; this moves it forward, so @value{GDBN} searches it sooner.
7304 @vindex $cdir@r{, convenience variable}
7305 @vindex $cwd@r{, convenience variable}
7306 @cindex compilation directory
7307 @cindex current directory
7308 @cindex working directory
7309 @cindex directory, current
7310 @cindex directory, compilation
7311 You can use the string @samp{$cdir} to refer to the compilation
7312 directory (if one is recorded), and @samp{$cwd} to refer to the current
7313 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7314 tracks the current working directory as it changes during your @value{GDBN}
7315 session, while the latter is immediately expanded to the current
7316 directory at the time you add an entry to the source path.
7319 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7321 @c RET-repeat for @code{directory} is explicitly disabled, but since
7322 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7324 @item set directories @var{path-list}
7325 @kindex set directories
7326 Set the source path to @var{path-list}.
7327 @samp{$cdir:$cwd} are added if missing.
7329 @item show directories
7330 @kindex show directories
7331 Print the source path: show which directories it contains.
7333 @anchor{set substitute-path}
7334 @item set substitute-path @var{from} @var{to}
7335 @kindex set substitute-path
7336 Define a source path substitution rule, and add it at the end of the
7337 current list of existing substitution rules. If a rule with the same
7338 @var{from} was already defined, then the old rule is also deleted.
7340 For example, if the file @file{/foo/bar/baz.c} was moved to
7341 @file{/mnt/cross/baz.c}, then the command
7344 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7348 will tell @value{GDBN} to replace @samp{/usr/src} with
7349 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7350 @file{baz.c} even though it was moved.
7352 In the case when more than one substitution rule have been defined,
7353 the rules are evaluated one by one in the order where they have been
7354 defined. The first one matching, if any, is selected to perform
7357 For instance, if we had entered the following commands:
7360 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7361 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7365 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7366 @file{/mnt/include/defs.h} by using the first rule. However, it would
7367 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7368 @file{/mnt/src/lib/foo.c}.
7371 @item unset substitute-path [path]
7372 @kindex unset substitute-path
7373 If a path is specified, search the current list of substitution rules
7374 for a rule that would rewrite that path. Delete that rule if found.
7375 A warning is emitted by the debugger if no rule could be found.
7377 If no path is specified, then all substitution rules are deleted.
7379 @item show substitute-path [path]
7380 @kindex show substitute-path
7381 If a path is specified, then print the source path substitution rule
7382 which would rewrite that path, if any.
7384 If no path is specified, then print all existing source path substitution
7389 If your source path is cluttered with directories that are no longer of
7390 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7391 versions of source. You can correct the situation as follows:
7395 Use @code{directory} with no argument to reset the source path to its default value.
7398 Use @code{directory} with suitable arguments to reinstall the
7399 directories you want in the source path. You can add all the
7400 directories in one command.
7404 @section Source and Machine Code
7405 @cindex source line and its code address
7407 You can use the command @code{info line} to map source lines to program
7408 addresses (and vice versa), and the command @code{disassemble} to display
7409 a range of addresses as machine instructions. You can use the command
7410 @code{set disassemble-next-line} to set whether to disassemble next
7411 source line when execution stops. When run under @sc{gnu} Emacs
7412 mode, the @code{info line} command causes the arrow to point to the
7413 line specified. Also, @code{info line} prints addresses in symbolic form as
7418 @item info line @var{linespec}
7419 Print the starting and ending addresses of the compiled code for
7420 source line @var{linespec}. You can specify source lines in any of
7421 the ways documented in @ref{Specify Location}.
7424 For example, we can use @code{info line} to discover the location of
7425 the object code for the first line of function
7426 @code{m4_changequote}:
7428 @c FIXME: I think this example should also show the addresses in
7429 @c symbolic form, as they usually would be displayed.
7431 (@value{GDBP}) info line m4_changequote
7432 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7436 @cindex code address and its source line
7437 We can also inquire (using @code{*@var{addr}} as the form for
7438 @var{linespec}) what source line covers a particular address:
7440 (@value{GDBP}) info line *0x63ff
7441 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7444 @cindex @code{$_} and @code{info line}
7445 @cindex @code{x} command, default address
7446 @kindex x@r{(examine), and} info line
7447 After @code{info line}, the default address for the @code{x} command
7448 is changed to the starting address of the line, so that @samp{x/i} is
7449 sufficient to begin examining the machine code (@pxref{Memory,
7450 ,Examining Memory}). Also, this address is saved as the value of the
7451 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7456 @cindex assembly instructions
7457 @cindex instructions, assembly
7458 @cindex machine instructions
7459 @cindex listing machine instructions
7461 @itemx disassemble /m
7462 @itemx disassemble /r
7463 This specialized command dumps a range of memory as machine
7464 instructions. It can also print mixed source+disassembly by specifying
7465 the @code{/m} modifier and print the raw instructions in hex as well as
7466 in symbolic form by specifying the @code{/r}.
7467 The default memory range is the function surrounding the
7468 program counter of the selected frame. A single argument to this
7469 command is a program counter value; @value{GDBN} dumps the function
7470 surrounding this value. When two arguments are given, they should
7471 be separated by a comma, possibly surrounded by whitespace. The
7472 arguments specify a range of addresses to dump, in one of two forms:
7475 @item @var{start},@var{end}
7476 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
7477 @item @var{start},+@var{length}
7478 the addresses from @var{start} (inclusive) to
7479 @code{@var{start}+@var{length}} (exclusive).
7483 When 2 arguments are specified, the name of the function is also
7484 printed (since there could be several functions in the given range).
7486 The argument(s) can be any expression yielding a numeric value, such as
7487 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
7489 If the range of memory being disassembled contains current program counter,
7490 the instruction at that location is shown with a @code{=>} marker.
7493 The following example shows the disassembly of a range of addresses of
7494 HP PA-RISC 2.0 code:
7497 (@value{GDBP}) disas 0x32c4, 0x32e4
7498 Dump of assembler code from 0x32c4 to 0x32e4:
7499 0x32c4 <main+204>: addil 0,dp
7500 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
7501 0x32cc <main+212>: ldil 0x3000,r31
7502 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
7503 0x32d4 <main+220>: ldo 0(r31),rp
7504 0x32d8 <main+224>: addil -0x800,dp
7505 0x32dc <main+228>: ldo 0x588(r1),r26
7506 0x32e0 <main+232>: ldil 0x3000,r31
7507 End of assembler dump.
7510 Here is an example showing mixed source+assembly for Intel x86, when the
7511 program is stopped just after function prologue:
7514 (@value{GDBP}) disas /m main
7515 Dump of assembler code for function main:
7517 0x08048330 <+0>: push %ebp
7518 0x08048331 <+1>: mov %esp,%ebp
7519 0x08048333 <+3>: sub $0x8,%esp
7520 0x08048336 <+6>: and $0xfffffff0,%esp
7521 0x08048339 <+9>: sub $0x10,%esp
7523 6 printf ("Hello.\n");
7524 => 0x0804833c <+12>: movl $0x8048440,(%esp)
7525 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7529 0x08048348 <+24>: mov $0x0,%eax
7530 0x0804834d <+29>: leave
7531 0x0804834e <+30>: ret
7533 End of assembler dump.
7536 Here is another example showing raw instructions in hex for AMD x86-64,
7539 (gdb) disas /r 0x400281,+10
7540 Dump of assembler code from 0x400281 to 0x40028b:
7541 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7542 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7543 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7544 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7545 End of assembler dump.
7548 Addresses cannot be specified as a linespec (@pxref{Specify Location}).
7549 So, for example, if you want to disassemble function @code{bar}
7550 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
7551 and not @samp{disassemble foo.c:bar}.
7553 Some architectures have more than one commonly-used set of instruction
7554 mnemonics or other syntax.
7556 For programs that were dynamically linked and use shared libraries,
7557 instructions that call functions or branch to locations in the shared
7558 libraries might show a seemingly bogus location---it's actually a
7559 location of the relocation table. On some architectures, @value{GDBN}
7560 might be able to resolve these to actual function names.
7563 @kindex set disassembly-flavor
7564 @cindex Intel disassembly flavor
7565 @cindex AT&T disassembly flavor
7566 @item set disassembly-flavor @var{instruction-set}
7567 Select the instruction set to use when disassembling the
7568 program via the @code{disassemble} or @code{x/i} commands.
7570 Currently this command is only defined for the Intel x86 family. You
7571 can set @var{instruction-set} to either @code{intel} or @code{att}.
7572 The default is @code{att}, the AT&T flavor used by default by Unix
7573 assemblers for x86-based targets.
7575 @kindex show disassembly-flavor
7576 @item show disassembly-flavor
7577 Show the current setting of the disassembly flavor.
7581 @kindex set disassemble-next-line
7582 @kindex show disassemble-next-line
7583 @item set disassemble-next-line
7584 @itemx show disassemble-next-line
7585 Control whether or not @value{GDBN} will disassemble the next source
7586 line or instruction when execution stops. If ON, @value{GDBN} will
7587 display disassembly of the next source line when execution of the
7588 program being debugged stops. This is @emph{in addition} to
7589 displaying the source line itself, which @value{GDBN} always does if
7590 possible. If the next source line cannot be displayed for some reason
7591 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7592 info in the debug info), @value{GDBN} will display disassembly of the
7593 next @emph{instruction} instead of showing the next source line. If
7594 AUTO, @value{GDBN} will display disassembly of next instruction only
7595 if the source line cannot be displayed. This setting causes
7596 @value{GDBN} to display some feedback when you step through a function
7597 with no line info or whose source file is unavailable. The default is
7598 OFF, which means never display the disassembly of the next line or
7604 @chapter Examining Data
7606 @cindex printing data
7607 @cindex examining data
7610 The usual way to examine data in your program is with the @code{print}
7611 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7612 evaluates and prints the value of an expression of the language your
7613 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7614 Different Languages}). It may also print the expression using a
7615 Python-based pretty-printer (@pxref{Pretty Printing}).
7618 @item print @var{expr}
7619 @itemx print /@var{f} @var{expr}
7620 @var{expr} is an expression (in the source language). By default the
7621 value of @var{expr} is printed in a format appropriate to its data type;
7622 you can choose a different format by specifying @samp{/@var{f}}, where
7623 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7627 @itemx print /@var{f}
7628 @cindex reprint the last value
7629 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7630 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7631 conveniently inspect the same value in an alternative format.
7634 A more low-level way of examining data is with the @code{x} command.
7635 It examines data in memory at a specified address and prints it in a
7636 specified format. @xref{Memory, ,Examining Memory}.
7638 If you are interested in information about types, or about how the
7639 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7640 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7643 @cindex exploring hierarchical data structures
7645 Another way of examining values of expressions and type information is
7646 through the Python extension command @code{explore} (available only if
7647 the @value{GDBN} build is configured with @code{--with-python}). It
7648 offers an interactive way to start at the highest level (or, the most
7649 abstract level) of the data type of an expression (or, the data type
7650 itself) and explore all the way down to leaf scalar values/fields
7651 embedded in the higher level data types.
7654 @item explore @var{arg}
7655 @var{arg} is either an expression (in the source language), or a type
7656 visible in the current context of the program being debugged.
7659 The working of the @code{explore} command can be illustrated with an
7660 example. If a data type @code{struct ComplexStruct} is defined in your
7670 struct ComplexStruct
7672 struct SimpleStruct *ss_p;
7678 followed by variable declarations as
7681 struct SimpleStruct ss = @{ 10, 1.11 @};
7682 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
7686 then, the value of the variable @code{cs} can be explored using the
7687 @code{explore} command as follows.
7691 The value of `cs' is a struct/class of type `struct ComplexStruct' with
7692 the following fields:
7694 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
7695 arr = <Enter 1 to explore this field of type `int [10]'>
7697 Enter the field number of choice:
7701 Since the fields of @code{cs} are not scalar values, you are being
7702 prompted to chose the field you want to explore. Let's say you choose
7703 the field @code{ss_p} by entering @code{0}. Then, since this field is a
7704 pointer, you will be asked if it is pointing to a single value. From
7705 the declaration of @code{cs} above, it is indeed pointing to a single
7706 value, hence you enter @code{y}. If you enter @code{n}, then you will
7707 be asked if it were pointing to an array of values, in which case this
7708 field will be explored as if it were an array.
7711 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
7712 Continue exploring it as a pointer to a single value [y/n]: y
7713 The value of `*(cs.ss_p)' is a struct/class of type `struct
7714 SimpleStruct' with the following fields:
7716 i = 10 .. (Value of type `int')
7717 d = 1.1100000000000001 .. (Value of type `double')
7719 Press enter to return to parent value:
7723 If the field @code{arr} of @code{cs} was chosen for exploration by
7724 entering @code{1} earlier, then since it is as array, you will be
7725 prompted to enter the index of the element in the array that you want
7729 `cs.arr' is an array of `int'.
7730 Enter the index of the element you want to explore in `cs.arr': 5
7732 `(cs.arr)[5]' is a scalar value of type `int'.
7736 Press enter to return to parent value:
7739 In general, at any stage of exploration, you can go deeper towards the
7740 leaf values by responding to the prompts appropriately, or hit the
7741 return key to return to the enclosing data structure (the @i{higher}
7742 level data structure).
7744 Similar to exploring values, you can use the @code{explore} command to
7745 explore types. Instead of specifying a value (which is typically a
7746 variable name or an expression valid in the current context of the
7747 program being debugged), you specify a type name. If you consider the
7748 same example as above, your can explore the type
7749 @code{struct ComplexStruct} by passing the argument
7750 @code{struct ComplexStruct} to the @code{explore} command.
7753 (gdb) explore struct ComplexStruct
7757 By responding to the prompts appropriately in the subsequent interactive
7758 session, you can explore the type @code{struct ComplexStruct} in a
7759 manner similar to how the value @code{cs} was explored in the above
7762 The @code{explore} command also has two sub-commands,
7763 @code{explore value} and @code{explore type}. The former sub-command is
7764 a way to explicitly specify that value exploration of the argument is
7765 being invoked, while the latter is a way to explicitly specify that type
7766 exploration of the argument is being invoked.
7769 @item explore value @var{expr}
7770 @cindex explore value
7771 This sub-command of @code{explore} explores the value of the
7772 expression @var{expr} (if @var{expr} is an expression valid in the
7773 current context of the program being debugged). The behavior of this
7774 command is identical to that of the behavior of the @code{explore}
7775 command being passed the argument @var{expr}.
7777 @item explore type @var{arg}
7778 @cindex explore type
7779 This sub-command of @code{explore} explores the type of @var{arg} (if
7780 @var{arg} is a type visible in the current context of program being
7781 debugged), or the type of the value/expression @var{arg} (if @var{arg}
7782 is an expression valid in the current context of the program being
7783 debugged). If @var{arg} is a type, then the behavior of this command is
7784 identical to that of the @code{explore} command being passed the
7785 argument @var{arg}. If @var{arg} is an expression, then the behavior of
7786 this command will be identical to that of the @code{explore} command
7787 being passed the type of @var{arg} as the argument.
7791 * Expressions:: Expressions
7792 * Ambiguous Expressions:: Ambiguous Expressions
7793 * Variables:: Program variables
7794 * Arrays:: Artificial arrays
7795 * Output Formats:: Output formats
7796 * Memory:: Examining memory
7797 * Auto Display:: Automatic display
7798 * Print Settings:: Print settings
7799 * Pretty Printing:: Python pretty printing
7800 * Value History:: Value history
7801 * Convenience Vars:: Convenience variables
7802 * Convenience Funs:: Convenience functions
7803 * Registers:: Registers
7804 * Floating Point Hardware:: Floating point hardware
7805 * Vector Unit:: Vector Unit
7806 * OS Information:: Auxiliary data provided by operating system
7807 * Memory Region Attributes:: Memory region attributes
7808 * Dump/Restore Files:: Copy between memory and a file
7809 * Core File Generation:: Cause a program dump its core
7810 * Character Sets:: Debugging programs that use a different
7811 character set than GDB does
7812 * Caching Remote Data:: Data caching for remote targets
7813 * Searching Memory:: Searching memory for a sequence of bytes
7817 @section Expressions
7820 @code{print} and many other @value{GDBN} commands accept an expression and
7821 compute its value. Any kind of constant, variable or operator defined
7822 by the programming language you are using is valid in an expression in
7823 @value{GDBN}. This includes conditional expressions, function calls,
7824 casts, and string constants. It also includes preprocessor macros, if
7825 you compiled your program to include this information; see
7828 @cindex arrays in expressions
7829 @value{GDBN} supports array constants in expressions input by
7830 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7831 you can use the command @code{print @{1, 2, 3@}} to create an array
7832 of three integers. If you pass an array to a function or assign it
7833 to a program variable, @value{GDBN} copies the array to memory that
7834 is @code{malloc}ed in the target program.
7836 Because C is so widespread, most of the expressions shown in examples in
7837 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7838 Languages}, for information on how to use expressions in other
7841 In this section, we discuss operators that you can use in @value{GDBN}
7842 expressions regardless of your programming language.
7844 @cindex casts, in expressions
7845 Casts are supported in all languages, not just in C, because it is so
7846 useful to cast a number into a pointer in order to examine a structure
7847 at that address in memory.
7848 @c FIXME: casts supported---Mod2 true?
7850 @value{GDBN} supports these operators, in addition to those common
7851 to programming languages:
7855 @samp{@@} is a binary operator for treating parts of memory as arrays.
7856 @xref{Arrays, ,Artificial Arrays}, for more information.
7859 @samp{::} allows you to specify a variable in terms of the file or
7860 function where it is defined. @xref{Variables, ,Program Variables}.
7862 @cindex @{@var{type}@}
7863 @cindex type casting memory
7864 @cindex memory, viewing as typed object
7865 @cindex casts, to view memory
7866 @item @{@var{type}@} @var{addr}
7867 Refers to an object of type @var{type} stored at address @var{addr} in
7868 memory. @var{addr} may be any expression whose value is an integer or
7869 pointer (but parentheses are required around binary operators, just as in
7870 a cast). This construct is allowed regardless of what kind of data is
7871 normally supposed to reside at @var{addr}.
7874 @node Ambiguous Expressions
7875 @section Ambiguous Expressions
7876 @cindex ambiguous expressions
7878 Expressions can sometimes contain some ambiguous elements. For instance,
7879 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7880 a single function name to be defined several times, for application in
7881 different contexts. This is called @dfn{overloading}. Another example
7882 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7883 templates and is typically instantiated several times, resulting in
7884 the same function name being defined in different contexts.
7886 In some cases and depending on the language, it is possible to adjust
7887 the expression to remove the ambiguity. For instance in C@t{++}, you
7888 can specify the signature of the function you want to break on, as in
7889 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7890 qualified name of your function often makes the expression unambiguous
7893 When an ambiguity that needs to be resolved is detected, the debugger
7894 has the capability to display a menu of numbered choices for each
7895 possibility, and then waits for the selection with the prompt @samp{>}.
7896 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7897 aborts the current command. If the command in which the expression was
7898 used allows more than one choice to be selected, the next option in the
7899 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7902 For example, the following session excerpt shows an attempt to set a
7903 breakpoint at the overloaded symbol @code{String::after}.
7904 We choose three particular definitions of that function name:
7906 @c FIXME! This is likely to change to show arg type lists, at least
7909 (@value{GDBP}) b String::after
7912 [2] file:String.cc; line number:867
7913 [3] file:String.cc; line number:860
7914 [4] file:String.cc; line number:875
7915 [5] file:String.cc; line number:853
7916 [6] file:String.cc; line number:846
7917 [7] file:String.cc; line number:735
7919 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7920 Breakpoint 2 at 0xb344: file String.cc, line 875.
7921 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7922 Multiple breakpoints were set.
7923 Use the "delete" command to delete unwanted
7930 @kindex set multiple-symbols
7931 @item set multiple-symbols @var{mode}
7932 @cindex multiple-symbols menu
7934 This option allows you to adjust the debugger behavior when an expression
7937 By default, @var{mode} is set to @code{all}. If the command with which
7938 the expression is used allows more than one choice, then @value{GDBN}
7939 automatically selects all possible choices. For instance, inserting
7940 a breakpoint on a function using an ambiguous name results in a breakpoint
7941 inserted on each possible match. However, if a unique choice must be made,
7942 then @value{GDBN} uses the menu to help you disambiguate the expression.
7943 For instance, printing the address of an overloaded function will result
7944 in the use of the menu.
7946 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7947 when an ambiguity is detected.
7949 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7950 an error due to the ambiguity and the command is aborted.
7952 @kindex show multiple-symbols
7953 @item show multiple-symbols
7954 Show the current value of the @code{multiple-symbols} setting.
7958 @section Program Variables
7960 The most common kind of expression to use is the name of a variable
7963 Variables in expressions are understood in the selected stack frame
7964 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7968 global (or file-static)
7975 visible according to the scope rules of the
7976 programming language from the point of execution in that frame
7979 @noindent This means that in the function
7994 you can examine and use the variable @code{a} whenever your program is
7995 executing within the function @code{foo}, but you can only use or
7996 examine the variable @code{b} while your program is executing inside
7997 the block where @code{b} is declared.
7999 @cindex variable name conflict
8000 There is an exception: you can refer to a variable or function whose
8001 scope is a single source file even if the current execution point is not
8002 in this file. But it is possible to have more than one such variable or
8003 function with the same name (in different source files). If that
8004 happens, referring to that name has unpredictable effects. If you wish,
8005 you can specify a static variable in a particular function or file by
8006 using the colon-colon (@code{::}) notation:
8008 @cindex colon-colon, context for variables/functions
8010 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8011 @cindex @code{::}, context for variables/functions
8014 @var{file}::@var{variable}
8015 @var{function}::@var{variable}
8019 Here @var{file} or @var{function} is the name of the context for the
8020 static @var{variable}. In the case of file names, you can use quotes to
8021 make sure @value{GDBN} parses the file name as a single word---for example,
8022 to print a global value of @code{x} defined in @file{f2.c}:
8025 (@value{GDBP}) p 'f2.c'::x
8028 The @code{::} notation is normally used for referring to
8029 static variables, since you typically disambiguate uses of local variables
8030 in functions by selecting the appropriate frame and using the
8031 simple name of the variable. However, you may also use this notation
8032 to refer to local variables in frames enclosing the selected frame:
8041 process (a); /* Stop here */
8052 For example, if there is a breakpoint at the commented line,
8053 here is what you might see
8054 when the program stops after executing the call @code{bar(0)}:
8059 (@value{GDBP}) p bar::a
8062 #2 0x080483d0 in foo (a=5) at foobar.c:12
8065 (@value{GDBP}) p bar::a
8069 @cindex C@t{++} scope resolution
8070 These uses of @samp{::} are very rarely in conflict with the very similar
8071 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
8072 scope resolution operator in @value{GDBN} expressions.
8073 @c FIXME: Um, so what happens in one of those rare cases where it's in
8076 @cindex wrong values
8077 @cindex variable values, wrong
8078 @cindex function entry/exit, wrong values of variables
8079 @cindex optimized code, wrong values of variables
8081 @emph{Warning:} Occasionally, a local variable may appear to have the
8082 wrong value at certain points in a function---just after entry to a new
8083 scope, and just before exit.
8085 You may see this problem when you are stepping by machine instructions.
8086 This is because, on most machines, it takes more than one instruction to
8087 set up a stack frame (including local variable definitions); if you are
8088 stepping by machine instructions, variables may appear to have the wrong
8089 values until the stack frame is completely built. On exit, it usually
8090 also takes more than one machine instruction to destroy a stack frame;
8091 after you begin stepping through that group of instructions, local
8092 variable definitions may be gone.
8094 This may also happen when the compiler does significant optimizations.
8095 To be sure of always seeing accurate values, turn off all optimization
8098 @cindex ``No symbol "foo" in current context''
8099 Another possible effect of compiler optimizations is to optimize
8100 unused variables out of existence, or assign variables to registers (as
8101 opposed to memory addresses). Depending on the support for such cases
8102 offered by the debug info format used by the compiler, @value{GDBN}
8103 might not be able to display values for such local variables. If that
8104 happens, @value{GDBN} will print a message like this:
8107 No symbol "foo" in current context.
8110 To solve such problems, either recompile without optimizations, or use a
8111 different debug info format, if the compiler supports several such
8112 formats. @xref{Compilation}, for more information on choosing compiler
8113 options. @xref{C, ,C and C@t{++}}, for more information about debug
8114 info formats that are best suited to C@t{++} programs.
8116 If you ask to print an object whose contents are unknown to
8117 @value{GDBN}, e.g., because its data type is not completely specified
8118 by the debug information, @value{GDBN} will say @samp{<incomplete
8119 type>}. @xref{Symbols, incomplete type}, for more about this.
8121 If you append @kbd{@@entry} string to a function parameter name you get its
8122 value at the time the function got called. If the value is not available an
8123 error message is printed. Entry values are available only with some compilers.
8124 Entry values are normally also printed at the function parameter list according
8125 to @ref{set print entry-values}.
8128 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8134 (gdb) print i@@entry
8138 Strings are identified as arrays of @code{char} values without specified
8139 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8140 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8141 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8142 defines literal string type @code{"char"} as @code{char} without a sign.
8147 signed char var1[] = "A";
8150 You get during debugging
8155 $2 = @{65 'A', 0 '\0'@}
8159 @section Artificial Arrays
8161 @cindex artificial array
8163 @kindex @@@r{, referencing memory as an array}
8164 It is often useful to print out several successive objects of the
8165 same type in memory; a section of an array, or an array of
8166 dynamically determined size for which only a pointer exists in the
8169 You can do this by referring to a contiguous span of memory as an
8170 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8171 operand of @samp{@@} should be the first element of the desired array
8172 and be an individual object. The right operand should be the desired length
8173 of the array. The result is an array value whose elements are all of
8174 the type of the left argument. The first element is actually the left
8175 argument; the second element comes from bytes of memory immediately
8176 following those that hold the first element, and so on. Here is an
8177 example. If a program says
8180 int *array = (int *) malloc (len * sizeof (int));
8184 you can print the contents of @code{array} with
8190 The left operand of @samp{@@} must reside in memory. Array values made
8191 with @samp{@@} in this way behave just like other arrays in terms of
8192 subscripting, and are coerced to pointers when used in expressions.
8193 Artificial arrays most often appear in expressions via the value history
8194 (@pxref{Value History, ,Value History}), after printing one out.
8196 Another way to create an artificial array is to use a cast.
8197 This re-interprets a value as if it were an array.
8198 The value need not be in memory:
8200 (@value{GDBP}) p/x (short[2])0x12345678
8201 $1 = @{0x1234, 0x5678@}
8204 As a convenience, if you leave the array length out (as in
8205 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8206 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8208 (@value{GDBP}) p/x (short[])0x12345678
8209 $2 = @{0x1234, 0x5678@}
8212 Sometimes the artificial array mechanism is not quite enough; in
8213 moderately complex data structures, the elements of interest may not
8214 actually be adjacent---for example, if you are interested in the values
8215 of pointers in an array. One useful work-around in this situation is
8216 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8217 Variables}) as a counter in an expression that prints the first
8218 interesting value, and then repeat that expression via @key{RET}. For
8219 instance, suppose you have an array @code{dtab} of pointers to
8220 structures, and you are interested in the values of a field @code{fv}
8221 in each structure. Here is an example of what you might type:
8231 @node Output Formats
8232 @section Output Formats
8234 @cindex formatted output
8235 @cindex output formats
8236 By default, @value{GDBN} prints a value according to its data type. Sometimes
8237 this is not what you want. For example, you might want to print a number
8238 in hex, or a pointer in decimal. Or you might want to view data in memory
8239 at a certain address as a character string or as an instruction. To do
8240 these things, specify an @dfn{output format} when you print a value.
8242 The simplest use of output formats is to say how to print a value
8243 already computed. This is done by starting the arguments of the
8244 @code{print} command with a slash and a format letter. The format
8245 letters supported are:
8249 Regard the bits of the value as an integer, and print the integer in
8253 Print as integer in signed decimal.
8256 Print as integer in unsigned decimal.
8259 Print as integer in octal.
8262 Print as integer in binary. The letter @samp{t} stands for ``two''.
8263 @footnote{@samp{b} cannot be used because these format letters are also
8264 used with the @code{x} command, where @samp{b} stands for ``byte'';
8265 see @ref{Memory,,Examining Memory}.}
8268 @cindex unknown address, locating
8269 @cindex locate address
8270 Print as an address, both absolute in hexadecimal and as an offset from
8271 the nearest preceding symbol. You can use this format used to discover
8272 where (in what function) an unknown address is located:
8275 (@value{GDBP}) p/a 0x54320
8276 $3 = 0x54320 <_initialize_vx+396>
8280 The command @code{info symbol 0x54320} yields similar results.
8281 @xref{Symbols, info symbol}.
8284 Regard as an integer and print it as a character constant. This
8285 prints both the numerical value and its character representation. The
8286 character representation is replaced with the octal escape @samp{\nnn}
8287 for characters outside the 7-bit @sc{ascii} range.
8289 Without this format, @value{GDBN} displays @code{char},
8290 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8291 constants. Single-byte members of vectors are displayed as integer
8295 Regard the bits of the value as a floating point number and print
8296 using typical floating point syntax.
8299 @cindex printing strings
8300 @cindex printing byte arrays
8301 Regard as a string, if possible. With this format, pointers to single-byte
8302 data are displayed as null-terminated strings and arrays of single-byte data
8303 are displayed as fixed-length strings. Other values are displayed in their
8306 Without this format, @value{GDBN} displays pointers to and arrays of
8307 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8308 strings. Single-byte members of a vector are displayed as an integer
8312 @cindex raw printing
8313 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8314 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8315 Printing}). This typically results in a higher-level display of the
8316 value's contents. The @samp{r} format bypasses any Python
8317 pretty-printer which might exist.
8320 For example, to print the program counter in hex (@pxref{Registers}), type
8327 Note that no space is required before the slash; this is because command
8328 names in @value{GDBN} cannot contain a slash.
8330 To reprint the last value in the value history with a different format,
8331 you can use the @code{print} command with just a format and no
8332 expression. For example, @samp{p/x} reprints the last value in hex.
8335 @section Examining Memory
8337 You can use the command @code{x} (for ``examine'') to examine memory in
8338 any of several formats, independently of your program's data types.
8340 @cindex examining memory
8342 @kindex x @r{(examine memory)}
8343 @item x/@var{nfu} @var{addr}
8346 Use the @code{x} command to examine memory.
8349 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8350 much memory to display and how to format it; @var{addr} is an
8351 expression giving the address where you want to start displaying memory.
8352 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8353 Several commands set convenient defaults for @var{addr}.
8356 @item @var{n}, the repeat count
8357 The repeat count is a decimal integer; the default is 1. It specifies
8358 how much memory (counting by units @var{u}) to display.
8359 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8362 @item @var{f}, the display format
8363 The display format is one of the formats used by @code{print}
8364 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8365 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8366 The default is @samp{x} (hexadecimal) initially. The default changes
8367 each time you use either @code{x} or @code{print}.
8369 @item @var{u}, the unit size
8370 The unit size is any of
8376 Halfwords (two bytes).
8378 Words (four bytes). This is the initial default.
8380 Giant words (eight bytes).
8383 Each time you specify a unit size with @code{x}, that size becomes the
8384 default unit the next time you use @code{x}. For the @samp{i} format,
8385 the unit size is ignored and is normally not written. For the @samp{s} format,
8386 the unit size defaults to @samp{b}, unless it is explicitly given.
8387 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8388 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8389 Note that the results depend on the programming language of the
8390 current compilation unit. If the language is C, the @samp{s}
8391 modifier will use the UTF-16 encoding while @samp{w} will use
8392 UTF-32. The encoding is set by the programming language and cannot
8395 @item @var{addr}, starting display address
8396 @var{addr} is the address where you want @value{GDBN} to begin displaying
8397 memory. The expression need not have a pointer value (though it may);
8398 it is always interpreted as an integer address of a byte of memory.
8399 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8400 @var{addr} is usually just after the last address examined---but several
8401 other commands also set the default address: @code{info breakpoints} (to
8402 the address of the last breakpoint listed), @code{info line} (to the
8403 starting address of a line), and @code{print} (if you use it to display
8404 a value from memory).
8407 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8408 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8409 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8410 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8411 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8413 Since the letters indicating unit sizes are all distinct from the
8414 letters specifying output formats, you do not have to remember whether
8415 unit size or format comes first; either order works. The output
8416 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8417 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8419 Even though the unit size @var{u} is ignored for the formats @samp{s}
8420 and @samp{i}, you might still want to use a count @var{n}; for example,
8421 @samp{3i} specifies that you want to see three machine instructions,
8422 including any operands. For convenience, especially when used with
8423 the @code{display} command, the @samp{i} format also prints branch delay
8424 slot instructions, if any, beyond the count specified, which immediately
8425 follow the last instruction that is within the count. The command
8426 @code{disassemble} gives an alternative way of inspecting machine
8427 instructions; see @ref{Machine Code,,Source and Machine Code}.
8429 All the defaults for the arguments to @code{x} are designed to make it
8430 easy to continue scanning memory with minimal specifications each time
8431 you use @code{x}. For example, after you have inspected three machine
8432 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8433 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8434 the repeat count @var{n} is used again; the other arguments default as
8435 for successive uses of @code{x}.
8437 When examining machine instructions, the instruction at current program
8438 counter is shown with a @code{=>} marker. For example:
8441 (@value{GDBP}) x/5i $pc-6
8442 0x804837f <main+11>: mov %esp,%ebp
8443 0x8048381 <main+13>: push %ecx
8444 0x8048382 <main+14>: sub $0x4,%esp
8445 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8446 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8449 @cindex @code{$_}, @code{$__}, and value history
8450 The addresses and contents printed by the @code{x} command are not saved
8451 in the value history because there is often too much of them and they
8452 would get in the way. Instead, @value{GDBN} makes these values available for
8453 subsequent use in expressions as values of the convenience variables
8454 @code{$_} and @code{$__}. After an @code{x} command, the last address
8455 examined is available for use in expressions in the convenience variable
8456 @code{$_}. The contents of that address, as examined, are available in
8457 the convenience variable @code{$__}.
8459 If the @code{x} command has a repeat count, the address and contents saved
8460 are from the last memory unit printed; this is not the same as the last
8461 address printed if several units were printed on the last line of output.
8463 @cindex remote memory comparison
8464 @cindex verify remote memory image
8465 When you are debugging a program running on a remote target machine
8466 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
8467 remote machine's memory against the executable file you downloaded to
8468 the target. The @code{compare-sections} command is provided for such
8472 @kindex compare-sections
8473 @item compare-sections @r{[}@var{section-name}@r{]}
8474 Compare the data of a loadable section @var{section-name} in the
8475 executable file of the program being debugged with the same section in
8476 the remote machine's memory, and report any mismatches. With no
8477 arguments, compares all loadable sections. This command's
8478 availability depends on the target's support for the @code{"qCRC"}
8483 @section Automatic Display
8484 @cindex automatic display
8485 @cindex display of expressions
8487 If you find that you want to print the value of an expression frequently
8488 (to see how it changes), you might want to add it to the @dfn{automatic
8489 display list} so that @value{GDBN} prints its value each time your program stops.
8490 Each expression added to the list is given a number to identify it;
8491 to remove an expression from the list, you specify that number.
8492 The automatic display looks like this:
8496 3: bar[5] = (struct hack *) 0x3804
8500 This display shows item numbers, expressions and their current values. As with
8501 displays you request manually using @code{x} or @code{print}, you can
8502 specify the output format you prefer; in fact, @code{display} decides
8503 whether to use @code{print} or @code{x} depending your format
8504 specification---it uses @code{x} if you specify either the @samp{i}
8505 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
8509 @item display @var{expr}
8510 Add the expression @var{expr} to the list of expressions to display
8511 each time your program stops. @xref{Expressions, ,Expressions}.
8513 @code{display} does not repeat if you press @key{RET} again after using it.
8515 @item display/@var{fmt} @var{expr}
8516 For @var{fmt} specifying only a display format and not a size or
8517 count, add the expression @var{expr} to the auto-display list but
8518 arrange to display it each time in the specified format @var{fmt}.
8519 @xref{Output Formats,,Output Formats}.
8521 @item display/@var{fmt} @var{addr}
8522 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
8523 number of units, add the expression @var{addr} as a memory address to
8524 be examined each time your program stops. Examining means in effect
8525 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
8528 For example, @samp{display/i $pc} can be helpful, to see the machine
8529 instruction about to be executed each time execution stops (@samp{$pc}
8530 is a common name for the program counter; @pxref{Registers, ,Registers}).
8533 @kindex delete display
8535 @item undisplay @var{dnums}@dots{}
8536 @itemx delete display @var{dnums}@dots{}
8537 Remove items from the list of expressions to display. Specify the
8538 numbers of the displays that you want affected with the command
8539 argument @var{dnums}. It can be a single display number, one of the
8540 numbers shown in the first field of the @samp{info display} display;
8541 or it could be a range of display numbers, as in @code{2-4}.
8543 @code{undisplay} does not repeat if you press @key{RET} after using it.
8544 (Otherwise you would just get the error @samp{No display number @dots{}}.)
8546 @kindex disable display
8547 @item disable display @var{dnums}@dots{}
8548 Disable the display of item numbers @var{dnums}. A disabled display
8549 item is not printed automatically, but is not forgotten. It may be
8550 enabled again later. Specify the numbers of the displays that you
8551 want affected with the command argument @var{dnums}. It can be a
8552 single display number, one of the numbers shown in the first field of
8553 the @samp{info display} display; or it could be a range of display
8554 numbers, as in @code{2-4}.
8556 @kindex enable display
8557 @item enable display @var{dnums}@dots{}
8558 Enable display of item numbers @var{dnums}. It becomes effective once
8559 again in auto display of its expression, until you specify otherwise.
8560 Specify the numbers of the displays that you want affected with the
8561 command argument @var{dnums}. It can be a single display number, one
8562 of the numbers shown in the first field of the @samp{info display}
8563 display; or it could be a range of display numbers, as in @code{2-4}.
8566 Display the current values of the expressions on the list, just as is
8567 done when your program stops.
8569 @kindex info display
8571 Print the list of expressions previously set up to display
8572 automatically, each one with its item number, but without showing the
8573 values. This includes disabled expressions, which are marked as such.
8574 It also includes expressions which would not be displayed right now
8575 because they refer to automatic variables not currently available.
8578 @cindex display disabled out of scope
8579 If a display expression refers to local variables, then it does not make
8580 sense outside the lexical context for which it was set up. Such an
8581 expression is disabled when execution enters a context where one of its
8582 variables is not defined. For example, if you give the command
8583 @code{display last_char} while inside a function with an argument
8584 @code{last_char}, @value{GDBN} displays this argument while your program
8585 continues to stop inside that function. When it stops elsewhere---where
8586 there is no variable @code{last_char}---the display is disabled
8587 automatically. The next time your program stops where @code{last_char}
8588 is meaningful, you can enable the display expression once again.
8590 @node Print Settings
8591 @section Print Settings
8593 @cindex format options
8594 @cindex print settings
8595 @value{GDBN} provides the following ways to control how arrays, structures,
8596 and symbols are printed.
8599 These settings are useful for debugging programs in any language:
8603 @item set print address
8604 @itemx set print address on
8605 @cindex print/don't print memory addresses
8606 @value{GDBN} prints memory addresses showing the location of stack
8607 traces, structure values, pointer values, breakpoints, and so forth,
8608 even when it also displays the contents of those addresses. The default
8609 is @code{on}. For example, this is what a stack frame display looks like with
8610 @code{set print address on}:
8615 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
8617 530 if (lquote != def_lquote)
8621 @item set print address off
8622 Do not print addresses when displaying their contents. For example,
8623 this is the same stack frame displayed with @code{set print address off}:
8627 (@value{GDBP}) set print addr off
8629 #0 set_quotes (lq="<<", rq=">>") at input.c:530
8630 530 if (lquote != def_lquote)
8634 You can use @samp{set print address off} to eliminate all machine
8635 dependent displays from the @value{GDBN} interface. For example, with
8636 @code{print address off}, you should get the same text for backtraces on
8637 all machines---whether or not they involve pointer arguments.
8640 @item show print address
8641 Show whether or not addresses are to be printed.
8644 When @value{GDBN} prints a symbolic address, it normally prints the
8645 closest earlier symbol plus an offset. If that symbol does not uniquely
8646 identify the address (for example, it is a name whose scope is a single
8647 source file), you may need to clarify. One way to do this is with
8648 @code{info line}, for example @samp{info line *0x4537}. Alternately,
8649 you can set @value{GDBN} to print the source file and line number when
8650 it prints a symbolic address:
8653 @item set print symbol-filename on
8654 @cindex source file and line of a symbol
8655 @cindex symbol, source file and line
8656 Tell @value{GDBN} to print the source file name and line number of a
8657 symbol in the symbolic form of an address.
8659 @item set print symbol-filename off
8660 Do not print source file name and line number of a symbol. This is the
8663 @item show print symbol-filename
8664 Show whether or not @value{GDBN} will print the source file name and
8665 line number of a symbol in the symbolic form of an address.
8668 Another situation where it is helpful to show symbol filenames and line
8669 numbers is when disassembling code; @value{GDBN} shows you the line
8670 number and source file that corresponds to each instruction.
8672 Also, you may wish to see the symbolic form only if the address being
8673 printed is reasonably close to the closest earlier symbol:
8676 @item set print max-symbolic-offset @var{max-offset}
8677 @itemx set print max-symbolic-offset unlimited
8678 @cindex maximum value for offset of closest symbol
8679 Tell @value{GDBN} to only display the symbolic form of an address if the
8680 offset between the closest earlier symbol and the address is less than
8681 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
8682 to always print the symbolic form of an address if any symbol precedes
8683 it. Zero is equivalent to @code{unlimited}.
8685 @item show print max-symbolic-offset
8686 Ask how large the maximum offset is that @value{GDBN} prints in a
8690 @cindex wild pointer, interpreting
8691 @cindex pointer, finding referent
8692 If you have a pointer and you are not sure where it points, try
8693 @samp{set print symbol-filename on}. Then you can determine the name
8694 and source file location of the variable where it points, using
8695 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
8696 For example, here @value{GDBN} shows that a variable @code{ptt} points
8697 at another variable @code{t}, defined in @file{hi2.c}:
8700 (@value{GDBP}) set print symbol-filename on
8701 (@value{GDBP}) p/a ptt
8702 $4 = 0xe008 <t in hi2.c>
8706 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
8707 does not show the symbol name and filename of the referent, even with
8708 the appropriate @code{set print} options turned on.
8711 You can also enable @samp{/a}-like formatting all the time using
8712 @samp{set print symbol on}:
8715 @item set print symbol on
8716 Tell @value{GDBN} to print the symbol corresponding to an address, if
8719 @item set print symbol off
8720 Tell @value{GDBN} not to print the symbol corresponding to an
8721 address. In this mode, @value{GDBN} will still print the symbol
8722 corresponding to pointers to functions. This is the default.
8724 @item show print symbol
8725 Show whether @value{GDBN} will display the symbol corresponding to an
8729 Other settings control how different kinds of objects are printed:
8732 @item set print array
8733 @itemx set print array on
8734 @cindex pretty print arrays
8735 Pretty print arrays. This format is more convenient to read,
8736 but uses more space. The default is off.
8738 @item set print array off
8739 Return to compressed format for arrays.
8741 @item show print array
8742 Show whether compressed or pretty format is selected for displaying
8745 @cindex print array indexes
8746 @item set print array-indexes
8747 @itemx set print array-indexes on
8748 Print the index of each element when displaying arrays. May be more
8749 convenient to locate a given element in the array or quickly find the
8750 index of a given element in that printed array. The default is off.
8752 @item set print array-indexes off
8753 Stop printing element indexes when displaying arrays.
8755 @item show print array-indexes
8756 Show whether the index of each element is printed when displaying
8759 @item set print elements @var{number-of-elements}
8760 @itemx set print elements unlimited
8761 @cindex number of array elements to print
8762 @cindex limit on number of printed array elements
8763 Set a limit on how many elements of an array @value{GDBN} will print.
8764 If @value{GDBN} is printing a large array, it stops printing after it has
8765 printed the number of elements set by the @code{set print elements} command.
8766 This limit also applies to the display of strings.
8767 When @value{GDBN} starts, this limit is set to 200.
8768 Setting @var{number-of-elements} to @code{unlimited} or zero means
8769 that the number of elements to print is unlimited.
8771 @item show print elements
8772 Display the number of elements of a large array that @value{GDBN} will print.
8773 If the number is 0, then the printing is unlimited.
8775 @item set print frame-arguments @var{value}
8776 @kindex set print frame-arguments
8777 @cindex printing frame argument values
8778 @cindex print all frame argument values
8779 @cindex print frame argument values for scalars only
8780 @cindex do not print frame argument values
8781 This command allows to control how the values of arguments are printed
8782 when the debugger prints a frame (@pxref{Frames}). The possible
8787 The values of all arguments are printed.
8790 Print the value of an argument only if it is a scalar. The value of more
8791 complex arguments such as arrays, structures, unions, etc, is replaced
8792 by @code{@dots{}}. This is the default. Here is an example where
8793 only scalar arguments are shown:
8796 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
8801 None of the argument values are printed. Instead, the value of each argument
8802 is replaced by @code{@dots{}}. In this case, the example above now becomes:
8805 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
8810 By default, only scalar arguments are printed. This command can be used
8811 to configure the debugger to print the value of all arguments, regardless
8812 of their type. However, it is often advantageous to not print the value
8813 of more complex parameters. For instance, it reduces the amount of
8814 information printed in each frame, making the backtrace more readable.
8815 Also, it improves performance when displaying Ada frames, because
8816 the computation of large arguments can sometimes be CPU-intensive,
8817 especially in large applications. Setting @code{print frame-arguments}
8818 to @code{scalars} (the default) or @code{none} avoids this computation,
8819 thus speeding up the display of each Ada frame.
8821 @item show print frame-arguments
8822 Show how the value of arguments should be displayed when printing a frame.
8824 @anchor{set print entry-values}
8825 @item set print entry-values @var{value}
8826 @kindex set print entry-values
8827 Set printing of frame argument values at function entry. In some cases
8828 @value{GDBN} can determine the value of function argument which was passed by
8829 the function caller, even if the value was modified inside the called function
8830 and therefore is different. With optimized code, the current value could be
8831 unavailable, but the entry value may still be known.
8833 The default value is @code{default} (see below for its description). Older
8834 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
8835 this feature will behave in the @code{default} setting the same way as with the
8838 This functionality is currently supported only by DWARF 2 debugging format and
8839 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
8840 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
8843 The @var{value} parameter can be one of the following:
8847 Print only actual parameter values, never print values from function entry
8851 #0 different (val=6)
8852 #0 lost (val=<optimized out>)
8854 #0 invalid (val=<optimized out>)
8858 Print only parameter values from function entry point. The actual parameter
8859 values are never printed.
8861 #0 equal (val@@entry=5)
8862 #0 different (val@@entry=5)
8863 #0 lost (val@@entry=5)
8864 #0 born (val@@entry=<optimized out>)
8865 #0 invalid (val@@entry=<optimized out>)
8869 Print only parameter values from function entry point. If value from function
8870 entry point is not known while the actual value is known, print the actual
8871 value for such parameter.
8873 #0 equal (val@@entry=5)
8874 #0 different (val@@entry=5)
8875 #0 lost (val@@entry=5)
8877 #0 invalid (val@@entry=<optimized out>)
8881 Print actual parameter values. If actual parameter value is not known while
8882 value from function entry point is known, print the entry point value for such
8886 #0 different (val=6)
8887 #0 lost (val@@entry=5)
8889 #0 invalid (val=<optimized out>)
8893 Always print both the actual parameter value and its value from function entry
8894 point, even if values of one or both are not available due to compiler
8897 #0 equal (val=5, val@@entry=5)
8898 #0 different (val=6, val@@entry=5)
8899 #0 lost (val=<optimized out>, val@@entry=5)
8900 #0 born (val=10, val@@entry=<optimized out>)
8901 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
8905 Print the actual parameter value if it is known and also its value from
8906 function entry point if it is known. If neither is known, print for the actual
8907 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
8908 values are known and identical, print the shortened
8909 @code{param=param@@entry=VALUE} notation.
8911 #0 equal (val=val@@entry=5)
8912 #0 different (val=6, val@@entry=5)
8913 #0 lost (val@@entry=5)
8915 #0 invalid (val=<optimized out>)
8919 Always print the actual parameter value. Print also its value from function
8920 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
8921 if both values are known and identical, print the shortened
8922 @code{param=param@@entry=VALUE} notation.
8924 #0 equal (val=val@@entry=5)
8925 #0 different (val=6, val@@entry=5)
8926 #0 lost (val=<optimized out>, val@@entry=5)
8928 #0 invalid (val=<optimized out>)
8932 For analysis messages on possible failures of frame argument values at function
8933 entry resolution see @ref{set debug entry-values}.
8935 @item show print entry-values
8936 Show the method being used for printing of frame argument values at function
8939 @item set print repeats @var{number-of-repeats}
8940 @itemx set print repeats unlimited
8941 @cindex repeated array elements
8942 Set the threshold for suppressing display of repeated array
8943 elements. When the number of consecutive identical elements of an
8944 array exceeds the threshold, @value{GDBN} prints the string
8945 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
8946 identical repetitions, instead of displaying the identical elements
8947 themselves. Setting the threshold to @code{unlimited} or zero will
8948 cause all elements to be individually printed. The default threshold
8951 @item show print repeats
8952 Display the current threshold for printing repeated identical
8955 @item set print null-stop
8956 @cindex @sc{null} elements in arrays
8957 Cause @value{GDBN} to stop printing the characters of an array when the first
8958 @sc{null} is encountered. This is useful when large arrays actually
8959 contain only short strings.
8962 @item show print null-stop
8963 Show whether @value{GDBN} stops printing an array on the first
8964 @sc{null} character.
8966 @item set print pretty on
8967 @cindex print structures in indented form
8968 @cindex indentation in structure display
8969 Cause @value{GDBN} to print structures in an indented format with one member
8970 per line, like this:
8985 @item set print pretty off
8986 Cause @value{GDBN} to print structures in a compact format, like this:
8990 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
8991 meat = 0x54 "Pork"@}
8996 This is the default format.
8998 @item show print pretty
8999 Show which format @value{GDBN} is using to print structures.
9001 @item set print sevenbit-strings on
9002 @cindex eight-bit characters in strings
9003 @cindex octal escapes in strings
9004 Print using only seven-bit characters; if this option is set,
9005 @value{GDBN} displays any eight-bit characters (in strings or
9006 character values) using the notation @code{\}@var{nnn}. This setting is
9007 best if you are working in English (@sc{ascii}) and you use the
9008 high-order bit of characters as a marker or ``meta'' bit.
9010 @item set print sevenbit-strings off
9011 Print full eight-bit characters. This allows the use of more
9012 international character sets, and is the default.
9014 @item show print sevenbit-strings
9015 Show whether or not @value{GDBN} is printing only seven-bit characters.
9017 @item set print union on
9018 @cindex unions in structures, printing
9019 Tell @value{GDBN} to print unions which are contained in structures
9020 and other unions. This is the default setting.
9022 @item set print union off
9023 Tell @value{GDBN} not to print unions which are contained in
9024 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9027 @item show print union
9028 Ask @value{GDBN} whether or not it will print unions which are contained in
9029 structures and other unions.
9031 For example, given the declarations
9034 typedef enum @{Tree, Bug@} Species;
9035 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9036 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9047 struct thing foo = @{Tree, @{Acorn@}@};
9051 with @code{set print union on} in effect @samp{p foo} would print
9054 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9058 and with @code{set print union off} in effect it would print
9061 $1 = @{it = Tree, form = @{...@}@}
9065 @code{set print union} affects programs written in C-like languages
9071 These settings are of interest when debugging C@t{++} programs:
9074 @cindex demangling C@t{++} names
9075 @item set print demangle
9076 @itemx set print demangle on
9077 Print C@t{++} names in their source form rather than in the encoded
9078 (``mangled'') form passed to the assembler and linker for type-safe
9079 linkage. The default is on.
9081 @item show print demangle
9082 Show whether C@t{++} names are printed in mangled or demangled form.
9084 @item set print asm-demangle
9085 @itemx set print asm-demangle on
9086 Print C@t{++} names in their source form rather than their mangled form, even
9087 in assembler code printouts such as instruction disassemblies.
9090 @item show print asm-demangle
9091 Show whether C@t{++} names in assembly listings are printed in mangled
9094 @cindex C@t{++} symbol decoding style
9095 @cindex symbol decoding style, C@t{++}
9096 @kindex set demangle-style
9097 @item set demangle-style @var{style}
9098 Choose among several encoding schemes used by different compilers to
9099 represent C@t{++} names. The choices for @var{style} are currently:
9103 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9104 This is the default.
9107 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9110 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9113 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9116 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9117 @strong{Warning:} this setting alone is not sufficient to allow
9118 debugging @code{cfront}-generated executables. @value{GDBN} would
9119 require further enhancement to permit that.
9122 If you omit @var{style}, you will see a list of possible formats.
9124 @item show demangle-style
9125 Display the encoding style currently in use for decoding C@t{++} symbols.
9127 @item set print object
9128 @itemx set print object on
9129 @cindex derived type of an object, printing
9130 @cindex display derived types
9131 When displaying a pointer to an object, identify the @emph{actual}
9132 (derived) type of the object rather than the @emph{declared} type, using
9133 the virtual function table. Note that the virtual function table is
9134 required---this feature can only work for objects that have run-time
9135 type identification; a single virtual method in the object's declared
9136 type is sufficient. Note that this setting is also taken into account when
9137 working with variable objects via MI (@pxref{GDB/MI}).
9139 @item set print object off
9140 Display only the declared type of objects, without reference to the
9141 virtual function table. This is the default setting.
9143 @item show print object
9144 Show whether actual, or declared, object types are displayed.
9146 @item set print static-members
9147 @itemx set print static-members on
9148 @cindex static members of C@t{++} objects
9149 Print static members when displaying a C@t{++} object. The default is on.
9151 @item set print static-members off
9152 Do not print static members when displaying a C@t{++} object.
9154 @item show print static-members
9155 Show whether C@t{++} static members are printed or not.
9157 @item set print pascal_static-members
9158 @itemx set print pascal_static-members on
9159 @cindex static members of Pascal objects
9160 @cindex Pascal objects, static members display
9161 Print static members when displaying a Pascal object. The default is on.
9163 @item set print pascal_static-members off
9164 Do not print static members when displaying a Pascal object.
9166 @item show print pascal_static-members
9167 Show whether Pascal static members are printed or not.
9169 @c These don't work with HP ANSI C++ yet.
9170 @item set print vtbl
9171 @itemx set print vtbl on
9172 @cindex pretty print C@t{++} virtual function tables
9173 @cindex virtual functions (C@t{++}) display
9174 @cindex VTBL display
9175 Pretty print C@t{++} virtual function tables. The default is off.
9176 (The @code{vtbl} commands do not work on programs compiled with the HP
9177 ANSI C@t{++} compiler (@code{aCC}).)
9179 @item set print vtbl off
9180 Do not pretty print C@t{++} virtual function tables.
9182 @item show print vtbl
9183 Show whether C@t{++} virtual function tables are pretty printed, or not.
9186 @node Pretty Printing
9187 @section Pretty Printing
9189 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9190 Python code. It greatly simplifies the display of complex objects. This
9191 mechanism works for both MI and the CLI.
9194 * Pretty-Printer Introduction:: Introduction to pretty-printers
9195 * Pretty-Printer Example:: An example pretty-printer
9196 * Pretty-Printer Commands:: Pretty-printer commands
9199 @node Pretty-Printer Introduction
9200 @subsection Pretty-Printer Introduction
9202 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9203 registered for the value. If there is then @value{GDBN} invokes the
9204 pretty-printer to print the value. Otherwise the value is printed normally.
9206 Pretty-printers are normally named. This makes them easy to manage.
9207 The @samp{info pretty-printer} command will list all the installed
9208 pretty-printers with their names.
9209 If a pretty-printer can handle multiple data types, then its
9210 @dfn{subprinters} are the printers for the individual data types.
9211 Each such subprinter has its own name.
9212 The format of the name is @var{printer-name};@var{subprinter-name}.
9214 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9215 Typically they are automatically loaded and registered when the corresponding
9216 debug information is loaded, thus making them available without having to
9217 do anything special.
9219 There are three places where a pretty-printer can be registered.
9223 Pretty-printers registered globally are available when debugging
9227 Pretty-printers registered with a program space are available only
9228 when debugging that program.
9229 @xref{Progspaces In Python}, for more details on program spaces in Python.
9232 Pretty-printers registered with an objfile are loaded and unloaded
9233 with the corresponding objfile (e.g., shared library).
9234 @xref{Objfiles In Python}, for more details on objfiles in Python.
9237 @xref{Selecting Pretty-Printers}, for further information on how
9238 pretty-printers are selected,
9240 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9243 @node Pretty-Printer Example
9244 @subsection Pretty-Printer Example
9246 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9249 (@value{GDBP}) print s
9251 static npos = 4294967295,
9253 <std::allocator<char>> = @{
9254 <__gnu_cxx::new_allocator<char>> = @{
9255 <No data fields>@}, <No data fields>
9257 members of std::basic_string<char, std::char_traits<char>,
9258 std::allocator<char> >::_Alloc_hider:
9259 _M_p = 0x804a014 "abcd"
9264 With a pretty-printer for @code{std::string} only the contents are printed:
9267 (@value{GDBP}) print s
9271 @node Pretty-Printer Commands
9272 @subsection Pretty-Printer Commands
9273 @cindex pretty-printer commands
9276 @kindex info pretty-printer
9277 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9278 Print the list of installed pretty-printers.
9279 This includes disabled pretty-printers, which are marked as such.
9281 @var{object-regexp} is a regular expression matching the objects
9282 whose pretty-printers to list.
9283 Objects can be @code{global}, the program space's file
9284 (@pxref{Progspaces In Python}),
9285 and the object files within that program space (@pxref{Objfiles In Python}).
9286 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9287 looks up a printer from these three objects.
9289 @var{name-regexp} is a regular expression matching the name of the printers
9292 @kindex disable pretty-printer
9293 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9294 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9295 A disabled pretty-printer is not forgotten, it may be enabled again later.
9297 @kindex enable pretty-printer
9298 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9299 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9304 Suppose we have three pretty-printers installed: one from library1.so
9305 named @code{foo} that prints objects of type @code{foo}, and
9306 another from library2.so named @code{bar} that prints two types of objects,
9307 @code{bar1} and @code{bar2}.
9310 (gdb) info pretty-printer
9317 (gdb) info pretty-printer library2
9322 (gdb) disable pretty-printer library1
9324 2 of 3 printers enabled
9325 (gdb) info pretty-printer
9332 (gdb) disable pretty-printer library2 bar:bar1
9334 1 of 3 printers enabled
9335 (gdb) info pretty-printer library2
9342 (gdb) disable pretty-printer library2 bar
9344 0 of 3 printers enabled
9345 (gdb) info pretty-printer library2
9354 Note that for @code{bar} the entire printer can be disabled,
9355 as can each individual subprinter.
9358 @section Value History
9360 @cindex value history
9361 @cindex history of values printed by @value{GDBN}
9362 Values printed by the @code{print} command are saved in the @value{GDBN}
9363 @dfn{value history}. This allows you to refer to them in other expressions.
9364 Values are kept until the symbol table is re-read or discarded
9365 (for example with the @code{file} or @code{symbol-file} commands).
9366 When the symbol table changes, the value history is discarded,
9367 since the values may contain pointers back to the types defined in the
9372 @cindex history number
9373 The values printed are given @dfn{history numbers} by which you can
9374 refer to them. These are successive integers starting with one.
9375 @code{print} shows you the history number assigned to a value by
9376 printing @samp{$@var{num} = } before the value; here @var{num} is the
9379 To refer to any previous value, use @samp{$} followed by the value's
9380 history number. The way @code{print} labels its output is designed to
9381 remind you of this. Just @code{$} refers to the most recent value in
9382 the history, and @code{$$} refers to the value before that.
9383 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9384 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9385 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9387 For example, suppose you have just printed a pointer to a structure and
9388 want to see the contents of the structure. It suffices to type
9394 If you have a chain of structures where the component @code{next} points
9395 to the next one, you can print the contents of the next one with this:
9402 You can print successive links in the chain by repeating this
9403 command---which you can do by just typing @key{RET}.
9405 Note that the history records values, not expressions. If the value of
9406 @code{x} is 4 and you type these commands:
9414 then the value recorded in the value history by the @code{print} command
9415 remains 4 even though the value of @code{x} has changed.
9420 Print the last ten values in the value history, with their item numbers.
9421 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9422 values} does not change the history.
9424 @item show values @var{n}
9425 Print ten history values centered on history item number @var{n}.
9428 Print ten history values just after the values last printed. If no more
9429 values are available, @code{show values +} produces no display.
9432 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
9433 same effect as @samp{show values +}.
9435 @node Convenience Vars
9436 @section Convenience Variables
9438 @cindex convenience variables
9439 @cindex user-defined variables
9440 @value{GDBN} provides @dfn{convenience variables} that you can use within
9441 @value{GDBN} to hold on to a value and refer to it later. These variables
9442 exist entirely within @value{GDBN}; they are not part of your program, and
9443 setting a convenience variable has no direct effect on further execution
9444 of your program. That is why you can use them freely.
9446 Convenience variables are prefixed with @samp{$}. Any name preceded by
9447 @samp{$} can be used for a convenience variable, unless it is one of
9448 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
9449 (Value history references, in contrast, are @emph{numbers} preceded
9450 by @samp{$}. @xref{Value History, ,Value History}.)
9452 You can save a value in a convenience variable with an assignment
9453 expression, just as you would set a variable in your program.
9457 set $foo = *object_ptr
9461 would save in @code{$foo} the value contained in the object pointed to by
9464 Using a convenience variable for the first time creates it, but its
9465 value is @code{void} until you assign a new value. You can alter the
9466 value with another assignment at any time.
9468 Convenience variables have no fixed types. You can assign a convenience
9469 variable any type of value, including structures and arrays, even if
9470 that variable already has a value of a different type. The convenience
9471 variable, when used as an expression, has the type of its current value.
9474 @kindex show convenience
9475 @cindex show all user variables and functions
9476 @item show convenience
9477 Print a list of convenience variables used so far, and their values,
9478 as well as a list of the convenience functions.
9479 Abbreviated @code{show conv}.
9481 @kindex init-if-undefined
9482 @cindex convenience variables, initializing
9483 @item init-if-undefined $@var{variable} = @var{expression}
9484 Set a convenience variable if it has not already been set. This is useful
9485 for user-defined commands that keep some state. It is similar, in concept,
9486 to using local static variables with initializers in C (except that
9487 convenience variables are global). It can also be used to allow users to
9488 override default values used in a command script.
9490 If the variable is already defined then the expression is not evaluated so
9491 any side-effects do not occur.
9494 One of the ways to use a convenience variable is as a counter to be
9495 incremented or a pointer to be advanced. For example, to print
9496 a field from successive elements of an array of structures:
9500 print bar[$i++]->contents
9504 Repeat that command by typing @key{RET}.
9506 Some convenience variables are created automatically by @value{GDBN} and given
9507 values likely to be useful.
9510 @vindex $_@r{, convenience variable}
9512 The variable @code{$_} is automatically set by the @code{x} command to
9513 the last address examined (@pxref{Memory, ,Examining Memory}). Other
9514 commands which provide a default address for @code{x} to examine also
9515 set @code{$_} to that address; these commands include @code{info line}
9516 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
9517 except when set by the @code{x} command, in which case it is a pointer
9518 to the type of @code{$__}.
9520 @vindex $__@r{, convenience variable}
9522 The variable @code{$__} is automatically set by the @code{x} command
9523 to the value found in the last address examined. Its type is chosen
9524 to match the format in which the data was printed.
9527 @vindex $_exitcode@r{, convenience variable}
9528 The variable @code{$_exitcode} is automatically set to the exit code when
9529 the program being debugged terminates.
9532 @itemx $_probe_arg0@dots{}$_probe_arg11
9533 Arguments to a static probe. @xref{Static Probe Points}.
9536 @vindex $_sdata@r{, inspect, convenience variable}
9537 The variable @code{$_sdata} contains extra collected static tracepoint
9538 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
9539 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
9540 if extra static tracepoint data has not been collected.
9543 @vindex $_siginfo@r{, convenience variable}
9544 The variable @code{$_siginfo} contains extra signal information
9545 (@pxref{extra signal information}). Note that @code{$_siginfo}
9546 could be empty, if the application has not yet received any signals.
9547 For example, it will be empty before you execute the @code{run} command.
9550 @vindex $_tlb@r{, convenience variable}
9551 The variable @code{$_tlb} is automatically set when debugging
9552 applications running on MS-Windows in native mode or connected to
9553 gdbserver that supports the @code{qGetTIBAddr} request.
9554 @xref{General Query Packets}.
9555 This variable contains the address of the thread information block.
9559 On HP-UX systems, if you refer to a function or variable name that
9560 begins with a dollar sign, @value{GDBN} searches for a user or system
9561 name first, before it searches for a convenience variable.
9563 @node Convenience Funs
9564 @section Convenience Functions
9566 @cindex convenience functions
9567 @value{GDBN} also supplies some @dfn{convenience functions}. These
9568 have a syntax similar to convenience variables. A convenience
9569 function can be used in an expression just like an ordinary function;
9570 however, a convenience function is implemented internally to
9573 These functions require @value{GDBN} to be configured with
9574 @code{Python} support.
9578 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
9579 @findex $_memeq@r{, convenience function}
9580 Returns one if the @var{length} bytes at the addresses given by
9581 @var{buf1} and @var{buf2} are equal.
9582 Otherwise it returns zero.
9584 @item $_regex(@var{str}, @var{regex})
9585 @findex $_regex@r{, convenience function}
9586 Returns one if the string @var{str} matches the regular expression
9587 @var{regex}. Otherwise it returns zero.
9588 The syntax of the regular expression is that specified by @code{Python}'s
9589 regular expression support.
9591 @item $_streq(@var{str1}, @var{str2})
9592 @findex $_streq@r{, convenience function}
9593 Returns one if the strings @var{str1} and @var{str2} are equal.
9594 Otherwise it returns zero.
9596 @item $_strlen(@var{str})
9597 @findex $_strlen@r{, convenience function}
9598 Returns the length of string @var{str}.
9602 @value{GDBN} provides the ability to list and get help on
9603 convenience functions.
9607 @kindex help function
9608 @cindex show all convenience functions
9609 Print a list of all convenience functions.
9616 You can refer to machine register contents, in expressions, as variables
9617 with names starting with @samp{$}. The names of registers are different
9618 for each machine; use @code{info registers} to see the names used on
9622 @kindex info registers
9623 @item info registers
9624 Print the names and values of all registers except floating-point
9625 and vector registers (in the selected stack frame).
9627 @kindex info all-registers
9628 @cindex floating point registers
9629 @item info all-registers
9630 Print the names and values of all registers, including floating-point
9631 and vector registers (in the selected stack frame).
9633 @item info registers @var{regname} @dots{}
9634 Print the @dfn{relativized} value of each specified register @var{regname}.
9635 As discussed in detail below, register values are normally relative to
9636 the selected stack frame. @var{regname} may be any register name valid on
9637 the machine you are using, with or without the initial @samp{$}.
9640 @cindex stack pointer register
9641 @cindex program counter register
9642 @cindex process status register
9643 @cindex frame pointer register
9644 @cindex standard registers
9645 @value{GDBN} has four ``standard'' register names that are available (in
9646 expressions) on most machines---whenever they do not conflict with an
9647 architecture's canonical mnemonics for registers. The register names
9648 @code{$pc} and @code{$sp} are used for the program counter register and
9649 the stack pointer. @code{$fp} is used for a register that contains a
9650 pointer to the current stack frame, and @code{$ps} is used for a
9651 register that contains the processor status. For example,
9652 you could print the program counter in hex with
9659 or print the instruction to be executed next with
9666 or add four to the stack pointer@footnote{This is a way of removing
9667 one word from the stack, on machines where stacks grow downward in
9668 memory (most machines, nowadays). This assumes that the innermost
9669 stack frame is selected; setting @code{$sp} is not allowed when other
9670 stack frames are selected. To pop entire frames off the stack,
9671 regardless of machine architecture, use @code{return};
9672 see @ref{Returning, ,Returning from a Function}.} with
9678 Whenever possible, these four standard register names are available on
9679 your machine even though the machine has different canonical mnemonics,
9680 so long as there is no conflict. The @code{info registers} command
9681 shows the canonical names. For example, on the SPARC, @code{info
9682 registers} displays the processor status register as @code{$psr} but you
9683 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
9684 is an alias for the @sc{eflags} register.
9686 @value{GDBN} always considers the contents of an ordinary register as an
9687 integer when the register is examined in this way. Some machines have
9688 special registers which can hold nothing but floating point; these
9689 registers are considered to have floating point values. There is no way
9690 to refer to the contents of an ordinary register as floating point value
9691 (although you can @emph{print} it as a floating point value with
9692 @samp{print/f $@var{regname}}).
9694 Some registers have distinct ``raw'' and ``virtual'' data formats. This
9695 means that the data format in which the register contents are saved by
9696 the operating system is not the same one that your program normally
9697 sees. For example, the registers of the 68881 floating point
9698 coprocessor are always saved in ``extended'' (raw) format, but all C
9699 programs expect to work with ``double'' (virtual) format. In such
9700 cases, @value{GDBN} normally works with the virtual format only (the format
9701 that makes sense for your program), but the @code{info registers} command
9702 prints the data in both formats.
9704 @cindex SSE registers (x86)
9705 @cindex MMX registers (x86)
9706 Some machines have special registers whose contents can be interpreted
9707 in several different ways. For example, modern x86-based machines
9708 have SSE and MMX registers that can hold several values packed
9709 together in several different formats. @value{GDBN} refers to such
9710 registers in @code{struct} notation:
9713 (@value{GDBP}) print $xmm1
9715 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
9716 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
9717 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
9718 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
9719 v4_int32 = @{0, 20657912, 11, 13@},
9720 v2_int64 = @{88725056443645952, 55834574859@},
9721 uint128 = 0x0000000d0000000b013b36f800000000
9726 To set values of such registers, you need to tell @value{GDBN} which
9727 view of the register you wish to change, as if you were assigning
9728 value to a @code{struct} member:
9731 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
9734 Normally, register values are relative to the selected stack frame
9735 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
9736 value that the register would contain if all stack frames farther in
9737 were exited and their saved registers restored. In order to see the
9738 true contents of hardware registers, you must select the innermost
9739 frame (with @samp{frame 0}).
9741 However, @value{GDBN} must deduce where registers are saved, from the machine
9742 code generated by your compiler. If some registers are not saved, or if
9743 @value{GDBN} is unable to locate the saved registers, the selected stack
9744 frame makes no difference.
9746 @node Floating Point Hardware
9747 @section Floating Point Hardware
9748 @cindex floating point
9750 Depending on the configuration, @value{GDBN} may be able to give
9751 you more information about the status of the floating point hardware.
9756 Display hardware-dependent information about the floating
9757 point unit. The exact contents and layout vary depending on the
9758 floating point chip. Currently, @samp{info float} is supported on
9759 the ARM and x86 machines.
9763 @section Vector Unit
9766 Depending on the configuration, @value{GDBN} may be able to give you
9767 more information about the status of the vector unit.
9772 Display information about the vector unit. The exact contents and
9773 layout vary depending on the hardware.
9776 @node OS Information
9777 @section Operating System Auxiliary Information
9778 @cindex OS information
9780 @value{GDBN} provides interfaces to useful OS facilities that can help
9781 you debug your program.
9783 @cindex auxiliary vector
9784 @cindex vector, auxiliary
9785 Some operating systems supply an @dfn{auxiliary vector} to programs at
9786 startup. This is akin to the arguments and environment that you
9787 specify for a program, but contains a system-dependent variety of
9788 binary values that tell system libraries important details about the
9789 hardware, operating system, and process. Each value's purpose is
9790 identified by an integer tag; the meanings are well-known but system-specific.
9791 Depending on the configuration and operating system facilities,
9792 @value{GDBN} may be able to show you this information. For remote
9793 targets, this functionality may further depend on the remote stub's
9794 support of the @samp{qXfer:auxv:read} packet, see
9795 @ref{qXfer auxiliary vector read}.
9800 Display the auxiliary vector of the inferior, which can be either a
9801 live process or a core dump file. @value{GDBN} prints each tag value
9802 numerically, and also shows names and text descriptions for recognized
9803 tags. Some values in the vector are numbers, some bit masks, and some
9804 pointers to strings or other data. @value{GDBN} displays each value in the
9805 most appropriate form for a recognized tag, and in hexadecimal for
9806 an unrecognized tag.
9809 On some targets, @value{GDBN} can access operating system-specific
9810 information and show it to you. The types of information available
9811 will differ depending on the type of operating system running on the
9812 target. The mechanism used to fetch the data is described in
9813 @ref{Operating System Information}. For remote targets, this
9814 functionality depends on the remote stub's support of the
9815 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
9819 @item info os @var{infotype}
9821 Display OS information of the requested type.
9823 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
9825 @anchor{linux info os infotypes}
9827 @kindex info os processes
9829 Display the list of processes on the target. For each process,
9830 @value{GDBN} prints the process identifier, the name of the user, the
9831 command corresponding to the process, and the list of processor cores
9832 that the process is currently running on. (To understand what these
9833 properties mean, for this and the following info types, please consult
9834 the general @sc{gnu}/Linux documentation.)
9836 @kindex info os procgroups
9838 Display the list of process groups on the target. For each process,
9839 @value{GDBN} prints the identifier of the process group that it belongs
9840 to, the command corresponding to the process group leader, the process
9841 identifier, and the command line of the process. The list is sorted
9842 first by the process group identifier, then by the process identifier,
9843 so that processes belonging to the same process group are grouped together
9844 and the process group leader is listed first.
9846 @kindex info os threads
9848 Display the list of threads running on the target. For each thread,
9849 @value{GDBN} prints the identifier of the process that the thread
9850 belongs to, the command of the process, the thread identifier, and the
9851 processor core that it is currently running on. The main thread of a
9852 process is not listed.
9854 @kindex info os files
9856 Display the list of open file descriptors on the target. For each
9857 file descriptor, @value{GDBN} prints the identifier of the process
9858 owning the descriptor, the command of the owning process, the value
9859 of the descriptor, and the target of the descriptor.
9861 @kindex info os sockets
9863 Display the list of Internet-domain sockets on the target. For each
9864 socket, @value{GDBN} prints the address and port of the local and
9865 remote endpoints, the current state of the connection, the creator of
9866 the socket, the IP address family of the socket, and the type of the
9871 Display the list of all System V shared-memory regions on the target.
9872 For each shared-memory region, @value{GDBN} prints the region key,
9873 the shared-memory identifier, the access permissions, the size of the
9874 region, the process that created the region, the process that last
9875 attached to or detached from the region, the current number of live
9876 attaches to the region, and the times at which the region was last
9877 attached to, detach from, and changed.
9879 @kindex info os semaphores
9881 Display the list of all System V semaphore sets on the target. For each
9882 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
9883 set identifier, the access permissions, the number of semaphores in the
9884 set, the user and group of the owner and creator of the semaphore set,
9885 and the times at which the semaphore set was operated upon and changed.
9889 Display the list of all System V message queues on the target. For each
9890 message queue, @value{GDBN} prints the message queue key, the message
9891 queue identifier, the access permissions, the current number of bytes
9892 on the queue, the current number of messages on the queue, the processes
9893 that last sent and received a message on the queue, the user and group
9894 of the owner and creator of the message queue, the times at which a
9895 message was last sent and received on the queue, and the time at which
9896 the message queue was last changed.
9898 @kindex info os modules
9900 Display the list of all loaded kernel modules on the target. For each
9901 module, @value{GDBN} prints the module name, the size of the module in
9902 bytes, the number of times the module is used, the dependencies of the
9903 module, the status of the module, and the address of the loaded module
9908 If @var{infotype} is omitted, then list the possible values for
9909 @var{infotype} and the kind of OS information available for each
9910 @var{infotype}. If the target does not return a list of possible
9911 types, this command will report an error.
9914 @node Memory Region Attributes
9915 @section Memory Region Attributes
9916 @cindex memory region attributes
9918 @dfn{Memory region attributes} allow you to describe special handling
9919 required by regions of your target's memory. @value{GDBN} uses
9920 attributes to determine whether to allow certain types of memory
9921 accesses; whether to use specific width accesses; and whether to cache
9922 target memory. By default the description of memory regions is
9923 fetched from the target (if the current target supports this), but the
9924 user can override the fetched regions.
9926 Defined memory regions can be individually enabled and disabled. When a
9927 memory region is disabled, @value{GDBN} uses the default attributes when
9928 accessing memory in that region. Similarly, if no memory regions have
9929 been defined, @value{GDBN} uses the default attributes when accessing
9932 When a memory region is defined, it is given a number to identify it;
9933 to enable, disable, or remove a memory region, you specify that number.
9937 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
9938 Define a memory region bounded by @var{lower} and @var{upper} with
9939 attributes @var{attributes}@dots{}, and add it to the list of regions
9940 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
9941 case: it is treated as the target's maximum memory address.
9942 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
9945 Discard any user changes to the memory regions and use target-supplied
9946 regions, if available, or no regions if the target does not support.
9949 @item delete mem @var{nums}@dots{}
9950 Remove memory regions @var{nums}@dots{} from the list of regions
9951 monitored by @value{GDBN}.
9954 @item disable mem @var{nums}@dots{}
9955 Disable monitoring of memory regions @var{nums}@dots{}.
9956 A disabled memory region is not forgotten.
9957 It may be enabled again later.
9960 @item enable mem @var{nums}@dots{}
9961 Enable monitoring of memory regions @var{nums}@dots{}.
9965 Print a table of all defined memory regions, with the following columns
9969 @item Memory Region Number
9970 @item Enabled or Disabled.
9971 Enabled memory regions are marked with @samp{y}.
9972 Disabled memory regions are marked with @samp{n}.
9975 The address defining the inclusive lower bound of the memory region.
9978 The address defining the exclusive upper bound of the memory region.
9981 The list of attributes set for this memory region.
9986 @subsection Attributes
9988 @subsubsection Memory Access Mode
9989 The access mode attributes set whether @value{GDBN} may make read or
9990 write accesses to a memory region.
9992 While these attributes prevent @value{GDBN} from performing invalid
9993 memory accesses, they do nothing to prevent the target system, I/O DMA,
9994 etc.@: from accessing memory.
9998 Memory is read only.
10000 Memory is write only.
10002 Memory is read/write. This is the default.
10005 @subsubsection Memory Access Size
10006 The access size attribute tells @value{GDBN} to use specific sized
10007 accesses in the memory region. Often memory mapped device registers
10008 require specific sized accesses. If no access size attribute is
10009 specified, @value{GDBN} may use accesses of any size.
10013 Use 8 bit memory accesses.
10015 Use 16 bit memory accesses.
10017 Use 32 bit memory accesses.
10019 Use 64 bit memory accesses.
10022 @c @subsubsection Hardware/Software Breakpoints
10023 @c The hardware/software breakpoint attributes set whether @value{GDBN}
10024 @c will use hardware or software breakpoints for the internal breakpoints
10025 @c used by the step, next, finish, until, etc. commands.
10029 @c Always use hardware breakpoints
10030 @c @item swbreak (default)
10033 @subsubsection Data Cache
10034 The data cache attributes set whether @value{GDBN} will cache target
10035 memory. While this generally improves performance by reducing debug
10036 protocol overhead, it can lead to incorrect results because @value{GDBN}
10037 does not know about volatile variables or memory mapped device
10042 Enable @value{GDBN} to cache target memory.
10044 Disable @value{GDBN} from caching target memory. This is the default.
10047 @subsection Memory Access Checking
10048 @value{GDBN} can be instructed to refuse accesses to memory that is
10049 not explicitly described. This can be useful if accessing such
10050 regions has undesired effects for a specific target, or to provide
10051 better error checking. The following commands control this behaviour.
10054 @kindex set mem inaccessible-by-default
10055 @item set mem inaccessible-by-default [on|off]
10056 If @code{on} is specified, make @value{GDBN} treat memory not
10057 explicitly described by the memory ranges as non-existent and refuse accesses
10058 to such memory. The checks are only performed if there's at least one
10059 memory range defined. If @code{off} is specified, make @value{GDBN}
10060 treat the memory not explicitly described by the memory ranges as RAM.
10061 The default value is @code{on}.
10062 @kindex show mem inaccessible-by-default
10063 @item show mem inaccessible-by-default
10064 Show the current handling of accesses to unknown memory.
10068 @c @subsubsection Memory Write Verification
10069 @c The memory write verification attributes set whether @value{GDBN}
10070 @c will re-reads data after each write to verify the write was successful.
10074 @c @item noverify (default)
10077 @node Dump/Restore Files
10078 @section Copy Between Memory and a File
10079 @cindex dump/restore files
10080 @cindex append data to a file
10081 @cindex dump data to a file
10082 @cindex restore data from a file
10084 You can use the commands @code{dump}, @code{append}, and
10085 @code{restore} to copy data between target memory and a file. The
10086 @code{dump} and @code{append} commands write data to a file, and the
10087 @code{restore} command reads data from a file back into the inferior's
10088 memory. Files may be in binary, Motorola S-record, Intel hex, or
10089 Tektronix Hex format; however, @value{GDBN} can only append to binary
10095 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10096 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
10097 Dump the contents of memory from @var{start_addr} to @var{end_addr},
10098 or the value of @var{expr}, to @var{filename} in the given format.
10100 The @var{format} parameter may be any one of:
10107 Motorola S-record format.
10109 Tektronix Hex format.
10112 @value{GDBN} uses the same definitions of these formats as the
10113 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
10114 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
10118 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10119 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
10120 Append the contents of memory from @var{start_addr} to @var{end_addr},
10121 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
10122 (@value{GDBN} can only append data to files in raw binary form.)
10125 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
10126 Restore the contents of file @var{filename} into memory. The
10127 @code{restore} command can automatically recognize any known @sc{bfd}
10128 file format, except for raw binary. To restore a raw binary file you
10129 must specify the optional keyword @code{binary} after the filename.
10131 If @var{bias} is non-zero, its value will be added to the addresses
10132 contained in the file. Binary files always start at address zero, so
10133 they will be restored at address @var{bias}. Other bfd files have
10134 a built-in location; they will be restored at offset @var{bias}
10135 from that location.
10137 If @var{start} and/or @var{end} are non-zero, then only data between
10138 file offset @var{start} and file offset @var{end} will be restored.
10139 These offsets are relative to the addresses in the file, before
10140 the @var{bias} argument is applied.
10144 @node Core File Generation
10145 @section How to Produce a Core File from Your Program
10146 @cindex dump core from inferior
10148 A @dfn{core file} or @dfn{core dump} is a file that records the memory
10149 image of a running process and its process status (register values
10150 etc.). Its primary use is post-mortem debugging of a program that
10151 crashed while it ran outside a debugger. A program that crashes
10152 automatically produces a core file, unless this feature is disabled by
10153 the user. @xref{Files}, for information on invoking @value{GDBN} in
10154 the post-mortem debugging mode.
10156 Occasionally, you may wish to produce a core file of the program you
10157 are debugging in order to preserve a snapshot of its state.
10158 @value{GDBN} has a special command for that.
10162 @kindex generate-core-file
10163 @item generate-core-file [@var{file}]
10164 @itemx gcore [@var{file}]
10165 Produce a core dump of the inferior process. The optional argument
10166 @var{file} specifies the file name where to put the core dump. If not
10167 specified, the file name defaults to @file{core.@var{pid}}, where
10168 @var{pid} is the inferior process ID.
10170 Note that this command is implemented only for some systems (as of
10171 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
10174 @node Character Sets
10175 @section Character Sets
10176 @cindex character sets
10178 @cindex translating between character sets
10179 @cindex host character set
10180 @cindex target character set
10182 If the program you are debugging uses a different character set to
10183 represent characters and strings than the one @value{GDBN} uses itself,
10184 @value{GDBN} can automatically translate between the character sets for
10185 you. The character set @value{GDBN} uses we call the @dfn{host
10186 character set}; the one the inferior program uses we call the
10187 @dfn{target character set}.
10189 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
10190 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
10191 remote protocol (@pxref{Remote Debugging}) to debug a program
10192 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
10193 then the host character set is Latin-1, and the target character set is
10194 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
10195 target-charset EBCDIC-US}, then @value{GDBN} translates between
10196 @sc{ebcdic} and Latin 1 as you print character or string values, or use
10197 character and string literals in expressions.
10199 @value{GDBN} has no way to automatically recognize which character set
10200 the inferior program uses; you must tell it, using the @code{set
10201 target-charset} command, described below.
10203 Here are the commands for controlling @value{GDBN}'s character set
10207 @item set target-charset @var{charset}
10208 @kindex set target-charset
10209 Set the current target character set to @var{charset}. To display the
10210 list of supported target character sets, type
10211 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
10213 @item set host-charset @var{charset}
10214 @kindex set host-charset
10215 Set the current host character set to @var{charset}.
10217 By default, @value{GDBN} uses a host character set appropriate to the
10218 system it is running on; you can override that default using the
10219 @code{set host-charset} command. On some systems, @value{GDBN} cannot
10220 automatically determine the appropriate host character set. In this
10221 case, @value{GDBN} uses @samp{UTF-8}.
10223 @value{GDBN} can only use certain character sets as its host character
10224 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
10225 @value{GDBN} will list the host character sets it supports.
10227 @item set charset @var{charset}
10228 @kindex set charset
10229 Set the current host and target character sets to @var{charset}. As
10230 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
10231 @value{GDBN} will list the names of the character sets that can be used
10232 for both host and target.
10235 @kindex show charset
10236 Show the names of the current host and target character sets.
10238 @item show host-charset
10239 @kindex show host-charset
10240 Show the name of the current host character set.
10242 @item show target-charset
10243 @kindex show target-charset
10244 Show the name of the current target character set.
10246 @item set target-wide-charset @var{charset}
10247 @kindex set target-wide-charset
10248 Set the current target's wide character set to @var{charset}. This is
10249 the character set used by the target's @code{wchar_t} type. To
10250 display the list of supported wide character sets, type
10251 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
10253 @item show target-wide-charset
10254 @kindex show target-wide-charset
10255 Show the name of the current target's wide character set.
10258 Here is an example of @value{GDBN}'s character set support in action.
10259 Assume that the following source code has been placed in the file
10260 @file{charset-test.c}:
10266 = @{72, 101, 108, 108, 111, 44, 32, 119,
10267 111, 114, 108, 100, 33, 10, 0@};
10268 char ibm1047_hello[]
10269 = @{200, 133, 147, 147, 150, 107, 64, 166,
10270 150, 153, 147, 132, 90, 37, 0@};
10274 printf ("Hello, world!\n");
10278 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
10279 containing the string @samp{Hello, world!} followed by a newline,
10280 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
10282 We compile the program, and invoke the debugger on it:
10285 $ gcc -g charset-test.c -o charset-test
10286 $ gdb -nw charset-test
10287 GNU gdb 2001-12-19-cvs
10288 Copyright 2001 Free Software Foundation, Inc.
10293 We can use the @code{show charset} command to see what character sets
10294 @value{GDBN} is currently using to interpret and display characters and
10298 (@value{GDBP}) show charset
10299 The current host and target character set is `ISO-8859-1'.
10303 For the sake of printing this manual, let's use @sc{ascii} as our
10304 initial character set:
10306 (@value{GDBP}) set charset ASCII
10307 (@value{GDBP}) show charset
10308 The current host and target character set is `ASCII'.
10312 Let's assume that @sc{ascii} is indeed the correct character set for our
10313 host system --- in other words, let's assume that if @value{GDBN} prints
10314 characters using the @sc{ascii} character set, our terminal will display
10315 them properly. Since our current target character set is also
10316 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
10319 (@value{GDBP}) print ascii_hello
10320 $1 = 0x401698 "Hello, world!\n"
10321 (@value{GDBP}) print ascii_hello[0]
10326 @value{GDBN} uses the target character set for character and string
10327 literals you use in expressions:
10330 (@value{GDBP}) print '+'
10335 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
10338 @value{GDBN} relies on the user to tell it which character set the
10339 target program uses. If we print @code{ibm1047_hello} while our target
10340 character set is still @sc{ascii}, we get jibberish:
10343 (@value{GDBP}) print ibm1047_hello
10344 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
10345 (@value{GDBP}) print ibm1047_hello[0]
10350 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
10351 @value{GDBN} tells us the character sets it supports:
10354 (@value{GDBP}) set target-charset
10355 ASCII EBCDIC-US IBM1047 ISO-8859-1
10356 (@value{GDBP}) set target-charset
10359 We can select @sc{ibm1047} as our target character set, and examine the
10360 program's strings again. Now the @sc{ascii} string is wrong, but
10361 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
10362 target character set, @sc{ibm1047}, to the host character set,
10363 @sc{ascii}, and they display correctly:
10366 (@value{GDBP}) set target-charset IBM1047
10367 (@value{GDBP}) show charset
10368 The current host character set is `ASCII'.
10369 The current target character set is `IBM1047'.
10370 (@value{GDBP}) print ascii_hello
10371 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
10372 (@value{GDBP}) print ascii_hello[0]
10374 (@value{GDBP}) print ibm1047_hello
10375 $8 = 0x4016a8 "Hello, world!\n"
10376 (@value{GDBP}) print ibm1047_hello[0]
10381 As above, @value{GDBN} uses the target character set for character and
10382 string literals you use in expressions:
10385 (@value{GDBP}) print '+'
10390 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
10393 @node Caching Remote Data
10394 @section Caching Data of Remote Targets
10395 @cindex caching data of remote targets
10397 @value{GDBN} caches data exchanged between the debugger and a
10398 remote target (@pxref{Remote Debugging}). Such caching generally improves
10399 performance, because it reduces the overhead of the remote protocol by
10400 bundling memory reads and writes into large chunks. Unfortunately, simply
10401 caching everything would lead to incorrect results, since @value{GDBN}
10402 does not necessarily know anything about volatile values, memory-mapped I/O
10403 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
10404 memory can be changed @emph{while} a gdb command is executing.
10405 Therefore, by default, @value{GDBN} only caches data
10406 known to be on the stack@footnote{In non-stop mode, it is moderately
10407 rare for a running thread to modify the stack of a stopped thread
10408 in a way that would interfere with a backtrace, and caching of
10409 stack reads provides a significant speed up of remote backtraces.}.
10410 Other regions of memory can be explicitly marked as
10411 cacheable; see @pxref{Memory Region Attributes}.
10414 @kindex set remotecache
10415 @item set remotecache on
10416 @itemx set remotecache off
10417 This option no longer does anything; it exists for compatibility
10420 @kindex show remotecache
10421 @item show remotecache
10422 Show the current state of the obsolete remotecache flag.
10424 @kindex set stack-cache
10425 @item set stack-cache on
10426 @itemx set stack-cache off
10427 Enable or disable caching of stack accesses. When @code{ON}, use
10428 caching. By default, this option is @code{ON}.
10430 @kindex show stack-cache
10431 @item show stack-cache
10432 Show the current state of data caching for memory accesses.
10434 @kindex info dcache
10435 @item info dcache @r{[}line@r{]}
10436 Print the information about the data cache performance. The
10437 information displayed includes the dcache width and depth, and for
10438 each cache line, its number, address, and how many times it was
10439 referenced. This command is useful for debugging the data cache
10442 If a line number is specified, the contents of that line will be
10445 @item set dcache size @var{size}
10446 @cindex dcache size
10447 @kindex set dcache size
10448 Set maximum number of entries in dcache (dcache depth above).
10450 @item set dcache line-size @var{line-size}
10451 @cindex dcache line-size
10452 @kindex set dcache line-size
10453 Set number of bytes each dcache entry caches (dcache width above).
10454 Must be a power of 2.
10456 @item show dcache size
10457 @kindex show dcache size
10458 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
10460 @item show dcache line-size
10461 @kindex show dcache line-size
10462 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
10466 @node Searching Memory
10467 @section Search Memory
10468 @cindex searching memory
10470 Memory can be searched for a particular sequence of bytes with the
10471 @code{find} command.
10475 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10476 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10477 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
10478 etc. The search begins at address @var{start_addr} and continues for either
10479 @var{len} bytes or through to @var{end_addr} inclusive.
10482 @var{s} and @var{n} are optional parameters.
10483 They may be specified in either order, apart or together.
10486 @item @var{s}, search query size
10487 The size of each search query value.
10493 halfwords (two bytes)
10497 giant words (eight bytes)
10500 All values are interpreted in the current language.
10501 This means, for example, that if the current source language is C/C@t{++}
10502 then searching for the string ``hello'' includes the trailing '\0'.
10504 If the value size is not specified, it is taken from the
10505 value's type in the current language.
10506 This is useful when one wants to specify the search
10507 pattern as a mixture of types.
10508 Note that this means, for example, that in the case of C-like languages
10509 a search for an untyped 0x42 will search for @samp{(int) 0x42}
10510 which is typically four bytes.
10512 @item @var{n}, maximum number of finds
10513 The maximum number of matches to print. The default is to print all finds.
10516 You can use strings as search values. Quote them with double-quotes
10518 The string value is copied into the search pattern byte by byte,
10519 regardless of the endianness of the target and the size specification.
10521 The address of each match found is printed as well as a count of the
10522 number of matches found.
10524 The address of the last value found is stored in convenience variable
10526 A count of the number of matches is stored in @samp{$numfound}.
10528 For example, if stopped at the @code{printf} in this function:
10534 static char hello[] = "hello-hello";
10535 static struct @{ char c; short s; int i; @}
10536 __attribute__ ((packed)) mixed
10537 = @{ 'c', 0x1234, 0x87654321 @};
10538 printf ("%s\n", hello);
10543 you get during debugging:
10546 (gdb) find &hello[0], +sizeof(hello), "hello"
10547 0x804956d <hello.1620+6>
10549 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
10550 0x8049567 <hello.1620>
10551 0x804956d <hello.1620+6>
10553 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
10554 0x8049567 <hello.1620>
10556 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
10557 0x8049560 <mixed.1625>
10559 (gdb) print $numfound
10562 $2 = (void *) 0x8049560
10565 @node Optimized Code
10566 @chapter Debugging Optimized Code
10567 @cindex optimized code, debugging
10568 @cindex debugging optimized code
10570 Almost all compilers support optimization. With optimization
10571 disabled, the compiler generates assembly code that corresponds
10572 directly to your source code, in a simplistic way. As the compiler
10573 applies more powerful optimizations, the generated assembly code
10574 diverges from your original source code. With help from debugging
10575 information generated by the compiler, @value{GDBN} can map from
10576 the running program back to constructs from your original source.
10578 @value{GDBN} is more accurate with optimization disabled. If you
10579 can recompile without optimization, it is easier to follow the
10580 progress of your program during debugging. But, there are many cases
10581 where you may need to debug an optimized version.
10583 When you debug a program compiled with @samp{-g -O}, remember that the
10584 optimizer has rearranged your code; the debugger shows you what is
10585 really there. Do not be too surprised when the execution path does not
10586 exactly match your source file! An extreme example: if you define a
10587 variable, but never use it, @value{GDBN} never sees that
10588 variable---because the compiler optimizes it out of existence.
10590 Some things do not work as well with @samp{-g -O} as with just
10591 @samp{-g}, particularly on machines with instruction scheduling. If in
10592 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
10593 please report it to us as a bug (including a test case!).
10594 @xref{Variables}, for more information about debugging optimized code.
10597 * Inline Functions:: How @value{GDBN} presents inlining
10598 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
10601 @node Inline Functions
10602 @section Inline Functions
10603 @cindex inline functions, debugging
10605 @dfn{Inlining} is an optimization that inserts a copy of the function
10606 body directly at each call site, instead of jumping to a shared
10607 routine. @value{GDBN} displays inlined functions just like
10608 non-inlined functions. They appear in backtraces. You can view their
10609 arguments and local variables, step into them with @code{step}, skip
10610 them with @code{next}, and escape from them with @code{finish}.
10611 You can check whether a function was inlined by using the
10612 @code{info frame} command.
10614 For @value{GDBN} to support inlined functions, the compiler must
10615 record information about inlining in the debug information ---
10616 @value{NGCC} using the @sc{dwarf 2} format does this, and several
10617 other compilers do also. @value{GDBN} only supports inlined functions
10618 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
10619 do not emit two required attributes (@samp{DW_AT_call_file} and
10620 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
10621 function calls with earlier versions of @value{NGCC}. It instead
10622 displays the arguments and local variables of inlined functions as
10623 local variables in the caller.
10625 The body of an inlined function is directly included at its call site;
10626 unlike a non-inlined function, there are no instructions devoted to
10627 the call. @value{GDBN} still pretends that the call site and the
10628 start of the inlined function are different instructions. Stepping to
10629 the call site shows the call site, and then stepping again shows
10630 the first line of the inlined function, even though no additional
10631 instructions are executed.
10633 This makes source-level debugging much clearer; you can see both the
10634 context of the call and then the effect of the call. Only stepping by
10635 a single instruction using @code{stepi} or @code{nexti} does not do
10636 this; single instruction steps always show the inlined body.
10638 There are some ways that @value{GDBN} does not pretend that inlined
10639 function calls are the same as normal calls:
10643 Setting breakpoints at the call site of an inlined function may not
10644 work, because the call site does not contain any code. @value{GDBN}
10645 may incorrectly move the breakpoint to the next line of the enclosing
10646 function, after the call. This limitation will be removed in a future
10647 version of @value{GDBN}; until then, set a breakpoint on an earlier line
10648 or inside the inlined function instead.
10651 @value{GDBN} cannot locate the return value of inlined calls after
10652 using the @code{finish} command. This is a limitation of compiler-generated
10653 debugging information; after @code{finish}, you can step to the next line
10654 and print a variable where your program stored the return value.
10658 @node Tail Call Frames
10659 @section Tail Call Frames
10660 @cindex tail call frames, debugging
10662 Function @code{B} can call function @code{C} in its very last statement. In
10663 unoptimized compilation the call of @code{C} is immediately followed by return
10664 instruction at the end of @code{B} code. Optimizing compiler may replace the
10665 call and return in function @code{B} into one jump to function @code{C}
10666 instead. Such use of a jump instruction is called @dfn{tail call}.
10668 During execution of function @code{C}, there will be no indication in the
10669 function call stack frames that it was tail-called from @code{B}. If function
10670 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
10671 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
10672 some cases @value{GDBN} can determine that @code{C} was tail-called from
10673 @code{B}, and it will then create fictitious call frame for that, with the
10674 return address set up as if @code{B} called @code{C} normally.
10676 This functionality is currently supported only by DWARF 2 debugging format and
10677 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
10678 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10681 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
10682 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
10686 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
10688 Stack level 1, frame at 0x7fffffffda30:
10689 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
10690 tail call frame, caller of frame at 0x7fffffffda30
10691 source language c++.
10692 Arglist at unknown address.
10693 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
10696 The detection of all the possible code path executions can find them ambiguous.
10697 There is no execution history stored (possible @ref{Reverse Execution} is never
10698 used for this purpose) and the last known caller could have reached the known
10699 callee by multiple different jump sequences. In such case @value{GDBN} still
10700 tries to show at least all the unambiguous top tail callers and all the
10701 unambiguous bottom tail calees, if any.
10704 @anchor{set debug entry-values}
10705 @item set debug entry-values
10706 @kindex set debug entry-values
10707 When set to on, enables printing of analysis messages for both frame argument
10708 values at function entry and tail calls. It will show all the possible valid
10709 tail calls code paths it has considered. It will also print the intersection
10710 of them with the final unambiguous (possibly partial or even empty) code path
10713 @item show debug entry-values
10714 @kindex show debug entry-values
10715 Show the current state of analysis messages printing for both frame argument
10716 values at function entry and tail calls.
10719 The analysis messages for tail calls can for example show why the virtual tail
10720 call frame for function @code{c} has not been recognized (due to the indirect
10721 reference by variable @code{x}):
10724 static void __attribute__((noinline, noclone)) c (void);
10725 void (*x) (void) = c;
10726 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10727 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
10728 int main (void) @{ x (); return 0; @}
10730 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
10731 DW_TAG_GNU_call_site 0x40039a in main
10733 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10736 #1 0x000000000040039a in main () at t.c:5
10739 Another possibility is an ambiguous virtual tail call frames resolution:
10743 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
10744 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
10745 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
10746 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
10747 static void __attribute__((noinline, noclone)) b (void)
10748 @{ if (i) c (); else e (); @}
10749 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
10750 int main (void) @{ a (); return 0; @}
10752 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
10753 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
10754 tailcall: reduced: 0x4004d2(a) |
10757 #1 0x00000000004004d2 in a () at t.c:8
10758 #2 0x0000000000400395 in main () at t.c:9
10761 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
10762 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
10764 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
10765 @ifset HAVE_MAKEINFO_CLICK
10766 @set ARROW @click{}
10767 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
10768 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
10770 @ifclear HAVE_MAKEINFO_CLICK
10772 @set CALLSEQ1B @value{CALLSEQ1A}
10773 @set CALLSEQ2B @value{CALLSEQ2A}
10776 Frames #0 and #2 are real, #1 is a virtual tail call frame.
10777 The code can have possible execution paths @value{CALLSEQ1B} or
10778 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
10780 @code{initial:} state shows some random possible calling sequence @value{GDBN}
10781 has found. It then finds another possible calling sequcen - that one is
10782 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
10783 printed as the @code{reduced:} calling sequence. That one could have many
10784 futher @code{compare:} and @code{reduced:} statements as long as there remain
10785 any non-ambiguous sequence entries.
10787 For the frame of function @code{b} in both cases there are different possible
10788 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
10789 also ambigous. The only non-ambiguous frame is the one for function @code{a},
10790 therefore this one is displayed to the user while the ambiguous frames are
10793 There can be also reasons why printing of frame argument values at function
10798 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
10799 static void __attribute__((noinline, noclone)) a (int i);
10800 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
10801 static void __attribute__((noinline, noclone)) a (int i)
10802 @{ if (i) b (i - 1); else c (0); @}
10803 int main (void) @{ a (5); return 0; @}
10806 #0 c (i=i@@entry=0) at t.c:2
10807 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
10808 function "a" at 0x400420 can call itself via tail calls
10809 i=<optimized out>) at t.c:6
10810 #2 0x000000000040036e in main () at t.c:7
10813 @value{GDBN} cannot find out from the inferior state if and how many times did
10814 function @code{a} call itself (via function @code{b}) as these calls would be
10815 tail calls. Such tail calls would modify thue @code{i} variable, therefore
10816 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
10817 prints @code{<optimized out>} instead.
10820 @chapter C Preprocessor Macros
10822 Some languages, such as C and C@t{++}, provide a way to define and invoke
10823 ``preprocessor macros'' which expand into strings of tokens.
10824 @value{GDBN} can evaluate expressions containing macro invocations, show
10825 the result of macro expansion, and show a macro's definition, including
10826 where it was defined.
10828 You may need to compile your program specially to provide @value{GDBN}
10829 with information about preprocessor macros. Most compilers do not
10830 include macros in their debugging information, even when you compile
10831 with the @option{-g} flag. @xref{Compilation}.
10833 A program may define a macro at one point, remove that definition later,
10834 and then provide a different definition after that. Thus, at different
10835 points in the program, a macro may have different definitions, or have
10836 no definition at all. If there is a current stack frame, @value{GDBN}
10837 uses the macros in scope at that frame's source code line. Otherwise,
10838 @value{GDBN} uses the macros in scope at the current listing location;
10841 Whenever @value{GDBN} evaluates an expression, it always expands any
10842 macro invocations present in the expression. @value{GDBN} also provides
10843 the following commands for working with macros explicitly.
10847 @kindex macro expand
10848 @cindex macro expansion, showing the results of preprocessor
10849 @cindex preprocessor macro expansion, showing the results of
10850 @cindex expanding preprocessor macros
10851 @item macro expand @var{expression}
10852 @itemx macro exp @var{expression}
10853 Show the results of expanding all preprocessor macro invocations in
10854 @var{expression}. Since @value{GDBN} simply expands macros, but does
10855 not parse the result, @var{expression} need not be a valid expression;
10856 it can be any string of tokens.
10859 @item macro expand-once @var{expression}
10860 @itemx macro exp1 @var{expression}
10861 @cindex expand macro once
10862 @i{(This command is not yet implemented.)} Show the results of
10863 expanding those preprocessor macro invocations that appear explicitly in
10864 @var{expression}. Macro invocations appearing in that expansion are
10865 left unchanged. This command allows you to see the effect of a
10866 particular macro more clearly, without being confused by further
10867 expansions. Since @value{GDBN} simply expands macros, but does not
10868 parse the result, @var{expression} need not be a valid expression; it
10869 can be any string of tokens.
10872 @cindex macro definition, showing
10873 @cindex definition of a macro, showing
10874 @cindex macros, from debug info
10875 @item info macro [-a|-all] [--] @var{macro}
10876 Show the current definition or all definitions of the named @var{macro},
10877 and describe the source location or compiler command-line where that
10878 definition was established. The optional double dash is to signify the end of
10879 argument processing and the beginning of @var{macro} for non C-like macros where
10880 the macro may begin with a hyphen.
10882 @kindex info macros
10883 @item info macros @var{linespec}
10884 Show all macro definitions that are in effect at the location specified
10885 by @var{linespec}, and describe the source location or compiler
10886 command-line where those definitions were established.
10888 @kindex macro define
10889 @cindex user-defined macros
10890 @cindex defining macros interactively
10891 @cindex macros, user-defined
10892 @item macro define @var{macro} @var{replacement-list}
10893 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
10894 Introduce a definition for a preprocessor macro named @var{macro},
10895 invocations of which are replaced by the tokens given in
10896 @var{replacement-list}. The first form of this command defines an
10897 ``object-like'' macro, which takes no arguments; the second form
10898 defines a ``function-like'' macro, which takes the arguments given in
10901 A definition introduced by this command is in scope in every
10902 expression evaluated in @value{GDBN}, until it is removed with the
10903 @code{macro undef} command, described below. The definition overrides
10904 all definitions for @var{macro} present in the program being debugged,
10905 as well as any previous user-supplied definition.
10907 @kindex macro undef
10908 @item macro undef @var{macro}
10909 Remove any user-supplied definition for the macro named @var{macro}.
10910 This command only affects definitions provided with the @code{macro
10911 define} command, described above; it cannot remove definitions present
10912 in the program being debugged.
10916 List all the macros defined using the @code{macro define} command.
10919 @cindex macros, example of debugging with
10920 Here is a transcript showing the above commands in action. First, we
10921 show our source files:
10926 #include "sample.h"
10929 #define ADD(x) (M + x)
10934 printf ("Hello, world!\n");
10936 printf ("We're so creative.\n");
10938 printf ("Goodbye, world!\n");
10945 Now, we compile the program using the @sc{gnu} C compiler,
10946 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
10947 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
10948 and @option{-gdwarf-4}; we recommend always choosing the most recent
10949 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
10950 includes information about preprocessor macros in the debugging
10954 $ gcc -gdwarf-2 -g3 sample.c -o sample
10958 Now, we start @value{GDBN} on our sample program:
10962 GNU gdb 2002-05-06-cvs
10963 Copyright 2002 Free Software Foundation, Inc.
10964 GDB is free software, @dots{}
10968 We can expand macros and examine their definitions, even when the
10969 program is not running. @value{GDBN} uses the current listing position
10970 to decide which macro definitions are in scope:
10973 (@value{GDBP}) list main
10976 5 #define ADD(x) (M + x)
10981 10 printf ("Hello, world!\n");
10983 12 printf ("We're so creative.\n");
10984 (@value{GDBP}) info macro ADD
10985 Defined at /home/jimb/gdb/macros/play/sample.c:5
10986 #define ADD(x) (M + x)
10987 (@value{GDBP}) info macro Q
10988 Defined at /home/jimb/gdb/macros/play/sample.h:1
10989 included at /home/jimb/gdb/macros/play/sample.c:2
10991 (@value{GDBP}) macro expand ADD(1)
10992 expands to: (42 + 1)
10993 (@value{GDBP}) macro expand-once ADD(1)
10994 expands to: once (M + 1)
10998 In the example above, note that @code{macro expand-once} expands only
10999 the macro invocation explicit in the original text --- the invocation of
11000 @code{ADD} --- but does not expand the invocation of the macro @code{M},
11001 which was introduced by @code{ADD}.
11003 Once the program is running, @value{GDBN} uses the macro definitions in
11004 force at the source line of the current stack frame:
11007 (@value{GDBP}) break main
11008 Breakpoint 1 at 0x8048370: file sample.c, line 10.
11010 Starting program: /home/jimb/gdb/macros/play/sample
11012 Breakpoint 1, main () at sample.c:10
11013 10 printf ("Hello, world!\n");
11017 At line 10, the definition of the macro @code{N} at line 9 is in force:
11020 (@value{GDBP}) info macro N
11021 Defined at /home/jimb/gdb/macros/play/sample.c:9
11023 (@value{GDBP}) macro expand N Q M
11024 expands to: 28 < 42
11025 (@value{GDBP}) print N Q M
11030 As we step over directives that remove @code{N}'s definition, and then
11031 give it a new definition, @value{GDBN} finds the definition (or lack
11032 thereof) in force at each point:
11035 (@value{GDBP}) next
11037 12 printf ("We're so creative.\n");
11038 (@value{GDBP}) info macro N
11039 The symbol `N' has no definition as a C/C++ preprocessor macro
11040 at /home/jimb/gdb/macros/play/sample.c:12
11041 (@value{GDBP}) next
11043 14 printf ("Goodbye, world!\n");
11044 (@value{GDBP}) info macro N
11045 Defined at /home/jimb/gdb/macros/play/sample.c:13
11047 (@value{GDBP}) macro expand N Q M
11048 expands to: 1729 < 42
11049 (@value{GDBP}) print N Q M
11054 In addition to source files, macros can be defined on the compilation command
11055 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
11056 such a way, @value{GDBN} displays the location of their definition as line zero
11057 of the source file submitted to the compiler.
11060 (@value{GDBP}) info macro __STDC__
11061 Defined at /home/jimb/gdb/macros/play/sample.c:0
11068 @chapter Tracepoints
11069 @c This chapter is based on the documentation written by Michael
11070 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
11072 @cindex tracepoints
11073 In some applications, it is not feasible for the debugger to interrupt
11074 the program's execution long enough for the developer to learn
11075 anything helpful about its behavior. If the program's correctness
11076 depends on its real-time behavior, delays introduced by a debugger
11077 might cause the program to change its behavior drastically, or perhaps
11078 fail, even when the code itself is correct. It is useful to be able
11079 to observe the program's behavior without interrupting it.
11081 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
11082 specify locations in the program, called @dfn{tracepoints}, and
11083 arbitrary expressions to evaluate when those tracepoints are reached.
11084 Later, using the @code{tfind} command, you can examine the values
11085 those expressions had when the program hit the tracepoints. The
11086 expressions may also denote objects in memory---structures or arrays,
11087 for example---whose values @value{GDBN} should record; while visiting
11088 a particular tracepoint, you may inspect those objects as if they were
11089 in memory at that moment. However, because @value{GDBN} records these
11090 values without interacting with you, it can do so quickly and
11091 unobtrusively, hopefully not disturbing the program's behavior.
11093 The tracepoint facility is currently available only for remote
11094 targets. @xref{Targets}. In addition, your remote target must know
11095 how to collect trace data. This functionality is implemented in the
11096 remote stub; however, none of the stubs distributed with @value{GDBN}
11097 support tracepoints as of this writing. The format of the remote
11098 packets used to implement tracepoints are described in @ref{Tracepoint
11101 It is also possible to get trace data from a file, in a manner reminiscent
11102 of corefiles; you specify the filename, and use @code{tfind} to search
11103 through the file. @xref{Trace Files}, for more details.
11105 This chapter describes the tracepoint commands and features.
11108 * Set Tracepoints::
11109 * Analyze Collected Data::
11110 * Tracepoint Variables::
11114 @node Set Tracepoints
11115 @section Commands to Set Tracepoints
11117 Before running such a @dfn{trace experiment}, an arbitrary number of
11118 tracepoints can be set. A tracepoint is actually a special type of
11119 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
11120 standard breakpoint commands. For instance, as with breakpoints,
11121 tracepoint numbers are successive integers starting from one, and many
11122 of the commands associated with tracepoints take the tracepoint number
11123 as their argument, to identify which tracepoint to work on.
11125 For each tracepoint, you can specify, in advance, some arbitrary set
11126 of data that you want the target to collect in the trace buffer when
11127 it hits that tracepoint. The collected data can include registers,
11128 local variables, or global data. Later, you can use @value{GDBN}
11129 commands to examine the values these data had at the time the
11130 tracepoint was hit.
11132 Tracepoints do not support every breakpoint feature. Ignore counts on
11133 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
11134 commands when they are hit. Tracepoints may not be thread-specific
11137 @cindex fast tracepoints
11138 Some targets may support @dfn{fast tracepoints}, which are inserted in
11139 a different way (such as with a jump instead of a trap), that is
11140 faster but possibly restricted in where they may be installed.
11142 @cindex static tracepoints
11143 @cindex markers, static tracepoints
11144 @cindex probing markers, static tracepoints
11145 Regular and fast tracepoints are dynamic tracing facilities, meaning
11146 that they can be used to insert tracepoints at (almost) any location
11147 in the target. Some targets may also support controlling @dfn{static
11148 tracepoints} from @value{GDBN}. With static tracing, a set of
11149 instrumentation points, also known as @dfn{markers}, are embedded in
11150 the target program, and can be activated or deactivated by name or
11151 address. These are usually placed at locations which facilitate
11152 investigating what the target is actually doing. @value{GDBN}'s
11153 support for static tracing includes being able to list instrumentation
11154 points, and attach them with @value{GDBN} defined high level
11155 tracepoints that expose the whole range of convenience of
11156 @value{GDBN}'s tracepoints support. Namely, support for collecting
11157 registers values and values of global or local (to the instrumentation
11158 point) variables; tracepoint conditions and trace state variables.
11159 The act of installing a @value{GDBN} static tracepoint on an
11160 instrumentation point, or marker, is referred to as @dfn{probing} a
11161 static tracepoint marker.
11163 @code{gdbserver} supports tracepoints on some target systems.
11164 @xref{Server,,Tracepoints support in @code{gdbserver}}.
11166 This section describes commands to set tracepoints and associated
11167 conditions and actions.
11170 * Create and Delete Tracepoints::
11171 * Enable and Disable Tracepoints::
11172 * Tracepoint Passcounts::
11173 * Tracepoint Conditions::
11174 * Trace State Variables::
11175 * Tracepoint Actions::
11176 * Listing Tracepoints::
11177 * Listing Static Tracepoint Markers::
11178 * Starting and Stopping Trace Experiments::
11179 * Tracepoint Restrictions::
11182 @node Create and Delete Tracepoints
11183 @subsection Create and Delete Tracepoints
11186 @cindex set tracepoint
11188 @item trace @var{location}
11189 The @code{trace} command is very similar to the @code{break} command.
11190 Its argument @var{location} can be a source line, a function name, or
11191 an address in the target program. @xref{Specify Location}. The
11192 @code{trace} command defines a tracepoint, which is a point in the
11193 target program where the debugger will briefly stop, collect some
11194 data, and then allow the program to continue. Setting a tracepoint or
11195 changing its actions takes effect immediately if the remote stub
11196 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
11198 If remote stub doesn't support the @samp{InstallInTrace} feature, all
11199 these changes don't take effect until the next @code{tstart}
11200 command, and once a trace experiment is running, further changes will
11201 not have any effect until the next trace experiment starts. In addition,
11202 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
11203 address is not yet resolved. (This is similar to pending breakpoints.)
11204 Pending tracepoints are not downloaded to the target and not installed
11205 until they are resolved. The resolution of pending tracepoints requires
11206 @value{GDBN} support---when debugging with the remote target, and
11207 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
11208 tracing}), pending tracepoints can not be resolved (and downloaded to
11209 the remote stub) while @value{GDBN} is disconnected.
11211 Here are some examples of using the @code{trace} command:
11214 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
11216 (@value{GDBP}) @b{trace +2} // 2 lines forward
11218 (@value{GDBP}) @b{trace my_function} // first source line of function
11220 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
11222 (@value{GDBP}) @b{trace *0x2117c4} // an address
11226 You can abbreviate @code{trace} as @code{tr}.
11228 @item trace @var{location} if @var{cond}
11229 Set a tracepoint with condition @var{cond}; evaluate the expression
11230 @var{cond} each time the tracepoint is reached, and collect data only
11231 if the value is nonzero---that is, if @var{cond} evaluates as true.
11232 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
11233 information on tracepoint conditions.
11235 @item ftrace @var{location} [ if @var{cond} ]
11236 @cindex set fast tracepoint
11237 @cindex fast tracepoints, setting
11239 The @code{ftrace} command sets a fast tracepoint. For targets that
11240 support them, fast tracepoints will use a more efficient but possibly
11241 less general technique to trigger data collection, such as a jump
11242 instruction instead of a trap, or some sort of hardware support. It
11243 may not be possible to create a fast tracepoint at the desired
11244 location, in which case the command will exit with an explanatory
11247 @value{GDBN} handles arguments to @code{ftrace} exactly as for
11250 On 32-bit x86-architecture systems, fast tracepoints normally need to
11251 be placed at an instruction that is 5 bytes or longer, but can be
11252 placed at 4-byte instructions if the low 64K of memory of the target
11253 program is available to install trampolines. Some Unix-type systems,
11254 such as @sc{gnu}/Linux, exclude low addresses from the program's
11255 address space; but for instance with the Linux kernel it is possible
11256 to let @value{GDBN} use this area by doing a @command{sysctl} command
11257 to set the @code{mmap_min_addr} kernel parameter, as in
11260 sudo sysctl -w vm.mmap_min_addr=32768
11264 which sets the low address to 32K, which leaves plenty of room for
11265 trampolines. The minimum address should be set to a page boundary.
11267 @item strace @var{location} [ if @var{cond} ]
11268 @cindex set static tracepoint
11269 @cindex static tracepoints, setting
11270 @cindex probe static tracepoint marker
11272 The @code{strace} command sets a static tracepoint. For targets that
11273 support it, setting a static tracepoint probes a static
11274 instrumentation point, or marker, found at @var{location}. It may not
11275 be possible to set a static tracepoint at the desired location, in
11276 which case the command will exit with an explanatory message.
11278 @value{GDBN} handles arguments to @code{strace} exactly as for
11279 @code{trace}, with the addition that the user can also specify
11280 @code{-m @var{marker}} as @var{location}. This probes the marker
11281 identified by the @var{marker} string identifier. This identifier
11282 depends on the static tracepoint backend library your program is
11283 using. You can find all the marker identifiers in the @samp{ID} field
11284 of the @code{info static-tracepoint-markers} command output.
11285 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
11286 Markers}. For example, in the following small program using the UST
11292 trace_mark(ust, bar33, "str %s", "FOOBAZ");
11297 the marker id is composed of joining the first two arguments to the
11298 @code{trace_mark} call with a slash, which translates to:
11301 (@value{GDBP}) info static-tracepoint-markers
11302 Cnt Enb ID Address What
11303 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
11309 so you may probe the marker above with:
11312 (@value{GDBP}) strace -m ust/bar33
11315 Static tracepoints accept an extra collect action --- @code{collect
11316 $_sdata}. This collects arbitrary user data passed in the probe point
11317 call to the tracing library. In the UST example above, you'll see
11318 that the third argument to @code{trace_mark} is a printf-like format
11319 string. The user data is then the result of running that formating
11320 string against the following arguments. Note that @code{info
11321 static-tracepoint-markers} command output lists that format string in
11322 the @samp{Data:} field.
11324 You can inspect this data when analyzing the trace buffer, by printing
11325 the $_sdata variable like any other variable available to
11326 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
11329 @cindex last tracepoint number
11330 @cindex recent tracepoint number
11331 @cindex tracepoint number
11332 The convenience variable @code{$tpnum} records the tracepoint number
11333 of the most recently set tracepoint.
11335 @kindex delete tracepoint
11336 @cindex tracepoint deletion
11337 @item delete tracepoint @r{[}@var{num}@r{]}
11338 Permanently delete one or more tracepoints. With no argument, the
11339 default is to delete all tracepoints. Note that the regular
11340 @code{delete} command can remove tracepoints also.
11345 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
11347 (@value{GDBP}) @b{delete trace} // remove all tracepoints
11351 You can abbreviate this command as @code{del tr}.
11354 @node Enable and Disable Tracepoints
11355 @subsection Enable and Disable Tracepoints
11357 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
11360 @kindex disable tracepoint
11361 @item disable tracepoint @r{[}@var{num}@r{]}
11362 Disable tracepoint @var{num}, or all tracepoints if no argument
11363 @var{num} is given. A disabled tracepoint will have no effect during
11364 a trace experiment, but it is not forgotten. You can re-enable
11365 a disabled tracepoint using the @code{enable tracepoint} command.
11366 If the command is issued during a trace experiment and the debug target
11367 has support for disabling tracepoints during a trace experiment, then the
11368 change will be effective immediately. Otherwise, it will be applied to the
11369 next trace experiment.
11371 @kindex enable tracepoint
11372 @item enable tracepoint @r{[}@var{num}@r{]}
11373 Enable tracepoint @var{num}, or all tracepoints. If this command is
11374 issued during a trace experiment and the debug target supports enabling
11375 tracepoints during a trace experiment, then the enabled tracepoints will
11376 become effective immediately. Otherwise, they will become effective the
11377 next time a trace experiment is run.
11380 @node Tracepoint Passcounts
11381 @subsection Tracepoint Passcounts
11385 @cindex tracepoint pass count
11386 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
11387 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
11388 automatically stop a trace experiment. If a tracepoint's passcount is
11389 @var{n}, then the trace experiment will be automatically stopped on
11390 the @var{n}'th time that tracepoint is hit. If the tracepoint number
11391 @var{num} is not specified, the @code{passcount} command sets the
11392 passcount of the most recently defined tracepoint. If no passcount is
11393 given, the trace experiment will run until stopped explicitly by the
11399 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
11400 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
11402 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
11403 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
11404 (@value{GDBP}) @b{trace foo}
11405 (@value{GDBP}) @b{pass 3}
11406 (@value{GDBP}) @b{trace bar}
11407 (@value{GDBP}) @b{pass 2}
11408 (@value{GDBP}) @b{trace baz}
11409 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
11410 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
11411 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
11412 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
11416 @node Tracepoint Conditions
11417 @subsection Tracepoint Conditions
11418 @cindex conditional tracepoints
11419 @cindex tracepoint conditions
11421 The simplest sort of tracepoint collects data every time your program
11422 reaches a specified place. You can also specify a @dfn{condition} for
11423 a tracepoint. A condition is just a Boolean expression in your
11424 programming language (@pxref{Expressions, ,Expressions}). A
11425 tracepoint with a condition evaluates the expression each time your
11426 program reaches it, and data collection happens only if the condition
11429 Tracepoint conditions can be specified when a tracepoint is set, by
11430 using @samp{if} in the arguments to the @code{trace} command.
11431 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
11432 also be set or changed at any time with the @code{condition} command,
11433 just as with breakpoints.
11435 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
11436 the conditional expression itself. Instead, @value{GDBN} encodes the
11437 expression into an agent expression (@pxref{Agent Expressions})
11438 suitable for execution on the target, independently of @value{GDBN}.
11439 Global variables become raw memory locations, locals become stack
11440 accesses, and so forth.
11442 For instance, suppose you have a function that is usually called
11443 frequently, but should not be called after an error has occurred. You
11444 could use the following tracepoint command to collect data about calls
11445 of that function that happen while the error code is propagating
11446 through the program; an unconditional tracepoint could end up
11447 collecting thousands of useless trace frames that you would have to
11451 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
11454 @node Trace State Variables
11455 @subsection Trace State Variables
11456 @cindex trace state variables
11458 A @dfn{trace state variable} is a special type of variable that is
11459 created and managed by target-side code. The syntax is the same as
11460 that for GDB's convenience variables (a string prefixed with ``$''),
11461 but they are stored on the target. They must be created explicitly,
11462 using a @code{tvariable} command. They are always 64-bit signed
11465 Trace state variables are remembered by @value{GDBN}, and downloaded
11466 to the target along with tracepoint information when the trace
11467 experiment starts. There are no intrinsic limits on the number of
11468 trace state variables, beyond memory limitations of the target.
11470 @cindex convenience variables, and trace state variables
11471 Although trace state variables are managed by the target, you can use
11472 them in print commands and expressions as if they were convenience
11473 variables; @value{GDBN} will get the current value from the target
11474 while the trace experiment is running. Trace state variables share
11475 the same namespace as other ``$'' variables, which means that you
11476 cannot have trace state variables with names like @code{$23} or
11477 @code{$pc}, nor can you have a trace state variable and a convenience
11478 variable with the same name.
11482 @item tvariable $@var{name} [ = @var{expression} ]
11484 The @code{tvariable} command creates a new trace state variable named
11485 @code{$@var{name}}, and optionally gives it an initial value of
11486 @var{expression}. @var{expression} is evaluated when this command is
11487 entered; the result will be converted to an integer if possible,
11488 otherwise @value{GDBN} will report an error. A subsequent
11489 @code{tvariable} command specifying the same name does not create a
11490 variable, but instead assigns the supplied initial value to the
11491 existing variable of that name, overwriting any previous initial
11492 value. The default initial value is 0.
11494 @item info tvariables
11495 @kindex info tvariables
11496 List all the trace state variables along with their initial values.
11497 Their current values may also be displayed, if the trace experiment is
11500 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
11501 @kindex delete tvariable
11502 Delete the given trace state variables, or all of them if no arguments
11507 @node Tracepoint Actions
11508 @subsection Tracepoint Action Lists
11512 @cindex tracepoint actions
11513 @item actions @r{[}@var{num}@r{]}
11514 This command will prompt for a list of actions to be taken when the
11515 tracepoint is hit. If the tracepoint number @var{num} is not
11516 specified, this command sets the actions for the one that was most
11517 recently defined (so that you can define a tracepoint and then say
11518 @code{actions} without bothering about its number). You specify the
11519 actions themselves on the following lines, one action at a time, and
11520 terminate the actions list with a line containing just @code{end}. So
11521 far, the only defined actions are @code{collect}, @code{teval}, and
11522 @code{while-stepping}.
11524 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
11525 Commands, ,Breakpoint Command Lists}), except that only the defined
11526 actions are allowed; any other @value{GDBN} command is rejected.
11528 @cindex remove actions from a tracepoint
11529 To remove all actions from a tracepoint, type @samp{actions @var{num}}
11530 and follow it immediately with @samp{end}.
11533 (@value{GDBP}) @b{collect @var{data}} // collect some data
11535 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
11537 (@value{GDBP}) @b{end} // signals the end of actions.
11540 In the following example, the action list begins with @code{collect}
11541 commands indicating the things to be collected when the tracepoint is
11542 hit. Then, in order to single-step and collect additional data
11543 following the tracepoint, a @code{while-stepping} command is used,
11544 followed by the list of things to be collected after each step in a
11545 sequence of single steps. The @code{while-stepping} command is
11546 terminated by its own separate @code{end} command. Lastly, the action
11547 list is terminated by an @code{end} command.
11550 (@value{GDBP}) @b{trace foo}
11551 (@value{GDBP}) @b{actions}
11552 Enter actions for tracepoint 1, one per line:
11555 > while-stepping 12
11556 > collect $pc, arr[i]
11561 @kindex collect @r{(tracepoints)}
11562 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
11563 Collect values of the given expressions when the tracepoint is hit.
11564 This command accepts a comma-separated list of any valid expressions.
11565 In addition to global, static, or local variables, the following
11566 special arguments are supported:
11570 Collect all registers.
11573 Collect all function arguments.
11576 Collect all local variables.
11579 Collect the return address. This is helpful if you want to see more
11583 Collects the number of arguments from the static probe at which the
11584 tracepoint is located.
11585 @xref{Static Probe Points}.
11587 @item $_probe_arg@var{n}
11588 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
11589 from the static probe at which the tracepoint is located.
11590 @xref{Static Probe Points}.
11593 @vindex $_sdata@r{, collect}
11594 Collect static tracepoint marker specific data. Only available for
11595 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
11596 Lists}. On the UST static tracepoints library backend, an
11597 instrumentation point resembles a @code{printf} function call. The
11598 tracing library is able to collect user specified data formatted to a
11599 character string using the format provided by the programmer that
11600 instrumented the program. Other backends have similar mechanisms.
11601 Here's an example of a UST marker call:
11604 const char master_name[] = "$your_name";
11605 trace_mark(channel1, marker1, "hello %s", master_name)
11608 In this case, collecting @code{$_sdata} collects the string
11609 @samp{hello $yourname}. When analyzing the trace buffer, you can
11610 inspect @samp{$_sdata} like any other variable available to
11614 You can give several consecutive @code{collect} commands, each one
11615 with a single argument, or one @code{collect} command with several
11616 arguments separated by commas; the effect is the same.
11618 The optional @var{mods} changes the usual handling of the arguments.
11619 @code{s} requests that pointers to chars be handled as strings, in
11620 particular collecting the contents of the memory being pointed at, up
11621 to the first zero. The upper bound is by default the value of the
11622 @code{print elements} variable; if @code{s} is followed by a decimal
11623 number, that is the upper bound instead. So for instance
11624 @samp{collect/s25 mystr} collects as many as 25 characters at
11627 The command @code{info scope} (@pxref{Symbols, info scope}) is
11628 particularly useful for figuring out what data to collect.
11630 @kindex teval @r{(tracepoints)}
11631 @item teval @var{expr1}, @var{expr2}, @dots{}
11632 Evaluate the given expressions when the tracepoint is hit. This
11633 command accepts a comma-separated list of expressions. The results
11634 are discarded, so this is mainly useful for assigning values to trace
11635 state variables (@pxref{Trace State Variables}) without adding those
11636 values to the trace buffer, as would be the case if the @code{collect}
11639 @kindex while-stepping @r{(tracepoints)}
11640 @item while-stepping @var{n}
11641 Perform @var{n} single-step instruction traces after the tracepoint,
11642 collecting new data after each step. The @code{while-stepping}
11643 command is followed by the list of what to collect while stepping
11644 (followed by its own @code{end} command):
11647 > while-stepping 12
11648 > collect $regs, myglobal
11654 Note that @code{$pc} is not automatically collected by
11655 @code{while-stepping}; you need to explicitly collect that register if
11656 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
11659 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
11660 @kindex set default-collect
11661 @cindex default collection action
11662 This variable is a list of expressions to collect at each tracepoint
11663 hit. It is effectively an additional @code{collect} action prepended
11664 to every tracepoint action list. The expressions are parsed
11665 individually for each tracepoint, so for instance a variable named
11666 @code{xyz} may be interpreted as a global for one tracepoint, and a
11667 local for another, as appropriate to the tracepoint's location.
11669 @item show default-collect
11670 @kindex show default-collect
11671 Show the list of expressions that are collected by default at each
11676 @node Listing Tracepoints
11677 @subsection Listing Tracepoints
11680 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
11681 @kindex info tp @r{[}@var{n}@dots{}@r{]}
11682 @cindex information about tracepoints
11683 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
11684 Display information about the tracepoint @var{num}. If you don't
11685 specify a tracepoint number, displays information about all the
11686 tracepoints defined so far. The format is similar to that used for
11687 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
11688 command, simply restricting itself to tracepoints.
11690 A tracepoint's listing may include additional information specific to
11695 its passcount as given by the @code{passcount @var{n}} command
11698 the state about installed on target of each location
11702 (@value{GDBP}) @b{info trace}
11703 Num Type Disp Enb Address What
11704 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
11706 collect globfoo, $regs
11711 2 tracepoint keep y <MULTIPLE>
11713 2.1 y 0x0804859c in func4 at change-loc.h:35
11714 installed on target
11715 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
11716 installed on target
11717 2.3 y <PENDING> set_tracepoint
11718 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
11719 not installed on target
11724 This command can be abbreviated @code{info tp}.
11727 @node Listing Static Tracepoint Markers
11728 @subsection Listing Static Tracepoint Markers
11731 @kindex info static-tracepoint-markers
11732 @cindex information about static tracepoint markers
11733 @item info static-tracepoint-markers
11734 Display information about all static tracepoint markers defined in the
11737 For each marker, the following columns are printed:
11741 An incrementing counter, output to help readability. This is not a
11744 The marker ID, as reported by the target.
11745 @item Enabled or Disabled
11746 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
11747 that are not enabled.
11749 Where the marker is in your program, as a memory address.
11751 Where the marker is in the source for your program, as a file and line
11752 number. If the debug information included in the program does not
11753 allow @value{GDBN} to locate the source of the marker, this column
11754 will be left blank.
11758 In addition, the following information may be printed for each marker:
11762 User data passed to the tracing library by the marker call. In the
11763 UST backend, this is the format string passed as argument to the
11765 @item Static tracepoints probing the marker
11766 The list of static tracepoints attached to the marker.
11770 (@value{GDBP}) info static-tracepoint-markers
11771 Cnt ID Enb Address What
11772 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
11773 Data: number1 %d number2 %d
11774 Probed by static tracepoints: #2
11775 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
11781 @node Starting and Stopping Trace Experiments
11782 @subsection Starting and Stopping Trace Experiments
11785 @kindex tstart [ @var{notes} ]
11786 @cindex start a new trace experiment
11787 @cindex collected data discarded
11789 This command starts the trace experiment, and begins collecting data.
11790 It has the side effect of discarding all the data collected in the
11791 trace buffer during the previous trace experiment. If any arguments
11792 are supplied, they are taken as a note and stored with the trace
11793 experiment's state. The notes may be arbitrary text, and are
11794 especially useful with disconnected tracing in a multi-user context;
11795 the notes can explain what the trace is doing, supply user contact
11796 information, and so forth.
11798 @kindex tstop [ @var{notes} ]
11799 @cindex stop a running trace experiment
11801 This command stops the trace experiment. If any arguments are
11802 supplied, they are recorded with the experiment as a note. This is
11803 useful if you are stopping a trace started by someone else, for
11804 instance if the trace is interfering with the system's behavior and
11805 needs to be stopped quickly.
11807 @strong{Note}: a trace experiment and data collection may stop
11808 automatically if any tracepoint's passcount is reached
11809 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
11812 @cindex status of trace data collection
11813 @cindex trace experiment, status of
11815 This command displays the status of the current trace data
11819 Here is an example of the commands we described so far:
11822 (@value{GDBP}) @b{trace gdb_c_test}
11823 (@value{GDBP}) @b{actions}
11824 Enter actions for tracepoint #1, one per line.
11825 > collect $regs,$locals,$args
11826 > while-stepping 11
11830 (@value{GDBP}) @b{tstart}
11831 [time passes @dots{}]
11832 (@value{GDBP}) @b{tstop}
11835 @anchor{disconnected tracing}
11836 @cindex disconnected tracing
11837 You can choose to continue running the trace experiment even if
11838 @value{GDBN} disconnects from the target, voluntarily or
11839 involuntarily. For commands such as @code{detach}, the debugger will
11840 ask what you want to do with the trace. But for unexpected
11841 terminations (@value{GDBN} crash, network outage), it would be
11842 unfortunate to lose hard-won trace data, so the variable
11843 @code{disconnected-tracing} lets you decide whether the trace should
11844 continue running without @value{GDBN}.
11847 @item set disconnected-tracing on
11848 @itemx set disconnected-tracing off
11849 @kindex set disconnected-tracing
11850 Choose whether a tracing run should continue to run if @value{GDBN}
11851 has disconnected from the target. Note that @code{detach} or
11852 @code{quit} will ask you directly what to do about a running trace no
11853 matter what this variable's setting, so the variable is mainly useful
11854 for handling unexpected situations, such as loss of the network.
11856 @item show disconnected-tracing
11857 @kindex show disconnected-tracing
11858 Show the current choice for disconnected tracing.
11862 When you reconnect to the target, the trace experiment may or may not
11863 still be running; it might have filled the trace buffer in the
11864 meantime, or stopped for one of the other reasons. If it is running,
11865 it will continue after reconnection.
11867 Upon reconnection, the target will upload information about the
11868 tracepoints in effect. @value{GDBN} will then compare that
11869 information to the set of tracepoints currently defined, and attempt
11870 to match them up, allowing for the possibility that the numbers may
11871 have changed due to creation and deletion in the meantime. If one of
11872 the target's tracepoints does not match any in @value{GDBN}, the
11873 debugger will create a new tracepoint, so that you have a number with
11874 which to specify that tracepoint. This matching-up process is
11875 necessarily heuristic, and it may result in useless tracepoints being
11876 created; you may simply delete them if they are of no use.
11878 @cindex circular trace buffer
11879 If your target agent supports a @dfn{circular trace buffer}, then you
11880 can run a trace experiment indefinitely without filling the trace
11881 buffer; when space runs out, the agent deletes already-collected trace
11882 frames, oldest first, until there is enough room to continue
11883 collecting. This is especially useful if your tracepoints are being
11884 hit too often, and your trace gets terminated prematurely because the
11885 buffer is full. To ask for a circular trace buffer, simply set
11886 @samp{circular-trace-buffer} to on. You can set this at any time,
11887 including during tracing; if the agent can do it, it will change
11888 buffer handling on the fly, otherwise it will not take effect until
11892 @item set circular-trace-buffer on
11893 @itemx set circular-trace-buffer off
11894 @kindex set circular-trace-buffer
11895 Choose whether a tracing run should use a linear or circular buffer
11896 for trace data. A linear buffer will not lose any trace data, but may
11897 fill up prematurely, while a circular buffer will discard old trace
11898 data, but it will have always room for the latest tracepoint hits.
11900 @item show circular-trace-buffer
11901 @kindex show circular-trace-buffer
11902 Show the current choice for the trace buffer. Note that this may not
11903 match the agent's current buffer handling, nor is it guaranteed to
11904 match the setting that might have been in effect during a past run,
11905 for instance if you are looking at frames from a trace file.
11910 @item set trace-buffer-size @var{n}
11911 @itemx set trace-buffer-size unlimited
11912 @kindex set trace-buffer-size
11913 Request that the target use a trace buffer of @var{n} bytes. Not all
11914 targets will honor the request; they may have a compiled-in size for
11915 the trace buffer, or some other limitation. Set to a value of
11916 @code{unlimited} or @code{-1} to let the target use whatever size it
11917 likes. This is also the default.
11919 @item show trace-buffer-size
11920 @kindex show trace-buffer-size
11921 Show the current requested size for the trace buffer. Note that this
11922 will only match the actual size if the target supports size-setting,
11923 and was able to handle the requested size. For instance, if the
11924 target can only change buffer size between runs, this variable will
11925 not reflect the change until the next run starts. Use @code{tstatus}
11926 to get a report of the actual buffer size.
11930 @item set trace-user @var{text}
11931 @kindex set trace-user
11933 @item show trace-user
11934 @kindex show trace-user
11936 @item set trace-notes @var{text}
11937 @kindex set trace-notes
11938 Set the trace run's notes.
11940 @item show trace-notes
11941 @kindex show trace-notes
11942 Show the trace run's notes.
11944 @item set trace-stop-notes @var{text}
11945 @kindex set trace-stop-notes
11946 Set the trace run's stop notes. The handling of the note is as for
11947 @code{tstop} arguments; the set command is convenient way to fix a
11948 stop note that is mistaken or incomplete.
11950 @item show trace-stop-notes
11951 @kindex show trace-stop-notes
11952 Show the trace run's stop notes.
11956 @node Tracepoint Restrictions
11957 @subsection Tracepoint Restrictions
11959 @cindex tracepoint restrictions
11960 There are a number of restrictions on the use of tracepoints. As
11961 described above, tracepoint data gathering occurs on the target
11962 without interaction from @value{GDBN}. Thus the full capabilities of
11963 the debugger are not available during data gathering, and then at data
11964 examination time, you will be limited by only having what was
11965 collected. The following items describe some common problems, but it
11966 is not exhaustive, and you may run into additional difficulties not
11972 Tracepoint expressions are intended to gather objects (lvalues). Thus
11973 the full flexibility of GDB's expression evaluator is not available.
11974 You cannot call functions, cast objects to aggregate types, access
11975 convenience variables or modify values (except by assignment to trace
11976 state variables). Some language features may implicitly call
11977 functions (for instance Objective-C fields with accessors), and therefore
11978 cannot be collected either.
11981 Collection of local variables, either individually or in bulk with
11982 @code{$locals} or @code{$args}, during @code{while-stepping} may
11983 behave erratically. The stepping action may enter a new scope (for
11984 instance by stepping into a function), or the location of the variable
11985 may change (for instance it is loaded into a register). The
11986 tracepoint data recorded uses the location information for the
11987 variables that is correct for the tracepoint location. When the
11988 tracepoint is created, it is not possible, in general, to determine
11989 where the steps of a @code{while-stepping} sequence will advance the
11990 program---particularly if a conditional branch is stepped.
11993 Collection of an incompletely-initialized or partially-destroyed object
11994 may result in something that @value{GDBN} cannot display, or displays
11995 in a misleading way.
11998 When @value{GDBN} displays a pointer to character it automatically
11999 dereferences the pointer to also display characters of the string
12000 being pointed to. However, collecting the pointer during tracing does
12001 not automatically collect the string. You need to explicitly
12002 dereference the pointer and provide size information if you want to
12003 collect not only the pointer, but the memory pointed to. For example,
12004 @code{*ptr@@50} can be used to collect the 50 element array pointed to
12008 It is not possible to collect a complete stack backtrace at a
12009 tracepoint. Instead, you may collect the registers and a few hundred
12010 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
12011 (adjust to use the name of the actual stack pointer register on your
12012 target architecture, and the amount of stack you wish to capture).
12013 Then the @code{backtrace} command will show a partial backtrace when
12014 using a trace frame. The number of stack frames that can be examined
12015 depends on the sizes of the frames in the collected stack. Note that
12016 if you ask for a block so large that it goes past the bottom of the
12017 stack, the target agent may report an error trying to read from an
12021 If you do not collect registers at a tracepoint, @value{GDBN} can
12022 infer that the value of @code{$pc} must be the same as the address of
12023 the tracepoint and use that when you are looking at a trace frame
12024 for that tracepoint. However, this cannot work if the tracepoint has
12025 multiple locations (for instance if it was set in a function that was
12026 inlined), or if it has a @code{while-stepping} loop. In those cases
12027 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
12032 @node Analyze Collected Data
12033 @section Using the Collected Data
12035 After the tracepoint experiment ends, you use @value{GDBN} commands
12036 for examining the trace data. The basic idea is that each tracepoint
12037 collects a trace @dfn{snapshot} every time it is hit and another
12038 snapshot every time it single-steps. All these snapshots are
12039 consecutively numbered from zero and go into a buffer, and you can
12040 examine them later. The way you examine them is to @dfn{focus} on a
12041 specific trace snapshot. When the remote stub is focused on a trace
12042 snapshot, it will respond to all @value{GDBN} requests for memory and
12043 registers by reading from the buffer which belongs to that snapshot,
12044 rather than from @emph{real} memory or registers of the program being
12045 debugged. This means that @strong{all} @value{GDBN} commands
12046 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
12047 behave as if we were currently debugging the program state as it was
12048 when the tracepoint occurred. Any requests for data that are not in
12049 the buffer will fail.
12052 * tfind:: How to select a trace snapshot
12053 * tdump:: How to display all data for a snapshot
12054 * save tracepoints:: How to save tracepoints for a future run
12058 @subsection @code{tfind @var{n}}
12061 @cindex select trace snapshot
12062 @cindex find trace snapshot
12063 The basic command for selecting a trace snapshot from the buffer is
12064 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
12065 counting from zero. If no argument @var{n} is given, the next
12066 snapshot is selected.
12068 Here are the various forms of using the @code{tfind} command.
12072 Find the first snapshot in the buffer. This is a synonym for
12073 @code{tfind 0} (since 0 is the number of the first snapshot).
12076 Stop debugging trace snapshots, resume @emph{live} debugging.
12079 Same as @samp{tfind none}.
12082 No argument means find the next trace snapshot.
12085 Find the previous trace snapshot before the current one. This permits
12086 retracing earlier steps.
12088 @item tfind tracepoint @var{num}
12089 Find the next snapshot associated with tracepoint @var{num}. Search
12090 proceeds forward from the last examined trace snapshot. If no
12091 argument @var{num} is given, it means find the next snapshot collected
12092 for the same tracepoint as the current snapshot.
12094 @item tfind pc @var{addr}
12095 Find the next snapshot associated with the value @var{addr} of the
12096 program counter. Search proceeds forward from the last examined trace
12097 snapshot. If no argument @var{addr} is given, it means find the next
12098 snapshot with the same value of PC as the current snapshot.
12100 @item tfind outside @var{addr1}, @var{addr2}
12101 Find the next snapshot whose PC is outside the given range of
12102 addresses (exclusive).
12104 @item tfind range @var{addr1}, @var{addr2}
12105 Find the next snapshot whose PC is between @var{addr1} and
12106 @var{addr2} (inclusive).
12108 @item tfind line @r{[}@var{file}:@r{]}@var{n}
12109 Find the next snapshot associated with the source line @var{n}. If
12110 the optional argument @var{file} is given, refer to line @var{n} in
12111 that source file. Search proceeds forward from the last examined
12112 trace snapshot. If no argument @var{n} is given, it means find the
12113 next line other than the one currently being examined; thus saying
12114 @code{tfind line} repeatedly can appear to have the same effect as
12115 stepping from line to line in a @emph{live} debugging session.
12118 The default arguments for the @code{tfind} commands are specifically
12119 designed to make it easy to scan through the trace buffer. For
12120 instance, @code{tfind} with no argument selects the next trace
12121 snapshot, and @code{tfind -} with no argument selects the previous
12122 trace snapshot. So, by giving one @code{tfind} command, and then
12123 simply hitting @key{RET} repeatedly you can examine all the trace
12124 snapshots in order. Or, by saying @code{tfind -} and then hitting
12125 @key{RET} repeatedly you can examine the snapshots in reverse order.
12126 The @code{tfind line} command with no argument selects the snapshot
12127 for the next source line executed. The @code{tfind pc} command with
12128 no argument selects the next snapshot with the same program counter
12129 (PC) as the current frame. The @code{tfind tracepoint} command with
12130 no argument selects the next trace snapshot collected by the same
12131 tracepoint as the current one.
12133 In addition to letting you scan through the trace buffer manually,
12134 these commands make it easy to construct @value{GDBN} scripts that
12135 scan through the trace buffer and print out whatever collected data
12136 you are interested in. Thus, if we want to examine the PC, FP, and SP
12137 registers from each trace frame in the buffer, we can say this:
12140 (@value{GDBP}) @b{tfind start}
12141 (@value{GDBP}) @b{while ($trace_frame != -1)}
12142 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
12143 $trace_frame, $pc, $sp, $fp
12147 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
12148 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
12149 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
12150 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
12151 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
12152 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
12153 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
12154 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
12155 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
12156 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
12157 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
12160 Or, if we want to examine the variable @code{X} at each source line in
12164 (@value{GDBP}) @b{tfind start}
12165 (@value{GDBP}) @b{while ($trace_frame != -1)}
12166 > printf "Frame %d, X == %d\n", $trace_frame, X
12176 @subsection @code{tdump}
12178 @cindex dump all data collected at tracepoint
12179 @cindex tracepoint data, display
12181 This command takes no arguments. It prints all the data collected at
12182 the current trace snapshot.
12185 (@value{GDBP}) @b{trace 444}
12186 (@value{GDBP}) @b{actions}
12187 Enter actions for tracepoint #2, one per line:
12188 > collect $regs, $locals, $args, gdb_long_test
12191 (@value{GDBP}) @b{tstart}
12193 (@value{GDBP}) @b{tfind line 444}
12194 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
12196 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
12198 (@value{GDBP}) @b{tdump}
12199 Data collected at tracepoint 2, trace frame 1:
12200 d0 0xc4aa0085 -995491707
12204 d4 0x71aea3d 119204413
12207 d7 0x380035 3670069
12208 a0 0x19e24a 1696330
12209 a1 0x3000668 50333288
12211 a3 0x322000 3284992
12212 a4 0x3000698 50333336
12213 a5 0x1ad3cc 1758156
12214 fp 0x30bf3c 0x30bf3c
12215 sp 0x30bf34 0x30bf34
12217 pc 0x20b2c8 0x20b2c8
12221 p = 0x20e5b4 "gdb-test"
12228 gdb_long_test = 17 '\021'
12233 @code{tdump} works by scanning the tracepoint's current collection
12234 actions and printing the value of each expression listed. So
12235 @code{tdump} can fail, if after a run, you change the tracepoint's
12236 actions to mention variables that were not collected during the run.
12238 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
12239 uses the collected value of @code{$pc} to distinguish between trace
12240 frames that were collected at the tracepoint hit, and frames that were
12241 collected while stepping. This allows it to correctly choose whether
12242 to display the basic list of collections, or the collections from the
12243 body of the while-stepping loop. However, if @code{$pc} was not collected,
12244 then @code{tdump} will always attempt to dump using the basic collection
12245 list, and may fail if a while-stepping frame does not include all the
12246 same data that is collected at the tracepoint hit.
12247 @c This is getting pretty arcane, example would be good.
12249 @node save tracepoints
12250 @subsection @code{save tracepoints @var{filename}}
12251 @kindex save tracepoints
12252 @kindex save-tracepoints
12253 @cindex save tracepoints for future sessions
12255 This command saves all current tracepoint definitions together with
12256 their actions and passcounts, into a file @file{@var{filename}}
12257 suitable for use in a later debugging session. To read the saved
12258 tracepoint definitions, use the @code{source} command (@pxref{Command
12259 Files}). The @w{@code{save-tracepoints}} command is a deprecated
12260 alias for @w{@code{save tracepoints}}
12262 @node Tracepoint Variables
12263 @section Convenience Variables for Tracepoints
12264 @cindex tracepoint variables
12265 @cindex convenience variables for tracepoints
12268 @vindex $trace_frame
12269 @item (int) $trace_frame
12270 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
12271 snapshot is selected.
12273 @vindex $tracepoint
12274 @item (int) $tracepoint
12275 The tracepoint for the current trace snapshot.
12277 @vindex $trace_line
12278 @item (int) $trace_line
12279 The line number for the current trace snapshot.
12281 @vindex $trace_file
12282 @item (char []) $trace_file
12283 The source file for the current trace snapshot.
12285 @vindex $trace_func
12286 @item (char []) $trace_func
12287 The name of the function containing @code{$tracepoint}.
12290 Note: @code{$trace_file} is not suitable for use in @code{printf},
12291 use @code{output} instead.
12293 Here's a simple example of using these convenience variables for
12294 stepping through all the trace snapshots and printing some of their
12295 data. Note that these are not the same as trace state variables,
12296 which are managed by the target.
12299 (@value{GDBP}) @b{tfind start}
12301 (@value{GDBP}) @b{while $trace_frame != -1}
12302 > output $trace_file
12303 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
12309 @section Using Trace Files
12310 @cindex trace files
12312 In some situations, the target running a trace experiment may no
12313 longer be available; perhaps it crashed, or the hardware was needed
12314 for a different activity. To handle these cases, you can arrange to
12315 dump the trace data into a file, and later use that file as a source
12316 of trace data, via the @code{target tfile} command.
12321 @item tsave [ -r ] @var{filename}
12322 @itemx tsave [-ctf] @var{dirname}
12323 Save the trace data to @var{filename}. By default, this command
12324 assumes that @var{filename} refers to the host filesystem, so if
12325 necessary @value{GDBN} will copy raw trace data up from the target and
12326 then save it. If the target supports it, you can also supply the
12327 optional argument @code{-r} (``remote'') to direct the target to save
12328 the data directly into @var{filename} in its own filesystem, which may be
12329 more efficient if the trace buffer is very large. (Note, however, that
12330 @code{target tfile} can only read from files accessible to the host.)
12331 By default, this command will save trace frame in tfile format.
12332 You can supply the optional argument @code{-ctf} to save date in CTF
12333 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
12334 that can be shared by multiple debugging and tracing tools. Please go to
12335 @indicateurl{http://www.efficios.com/ctf} to get more information.
12337 @kindex target tfile
12341 @item target tfile @var{filename}
12342 @itemx target ctf @var{dirname}
12343 Use the file named @var{filename} or directory named @var{dirname} as
12344 a source of trace data. Commands that examine data work as they do with
12345 a live target, but it is not possible to run any new trace experiments.
12346 @code{tstatus} will report the state of the trace run at the moment
12347 the data was saved, as well as the current trace frame you are examining.
12348 @var{filename} or @var{dirname} must be on a filesystem accessible to
12352 (@value{GDBP}) target ctf ctf.ctf
12353 (@value{GDBP}) tfind
12354 Found trace frame 0, tracepoint 2
12355 39 ++a; /* set tracepoint 1 here */
12356 (@value{GDBP}) tdump
12357 Data collected at tracepoint 2, trace frame 0:
12361 c = @{"123", "456", "789", "123", "456", "789"@}
12362 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
12370 @chapter Debugging Programs That Use Overlays
12373 If your program is too large to fit completely in your target system's
12374 memory, you can sometimes use @dfn{overlays} to work around this
12375 problem. @value{GDBN} provides some support for debugging programs that
12379 * How Overlays Work:: A general explanation of overlays.
12380 * Overlay Commands:: Managing overlays in @value{GDBN}.
12381 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
12382 mapped by asking the inferior.
12383 * Overlay Sample Program:: A sample program using overlays.
12386 @node How Overlays Work
12387 @section How Overlays Work
12388 @cindex mapped overlays
12389 @cindex unmapped overlays
12390 @cindex load address, overlay's
12391 @cindex mapped address
12392 @cindex overlay area
12394 Suppose you have a computer whose instruction address space is only 64
12395 kilobytes long, but which has much more memory which can be accessed by
12396 other means: special instructions, segment registers, or memory
12397 management hardware, for example. Suppose further that you want to
12398 adapt a program which is larger than 64 kilobytes to run on this system.
12400 One solution is to identify modules of your program which are relatively
12401 independent, and need not call each other directly; call these modules
12402 @dfn{overlays}. Separate the overlays from the main program, and place
12403 their machine code in the larger memory. Place your main program in
12404 instruction memory, but leave at least enough space there to hold the
12405 largest overlay as well.
12407 Now, to call a function located in an overlay, you must first copy that
12408 overlay's machine code from the large memory into the space set aside
12409 for it in the instruction memory, and then jump to its entry point
12412 @c NB: In the below the mapped area's size is greater or equal to the
12413 @c size of all overlays. This is intentional to remind the developer
12414 @c that overlays don't necessarily need to be the same size.
12418 Data Instruction Larger
12419 Address Space Address Space Address Space
12420 +-----------+ +-----------+ +-----------+
12422 +-----------+ +-----------+ +-----------+<-- overlay 1
12423 | program | | main | .----| overlay 1 | load address
12424 | variables | | program | | +-----------+
12425 | and heap | | | | | |
12426 +-----------+ | | | +-----------+<-- overlay 2
12427 | | +-----------+ | | | load address
12428 +-----------+ | | | .-| overlay 2 |
12430 mapped --->+-----------+ | | +-----------+
12431 address | | | | | |
12432 | overlay | <-' | | |
12433 | area | <---' +-----------+<-- overlay 3
12434 | | <---. | | load address
12435 +-----------+ `--| overlay 3 |
12442 @anchor{A code overlay}A code overlay
12446 The diagram (@pxref{A code overlay}) shows a system with separate data
12447 and instruction address spaces. To map an overlay, the program copies
12448 its code from the larger address space to the instruction address space.
12449 Since the overlays shown here all use the same mapped address, only one
12450 may be mapped at a time. For a system with a single address space for
12451 data and instructions, the diagram would be similar, except that the
12452 program variables and heap would share an address space with the main
12453 program and the overlay area.
12455 An overlay loaded into instruction memory and ready for use is called a
12456 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
12457 instruction memory. An overlay not present (or only partially present)
12458 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
12459 is its address in the larger memory. The mapped address is also called
12460 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
12461 called the @dfn{load memory address}, or @dfn{LMA}.
12463 Unfortunately, overlays are not a completely transparent way to adapt a
12464 program to limited instruction memory. They introduce a new set of
12465 global constraints you must keep in mind as you design your program:
12470 Before calling or returning to a function in an overlay, your program
12471 must make sure that overlay is actually mapped. Otherwise, the call or
12472 return will transfer control to the right address, but in the wrong
12473 overlay, and your program will probably crash.
12476 If the process of mapping an overlay is expensive on your system, you
12477 will need to choose your overlays carefully to minimize their effect on
12478 your program's performance.
12481 The executable file you load onto your system must contain each
12482 overlay's instructions, appearing at the overlay's load address, not its
12483 mapped address. However, each overlay's instructions must be relocated
12484 and its symbols defined as if the overlay were at its mapped address.
12485 You can use GNU linker scripts to specify different load and relocation
12486 addresses for pieces of your program; see @ref{Overlay Description,,,
12487 ld.info, Using ld: the GNU linker}.
12490 The procedure for loading executable files onto your system must be able
12491 to load their contents into the larger address space as well as the
12492 instruction and data spaces.
12496 The overlay system described above is rather simple, and could be
12497 improved in many ways:
12502 If your system has suitable bank switch registers or memory management
12503 hardware, you could use those facilities to make an overlay's load area
12504 contents simply appear at their mapped address in instruction space.
12505 This would probably be faster than copying the overlay to its mapped
12506 area in the usual way.
12509 If your overlays are small enough, you could set aside more than one
12510 overlay area, and have more than one overlay mapped at a time.
12513 You can use overlays to manage data, as well as instructions. In
12514 general, data overlays are even less transparent to your design than
12515 code overlays: whereas code overlays only require care when you call or
12516 return to functions, data overlays require care every time you access
12517 the data. Also, if you change the contents of a data overlay, you
12518 must copy its contents back out to its load address before you can copy a
12519 different data overlay into the same mapped area.
12524 @node Overlay Commands
12525 @section Overlay Commands
12527 To use @value{GDBN}'s overlay support, each overlay in your program must
12528 correspond to a separate section of the executable file. The section's
12529 virtual memory address and load memory address must be the overlay's
12530 mapped and load addresses. Identifying overlays with sections allows
12531 @value{GDBN} to determine the appropriate address of a function or
12532 variable, depending on whether the overlay is mapped or not.
12534 @value{GDBN}'s overlay commands all start with the word @code{overlay};
12535 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
12540 Disable @value{GDBN}'s overlay support. When overlay support is
12541 disabled, @value{GDBN} assumes that all functions and variables are
12542 always present at their mapped addresses. By default, @value{GDBN}'s
12543 overlay support is disabled.
12545 @item overlay manual
12546 @cindex manual overlay debugging
12547 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
12548 relies on you to tell it which overlays are mapped, and which are not,
12549 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
12550 commands described below.
12552 @item overlay map-overlay @var{overlay}
12553 @itemx overlay map @var{overlay}
12554 @cindex map an overlay
12555 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
12556 be the name of the object file section containing the overlay. When an
12557 overlay is mapped, @value{GDBN} assumes it can find the overlay's
12558 functions and variables at their mapped addresses. @value{GDBN} assumes
12559 that any other overlays whose mapped ranges overlap that of
12560 @var{overlay} are now unmapped.
12562 @item overlay unmap-overlay @var{overlay}
12563 @itemx overlay unmap @var{overlay}
12564 @cindex unmap an overlay
12565 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
12566 must be the name of the object file section containing the overlay.
12567 When an overlay is unmapped, @value{GDBN} assumes it can find the
12568 overlay's functions and variables at their load addresses.
12571 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
12572 consults a data structure the overlay manager maintains in the inferior
12573 to see which overlays are mapped. For details, see @ref{Automatic
12574 Overlay Debugging}.
12576 @item overlay load-target
12577 @itemx overlay load
12578 @cindex reloading the overlay table
12579 Re-read the overlay table from the inferior. Normally, @value{GDBN}
12580 re-reads the table @value{GDBN} automatically each time the inferior
12581 stops, so this command should only be necessary if you have changed the
12582 overlay mapping yourself using @value{GDBN}. This command is only
12583 useful when using automatic overlay debugging.
12585 @item overlay list-overlays
12586 @itemx overlay list
12587 @cindex listing mapped overlays
12588 Display a list of the overlays currently mapped, along with their mapped
12589 addresses, load addresses, and sizes.
12593 Normally, when @value{GDBN} prints a code address, it includes the name
12594 of the function the address falls in:
12597 (@value{GDBP}) print main
12598 $3 = @{int ()@} 0x11a0 <main>
12601 When overlay debugging is enabled, @value{GDBN} recognizes code in
12602 unmapped overlays, and prints the names of unmapped functions with
12603 asterisks around them. For example, if @code{foo} is a function in an
12604 unmapped overlay, @value{GDBN} prints it this way:
12607 (@value{GDBP}) overlay list
12608 No sections are mapped.
12609 (@value{GDBP}) print foo
12610 $5 = @{int (int)@} 0x100000 <*foo*>
12613 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
12617 (@value{GDBP}) overlay list
12618 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
12619 mapped at 0x1016 - 0x104a
12620 (@value{GDBP}) print foo
12621 $6 = @{int (int)@} 0x1016 <foo>
12624 When overlay debugging is enabled, @value{GDBN} can find the correct
12625 address for functions and variables in an overlay, whether or not the
12626 overlay is mapped. This allows most @value{GDBN} commands, like
12627 @code{break} and @code{disassemble}, to work normally, even on unmapped
12628 code. However, @value{GDBN}'s breakpoint support has some limitations:
12632 @cindex breakpoints in overlays
12633 @cindex overlays, setting breakpoints in
12634 You can set breakpoints in functions in unmapped overlays, as long as
12635 @value{GDBN} can write to the overlay at its load address.
12637 @value{GDBN} can not set hardware or simulator-based breakpoints in
12638 unmapped overlays. However, if you set a breakpoint at the end of your
12639 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
12640 you are using manual overlay management), @value{GDBN} will re-set its
12641 breakpoints properly.
12645 @node Automatic Overlay Debugging
12646 @section Automatic Overlay Debugging
12647 @cindex automatic overlay debugging
12649 @value{GDBN} can automatically track which overlays are mapped and which
12650 are not, given some simple co-operation from the overlay manager in the
12651 inferior. If you enable automatic overlay debugging with the
12652 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
12653 looks in the inferior's memory for certain variables describing the
12654 current state of the overlays.
12656 Here are the variables your overlay manager must define to support
12657 @value{GDBN}'s automatic overlay debugging:
12661 @item @code{_ovly_table}:
12662 This variable must be an array of the following structures:
12667 /* The overlay's mapped address. */
12670 /* The size of the overlay, in bytes. */
12671 unsigned long size;
12673 /* The overlay's load address. */
12676 /* Non-zero if the overlay is currently mapped;
12678 unsigned long mapped;
12682 @item @code{_novlys}:
12683 This variable must be a four-byte signed integer, holding the total
12684 number of elements in @code{_ovly_table}.
12688 To decide whether a particular overlay is mapped or not, @value{GDBN}
12689 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
12690 @code{lma} members equal the VMA and LMA of the overlay's section in the
12691 executable file. When @value{GDBN} finds a matching entry, it consults
12692 the entry's @code{mapped} member to determine whether the overlay is
12695 In addition, your overlay manager may define a function called
12696 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
12697 will silently set a breakpoint there. If the overlay manager then
12698 calls this function whenever it has changed the overlay table, this
12699 will enable @value{GDBN} to accurately keep track of which overlays
12700 are in program memory, and update any breakpoints that may be set
12701 in overlays. This will allow breakpoints to work even if the
12702 overlays are kept in ROM or other non-writable memory while they
12703 are not being executed.
12705 @node Overlay Sample Program
12706 @section Overlay Sample Program
12707 @cindex overlay example program
12709 When linking a program which uses overlays, you must place the overlays
12710 at their load addresses, while relocating them to run at their mapped
12711 addresses. To do this, you must write a linker script (@pxref{Overlay
12712 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
12713 since linker scripts are specific to a particular host system, target
12714 architecture, and target memory layout, this manual cannot provide
12715 portable sample code demonstrating @value{GDBN}'s overlay support.
12717 However, the @value{GDBN} source distribution does contain an overlaid
12718 program, with linker scripts for a few systems, as part of its test
12719 suite. The program consists of the following files from
12720 @file{gdb/testsuite/gdb.base}:
12724 The main program file.
12726 A simple overlay manager, used by @file{overlays.c}.
12731 Overlay modules, loaded and used by @file{overlays.c}.
12734 Linker scripts for linking the test program on the @code{d10v-elf}
12735 and @code{m32r-elf} targets.
12738 You can build the test program using the @code{d10v-elf} GCC
12739 cross-compiler like this:
12742 $ d10v-elf-gcc -g -c overlays.c
12743 $ d10v-elf-gcc -g -c ovlymgr.c
12744 $ d10v-elf-gcc -g -c foo.c
12745 $ d10v-elf-gcc -g -c bar.c
12746 $ d10v-elf-gcc -g -c baz.c
12747 $ d10v-elf-gcc -g -c grbx.c
12748 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
12749 baz.o grbx.o -Wl,-Td10v.ld -o overlays
12752 The build process is identical for any other architecture, except that
12753 you must substitute the appropriate compiler and linker script for the
12754 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
12758 @chapter Using @value{GDBN} with Different Languages
12761 Although programming languages generally have common aspects, they are
12762 rarely expressed in the same manner. For instance, in ANSI C,
12763 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
12764 Modula-2, it is accomplished by @code{p^}. Values can also be
12765 represented (and displayed) differently. Hex numbers in C appear as
12766 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
12768 @cindex working language
12769 Language-specific information is built into @value{GDBN} for some languages,
12770 allowing you to express operations like the above in your program's
12771 native language, and allowing @value{GDBN} to output values in a manner
12772 consistent with the syntax of your program's native language. The
12773 language you use to build expressions is called the @dfn{working
12777 * Setting:: Switching between source languages
12778 * Show:: Displaying the language
12779 * Checks:: Type and range checks
12780 * Supported Languages:: Supported languages
12781 * Unsupported Languages:: Unsupported languages
12785 @section Switching Between Source Languages
12787 There are two ways to control the working language---either have @value{GDBN}
12788 set it automatically, or select it manually yourself. You can use the
12789 @code{set language} command for either purpose. On startup, @value{GDBN}
12790 defaults to setting the language automatically. The working language is
12791 used to determine how expressions you type are interpreted, how values
12794 In addition to the working language, every source file that
12795 @value{GDBN} knows about has its own working language. For some object
12796 file formats, the compiler might indicate which language a particular
12797 source file is in. However, most of the time @value{GDBN} infers the
12798 language from the name of the file. The language of a source file
12799 controls whether C@t{++} names are demangled---this way @code{backtrace} can
12800 show each frame appropriately for its own language. There is no way to
12801 set the language of a source file from within @value{GDBN}, but you can
12802 set the language associated with a filename extension. @xref{Show, ,
12803 Displaying the Language}.
12805 This is most commonly a problem when you use a program, such
12806 as @code{cfront} or @code{f2c}, that generates C but is written in
12807 another language. In that case, make the
12808 program use @code{#line} directives in its C output; that way
12809 @value{GDBN} will know the correct language of the source code of the original
12810 program, and will display that source code, not the generated C code.
12813 * Filenames:: Filename extensions and languages.
12814 * Manually:: Setting the working language manually
12815 * Automatically:: Having @value{GDBN} infer the source language
12819 @subsection List of Filename Extensions and Languages
12821 If a source file name ends in one of the following extensions, then
12822 @value{GDBN} infers that its language is the one indicated.
12840 C@t{++} source file
12846 Objective-C source file
12850 Fortran source file
12853 Modula-2 source file
12857 Assembler source file. This actually behaves almost like C, but
12858 @value{GDBN} does not skip over function prologues when stepping.
12861 In addition, you may set the language associated with a filename
12862 extension. @xref{Show, , Displaying the Language}.
12865 @subsection Setting the Working Language
12867 If you allow @value{GDBN} to set the language automatically,
12868 expressions are interpreted the same way in your debugging session and
12871 @kindex set language
12872 If you wish, you may set the language manually. To do this, issue the
12873 command @samp{set language @var{lang}}, where @var{lang} is the name of
12874 a language, such as
12875 @code{c} or @code{modula-2}.
12876 For a list of the supported languages, type @samp{set language}.
12878 Setting the language manually prevents @value{GDBN} from updating the working
12879 language automatically. This can lead to confusion if you try
12880 to debug a program when the working language is not the same as the
12881 source language, when an expression is acceptable to both
12882 languages---but means different things. For instance, if the current
12883 source file were written in C, and @value{GDBN} was parsing Modula-2, a
12891 might not have the effect you intended. In C, this means to add
12892 @code{b} and @code{c} and place the result in @code{a}. The result
12893 printed would be the value of @code{a}. In Modula-2, this means to compare
12894 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
12896 @node Automatically
12897 @subsection Having @value{GDBN} Infer the Source Language
12899 To have @value{GDBN} set the working language automatically, use
12900 @samp{set language local} or @samp{set language auto}. @value{GDBN}
12901 then infers the working language. That is, when your program stops in a
12902 frame (usually by encountering a breakpoint), @value{GDBN} sets the
12903 working language to the language recorded for the function in that
12904 frame. If the language for a frame is unknown (that is, if the function
12905 or block corresponding to the frame was defined in a source file that
12906 does not have a recognized extension), the current working language is
12907 not changed, and @value{GDBN} issues a warning.
12909 This may not seem necessary for most programs, which are written
12910 entirely in one source language. However, program modules and libraries
12911 written in one source language can be used by a main program written in
12912 a different source language. Using @samp{set language auto} in this
12913 case frees you from having to set the working language manually.
12916 @section Displaying the Language
12918 The following commands help you find out which language is the
12919 working language, and also what language source files were written in.
12922 @item show language
12923 @kindex show language
12924 Display the current working language. This is the
12925 language you can use with commands such as @code{print} to
12926 build and compute expressions that may involve variables in your program.
12929 @kindex info frame@r{, show the source language}
12930 Display the source language for this frame. This language becomes the
12931 working language if you use an identifier from this frame.
12932 @xref{Frame Info, ,Information about a Frame}, to identify the other
12933 information listed here.
12936 @kindex info source@r{, show the source language}
12937 Display the source language of this source file.
12938 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
12939 information listed here.
12942 In unusual circumstances, you may have source files with extensions
12943 not in the standard list. You can then set the extension associated
12944 with a language explicitly:
12947 @item set extension-language @var{ext} @var{language}
12948 @kindex set extension-language
12949 Tell @value{GDBN} that source files with extension @var{ext} are to be
12950 assumed as written in the source language @var{language}.
12952 @item info extensions
12953 @kindex info extensions
12954 List all the filename extensions and the associated languages.
12958 @section Type and Range Checking
12960 Some languages are designed to guard you against making seemingly common
12961 errors through a series of compile- and run-time checks. These include
12962 checking the type of arguments to functions and operators and making
12963 sure mathematical overflows are caught at run time. Checks such as
12964 these help to ensure a program's correctness once it has been compiled
12965 by eliminating type mismatches and providing active checks for range
12966 errors when your program is running.
12968 By default @value{GDBN} checks for these errors according to the
12969 rules of the current source language. Although @value{GDBN} does not check
12970 the statements in your program, it can check expressions entered directly
12971 into @value{GDBN} for evaluation via the @code{print} command, for example.
12974 * Type Checking:: An overview of type checking
12975 * Range Checking:: An overview of range checking
12978 @cindex type checking
12979 @cindex checks, type
12980 @node Type Checking
12981 @subsection An Overview of Type Checking
12983 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
12984 arguments to operators and functions have to be of the correct type,
12985 otherwise an error occurs. These checks prevent type mismatch
12986 errors from ever causing any run-time problems. For example,
12989 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
12991 (@value{GDBP}) print obj.my_method (0)
12994 (@value{GDBP}) print obj.my_method (0x1234)
12995 Cannot resolve method klass::my_method to any overloaded instance
12998 The second example fails because in C@t{++} the integer constant
12999 @samp{0x1234} is not type-compatible with the pointer parameter type.
13001 For the expressions you use in @value{GDBN} commands, you can tell
13002 @value{GDBN} to not enforce strict type checking or
13003 to treat any mismatches as errors and abandon the expression;
13004 When type checking is disabled, @value{GDBN} successfully evaluates
13005 expressions like the second example above.
13007 Even if type checking is off, there may be other reasons
13008 related to type that prevent @value{GDBN} from evaluating an expression.
13009 For instance, @value{GDBN} does not know how to add an @code{int} and
13010 a @code{struct foo}. These particular type errors have nothing to do
13011 with the language in use and usually arise from expressions which make
13012 little sense to evaluate anyway.
13014 @value{GDBN} provides some additional commands for controlling type checking:
13016 @kindex set check type
13017 @kindex show check type
13019 @item set check type on
13020 @itemx set check type off
13021 Set strict type checking on or off. If any type mismatches occur in
13022 evaluating an expression while type checking is on, @value{GDBN} prints a
13023 message and aborts evaluation of the expression.
13025 @item show check type
13026 Show the current setting of type checking and whether @value{GDBN}
13027 is enforcing strict type checking rules.
13030 @cindex range checking
13031 @cindex checks, range
13032 @node Range Checking
13033 @subsection An Overview of Range Checking
13035 In some languages (such as Modula-2), it is an error to exceed the
13036 bounds of a type; this is enforced with run-time checks. Such range
13037 checking is meant to ensure program correctness by making sure
13038 computations do not overflow, or indices on an array element access do
13039 not exceed the bounds of the array.
13041 For expressions you use in @value{GDBN} commands, you can tell
13042 @value{GDBN} to treat range errors in one of three ways: ignore them,
13043 always treat them as errors and abandon the expression, or issue
13044 warnings but evaluate the expression anyway.
13046 A range error can result from numerical overflow, from exceeding an
13047 array index bound, or when you type a constant that is not a member
13048 of any type. Some languages, however, do not treat overflows as an
13049 error. In many implementations of C, mathematical overflow causes the
13050 result to ``wrap around'' to lower values---for example, if @var{m} is
13051 the largest integer value, and @var{s} is the smallest, then
13054 @var{m} + 1 @result{} @var{s}
13057 This, too, is specific to individual languages, and in some cases
13058 specific to individual compilers or machines. @xref{Supported Languages, ,
13059 Supported Languages}, for further details on specific languages.
13061 @value{GDBN} provides some additional commands for controlling the range checker:
13063 @kindex set check range
13064 @kindex show check range
13066 @item set check range auto
13067 Set range checking on or off based on the current working language.
13068 @xref{Supported Languages, ,Supported Languages}, for the default settings for
13071 @item set check range on
13072 @itemx set check range off
13073 Set range checking on or off, overriding the default setting for the
13074 current working language. A warning is issued if the setting does not
13075 match the language default. If a range error occurs and range checking is on,
13076 then a message is printed and evaluation of the expression is aborted.
13078 @item set check range warn
13079 Output messages when the @value{GDBN} range checker detects a range error,
13080 but attempt to evaluate the expression anyway. Evaluating the
13081 expression may still be impossible for other reasons, such as accessing
13082 memory that the process does not own (a typical example from many Unix
13086 Show the current setting of the range checker, and whether or not it is
13087 being set automatically by @value{GDBN}.
13090 @node Supported Languages
13091 @section Supported Languages
13093 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
13094 OpenCL C, Pascal, assembly, Modula-2, and Ada.
13095 @c This is false ...
13096 Some @value{GDBN} features may be used in expressions regardless of the
13097 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
13098 and the @samp{@{type@}addr} construct (@pxref{Expressions,
13099 ,Expressions}) can be used with the constructs of any supported
13102 The following sections detail to what degree each source language is
13103 supported by @value{GDBN}. These sections are not meant to be language
13104 tutorials or references, but serve only as a reference guide to what the
13105 @value{GDBN} expression parser accepts, and what input and output
13106 formats should look like for different languages. There are many good
13107 books written on each of these languages; please look to these for a
13108 language reference or tutorial.
13111 * C:: C and C@t{++}
13114 * Objective-C:: Objective-C
13115 * OpenCL C:: OpenCL C
13116 * Fortran:: Fortran
13118 * Modula-2:: Modula-2
13123 @subsection C and C@t{++}
13125 @cindex C and C@t{++}
13126 @cindex expressions in C or C@t{++}
13128 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
13129 to both languages. Whenever this is the case, we discuss those languages
13133 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
13134 @cindex @sc{gnu} C@t{++}
13135 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
13136 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
13137 effectively, you must compile your C@t{++} programs with a supported
13138 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
13139 compiler (@code{aCC}).
13142 * C Operators:: C and C@t{++} operators
13143 * C Constants:: C and C@t{++} constants
13144 * C Plus Plus Expressions:: C@t{++} expressions
13145 * C Defaults:: Default settings for C and C@t{++}
13146 * C Checks:: C and C@t{++} type and range checks
13147 * Debugging C:: @value{GDBN} and C
13148 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
13149 * Decimal Floating Point:: Numbers in Decimal Floating Point format
13153 @subsubsection C and C@t{++} Operators
13155 @cindex C and C@t{++} operators
13157 Operators must be defined on values of specific types. For instance,
13158 @code{+} is defined on numbers, but not on structures. Operators are
13159 often defined on groups of types.
13161 For the purposes of C and C@t{++}, the following definitions hold:
13166 @emph{Integral types} include @code{int} with any of its storage-class
13167 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
13170 @emph{Floating-point types} include @code{float}, @code{double}, and
13171 @code{long double} (if supported by the target platform).
13174 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
13177 @emph{Scalar types} include all of the above.
13182 The following operators are supported. They are listed here
13183 in order of increasing precedence:
13187 The comma or sequencing operator. Expressions in a comma-separated list
13188 are evaluated from left to right, with the result of the entire
13189 expression being the last expression evaluated.
13192 Assignment. The value of an assignment expression is the value
13193 assigned. Defined on scalar types.
13196 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
13197 and translated to @w{@code{@var{a} = @var{a op b}}}.
13198 @w{@code{@var{op}=}} and @code{=} have the same precedence.
13199 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
13200 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
13203 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
13204 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
13208 Logical @sc{or}. Defined on integral types.
13211 Logical @sc{and}. Defined on integral types.
13214 Bitwise @sc{or}. Defined on integral types.
13217 Bitwise exclusive-@sc{or}. Defined on integral types.
13220 Bitwise @sc{and}. Defined on integral types.
13223 Equality and inequality. Defined on scalar types. The value of these
13224 expressions is 0 for false and non-zero for true.
13226 @item <@r{, }>@r{, }<=@r{, }>=
13227 Less than, greater than, less than or equal, greater than or equal.
13228 Defined on scalar types. The value of these expressions is 0 for false
13229 and non-zero for true.
13232 left shift, and right shift. Defined on integral types.
13235 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13238 Addition and subtraction. Defined on integral types, floating-point types and
13241 @item *@r{, }/@r{, }%
13242 Multiplication, division, and modulus. Multiplication and division are
13243 defined on integral and floating-point types. Modulus is defined on
13247 Increment and decrement. When appearing before a variable, the
13248 operation is performed before the variable is used in an expression;
13249 when appearing after it, the variable's value is used before the
13250 operation takes place.
13253 Pointer dereferencing. Defined on pointer types. Same precedence as
13257 Address operator. Defined on variables. Same precedence as @code{++}.
13259 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
13260 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
13261 to examine the address
13262 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
13266 Negative. Defined on integral and floating-point types. Same
13267 precedence as @code{++}.
13270 Logical negation. Defined on integral types. Same precedence as
13274 Bitwise complement operator. Defined on integral types. Same precedence as
13279 Structure member, and pointer-to-structure member. For convenience,
13280 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
13281 pointer based on the stored type information.
13282 Defined on @code{struct} and @code{union} data.
13285 Dereferences of pointers to members.
13288 Array indexing. @code{@var{a}[@var{i}]} is defined as
13289 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
13292 Function parameter list. Same precedence as @code{->}.
13295 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
13296 and @code{class} types.
13299 Doubled colons also represent the @value{GDBN} scope operator
13300 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
13304 If an operator is redefined in the user code, @value{GDBN} usually
13305 attempts to invoke the redefined version instead of using the operator's
13306 predefined meaning.
13309 @subsubsection C and C@t{++} Constants
13311 @cindex C and C@t{++} constants
13313 @value{GDBN} allows you to express the constants of C and C@t{++} in the
13318 Integer constants are a sequence of digits. Octal constants are
13319 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
13320 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
13321 @samp{l}, specifying that the constant should be treated as a
13325 Floating point constants are a sequence of digits, followed by a decimal
13326 point, followed by a sequence of digits, and optionally followed by an
13327 exponent. An exponent is of the form:
13328 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
13329 sequence of digits. The @samp{+} is optional for positive exponents.
13330 A floating-point constant may also end with a letter @samp{f} or
13331 @samp{F}, specifying that the constant should be treated as being of
13332 the @code{float} (as opposed to the default @code{double}) type; or with
13333 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
13337 Enumerated constants consist of enumerated identifiers, or their
13338 integral equivalents.
13341 Character constants are a single character surrounded by single quotes
13342 (@code{'}), or a number---the ordinal value of the corresponding character
13343 (usually its @sc{ascii} value). Within quotes, the single character may
13344 be represented by a letter or by @dfn{escape sequences}, which are of
13345 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
13346 of the character's ordinal value; or of the form @samp{\@var{x}}, where
13347 @samp{@var{x}} is a predefined special character---for example,
13348 @samp{\n} for newline.
13350 Wide character constants can be written by prefixing a character
13351 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
13352 form of @samp{x}. The target wide character set is used when
13353 computing the value of this constant (@pxref{Character Sets}).
13356 String constants are a sequence of character constants surrounded by
13357 double quotes (@code{"}). Any valid character constant (as described
13358 above) may appear. Double quotes within the string must be preceded by
13359 a backslash, so for instance @samp{"a\"b'c"} is a string of five
13362 Wide string constants can be written by prefixing a string constant
13363 with @samp{L}, as in C. The target wide character set is used when
13364 computing the value of this constant (@pxref{Character Sets}).
13367 Pointer constants are an integral value. You can also write pointers
13368 to constants using the C operator @samp{&}.
13371 Array constants are comma-separated lists surrounded by braces @samp{@{}
13372 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
13373 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
13374 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
13377 @node C Plus Plus Expressions
13378 @subsubsection C@t{++} Expressions
13380 @cindex expressions in C@t{++}
13381 @value{GDBN} expression handling can interpret most C@t{++} expressions.
13383 @cindex debugging C@t{++} programs
13384 @cindex C@t{++} compilers
13385 @cindex debug formats and C@t{++}
13386 @cindex @value{NGCC} and C@t{++}
13388 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
13389 the proper compiler and the proper debug format. Currently,
13390 @value{GDBN} works best when debugging C@t{++} code that is compiled
13391 with the most recent version of @value{NGCC} possible. The DWARF
13392 debugging format is preferred; @value{NGCC} defaults to this on most
13393 popular platforms. Other compilers and/or debug formats are likely to
13394 work badly or not at all when using @value{GDBN} to debug C@t{++}
13395 code. @xref{Compilation}.
13400 @cindex member functions
13402 Member function calls are allowed; you can use expressions like
13405 count = aml->GetOriginal(x, y)
13408 @vindex this@r{, inside C@t{++} member functions}
13409 @cindex namespace in C@t{++}
13411 While a member function is active (in the selected stack frame), your
13412 expressions have the same namespace available as the member function;
13413 that is, @value{GDBN} allows implicit references to the class instance
13414 pointer @code{this} following the same rules as C@t{++}. @code{using}
13415 declarations in the current scope are also respected by @value{GDBN}.
13417 @cindex call overloaded functions
13418 @cindex overloaded functions, calling
13419 @cindex type conversions in C@t{++}
13421 You can call overloaded functions; @value{GDBN} resolves the function
13422 call to the right definition, with some restrictions. @value{GDBN} does not
13423 perform overload resolution involving user-defined type conversions,
13424 calls to constructors, or instantiations of templates that do not exist
13425 in the program. It also cannot handle ellipsis argument lists or
13428 It does perform integral conversions and promotions, floating-point
13429 promotions, arithmetic conversions, pointer conversions, conversions of
13430 class objects to base classes, and standard conversions such as those of
13431 functions or arrays to pointers; it requires an exact match on the
13432 number of function arguments.
13434 Overload resolution is always performed, unless you have specified
13435 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
13436 ,@value{GDBN} Features for C@t{++}}.
13438 You must specify @code{set overload-resolution off} in order to use an
13439 explicit function signature to call an overloaded function, as in
13441 p 'foo(char,int)'('x', 13)
13444 The @value{GDBN} command-completion facility can simplify this;
13445 see @ref{Completion, ,Command Completion}.
13447 @cindex reference declarations
13449 @value{GDBN} understands variables declared as C@t{++} references; you can use
13450 them in expressions just as you do in C@t{++} source---they are automatically
13453 In the parameter list shown when @value{GDBN} displays a frame, the values of
13454 reference variables are not displayed (unlike other variables); this
13455 avoids clutter, since references are often used for large structures.
13456 The @emph{address} of a reference variable is always shown, unless
13457 you have specified @samp{set print address off}.
13460 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
13461 expressions can use it just as expressions in your program do. Since
13462 one scope may be defined in another, you can use @code{::} repeatedly if
13463 necessary, for example in an expression like
13464 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
13465 resolving name scope by reference to source files, in both C and C@t{++}
13466 debugging (@pxref{Variables, ,Program Variables}).
13469 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
13474 @subsubsection C and C@t{++} Defaults
13476 @cindex C and C@t{++} defaults
13478 If you allow @value{GDBN} to set range checking automatically, it
13479 defaults to @code{off} whenever the working language changes to
13480 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
13481 selects the working language.
13483 If you allow @value{GDBN} to set the language automatically, it
13484 recognizes source files whose names end with @file{.c}, @file{.C}, or
13485 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
13486 these files, it sets the working language to C or C@t{++}.
13487 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
13488 for further details.
13491 @subsubsection C and C@t{++} Type and Range Checks
13493 @cindex C and C@t{++} checks
13495 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
13496 checking is used. However, if you turn type checking off, @value{GDBN}
13497 will allow certain non-standard conversions, such as promoting integer
13498 constants to pointers.
13500 Range checking, if turned on, is done on mathematical operations. Array
13501 indices are not checked, since they are often used to index a pointer
13502 that is not itself an array.
13505 @subsubsection @value{GDBN} and C
13507 The @code{set print union} and @code{show print union} commands apply to
13508 the @code{union} type. When set to @samp{on}, any @code{union} that is
13509 inside a @code{struct} or @code{class} is also printed. Otherwise, it
13510 appears as @samp{@{...@}}.
13512 The @code{@@} operator aids in the debugging of dynamic arrays, formed
13513 with pointers and a memory allocation function. @xref{Expressions,
13516 @node Debugging C Plus Plus
13517 @subsubsection @value{GDBN} Features for C@t{++}
13519 @cindex commands for C@t{++}
13521 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
13522 designed specifically for use with C@t{++}. Here is a summary:
13525 @cindex break in overloaded functions
13526 @item @r{breakpoint menus}
13527 When you want a breakpoint in a function whose name is overloaded,
13528 @value{GDBN} has the capability to display a menu of possible breakpoint
13529 locations to help you specify which function definition you want.
13530 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
13532 @cindex overloading in C@t{++}
13533 @item rbreak @var{regex}
13534 Setting breakpoints using regular expressions is helpful for setting
13535 breakpoints on overloaded functions that are not members of any special
13537 @xref{Set Breaks, ,Setting Breakpoints}.
13539 @cindex C@t{++} exception handling
13542 Debug C@t{++} exception handling using these commands. @xref{Set
13543 Catchpoints, , Setting Catchpoints}.
13545 @cindex inheritance
13546 @item ptype @var{typename}
13547 Print inheritance relationships as well as other information for type
13549 @xref{Symbols, ,Examining the Symbol Table}.
13551 @item info vtbl @var{expression}.
13552 The @code{info vtbl} command can be used to display the virtual
13553 method tables of the object computed by @var{expression}. This shows
13554 one entry per virtual table; there may be multiple virtual tables when
13555 multiple inheritance is in use.
13557 @cindex C@t{++} symbol display
13558 @item set print demangle
13559 @itemx show print demangle
13560 @itemx set print asm-demangle
13561 @itemx show print asm-demangle
13562 Control whether C@t{++} symbols display in their source form, both when
13563 displaying code as C@t{++} source and when displaying disassemblies.
13564 @xref{Print Settings, ,Print Settings}.
13566 @item set print object
13567 @itemx show print object
13568 Choose whether to print derived (actual) or declared types of objects.
13569 @xref{Print Settings, ,Print Settings}.
13571 @item set print vtbl
13572 @itemx show print vtbl
13573 Control the format for printing virtual function tables.
13574 @xref{Print Settings, ,Print Settings}.
13575 (The @code{vtbl} commands do not work on programs compiled with the HP
13576 ANSI C@t{++} compiler (@code{aCC}).)
13578 @kindex set overload-resolution
13579 @cindex overloaded functions, overload resolution
13580 @item set overload-resolution on
13581 Enable overload resolution for C@t{++} expression evaluation. The default
13582 is on. For overloaded functions, @value{GDBN} evaluates the arguments
13583 and searches for a function whose signature matches the argument types,
13584 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
13585 Expressions, ,C@t{++} Expressions}, for details).
13586 If it cannot find a match, it emits a message.
13588 @item set overload-resolution off
13589 Disable overload resolution for C@t{++} expression evaluation. For
13590 overloaded functions that are not class member functions, @value{GDBN}
13591 chooses the first function of the specified name that it finds in the
13592 symbol table, whether or not its arguments are of the correct type. For
13593 overloaded functions that are class member functions, @value{GDBN}
13594 searches for a function whose signature @emph{exactly} matches the
13597 @kindex show overload-resolution
13598 @item show overload-resolution
13599 Show the current setting of overload resolution.
13601 @item @r{Overloaded symbol names}
13602 You can specify a particular definition of an overloaded symbol, using
13603 the same notation that is used to declare such symbols in C@t{++}: type
13604 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
13605 also use the @value{GDBN} command-line word completion facilities to list the
13606 available choices, or to finish the type list for you.
13607 @xref{Completion,, Command Completion}, for details on how to do this.
13610 @node Decimal Floating Point
13611 @subsubsection Decimal Floating Point format
13612 @cindex decimal floating point format
13614 @value{GDBN} can examine, set and perform computations with numbers in
13615 decimal floating point format, which in the C language correspond to the
13616 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
13617 specified by the extension to support decimal floating-point arithmetic.
13619 There are two encodings in use, depending on the architecture: BID (Binary
13620 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
13621 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
13624 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
13625 to manipulate decimal floating point numbers, it is not possible to convert
13626 (using a cast, for example) integers wider than 32-bit to decimal float.
13628 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
13629 point computations, error checking in decimal float operations ignores
13630 underflow, overflow and divide by zero exceptions.
13632 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
13633 to inspect @code{_Decimal128} values stored in floating point registers.
13634 See @ref{PowerPC,,PowerPC} for more details.
13640 @value{GDBN} can be used to debug programs written in D and compiled with
13641 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
13642 specific feature --- dynamic arrays.
13647 @cindex Go (programming language)
13648 @value{GDBN} can be used to debug programs written in Go and compiled with
13649 @file{gccgo} or @file{6g} compilers.
13651 Here is a summary of the Go-specific features and restrictions:
13654 @cindex current Go package
13655 @item The current Go package
13656 The name of the current package does not need to be specified when
13657 specifying global variables and functions.
13659 For example, given the program:
13663 var myglob = "Shall we?"
13669 When stopped inside @code{main} either of these work:
13673 (gdb) p main.myglob
13676 @cindex builtin Go types
13677 @item Builtin Go types
13678 The @code{string} type is recognized by @value{GDBN} and is printed
13681 @cindex builtin Go functions
13682 @item Builtin Go functions
13683 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
13684 function and handles it internally.
13686 @cindex restrictions on Go expressions
13687 @item Restrictions on Go expressions
13688 All Go operators are supported except @code{&^}.
13689 The Go @code{_} ``blank identifier'' is not supported.
13690 Automatic dereferencing of pointers is not supported.
13694 @subsection Objective-C
13696 @cindex Objective-C
13697 This section provides information about some commands and command
13698 options that are useful for debugging Objective-C code. See also
13699 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
13700 few more commands specific to Objective-C support.
13703 * Method Names in Commands::
13704 * The Print Command with Objective-C::
13707 @node Method Names in Commands
13708 @subsubsection Method Names in Commands
13710 The following commands have been extended to accept Objective-C method
13711 names as line specifications:
13713 @kindex clear@r{, and Objective-C}
13714 @kindex break@r{, and Objective-C}
13715 @kindex info line@r{, and Objective-C}
13716 @kindex jump@r{, and Objective-C}
13717 @kindex list@r{, and Objective-C}
13721 @item @code{info line}
13726 A fully qualified Objective-C method name is specified as
13729 -[@var{Class} @var{methodName}]
13732 where the minus sign is used to indicate an instance method and a
13733 plus sign (not shown) is used to indicate a class method. The class
13734 name @var{Class} and method name @var{methodName} are enclosed in
13735 brackets, similar to the way messages are specified in Objective-C
13736 source code. For example, to set a breakpoint at the @code{create}
13737 instance method of class @code{Fruit} in the program currently being
13741 break -[Fruit create]
13744 To list ten program lines around the @code{initialize} class method,
13748 list +[NSText initialize]
13751 In the current version of @value{GDBN}, the plus or minus sign is
13752 required. In future versions of @value{GDBN}, the plus or minus
13753 sign will be optional, but you can use it to narrow the search. It
13754 is also possible to specify just a method name:
13760 You must specify the complete method name, including any colons. If
13761 your program's source files contain more than one @code{create} method,
13762 you'll be presented with a numbered list of classes that implement that
13763 method. Indicate your choice by number, or type @samp{0} to exit if
13766 As another example, to clear a breakpoint established at the
13767 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
13770 clear -[NSWindow makeKeyAndOrderFront:]
13773 @node The Print Command with Objective-C
13774 @subsubsection The Print Command With Objective-C
13775 @cindex Objective-C, print objects
13776 @kindex print-object
13777 @kindex po @r{(@code{print-object})}
13779 The print command has also been extended to accept methods. For example:
13782 print -[@var{object} hash]
13785 @cindex print an Objective-C object description
13786 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
13788 will tell @value{GDBN} to send the @code{hash} message to @var{object}
13789 and print the result. Also, an additional command has been added,
13790 @code{print-object} or @code{po} for short, which is meant to print
13791 the description of an object. However, this command may only work
13792 with certain Objective-C libraries that have a particular hook
13793 function, @code{_NSPrintForDebugger}, defined.
13796 @subsection OpenCL C
13799 This section provides information about @value{GDBN}s OpenCL C support.
13802 * OpenCL C Datatypes::
13803 * OpenCL C Expressions::
13804 * OpenCL C Operators::
13807 @node OpenCL C Datatypes
13808 @subsubsection OpenCL C Datatypes
13810 @cindex OpenCL C Datatypes
13811 @value{GDBN} supports the builtin scalar and vector datatypes specified
13812 by OpenCL 1.1. In addition the half- and double-precision floating point
13813 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
13814 extensions are also known to @value{GDBN}.
13816 @node OpenCL C Expressions
13817 @subsubsection OpenCL C Expressions
13819 @cindex OpenCL C Expressions
13820 @value{GDBN} supports accesses to vector components including the access as
13821 lvalue where possible. Since OpenCL C is based on C99 most C expressions
13822 supported by @value{GDBN} can be used as well.
13824 @node OpenCL C Operators
13825 @subsubsection OpenCL C Operators
13827 @cindex OpenCL C Operators
13828 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
13832 @subsection Fortran
13833 @cindex Fortran-specific support in @value{GDBN}
13835 @value{GDBN} can be used to debug programs written in Fortran, but it
13836 currently supports only the features of Fortran 77 language.
13838 @cindex trailing underscore, in Fortran symbols
13839 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
13840 among them) append an underscore to the names of variables and
13841 functions. When you debug programs compiled by those compilers, you
13842 will need to refer to variables and functions with a trailing
13846 * Fortran Operators:: Fortran operators and expressions
13847 * Fortran Defaults:: Default settings for Fortran
13848 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
13851 @node Fortran Operators
13852 @subsubsection Fortran Operators and Expressions
13854 @cindex Fortran operators and expressions
13856 Operators must be defined on values of specific types. For instance,
13857 @code{+} is defined on numbers, but not on characters or other non-
13858 arithmetic types. Operators are often defined on groups of types.
13862 The exponentiation operator. It raises the first operand to the power
13866 The range operator. Normally used in the form of array(low:high) to
13867 represent a section of array.
13870 The access component operator. Normally used to access elements in derived
13871 types. Also suitable for unions. As unions aren't part of regular Fortran,
13872 this can only happen when accessing a register that uses a gdbarch-defined
13876 @node Fortran Defaults
13877 @subsubsection Fortran Defaults
13879 @cindex Fortran Defaults
13881 Fortran symbols are usually case-insensitive, so @value{GDBN} by
13882 default uses case-insensitive matches for Fortran symbols. You can
13883 change that with the @samp{set case-insensitive} command, see
13884 @ref{Symbols}, for the details.
13886 @node Special Fortran Commands
13887 @subsubsection Special Fortran Commands
13889 @cindex Special Fortran commands
13891 @value{GDBN} has some commands to support Fortran-specific features,
13892 such as displaying common blocks.
13895 @cindex @code{COMMON} blocks, Fortran
13896 @kindex info common
13897 @item info common @r{[}@var{common-name}@r{]}
13898 This command prints the values contained in the Fortran @code{COMMON}
13899 block whose name is @var{common-name}. With no argument, the names of
13900 all @code{COMMON} blocks visible at the current program location are
13907 @cindex Pascal support in @value{GDBN}, limitations
13908 Debugging Pascal programs which use sets, subranges, file variables, or
13909 nested functions does not currently work. @value{GDBN} does not support
13910 entering expressions, printing values, or similar features using Pascal
13913 The Pascal-specific command @code{set print pascal_static-members}
13914 controls whether static members of Pascal objects are displayed.
13915 @xref{Print Settings, pascal_static-members}.
13918 @subsection Modula-2
13920 @cindex Modula-2, @value{GDBN} support
13922 The extensions made to @value{GDBN} to support Modula-2 only support
13923 output from the @sc{gnu} Modula-2 compiler (which is currently being
13924 developed). Other Modula-2 compilers are not currently supported, and
13925 attempting to debug executables produced by them is most likely
13926 to give an error as @value{GDBN} reads in the executable's symbol
13929 @cindex expressions in Modula-2
13931 * M2 Operators:: Built-in operators
13932 * Built-In Func/Proc:: Built-in functions and procedures
13933 * M2 Constants:: Modula-2 constants
13934 * M2 Types:: Modula-2 types
13935 * M2 Defaults:: Default settings for Modula-2
13936 * Deviations:: Deviations from standard Modula-2
13937 * M2 Checks:: Modula-2 type and range checks
13938 * M2 Scope:: The scope operators @code{::} and @code{.}
13939 * GDB/M2:: @value{GDBN} and Modula-2
13943 @subsubsection Operators
13944 @cindex Modula-2 operators
13946 Operators must be defined on values of specific types. For instance,
13947 @code{+} is defined on numbers, but not on structures. Operators are
13948 often defined on groups of types. For the purposes of Modula-2, the
13949 following definitions hold:
13954 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
13958 @emph{Character types} consist of @code{CHAR} and its subranges.
13961 @emph{Floating-point types} consist of @code{REAL}.
13964 @emph{Pointer types} consist of anything declared as @code{POINTER TO
13968 @emph{Scalar types} consist of all of the above.
13971 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
13974 @emph{Boolean types} consist of @code{BOOLEAN}.
13978 The following operators are supported, and appear in order of
13979 increasing precedence:
13983 Function argument or array index separator.
13986 Assignment. The value of @var{var} @code{:=} @var{value} is
13990 Less than, greater than on integral, floating-point, or enumerated
13994 Less than or equal to, greater than or equal to
13995 on integral, floating-point and enumerated types, or set inclusion on
13996 set types. Same precedence as @code{<}.
13998 @item =@r{, }<>@r{, }#
13999 Equality and two ways of expressing inequality, valid on scalar types.
14000 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
14001 available for inequality, since @code{#} conflicts with the script
14005 Set membership. Defined on set types and the types of their members.
14006 Same precedence as @code{<}.
14009 Boolean disjunction. Defined on boolean types.
14012 Boolean conjunction. Defined on boolean types.
14015 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14018 Addition and subtraction on integral and floating-point types, or union
14019 and difference on set types.
14022 Multiplication on integral and floating-point types, or set intersection
14026 Division on floating-point types, or symmetric set difference on set
14027 types. Same precedence as @code{*}.
14030 Integer division and remainder. Defined on integral types. Same
14031 precedence as @code{*}.
14034 Negative. Defined on @code{INTEGER} and @code{REAL} data.
14037 Pointer dereferencing. Defined on pointer types.
14040 Boolean negation. Defined on boolean types. Same precedence as
14044 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
14045 precedence as @code{^}.
14048 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
14051 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
14055 @value{GDBN} and Modula-2 scope operators.
14059 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
14060 treats the use of the operator @code{IN}, or the use of operators
14061 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
14062 @code{<=}, and @code{>=} on sets as an error.
14066 @node Built-In Func/Proc
14067 @subsubsection Built-in Functions and Procedures
14068 @cindex Modula-2 built-ins
14070 Modula-2 also makes available several built-in procedures and functions.
14071 In describing these, the following metavariables are used:
14076 represents an @code{ARRAY} variable.
14079 represents a @code{CHAR} constant or variable.
14082 represents a variable or constant of integral type.
14085 represents an identifier that belongs to a set. Generally used in the
14086 same function with the metavariable @var{s}. The type of @var{s} should
14087 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
14090 represents a variable or constant of integral or floating-point type.
14093 represents a variable or constant of floating-point type.
14099 represents a variable.
14102 represents a variable or constant of one of many types. See the
14103 explanation of the function for details.
14106 All Modula-2 built-in procedures also return a result, described below.
14110 Returns the absolute value of @var{n}.
14113 If @var{c} is a lower case letter, it returns its upper case
14114 equivalent, otherwise it returns its argument.
14117 Returns the character whose ordinal value is @var{i}.
14120 Decrements the value in the variable @var{v} by one. Returns the new value.
14122 @item DEC(@var{v},@var{i})
14123 Decrements the value in the variable @var{v} by @var{i}. Returns the
14126 @item EXCL(@var{m},@var{s})
14127 Removes the element @var{m} from the set @var{s}. Returns the new
14130 @item FLOAT(@var{i})
14131 Returns the floating point equivalent of the integer @var{i}.
14133 @item HIGH(@var{a})
14134 Returns the index of the last member of @var{a}.
14137 Increments the value in the variable @var{v} by one. Returns the new value.
14139 @item INC(@var{v},@var{i})
14140 Increments the value in the variable @var{v} by @var{i}. Returns the
14143 @item INCL(@var{m},@var{s})
14144 Adds the element @var{m} to the set @var{s} if it is not already
14145 there. Returns the new set.
14148 Returns the maximum value of the type @var{t}.
14151 Returns the minimum value of the type @var{t}.
14154 Returns boolean TRUE if @var{i} is an odd number.
14157 Returns the ordinal value of its argument. For example, the ordinal
14158 value of a character is its @sc{ascii} value (on machines supporting the
14159 @sc{ascii} character set). @var{x} must be of an ordered type, which include
14160 integral, character and enumerated types.
14162 @item SIZE(@var{x})
14163 Returns the size of its argument. @var{x} can be a variable or a type.
14165 @item TRUNC(@var{r})
14166 Returns the integral part of @var{r}.
14168 @item TSIZE(@var{x})
14169 Returns the size of its argument. @var{x} can be a variable or a type.
14171 @item VAL(@var{t},@var{i})
14172 Returns the member of the type @var{t} whose ordinal value is @var{i}.
14176 @emph{Warning:} Sets and their operations are not yet supported, so
14177 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
14181 @cindex Modula-2 constants
14183 @subsubsection Constants
14185 @value{GDBN} allows you to express the constants of Modula-2 in the following
14191 Integer constants are simply a sequence of digits. When used in an
14192 expression, a constant is interpreted to be type-compatible with the
14193 rest of the expression. Hexadecimal integers are specified by a
14194 trailing @samp{H}, and octal integers by a trailing @samp{B}.
14197 Floating point constants appear as a sequence of digits, followed by a
14198 decimal point and another sequence of digits. An optional exponent can
14199 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
14200 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
14201 digits of the floating point constant must be valid decimal (base 10)
14205 Character constants consist of a single character enclosed by a pair of
14206 like quotes, either single (@code{'}) or double (@code{"}). They may
14207 also be expressed by their ordinal value (their @sc{ascii} value, usually)
14208 followed by a @samp{C}.
14211 String constants consist of a sequence of characters enclosed by a
14212 pair of like quotes, either single (@code{'}) or double (@code{"}).
14213 Escape sequences in the style of C are also allowed. @xref{C
14214 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
14218 Enumerated constants consist of an enumerated identifier.
14221 Boolean constants consist of the identifiers @code{TRUE} and
14225 Pointer constants consist of integral values only.
14228 Set constants are not yet supported.
14232 @subsubsection Modula-2 Types
14233 @cindex Modula-2 types
14235 Currently @value{GDBN} can print the following data types in Modula-2
14236 syntax: array types, record types, set types, pointer types, procedure
14237 types, enumerated types, subrange types and base types. You can also
14238 print the contents of variables declared using these type.
14239 This section gives a number of simple source code examples together with
14240 sample @value{GDBN} sessions.
14242 The first example contains the following section of code:
14251 and you can request @value{GDBN} to interrogate the type and value of
14252 @code{r} and @code{s}.
14255 (@value{GDBP}) print s
14257 (@value{GDBP}) ptype s
14259 (@value{GDBP}) print r
14261 (@value{GDBP}) ptype r
14266 Likewise if your source code declares @code{s} as:
14270 s: SET ['A'..'Z'] ;
14274 then you may query the type of @code{s} by:
14277 (@value{GDBP}) ptype s
14278 type = SET ['A'..'Z']
14282 Note that at present you cannot interactively manipulate set
14283 expressions using the debugger.
14285 The following example shows how you might declare an array in Modula-2
14286 and how you can interact with @value{GDBN} to print its type and contents:
14290 s: ARRAY [-10..10] OF CHAR ;
14294 (@value{GDBP}) ptype s
14295 ARRAY [-10..10] OF CHAR
14298 Note that the array handling is not yet complete and although the type
14299 is printed correctly, expression handling still assumes that all
14300 arrays have a lower bound of zero and not @code{-10} as in the example
14303 Here are some more type related Modula-2 examples:
14307 colour = (blue, red, yellow, green) ;
14308 t = [blue..yellow] ;
14316 The @value{GDBN} interaction shows how you can query the data type
14317 and value of a variable.
14320 (@value{GDBP}) print s
14322 (@value{GDBP}) ptype t
14323 type = [blue..yellow]
14327 In this example a Modula-2 array is declared and its contents
14328 displayed. Observe that the contents are written in the same way as
14329 their @code{C} counterparts.
14333 s: ARRAY [1..5] OF CARDINAL ;
14339 (@value{GDBP}) print s
14340 $1 = @{1, 0, 0, 0, 0@}
14341 (@value{GDBP}) ptype s
14342 type = ARRAY [1..5] OF CARDINAL
14345 The Modula-2 language interface to @value{GDBN} also understands
14346 pointer types as shown in this example:
14350 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
14357 and you can request that @value{GDBN} describes the type of @code{s}.
14360 (@value{GDBP}) ptype s
14361 type = POINTER TO ARRAY [1..5] OF CARDINAL
14364 @value{GDBN} handles compound types as we can see in this example.
14365 Here we combine array types, record types, pointer types and subrange
14376 myarray = ARRAY myrange OF CARDINAL ;
14377 myrange = [-2..2] ;
14379 s: POINTER TO ARRAY myrange OF foo ;
14383 and you can ask @value{GDBN} to describe the type of @code{s} as shown
14387 (@value{GDBP}) ptype s
14388 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
14391 f3 : ARRAY [-2..2] OF CARDINAL;
14396 @subsubsection Modula-2 Defaults
14397 @cindex Modula-2 defaults
14399 If type and range checking are set automatically by @value{GDBN}, they
14400 both default to @code{on} whenever the working language changes to
14401 Modula-2. This happens regardless of whether you or @value{GDBN}
14402 selected the working language.
14404 If you allow @value{GDBN} to set the language automatically, then entering
14405 code compiled from a file whose name ends with @file{.mod} sets the
14406 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
14407 Infer the Source Language}, for further details.
14410 @subsubsection Deviations from Standard Modula-2
14411 @cindex Modula-2, deviations from
14413 A few changes have been made to make Modula-2 programs easier to debug.
14414 This is done primarily via loosening its type strictness:
14418 Unlike in standard Modula-2, pointer constants can be formed by
14419 integers. This allows you to modify pointer variables during
14420 debugging. (In standard Modula-2, the actual address contained in a
14421 pointer variable is hidden from you; it can only be modified
14422 through direct assignment to another pointer variable or expression that
14423 returned a pointer.)
14426 C escape sequences can be used in strings and characters to represent
14427 non-printable characters. @value{GDBN} prints out strings with these
14428 escape sequences embedded. Single non-printable characters are
14429 printed using the @samp{CHR(@var{nnn})} format.
14432 The assignment operator (@code{:=}) returns the value of its right-hand
14436 All built-in procedures both modify @emph{and} return their argument.
14440 @subsubsection Modula-2 Type and Range Checks
14441 @cindex Modula-2 checks
14444 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
14447 @c FIXME remove warning when type/range checks added
14449 @value{GDBN} considers two Modula-2 variables type equivalent if:
14453 They are of types that have been declared equivalent via a @code{TYPE
14454 @var{t1} = @var{t2}} statement
14457 They have been declared on the same line. (Note: This is true of the
14458 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
14461 As long as type checking is enabled, any attempt to combine variables
14462 whose types are not equivalent is an error.
14464 Range checking is done on all mathematical operations, assignment, array
14465 index bounds, and all built-in functions and procedures.
14468 @subsubsection The Scope Operators @code{::} and @code{.}
14470 @cindex @code{.}, Modula-2 scope operator
14471 @cindex colon, doubled as scope operator
14473 @vindex colon-colon@r{, in Modula-2}
14474 @c Info cannot handle :: but TeX can.
14477 @vindex ::@r{, in Modula-2}
14480 There are a few subtle differences between the Modula-2 scope operator
14481 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
14486 @var{module} . @var{id}
14487 @var{scope} :: @var{id}
14491 where @var{scope} is the name of a module or a procedure,
14492 @var{module} the name of a module, and @var{id} is any declared
14493 identifier within your program, except another module.
14495 Using the @code{::} operator makes @value{GDBN} search the scope
14496 specified by @var{scope} for the identifier @var{id}. If it is not
14497 found in the specified scope, then @value{GDBN} searches all scopes
14498 enclosing the one specified by @var{scope}.
14500 Using the @code{.} operator makes @value{GDBN} search the current scope for
14501 the identifier specified by @var{id} that was imported from the
14502 definition module specified by @var{module}. With this operator, it is
14503 an error if the identifier @var{id} was not imported from definition
14504 module @var{module}, or if @var{id} is not an identifier in
14508 @subsubsection @value{GDBN} and Modula-2
14510 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
14511 Five subcommands of @code{set print} and @code{show print} apply
14512 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
14513 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
14514 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
14515 analogue in Modula-2.
14517 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
14518 with any language, is not useful with Modula-2. Its
14519 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
14520 created in Modula-2 as they can in C or C@t{++}. However, because an
14521 address can be specified by an integral constant, the construct
14522 @samp{@{@var{type}@}@var{adrexp}} is still useful.
14524 @cindex @code{#} in Modula-2
14525 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
14526 interpreted as the beginning of a comment. Use @code{<>} instead.
14532 The extensions made to @value{GDBN} for Ada only support
14533 output from the @sc{gnu} Ada (GNAT) compiler.
14534 Other Ada compilers are not currently supported, and
14535 attempting to debug executables produced by them is most likely
14539 @cindex expressions in Ada
14541 * Ada Mode Intro:: General remarks on the Ada syntax
14542 and semantics supported by Ada mode
14544 * Omissions from Ada:: Restrictions on the Ada expression syntax.
14545 * Additions to Ada:: Extensions of the Ada expression syntax.
14546 * Stopping Before Main Program:: Debugging the program during elaboration.
14547 * Ada Tasks:: Listing and setting breakpoints in tasks.
14548 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
14549 * Ravenscar Profile:: Tasking Support when using the Ravenscar
14551 * Ada Glitches:: Known peculiarities of Ada mode.
14554 @node Ada Mode Intro
14555 @subsubsection Introduction
14556 @cindex Ada mode, general
14558 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
14559 syntax, with some extensions.
14560 The philosophy behind the design of this subset is
14564 That @value{GDBN} should provide basic literals and access to operations for
14565 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
14566 leaving more sophisticated computations to subprograms written into the
14567 program (which therefore may be called from @value{GDBN}).
14570 That type safety and strict adherence to Ada language restrictions
14571 are not particularly important to the @value{GDBN} user.
14574 That brevity is important to the @value{GDBN} user.
14577 Thus, for brevity, the debugger acts as if all names declared in
14578 user-written packages are directly visible, even if they are not visible
14579 according to Ada rules, thus making it unnecessary to fully qualify most
14580 names with their packages, regardless of context. Where this causes
14581 ambiguity, @value{GDBN} asks the user's intent.
14583 The debugger will start in Ada mode if it detects an Ada main program.
14584 As for other languages, it will enter Ada mode when stopped in a program that
14585 was translated from an Ada source file.
14587 While in Ada mode, you may use `@t{--}' for comments. This is useful
14588 mostly for documenting command files. The standard @value{GDBN} comment
14589 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
14590 middle (to allow based literals).
14592 The debugger supports limited overloading. Given a subprogram call in which
14593 the function symbol has multiple definitions, it will use the number of
14594 actual parameters and some information about their types to attempt to narrow
14595 the set of definitions. It also makes very limited use of context, preferring
14596 procedures to functions in the context of the @code{call} command, and
14597 functions to procedures elsewhere.
14599 @node Omissions from Ada
14600 @subsubsection Omissions from Ada
14601 @cindex Ada, omissions from
14603 Here are the notable omissions from the subset:
14607 Only a subset of the attributes are supported:
14611 @t{'First}, @t{'Last}, and @t{'Length}
14612 on array objects (not on types and subtypes).
14615 @t{'Min} and @t{'Max}.
14618 @t{'Pos} and @t{'Val}.
14624 @t{'Range} on array objects (not subtypes), but only as the right
14625 operand of the membership (@code{in}) operator.
14628 @t{'Access}, @t{'Unchecked_Access}, and
14629 @t{'Unrestricted_Access} (a GNAT extension).
14637 @code{Characters.Latin_1} are not available and
14638 concatenation is not implemented. Thus, escape characters in strings are
14639 not currently available.
14642 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
14643 equality of representations. They will generally work correctly
14644 for strings and arrays whose elements have integer or enumeration types.
14645 They may not work correctly for arrays whose element
14646 types have user-defined equality, for arrays of real values
14647 (in particular, IEEE-conformant floating point, because of negative
14648 zeroes and NaNs), and for arrays whose elements contain unused bits with
14649 indeterminate values.
14652 The other component-by-component array operations (@code{and}, @code{or},
14653 @code{xor}, @code{not}, and relational tests other than equality)
14654 are not implemented.
14657 @cindex array aggregates (Ada)
14658 @cindex record aggregates (Ada)
14659 @cindex aggregates (Ada)
14660 There is limited support for array and record aggregates. They are
14661 permitted only on the right sides of assignments, as in these examples:
14664 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
14665 (@value{GDBP}) set An_Array := (1, others => 0)
14666 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
14667 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
14668 (@value{GDBP}) set A_Record := (1, "Peter", True);
14669 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
14673 discriminant's value by assigning an aggregate has an
14674 undefined effect if that discriminant is used within the record.
14675 However, you can first modify discriminants by directly assigning to
14676 them (which normally would not be allowed in Ada), and then performing an
14677 aggregate assignment. For example, given a variable @code{A_Rec}
14678 declared to have a type such as:
14681 type Rec (Len : Small_Integer := 0) is record
14683 Vals : IntArray (1 .. Len);
14687 you can assign a value with a different size of @code{Vals} with two
14691 (@value{GDBP}) set A_Rec.Len := 4
14692 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
14695 As this example also illustrates, @value{GDBN} is very loose about the usual
14696 rules concerning aggregates. You may leave out some of the
14697 components of an array or record aggregate (such as the @code{Len}
14698 component in the assignment to @code{A_Rec} above); they will retain their
14699 original values upon assignment. You may freely use dynamic values as
14700 indices in component associations. You may even use overlapping or
14701 redundant component associations, although which component values are
14702 assigned in such cases is not defined.
14705 Calls to dispatching subprograms are not implemented.
14708 The overloading algorithm is much more limited (i.e., less selective)
14709 than that of real Ada. It makes only limited use of the context in
14710 which a subexpression appears to resolve its meaning, and it is much
14711 looser in its rules for allowing type matches. As a result, some
14712 function calls will be ambiguous, and the user will be asked to choose
14713 the proper resolution.
14716 The @code{new} operator is not implemented.
14719 Entry calls are not implemented.
14722 Aside from printing, arithmetic operations on the native VAX floating-point
14723 formats are not supported.
14726 It is not possible to slice a packed array.
14729 The names @code{True} and @code{False}, when not part of a qualified name,
14730 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
14732 Should your program
14733 redefine these names in a package or procedure (at best a dubious practice),
14734 you will have to use fully qualified names to access their new definitions.
14737 @node Additions to Ada
14738 @subsubsection Additions to Ada
14739 @cindex Ada, deviations from
14741 As it does for other languages, @value{GDBN} makes certain generic
14742 extensions to Ada (@pxref{Expressions}):
14746 If the expression @var{E} is a variable residing in memory (typically
14747 a local variable or array element) and @var{N} is a positive integer,
14748 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
14749 @var{N}-1 adjacent variables following it in memory as an array. In
14750 Ada, this operator is generally not necessary, since its prime use is
14751 in displaying parts of an array, and slicing will usually do this in
14752 Ada. However, there are occasional uses when debugging programs in
14753 which certain debugging information has been optimized away.
14756 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
14757 appears in function or file @var{B}.'' When @var{B} is a file name,
14758 you must typically surround it in single quotes.
14761 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
14762 @var{type} that appears at address @var{addr}.''
14765 A name starting with @samp{$} is a convenience variable
14766 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
14769 In addition, @value{GDBN} provides a few other shortcuts and outright
14770 additions specific to Ada:
14774 The assignment statement is allowed as an expression, returning
14775 its right-hand operand as its value. Thus, you may enter
14778 (@value{GDBP}) set x := y + 3
14779 (@value{GDBP}) print A(tmp := y + 1)
14783 The semicolon is allowed as an ``operator,'' returning as its value
14784 the value of its right-hand operand.
14785 This allows, for example,
14786 complex conditional breaks:
14789 (@value{GDBP}) break f
14790 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
14794 Rather than use catenation and symbolic character names to introduce special
14795 characters into strings, one may instead use a special bracket notation,
14796 which is also used to print strings. A sequence of characters of the form
14797 @samp{["@var{XX}"]} within a string or character literal denotes the
14798 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
14799 sequence of characters @samp{["""]} also denotes a single quotation mark
14800 in strings. For example,
14802 "One line.["0a"]Next line.["0a"]"
14805 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
14809 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
14810 @t{'Max} is optional (and is ignored in any case). For example, it is valid
14814 (@value{GDBP}) print 'max(x, y)
14818 When printing arrays, @value{GDBN} uses positional notation when the
14819 array has a lower bound of 1, and uses a modified named notation otherwise.
14820 For example, a one-dimensional array of three integers with a lower bound
14821 of 3 might print as
14828 That is, in contrast to valid Ada, only the first component has a @code{=>}
14832 You may abbreviate attributes in expressions with any unique,
14833 multi-character subsequence of
14834 their names (an exact match gets preference).
14835 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
14836 in place of @t{a'length}.
14839 @cindex quoting Ada internal identifiers
14840 Since Ada is case-insensitive, the debugger normally maps identifiers you type
14841 to lower case. The GNAT compiler uses upper-case characters for
14842 some of its internal identifiers, which are normally of no interest to users.
14843 For the rare occasions when you actually have to look at them,
14844 enclose them in angle brackets to avoid the lower-case mapping.
14847 (@value{GDBP}) print <JMPBUF_SAVE>[0]
14851 Printing an object of class-wide type or dereferencing an
14852 access-to-class-wide value will display all the components of the object's
14853 specific type (as indicated by its run-time tag). Likewise, component
14854 selection on such a value will operate on the specific type of the
14859 @node Stopping Before Main Program
14860 @subsubsection Stopping at the Very Beginning
14862 @cindex breakpointing Ada elaboration code
14863 It is sometimes necessary to debug the program during elaboration, and
14864 before reaching the main procedure.
14865 As defined in the Ada Reference
14866 Manual, the elaboration code is invoked from a procedure called
14867 @code{adainit}. To run your program up to the beginning of
14868 elaboration, simply use the following two commands:
14869 @code{tbreak adainit} and @code{run}.
14872 @subsubsection Extensions for Ada Tasks
14873 @cindex Ada, tasking
14875 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
14876 @value{GDBN} provides the following task-related commands:
14881 This command shows a list of current Ada tasks, as in the following example:
14888 (@value{GDBP}) info tasks
14889 ID TID P-ID Pri State Name
14890 1 8088000 0 15 Child Activation Wait main_task
14891 2 80a4000 1 15 Accept Statement b
14892 3 809a800 1 15 Child Activation Wait a
14893 * 4 80ae800 3 15 Runnable c
14898 In this listing, the asterisk before the last task indicates it to be the
14899 task currently being inspected.
14903 Represents @value{GDBN}'s internal task number.
14909 The parent's task ID (@value{GDBN}'s internal task number).
14912 The base priority of the task.
14915 Current state of the task.
14919 The task has been created but has not been activated. It cannot be
14923 The task is not blocked for any reason known to Ada. (It may be waiting
14924 for a mutex, though.) It is conceptually "executing" in normal mode.
14927 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
14928 that were waiting on terminate alternatives have been awakened and have
14929 terminated themselves.
14931 @item Child Activation Wait
14932 The task is waiting for created tasks to complete activation.
14934 @item Accept Statement
14935 The task is waiting on an accept or selective wait statement.
14937 @item Waiting on entry call
14938 The task is waiting on an entry call.
14940 @item Async Select Wait
14941 The task is waiting to start the abortable part of an asynchronous
14945 The task is waiting on a select statement with only a delay
14948 @item Child Termination Wait
14949 The task is sleeping having completed a master within itself, and is
14950 waiting for the tasks dependent on that master to become terminated or
14951 waiting on a terminate Phase.
14953 @item Wait Child in Term Alt
14954 The task is sleeping waiting for tasks on terminate alternatives to
14955 finish terminating.
14957 @item Accepting RV with @var{taskno}
14958 The task is accepting a rendez-vous with the task @var{taskno}.
14962 Name of the task in the program.
14966 @kindex info task @var{taskno}
14967 @item info task @var{taskno}
14968 This command shows detailled informations on the specified task, as in
14969 the following example:
14974 (@value{GDBP}) info tasks
14975 ID TID P-ID Pri State Name
14976 1 8077880 0 15 Child Activation Wait main_task
14977 * 2 807c468 1 15 Runnable task_1
14978 (@value{GDBP}) info task 2
14979 Ada Task: 0x807c468
14982 Parent: 1 (main_task)
14988 @kindex task@r{ (Ada)}
14989 @cindex current Ada task ID
14990 This command prints the ID of the current task.
14996 (@value{GDBP}) info tasks
14997 ID TID P-ID Pri State Name
14998 1 8077870 0 15 Child Activation Wait main_task
14999 * 2 807c458 1 15 Runnable t
15000 (@value{GDBP}) task
15001 [Current task is 2]
15004 @item task @var{taskno}
15005 @cindex Ada task switching
15006 This command is like the @code{thread @var{threadno}}
15007 command (@pxref{Threads}). It switches the context of debugging
15008 from the current task to the given task.
15014 (@value{GDBP}) info tasks
15015 ID TID P-ID Pri State Name
15016 1 8077870 0 15 Child Activation Wait main_task
15017 * 2 807c458 1 15 Runnable t
15018 (@value{GDBP}) task 1
15019 [Switching to task 1]
15020 #0 0x8067726 in pthread_cond_wait ()
15022 #0 0x8067726 in pthread_cond_wait ()
15023 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
15024 #2 0x805cb63 in system.task_primitives.operations.sleep ()
15025 #3 0x806153e in system.tasking.stages.activate_tasks ()
15026 #4 0x804aacc in un () at un.adb:5
15029 @item break @var{linespec} task @var{taskno}
15030 @itemx break @var{linespec} task @var{taskno} if @dots{}
15031 @cindex breakpoints and tasks, in Ada
15032 @cindex task breakpoints, in Ada
15033 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
15034 These commands are like the @code{break @dots{} thread @dots{}}
15035 command (@pxref{Thread Stops}).
15036 @var{linespec} specifies source lines, as described
15037 in @ref{Specify Location}.
15039 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
15040 to specify that you only want @value{GDBN} to stop the program when a
15041 particular Ada task reaches this breakpoint. @var{taskno} is one of the
15042 numeric task identifiers assigned by @value{GDBN}, shown in the first
15043 column of the @samp{info tasks} display.
15045 If you do not specify @samp{task @var{taskno}} when you set a
15046 breakpoint, the breakpoint applies to @emph{all} tasks of your
15049 You can use the @code{task} qualifier on conditional breakpoints as
15050 well; in this case, place @samp{task @var{taskno}} before the
15051 breakpoint condition (before the @code{if}).
15059 (@value{GDBP}) info tasks
15060 ID TID P-ID Pri State Name
15061 1 140022020 0 15 Child Activation Wait main_task
15062 2 140045060 1 15 Accept/Select Wait t2
15063 3 140044840 1 15 Runnable t1
15064 * 4 140056040 1 15 Runnable t3
15065 (@value{GDBP}) b 15 task 2
15066 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
15067 (@value{GDBP}) cont
15072 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
15074 (@value{GDBP}) info tasks
15075 ID TID P-ID Pri State Name
15076 1 140022020 0 15 Child Activation Wait main_task
15077 * 2 140045060 1 15 Runnable t2
15078 3 140044840 1 15 Runnable t1
15079 4 140056040 1 15 Delay Sleep t3
15083 @node Ada Tasks and Core Files
15084 @subsubsection Tasking Support when Debugging Core Files
15085 @cindex Ada tasking and core file debugging
15087 When inspecting a core file, as opposed to debugging a live program,
15088 tasking support may be limited or even unavailable, depending on
15089 the platform being used.
15090 For instance, on x86-linux, the list of tasks is available, but task
15091 switching is not supported. On Tru64, however, task switching will work
15094 On certain platforms, including Tru64, the debugger needs to perform some
15095 memory writes in order to provide Ada tasking support. When inspecting
15096 a core file, this means that the core file must be opened with read-write
15097 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
15098 Under these circumstances, you should make a backup copy of the core
15099 file before inspecting it with @value{GDBN}.
15101 @node Ravenscar Profile
15102 @subsubsection Tasking Support when using the Ravenscar Profile
15103 @cindex Ravenscar Profile
15105 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
15106 specifically designed for systems with safety-critical real-time
15110 @kindex set ravenscar task-switching on
15111 @cindex task switching with program using Ravenscar Profile
15112 @item set ravenscar task-switching on
15113 Allows task switching when debugging a program that uses the Ravenscar
15114 Profile. This is the default.
15116 @kindex set ravenscar task-switching off
15117 @item set ravenscar task-switching off
15118 Turn off task switching when debugging a program that uses the Ravenscar
15119 Profile. This is mostly intended to disable the code that adds support
15120 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
15121 the Ravenscar runtime is preventing @value{GDBN} from working properly.
15122 To be effective, this command should be run before the program is started.
15124 @kindex show ravenscar task-switching
15125 @item show ravenscar task-switching
15126 Show whether it is possible to switch from task to task in a program
15127 using the Ravenscar Profile.
15132 @subsubsection Known Peculiarities of Ada Mode
15133 @cindex Ada, problems
15135 Besides the omissions listed previously (@pxref{Omissions from Ada}),
15136 we know of several problems with and limitations of Ada mode in
15138 some of which will be fixed with planned future releases of the debugger
15139 and the GNU Ada compiler.
15143 Static constants that the compiler chooses not to materialize as objects in
15144 storage are invisible to the debugger.
15147 Named parameter associations in function argument lists are ignored (the
15148 argument lists are treated as positional).
15151 Many useful library packages are currently invisible to the debugger.
15154 Fixed-point arithmetic, conversions, input, and output is carried out using
15155 floating-point arithmetic, and may give results that only approximate those on
15159 The GNAT compiler never generates the prefix @code{Standard} for any of
15160 the standard symbols defined by the Ada language. @value{GDBN} knows about
15161 this: it will strip the prefix from names when you use it, and will never
15162 look for a name you have so qualified among local symbols, nor match against
15163 symbols in other packages or subprograms. If you have
15164 defined entities anywhere in your program other than parameters and
15165 local variables whose simple names match names in @code{Standard},
15166 GNAT's lack of qualification here can cause confusion. When this happens,
15167 you can usually resolve the confusion
15168 by qualifying the problematic names with package
15169 @code{Standard} explicitly.
15172 Older versions of the compiler sometimes generate erroneous debugging
15173 information, resulting in the debugger incorrectly printing the value
15174 of affected entities. In some cases, the debugger is able to work
15175 around an issue automatically. In other cases, the debugger is able
15176 to work around the issue, but the work-around has to be specifically
15179 @kindex set ada trust-PAD-over-XVS
15180 @kindex show ada trust-PAD-over-XVS
15183 @item set ada trust-PAD-over-XVS on
15184 Configure GDB to strictly follow the GNAT encoding when computing the
15185 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
15186 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
15187 a complete description of the encoding used by the GNAT compiler).
15188 This is the default.
15190 @item set ada trust-PAD-over-XVS off
15191 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
15192 sometimes prints the wrong value for certain entities, changing @code{ada
15193 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
15194 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
15195 @code{off}, but this incurs a slight performance penalty, so it is
15196 recommended to leave this setting to @code{on} unless necessary.
15200 @node Unsupported Languages
15201 @section Unsupported Languages
15203 @cindex unsupported languages
15204 @cindex minimal language
15205 In addition to the other fully-supported programming languages,
15206 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
15207 It does not represent a real programming language, but provides a set
15208 of capabilities close to what the C or assembly languages provide.
15209 This should allow most simple operations to be performed while debugging
15210 an application that uses a language currently not supported by @value{GDBN}.
15212 If the language is set to @code{auto}, @value{GDBN} will automatically
15213 select this language if the current frame corresponds to an unsupported
15217 @chapter Examining the Symbol Table
15219 The commands described in this chapter allow you to inquire about the
15220 symbols (names of variables, functions and types) defined in your
15221 program. This information is inherent in the text of your program and
15222 does not change as your program executes. @value{GDBN} finds it in your
15223 program's symbol table, in the file indicated when you started @value{GDBN}
15224 (@pxref{File Options, ,Choosing Files}), or by one of the
15225 file-management commands (@pxref{Files, ,Commands to Specify Files}).
15227 @cindex symbol names
15228 @cindex names of symbols
15229 @cindex quoting names
15230 Occasionally, you may need to refer to symbols that contain unusual
15231 characters, which @value{GDBN} ordinarily treats as word delimiters. The
15232 most frequent case is in referring to static variables in other
15233 source files (@pxref{Variables,,Program Variables}). File names
15234 are recorded in object files as debugging symbols, but @value{GDBN} would
15235 ordinarily parse a typical file name, like @file{foo.c}, as the three words
15236 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
15237 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
15244 looks up the value of @code{x} in the scope of the file @file{foo.c}.
15247 @cindex case-insensitive symbol names
15248 @cindex case sensitivity in symbol names
15249 @kindex set case-sensitive
15250 @item set case-sensitive on
15251 @itemx set case-sensitive off
15252 @itemx set case-sensitive auto
15253 Normally, when @value{GDBN} looks up symbols, it matches their names
15254 with case sensitivity determined by the current source language.
15255 Occasionally, you may wish to control that. The command @code{set
15256 case-sensitive} lets you do that by specifying @code{on} for
15257 case-sensitive matches or @code{off} for case-insensitive ones. If
15258 you specify @code{auto}, case sensitivity is reset to the default
15259 suitable for the source language. The default is case-sensitive
15260 matches for all languages except for Fortran, for which the default is
15261 case-insensitive matches.
15263 @kindex show case-sensitive
15264 @item show case-sensitive
15265 This command shows the current setting of case sensitivity for symbols
15268 @kindex set print type methods
15269 @item set print type methods
15270 @itemx set print type methods on
15271 @itemx set print type methods off
15272 Normally, when @value{GDBN} prints a class, it displays any methods
15273 declared in that class. You can control this behavior either by
15274 passing the appropriate flag to @code{ptype}, or using @command{set
15275 print type methods}. Specifying @code{on} will cause @value{GDBN} to
15276 display the methods; this is the default. Specifying @code{off} will
15277 cause @value{GDBN} to omit the methods.
15279 @kindex show print type methods
15280 @item show print type methods
15281 This command shows the current setting of method display when printing
15284 @kindex set print type typedefs
15285 @item set print type typedefs
15286 @itemx set print type typedefs on
15287 @itemx set print type typedefs off
15289 Normally, when @value{GDBN} prints a class, it displays any typedefs
15290 defined in that class. You can control this behavior either by
15291 passing the appropriate flag to @code{ptype}, or using @command{set
15292 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
15293 display the typedef definitions; this is the default. Specifying
15294 @code{off} will cause @value{GDBN} to omit the typedef definitions.
15295 Note that this controls whether the typedef definition itself is
15296 printed, not whether typedef names are substituted when printing other
15299 @kindex show print type typedefs
15300 @item show print type typedefs
15301 This command shows the current setting of typedef display when
15304 @kindex info address
15305 @cindex address of a symbol
15306 @item info address @var{symbol}
15307 Describe where the data for @var{symbol} is stored. For a register
15308 variable, this says which register it is kept in. For a non-register
15309 local variable, this prints the stack-frame offset at which the variable
15312 Note the contrast with @samp{print &@var{symbol}}, which does not work
15313 at all for a register variable, and for a stack local variable prints
15314 the exact address of the current instantiation of the variable.
15316 @kindex info symbol
15317 @cindex symbol from address
15318 @cindex closest symbol and offset for an address
15319 @item info symbol @var{addr}
15320 Print the name of a symbol which is stored at the address @var{addr}.
15321 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
15322 nearest symbol and an offset from it:
15325 (@value{GDBP}) info symbol 0x54320
15326 _initialize_vx + 396 in section .text
15330 This is the opposite of the @code{info address} command. You can use
15331 it to find out the name of a variable or a function given its address.
15333 For dynamically linked executables, the name of executable or shared
15334 library containing the symbol is also printed:
15337 (@value{GDBP}) info symbol 0x400225
15338 _start + 5 in section .text of /tmp/a.out
15339 (@value{GDBP}) info symbol 0x2aaaac2811cf
15340 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
15344 @item whatis[/@var{flags}] [@var{arg}]
15345 Print the data type of @var{arg}, which can be either an expression
15346 or a name of a data type. With no argument, print the data type of
15347 @code{$}, the last value in the value history.
15349 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
15350 is not actually evaluated, and any side-effecting operations (such as
15351 assignments or function calls) inside it do not take place.
15353 If @var{arg} is a variable or an expression, @code{whatis} prints its
15354 literal type as it is used in the source code. If the type was
15355 defined using a @code{typedef}, @code{whatis} will @emph{not} print
15356 the data type underlying the @code{typedef}. If the type of the
15357 variable or the expression is a compound data type, such as
15358 @code{struct} or @code{class}, @code{whatis} never prints their
15359 fields or methods. It just prints the @code{struct}/@code{class}
15360 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
15361 such a compound data type, use @code{ptype}.
15363 If @var{arg} is a type name that was defined using @code{typedef},
15364 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
15365 Unrolling means that @code{whatis} will show the underlying type used
15366 in the @code{typedef} declaration of @var{arg}. However, if that
15367 underlying type is also a @code{typedef}, @code{whatis} will not
15370 For C code, the type names may also have the form @samp{class
15371 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
15372 @var{union-tag}} or @samp{enum @var{enum-tag}}.
15374 @var{flags} can be used to modify how the type is displayed.
15375 Available flags are:
15379 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
15380 parameters and typedefs defined in a class when printing the class'
15381 members. The @code{/r} flag disables this.
15384 Do not print methods defined in the class.
15387 Print methods defined in the class. This is the default, but the flag
15388 exists in case you change the default with @command{set print type methods}.
15391 Do not print typedefs defined in the class. Note that this controls
15392 whether the typedef definition itself is printed, not whether typedef
15393 names are substituted when printing other types.
15396 Print typedefs defined in the class. This is the default, but the flag
15397 exists in case you change the default with @command{set print type typedefs}.
15401 @item ptype[/@var{flags}] [@var{arg}]
15402 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
15403 detailed description of the type, instead of just the name of the type.
15404 @xref{Expressions, ,Expressions}.
15406 Contrary to @code{whatis}, @code{ptype} always unrolls any
15407 @code{typedef}s in its argument declaration, whether the argument is
15408 a variable, expression, or a data type. This means that @code{ptype}
15409 of a variable or an expression will not print literally its type as
15410 present in the source code---use @code{whatis} for that. @code{typedef}s at
15411 the pointer or reference targets are also unrolled. Only @code{typedef}s of
15412 fields, methods and inner @code{class typedef}s of @code{struct}s,
15413 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
15415 For example, for this variable declaration:
15418 typedef double real_t;
15419 struct complex @{ real_t real; double imag; @};
15420 typedef struct complex complex_t;
15422 real_t *real_pointer_var;
15426 the two commands give this output:
15430 (@value{GDBP}) whatis var
15432 (@value{GDBP}) ptype var
15433 type = struct complex @{
15437 (@value{GDBP}) whatis complex_t
15438 type = struct complex
15439 (@value{GDBP}) whatis struct complex
15440 type = struct complex
15441 (@value{GDBP}) ptype struct complex
15442 type = struct complex @{
15446 (@value{GDBP}) whatis real_pointer_var
15448 (@value{GDBP}) ptype real_pointer_var
15454 As with @code{whatis}, using @code{ptype} without an argument refers to
15455 the type of @code{$}, the last value in the value history.
15457 @cindex incomplete type
15458 Sometimes, programs use opaque data types or incomplete specifications
15459 of complex data structure. If the debug information included in the
15460 program does not allow @value{GDBN} to display a full declaration of
15461 the data type, it will say @samp{<incomplete type>}. For example,
15462 given these declarations:
15466 struct foo *fooptr;
15470 but no definition for @code{struct foo} itself, @value{GDBN} will say:
15473 (@value{GDBP}) ptype foo
15474 $1 = <incomplete type>
15478 ``Incomplete type'' is C terminology for data types that are not
15479 completely specified.
15482 @item info types @var{regexp}
15484 Print a brief description of all types whose names match the regular
15485 expression @var{regexp} (or all types in your program, if you supply
15486 no argument). Each complete typename is matched as though it were a
15487 complete line; thus, @samp{i type value} gives information on all
15488 types in your program whose names include the string @code{value}, but
15489 @samp{i type ^value$} gives information only on types whose complete
15490 name is @code{value}.
15492 This command differs from @code{ptype} in two ways: first, like
15493 @code{whatis}, it does not print a detailed description; second, it
15494 lists all source files where a type is defined.
15496 @kindex info type-printers
15497 @item info type-printers
15498 Versions of @value{GDBN} that ship with Python scripting enabled may
15499 have ``type printers'' available. When using @command{ptype} or
15500 @command{whatis}, these printers are consulted when the name of a type
15501 is needed. @xref{Type Printing API}, for more information on writing
15504 @code{info type-printers} displays all the available type printers.
15506 @kindex enable type-printer
15507 @kindex disable type-printer
15508 @item enable type-printer @var{name}@dots{}
15509 @item disable type-printer @var{name}@dots{}
15510 These commands can be used to enable or disable type printers.
15513 @cindex local variables
15514 @item info scope @var{location}
15515 List all the variables local to a particular scope. This command
15516 accepts a @var{location} argument---a function name, a source line, or
15517 an address preceded by a @samp{*}, and prints all the variables local
15518 to the scope defined by that location. (@xref{Specify Location}, for
15519 details about supported forms of @var{location}.) For example:
15522 (@value{GDBP}) @b{info scope command_line_handler}
15523 Scope for command_line_handler:
15524 Symbol rl is an argument at stack/frame offset 8, length 4.
15525 Symbol linebuffer is in static storage at address 0x150a18, length 4.
15526 Symbol linelength is in static storage at address 0x150a1c, length 4.
15527 Symbol p is a local variable in register $esi, length 4.
15528 Symbol p1 is a local variable in register $ebx, length 4.
15529 Symbol nline is a local variable in register $edx, length 4.
15530 Symbol repeat is a local variable at frame offset -8, length 4.
15534 This command is especially useful for determining what data to collect
15535 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
15538 @kindex info source
15540 Show information about the current source file---that is, the source file for
15541 the function containing the current point of execution:
15544 the name of the source file, and the directory containing it,
15546 the directory it was compiled in,
15548 its length, in lines,
15550 which programming language it is written in,
15552 whether the executable includes debugging information for that file, and
15553 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
15555 whether the debugging information includes information about
15556 preprocessor macros.
15560 @kindex info sources
15562 Print the names of all source files in your program for which there is
15563 debugging information, organized into two lists: files whose symbols
15564 have already been read, and files whose symbols will be read when needed.
15566 @kindex info functions
15567 @item info functions
15568 Print the names and data types of all defined functions.
15570 @item info functions @var{regexp}
15571 Print the names and data types of all defined functions
15572 whose names contain a match for regular expression @var{regexp}.
15573 Thus, @samp{info fun step} finds all functions whose names
15574 include @code{step}; @samp{info fun ^step} finds those whose names
15575 start with @code{step}. If a function name contains characters
15576 that conflict with the regular expression language (e.g.@:
15577 @samp{operator*()}), they may be quoted with a backslash.
15579 @kindex info variables
15580 @item info variables
15581 Print the names and data types of all variables that are defined
15582 outside of functions (i.e.@: excluding local variables).
15584 @item info variables @var{regexp}
15585 Print the names and data types of all variables (except for local
15586 variables) whose names contain a match for regular expression
15589 @kindex info classes
15590 @cindex Objective-C, classes and selectors
15592 @itemx info classes @var{regexp}
15593 Display all Objective-C classes in your program, or
15594 (with the @var{regexp} argument) all those matching a particular regular
15597 @kindex info selectors
15598 @item info selectors
15599 @itemx info selectors @var{regexp}
15600 Display all Objective-C selectors in your program, or
15601 (with the @var{regexp} argument) all those matching a particular regular
15605 This was never implemented.
15606 @kindex info methods
15608 @itemx info methods @var{regexp}
15609 The @code{info methods} command permits the user to examine all defined
15610 methods within C@t{++} program, or (with the @var{regexp} argument) a
15611 specific set of methods found in the various C@t{++} classes. Many
15612 C@t{++} classes provide a large number of methods. Thus, the output
15613 from the @code{ptype} command can be overwhelming and hard to use. The
15614 @code{info-methods} command filters the methods, printing only those
15615 which match the regular-expression @var{regexp}.
15618 @cindex opaque data types
15619 @kindex set opaque-type-resolution
15620 @item set opaque-type-resolution on
15621 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
15622 declared as a pointer to a @code{struct}, @code{class}, or
15623 @code{union}---for example, @code{struct MyType *}---that is used in one
15624 source file although the full declaration of @code{struct MyType} is in
15625 another source file. The default is on.
15627 A change in the setting of this subcommand will not take effect until
15628 the next time symbols for a file are loaded.
15630 @item set opaque-type-resolution off
15631 Tell @value{GDBN} not to resolve opaque types. In this case, the type
15632 is printed as follows:
15634 @{<no data fields>@}
15637 @kindex show opaque-type-resolution
15638 @item show opaque-type-resolution
15639 Show whether opaque types are resolved or not.
15641 @kindex maint print symbols
15642 @cindex symbol dump
15643 @kindex maint print psymbols
15644 @cindex partial symbol dump
15645 @item maint print symbols @var{filename}
15646 @itemx maint print psymbols @var{filename}
15647 @itemx maint print msymbols @var{filename}
15648 Write a dump of debugging symbol data into the file @var{filename}.
15649 These commands are used to debug the @value{GDBN} symbol-reading code. Only
15650 symbols with debugging data are included. If you use @samp{maint print
15651 symbols}, @value{GDBN} includes all the symbols for which it has already
15652 collected full details: that is, @var{filename} reflects symbols for
15653 only those files whose symbols @value{GDBN} has read. You can use the
15654 command @code{info sources} to find out which files these are. If you
15655 use @samp{maint print psymbols} instead, the dump shows information about
15656 symbols that @value{GDBN} only knows partially---that is, symbols defined in
15657 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
15658 @samp{maint print msymbols} dumps just the minimal symbol information
15659 required for each object file from which @value{GDBN} has read some symbols.
15660 @xref{Files, ,Commands to Specify Files}, for a discussion of how
15661 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
15663 @kindex maint info symtabs
15664 @kindex maint info psymtabs
15665 @cindex listing @value{GDBN}'s internal symbol tables
15666 @cindex symbol tables, listing @value{GDBN}'s internal
15667 @cindex full symbol tables, listing @value{GDBN}'s internal
15668 @cindex partial symbol tables, listing @value{GDBN}'s internal
15669 @item maint info symtabs @r{[} @var{regexp} @r{]}
15670 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
15672 List the @code{struct symtab} or @code{struct partial_symtab}
15673 structures whose names match @var{regexp}. If @var{regexp} is not
15674 given, list them all. The output includes expressions which you can
15675 copy into a @value{GDBN} debugging this one to examine a particular
15676 structure in more detail. For example:
15679 (@value{GDBP}) maint info psymtabs dwarf2read
15680 @{ objfile /home/gnu/build/gdb/gdb
15681 ((struct objfile *) 0x82e69d0)
15682 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
15683 ((struct partial_symtab *) 0x8474b10)
15686 text addresses 0x814d3c8 -- 0x8158074
15687 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
15688 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
15689 dependencies (none)
15692 (@value{GDBP}) maint info symtabs
15696 We see that there is one partial symbol table whose filename contains
15697 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
15698 and we see that @value{GDBN} has not read in any symtabs yet at all.
15699 If we set a breakpoint on a function, that will cause @value{GDBN} to
15700 read the symtab for the compilation unit containing that function:
15703 (@value{GDBP}) break dwarf2_psymtab_to_symtab
15704 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
15706 (@value{GDBP}) maint info symtabs
15707 @{ objfile /home/gnu/build/gdb/gdb
15708 ((struct objfile *) 0x82e69d0)
15709 @{ symtab /home/gnu/src/gdb/dwarf2read.c
15710 ((struct symtab *) 0x86c1f38)
15713 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
15714 linetable ((struct linetable *) 0x8370fa0)
15715 debugformat DWARF 2
15724 @chapter Altering Execution
15726 Once you think you have found an error in your program, you might want to
15727 find out for certain whether correcting the apparent error would lead to
15728 correct results in the rest of the run. You can find the answer by
15729 experiment, using the @value{GDBN} features for altering execution of the
15732 For example, you can store new values into variables or memory
15733 locations, give your program a signal, restart it at a different
15734 address, or even return prematurely from a function.
15737 * Assignment:: Assignment to variables
15738 * Jumping:: Continuing at a different address
15739 * Signaling:: Giving your program a signal
15740 * Returning:: Returning from a function
15741 * Calling:: Calling your program's functions
15742 * Patching:: Patching your program
15746 @section Assignment to Variables
15749 @cindex setting variables
15750 To alter the value of a variable, evaluate an assignment expression.
15751 @xref{Expressions, ,Expressions}. For example,
15758 stores the value 4 into the variable @code{x}, and then prints the
15759 value of the assignment expression (which is 4).
15760 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
15761 information on operators in supported languages.
15763 @kindex set variable
15764 @cindex variables, setting
15765 If you are not interested in seeing the value of the assignment, use the
15766 @code{set} command instead of the @code{print} command. @code{set} is
15767 really the same as @code{print} except that the expression's value is
15768 not printed and is not put in the value history (@pxref{Value History,
15769 ,Value History}). The expression is evaluated only for its effects.
15771 If the beginning of the argument string of the @code{set} command
15772 appears identical to a @code{set} subcommand, use the @code{set
15773 variable} command instead of just @code{set}. This command is identical
15774 to @code{set} except for its lack of subcommands. For example, if your
15775 program has a variable @code{width}, you get an error if you try to set
15776 a new value with just @samp{set width=13}, because @value{GDBN} has the
15777 command @code{set width}:
15780 (@value{GDBP}) whatis width
15782 (@value{GDBP}) p width
15784 (@value{GDBP}) set width=47
15785 Invalid syntax in expression.
15789 The invalid expression, of course, is @samp{=47}. In
15790 order to actually set the program's variable @code{width}, use
15793 (@value{GDBP}) set var width=47
15796 Because the @code{set} command has many subcommands that can conflict
15797 with the names of program variables, it is a good idea to use the
15798 @code{set variable} command instead of just @code{set}. For example, if
15799 your program has a variable @code{g}, you run into problems if you try
15800 to set a new value with just @samp{set g=4}, because @value{GDBN} has
15801 the command @code{set gnutarget}, abbreviated @code{set g}:
15805 (@value{GDBP}) whatis g
15809 (@value{GDBP}) set g=4
15813 The program being debugged has been started already.
15814 Start it from the beginning? (y or n) y
15815 Starting program: /home/smith/cc_progs/a.out
15816 "/home/smith/cc_progs/a.out": can't open to read symbols:
15817 Invalid bfd target.
15818 (@value{GDBP}) show g
15819 The current BFD target is "=4".
15824 The program variable @code{g} did not change, and you silently set the
15825 @code{gnutarget} to an invalid value. In order to set the variable
15829 (@value{GDBP}) set var g=4
15832 @value{GDBN} allows more implicit conversions in assignments than C; you can
15833 freely store an integer value into a pointer variable or vice versa,
15834 and you can convert any structure to any other structure that is the
15835 same length or shorter.
15836 @comment FIXME: how do structs align/pad in these conversions?
15837 @comment /doc@cygnus.com 18dec1990
15839 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
15840 construct to generate a value of specified type at a specified address
15841 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
15842 to memory location @code{0x83040} as an integer (which implies a certain size
15843 and representation in memory), and
15846 set @{int@}0x83040 = 4
15850 stores the value 4 into that memory location.
15853 @section Continuing at a Different Address
15855 Ordinarily, when you continue your program, you do so at the place where
15856 it stopped, with the @code{continue} command. You can instead continue at
15857 an address of your own choosing, with the following commands:
15861 @kindex j @r{(@code{jump})}
15862 @item jump @var{linespec}
15863 @itemx j @var{linespec}
15864 @itemx jump @var{location}
15865 @itemx j @var{location}
15866 Resume execution at line @var{linespec} or at address given by
15867 @var{location}. Execution stops again immediately if there is a
15868 breakpoint there. @xref{Specify Location}, for a description of the
15869 different forms of @var{linespec} and @var{location}. It is common
15870 practice to use the @code{tbreak} command in conjunction with
15871 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
15873 The @code{jump} command does not change the current stack frame, or
15874 the stack pointer, or the contents of any memory location or any
15875 register other than the program counter. If line @var{linespec} is in
15876 a different function from the one currently executing, the results may
15877 be bizarre if the two functions expect different patterns of arguments or
15878 of local variables. For this reason, the @code{jump} command requests
15879 confirmation if the specified line is not in the function currently
15880 executing. However, even bizarre results are predictable if you are
15881 well acquainted with the machine-language code of your program.
15884 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
15885 On many systems, you can get much the same effect as the @code{jump}
15886 command by storing a new value into the register @code{$pc}. The
15887 difference is that this does not start your program running; it only
15888 changes the address of where it @emph{will} run when you continue. For
15896 makes the next @code{continue} command or stepping command execute at
15897 address @code{0x485}, rather than at the address where your program stopped.
15898 @xref{Continuing and Stepping, ,Continuing and Stepping}.
15900 The most common occasion to use the @code{jump} command is to back
15901 up---perhaps with more breakpoints set---over a portion of a program
15902 that has already executed, in order to examine its execution in more
15907 @section Giving your Program a Signal
15908 @cindex deliver a signal to a program
15912 @item signal @var{signal}
15913 Resume execution where your program stopped, but immediately give it the
15914 signal @var{signal}. @var{signal} can be the name or the number of a
15915 signal. For example, on many systems @code{signal 2} and @code{signal
15916 SIGINT} are both ways of sending an interrupt signal.
15918 Alternatively, if @var{signal} is zero, continue execution without
15919 giving a signal. This is useful when your program stopped on account of
15920 a signal and would ordinarily see the signal when resumed with the
15921 @code{continue} command; @samp{signal 0} causes it to resume without a
15924 @code{signal} does not repeat when you press @key{RET} a second time
15925 after executing the command.
15929 Invoking the @code{signal} command is not the same as invoking the
15930 @code{kill} utility from the shell. Sending a signal with @code{kill}
15931 causes @value{GDBN} to decide what to do with the signal depending on
15932 the signal handling tables (@pxref{Signals}). The @code{signal} command
15933 passes the signal directly to your program.
15937 @section Returning from a Function
15940 @cindex returning from a function
15943 @itemx return @var{expression}
15944 You can cancel execution of a function call with the @code{return}
15945 command. If you give an
15946 @var{expression} argument, its value is used as the function's return
15950 When you use @code{return}, @value{GDBN} discards the selected stack frame
15951 (and all frames within it). You can think of this as making the
15952 discarded frame return prematurely. If you wish to specify a value to
15953 be returned, give that value as the argument to @code{return}.
15955 This pops the selected stack frame (@pxref{Selection, ,Selecting a
15956 Frame}), and any other frames inside of it, leaving its caller as the
15957 innermost remaining frame. That frame becomes selected. The
15958 specified value is stored in the registers used for returning values
15961 The @code{return} command does not resume execution; it leaves the
15962 program stopped in the state that would exist if the function had just
15963 returned. In contrast, the @code{finish} command (@pxref{Continuing
15964 and Stepping, ,Continuing and Stepping}) resumes execution until the
15965 selected stack frame returns naturally.
15967 @value{GDBN} needs to know how the @var{expression} argument should be set for
15968 the inferior. The concrete registers assignment depends on the OS ABI and the
15969 type being returned by the selected stack frame. For example it is common for
15970 OS ABI to return floating point values in FPU registers while integer values in
15971 CPU registers. Still some ABIs return even floating point values in CPU
15972 registers. Larger integer widths (such as @code{long long int}) also have
15973 specific placement rules. @value{GDBN} already knows the OS ABI from its
15974 current target so it needs to find out also the type being returned to make the
15975 assignment into the right register(s).
15977 Normally, the selected stack frame has debug info. @value{GDBN} will always
15978 use the debug info instead of the implicit type of @var{expression} when the
15979 debug info is available. For example, if you type @kbd{return -1}, and the
15980 function in the current stack frame is declared to return a @code{long long
15981 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
15982 into a @code{long long int}:
15985 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
15987 (@value{GDBP}) return -1
15988 Make func return now? (y or n) y
15989 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
15990 43 printf ("result=%lld\n", func ());
15994 However, if the selected stack frame does not have a debug info, e.g., if the
15995 function was compiled without debug info, @value{GDBN} has to find out the type
15996 to return from user. Specifying a different type by mistake may set the value
15997 in different inferior registers than the caller code expects. For example,
15998 typing @kbd{return -1} with its implicit type @code{int} would set only a part
15999 of a @code{long long int} result for a debug info less function (on 32-bit
16000 architectures). Therefore the user is required to specify the return type by
16001 an appropriate cast explicitly:
16004 Breakpoint 2, 0x0040050b in func ()
16005 (@value{GDBP}) return -1
16006 Return value type not available for selected stack frame.
16007 Please use an explicit cast of the value to return.
16008 (@value{GDBP}) return (long long int) -1
16009 Make selected stack frame return now? (y or n) y
16010 #0 0x00400526 in main ()
16015 @section Calling Program Functions
16018 @cindex calling functions
16019 @cindex inferior functions, calling
16020 @item print @var{expr}
16021 Evaluate the expression @var{expr} and display the resulting value.
16022 @var{expr} may include calls to functions in the program being
16026 @item call @var{expr}
16027 Evaluate the expression @var{expr} without displaying @code{void}
16030 You can use this variant of the @code{print} command if you want to
16031 execute a function from your program that does not return anything
16032 (a.k.a.@: @dfn{a void function}), but without cluttering the output
16033 with @code{void} returned values that @value{GDBN} will otherwise
16034 print. If the result is not void, it is printed and saved in the
16038 It is possible for the function you call via the @code{print} or
16039 @code{call} command to generate a signal (e.g., if there's a bug in
16040 the function, or if you passed it incorrect arguments). What happens
16041 in that case is controlled by the @code{set unwindonsignal} command.
16043 Similarly, with a C@t{++} program it is possible for the function you
16044 call via the @code{print} or @code{call} command to generate an
16045 exception that is not handled due to the constraints of the dummy
16046 frame. In this case, any exception that is raised in the frame, but has
16047 an out-of-frame exception handler will not be found. GDB builds a
16048 dummy-frame for the inferior function call, and the unwinder cannot
16049 seek for exception handlers outside of this dummy-frame. What happens
16050 in that case is controlled by the
16051 @code{set unwind-on-terminating-exception} command.
16054 @item set unwindonsignal
16055 @kindex set unwindonsignal
16056 @cindex unwind stack in called functions
16057 @cindex call dummy stack unwinding
16058 Set unwinding of the stack if a signal is received while in a function
16059 that @value{GDBN} called in the program being debugged. If set to on,
16060 @value{GDBN} unwinds the stack it created for the call and restores
16061 the context to what it was before the call. If set to off (the
16062 default), @value{GDBN} stops in the frame where the signal was
16065 @item show unwindonsignal
16066 @kindex show unwindonsignal
16067 Show the current setting of stack unwinding in the functions called by
16070 @item set unwind-on-terminating-exception
16071 @kindex set unwind-on-terminating-exception
16072 @cindex unwind stack in called functions with unhandled exceptions
16073 @cindex call dummy stack unwinding on unhandled exception.
16074 Set unwinding of the stack if a C@t{++} exception is raised, but left
16075 unhandled while in a function that @value{GDBN} called in the program being
16076 debugged. If set to on (the default), @value{GDBN} unwinds the stack
16077 it created for the call and restores the context to what it was before
16078 the call. If set to off, @value{GDBN} the exception is delivered to
16079 the default C@t{++} exception handler and the inferior terminated.
16081 @item show unwind-on-terminating-exception
16082 @kindex show unwind-on-terminating-exception
16083 Show the current setting of stack unwinding in the functions called by
16088 @cindex weak alias functions
16089 Sometimes, a function you wish to call is actually a @dfn{weak alias}
16090 for another function. In such case, @value{GDBN} might not pick up
16091 the type information, including the types of the function arguments,
16092 which causes @value{GDBN} to call the inferior function incorrectly.
16093 As a result, the called function will function erroneously and may
16094 even crash. A solution to that is to use the name of the aliased
16098 @section Patching Programs
16100 @cindex patching binaries
16101 @cindex writing into executables
16102 @cindex writing into corefiles
16104 By default, @value{GDBN} opens the file containing your program's
16105 executable code (or the corefile) read-only. This prevents accidental
16106 alterations to machine code; but it also prevents you from intentionally
16107 patching your program's binary.
16109 If you'd like to be able to patch the binary, you can specify that
16110 explicitly with the @code{set write} command. For example, you might
16111 want to turn on internal debugging flags, or even to make emergency
16117 @itemx set write off
16118 If you specify @samp{set write on}, @value{GDBN} opens executable and
16119 core files for both reading and writing; if you specify @kbd{set write
16120 off} (the default), @value{GDBN} opens them read-only.
16122 If you have already loaded a file, you must load it again (using the
16123 @code{exec-file} or @code{core-file} command) after changing @code{set
16124 write}, for your new setting to take effect.
16128 Display whether executable files and core files are opened for writing
16129 as well as reading.
16133 @chapter @value{GDBN} Files
16135 @value{GDBN} needs to know the file name of the program to be debugged,
16136 both in order to read its symbol table and in order to start your
16137 program. To debug a core dump of a previous run, you must also tell
16138 @value{GDBN} the name of the core dump file.
16141 * Files:: Commands to specify files
16142 * Separate Debug Files:: Debugging information in separate files
16143 * MiniDebugInfo:: Debugging information in a special section
16144 * Index Files:: Index files speed up GDB
16145 * Symbol Errors:: Errors reading symbol files
16146 * Data Files:: GDB data files
16150 @section Commands to Specify Files
16152 @cindex symbol table
16153 @cindex core dump file
16155 You may want to specify executable and core dump file names. The usual
16156 way to do this is at start-up time, using the arguments to
16157 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
16158 Out of @value{GDBN}}).
16160 Occasionally it is necessary to change to a different file during a
16161 @value{GDBN} session. Or you may run @value{GDBN} and forget to
16162 specify a file you want to use. Or you are debugging a remote target
16163 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
16164 Program}). In these situations the @value{GDBN} commands to specify
16165 new files are useful.
16168 @cindex executable file
16170 @item file @var{filename}
16171 Use @var{filename} as the program to be debugged. It is read for its
16172 symbols and for the contents of pure memory. It is also the program
16173 executed when you use the @code{run} command. If you do not specify a
16174 directory and the file is not found in the @value{GDBN} working directory,
16175 @value{GDBN} uses the environment variable @code{PATH} as a list of
16176 directories to search, just as the shell does when looking for a program
16177 to run. You can change the value of this variable, for both @value{GDBN}
16178 and your program, using the @code{path} command.
16180 @cindex unlinked object files
16181 @cindex patching object files
16182 You can load unlinked object @file{.o} files into @value{GDBN} using
16183 the @code{file} command. You will not be able to ``run'' an object
16184 file, but you can disassemble functions and inspect variables. Also,
16185 if the underlying BFD functionality supports it, you could use
16186 @kbd{gdb -write} to patch object files using this technique. Note
16187 that @value{GDBN} can neither interpret nor modify relocations in this
16188 case, so branches and some initialized variables will appear to go to
16189 the wrong place. But this feature is still handy from time to time.
16192 @code{file} with no argument makes @value{GDBN} discard any information it
16193 has on both executable file and the symbol table.
16196 @item exec-file @r{[} @var{filename} @r{]}
16197 Specify that the program to be run (but not the symbol table) is found
16198 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
16199 if necessary to locate your program. Omitting @var{filename} means to
16200 discard information on the executable file.
16202 @kindex symbol-file
16203 @item symbol-file @r{[} @var{filename} @r{]}
16204 Read symbol table information from file @var{filename}. @code{PATH} is
16205 searched when necessary. Use the @code{file} command to get both symbol
16206 table and program to run from the same file.
16208 @code{symbol-file} with no argument clears out @value{GDBN} information on your
16209 program's symbol table.
16211 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
16212 some breakpoints and auto-display expressions. This is because they may
16213 contain pointers to the internal data recording symbols and data types,
16214 which are part of the old symbol table data being discarded inside
16217 @code{symbol-file} does not repeat if you press @key{RET} again after
16220 When @value{GDBN} is configured for a particular environment, it
16221 understands debugging information in whatever format is the standard
16222 generated for that environment; you may use either a @sc{gnu} compiler, or
16223 other compilers that adhere to the local conventions.
16224 Best results are usually obtained from @sc{gnu} compilers; for example,
16225 using @code{@value{NGCC}} you can generate debugging information for
16228 For most kinds of object files, with the exception of old SVR3 systems
16229 using COFF, the @code{symbol-file} command does not normally read the
16230 symbol table in full right away. Instead, it scans the symbol table
16231 quickly to find which source files and which symbols are present. The
16232 details are read later, one source file at a time, as they are needed.
16234 The purpose of this two-stage reading strategy is to make @value{GDBN}
16235 start up faster. For the most part, it is invisible except for
16236 occasional pauses while the symbol table details for a particular source
16237 file are being read. (The @code{set verbose} command can turn these
16238 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
16239 Warnings and Messages}.)
16241 We have not implemented the two-stage strategy for COFF yet. When the
16242 symbol table is stored in COFF format, @code{symbol-file} reads the
16243 symbol table data in full right away. Note that ``stabs-in-COFF''
16244 still does the two-stage strategy, since the debug info is actually
16248 @cindex reading symbols immediately
16249 @cindex symbols, reading immediately
16250 @item symbol-file @r{[} -readnow @r{]} @var{filename}
16251 @itemx file @r{[} -readnow @r{]} @var{filename}
16252 You can override the @value{GDBN} two-stage strategy for reading symbol
16253 tables by using the @samp{-readnow} option with any of the commands that
16254 load symbol table information, if you want to be sure @value{GDBN} has the
16255 entire symbol table available.
16257 @c FIXME: for now no mention of directories, since this seems to be in
16258 @c flux. 13mar1992 status is that in theory GDB would look either in
16259 @c current dir or in same dir as myprog; but issues like competing
16260 @c GDB's, or clutter in system dirs, mean that in practice right now
16261 @c only current dir is used. FFish says maybe a special GDB hierarchy
16262 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
16266 @item core-file @r{[}@var{filename}@r{]}
16268 Specify the whereabouts of a core dump file to be used as the ``contents
16269 of memory''. Traditionally, core files contain only some parts of the
16270 address space of the process that generated them; @value{GDBN} can access the
16271 executable file itself for other parts.
16273 @code{core-file} with no argument specifies that no core file is
16276 Note that the core file is ignored when your program is actually running
16277 under @value{GDBN}. So, if you have been running your program and you
16278 wish to debug a core file instead, you must kill the subprocess in which
16279 the program is running. To do this, use the @code{kill} command
16280 (@pxref{Kill Process, ,Killing the Child Process}).
16282 @kindex add-symbol-file
16283 @cindex dynamic linking
16284 @item add-symbol-file @var{filename} @var{address}
16285 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
16286 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
16287 The @code{add-symbol-file} command reads additional symbol table
16288 information from the file @var{filename}. You would use this command
16289 when @var{filename} has been dynamically loaded (by some other means)
16290 into the program that is running. @var{address} should be the memory
16291 address at which the file has been loaded; @value{GDBN} cannot figure
16292 this out for itself. You can additionally specify an arbitrary number
16293 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
16294 section name and base address for that section. You can specify any
16295 @var{address} as an expression.
16297 The symbol table of the file @var{filename} is added to the symbol table
16298 originally read with the @code{symbol-file} command. You can use the
16299 @code{add-symbol-file} command any number of times; the new symbol data
16300 thus read keeps adding to the old. To discard all old symbol data
16301 instead, use the @code{symbol-file} command without any arguments.
16303 @cindex relocatable object files, reading symbols from
16304 @cindex object files, relocatable, reading symbols from
16305 @cindex reading symbols from relocatable object files
16306 @cindex symbols, reading from relocatable object files
16307 @cindex @file{.o} files, reading symbols from
16308 Although @var{filename} is typically a shared library file, an
16309 executable file, or some other object file which has been fully
16310 relocated for loading into a process, you can also load symbolic
16311 information from relocatable @file{.o} files, as long as:
16315 the file's symbolic information refers only to linker symbols defined in
16316 that file, not to symbols defined by other object files,
16318 every section the file's symbolic information refers to has actually
16319 been loaded into the inferior, as it appears in the file, and
16321 you can determine the address at which every section was loaded, and
16322 provide these to the @code{add-symbol-file} command.
16326 Some embedded operating systems, like Sun Chorus and VxWorks, can load
16327 relocatable files into an already running program; such systems
16328 typically make the requirements above easy to meet. However, it's
16329 important to recognize that many native systems use complex link
16330 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
16331 assembly, for example) that make the requirements difficult to meet. In
16332 general, one cannot assume that using @code{add-symbol-file} to read a
16333 relocatable object file's symbolic information will have the same effect
16334 as linking the relocatable object file into the program in the normal
16337 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
16339 @kindex add-symbol-file-from-memory
16340 @cindex @code{syscall DSO}
16341 @cindex load symbols from memory
16342 @item add-symbol-file-from-memory @var{address}
16343 Load symbols from the given @var{address} in a dynamically loaded
16344 object file whose image is mapped directly into the inferior's memory.
16345 For example, the Linux kernel maps a @code{syscall DSO} into each
16346 process's address space; this DSO provides kernel-specific code for
16347 some system calls. The argument can be any expression whose
16348 evaluation yields the address of the file's shared object file header.
16349 For this command to work, you must have used @code{symbol-file} or
16350 @code{exec-file} commands in advance.
16352 @kindex add-shared-symbol-files
16354 @item add-shared-symbol-files @var{library-file}
16355 @itemx assf @var{library-file}
16356 The @code{add-shared-symbol-files} command can currently be used only
16357 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
16358 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
16359 @value{GDBN} automatically looks for shared libraries, however if
16360 @value{GDBN} does not find yours, you can invoke
16361 @code{add-shared-symbol-files}. It takes one argument: the shared
16362 library's file name. @code{assf} is a shorthand alias for
16363 @code{add-shared-symbol-files}.
16366 @item section @var{section} @var{addr}
16367 The @code{section} command changes the base address of the named
16368 @var{section} of the exec file to @var{addr}. This can be used if the
16369 exec file does not contain section addresses, (such as in the
16370 @code{a.out} format), or when the addresses specified in the file
16371 itself are wrong. Each section must be changed separately. The
16372 @code{info files} command, described below, lists all the sections and
16376 @kindex info target
16379 @code{info files} and @code{info target} are synonymous; both print the
16380 current target (@pxref{Targets, ,Specifying a Debugging Target}),
16381 including the names of the executable and core dump files currently in
16382 use by @value{GDBN}, and the files from which symbols were loaded. The
16383 command @code{help target} lists all possible targets rather than
16386 @kindex maint info sections
16387 @item maint info sections
16388 Another command that can give you extra information about program sections
16389 is @code{maint info sections}. In addition to the section information
16390 displayed by @code{info files}, this command displays the flags and file
16391 offset of each section in the executable and core dump files. In addition,
16392 @code{maint info sections} provides the following command options (which
16393 may be arbitrarily combined):
16397 Display sections for all loaded object files, including shared libraries.
16398 @item @var{sections}
16399 Display info only for named @var{sections}.
16400 @item @var{section-flags}
16401 Display info only for sections for which @var{section-flags} are true.
16402 The section flags that @value{GDBN} currently knows about are:
16405 Section will have space allocated in the process when loaded.
16406 Set for all sections except those containing debug information.
16408 Section will be loaded from the file into the child process memory.
16409 Set for pre-initialized code and data, clear for @code{.bss} sections.
16411 Section needs to be relocated before loading.
16413 Section cannot be modified by the child process.
16415 Section contains executable code only.
16417 Section contains data only (no executable code).
16419 Section will reside in ROM.
16421 Section contains data for constructor/destructor lists.
16423 Section is not empty.
16425 An instruction to the linker to not output the section.
16426 @item COFF_SHARED_LIBRARY
16427 A notification to the linker that the section contains
16428 COFF shared library information.
16430 Section contains common symbols.
16433 @kindex set trust-readonly-sections
16434 @cindex read-only sections
16435 @item set trust-readonly-sections on
16436 Tell @value{GDBN} that readonly sections in your object file
16437 really are read-only (i.e.@: that their contents will not change).
16438 In that case, @value{GDBN} can fetch values from these sections
16439 out of the object file, rather than from the target program.
16440 For some targets (notably embedded ones), this can be a significant
16441 enhancement to debugging performance.
16443 The default is off.
16445 @item set trust-readonly-sections off
16446 Tell @value{GDBN} not to trust readonly sections. This means that
16447 the contents of the section might change while the program is running,
16448 and must therefore be fetched from the target when needed.
16450 @item show trust-readonly-sections
16451 Show the current setting of trusting readonly sections.
16454 All file-specifying commands allow both absolute and relative file names
16455 as arguments. @value{GDBN} always converts the file name to an absolute file
16456 name and remembers it that way.
16458 @cindex shared libraries
16459 @anchor{Shared Libraries}
16460 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
16461 and IBM RS/6000 AIX shared libraries.
16463 On MS-Windows @value{GDBN} must be linked with the Expat library to support
16464 shared libraries. @xref{Expat}.
16466 @value{GDBN} automatically loads symbol definitions from shared libraries
16467 when you use the @code{run} command, or when you examine a core file.
16468 (Before you issue the @code{run} command, @value{GDBN} does not understand
16469 references to a function in a shared library, however---unless you are
16470 debugging a core file).
16472 On HP-UX, if the program loads a library explicitly, @value{GDBN}
16473 automatically loads the symbols at the time of the @code{shl_load} call.
16475 @c FIXME: some @value{GDBN} release may permit some refs to undef
16476 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
16477 @c FIXME...lib; check this from time to time when updating manual
16479 There are times, however, when you may wish to not automatically load
16480 symbol definitions from shared libraries, such as when they are
16481 particularly large or there are many of them.
16483 To control the automatic loading of shared library symbols, use the
16487 @kindex set auto-solib-add
16488 @item set auto-solib-add @var{mode}
16489 If @var{mode} is @code{on}, symbols from all shared object libraries
16490 will be loaded automatically when the inferior begins execution, you
16491 attach to an independently started inferior, or when the dynamic linker
16492 informs @value{GDBN} that a new library has been loaded. If @var{mode}
16493 is @code{off}, symbols must be loaded manually, using the
16494 @code{sharedlibrary} command. The default value is @code{on}.
16496 @cindex memory used for symbol tables
16497 If your program uses lots of shared libraries with debug info that
16498 takes large amounts of memory, you can decrease the @value{GDBN}
16499 memory footprint by preventing it from automatically loading the
16500 symbols from shared libraries. To that end, type @kbd{set
16501 auto-solib-add off} before running the inferior, then load each
16502 library whose debug symbols you do need with @kbd{sharedlibrary
16503 @var{regexp}}, where @var{regexp} is a regular expression that matches
16504 the libraries whose symbols you want to be loaded.
16506 @kindex show auto-solib-add
16507 @item show auto-solib-add
16508 Display the current autoloading mode.
16511 @cindex load shared library
16512 To explicitly load shared library symbols, use the @code{sharedlibrary}
16516 @kindex info sharedlibrary
16518 @item info share @var{regex}
16519 @itemx info sharedlibrary @var{regex}
16520 Print the names of the shared libraries which are currently loaded
16521 that match @var{regex}. If @var{regex} is omitted then print
16522 all shared libraries that are loaded.
16524 @kindex sharedlibrary
16526 @item sharedlibrary @var{regex}
16527 @itemx share @var{regex}
16528 Load shared object library symbols for files matching a
16529 Unix regular expression.
16530 As with files loaded automatically, it only loads shared libraries
16531 required by your program for a core file or after typing @code{run}. If
16532 @var{regex} is omitted all shared libraries required by your program are
16535 @item nosharedlibrary
16536 @kindex nosharedlibrary
16537 @cindex unload symbols from shared libraries
16538 Unload all shared object library symbols. This discards all symbols
16539 that have been loaded from all shared libraries. Symbols from shared
16540 libraries that were loaded by explicit user requests are not
16544 Sometimes you may wish that @value{GDBN} stops and gives you control
16545 when any of shared library events happen. The best way to do this is
16546 to use @code{catch load} and @code{catch unload} (@pxref{Set
16549 @value{GDBN} also supports the the @code{set stop-on-solib-events}
16550 command for this. This command exists for historical reasons. It is
16551 less useful than setting a catchpoint, because it does not allow for
16552 conditions or commands as a catchpoint does.
16555 @item set stop-on-solib-events
16556 @kindex set stop-on-solib-events
16557 This command controls whether @value{GDBN} should give you control
16558 when the dynamic linker notifies it about some shared library event.
16559 The most common event of interest is loading or unloading of a new
16562 @item show stop-on-solib-events
16563 @kindex show stop-on-solib-events
16564 Show whether @value{GDBN} stops and gives you control when shared
16565 library events happen.
16568 Shared libraries are also supported in many cross or remote debugging
16569 configurations. @value{GDBN} needs to have access to the target's libraries;
16570 this can be accomplished either by providing copies of the libraries
16571 on the host system, or by asking @value{GDBN} to automatically retrieve the
16572 libraries from the target. If copies of the target libraries are
16573 provided, they need to be the same as the target libraries, although the
16574 copies on the target can be stripped as long as the copies on the host are
16577 @cindex where to look for shared libraries
16578 For remote debugging, you need to tell @value{GDBN} where the target
16579 libraries are, so that it can load the correct copies---otherwise, it
16580 may try to load the host's libraries. @value{GDBN} has two variables
16581 to specify the search directories for target libraries.
16584 @cindex prefix for shared library file names
16585 @cindex system root, alternate
16586 @kindex set solib-absolute-prefix
16587 @kindex set sysroot
16588 @item set sysroot @var{path}
16589 Use @var{path} as the system root for the program being debugged. Any
16590 absolute shared library paths will be prefixed with @var{path}; many
16591 runtime loaders store the absolute paths to the shared library in the
16592 target program's memory. If you use @code{set sysroot} to find shared
16593 libraries, they need to be laid out in the same way that they are on
16594 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
16597 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
16598 retrieve the target libraries from the remote system. This is only
16599 supported when using a remote target that supports the @code{remote get}
16600 command (@pxref{File Transfer,,Sending files to a remote system}).
16601 The part of @var{path} following the initial @file{remote:}
16602 (if present) is used as system root prefix on the remote file system.
16603 @footnote{If you want to specify a local system root using a directory
16604 that happens to be named @file{remote:}, you need to use some equivalent
16605 variant of the name like @file{./remote:}.}
16607 For targets with an MS-DOS based filesystem, such as MS-Windows and
16608 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
16609 absolute file name with @var{path}. But first, on Unix hosts,
16610 @value{GDBN} converts all backslash directory separators into forward
16611 slashes, because the backslash is not a directory separator on Unix:
16614 c:\foo\bar.dll @result{} c:/foo/bar.dll
16617 Then, @value{GDBN} attempts prefixing the target file name with
16618 @var{path}, and looks for the resulting file name in the host file
16622 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
16625 If that does not find the shared library, @value{GDBN} tries removing
16626 the @samp{:} character from the drive spec, both for convenience, and,
16627 for the case of the host file system not supporting file names with
16631 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
16634 This makes it possible to have a system root that mirrors a target
16635 with more than one drive. E.g., you may want to setup your local
16636 copies of the target system shared libraries like so (note @samp{c} vs
16640 @file{/path/to/sysroot/c/sys/bin/foo.dll}
16641 @file{/path/to/sysroot/c/sys/bin/bar.dll}
16642 @file{/path/to/sysroot/z/sys/bin/bar.dll}
16646 and point the system root at @file{/path/to/sysroot}, so that
16647 @value{GDBN} can find the correct copies of both
16648 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
16650 If that still does not find the shared library, @value{GDBN} tries
16651 removing the whole drive spec from the target file name:
16654 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
16657 This last lookup makes it possible to not care about the drive name,
16658 if you don't want or need to.
16660 The @code{set solib-absolute-prefix} command is an alias for @code{set
16663 @cindex default system root
16664 @cindex @samp{--with-sysroot}
16665 You can set the default system root by using the configure-time
16666 @samp{--with-sysroot} option. If the system root is inside
16667 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16668 @samp{--exec-prefix}), then the default system root will be updated
16669 automatically if the installed @value{GDBN} is moved to a new
16672 @kindex show sysroot
16674 Display the current shared library prefix.
16676 @kindex set solib-search-path
16677 @item set solib-search-path @var{path}
16678 If this variable is set, @var{path} is a colon-separated list of
16679 directories to search for shared libraries. @samp{solib-search-path}
16680 is used after @samp{sysroot} fails to locate the library, or if the
16681 path to the library is relative instead of absolute. If you want to
16682 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
16683 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
16684 finding your host's libraries. @samp{sysroot} is preferred; setting
16685 it to a nonexistent directory may interfere with automatic loading
16686 of shared library symbols.
16688 @kindex show solib-search-path
16689 @item show solib-search-path
16690 Display the current shared library search path.
16692 @cindex DOS file-name semantics of file names.
16693 @kindex set target-file-system-kind (unix|dos-based|auto)
16694 @kindex show target-file-system-kind
16695 @item set target-file-system-kind @var{kind}
16696 Set assumed file system kind for target reported file names.
16698 Shared library file names as reported by the target system may not
16699 make sense as is on the system @value{GDBN} is running on. For
16700 example, when remote debugging a target that has MS-DOS based file
16701 system semantics, from a Unix host, the target may be reporting to
16702 @value{GDBN} a list of loaded shared libraries with file names such as
16703 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
16704 drive letters, so the @samp{c:\} prefix is not normally understood as
16705 indicating an absolute file name, and neither is the backslash
16706 normally considered a directory separator character. In that case,
16707 the native file system would interpret this whole absolute file name
16708 as a relative file name with no directory components. This would make
16709 it impossible to point @value{GDBN} at a copy of the remote target's
16710 shared libraries on the host using @code{set sysroot}, and impractical
16711 with @code{set solib-search-path}. Setting
16712 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
16713 to interpret such file names similarly to how the target would, and to
16714 map them to file names valid on @value{GDBN}'s native file system
16715 semantics. The value of @var{kind} can be @code{"auto"}, in addition
16716 to one of the supported file system kinds. In that case, @value{GDBN}
16717 tries to determine the appropriate file system variant based on the
16718 current target's operating system (@pxref{ABI, ,Configuring the
16719 Current ABI}). The supported file system settings are:
16723 Instruct @value{GDBN} to assume the target file system is of Unix
16724 kind. Only file names starting the forward slash (@samp{/}) character
16725 are considered absolute, and the directory separator character is also
16729 Instruct @value{GDBN} to assume the target file system is DOS based.
16730 File names starting with either a forward slash, or a drive letter
16731 followed by a colon (e.g., @samp{c:}), are considered absolute, and
16732 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
16733 considered directory separators.
16736 Instruct @value{GDBN} to use the file system kind associated with the
16737 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
16738 This is the default.
16742 @cindex file name canonicalization
16743 @cindex base name differences
16744 When processing file names provided by the user, @value{GDBN}
16745 frequently needs to compare them to the file names recorded in the
16746 program's debug info. Normally, @value{GDBN} compares just the
16747 @dfn{base names} of the files as strings, which is reasonably fast
16748 even for very large programs. (The base name of a file is the last
16749 portion of its name, after stripping all the leading directories.)
16750 This shortcut in comparison is based upon the assumption that files
16751 cannot have more than one base name. This is usually true, but
16752 references to files that use symlinks or similar filesystem
16753 facilities violate that assumption. If your program records files
16754 using such facilities, or if you provide file names to @value{GDBN}
16755 using symlinks etc., you can set @code{basenames-may-differ} to
16756 @code{true} to instruct @value{GDBN} to completely canonicalize each
16757 pair of file names it needs to compare. This will make file-name
16758 comparisons accurate, but at a price of a significant slowdown.
16761 @item set basenames-may-differ
16762 @kindex set basenames-may-differ
16763 Set whether a source file may have multiple base names.
16765 @item show basenames-may-differ
16766 @kindex show basenames-may-differ
16767 Show whether a source file may have multiple base names.
16770 @node Separate Debug Files
16771 @section Debugging Information in Separate Files
16772 @cindex separate debugging information files
16773 @cindex debugging information in separate files
16774 @cindex @file{.debug} subdirectories
16775 @cindex debugging information directory, global
16776 @cindex global debugging information directories
16777 @cindex build ID, and separate debugging files
16778 @cindex @file{.build-id} directory
16780 @value{GDBN} allows you to put a program's debugging information in a
16781 file separate from the executable itself, in a way that allows
16782 @value{GDBN} to find and load the debugging information automatically.
16783 Since debugging information can be very large---sometimes larger
16784 than the executable code itself---some systems distribute debugging
16785 information for their executables in separate files, which users can
16786 install only when they need to debug a problem.
16788 @value{GDBN} supports two ways of specifying the separate debug info
16793 The executable contains a @dfn{debug link} that specifies the name of
16794 the separate debug info file. The separate debug file's name is
16795 usually @file{@var{executable}.debug}, where @var{executable} is the
16796 name of the corresponding executable file without leading directories
16797 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
16798 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
16799 checksum for the debug file, which @value{GDBN} uses to validate that
16800 the executable and the debug file came from the same build.
16803 The executable contains a @dfn{build ID}, a unique bit string that is
16804 also present in the corresponding debug info file. (This is supported
16805 only on some operating systems, notably those which use the ELF format
16806 for binary files and the @sc{gnu} Binutils.) For more details about
16807 this feature, see the description of the @option{--build-id}
16808 command-line option in @ref{Options, , Command Line Options, ld.info,
16809 The GNU Linker}. The debug info file's name is not specified
16810 explicitly by the build ID, but can be computed from the build ID, see
16814 Depending on the way the debug info file is specified, @value{GDBN}
16815 uses two different methods of looking for the debug file:
16819 For the ``debug link'' method, @value{GDBN} looks up the named file in
16820 the directory of the executable file, then in a subdirectory of that
16821 directory named @file{.debug}, and finally under each one of the global debug
16822 directories, in a subdirectory whose name is identical to the leading
16823 directories of the executable's absolute file name.
16826 For the ``build ID'' method, @value{GDBN} looks in the
16827 @file{.build-id} subdirectory of each one of the global debug directories for
16828 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
16829 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
16830 are the rest of the bit string. (Real build ID strings are 32 or more
16831 hex characters, not 10.)
16834 So, for example, suppose you ask @value{GDBN} to debug
16835 @file{/usr/bin/ls}, which has a debug link that specifies the
16836 file @file{ls.debug}, and a build ID whose value in hex is
16837 @code{abcdef1234}. If the list of the global debug directories includes
16838 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
16839 debug information files, in the indicated order:
16843 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
16845 @file{/usr/bin/ls.debug}
16847 @file{/usr/bin/.debug/ls.debug}
16849 @file{/usr/lib/debug/usr/bin/ls.debug}.
16852 @anchor{debug-file-directory}
16853 Global debugging info directories default to what is set by @value{GDBN}
16854 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
16855 you can also set the global debugging info directories, and view the list
16856 @value{GDBN} is currently using.
16860 @kindex set debug-file-directory
16861 @item set debug-file-directory @var{directories}
16862 Set the directories which @value{GDBN} searches for separate debugging
16863 information files to @var{directory}. Multiple path components can be set
16864 concatenating them by a path separator.
16866 @kindex show debug-file-directory
16867 @item show debug-file-directory
16868 Show the directories @value{GDBN} searches for separate debugging
16873 @cindex @code{.gnu_debuglink} sections
16874 @cindex debug link sections
16875 A debug link is a special section of the executable file named
16876 @code{.gnu_debuglink}. The section must contain:
16880 A filename, with any leading directory components removed, followed by
16883 zero to three bytes of padding, as needed to reach the next four-byte
16884 boundary within the section, and
16886 a four-byte CRC checksum, stored in the same endianness used for the
16887 executable file itself. The checksum is computed on the debugging
16888 information file's full contents by the function given below, passing
16889 zero as the @var{crc} argument.
16892 Any executable file format can carry a debug link, as long as it can
16893 contain a section named @code{.gnu_debuglink} with the contents
16896 @cindex @code{.note.gnu.build-id} sections
16897 @cindex build ID sections
16898 The build ID is a special section in the executable file (and in other
16899 ELF binary files that @value{GDBN} may consider). This section is
16900 often named @code{.note.gnu.build-id}, but that name is not mandatory.
16901 It contains unique identification for the built files---the ID remains
16902 the same across multiple builds of the same build tree. The default
16903 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
16904 content for the build ID string. The same section with an identical
16905 value is present in the original built binary with symbols, in its
16906 stripped variant, and in the separate debugging information file.
16908 The debugging information file itself should be an ordinary
16909 executable, containing a full set of linker symbols, sections, and
16910 debugging information. The sections of the debugging information file
16911 should have the same names, addresses, and sizes as the original file,
16912 but they need not contain any data---much like a @code{.bss} section
16913 in an ordinary executable.
16915 The @sc{gnu} binary utilities (Binutils) package includes the
16916 @samp{objcopy} utility that can produce
16917 the separated executable / debugging information file pairs using the
16918 following commands:
16921 @kbd{objcopy --only-keep-debug foo foo.debug}
16926 These commands remove the debugging
16927 information from the executable file @file{foo} and place it in the file
16928 @file{foo.debug}. You can use the first, second or both methods to link the
16933 The debug link method needs the following additional command to also leave
16934 behind a debug link in @file{foo}:
16937 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
16940 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
16941 a version of the @code{strip} command such that the command @kbd{strip foo -f
16942 foo.debug} has the same functionality as the two @code{objcopy} commands and
16943 the @code{ln -s} command above, together.
16946 Build ID gets embedded into the main executable using @code{ld --build-id} or
16947 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
16948 compatibility fixes for debug files separation are present in @sc{gnu} binary
16949 utilities (Binutils) package since version 2.18.
16954 @cindex CRC algorithm definition
16955 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
16956 IEEE 802.3 using the polynomial:
16958 @c TexInfo requires naked braces for multi-digit exponents for Tex
16959 @c output, but this causes HTML output to barf. HTML has to be set using
16960 @c raw commands. So we end up having to specify this equation in 2
16965 <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>
16966 + <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
16972 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
16973 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
16977 The function is computed byte at a time, taking the least
16978 significant bit of each byte first. The initial pattern
16979 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
16980 the final result is inverted to ensure trailing zeros also affect the
16983 @emph{Note:} This is the same CRC polynomial as used in handling the
16984 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
16985 , @value{GDBN} Remote Serial Protocol}). However in the
16986 case of the Remote Serial Protocol, the CRC is computed @emph{most}
16987 significant bit first, and the result is not inverted, so trailing
16988 zeros have no effect on the CRC value.
16990 To complete the description, we show below the code of the function
16991 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
16992 initially supplied @code{crc} argument means that an initial call to
16993 this function passing in zero will start computing the CRC using
16996 @kindex gnu_debuglink_crc32
16999 gnu_debuglink_crc32 (unsigned long crc,
17000 unsigned char *buf, size_t len)
17002 static const unsigned long crc32_table[256] =
17004 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
17005 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
17006 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
17007 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
17008 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
17009 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
17010 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
17011 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
17012 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
17013 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
17014 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
17015 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
17016 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
17017 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
17018 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
17019 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
17020 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
17021 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
17022 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
17023 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
17024 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
17025 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
17026 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
17027 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
17028 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
17029 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
17030 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
17031 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
17032 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
17033 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
17034 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
17035 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
17036 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
17037 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
17038 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
17039 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
17040 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
17041 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
17042 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
17043 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
17044 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
17045 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
17046 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
17047 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
17048 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
17049 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
17050 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
17051 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
17052 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
17053 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
17054 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
17057 unsigned char *end;
17059 crc = ~crc & 0xffffffff;
17060 for (end = buf + len; buf < end; ++buf)
17061 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
17062 return ~crc & 0xffffffff;
17067 This computation does not apply to the ``build ID'' method.
17069 @node MiniDebugInfo
17070 @section Debugging information in a special section
17071 @cindex separate debug sections
17072 @cindex @samp{.gnu_debugdata} section
17074 Some systems ship pre-built executables and libraries that have a
17075 special @samp{.gnu_debugdata} section. This feature is called
17076 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
17077 is used to supply extra symbols for backtraces.
17079 The intent of this section is to provide extra minimal debugging
17080 information for use in simple backtraces. It is not intended to be a
17081 replacement for full separate debugging information (@pxref{Separate
17082 Debug Files}). The example below shows the intended use; however,
17083 @value{GDBN} does not currently put restrictions on what sort of
17084 debugging information might be included in the section.
17086 @value{GDBN} has support for this extension. If the section exists,
17087 then it is used provided that no other source of debugging information
17088 can be found, and that @value{GDBN} was configured with LZMA support.
17090 This section can be easily created using @command{objcopy} and other
17091 standard utilities:
17094 # Extract the dynamic symbols from the main binary, there is no need
17095 # to also have these in the normal symbol table
17096 nm -D @var{binary} --format=posix --defined-only \
17097 | awk '@{ print $1 @}' | sort > dynsyms
17099 # Extract all the text (i.e. function) symbols from the debuginfo .
17100 nm @var{binary} --format=posix --defined-only \
17101 | awk '@{ if ($2 == "T" || $2 == "t") print $1 @}' \
17104 # Keep all the function symbols not already in the dynamic symbol
17106 comm -13 dynsyms funcsyms > keep_symbols
17108 # Copy the full debuginfo, keeping only a minimal set of symbols and
17109 # removing some unnecessary sections.
17110 objcopy -S --remove-section .gdb_index --remove-section .comment \
17111 --keep-symbols=keep_symbols @var{binary} mini_debuginfo
17113 # Inject the compressed data into the .gnu_debugdata section of the
17116 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
17120 @section Index Files Speed Up @value{GDBN}
17121 @cindex index files
17122 @cindex @samp{.gdb_index} section
17124 When @value{GDBN} finds a symbol file, it scans the symbols in the
17125 file in order to construct an internal symbol table. This lets most
17126 @value{GDBN} operations work quickly---at the cost of a delay early
17127 on. For large programs, this delay can be quite lengthy, so
17128 @value{GDBN} provides a way to build an index, which speeds up
17131 The index is stored as a section in the symbol file. @value{GDBN} can
17132 write the index to a file, then you can put it into the symbol file
17133 using @command{objcopy}.
17135 To create an index file, use the @code{save gdb-index} command:
17138 @item save gdb-index @var{directory}
17139 @kindex save gdb-index
17140 Create an index file for each symbol file currently known by
17141 @value{GDBN}. Each file is named after its corresponding symbol file,
17142 with @samp{.gdb-index} appended, and is written into the given
17146 Once you have created an index file you can merge it into your symbol
17147 file, here named @file{symfile}, using @command{objcopy}:
17150 $ objcopy --add-section .gdb_index=symfile.gdb-index \
17151 --set-section-flags .gdb_index=readonly symfile symfile
17154 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
17155 sections that have been deprecated. Usually they are deprecated because
17156 they are missing a new feature or have performance issues.
17157 To tell @value{GDBN} to use a deprecated index section anyway
17158 specify @code{set use-deprecated-index-sections on}.
17159 The default is @code{off}.
17160 This can speed up startup, but may result in some functionality being lost.
17161 @xref{Index Section Format}.
17163 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
17164 must be done before gdb reads the file. The following will not work:
17167 $ gdb -ex "set use-deprecated-index-sections on" <program>
17170 Instead you must do, for example,
17173 $ gdb -iex "set use-deprecated-index-sections on" <program>
17176 There are currently some limitation on indices. They only work when
17177 for DWARF debugging information, not stabs. And, they do not
17178 currently work for programs using Ada.
17180 @node Symbol Errors
17181 @section Errors Reading Symbol Files
17183 While reading a symbol file, @value{GDBN} occasionally encounters problems,
17184 such as symbol types it does not recognize, or known bugs in compiler
17185 output. By default, @value{GDBN} does not notify you of such problems, since
17186 they are relatively common and primarily of interest to people
17187 debugging compilers. If you are interested in seeing information
17188 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
17189 only one message about each such type of problem, no matter how many
17190 times the problem occurs; or you can ask @value{GDBN} to print more messages,
17191 to see how many times the problems occur, with the @code{set
17192 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
17195 The messages currently printed, and their meanings, include:
17198 @item inner block not inside outer block in @var{symbol}
17200 The symbol information shows where symbol scopes begin and end
17201 (such as at the start of a function or a block of statements). This
17202 error indicates that an inner scope block is not fully contained
17203 in its outer scope blocks.
17205 @value{GDBN} circumvents the problem by treating the inner block as if it had
17206 the same scope as the outer block. In the error message, @var{symbol}
17207 may be shown as ``@code{(don't know)}'' if the outer block is not a
17210 @item block at @var{address} out of order
17212 The symbol information for symbol scope blocks should occur in
17213 order of increasing addresses. This error indicates that it does not
17216 @value{GDBN} does not circumvent this problem, and has trouble
17217 locating symbols in the source file whose symbols it is reading. (You
17218 can often determine what source file is affected by specifying
17219 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
17222 @item bad block start address patched
17224 The symbol information for a symbol scope block has a start address
17225 smaller than the address of the preceding source line. This is known
17226 to occur in the SunOS 4.1.1 (and earlier) C compiler.
17228 @value{GDBN} circumvents the problem by treating the symbol scope block as
17229 starting on the previous source line.
17231 @item bad string table offset in symbol @var{n}
17234 Symbol number @var{n} contains a pointer into the string table which is
17235 larger than the size of the string table.
17237 @value{GDBN} circumvents the problem by considering the symbol to have the
17238 name @code{foo}, which may cause other problems if many symbols end up
17241 @item unknown symbol type @code{0x@var{nn}}
17243 The symbol information contains new data types that @value{GDBN} does
17244 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
17245 uncomprehended information, in hexadecimal.
17247 @value{GDBN} circumvents the error by ignoring this symbol information.
17248 This usually allows you to debug your program, though certain symbols
17249 are not accessible. If you encounter such a problem and feel like
17250 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
17251 on @code{complain}, then go up to the function @code{read_dbx_symtab}
17252 and examine @code{*bufp} to see the symbol.
17254 @item stub type has NULL name
17256 @value{GDBN} could not find the full definition for a struct or class.
17258 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
17259 The symbol information for a C@t{++} member function is missing some
17260 information that recent versions of the compiler should have output for
17263 @item info mismatch between compiler and debugger
17265 @value{GDBN} could not parse a type specification output by the compiler.
17270 @section GDB Data Files
17272 @cindex prefix for data files
17273 @value{GDBN} will sometimes read an auxiliary data file. These files
17274 are kept in a directory known as the @dfn{data directory}.
17276 You can set the data directory's name, and view the name @value{GDBN}
17277 is currently using.
17280 @kindex set data-directory
17281 @item set data-directory @var{directory}
17282 Set the directory which @value{GDBN} searches for auxiliary data files
17283 to @var{directory}.
17285 @kindex show data-directory
17286 @item show data-directory
17287 Show the directory @value{GDBN} searches for auxiliary data files.
17290 @cindex default data directory
17291 @cindex @samp{--with-gdb-datadir}
17292 You can set the default data directory by using the configure-time
17293 @samp{--with-gdb-datadir} option. If the data directory is inside
17294 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17295 @samp{--exec-prefix}), then the default data directory will be updated
17296 automatically if the installed @value{GDBN} is moved to a new
17299 The data directory may also be specified with the
17300 @code{--data-directory} command line option.
17301 @xref{Mode Options}.
17304 @chapter Specifying a Debugging Target
17306 @cindex debugging target
17307 A @dfn{target} is the execution environment occupied by your program.
17309 Often, @value{GDBN} runs in the same host environment as your program;
17310 in that case, the debugging target is specified as a side effect when
17311 you use the @code{file} or @code{core} commands. When you need more
17312 flexibility---for example, running @value{GDBN} on a physically separate
17313 host, or controlling a standalone system over a serial port or a
17314 realtime system over a TCP/IP connection---you can use the @code{target}
17315 command to specify one of the target types configured for @value{GDBN}
17316 (@pxref{Target Commands, ,Commands for Managing Targets}).
17318 @cindex target architecture
17319 It is possible to build @value{GDBN} for several different @dfn{target
17320 architectures}. When @value{GDBN} is built like that, you can choose
17321 one of the available architectures with the @kbd{set architecture}
17325 @kindex set architecture
17326 @kindex show architecture
17327 @item set architecture @var{arch}
17328 This command sets the current target architecture to @var{arch}. The
17329 value of @var{arch} can be @code{"auto"}, in addition to one of the
17330 supported architectures.
17332 @item show architecture
17333 Show the current target architecture.
17335 @item set processor
17337 @kindex set processor
17338 @kindex show processor
17339 These are alias commands for, respectively, @code{set architecture}
17340 and @code{show architecture}.
17344 * Active Targets:: Active targets
17345 * Target Commands:: Commands for managing targets
17346 * Byte Order:: Choosing target byte order
17349 @node Active Targets
17350 @section Active Targets
17352 @cindex stacking targets
17353 @cindex active targets
17354 @cindex multiple targets
17356 There are multiple classes of targets such as: processes, executable files or
17357 recording sessions. Core files belong to the process class, making core file
17358 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
17359 on multiple active targets, one in each class. This allows you to (for
17360 example) start a process and inspect its activity, while still having access to
17361 the executable file after the process finishes. Or if you start process
17362 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
17363 presented a virtual layer of the recording target, while the process target
17364 remains stopped at the chronologically last point of the process execution.
17366 Use the @code{core-file} and @code{exec-file} commands to select a new core
17367 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
17368 specify as a target a process that is already running, use the @code{attach}
17369 command (@pxref{Attach, ,Debugging an Already-running Process}).
17371 @node Target Commands
17372 @section Commands for Managing Targets
17375 @item target @var{type} @var{parameters}
17376 Connects the @value{GDBN} host environment to a target machine or
17377 process. A target is typically a protocol for talking to debugging
17378 facilities. You use the argument @var{type} to specify the type or
17379 protocol of the target machine.
17381 Further @var{parameters} are interpreted by the target protocol, but
17382 typically include things like device names or host names to connect
17383 with, process numbers, and baud rates.
17385 The @code{target} command does not repeat if you press @key{RET} again
17386 after executing the command.
17388 @kindex help target
17390 Displays the names of all targets available. To display targets
17391 currently selected, use either @code{info target} or @code{info files}
17392 (@pxref{Files, ,Commands to Specify Files}).
17394 @item help target @var{name}
17395 Describe a particular target, including any parameters necessary to
17398 @kindex set gnutarget
17399 @item set gnutarget @var{args}
17400 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
17401 knows whether it is reading an @dfn{executable},
17402 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
17403 with the @code{set gnutarget} command. Unlike most @code{target} commands,
17404 with @code{gnutarget} the @code{target} refers to a program, not a machine.
17407 @emph{Warning:} To specify a file format with @code{set gnutarget},
17408 you must know the actual BFD name.
17412 @xref{Files, , Commands to Specify Files}.
17414 @kindex show gnutarget
17415 @item show gnutarget
17416 Use the @code{show gnutarget} command to display what file format
17417 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
17418 @value{GDBN} will determine the file format for each file automatically,
17419 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
17422 @cindex common targets
17423 Here are some common targets (available, or not, depending on the GDB
17428 @item target exec @var{program}
17429 @cindex executable file target
17430 An executable file. @samp{target exec @var{program}} is the same as
17431 @samp{exec-file @var{program}}.
17433 @item target core @var{filename}
17434 @cindex core dump file target
17435 A core dump file. @samp{target core @var{filename}} is the same as
17436 @samp{core-file @var{filename}}.
17438 @item target remote @var{medium}
17439 @cindex remote target
17440 A remote system connected to @value{GDBN} via a serial line or network
17441 connection. This command tells @value{GDBN} to use its own remote
17442 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
17444 For example, if you have a board connected to @file{/dev/ttya} on the
17445 machine running @value{GDBN}, you could say:
17448 target remote /dev/ttya
17451 @code{target remote} supports the @code{load} command. This is only
17452 useful if you have some other way of getting the stub to the target
17453 system, and you can put it somewhere in memory where it won't get
17454 clobbered by the download.
17456 @item target sim @r{[}@var{simargs}@r{]} @dots{}
17457 @cindex built-in simulator target
17458 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
17466 works; however, you cannot assume that a specific memory map, device
17467 drivers, or even basic I/O is available, although some simulators do
17468 provide these. For info about any processor-specific simulator details,
17469 see the appropriate section in @ref{Embedded Processors, ,Embedded
17474 Some configurations may include these targets as well:
17478 @item target nrom @var{dev}
17479 @cindex NetROM ROM emulator target
17480 NetROM ROM emulator. This target only supports downloading.
17484 Different targets are available on different configurations of @value{GDBN};
17485 your configuration may have more or fewer targets.
17487 Many remote targets require you to download the executable's code once
17488 you've successfully established a connection. You may wish to control
17489 various aspects of this process.
17494 @kindex set hash@r{, for remote monitors}
17495 @cindex hash mark while downloading
17496 This command controls whether a hash mark @samp{#} is displayed while
17497 downloading a file to the remote monitor. If on, a hash mark is
17498 displayed after each S-record is successfully downloaded to the
17502 @kindex show hash@r{, for remote monitors}
17503 Show the current status of displaying the hash mark.
17505 @item set debug monitor
17506 @kindex set debug monitor
17507 @cindex display remote monitor communications
17508 Enable or disable display of communications messages between
17509 @value{GDBN} and the remote monitor.
17511 @item show debug monitor
17512 @kindex show debug monitor
17513 Show the current status of displaying communications between
17514 @value{GDBN} and the remote monitor.
17519 @kindex load @var{filename}
17520 @item load @var{filename}
17522 Depending on what remote debugging facilities are configured into
17523 @value{GDBN}, the @code{load} command may be available. Where it exists, it
17524 is meant to make @var{filename} (an executable) available for debugging
17525 on the remote system---by downloading, or dynamic linking, for example.
17526 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
17527 the @code{add-symbol-file} command.
17529 If your @value{GDBN} does not have a @code{load} command, attempting to
17530 execute it gets the error message ``@code{You can't do that when your
17531 target is @dots{}}''
17533 The file is loaded at whatever address is specified in the executable.
17534 For some object file formats, you can specify the load address when you
17535 link the program; for other formats, like a.out, the object file format
17536 specifies a fixed address.
17537 @c FIXME! This would be a good place for an xref to the GNU linker doc.
17539 Depending on the remote side capabilities, @value{GDBN} may be able to
17540 load programs into flash memory.
17542 @code{load} does not repeat if you press @key{RET} again after using it.
17546 @section Choosing Target Byte Order
17548 @cindex choosing target byte order
17549 @cindex target byte order
17551 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
17552 offer the ability to run either big-endian or little-endian byte
17553 orders. Usually the executable or symbol will include a bit to
17554 designate the endian-ness, and you will not need to worry about
17555 which to use. However, you may still find it useful to adjust
17556 @value{GDBN}'s idea of processor endian-ness manually.
17560 @item set endian big
17561 Instruct @value{GDBN} to assume the target is big-endian.
17563 @item set endian little
17564 Instruct @value{GDBN} to assume the target is little-endian.
17566 @item set endian auto
17567 Instruct @value{GDBN} to use the byte order associated with the
17571 Display @value{GDBN}'s current idea of the target byte order.
17575 Note that these commands merely adjust interpretation of symbolic
17576 data on the host, and that they have absolutely no effect on the
17580 @node Remote Debugging
17581 @chapter Debugging Remote Programs
17582 @cindex remote debugging
17584 If you are trying to debug a program running on a machine that cannot run
17585 @value{GDBN} in the usual way, it is often useful to use remote debugging.
17586 For example, you might use remote debugging on an operating system kernel,
17587 or on a small system which does not have a general purpose operating system
17588 powerful enough to run a full-featured debugger.
17590 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
17591 to make this work with particular debugging targets. In addition,
17592 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
17593 but not specific to any particular target system) which you can use if you
17594 write the remote stubs---the code that runs on the remote system to
17595 communicate with @value{GDBN}.
17597 Other remote targets may be available in your
17598 configuration of @value{GDBN}; use @code{help target} to list them.
17601 * Connecting:: Connecting to a remote target
17602 * File Transfer:: Sending files to a remote system
17603 * Server:: Using the gdbserver program
17604 * Remote Configuration:: Remote configuration
17605 * Remote Stub:: Implementing a remote stub
17609 @section Connecting to a Remote Target
17611 On the @value{GDBN} host machine, you will need an unstripped copy of
17612 your program, since @value{GDBN} needs symbol and debugging information.
17613 Start up @value{GDBN} as usual, using the name of the local copy of your
17614 program as the first argument.
17616 @cindex @code{target remote}
17617 @value{GDBN} can communicate with the target over a serial line, or
17618 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
17619 each case, @value{GDBN} uses the same protocol for debugging your
17620 program; only the medium carrying the debugging packets varies. The
17621 @code{target remote} command establishes a connection to the target.
17622 Its arguments indicate which medium to use:
17626 @item target remote @var{serial-device}
17627 @cindex serial line, @code{target remote}
17628 Use @var{serial-device} to communicate with the target. For example,
17629 to use a serial line connected to the device named @file{/dev/ttyb}:
17632 target remote /dev/ttyb
17635 If you're using a serial line, you may want to give @value{GDBN} the
17636 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
17637 (@pxref{Remote Configuration, set remotebaud}) before the
17638 @code{target} command.
17640 @item target remote @code{@var{host}:@var{port}}
17641 @itemx target remote @code{tcp:@var{host}:@var{port}}
17642 @cindex @acronym{TCP} port, @code{target remote}
17643 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
17644 The @var{host} may be either a host name or a numeric @acronym{IP}
17645 address; @var{port} must be a decimal number. The @var{host} could be
17646 the target machine itself, if it is directly connected to the net, or
17647 it might be a terminal server which in turn has a serial line to the
17650 For example, to connect to port 2828 on a terminal server named
17654 target remote manyfarms:2828
17657 If your remote target is actually running on the same machine as your
17658 debugger session (e.g.@: a simulator for your target running on the
17659 same host), you can omit the hostname. For example, to connect to
17660 port 1234 on your local machine:
17663 target remote :1234
17667 Note that the colon is still required here.
17669 @item target remote @code{udp:@var{host}:@var{port}}
17670 @cindex @acronym{UDP} port, @code{target remote}
17671 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
17672 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
17675 target remote udp:manyfarms:2828
17678 When using a @acronym{UDP} connection for remote debugging, you should
17679 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
17680 can silently drop packets on busy or unreliable networks, which will
17681 cause havoc with your debugging session.
17683 @item target remote | @var{command}
17684 @cindex pipe, @code{target remote} to
17685 Run @var{command} in the background and communicate with it using a
17686 pipe. The @var{command} is a shell command, to be parsed and expanded
17687 by the system's command shell, @code{/bin/sh}; it should expect remote
17688 protocol packets on its standard input, and send replies on its
17689 standard output. You could use this to run a stand-alone simulator
17690 that speaks the remote debugging protocol, to make net connections
17691 using programs like @code{ssh}, or for other similar tricks.
17693 If @var{command} closes its standard output (perhaps by exiting),
17694 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
17695 program has already exited, this will have no effect.)
17699 Once the connection has been established, you can use all the usual
17700 commands to examine and change data. The remote program is already
17701 running; you can use @kbd{step} and @kbd{continue}, and you do not
17702 need to use @kbd{run}.
17704 @cindex interrupting remote programs
17705 @cindex remote programs, interrupting
17706 Whenever @value{GDBN} is waiting for the remote program, if you type the
17707 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
17708 program. This may or may not succeed, depending in part on the hardware
17709 and the serial drivers the remote system uses. If you type the
17710 interrupt character once again, @value{GDBN} displays this prompt:
17713 Interrupted while waiting for the program.
17714 Give up (and stop debugging it)? (y or n)
17717 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
17718 (If you decide you want to try again later, you can use @samp{target
17719 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
17720 goes back to waiting.
17723 @kindex detach (remote)
17725 When you have finished debugging the remote program, you can use the
17726 @code{detach} command to release it from @value{GDBN} control.
17727 Detaching from the target normally resumes its execution, but the results
17728 will depend on your particular remote stub. After the @code{detach}
17729 command, @value{GDBN} is free to connect to another target.
17733 The @code{disconnect} command behaves like @code{detach}, except that
17734 the target is generally not resumed. It will wait for @value{GDBN}
17735 (this instance or another one) to connect and continue debugging. After
17736 the @code{disconnect} command, @value{GDBN} is again free to connect to
17739 @cindex send command to remote monitor
17740 @cindex extend @value{GDBN} for remote targets
17741 @cindex add new commands for external monitor
17743 @item monitor @var{cmd}
17744 This command allows you to send arbitrary commands directly to the
17745 remote monitor. Since @value{GDBN} doesn't care about the commands it
17746 sends like this, this command is the way to extend @value{GDBN}---you
17747 can add new commands that only the external monitor will understand
17751 @node File Transfer
17752 @section Sending files to a remote system
17753 @cindex remote target, file transfer
17754 @cindex file transfer
17755 @cindex sending files to remote systems
17757 Some remote targets offer the ability to transfer files over the same
17758 connection used to communicate with @value{GDBN}. This is convenient
17759 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
17760 running @code{gdbserver} over a network interface. For other targets,
17761 e.g.@: embedded devices with only a single serial port, this may be
17762 the only way to upload or download files.
17764 Not all remote targets support these commands.
17768 @item remote put @var{hostfile} @var{targetfile}
17769 Copy file @var{hostfile} from the host system (the machine running
17770 @value{GDBN}) to @var{targetfile} on the target system.
17773 @item remote get @var{targetfile} @var{hostfile}
17774 Copy file @var{targetfile} from the target system to @var{hostfile}
17775 on the host system.
17777 @kindex remote delete
17778 @item remote delete @var{targetfile}
17779 Delete @var{targetfile} from the target system.
17784 @section Using the @code{gdbserver} Program
17787 @cindex remote connection without stubs
17788 @code{gdbserver} is a control program for Unix-like systems, which
17789 allows you to connect your program with a remote @value{GDBN} via
17790 @code{target remote}---but without linking in the usual debugging stub.
17792 @code{gdbserver} is not a complete replacement for the debugging stubs,
17793 because it requires essentially the same operating-system facilities
17794 that @value{GDBN} itself does. In fact, a system that can run
17795 @code{gdbserver} to connect to a remote @value{GDBN} could also run
17796 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
17797 because it is a much smaller program than @value{GDBN} itself. It is
17798 also easier to port than all of @value{GDBN}, so you may be able to get
17799 started more quickly on a new system by using @code{gdbserver}.
17800 Finally, if you develop code for real-time systems, you may find that
17801 the tradeoffs involved in real-time operation make it more convenient to
17802 do as much development work as possible on another system, for example
17803 by cross-compiling. You can use @code{gdbserver} to make a similar
17804 choice for debugging.
17806 @value{GDBN} and @code{gdbserver} communicate via either a serial line
17807 or a TCP connection, using the standard @value{GDBN} remote serial
17811 @emph{Warning:} @code{gdbserver} does not have any built-in security.
17812 Do not run @code{gdbserver} connected to any public network; a
17813 @value{GDBN} connection to @code{gdbserver} provides access to the
17814 target system with the same privileges as the user running
17818 @subsection Running @code{gdbserver}
17819 @cindex arguments, to @code{gdbserver}
17820 @cindex @code{gdbserver}, command-line arguments
17822 Run @code{gdbserver} on the target system. You need a copy of the
17823 program you want to debug, including any libraries it requires.
17824 @code{gdbserver} does not need your program's symbol table, so you can
17825 strip the program if necessary to save space. @value{GDBN} on the host
17826 system does all the symbol handling.
17828 To use the server, you must tell it how to communicate with @value{GDBN};
17829 the name of your program; and the arguments for your program. The usual
17833 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
17836 @var{comm} is either a device name (to use a serial line), or a TCP
17837 hostname and portnumber, or @code{-} or @code{stdio} to use
17838 stdin/stdout of @code{gdbserver}.
17839 For example, to debug Emacs with the argument
17840 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
17844 target> gdbserver /dev/com1 emacs foo.txt
17847 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
17850 To use a TCP connection instead of a serial line:
17853 target> gdbserver host:2345 emacs foo.txt
17856 The only difference from the previous example is the first argument,
17857 specifying that you are communicating with the host @value{GDBN} via
17858 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
17859 expect a TCP connection from machine @samp{host} to local TCP port 2345.
17860 (Currently, the @samp{host} part is ignored.) You can choose any number
17861 you want for the port number as long as it does not conflict with any
17862 TCP ports already in use on the target system (for example, @code{23} is
17863 reserved for @code{telnet}).@footnote{If you choose a port number that
17864 conflicts with another service, @code{gdbserver} prints an error message
17865 and exits.} You must use the same port number with the host @value{GDBN}
17866 @code{target remote} command.
17868 The @code{stdio} connection is useful when starting @code{gdbserver}
17872 (gdb) target remote | ssh -T hostname gdbserver - hello
17875 The @samp{-T} option to ssh is provided because we don't need a remote pty,
17876 and we don't want escape-character handling. Ssh does this by default when
17877 a command is provided, the flag is provided to make it explicit.
17878 You could elide it if you want to.
17880 Programs started with stdio-connected gdbserver have @file{/dev/null} for
17881 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
17882 display through a pipe connected to gdbserver.
17883 Both @code{stdout} and @code{stderr} use the same pipe.
17885 @subsubsection Attaching to a Running Program
17886 @cindex attach to a program, @code{gdbserver}
17887 @cindex @option{--attach}, @code{gdbserver} option
17889 On some targets, @code{gdbserver} can also attach to running programs.
17890 This is accomplished via the @code{--attach} argument. The syntax is:
17893 target> gdbserver --attach @var{comm} @var{pid}
17896 @var{pid} is the process ID of a currently running process. It isn't necessary
17897 to point @code{gdbserver} at a binary for the running process.
17900 You can debug processes by name instead of process ID if your target has the
17901 @code{pidof} utility:
17904 target> gdbserver --attach @var{comm} `pidof @var{program}`
17907 In case more than one copy of @var{program} is running, or @var{program}
17908 has multiple threads, most versions of @code{pidof} support the
17909 @code{-s} option to only return the first process ID.
17911 @subsubsection Multi-Process Mode for @code{gdbserver}
17912 @cindex @code{gdbserver}, multiple processes
17913 @cindex multiple processes with @code{gdbserver}
17915 When you connect to @code{gdbserver} using @code{target remote},
17916 @code{gdbserver} debugs the specified program only once. When the
17917 program exits, or you detach from it, @value{GDBN} closes the connection
17918 and @code{gdbserver} exits.
17920 If you connect using @kbd{target extended-remote}, @code{gdbserver}
17921 enters multi-process mode. When the debugged program exits, or you
17922 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
17923 though no program is running. The @code{run} and @code{attach}
17924 commands instruct @code{gdbserver} to run or attach to a new program.
17925 The @code{run} command uses @code{set remote exec-file} (@pxref{set
17926 remote exec-file}) to select the program to run. Command line
17927 arguments are supported, except for wildcard expansion and I/O
17928 redirection (@pxref{Arguments}).
17930 @cindex @option{--multi}, @code{gdbserver} option
17931 To start @code{gdbserver} without supplying an initial command to run
17932 or process ID to attach, use the @option{--multi} command line option.
17933 Then you can connect using @kbd{target extended-remote} and start
17934 the program you want to debug.
17936 In multi-process mode @code{gdbserver} does not automatically exit unless you
17937 use the option @option{--once}. You can terminate it by using
17938 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
17939 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
17940 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
17941 @option{--multi} option to @code{gdbserver} has no influence on that.
17943 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
17945 This section applies only when @code{gdbserver} is run to listen on a TCP port.
17947 @code{gdbserver} normally terminates after all of its debugged processes have
17948 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
17949 extended-remote}, @code{gdbserver} stays running even with no processes left.
17950 @value{GDBN} normally terminates the spawned debugged process on its exit,
17951 which normally also terminates @code{gdbserver} in the @kbd{target remote}
17952 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
17953 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
17954 stays running even in the @kbd{target remote} mode.
17956 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
17957 Such reconnecting is useful for features like @ref{disconnected tracing}. For
17958 completeness, at most one @value{GDBN} can be connected at a time.
17960 @cindex @option{--once}, @code{gdbserver} option
17961 By default, @code{gdbserver} keeps the listening TCP port open, so that
17962 additional connections are possible. However, if you start @code{gdbserver}
17963 with the @option{--once} option, it will stop listening for any further
17964 connection attempts after connecting to the first @value{GDBN} session. This
17965 means no further connections to @code{gdbserver} will be possible after the
17966 first one. It also means @code{gdbserver} will terminate after the first
17967 connection with remote @value{GDBN} has closed, even for unexpectedly closed
17968 connections and even in the @kbd{target extended-remote} mode. The
17969 @option{--once} option allows reusing the same port number for connecting to
17970 multiple instances of @code{gdbserver} running on the same host, since each
17971 instance closes its port after the first connection.
17973 @subsubsection Other Command-Line Arguments for @code{gdbserver}
17975 @cindex @option{--debug}, @code{gdbserver} option
17976 The @option{--debug} option tells @code{gdbserver} to display extra
17977 status information about the debugging process.
17978 @cindex @option{--remote-debug}, @code{gdbserver} option
17979 The @option{--remote-debug} option tells @code{gdbserver} to display
17980 remote protocol debug output. These options are intended for
17981 @code{gdbserver} development and for bug reports to the developers.
17983 @cindex @option{--wrapper}, @code{gdbserver} option
17984 The @option{--wrapper} option specifies a wrapper to launch programs
17985 for debugging. The option should be followed by the name of the
17986 wrapper, then any command-line arguments to pass to the wrapper, then
17987 @kbd{--} indicating the end of the wrapper arguments.
17989 @code{gdbserver} runs the specified wrapper program with a combined
17990 command line including the wrapper arguments, then the name of the
17991 program to debug, then any arguments to the program. The wrapper
17992 runs until it executes your program, and then @value{GDBN} gains control.
17994 You can use any program that eventually calls @code{execve} with
17995 its arguments as a wrapper. Several standard Unix utilities do
17996 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
17997 with @code{exec "$@@"} will also work.
17999 For example, you can use @code{env} to pass an environment variable to
18000 the debugged program, without setting the variable in @code{gdbserver}'s
18004 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
18007 @subsection Connecting to @code{gdbserver}
18009 Run @value{GDBN} on the host system.
18011 First make sure you have the necessary symbol files. Load symbols for
18012 your application using the @code{file} command before you connect. Use
18013 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
18014 was compiled with the correct sysroot using @code{--with-sysroot}).
18016 The symbol file and target libraries must exactly match the executable
18017 and libraries on the target, with one exception: the files on the host
18018 system should not be stripped, even if the files on the target system
18019 are. Mismatched or missing files will lead to confusing results
18020 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
18021 files may also prevent @code{gdbserver} from debugging multi-threaded
18024 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
18025 For TCP connections, you must start up @code{gdbserver} prior to using
18026 the @code{target remote} command. Otherwise you may get an error whose
18027 text depends on the host system, but which usually looks something like
18028 @samp{Connection refused}. Don't use the @code{load}
18029 command in @value{GDBN} when using @code{gdbserver}, since the program is
18030 already on the target.
18032 @subsection Monitor Commands for @code{gdbserver}
18033 @cindex monitor commands, for @code{gdbserver}
18034 @anchor{Monitor Commands for gdbserver}
18036 During a @value{GDBN} session using @code{gdbserver}, you can use the
18037 @code{monitor} command to send special requests to @code{gdbserver}.
18038 Here are the available commands.
18042 List the available monitor commands.
18044 @item monitor set debug 0
18045 @itemx monitor set debug 1
18046 Disable or enable general debugging messages.
18048 @item monitor set remote-debug 0
18049 @itemx monitor set remote-debug 1
18050 Disable or enable specific debugging messages associated with the remote
18051 protocol (@pxref{Remote Protocol}).
18053 @item monitor set libthread-db-search-path [PATH]
18054 @cindex gdbserver, search path for @code{libthread_db}
18055 When this command is issued, @var{path} is a colon-separated list of
18056 directories to search for @code{libthread_db} (@pxref{Threads,,set
18057 libthread-db-search-path}). If you omit @var{path},
18058 @samp{libthread-db-search-path} will be reset to its default value.
18060 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
18061 not supported in @code{gdbserver}.
18064 Tell gdbserver to exit immediately. This command should be followed by
18065 @code{disconnect} to close the debugging session. @code{gdbserver} will
18066 detach from any attached processes and kill any processes it created.
18067 Use @code{monitor exit} to terminate @code{gdbserver} at the end
18068 of a multi-process mode debug session.
18072 @subsection Tracepoints support in @code{gdbserver}
18073 @cindex tracepoints support in @code{gdbserver}
18075 On some targets, @code{gdbserver} supports tracepoints, fast
18076 tracepoints and static tracepoints.
18078 For fast or static tracepoints to work, a special library called the
18079 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
18080 This library is built and distributed as an integral part of
18081 @code{gdbserver}. In addition, support for static tracepoints
18082 requires building the in-process agent library with static tracepoints
18083 support. At present, the UST (LTTng Userspace Tracer,
18084 @url{http://lttng.org/ust}) tracing engine is supported. This support
18085 is automatically available if UST development headers are found in the
18086 standard include path when @code{gdbserver} is built, or if
18087 @code{gdbserver} was explicitly configured using @option{--with-ust}
18088 to point at such headers. You can explicitly disable the support
18089 using @option{--with-ust=no}.
18091 There are several ways to load the in-process agent in your program:
18094 @item Specifying it as dependency at link time
18096 You can link your program dynamically with the in-process agent
18097 library. On most systems, this is accomplished by adding
18098 @code{-linproctrace} to the link command.
18100 @item Using the system's preloading mechanisms
18102 You can force loading the in-process agent at startup time by using
18103 your system's support for preloading shared libraries. Many Unixes
18104 support the concept of preloading user defined libraries. In most
18105 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
18106 in the environment. See also the description of @code{gdbserver}'s
18107 @option{--wrapper} command line option.
18109 @item Using @value{GDBN} to force loading the agent at run time
18111 On some systems, you can force the inferior to load a shared library,
18112 by calling a dynamic loader function in the inferior that takes care
18113 of dynamically looking up and loading a shared library. On most Unix
18114 systems, the function is @code{dlopen}. You'll use the @code{call}
18115 command for that. For example:
18118 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
18121 Note that on most Unix systems, for the @code{dlopen} function to be
18122 available, the program needs to be linked with @code{-ldl}.
18125 On systems that have a userspace dynamic loader, like most Unix
18126 systems, when you connect to @code{gdbserver} using @code{target
18127 remote}, you'll find that the program is stopped at the dynamic
18128 loader's entry point, and no shared library has been loaded in the
18129 program's address space yet, including the in-process agent. In that
18130 case, before being able to use any of the fast or static tracepoints
18131 features, you need to let the loader run and load the shared
18132 libraries. The simplest way to do that is to run the program to the
18133 main procedure. E.g., if debugging a C or C@t{++} program, start
18134 @code{gdbserver} like so:
18137 $ gdbserver :9999 myprogram
18140 Start GDB and connect to @code{gdbserver} like so, and run to main:
18144 (@value{GDBP}) target remote myhost:9999
18145 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
18146 (@value{GDBP}) b main
18147 (@value{GDBP}) continue
18150 The in-process tracing agent library should now be loaded into the
18151 process; you can confirm it with the @code{info sharedlibrary}
18152 command, which will list @file{libinproctrace.so} as loaded in the
18153 process. You are now ready to install fast tracepoints, list static
18154 tracepoint markers, probe static tracepoints markers, and start
18157 @node Remote Configuration
18158 @section Remote Configuration
18161 @kindex show remote
18162 This section documents the configuration options available when
18163 debugging remote programs. For the options related to the File I/O
18164 extensions of the remote protocol, see @ref{system,
18165 system-call-allowed}.
18168 @item set remoteaddresssize @var{bits}
18169 @cindex address size for remote targets
18170 @cindex bits in remote address
18171 Set the maximum size of address in a memory packet to the specified
18172 number of bits. @value{GDBN} will mask off the address bits above
18173 that number, when it passes addresses to the remote target. The
18174 default value is the number of bits in the target's address.
18176 @item show remoteaddresssize
18177 Show the current value of remote address size in bits.
18179 @item set remotebaud @var{n}
18180 @cindex baud rate for remote targets
18181 Set the baud rate for the remote serial I/O to @var{n} baud. The
18182 value is used to set the speed of the serial port used for debugging
18185 @item show remotebaud
18186 Show the current speed of the remote connection.
18188 @item set remotebreak
18189 @cindex interrupt remote programs
18190 @cindex BREAK signal instead of Ctrl-C
18191 @anchor{set remotebreak}
18192 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
18193 when you type @kbd{Ctrl-c} to interrupt the program running
18194 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
18195 character instead. The default is off, since most remote systems
18196 expect to see @samp{Ctrl-C} as the interrupt signal.
18198 @item show remotebreak
18199 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
18200 interrupt the remote program.
18202 @item set remoteflow on
18203 @itemx set remoteflow off
18204 @kindex set remoteflow
18205 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
18206 on the serial port used to communicate to the remote target.
18208 @item show remoteflow
18209 @kindex show remoteflow
18210 Show the current setting of hardware flow control.
18212 @item set remotelogbase @var{base}
18213 Set the base (a.k.a.@: radix) of logging serial protocol
18214 communications to @var{base}. Supported values of @var{base} are:
18215 @code{ascii}, @code{octal}, and @code{hex}. The default is
18218 @item show remotelogbase
18219 Show the current setting of the radix for logging remote serial
18222 @item set remotelogfile @var{file}
18223 @cindex record serial communications on file
18224 Record remote serial communications on the named @var{file}. The
18225 default is not to record at all.
18227 @item show remotelogfile.
18228 Show the current setting of the file name on which to record the
18229 serial communications.
18231 @item set remotetimeout @var{num}
18232 @cindex timeout for serial communications
18233 @cindex remote timeout
18234 Set the timeout limit to wait for the remote target to respond to
18235 @var{num} seconds. The default is 2 seconds.
18237 @item show remotetimeout
18238 Show the current number of seconds to wait for the remote target
18241 @cindex limit hardware breakpoints and watchpoints
18242 @cindex remote target, limit break- and watchpoints
18243 @anchor{set remote hardware-watchpoint-limit}
18244 @anchor{set remote hardware-breakpoint-limit}
18245 @item set remote hardware-watchpoint-limit @var{limit}
18246 @itemx set remote hardware-breakpoint-limit @var{limit}
18247 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
18248 watchpoints. A limit of -1, the default, is treated as unlimited.
18250 @cindex limit hardware watchpoints length
18251 @cindex remote target, limit watchpoints length
18252 @anchor{set remote hardware-watchpoint-length-limit}
18253 @item set remote hardware-watchpoint-length-limit @var{limit}
18254 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
18255 a remote hardware watchpoint. A limit of -1, the default, is treated
18258 @item show remote hardware-watchpoint-length-limit
18259 Show the current limit (in bytes) of the maximum length of
18260 a remote hardware watchpoint.
18262 @item set remote exec-file @var{filename}
18263 @itemx show remote exec-file
18264 @anchor{set remote exec-file}
18265 @cindex executable file, for remote target
18266 Select the file used for @code{run} with @code{target
18267 extended-remote}. This should be set to a filename valid on the
18268 target system. If it is not set, the target will use a default
18269 filename (e.g.@: the last program run).
18271 @item set remote interrupt-sequence
18272 @cindex interrupt remote programs
18273 @cindex select Ctrl-C, BREAK or BREAK-g
18274 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
18275 @samp{BREAK-g} as the
18276 sequence to the remote target in order to interrupt the execution.
18277 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
18278 is high level of serial line for some certain time.
18279 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
18280 It is @code{BREAK} signal followed by character @code{g}.
18282 @item show interrupt-sequence
18283 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
18284 is sent by @value{GDBN} to interrupt the remote program.
18285 @code{BREAK-g} is BREAK signal followed by @code{g} and
18286 also known as Magic SysRq g.
18288 @item set remote interrupt-on-connect
18289 @cindex send interrupt-sequence on start
18290 Specify whether interrupt-sequence is sent to remote target when
18291 @value{GDBN} connects to it. This is mostly needed when you debug
18292 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
18293 which is known as Magic SysRq g in order to connect @value{GDBN}.
18295 @item show interrupt-on-connect
18296 Show whether interrupt-sequence is sent
18297 to remote target when @value{GDBN} connects to it.
18301 @item set tcp auto-retry on
18302 @cindex auto-retry, for remote TCP target
18303 Enable auto-retry for remote TCP connections. This is useful if the remote
18304 debugging agent is launched in parallel with @value{GDBN}; there is a race
18305 condition because the agent may not become ready to accept the connection
18306 before @value{GDBN} attempts to connect. When auto-retry is
18307 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
18308 to establish the connection using the timeout specified by
18309 @code{set tcp connect-timeout}.
18311 @item set tcp auto-retry off
18312 Do not auto-retry failed TCP connections.
18314 @item show tcp auto-retry
18315 Show the current auto-retry setting.
18317 @item set tcp connect-timeout @var{seconds}
18318 @itemx set tcp connect-timeout unlimited
18319 @cindex connection timeout, for remote TCP target
18320 @cindex timeout, for remote target connection
18321 Set the timeout for establishing a TCP connection to the remote target to
18322 @var{seconds}. The timeout affects both polling to retry failed connections
18323 (enabled by @code{set tcp auto-retry on}) and waiting for connections
18324 that are merely slow to complete, and represents an approximate cumulative
18325 value. If @var{seconds} is @code{unlimited}, there is no timeout and
18326 @value{GDBN} will keep attempting to establish a connection forever,
18327 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
18329 @item show tcp connect-timeout
18330 Show the current connection timeout setting.
18333 @cindex remote packets, enabling and disabling
18334 The @value{GDBN} remote protocol autodetects the packets supported by
18335 your debugging stub. If you need to override the autodetection, you
18336 can use these commands to enable or disable individual packets. Each
18337 packet can be set to @samp{on} (the remote target supports this
18338 packet), @samp{off} (the remote target does not support this packet),
18339 or @samp{auto} (detect remote target support for this packet). They
18340 all default to @samp{auto}. For more information about each packet,
18341 see @ref{Remote Protocol}.
18343 During normal use, you should not have to use any of these commands.
18344 If you do, that may be a bug in your remote debugging stub, or a bug
18345 in @value{GDBN}. You may want to report the problem to the
18346 @value{GDBN} developers.
18348 For each packet @var{name}, the command to enable or disable the
18349 packet is @code{set remote @var{name}-packet}. The available settings
18352 @multitable @columnfractions 0.28 0.32 0.25
18355 @tab Related Features
18357 @item @code{fetch-register}
18359 @tab @code{info registers}
18361 @item @code{set-register}
18365 @item @code{binary-download}
18367 @tab @code{load}, @code{set}
18369 @item @code{read-aux-vector}
18370 @tab @code{qXfer:auxv:read}
18371 @tab @code{info auxv}
18373 @item @code{symbol-lookup}
18374 @tab @code{qSymbol}
18375 @tab Detecting multiple threads
18377 @item @code{attach}
18378 @tab @code{vAttach}
18381 @item @code{verbose-resume}
18383 @tab Stepping or resuming multiple threads
18389 @item @code{software-breakpoint}
18393 @item @code{hardware-breakpoint}
18397 @item @code{write-watchpoint}
18401 @item @code{read-watchpoint}
18405 @item @code{access-watchpoint}
18409 @item @code{target-features}
18410 @tab @code{qXfer:features:read}
18411 @tab @code{set architecture}
18413 @item @code{library-info}
18414 @tab @code{qXfer:libraries:read}
18415 @tab @code{info sharedlibrary}
18417 @item @code{memory-map}
18418 @tab @code{qXfer:memory-map:read}
18419 @tab @code{info mem}
18421 @item @code{read-sdata-object}
18422 @tab @code{qXfer:sdata:read}
18423 @tab @code{print $_sdata}
18425 @item @code{read-spu-object}
18426 @tab @code{qXfer:spu:read}
18427 @tab @code{info spu}
18429 @item @code{write-spu-object}
18430 @tab @code{qXfer:spu:write}
18431 @tab @code{info spu}
18433 @item @code{read-siginfo-object}
18434 @tab @code{qXfer:siginfo:read}
18435 @tab @code{print $_siginfo}
18437 @item @code{write-siginfo-object}
18438 @tab @code{qXfer:siginfo:write}
18439 @tab @code{set $_siginfo}
18441 @item @code{threads}
18442 @tab @code{qXfer:threads:read}
18443 @tab @code{info threads}
18445 @item @code{get-thread-local-@*storage-address}
18446 @tab @code{qGetTLSAddr}
18447 @tab Displaying @code{__thread} variables
18449 @item @code{get-thread-information-block-address}
18450 @tab @code{qGetTIBAddr}
18451 @tab Display MS-Windows Thread Information Block.
18453 @item @code{search-memory}
18454 @tab @code{qSearch:memory}
18457 @item @code{supported-packets}
18458 @tab @code{qSupported}
18459 @tab Remote communications parameters
18461 @item @code{pass-signals}
18462 @tab @code{QPassSignals}
18463 @tab @code{handle @var{signal}}
18465 @item @code{program-signals}
18466 @tab @code{QProgramSignals}
18467 @tab @code{handle @var{signal}}
18469 @item @code{hostio-close-packet}
18470 @tab @code{vFile:close}
18471 @tab @code{remote get}, @code{remote put}
18473 @item @code{hostio-open-packet}
18474 @tab @code{vFile:open}
18475 @tab @code{remote get}, @code{remote put}
18477 @item @code{hostio-pread-packet}
18478 @tab @code{vFile:pread}
18479 @tab @code{remote get}, @code{remote put}
18481 @item @code{hostio-pwrite-packet}
18482 @tab @code{vFile:pwrite}
18483 @tab @code{remote get}, @code{remote put}
18485 @item @code{hostio-unlink-packet}
18486 @tab @code{vFile:unlink}
18487 @tab @code{remote delete}
18489 @item @code{hostio-readlink-packet}
18490 @tab @code{vFile:readlink}
18493 @item @code{noack-packet}
18494 @tab @code{QStartNoAckMode}
18495 @tab Packet acknowledgment
18497 @item @code{osdata}
18498 @tab @code{qXfer:osdata:read}
18499 @tab @code{info os}
18501 @item @code{query-attached}
18502 @tab @code{qAttached}
18503 @tab Querying remote process attach state.
18505 @item @code{trace-buffer-size}
18506 @tab @code{QTBuffer:size}
18507 @tab @code{set trace-buffer-size}
18509 @item @code{trace-status}
18510 @tab @code{qTStatus}
18511 @tab @code{tstatus}
18513 @item @code{traceframe-info}
18514 @tab @code{qXfer:traceframe-info:read}
18515 @tab Traceframe info
18517 @item @code{install-in-trace}
18518 @tab @code{InstallInTrace}
18519 @tab Install tracepoint in tracing
18521 @item @code{disable-randomization}
18522 @tab @code{QDisableRandomization}
18523 @tab @code{set disable-randomization}
18525 @item @code{conditional-breakpoints-packet}
18526 @tab @code{Z0 and Z1}
18527 @tab @code{Support for target-side breakpoint condition evaluation}
18531 @section Implementing a Remote Stub
18533 @cindex debugging stub, example
18534 @cindex remote stub, example
18535 @cindex stub example, remote debugging
18536 The stub files provided with @value{GDBN} implement the target side of the
18537 communication protocol, and the @value{GDBN} side is implemented in the
18538 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
18539 these subroutines to communicate, and ignore the details. (If you're
18540 implementing your own stub file, you can still ignore the details: start
18541 with one of the existing stub files. @file{sparc-stub.c} is the best
18542 organized, and therefore the easiest to read.)
18544 @cindex remote serial debugging, overview
18545 To debug a program running on another machine (the debugging
18546 @dfn{target} machine), you must first arrange for all the usual
18547 prerequisites for the program to run by itself. For example, for a C
18552 A startup routine to set up the C runtime environment; these usually
18553 have a name like @file{crt0}. The startup routine may be supplied by
18554 your hardware supplier, or you may have to write your own.
18557 A C subroutine library to support your program's
18558 subroutine calls, notably managing input and output.
18561 A way of getting your program to the other machine---for example, a
18562 download program. These are often supplied by the hardware
18563 manufacturer, but you may have to write your own from hardware
18567 The next step is to arrange for your program to use a serial port to
18568 communicate with the machine where @value{GDBN} is running (the @dfn{host}
18569 machine). In general terms, the scheme looks like this:
18573 @value{GDBN} already understands how to use this protocol; when everything
18574 else is set up, you can simply use the @samp{target remote} command
18575 (@pxref{Targets,,Specifying a Debugging Target}).
18577 @item On the target,
18578 you must link with your program a few special-purpose subroutines that
18579 implement the @value{GDBN} remote serial protocol. The file containing these
18580 subroutines is called a @dfn{debugging stub}.
18582 On certain remote targets, you can use an auxiliary program
18583 @code{gdbserver} instead of linking a stub into your program.
18584 @xref{Server,,Using the @code{gdbserver} Program}, for details.
18587 The debugging stub is specific to the architecture of the remote
18588 machine; for example, use @file{sparc-stub.c} to debug programs on
18591 @cindex remote serial stub list
18592 These working remote stubs are distributed with @value{GDBN}:
18597 @cindex @file{i386-stub.c}
18600 For Intel 386 and compatible architectures.
18603 @cindex @file{m68k-stub.c}
18604 @cindex Motorola 680x0
18606 For Motorola 680x0 architectures.
18609 @cindex @file{sh-stub.c}
18612 For Renesas SH architectures.
18615 @cindex @file{sparc-stub.c}
18617 For @sc{sparc} architectures.
18619 @item sparcl-stub.c
18620 @cindex @file{sparcl-stub.c}
18623 For Fujitsu @sc{sparclite} architectures.
18627 The @file{README} file in the @value{GDBN} distribution may list other
18628 recently added stubs.
18631 * Stub Contents:: What the stub can do for you
18632 * Bootstrapping:: What you must do for the stub
18633 * Debug Session:: Putting it all together
18636 @node Stub Contents
18637 @subsection What the Stub Can Do for You
18639 @cindex remote serial stub
18640 The debugging stub for your architecture supplies these three
18644 @item set_debug_traps
18645 @findex set_debug_traps
18646 @cindex remote serial stub, initialization
18647 This routine arranges for @code{handle_exception} to run when your
18648 program stops. You must call this subroutine explicitly in your
18649 program's startup code.
18651 @item handle_exception
18652 @findex handle_exception
18653 @cindex remote serial stub, main routine
18654 This is the central workhorse, but your program never calls it
18655 explicitly---the setup code arranges for @code{handle_exception} to
18656 run when a trap is triggered.
18658 @code{handle_exception} takes control when your program stops during
18659 execution (for example, on a breakpoint), and mediates communications
18660 with @value{GDBN} on the host machine. This is where the communications
18661 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
18662 representative on the target machine. It begins by sending summary
18663 information on the state of your program, then continues to execute,
18664 retrieving and transmitting any information @value{GDBN} needs, until you
18665 execute a @value{GDBN} command that makes your program resume; at that point,
18666 @code{handle_exception} returns control to your own code on the target
18670 @cindex @code{breakpoint} subroutine, remote
18671 Use this auxiliary subroutine to make your program contain a
18672 breakpoint. Depending on the particular situation, this may be the only
18673 way for @value{GDBN} to get control. For instance, if your target
18674 machine has some sort of interrupt button, you won't need to call this;
18675 pressing the interrupt button transfers control to
18676 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
18677 simply receiving characters on the serial port may also trigger a trap;
18678 again, in that situation, you don't need to call @code{breakpoint} from
18679 your own program---simply running @samp{target remote} from the host
18680 @value{GDBN} session gets control.
18682 Call @code{breakpoint} if none of these is true, or if you simply want
18683 to make certain your program stops at a predetermined point for the
18684 start of your debugging session.
18687 @node Bootstrapping
18688 @subsection What You Must Do for the Stub
18690 @cindex remote stub, support routines
18691 The debugging stubs that come with @value{GDBN} are set up for a particular
18692 chip architecture, but they have no information about the rest of your
18693 debugging target machine.
18695 First of all you need to tell the stub how to communicate with the
18699 @item int getDebugChar()
18700 @findex getDebugChar
18701 Write this subroutine to read a single character from the serial port.
18702 It may be identical to @code{getchar} for your target system; a
18703 different name is used to allow you to distinguish the two if you wish.
18705 @item void putDebugChar(int)
18706 @findex putDebugChar
18707 Write this subroutine to write a single character to the serial port.
18708 It may be identical to @code{putchar} for your target system; a
18709 different name is used to allow you to distinguish the two if you wish.
18712 @cindex control C, and remote debugging
18713 @cindex interrupting remote targets
18714 If you want @value{GDBN} to be able to stop your program while it is
18715 running, you need to use an interrupt-driven serial driver, and arrange
18716 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
18717 character). That is the character which @value{GDBN} uses to tell the
18718 remote system to stop.
18720 Getting the debugging target to return the proper status to @value{GDBN}
18721 probably requires changes to the standard stub; one quick and dirty way
18722 is to just execute a breakpoint instruction (the ``dirty'' part is that
18723 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
18725 Other routines you need to supply are:
18728 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
18729 @findex exceptionHandler
18730 Write this function to install @var{exception_address} in the exception
18731 handling tables. You need to do this because the stub does not have any
18732 way of knowing what the exception handling tables on your target system
18733 are like (for example, the processor's table might be in @sc{rom},
18734 containing entries which point to a table in @sc{ram}).
18735 @var{exception_number} is the exception number which should be changed;
18736 its meaning is architecture-dependent (for example, different numbers
18737 might represent divide by zero, misaligned access, etc). When this
18738 exception occurs, control should be transferred directly to
18739 @var{exception_address}, and the processor state (stack, registers,
18740 and so on) should be just as it is when a processor exception occurs. So if
18741 you want to use a jump instruction to reach @var{exception_address}, it
18742 should be a simple jump, not a jump to subroutine.
18744 For the 386, @var{exception_address} should be installed as an interrupt
18745 gate so that interrupts are masked while the handler runs. The gate
18746 should be at privilege level 0 (the most privileged level). The
18747 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
18748 help from @code{exceptionHandler}.
18750 @item void flush_i_cache()
18751 @findex flush_i_cache
18752 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
18753 instruction cache, if any, on your target machine. If there is no
18754 instruction cache, this subroutine may be a no-op.
18756 On target machines that have instruction caches, @value{GDBN} requires this
18757 function to make certain that the state of your program is stable.
18761 You must also make sure this library routine is available:
18764 @item void *memset(void *, int, int)
18766 This is the standard library function @code{memset} that sets an area of
18767 memory to a known value. If you have one of the free versions of
18768 @code{libc.a}, @code{memset} can be found there; otherwise, you must
18769 either obtain it from your hardware manufacturer, or write your own.
18772 If you do not use the GNU C compiler, you may need other standard
18773 library subroutines as well; this varies from one stub to another,
18774 but in general the stubs are likely to use any of the common library
18775 subroutines which @code{@value{NGCC}} generates as inline code.
18778 @node Debug Session
18779 @subsection Putting it All Together
18781 @cindex remote serial debugging summary
18782 In summary, when your program is ready to debug, you must follow these
18787 Make sure you have defined the supporting low-level routines
18788 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
18790 @code{getDebugChar}, @code{putDebugChar},
18791 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
18795 Insert these lines in your program's startup code, before the main
18796 procedure is called:
18803 On some machines, when a breakpoint trap is raised, the hardware
18804 automatically makes the PC point to the instruction after the
18805 breakpoint. If your machine doesn't do that, you may need to adjust
18806 @code{handle_exception} to arrange for it to return to the instruction
18807 after the breakpoint on this first invocation, so that your program
18808 doesn't keep hitting the initial breakpoint instead of making
18812 For the 680x0 stub only, you need to provide a variable called
18813 @code{exceptionHook}. Normally you just use:
18816 void (*exceptionHook)() = 0;
18820 but if before calling @code{set_debug_traps}, you set it to point to a
18821 function in your program, that function is called when
18822 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
18823 error). The function indicated by @code{exceptionHook} is called with
18824 one parameter: an @code{int} which is the exception number.
18827 Compile and link together: your program, the @value{GDBN} debugging stub for
18828 your target architecture, and the supporting subroutines.
18831 Make sure you have a serial connection between your target machine and
18832 the @value{GDBN} host, and identify the serial port on the host.
18835 @c The "remote" target now provides a `load' command, so we should
18836 @c document that. FIXME.
18837 Download your program to your target machine (or get it there by
18838 whatever means the manufacturer provides), and start it.
18841 Start @value{GDBN} on the host, and connect to the target
18842 (@pxref{Connecting,,Connecting to a Remote Target}).
18846 @node Configurations
18847 @chapter Configuration-Specific Information
18849 While nearly all @value{GDBN} commands are available for all native and
18850 cross versions of the debugger, there are some exceptions. This chapter
18851 describes things that are only available in certain configurations.
18853 There are three major categories of configurations: native
18854 configurations, where the host and target are the same, embedded
18855 operating system configurations, which are usually the same for several
18856 different processor architectures, and bare embedded processors, which
18857 are quite different from each other.
18862 * Embedded Processors::
18869 This section describes details specific to particular native
18874 * BSD libkvm Interface:: Debugging BSD kernel memory images
18875 * SVR4 Process Information:: SVR4 process information
18876 * DJGPP Native:: Features specific to the DJGPP port
18877 * Cygwin Native:: Features specific to the Cygwin port
18878 * Hurd Native:: Features specific to @sc{gnu} Hurd
18879 * Darwin:: Features specific to Darwin
18885 On HP-UX systems, if you refer to a function or variable name that
18886 begins with a dollar sign, @value{GDBN} searches for a user or system
18887 name first, before it searches for a convenience variable.
18890 @node BSD libkvm Interface
18891 @subsection BSD libkvm Interface
18894 @cindex kernel memory image
18895 @cindex kernel crash dump
18897 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
18898 interface that provides a uniform interface for accessing kernel virtual
18899 memory images, including live systems and crash dumps. @value{GDBN}
18900 uses this interface to allow you to debug live kernels and kernel crash
18901 dumps on many native BSD configurations. This is implemented as a
18902 special @code{kvm} debugging target. For debugging a live system, load
18903 the currently running kernel into @value{GDBN} and connect to the
18907 (@value{GDBP}) @b{target kvm}
18910 For debugging crash dumps, provide the file name of the crash dump as an
18914 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
18917 Once connected to the @code{kvm} target, the following commands are
18923 Set current context from the @dfn{Process Control Block} (PCB) address.
18926 Set current context from proc address. This command isn't available on
18927 modern FreeBSD systems.
18930 @node SVR4 Process Information
18931 @subsection SVR4 Process Information
18933 @cindex examine process image
18934 @cindex process info via @file{/proc}
18936 Many versions of SVR4 and compatible systems provide a facility called
18937 @samp{/proc} that can be used to examine the image of a running
18938 process using file-system subroutines.
18940 If @value{GDBN} is configured for an operating system with this
18941 facility, the command @code{info proc} is available to report
18942 information about the process running your program, or about any
18943 process running on your system. This includes, as of this writing,
18944 @sc{gnu}/Linux, OSF/1 (Digital Unix), Solaris, and Irix, but
18945 not HP-UX, for example.
18947 This command may also work on core files that were created on a system
18948 that has the @samp{/proc} facility.
18954 @itemx info proc @var{process-id}
18955 Summarize available information about any running process. If a
18956 process ID is specified by @var{process-id}, display information about
18957 that process; otherwise display information about the program being
18958 debugged. The summary includes the debugged process ID, the command
18959 line used to invoke it, its current working directory, and its
18960 executable file's absolute file name.
18962 On some systems, @var{process-id} can be of the form
18963 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
18964 within a process. If the optional @var{pid} part is missing, it means
18965 a thread from the process being debugged (the leading @samp{/} still
18966 needs to be present, or else @value{GDBN} will interpret the number as
18967 a process ID rather than a thread ID).
18969 @item info proc cmdline
18970 @cindex info proc cmdline
18971 Show the original command line of the process. This command is
18972 specific to @sc{gnu}/Linux.
18974 @item info proc cwd
18975 @cindex info proc cwd
18976 Show the current working directory of the process. This command is
18977 specific to @sc{gnu}/Linux.
18979 @item info proc exe
18980 @cindex info proc exe
18981 Show the name of executable of the process. This command is specific
18984 @item info proc mappings
18985 @cindex memory address space mappings
18986 Report the memory address space ranges accessible in the program, with
18987 information on whether the process has read, write, or execute access
18988 rights to each range. On @sc{gnu}/Linux systems, each memory range
18989 includes the object file which is mapped to that range, instead of the
18990 memory access rights to that range.
18992 @item info proc stat
18993 @itemx info proc status
18994 @cindex process detailed status information
18995 These subcommands are specific to @sc{gnu}/Linux systems. They show
18996 the process-related information, including the user ID and group ID;
18997 how many threads are there in the process; its virtual memory usage;
18998 the signals that are pending, blocked, and ignored; its TTY; its
18999 consumption of system and user time; its stack size; its @samp{nice}
19000 value; etc. For more information, see the @samp{proc} man page
19001 (type @kbd{man 5 proc} from your shell prompt).
19003 @item info proc all
19004 Show all the information about the process described under all of the
19005 above @code{info proc} subcommands.
19008 @comment These sub-options of 'info proc' were not included when
19009 @comment procfs.c was re-written. Keep their descriptions around
19010 @comment against the day when someone finds the time to put them back in.
19011 @kindex info proc times
19012 @item info proc times
19013 Starting time, user CPU time, and system CPU time for your program and
19016 @kindex info proc id
19018 Report on the process IDs related to your program: its own process ID,
19019 the ID of its parent, the process group ID, and the session ID.
19022 @item set procfs-trace
19023 @kindex set procfs-trace
19024 @cindex @code{procfs} API calls
19025 This command enables and disables tracing of @code{procfs} API calls.
19027 @item show procfs-trace
19028 @kindex show procfs-trace
19029 Show the current state of @code{procfs} API call tracing.
19031 @item set procfs-file @var{file}
19032 @kindex set procfs-file
19033 Tell @value{GDBN} to write @code{procfs} API trace to the named
19034 @var{file}. @value{GDBN} appends the trace info to the previous
19035 contents of the file. The default is to display the trace on the
19038 @item show procfs-file
19039 @kindex show procfs-file
19040 Show the file to which @code{procfs} API trace is written.
19042 @item proc-trace-entry
19043 @itemx proc-trace-exit
19044 @itemx proc-untrace-entry
19045 @itemx proc-untrace-exit
19046 @kindex proc-trace-entry
19047 @kindex proc-trace-exit
19048 @kindex proc-untrace-entry
19049 @kindex proc-untrace-exit
19050 These commands enable and disable tracing of entries into and exits
19051 from the @code{syscall} interface.
19054 @kindex info pidlist
19055 @cindex process list, QNX Neutrino
19056 For QNX Neutrino only, this command displays the list of all the
19057 processes and all the threads within each process.
19060 @kindex info meminfo
19061 @cindex mapinfo list, QNX Neutrino
19062 For QNX Neutrino only, this command displays the list of all mapinfos.
19066 @subsection Features for Debugging @sc{djgpp} Programs
19067 @cindex @sc{djgpp} debugging
19068 @cindex native @sc{djgpp} debugging
19069 @cindex MS-DOS-specific commands
19072 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
19073 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
19074 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
19075 top of real-mode DOS systems and their emulations.
19077 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
19078 defines a few commands specific to the @sc{djgpp} port. This
19079 subsection describes those commands.
19084 This is a prefix of @sc{djgpp}-specific commands which print
19085 information about the target system and important OS structures.
19088 @cindex MS-DOS system info
19089 @cindex free memory information (MS-DOS)
19090 @item info dos sysinfo
19091 This command displays assorted information about the underlying
19092 platform: the CPU type and features, the OS version and flavor, the
19093 DPMI version, and the available conventional and DPMI memory.
19098 @cindex segment descriptor tables
19099 @cindex descriptor tables display
19101 @itemx info dos ldt
19102 @itemx info dos idt
19103 These 3 commands display entries from, respectively, Global, Local,
19104 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
19105 tables are data structures which store a descriptor for each segment
19106 that is currently in use. The segment's selector is an index into a
19107 descriptor table; the table entry for that index holds the
19108 descriptor's base address and limit, and its attributes and access
19111 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
19112 segment (used for both data and the stack), and a DOS segment (which
19113 allows access to DOS/BIOS data structures and absolute addresses in
19114 conventional memory). However, the DPMI host will usually define
19115 additional segments in order to support the DPMI environment.
19117 @cindex garbled pointers
19118 These commands allow to display entries from the descriptor tables.
19119 Without an argument, all entries from the specified table are
19120 displayed. An argument, which should be an integer expression, means
19121 display a single entry whose index is given by the argument. For
19122 example, here's a convenient way to display information about the
19123 debugged program's data segment:
19126 @exdent @code{(@value{GDBP}) info dos ldt $ds}
19127 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
19131 This comes in handy when you want to see whether a pointer is outside
19132 the data segment's limit (i.e.@: @dfn{garbled}).
19134 @cindex page tables display (MS-DOS)
19136 @itemx info dos pte
19137 These two commands display entries from, respectively, the Page
19138 Directory and the Page Tables. Page Directories and Page Tables are
19139 data structures which control how virtual memory addresses are mapped
19140 into physical addresses. A Page Table includes an entry for every
19141 page of memory that is mapped into the program's address space; there
19142 may be several Page Tables, each one holding up to 4096 entries. A
19143 Page Directory has up to 4096 entries, one each for every Page Table
19144 that is currently in use.
19146 Without an argument, @kbd{info dos pde} displays the entire Page
19147 Directory, and @kbd{info dos pte} displays all the entries in all of
19148 the Page Tables. An argument, an integer expression, given to the
19149 @kbd{info dos pde} command means display only that entry from the Page
19150 Directory table. An argument given to the @kbd{info dos pte} command
19151 means display entries from a single Page Table, the one pointed to by
19152 the specified entry in the Page Directory.
19154 @cindex direct memory access (DMA) on MS-DOS
19155 These commands are useful when your program uses @dfn{DMA} (Direct
19156 Memory Access), which needs physical addresses to program the DMA
19159 These commands are supported only with some DPMI servers.
19161 @cindex physical address from linear address
19162 @item info dos address-pte @var{addr}
19163 This command displays the Page Table entry for a specified linear
19164 address. The argument @var{addr} is a linear address which should
19165 already have the appropriate segment's base address added to it,
19166 because this command accepts addresses which may belong to @emph{any}
19167 segment. For example, here's how to display the Page Table entry for
19168 the page where a variable @code{i} is stored:
19171 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
19172 @exdent @code{Page Table entry for address 0x11a00d30:}
19173 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
19177 This says that @code{i} is stored at offset @code{0xd30} from the page
19178 whose physical base address is @code{0x02698000}, and shows all the
19179 attributes of that page.
19181 Note that you must cast the addresses of variables to a @code{char *},
19182 since otherwise the value of @code{__djgpp_base_address}, the base
19183 address of all variables and functions in a @sc{djgpp} program, will
19184 be added using the rules of C pointer arithmetics: if @code{i} is
19185 declared an @code{int}, @value{GDBN} will add 4 times the value of
19186 @code{__djgpp_base_address} to the address of @code{i}.
19188 Here's another example, it displays the Page Table entry for the
19192 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
19193 @exdent @code{Page Table entry for address 0x29110:}
19194 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
19198 (The @code{+ 3} offset is because the transfer buffer's address is the
19199 3rd member of the @code{_go32_info_block} structure.) The output
19200 clearly shows that this DPMI server maps the addresses in conventional
19201 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
19202 linear (@code{0x29110}) addresses are identical.
19204 This command is supported only with some DPMI servers.
19207 @cindex DOS serial data link, remote debugging
19208 In addition to native debugging, the DJGPP port supports remote
19209 debugging via a serial data link. The following commands are specific
19210 to remote serial debugging in the DJGPP port of @value{GDBN}.
19213 @kindex set com1base
19214 @kindex set com1irq
19215 @kindex set com2base
19216 @kindex set com2irq
19217 @kindex set com3base
19218 @kindex set com3irq
19219 @kindex set com4base
19220 @kindex set com4irq
19221 @item set com1base @var{addr}
19222 This command sets the base I/O port address of the @file{COM1} serial
19225 @item set com1irq @var{irq}
19226 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
19227 for the @file{COM1} serial port.
19229 There are similar commands @samp{set com2base}, @samp{set com3irq},
19230 etc.@: for setting the port address and the @code{IRQ} lines for the
19233 @kindex show com1base
19234 @kindex show com1irq
19235 @kindex show com2base
19236 @kindex show com2irq
19237 @kindex show com3base
19238 @kindex show com3irq
19239 @kindex show com4base
19240 @kindex show com4irq
19241 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
19242 display the current settings of the base address and the @code{IRQ}
19243 lines used by the COM ports.
19246 @kindex info serial
19247 @cindex DOS serial port status
19248 This command prints the status of the 4 DOS serial ports. For each
19249 port, it prints whether it's active or not, its I/O base address and
19250 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
19251 counts of various errors encountered so far.
19255 @node Cygwin Native
19256 @subsection Features for Debugging MS Windows PE Executables
19257 @cindex MS Windows debugging
19258 @cindex native Cygwin debugging
19259 @cindex Cygwin-specific commands
19261 @value{GDBN} supports native debugging of MS Windows programs, including
19262 DLLs with and without symbolic debugging information.
19264 @cindex Ctrl-BREAK, MS-Windows
19265 @cindex interrupt debuggee on MS-Windows
19266 MS-Windows programs that call @code{SetConsoleMode} to switch off the
19267 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
19268 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
19269 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
19270 sequence, which can be used to interrupt the debuggee even if it
19273 There are various additional Cygwin-specific commands, described in
19274 this section. Working with DLLs that have no debugging symbols is
19275 described in @ref{Non-debug DLL Symbols}.
19280 This is a prefix of MS Windows-specific commands which print
19281 information about the target system and important OS structures.
19283 @item info w32 selector
19284 This command displays information returned by
19285 the Win32 API @code{GetThreadSelectorEntry} function.
19286 It takes an optional argument that is evaluated to
19287 a long value to give the information about this given selector.
19288 Without argument, this command displays information
19289 about the six segment registers.
19291 @item info w32 thread-information-block
19292 This command displays thread specific information stored in the
19293 Thread Information Block (readable on the X86 CPU family using @code{$fs}
19294 selector for 32-bit programs and @code{$gs} for 64-bit programs).
19298 This is a Cygwin-specific alias of @code{info shared}.
19300 @kindex dll-symbols
19302 This command loads symbols from a dll similarly to
19303 add-sym command but without the need to specify a base address.
19305 @kindex set cygwin-exceptions
19306 @cindex debugging the Cygwin DLL
19307 @cindex Cygwin DLL, debugging
19308 @item set cygwin-exceptions @var{mode}
19309 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
19310 happen inside the Cygwin DLL. If @var{mode} is @code{off},
19311 @value{GDBN} will delay recognition of exceptions, and may ignore some
19312 exceptions which seem to be caused by internal Cygwin DLL
19313 ``bookkeeping''. This option is meant primarily for debugging the
19314 Cygwin DLL itself; the default value is @code{off} to avoid annoying
19315 @value{GDBN} users with false @code{SIGSEGV} signals.
19317 @kindex show cygwin-exceptions
19318 @item show cygwin-exceptions
19319 Displays whether @value{GDBN} will break on exceptions that happen
19320 inside the Cygwin DLL itself.
19322 @kindex set new-console
19323 @item set new-console @var{mode}
19324 If @var{mode} is @code{on} the debuggee will
19325 be started in a new console on next start.
19326 If @var{mode} is @code{off}, the debuggee will
19327 be started in the same console as the debugger.
19329 @kindex show new-console
19330 @item show new-console
19331 Displays whether a new console is used
19332 when the debuggee is started.
19334 @kindex set new-group
19335 @item set new-group @var{mode}
19336 This boolean value controls whether the debuggee should
19337 start a new group or stay in the same group as the debugger.
19338 This affects the way the Windows OS handles
19341 @kindex show new-group
19342 @item show new-group
19343 Displays current value of new-group boolean.
19345 @kindex set debugevents
19346 @item set debugevents
19347 This boolean value adds debug output concerning kernel events related
19348 to the debuggee seen by the debugger. This includes events that
19349 signal thread and process creation and exit, DLL loading and
19350 unloading, console interrupts, and debugging messages produced by the
19351 Windows @code{OutputDebugString} API call.
19353 @kindex set debugexec
19354 @item set debugexec
19355 This boolean value adds debug output concerning execute events
19356 (such as resume thread) seen by the debugger.
19358 @kindex set debugexceptions
19359 @item set debugexceptions
19360 This boolean value adds debug output concerning exceptions in the
19361 debuggee seen by the debugger.
19363 @kindex set debugmemory
19364 @item set debugmemory
19365 This boolean value adds debug output concerning debuggee memory reads
19366 and writes by the debugger.
19370 This boolean values specifies whether the debuggee is called
19371 via a shell or directly (default value is on).
19375 Displays if the debuggee will be started with a shell.
19380 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
19383 @node Non-debug DLL Symbols
19384 @subsubsection Support for DLLs without Debugging Symbols
19385 @cindex DLLs with no debugging symbols
19386 @cindex Minimal symbols and DLLs
19388 Very often on windows, some of the DLLs that your program relies on do
19389 not include symbolic debugging information (for example,
19390 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
19391 symbols in a DLL, it relies on the minimal amount of symbolic
19392 information contained in the DLL's export table. This section
19393 describes working with such symbols, known internally to @value{GDBN} as
19394 ``minimal symbols''.
19396 Note that before the debugged program has started execution, no DLLs
19397 will have been loaded. The easiest way around this problem is simply to
19398 start the program --- either by setting a breakpoint or letting the
19399 program run once to completion. It is also possible to force
19400 @value{GDBN} to load a particular DLL before starting the executable ---
19401 see the shared library information in @ref{Files}, or the
19402 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
19403 explicitly loading symbols from a DLL with no debugging information will
19404 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
19405 which may adversely affect symbol lookup performance.
19407 @subsubsection DLL Name Prefixes
19409 In keeping with the naming conventions used by the Microsoft debugging
19410 tools, DLL export symbols are made available with a prefix based on the
19411 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
19412 also entered into the symbol table, so @code{CreateFileA} is often
19413 sufficient. In some cases there will be name clashes within a program
19414 (particularly if the executable itself includes full debugging symbols)
19415 necessitating the use of the fully qualified name when referring to the
19416 contents of the DLL. Use single-quotes around the name to avoid the
19417 exclamation mark (``!'') being interpreted as a language operator.
19419 Note that the internal name of the DLL may be all upper-case, even
19420 though the file name of the DLL is lower-case, or vice-versa. Since
19421 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
19422 some confusion. If in doubt, try the @code{info functions} and
19423 @code{info variables} commands or even @code{maint print msymbols}
19424 (@pxref{Symbols}). Here's an example:
19427 (@value{GDBP}) info function CreateFileA
19428 All functions matching regular expression "CreateFileA":
19430 Non-debugging symbols:
19431 0x77e885f4 CreateFileA
19432 0x77e885f4 KERNEL32!CreateFileA
19436 (@value{GDBP}) info function !
19437 All functions matching regular expression "!":
19439 Non-debugging symbols:
19440 0x6100114c cygwin1!__assert
19441 0x61004034 cygwin1!_dll_crt0@@0
19442 0x61004240 cygwin1!dll_crt0(per_process *)
19446 @subsubsection Working with Minimal Symbols
19448 Symbols extracted from a DLL's export table do not contain very much
19449 type information. All that @value{GDBN} can do is guess whether a symbol
19450 refers to a function or variable depending on the linker section that
19451 contains the symbol. Also note that the actual contents of the memory
19452 contained in a DLL are not available unless the program is running. This
19453 means that you cannot examine the contents of a variable or disassemble
19454 a function within a DLL without a running program.
19456 Variables are generally treated as pointers and dereferenced
19457 automatically. For this reason, it is often necessary to prefix a
19458 variable name with the address-of operator (``&'') and provide explicit
19459 type information in the command. Here's an example of the type of
19463 (@value{GDBP}) print 'cygwin1!__argv'
19468 (@value{GDBP}) x 'cygwin1!__argv'
19469 0x10021610: "\230y\""
19472 And two possible solutions:
19475 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
19476 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
19480 (@value{GDBP}) x/2x &'cygwin1!__argv'
19481 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
19482 (@value{GDBP}) x/x 0x10021608
19483 0x10021608: 0x0022fd98
19484 (@value{GDBP}) x/s 0x0022fd98
19485 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
19488 Setting a break point within a DLL is possible even before the program
19489 starts execution. However, under these circumstances, @value{GDBN} can't
19490 examine the initial instructions of the function in order to skip the
19491 function's frame set-up code. You can work around this by using ``*&''
19492 to set the breakpoint at a raw memory address:
19495 (@value{GDBP}) break *&'python22!PyOS_Readline'
19496 Breakpoint 1 at 0x1e04eff0
19499 The author of these extensions is not entirely convinced that setting a
19500 break point within a shared DLL like @file{kernel32.dll} is completely
19504 @subsection Commands Specific to @sc{gnu} Hurd Systems
19505 @cindex @sc{gnu} Hurd debugging
19507 This subsection describes @value{GDBN} commands specific to the
19508 @sc{gnu} Hurd native debugging.
19513 @kindex set signals@r{, Hurd command}
19514 @kindex set sigs@r{, Hurd command}
19515 This command toggles the state of inferior signal interception by
19516 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
19517 affected by this command. @code{sigs} is a shorthand alias for
19522 @kindex show signals@r{, Hurd command}
19523 @kindex show sigs@r{, Hurd command}
19524 Show the current state of intercepting inferior's signals.
19526 @item set signal-thread
19527 @itemx set sigthread
19528 @kindex set signal-thread
19529 @kindex set sigthread
19530 This command tells @value{GDBN} which thread is the @code{libc} signal
19531 thread. That thread is run when a signal is delivered to a running
19532 process. @code{set sigthread} is the shorthand alias of @code{set
19535 @item show signal-thread
19536 @itemx show sigthread
19537 @kindex show signal-thread
19538 @kindex show sigthread
19539 These two commands show which thread will run when the inferior is
19540 delivered a signal.
19543 @kindex set stopped@r{, Hurd command}
19544 This commands tells @value{GDBN} that the inferior process is stopped,
19545 as with the @code{SIGSTOP} signal. The stopped process can be
19546 continued by delivering a signal to it.
19549 @kindex show stopped@r{, Hurd command}
19550 This command shows whether @value{GDBN} thinks the debuggee is
19553 @item set exceptions
19554 @kindex set exceptions@r{, Hurd command}
19555 Use this command to turn off trapping of exceptions in the inferior.
19556 When exception trapping is off, neither breakpoints nor
19557 single-stepping will work. To restore the default, set exception
19560 @item show exceptions
19561 @kindex show exceptions@r{, Hurd command}
19562 Show the current state of trapping exceptions in the inferior.
19564 @item set task pause
19565 @kindex set task@r{, Hurd commands}
19566 @cindex task attributes (@sc{gnu} Hurd)
19567 @cindex pause current task (@sc{gnu} Hurd)
19568 This command toggles task suspension when @value{GDBN} has control.
19569 Setting it to on takes effect immediately, and the task is suspended
19570 whenever @value{GDBN} gets control. Setting it to off will take
19571 effect the next time the inferior is continued. If this option is set
19572 to off, you can use @code{set thread default pause on} or @code{set
19573 thread pause on} (see below) to pause individual threads.
19575 @item show task pause
19576 @kindex show task@r{, Hurd commands}
19577 Show the current state of task suspension.
19579 @item set task detach-suspend-count
19580 @cindex task suspend count
19581 @cindex detach from task, @sc{gnu} Hurd
19582 This command sets the suspend count the task will be left with when
19583 @value{GDBN} detaches from it.
19585 @item show task detach-suspend-count
19586 Show the suspend count the task will be left with when detaching.
19588 @item set task exception-port
19589 @itemx set task excp
19590 @cindex task exception port, @sc{gnu} Hurd
19591 This command sets the task exception port to which @value{GDBN} will
19592 forward exceptions. The argument should be the value of the @dfn{send
19593 rights} of the task. @code{set task excp} is a shorthand alias.
19595 @item set noninvasive
19596 @cindex noninvasive task options
19597 This command switches @value{GDBN} to a mode that is the least
19598 invasive as far as interfering with the inferior is concerned. This
19599 is the same as using @code{set task pause}, @code{set exceptions}, and
19600 @code{set signals} to values opposite to the defaults.
19602 @item info send-rights
19603 @itemx info receive-rights
19604 @itemx info port-rights
19605 @itemx info port-sets
19606 @itemx info dead-names
19609 @cindex send rights, @sc{gnu} Hurd
19610 @cindex receive rights, @sc{gnu} Hurd
19611 @cindex port rights, @sc{gnu} Hurd
19612 @cindex port sets, @sc{gnu} Hurd
19613 @cindex dead names, @sc{gnu} Hurd
19614 These commands display information about, respectively, send rights,
19615 receive rights, port rights, port sets, and dead names of a task.
19616 There are also shorthand aliases: @code{info ports} for @code{info
19617 port-rights} and @code{info psets} for @code{info port-sets}.
19619 @item set thread pause
19620 @kindex set thread@r{, Hurd command}
19621 @cindex thread properties, @sc{gnu} Hurd
19622 @cindex pause current thread (@sc{gnu} Hurd)
19623 This command toggles current thread suspension when @value{GDBN} has
19624 control. Setting it to on takes effect immediately, and the current
19625 thread is suspended whenever @value{GDBN} gets control. Setting it to
19626 off will take effect the next time the inferior is continued.
19627 Normally, this command has no effect, since when @value{GDBN} has
19628 control, the whole task is suspended. However, if you used @code{set
19629 task pause off} (see above), this command comes in handy to suspend
19630 only the current thread.
19632 @item show thread pause
19633 @kindex show thread@r{, Hurd command}
19634 This command shows the state of current thread suspension.
19636 @item set thread run
19637 This command sets whether the current thread is allowed to run.
19639 @item show thread run
19640 Show whether the current thread is allowed to run.
19642 @item set thread detach-suspend-count
19643 @cindex thread suspend count, @sc{gnu} Hurd
19644 @cindex detach from thread, @sc{gnu} Hurd
19645 This command sets the suspend count @value{GDBN} will leave on a
19646 thread when detaching. This number is relative to the suspend count
19647 found by @value{GDBN} when it notices the thread; use @code{set thread
19648 takeover-suspend-count} to force it to an absolute value.
19650 @item show thread detach-suspend-count
19651 Show the suspend count @value{GDBN} will leave on the thread when
19654 @item set thread exception-port
19655 @itemx set thread excp
19656 Set the thread exception port to which to forward exceptions. This
19657 overrides the port set by @code{set task exception-port} (see above).
19658 @code{set thread excp} is the shorthand alias.
19660 @item set thread takeover-suspend-count
19661 Normally, @value{GDBN}'s thread suspend counts are relative to the
19662 value @value{GDBN} finds when it notices each thread. This command
19663 changes the suspend counts to be absolute instead.
19665 @item set thread default
19666 @itemx show thread default
19667 @cindex thread default settings, @sc{gnu} Hurd
19668 Each of the above @code{set thread} commands has a @code{set thread
19669 default} counterpart (e.g., @code{set thread default pause}, @code{set
19670 thread default exception-port}, etc.). The @code{thread default}
19671 variety of commands sets the default thread properties for all
19672 threads; you can then change the properties of individual threads with
19673 the non-default commands.
19680 @value{GDBN} provides the following commands specific to the Darwin target:
19683 @item set debug darwin @var{num}
19684 @kindex set debug darwin
19685 When set to a non zero value, enables debugging messages specific to
19686 the Darwin support. Higher values produce more verbose output.
19688 @item show debug darwin
19689 @kindex show debug darwin
19690 Show the current state of Darwin messages.
19692 @item set debug mach-o @var{num}
19693 @kindex set debug mach-o
19694 When set to a non zero value, enables debugging messages while
19695 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
19696 file format used on Darwin for object and executable files.) Higher
19697 values produce more verbose output. This is a command to diagnose
19698 problems internal to @value{GDBN} and should not be needed in normal
19701 @item show debug mach-o
19702 @kindex show debug mach-o
19703 Show the current state of Mach-O file messages.
19705 @item set mach-exceptions on
19706 @itemx set mach-exceptions off
19707 @kindex set mach-exceptions
19708 On Darwin, faults are first reported as a Mach exception and are then
19709 mapped to a Posix signal. Use this command to turn on trapping of
19710 Mach exceptions in the inferior. This might be sometimes useful to
19711 better understand the cause of a fault. The default is off.
19713 @item show mach-exceptions
19714 @kindex show mach-exceptions
19715 Show the current state of exceptions trapping.
19720 @section Embedded Operating Systems
19722 This section describes configurations involving the debugging of
19723 embedded operating systems that are available for several different
19727 * VxWorks:: Using @value{GDBN} with VxWorks
19730 @value{GDBN} includes the ability to debug programs running on
19731 various real-time operating systems.
19734 @subsection Using @value{GDBN} with VxWorks
19740 @kindex target vxworks
19741 @item target vxworks @var{machinename}
19742 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
19743 is the target system's machine name or IP address.
19747 On VxWorks, @code{load} links @var{filename} dynamically on the
19748 current target system as well as adding its symbols in @value{GDBN}.
19750 @value{GDBN} enables developers to spawn and debug tasks running on networked
19751 VxWorks targets from a Unix host. Already-running tasks spawned from
19752 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
19753 both the Unix host and on the VxWorks target. The program
19754 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
19755 installed with the name @code{vxgdb}, to distinguish it from a
19756 @value{GDBN} for debugging programs on the host itself.)
19759 @item VxWorks-timeout @var{args}
19760 @kindex vxworks-timeout
19761 All VxWorks-based targets now support the option @code{vxworks-timeout}.
19762 This option is set by the user, and @var{args} represents the number of
19763 seconds @value{GDBN} waits for responses to rpc's. You might use this if
19764 your VxWorks target is a slow software simulator or is on the far side
19765 of a thin network line.
19768 The following information on connecting to VxWorks was current when
19769 this manual was produced; newer releases of VxWorks may use revised
19772 @findex INCLUDE_RDB
19773 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
19774 to include the remote debugging interface routines in the VxWorks
19775 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
19776 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
19777 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
19778 source debugging task @code{tRdbTask} when VxWorks is booted. For more
19779 information on configuring and remaking VxWorks, see the manufacturer's
19781 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
19783 Once you have included @file{rdb.a} in your VxWorks system image and set
19784 your Unix execution search path to find @value{GDBN}, you are ready to
19785 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
19786 @code{vxgdb}, depending on your installation).
19788 @value{GDBN} comes up showing the prompt:
19795 * VxWorks Connection:: Connecting to VxWorks
19796 * VxWorks Download:: VxWorks download
19797 * VxWorks Attach:: Running tasks
19800 @node VxWorks Connection
19801 @subsubsection Connecting to VxWorks
19803 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
19804 network. To connect to a target whose host name is ``@code{tt}'', type:
19807 (vxgdb) target vxworks tt
19811 @value{GDBN} displays messages like these:
19814 Attaching remote machine across net...
19819 @value{GDBN} then attempts to read the symbol tables of any object modules
19820 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
19821 these files by searching the directories listed in the command search
19822 path (@pxref{Environment, ,Your Program's Environment}); if it fails
19823 to find an object file, it displays a message such as:
19826 prog.o: No such file or directory.
19829 When this happens, add the appropriate directory to the search path with
19830 the @value{GDBN} command @code{path}, and execute the @code{target}
19833 @node VxWorks Download
19834 @subsubsection VxWorks Download
19836 @cindex download to VxWorks
19837 If you have connected to the VxWorks target and you want to debug an
19838 object that has not yet been loaded, you can use the @value{GDBN}
19839 @code{load} command to download a file from Unix to VxWorks
19840 incrementally. The object file given as an argument to the @code{load}
19841 command is actually opened twice: first by the VxWorks target in order
19842 to download the code, then by @value{GDBN} in order to read the symbol
19843 table. This can lead to problems if the current working directories on
19844 the two systems differ. If both systems have NFS mounted the same
19845 filesystems, you can avoid these problems by using absolute paths.
19846 Otherwise, it is simplest to set the working directory on both systems
19847 to the directory in which the object file resides, and then to reference
19848 the file by its name, without any path. For instance, a program
19849 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
19850 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
19851 program, type this on VxWorks:
19854 -> cd "@var{vxpath}/vw/demo/rdb"
19858 Then, in @value{GDBN}, type:
19861 (vxgdb) cd @var{hostpath}/vw/demo/rdb
19862 (vxgdb) load prog.o
19865 @value{GDBN} displays a response similar to this:
19868 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
19871 You can also use the @code{load} command to reload an object module
19872 after editing and recompiling the corresponding source file. Note that
19873 this makes @value{GDBN} delete all currently-defined breakpoints,
19874 auto-displays, and convenience variables, and to clear the value
19875 history. (This is necessary in order to preserve the integrity of
19876 debugger's data structures that reference the target system's symbol
19879 @node VxWorks Attach
19880 @subsubsection Running Tasks
19882 @cindex running VxWorks tasks
19883 You can also attach to an existing task using the @code{attach} command as
19887 (vxgdb) attach @var{task}
19891 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
19892 or suspended when you attach to it. Running tasks are suspended at
19893 the time of attachment.
19895 @node Embedded Processors
19896 @section Embedded Processors
19898 This section goes into details specific to particular embedded
19901 @cindex send command to simulator
19902 Whenever a specific embedded processor has a simulator, @value{GDBN}
19903 allows to send an arbitrary command to the simulator.
19906 @item sim @var{command}
19907 @kindex sim@r{, a command}
19908 Send an arbitrary @var{command} string to the simulator. Consult the
19909 documentation for the specific simulator in use for information about
19910 acceptable commands.
19916 * M32R/D:: Renesas M32R/D
19917 * M68K:: Motorola M68K
19918 * MicroBlaze:: Xilinx MicroBlaze
19919 * MIPS Embedded:: MIPS Embedded
19920 * PowerPC Embedded:: PowerPC Embedded
19921 * PA:: HP PA Embedded
19922 * Sparclet:: Tsqware Sparclet
19923 * Sparclite:: Fujitsu Sparclite
19924 * Z8000:: Zilog Z8000
19927 * Super-H:: Renesas Super-H
19936 @item target rdi @var{dev}
19937 ARM Angel monitor, via RDI library interface to ADP protocol. You may
19938 use this target to communicate with both boards running the Angel
19939 monitor, or with the EmbeddedICE JTAG debug device.
19942 @item target rdp @var{dev}
19947 @value{GDBN} provides the following ARM-specific commands:
19950 @item set arm disassembler
19952 This commands selects from a list of disassembly styles. The
19953 @code{"std"} style is the standard style.
19955 @item show arm disassembler
19957 Show the current disassembly style.
19959 @item set arm apcs32
19960 @cindex ARM 32-bit mode
19961 This command toggles ARM operation mode between 32-bit and 26-bit.
19963 @item show arm apcs32
19964 Display the current usage of the ARM 32-bit mode.
19966 @item set arm fpu @var{fputype}
19967 This command sets the ARM floating-point unit (FPU) type. The
19968 argument @var{fputype} can be one of these:
19972 Determine the FPU type by querying the OS ABI.
19974 Software FPU, with mixed-endian doubles on little-endian ARM
19977 GCC-compiled FPA co-processor.
19979 Software FPU with pure-endian doubles.
19985 Show the current type of the FPU.
19988 This command forces @value{GDBN} to use the specified ABI.
19991 Show the currently used ABI.
19993 @item set arm fallback-mode (arm|thumb|auto)
19994 @value{GDBN} uses the symbol table, when available, to determine
19995 whether instructions are ARM or Thumb. This command controls
19996 @value{GDBN}'s default behavior when the symbol table is not
19997 available. The default is @samp{auto}, which causes @value{GDBN} to
19998 use the current execution mode (from the @code{T} bit in the @code{CPSR}
20001 @item show arm fallback-mode
20002 Show the current fallback instruction mode.
20004 @item set arm force-mode (arm|thumb|auto)
20005 This command overrides use of the symbol table to determine whether
20006 instructions are ARM or Thumb. The default is @samp{auto}, which
20007 causes @value{GDBN} to use the symbol table and then the setting
20008 of @samp{set arm fallback-mode}.
20010 @item show arm force-mode
20011 Show the current forced instruction mode.
20013 @item set debug arm
20014 Toggle whether to display ARM-specific debugging messages from the ARM
20015 target support subsystem.
20017 @item show debug arm
20018 Show whether ARM-specific debugging messages are enabled.
20021 The following commands are available when an ARM target is debugged
20022 using the RDI interface:
20025 @item rdilogfile @r{[}@var{file}@r{]}
20027 @cindex ADP (Angel Debugger Protocol) logging
20028 Set the filename for the ADP (Angel Debugger Protocol) packet log.
20029 With an argument, sets the log file to the specified @var{file}. With
20030 no argument, show the current log file name. The default log file is
20033 @item rdilogenable @r{[}@var{arg}@r{]}
20034 @kindex rdilogenable
20035 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
20036 enables logging, with an argument 0 or @code{"no"} disables it. With
20037 no arguments displays the current setting. When logging is enabled,
20038 ADP packets exchanged between @value{GDBN} and the RDI target device
20039 are logged to a file.
20041 @item set rdiromatzero
20042 @kindex set rdiromatzero
20043 @cindex ROM at zero address, RDI
20044 Tell @value{GDBN} whether the target has ROM at address 0. If on,
20045 vector catching is disabled, so that zero address can be used. If off
20046 (the default), vector catching is enabled. For this command to take
20047 effect, it needs to be invoked prior to the @code{target rdi} command.
20049 @item show rdiromatzero
20050 @kindex show rdiromatzero
20051 Show the current setting of ROM at zero address.
20053 @item set rdiheartbeat
20054 @kindex set rdiheartbeat
20055 @cindex RDI heartbeat
20056 Enable or disable RDI heartbeat packets. It is not recommended to
20057 turn on this option, since it confuses ARM and EPI JTAG interface, as
20058 well as the Angel monitor.
20060 @item show rdiheartbeat
20061 @kindex show rdiheartbeat
20062 Show the setting of RDI heartbeat packets.
20066 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20067 The @value{GDBN} ARM simulator accepts the following optional arguments.
20070 @item --swi-support=@var{type}
20071 Tell the simulator which SWI interfaces to support.
20072 @var{type} may be a comma separated list of the following values.
20073 The default value is @code{all}.
20086 @subsection Renesas M32R/D and M32R/SDI
20089 @kindex target m32r
20090 @item target m32r @var{dev}
20091 Renesas M32R/D ROM monitor.
20093 @kindex target m32rsdi
20094 @item target m32rsdi @var{dev}
20095 Renesas M32R SDI server, connected via parallel port to the board.
20098 The following @value{GDBN} commands are specific to the M32R monitor:
20101 @item set download-path @var{path}
20102 @kindex set download-path
20103 @cindex find downloadable @sc{srec} files (M32R)
20104 Set the default path for finding downloadable @sc{srec} files.
20106 @item show download-path
20107 @kindex show download-path
20108 Show the default path for downloadable @sc{srec} files.
20110 @item set board-address @var{addr}
20111 @kindex set board-address
20112 @cindex M32-EVA target board address
20113 Set the IP address for the M32R-EVA target board.
20115 @item show board-address
20116 @kindex show board-address
20117 Show the current IP address of the target board.
20119 @item set server-address @var{addr}
20120 @kindex set server-address
20121 @cindex download server address (M32R)
20122 Set the IP address for the download server, which is the @value{GDBN}'s
20125 @item show server-address
20126 @kindex show server-address
20127 Display the IP address of the download server.
20129 @item upload @r{[}@var{file}@r{]}
20130 @kindex upload@r{, M32R}
20131 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
20132 upload capability. If no @var{file} argument is given, the current
20133 executable file is uploaded.
20135 @item tload @r{[}@var{file}@r{]}
20136 @kindex tload@r{, M32R}
20137 Test the @code{upload} command.
20140 The following commands are available for M32R/SDI:
20145 @cindex reset SDI connection, M32R
20146 This command resets the SDI connection.
20150 This command shows the SDI connection status.
20153 @kindex debug_chaos
20154 @cindex M32R/Chaos debugging
20155 Instructs the remote that M32R/Chaos debugging is to be used.
20157 @item use_debug_dma
20158 @kindex use_debug_dma
20159 Instructs the remote to use the DEBUG_DMA method of accessing memory.
20162 @kindex use_mon_code
20163 Instructs the remote to use the MON_CODE method of accessing memory.
20166 @kindex use_ib_break
20167 Instructs the remote to set breakpoints by IB break.
20169 @item use_dbt_break
20170 @kindex use_dbt_break
20171 Instructs the remote to set breakpoints by DBT.
20177 The Motorola m68k configuration includes ColdFire support, and a
20178 target command for the following ROM monitor.
20182 @kindex target dbug
20183 @item target dbug @var{dev}
20184 dBUG ROM monitor for Motorola ColdFire.
20189 @subsection MicroBlaze
20190 @cindex Xilinx MicroBlaze
20191 @cindex XMD, Xilinx Microprocessor Debugger
20193 The MicroBlaze is a soft-core processor supported on various Xilinx
20194 FPGAs, such as Spartan or Virtex series. Boards with these processors
20195 usually have JTAG ports which connect to a host system running the Xilinx
20196 Embedded Development Kit (EDK) or Software Development Kit (SDK).
20197 This host system is used to download the configuration bitstream to
20198 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
20199 communicates with the target board using the JTAG interface and
20200 presents a @code{gdbserver} interface to the board. By default
20201 @code{xmd} uses port @code{1234}. (While it is possible to change
20202 this default port, it requires the use of undocumented @code{xmd}
20203 commands. Contact Xilinx support if you need to do this.)
20205 Use these GDB commands to connect to the MicroBlaze target processor.
20208 @item target remote :1234
20209 Use this command to connect to the target if you are running @value{GDBN}
20210 on the same system as @code{xmd}.
20212 @item target remote @var{xmd-host}:1234
20213 Use this command to connect to the target if it is connected to @code{xmd}
20214 running on a different system named @var{xmd-host}.
20217 Use this command to download a program to the MicroBlaze target.
20219 @item set debug microblaze @var{n}
20220 Enable MicroBlaze-specific debugging messages if non-zero.
20222 @item show debug microblaze @var{n}
20223 Show MicroBlaze-specific debugging level.
20226 @node MIPS Embedded
20227 @subsection @acronym{MIPS} Embedded
20229 @cindex @acronym{MIPS} boards
20230 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
20231 @acronym{MIPS} board attached to a serial line. This is available when
20232 you configure @value{GDBN} with @samp{--target=mips-elf}.
20235 Use these @value{GDBN} commands to specify the connection to your target board:
20238 @item target mips @var{port}
20239 @kindex target mips @var{port}
20240 To run a program on the board, start up @code{@value{GDBP}} with the
20241 name of your program as the argument. To connect to the board, use the
20242 command @samp{target mips @var{port}}, where @var{port} is the name of
20243 the serial port connected to the board. If the program has not already
20244 been downloaded to the board, you may use the @code{load} command to
20245 download it. You can then use all the usual @value{GDBN} commands.
20247 For example, this sequence connects to the target board through a serial
20248 port, and loads and runs a program called @var{prog} through the
20252 host$ @value{GDBP} @var{prog}
20253 @value{GDBN} is free software and @dots{}
20254 (@value{GDBP}) target mips /dev/ttyb
20255 (@value{GDBP}) load @var{prog}
20259 @item target mips @var{hostname}:@var{portnumber}
20260 On some @value{GDBN} host configurations, you can specify a TCP
20261 connection (for instance, to a serial line managed by a terminal
20262 concentrator) instead of a serial port, using the syntax
20263 @samp{@var{hostname}:@var{portnumber}}.
20265 @item target pmon @var{port}
20266 @kindex target pmon @var{port}
20269 @item target ddb @var{port}
20270 @kindex target ddb @var{port}
20271 NEC's DDB variant of PMON for Vr4300.
20273 @item target lsi @var{port}
20274 @kindex target lsi @var{port}
20275 LSI variant of PMON.
20277 @kindex target r3900
20278 @item target r3900 @var{dev}
20279 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
20281 @kindex target array
20282 @item target array @var{dev}
20283 Array Tech LSI33K RAID controller board.
20289 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
20292 @item set mipsfpu double
20293 @itemx set mipsfpu single
20294 @itemx set mipsfpu none
20295 @itemx set mipsfpu auto
20296 @itemx show mipsfpu
20297 @kindex set mipsfpu
20298 @kindex show mipsfpu
20299 @cindex @acronym{MIPS} remote floating point
20300 @cindex floating point, @acronym{MIPS} remote
20301 If your target board does not support the @acronym{MIPS} floating point
20302 coprocessor, you should use the command @samp{set mipsfpu none} (if you
20303 need this, you may wish to put the command in your @value{GDBN} init
20304 file). This tells @value{GDBN} how to find the return value of
20305 functions which return floating point values. It also allows
20306 @value{GDBN} to avoid saving the floating point registers when calling
20307 functions on the board. If you are using a floating point coprocessor
20308 with only single precision floating point support, as on the @sc{r4650}
20309 processor, use the command @samp{set mipsfpu single}. The default
20310 double precision floating point coprocessor may be selected using
20311 @samp{set mipsfpu double}.
20313 In previous versions the only choices were double precision or no
20314 floating point, so @samp{set mipsfpu on} will select double precision
20315 and @samp{set mipsfpu off} will select no floating point.
20317 As usual, you can inquire about the @code{mipsfpu} variable with
20318 @samp{show mipsfpu}.
20320 @item set timeout @var{seconds}
20321 @itemx set retransmit-timeout @var{seconds}
20322 @itemx show timeout
20323 @itemx show retransmit-timeout
20324 @cindex @code{timeout}, @acronym{MIPS} protocol
20325 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
20326 @kindex set timeout
20327 @kindex show timeout
20328 @kindex set retransmit-timeout
20329 @kindex show retransmit-timeout
20330 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
20331 remote protocol, with the @code{set timeout @var{seconds}} command. The
20332 default is 5 seconds. Similarly, you can control the timeout used while
20333 waiting for an acknowledgment of a packet with the @code{set
20334 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
20335 You can inspect both values with @code{show timeout} and @code{show
20336 retransmit-timeout}. (These commands are @emph{only} available when
20337 @value{GDBN} is configured for @samp{--target=mips-elf}.)
20339 The timeout set by @code{set timeout} does not apply when @value{GDBN}
20340 is waiting for your program to stop. In that case, @value{GDBN} waits
20341 forever because it has no way of knowing how long the program is going
20342 to run before stopping.
20344 @item set syn-garbage-limit @var{num}
20345 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
20346 @cindex synchronize with remote @acronym{MIPS} target
20347 Limit the maximum number of characters @value{GDBN} should ignore when
20348 it tries to synchronize with the remote target. The default is 10
20349 characters. Setting the limit to -1 means there's no limit.
20351 @item show syn-garbage-limit
20352 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
20353 Show the current limit on the number of characters to ignore when
20354 trying to synchronize with the remote system.
20356 @item set monitor-prompt @var{prompt}
20357 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
20358 @cindex remote monitor prompt
20359 Tell @value{GDBN} to expect the specified @var{prompt} string from the
20360 remote monitor. The default depends on the target:
20370 @item show monitor-prompt
20371 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
20372 Show the current strings @value{GDBN} expects as the prompt from the
20375 @item set monitor-warnings
20376 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
20377 Enable or disable monitor warnings about hardware breakpoints. This
20378 has effect only for the @code{lsi} target. When on, @value{GDBN} will
20379 display warning messages whose codes are returned by the @code{lsi}
20380 PMON monitor for breakpoint commands.
20382 @item show monitor-warnings
20383 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
20384 Show the current setting of printing monitor warnings.
20386 @item pmon @var{command}
20387 @kindex pmon@r{, @acronym{MIPS} remote}
20388 @cindex send PMON command
20389 This command allows sending an arbitrary @var{command} string to the
20390 monitor. The monitor must be in debug mode for this to work.
20393 @node PowerPC Embedded
20394 @subsection PowerPC Embedded
20396 @cindex DVC register
20397 @value{GDBN} supports using the DVC (Data Value Compare) register to
20398 implement in hardware simple hardware watchpoint conditions of the form:
20401 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
20402 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
20405 The DVC register will be automatically used when @value{GDBN} detects
20406 such pattern in a condition expression, and the created watchpoint uses one
20407 debug register (either the @code{exact-watchpoints} option is on and the
20408 variable is scalar, or the variable has a length of one byte). This feature
20409 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
20412 When running on PowerPC embedded processors, @value{GDBN} automatically uses
20413 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
20414 in which case watchpoints using only one debug register are created when
20415 watching variables of scalar types.
20417 You can create an artificial array to watch an arbitrary memory
20418 region using one of the following commands (@pxref{Expressions}):
20421 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
20422 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
20425 PowerPC embedded processors support masked watchpoints. See the discussion
20426 about the @code{mask} argument in @ref{Set Watchpoints}.
20428 @cindex ranged breakpoint
20429 PowerPC embedded processors support hardware accelerated
20430 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
20431 the inferior whenever it executes an instruction at any address within
20432 the range it specifies. To set a ranged breakpoint in @value{GDBN},
20433 use the @code{break-range} command.
20435 @value{GDBN} provides the following PowerPC-specific commands:
20438 @kindex break-range
20439 @item break-range @var{start-location}, @var{end-location}
20440 Set a breakpoint for an address range.
20441 @var{start-location} and @var{end-location} can specify a function name,
20442 a line number, an offset of lines from the current line or from the start
20443 location, or an address of an instruction (see @ref{Specify Location},
20444 for a list of all the possible ways to specify a @var{location}.)
20445 The breakpoint will stop execution of the inferior whenever it
20446 executes an instruction at any address within the specified range,
20447 (including @var{start-location} and @var{end-location}.)
20449 @kindex set powerpc
20450 @item set powerpc soft-float
20451 @itemx show powerpc soft-float
20452 Force @value{GDBN} to use (or not use) a software floating point calling
20453 convention. By default, @value{GDBN} selects the calling convention based
20454 on the selected architecture and the provided executable file.
20456 @item set powerpc vector-abi
20457 @itemx show powerpc vector-abi
20458 Force @value{GDBN} to use the specified calling convention for vector
20459 arguments and return values. The valid options are @samp{auto};
20460 @samp{generic}, to avoid vector registers even if they are present;
20461 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
20462 registers. By default, @value{GDBN} selects the calling convention
20463 based on the selected architecture and the provided executable file.
20465 @item set powerpc exact-watchpoints
20466 @itemx show powerpc exact-watchpoints
20467 Allow @value{GDBN} to use only one debug register when watching a variable
20468 of scalar type, thus assuming that the variable is accessed through the
20469 address of its first byte.
20471 @kindex target dink32
20472 @item target dink32 @var{dev}
20473 DINK32 ROM monitor.
20475 @kindex target ppcbug
20476 @item target ppcbug @var{dev}
20477 @kindex target ppcbug1
20478 @item target ppcbug1 @var{dev}
20479 PPCBUG ROM monitor for PowerPC.
20482 @item target sds @var{dev}
20483 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
20486 @cindex SDS protocol
20487 The following commands specific to the SDS protocol are supported
20491 @item set sdstimeout @var{nsec}
20492 @kindex set sdstimeout
20493 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
20494 default is 2 seconds.
20496 @item show sdstimeout
20497 @kindex show sdstimeout
20498 Show the current value of the SDS timeout.
20500 @item sds @var{command}
20501 @kindex sds@r{, a command}
20502 Send the specified @var{command} string to the SDS monitor.
20507 @subsection HP PA Embedded
20511 @kindex target op50n
20512 @item target op50n @var{dev}
20513 OP50N monitor, running on an OKI HPPA board.
20515 @kindex target w89k
20516 @item target w89k @var{dev}
20517 W89K monitor, running on a Winbond HPPA board.
20522 @subsection Tsqware Sparclet
20526 @value{GDBN} enables developers to debug tasks running on
20527 Sparclet targets from a Unix host.
20528 @value{GDBN} uses code that runs on
20529 both the Unix host and on the Sparclet target. The program
20530 @code{@value{GDBP}} is installed and executed on the Unix host.
20533 @item remotetimeout @var{args}
20534 @kindex remotetimeout
20535 @value{GDBN} supports the option @code{remotetimeout}.
20536 This option is set by the user, and @var{args} represents the number of
20537 seconds @value{GDBN} waits for responses.
20540 @cindex compiling, on Sparclet
20541 When compiling for debugging, include the options @samp{-g} to get debug
20542 information and @samp{-Ttext} to relocate the program to where you wish to
20543 load it on the target. You may also want to add the options @samp{-n} or
20544 @samp{-N} in order to reduce the size of the sections. Example:
20547 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
20550 You can use @code{objdump} to verify that the addresses are what you intended:
20553 sparclet-aout-objdump --headers --syms prog
20556 @cindex running, on Sparclet
20558 your Unix execution search path to find @value{GDBN}, you are ready to
20559 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
20560 (or @code{sparclet-aout-gdb}, depending on your installation).
20562 @value{GDBN} comes up showing the prompt:
20569 * Sparclet File:: Setting the file to debug
20570 * Sparclet Connection:: Connecting to Sparclet
20571 * Sparclet Download:: Sparclet download
20572 * Sparclet Execution:: Running and debugging
20575 @node Sparclet File
20576 @subsubsection Setting File to Debug
20578 The @value{GDBN} command @code{file} lets you choose with program to debug.
20581 (gdbslet) file prog
20585 @value{GDBN} then attempts to read the symbol table of @file{prog}.
20586 @value{GDBN} locates
20587 the file by searching the directories listed in the command search
20589 If the file was compiled with debug information (option @samp{-g}), source
20590 files will be searched as well.
20591 @value{GDBN} locates
20592 the source files by searching the directories listed in the directory search
20593 path (@pxref{Environment, ,Your Program's Environment}).
20595 to find a file, it displays a message such as:
20598 prog: No such file or directory.
20601 When this happens, add the appropriate directories to the search paths with
20602 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
20603 @code{target} command again.
20605 @node Sparclet Connection
20606 @subsubsection Connecting to Sparclet
20608 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
20609 To connect to a target on serial port ``@code{ttya}'', type:
20612 (gdbslet) target sparclet /dev/ttya
20613 Remote target sparclet connected to /dev/ttya
20614 main () at ../prog.c:3
20618 @value{GDBN} displays messages like these:
20624 @node Sparclet Download
20625 @subsubsection Sparclet Download
20627 @cindex download to Sparclet
20628 Once connected to the Sparclet target,
20629 you can use the @value{GDBN}
20630 @code{load} command to download the file from the host to the target.
20631 The file name and load offset should be given as arguments to the @code{load}
20633 Since the file format is aout, the program must be loaded to the starting
20634 address. You can use @code{objdump} to find out what this value is. The load
20635 offset is an offset which is added to the VMA (virtual memory address)
20636 of each of the file's sections.
20637 For instance, if the program
20638 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
20639 and bss at 0x12010170, in @value{GDBN}, type:
20642 (gdbslet) load prog 0x12010000
20643 Loading section .text, size 0xdb0 vma 0x12010000
20646 If the code is loaded at a different address then what the program was linked
20647 to, you may need to use the @code{section} and @code{add-symbol-file} commands
20648 to tell @value{GDBN} where to map the symbol table.
20650 @node Sparclet Execution
20651 @subsubsection Running and Debugging
20653 @cindex running and debugging Sparclet programs
20654 You can now begin debugging the task using @value{GDBN}'s execution control
20655 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
20656 manual for the list of commands.
20660 Breakpoint 1 at 0x12010000: file prog.c, line 3.
20662 Starting program: prog
20663 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
20664 3 char *symarg = 0;
20666 4 char *execarg = "hello!";
20671 @subsection Fujitsu Sparclite
20675 @kindex target sparclite
20676 @item target sparclite @var{dev}
20677 Fujitsu sparclite boards, used only for the purpose of loading.
20678 You must use an additional command to debug the program.
20679 For example: target remote @var{dev} using @value{GDBN} standard
20685 @subsection Zilog Z8000
20688 @cindex simulator, Z8000
20689 @cindex Zilog Z8000 simulator
20691 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
20694 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
20695 unsegmented variant of the Z8000 architecture) or the Z8001 (the
20696 segmented variant). The simulator recognizes which architecture is
20697 appropriate by inspecting the object code.
20700 @item target sim @var{args}
20702 @kindex target sim@r{, with Z8000}
20703 Debug programs on a simulated CPU. If the simulator supports setup
20704 options, specify them via @var{args}.
20708 After specifying this target, you can debug programs for the simulated
20709 CPU in the same style as programs for your host computer; use the
20710 @code{file} command to load a new program image, the @code{run} command
20711 to run your program, and so on.
20713 As well as making available all the usual machine registers
20714 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
20715 additional items of information as specially named registers:
20720 Counts clock-ticks in the simulator.
20723 Counts instructions run in the simulator.
20726 Execution time in 60ths of a second.
20730 You can refer to these values in @value{GDBN} expressions with the usual
20731 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
20732 conditional breakpoint that suspends only after at least 5000
20733 simulated clock ticks.
20736 @subsection Atmel AVR
20739 When configured for debugging the Atmel AVR, @value{GDBN} supports the
20740 following AVR-specific commands:
20743 @item info io_registers
20744 @kindex info io_registers@r{, AVR}
20745 @cindex I/O registers (Atmel AVR)
20746 This command displays information about the AVR I/O registers. For
20747 each register, @value{GDBN} prints its number and value.
20754 When configured for debugging CRIS, @value{GDBN} provides the
20755 following CRIS-specific commands:
20758 @item set cris-version @var{ver}
20759 @cindex CRIS version
20760 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
20761 The CRIS version affects register names and sizes. This command is useful in
20762 case autodetection of the CRIS version fails.
20764 @item show cris-version
20765 Show the current CRIS version.
20767 @item set cris-dwarf2-cfi
20768 @cindex DWARF-2 CFI and CRIS
20769 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
20770 Change to @samp{off} when using @code{gcc-cris} whose version is below
20773 @item show cris-dwarf2-cfi
20774 Show the current state of using DWARF-2 CFI.
20776 @item set cris-mode @var{mode}
20778 Set the current CRIS mode to @var{mode}. It should only be changed when
20779 debugging in guru mode, in which case it should be set to
20780 @samp{guru} (the default is @samp{normal}).
20782 @item show cris-mode
20783 Show the current CRIS mode.
20787 @subsection Renesas Super-H
20790 For the Renesas Super-H processor, @value{GDBN} provides these
20794 @item set sh calling-convention @var{convention}
20795 @kindex set sh calling-convention
20796 Set the calling-convention used when calling functions from @value{GDBN}.
20797 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
20798 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
20799 convention. If the DWARF-2 information of the called function specifies
20800 that the function follows the Renesas calling convention, the function
20801 is called using the Renesas calling convention. If the calling convention
20802 is set to @samp{renesas}, the Renesas calling convention is always used,
20803 regardless of the DWARF-2 information. This can be used to override the
20804 default of @samp{gcc} if debug information is missing, or the compiler
20805 does not emit the DWARF-2 calling convention entry for a function.
20807 @item show sh calling-convention
20808 @kindex show sh calling-convention
20809 Show the current calling convention setting.
20814 @node Architectures
20815 @section Architectures
20817 This section describes characteristics of architectures that affect
20818 all uses of @value{GDBN} with the architecture, both native and cross.
20825 * HPPA:: HP PA architecture
20826 * SPU:: Cell Broadband Engine SPU architecture
20831 @subsection AArch64
20832 @cindex AArch64 support
20834 When @value{GDBN} is debugging the AArch64 architecture, it provides the
20835 following special commands:
20838 @item set debug aarch64
20839 @kindex set debug aarch64
20840 This command determines whether AArch64 architecture-specific debugging
20841 messages are to be displayed.
20843 @item show debug aarch64
20844 Show whether AArch64 debugging messages are displayed.
20849 @subsection x86 Architecture-specific Issues
20852 @item set struct-convention @var{mode}
20853 @kindex set struct-convention
20854 @cindex struct return convention
20855 @cindex struct/union returned in registers
20856 Set the convention used by the inferior to return @code{struct}s and
20857 @code{union}s from functions to @var{mode}. Possible values of
20858 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
20859 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
20860 are returned on the stack, while @code{"reg"} means that a
20861 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
20862 be returned in a register.
20864 @item show struct-convention
20865 @kindex show struct-convention
20866 Show the current setting of the convention to return @code{struct}s
20873 See the following section.
20876 @subsection @acronym{MIPS}
20878 @cindex stack on Alpha
20879 @cindex stack on @acronym{MIPS}
20880 @cindex Alpha stack
20881 @cindex @acronym{MIPS} stack
20882 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
20883 sometimes requires @value{GDBN} to search backward in the object code to
20884 find the beginning of a function.
20886 @cindex response time, @acronym{MIPS} debugging
20887 To improve response time (especially for embedded applications, where
20888 @value{GDBN} may be restricted to a slow serial line for this search)
20889 you may want to limit the size of this search, using one of these
20893 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
20894 @item set heuristic-fence-post @var{limit}
20895 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
20896 search for the beginning of a function. A value of @var{0} (the
20897 default) means there is no limit. However, except for @var{0}, the
20898 larger the limit the more bytes @code{heuristic-fence-post} must search
20899 and therefore the longer it takes to run. You should only need to use
20900 this command when debugging a stripped executable.
20902 @item show heuristic-fence-post
20903 Display the current limit.
20907 These commands are available @emph{only} when @value{GDBN} is configured
20908 for debugging programs on Alpha or @acronym{MIPS} processors.
20910 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
20914 @item set mips abi @var{arg}
20915 @kindex set mips abi
20916 @cindex set ABI for @acronym{MIPS}
20917 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
20918 values of @var{arg} are:
20922 The default ABI associated with the current binary (this is the
20932 @item show mips abi
20933 @kindex show mips abi
20934 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
20936 @item set mips compression @var{arg}
20937 @kindex set mips compression
20938 @cindex code compression, @acronym{MIPS}
20939 Tell @value{GDBN} which @acronym{MIPS} compressed
20940 @acronym{ISA, Instruction Set Architecture} encoding is used by the
20941 inferior. @value{GDBN} uses this for code disassembly and other
20942 internal interpretation purposes. This setting is only referred to
20943 when no executable has been associated with the debugging session or
20944 the executable does not provide information about the encoding it uses.
20945 Otherwise this setting is automatically updated from information
20946 provided by the executable.
20948 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
20949 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
20950 executables containing @acronym{MIPS16} code frequently are not
20951 identified as such.
20953 This setting is ``sticky''; that is, it retains its value across
20954 debugging sessions until reset either explicitly with this command or
20955 implicitly from an executable.
20957 The compiler and/or assembler typically add symbol table annotations to
20958 identify functions compiled for the @acronym{MIPS16} or
20959 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
20960 are present, @value{GDBN} uses them in preference to the global
20961 compressed @acronym{ISA} encoding setting.
20963 @item show mips compression
20964 @kindex show mips compression
20965 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
20966 @value{GDBN} to debug the inferior.
20969 @itemx show mipsfpu
20970 @xref{MIPS Embedded, set mipsfpu}.
20972 @item set mips mask-address @var{arg}
20973 @kindex set mips mask-address
20974 @cindex @acronym{MIPS} addresses, masking
20975 This command determines whether the most-significant 32 bits of 64-bit
20976 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
20977 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
20978 setting, which lets @value{GDBN} determine the correct value.
20980 @item show mips mask-address
20981 @kindex show mips mask-address
20982 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
20985 @item set remote-mips64-transfers-32bit-regs
20986 @kindex set remote-mips64-transfers-32bit-regs
20987 This command controls compatibility with 64-bit @acronym{MIPS} targets that
20988 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
20989 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
20990 and 64 bits for other registers, set this option to @samp{on}.
20992 @item show remote-mips64-transfers-32bit-regs
20993 @kindex show remote-mips64-transfers-32bit-regs
20994 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
20996 @item set debug mips
20997 @kindex set debug mips
20998 This command turns on and off debugging messages for the @acronym{MIPS}-specific
20999 target code in @value{GDBN}.
21001 @item show debug mips
21002 @kindex show debug mips
21003 Show the current setting of @acronym{MIPS} debugging messages.
21009 @cindex HPPA support
21011 When @value{GDBN} is debugging the HP PA architecture, it provides the
21012 following special commands:
21015 @item set debug hppa
21016 @kindex set debug hppa
21017 This command determines whether HPPA architecture-specific debugging
21018 messages are to be displayed.
21020 @item show debug hppa
21021 Show whether HPPA debugging messages are displayed.
21023 @item maint print unwind @var{address}
21024 @kindex maint print unwind@r{, HPPA}
21025 This command displays the contents of the unwind table entry at the
21026 given @var{address}.
21032 @subsection Cell Broadband Engine SPU architecture
21033 @cindex Cell Broadband Engine
21036 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
21037 it provides the following special commands:
21040 @item info spu event
21042 Display SPU event facility status. Shows current event mask
21043 and pending event status.
21045 @item info spu signal
21046 Display SPU signal notification facility status. Shows pending
21047 signal-control word and signal notification mode of both signal
21048 notification channels.
21050 @item info spu mailbox
21051 Display SPU mailbox facility status. Shows all pending entries,
21052 in order of processing, in each of the SPU Write Outbound,
21053 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
21056 Display MFC DMA status. Shows all pending commands in the MFC
21057 DMA queue. For each entry, opcode, tag, class IDs, effective
21058 and local store addresses and transfer size are shown.
21060 @item info spu proxydma
21061 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
21062 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
21063 and local store addresses and transfer size are shown.
21067 When @value{GDBN} is debugging a combined PowerPC/SPU application
21068 on the Cell Broadband Engine, it provides in addition the following
21072 @item set spu stop-on-load @var{arg}
21074 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
21075 will give control to the user when a new SPE thread enters its @code{main}
21076 function. The default is @code{off}.
21078 @item show spu stop-on-load
21080 Show whether to stop for new SPE threads.
21082 @item set spu auto-flush-cache @var{arg}
21083 Set whether to automatically flush the software-managed cache. When set to
21084 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
21085 cache to be flushed whenever SPE execution stops. This provides a consistent
21086 view of PowerPC memory that is accessed via the cache. If an application
21087 does not use the software-managed cache, this option has no effect.
21089 @item show spu auto-flush-cache
21090 Show whether to automatically flush the software-managed cache.
21095 @subsection PowerPC
21096 @cindex PowerPC architecture
21098 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
21099 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
21100 numbers stored in the floating point registers. These values must be stored
21101 in two consecutive registers, always starting at an even register like
21102 @code{f0} or @code{f2}.
21104 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
21105 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
21106 @code{f2} and @code{f3} for @code{$dl1} and so on.
21108 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
21109 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
21112 @node Controlling GDB
21113 @chapter Controlling @value{GDBN}
21115 You can alter the way @value{GDBN} interacts with you by using the
21116 @code{set} command. For commands controlling how @value{GDBN} displays
21117 data, see @ref{Print Settings, ,Print Settings}. Other settings are
21122 * Editing:: Command editing
21123 * Command History:: Command history
21124 * Screen Size:: Screen size
21125 * Numbers:: Numbers
21126 * ABI:: Configuring the current ABI
21127 * Auto-loading:: Automatically loading associated files
21128 * Messages/Warnings:: Optional warnings and messages
21129 * Debugging Output:: Optional messages about internal happenings
21130 * Other Misc Settings:: Other Miscellaneous Settings
21138 @value{GDBN} indicates its readiness to read a command by printing a string
21139 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
21140 can change the prompt string with the @code{set prompt} command. For
21141 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
21142 the prompt in one of the @value{GDBN} sessions so that you can always tell
21143 which one you are talking to.
21145 @emph{Note:} @code{set prompt} does not add a space for you after the
21146 prompt you set. This allows you to set a prompt which ends in a space
21147 or a prompt that does not.
21151 @item set prompt @var{newprompt}
21152 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
21154 @kindex show prompt
21156 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
21159 Versions of @value{GDBN} that ship with Python scripting enabled have
21160 prompt extensions. The commands for interacting with these extensions
21164 @kindex set extended-prompt
21165 @item set extended-prompt @var{prompt}
21166 Set an extended prompt that allows for substitutions.
21167 @xref{gdb.prompt}, for a list of escape sequences that can be used for
21168 substitution. Any escape sequences specified as part of the prompt
21169 string are replaced with the corresponding strings each time the prompt
21175 set extended-prompt Current working directory: \w (gdb)
21178 Note that when an extended-prompt is set, it takes control of the
21179 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
21181 @kindex show extended-prompt
21182 @item show extended-prompt
21183 Prints the extended prompt. Any escape sequences specified as part of
21184 the prompt string with @code{set extended-prompt}, are replaced with the
21185 corresponding strings each time the prompt is displayed.
21189 @section Command Editing
21191 @cindex command line editing
21193 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
21194 @sc{gnu} library provides consistent behavior for programs which provide a
21195 command line interface to the user. Advantages are @sc{gnu} Emacs-style
21196 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
21197 substitution, and a storage and recall of command history across
21198 debugging sessions.
21200 You may control the behavior of command line editing in @value{GDBN} with the
21201 command @code{set}.
21204 @kindex set editing
21207 @itemx set editing on
21208 Enable command line editing (enabled by default).
21210 @item set editing off
21211 Disable command line editing.
21213 @kindex show editing
21215 Show whether command line editing is enabled.
21218 @ifset SYSTEM_READLINE
21219 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
21221 @ifclear SYSTEM_READLINE
21222 @xref{Command Line Editing},
21224 for more details about the Readline
21225 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
21226 encouraged to read that chapter.
21228 @node Command History
21229 @section Command History
21230 @cindex command history
21232 @value{GDBN} can keep track of the commands you type during your
21233 debugging sessions, so that you can be certain of precisely what
21234 happened. Use these commands to manage the @value{GDBN} command
21237 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
21238 package, to provide the history facility.
21239 @ifset SYSTEM_READLINE
21240 @xref{Using History Interactively, , , history, GNU History Library},
21242 @ifclear SYSTEM_READLINE
21243 @xref{Using History Interactively},
21245 for the detailed description of the History library.
21247 To issue a command to @value{GDBN} without affecting certain aspects of
21248 the state which is seen by users, prefix it with @samp{server }
21249 (@pxref{Server Prefix}). This
21250 means that this command will not affect the command history, nor will it
21251 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
21252 pressed on a line by itself.
21254 @cindex @code{server}, command prefix
21255 The server prefix does not affect the recording of values into the value
21256 history; to print a value without recording it into the value history,
21257 use the @code{output} command instead of the @code{print} command.
21259 Here is the description of @value{GDBN} commands related to command
21263 @cindex history substitution
21264 @cindex history file
21265 @kindex set history filename
21266 @cindex @env{GDBHISTFILE}, environment variable
21267 @item set history filename @var{fname}
21268 Set the name of the @value{GDBN} command history file to @var{fname}.
21269 This is the file where @value{GDBN} reads an initial command history
21270 list, and where it writes the command history from this session when it
21271 exits. You can access this list through history expansion or through
21272 the history command editing characters listed below. This file defaults
21273 to the value of the environment variable @code{GDBHISTFILE}, or to
21274 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
21277 @cindex save command history
21278 @kindex set history save
21279 @item set history save
21280 @itemx set history save on
21281 Record command history in a file, whose name may be specified with the
21282 @code{set history filename} command. By default, this option is disabled.
21284 @item set history save off
21285 Stop recording command history in a file.
21287 @cindex history size
21288 @kindex set history size
21289 @cindex @env{HISTSIZE}, environment variable
21290 @item set history size @var{size}
21291 @itemx set history size unlimited
21292 Set the number of commands which @value{GDBN} keeps in its history list.
21293 This defaults to the value of the environment variable
21294 @code{HISTSIZE}, or to 256 if this variable is not set. If @var{size}
21295 is @code{unlimited}, the number of commands @value{GDBN} keeps in the
21296 history list is unlimited.
21299 History expansion assigns special meaning to the character @kbd{!}.
21300 @ifset SYSTEM_READLINE
21301 @xref{Event Designators, , , history, GNU History Library},
21303 @ifclear SYSTEM_READLINE
21304 @xref{Event Designators},
21308 @cindex history expansion, turn on/off
21309 Since @kbd{!} is also the logical not operator in C, history expansion
21310 is off by default. If you decide to enable history expansion with the
21311 @code{set history expansion on} command, you may sometimes need to
21312 follow @kbd{!} (when it is used as logical not, in an expression) with
21313 a space or a tab to prevent it from being expanded. The readline
21314 history facilities do not attempt substitution on the strings
21315 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
21317 The commands to control history expansion are:
21320 @item set history expansion on
21321 @itemx set history expansion
21322 @kindex set history expansion
21323 Enable history expansion. History expansion is off by default.
21325 @item set history expansion off
21326 Disable history expansion.
21329 @kindex show history
21331 @itemx show history filename
21332 @itemx show history save
21333 @itemx show history size
21334 @itemx show history expansion
21335 These commands display the state of the @value{GDBN} history parameters.
21336 @code{show history} by itself displays all four states.
21341 @kindex show commands
21342 @cindex show last commands
21343 @cindex display command history
21344 @item show commands
21345 Display the last ten commands in the command history.
21347 @item show commands @var{n}
21348 Print ten commands centered on command number @var{n}.
21350 @item show commands +
21351 Print ten commands just after the commands last printed.
21355 @section Screen Size
21356 @cindex size of screen
21357 @cindex pauses in output
21359 Certain commands to @value{GDBN} may produce large amounts of
21360 information output to the screen. To help you read all of it,
21361 @value{GDBN} pauses and asks you for input at the end of each page of
21362 output. Type @key{RET} when you want to continue the output, or @kbd{q}
21363 to discard the remaining output. Also, the screen width setting
21364 determines when to wrap lines of output. Depending on what is being
21365 printed, @value{GDBN} tries to break the line at a readable place,
21366 rather than simply letting it overflow onto the following line.
21368 Normally @value{GDBN} knows the size of the screen from the terminal
21369 driver software. For example, on Unix @value{GDBN} uses the termcap data base
21370 together with the value of the @code{TERM} environment variable and the
21371 @code{stty rows} and @code{stty cols} settings. If this is not correct,
21372 you can override it with the @code{set height} and @code{set
21379 @kindex show height
21380 @item set height @var{lpp}
21381 @itemx set height unlimited
21383 @itemx set width @var{cpl}
21384 @itemx set width unlimited
21386 These @code{set} commands specify a screen height of @var{lpp} lines and
21387 a screen width of @var{cpl} characters. The associated @code{show}
21388 commands display the current settings.
21390 If you specify a height of either @code{unlimited} or zero lines,
21391 @value{GDBN} does not pause during output no matter how long the
21392 output is. This is useful if output is to a file or to an editor
21395 Likewise, you can specify @samp{set width unlimited} or @samp{set
21396 width 0} to prevent @value{GDBN} from wrapping its output.
21398 @item set pagination on
21399 @itemx set pagination off
21400 @kindex set pagination
21401 Turn the output pagination on or off; the default is on. Turning
21402 pagination off is the alternative to @code{set height unlimited}. Note that
21403 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
21404 Options, -batch}) also automatically disables pagination.
21406 @item show pagination
21407 @kindex show pagination
21408 Show the current pagination mode.
21413 @cindex number representation
21414 @cindex entering numbers
21416 You can always enter numbers in octal, decimal, or hexadecimal in
21417 @value{GDBN} by the usual conventions: octal numbers begin with
21418 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
21419 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
21420 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
21421 10; likewise, the default display for numbers---when no particular
21422 format is specified---is base 10. You can change the default base for
21423 both input and output with the commands described below.
21426 @kindex set input-radix
21427 @item set input-radix @var{base}
21428 Set the default base for numeric input. Supported choices
21429 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21430 specified either unambiguously or using the current input radix; for
21434 set input-radix 012
21435 set input-radix 10.
21436 set input-radix 0xa
21440 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
21441 leaves the input radix unchanged, no matter what it was, since
21442 @samp{10}, being without any leading or trailing signs of its base, is
21443 interpreted in the current radix. Thus, if the current radix is 16,
21444 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
21447 @kindex set output-radix
21448 @item set output-radix @var{base}
21449 Set the default base for numeric display. Supported choices
21450 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21451 specified either unambiguously or using the current input radix.
21453 @kindex show input-radix
21454 @item show input-radix
21455 Display the current default base for numeric input.
21457 @kindex show output-radix
21458 @item show output-radix
21459 Display the current default base for numeric display.
21461 @item set radix @r{[}@var{base}@r{]}
21465 These commands set and show the default base for both input and output
21466 of numbers. @code{set radix} sets the radix of input and output to
21467 the same base; without an argument, it resets the radix back to its
21468 default value of 10.
21473 @section Configuring the Current ABI
21475 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
21476 application automatically. However, sometimes you need to override its
21477 conclusions. Use these commands to manage @value{GDBN}'s view of the
21483 @cindex Newlib OS ABI and its influence on the longjmp handling
21485 One @value{GDBN} configuration can debug binaries for multiple operating
21486 system targets, either via remote debugging or native emulation.
21487 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
21488 but you can override its conclusion using the @code{set osabi} command.
21489 One example where this is useful is in debugging of binaries which use
21490 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
21491 not have the same identifying marks that the standard C library for your
21494 When @value{GDBN} is debugging the AArch64 architecture, it provides a
21495 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
21496 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
21497 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
21501 Show the OS ABI currently in use.
21504 With no argument, show the list of registered available OS ABI's.
21506 @item set osabi @var{abi}
21507 Set the current OS ABI to @var{abi}.
21510 @cindex float promotion
21512 Generally, the way that an argument of type @code{float} is passed to a
21513 function depends on whether the function is prototyped. For a prototyped
21514 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
21515 according to the architecture's convention for @code{float}. For unprototyped
21516 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
21517 @code{double} and then passed.
21519 Unfortunately, some forms of debug information do not reliably indicate whether
21520 a function is prototyped. If @value{GDBN} calls a function that is not marked
21521 as prototyped, it consults @kbd{set coerce-float-to-double}.
21524 @kindex set coerce-float-to-double
21525 @item set coerce-float-to-double
21526 @itemx set coerce-float-to-double on
21527 Arguments of type @code{float} will be promoted to @code{double} when passed
21528 to an unprototyped function. This is the default setting.
21530 @item set coerce-float-to-double off
21531 Arguments of type @code{float} will be passed directly to unprototyped
21534 @kindex show coerce-float-to-double
21535 @item show coerce-float-to-double
21536 Show the current setting of promoting @code{float} to @code{double}.
21540 @kindex show cp-abi
21541 @value{GDBN} needs to know the ABI used for your program's C@t{++}
21542 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
21543 used to build your application. @value{GDBN} only fully supports
21544 programs with a single C@t{++} ABI; if your program contains code using
21545 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
21546 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
21547 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
21548 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
21549 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
21550 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
21555 Show the C@t{++} ABI currently in use.
21558 With no argument, show the list of supported C@t{++} ABI's.
21560 @item set cp-abi @var{abi}
21561 @itemx set cp-abi auto
21562 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
21566 @section Automatically loading associated files
21567 @cindex auto-loading
21569 @value{GDBN} sometimes reads files with commands and settings automatically,
21570 without being explicitly told so by the user. We call this feature
21571 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
21572 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
21573 results or introduce security risks (e.g., if the file comes from untrusted
21576 Note that loading of these associated files (including the local @file{.gdbinit}
21577 file) requires accordingly configured @code{auto-load safe-path}
21578 (@pxref{Auto-loading safe path}).
21580 For these reasons, @value{GDBN} includes commands and options to let you
21581 control when to auto-load files and which files should be auto-loaded.
21584 @anchor{set auto-load off}
21585 @kindex set auto-load off
21586 @item set auto-load off
21587 Globally disable loading of all auto-loaded files.
21588 You may want to use this command with the @samp{-iex} option
21589 (@pxref{Option -init-eval-command}) such as:
21591 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
21594 Be aware that system init file (@pxref{System-wide configuration})
21595 and init files from your home directory (@pxref{Home Directory Init File})
21596 still get read (as they come from generally trusted directories).
21597 To prevent @value{GDBN} from auto-loading even those init files, use the
21598 @option{-nx} option (@pxref{Mode Options}), in addition to
21599 @code{set auto-load no}.
21601 @anchor{show auto-load}
21602 @kindex show auto-load
21603 @item show auto-load
21604 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
21608 (gdb) show auto-load
21609 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
21610 libthread-db: Auto-loading of inferior specific libthread_db is on.
21611 local-gdbinit: Auto-loading of .gdbinit script from current directory
21613 python-scripts: Auto-loading of Python scripts is on.
21614 safe-path: List of directories from which it is safe to auto-load files
21615 is $debugdir:$datadir/auto-load.
21616 scripts-directory: List of directories from which to load auto-loaded scripts
21617 is $debugdir:$datadir/auto-load.
21620 @anchor{info auto-load}
21621 @kindex info auto-load
21622 @item info auto-load
21623 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
21627 (gdb) info auto-load
21630 Yes /home/user/gdb/gdb-gdb.gdb
21631 libthread-db: No auto-loaded libthread-db.
21632 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
21636 Yes /home/user/gdb/gdb-gdb.py
21640 These are various kinds of files @value{GDBN} can automatically load:
21644 @xref{objfile-gdb.py file}, controlled by @ref{set auto-load python-scripts}.
21646 @xref{objfile-gdb.gdb file}, controlled by @ref{set auto-load gdb-scripts}.
21648 @xref{dotdebug_gdb_scripts section},
21649 controlled by @ref{set auto-load python-scripts}.
21651 @xref{Init File in the Current Directory},
21652 controlled by @ref{set auto-load local-gdbinit}.
21654 @xref{libthread_db.so.1 file}, controlled by @ref{set auto-load libthread-db}.
21657 These are @value{GDBN} control commands for the auto-loading:
21659 @multitable @columnfractions .5 .5
21660 @item @xref{set auto-load off}.
21661 @tab Disable auto-loading globally.
21662 @item @xref{show auto-load}.
21663 @tab Show setting of all kinds of files.
21664 @item @xref{info auto-load}.
21665 @tab Show state of all kinds of files.
21666 @item @xref{set auto-load gdb-scripts}.
21667 @tab Control for @value{GDBN} command scripts.
21668 @item @xref{show auto-load gdb-scripts}.
21669 @tab Show setting of @value{GDBN} command scripts.
21670 @item @xref{info auto-load gdb-scripts}.
21671 @tab Show state of @value{GDBN} command scripts.
21672 @item @xref{set auto-load python-scripts}.
21673 @tab Control for @value{GDBN} Python scripts.
21674 @item @xref{show auto-load python-scripts}.
21675 @tab Show setting of @value{GDBN} Python scripts.
21676 @item @xref{info auto-load python-scripts}.
21677 @tab Show state of @value{GDBN} Python scripts.
21678 @item @xref{set auto-load scripts-directory}.
21679 @tab Control for @value{GDBN} auto-loaded scripts location.
21680 @item @xref{show auto-load scripts-directory}.
21681 @tab Show @value{GDBN} auto-loaded scripts location.
21682 @item @xref{set auto-load local-gdbinit}.
21683 @tab Control for init file in the current directory.
21684 @item @xref{show auto-load local-gdbinit}.
21685 @tab Show setting of init file in the current directory.
21686 @item @xref{info auto-load local-gdbinit}.
21687 @tab Show state of init file in the current directory.
21688 @item @xref{set auto-load libthread-db}.
21689 @tab Control for thread debugging library.
21690 @item @xref{show auto-load libthread-db}.
21691 @tab Show setting of thread debugging library.
21692 @item @xref{info auto-load libthread-db}.
21693 @tab Show state of thread debugging library.
21694 @item @xref{set auto-load safe-path}.
21695 @tab Control directories trusted for automatic loading.
21696 @item @xref{show auto-load safe-path}.
21697 @tab Show directories trusted for automatic loading.
21698 @item @xref{add-auto-load-safe-path}.
21699 @tab Add directory trusted for automatic loading.
21703 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
21704 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
21705 * objfile-gdb.gdb file:: @samp{set/show/info auto-load gdb-script}
21706 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
21707 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
21708 @xref{Python Auto-loading}.
21711 @node Init File in the Current Directory
21712 @subsection Automatically loading init file in the current directory
21713 @cindex auto-loading init file in the current directory
21715 By default, @value{GDBN} reads and executes the canned sequences of commands
21716 from init file (if any) in the current working directory,
21717 see @ref{Init File in the Current Directory during Startup}.
21719 Note that loading of this local @file{.gdbinit} file also requires accordingly
21720 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21723 @anchor{set auto-load local-gdbinit}
21724 @kindex set auto-load local-gdbinit
21725 @item set auto-load local-gdbinit [on|off]
21726 Enable or disable the auto-loading of canned sequences of commands
21727 (@pxref{Sequences}) found in init file in the current directory.
21729 @anchor{show auto-load local-gdbinit}
21730 @kindex show auto-load local-gdbinit
21731 @item show auto-load local-gdbinit
21732 Show whether auto-loading of canned sequences of commands from init file in the
21733 current directory is enabled or disabled.
21735 @anchor{info auto-load local-gdbinit}
21736 @kindex info auto-load local-gdbinit
21737 @item info auto-load local-gdbinit
21738 Print whether canned sequences of commands from init file in the
21739 current directory have been auto-loaded.
21742 @node libthread_db.so.1 file
21743 @subsection Automatically loading thread debugging library
21744 @cindex auto-loading libthread_db.so.1
21746 This feature is currently present only on @sc{gnu}/Linux native hosts.
21748 @value{GDBN} reads in some cases thread debugging library from places specific
21749 to the inferior (@pxref{set libthread-db-search-path}).
21751 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
21752 without checking this @samp{set auto-load libthread-db} switch as system
21753 libraries have to be trusted in general. In all other cases of
21754 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
21755 auto-load libthread-db} is enabled before trying to open such thread debugging
21758 Note that loading of this debugging library also requires accordingly configured
21759 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21762 @anchor{set auto-load libthread-db}
21763 @kindex set auto-load libthread-db
21764 @item set auto-load libthread-db [on|off]
21765 Enable or disable the auto-loading of inferior specific thread debugging library.
21767 @anchor{show auto-load libthread-db}
21768 @kindex show auto-load libthread-db
21769 @item show auto-load libthread-db
21770 Show whether auto-loading of inferior specific thread debugging library is
21771 enabled or disabled.
21773 @anchor{info auto-load libthread-db}
21774 @kindex info auto-load libthread-db
21775 @item info auto-load libthread-db
21776 Print the list of all loaded inferior specific thread debugging libraries and
21777 for each such library print list of inferior @var{pid}s using it.
21780 @node objfile-gdb.gdb file
21781 @subsection The @file{@var{objfile}-gdb.gdb} file
21782 @cindex auto-loading @file{@var{objfile}-gdb.gdb}
21784 @value{GDBN} tries to load an @file{@var{objfile}-gdb.gdb} file containing
21785 canned sequences of commands (@pxref{Sequences}), as long as @samp{set
21786 auto-load gdb-scripts} is set to @samp{on}.
21788 Note that loading of this script file also requires accordingly configured
21789 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21791 For more background refer to the similar Python scripts auto-loading
21792 description (@pxref{objfile-gdb.py file}).
21795 @anchor{set auto-load gdb-scripts}
21796 @kindex set auto-load gdb-scripts
21797 @item set auto-load gdb-scripts [on|off]
21798 Enable or disable the auto-loading of canned sequences of commands scripts.
21800 @anchor{show auto-load gdb-scripts}
21801 @kindex show auto-load gdb-scripts
21802 @item show auto-load gdb-scripts
21803 Show whether auto-loading of canned sequences of commands scripts is enabled or
21806 @anchor{info auto-load gdb-scripts}
21807 @kindex info auto-load gdb-scripts
21808 @cindex print list of auto-loaded canned sequences of commands scripts
21809 @item info auto-load gdb-scripts [@var{regexp}]
21810 Print the list of all canned sequences of commands scripts that @value{GDBN}
21814 If @var{regexp} is supplied only canned sequences of commands scripts with
21815 matching names are printed.
21817 @node Auto-loading safe path
21818 @subsection Security restriction for auto-loading
21819 @cindex auto-loading safe-path
21821 As the files of inferior can come from untrusted source (such as submitted by
21822 an application user) @value{GDBN} does not always load any files automatically.
21823 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
21824 directories trusted for loading files not explicitly requested by user.
21825 Each directory can also be a shell wildcard pattern.
21827 If the path is not set properly you will see a warning and the file will not
21832 Reading symbols from /home/user/gdb/gdb...done.
21833 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
21834 declined by your `auto-load safe-path' set
21835 to "$debugdir:$datadir/auto-load".
21836 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
21837 declined by your `auto-load safe-path' set
21838 to "$debugdir:$datadir/auto-load".
21841 The list of trusted directories is controlled by the following commands:
21844 @anchor{set auto-load safe-path}
21845 @kindex set auto-load safe-path
21846 @item set auto-load safe-path @r{[}@var{directories}@r{]}
21847 Set the list of directories (and their subdirectories) trusted for automatic
21848 loading and execution of scripts. You can also enter a specific trusted file.
21849 Each directory can also be a shell wildcard pattern; wildcards do not match
21850 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
21851 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
21852 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
21853 its default value as specified during @value{GDBN} compilation.
21855 The list of directories uses path separator (@samp{:} on GNU and Unix
21856 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
21857 to the @env{PATH} environment variable.
21859 @anchor{show auto-load safe-path}
21860 @kindex show auto-load safe-path
21861 @item show auto-load safe-path
21862 Show the list of directories trusted for automatic loading and execution of
21865 @anchor{add-auto-load-safe-path}
21866 @kindex add-auto-load-safe-path
21867 @item add-auto-load-safe-path
21868 Add an entry (or list of entries) the list of directories trusted for automatic
21869 loading and execution of scripts. Multiple entries may be delimited by the
21870 host platform path separator in use.
21873 This variable defaults to what @code{--with-auto-load-dir} has been configured
21874 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
21875 substitution applies the same as for @ref{set auto-load scripts-directory}.
21876 The default @code{set auto-load safe-path} value can be also overriden by
21877 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
21879 Setting this variable to @file{/} disables this security protection,
21880 corresponding @value{GDBN} configuration option is
21881 @option{--without-auto-load-safe-path}.
21882 This variable is supposed to be set to the system directories writable by the
21883 system superuser only. Users can add their source directories in init files in
21884 their home directories (@pxref{Home Directory Init File}). See also deprecated
21885 init file in the current directory
21886 (@pxref{Init File in the Current Directory during Startup}).
21888 To force @value{GDBN} to load the files it declined to load in the previous
21889 example, you could use one of the following ways:
21892 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
21893 Specify this trusted directory (or a file) as additional component of the list.
21894 You have to specify also any existing directories displayed by
21895 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
21897 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
21898 Specify this directory as in the previous case but just for a single
21899 @value{GDBN} session.
21901 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
21902 Disable auto-loading safety for a single @value{GDBN} session.
21903 This assumes all the files you debug during this @value{GDBN} session will come
21904 from trusted sources.
21906 @item @kbd{./configure --without-auto-load-safe-path}
21907 During compilation of @value{GDBN} you may disable any auto-loading safety.
21908 This assumes all the files you will ever debug with this @value{GDBN} come from
21912 On the other hand you can also explicitly forbid automatic files loading which
21913 also suppresses any such warning messages:
21916 @item @kbd{gdb -iex "set auto-load no" @dots{}}
21917 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
21919 @item @file{~/.gdbinit}: @samp{set auto-load no}
21920 Disable auto-loading globally for the user
21921 (@pxref{Home Directory Init File}). While it is improbable, you could also
21922 use system init file instead (@pxref{System-wide configuration}).
21925 This setting applies to the file names as entered by user. If no entry matches
21926 @value{GDBN} tries as a last resort to also resolve all the file names into
21927 their canonical form (typically resolving symbolic links) and compare the
21928 entries again. @value{GDBN} already canonicalizes most of the filenames on its
21929 own before starting the comparison so a canonical form of directories is
21930 recommended to be entered.
21932 @node Auto-loading verbose mode
21933 @subsection Displaying files tried for auto-load
21934 @cindex auto-loading verbose mode
21936 For better visibility of all the file locations where you can place scripts to
21937 be auto-loaded with inferior --- or to protect yourself against accidental
21938 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
21939 all the files attempted to be loaded. Both existing and non-existing files may
21942 For example the list of directories from which it is safe to auto-load files
21943 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
21944 may not be too obvious while setting it up.
21947 (gdb) set debug auto-load on
21948 (gdb) file ~/src/t/true
21949 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
21950 for objfile "/tmp/true".
21951 auto-load: Updating directories of "/usr:/opt".
21952 auto-load: Using directory "/usr".
21953 auto-load: Using directory "/opt".
21954 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
21955 by your `auto-load safe-path' set to "/usr:/opt".
21959 @anchor{set debug auto-load}
21960 @kindex set debug auto-load
21961 @item set debug auto-load [on|off]
21962 Set whether to print the filenames attempted to be auto-loaded.
21964 @anchor{show debug auto-load}
21965 @kindex show debug auto-load
21966 @item show debug auto-load
21967 Show whether printing of the filenames attempted to be auto-loaded is turned
21971 @node Messages/Warnings
21972 @section Optional Warnings and Messages
21974 @cindex verbose operation
21975 @cindex optional warnings
21976 By default, @value{GDBN} is silent about its inner workings. If you are
21977 running on a slow machine, you may want to use the @code{set verbose}
21978 command. This makes @value{GDBN} tell you when it does a lengthy
21979 internal operation, so you will not think it has crashed.
21981 Currently, the messages controlled by @code{set verbose} are those
21982 which announce that the symbol table for a source file is being read;
21983 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
21986 @kindex set verbose
21987 @item set verbose on
21988 Enables @value{GDBN} output of certain informational messages.
21990 @item set verbose off
21991 Disables @value{GDBN} output of certain informational messages.
21993 @kindex show verbose
21995 Displays whether @code{set verbose} is on or off.
21998 By default, if @value{GDBN} encounters bugs in the symbol table of an
21999 object file, it is silent; but if you are debugging a compiler, you may
22000 find this information useful (@pxref{Symbol Errors, ,Errors Reading
22005 @kindex set complaints
22006 @item set complaints @var{limit}
22007 Permits @value{GDBN} to output @var{limit} complaints about each type of
22008 unusual symbols before becoming silent about the problem. Set
22009 @var{limit} to zero to suppress all complaints; set it to a large number
22010 to prevent complaints from being suppressed.
22012 @kindex show complaints
22013 @item show complaints
22014 Displays how many symbol complaints @value{GDBN} is permitted to produce.
22018 @anchor{confirmation requests}
22019 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
22020 lot of stupid questions to confirm certain commands. For example, if
22021 you try to run a program which is already running:
22025 The program being debugged has been started already.
22026 Start it from the beginning? (y or n)
22029 If you are willing to unflinchingly face the consequences of your own
22030 commands, you can disable this ``feature'':
22034 @kindex set confirm
22036 @cindex confirmation
22037 @cindex stupid questions
22038 @item set confirm off
22039 Disables confirmation requests. Note that running @value{GDBN} with
22040 the @option{--batch} option (@pxref{Mode Options, -batch}) also
22041 automatically disables confirmation requests.
22043 @item set confirm on
22044 Enables confirmation requests (the default).
22046 @kindex show confirm
22048 Displays state of confirmation requests.
22052 @cindex command tracing
22053 If you need to debug user-defined commands or sourced files you may find it
22054 useful to enable @dfn{command tracing}. In this mode each command will be
22055 printed as it is executed, prefixed with one or more @samp{+} symbols, the
22056 quantity denoting the call depth of each command.
22059 @kindex set trace-commands
22060 @cindex command scripts, debugging
22061 @item set trace-commands on
22062 Enable command tracing.
22063 @item set trace-commands off
22064 Disable command tracing.
22065 @item show trace-commands
22066 Display the current state of command tracing.
22069 @node Debugging Output
22070 @section Optional Messages about Internal Happenings
22071 @cindex optional debugging messages
22073 @value{GDBN} has commands that enable optional debugging messages from
22074 various @value{GDBN} subsystems; normally these commands are of
22075 interest to @value{GDBN} maintainers, or when reporting a bug. This
22076 section documents those commands.
22079 @kindex set exec-done-display
22080 @item set exec-done-display
22081 Turns on or off the notification of asynchronous commands'
22082 completion. When on, @value{GDBN} will print a message when an
22083 asynchronous command finishes its execution. The default is off.
22084 @kindex show exec-done-display
22085 @item show exec-done-display
22086 Displays the current setting of asynchronous command completion
22089 @cindex ARM AArch64
22090 @item set debug aarch64
22091 Turns on or off display of debugging messages related to ARM AArch64.
22092 The default is off.
22094 @item show debug aarch64
22095 Displays the current state of displaying debugging messages related to
22097 @cindex gdbarch debugging info
22098 @cindex architecture debugging info
22099 @item set debug arch
22100 Turns on or off display of gdbarch debugging info. The default is off
22101 @item show debug arch
22102 Displays the current state of displaying gdbarch debugging info.
22103 @item set debug aix-thread
22104 @cindex AIX threads
22105 Display debugging messages about inner workings of the AIX thread
22107 @item show debug aix-thread
22108 Show the current state of AIX thread debugging info display.
22109 @item set debug check-physname
22111 Check the results of the ``physname'' computation. When reading DWARF
22112 debugging information for C@t{++}, @value{GDBN} attempts to compute
22113 each entity's name. @value{GDBN} can do this computation in two
22114 different ways, depending on exactly what information is present.
22115 When enabled, this setting causes @value{GDBN} to compute the names
22116 both ways and display any discrepancies.
22117 @item show debug check-physname
22118 Show the current state of ``physname'' checking.
22119 @item set debug coff-pe-read
22120 @cindex COFF/PE exported symbols
22121 Control display of debugging messages related to reading of COFF/PE
22122 exported symbols. The default is off.
22123 @item show debug coff-pe-read
22124 Displays the current state of displaying debugging messages related to
22125 reading of COFF/PE exported symbols.
22126 @item set debug dwarf2-die
22127 @cindex DWARF2 DIEs
22128 Dump DWARF2 DIEs after they are read in.
22129 The value is the number of nesting levels to print.
22130 A value of zero turns off the display.
22131 @item show debug dwarf2-die
22132 Show the current state of DWARF2 DIE debugging.
22133 @item set debug dwarf2-read
22134 @cindex DWARF2 Reading
22135 Turns on or off display of debugging messages related to reading
22136 DWARF debug info. The default is off.
22137 @item show debug dwarf2-read
22138 Show the current state of DWARF2 reader debugging.
22139 @item set debug displaced
22140 @cindex displaced stepping debugging info
22141 Turns on or off display of @value{GDBN} debugging info for the
22142 displaced stepping support. The default is off.
22143 @item show debug displaced
22144 Displays the current state of displaying @value{GDBN} debugging info
22145 related to displaced stepping.
22146 @item set debug event
22147 @cindex event debugging info
22148 Turns on or off display of @value{GDBN} event debugging info. The
22150 @item show debug event
22151 Displays the current state of displaying @value{GDBN} event debugging
22153 @item set debug expression
22154 @cindex expression debugging info
22155 Turns on or off display of debugging info about @value{GDBN}
22156 expression parsing. The default is off.
22157 @item show debug expression
22158 Displays the current state of displaying debugging info about
22159 @value{GDBN} expression parsing.
22160 @item set debug frame
22161 @cindex frame debugging info
22162 Turns on or off display of @value{GDBN} frame debugging info. The
22164 @item show debug frame
22165 Displays the current state of displaying @value{GDBN} frame debugging
22167 @item set debug gnu-nat
22168 @cindex @sc{gnu}/Hurd debug messages
22169 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
22170 @item show debug gnu-nat
22171 Show the current state of @sc{gnu}/Hurd debugging messages.
22172 @item set debug infrun
22173 @cindex inferior debugging info
22174 Turns on or off display of @value{GDBN} debugging info for running the inferior.
22175 The default is off. @file{infrun.c} contains GDB's runtime state machine used
22176 for implementing operations such as single-stepping the inferior.
22177 @item show debug infrun
22178 Displays the current state of @value{GDBN} inferior debugging.
22179 @item set debug jit
22180 @cindex just-in-time compilation, debugging messages
22181 Turns on or off debugging messages from JIT debug support.
22182 @item show debug jit
22183 Displays the current state of @value{GDBN} JIT debugging.
22184 @item set debug lin-lwp
22185 @cindex @sc{gnu}/Linux LWP debug messages
22186 @cindex Linux lightweight processes
22187 Turns on or off debugging messages from the Linux LWP debug support.
22188 @item show debug lin-lwp
22189 Show the current state of Linux LWP debugging messages.
22190 @item set debug mach-o
22191 @cindex Mach-O symbols processing
22192 Control display of debugging messages related to Mach-O symbols
22193 processing. The default is off.
22194 @item show debug mach-o
22195 Displays the current state of displaying debugging messages related to
22196 reading of COFF/PE exported symbols.
22197 @item set debug notification
22198 @cindex remote async notification debugging info
22199 Turns on or off debugging messages about remote async notification.
22200 The default is off.
22201 @item show debug notification
22202 Displays the current state of remote async notification debugging messages.
22203 @item set debug observer
22204 @cindex observer debugging info
22205 Turns on or off display of @value{GDBN} observer debugging. This
22206 includes info such as the notification of observable events.
22207 @item show debug observer
22208 Displays the current state of observer debugging.
22209 @item set debug overload
22210 @cindex C@t{++} overload debugging info
22211 Turns on or off display of @value{GDBN} C@t{++} overload debugging
22212 info. This includes info such as ranking of functions, etc. The default
22214 @item show debug overload
22215 Displays the current state of displaying @value{GDBN} C@t{++} overload
22217 @cindex expression parser, debugging info
22218 @cindex debug expression parser
22219 @item set debug parser
22220 Turns on or off the display of expression parser debugging output.
22221 Internally, this sets the @code{yydebug} variable in the expression
22222 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
22223 details. The default is off.
22224 @item show debug parser
22225 Show the current state of expression parser debugging.
22226 @cindex packets, reporting on stdout
22227 @cindex serial connections, debugging
22228 @cindex debug remote protocol
22229 @cindex remote protocol debugging
22230 @cindex display remote packets
22231 @item set debug remote
22232 Turns on or off display of reports on all packets sent back and forth across
22233 the serial line to the remote machine. The info is printed on the
22234 @value{GDBN} standard output stream. The default is off.
22235 @item show debug remote
22236 Displays the state of display of remote packets.
22237 @item set debug serial
22238 Turns on or off display of @value{GDBN} serial debugging info. The
22240 @item show debug serial
22241 Displays the current state of displaying @value{GDBN} serial debugging
22243 @item set debug solib-frv
22244 @cindex FR-V shared-library debugging
22245 Turns on or off debugging messages for FR-V shared-library code.
22246 @item show debug solib-frv
22247 Display the current state of FR-V shared-library code debugging
22249 @item set debug symtab-create
22250 @cindex symbol table creation
22251 Turns on or off display of debugging messages related to symbol table creation.
22252 The default is off.
22253 @item show debug symtab-create
22254 Show the current state of symbol table creation debugging.
22255 @item set debug target
22256 @cindex target debugging info
22257 Turns on or off display of @value{GDBN} target debugging info. This info
22258 includes what is going on at the target level of GDB, as it happens. The
22259 default is 0. Set it to 1 to track events, and to 2 to also track the
22260 value of large memory transfers. Changes to this flag do not take effect
22261 until the next time you connect to a target or use the @code{run} command.
22262 @item show debug target
22263 Displays the current state of displaying @value{GDBN} target debugging
22265 @item set debug timestamp
22266 @cindex timestampping debugging info
22267 Turns on or off display of timestamps with @value{GDBN} debugging info.
22268 When enabled, seconds and microseconds are displayed before each debugging
22270 @item show debug timestamp
22271 Displays the current state of displaying timestamps with @value{GDBN}
22273 @item set debugvarobj
22274 @cindex variable object debugging info
22275 Turns on or off display of @value{GDBN} variable object debugging
22276 info. The default is off.
22277 @item show debugvarobj
22278 Displays the current state of displaying @value{GDBN} variable object
22280 @item set debug xml
22281 @cindex XML parser debugging
22282 Turns on or off debugging messages for built-in XML parsers.
22283 @item show debug xml
22284 Displays the current state of XML debugging messages.
22287 @node Other Misc Settings
22288 @section Other Miscellaneous Settings
22289 @cindex miscellaneous settings
22292 @kindex set interactive-mode
22293 @item set interactive-mode
22294 If @code{on}, forces @value{GDBN} to assume that GDB was started
22295 in a terminal. In practice, this means that @value{GDBN} should wait
22296 for the user to answer queries generated by commands entered at
22297 the command prompt. If @code{off}, forces @value{GDBN} to operate
22298 in the opposite mode, and it uses the default answers to all queries.
22299 If @code{auto} (the default), @value{GDBN} tries to determine whether
22300 its standard input is a terminal, and works in interactive-mode if it
22301 is, non-interactively otherwise.
22303 In the vast majority of cases, the debugger should be able to guess
22304 correctly which mode should be used. But this setting can be useful
22305 in certain specific cases, such as running a MinGW @value{GDBN}
22306 inside a cygwin window.
22308 @kindex show interactive-mode
22309 @item show interactive-mode
22310 Displays whether the debugger is operating in interactive mode or not.
22313 @node Extending GDB
22314 @chapter Extending @value{GDBN}
22315 @cindex extending GDB
22317 @value{GDBN} provides three mechanisms for extension. The first is based
22318 on composition of @value{GDBN} commands, the second is based on the
22319 Python scripting language, and the third is for defining new aliases of
22322 To facilitate the use of the first two extensions, @value{GDBN} is capable
22323 of evaluating the contents of a file. When doing so, @value{GDBN}
22324 can recognize which scripting language is being used by looking at
22325 the filename extension. Files with an unrecognized filename extension
22326 are always treated as a @value{GDBN} Command Files.
22327 @xref{Command Files,, Command files}.
22329 You can control how @value{GDBN} evaluates these files with the following
22333 @kindex set script-extension
22334 @kindex show script-extension
22335 @item set script-extension off
22336 All scripts are always evaluated as @value{GDBN} Command Files.
22338 @item set script-extension soft
22339 The debugger determines the scripting language based on filename
22340 extension. If this scripting language is supported, @value{GDBN}
22341 evaluates the script using that language. Otherwise, it evaluates
22342 the file as a @value{GDBN} Command File.
22344 @item set script-extension strict
22345 The debugger determines the scripting language based on filename
22346 extension, and evaluates the script using that language. If the
22347 language is not supported, then the evaluation fails.
22349 @item show script-extension
22350 Display the current value of the @code{script-extension} option.
22355 * Sequences:: Canned Sequences of Commands
22356 * Python:: Scripting @value{GDBN} using Python
22357 * Aliases:: Creating new spellings of existing commands
22361 @section Canned Sequences of Commands
22363 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
22364 Command Lists}), @value{GDBN} provides two ways to store sequences of
22365 commands for execution as a unit: user-defined commands and command
22369 * Define:: How to define your own commands
22370 * Hooks:: Hooks for user-defined commands
22371 * Command Files:: How to write scripts of commands to be stored in a file
22372 * Output:: Commands for controlled output
22376 @subsection User-defined Commands
22378 @cindex user-defined command
22379 @cindex arguments, to user-defined commands
22380 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
22381 which you assign a new name as a command. This is done with the
22382 @code{define} command. User commands may accept up to 10 arguments
22383 separated by whitespace. Arguments are accessed within the user command
22384 via @code{$arg0@dots{}$arg9}. A trivial example:
22388 print $arg0 + $arg1 + $arg2
22393 To execute the command use:
22400 This defines the command @code{adder}, which prints the sum of
22401 its three arguments. Note the arguments are text substitutions, so they may
22402 reference variables, use complex expressions, or even perform inferior
22405 @cindex argument count in user-defined commands
22406 @cindex how many arguments (user-defined commands)
22407 In addition, @code{$argc} may be used to find out how many arguments have
22408 been passed. This expands to a number in the range 0@dots{}10.
22413 print $arg0 + $arg1
22416 print $arg0 + $arg1 + $arg2
22424 @item define @var{commandname}
22425 Define a command named @var{commandname}. If there is already a command
22426 by that name, you are asked to confirm that you want to redefine it.
22427 @var{commandname} may be a bare command name consisting of letters,
22428 numbers, dashes, and underscores. It may also start with any predefined
22429 prefix command. For example, @samp{define target my-target} creates
22430 a user-defined @samp{target my-target} command.
22432 The definition of the command is made up of other @value{GDBN} command lines,
22433 which are given following the @code{define} command. The end of these
22434 commands is marked by a line containing @code{end}.
22437 @kindex end@r{ (user-defined commands)}
22438 @item document @var{commandname}
22439 Document the user-defined command @var{commandname}, so that it can be
22440 accessed by @code{help}. The command @var{commandname} must already be
22441 defined. This command reads lines of documentation just as @code{define}
22442 reads the lines of the command definition, ending with @code{end}.
22443 After the @code{document} command is finished, @code{help} on command
22444 @var{commandname} displays the documentation you have written.
22446 You may use the @code{document} command again to change the
22447 documentation of a command. Redefining the command with @code{define}
22448 does not change the documentation.
22450 @kindex dont-repeat
22451 @cindex don't repeat command
22453 Used inside a user-defined command, this tells @value{GDBN} that this
22454 command should not be repeated when the user hits @key{RET}
22455 (@pxref{Command Syntax, repeat last command}).
22457 @kindex help user-defined
22458 @item help user-defined
22459 List all user-defined commands and all python commands defined in class
22460 COMAND_USER. The first line of the documentation or docstring is
22465 @itemx show user @var{commandname}
22466 Display the @value{GDBN} commands used to define @var{commandname} (but
22467 not its documentation). If no @var{commandname} is given, display the
22468 definitions for all user-defined commands.
22469 This does not work for user-defined python commands.
22471 @cindex infinite recursion in user-defined commands
22472 @kindex show max-user-call-depth
22473 @kindex set max-user-call-depth
22474 @item show max-user-call-depth
22475 @itemx set max-user-call-depth
22476 The value of @code{max-user-call-depth} controls how many recursion
22477 levels are allowed in user-defined commands before @value{GDBN} suspects an
22478 infinite recursion and aborts the command.
22479 This does not apply to user-defined python commands.
22482 In addition to the above commands, user-defined commands frequently
22483 use control flow commands, described in @ref{Command Files}.
22485 When user-defined commands are executed, the
22486 commands of the definition are not printed. An error in any command
22487 stops execution of the user-defined command.
22489 If used interactively, commands that would ask for confirmation proceed
22490 without asking when used inside a user-defined command. Many @value{GDBN}
22491 commands that normally print messages to say what they are doing omit the
22492 messages when used in a user-defined command.
22495 @subsection User-defined Command Hooks
22496 @cindex command hooks
22497 @cindex hooks, for commands
22498 @cindex hooks, pre-command
22501 You may define @dfn{hooks}, which are a special kind of user-defined
22502 command. Whenever you run the command @samp{foo}, if the user-defined
22503 command @samp{hook-foo} exists, it is executed (with no arguments)
22504 before that command.
22506 @cindex hooks, post-command
22508 A hook may also be defined which is run after the command you executed.
22509 Whenever you run the command @samp{foo}, if the user-defined command
22510 @samp{hookpost-foo} exists, it is executed (with no arguments) after
22511 that command. Post-execution hooks may exist simultaneously with
22512 pre-execution hooks, for the same command.
22514 It is valid for a hook to call the command which it hooks. If this
22515 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
22517 @c It would be nice if hookpost could be passed a parameter indicating
22518 @c if the command it hooks executed properly or not. FIXME!
22520 @kindex stop@r{, a pseudo-command}
22521 In addition, a pseudo-command, @samp{stop} exists. Defining
22522 (@samp{hook-stop}) makes the associated commands execute every time
22523 execution stops in your program: before breakpoint commands are run,
22524 displays are printed, or the stack frame is printed.
22526 For example, to ignore @code{SIGALRM} signals while
22527 single-stepping, but treat them normally during normal execution,
22532 handle SIGALRM nopass
22536 handle SIGALRM pass
22539 define hook-continue
22540 handle SIGALRM pass
22544 As a further example, to hook at the beginning and end of the @code{echo}
22545 command, and to add extra text to the beginning and end of the message,
22553 define hookpost-echo
22557 (@value{GDBP}) echo Hello World
22558 <<<---Hello World--->>>
22563 You can define a hook for any single-word command in @value{GDBN}, but
22564 not for command aliases; you should define a hook for the basic command
22565 name, e.g.@: @code{backtrace} rather than @code{bt}.
22566 @c FIXME! So how does Joe User discover whether a command is an alias
22568 You can hook a multi-word command by adding @code{hook-} or
22569 @code{hookpost-} to the last word of the command, e.g.@:
22570 @samp{define target hook-remote} to add a hook to @samp{target remote}.
22572 If an error occurs during the execution of your hook, execution of
22573 @value{GDBN} commands stops and @value{GDBN} issues a prompt
22574 (before the command that you actually typed had a chance to run).
22576 If you try to define a hook which does not match any known command, you
22577 get a warning from the @code{define} command.
22579 @node Command Files
22580 @subsection Command Files
22582 @cindex command files
22583 @cindex scripting commands
22584 A command file for @value{GDBN} is a text file made of lines that are
22585 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
22586 also be included. An empty line in a command file does nothing; it
22587 does not mean to repeat the last command, as it would from the
22590 You can request the execution of a command file with the @code{source}
22591 command. Note that the @code{source} command is also used to evaluate
22592 scripts that are not Command Files. The exact behavior can be configured
22593 using the @code{script-extension} setting.
22594 @xref{Extending GDB,, Extending GDB}.
22598 @cindex execute commands from a file
22599 @item source [-s] [-v] @var{filename}
22600 Execute the command file @var{filename}.
22603 The lines in a command file are generally executed sequentially,
22604 unless the order of execution is changed by one of the
22605 @emph{flow-control commands} described below. The commands are not
22606 printed as they are executed. An error in any command terminates
22607 execution of the command file and control is returned to the console.
22609 @value{GDBN} first searches for @var{filename} in the current directory.
22610 If the file is not found there, and @var{filename} does not specify a
22611 directory, then @value{GDBN} also looks for the file on the source search path
22612 (specified with the @samp{directory} command);
22613 except that @file{$cdir} is not searched because the compilation directory
22614 is not relevant to scripts.
22616 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
22617 on the search path even if @var{filename} specifies a directory.
22618 The search is done by appending @var{filename} to each element of the
22619 search path. So, for example, if @var{filename} is @file{mylib/myscript}
22620 and the search path contains @file{/home/user} then @value{GDBN} will
22621 look for the script @file{/home/user/mylib/myscript}.
22622 The search is also done if @var{filename} is an absolute path.
22623 For example, if @var{filename} is @file{/tmp/myscript} and
22624 the search path contains @file{/home/user} then @value{GDBN} will
22625 look for the script @file{/home/user/tmp/myscript}.
22626 For DOS-like systems, if @var{filename} contains a drive specification,
22627 it is stripped before concatenation. For example, if @var{filename} is
22628 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
22629 will look for the script @file{c:/tmp/myscript}.
22631 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
22632 each command as it is executed. The option must be given before
22633 @var{filename}, and is interpreted as part of the filename anywhere else.
22635 Commands that would ask for confirmation if used interactively proceed
22636 without asking when used in a command file. Many @value{GDBN} commands that
22637 normally print messages to say what they are doing omit the messages
22638 when called from command files.
22640 @value{GDBN} also accepts command input from standard input. In this
22641 mode, normal output goes to standard output and error output goes to
22642 standard error. Errors in a command file supplied on standard input do
22643 not terminate execution of the command file---execution continues with
22647 gdb < cmds > log 2>&1
22650 (The syntax above will vary depending on the shell used.) This example
22651 will execute commands from the file @file{cmds}. All output and errors
22652 would be directed to @file{log}.
22654 Since commands stored on command files tend to be more general than
22655 commands typed interactively, they frequently need to deal with
22656 complicated situations, such as different or unexpected values of
22657 variables and symbols, changes in how the program being debugged is
22658 built, etc. @value{GDBN} provides a set of flow-control commands to
22659 deal with these complexities. Using these commands, you can write
22660 complex scripts that loop over data structures, execute commands
22661 conditionally, etc.
22668 This command allows to include in your script conditionally executed
22669 commands. The @code{if} command takes a single argument, which is an
22670 expression to evaluate. It is followed by a series of commands that
22671 are executed only if the expression is true (its value is nonzero).
22672 There can then optionally be an @code{else} line, followed by a series
22673 of commands that are only executed if the expression was false. The
22674 end of the list is marked by a line containing @code{end}.
22678 This command allows to write loops. Its syntax is similar to
22679 @code{if}: the command takes a single argument, which is an expression
22680 to evaluate, and must be followed by the commands to execute, one per
22681 line, terminated by an @code{end}. These commands are called the
22682 @dfn{body} of the loop. The commands in the body of @code{while} are
22683 executed repeatedly as long as the expression evaluates to true.
22687 This command exits the @code{while} loop in whose body it is included.
22688 Execution of the script continues after that @code{while}s @code{end}
22691 @kindex loop_continue
22692 @item loop_continue
22693 This command skips the execution of the rest of the body of commands
22694 in the @code{while} loop in whose body it is included. Execution
22695 branches to the beginning of the @code{while} loop, where it evaluates
22696 the controlling expression.
22698 @kindex end@r{ (if/else/while commands)}
22700 Terminate the block of commands that are the body of @code{if},
22701 @code{else}, or @code{while} flow-control commands.
22706 @subsection Commands for Controlled Output
22708 During the execution of a command file or a user-defined command, normal
22709 @value{GDBN} output is suppressed; the only output that appears is what is
22710 explicitly printed by the commands in the definition. This section
22711 describes three commands useful for generating exactly the output you
22716 @item echo @var{text}
22717 @c I do not consider backslash-space a standard C escape sequence
22718 @c because it is not in ANSI.
22719 Print @var{text}. Nonprinting characters can be included in
22720 @var{text} using C escape sequences, such as @samp{\n} to print a
22721 newline. @strong{No newline is printed unless you specify one.}
22722 In addition to the standard C escape sequences, a backslash followed
22723 by a space stands for a space. This is useful for displaying a
22724 string with spaces at the beginning or the end, since leading and
22725 trailing spaces are otherwise trimmed from all arguments.
22726 To print @samp{@w{ }and foo =@w{ }}, use the command
22727 @samp{echo \@w{ }and foo = \@w{ }}.
22729 A backslash at the end of @var{text} can be used, as in C, to continue
22730 the command onto subsequent lines. For example,
22733 echo This is some text\n\
22734 which is continued\n\
22735 onto several lines.\n
22738 produces the same output as
22741 echo This is some text\n
22742 echo which is continued\n
22743 echo onto several lines.\n
22747 @item output @var{expression}
22748 Print the value of @var{expression} and nothing but that value: no
22749 newlines, no @samp{$@var{nn} = }. The value is not entered in the
22750 value history either. @xref{Expressions, ,Expressions}, for more information
22753 @item output/@var{fmt} @var{expression}
22754 Print the value of @var{expression} in format @var{fmt}. You can use
22755 the same formats as for @code{print}. @xref{Output Formats,,Output
22756 Formats}, for more information.
22759 @item printf @var{template}, @var{expressions}@dots{}
22760 Print the values of one or more @var{expressions} under the control of
22761 the string @var{template}. To print several values, make
22762 @var{expressions} be a comma-separated list of individual expressions,
22763 which may be either numbers or pointers. Their values are printed as
22764 specified by @var{template}, exactly as a C program would do by
22765 executing the code below:
22768 printf (@var{template}, @var{expressions}@dots{});
22771 As in @code{C} @code{printf}, ordinary characters in @var{template}
22772 are printed verbatim, while @dfn{conversion specification} introduced
22773 by the @samp{%} character cause subsequent @var{expressions} to be
22774 evaluated, their values converted and formatted according to type and
22775 style information encoded in the conversion specifications, and then
22778 For example, you can print two values in hex like this:
22781 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
22784 @code{printf} supports all the standard @code{C} conversion
22785 specifications, including the flags and modifiers between the @samp{%}
22786 character and the conversion letter, with the following exceptions:
22790 The argument-ordering modifiers, such as @samp{2$}, are not supported.
22793 The modifier @samp{*} is not supported for specifying precision or
22797 The @samp{'} flag (for separation of digits into groups according to
22798 @code{LC_NUMERIC'}) is not supported.
22801 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
22805 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
22808 The conversion letters @samp{a} and @samp{A} are not supported.
22812 Note that the @samp{ll} type modifier is supported only if the
22813 underlying @code{C} implementation used to build @value{GDBN} supports
22814 the @code{long long int} type, and the @samp{L} type modifier is
22815 supported only if @code{long double} type is available.
22817 As in @code{C}, @code{printf} supports simple backslash-escape
22818 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
22819 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
22820 single character. Octal and hexadecimal escape sequences are not
22823 Additionally, @code{printf} supports conversion specifications for DFP
22824 (@dfn{Decimal Floating Point}) types using the following length modifiers
22825 together with a floating point specifier.
22830 @samp{H} for printing @code{Decimal32} types.
22833 @samp{D} for printing @code{Decimal64} types.
22836 @samp{DD} for printing @code{Decimal128} types.
22839 If the underlying @code{C} implementation used to build @value{GDBN} has
22840 support for the three length modifiers for DFP types, other modifiers
22841 such as width and precision will also be available for @value{GDBN} to use.
22843 In case there is no such @code{C} support, no additional modifiers will be
22844 available and the value will be printed in the standard way.
22846 Here's an example of printing DFP types using the above conversion letters:
22848 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
22852 @item eval @var{template}, @var{expressions}@dots{}
22853 Convert the values of one or more @var{expressions} under the control of
22854 the string @var{template} to a command line, and call it.
22859 @section Scripting @value{GDBN} using Python
22860 @cindex python scripting
22861 @cindex scripting with python
22863 You can script @value{GDBN} using the @uref{http://www.python.org/,
22864 Python programming language}. This feature is available only if
22865 @value{GDBN} was configured using @option{--with-python}.
22867 @cindex python directory
22868 Python scripts used by @value{GDBN} should be installed in
22869 @file{@var{data-directory}/python}, where @var{data-directory} is
22870 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
22871 This directory, known as the @dfn{python directory},
22872 is automatically added to the Python Search Path in order to allow
22873 the Python interpreter to locate all scripts installed at this location.
22875 Additionally, @value{GDBN} commands and convenience functions which
22876 are written in Python and are located in the
22877 @file{@var{data-directory}/python/gdb/command} or
22878 @file{@var{data-directory}/python/gdb/function} directories are
22879 automatically imported when @value{GDBN} starts.
22882 * Python Commands:: Accessing Python from @value{GDBN}.
22883 * Python API:: Accessing @value{GDBN} from Python.
22884 * Python Auto-loading:: Automatically loading Python code.
22885 * Python modules:: Python modules provided by @value{GDBN}.
22888 @node Python Commands
22889 @subsection Python Commands
22890 @cindex python commands
22891 @cindex commands to access python
22893 @value{GDBN} provides two commands for accessing the Python interpreter,
22894 and one related setting:
22897 @kindex python-interactive
22899 @item python-interactive @r{[}@var{command}@r{]}
22900 @itemx pi @r{[}@var{command}@r{]}
22901 Without an argument, the @code{python-interactive} command can be used
22902 to start an interactive Python prompt. To return to @value{GDBN},
22903 type the @code{EOF} character (e.g., @kbd{Ctrl-D} on an empty prompt).
22905 Alternatively, a single-line Python command can be given as an
22906 argument and evaluated. If the command is an expression, the result
22907 will be printed; otherwise, nothing will be printed. For example:
22910 (@value{GDBP}) python-interactive 2 + 3
22916 @item python @r{[}@var{command}@r{]}
22917 @itemx py @r{[}@var{command}@r{]}
22918 The @code{python} command can be used to evaluate Python code.
22920 If given an argument, the @code{python} command will evaluate the
22921 argument as a Python command. For example:
22924 (@value{GDBP}) python print 23
22928 If you do not provide an argument to @code{python}, it will act as a
22929 multi-line command, like @code{define}. In this case, the Python
22930 script is made up of subsequent command lines, given after the
22931 @code{python} command. This command list is terminated using a line
22932 containing @code{end}. For example:
22935 (@value{GDBP}) python
22937 End with a line saying just "end".
22943 @kindex set python print-stack
22944 @item set python print-stack
22945 By default, @value{GDBN} will print only the message component of a
22946 Python exception when an error occurs in a Python script. This can be
22947 controlled using @code{set python print-stack}: if @code{full}, then
22948 full Python stack printing is enabled; if @code{none}, then Python stack
22949 and message printing is disabled; if @code{message}, the default, only
22950 the message component of the error is printed.
22953 It is also possible to execute a Python script from the @value{GDBN}
22957 @item source @file{script-name}
22958 The script name must end with @samp{.py} and @value{GDBN} must be configured
22959 to recognize the script language based on filename extension using
22960 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
22962 @item python execfile ("script-name")
22963 This method is based on the @code{execfile} Python built-in function,
22964 and thus is always available.
22968 @subsection Python API
22970 @cindex programming in python
22972 @cindex python stdout
22973 @cindex python pagination
22974 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
22975 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
22976 A Python program which outputs to one of these streams may have its
22977 output interrupted by the user (@pxref{Screen Size}). In this
22978 situation, a Python @code{KeyboardInterrupt} exception is thrown.
22981 * Basic Python:: Basic Python Functions.
22982 * Exception Handling:: How Python exceptions are translated.
22983 * Values From Inferior:: Python representation of values.
22984 * Types In Python:: Python representation of types.
22985 * Pretty Printing API:: Pretty-printing values.
22986 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
22987 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
22988 * Type Printing API:: Pretty-printing types.
22989 * Inferiors In Python:: Python representation of inferiors (processes)
22990 * Events In Python:: Listening for events from @value{GDBN}.
22991 * Threads In Python:: Accessing inferior threads from Python.
22992 * Commands In Python:: Implementing new commands in Python.
22993 * Parameters In Python:: Adding new @value{GDBN} parameters.
22994 * Functions In Python:: Writing new convenience functions.
22995 * Progspaces In Python:: Program spaces.
22996 * Objfiles In Python:: Object files.
22997 * Frames In Python:: Accessing inferior stack frames from Python.
22998 * Blocks In Python:: Accessing frame blocks from Python.
22999 * Symbols In Python:: Python representation of symbols.
23000 * Symbol Tables In Python:: Python representation of symbol tables.
23001 * Breakpoints In Python:: Manipulating breakpoints using Python.
23002 * Finish Breakpoints in Python:: Setting Breakpoints on function return
23004 * Lazy Strings In Python:: Python representation of lazy strings.
23005 * Architectures In Python:: Python representation of architectures.
23009 @subsubsection Basic Python
23011 @cindex python functions
23012 @cindex python module
23014 @value{GDBN} introduces a new Python module, named @code{gdb}. All
23015 methods and classes added by @value{GDBN} are placed in this module.
23016 @value{GDBN} automatically @code{import}s the @code{gdb} module for
23017 use in all scripts evaluated by the @code{python} command.
23019 @findex gdb.PYTHONDIR
23020 @defvar gdb.PYTHONDIR
23021 A string containing the python directory (@pxref{Python}).
23024 @findex gdb.execute
23025 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
23026 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
23027 If a GDB exception happens while @var{command} runs, it is
23028 translated as described in @ref{Exception Handling,,Exception Handling}.
23030 @var{from_tty} specifies whether @value{GDBN} ought to consider this
23031 command as having originated from the user invoking it interactively.
23032 It must be a boolean value. If omitted, it defaults to @code{False}.
23034 By default, any output produced by @var{command} is sent to
23035 @value{GDBN}'s standard output. If the @var{to_string} parameter is
23036 @code{True}, then output will be collected by @code{gdb.execute} and
23037 returned as a string. The default is @code{False}, in which case the
23038 return value is @code{None}. If @var{to_string} is @code{True}, the
23039 @value{GDBN} virtual terminal will be temporarily set to unlimited width
23040 and height, and its pagination will be disabled; @pxref{Screen Size}.
23043 @findex gdb.breakpoints
23044 @defun gdb.breakpoints ()
23045 Return a sequence holding all of @value{GDBN}'s breakpoints.
23046 @xref{Breakpoints In Python}, for more information.
23049 @findex gdb.parameter
23050 @defun gdb.parameter (parameter)
23051 Return the value of a @value{GDBN} parameter. @var{parameter} is a
23052 string naming the parameter to look up; @var{parameter} may contain
23053 spaces if the parameter has a multi-part name. For example,
23054 @samp{print object} is a valid parameter name.
23056 If the named parameter does not exist, this function throws a
23057 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
23058 parameter's value is converted to a Python value of the appropriate
23059 type, and returned.
23062 @findex gdb.history
23063 @defun gdb.history (number)
23064 Return a value from @value{GDBN}'s value history (@pxref{Value
23065 History}). @var{number} indicates which history element to return.
23066 If @var{number} is negative, then @value{GDBN} will take its absolute value
23067 and count backward from the last element (i.e., the most recent element) to
23068 find the value to return. If @var{number} is zero, then @value{GDBN} will
23069 return the most recent element. If the element specified by @var{number}
23070 doesn't exist in the value history, a @code{gdb.error} exception will be
23073 If no exception is raised, the return value is always an instance of
23074 @code{gdb.Value} (@pxref{Values From Inferior}).
23077 @findex gdb.parse_and_eval
23078 @defun gdb.parse_and_eval (expression)
23079 Parse @var{expression} as an expression in the current language,
23080 evaluate it, and return the result as a @code{gdb.Value}.
23081 @var{expression} must be a string.
23083 This function can be useful when implementing a new command
23084 (@pxref{Commands In Python}), as it provides a way to parse the
23085 command's argument as an expression. It is also useful simply to
23086 compute values, for example, it is the only way to get the value of a
23087 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
23090 @findex gdb.find_pc_line
23091 @defun gdb.find_pc_line (pc)
23092 Return the @code{gdb.Symtab_and_line} object corresponding to the
23093 @var{pc} value. @xref{Symbol Tables In Python}. If an invalid
23094 value of @var{pc} is passed as an argument, then the @code{symtab} and
23095 @code{line} attributes of the returned @code{gdb.Symtab_and_line} object
23096 will be @code{None} and 0 respectively.
23099 @findex gdb.post_event
23100 @defun gdb.post_event (event)
23101 Put @var{event}, a callable object taking no arguments, into
23102 @value{GDBN}'s internal event queue. This callable will be invoked at
23103 some later point, during @value{GDBN}'s event processing. Events
23104 posted using @code{post_event} will be run in the order in which they
23105 were posted; however, there is no way to know when they will be
23106 processed relative to other events inside @value{GDBN}.
23108 @value{GDBN} is not thread-safe. If your Python program uses multiple
23109 threads, you must be careful to only call @value{GDBN}-specific
23110 functions in the main @value{GDBN} thread. @code{post_event} ensures
23114 (@value{GDBP}) python
23118 > def __init__(self, message):
23119 > self.message = message;
23120 > def __call__(self):
23121 > gdb.write(self.message)
23123 >class MyThread1 (threading.Thread):
23125 > gdb.post_event(Writer("Hello "))
23127 >class MyThread2 (threading.Thread):
23129 > gdb.post_event(Writer("World\n"))
23131 >MyThread1().start()
23132 >MyThread2().start()
23134 (@value{GDBP}) Hello World
23139 @defun gdb.write (string @r{[}, stream{]})
23140 Print a string to @value{GDBN}'s paginated output stream. The
23141 optional @var{stream} determines the stream to print to. The default
23142 stream is @value{GDBN}'s standard output stream. Possible stream
23149 @value{GDBN}'s standard output stream.
23154 @value{GDBN}'s standard error stream.
23159 @value{GDBN}'s log stream (@pxref{Logging Output}).
23162 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
23163 call this function and will automatically direct the output to the
23168 @defun gdb.flush ()
23169 Flush the buffer of a @value{GDBN} paginated stream so that the
23170 contents are displayed immediately. @value{GDBN} will flush the
23171 contents of a stream automatically when it encounters a newline in the
23172 buffer. The optional @var{stream} determines the stream to flush. The
23173 default stream is @value{GDBN}'s standard output stream. Possible
23180 @value{GDBN}'s standard output stream.
23185 @value{GDBN}'s standard error stream.
23190 @value{GDBN}'s log stream (@pxref{Logging Output}).
23194 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
23195 call this function for the relevant stream.
23198 @findex gdb.target_charset
23199 @defun gdb.target_charset ()
23200 Return the name of the current target character set (@pxref{Character
23201 Sets}). This differs from @code{gdb.parameter('target-charset')} in
23202 that @samp{auto} is never returned.
23205 @findex gdb.target_wide_charset
23206 @defun gdb.target_wide_charset ()
23207 Return the name of the current target wide character set
23208 (@pxref{Character Sets}). This differs from
23209 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
23213 @findex gdb.solib_name
23214 @defun gdb.solib_name (address)
23215 Return the name of the shared library holding the given @var{address}
23216 as a string, or @code{None}.
23219 @findex gdb.decode_line
23220 @defun gdb.decode_line @r{[}expression@r{]}
23221 Return locations of the line specified by @var{expression}, or of the
23222 current line if no argument was given. This function returns a Python
23223 tuple containing two elements. The first element contains a string
23224 holding any unparsed section of @var{expression} (or @code{None} if
23225 the expression has been fully parsed). The second element contains
23226 either @code{None} or another tuple that contains all the locations
23227 that match the expression represented as @code{gdb.Symtab_and_line}
23228 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
23229 provided, it is decoded the way that @value{GDBN}'s inbuilt
23230 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
23233 @defun gdb.prompt_hook (current_prompt)
23234 @anchor{prompt_hook}
23236 If @var{prompt_hook} is callable, @value{GDBN} will call the method
23237 assigned to this operation before a prompt is displayed by
23240 The parameter @code{current_prompt} contains the current @value{GDBN}
23241 prompt. This method must return a Python string, or @code{None}. If
23242 a string is returned, the @value{GDBN} prompt will be set to that
23243 string. If @code{None} is returned, @value{GDBN} will continue to use
23244 the current prompt.
23246 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
23247 such as those used by readline for command input, and annotation
23248 related prompts are prohibited from being changed.
23251 @node Exception Handling
23252 @subsubsection Exception Handling
23253 @cindex python exceptions
23254 @cindex exceptions, python
23256 When executing the @code{python} command, Python exceptions
23257 uncaught within the Python code are translated to calls to
23258 @value{GDBN} error-reporting mechanism. If the command that called
23259 @code{python} does not handle the error, @value{GDBN} will
23260 terminate it and print an error message containing the Python
23261 exception name, the associated value, and the Python call stack
23262 backtrace at the point where the exception was raised. Example:
23265 (@value{GDBP}) python print foo
23266 Traceback (most recent call last):
23267 File "<string>", line 1, in <module>
23268 NameError: name 'foo' is not defined
23271 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
23272 Python code are converted to Python exceptions. The type of the
23273 Python exception depends on the error.
23277 This is the base class for most exceptions generated by @value{GDBN}.
23278 It is derived from @code{RuntimeError}, for compatibility with earlier
23279 versions of @value{GDBN}.
23281 If an error occurring in @value{GDBN} does not fit into some more
23282 specific category, then the generated exception will have this type.
23284 @item gdb.MemoryError
23285 This is a subclass of @code{gdb.error} which is thrown when an
23286 operation tried to access invalid memory in the inferior.
23288 @item KeyboardInterrupt
23289 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
23290 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
23293 In all cases, your exception handler will see the @value{GDBN} error
23294 message as its value and the Python call stack backtrace at the Python
23295 statement closest to where the @value{GDBN} error occured as the
23298 @findex gdb.GdbError
23299 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
23300 it is useful to be able to throw an exception that doesn't cause a
23301 traceback to be printed. For example, the user may have invoked the
23302 command incorrectly. Use the @code{gdb.GdbError} exception
23303 to handle this case. Example:
23307 >class HelloWorld (gdb.Command):
23308 > """Greet the whole world."""
23309 > def __init__ (self):
23310 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
23311 > def invoke (self, args, from_tty):
23312 > argv = gdb.string_to_argv (args)
23313 > if len (argv) != 0:
23314 > raise gdb.GdbError ("hello-world takes no arguments")
23315 > print "Hello, World!"
23318 (gdb) hello-world 42
23319 hello-world takes no arguments
23322 @node Values From Inferior
23323 @subsubsection Values From Inferior
23324 @cindex values from inferior, with Python
23325 @cindex python, working with values from inferior
23327 @cindex @code{gdb.Value}
23328 @value{GDBN} provides values it obtains from the inferior program in
23329 an object of type @code{gdb.Value}. @value{GDBN} uses this object
23330 for its internal bookkeeping of the inferior's values, and for
23331 fetching values when necessary.
23333 Inferior values that are simple scalars can be used directly in
23334 Python expressions that are valid for the value's data type. Here's
23335 an example for an integer or floating-point value @code{some_val}:
23342 As result of this, @code{bar} will also be a @code{gdb.Value} object
23343 whose values are of the same type as those of @code{some_val}.
23345 Inferior values that are structures or instances of some class can
23346 be accessed using the Python @dfn{dictionary syntax}. For example, if
23347 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
23348 can access its @code{foo} element with:
23351 bar = some_val['foo']
23354 Again, @code{bar} will also be a @code{gdb.Value} object.
23356 A @code{gdb.Value} that represents a function can be executed via
23357 inferior function call. Any arguments provided to the call must match
23358 the function's prototype, and must be provided in the order specified
23361 For example, @code{some_val} is a @code{gdb.Value} instance
23362 representing a function that takes two integers as arguments. To
23363 execute this function, call it like so:
23366 result = some_val (10,20)
23369 Any values returned from a function call will be stored as a
23372 The following attributes are provided:
23374 @defvar Value.address
23375 If this object is addressable, this read-only attribute holds a
23376 @code{gdb.Value} object representing the address. Otherwise,
23377 this attribute holds @code{None}.
23380 @cindex optimized out value in Python
23381 @defvar Value.is_optimized_out
23382 This read-only boolean attribute is true if the compiler optimized out
23383 this value, thus it is not available for fetching from the inferior.
23387 The type of this @code{gdb.Value}. The value of this attribute is a
23388 @code{gdb.Type} object (@pxref{Types In Python}).
23391 @defvar Value.dynamic_type
23392 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
23393 type information (@acronym{RTTI}) to determine the dynamic type of the
23394 value. If this value is of class type, it will return the class in
23395 which the value is embedded, if any. If this value is of pointer or
23396 reference to a class type, it will compute the dynamic type of the
23397 referenced object, and return a pointer or reference to that type,
23398 respectively. In all other cases, it will return the value's static
23401 Note that this feature will only work when debugging a C@t{++} program
23402 that includes @acronym{RTTI} for the object in question. Otherwise,
23403 it will just return the static type of the value as in @kbd{ptype foo}
23404 (@pxref{Symbols, ptype}).
23407 @defvar Value.is_lazy
23408 The value of this read-only boolean attribute is @code{True} if this
23409 @code{gdb.Value} has not yet been fetched from the inferior.
23410 @value{GDBN} does not fetch values until necessary, for efficiency.
23414 myval = gdb.parse_and_eval ('somevar')
23417 The value of @code{somevar} is not fetched at this time. It will be
23418 fetched when the value is needed, or when the @code{fetch_lazy}
23422 The following methods are provided:
23424 @defun Value.__init__ (@var{val})
23425 Many Python values can be converted directly to a @code{gdb.Value} via
23426 this object initializer. Specifically:
23429 @item Python boolean
23430 A Python boolean is converted to the boolean type from the current
23433 @item Python integer
23434 A Python integer is converted to the C @code{long} type for the
23435 current architecture.
23438 A Python long is converted to the C @code{long long} type for the
23439 current architecture.
23442 A Python float is converted to the C @code{double} type for the
23443 current architecture.
23445 @item Python string
23446 A Python string is converted to a target string, using the current
23449 @item @code{gdb.Value}
23450 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
23452 @item @code{gdb.LazyString}
23453 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
23454 Python}), then the lazy string's @code{value} method is called, and
23455 its result is used.
23459 @defun Value.cast (type)
23460 Return a new instance of @code{gdb.Value} that is the result of
23461 casting this instance to the type described by @var{type}, which must
23462 be a @code{gdb.Type} object. If the cast cannot be performed for some
23463 reason, this method throws an exception.
23466 @defun Value.dereference ()
23467 For pointer data types, this method returns a new @code{gdb.Value} object
23468 whose contents is the object pointed to by the pointer. For example, if
23469 @code{foo} is a C pointer to an @code{int}, declared in your C program as
23476 then you can use the corresponding @code{gdb.Value} to access what
23477 @code{foo} points to like this:
23480 bar = foo.dereference ()
23483 The result @code{bar} will be a @code{gdb.Value} object holding the
23484 value pointed to by @code{foo}.
23486 A similar function @code{Value.referenced_value} exists which also
23487 returns @code{gdb.Value} objects corresonding to the values pointed to
23488 by pointer values (and additionally, values referenced by reference
23489 values). However, the behavior of @code{Value.dereference}
23490 differs from @code{Value.referenced_value} by the fact that the
23491 behavior of @code{Value.dereference} is identical to applying the C
23492 unary operator @code{*} on a given value. For example, consider a
23493 reference to a pointer @code{ptrref}, declared in your C@t{++} program
23497 typedef int *intptr;
23501 intptr &ptrref = ptr;
23504 Though @code{ptrref} is a reference value, one can apply the method
23505 @code{Value.dereference} to the @code{gdb.Value} object corresponding
23506 to it and obtain a @code{gdb.Value} which is identical to that
23507 corresponding to @code{val}. However, if you apply the method
23508 @code{Value.referenced_value}, the result would be a @code{gdb.Value}
23509 object identical to that corresponding to @code{ptr}.
23512 py_ptrref = gdb.parse_and_eval ("ptrref")
23513 py_val = py_ptrref.dereference ()
23514 py_ptr = py_ptrref.referenced_value ()
23517 The @code{gdb.Value} object @code{py_val} is identical to that
23518 corresponding to @code{val}, and @code{py_ptr} is identical to that
23519 corresponding to @code{ptr}. In general, @code{Value.dereference} can
23520 be applied whenever the C unary operator @code{*} can be applied
23521 to the corresponding C value. For those cases where applying both
23522 @code{Value.dereference} and @code{Value.referenced_value} is allowed,
23523 the results obtained need not be identical (as we have seen in the above
23524 example). The results are however identical when applied on
23525 @code{gdb.Value} objects corresponding to pointers (@code{gdb.Value}
23526 objects with type code @code{TYPE_CODE_PTR}) in a C/C@t{++} program.
23529 @defun Value.referenced_value ()
23530 For pointer or reference data types, this method returns a new
23531 @code{gdb.Value} object corresponding to the value referenced by the
23532 pointer/reference value. For pointer data types,
23533 @code{Value.dereference} and @code{Value.referenced_value} produce
23534 identical results. The difference between these methods is that
23535 @code{Value.dereference} cannot get the values referenced by reference
23536 values. For example, consider a reference to an @code{int}, declared
23537 in your C@t{++} program as
23545 then applying @code{Value.dereference} to the @code{gdb.Value} object
23546 corresponding to @code{ref} will result in an error, while applying
23547 @code{Value.referenced_value} will result in a @code{gdb.Value} object
23548 identical to that corresponding to @code{val}.
23551 py_ref = gdb.parse_and_eval ("ref")
23552 er_ref = py_ref.dereference () # Results in error
23553 py_val = py_ref.referenced_value () # Returns the referenced value
23556 The @code{gdb.Value} object @code{py_val} is identical to that
23557 corresponding to @code{val}.
23560 @defun Value.dynamic_cast (type)
23561 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
23562 operator were used. Consult a C@t{++} reference for details.
23565 @defun Value.reinterpret_cast (type)
23566 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
23567 operator were used. Consult a C@t{++} reference for details.
23570 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
23571 If this @code{gdb.Value} represents a string, then this method
23572 converts the contents to a Python string. Otherwise, this method will
23573 throw an exception.
23575 Strings are recognized in a language-specific way; whether a given
23576 @code{gdb.Value} represents a string is determined by the current
23579 For C-like languages, a value is a string if it is a pointer to or an
23580 array of characters or ints. The string is assumed to be terminated
23581 by a zero of the appropriate width. However if the optional length
23582 argument is given, the string will be converted to that given length,
23583 ignoring any embedded zeros that the string may contain.
23585 If the optional @var{encoding} argument is given, it must be a string
23586 naming the encoding of the string in the @code{gdb.Value}, such as
23587 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
23588 the same encodings as the corresponding argument to Python's
23589 @code{string.decode} method, and the Python codec machinery will be used
23590 to convert the string. If @var{encoding} is not given, or if
23591 @var{encoding} is the empty string, then either the @code{target-charset}
23592 (@pxref{Character Sets}) will be used, or a language-specific encoding
23593 will be used, if the current language is able to supply one.
23595 The optional @var{errors} argument is the same as the corresponding
23596 argument to Python's @code{string.decode} method.
23598 If the optional @var{length} argument is given, the string will be
23599 fetched and converted to the given length.
23602 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
23603 If this @code{gdb.Value} represents a string, then this method
23604 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
23605 In Python}). Otherwise, this method will throw an exception.
23607 If the optional @var{encoding} argument is given, it must be a string
23608 naming the encoding of the @code{gdb.LazyString}. Some examples are:
23609 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
23610 @var{encoding} argument is an encoding that @value{GDBN} does
23611 recognize, @value{GDBN} will raise an error.
23613 When a lazy string is printed, the @value{GDBN} encoding machinery is
23614 used to convert the string during printing. If the optional
23615 @var{encoding} argument is not provided, or is an empty string,
23616 @value{GDBN} will automatically select the encoding most suitable for
23617 the string type. For further information on encoding in @value{GDBN}
23618 please see @ref{Character Sets}.
23620 If the optional @var{length} argument is given, the string will be
23621 fetched and encoded to the length of characters specified. If
23622 the @var{length} argument is not provided, the string will be fetched
23623 and encoded until a null of appropriate width is found.
23626 @defun Value.fetch_lazy ()
23627 If the @code{gdb.Value} object is currently a lazy value
23628 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
23629 fetched from the inferior. Any errors that occur in the process
23630 will produce a Python exception.
23632 If the @code{gdb.Value} object is not a lazy value, this method
23635 This method does not return a value.
23639 @node Types In Python
23640 @subsubsection Types In Python
23641 @cindex types in Python
23642 @cindex Python, working with types
23645 @value{GDBN} represents types from the inferior using the class
23648 The following type-related functions are available in the @code{gdb}
23651 @findex gdb.lookup_type
23652 @defun gdb.lookup_type (name @r{[}, block@r{]})
23653 This function looks up a type by name. @var{name} is the name of the
23654 type to look up. It must be a string.
23656 If @var{block} is given, then @var{name} is looked up in that scope.
23657 Otherwise, it is searched for globally.
23659 Ordinarily, this function will return an instance of @code{gdb.Type}.
23660 If the named type cannot be found, it will throw an exception.
23663 If the type is a structure or class type, or an enum type, the fields
23664 of that type can be accessed using the Python @dfn{dictionary syntax}.
23665 For example, if @code{some_type} is a @code{gdb.Type} instance holding
23666 a structure type, you can access its @code{foo} field with:
23669 bar = some_type['foo']
23672 @code{bar} will be a @code{gdb.Field} object; see below under the
23673 description of the @code{Type.fields} method for a description of the
23674 @code{gdb.Field} class.
23676 An instance of @code{Type} has the following attributes:
23679 The type code for this type. The type code will be one of the
23680 @code{TYPE_CODE_} constants defined below.
23683 @defvar Type.sizeof
23684 The size of this type, in target @code{char} units. Usually, a
23685 target's @code{char} type will be an 8-bit byte. However, on some
23686 unusual platforms, this type may have a different size.
23690 The tag name for this type. The tag name is the name after
23691 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
23692 languages have this concept. If this type has no tag name, then
23693 @code{None} is returned.
23696 The following methods are provided:
23698 @defun Type.fields ()
23699 For structure and union types, this method returns the fields. Range
23700 types have two fields, the minimum and maximum values. Enum types
23701 have one field per enum constant. Function and method types have one
23702 field per parameter. The base types of C@t{++} classes are also
23703 represented as fields. If the type has no fields, or does not fit
23704 into one of these categories, an empty sequence will be returned.
23706 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
23709 This attribute is not available for @code{static} fields (as in
23710 C@t{++} or Java). For non-@code{static} fields, the value is the bit
23711 position of the field. For @code{enum} fields, the value is the
23712 enumeration member's integer representation.
23715 The name of the field, or @code{None} for anonymous fields.
23718 This is @code{True} if the field is artificial, usually meaning that
23719 it was provided by the compiler and not the user. This attribute is
23720 always provided, and is @code{False} if the field is not artificial.
23722 @item is_base_class
23723 This is @code{True} if the field represents a base class of a C@t{++}
23724 structure. This attribute is always provided, and is @code{False}
23725 if the field is not a base class of the type that is the argument of
23726 @code{fields}, or if that type was not a C@t{++} class.
23729 If the field is packed, or is a bitfield, then this will have a
23730 non-zero value, which is the size of the field in bits. Otherwise,
23731 this will be zero; in this case the field's size is given by its type.
23734 The type of the field. This is usually an instance of @code{Type},
23735 but it can be @code{None} in some situations.
23739 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
23740 Return a new @code{gdb.Type} object which represents an array of this
23741 type. If one argument is given, it is the inclusive upper bound of
23742 the array; in this case the lower bound is zero. If two arguments are
23743 given, the first argument is the lower bound of the array, and the
23744 second argument is the upper bound of the array. An array's length
23745 must not be negative, but the bounds can be.
23748 @defun Type.vector (@var{n1} @r{[}, @var{n2}@r{]})
23749 Return a new @code{gdb.Type} object which represents a vector of this
23750 type. If one argument is given, it is the inclusive upper bound of
23751 the vector; in this case the lower bound is zero. If two arguments are
23752 given, the first argument is the lower bound of the vector, and the
23753 second argument is the upper bound of the vector. A vector's length
23754 must not be negative, but the bounds can be.
23756 The difference between an @code{array} and a @code{vector} is that
23757 arrays behave like in C: when used in expressions they decay to a pointer
23758 to the first element whereas vectors are treated as first class values.
23761 @defun Type.const ()
23762 Return a new @code{gdb.Type} object which represents a
23763 @code{const}-qualified variant of this type.
23766 @defun Type.volatile ()
23767 Return a new @code{gdb.Type} object which represents a
23768 @code{volatile}-qualified variant of this type.
23771 @defun Type.unqualified ()
23772 Return a new @code{gdb.Type} object which represents an unqualified
23773 variant of this type. That is, the result is neither @code{const} nor
23777 @defun Type.range ()
23778 Return a Python @code{Tuple} object that contains two elements: the
23779 low bound of the argument type and the high bound of that type. If
23780 the type does not have a range, @value{GDBN} will raise a
23781 @code{gdb.error} exception (@pxref{Exception Handling}).
23784 @defun Type.reference ()
23785 Return a new @code{gdb.Type} object which represents a reference to this
23789 @defun Type.pointer ()
23790 Return a new @code{gdb.Type} object which represents a pointer to this
23794 @defun Type.strip_typedefs ()
23795 Return a new @code{gdb.Type} that represents the real type,
23796 after removing all layers of typedefs.
23799 @defun Type.target ()
23800 Return a new @code{gdb.Type} object which represents the target type
23803 For a pointer type, the target type is the type of the pointed-to
23804 object. For an array type (meaning C-like arrays), the target type is
23805 the type of the elements of the array. For a function or method type,
23806 the target type is the type of the return value. For a complex type,
23807 the target type is the type of the elements. For a typedef, the
23808 target type is the aliased type.
23810 If the type does not have a target, this method will throw an
23814 @defun Type.template_argument (n @r{[}, block@r{]})
23815 If this @code{gdb.Type} is an instantiation of a template, this will
23816 return a new @code{gdb.Type} which represents the type of the
23817 @var{n}th template argument.
23819 If this @code{gdb.Type} is not a template type, this will throw an
23820 exception. Ordinarily, only C@t{++} code will have template types.
23822 If @var{block} is given, then @var{name} is looked up in that scope.
23823 Otherwise, it is searched for globally.
23827 Each type has a code, which indicates what category this type falls
23828 into. The available type categories are represented by constants
23829 defined in the @code{gdb} module:
23832 @findex TYPE_CODE_PTR
23833 @findex gdb.TYPE_CODE_PTR
23834 @item gdb.TYPE_CODE_PTR
23835 The type is a pointer.
23837 @findex TYPE_CODE_ARRAY
23838 @findex gdb.TYPE_CODE_ARRAY
23839 @item gdb.TYPE_CODE_ARRAY
23840 The type is an array.
23842 @findex TYPE_CODE_STRUCT
23843 @findex gdb.TYPE_CODE_STRUCT
23844 @item gdb.TYPE_CODE_STRUCT
23845 The type is a structure.
23847 @findex TYPE_CODE_UNION
23848 @findex gdb.TYPE_CODE_UNION
23849 @item gdb.TYPE_CODE_UNION
23850 The type is a union.
23852 @findex TYPE_CODE_ENUM
23853 @findex gdb.TYPE_CODE_ENUM
23854 @item gdb.TYPE_CODE_ENUM
23855 The type is an enum.
23857 @findex TYPE_CODE_FLAGS
23858 @findex gdb.TYPE_CODE_FLAGS
23859 @item gdb.TYPE_CODE_FLAGS
23860 A bit flags type, used for things such as status registers.
23862 @findex TYPE_CODE_FUNC
23863 @findex gdb.TYPE_CODE_FUNC
23864 @item gdb.TYPE_CODE_FUNC
23865 The type is a function.
23867 @findex TYPE_CODE_INT
23868 @findex gdb.TYPE_CODE_INT
23869 @item gdb.TYPE_CODE_INT
23870 The type is an integer type.
23872 @findex TYPE_CODE_FLT
23873 @findex gdb.TYPE_CODE_FLT
23874 @item gdb.TYPE_CODE_FLT
23875 A floating point type.
23877 @findex TYPE_CODE_VOID
23878 @findex gdb.TYPE_CODE_VOID
23879 @item gdb.TYPE_CODE_VOID
23880 The special type @code{void}.
23882 @findex TYPE_CODE_SET
23883 @findex gdb.TYPE_CODE_SET
23884 @item gdb.TYPE_CODE_SET
23887 @findex TYPE_CODE_RANGE
23888 @findex gdb.TYPE_CODE_RANGE
23889 @item gdb.TYPE_CODE_RANGE
23890 A range type, that is, an integer type with bounds.
23892 @findex TYPE_CODE_STRING
23893 @findex gdb.TYPE_CODE_STRING
23894 @item gdb.TYPE_CODE_STRING
23895 A string type. Note that this is only used for certain languages with
23896 language-defined string types; C strings are not represented this way.
23898 @findex TYPE_CODE_BITSTRING
23899 @findex gdb.TYPE_CODE_BITSTRING
23900 @item gdb.TYPE_CODE_BITSTRING
23901 A string of bits. It is deprecated.
23903 @findex TYPE_CODE_ERROR
23904 @findex gdb.TYPE_CODE_ERROR
23905 @item gdb.TYPE_CODE_ERROR
23906 An unknown or erroneous type.
23908 @findex TYPE_CODE_METHOD
23909 @findex gdb.TYPE_CODE_METHOD
23910 @item gdb.TYPE_CODE_METHOD
23911 A method type, as found in C@t{++} or Java.
23913 @findex TYPE_CODE_METHODPTR
23914 @findex gdb.TYPE_CODE_METHODPTR
23915 @item gdb.TYPE_CODE_METHODPTR
23916 A pointer-to-member-function.
23918 @findex TYPE_CODE_MEMBERPTR
23919 @findex gdb.TYPE_CODE_MEMBERPTR
23920 @item gdb.TYPE_CODE_MEMBERPTR
23921 A pointer-to-member.
23923 @findex TYPE_CODE_REF
23924 @findex gdb.TYPE_CODE_REF
23925 @item gdb.TYPE_CODE_REF
23928 @findex TYPE_CODE_CHAR
23929 @findex gdb.TYPE_CODE_CHAR
23930 @item gdb.TYPE_CODE_CHAR
23933 @findex TYPE_CODE_BOOL
23934 @findex gdb.TYPE_CODE_BOOL
23935 @item gdb.TYPE_CODE_BOOL
23938 @findex TYPE_CODE_COMPLEX
23939 @findex gdb.TYPE_CODE_COMPLEX
23940 @item gdb.TYPE_CODE_COMPLEX
23941 A complex float type.
23943 @findex TYPE_CODE_TYPEDEF
23944 @findex gdb.TYPE_CODE_TYPEDEF
23945 @item gdb.TYPE_CODE_TYPEDEF
23946 A typedef to some other type.
23948 @findex TYPE_CODE_NAMESPACE
23949 @findex gdb.TYPE_CODE_NAMESPACE
23950 @item gdb.TYPE_CODE_NAMESPACE
23951 A C@t{++} namespace.
23953 @findex TYPE_CODE_DECFLOAT
23954 @findex gdb.TYPE_CODE_DECFLOAT
23955 @item gdb.TYPE_CODE_DECFLOAT
23956 A decimal floating point type.
23958 @findex TYPE_CODE_INTERNAL_FUNCTION
23959 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
23960 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
23961 A function internal to @value{GDBN}. This is the type used to represent
23962 convenience functions.
23965 Further support for types is provided in the @code{gdb.types}
23966 Python module (@pxref{gdb.types}).
23968 @node Pretty Printing API
23969 @subsubsection Pretty Printing API
23971 An example output is provided (@pxref{Pretty Printing}).
23973 A pretty-printer is just an object that holds a value and implements a
23974 specific interface, defined here.
23976 @defun pretty_printer.children (self)
23977 @value{GDBN} will call this method on a pretty-printer to compute the
23978 children of the pretty-printer's value.
23980 This method must return an object conforming to the Python iterator
23981 protocol. Each item returned by the iterator must be a tuple holding
23982 two elements. The first element is the ``name'' of the child; the
23983 second element is the child's value. The value can be any Python
23984 object which is convertible to a @value{GDBN} value.
23986 This method is optional. If it does not exist, @value{GDBN} will act
23987 as though the value has no children.
23990 @defun pretty_printer.display_hint (self)
23991 The CLI may call this method and use its result to change the
23992 formatting of a value. The result will also be supplied to an MI
23993 consumer as a @samp{displayhint} attribute of the variable being
23996 This method is optional. If it does exist, this method must return a
23999 Some display hints are predefined by @value{GDBN}:
24003 Indicate that the object being printed is ``array-like''. The CLI
24004 uses this to respect parameters such as @code{set print elements} and
24005 @code{set print array}.
24008 Indicate that the object being printed is ``map-like'', and that the
24009 children of this value can be assumed to alternate between keys and
24013 Indicate that the object being printed is ``string-like''. If the
24014 printer's @code{to_string} method returns a Python string of some
24015 kind, then @value{GDBN} will call its internal language-specific
24016 string-printing function to format the string. For the CLI this means
24017 adding quotation marks, possibly escaping some characters, respecting
24018 @code{set print elements}, and the like.
24022 @defun pretty_printer.to_string (self)
24023 @value{GDBN} will call this method to display the string
24024 representation of the value passed to the object's constructor.
24026 When printing from the CLI, if the @code{to_string} method exists,
24027 then @value{GDBN} will prepend its result to the values returned by
24028 @code{children}. Exactly how this formatting is done is dependent on
24029 the display hint, and may change as more hints are added. Also,
24030 depending on the print settings (@pxref{Print Settings}), the CLI may
24031 print just the result of @code{to_string} in a stack trace, omitting
24032 the result of @code{children}.
24034 If this method returns a string, it is printed verbatim.
24036 Otherwise, if this method returns an instance of @code{gdb.Value},
24037 then @value{GDBN} prints this value. This may result in a call to
24038 another pretty-printer.
24040 If instead the method returns a Python value which is convertible to a
24041 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
24042 the resulting value. Again, this may result in a call to another
24043 pretty-printer. Python scalars (integers, floats, and booleans) and
24044 strings are convertible to @code{gdb.Value}; other types are not.
24046 Finally, if this method returns @code{None} then no further operations
24047 are peformed in this method and nothing is printed.
24049 If the result is not one of these types, an exception is raised.
24052 @value{GDBN} provides a function which can be used to look up the
24053 default pretty-printer for a @code{gdb.Value}:
24055 @findex gdb.default_visualizer
24056 @defun gdb.default_visualizer (value)
24057 This function takes a @code{gdb.Value} object as an argument. If a
24058 pretty-printer for this value exists, then it is returned. If no such
24059 printer exists, then this returns @code{None}.
24062 @node Selecting Pretty-Printers
24063 @subsubsection Selecting Pretty-Printers
24065 The Python list @code{gdb.pretty_printers} contains an array of
24066 functions or callable objects that have been registered via addition
24067 as a pretty-printer. Printers in this list are called @code{global}
24068 printers, they're available when debugging all inferiors.
24069 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
24070 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
24073 Each function on these lists is passed a single @code{gdb.Value}
24074 argument and should return a pretty-printer object conforming to the
24075 interface definition above (@pxref{Pretty Printing API}). If a function
24076 cannot create a pretty-printer for the value, it should return
24079 @value{GDBN} first checks the @code{pretty_printers} attribute of each
24080 @code{gdb.Objfile} in the current program space and iteratively calls
24081 each enabled lookup routine in the list for that @code{gdb.Objfile}
24082 until it receives a pretty-printer object.
24083 If no pretty-printer is found in the objfile lists, @value{GDBN} then
24084 searches the pretty-printer list of the current program space,
24085 calling each enabled function until an object is returned.
24086 After these lists have been exhausted, it tries the global
24087 @code{gdb.pretty_printers} list, again calling each enabled function until an
24088 object is returned.
24090 The order in which the objfiles are searched is not specified. For a
24091 given list, functions are always invoked from the head of the list,
24092 and iterated over sequentially until the end of the list, or a printer
24093 object is returned.
24095 For various reasons a pretty-printer may not work.
24096 For example, the underlying data structure may have changed and
24097 the pretty-printer is out of date.
24099 The consequences of a broken pretty-printer are severe enough that
24100 @value{GDBN} provides support for enabling and disabling individual
24101 printers. For example, if @code{print frame-arguments} is on,
24102 a backtrace can become highly illegible if any argument is printed
24103 with a broken printer.
24105 Pretty-printers are enabled and disabled by attaching an @code{enabled}
24106 attribute to the registered function or callable object. If this attribute
24107 is present and its value is @code{False}, the printer is disabled, otherwise
24108 the printer is enabled.
24110 @node Writing a Pretty-Printer
24111 @subsubsection Writing a Pretty-Printer
24112 @cindex writing a pretty-printer
24114 A pretty-printer consists of two parts: a lookup function to detect
24115 if the type is supported, and the printer itself.
24117 Here is an example showing how a @code{std::string} printer might be
24118 written. @xref{Pretty Printing API}, for details on the API this class
24122 class StdStringPrinter(object):
24123 "Print a std::string"
24125 def __init__(self, val):
24128 def to_string(self):
24129 return self.val['_M_dataplus']['_M_p']
24131 def display_hint(self):
24135 And here is an example showing how a lookup function for the printer
24136 example above might be written.
24139 def str_lookup_function(val):
24140 lookup_tag = val.type.tag
24141 if lookup_tag == None:
24143 regex = re.compile("^std::basic_string<char,.*>$")
24144 if regex.match(lookup_tag):
24145 return StdStringPrinter(val)
24149 The example lookup function extracts the value's type, and attempts to
24150 match it to a type that it can pretty-print. If it is a type the
24151 printer can pretty-print, it will return a printer object. If not, it
24152 returns @code{None}.
24154 We recommend that you put your core pretty-printers into a Python
24155 package. If your pretty-printers are for use with a library, we
24156 further recommend embedding a version number into the package name.
24157 This practice will enable @value{GDBN} to load multiple versions of
24158 your pretty-printers at the same time, because they will have
24161 You should write auto-loaded code (@pxref{Python Auto-loading}) such that it
24162 can be evaluated multiple times without changing its meaning. An
24163 ideal auto-load file will consist solely of @code{import}s of your
24164 printer modules, followed by a call to a register pretty-printers with
24165 the current objfile.
24167 Taken as a whole, this approach will scale nicely to multiple
24168 inferiors, each potentially using a different library version.
24169 Embedding a version number in the Python package name will ensure that
24170 @value{GDBN} is able to load both sets of printers simultaneously.
24171 Then, because the search for pretty-printers is done by objfile, and
24172 because your auto-loaded code took care to register your library's
24173 printers with a specific objfile, @value{GDBN} will find the correct
24174 printers for the specific version of the library used by each
24177 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
24178 this code might appear in @code{gdb.libstdcxx.v6}:
24181 def register_printers(objfile):
24182 objfile.pretty_printers.append(str_lookup_function)
24186 And then the corresponding contents of the auto-load file would be:
24189 import gdb.libstdcxx.v6
24190 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
24193 The previous example illustrates a basic pretty-printer.
24194 There are a few things that can be improved on.
24195 The printer doesn't have a name, making it hard to identify in a
24196 list of installed printers. The lookup function has a name, but
24197 lookup functions can have arbitrary, even identical, names.
24199 Second, the printer only handles one type, whereas a library typically has
24200 several types. One could install a lookup function for each desired type
24201 in the library, but one could also have a single lookup function recognize
24202 several types. The latter is the conventional way this is handled.
24203 If a pretty-printer can handle multiple data types, then its
24204 @dfn{subprinters} are the printers for the individual data types.
24206 The @code{gdb.printing} module provides a formal way of solving these
24207 problems (@pxref{gdb.printing}).
24208 Here is another example that handles multiple types.
24210 These are the types we are going to pretty-print:
24213 struct foo @{ int a, b; @};
24214 struct bar @{ struct foo x, y; @};
24217 Here are the printers:
24221 """Print a foo object."""
24223 def __init__(self, val):
24226 def to_string(self):
24227 return ("a=<" + str(self.val["a"]) +
24228 "> b=<" + str(self.val["b"]) + ">")
24231 """Print a bar object."""
24233 def __init__(self, val):
24236 def to_string(self):
24237 return ("x=<" + str(self.val["x"]) +
24238 "> y=<" + str(self.val["y"]) + ">")
24241 This example doesn't need a lookup function, that is handled by the
24242 @code{gdb.printing} module. Instead a function is provided to build up
24243 the object that handles the lookup.
24246 import gdb.printing
24248 def build_pretty_printer():
24249 pp = gdb.printing.RegexpCollectionPrettyPrinter(
24251 pp.add_printer('foo', '^foo$', fooPrinter)
24252 pp.add_printer('bar', '^bar$', barPrinter)
24256 And here is the autoload support:
24259 import gdb.printing
24261 gdb.printing.register_pretty_printer(
24262 gdb.current_objfile(),
24263 my_library.build_pretty_printer())
24266 Finally, when this printer is loaded into @value{GDBN}, here is the
24267 corresponding output of @samp{info pretty-printer}:
24270 (gdb) info pretty-printer
24277 @node Type Printing API
24278 @subsubsection Type Printing API
24279 @cindex type printing API for Python
24281 @value{GDBN} provides a way for Python code to customize type display.
24282 This is mainly useful for substituting canonical typedef names for
24285 @cindex type printer
24286 A @dfn{type printer} is just a Python object conforming to a certain
24287 protocol. A simple base class implementing the protocol is provided;
24288 see @ref{gdb.types}. A type printer must supply at least:
24290 @defivar type_printer enabled
24291 A boolean which is True if the printer is enabled, and False
24292 otherwise. This is manipulated by the @code{enable type-printer}
24293 and @code{disable type-printer} commands.
24296 @defivar type_printer name
24297 The name of the type printer. This must be a string. This is used by
24298 the @code{enable type-printer} and @code{disable type-printer}
24302 @defmethod type_printer instantiate (self)
24303 This is called by @value{GDBN} at the start of type-printing. It is
24304 only called if the type printer is enabled. This method must return a
24305 new object that supplies a @code{recognize} method, as described below.
24309 When displaying a type, say via the @code{ptype} command, @value{GDBN}
24310 will compute a list of type recognizers. This is done by iterating
24311 first over the per-objfile type printers (@pxref{Objfiles In Python}),
24312 followed by the per-progspace type printers (@pxref{Progspaces In
24313 Python}), and finally the global type printers.
24315 @value{GDBN} will call the @code{instantiate} method of each enabled
24316 type printer. If this method returns @code{None}, then the result is
24317 ignored; otherwise, it is appended to the list of recognizers.
24319 Then, when @value{GDBN} is going to display a type name, it iterates
24320 over the list of recognizers. For each one, it calls the recognition
24321 function, stopping if the function returns a non-@code{None} value.
24322 The recognition function is defined as:
24324 @defmethod type_recognizer recognize (self, type)
24325 If @var{type} is not recognized, return @code{None}. Otherwise,
24326 return a string which is to be printed as the name of @var{type}.
24327 @var{type} will be an instance of @code{gdb.Type} (@pxref{Types In
24331 @value{GDBN} uses this two-pass approach so that type printers can
24332 efficiently cache information without holding on to it too long. For
24333 example, it can be convenient to look up type information in a type
24334 printer and hold it for a recognizer's lifetime; if a single pass were
24335 done then type printers would have to make use of the event system in
24336 order to avoid holding information that could become stale as the
24339 @node Inferiors In Python
24340 @subsubsection Inferiors In Python
24341 @cindex inferiors in Python
24343 @findex gdb.Inferior
24344 Programs which are being run under @value{GDBN} are called inferiors
24345 (@pxref{Inferiors and Programs}). Python scripts can access
24346 information about and manipulate inferiors controlled by @value{GDBN}
24347 via objects of the @code{gdb.Inferior} class.
24349 The following inferior-related functions are available in the @code{gdb}
24352 @defun gdb.inferiors ()
24353 Return a tuple containing all inferior objects.
24356 @defun gdb.selected_inferior ()
24357 Return an object representing the current inferior.
24360 A @code{gdb.Inferior} object has the following attributes:
24362 @defvar Inferior.num
24363 ID of inferior, as assigned by GDB.
24366 @defvar Inferior.pid
24367 Process ID of the inferior, as assigned by the underlying operating
24371 @defvar Inferior.was_attached
24372 Boolean signaling whether the inferior was created using `attach', or
24373 started by @value{GDBN} itself.
24376 A @code{gdb.Inferior} object has the following methods:
24378 @defun Inferior.is_valid ()
24379 Returns @code{True} if the @code{gdb.Inferior} object is valid,
24380 @code{False} if not. A @code{gdb.Inferior} object will become invalid
24381 if the inferior no longer exists within @value{GDBN}. All other
24382 @code{gdb.Inferior} methods will throw an exception if it is invalid
24383 at the time the method is called.
24386 @defun Inferior.threads ()
24387 This method returns a tuple holding all the threads which are valid
24388 when it is called. If there are no valid threads, the method will
24389 return an empty tuple.
24392 @findex Inferior.read_memory
24393 @defun Inferior.read_memory (address, length)
24394 Read @var{length} bytes of memory from the inferior, starting at
24395 @var{address}. Returns a buffer object, which behaves much like an array
24396 or a string. It can be modified and given to the
24397 @code{Inferior.write_memory} function. In @code{Python} 3, the return
24398 value is a @code{memoryview} object.
24401 @findex Inferior.write_memory
24402 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
24403 Write the contents of @var{buffer} to the inferior, starting at
24404 @var{address}. The @var{buffer} parameter must be a Python object
24405 which supports the buffer protocol, i.e., a string, an array or the
24406 object returned from @code{Inferior.read_memory}. If given, @var{length}
24407 determines the number of bytes from @var{buffer} to be written.
24410 @findex gdb.search_memory
24411 @defun Inferior.search_memory (address, length, pattern)
24412 Search a region of the inferior memory starting at @var{address} with
24413 the given @var{length} using the search pattern supplied in
24414 @var{pattern}. The @var{pattern} parameter must be a Python object
24415 which supports the buffer protocol, i.e., a string, an array or the
24416 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
24417 containing the address where the pattern was found, or @code{None} if
24418 the pattern could not be found.
24421 @node Events In Python
24422 @subsubsection Events In Python
24423 @cindex inferior events in Python
24425 @value{GDBN} provides a general event facility so that Python code can be
24426 notified of various state changes, particularly changes that occur in
24429 An @dfn{event} is just an object that describes some state change. The
24430 type of the object and its attributes will vary depending on the details
24431 of the change. All the existing events are described below.
24433 In order to be notified of an event, you must register an event handler
24434 with an @dfn{event registry}. An event registry is an object in the
24435 @code{gdb.events} module which dispatches particular events. A registry
24436 provides methods to register and unregister event handlers:
24438 @defun EventRegistry.connect (object)
24439 Add the given callable @var{object} to the registry. This object will be
24440 called when an event corresponding to this registry occurs.
24443 @defun EventRegistry.disconnect (object)
24444 Remove the given @var{object} from the registry. Once removed, the object
24445 will no longer receive notifications of events.
24448 Here is an example:
24451 def exit_handler (event):
24452 print "event type: exit"
24453 print "exit code: %d" % (event.exit_code)
24455 gdb.events.exited.connect (exit_handler)
24458 In the above example we connect our handler @code{exit_handler} to the
24459 registry @code{events.exited}. Once connected, @code{exit_handler} gets
24460 called when the inferior exits. The argument @dfn{event} in this example is
24461 of type @code{gdb.ExitedEvent}. As you can see in the example the
24462 @code{ExitedEvent} object has an attribute which indicates the exit code of
24465 The following is a listing of the event registries that are available and
24466 details of the events they emit:
24471 Emits @code{gdb.ThreadEvent}.
24473 Some events can be thread specific when @value{GDBN} is running in non-stop
24474 mode. When represented in Python, these events all extend
24475 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
24476 events which are emitted by this or other modules might extend this event.
24477 Examples of these events are @code{gdb.BreakpointEvent} and
24478 @code{gdb.ContinueEvent}.
24480 @defvar ThreadEvent.inferior_thread
24481 In non-stop mode this attribute will be set to the specific thread which was
24482 involved in the emitted event. Otherwise, it will be set to @code{None}.
24485 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
24487 This event indicates that the inferior has been continued after a stop. For
24488 inherited attribute refer to @code{gdb.ThreadEvent} above.
24490 @item events.exited
24491 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
24492 @code{events.ExitedEvent} has two attributes:
24493 @defvar ExitedEvent.exit_code
24494 An integer representing the exit code, if available, which the inferior
24495 has returned. (The exit code could be unavailable if, for example,
24496 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
24497 the attribute does not exist.
24499 @defvar ExitedEvent inferior
24500 A reference to the inferior which triggered the @code{exited} event.
24504 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
24506 Indicates that the inferior has stopped. All events emitted by this registry
24507 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
24508 will indicate the stopped thread when @value{GDBN} is running in non-stop
24509 mode. Refer to @code{gdb.ThreadEvent} above for more details.
24511 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
24513 This event indicates that the inferior or one of its threads has received as
24514 signal. @code{gdb.SignalEvent} has the following attributes:
24516 @defvar SignalEvent.stop_signal
24517 A string representing the signal received by the inferior. A list of possible
24518 signal values can be obtained by running the command @code{info signals} in
24519 the @value{GDBN} command prompt.
24522 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
24524 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
24525 been hit, and has the following attributes:
24527 @defvar BreakpointEvent.breakpoints
24528 A sequence containing references to all the breakpoints (type
24529 @code{gdb.Breakpoint}) that were hit.
24530 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
24532 @defvar BreakpointEvent.breakpoint
24533 A reference to the first breakpoint that was hit.
24534 This function is maintained for backward compatibility and is now deprecated
24535 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
24538 @item events.new_objfile
24539 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
24540 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
24542 @defvar NewObjFileEvent.new_objfile
24543 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
24544 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
24549 @node Threads In Python
24550 @subsubsection Threads In Python
24551 @cindex threads in python
24553 @findex gdb.InferiorThread
24554 Python scripts can access information about, and manipulate inferior threads
24555 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
24557 The following thread-related functions are available in the @code{gdb}
24560 @findex gdb.selected_thread
24561 @defun gdb.selected_thread ()
24562 This function returns the thread object for the selected thread. If there
24563 is no selected thread, this will return @code{None}.
24566 A @code{gdb.InferiorThread} object has the following attributes:
24568 @defvar InferiorThread.name
24569 The name of the thread. If the user specified a name using
24570 @code{thread name}, then this returns that name. Otherwise, if an
24571 OS-supplied name is available, then it is returned. Otherwise, this
24572 returns @code{None}.
24574 This attribute can be assigned to. The new value must be a string
24575 object, which sets the new name, or @code{None}, which removes any
24576 user-specified thread name.
24579 @defvar InferiorThread.num
24580 ID of the thread, as assigned by GDB.
24583 @defvar InferiorThread.ptid
24584 ID of the thread, as assigned by the operating system. This attribute is a
24585 tuple containing three integers. The first is the Process ID (PID); the second
24586 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
24587 Either the LWPID or TID may be 0, which indicates that the operating system
24588 does not use that identifier.
24591 A @code{gdb.InferiorThread} object has the following methods:
24593 @defun InferiorThread.is_valid ()
24594 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
24595 @code{False} if not. A @code{gdb.InferiorThread} object will become
24596 invalid if the thread exits, or the inferior that the thread belongs
24597 is deleted. All other @code{gdb.InferiorThread} methods will throw an
24598 exception if it is invalid at the time the method is called.
24601 @defun InferiorThread.switch ()
24602 This changes @value{GDBN}'s currently selected thread to the one represented
24606 @defun InferiorThread.is_stopped ()
24607 Return a Boolean indicating whether the thread is stopped.
24610 @defun InferiorThread.is_running ()
24611 Return a Boolean indicating whether the thread is running.
24614 @defun InferiorThread.is_exited ()
24615 Return a Boolean indicating whether the thread is exited.
24618 @node Commands In Python
24619 @subsubsection Commands In Python
24621 @cindex commands in python
24622 @cindex python commands
24623 You can implement new @value{GDBN} CLI commands in Python. A CLI
24624 command is implemented using an instance of the @code{gdb.Command}
24625 class, most commonly using a subclass.
24627 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
24628 The object initializer for @code{Command} registers the new command
24629 with @value{GDBN}. This initializer is normally invoked from the
24630 subclass' own @code{__init__} method.
24632 @var{name} is the name of the command. If @var{name} consists of
24633 multiple words, then the initial words are looked for as prefix
24634 commands. In this case, if one of the prefix commands does not exist,
24635 an exception is raised.
24637 There is no support for multi-line commands.
24639 @var{command_class} should be one of the @samp{COMMAND_} constants
24640 defined below. This argument tells @value{GDBN} how to categorize the
24641 new command in the help system.
24643 @var{completer_class} is an optional argument. If given, it should be
24644 one of the @samp{COMPLETE_} constants defined below. This argument
24645 tells @value{GDBN} how to perform completion for this command. If not
24646 given, @value{GDBN} will attempt to complete using the object's
24647 @code{complete} method (see below); if no such method is found, an
24648 error will occur when completion is attempted.
24650 @var{prefix} is an optional argument. If @code{True}, then the new
24651 command is a prefix command; sub-commands of this command may be
24654 The help text for the new command is taken from the Python
24655 documentation string for the command's class, if there is one. If no
24656 documentation string is provided, the default value ``This command is
24657 not documented.'' is used.
24660 @cindex don't repeat Python command
24661 @defun Command.dont_repeat ()
24662 By default, a @value{GDBN} command is repeated when the user enters a
24663 blank line at the command prompt. A command can suppress this
24664 behavior by invoking the @code{dont_repeat} method. This is similar
24665 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
24668 @defun Command.invoke (argument, from_tty)
24669 This method is called by @value{GDBN} when this command is invoked.
24671 @var{argument} is a string. It is the argument to the command, after
24672 leading and trailing whitespace has been stripped.
24674 @var{from_tty} is a boolean argument. When true, this means that the
24675 command was entered by the user at the terminal; when false it means
24676 that the command came from elsewhere.
24678 If this method throws an exception, it is turned into a @value{GDBN}
24679 @code{error} call. Otherwise, the return value is ignored.
24681 @findex gdb.string_to_argv
24682 To break @var{argument} up into an argv-like string use
24683 @code{gdb.string_to_argv}. This function behaves identically to
24684 @value{GDBN}'s internal argument lexer @code{buildargv}.
24685 It is recommended to use this for consistency.
24686 Arguments are separated by spaces and may be quoted.
24690 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
24691 ['1', '2 "3', '4 "5', "6 '7"]
24696 @cindex completion of Python commands
24697 @defun Command.complete (text, word)
24698 This method is called by @value{GDBN} when the user attempts
24699 completion on this command. All forms of completion are handled by
24700 this method, that is, the @key{TAB} and @key{M-?} key bindings
24701 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
24704 The arguments @var{text} and @var{word} are both strings. @var{text}
24705 holds the complete command line up to the cursor's location.
24706 @var{word} holds the last word of the command line; this is computed
24707 using a word-breaking heuristic.
24709 The @code{complete} method can return several values:
24712 If the return value is a sequence, the contents of the sequence are
24713 used as the completions. It is up to @code{complete} to ensure that the
24714 contents actually do complete the word. A zero-length sequence is
24715 allowed, it means that there were no completions available. Only
24716 string elements of the sequence are used; other elements in the
24717 sequence are ignored.
24720 If the return value is one of the @samp{COMPLETE_} constants defined
24721 below, then the corresponding @value{GDBN}-internal completion
24722 function is invoked, and its result is used.
24725 All other results are treated as though there were no available
24730 When a new command is registered, it must be declared as a member of
24731 some general class of commands. This is used to classify top-level
24732 commands in the on-line help system; note that prefix commands are not
24733 listed under their own category but rather that of their top-level
24734 command. The available classifications are represented by constants
24735 defined in the @code{gdb} module:
24738 @findex COMMAND_NONE
24739 @findex gdb.COMMAND_NONE
24740 @item gdb.COMMAND_NONE
24741 The command does not belong to any particular class. A command in
24742 this category will not be displayed in any of the help categories.
24744 @findex COMMAND_RUNNING
24745 @findex gdb.COMMAND_RUNNING
24746 @item gdb.COMMAND_RUNNING
24747 The command is related to running the inferior. For example,
24748 @code{start}, @code{step}, and @code{continue} are in this category.
24749 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
24750 commands in this category.
24752 @findex COMMAND_DATA
24753 @findex gdb.COMMAND_DATA
24754 @item gdb.COMMAND_DATA
24755 The command is related to data or variables. For example,
24756 @code{call}, @code{find}, and @code{print} are in this category. Type
24757 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
24760 @findex COMMAND_STACK
24761 @findex gdb.COMMAND_STACK
24762 @item gdb.COMMAND_STACK
24763 The command has to do with manipulation of the stack. For example,
24764 @code{backtrace}, @code{frame}, and @code{return} are in this
24765 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
24766 list of commands in this category.
24768 @findex COMMAND_FILES
24769 @findex gdb.COMMAND_FILES
24770 @item gdb.COMMAND_FILES
24771 This class is used for file-related commands. For example,
24772 @code{file}, @code{list} and @code{section} are in this category.
24773 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
24774 commands in this category.
24776 @findex COMMAND_SUPPORT
24777 @findex gdb.COMMAND_SUPPORT
24778 @item gdb.COMMAND_SUPPORT
24779 This should be used for ``support facilities'', generally meaning
24780 things that are useful to the user when interacting with @value{GDBN},
24781 but not related to the state of the inferior. For example,
24782 @code{help}, @code{make}, and @code{shell} are in this category. Type
24783 @kbd{help support} at the @value{GDBN} prompt to see a list of
24784 commands in this category.
24786 @findex COMMAND_STATUS
24787 @findex gdb.COMMAND_STATUS
24788 @item gdb.COMMAND_STATUS
24789 The command is an @samp{info}-related command, that is, related to the
24790 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
24791 and @code{show} are in this category. Type @kbd{help status} at the
24792 @value{GDBN} prompt to see a list of commands in this category.
24794 @findex COMMAND_BREAKPOINTS
24795 @findex gdb.COMMAND_BREAKPOINTS
24796 @item gdb.COMMAND_BREAKPOINTS
24797 The command has to do with breakpoints. For example, @code{break},
24798 @code{clear}, and @code{delete} are in this category. Type @kbd{help
24799 breakpoints} at the @value{GDBN} prompt to see a list of commands in
24802 @findex COMMAND_TRACEPOINTS
24803 @findex gdb.COMMAND_TRACEPOINTS
24804 @item gdb.COMMAND_TRACEPOINTS
24805 The command has to do with tracepoints. For example, @code{trace},
24806 @code{actions}, and @code{tfind} are in this category. Type
24807 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
24808 commands in this category.
24810 @findex COMMAND_USER
24811 @findex gdb.COMMAND_USER
24812 @item gdb.COMMAND_USER
24813 The command is a general purpose command for the user, and typically
24814 does not fit in one of the other categories.
24815 Type @kbd{help user-defined} at the @value{GDBN} prompt to see
24816 a list of commands in this category, as well as the list of gdb macros
24817 (@pxref{Sequences}).
24819 @findex COMMAND_OBSCURE
24820 @findex gdb.COMMAND_OBSCURE
24821 @item gdb.COMMAND_OBSCURE
24822 The command is only used in unusual circumstances, or is not of
24823 general interest to users. For example, @code{checkpoint},
24824 @code{fork}, and @code{stop} are in this category. Type @kbd{help
24825 obscure} at the @value{GDBN} prompt to see a list of commands in this
24828 @findex COMMAND_MAINTENANCE
24829 @findex gdb.COMMAND_MAINTENANCE
24830 @item gdb.COMMAND_MAINTENANCE
24831 The command is only useful to @value{GDBN} maintainers. The
24832 @code{maintenance} and @code{flushregs} commands are in this category.
24833 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
24834 commands in this category.
24837 A new command can use a predefined completion function, either by
24838 specifying it via an argument at initialization, or by returning it
24839 from the @code{complete} method. These predefined completion
24840 constants are all defined in the @code{gdb} module:
24843 @findex COMPLETE_NONE
24844 @findex gdb.COMPLETE_NONE
24845 @item gdb.COMPLETE_NONE
24846 This constant means that no completion should be done.
24848 @findex COMPLETE_FILENAME
24849 @findex gdb.COMPLETE_FILENAME
24850 @item gdb.COMPLETE_FILENAME
24851 This constant means that filename completion should be performed.
24853 @findex COMPLETE_LOCATION
24854 @findex gdb.COMPLETE_LOCATION
24855 @item gdb.COMPLETE_LOCATION
24856 This constant means that location completion should be done.
24857 @xref{Specify Location}.
24859 @findex COMPLETE_COMMAND
24860 @findex gdb.COMPLETE_COMMAND
24861 @item gdb.COMPLETE_COMMAND
24862 This constant means that completion should examine @value{GDBN}
24865 @findex COMPLETE_SYMBOL
24866 @findex gdb.COMPLETE_SYMBOL
24867 @item gdb.COMPLETE_SYMBOL
24868 This constant means that completion should be done using symbol names
24872 The following code snippet shows how a trivial CLI command can be
24873 implemented in Python:
24876 class HelloWorld (gdb.Command):
24877 """Greet the whole world."""
24879 def __init__ (self):
24880 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
24882 def invoke (self, arg, from_tty):
24883 print "Hello, World!"
24888 The last line instantiates the class, and is necessary to trigger the
24889 registration of the command with @value{GDBN}. Depending on how the
24890 Python code is read into @value{GDBN}, you may need to import the
24891 @code{gdb} module explicitly.
24893 @node Parameters In Python
24894 @subsubsection Parameters In Python
24896 @cindex parameters in python
24897 @cindex python parameters
24898 @tindex gdb.Parameter
24900 You can implement new @value{GDBN} parameters using Python. A new
24901 parameter is implemented as an instance of the @code{gdb.Parameter}
24904 Parameters are exposed to the user via the @code{set} and
24905 @code{show} commands. @xref{Help}.
24907 There are many parameters that already exist and can be set in
24908 @value{GDBN}. Two examples are: @code{set follow fork} and
24909 @code{set charset}. Setting these parameters influences certain
24910 behavior in @value{GDBN}. Similarly, you can define parameters that
24911 can be used to influence behavior in custom Python scripts and commands.
24913 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
24914 The object initializer for @code{Parameter} registers the new
24915 parameter with @value{GDBN}. This initializer is normally invoked
24916 from the subclass' own @code{__init__} method.
24918 @var{name} is the name of the new parameter. If @var{name} consists
24919 of multiple words, then the initial words are looked for as prefix
24920 parameters. An example of this can be illustrated with the
24921 @code{set print} set of parameters. If @var{name} is
24922 @code{print foo}, then @code{print} will be searched as the prefix
24923 parameter. In this case the parameter can subsequently be accessed in
24924 @value{GDBN} as @code{set print foo}.
24926 If @var{name} consists of multiple words, and no prefix parameter group
24927 can be found, an exception is raised.
24929 @var{command-class} should be one of the @samp{COMMAND_} constants
24930 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
24931 categorize the new parameter in the help system.
24933 @var{parameter-class} should be one of the @samp{PARAM_} constants
24934 defined below. This argument tells @value{GDBN} the type of the new
24935 parameter; this information is used for input validation and
24938 If @var{parameter-class} is @code{PARAM_ENUM}, then
24939 @var{enum-sequence} must be a sequence of strings. These strings
24940 represent the possible values for the parameter.
24942 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
24943 of a fourth argument will cause an exception to be thrown.
24945 The help text for the new parameter is taken from the Python
24946 documentation string for the parameter's class, if there is one. If
24947 there is no documentation string, a default value is used.
24950 @defvar Parameter.set_doc
24951 If this attribute exists, and is a string, then its value is used as
24952 the help text for this parameter's @code{set} command. The value is
24953 examined when @code{Parameter.__init__} is invoked; subsequent changes
24957 @defvar Parameter.show_doc
24958 If this attribute exists, and is a string, then its value is used as
24959 the help text for this parameter's @code{show} command. The value is
24960 examined when @code{Parameter.__init__} is invoked; subsequent changes
24964 @defvar Parameter.value
24965 The @code{value} attribute holds the underlying value of the
24966 parameter. It can be read and assigned to just as any other
24967 attribute. @value{GDBN} does validation when assignments are made.
24970 There are two methods that should be implemented in any
24971 @code{Parameter} class. These are:
24973 @defun Parameter.get_set_string (self)
24974 @value{GDBN} will call this method when a @var{parameter}'s value has
24975 been changed via the @code{set} API (for example, @kbd{set foo off}).
24976 The @code{value} attribute has already been populated with the new
24977 value and may be used in output. This method must return a string.
24980 @defun Parameter.get_show_string (self, svalue)
24981 @value{GDBN} will call this method when a @var{parameter}'s
24982 @code{show} API has been invoked (for example, @kbd{show foo}). The
24983 argument @code{svalue} receives the string representation of the
24984 current value. This method must return a string.
24987 When a new parameter is defined, its type must be specified. The
24988 available types are represented by constants defined in the @code{gdb}
24992 @findex PARAM_BOOLEAN
24993 @findex gdb.PARAM_BOOLEAN
24994 @item gdb.PARAM_BOOLEAN
24995 The value is a plain boolean. The Python boolean values, @code{True}
24996 and @code{False} are the only valid values.
24998 @findex PARAM_AUTO_BOOLEAN
24999 @findex gdb.PARAM_AUTO_BOOLEAN
25000 @item gdb.PARAM_AUTO_BOOLEAN
25001 The value has three possible states: true, false, and @samp{auto}. In
25002 Python, true and false are represented using boolean constants, and
25003 @samp{auto} is represented using @code{None}.
25005 @findex PARAM_UINTEGER
25006 @findex gdb.PARAM_UINTEGER
25007 @item gdb.PARAM_UINTEGER
25008 The value is an unsigned integer. The value of 0 should be
25009 interpreted to mean ``unlimited''.
25011 @findex PARAM_INTEGER
25012 @findex gdb.PARAM_INTEGER
25013 @item gdb.PARAM_INTEGER
25014 The value is a signed integer. The value of 0 should be interpreted
25015 to mean ``unlimited''.
25017 @findex PARAM_STRING
25018 @findex gdb.PARAM_STRING
25019 @item gdb.PARAM_STRING
25020 The value is a string. When the user modifies the string, any escape
25021 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
25022 translated into corresponding characters and encoded into the current
25025 @findex PARAM_STRING_NOESCAPE
25026 @findex gdb.PARAM_STRING_NOESCAPE
25027 @item gdb.PARAM_STRING_NOESCAPE
25028 The value is a string. When the user modifies the string, escapes are
25029 passed through untranslated.
25031 @findex PARAM_OPTIONAL_FILENAME
25032 @findex gdb.PARAM_OPTIONAL_FILENAME
25033 @item gdb.PARAM_OPTIONAL_FILENAME
25034 The value is a either a filename (a string), or @code{None}.
25036 @findex PARAM_FILENAME
25037 @findex gdb.PARAM_FILENAME
25038 @item gdb.PARAM_FILENAME
25039 The value is a filename. This is just like
25040 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
25042 @findex PARAM_ZINTEGER
25043 @findex gdb.PARAM_ZINTEGER
25044 @item gdb.PARAM_ZINTEGER
25045 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
25046 is interpreted as itself.
25049 @findex gdb.PARAM_ENUM
25050 @item gdb.PARAM_ENUM
25051 The value is a string, which must be one of a collection string
25052 constants provided when the parameter is created.
25055 @node Functions In Python
25056 @subsubsection Writing new convenience functions
25058 @cindex writing convenience functions
25059 @cindex convenience functions in python
25060 @cindex python convenience functions
25061 @tindex gdb.Function
25063 You can implement new convenience functions (@pxref{Convenience Vars})
25064 in Python. A convenience function is an instance of a subclass of the
25065 class @code{gdb.Function}.
25067 @defun Function.__init__ (name)
25068 The initializer for @code{Function} registers the new function with
25069 @value{GDBN}. The argument @var{name} is the name of the function,
25070 a string. The function will be visible to the user as a convenience
25071 variable of type @code{internal function}, whose name is the same as
25072 the given @var{name}.
25074 The documentation for the new function is taken from the documentation
25075 string for the new class.
25078 @defun Function.invoke (@var{*args})
25079 When a convenience function is evaluated, its arguments are converted
25080 to instances of @code{gdb.Value}, and then the function's
25081 @code{invoke} method is called. Note that @value{GDBN} does not
25082 predetermine the arity of convenience functions. Instead, all
25083 available arguments are passed to @code{invoke}, following the
25084 standard Python calling convention. In particular, a convenience
25085 function can have default values for parameters without ill effect.
25087 The return value of this method is used as its value in the enclosing
25088 expression. If an ordinary Python value is returned, it is converted
25089 to a @code{gdb.Value} following the usual rules.
25092 The following code snippet shows how a trivial convenience function can
25093 be implemented in Python:
25096 class Greet (gdb.Function):
25097 """Return string to greet someone.
25098 Takes a name as argument."""
25100 def __init__ (self):
25101 super (Greet, self).__init__ ("greet")
25103 def invoke (self, name):
25104 return "Hello, %s!" % name.string ()
25109 The last line instantiates the class, and is necessary to trigger the
25110 registration of the function with @value{GDBN}. Depending on how the
25111 Python code is read into @value{GDBN}, you may need to import the
25112 @code{gdb} module explicitly.
25114 Now you can use the function in an expression:
25117 (gdb) print $greet("Bob")
25121 @node Progspaces In Python
25122 @subsubsection Program Spaces In Python
25124 @cindex progspaces in python
25125 @tindex gdb.Progspace
25127 A program space, or @dfn{progspace}, represents a symbolic view
25128 of an address space.
25129 It consists of all of the objfiles of the program.
25130 @xref{Objfiles In Python}.
25131 @xref{Inferiors and Programs, program spaces}, for more details
25132 about program spaces.
25134 The following progspace-related functions are available in the
25137 @findex gdb.current_progspace
25138 @defun gdb.current_progspace ()
25139 This function returns the program space of the currently selected inferior.
25140 @xref{Inferiors and Programs}.
25143 @findex gdb.progspaces
25144 @defun gdb.progspaces ()
25145 Return a sequence of all the progspaces currently known to @value{GDBN}.
25148 Each progspace is represented by an instance of the @code{gdb.Progspace}
25151 @defvar Progspace.filename
25152 The file name of the progspace as a string.
25155 @defvar Progspace.pretty_printers
25156 The @code{pretty_printers} attribute is a list of functions. It is
25157 used to look up pretty-printers. A @code{Value} is passed to each
25158 function in order; if the function returns @code{None}, then the
25159 search continues. Otherwise, the return value should be an object
25160 which is used to format the value. @xref{Pretty Printing API}, for more
25164 @defvar Progspace.type_printers
25165 The @code{type_printers} attribute is a list of type printer objects.
25166 @xref{Type Printing API}, for more information.
25169 @node Objfiles In Python
25170 @subsubsection Objfiles In Python
25172 @cindex objfiles in python
25173 @tindex gdb.Objfile
25175 @value{GDBN} loads symbols for an inferior from various
25176 symbol-containing files (@pxref{Files}). These include the primary
25177 executable file, any shared libraries used by the inferior, and any
25178 separate debug info files (@pxref{Separate Debug Files}).
25179 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
25181 The following objfile-related functions are available in the
25184 @findex gdb.current_objfile
25185 @defun gdb.current_objfile ()
25186 When auto-loading a Python script (@pxref{Python Auto-loading}), @value{GDBN}
25187 sets the ``current objfile'' to the corresponding objfile. This
25188 function returns the current objfile. If there is no current objfile,
25189 this function returns @code{None}.
25192 @findex gdb.objfiles
25193 @defun gdb.objfiles ()
25194 Return a sequence of all the objfiles current known to @value{GDBN}.
25195 @xref{Objfiles In Python}.
25198 Each objfile is represented by an instance of the @code{gdb.Objfile}
25201 @defvar Objfile.filename
25202 The file name of the objfile as a string.
25205 @defvar Objfile.pretty_printers
25206 The @code{pretty_printers} attribute is a list of functions. It is
25207 used to look up pretty-printers. A @code{Value} is passed to each
25208 function in order; if the function returns @code{None}, then the
25209 search continues. Otherwise, the return value should be an object
25210 which is used to format the value. @xref{Pretty Printing API}, for more
25214 @defvar Objfile.type_printers
25215 The @code{type_printers} attribute is a list of type printer objects.
25216 @xref{Type Printing API}, for more information.
25219 A @code{gdb.Objfile} object has the following methods:
25221 @defun Objfile.is_valid ()
25222 Returns @code{True} if the @code{gdb.Objfile} object is valid,
25223 @code{False} if not. A @code{gdb.Objfile} object can become invalid
25224 if the object file it refers to is not loaded in @value{GDBN} any
25225 longer. All other @code{gdb.Objfile} methods will throw an exception
25226 if it is invalid at the time the method is called.
25229 @node Frames In Python
25230 @subsubsection Accessing inferior stack frames from Python.
25232 @cindex frames in python
25233 When the debugged program stops, @value{GDBN} is able to analyze its call
25234 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
25235 represents a frame in the stack. A @code{gdb.Frame} object is only valid
25236 while its corresponding frame exists in the inferior's stack. If you try
25237 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
25238 exception (@pxref{Exception Handling}).
25240 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
25244 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
25248 The following frame-related functions are available in the @code{gdb} module:
25250 @findex gdb.selected_frame
25251 @defun gdb.selected_frame ()
25252 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
25255 @findex gdb.newest_frame
25256 @defun gdb.newest_frame ()
25257 Return the newest frame object for the selected thread.
25260 @defun gdb.frame_stop_reason_string (reason)
25261 Return a string explaining the reason why @value{GDBN} stopped unwinding
25262 frames, as expressed by the given @var{reason} code (an integer, see the
25263 @code{unwind_stop_reason} method further down in this section).
25266 A @code{gdb.Frame} object has the following methods:
25268 @defun Frame.is_valid ()
25269 Returns true if the @code{gdb.Frame} object is valid, false if not.
25270 A frame object can become invalid if the frame it refers to doesn't
25271 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
25272 an exception if it is invalid at the time the method is called.
25275 @defun Frame.name ()
25276 Returns the function name of the frame, or @code{None} if it can't be
25280 @defun Frame.architecture ()
25281 Returns the @code{gdb.Architecture} object corresponding to the frame's
25282 architecture. @xref{Architectures In Python}.
25285 @defun Frame.type ()
25286 Returns the type of the frame. The value can be one of:
25288 @item gdb.NORMAL_FRAME
25289 An ordinary stack frame.
25291 @item gdb.DUMMY_FRAME
25292 A fake stack frame that was created by @value{GDBN} when performing an
25293 inferior function call.
25295 @item gdb.INLINE_FRAME
25296 A frame representing an inlined function. The function was inlined
25297 into a @code{gdb.NORMAL_FRAME} that is older than this one.
25299 @item gdb.TAILCALL_FRAME
25300 A frame representing a tail call. @xref{Tail Call Frames}.
25302 @item gdb.SIGTRAMP_FRAME
25303 A signal trampoline frame. This is the frame created by the OS when
25304 it calls into a signal handler.
25306 @item gdb.ARCH_FRAME
25307 A fake stack frame representing a cross-architecture call.
25309 @item gdb.SENTINEL_FRAME
25310 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
25315 @defun Frame.unwind_stop_reason ()
25316 Return an integer representing the reason why it's not possible to find
25317 more frames toward the outermost frame. Use
25318 @code{gdb.frame_stop_reason_string} to convert the value returned by this
25319 function to a string. The value can be one of:
25322 @item gdb.FRAME_UNWIND_NO_REASON
25323 No particular reason (older frames should be available).
25325 @item gdb.FRAME_UNWIND_NULL_ID
25326 The previous frame's analyzer returns an invalid result.
25328 @item gdb.FRAME_UNWIND_OUTERMOST
25329 This frame is the outermost.
25331 @item gdb.FRAME_UNWIND_UNAVAILABLE
25332 Cannot unwind further, because that would require knowing the
25333 values of registers or memory that have not been collected.
25335 @item gdb.FRAME_UNWIND_INNER_ID
25336 This frame ID looks like it ought to belong to a NEXT frame,
25337 but we got it for a PREV frame. Normally, this is a sign of
25338 unwinder failure. It could also indicate stack corruption.
25340 @item gdb.FRAME_UNWIND_SAME_ID
25341 This frame has the same ID as the previous one. That means
25342 that unwinding further would almost certainly give us another
25343 frame with exactly the same ID, so break the chain. Normally,
25344 this is a sign of unwinder failure. It could also indicate
25347 @item gdb.FRAME_UNWIND_NO_SAVED_PC
25348 The frame unwinder did not find any saved PC, but we needed
25349 one to unwind further.
25351 @item gdb.FRAME_UNWIND_FIRST_ERROR
25352 Any stop reason greater or equal to this value indicates some kind
25353 of error. This special value facilitates writing code that tests
25354 for errors in unwinding in a way that will work correctly even if
25355 the list of the other values is modified in future @value{GDBN}
25356 versions. Using it, you could write:
25358 reason = gdb.selected_frame().unwind_stop_reason ()
25359 reason_str = gdb.frame_stop_reason_string (reason)
25360 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
25361 print "An error occured: %s" % reason_str
25368 Returns the frame's resume address.
25371 @defun Frame.block ()
25372 Return the frame's code block. @xref{Blocks In Python}.
25375 @defun Frame.function ()
25376 Return the symbol for the function corresponding to this frame.
25377 @xref{Symbols In Python}.
25380 @defun Frame.older ()
25381 Return the frame that called this frame.
25384 @defun Frame.newer ()
25385 Return the frame called by this frame.
25388 @defun Frame.find_sal ()
25389 Return the frame's symtab and line object.
25390 @xref{Symbol Tables In Python}.
25393 @defun Frame.read_var (variable @r{[}, block@r{]})
25394 Return the value of @var{variable} in this frame. If the optional
25395 argument @var{block} is provided, search for the variable from that
25396 block; otherwise start at the frame's current block (which is
25397 determined by the frame's current program counter). @var{variable}
25398 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
25399 @code{gdb.Block} object.
25402 @defun Frame.select ()
25403 Set this frame to be the selected frame. @xref{Stack, ,Examining the
25407 @node Blocks In Python
25408 @subsubsection Accessing frame blocks from Python.
25410 @cindex blocks in python
25413 Within each frame, @value{GDBN} maintains information on each block
25414 stored in that frame. These blocks are organized hierarchically, and
25415 are represented individually in Python as a @code{gdb.Block}.
25416 Please see @ref{Frames In Python}, for a more in-depth discussion on
25417 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
25418 detailed technical information on @value{GDBN}'s book-keeping of the
25421 A @code{gdb.Block} is iterable. The iterator returns the symbols
25422 (@pxref{Symbols In Python}) local to the block. Python programs
25423 should not assume that a specific block object will always contain a
25424 given symbol, since changes in @value{GDBN} features and
25425 infrastructure may cause symbols move across blocks in a symbol
25428 The following block-related functions are available in the @code{gdb}
25431 @findex gdb.block_for_pc
25432 @defun gdb.block_for_pc (pc)
25433 Return the @code{gdb.Block} containing the given @var{pc} value. If the
25434 block cannot be found for the @var{pc} value specified, the function
25435 will return @code{None}.
25438 A @code{gdb.Block} object has the following methods:
25440 @defun Block.is_valid ()
25441 Returns @code{True} if the @code{gdb.Block} object is valid,
25442 @code{False} if not. A block object can become invalid if the block it
25443 refers to doesn't exist anymore in the inferior. All other
25444 @code{gdb.Block} methods will throw an exception if it is invalid at
25445 the time the method is called. The block's validity is also checked
25446 during iteration over symbols of the block.
25449 A @code{gdb.Block} object has the following attributes:
25451 @defvar Block.start
25452 The start address of the block. This attribute is not writable.
25456 The end address of the block. This attribute is not writable.
25459 @defvar Block.function
25460 The name of the block represented as a @code{gdb.Symbol}. If the
25461 block is not named, then this attribute holds @code{None}. This
25462 attribute is not writable.
25465 @defvar Block.superblock
25466 The block containing this block. If this parent block does not exist,
25467 this attribute holds @code{None}. This attribute is not writable.
25470 @defvar Block.global_block
25471 The global block associated with this block. This attribute is not
25475 @defvar Block.static_block
25476 The static block associated with this block. This attribute is not
25480 @defvar Block.is_global
25481 @code{True} if the @code{gdb.Block} object is a global block,
25482 @code{False} if not. This attribute is not
25486 @defvar Block.is_static
25487 @code{True} if the @code{gdb.Block} object is a static block,
25488 @code{False} if not. This attribute is not writable.
25491 @node Symbols In Python
25492 @subsubsection Python representation of Symbols.
25494 @cindex symbols in python
25497 @value{GDBN} represents every variable, function and type as an
25498 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
25499 Similarly, Python represents these symbols in @value{GDBN} with the
25500 @code{gdb.Symbol} object.
25502 The following symbol-related functions are available in the @code{gdb}
25505 @findex gdb.lookup_symbol
25506 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
25507 This function searches for a symbol by name. The search scope can be
25508 restricted to the parameters defined in the optional domain and block
25511 @var{name} is the name of the symbol. It must be a string. The
25512 optional @var{block} argument restricts the search to symbols visible
25513 in that @var{block}. The @var{block} argument must be a
25514 @code{gdb.Block} object. If omitted, the block for the current frame
25515 is used. The optional @var{domain} argument restricts
25516 the search to the domain type. The @var{domain} argument must be a
25517 domain constant defined in the @code{gdb} module and described later
25520 The result is a tuple of two elements.
25521 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
25523 If the symbol is found, the second element is @code{True} if the symbol
25524 is a field of a method's object (e.g., @code{this} in C@t{++}),
25525 otherwise it is @code{False}.
25526 If the symbol is not found, the second element is @code{False}.
25529 @findex gdb.lookup_global_symbol
25530 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
25531 This function searches for a global symbol by name.
25532 The search scope can be restricted to by the domain argument.
25534 @var{name} is the name of the symbol. It must be a string.
25535 The optional @var{domain} argument restricts the search to the domain type.
25536 The @var{domain} argument must be a domain constant defined in the @code{gdb}
25537 module and described later in this chapter.
25539 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
25543 A @code{gdb.Symbol} object has the following attributes:
25545 @defvar Symbol.type
25546 The type of the symbol or @code{None} if no type is recorded.
25547 This attribute is represented as a @code{gdb.Type} object.
25548 @xref{Types In Python}. This attribute is not writable.
25551 @defvar Symbol.symtab
25552 The symbol table in which the symbol appears. This attribute is
25553 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
25554 Python}. This attribute is not writable.
25557 @defvar Symbol.line
25558 The line number in the source code at which the symbol was defined.
25559 This is an integer.
25562 @defvar Symbol.name
25563 The name of the symbol as a string. This attribute is not writable.
25566 @defvar Symbol.linkage_name
25567 The name of the symbol, as used by the linker (i.e., may be mangled).
25568 This attribute is not writable.
25571 @defvar Symbol.print_name
25572 The name of the symbol in a form suitable for output. This is either
25573 @code{name} or @code{linkage_name}, depending on whether the user
25574 asked @value{GDBN} to display demangled or mangled names.
25577 @defvar Symbol.addr_class
25578 The address class of the symbol. This classifies how to find the value
25579 of a symbol. Each address class is a constant defined in the
25580 @code{gdb} module and described later in this chapter.
25583 @defvar Symbol.needs_frame
25584 This is @code{True} if evaluating this symbol's value requires a frame
25585 (@pxref{Frames In Python}) and @code{False} otherwise. Typically,
25586 local variables will require a frame, but other symbols will not.
25589 @defvar Symbol.is_argument
25590 @code{True} if the symbol is an argument of a function.
25593 @defvar Symbol.is_constant
25594 @code{True} if the symbol is a constant.
25597 @defvar Symbol.is_function
25598 @code{True} if the symbol is a function or a method.
25601 @defvar Symbol.is_variable
25602 @code{True} if the symbol is a variable.
25605 A @code{gdb.Symbol} object has the following methods:
25607 @defun Symbol.is_valid ()
25608 Returns @code{True} if the @code{gdb.Symbol} object is valid,
25609 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
25610 the symbol it refers to does not exist in @value{GDBN} any longer.
25611 All other @code{gdb.Symbol} methods will throw an exception if it is
25612 invalid at the time the method is called.
25615 @defun Symbol.value (@r{[}frame@r{]})
25616 Compute the value of the symbol, as a @code{gdb.Value}. For
25617 functions, this computes the address of the function, cast to the
25618 appropriate type. If the symbol requires a frame in order to compute
25619 its value, then @var{frame} must be given. If @var{frame} is not
25620 given, or if @var{frame} is invalid, then this method will throw an
25624 The available domain categories in @code{gdb.Symbol} are represented
25625 as constants in the @code{gdb} module:
25628 @findex SYMBOL_UNDEF_DOMAIN
25629 @findex gdb.SYMBOL_UNDEF_DOMAIN
25630 @item gdb.SYMBOL_UNDEF_DOMAIN
25631 This is used when a domain has not been discovered or none of the
25632 following domains apply. This usually indicates an error either
25633 in the symbol information or in @value{GDBN}'s handling of symbols.
25634 @findex SYMBOL_VAR_DOMAIN
25635 @findex gdb.SYMBOL_VAR_DOMAIN
25636 @item gdb.SYMBOL_VAR_DOMAIN
25637 This domain contains variables, function names, typedef names and enum
25639 @findex SYMBOL_STRUCT_DOMAIN
25640 @findex gdb.SYMBOL_STRUCT_DOMAIN
25641 @item gdb.SYMBOL_STRUCT_DOMAIN
25642 This domain holds struct, union and enum type names.
25643 @findex SYMBOL_LABEL_DOMAIN
25644 @findex gdb.SYMBOL_LABEL_DOMAIN
25645 @item gdb.SYMBOL_LABEL_DOMAIN
25646 This domain contains names of labels (for gotos).
25647 @findex SYMBOL_VARIABLES_DOMAIN
25648 @findex gdb.SYMBOL_VARIABLES_DOMAIN
25649 @item gdb.SYMBOL_VARIABLES_DOMAIN
25650 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
25651 contains everything minus functions and types.
25652 @findex SYMBOL_FUNCTIONS_DOMAIN
25653 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
25654 @item gdb.SYMBOL_FUNCTION_DOMAIN
25655 This domain contains all functions.
25656 @findex SYMBOL_TYPES_DOMAIN
25657 @findex gdb.SYMBOL_TYPES_DOMAIN
25658 @item gdb.SYMBOL_TYPES_DOMAIN
25659 This domain contains all types.
25662 The available address class categories in @code{gdb.Symbol} are represented
25663 as constants in the @code{gdb} module:
25666 @findex SYMBOL_LOC_UNDEF
25667 @findex gdb.SYMBOL_LOC_UNDEF
25668 @item gdb.SYMBOL_LOC_UNDEF
25669 If this is returned by address class, it indicates an error either in
25670 the symbol information or in @value{GDBN}'s handling of symbols.
25671 @findex SYMBOL_LOC_CONST
25672 @findex gdb.SYMBOL_LOC_CONST
25673 @item gdb.SYMBOL_LOC_CONST
25674 Value is constant int.
25675 @findex SYMBOL_LOC_STATIC
25676 @findex gdb.SYMBOL_LOC_STATIC
25677 @item gdb.SYMBOL_LOC_STATIC
25678 Value is at a fixed address.
25679 @findex SYMBOL_LOC_REGISTER
25680 @findex gdb.SYMBOL_LOC_REGISTER
25681 @item gdb.SYMBOL_LOC_REGISTER
25682 Value is in a register.
25683 @findex SYMBOL_LOC_ARG
25684 @findex gdb.SYMBOL_LOC_ARG
25685 @item gdb.SYMBOL_LOC_ARG
25686 Value is an argument. This value is at the offset stored within the
25687 symbol inside the frame's argument list.
25688 @findex SYMBOL_LOC_REF_ARG
25689 @findex gdb.SYMBOL_LOC_REF_ARG
25690 @item gdb.SYMBOL_LOC_REF_ARG
25691 Value address is stored in the frame's argument list. Just like
25692 @code{LOC_ARG} except that the value's address is stored at the
25693 offset, not the value itself.
25694 @findex SYMBOL_LOC_REGPARM_ADDR
25695 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
25696 @item gdb.SYMBOL_LOC_REGPARM_ADDR
25697 Value is a specified register. Just like @code{LOC_REGISTER} except
25698 the register holds the address of the argument instead of the argument
25700 @findex SYMBOL_LOC_LOCAL
25701 @findex gdb.SYMBOL_LOC_LOCAL
25702 @item gdb.SYMBOL_LOC_LOCAL
25703 Value is a local variable.
25704 @findex SYMBOL_LOC_TYPEDEF
25705 @findex gdb.SYMBOL_LOC_TYPEDEF
25706 @item gdb.SYMBOL_LOC_TYPEDEF
25707 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
25709 @findex SYMBOL_LOC_BLOCK
25710 @findex gdb.SYMBOL_LOC_BLOCK
25711 @item gdb.SYMBOL_LOC_BLOCK
25713 @findex SYMBOL_LOC_CONST_BYTES
25714 @findex gdb.SYMBOL_LOC_CONST_BYTES
25715 @item gdb.SYMBOL_LOC_CONST_BYTES
25716 Value is a byte-sequence.
25717 @findex SYMBOL_LOC_UNRESOLVED
25718 @findex gdb.SYMBOL_LOC_UNRESOLVED
25719 @item gdb.SYMBOL_LOC_UNRESOLVED
25720 Value is at a fixed address, but the address of the variable has to be
25721 determined from the minimal symbol table whenever the variable is
25723 @findex SYMBOL_LOC_OPTIMIZED_OUT
25724 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
25725 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
25726 The value does not actually exist in the program.
25727 @findex SYMBOL_LOC_COMPUTED
25728 @findex gdb.SYMBOL_LOC_COMPUTED
25729 @item gdb.SYMBOL_LOC_COMPUTED
25730 The value's address is a computed location.
25733 @node Symbol Tables In Python
25734 @subsubsection Symbol table representation in Python.
25736 @cindex symbol tables in python
25738 @tindex gdb.Symtab_and_line
25740 Access to symbol table data maintained by @value{GDBN} on the inferior
25741 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
25742 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
25743 from the @code{find_sal} method in @code{gdb.Frame} object.
25744 @xref{Frames In Python}.
25746 For more information on @value{GDBN}'s symbol table management, see
25747 @ref{Symbols, ,Examining the Symbol Table}, for more information.
25749 A @code{gdb.Symtab_and_line} object has the following attributes:
25751 @defvar Symtab_and_line.symtab
25752 The symbol table object (@code{gdb.Symtab}) for this frame.
25753 This attribute is not writable.
25756 @defvar Symtab_and_line.pc
25757 Indicates the start of the address range occupied by code for the
25758 current source line. This attribute is not writable.
25761 @defvar Symtab_and_line.last
25762 Indicates the end of the address range occupied by code for the current
25763 source line. This attribute is not writable.
25766 @defvar Symtab_and_line.line
25767 Indicates the current line number for this object. This
25768 attribute is not writable.
25771 A @code{gdb.Symtab_and_line} object has the following methods:
25773 @defun Symtab_and_line.is_valid ()
25774 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
25775 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
25776 invalid if the Symbol table and line object it refers to does not
25777 exist in @value{GDBN} any longer. All other
25778 @code{gdb.Symtab_and_line} methods will throw an exception if it is
25779 invalid at the time the method is called.
25782 A @code{gdb.Symtab} object has the following attributes:
25784 @defvar Symtab.filename
25785 The symbol table's source filename. This attribute is not writable.
25788 @defvar Symtab.objfile
25789 The symbol table's backing object file. @xref{Objfiles In Python}.
25790 This attribute is not writable.
25793 A @code{gdb.Symtab} object has the following methods:
25795 @defun Symtab.is_valid ()
25796 Returns @code{True} if the @code{gdb.Symtab} object is valid,
25797 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
25798 the symbol table it refers to does not exist in @value{GDBN} any
25799 longer. All other @code{gdb.Symtab} methods will throw an exception
25800 if it is invalid at the time the method is called.
25803 @defun Symtab.fullname ()
25804 Return the symbol table's source absolute file name.
25807 @defun Symtab.global_block ()
25808 Return the global block of the underlying symbol table.
25809 @xref{Blocks In Python}.
25812 @defun Symtab.static_block ()
25813 Return the static block of the underlying symbol table.
25814 @xref{Blocks In Python}.
25817 @node Breakpoints In Python
25818 @subsubsection Manipulating breakpoints using Python
25820 @cindex breakpoints in python
25821 @tindex gdb.Breakpoint
25823 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
25826 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
25827 Create a new breakpoint. @var{spec} is a string naming the
25828 location of the breakpoint, or an expression that defines a
25829 watchpoint. The contents can be any location recognized by the
25830 @code{break} command, or in the case of a watchpoint, by the @code{watch}
25831 command. The optional @var{type} denotes the breakpoint to create
25832 from the types defined later in this chapter. This argument can be
25833 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
25834 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
25835 allows the breakpoint to become invisible to the user. The breakpoint
25836 will neither be reported when created, nor will it be listed in the
25837 output from @code{info breakpoints} (but will be listed with the
25838 @code{maint info breakpoints} command). The optional @var{wp_class}
25839 argument defines the class of watchpoint to create, if @var{type} is
25840 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
25841 assumed to be a @code{gdb.WP_WRITE} class.
25844 @defun Breakpoint.stop (self)
25845 The @code{gdb.Breakpoint} class can be sub-classed and, in
25846 particular, you may choose to implement the @code{stop} method.
25847 If this method is defined as a sub-class of @code{gdb.Breakpoint},
25848 it will be called when the inferior reaches any location of a
25849 breakpoint which instantiates that sub-class. If the method returns
25850 @code{True}, the inferior will be stopped at the location of the
25851 breakpoint, otherwise the inferior will continue.
25853 If there are multiple breakpoints at the same location with a
25854 @code{stop} method, each one will be called regardless of the
25855 return status of the previous. This ensures that all @code{stop}
25856 methods have a chance to execute at that location. In this scenario
25857 if one of the methods returns @code{True} but the others return
25858 @code{False}, the inferior will still be stopped.
25860 You should not alter the execution state of the inferior (i.e.@:, step,
25861 next, etc.), alter the current frame context (i.e.@:, change the current
25862 active frame), or alter, add or delete any breakpoint. As a general
25863 rule, you should not alter any data within @value{GDBN} or the inferior
25866 Example @code{stop} implementation:
25869 class MyBreakpoint (gdb.Breakpoint):
25871 inf_val = gdb.parse_and_eval("foo")
25878 The available watchpoint types represented by constants are defined in the
25883 @findex gdb.WP_READ
25885 Read only watchpoint.
25888 @findex gdb.WP_WRITE
25890 Write only watchpoint.
25893 @findex gdb.WP_ACCESS
25894 @item gdb.WP_ACCESS
25895 Read/Write watchpoint.
25898 @defun Breakpoint.is_valid ()
25899 Return @code{True} if this @code{Breakpoint} object is valid,
25900 @code{False} otherwise. A @code{Breakpoint} object can become invalid
25901 if the user deletes the breakpoint. In this case, the object still
25902 exists, but the underlying breakpoint does not. In the cases of
25903 watchpoint scope, the watchpoint remains valid even if execution of the
25904 inferior leaves the scope of that watchpoint.
25907 @defun Breakpoint.delete
25908 Permanently deletes the @value{GDBN} breakpoint. This also
25909 invalidates the Python @code{Breakpoint} object. Any further access
25910 to this object's attributes or methods will raise an error.
25913 @defvar Breakpoint.enabled
25914 This attribute is @code{True} if the breakpoint is enabled, and
25915 @code{False} otherwise. This attribute is writable.
25918 @defvar Breakpoint.silent
25919 This attribute is @code{True} if the breakpoint is silent, and
25920 @code{False} otherwise. This attribute is writable.
25922 Note that a breakpoint can also be silent if it has commands and the
25923 first command is @code{silent}. This is not reported by the
25924 @code{silent} attribute.
25927 @defvar Breakpoint.thread
25928 If the breakpoint is thread-specific, this attribute holds the thread
25929 id. If the breakpoint is not thread-specific, this attribute is
25930 @code{None}. This attribute is writable.
25933 @defvar Breakpoint.task
25934 If the breakpoint is Ada task-specific, this attribute holds the Ada task
25935 id. If the breakpoint is not task-specific (or the underlying
25936 language is not Ada), this attribute is @code{None}. This attribute
25940 @defvar Breakpoint.ignore_count
25941 This attribute holds the ignore count for the breakpoint, an integer.
25942 This attribute is writable.
25945 @defvar Breakpoint.number
25946 This attribute holds the breakpoint's number --- the identifier used by
25947 the user to manipulate the breakpoint. This attribute is not writable.
25950 @defvar Breakpoint.type
25951 This attribute holds the breakpoint's type --- the identifier used to
25952 determine the actual breakpoint type or use-case. This attribute is not
25956 @defvar Breakpoint.visible
25957 This attribute tells whether the breakpoint is visible to the user
25958 when set, or when the @samp{info breakpoints} command is run. This
25959 attribute is not writable.
25962 The available types are represented by constants defined in the @code{gdb}
25966 @findex BP_BREAKPOINT
25967 @findex gdb.BP_BREAKPOINT
25968 @item gdb.BP_BREAKPOINT
25969 Normal code breakpoint.
25971 @findex BP_WATCHPOINT
25972 @findex gdb.BP_WATCHPOINT
25973 @item gdb.BP_WATCHPOINT
25974 Watchpoint breakpoint.
25976 @findex BP_HARDWARE_WATCHPOINT
25977 @findex gdb.BP_HARDWARE_WATCHPOINT
25978 @item gdb.BP_HARDWARE_WATCHPOINT
25979 Hardware assisted watchpoint.
25981 @findex BP_READ_WATCHPOINT
25982 @findex gdb.BP_READ_WATCHPOINT
25983 @item gdb.BP_READ_WATCHPOINT
25984 Hardware assisted read watchpoint.
25986 @findex BP_ACCESS_WATCHPOINT
25987 @findex gdb.BP_ACCESS_WATCHPOINT
25988 @item gdb.BP_ACCESS_WATCHPOINT
25989 Hardware assisted access watchpoint.
25992 @defvar Breakpoint.hit_count
25993 This attribute holds the hit count for the breakpoint, an integer.
25994 This attribute is writable, but currently it can only be set to zero.
25997 @defvar Breakpoint.location
25998 This attribute holds the location of the breakpoint, as specified by
25999 the user. It is a string. If the breakpoint does not have a location
26000 (that is, it is a watchpoint) the attribute's value is @code{None}. This
26001 attribute is not writable.
26004 @defvar Breakpoint.expression
26005 This attribute holds a breakpoint expression, as specified by
26006 the user. It is a string. If the breakpoint does not have an
26007 expression (the breakpoint is not a watchpoint) the attribute's value
26008 is @code{None}. This attribute is not writable.
26011 @defvar Breakpoint.condition
26012 This attribute holds the condition of the breakpoint, as specified by
26013 the user. It is a string. If there is no condition, this attribute's
26014 value is @code{None}. This attribute is writable.
26017 @defvar Breakpoint.commands
26018 This attribute holds the commands attached to the breakpoint. If
26019 there are commands, this attribute's value is a string holding all the
26020 commands, separated by newlines. If there are no commands, this
26021 attribute is @code{None}. This attribute is not writable.
26024 @node Finish Breakpoints in Python
26025 @subsubsection Finish Breakpoints
26027 @cindex python finish breakpoints
26028 @tindex gdb.FinishBreakpoint
26030 A finish breakpoint is a temporary breakpoint set at the return address of
26031 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
26032 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
26033 and deleted when the execution will run out of the breakpoint scope (i.e.@:
26034 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
26035 Finish breakpoints are thread specific and must be create with the right
26038 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
26039 Create a finish breakpoint at the return address of the @code{gdb.Frame}
26040 object @var{frame}. If @var{frame} is not provided, this defaults to the
26041 newest frame. The optional @var{internal} argument allows the breakpoint to
26042 become invisible to the user. @xref{Breakpoints In Python}, for further
26043 details about this argument.
26046 @defun FinishBreakpoint.out_of_scope (self)
26047 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
26048 @code{return} command, @dots{}), a function may not properly terminate, and
26049 thus never hit the finish breakpoint. When @value{GDBN} notices such a
26050 situation, the @code{out_of_scope} callback will be triggered.
26052 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
26056 class MyFinishBreakpoint (gdb.FinishBreakpoint)
26058 print "normal finish"
26061 def out_of_scope ():
26062 print "abnormal finish"
26066 @defvar FinishBreakpoint.return_value
26067 When @value{GDBN} is stopped at a finish breakpoint and the frame
26068 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
26069 attribute will contain a @code{gdb.Value} object corresponding to the return
26070 value of the function. The value will be @code{None} if the function return
26071 type is @code{void} or if the return value was not computable. This attribute
26075 @node Lazy Strings In Python
26076 @subsubsection Python representation of lazy strings.
26078 @cindex lazy strings in python
26079 @tindex gdb.LazyString
26081 A @dfn{lazy string} is a string whose contents is not retrieved or
26082 encoded until it is needed.
26084 A @code{gdb.LazyString} is represented in @value{GDBN} as an
26085 @code{address} that points to a region of memory, an @code{encoding}
26086 that will be used to encode that region of memory, and a @code{length}
26087 to delimit the region of memory that represents the string. The
26088 difference between a @code{gdb.LazyString} and a string wrapped within
26089 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
26090 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
26091 retrieved and encoded during printing, while a @code{gdb.Value}
26092 wrapping a string is immediately retrieved and encoded on creation.
26094 A @code{gdb.LazyString} object has the following functions:
26096 @defun LazyString.value ()
26097 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
26098 will point to the string in memory, but will lose all the delayed
26099 retrieval, encoding and handling that @value{GDBN} applies to a
26100 @code{gdb.LazyString}.
26103 @defvar LazyString.address
26104 This attribute holds the address of the string. This attribute is not
26108 @defvar LazyString.length
26109 This attribute holds the length of the string in characters. If the
26110 length is -1, then the string will be fetched and encoded up to the
26111 first null of appropriate width. This attribute is not writable.
26114 @defvar LazyString.encoding
26115 This attribute holds the encoding that will be applied to the string
26116 when the string is printed by @value{GDBN}. If the encoding is not
26117 set, or contains an empty string, then @value{GDBN} will select the
26118 most appropriate encoding when the string is printed. This attribute
26122 @defvar LazyString.type
26123 This attribute holds the type that is represented by the lazy string's
26124 type. For a lazy string this will always be a pointer type. To
26125 resolve this to the lazy string's character type, use the type's
26126 @code{target} method. @xref{Types In Python}. This attribute is not
26130 @node Architectures In Python
26131 @subsubsection Python representation of architectures
26132 @cindex Python architectures
26134 @value{GDBN} uses architecture specific parameters and artifacts in a
26135 number of its various computations. An architecture is represented
26136 by an instance of the @code{gdb.Architecture} class.
26138 A @code{gdb.Architecture} class has the following methods:
26140 @defun Architecture.name ()
26141 Return the name (string value) of the architecture.
26144 @defun Architecture.disassemble (@var{start_pc} @r{[}, @var{end_pc} @r{[}, @var{count}@r{]]})
26145 Return a list of disassembled instructions starting from the memory
26146 address @var{start_pc}. The optional arguments @var{end_pc} and
26147 @var{count} determine the number of instructions in the returned list.
26148 If both the optional arguments @var{end_pc} and @var{count} are
26149 specified, then a list of at most @var{count} disassembled instructions
26150 whose start address falls in the closed memory address interval from
26151 @var{start_pc} to @var{end_pc} are returned. If @var{end_pc} is not
26152 specified, but @var{count} is specified, then @var{count} number of
26153 instructions starting from the address @var{start_pc} are returned. If
26154 @var{count} is not specified but @var{end_pc} is specified, then all
26155 instructions whose start address falls in the closed memory address
26156 interval from @var{start_pc} to @var{end_pc} are returned. If neither
26157 @var{end_pc} nor @var{count} are specified, then a single instruction at
26158 @var{start_pc} is returned. For all of these cases, each element of the
26159 returned list is a Python @code{dict} with the following string keys:
26164 The value corresponding to this key is a Python long integer capturing
26165 the memory address of the instruction.
26168 The value corresponding to this key is a string value which represents
26169 the instruction with assembly language mnemonics. The assembly
26170 language flavor used is the same as that specified by the current CLI
26171 variable @code{disassembly-flavor}. @xref{Machine Code}.
26174 The value corresponding to this key is the length (integer value) of the
26175 instruction in bytes.
26180 @node Python Auto-loading
26181 @subsection Python Auto-loading
26182 @cindex Python auto-loading
26184 When a new object file is read (for example, due to the @code{file}
26185 command, or because the inferior has loaded a shared library),
26186 @value{GDBN} will look for Python support scripts in several ways:
26187 @file{@var{objfile}-gdb.py} (@pxref{objfile-gdb.py file})
26188 and @code{.debug_gdb_scripts} section
26189 (@pxref{dotdebug_gdb_scripts section}).
26191 The auto-loading feature is useful for supplying application-specific
26192 debugging commands and scripts.
26194 Auto-loading can be enabled or disabled,
26195 and the list of auto-loaded scripts can be printed.
26198 @anchor{set auto-load python-scripts}
26199 @kindex set auto-load python-scripts
26200 @item set auto-load python-scripts [on|off]
26201 Enable or disable the auto-loading of Python scripts.
26203 @anchor{show auto-load python-scripts}
26204 @kindex show auto-load python-scripts
26205 @item show auto-load python-scripts
26206 Show whether auto-loading of Python scripts is enabled or disabled.
26208 @anchor{info auto-load python-scripts}
26209 @kindex info auto-load python-scripts
26210 @cindex print list of auto-loaded Python scripts
26211 @item info auto-load python-scripts [@var{regexp}]
26212 Print the list of all Python scripts that @value{GDBN} auto-loaded.
26214 Also printed is the list of Python scripts that were mentioned in
26215 the @code{.debug_gdb_scripts} section and were not found
26216 (@pxref{dotdebug_gdb_scripts section}).
26217 This is useful because their names are not printed when @value{GDBN}
26218 tries to load them and fails. There may be many of them, and printing
26219 an error message for each one is problematic.
26221 If @var{regexp} is supplied only Python scripts with matching names are printed.
26226 (gdb) info auto-load python-scripts
26228 Yes py-section-script.py
26229 full name: /tmp/py-section-script.py
26230 No my-foo-pretty-printers.py
26234 When reading an auto-loaded file, @value{GDBN} sets the
26235 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
26236 function (@pxref{Objfiles In Python}). This can be useful for
26237 registering objfile-specific pretty-printers.
26240 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
26241 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
26242 * Which flavor to choose?::
26245 @node objfile-gdb.py file
26246 @subsubsection The @file{@var{objfile}-gdb.py} file
26247 @cindex @file{@var{objfile}-gdb.py}
26249 When a new object file is read, @value{GDBN} looks for
26250 a file named @file{@var{objfile}-gdb.py} (we call it @var{script-name} below),
26251 where @var{objfile} is the object file's real name, formed by ensuring
26252 that the file name is absolute, following all symlinks, and resolving
26253 @code{.} and @code{..} components. If this file exists and is
26254 readable, @value{GDBN} will evaluate it as a Python script.
26256 If this file does not exist, then @value{GDBN} will look for
26257 @var{script-name} file in all of the directories as specified below.
26259 Note that loading of this script file also requires accordingly configured
26260 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26262 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
26263 scripts normally according to its @file{.exe} filename. But if no scripts are
26264 found @value{GDBN} also tries script filenames matching the object file without
26265 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
26266 is attempted on any platform. This makes the script filenames compatible
26267 between Unix and MS-Windows hosts.
26270 @anchor{set auto-load scripts-directory}
26271 @kindex set auto-load scripts-directory
26272 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
26273 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
26274 may be delimited by the host platform path separator in use
26275 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
26277 Each entry here needs to be covered also by the security setting
26278 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
26280 @anchor{with-auto-load-dir}
26281 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
26282 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
26283 configuration option @option{--with-auto-load-dir}.
26285 Any reference to @file{$debugdir} will get replaced by
26286 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
26287 reference to @file{$datadir} will get replaced by @var{data-directory} which is
26288 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
26289 @file{$datadir} must be placed as a directory component --- either alone or
26290 delimited by @file{/} or @file{\} directory separators, depending on the host
26293 The list of directories uses path separator (@samp{:} on GNU and Unix
26294 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
26295 to the @env{PATH} environment variable.
26297 @anchor{show auto-load scripts-directory}
26298 @kindex show auto-load scripts-directory
26299 @item show auto-load scripts-directory
26300 Show @value{GDBN} auto-loaded scripts location.
26303 @value{GDBN} does not track which files it has already auto-loaded this way.
26304 @value{GDBN} will load the associated script every time the corresponding
26305 @var{objfile} is opened.
26306 So your @file{-gdb.py} file should be careful to avoid errors if it
26307 is evaluated more than once.
26309 @node dotdebug_gdb_scripts section
26310 @subsubsection The @code{.debug_gdb_scripts} section
26311 @cindex @code{.debug_gdb_scripts} section
26313 For systems using file formats like ELF and COFF,
26314 when @value{GDBN} loads a new object file
26315 it will look for a special section named @samp{.debug_gdb_scripts}.
26316 If this section exists, its contents is a list of names of scripts to load.
26318 @value{GDBN} will look for each specified script file first in the
26319 current directory and then along the source search path
26320 (@pxref{Source Path, ,Specifying Source Directories}),
26321 except that @file{$cdir} is not searched, since the compilation
26322 directory is not relevant to scripts.
26324 Entries can be placed in section @code{.debug_gdb_scripts} with,
26325 for example, this GCC macro:
26328 /* Note: The "MS" section flags are to remove duplicates. */
26329 #define DEFINE_GDB_SCRIPT(script_name) \
26331 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
26333 .asciz \"" script_name "\"\n\
26339 Then one can reference the macro in a header or source file like this:
26342 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
26345 The script name may include directories if desired.
26347 Note that loading of this script file also requires accordingly configured
26348 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26350 If the macro is put in a header, any application or library
26351 using this header will get a reference to the specified script.
26353 @node Which flavor to choose?
26354 @subsubsection Which flavor to choose?
26356 Given the multiple ways of auto-loading Python scripts, it might not always
26357 be clear which one to choose. This section provides some guidance.
26359 Benefits of the @file{-gdb.py} way:
26363 Can be used with file formats that don't support multiple sections.
26366 Ease of finding scripts for public libraries.
26368 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
26369 in the source search path.
26370 For publicly installed libraries, e.g., @file{libstdc++}, there typically
26371 isn't a source directory in which to find the script.
26374 Doesn't require source code additions.
26377 Benefits of the @code{.debug_gdb_scripts} way:
26381 Works with static linking.
26383 Scripts for libraries done the @file{-gdb.py} way require an objfile to
26384 trigger their loading. When an application is statically linked the only
26385 objfile available is the executable, and it is cumbersome to attach all the
26386 scripts from all the input libraries to the executable's @file{-gdb.py} script.
26389 Works with classes that are entirely inlined.
26391 Some classes can be entirely inlined, and thus there may not be an associated
26392 shared library to attach a @file{-gdb.py} script to.
26395 Scripts needn't be copied out of the source tree.
26397 In some circumstances, apps can be built out of large collections of internal
26398 libraries, and the build infrastructure necessary to install the
26399 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
26400 cumbersome. It may be easier to specify the scripts in the
26401 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
26402 top of the source tree to the source search path.
26405 @node Python modules
26406 @subsection Python modules
26407 @cindex python modules
26409 @value{GDBN} comes with several modules to assist writing Python code.
26412 * gdb.printing:: Building and registering pretty-printers.
26413 * gdb.types:: Utilities for working with types.
26414 * gdb.prompt:: Utilities for prompt value substitution.
26418 @subsubsection gdb.printing
26419 @cindex gdb.printing
26421 This module provides a collection of utilities for working with
26425 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
26426 This class specifies the API that makes @samp{info pretty-printer},
26427 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
26428 Pretty-printers should generally inherit from this class.
26430 @item SubPrettyPrinter (@var{name})
26431 For printers that handle multiple types, this class specifies the
26432 corresponding API for the subprinters.
26434 @item RegexpCollectionPrettyPrinter (@var{name})
26435 Utility class for handling multiple printers, all recognized via
26436 regular expressions.
26437 @xref{Writing a Pretty-Printer}, for an example.
26439 @item FlagEnumerationPrinter (@var{name})
26440 A pretty-printer which handles printing of @code{enum} values. Unlike
26441 @value{GDBN}'s built-in @code{enum} printing, this printer attempts to
26442 work properly when there is some overlap between the enumeration
26443 constants. @var{name} is the name of the printer and also the name of
26444 the @code{enum} type to look up.
26446 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
26447 Register @var{printer} with the pretty-printer list of @var{obj}.
26448 If @var{replace} is @code{True} then any existing copy of the printer
26449 is replaced. Otherwise a @code{RuntimeError} exception is raised
26450 if a printer with the same name already exists.
26454 @subsubsection gdb.types
26457 This module provides a collection of utilities for working with
26458 @code{gdb.Type} objects.
26461 @item get_basic_type (@var{type})
26462 Return @var{type} with const and volatile qualifiers stripped,
26463 and with typedefs and C@t{++} references converted to the underlying type.
26468 typedef const int const_int;
26470 const_int& foo_ref (foo);
26471 int main () @{ return 0; @}
26478 (gdb) python import gdb.types
26479 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
26480 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
26484 @item has_field (@var{type}, @var{field})
26485 Return @code{True} if @var{type}, assumed to be a type with fields
26486 (e.g., a structure or union), has field @var{field}.
26488 @item make_enum_dict (@var{enum_type})
26489 Return a Python @code{dictionary} type produced from @var{enum_type}.
26491 @item deep_items (@var{type})
26492 Returns a Python iterator similar to the standard
26493 @code{gdb.Type.iteritems} method, except that the iterator returned
26494 by @code{deep_items} will recursively traverse anonymous struct or
26495 union fields. For example:
26509 Then in @value{GDBN}:
26511 (@value{GDBP}) python import gdb.types
26512 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
26513 (@value{GDBP}) python print struct_a.keys ()
26515 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
26516 @{['a', 'b0', 'b1']@}
26519 @item get_type_recognizers ()
26520 Return a list of the enabled type recognizers for the current context.
26521 This is called by @value{GDBN} during the type-printing process
26522 (@pxref{Type Printing API}).
26524 @item apply_type_recognizers (recognizers, type_obj)
26525 Apply the type recognizers, @var{recognizers}, to the type object
26526 @var{type_obj}. If any recognizer returns a string, return that
26527 string. Otherwise, return @code{None}. This is called by
26528 @value{GDBN} during the type-printing process (@pxref{Type Printing
26531 @item register_type_printer (locus, printer)
26532 This is a convenience function to register a type printer.
26533 @var{printer} is the type printer to register. It must implement the
26534 type printer protocol. @var{locus} is either a @code{gdb.Objfile}, in
26535 which case the printer is registered with that objfile; a
26536 @code{gdb.Progspace}, in which case the printer is registered with
26537 that progspace; or @code{None}, in which case the printer is
26538 registered globally.
26541 This is a base class that implements the type printer protocol. Type
26542 printers are encouraged, but not required, to derive from this class.
26543 It defines a constructor:
26545 @defmethod TypePrinter __init__ (self, name)
26546 Initialize the type printer with the given name. The new printer
26547 starts in the enabled state.
26553 @subsubsection gdb.prompt
26556 This module provides a method for prompt value-substitution.
26559 @item substitute_prompt (@var{string})
26560 Return @var{string} with escape sequences substituted by values. Some
26561 escape sequences take arguments. You can specify arguments inside
26562 ``@{@}'' immediately following the escape sequence.
26564 The escape sequences you can pass to this function are:
26568 Substitute a backslash.
26570 Substitute an ESC character.
26572 Substitute the selected frame; an argument names a frame parameter.
26574 Substitute a newline.
26576 Substitute a parameter's value; the argument names the parameter.
26578 Substitute a carriage return.
26580 Substitute the selected thread; an argument names a thread parameter.
26582 Substitute the version of GDB.
26584 Substitute the current working directory.
26586 Begin a sequence of non-printing characters. These sequences are
26587 typically used with the ESC character, and are not counted in the string
26588 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
26589 blue-colored ``(gdb)'' prompt where the length is five.
26591 End a sequence of non-printing characters.
26597 substitute_prompt (``frame: \f,
26598 print arguments: \p@{print frame-arguments@}'')
26601 @exdent will return the string:
26604 "frame: main, print arguments: scalars"
26609 @section Creating new spellings of existing commands
26610 @cindex aliases for commands
26612 It is often useful to define alternate spellings of existing commands.
26613 For example, if a new @value{GDBN} command defined in Python has
26614 a long name to type, it is handy to have an abbreviated version of it
26615 that involves less typing.
26617 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
26618 of the @samp{step} command even though it is otherwise an ambiguous
26619 abbreviation of other commands like @samp{set} and @samp{show}.
26621 Aliases are also used to provide shortened or more common versions
26622 of multi-word commands. For example, @value{GDBN} provides the
26623 @samp{tty} alias of the @samp{set inferior-tty} command.
26625 You can define a new alias with the @samp{alias} command.
26630 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
26634 @var{ALIAS} specifies the name of the new alias.
26635 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
26638 @var{COMMAND} specifies the name of an existing command
26639 that is being aliased.
26641 The @samp{-a} option specifies that the new alias is an abbreviation
26642 of the command. Abbreviations are not shown in command
26643 lists displayed by the @samp{help} command.
26645 The @samp{--} option specifies the end of options,
26646 and is useful when @var{ALIAS} begins with a dash.
26648 Here is a simple example showing how to make an abbreviation
26649 of a command so that there is less to type.
26650 Suppose you were tired of typing @samp{disas}, the current
26651 shortest unambiguous abbreviation of the @samp{disassemble} command
26652 and you wanted an even shorter version named @samp{di}.
26653 The following will accomplish this.
26656 (gdb) alias -a di = disas
26659 Note that aliases are different from user-defined commands.
26660 With a user-defined command, you also need to write documentation
26661 for it with the @samp{document} command.
26662 An alias automatically picks up the documentation of the existing command.
26664 Here is an example where we make @samp{elms} an abbreviation of
26665 @samp{elements} in the @samp{set print elements} command.
26666 This is to show that you can make an abbreviation of any part
26670 (gdb) alias -a set print elms = set print elements
26671 (gdb) alias -a show print elms = show print elements
26672 (gdb) set p elms 20
26674 Limit on string chars or array elements to print is 200.
26677 Note that if you are defining an alias of a @samp{set} command,
26678 and you want to have an alias for the corresponding @samp{show}
26679 command, then you need to define the latter separately.
26681 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
26682 @var{ALIAS}, just as they are normally.
26685 (gdb) alias -a set pr elms = set p ele
26688 Finally, here is an example showing the creation of a one word
26689 alias for a more complex command.
26690 This creates alias @samp{spe} of the command @samp{set print elements}.
26693 (gdb) alias spe = set print elements
26698 @chapter Command Interpreters
26699 @cindex command interpreters
26701 @value{GDBN} supports multiple command interpreters, and some command
26702 infrastructure to allow users or user interface writers to switch
26703 between interpreters or run commands in other interpreters.
26705 @value{GDBN} currently supports two command interpreters, the console
26706 interpreter (sometimes called the command-line interpreter or @sc{cli})
26707 and the machine interface interpreter (or @sc{gdb/mi}). This manual
26708 describes both of these interfaces in great detail.
26710 By default, @value{GDBN} will start with the console interpreter.
26711 However, the user may choose to start @value{GDBN} with another
26712 interpreter by specifying the @option{-i} or @option{--interpreter}
26713 startup options. Defined interpreters include:
26717 @cindex console interpreter
26718 The traditional console or command-line interpreter. This is the most often
26719 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
26720 @value{GDBN} will use this interpreter.
26723 @cindex mi interpreter
26724 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
26725 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
26726 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
26730 @cindex mi2 interpreter
26731 The current @sc{gdb/mi} interface.
26734 @cindex mi1 interpreter
26735 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
26739 @cindex invoke another interpreter
26740 The interpreter being used by @value{GDBN} may not be dynamically
26741 switched at runtime. Although possible, this could lead to a very
26742 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
26743 enters the command "interpreter-set console" in a console view,
26744 @value{GDBN} would switch to using the console interpreter, rendering
26745 the IDE inoperable!
26747 @kindex interpreter-exec
26748 Although you may only choose a single interpreter at startup, you may execute
26749 commands in any interpreter from the current interpreter using the appropriate
26750 command. If you are running the console interpreter, simply use the
26751 @code{interpreter-exec} command:
26754 interpreter-exec mi "-data-list-register-names"
26757 @sc{gdb/mi} has a similar command, although it is only available in versions of
26758 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
26761 @chapter @value{GDBN} Text User Interface
26763 @cindex Text User Interface
26766 * TUI Overview:: TUI overview
26767 * TUI Keys:: TUI key bindings
26768 * TUI Single Key Mode:: TUI single key mode
26769 * TUI Commands:: TUI-specific commands
26770 * TUI Configuration:: TUI configuration variables
26773 The @value{GDBN} Text User Interface (TUI) is a terminal
26774 interface which uses the @code{curses} library to show the source
26775 file, the assembly output, the program registers and @value{GDBN}
26776 commands in separate text windows. The TUI mode is supported only
26777 on platforms where a suitable version of the @code{curses} library
26780 The TUI mode is enabled by default when you invoke @value{GDBN} as
26781 @samp{@value{GDBP} -tui}.
26782 You can also switch in and out of TUI mode while @value{GDBN} runs by
26783 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
26784 @xref{TUI Keys, ,TUI Key Bindings}.
26787 @section TUI Overview
26789 In TUI mode, @value{GDBN} can display several text windows:
26793 This window is the @value{GDBN} command window with the @value{GDBN}
26794 prompt and the @value{GDBN} output. The @value{GDBN} input is still
26795 managed using readline.
26798 The source window shows the source file of the program. The current
26799 line and active breakpoints are displayed in this window.
26802 The assembly window shows the disassembly output of the program.
26805 This window shows the processor registers. Registers are highlighted
26806 when their values change.
26809 The source and assembly windows show the current program position
26810 by highlighting the current line and marking it with a @samp{>} marker.
26811 Breakpoints are indicated with two markers. The first marker
26812 indicates the breakpoint type:
26816 Breakpoint which was hit at least once.
26819 Breakpoint which was never hit.
26822 Hardware breakpoint which was hit at least once.
26825 Hardware breakpoint which was never hit.
26828 The second marker indicates whether the breakpoint is enabled or not:
26832 Breakpoint is enabled.
26835 Breakpoint is disabled.
26838 The source, assembly and register windows are updated when the current
26839 thread changes, when the frame changes, or when the program counter
26842 These windows are not all visible at the same time. The command
26843 window is always visible. The others can be arranged in several
26854 source and assembly,
26857 source and registers, or
26860 assembly and registers.
26863 A status line above the command window shows the following information:
26867 Indicates the current @value{GDBN} target.
26868 (@pxref{Targets, ,Specifying a Debugging Target}).
26871 Gives the current process or thread number.
26872 When no process is being debugged, this field is set to @code{No process}.
26875 Gives the current function name for the selected frame.
26876 The name is demangled if demangling is turned on (@pxref{Print Settings}).
26877 When there is no symbol corresponding to the current program counter,
26878 the string @code{??} is displayed.
26881 Indicates the current line number for the selected frame.
26882 When the current line number is not known, the string @code{??} is displayed.
26885 Indicates the current program counter address.
26889 @section TUI Key Bindings
26890 @cindex TUI key bindings
26892 The TUI installs several key bindings in the readline keymaps
26893 @ifset SYSTEM_READLINE
26894 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
26896 @ifclear SYSTEM_READLINE
26897 (@pxref{Command Line Editing}).
26899 The following key bindings are installed for both TUI mode and the
26900 @value{GDBN} standard mode.
26909 Enter or leave the TUI mode. When leaving the TUI mode,
26910 the curses window management stops and @value{GDBN} operates using
26911 its standard mode, writing on the terminal directly. When reentering
26912 the TUI mode, control is given back to the curses windows.
26913 The screen is then refreshed.
26917 Use a TUI layout with only one window. The layout will
26918 either be @samp{source} or @samp{assembly}. When the TUI mode
26919 is not active, it will switch to the TUI mode.
26921 Think of this key binding as the Emacs @kbd{C-x 1} binding.
26925 Use a TUI layout with at least two windows. When the current
26926 layout already has two windows, the next layout with two windows is used.
26927 When a new layout is chosen, one window will always be common to the
26928 previous layout and the new one.
26930 Think of it as the Emacs @kbd{C-x 2} binding.
26934 Change the active window. The TUI associates several key bindings
26935 (like scrolling and arrow keys) with the active window. This command
26936 gives the focus to the next TUI window.
26938 Think of it as the Emacs @kbd{C-x o} binding.
26942 Switch in and out of the TUI SingleKey mode that binds single
26943 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
26946 The following key bindings only work in the TUI mode:
26951 Scroll the active window one page up.
26955 Scroll the active window one page down.
26959 Scroll the active window one line up.
26963 Scroll the active window one line down.
26967 Scroll the active window one column left.
26971 Scroll the active window one column right.
26975 Refresh the screen.
26978 Because the arrow keys scroll the active window in the TUI mode, they
26979 are not available for their normal use by readline unless the command
26980 window has the focus. When another window is active, you must use
26981 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
26982 and @kbd{C-f} to control the command window.
26984 @node TUI Single Key Mode
26985 @section TUI Single Key Mode
26986 @cindex TUI single key mode
26988 The TUI also provides a @dfn{SingleKey} mode, which binds several
26989 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
26990 switch into this mode, where the following key bindings are used:
26993 @kindex c @r{(SingleKey TUI key)}
26997 @kindex d @r{(SingleKey TUI key)}
27001 @kindex f @r{(SingleKey TUI key)}
27005 @kindex n @r{(SingleKey TUI key)}
27009 @kindex q @r{(SingleKey TUI key)}
27011 exit the SingleKey mode.
27013 @kindex r @r{(SingleKey TUI key)}
27017 @kindex s @r{(SingleKey TUI key)}
27021 @kindex u @r{(SingleKey TUI key)}
27025 @kindex v @r{(SingleKey TUI key)}
27029 @kindex w @r{(SingleKey TUI key)}
27034 Other keys temporarily switch to the @value{GDBN} command prompt.
27035 The key that was pressed is inserted in the editing buffer so that
27036 it is possible to type most @value{GDBN} commands without interaction
27037 with the TUI SingleKey mode. Once the command is entered the TUI
27038 SingleKey mode is restored. The only way to permanently leave
27039 this mode is by typing @kbd{q} or @kbd{C-x s}.
27043 @section TUI-specific Commands
27044 @cindex TUI commands
27046 The TUI has specific commands to control the text windows.
27047 These commands are always available, even when @value{GDBN} is not in
27048 the TUI mode. When @value{GDBN} is in the standard mode, most
27049 of these commands will automatically switch to the TUI mode.
27051 Note that if @value{GDBN}'s @code{stdout} is not connected to a
27052 terminal, or @value{GDBN} has been started with the machine interface
27053 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
27054 these commands will fail with an error, because it would not be
27055 possible or desirable to enable curses window management.
27060 List and give the size of all displayed windows.
27064 Display the next layout.
27067 Display the previous layout.
27070 Display the source window only.
27073 Display the assembly window only.
27076 Display the source and assembly window.
27079 Display the register window together with the source or assembly window.
27083 Make the next window active for scrolling.
27086 Make the previous window active for scrolling.
27089 Make the source window active for scrolling.
27092 Make the assembly window active for scrolling.
27095 Make the register window active for scrolling.
27098 Make the command window active for scrolling.
27102 Refresh the screen. This is similar to typing @kbd{C-L}.
27104 @item tui reg float
27106 Show the floating point registers in the register window.
27108 @item tui reg general
27109 Show the general registers in the register window.
27112 Show the next register group. The list of register groups as well as
27113 their order is target specific. The predefined register groups are the
27114 following: @code{general}, @code{float}, @code{system}, @code{vector},
27115 @code{all}, @code{save}, @code{restore}.
27117 @item tui reg system
27118 Show the system registers in the register window.
27122 Update the source window and the current execution point.
27124 @item winheight @var{name} +@var{count}
27125 @itemx winheight @var{name} -@var{count}
27127 Change the height of the window @var{name} by @var{count}
27128 lines. Positive counts increase the height, while negative counts
27131 @item tabset @var{nchars}
27133 Set the width of tab stops to be @var{nchars} characters.
27136 @node TUI Configuration
27137 @section TUI Configuration Variables
27138 @cindex TUI configuration variables
27140 Several configuration variables control the appearance of TUI windows.
27143 @item set tui border-kind @var{kind}
27144 @kindex set tui border-kind
27145 Select the border appearance for the source, assembly and register windows.
27146 The possible values are the following:
27149 Use a space character to draw the border.
27152 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
27155 Use the Alternate Character Set to draw the border. The border is
27156 drawn using character line graphics if the terminal supports them.
27159 @item set tui border-mode @var{mode}
27160 @kindex set tui border-mode
27161 @itemx set tui active-border-mode @var{mode}
27162 @kindex set tui active-border-mode
27163 Select the display attributes for the borders of the inactive windows
27164 or the active window. The @var{mode} can be one of the following:
27167 Use normal attributes to display the border.
27173 Use reverse video mode.
27176 Use half bright mode.
27178 @item half-standout
27179 Use half bright and standout mode.
27182 Use extra bright or bold mode.
27184 @item bold-standout
27185 Use extra bright or bold and standout mode.
27190 @chapter Using @value{GDBN} under @sc{gnu} Emacs
27193 @cindex @sc{gnu} Emacs
27194 A special interface allows you to use @sc{gnu} Emacs to view (and
27195 edit) the source files for the program you are debugging with
27198 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
27199 executable file you want to debug as an argument. This command starts
27200 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
27201 created Emacs buffer.
27202 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
27204 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
27209 All ``terminal'' input and output goes through an Emacs buffer, called
27212 This applies both to @value{GDBN} commands and their output, and to the input
27213 and output done by the program you are debugging.
27215 This is useful because it means that you can copy the text of previous
27216 commands and input them again; you can even use parts of the output
27219 All the facilities of Emacs' Shell mode are available for interacting
27220 with your program. In particular, you can send signals the usual
27221 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
27225 @value{GDBN} displays source code through Emacs.
27227 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
27228 source file for that frame and puts an arrow (@samp{=>}) at the
27229 left margin of the current line. Emacs uses a separate buffer for
27230 source display, and splits the screen to show both your @value{GDBN} session
27233 Explicit @value{GDBN} @code{list} or search commands still produce output as
27234 usual, but you probably have no reason to use them from Emacs.
27237 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
27238 a graphical mode, enabled by default, which provides further buffers
27239 that can control the execution and describe the state of your program.
27240 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
27242 If you specify an absolute file name when prompted for the @kbd{M-x
27243 gdb} argument, then Emacs sets your current working directory to where
27244 your program resides. If you only specify the file name, then Emacs
27245 sets your current working directory to the directory associated
27246 with the previous buffer. In this case, @value{GDBN} may find your
27247 program by searching your environment's @code{PATH} variable, but on
27248 some operating systems it might not find the source. So, although the
27249 @value{GDBN} input and output session proceeds normally, the auxiliary
27250 buffer does not display the current source and line of execution.
27252 The initial working directory of @value{GDBN} is printed on the top
27253 line of the GUD buffer and this serves as a default for the commands
27254 that specify files for @value{GDBN} to operate on. @xref{Files,
27255 ,Commands to Specify Files}.
27257 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
27258 need to call @value{GDBN} by a different name (for example, if you
27259 keep several configurations around, with different names) you can
27260 customize the Emacs variable @code{gud-gdb-command-name} to run the
27263 In the GUD buffer, you can use these special Emacs commands in
27264 addition to the standard Shell mode commands:
27268 Describe the features of Emacs' GUD Mode.
27271 Execute to another source line, like the @value{GDBN} @code{step} command; also
27272 update the display window to show the current file and location.
27275 Execute to next source line in this function, skipping all function
27276 calls, like the @value{GDBN} @code{next} command. Then update the display window
27277 to show the current file and location.
27280 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
27281 display window accordingly.
27284 Execute until exit from the selected stack frame, like the @value{GDBN}
27285 @code{finish} command.
27288 Continue execution of your program, like the @value{GDBN} @code{continue}
27292 Go up the number of frames indicated by the numeric argument
27293 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
27294 like the @value{GDBN} @code{up} command.
27297 Go down the number of frames indicated by the numeric argument, like the
27298 @value{GDBN} @code{down} command.
27301 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
27302 tells @value{GDBN} to set a breakpoint on the source line point is on.
27304 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
27305 separate frame which shows a backtrace when the GUD buffer is current.
27306 Move point to any frame in the stack and type @key{RET} to make it
27307 become the current frame and display the associated source in the
27308 source buffer. Alternatively, click @kbd{Mouse-2} to make the
27309 selected frame become the current one. In graphical mode, the
27310 speedbar displays watch expressions.
27312 If you accidentally delete the source-display buffer, an easy way to get
27313 it back is to type the command @code{f} in the @value{GDBN} buffer, to
27314 request a frame display; when you run under Emacs, this recreates
27315 the source buffer if necessary to show you the context of the current
27318 The source files displayed in Emacs are in ordinary Emacs buffers
27319 which are visiting the source files in the usual way. You can edit
27320 the files with these buffers if you wish; but keep in mind that @value{GDBN}
27321 communicates with Emacs in terms of line numbers. If you add or
27322 delete lines from the text, the line numbers that @value{GDBN} knows cease
27323 to correspond properly with the code.
27325 A more detailed description of Emacs' interaction with @value{GDBN} is
27326 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
27330 @chapter The @sc{gdb/mi} Interface
27332 @unnumberedsec Function and Purpose
27334 @cindex @sc{gdb/mi}, its purpose
27335 @sc{gdb/mi} is a line based machine oriented text interface to
27336 @value{GDBN} and is activated by specifying using the
27337 @option{--interpreter} command line option (@pxref{Mode Options}). It
27338 is specifically intended to support the development of systems which
27339 use the debugger as just one small component of a larger system.
27341 This chapter is a specification of the @sc{gdb/mi} interface. It is written
27342 in the form of a reference manual.
27344 Note that @sc{gdb/mi} is still under construction, so some of the
27345 features described below are incomplete and subject to change
27346 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
27348 @unnumberedsec Notation and Terminology
27350 @cindex notational conventions, for @sc{gdb/mi}
27351 This chapter uses the following notation:
27355 @code{|} separates two alternatives.
27358 @code{[ @var{something} ]} indicates that @var{something} is optional:
27359 it may or may not be given.
27362 @code{( @var{group} )*} means that @var{group} inside the parentheses
27363 may repeat zero or more times.
27366 @code{( @var{group} )+} means that @var{group} inside the parentheses
27367 may repeat one or more times.
27370 @code{"@var{string}"} means a literal @var{string}.
27374 @heading Dependencies
27378 * GDB/MI General Design::
27379 * GDB/MI Command Syntax::
27380 * GDB/MI Compatibility with CLI::
27381 * GDB/MI Development and Front Ends::
27382 * GDB/MI Output Records::
27383 * GDB/MI Simple Examples::
27384 * GDB/MI Command Description Format::
27385 * GDB/MI Breakpoint Commands::
27386 * GDB/MI Catchpoint Commands::
27387 * GDB/MI Program Context::
27388 * GDB/MI Thread Commands::
27389 * GDB/MI Ada Tasking Commands::
27390 * GDB/MI Program Execution::
27391 * GDB/MI Stack Manipulation::
27392 * GDB/MI Variable Objects::
27393 * GDB/MI Data Manipulation::
27394 * GDB/MI Tracepoint Commands::
27395 * GDB/MI Symbol Query::
27396 * GDB/MI File Commands::
27398 * GDB/MI Kod Commands::
27399 * GDB/MI Memory Overlay Commands::
27400 * GDB/MI Signal Handling Commands::
27402 * GDB/MI Target Manipulation::
27403 * GDB/MI File Transfer Commands::
27404 * GDB/MI Miscellaneous Commands::
27407 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27408 @node GDB/MI General Design
27409 @section @sc{gdb/mi} General Design
27410 @cindex GDB/MI General Design
27412 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
27413 parts---commands sent to @value{GDBN}, responses to those commands
27414 and notifications. Each command results in exactly one response,
27415 indicating either successful completion of the command, or an error.
27416 For the commands that do not resume the target, the response contains the
27417 requested information. For the commands that resume the target, the
27418 response only indicates whether the target was successfully resumed.
27419 Notifications is the mechanism for reporting changes in the state of the
27420 target, or in @value{GDBN} state, that cannot conveniently be associated with
27421 a command and reported as part of that command response.
27423 The important examples of notifications are:
27427 Exec notifications. These are used to report changes in
27428 target state---when a target is resumed, or stopped. It would not
27429 be feasible to include this information in response of resuming
27430 commands, because one resume commands can result in multiple events in
27431 different threads. Also, quite some time may pass before any event
27432 happens in the target, while a frontend needs to know whether the resuming
27433 command itself was successfully executed.
27436 Console output, and status notifications. Console output
27437 notifications are used to report output of CLI commands, as well as
27438 diagnostics for other commands. Status notifications are used to
27439 report the progress of a long-running operation. Naturally, including
27440 this information in command response would mean no output is produced
27441 until the command is finished, which is undesirable.
27444 General notifications. Commands may have various side effects on
27445 the @value{GDBN} or target state beyond their official purpose. For example,
27446 a command may change the selected thread. Although such changes can
27447 be included in command response, using notification allows for more
27448 orthogonal frontend design.
27452 There's no guarantee that whenever an MI command reports an error,
27453 @value{GDBN} or the target are in any specific state, and especially,
27454 the state is not reverted to the state before the MI command was
27455 processed. Therefore, whenever an MI command results in an error,
27456 we recommend that the frontend refreshes all the information shown in
27457 the user interface.
27461 * Context management::
27462 * Asynchronous and non-stop modes::
27466 @node Context management
27467 @subsection Context management
27469 In most cases when @value{GDBN} accesses the target, this access is
27470 done in context of a specific thread and frame (@pxref{Frames}).
27471 Often, even when accessing global data, the target requires that a thread
27472 be specified. The CLI interface maintains the selected thread and frame,
27473 and supplies them to target on each command. This is convenient,
27474 because a command line user would not want to specify that information
27475 explicitly on each command, and because user interacts with
27476 @value{GDBN} via a single terminal, so no confusion is possible as
27477 to what thread and frame are the current ones.
27479 In the case of MI, the concept of selected thread and frame is less
27480 useful. First, a frontend can easily remember this information
27481 itself. Second, a graphical frontend can have more than one window,
27482 each one used for debugging a different thread, and the frontend might
27483 want to access additional threads for internal purposes. This
27484 increases the risk that by relying on implicitly selected thread, the
27485 frontend may be operating on a wrong one. Therefore, each MI command
27486 should explicitly specify which thread and frame to operate on. To
27487 make it possible, each MI command accepts the @samp{--thread} and
27488 @samp{--frame} options, the value to each is @value{GDBN} identifier
27489 for thread and frame to operate on.
27491 Usually, each top-level window in a frontend allows the user to select
27492 a thread and a frame, and remembers the user selection for further
27493 operations. However, in some cases @value{GDBN} may suggest that the
27494 current thread be changed. For example, when stopping on a breakpoint
27495 it is reasonable to switch to the thread where breakpoint is hit. For
27496 another example, if the user issues the CLI @samp{thread} command via
27497 the frontend, it is desirable to change the frontend's selected thread to the
27498 one specified by user. @value{GDBN} communicates the suggestion to
27499 change current thread using the @samp{=thread-selected} notification.
27500 No such notification is available for the selected frame at the moment.
27502 Note that historically, MI shares the selected thread with CLI, so
27503 frontends used the @code{-thread-select} to execute commands in the
27504 right context. However, getting this to work right is cumbersome. The
27505 simplest way is for frontend to emit @code{-thread-select} command
27506 before every command. This doubles the number of commands that need
27507 to be sent. The alternative approach is to suppress @code{-thread-select}
27508 if the selected thread in @value{GDBN} is supposed to be identical to the
27509 thread the frontend wants to operate on. However, getting this
27510 optimization right can be tricky. In particular, if the frontend
27511 sends several commands to @value{GDBN}, and one of the commands changes the
27512 selected thread, then the behaviour of subsequent commands will
27513 change. So, a frontend should either wait for response from such
27514 problematic commands, or explicitly add @code{-thread-select} for
27515 all subsequent commands. No frontend is known to do this exactly
27516 right, so it is suggested to just always pass the @samp{--thread} and
27517 @samp{--frame} options.
27519 @node Asynchronous and non-stop modes
27520 @subsection Asynchronous command execution and non-stop mode
27522 On some targets, @value{GDBN} is capable of processing MI commands
27523 even while the target is running. This is called @dfn{asynchronous
27524 command execution} (@pxref{Background Execution}). The frontend may
27525 specify a preferrence for asynchronous execution using the
27526 @code{-gdb-set target-async 1} command, which should be emitted before
27527 either running the executable or attaching to the target. After the
27528 frontend has started the executable or attached to the target, it can
27529 find if asynchronous execution is enabled using the
27530 @code{-list-target-features} command.
27532 Even if @value{GDBN} can accept a command while target is running,
27533 many commands that access the target do not work when the target is
27534 running. Therefore, asynchronous command execution is most useful
27535 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
27536 it is possible to examine the state of one thread, while other threads
27539 When a given thread is running, MI commands that try to access the
27540 target in the context of that thread may not work, or may work only on
27541 some targets. In particular, commands that try to operate on thread's
27542 stack will not work, on any target. Commands that read memory, or
27543 modify breakpoints, may work or not work, depending on the target. Note
27544 that even commands that operate on global state, such as @code{print},
27545 @code{set}, and breakpoint commands, still access the target in the
27546 context of a specific thread, so frontend should try to find a
27547 stopped thread and perform the operation on that thread (using the
27548 @samp{--thread} option).
27550 Which commands will work in the context of a running thread is
27551 highly target dependent. However, the two commands
27552 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
27553 to find the state of a thread, will always work.
27555 @node Thread groups
27556 @subsection Thread groups
27557 @value{GDBN} may be used to debug several processes at the same time.
27558 On some platfroms, @value{GDBN} may support debugging of several
27559 hardware systems, each one having several cores with several different
27560 processes running on each core. This section describes the MI
27561 mechanism to support such debugging scenarios.
27563 The key observation is that regardless of the structure of the
27564 target, MI can have a global list of threads, because most commands that
27565 accept the @samp{--thread} option do not need to know what process that
27566 thread belongs to. Therefore, it is not necessary to introduce
27567 neither additional @samp{--process} option, nor an notion of the
27568 current process in the MI interface. The only strictly new feature
27569 that is required is the ability to find how the threads are grouped
27572 To allow the user to discover such grouping, and to support arbitrary
27573 hierarchy of machines/cores/processes, MI introduces the concept of a
27574 @dfn{thread group}. Thread group is a collection of threads and other
27575 thread groups. A thread group always has a string identifier, a type,
27576 and may have additional attributes specific to the type. A new
27577 command, @code{-list-thread-groups}, returns the list of top-level
27578 thread groups, which correspond to processes that @value{GDBN} is
27579 debugging at the moment. By passing an identifier of a thread group
27580 to the @code{-list-thread-groups} command, it is possible to obtain
27581 the members of specific thread group.
27583 To allow the user to easily discover processes, and other objects, he
27584 wishes to debug, a concept of @dfn{available thread group} is
27585 introduced. Available thread group is an thread group that
27586 @value{GDBN} is not debugging, but that can be attached to, using the
27587 @code{-target-attach} command. The list of available top-level thread
27588 groups can be obtained using @samp{-list-thread-groups --available}.
27589 In general, the content of a thread group may be only retrieved only
27590 after attaching to that thread group.
27592 Thread groups are related to inferiors (@pxref{Inferiors and
27593 Programs}). Each inferior corresponds to a thread group of a special
27594 type @samp{process}, and some additional operations are permitted on
27595 such thread groups.
27597 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27598 @node GDB/MI Command Syntax
27599 @section @sc{gdb/mi} Command Syntax
27602 * GDB/MI Input Syntax::
27603 * GDB/MI Output Syntax::
27606 @node GDB/MI Input Syntax
27607 @subsection @sc{gdb/mi} Input Syntax
27609 @cindex input syntax for @sc{gdb/mi}
27610 @cindex @sc{gdb/mi}, input syntax
27612 @item @var{command} @expansion{}
27613 @code{@var{cli-command} | @var{mi-command}}
27615 @item @var{cli-command} @expansion{}
27616 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
27617 @var{cli-command} is any existing @value{GDBN} CLI command.
27619 @item @var{mi-command} @expansion{}
27620 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
27621 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
27623 @item @var{token} @expansion{}
27624 "any sequence of digits"
27626 @item @var{option} @expansion{}
27627 @code{"-" @var{parameter} [ " " @var{parameter} ]}
27629 @item @var{parameter} @expansion{}
27630 @code{@var{non-blank-sequence} | @var{c-string}}
27632 @item @var{operation} @expansion{}
27633 @emph{any of the operations described in this chapter}
27635 @item @var{non-blank-sequence} @expansion{}
27636 @emph{anything, provided it doesn't contain special characters such as
27637 "-", @var{nl}, """ and of course " "}
27639 @item @var{c-string} @expansion{}
27640 @code{""" @var{seven-bit-iso-c-string-content} """}
27642 @item @var{nl} @expansion{}
27651 The CLI commands are still handled by the @sc{mi} interpreter; their
27652 output is described below.
27655 The @code{@var{token}}, when present, is passed back when the command
27659 Some @sc{mi} commands accept optional arguments as part of the parameter
27660 list. Each option is identified by a leading @samp{-} (dash) and may be
27661 followed by an optional argument parameter. Options occur first in the
27662 parameter list and can be delimited from normal parameters using
27663 @samp{--} (this is useful when some parameters begin with a dash).
27670 We want easy access to the existing CLI syntax (for debugging).
27673 We want it to be easy to spot a @sc{mi} operation.
27676 @node GDB/MI Output Syntax
27677 @subsection @sc{gdb/mi} Output Syntax
27679 @cindex output syntax of @sc{gdb/mi}
27680 @cindex @sc{gdb/mi}, output syntax
27681 The output from @sc{gdb/mi} consists of zero or more out-of-band records
27682 followed, optionally, by a single result record. This result record
27683 is for the most recent command. The sequence of output records is
27684 terminated by @samp{(gdb)}.
27686 If an input command was prefixed with a @code{@var{token}} then the
27687 corresponding output for that command will also be prefixed by that same
27691 @item @var{output} @expansion{}
27692 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
27694 @item @var{result-record} @expansion{}
27695 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
27697 @item @var{out-of-band-record} @expansion{}
27698 @code{@var{async-record} | @var{stream-record}}
27700 @item @var{async-record} @expansion{}
27701 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
27703 @item @var{exec-async-output} @expansion{}
27704 @code{[ @var{token} ] "*" @var{async-output}}
27706 @item @var{status-async-output} @expansion{}
27707 @code{[ @var{token} ] "+" @var{async-output}}
27709 @item @var{notify-async-output} @expansion{}
27710 @code{[ @var{token} ] "=" @var{async-output}}
27712 @item @var{async-output} @expansion{}
27713 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
27715 @item @var{result-class} @expansion{}
27716 @code{"done" | "running" | "connected" | "error" | "exit"}
27718 @item @var{async-class} @expansion{}
27719 @code{"stopped" | @var{others}} (where @var{others} will be added
27720 depending on the needs---this is still in development).
27722 @item @var{result} @expansion{}
27723 @code{ @var{variable} "=" @var{value}}
27725 @item @var{variable} @expansion{}
27726 @code{ @var{string} }
27728 @item @var{value} @expansion{}
27729 @code{ @var{const} | @var{tuple} | @var{list} }
27731 @item @var{const} @expansion{}
27732 @code{@var{c-string}}
27734 @item @var{tuple} @expansion{}
27735 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
27737 @item @var{list} @expansion{}
27738 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
27739 @var{result} ( "," @var{result} )* "]" }
27741 @item @var{stream-record} @expansion{}
27742 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
27744 @item @var{console-stream-output} @expansion{}
27745 @code{"~" @var{c-string}}
27747 @item @var{target-stream-output} @expansion{}
27748 @code{"@@" @var{c-string}}
27750 @item @var{log-stream-output} @expansion{}
27751 @code{"&" @var{c-string}}
27753 @item @var{nl} @expansion{}
27756 @item @var{token} @expansion{}
27757 @emph{any sequence of digits}.
27765 All output sequences end in a single line containing a period.
27768 The @code{@var{token}} is from the corresponding request. Note that
27769 for all async output, while the token is allowed by the grammar and
27770 may be output by future versions of @value{GDBN} for select async
27771 output messages, it is generally omitted. Frontends should treat
27772 all async output as reporting general changes in the state of the
27773 target and there should be no need to associate async output to any
27777 @cindex status output in @sc{gdb/mi}
27778 @var{status-async-output} contains on-going status information about the
27779 progress of a slow operation. It can be discarded. All status output is
27780 prefixed by @samp{+}.
27783 @cindex async output in @sc{gdb/mi}
27784 @var{exec-async-output} contains asynchronous state change on the target
27785 (stopped, started, disappeared). All async output is prefixed by
27789 @cindex notify output in @sc{gdb/mi}
27790 @var{notify-async-output} contains supplementary information that the
27791 client should handle (e.g., a new breakpoint information). All notify
27792 output is prefixed by @samp{=}.
27795 @cindex console output in @sc{gdb/mi}
27796 @var{console-stream-output} is output that should be displayed as is in the
27797 console. It is the textual response to a CLI command. All the console
27798 output is prefixed by @samp{~}.
27801 @cindex target output in @sc{gdb/mi}
27802 @var{target-stream-output} is the output produced by the target program.
27803 All the target output is prefixed by @samp{@@}.
27806 @cindex log output in @sc{gdb/mi}
27807 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
27808 instance messages that should be displayed as part of an error log. All
27809 the log output is prefixed by @samp{&}.
27812 @cindex list output in @sc{gdb/mi}
27813 New @sc{gdb/mi} commands should only output @var{lists} containing
27819 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
27820 details about the various output records.
27822 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27823 @node GDB/MI Compatibility with CLI
27824 @section @sc{gdb/mi} Compatibility with CLI
27826 @cindex compatibility, @sc{gdb/mi} and CLI
27827 @cindex @sc{gdb/mi}, compatibility with CLI
27829 For the developers convenience CLI commands can be entered directly,
27830 but there may be some unexpected behaviour. For example, commands
27831 that query the user will behave as if the user replied yes, breakpoint
27832 command lists are not executed and some CLI commands, such as
27833 @code{if}, @code{when} and @code{define}, prompt for further input with
27834 @samp{>}, which is not valid MI output.
27836 This feature may be removed at some stage in the future and it is
27837 recommended that front ends use the @code{-interpreter-exec} command
27838 (@pxref{-interpreter-exec}).
27840 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27841 @node GDB/MI Development and Front Ends
27842 @section @sc{gdb/mi} Development and Front Ends
27843 @cindex @sc{gdb/mi} development
27845 The application which takes the MI output and presents the state of the
27846 program being debugged to the user is called a @dfn{front end}.
27848 Although @sc{gdb/mi} is still incomplete, it is currently being used
27849 by a variety of front ends to @value{GDBN}. This makes it difficult
27850 to introduce new functionality without breaking existing usage. This
27851 section tries to minimize the problems by describing how the protocol
27854 Some changes in MI need not break a carefully designed front end, and
27855 for these the MI version will remain unchanged. The following is a
27856 list of changes that may occur within one level, so front ends should
27857 parse MI output in a way that can handle them:
27861 New MI commands may be added.
27864 New fields may be added to the output of any MI command.
27867 The range of values for fields with specified values, e.g.,
27868 @code{in_scope} (@pxref{-var-update}) may be extended.
27870 @c The format of field's content e.g type prefix, may change so parse it
27871 @c at your own risk. Yes, in general?
27873 @c The order of fields may change? Shouldn't really matter but it might
27874 @c resolve inconsistencies.
27877 If the changes are likely to break front ends, the MI version level
27878 will be increased by one. This will allow the front end to parse the
27879 output according to the MI version. Apart from mi0, new versions of
27880 @value{GDBN} will not support old versions of MI and it will be the
27881 responsibility of the front end to work with the new one.
27883 @c Starting with mi3, add a new command -mi-version that prints the MI
27886 The best way to avoid unexpected changes in MI that might break your front
27887 end is to make your project known to @value{GDBN} developers and
27888 follow development on @email{gdb@@sourceware.org} and
27889 @email{gdb-patches@@sourceware.org}.
27890 @cindex mailing lists
27892 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27893 @node GDB/MI Output Records
27894 @section @sc{gdb/mi} Output Records
27897 * GDB/MI Result Records::
27898 * GDB/MI Stream Records::
27899 * GDB/MI Async Records::
27900 * GDB/MI Breakpoint Information::
27901 * GDB/MI Frame Information::
27902 * GDB/MI Thread Information::
27903 * GDB/MI Ada Exception Information::
27906 @node GDB/MI Result Records
27907 @subsection @sc{gdb/mi} Result Records
27909 @cindex result records in @sc{gdb/mi}
27910 @cindex @sc{gdb/mi}, result records
27911 In addition to a number of out-of-band notifications, the response to a
27912 @sc{gdb/mi} command includes one of the following result indications:
27916 @item "^done" [ "," @var{results} ]
27917 The synchronous operation was successful, @code{@var{results}} are the return
27922 This result record is equivalent to @samp{^done}. Historically, it
27923 was output instead of @samp{^done} if the command has resumed the
27924 target. This behaviour is maintained for backward compatibility, but
27925 all frontends should treat @samp{^done} and @samp{^running}
27926 identically and rely on the @samp{*running} output record to determine
27927 which threads are resumed.
27931 @value{GDBN} has connected to a remote target.
27933 @item "^error" "," @var{c-string}
27935 The operation failed. The @code{@var{c-string}} contains the corresponding
27940 @value{GDBN} has terminated.
27944 @node GDB/MI Stream Records
27945 @subsection @sc{gdb/mi} Stream Records
27947 @cindex @sc{gdb/mi}, stream records
27948 @cindex stream records in @sc{gdb/mi}
27949 @value{GDBN} internally maintains a number of output streams: the console, the
27950 target, and the log. The output intended for each of these streams is
27951 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
27953 Each stream record begins with a unique @dfn{prefix character} which
27954 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
27955 Syntax}). In addition to the prefix, each stream record contains a
27956 @code{@var{string-output}}. This is either raw text (with an implicit new
27957 line) or a quoted C string (which does not contain an implicit newline).
27960 @item "~" @var{string-output}
27961 The console output stream contains text that should be displayed in the
27962 CLI console window. It contains the textual responses to CLI commands.
27964 @item "@@" @var{string-output}
27965 The target output stream contains any textual output from the running
27966 target. This is only present when GDB's event loop is truly
27967 asynchronous, which is currently only the case for remote targets.
27969 @item "&" @var{string-output}
27970 The log stream contains debugging messages being produced by @value{GDBN}'s
27974 @node GDB/MI Async Records
27975 @subsection @sc{gdb/mi} Async Records
27977 @cindex async records in @sc{gdb/mi}
27978 @cindex @sc{gdb/mi}, async records
27979 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
27980 additional changes that have occurred. Those changes can either be a
27981 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
27982 target activity (e.g., target stopped).
27984 The following is the list of possible async records:
27988 @item *running,thread-id="@var{thread}"
27989 The target is now running. The @var{thread} field tells which
27990 specific thread is now running, and can be @samp{all} if all threads
27991 are running. The frontend should assume that no interaction with a
27992 running thread is possible after this notification is produced.
27993 The frontend should not assume that this notification is output
27994 only once for any command. @value{GDBN} may emit this notification
27995 several times, either for different threads, because it cannot resume
27996 all threads together, or even for a single thread, if the thread must
27997 be stepped though some code before letting it run freely.
27999 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
28000 The target has stopped. The @var{reason} field can have one of the
28004 @item breakpoint-hit
28005 A breakpoint was reached.
28006 @item watchpoint-trigger
28007 A watchpoint was triggered.
28008 @item read-watchpoint-trigger
28009 A read watchpoint was triggered.
28010 @item access-watchpoint-trigger
28011 An access watchpoint was triggered.
28012 @item function-finished
28013 An -exec-finish or similar CLI command was accomplished.
28014 @item location-reached
28015 An -exec-until or similar CLI command was accomplished.
28016 @item watchpoint-scope
28017 A watchpoint has gone out of scope.
28018 @item end-stepping-range
28019 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
28020 similar CLI command was accomplished.
28021 @item exited-signalled
28022 The inferior exited because of a signal.
28024 The inferior exited.
28025 @item exited-normally
28026 The inferior exited normally.
28027 @item signal-received
28028 A signal was received by the inferior.
28030 The inferior has stopped due to a library being loaded or unloaded.
28031 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
28032 set or when a @code{catch load} or @code{catch unload} catchpoint is
28033 in use (@pxref{Set Catchpoints}).
28035 The inferior has forked. This is reported when @code{catch fork}
28036 (@pxref{Set Catchpoints}) has been used.
28038 The inferior has vforked. This is reported in when @code{catch vfork}
28039 (@pxref{Set Catchpoints}) has been used.
28040 @item syscall-entry
28041 The inferior entered a system call. This is reported when @code{catch
28042 syscall} (@pxref{Set Catchpoints}) has been used.
28043 @item syscall-entry
28044 The inferior returned from a system call. This is reported when
28045 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
28047 The inferior called @code{exec}. This is reported when @code{catch exec}
28048 (@pxref{Set Catchpoints}) has been used.
28051 The @var{id} field identifies the thread that directly caused the stop
28052 -- for example by hitting a breakpoint. Depending on whether all-stop
28053 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
28054 stop all threads, or only the thread that directly triggered the stop.
28055 If all threads are stopped, the @var{stopped} field will have the
28056 value of @code{"all"}. Otherwise, the value of the @var{stopped}
28057 field will be a list of thread identifiers. Presently, this list will
28058 always include a single thread, but frontend should be prepared to see
28059 several threads in the list. The @var{core} field reports the
28060 processor core on which the stop event has happened. This field may be absent
28061 if such information is not available.
28063 @item =thread-group-added,id="@var{id}"
28064 @itemx =thread-group-removed,id="@var{id}"
28065 A thread group was either added or removed. The @var{id} field
28066 contains the @value{GDBN} identifier of the thread group. When a thread
28067 group is added, it generally might not be associated with a running
28068 process. When a thread group is removed, its id becomes invalid and
28069 cannot be used in any way.
28071 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
28072 A thread group became associated with a running program,
28073 either because the program was just started or the thread group
28074 was attached to a program. The @var{id} field contains the
28075 @value{GDBN} identifier of the thread group. The @var{pid} field
28076 contains process identifier, specific to the operating system.
28078 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
28079 A thread group is no longer associated with a running program,
28080 either because the program has exited, or because it was detached
28081 from. The @var{id} field contains the @value{GDBN} identifier of the
28082 thread group. @var{code} is the exit code of the inferior; it exists
28083 only when the inferior exited with some code.
28085 @item =thread-created,id="@var{id}",group-id="@var{gid}"
28086 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
28087 A thread either was created, or has exited. The @var{id} field
28088 contains the @value{GDBN} identifier of the thread. The @var{gid}
28089 field identifies the thread group this thread belongs to.
28091 @item =thread-selected,id="@var{id}"
28092 Informs that the selected thread was changed as result of the last
28093 command. This notification is not emitted as result of @code{-thread-select}
28094 command but is emitted whenever an MI command that is not documented
28095 to change the selected thread actually changes it. In particular,
28096 invoking, directly or indirectly (via user-defined command), the CLI
28097 @code{thread} command, will generate this notification.
28099 We suggest that in response to this notification, front ends
28100 highlight the selected thread and cause subsequent commands to apply to
28103 @item =library-loaded,...
28104 Reports that a new library file was loaded by the program. This
28105 notification has 4 fields---@var{id}, @var{target-name},
28106 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
28107 opaque identifier of the library. For remote debugging case,
28108 @var{target-name} and @var{host-name} fields give the name of the
28109 library file on the target, and on the host respectively. For native
28110 debugging, both those fields have the same value. The
28111 @var{symbols-loaded} field is emitted only for backward compatibility
28112 and should not be relied on to convey any useful information. The
28113 @var{thread-group} field, if present, specifies the id of the thread
28114 group in whose context the library was loaded. If the field is
28115 absent, it means the library was loaded in the context of all present
28118 @item =library-unloaded,...
28119 Reports that a library was unloaded by the program. This notification
28120 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
28121 the same meaning as for the @code{=library-loaded} notification.
28122 The @var{thread-group} field, if present, specifies the id of the
28123 thread group in whose context the library was unloaded. If the field is
28124 absent, it means the library was unloaded in the context of all present
28127 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
28128 @itemx =traceframe-changed,end
28129 Reports that the trace frame was changed and its new number is
28130 @var{tfnum}. The number of the tracepoint associated with this trace
28131 frame is @var{tpnum}.
28133 @item =tsv-created,name=@var{name},initial=@var{initial}
28134 Reports that the new trace state variable @var{name} is created with
28135 initial value @var{initial}.
28137 @item =tsv-deleted,name=@var{name}
28138 @itemx =tsv-deleted
28139 Reports that the trace state variable @var{name} is deleted or all
28140 trace state variables are deleted.
28142 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
28143 Reports that the trace state variable @var{name} is modified with
28144 the initial value @var{initial}. The current value @var{current} of
28145 trace state variable is optional and is reported if the current
28146 value of trace state variable is known.
28148 @item =breakpoint-created,bkpt=@{...@}
28149 @itemx =breakpoint-modified,bkpt=@{...@}
28150 @itemx =breakpoint-deleted,id=@var{number}
28151 Reports that a breakpoint was created, modified, or deleted,
28152 respectively. Only user-visible breakpoints are reported to the MI
28155 The @var{bkpt} argument is of the same form as returned by the various
28156 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
28157 @var{number} is the ordinal number of the breakpoint.
28159 Note that if a breakpoint is emitted in the result record of a
28160 command, then it will not also be emitted in an async record.
28162 @item =record-started,thread-group="@var{id}"
28163 @itemx =record-stopped,thread-group="@var{id}"
28164 Execution log recording was either started or stopped on an
28165 inferior. The @var{id} is the @value{GDBN} identifier of the thread
28166 group corresponding to the affected inferior.
28168 @item =cmd-param-changed,param=@var{param},value=@var{value}
28169 Reports that a parameter of the command @code{set @var{param}} is
28170 changed to @var{value}. In the multi-word @code{set} command,
28171 the @var{param} is the whole parameter list to @code{set} command.
28172 For example, In command @code{set check type on}, @var{param}
28173 is @code{check type} and @var{value} is @code{on}.
28175 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
28176 Reports that bytes from @var{addr} to @var{data} + @var{len} were
28177 written in an inferior. The @var{id} is the identifier of the
28178 thread group corresponding to the affected inferior. The optional
28179 @code{type="code"} part is reported if the memory written to holds
28183 @node GDB/MI Breakpoint Information
28184 @subsection @sc{gdb/mi} Breakpoint Information
28186 When @value{GDBN} reports information about a breakpoint, a
28187 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
28192 The breakpoint number. For a breakpoint that represents one location
28193 of a multi-location breakpoint, this will be a dotted pair, like
28197 The type of the breakpoint. For ordinary breakpoints this will be
28198 @samp{breakpoint}, but many values are possible.
28201 If the type of the breakpoint is @samp{catchpoint}, then this
28202 indicates the exact type of catchpoint.
28205 This is the breakpoint disposition---either @samp{del}, meaning that
28206 the breakpoint will be deleted at the next stop, or @samp{keep},
28207 meaning that the breakpoint will not be deleted.
28210 This indicates whether the breakpoint is enabled, in which case the
28211 value is @samp{y}, or disabled, in which case the value is @samp{n}.
28212 Note that this is not the same as the field @code{enable}.
28215 The address of the breakpoint. This may be a hexidecimal number,
28216 giving the address; or the string @samp{<PENDING>}, for a pending
28217 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
28218 multiple locations. This field will not be present if no address can
28219 be determined. For example, a watchpoint does not have an address.
28222 If known, the function in which the breakpoint appears.
28223 If not known, this field is not present.
28226 The name of the source file which contains this function, if known.
28227 If not known, this field is not present.
28230 The full file name of the source file which contains this function, if
28231 known. If not known, this field is not present.
28234 The line number at which this breakpoint appears, if known.
28235 If not known, this field is not present.
28238 If the source file is not known, this field may be provided. If
28239 provided, this holds the address of the breakpoint, possibly followed
28243 If this breakpoint is pending, this field is present and holds the
28244 text used to set the breakpoint, as entered by the user.
28247 Where this breakpoint's condition is evaluated, either @samp{host} or
28251 If this is a thread-specific breakpoint, then this identifies the
28252 thread in which the breakpoint can trigger.
28255 If this breakpoint is restricted to a particular Ada task, then this
28256 field will hold the task identifier.
28259 If the breakpoint is conditional, this is the condition expression.
28262 The ignore count of the breakpoint.
28265 The enable count of the breakpoint.
28267 @item traceframe-usage
28270 @item static-tracepoint-marker-string-id
28271 For a static tracepoint, the name of the static tracepoint marker.
28274 For a masked watchpoint, this is the mask.
28277 A tracepoint's pass count.
28279 @item original-location
28280 The location of the breakpoint as originally specified by the user.
28281 This field is optional.
28284 The number of times the breakpoint has been hit.
28287 This field is only given for tracepoints. This is either @samp{y},
28288 meaning that the tracepoint is installed, or @samp{n}, meaning that it
28292 Some extra data, the exact contents of which are type-dependent.
28296 For example, here is what the output of @code{-break-insert}
28297 (@pxref{GDB/MI Breakpoint Commands}) might be:
28300 -> -break-insert main
28301 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28302 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28303 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28308 @node GDB/MI Frame Information
28309 @subsection @sc{gdb/mi} Frame Information
28311 Response from many MI commands includes an information about stack
28312 frame. This information is a tuple that may have the following
28317 The level of the stack frame. The innermost frame has the level of
28318 zero. This field is always present.
28321 The name of the function corresponding to the frame. This field may
28322 be absent if @value{GDBN} is unable to determine the function name.
28325 The code address for the frame. This field is always present.
28328 The name of the source files that correspond to the frame's code
28329 address. This field may be absent.
28332 The source line corresponding to the frames' code address. This field
28336 The name of the binary file (either executable or shared library) the
28337 corresponds to the frame's code address. This field may be absent.
28341 @node GDB/MI Thread Information
28342 @subsection @sc{gdb/mi} Thread Information
28344 Whenever @value{GDBN} has to report an information about a thread, it
28345 uses a tuple with the following fields:
28349 The numeric id assigned to the thread by @value{GDBN}. This field is
28353 Target-specific string identifying the thread. This field is always present.
28356 Additional information about the thread provided by the target.
28357 It is supposed to be human-readable and not interpreted by the
28358 frontend. This field is optional.
28361 Either @samp{stopped} or @samp{running}, depending on whether the
28362 thread is presently running. This field is always present.
28365 The value of this field is an integer number of the processor core the
28366 thread was last seen on. This field is optional.
28369 @node GDB/MI Ada Exception Information
28370 @subsection @sc{gdb/mi} Ada Exception Information
28372 Whenever a @code{*stopped} record is emitted because the program
28373 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
28374 @value{GDBN} provides the name of the exception that was raised via
28375 the @code{exception-name} field.
28377 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28378 @node GDB/MI Simple Examples
28379 @section Simple Examples of @sc{gdb/mi} Interaction
28380 @cindex @sc{gdb/mi}, simple examples
28382 This subsection presents several simple examples of interaction using
28383 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
28384 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
28385 the output received from @sc{gdb/mi}.
28387 Note the line breaks shown in the examples are here only for
28388 readability, they don't appear in the real output.
28390 @subheading Setting a Breakpoint
28392 Setting a breakpoint generates synchronous output which contains detailed
28393 information of the breakpoint.
28396 -> -break-insert main
28397 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28398 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28399 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28404 @subheading Program Execution
28406 Program execution generates asynchronous records and MI gives the
28407 reason that execution stopped.
28413 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
28414 frame=@{addr="0x08048564",func="main",
28415 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
28416 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
28421 <- *stopped,reason="exited-normally"
28425 @subheading Quitting @value{GDBN}
28427 Quitting @value{GDBN} just prints the result class @samp{^exit}.
28435 Please note that @samp{^exit} is printed immediately, but it might
28436 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
28437 performs necessary cleanups, including killing programs being debugged
28438 or disconnecting from debug hardware, so the frontend should wait till
28439 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
28440 fails to exit in reasonable time.
28442 @subheading A Bad Command
28444 Here's what happens if you pass a non-existent command:
28448 <- ^error,msg="Undefined MI command: rubbish"
28453 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28454 @node GDB/MI Command Description Format
28455 @section @sc{gdb/mi} Command Description Format
28457 The remaining sections describe blocks of commands. Each block of
28458 commands is laid out in a fashion similar to this section.
28460 @subheading Motivation
28462 The motivation for this collection of commands.
28464 @subheading Introduction
28466 A brief introduction to this collection of commands as a whole.
28468 @subheading Commands
28470 For each command in the block, the following is described:
28472 @subsubheading Synopsis
28475 -command @var{args}@dots{}
28478 @subsubheading Result
28480 @subsubheading @value{GDBN} Command
28482 The corresponding @value{GDBN} CLI command(s), if any.
28484 @subsubheading Example
28486 Example(s) formatted for readability. Some of the described commands have
28487 not been implemented yet and these are labeled N.A.@: (not available).
28490 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28491 @node GDB/MI Breakpoint Commands
28492 @section @sc{gdb/mi} Breakpoint Commands
28494 @cindex breakpoint commands for @sc{gdb/mi}
28495 @cindex @sc{gdb/mi}, breakpoint commands
28496 This section documents @sc{gdb/mi} commands for manipulating
28499 @subheading The @code{-break-after} Command
28500 @findex -break-after
28502 @subsubheading Synopsis
28505 -break-after @var{number} @var{count}
28508 The breakpoint number @var{number} is not in effect until it has been
28509 hit @var{count} times. To see how this is reflected in the output of
28510 the @samp{-break-list} command, see the description of the
28511 @samp{-break-list} command below.
28513 @subsubheading @value{GDBN} Command
28515 The corresponding @value{GDBN} command is @samp{ignore}.
28517 @subsubheading Example
28522 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28523 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28524 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28532 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28533 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28534 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28535 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28536 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28537 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28538 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28539 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28540 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28541 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
28546 @subheading The @code{-break-catch} Command
28547 @findex -break-catch
28550 @subheading The @code{-break-commands} Command
28551 @findex -break-commands
28553 @subsubheading Synopsis
28556 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
28559 Specifies the CLI commands that should be executed when breakpoint
28560 @var{number} is hit. The parameters @var{command1} to @var{commandN}
28561 are the commands. If no command is specified, any previously-set
28562 commands are cleared. @xref{Break Commands}. Typical use of this
28563 functionality is tracing a program, that is, printing of values of
28564 some variables whenever breakpoint is hit and then continuing.
28566 @subsubheading @value{GDBN} Command
28568 The corresponding @value{GDBN} command is @samp{commands}.
28570 @subsubheading Example
28575 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28576 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28577 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28580 -break-commands 1 "print v" "continue"
28585 @subheading The @code{-break-condition} Command
28586 @findex -break-condition
28588 @subsubheading Synopsis
28591 -break-condition @var{number} @var{expr}
28594 Breakpoint @var{number} will stop the program only if the condition in
28595 @var{expr} is true. The condition becomes part of the
28596 @samp{-break-list} output (see the description of the @samp{-break-list}
28599 @subsubheading @value{GDBN} Command
28601 The corresponding @value{GDBN} command is @samp{condition}.
28603 @subsubheading Example
28607 -break-condition 1 1
28611 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28612 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28613 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28614 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28615 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28616 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28617 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28618 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28619 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28620 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
28624 @subheading The @code{-break-delete} Command
28625 @findex -break-delete
28627 @subsubheading Synopsis
28630 -break-delete ( @var{breakpoint} )+
28633 Delete the breakpoint(s) whose number(s) are specified in the argument
28634 list. This is obviously reflected in the breakpoint list.
28636 @subsubheading @value{GDBN} Command
28638 The corresponding @value{GDBN} command is @samp{delete}.
28640 @subsubheading Example
28648 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28649 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28650 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28651 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28652 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28653 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28654 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28659 @subheading The @code{-break-disable} Command
28660 @findex -break-disable
28662 @subsubheading Synopsis
28665 -break-disable ( @var{breakpoint} )+
28668 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
28669 break list is now set to @samp{n} for the named @var{breakpoint}(s).
28671 @subsubheading @value{GDBN} Command
28673 The corresponding @value{GDBN} command is @samp{disable}.
28675 @subsubheading Example
28683 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28684 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28685 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28686 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28687 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28688 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28689 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28690 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
28691 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28692 line="5",thread-groups=["i1"],times="0"@}]@}
28696 @subheading The @code{-break-enable} Command
28697 @findex -break-enable
28699 @subsubheading Synopsis
28702 -break-enable ( @var{breakpoint} )+
28705 Enable (previously disabled) @var{breakpoint}(s).
28707 @subsubheading @value{GDBN} Command
28709 The corresponding @value{GDBN} command is @samp{enable}.
28711 @subsubheading Example
28719 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28720 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28721 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28722 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28723 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28724 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28725 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28726 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28727 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28728 line="5",thread-groups=["i1"],times="0"@}]@}
28732 @subheading The @code{-break-info} Command
28733 @findex -break-info
28735 @subsubheading Synopsis
28738 -break-info @var{breakpoint}
28742 Get information about a single breakpoint.
28744 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
28745 Information}, for details on the format of each breakpoint in the
28748 @subsubheading @value{GDBN} Command
28750 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
28752 @subsubheading Example
28755 @subheading The @code{-break-insert} Command
28756 @findex -break-insert
28758 @subsubheading Synopsis
28761 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
28762 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28763 [ -p @var{thread-id} ] [ @var{location} ]
28767 If specified, @var{location}, can be one of:
28774 @item filename:linenum
28775 @item filename:function
28779 The possible optional parameters of this command are:
28783 Insert a temporary breakpoint.
28785 Insert a hardware breakpoint.
28787 If @var{location} cannot be parsed (for example if it
28788 refers to unknown files or functions), create a pending
28789 breakpoint. Without this flag, @value{GDBN} will report
28790 an error, and won't create a breakpoint, if @var{location}
28793 Create a disabled breakpoint.
28795 Create a tracepoint. @xref{Tracepoints}. When this parameter
28796 is used together with @samp{-h}, a fast tracepoint is created.
28797 @item -c @var{condition}
28798 Make the breakpoint conditional on @var{condition}.
28799 @item -i @var{ignore-count}
28800 Initialize the @var{ignore-count}.
28801 @item -p @var{thread-id}
28802 Restrict the breakpoint to the specified @var{thread-id}.
28805 @subsubheading Result
28807 @xref{GDB/MI Breakpoint Information}, for details on the format of the
28808 resulting breakpoint.
28810 Note: this format is open to change.
28811 @c An out-of-band breakpoint instead of part of the result?
28813 @subsubheading @value{GDBN} Command
28815 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
28816 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
28818 @subsubheading Example
28823 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
28824 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
28827 -break-insert -t foo
28828 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
28829 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
28833 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28834 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28835 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28836 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28837 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28838 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28839 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28840 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28841 addr="0x0001072c", func="main",file="recursive2.c",
28842 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
28844 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
28845 addr="0x00010774",func="foo",file="recursive2.c",
28846 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28849 @c -break-insert -r foo.*
28850 @c ~int foo(int, int);
28851 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
28852 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28857 @subheading The @code{-break-list} Command
28858 @findex -break-list
28860 @subsubheading Synopsis
28866 Displays the list of inserted breakpoints, showing the following fields:
28870 number of the breakpoint
28872 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
28874 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
28877 is the breakpoint enabled or no: @samp{y} or @samp{n}
28879 memory location at which the breakpoint is set
28881 logical location of the breakpoint, expressed by function name, file
28883 @item Thread-groups
28884 list of thread groups to which this breakpoint applies
28886 number of times the breakpoint has been hit
28889 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
28890 @code{body} field is an empty list.
28892 @subsubheading @value{GDBN} Command
28894 The corresponding @value{GDBN} command is @samp{info break}.
28896 @subsubheading Example
28901 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28902 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28903 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28904 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28905 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28906 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28907 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28908 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28909 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
28911 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28912 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
28913 line="13",thread-groups=["i1"],times="0"@}]@}
28917 Here's an example of the result when there are no breakpoints:
28922 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28923 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28924 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28925 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28926 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28927 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28928 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28933 @subheading The @code{-break-passcount} Command
28934 @findex -break-passcount
28936 @subsubheading Synopsis
28939 -break-passcount @var{tracepoint-number} @var{passcount}
28942 Set the passcount for tracepoint @var{tracepoint-number} to
28943 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
28944 is not a tracepoint, error is emitted. This corresponds to CLI
28945 command @samp{passcount}.
28947 @subheading The @code{-break-watch} Command
28948 @findex -break-watch
28950 @subsubheading Synopsis
28953 -break-watch [ -a | -r ]
28956 Create a watchpoint. With the @samp{-a} option it will create an
28957 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
28958 read from or on a write to the memory location. With the @samp{-r}
28959 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
28960 trigger only when the memory location is accessed for reading. Without
28961 either of the options, the watchpoint created is a regular watchpoint,
28962 i.e., it will trigger when the memory location is accessed for writing.
28963 @xref{Set Watchpoints, , Setting Watchpoints}.
28965 Note that @samp{-break-list} will report a single list of watchpoints and
28966 breakpoints inserted.
28968 @subsubheading @value{GDBN} Command
28970 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
28973 @subsubheading Example
28975 Setting a watchpoint on a variable in the @code{main} function:
28980 ^done,wpt=@{number="2",exp="x"@}
28985 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
28986 value=@{old="-268439212",new="55"@},
28987 frame=@{func="main",args=[],file="recursive2.c",
28988 fullname="/home/foo/bar/recursive2.c",line="5"@}
28992 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
28993 the program execution twice: first for the variable changing value, then
28994 for the watchpoint going out of scope.
28999 ^done,wpt=@{number="5",exp="C"@}
29004 *stopped,reason="watchpoint-trigger",
29005 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
29006 frame=@{func="callee4",args=[],
29007 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29008 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
29013 *stopped,reason="watchpoint-scope",wpnum="5",
29014 frame=@{func="callee3",args=[@{name="strarg",
29015 value="0x11940 \"A string argument.\""@}],
29016 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29017 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29021 Listing breakpoints and watchpoints, at different points in the program
29022 execution. Note that once the watchpoint goes out of scope, it is
29028 ^done,wpt=@{number="2",exp="C"@}
29031 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29032 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29033 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29034 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29035 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29036 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29037 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29038 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29039 addr="0x00010734",func="callee4",
29040 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29041 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
29043 bkpt=@{number="2",type="watchpoint",disp="keep",
29044 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
29049 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
29050 value=@{old="-276895068",new="3"@},
29051 frame=@{func="callee4",args=[],
29052 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29053 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
29056 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29057 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29058 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29059 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29060 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29061 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29062 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29063 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29064 addr="0x00010734",func="callee4",
29065 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29066 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
29068 bkpt=@{number="2",type="watchpoint",disp="keep",
29069 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
29073 ^done,reason="watchpoint-scope",wpnum="2",
29074 frame=@{func="callee3",args=[@{name="strarg",
29075 value="0x11940 \"A string argument.\""@}],
29076 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29077 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29080 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29081 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29082 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29083 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29084 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29085 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29086 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29087 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29088 addr="0x00010734",func="callee4",
29089 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29090 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
29091 thread-groups=["i1"],times="1"@}]@}
29096 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29097 @node GDB/MI Catchpoint Commands
29098 @section @sc{gdb/mi} Catchpoint Commands
29100 This section documents @sc{gdb/mi} commands for manipulating
29103 @subheading The @code{-catch-load} Command
29104 @findex -catch-load
29106 @subsubheading Synopsis
29109 -catch-load [ -t ] [ -d ] @var{regexp}
29112 Add a catchpoint for library load events. If the @samp{-t} option is used,
29113 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
29114 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
29115 in a disabled state. The @samp{regexp} argument is a regular
29116 expression used to match the name of the loaded library.
29119 @subsubheading @value{GDBN} Command
29121 The corresponding @value{GDBN} command is @samp{catch load}.
29123 @subsubheading Example
29126 -catch-load -t foo.so
29127 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
29128 what="load of library matching foo.so",catch-type="load",times="0"@}
29133 @subheading The @code{-catch-unload} Command
29134 @findex -catch-unload
29136 @subsubheading Synopsis
29139 -catch-unload [ -t ] [ -d ] @var{regexp}
29142 Add a catchpoint for library unload events. If the @samp{-t} option is
29143 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
29144 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
29145 created in a disabled state. The @samp{regexp} argument is a regular
29146 expression used to match the name of the unloaded library.
29148 @subsubheading @value{GDBN} Command
29150 The corresponding @value{GDBN} command is @samp{catch unload}.
29152 @subsubheading Example
29155 -catch-unload -d bar.so
29156 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
29157 what="load of library matching bar.so",catch-type="unload",times="0"@}
29162 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29163 @node GDB/MI Program Context
29164 @section @sc{gdb/mi} Program Context
29166 @subheading The @code{-exec-arguments} Command
29167 @findex -exec-arguments
29170 @subsubheading Synopsis
29173 -exec-arguments @var{args}
29176 Set the inferior program arguments, to be used in the next
29179 @subsubheading @value{GDBN} Command
29181 The corresponding @value{GDBN} command is @samp{set args}.
29183 @subsubheading Example
29187 -exec-arguments -v word
29194 @subheading The @code{-exec-show-arguments} Command
29195 @findex -exec-show-arguments
29197 @subsubheading Synopsis
29200 -exec-show-arguments
29203 Print the arguments of the program.
29205 @subsubheading @value{GDBN} Command
29207 The corresponding @value{GDBN} command is @samp{show args}.
29209 @subsubheading Example
29214 @subheading The @code{-environment-cd} Command
29215 @findex -environment-cd
29217 @subsubheading Synopsis
29220 -environment-cd @var{pathdir}
29223 Set @value{GDBN}'s working directory.
29225 @subsubheading @value{GDBN} Command
29227 The corresponding @value{GDBN} command is @samp{cd}.
29229 @subsubheading Example
29233 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29239 @subheading The @code{-environment-directory} Command
29240 @findex -environment-directory
29242 @subsubheading Synopsis
29245 -environment-directory [ -r ] [ @var{pathdir} ]+
29248 Add directories @var{pathdir} to beginning of search path for source files.
29249 If the @samp{-r} option is used, the search path is reset to the default
29250 search path. If directories @var{pathdir} are supplied in addition to the
29251 @samp{-r} option, the search path is first reset and then addition
29253 Multiple directories may be specified, separated by blanks. Specifying
29254 multiple directories in a single command
29255 results in the directories added to the beginning of the
29256 search path in the same order they were presented in the command.
29257 If blanks are needed as
29258 part of a directory name, double-quotes should be used around
29259 the name. In the command output, the path will show up separated
29260 by the system directory-separator character. The directory-separator
29261 character must not be used
29262 in any directory name.
29263 If no directories are specified, the current search path is displayed.
29265 @subsubheading @value{GDBN} Command
29267 The corresponding @value{GDBN} command is @samp{dir}.
29269 @subsubheading Example
29273 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29274 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29276 -environment-directory ""
29277 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29279 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
29280 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
29282 -environment-directory -r
29283 ^done,source-path="$cdir:$cwd"
29288 @subheading The @code{-environment-path} Command
29289 @findex -environment-path
29291 @subsubheading Synopsis
29294 -environment-path [ -r ] [ @var{pathdir} ]+
29297 Add directories @var{pathdir} to beginning of search path for object files.
29298 If the @samp{-r} option is used, the search path is reset to the original
29299 search path that existed at gdb start-up. If directories @var{pathdir} are
29300 supplied in addition to the
29301 @samp{-r} option, the search path is first reset and then addition
29303 Multiple directories may be specified, separated by blanks. Specifying
29304 multiple directories in a single command
29305 results in the directories added to the beginning of the
29306 search path in the same order they were presented in the command.
29307 If blanks are needed as
29308 part of a directory name, double-quotes should be used around
29309 the name. In the command output, the path will show up separated
29310 by the system directory-separator character. The directory-separator
29311 character must not be used
29312 in any directory name.
29313 If no directories are specified, the current path is displayed.
29316 @subsubheading @value{GDBN} Command
29318 The corresponding @value{GDBN} command is @samp{path}.
29320 @subsubheading Example
29325 ^done,path="/usr/bin"
29327 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
29328 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
29330 -environment-path -r /usr/local/bin
29331 ^done,path="/usr/local/bin:/usr/bin"
29336 @subheading The @code{-environment-pwd} Command
29337 @findex -environment-pwd
29339 @subsubheading Synopsis
29345 Show the current working directory.
29347 @subsubheading @value{GDBN} Command
29349 The corresponding @value{GDBN} command is @samp{pwd}.
29351 @subsubheading Example
29356 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
29360 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29361 @node GDB/MI Thread Commands
29362 @section @sc{gdb/mi} Thread Commands
29365 @subheading The @code{-thread-info} Command
29366 @findex -thread-info
29368 @subsubheading Synopsis
29371 -thread-info [ @var{thread-id} ]
29374 Reports information about either a specific thread, if
29375 the @var{thread-id} parameter is present, or about all
29376 threads. When printing information about all threads,
29377 also reports the current thread.
29379 @subsubheading @value{GDBN} Command
29381 The @samp{info thread} command prints the same information
29384 @subsubheading Result
29386 The result is a list of threads. The following attributes are
29387 defined for a given thread:
29391 This field exists only for the current thread. It has the value @samp{*}.
29394 The identifier that @value{GDBN} uses to refer to the thread.
29397 The identifier that the target uses to refer to the thread.
29400 Extra information about the thread, in a target-specific format. This
29404 The name of the thread. If the user specified a name using the
29405 @code{thread name} command, then this name is given. Otherwise, if
29406 @value{GDBN} can extract the thread name from the target, then that
29407 name is given. If @value{GDBN} cannot find the thread name, then this
29411 The stack frame currently executing in the thread.
29414 The thread's state. The @samp{state} field may have the following
29419 The thread is stopped. Frame information is available for stopped
29423 The thread is running. There's no frame information for running
29429 If @value{GDBN} can find the CPU core on which this thread is running,
29430 then this field is the core identifier. This field is optional.
29434 @subsubheading Example
29439 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
29440 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
29441 args=[]@},state="running"@},
29442 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
29443 frame=@{level="0",addr="0x0804891f",func="foo",
29444 args=[@{name="i",value="10"@}],
29445 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
29446 state="running"@}],
29447 current-thread-id="1"
29451 @subheading The @code{-thread-list-ids} Command
29452 @findex -thread-list-ids
29454 @subsubheading Synopsis
29460 Produces a list of the currently known @value{GDBN} thread ids. At the
29461 end of the list it also prints the total number of such threads.
29463 This command is retained for historical reasons, the
29464 @code{-thread-info} command should be used instead.
29466 @subsubheading @value{GDBN} Command
29468 Part of @samp{info threads} supplies the same information.
29470 @subsubheading Example
29475 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29476 current-thread-id="1",number-of-threads="3"
29481 @subheading The @code{-thread-select} Command
29482 @findex -thread-select
29484 @subsubheading Synopsis
29487 -thread-select @var{threadnum}
29490 Make @var{threadnum} the current thread. It prints the number of the new
29491 current thread, and the topmost frame for that thread.
29493 This command is deprecated in favor of explicitly using the
29494 @samp{--thread} option to each command.
29496 @subsubheading @value{GDBN} Command
29498 The corresponding @value{GDBN} command is @samp{thread}.
29500 @subsubheading Example
29507 *stopped,reason="end-stepping-range",thread-id="2",line="187",
29508 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
29512 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29513 number-of-threads="3"
29516 ^done,new-thread-id="3",
29517 frame=@{level="0",func="vprintf",
29518 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
29519 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
29523 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29524 @node GDB/MI Ada Tasking Commands
29525 @section @sc{gdb/mi} Ada Tasking Commands
29527 @subheading The @code{-ada-task-info} Command
29528 @findex -ada-task-info
29530 @subsubheading Synopsis
29533 -ada-task-info [ @var{task-id} ]
29536 Reports information about either a specific Ada task, if the
29537 @var{task-id} parameter is present, or about all Ada tasks.
29539 @subsubheading @value{GDBN} Command
29541 The @samp{info tasks} command prints the same information
29542 about all Ada tasks (@pxref{Ada Tasks}).
29544 @subsubheading Result
29546 The result is a table of Ada tasks. The following columns are
29547 defined for each Ada task:
29551 This field exists only for the current thread. It has the value @samp{*}.
29554 The identifier that @value{GDBN} uses to refer to the Ada task.
29557 The identifier that the target uses to refer to the Ada task.
29560 The identifier of the thread corresponding to the Ada task.
29562 This field should always exist, as Ada tasks are always implemented
29563 on top of a thread. But if @value{GDBN} cannot find this corresponding
29564 thread for any reason, the field is omitted.
29567 This field exists only when the task was created by another task.
29568 In this case, it provides the ID of the parent task.
29571 The base priority of the task.
29574 The current state of the task. For a detailed description of the
29575 possible states, see @ref{Ada Tasks}.
29578 The name of the task.
29582 @subsubheading Example
29586 ^done,tasks=@{nr_rows="3",nr_cols="8",
29587 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
29588 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
29589 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
29590 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
29591 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
29592 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
29593 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
29594 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
29595 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
29596 state="Child Termination Wait",name="main_task"@}]@}
29600 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29601 @node GDB/MI Program Execution
29602 @section @sc{gdb/mi} Program Execution
29604 These are the asynchronous commands which generate the out-of-band
29605 record @samp{*stopped}. Currently @value{GDBN} only really executes
29606 asynchronously with remote targets and this interaction is mimicked in
29609 @subheading The @code{-exec-continue} Command
29610 @findex -exec-continue
29612 @subsubheading Synopsis
29615 -exec-continue [--reverse] [--all|--thread-group N]
29618 Resumes the execution of the inferior program, which will continue
29619 to execute until it reaches a debugger stop event. If the
29620 @samp{--reverse} option is specified, execution resumes in reverse until
29621 it reaches a stop event. Stop events may include
29624 breakpoints or watchpoints
29626 signals or exceptions
29628 the end of the process (or its beginning under @samp{--reverse})
29630 the end or beginning of a replay log if one is being used.
29632 In all-stop mode (@pxref{All-Stop
29633 Mode}), may resume only one thread, or all threads, depending on the
29634 value of the @samp{scheduler-locking} variable. If @samp{--all} is
29635 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
29636 ignored in all-stop mode. If the @samp{--thread-group} options is
29637 specified, then all threads in that thread group are resumed.
29639 @subsubheading @value{GDBN} Command
29641 The corresponding @value{GDBN} corresponding is @samp{continue}.
29643 @subsubheading Example
29650 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
29651 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
29657 @subheading The @code{-exec-finish} Command
29658 @findex -exec-finish
29660 @subsubheading Synopsis
29663 -exec-finish [--reverse]
29666 Resumes the execution of the inferior program until the current
29667 function is exited. Displays the results returned by the function.
29668 If the @samp{--reverse} option is specified, resumes the reverse
29669 execution of the inferior program until the point where current
29670 function was called.
29672 @subsubheading @value{GDBN} Command
29674 The corresponding @value{GDBN} command is @samp{finish}.
29676 @subsubheading Example
29678 Function returning @code{void}.
29685 *stopped,reason="function-finished",frame=@{func="main",args=[],
29686 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
29690 Function returning other than @code{void}. The name of the internal
29691 @value{GDBN} variable storing the result is printed, together with the
29698 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
29699 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
29700 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29701 gdb-result-var="$1",return-value="0"
29706 @subheading The @code{-exec-interrupt} Command
29707 @findex -exec-interrupt
29709 @subsubheading Synopsis
29712 -exec-interrupt [--all|--thread-group N]
29715 Interrupts the background execution of the target. Note how the token
29716 associated with the stop message is the one for the execution command
29717 that has been interrupted. The token for the interrupt itself only
29718 appears in the @samp{^done} output. If the user is trying to
29719 interrupt a non-running program, an error message will be printed.
29721 Note that when asynchronous execution is enabled, this command is
29722 asynchronous just like other execution commands. That is, first the
29723 @samp{^done} response will be printed, and the target stop will be
29724 reported after that using the @samp{*stopped} notification.
29726 In non-stop mode, only the context thread is interrupted by default.
29727 All threads (in all inferiors) will be interrupted if the
29728 @samp{--all} option is specified. If the @samp{--thread-group}
29729 option is specified, all threads in that group will be interrupted.
29731 @subsubheading @value{GDBN} Command
29733 The corresponding @value{GDBN} command is @samp{interrupt}.
29735 @subsubheading Example
29746 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
29747 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
29748 fullname="/home/foo/bar/try.c",line="13"@}
29753 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
29757 @subheading The @code{-exec-jump} Command
29760 @subsubheading Synopsis
29763 -exec-jump @var{location}
29766 Resumes execution of the inferior program at the location specified by
29767 parameter. @xref{Specify Location}, for a description of the
29768 different forms of @var{location}.
29770 @subsubheading @value{GDBN} Command
29772 The corresponding @value{GDBN} command is @samp{jump}.
29774 @subsubheading Example
29777 -exec-jump foo.c:10
29778 *running,thread-id="all"
29783 @subheading The @code{-exec-next} Command
29786 @subsubheading Synopsis
29789 -exec-next [--reverse]
29792 Resumes execution of the inferior program, stopping when the beginning
29793 of the next source line is reached.
29795 If the @samp{--reverse} option is specified, resumes reverse execution
29796 of the inferior program, stopping at the beginning of the previous
29797 source line. If you issue this command on the first line of a
29798 function, it will take you back to the caller of that function, to the
29799 source line where the function was called.
29802 @subsubheading @value{GDBN} Command
29804 The corresponding @value{GDBN} command is @samp{next}.
29806 @subsubheading Example
29812 *stopped,reason="end-stepping-range",line="8",file="hello.c"
29817 @subheading The @code{-exec-next-instruction} Command
29818 @findex -exec-next-instruction
29820 @subsubheading Synopsis
29823 -exec-next-instruction [--reverse]
29826 Executes one machine instruction. If the instruction is a function
29827 call, continues until the function returns. If the program stops at an
29828 instruction in the middle of a source line, the address will be
29831 If the @samp{--reverse} option is specified, resumes reverse execution
29832 of the inferior program, stopping at the previous instruction. If the
29833 previously executed instruction was a return from another function,
29834 it will continue to execute in reverse until the call to that function
29835 (from the current stack frame) is reached.
29837 @subsubheading @value{GDBN} Command
29839 The corresponding @value{GDBN} command is @samp{nexti}.
29841 @subsubheading Example
29845 -exec-next-instruction
29849 *stopped,reason="end-stepping-range",
29850 addr="0x000100d4",line="5",file="hello.c"
29855 @subheading The @code{-exec-return} Command
29856 @findex -exec-return
29858 @subsubheading Synopsis
29864 Makes current function return immediately. Doesn't execute the inferior.
29865 Displays the new current frame.
29867 @subsubheading @value{GDBN} Command
29869 The corresponding @value{GDBN} command is @samp{return}.
29871 @subsubheading Example
29875 200-break-insert callee4
29876 200^done,bkpt=@{number="1",addr="0x00010734",
29877 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29882 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29883 frame=@{func="callee4",args=[],
29884 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29885 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29891 111^done,frame=@{level="0",func="callee3",
29892 args=[@{name="strarg",
29893 value="0x11940 \"A string argument.\""@}],
29894 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29895 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29900 @subheading The @code{-exec-run} Command
29903 @subsubheading Synopsis
29906 -exec-run [--all | --thread-group N]
29909 Starts execution of the inferior from the beginning. The inferior
29910 executes until either a breakpoint is encountered or the program
29911 exits. In the latter case the output will include an exit code, if
29912 the program has exited exceptionally.
29914 When no option is specified, the current inferior is started. If the
29915 @samp{--thread-group} option is specified, it should refer to a thread
29916 group of type @samp{process}, and that thread group will be started.
29917 If the @samp{--all} option is specified, then all inferiors will be started.
29919 @subsubheading @value{GDBN} Command
29921 The corresponding @value{GDBN} command is @samp{run}.
29923 @subsubheading Examples
29928 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
29933 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29934 frame=@{func="main",args=[],file="recursive2.c",
29935 fullname="/home/foo/bar/recursive2.c",line="4"@}
29940 Program exited normally:
29948 *stopped,reason="exited-normally"
29953 Program exited exceptionally:
29961 *stopped,reason="exited",exit-code="01"
29965 Another way the program can terminate is if it receives a signal such as
29966 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
29970 *stopped,reason="exited-signalled",signal-name="SIGINT",
29971 signal-meaning="Interrupt"
29975 @c @subheading -exec-signal
29978 @subheading The @code{-exec-step} Command
29981 @subsubheading Synopsis
29984 -exec-step [--reverse]
29987 Resumes execution of the inferior program, stopping when the beginning
29988 of the next source line is reached, if the next source line is not a
29989 function call. If it is, stop at the first instruction of the called
29990 function. If the @samp{--reverse} option is specified, resumes reverse
29991 execution of the inferior program, stopping at the beginning of the
29992 previously executed source line.
29994 @subsubheading @value{GDBN} Command
29996 The corresponding @value{GDBN} command is @samp{step}.
29998 @subsubheading Example
30000 Stepping into a function:
30006 *stopped,reason="end-stepping-range",
30007 frame=@{func="foo",args=[@{name="a",value="10"@},
30008 @{name="b",value="0"@}],file="recursive2.c",
30009 fullname="/home/foo/bar/recursive2.c",line="11"@}
30019 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
30024 @subheading The @code{-exec-step-instruction} Command
30025 @findex -exec-step-instruction
30027 @subsubheading Synopsis
30030 -exec-step-instruction [--reverse]
30033 Resumes the inferior which executes one machine instruction. If the
30034 @samp{--reverse} option is specified, resumes reverse execution of the
30035 inferior program, stopping at the previously executed instruction.
30036 The output, once @value{GDBN} has stopped, will vary depending on
30037 whether we have stopped in the middle of a source line or not. In the
30038 former case, the address at which the program stopped will be printed
30041 @subsubheading @value{GDBN} Command
30043 The corresponding @value{GDBN} command is @samp{stepi}.
30045 @subsubheading Example
30049 -exec-step-instruction
30053 *stopped,reason="end-stepping-range",
30054 frame=@{func="foo",args=[],file="try.c",
30055 fullname="/home/foo/bar/try.c",line="10"@}
30057 -exec-step-instruction
30061 *stopped,reason="end-stepping-range",
30062 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
30063 fullname="/home/foo/bar/try.c",line="10"@}
30068 @subheading The @code{-exec-until} Command
30069 @findex -exec-until
30071 @subsubheading Synopsis
30074 -exec-until [ @var{location} ]
30077 Executes the inferior until the @var{location} specified in the
30078 argument is reached. If there is no argument, the inferior executes
30079 until a source line greater than the current one is reached. The
30080 reason for stopping in this case will be @samp{location-reached}.
30082 @subsubheading @value{GDBN} Command
30084 The corresponding @value{GDBN} command is @samp{until}.
30086 @subsubheading Example
30090 -exec-until recursive2.c:6
30094 *stopped,reason="location-reached",frame=@{func="main",args=[],
30095 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
30100 @subheading -file-clear
30101 Is this going away????
30104 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30105 @node GDB/MI Stack Manipulation
30106 @section @sc{gdb/mi} Stack Manipulation Commands
30109 @subheading The @code{-stack-info-frame} Command
30110 @findex -stack-info-frame
30112 @subsubheading Synopsis
30118 Get info on the selected frame.
30120 @subsubheading @value{GDBN} Command
30122 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
30123 (without arguments).
30125 @subsubheading Example
30130 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
30131 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30132 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
30136 @subheading The @code{-stack-info-depth} Command
30137 @findex -stack-info-depth
30139 @subsubheading Synopsis
30142 -stack-info-depth [ @var{max-depth} ]
30145 Return the depth of the stack. If the integer argument @var{max-depth}
30146 is specified, do not count beyond @var{max-depth} frames.
30148 @subsubheading @value{GDBN} Command
30150 There's no equivalent @value{GDBN} command.
30152 @subsubheading Example
30154 For a stack with frame levels 0 through 11:
30161 -stack-info-depth 4
30164 -stack-info-depth 12
30167 -stack-info-depth 11
30170 -stack-info-depth 13
30175 @subheading The @code{-stack-list-arguments} Command
30176 @findex -stack-list-arguments
30178 @subsubheading Synopsis
30181 -stack-list-arguments @var{print-values}
30182 [ @var{low-frame} @var{high-frame} ]
30185 Display a list of the arguments for the frames between @var{low-frame}
30186 and @var{high-frame} (inclusive). If @var{low-frame} and
30187 @var{high-frame} are not provided, list the arguments for the whole
30188 call stack. If the two arguments are equal, show the single frame
30189 at the corresponding level. It is an error if @var{low-frame} is
30190 larger than the actual number of frames. On the other hand,
30191 @var{high-frame} may be larger than the actual number of frames, in
30192 which case only existing frames will be returned.
30194 If @var{print-values} is 0 or @code{--no-values}, print only the names of
30195 the variables; if it is 1 or @code{--all-values}, print also their
30196 values; and if it is 2 or @code{--simple-values}, print the name,
30197 type and value for simple data types, and the name and type for arrays,
30198 structures and unions.
30200 Use of this command to obtain arguments in a single frame is
30201 deprecated in favor of the @samp{-stack-list-variables} command.
30203 @subsubheading @value{GDBN} Command
30205 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
30206 @samp{gdb_get_args} command which partially overlaps with the
30207 functionality of @samp{-stack-list-arguments}.
30209 @subsubheading Example
30216 frame=@{level="0",addr="0x00010734",func="callee4",
30217 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30218 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
30219 frame=@{level="1",addr="0x0001076c",func="callee3",
30220 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30221 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
30222 frame=@{level="2",addr="0x0001078c",func="callee2",
30223 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30224 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
30225 frame=@{level="3",addr="0x000107b4",func="callee1",
30226 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30227 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
30228 frame=@{level="4",addr="0x000107e0",func="main",
30229 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30230 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
30232 -stack-list-arguments 0
30235 frame=@{level="0",args=[]@},
30236 frame=@{level="1",args=[name="strarg"]@},
30237 frame=@{level="2",args=[name="intarg",name="strarg"]@},
30238 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
30239 frame=@{level="4",args=[]@}]
30241 -stack-list-arguments 1
30244 frame=@{level="0",args=[]@},
30246 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30247 frame=@{level="2",args=[
30248 @{name="intarg",value="2"@},
30249 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30250 @{frame=@{level="3",args=[
30251 @{name="intarg",value="2"@},
30252 @{name="strarg",value="0x11940 \"A string argument.\""@},
30253 @{name="fltarg",value="3.5"@}]@},
30254 frame=@{level="4",args=[]@}]
30256 -stack-list-arguments 0 2 2
30257 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
30259 -stack-list-arguments 1 2 2
30260 ^done,stack-args=[frame=@{level="2",
30261 args=[@{name="intarg",value="2"@},
30262 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
30266 @c @subheading -stack-list-exception-handlers
30269 @subheading The @code{-stack-list-frames} Command
30270 @findex -stack-list-frames
30272 @subsubheading Synopsis
30275 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
30278 List the frames currently on the stack. For each frame it displays the
30283 The frame number, 0 being the topmost frame, i.e., the innermost function.
30285 The @code{$pc} value for that frame.
30289 File name of the source file where the function lives.
30290 @item @var{fullname}
30291 The full file name of the source file where the function lives.
30293 Line number corresponding to the @code{$pc}.
30295 The shared library where this function is defined. This is only given
30296 if the frame's function is not known.
30299 If invoked without arguments, this command prints a backtrace for the
30300 whole stack. If given two integer arguments, it shows the frames whose
30301 levels are between the two arguments (inclusive). If the two arguments
30302 are equal, it shows the single frame at the corresponding level. It is
30303 an error if @var{low-frame} is larger than the actual number of
30304 frames. On the other hand, @var{high-frame} may be larger than the
30305 actual number of frames, in which case only existing frames will be returned.
30307 @subsubheading @value{GDBN} Command
30309 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
30311 @subsubheading Example
30313 Full stack backtrace:
30319 [frame=@{level="0",addr="0x0001076c",func="foo",
30320 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
30321 frame=@{level="1",addr="0x000107a4",func="foo",
30322 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30323 frame=@{level="2",addr="0x000107a4",func="foo",
30324 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30325 frame=@{level="3",addr="0x000107a4",func="foo",
30326 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30327 frame=@{level="4",addr="0x000107a4",func="foo",
30328 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30329 frame=@{level="5",addr="0x000107a4",func="foo",
30330 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30331 frame=@{level="6",addr="0x000107a4",func="foo",
30332 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30333 frame=@{level="7",addr="0x000107a4",func="foo",
30334 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30335 frame=@{level="8",addr="0x000107a4",func="foo",
30336 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30337 frame=@{level="9",addr="0x000107a4",func="foo",
30338 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30339 frame=@{level="10",addr="0x000107a4",func="foo",
30340 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30341 frame=@{level="11",addr="0x00010738",func="main",
30342 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
30346 Show frames between @var{low_frame} and @var{high_frame}:
30350 -stack-list-frames 3 5
30352 [frame=@{level="3",addr="0x000107a4",func="foo",
30353 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30354 frame=@{level="4",addr="0x000107a4",func="foo",
30355 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30356 frame=@{level="5",addr="0x000107a4",func="foo",
30357 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
30361 Show a single frame:
30365 -stack-list-frames 3 3
30367 [frame=@{level="3",addr="0x000107a4",func="foo",
30368 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
30373 @subheading The @code{-stack-list-locals} Command
30374 @findex -stack-list-locals
30376 @subsubheading Synopsis
30379 -stack-list-locals @var{print-values}
30382 Display the local variable names for the selected frame. If
30383 @var{print-values} is 0 or @code{--no-values}, print only the names of
30384 the variables; if it is 1 or @code{--all-values}, print also their
30385 values; and if it is 2 or @code{--simple-values}, print the name,
30386 type and value for simple data types, and the name and type for arrays,
30387 structures and unions. In this last case, a frontend can immediately
30388 display the value of simple data types and create variable objects for
30389 other data types when the user wishes to explore their values in
30392 This command is deprecated in favor of the
30393 @samp{-stack-list-variables} command.
30395 @subsubheading @value{GDBN} Command
30397 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
30399 @subsubheading Example
30403 -stack-list-locals 0
30404 ^done,locals=[name="A",name="B",name="C"]
30406 -stack-list-locals --all-values
30407 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
30408 @{name="C",value="@{1, 2, 3@}"@}]
30409 -stack-list-locals --simple-values
30410 ^done,locals=[@{name="A",type="int",value="1"@},
30411 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
30415 @subheading The @code{-stack-list-variables} Command
30416 @findex -stack-list-variables
30418 @subsubheading Synopsis
30421 -stack-list-variables @var{print-values}
30424 Display the names of local variables and function arguments for the selected frame. If
30425 @var{print-values} is 0 or @code{--no-values}, print only the names of
30426 the variables; if it is 1 or @code{--all-values}, print also their
30427 values; and if it is 2 or @code{--simple-values}, print the name,
30428 type and value for simple data types, and the name and type for arrays,
30429 structures and unions.
30431 @subsubheading Example
30435 -stack-list-variables --thread 1 --frame 0 --all-values
30436 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
30441 @subheading The @code{-stack-select-frame} Command
30442 @findex -stack-select-frame
30444 @subsubheading Synopsis
30447 -stack-select-frame @var{framenum}
30450 Change the selected frame. Select a different frame @var{framenum} on
30453 This command in deprecated in favor of passing the @samp{--frame}
30454 option to every command.
30456 @subsubheading @value{GDBN} Command
30458 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
30459 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
30461 @subsubheading Example
30465 -stack-select-frame 2
30470 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30471 @node GDB/MI Variable Objects
30472 @section @sc{gdb/mi} Variable Objects
30476 @subheading Motivation for Variable Objects in @sc{gdb/mi}
30478 For the implementation of a variable debugger window (locals, watched
30479 expressions, etc.), we are proposing the adaptation of the existing code
30480 used by @code{Insight}.
30482 The two main reasons for that are:
30486 It has been proven in practice (it is already on its second generation).
30489 It will shorten development time (needless to say how important it is
30493 The original interface was designed to be used by Tcl code, so it was
30494 slightly changed so it could be used through @sc{gdb/mi}. This section
30495 describes the @sc{gdb/mi} operations that will be available and gives some
30496 hints about their use.
30498 @emph{Note}: In addition to the set of operations described here, we
30499 expect the @sc{gui} implementation of a variable window to require, at
30500 least, the following operations:
30503 @item @code{-gdb-show} @code{output-radix}
30504 @item @code{-stack-list-arguments}
30505 @item @code{-stack-list-locals}
30506 @item @code{-stack-select-frame}
30511 @subheading Introduction to Variable Objects
30513 @cindex variable objects in @sc{gdb/mi}
30515 Variable objects are "object-oriented" MI interface for examining and
30516 changing values of expressions. Unlike some other MI interfaces that
30517 work with expressions, variable objects are specifically designed for
30518 simple and efficient presentation in the frontend. A variable object
30519 is identified by string name. When a variable object is created, the
30520 frontend specifies the expression for that variable object. The
30521 expression can be a simple variable, or it can be an arbitrary complex
30522 expression, and can even involve CPU registers. After creating a
30523 variable object, the frontend can invoke other variable object
30524 operations---for example to obtain or change the value of a variable
30525 object, or to change display format.
30527 Variable objects have hierarchical tree structure. Any variable object
30528 that corresponds to a composite type, such as structure in C, has
30529 a number of child variable objects, for example corresponding to each
30530 element of a structure. A child variable object can itself have
30531 children, recursively. Recursion ends when we reach
30532 leaf variable objects, which always have built-in types. Child variable
30533 objects are created only by explicit request, so if a frontend
30534 is not interested in the children of a particular variable object, no
30535 child will be created.
30537 For a leaf variable object it is possible to obtain its value as a
30538 string, or set the value from a string. String value can be also
30539 obtained for a non-leaf variable object, but it's generally a string
30540 that only indicates the type of the object, and does not list its
30541 contents. Assignment to a non-leaf variable object is not allowed.
30543 A frontend does not need to read the values of all variable objects each time
30544 the program stops. Instead, MI provides an update command that lists all
30545 variable objects whose values has changed since the last update
30546 operation. This considerably reduces the amount of data that must
30547 be transferred to the frontend. As noted above, children variable
30548 objects are created on demand, and only leaf variable objects have a
30549 real value. As result, gdb will read target memory only for leaf
30550 variables that frontend has created.
30552 The automatic update is not always desirable. For example, a frontend
30553 might want to keep a value of some expression for future reference,
30554 and never update it. For another example, fetching memory is
30555 relatively slow for embedded targets, so a frontend might want
30556 to disable automatic update for the variables that are either not
30557 visible on the screen, or ``closed''. This is possible using so
30558 called ``frozen variable objects''. Such variable objects are never
30559 implicitly updated.
30561 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
30562 fixed variable object, the expression is parsed when the variable
30563 object is created, including associating identifiers to specific
30564 variables. The meaning of expression never changes. For a floating
30565 variable object the values of variables whose names appear in the
30566 expressions are re-evaluated every time in the context of the current
30567 frame. Consider this example:
30572 struct work_state state;
30579 If a fixed variable object for the @code{state} variable is created in
30580 this function, and we enter the recursive call, the variable
30581 object will report the value of @code{state} in the top-level
30582 @code{do_work} invocation. On the other hand, a floating variable
30583 object will report the value of @code{state} in the current frame.
30585 If an expression specified when creating a fixed variable object
30586 refers to a local variable, the variable object becomes bound to the
30587 thread and frame in which the variable object is created. When such
30588 variable object is updated, @value{GDBN} makes sure that the
30589 thread/frame combination the variable object is bound to still exists,
30590 and re-evaluates the variable object in context of that thread/frame.
30592 The following is the complete set of @sc{gdb/mi} operations defined to
30593 access this functionality:
30595 @multitable @columnfractions .4 .6
30596 @item @strong{Operation}
30597 @tab @strong{Description}
30599 @item @code{-enable-pretty-printing}
30600 @tab enable Python-based pretty-printing
30601 @item @code{-var-create}
30602 @tab create a variable object
30603 @item @code{-var-delete}
30604 @tab delete the variable object and/or its children
30605 @item @code{-var-set-format}
30606 @tab set the display format of this variable
30607 @item @code{-var-show-format}
30608 @tab show the display format of this variable
30609 @item @code{-var-info-num-children}
30610 @tab tells how many children this object has
30611 @item @code{-var-list-children}
30612 @tab return a list of the object's children
30613 @item @code{-var-info-type}
30614 @tab show the type of this variable object
30615 @item @code{-var-info-expression}
30616 @tab print parent-relative expression that this variable object represents
30617 @item @code{-var-info-path-expression}
30618 @tab print full expression that this variable object represents
30619 @item @code{-var-show-attributes}
30620 @tab is this variable editable? does it exist here?
30621 @item @code{-var-evaluate-expression}
30622 @tab get the value of this variable
30623 @item @code{-var-assign}
30624 @tab set the value of this variable
30625 @item @code{-var-update}
30626 @tab update the variable and its children
30627 @item @code{-var-set-frozen}
30628 @tab set frozeness attribute
30629 @item @code{-var-set-update-range}
30630 @tab set range of children to display on update
30633 In the next subsection we describe each operation in detail and suggest
30634 how it can be used.
30636 @subheading Description And Use of Operations on Variable Objects
30638 @subheading The @code{-enable-pretty-printing} Command
30639 @findex -enable-pretty-printing
30642 -enable-pretty-printing
30645 @value{GDBN} allows Python-based visualizers to affect the output of the
30646 MI variable object commands. However, because there was no way to
30647 implement this in a fully backward-compatible way, a front end must
30648 request that this functionality be enabled.
30650 Once enabled, this feature cannot be disabled.
30652 Note that if Python support has not been compiled into @value{GDBN},
30653 this command will still succeed (and do nothing).
30655 This feature is currently (as of @value{GDBN} 7.0) experimental, and
30656 may work differently in future versions of @value{GDBN}.
30658 @subheading The @code{-var-create} Command
30659 @findex -var-create
30661 @subsubheading Synopsis
30664 -var-create @{@var{name} | "-"@}
30665 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
30668 This operation creates a variable object, which allows the monitoring of
30669 a variable, the result of an expression, a memory cell or a CPU
30672 The @var{name} parameter is the string by which the object can be
30673 referenced. It must be unique. If @samp{-} is specified, the varobj
30674 system will generate a string ``varNNNNNN'' automatically. It will be
30675 unique provided that one does not specify @var{name} of that format.
30676 The command fails if a duplicate name is found.
30678 The frame under which the expression should be evaluated can be
30679 specified by @var{frame-addr}. A @samp{*} indicates that the current
30680 frame should be used. A @samp{@@} indicates that a floating variable
30681 object must be created.
30683 @var{expression} is any expression valid on the current language set (must not
30684 begin with a @samp{*}), or one of the following:
30688 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
30691 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
30694 @samp{$@var{regname}} --- a CPU register name
30697 @cindex dynamic varobj
30698 A varobj's contents may be provided by a Python-based pretty-printer. In this
30699 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
30700 have slightly different semantics in some cases. If the
30701 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
30702 will never create a dynamic varobj. This ensures backward
30703 compatibility for existing clients.
30705 @subsubheading Result
30707 This operation returns attributes of the newly-created varobj. These
30712 The name of the varobj.
30715 The number of children of the varobj. This number is not necessarily
30716 reliable for a dynamic varobj. Instead, you must examine the
30717 @samp{has_more} attribute.
30720 The varobj's scalar value. For a varobj whose type is some sort of
30721 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
30722 will not be interesting.
30725 The varobj's type. This is a string representation of the type, as
30726 would be printed by the @value{GDBN} CLI. If @samp{print object}
30727 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30728 @emph{actual} (derived) type of the object is shown rather than the
30729 @emph{declared} one.
30732 If a variable object is bound to a specific thread, then this is the
30733 thread's identifier.
30736 For a dynamic varobj, this indicates whether there appear to be any
30737 children available. For a non-dynamic varobj, this will be 0.
30740 This attribute will be present and have the value @samp{1} if the
30741 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30742 then this attribute will not be present.
30745 A dynamic varobj can supply a display hint to the front end. The
30746 value comes directly from the Python pretty-printer object's
30747 @code{display_hint} method. @xref{Pretty Printing API}.
30750 Typical output will look like this:
30753 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
30754 has_more="@var{has_more}"
30758 @subheading The @code{-var-delete} Command
30759 @findex -var-delete
30761 @subsubheading Synopsis
30764 -var-delete [ -c ] @var{name}
30767 Deletes a previously created variable object and all of its children.
30768 With the @samp{-c} option, just deletes the children.
30770 Returns an error if the object @var{name} is not found.
30773 @subheading The @code{-var-set-format} Command
30774 @findex -var-set-format
30776 @subsubheading Synopsis
30779 -var-set-format @var{name} @var{format-spec}
30782 Sets the output format for the value of the object @var{name} to be
30785 @anchor{-var-set-format}
30786 The syntax for the @var{format-spec} is as follows:
30789 @var{format-spec} @expansion{}
30790 @{binary | decimal | hexadecimal | octal | natural@}
30793 The natural format is the default format choosen automatically
30794 based on the variable type (like decimal for an @code{int}, hex
30795 for pointers, etc.).
30797 For a variable with children, the format is set only on the
30798 variable itself, and the children are not affected.
30800 @subheading The @code{-var-show-format} Command
30801 @findex -var-show-format
30803 @subsubheading Synopsis
30806 -var-show-format @var{name}
30809 Returns the format used to display the value of the object @var{name}.
30812 @var{format} @expansion{}
30817 @subheading The @code{-var-info-num-children} Command
30818 @findex -var-info-num-children
30820 @subsubheading Synopsis
30823 -var-info-num-children @var{name}
30826 Returns the number of children of a variable object @var{name}:
30832 Note that this number is not completely reliable for a dynamic varobj.
30833 It will return the current number of children, but more children may
30837 @subheading The @code{-var-list-children} Command
30838 @findex -var-list-children
30840 @subsubheading Synopsis
30843 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
30845 @anchor{-var-list-children}
30847 Return a list of the children of the specified variable object and
30848 create variable objects for them, if they do not already exist. With
30849 a single argument or if @var{print-values} has a value of 0 or
30850 @code{--no-values}, print only the names of the variables; if
30851 @var{print-values} is 1 or @code{--all-values}, also print their
30852 values; and if it is 2 or @code{--simple-values} print the name and
30853 value for simple data types and just the name for arrays, structures
30856 @var{from} and @var{to}, if specified, indicate the range of children
30857 to report. If @var{from} or @var{to} is less than zero, the range is
30858 reset and all children will be reported. Otherwise, children starting
30859 at @var{from} (zero-based) and up to and excluding @var{to} will be
30862 If a child range is requested, it will only affect the current call to
30863 @code{-var-list-children}, but not future calls to @code{-var-update}.
30864 For this, you must instead use @code{-var-set-update-range}. The
30865 intent of this approach is to enable a front end to implement any
30866 update approach it likes; for example, scrolling a view may cause the
30867 front end to request more children with @code{-var-list-children}, and
30868 then the front end could call @code{-var-set-update-range} with a
30869 different range to ensure that future updates are restricted to just
30872 For each child the following results are returned:
30877 Name of the variable object created for this child.
30880 The expression to be shown to the user by the front end to designate this child.
30881 For example this may be the name of a structure member.
30883 For a dynamic varobj, this value cannot be used to form an
30884 expression. There is no way to do this at all with a dynamic varobj.
30886 For C/C@t{++} structures there are several pseudo children returned to
30887 designate access qualifiers. For these pseudo children @var{exp} is
30888 @samp{public}, @samp{private}, or @samp{protected}. In this case the
30889 type and value are not present.
30891 A dynamic varobj will not report the access qualifying
30892 pseudo-children, regardless of the language. This information is not
30893 available at all with a dynamic varobj.
30896 Number of children this child has. For a dynamic varobj, this will be
30900 The type of the child. If @samp{print object}
30901 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30902 @emph{actual} (derived) type of the object is shown rather than the
30903 @emph{declared} one.
30906 If values were requested, this is the value.
30909 If this variable object is associated with a thread, this is the thread id.
30910 Otherwise this result is not present.
30913 If the variable object is frozen, this variable will be present with a value of 1.
30916 The result may have its own attributes:
30920 A dynamic varobj can supply a display hint to the front end. The
30921 value comes directly from the Python pretty-printer object's
30922 @code{display_hint} method. @xref{Pretty Printing API}.
30925 This is an integer attribute which is nonzero if there are children
30926 remaining after the end of the selected range.
30929 @subsubheading Example
30933 -var-list-children n
30934 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30935 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
30937 -var-list-children --all-values n
30938 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30939 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
30943 @subheading The @code{-var-info-type} Command
30944 @findex -var-info-type
30946 @subsubheading Synopsis
30949 -var-info-type @var{name}
30952 Returns the type of the specified variable @var{name}. The type is
30953 returned as a string in the same format as it is output by the
30957 type=@var{typename}
30961 @subheading The @code{-var-info-expression} Command
30962 @findex -var-info-expression
30964 @subsubheading Synopsis
30967 -var-info-expression @var{name}
30970 Returns a string that is suitable for presenting this
30971 variable object in user interface. The string is generally
30972 not valid expression in the current language, and cannot be evaluated.
30974 For example, if @code{a} is an array, and variable object
30975 @code{A} was created for @code{a}, then we'll get this output:
30978 (gdb) -var-info-expression A.1
30979 ^done,lang="C",exp="1"
30983 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
30985 Note that the output of the @code{-var-list-children} command also
30986 includes those expressions, so the @code{-var-info-expression} command
30989 @subheading The @code{-var-info-path-expression} Command
30990 @findex -var-info-path-expression
30992 @subsubheading Synopsis
30995 -var-info-path-expression @var{name}
30998 Returns an expression that can be evaluated in the current
30999 context and will yield the same value that a variable object has.
31000 Compare this with the @code{-var-info-expression} command, which
31001 result can be used only for UI presentation. Typical use of
31002 the @code{-var-info-path-expression} command is creating a
31003 watchpoint from a variable object.
31005 This command is currently not valid for children of a dynamic varobj,
31006 and will give an error when invoked on one.
31008 For example, suppose @code{C} is a C@t{++} class, derived from class
31009 @code{Base}, and that the @code{Base} class has a member called
31010 @code{m_size}. Assume a variable @code{c} is has the type of
31011 @code{C} and a variable object @code{C} was created for variable
31012 @code{c}. Then, we'll get this output:
31014 (gdb) -var-info-path-expression C.Base.public.m_size
31015 ^done,path_expr=((Base)c).m_size)
31018 @subheading The @code{-var-show-attributes} Command
31019 @findex -var-show-attributes
31021 @subsubheading Synopsis
31024 -var-show-attributes @var{name}
31027 List attributes of the specified variable object @var{name}:
31030 status=@var{attr} [ ( ,@var{attr} )* ]
31034 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
31036 @subheading The @code{-var-evaluate-expression} Command
31037 @findex -var-evaluate-expression
31039 @subsubheading Synopsis
31042 -var-evaluate-expression [-f @var{format-spec}] @var{name}
31045 Evaluates the expression that is represented by the specified variable
31046 object and returns its value as a string. The format of the string
31047 can be specified with the @samp{-f} option. The possible values of
31048 this option are the same as for @code{-var-set-format}
31049 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
31050 the current display format will be used. The current display format
31051 can be changed using the @code{-var-set-format} command.
31057 Note that one must invoke @code{-var-list-children} for a variable
31058 before the value of a child variable can be evaluated.
31060 @subheading The @code{-var-assign} Command
31061 @findex -var-assign
31063 @subsubheading Synopsis
31066 -var-assign @var{name} @var{expression}
31069 Assigns the value of @var{expression} to the variable object specified
31070 by @var{name}. The object must be @samp{editable}. If the variable's
31071 value is altered by the assign, the variable will show up in any
31072 subsequent @code{-var-update} list.
31074 @subsubheading Example
31082 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
31086 @subheading The @code{-var-update} Command
31087 @findex -var-update
31089 @subsubheading Synopsis
31092 -var-update [@var{print-values}] @{@var{name} | "*"@}
31095 Reevaluate the expressions corresponding to the variable object
31096 @var{name} and all its direct and indirect children, and return the
31097 list of variable objects whose values have changed; @var{name} must
31098 be a root variable object. Here, ``changed'' means that the result of
31099 @code{-var-evaluate-expression} before and after the
31100 @code{-var-update} is different. If @samp{*} is used as the variable
31101 object names, all existing variable objects are updated, except
31102 for frozen ones (@pxref{-var-set-frozen}). The option
31103 @var{print-values} determines whether both names and values, or just
31104 names are printed. The possible values of this option are the same
31105 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
31106 recommended to use the @samp{--all-values} option, to reduce the
31107 number of MI commands needed on each program stop.
31109 With the @samp{*} parameter, if a variable object is bound to a
31110 currently running thread, it will not be updated, without any
31113 If @code{-var-set-update-range} was previously used on a varobj, then
31114 only the selected range of children will be reported.
31116 @code{-var-update} reports all the changed varobjs in a tuple named
31119 Each item in the change list is itself a tuple holding:
31123 The name of the varobj.
31126 If values were requested for this update, then this field will be
31127 present and will hold the value of the varobj.
31130 @anchor{-var-update}
31131 This field is a string which may take one of three values:
31135 The variable object's current value is valid.
31138 The variable object does not currently hold a valid value but it may
31139 hold one in the future if its associated expression comes back into
31143 The variable object no longer holds a valid value.
31144 This can occur when the executable file being debugged has changed,
31145 either through recompilation or by using the @value{GDBN} @code{file}
31146 command. The front end should normally choose to delete these variable
31150 In the future new values may be added to this list so the front should
31151 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
31154 This is only present if the varobj is still valid. If the type
31155 changed, then this will be the string @samp{true}; otherwise it will
31158 When a varobj's type changes, its children are also likely to have
31159 become incorrect. Therefore, the varobj's children are automatically
31160 deleted when this attribute is @samp{true}. Also, the varobj's update
31161 range, when set using the @code{-var-set-update-range} command, is
31165 If the varobj's type changed, then this field will be present and will
31168 @item new_num_children
31169 For a dynamic varobj, if the number of children changed, or if the
31170 type changed, this will be the new number of children.
31172 The @samp{numchild} field in other varobj responses is generally not
31173 valid for a dynamic varobj -- it will show the number of children that
31174 @value{GDBN} knows about, but because dynamic varobjs lazily
31175 instantiate their children, this will not reflect the number of
31176 children which may be available.
31178 The @samp{new_num_children} attribute only reports changes to the
31179 number of children known by @value{GDBN}. This is the only way to
31180 detect whether an update has removed children (which necessarily can
31181 only happen at the end of the update range).
31184 The display hint, if any.
31187 This is an integer value, which will be 1 if there are more children
31188 available outside the varobj's update range.
31191 This attribute will be present and have the value @samp{1} if the
31192 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31193 then this attribute will not be present.
31196 If new children were added to a dynamic varobj within the selected
31197 update range (as set by @code{-var-set-update-range}), then they will
31198 be listed in this attribute.
31201 @subsubheading Example
31208 -var-update --all-values var1
31209 ^done,changelist=[@{name="var1",value="3",in_scope="true",
31210 type_changed="false"@}]
31214 @subheading The @code{-var-set-frozen} Command
31215 @findex -var-set-frozen
31216 @anchor{-var-set-frozen}
31218 @subsubheading Synopsis
31221 -var-set-frozen @var{name} @var{flag}
31224 Set the frozenness flag on the variable object @var{name}. The
31225 @var{flag} parameter should be either @samp{1} to make the variable
31226 frozen or @samp{0} to make it unfrozen. If a variable object is
31227 frozen, then neither itself, nor any of its children, are
31228 implicitly updated by @code{-var-update} of
31229 a parent variable or by @code{-var-update *}. Only
31230 @code{-var-update} of the variable itself will update its value and
31231 values of its children. After a variable object is unfrozen, it is
31232 implicitly updated by all subsequent @code{-var-update} operations.
31233 Unfreezing a variable does not update it, only subsequent
31234 @code{-var-update} does.
31236 @subsubheading Example
31240 -var-set-frozen V 1
31245 @subheading The @code{-var-set-update-range} command
31246 @findex -var-set-update-range
31247 @anchor{-var-set-update-range}
31249 @subsubheading Synopsis
31252 -var-set-update-range @var{name} @var{from} @var{to}
31255 Set the range of children to be returned by future invocations of
31256 @code{-var-update}.
31258 @var{from} and @var{to} indicate the range of children to report. If
31259 @var{from} or @var{to} is less than zero, the range is reset and all
31260 children will be reported. Otherwise, children starting at @var{from}
31261 (zero-based) and up to and excluding @var{to} will be reported.
31263 @subsubheading Example
31267 -var-set-update-range V 1 2
31271 @subheading The @code{-var-set-visualizer} command
31272 @findex -var-set-visualizer
31273 @anchor{-var-set-visualizer}
31275 @subsubheading Synopsis
31278 -var-set-visualizer @var{name} @var{visualizer}
31281 Set a visualizer for the variable object @var{name}.
31283 @var{visualizer} is the visualizer to use. The special value
31284 @samp{None} means to disable any visualizer in use.
31286 If not @samp{None}, @var{visualizer} must be a Python expression.
31287 This expression must evaluate to a callable object which accepts a
31288 single argument. @value{GDBN} will call this object with the value of
31289 the varobj @var{name} as an argument (this is done so that the same
31290 Python pretty-printing code can be used for both the CLI and MI).
31291 When called, this object must return an object which conforms to the
31292 pretty-printing interface (@pxref{Pretty Printing API}).
31294 The pre-defined function @code{gdb.default_visualizer} may be used to
31295 select a visualizer by following the built-in process
31296 (@pxref{Selecting Pretty-Printers}). This is done automatically when
31297 a varobj is created, and so ordinarily is not needed.
31299 This feature is only available if Python support is enabled. The MI
31300 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
31301 can be used to check this.
31303 @subsubheading Example
31305 Resetting the visualizer:
31309 -var-set-visualizer V None
31313 Reselecting the default (type-based) visualizer:
31317 -var-set-visualizer V gdb.default_visualizer
31321 Suppose @code{SomeClass} is a visualizer class. A lambda expression
31322 can be used to instantiate this class for a varobj:
31326 -var-set-visualizer V "lambda val: SomeClass()"
31330 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31331 @node GDB/MI Data Manipulation
31332 @section @sc{gdb/mi} Data Manipulation
31334 @cindex data manipulation, in @sc{gdb/mi}
31335 @cindex @sc{gdb/mi}, data manipulation
31336 This section describes the @sc{gdb/mi} commands that manipulate data:
31337 examine memory and registers, evaluate expressions, etc.
31339 @c REMOVED FROM THE INTERFACE.
31340 @c @subheading -data-assign
31341 @c Change the value of a program variable. Plenty of side effects.
31342 @c @subsubheading GDB Command
31344 @c @subsubheading Example
31347 @subheading The @code{-data-disassemble} Command
31348 @findex -data-disassemble
31350 @subsubheading Synopsis
31354 [ -s @var{start-addr} -e @var{end-addr} ]
31355 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
31363 @item @var{start-addr}
31364 is the beginning address (or @code{$pc})
31365 @item @var{end-addr}
31367 @item @var{filename}
31368 is the name of the file to disassemble
31369 @item @var{linenum}
31370 is the line number to disassemble around
31372 is the number of disassembly lines to be produced. If it is -1,
31373 the whole function will be disassembled, in case no @var{end-addr} is
31374 specified. If @var{end-addr} is specified as a non-zero value, and
31375 @var{lines} is lower than the number of disassembly lines between
31376 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
31377 displayed; if @var{lines} is higher than the number of lines between
31378 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
31381 is either 0 (meaning only disassembly), 1 (meaning mixed source and
31382 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
31383 mixed source and disassembly with raw opcodes).
31386 @subsubheading Result
31388 The result of the @code{-data-disassemble} command will be a list named
31389 @samp{asm_insns}, the contents of this list depend on the @var{mode}
31390 used with the @code{-data-disassemble} command.
31392 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
31397 The address at which this instruction was disassembled.
31400 The name of the function this instruction is within.
31403 The decimal offset in bytes from the start of @samp{func-name}.
31406 The text disassembly for this @samp{address}.
31409 This field is only present for mode 2. This contains the raw opcode
31410 bytes for the @samp{inst} field.
31414 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
31415 @samp{src_and_asm_line}, each of which has the following fields:
31419 The line number within @samp{file}.
31422 The file name from the compilation unit. This might be an absolute
31423 file name or a relative file name depending on the compile command
31427 Absolute file name of @samp{file}. It is converted to a canonical form
31428 using the source file search path
31429 (@pxref{Source Path, ,Specifying Source Directories})
31430 and after resolving all the symbolic links.
31432 If the source file is not found this field will contain the path as
31433 present in the debug information.
31435 @item line_asm_insn
31436 This is a list of tuples containing the disassembly for @samp{line} in
31437 @samp{file}. The fields of each tuple are the same as for
31438 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
31439 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
31444 Note that whatever included in the @samp{inst} field, is not
31445 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
31448 @subsubheading @value{GDBN} Command
31450 The corresponding @value{GDBN} command is @samp{disassemble}.
31452 @subsubheading Example
31454 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
31458 -data-disassemble -s $pc -e "$pc + 20" -- 0
31461 @{address="0x000107c0",func-name="main",offset="4",
31462 inst="mov 2, %o0"@},
31463 @{address="0x000107c4",func-name="main",offset="8",
31464 inst="sethi %hi(0x11800), %o2"@},
31465 @{address="0x000107c8",func-name="main",offset="12",
31466 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
31467 @{address="0x000107cc",func-name="main",offset="16",
31468 inst="sethi %hi(0x11800), %o2"@},
31469 @{address="0x000107d0",func-name="main",offset="20",
31470 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
31474 Disassemble the whole @code{main} function. Line 32 is part of
31478 -data-disassemble -f basics.c -l 32 -- 0
31480 @{address="0x000107bc",func-name="main",offset="0",
31481 inst="save %sp, -112, %sp"@},
31482 @{address="0x000107c0",func-name="main",offset="4",
31483 inst="mov 2, %o0"@},
31484 @{address="0x000107c4",func-name="main",offset="8",
31485 inst="sethi %hi(0x11800), %o2"@},
31487 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
31488 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
31492 Disassemble 3 instructions from the start of @code{main}:
31496 -data-disassemble -f basics.c -l 32 -n 3 -- 0
31498 @{address="0x000107bc",func-name="main",offset="0",
31499 inst="save %sp, -112, %sp"@},
31500 @{address="0x000107c0",func-name="main",offset="4",
31501 inst="mov 2, %o0"@},
31502 @{address="0x000107c4",func-name="main",offset="8",
31503 inst="sethi %hi(0x11800), %o2"@}]
31507 Disassemble 3 instructions from the start of @code{main} in mixed mode:
31511 -data-disassemble -f basics.c -l 32 -n 3 -- 1
31513 src_and_asm_line=@{line="31",
31514 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31515 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31516 line_asm_insn=[@{address="0x000107bc",
31517 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
31518 src_and_asm_line=@{line="32",
31519 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31520 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31521 line_asm_insn=[@{address="0x000107c0",
31522 func-name="main",offset="4",inst="mov 2, %o0"@},
31523 @{address="0x000107c4",func-name="main",offset="8",
31524 inst="sethi %hi(0x11800), %o2"@}]@}]
31529 @subheading The @code{-data-evaluate-expression} Command
31530 @findex -data-evaluate-expression
31532 @subsubheading Synopsis
31535 -data-evaluate-expression @var{expr}
31538 Evaluate @var{expr} as an expression. The expression could contain an
31539 inferior function call. The function call will execute synchronously.
31540 If the expression contains spaces, it must be enclosed in double quotes.
31542 @subsubheading @value{GDBN} Command
31544 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
31545 @samp{call}. In @code{gdbtk} only, there's a corresponding
31546 @samp{gdb_eval} command.
31548 @subsubheading Example
31550 In the following example, the numbers that precede the commands are the
31551 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
31552 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
31556 211-data-evaluate-expression A
31559 311-data-evaluate-expression &A
31560 311^done,value="0xefffeb7c"
31562 411-data-evaluate-expression A+3
31565 511-data-evaluate-expression "A + 3"
31571 @subheading The @code{-data-list-changed-registers} Command
31572 @findex -data-list-changed-registers
31574 @subsubheading Synopsis
31577 -data-list-changed-registers
31580 Display a list of the registers that have changed.
31582 @subsubheading @value{GDBN} Command
31584 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
31585 has the corresponding command @samp{gdb_changed_register_list}.
31587 @subsubheading Example
31589 On a PPC MBX board:
31597 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
31598 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
31601 -data-list-changed-registers
31602 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
31603 "10","11","13","14","15","16","17","18","19","20","21","22","23",
31604 "24","25","26","27","28","30","31","64","65","66","67","69"]
31609 @subheading The @code{-data-list-register-names} Command
31610 @findex -data-list-register-names
31612 @subsubheading Synopsis
31615 -data-list-register-names [ ( @var{regno} )+ ]
31618 Show a list of register names for the current target. If no arguments
31619 are given, it shows a list of the names of all the registers. If
31620 integer numbers are given as arguments, it will print a list of the
31621 names of the registers corresponding to the arguments. To ensure
31622 consistency between a register name and its number, the output list may
31623 include empty register names.
31625 @subsubheading @value{GDBN} Command
31627 @value{GDBN} does not have a command which corresponds to
31628 @samp{-data-list-register-names}. In @code{gdbtk} there is a
31629 corresponding command @samp{gdb_regnames}.
31631 @subsubheading Example
31633 For the PPC MBX board:
31636 -data-list-register-names
31637 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
31638 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
31639 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
31640 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
31641 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
31642 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
31643 "", "pc","ps","cr","lr","ctr","xer"]
31645 -data-list-register-names 1 2 3
31646 ^done,register-names=["r1","r2","r3"]
31650 @subheading The @code{-data-list-register-values} Command
31651 @findex -data-list-register-values
31653 @subsubheading Synopsis
31656 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
31659 Display the registers' contents. @var{fmt} is the format according to
31660 which the registers' contents are to be returned, followed by an optional
31661 list of numbers specifying the registers to display. A missing list of
31662 numbers indicates that the contents of all the registers must be returned.
31664 Allowed formats for @var{fmt} are:
31681 @subsubheading @value{GDBN} Command
31683 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
31684 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
31686 @subsubheading Example
31688 For a PPC MBX board (note: line breaks are for readability only, they
31689 don't appear in the actual output):
31693 -data-list-register-values r 64 65
31694 ^done,register-values=[@{number="64",value="0xfe00a300"@},
31695 @{number="65",value="0x00029002"@}]
31697 -data-list-register-values x
31698 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
31699 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
31700 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
31701 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
31702 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
31703 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
31704 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
31705 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
31706 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
31707 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
31708 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
31709 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
31710 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
31711 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
31712 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
31713 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
31714 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
31715 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
31716 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
31717 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
31718 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
31719 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
31720 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
31721 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
31722 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
31723 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
31724 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
31725 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
31726 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
31727 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
31728 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
31729 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
31730 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
31731 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
31732 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
31733 @{number="69",value="0x20002b03"@}]
31738 @subheading The @code{-data-read-memory} Command
31739 @findex -data-read-memory
31741 This command is deprecated, use @code{-data-read-memory-bytes} instead.
31743 @subsubheading Synopsis
31746 -data-read-memory [ -o @var{byte-offset} ]
31747 @var{address} @var{word-format} @var{word-size}
31748 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
31755 @item @var{address}
31756 An expression specifying the address of the first memory word to be
31757 read. Complex expressions containing embedded white space should be
31758 quoted using the C convention.
31760 @item @var{word-format}
31761 The format to be used to print the memory words. The notation is the
31762 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
31765 @item @var{word-size}
31766 The size of each memory word in bytes.
31768 @item @var{nr-rows}
31769 The number of rows in the output table.
31771 @item @var{nr-cols}
31772 The number of columns in the output table.
31775 If present, indicates that each row should include an @sc{ascii} dump. The
31776 value of @var{aschar} is used as a padding character when a byte is not a
31777 member of the printable @sc{ascii} character set (printable @sc{ascii}
31778 characters are those whose code is between 32 and 126, inclusively).
31780 @item @var{byte-offset}
31781 An offset to add to the @var{address} before fetching memory.
31784 This command displays memory contents as a table of @var{nr-rows} by
31785 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
31786 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
31787 (returned as @samp{total-bytes}). Should less than the requested number
31788 of bytes be returned by the target, the missing words are identified
31789 using @samp{N/A}. The number of bytes read from the target is returned
31790 in @samp{nr-bytes} and the starting address used to read memory in
31793 The address of the next/previous row or page is available in
31794 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
31797 @subsubheading @value{GDBN} Command
31799 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
31800 @samp{gdb_get_mem} memory read command.
31802 @subsubheading Example
31804 Read six bytes of memory starting at @code{bytes+6} but then offset by
31805 @code{-6} bytes. Format as three rows of two columns. One byte per
31806 word. Display each word in hex.
31810 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
31811 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
31812 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
31813 prev-page="0x0000138a",memory=[
31814 @{addr="0x00001390",data=["0x00","0x01"]@},
31815 @{addr="0x00001392",data=["0x02","0x03"]@},
31816 @{addr="0x00001394",data=["0x04","0x05"]@}]
31820 Read two bytes of memory starting at address @code{shorts + 64} and
31821 display as a single word formatted in decimal.
31825 5-data-read-memory shorts+64 d 2 1 1
31826 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
31827 next-row="0x00001512",prev-row="0x0000150e",
31828 next-page="0x00001512",prev-page="0x0000150e",memory=[
31829 @{addr="0x00001510",data=["128"]@}]
31833 Read thirty two bytes of memory starting at @code{bytes+16} and format
31834 as eight rows of four columns. Include a string encoding with @samp{x}
31835 used as the non-printable character.
31839 4-data-read-memory bytes+16 x 1 8 4 x
31840 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
31841 next-row="0x000013c0",prev-row="0x0000139c",
31842 next-page="0x000013c0",prev-page="0x00001380",memory=[
31843 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
31844 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
31845 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
31846 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
31847 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
31848 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
31849 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
31850 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
31854 @subheading The @code{-data-read-memory-bytes} Command
31855 @findex -data-read-memory-bytes
31857 @subsubheading Synopsis
31860 -data-read-memory-bytes [ -o @var{byte-offset} ]
31861 @var{address} @var{count}
31868 @item @var{address}
31869 An expression specifying the address of the first memory word to be
31870 read. Complex expressions containing embedded white space should be
31871 quoted using the C convention.
31874 The number of bytes to read. This should be an integer literal.
31876 @item @var{byte-offset}
31877 The offsets in bytes relative to @var{address} at which to start
31878 reading. This should be an integer literal. This option is provided
31879 so that a frontend is not required to first evaluate address and then
31880 perform address arithmetics itself.
31884 This command attempts to read all accessible memory regions in the
31885 specified range. First, all regions marked as unreadable in the memory
31886 map (if one is defined) will be skipped. @xref{Memory Region
31887 Attributes}. Second, @value{GDBN} will attempt to read the remaining
31888 regions. For each one, if reading full region results in an errors,
31889 @value{GDBN} will try to read a subset of the region.
31891 In general, every single byte in the region may be readable or not,
31892 and the only way to read every readable byte is to try a read at
31893 every address, which is not practical. Therefore, @value{GDBN} will
31894 attempt to read all accessible bytes at either beginning or the end
31895 of the region, using a binary division scheme. This heuristic works
31896 well for reading accross a memory map boundary. Note that if a region
31897 has a readable range that is neither at the beginning or the end,
31898 @value{GDBN} will not read it.
31900 The result record (@pxref{GDB/MI Result Records}) that is output of
31901 the command includes a field named @samp{memory} whose content is a
31902 list of tuples. Each tuple represent a successfully read memory block
31903 and has the following fields:
31907 The start address of the memory block, as hexadecimal literal.
31910 The end address of the memory block, as hexadecimal literal.
31913 The offset of the memory block, as hexadecimal literal, relative to
31914 the start address passed to @code{-data-read-memory-bytes}.
31917 The contents of the memory block, in hex.
31923 @subsubheading @value{GDBN} Command
31925 The corresponding @value{GDBN} command is @samp{x}.
31927 @subsubheading Example
31931 -data-read-memory-bytes &a 10
31932 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
31934 contents="01000000020000000300"@}]
31939 @subheading The @code{-data-write-memory-bytes} Command
31940 @findex -data-write-memory-bytes
31942 @subsubheading Synopsis
31945 -data-write-memory-bytes @var{address} @var{contents}
31946 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
31953 @item @var{address}
31954 An expression specifying the address of the first memory word to be
31955 read. Complex expressions containing embedded white space should be
31956 quoted using the C convention.
31958 @item @var{contents}
31959 The hex-encoded bytes to write.
31962 Optional argument indicating the number of bytes to be written. If @var{count}
31963 is greater than @var{contents}' length, @value{GDBN} will repeatedly
31964 write @var{contents} until it fills @var{count} bytes.
31968 @subsubheading @value{GDBN} Command
31970 There's no corresponding @value{GDBN} command.
31972 @subsubheading Example
31976 -data-write-memory-bytes &a "aabbccdd"
31983 -data-write-memory-bytes &a "aabbccdd" 16e
31988 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31989 @node GDB/MI Tracepoint Commands
31990 @section @sc{gdb/mi} Tracepoint Commands
31992 The commands defined in this section implement MI support for
31993 tracepoints. For detailed introduction, see @ref{Tracepoints}.
31995 @subheading The @code{-trace-find} Command
31996 @findex -trace-find
31998 @subsubheading Synopsis
32001 -trace-find @var{mode} [@var{parameters}@dots{}]
32004 Find a trace frame using criteria defined by @var{mode} and
32005 @var{parameters}. The following table lists permissible
32006 modes and their parameters. For details of operation, see @ref{tfind}.
32011 No parameters are required. Stops examining trace frames.
32014 An integer is required as parameter. Selects tracepoint frame with
32017 @item tracepoint-number
32018 An integer is required as parameter. Finds next
32019 trace frame that corresponds to tracepoint with the specified number.
32022 An address is required as parameter. Finds
32023 next trace frame that corresponds to any tracepoint at the specified
32026 @item pc-inside-range
32027 Two addresses are required as parameters. Finds next trace
32028 frame that corresponds to a tracepoint at an address inside the
32029 specified range. Both bounds are considered to be inside the range.
32031 @item pc-outside-range
32032 Two addresses are required as parameters. Finds
32033 next trace frame that corresponds to a tracepoint at an address outside
32034 the specified range. Both bounds are considered to be inside the range.
32037 Line specification is required as parameter. @xref{Specify Location}.
32038 Finds next trace frame that corresponds to a tracepoint at
32039 the specified location.
32043 If @samp{none} was passed as @var{mode}, the response does not
32044 have fields. Otherwise, the response may have the following fields:
32048 This field has either @samp{0} or @samp{1} as the value, depending
32049 on whether a matching tracepoint was found.
32052 The index of the found traceframe. This field is present iff
32053 the @samp{found} field has value of @samp{1}.
32056 The index of the found tracepoint. This field is present iff
32057 the @samp{found} field has value of @samp{1}.
32060 The information about the frame corresponding to the found trace
32061 frame. This field is present only if a trace frame was found.
32062 @xref{GDB/MI Frame Information}, for description of this field.
32066 @subsubheading @value{GDBN} Command
32068 The corresponding @value{GDBN} command is @samp{tfind}.
32070 @subheading -trace-define-variable
32071 @findex -trace-define-variable
32073 @subsubheading Synopsis
32076 -trace-define-variable @var{name} [ @var{value} ]
32079 Create trace variable @var{name} if it does not exist. If
32080 @var{value} is specified, sets the initial value of the specified
32081 trace variable to that value. Note that the @var{name} should start
32082 with the @samp{$} character.
32084 @subsubheading @value{GDBN} Command
32086 The corresponding @value{GDBN} command is @samp{tvariable}.
32088 @subheading -trace-list-variables
32089 @findex -trace-list-variables
32091 @subsubheading Synopsis
32094 -trace-list-variables
32097 Return a table of all defined trace variables. Each element of the
32098 table has the following fields:
32102 The name of the trace variable. This field is always present.
32105 The initial value. This is a 64-bit signed integer. This
32106 field is always present.
32109 The value the trace variable has at the moment. This is a 64-bit
32110 signed integer. This field is absent iff current value is
32111 not defined, for example if the trace was never run, or is
32116 @subsubheading @value{GDBN} Command
32118 The corresponding @value{GDBN} command is @samp{tvariables}.
32120 @subsubheading Example
32124 -trace-list-variables
32125 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
32126 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
32127 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
32128 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
32129 body=[variable=@{name="$trace_timestamp",initial="0"@}
32130 variable=@{name="$foo",initial="10",current="15"@}]@}
32134 @subheading -trace-save
32135 @findex -trace-save
32137 @subsubheading Synopsis
32140 -trace-save [-r ] @var{filename}
32143 Saves the collected trace data to @var{filename}. Without the
32144 @samp{-r} option, the data is downloaded from the target and saved
32145 in a local file. With the @samp{-r} option the target is asked
32146 to perform the save.
32148 @subsubheading @value{GDBN} Command
32150 The corresponding @value{GDBN} command is @samp{tsave}.
32153 @subheading -trace-start
32154 @findex -trace-start
32156 @subsubheading Synopsis
32162 Starts a tracing experiments. The result of this command does not
32165 @subsubheading @value{GDBN} Command
32167 The corresponding @value{GDBN} command is @samp{tstart}.
32169 @subheading -trace-status
32170 @findex -trace-status
32172 @subsubheading Synopsis
32178 Obtains the status of a tracing experiment. The result may include
32179 the following fields:
32184 May have a value of either @samp{0}, when no tracing operations are
32185 supported, @samp{1}, when all tracing operations are supported, or
32186 @samp{file} when examining trace file. In the latter case, examining
32187 of trace frame is possible but new tracing experiement cannot be
32188 started. This field is always present.
32191 May have a value of either @samp{0} or @samp{1} depending on whether
32192 tracing experiement is in progress on target. This field is present
32193 if @samp{supported} field is not @samp{0}.
32196 Report the reason why the tracing was stopped last time. This field
32197 may be absent iff tracing was never stopped on target yet. The
32198 value of @samp{request} means the tracing was stopped as result of
32199 the @code{-trace-stop} command. The value of @samp{overflow} means
32200 the tracing buffer is full. The value of @samp{disconnection} means
32201 tracing was automatically stopped when @value{GDBN} has disconnected.
32202 The value of @samp{passcount} means tracing was stopped when a
32203 tracepoint was passed a maximal number of times for that tracepoint.
32204 This field is present if @samp{supported} field is not @samp{0}.
32206 @item stopping-tracepoint
32207 The number of tracepoint whose passcount as exceeded. This field is
32208 present iff the @samp{stop-reason} field has the value of
32212 @itemx frames-created
32213 The @samp{frames} field is a count of the total number of trace frames
32214 in the trace buffer, while @samp{frames-created} is the total created
32215 during the run, including ones that were discarded, such as when a
32216 circular trace buffer filled up. Both fields are optional.
32220 These fields tell the current size of the tracing buffer and the
32221 remaining space. These fields are optional.
32224 The value of the circular trace buffer flag. @code{1} means that the
32225 trace buffer is circular and old trace frames will be discarded if
32226 necessary to make room, @code{0} means that the trace buffer is linear
32230 The value of the disconnected tracing flag. @code{1} means that
32231 tracing will continue after @value{GDBN} disconnects, @code{0} means
32232 that the trace run will stop.
32235 The filename of the trace file being examined. This field is
32236 optional, and only present when examining a trace file.
32240 @subsubheading @value{GDBN} Command
32242 The corresponding @value{GDBN} command is @samp{tstatus}.
32244 @subheading -trace-stop
32245 @findex -trace-stop
32247 @subsubheading Synopsis
32253 Stops a tracing experiment. The result of this command has the same
32254 fields as @code{-trace-status}, except that the @samp{supported} and
32255 @samp{running} fields are not output.
32257 @subsubheading @value{GDBN} Command
32259 The corresponding @value{GDBN} command is @samp{tstop}.
32262 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32263 @node GDB/MI Symbol Query
32264 @section @sc{gdb/mi} Symbol Query Commands
32268 @subheading The @code{-symbol-info-address} Command
32269 @findex -symbol-info-address
32271 @subsubheading Synopsis
32274 -symbol-info-address @var{symbol}
32277 Describe where @var{symbol} is stored.
32279 @subsubheading @value{GDBN} Command
32281 The corresponding @value{GDBN} command is @samp{info address}.
32283 @subsubheading Example
32287 @subheading The @code{-symbol-info-file} Command
32288 @findex -symbol-info-file
32290 @subsubheading Synopsis
32296 Show the file for the symbol.
32298 @subsubheading @value{GDBN} Command
32300 There's no equivalent @value{GDBN} command. @code{gdbtk} has
32301 @samp{gdb_find_file}.
32303 @subsubheading Example
32307 @subheading The @code{-symbol-info-function} Command
32308 @findex -symbol-info-function
32310 @subsubheading Synopsis
32313 -symbol-info-function
32316 Show which function the symbol lives in.
32318 @subsubheading @value{GDBN} Command
32320 @samp{gdb_get_function} in @code{gdbtk}.
32322 @subsubheading Example
32326 @subheading The @code{-symbol-info-line} Command
32327 @findex -symbol-info-line
32329 @subsubheading Synopsis
32335 Show the core addresses of the code for a source line.
32337 @subsubheading @value{GDBN} Command
32339 The corresponding @value{GDBN} command is @samp{info line}.
32340 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
32342 @subsubheading Example
32346 @subheading The @code{-symbol-info-symbol} Command
32347 @findex -symbol-info-symbol
32349 @subsubheading Synopsis
32352 -symbol-info-symbol @var{addr}
32355 Describe what symbol is at location @var{addr}.
32357 @subsubheading @value{GDBN} Command
32359 The corresponding @value{GDBN} command is @samp{info symbol}.
32361 @subsubheading Example
32365 @subheading The @code{-symbol-list-functions} Command
32366 @findex -symbol-list-functions
32368 @subsubheading Synopsis
32371 -symbol-list-functions
32374 List the functions in the executable.
32376 @subsubheading @value{GDBN} Command
32378 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
32379 @samp{gdb_search} in @code{gdbtk}.
32381 @subsubheading Example
32386 @subheading The @code{-symbol-list-lines} Command
32387 @findex -symbol-list-lines
32389 @subsubheading Synopsis
32392 -symbol-list-lines @var{filename}
32395 Print the list of lines that contain code and their associated program
32396 addresses for the given source filename. The entries are sorted in
32397 ascending PC order.
32399 @subsubheading @value{GDBN} Command
32401 There is no corresponding @value{GDBN} command.
32403 @subsubheading Example
32406 -symbol-list-lines basics.c
32407 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
32413 @subheading The @code{-symbol-list-types} Command
32414 @findex -symbol-list-types
32416 @subsubheading Synopsis
32422 List all the type names.
32424 @subsubheading @value{GDBN} Command
32426 The corresponding commands are @samp{info types} in @value{GDBN},
32427 @samp{gdb_search} in @code{gdbtk}.
32429 @subsubheading Example
32433 @subheading The @code{-symbol-list-variables} Command
32434 @findex -symbol-list-variables
32436 @subsubheading Synopsis
32439 -symbol-list-variables
32442 List all the global and static variable names.
32444 @subsubheading @value{GDBN} Command
32446 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
32448 @subsubheading Example
32452 @subheading The @code{-symbol-locate} Command
32453 @findex -symbol-locate
32455 @subsubheading Synopsis
32461 @subsubheading @value{GDBN} Command
32463 @samp{gdb_loc} in @code{gdbtk}.
32465 @subsubheading Example
32469 @subheading The @code{-symbol-type} Command
32470 @findex -symbol-type
32472 @subsubheading Synopsis
32475 -symbol-type @var{variable}
32478 Show type of @var{variable}.
32480 @subsubheading @value{GDBN} Command
32482 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
32483 @samp{gdb_obj_variable}.
32485 @subsubheading Example
32490 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32491 @node GDB/MI File Commands
32492 @section @sc{gdb/mi} File Commands
32494 This section describes the GDB/MI commands to specify executable file names
32495 and to read in and obtain symbol table information.
32497 @subheading The @code{-file-exec-and-symbols} Command
32498 @findex -file-exec-and-symbols
32500 @subsubheading Synopsis
32503 -file-exec-and-symbols @var{file}
32506 Specify the executable file to be debugged. This file is the one from
32507 which the symbol table is also read. If no file is specified, the
32508 command clears the executable and symbol information. If breakpoints
32509 are set when using this command with no arguments, @value{GDBN} will produce
32510 error messages. Otherwise, no output is produced, except a completion
32513 @subsubheading @value{GDBN} Command
32515 The corresponding @value{GDBN} command is @samp{file}.
32517 @subsubheading Example
32521 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32527 @subheading The @code{-file-exec-file} Command
32528 @findex -file-exec-file
32530 @subsubheading Synopsis
32533 -file-exec-file @var{file}
32536 Specify the executable file to be debugged. Unlike
32537 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
32538 from this file. If used without argument, @value{GDBN} clears the information
32539 about the executable file. No output is produced, except a completion
32542 @subsubheading @value{GDBN} Command
32544 The corresponding @value{GDBN} command is @samp{exec-file}.
32546 @subsubheading Example
32550 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32557 @subheading The @code{-file-list-exec-sections} Command
32558 @findex -file-list-exec-sections
32560 @subsubheading Synopsis
32563 -file-list-exec-sections
32566 List the sections of the current executable file.
32568 @subsubheading @value{GDBN} Command
32570 The @value{GDBN} command @samp{info file} shows, among the rest, the same
32571 information as this command. @code{gdbtk} has a corresponding command
32572 @samp{gdb_load_info}.
32574 @subsubheading Example
32579 @subheading The @code{-file-list-exec-source-file} Command
32580 @findex -file-list-exec-source-file
32582 @subsubheading Synopsis
32585 -file-list-exec-source-file
32588 List the line number, the current source file, and the absolute path
32589 to the current source file for the current executable. The macro
32590 information field has a value of @samp{1} or @samp{0} depending on
32591 whether or not the file includes preprocessor macro information.
32593 @subsubheading @value{GDBN} Command
32595 The @value{GDBN} equivalent is @samp{info source}
32597 @subsubheading Example
32601 123-file-list-exec-source-file
32602 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
32607 @subheading The @code{-file-list-exec-source-files} Command
32608 @findex -file-list-exec-source-files
32610 @subsubheading Synopsis
32613 -file-list-exec-source-files
32616 List the source files for the current executable.
32618 It will always output both the filename and fullname (absolute file
32619 name) of a source file.
32621 @subsubheading @value{GDBN} Command
32623 The @value{GDBN} equivalent is @samp{info sources}.
32624 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
32626 @subsubheading Example
32629 -file-list-exec-source-files
32631 @{file=foo.c,fullname=/home/foo.c@},
32632 @{file=/home/bar.c,fullname=/home/bar.c@},
32633 @{file=gdb_could_not_find_fullpath.c@}]
32638 @subheading The @code{-file-list-shared-libraries} Command
32639 @findex -file-list-shared-libraries
32641 @subsubheading Synopsis
32644 -file-list-shared-libraries
32647 List the shared libraries in the program.
32649 @subsubheading @value{GDBN} Command
32651 The corresponding @value{GDBN} command is @samp{info shared}.
32653 @subsubheading Example
32657 @subheading The @code{-file-list-symbol-files} Command
32658 @findex -file-list-symbol-files
32660 @subsubheading Synopsis
32663 -file-list-symbol-files
32668 @subsubheading @value{GDBN} Command
32670 The corresponding @value{GDBN} command is @samp{info file} (part of it).
32672 @subsubheading Example
32677 @subheading The @code{-file-symbol-file} Command
32678 @findex -file-symbol-file
32680 @subsubheading Synopsis
32683 -file-symbol-file @var{file}
32686 Read symbol table info from the specified @var{file} argument. When
32687 used without arguments, clears @value{GDBN}'s symbol table info. No output is
32688 produced, except for a completion notification.
32690 @subsubheading @value{GDBN} Command
32692 The corresponding @value{GDBN} command is @samp{symbol-file}.
32694 @subsubheading Example
32698 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32704 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32705 @node GDB/MI Memory Overlay Commands
32706 @section @sc{gdb/mi} Memory Overlay Commands
32708 The memory overlay commands are not implemented.
32710 @c @subheading -overlay-auto
32712 @c @subheading -overlay-list-mapping-state
32714 @c @subheading -overlay-list-overlays
32716 @c @subheading -overlay-map
32718 @c @subheading -overlay-off
32720 @c @subheading -overlay-on
32722 @c @subheading -overlay-unmap
32724 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32725 @node GDB/MI Signal Handling Commands
32726 @section @sc{gdb/mi} Signal Handling Commands
32728 Signal handling commands are not implemented.
32730 @c @subheading -signal-handle
32732 @c @subheading -signal-list-handle-actions
32734 @c @subheading -signal-list-signal-types
32738 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32739 @node GDB/MI Target Manipulation
32740 @section @sc{gdb/mi} Target Manipulation Commands
32743 @subheading The @code{-target-attach} Command
32744 @findex -target-attach
32746 @subsubheading Synopsis
32749 -target-attach @var{pid} | @var{gid} | @var{file}
32752 Attach to a process @var{pid} or a file @var{file} outside of
32753 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
32754 group, the id previously returned by
32755 @samp{-list-thread-groups --available} must be used.
32757 @subsubheading @value{GDBN} Command
32759 The corresponding @value{GDBN} command is @samp{attach}.
32761 @subsubheading Example
32765 =thread-created,id="1"
32766 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
32772 @subheading The @code{-target-compare-sections} Command
32773 @findex -target-compare-sections
32775 @subsubheading Synopsis
32778 -target-compare-sections [ @var{section} ]
32781 Compare data of section @var{section} on target to the exec file.
32782 Without the argument, all sections are compared.
32784 @subsubheading @value{GDBN} Command
32786 The @value{GDBN} equivalent is @samp{compare-sections}.
32788 @subsubheading Example
32793 @subheading The @code{-target-detach} Command
32794 @findex -target-detach
32796 @subsubheading Synopsis
32799 -target-detach [ @var{pid} | @var{gid} ]
32802 Detach from the remote target which normally resumes its execution.
32803 If either @var{pid} or @var{gid} is specified, detaches from either
32804 the specified process, or specified thread group. There's no output.
32806 @subsubheading @value{GDBN} Command
32808 The corresponding @value{GDBN} command is @samp{detach}.
32810 @subsubheading Example
32820 @subheading The @code{-target-disconnect} Command
32821 @findex -target-disconnect
32823 @subsubheading Synopsis
32829 Disconnect from the remote target. There's no output and the target is
32830 generally not resumed.
32832 @subsubheading @value{GDBN} Command
32834 The corresponding @value{GDBN} command is @samp{disconnect}.
32836 @subsubheading Example
32846 @subheading The @code{-target-download} Command
32847 @findex -target-download
32849 @subsubheading Synopsis
32855 Loads the executable onto the remote target.
32856 It prints out an update message every half second, which includes the fields:
32860 The name of the section.
32862 The size of what has been sent so far for that section.
32864 The size of the section.
32866 The total size of what was sent so far (the current and the previous sections).
32868 The size of the overall executable to download.
32872 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
32873 @sc{gdb/mi} Output Syntax}).
32875 In addition, it prints the name and size of the sections, as they are
32876 downloaded. These messages include the following fields:
32880 The name of the section.
32882 The size of the section.
32884 The size of the overall executable to download.
32888 At the end, a summary is printed.
32890 @subsubheading @value{GDBN} Command
32892 The corresponding @value{GDBN} command is @samp{load}.
32894 @subsubheading Example
32896 Note: each status message appears on a single line. Here the messages
32897 have been broken down so that they can fit onto a page.
32902 +download,@{section=".text",section-size="6668",total-size="9880"@}
32903 +download,@{section=".text",section-sent="512",section-size="6668",
32904 total-sent="512",total-size="9880"@}
32905 +download,@{section=".text",section-sent="1024",section-size="6668",
32906 total-sent="1024",total-size="9880"@}
32907 +download,@{section=".text",section-sent="1536",section-size="6668",
32908 total-sent="1536",total-size="9880"@}
32909 +download,@{section=".text",section-sent="2048",section-size="6668",
32910 total-sent="2048",total-size="9880"@}
32911 +download,@{section=".text",section-sent="2560",section-size="6668",
32912 total-sent="2560",total-size="9880"@}
32913 +download,@{section=".text",section-sent="3072",section-size="6668",
32914 total-sent="3072",total-size="9880"@}
32915 +download,@{section=".text",section-sent="3584",section-size="6668",
32916 total-sent="3584",total-size="9880"@}
32917 +download,@{section=".text",section-sent="4096",section-size="6668",
32918 total-sent="4096",total-size="9880"@}
32919 +download,@{section=".text",section-sent="4608",section-size="6668",
32920 total-sent="4608",total-size="9880"@}
32921 +download,@{section=".text",section-sent="5120",section-size="6668",
32922 total-sent="5120",total-size="9880"@}
32923 +download,@{section=".text",section-sent="5632",section-size="6668",
32924 total-sent="5632",total-size="9880"@}
32925 +download,@{section=".text",section-sent="6144",section-size="6668",
32926 total-sent="6144",total-size="9880"@}
32927 +download,@{section=".text",section-sent="6656",section-size="6668",
32928 total-sent="6656",total-size="9880"@}
32929 +download,@{section=".init",section-size="28",total-size="9880"@}
32930 +download,@{section=".fini",section-size="28",total-size="9880"@}
32931 +download,@{section=".data",section-size="3156",total-size="9880"@}
32932 +download,@{section=".data",section-sent="512",section-size="3156",
32933 total-sent="7236",total-size="9880"@}
32934 +download,@{section=".data",section-sent="1024",section-size="3156",
32935 total-sent="7748",total-size="9880"@}
32936 +download,@{section=".data",section-sent="1536",section-size="3156",
32937 total-sent="8260",total-size="9880"@}
32938 +download,@{section=".data",section-sent="2048",section-size="3156",
32939 total-sent="8772",total-size="9880"@}
32940 +download,@{section=".data",section-sent="2560",section-size="3156",
32941 total-sent="9284",total-size="9880"@}
32942 +download,@{section=".data",section-sent="3072",section-size="3156",
32943 total-sent="9796",total-size="9880"@}
32944 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
32951 @subheading The @code{-target-exec-status} Command
32952 @findex -target-exec-status
32954 @subsubheading Synopsis
32957 -target-exec-status
32960 Provide information on the state of the target (whether it is running or
32961 not, for instance).
32963 @subsubheading @value{GDBN} Command
32965 There's no equivalent @value{GDBN} command.
32967 @subsubheading Example
32971 @subheading The @code{-target-list-available-targets} Command
32972 @findex -target-list-available-targets
32974 @subsubheading Synopsis
32977 -target-list-available-targets
32980 List the possible targets to connect to.
32982 @subsubheading @value{GDBN} Command
32984 The corresponding @value{GDBN} command is @samp{help target}.
32986 @subsubheading Example
32990 @subheading The @code{-target-list-current-targets} Command
32991 @findex -target-list-current-targets
32993 @subsubheading Synopsis
32996 -target-list-current-targets
32999 Describe the current target.
33001 @subsubheading @value{GDBN} Command
33003 The corresponding information is printed by @samp{info file} (among
33006 @subsubheading Example
33010 @subheading The @code{-target-list-parameters} Command
33011 @findex -target-list-parameters
33013 @subsubheading Synopsis
33016 -target-list-parameters
33022 @subsubheading @value{GDBN} Command
33026 @subsubheading Example
33030 @subheading The @code{-target-select} Command
33031 @findex -target-select
33033 @subsubheading Synopsis
33036 -target-select @var{type} @var{parameters @dots{}}
33039 Connect @value{GDBN} to the remote target. This command takes two args:
33043 The type of target, for instance @samp{remote}, etc.
33044 @item @var{parameters}
33045 Device names, host names and the like. @xref{Target Commands, ,
33046 Commands for Managing Targets}, for more details.
33049 The output is a connection notification, followed by the address at
33050 which the target program is, in the following form:
33053 ^connected,addr="@var{address}",func="@var{function name}",
33054 args=[@var{arg list}]
33057 @subsubheading @value{GDBN} Command
33059 The corresponding @value{GDBN} command is @samp{target}.
33061 @subsubheading Example
33065 -target-select remote /dev/ttya
33066 ^connected,addr="0xfe00a300",func="??",args=[]
33070 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33071 @node GDB/MI File Transfer Commands
33072 @section @sc{gdb/mi} File Transfer Commands
33075 @subheading The @code{-target-file-put} Command
33076 @findex -target-file-put
33078 @subsubheading Synopsis
33081 -target-file-put @var{hostfile} @var{targetfile}
33084 Copy file @var{hostfile} from the host system (the machine running
33085 @value{GDBN}) to @var{targetfile} on the target system.
33087 @subsubheading @value{GDBN} Command
33089 The corresponding @value{GDBN} command is @samp{remote put}.
33091 @subsubheading Example
33095 -target-file-put localfile remotefile
33101 @subheading The @code{-target-file-get} Command
33102 @findex -target-file-get
33104 @subsubheading Synopsis
33107 -target-file-get @var{targetfile} @var{hostfile}
33110 Copy file @var{targetfile} from the target system to @var{hostfile}
33111 on the host system.
33113 @subsubheading @value{GDBN} Command
33115 The corresponding @value{GDBN} command is @samp{remote get}.
33117 @subsubheading Example
33121 -target-file-get remotefile localfile
33127 @subheading The @code{-target-file-delete} Command
33128 @findex -target-file-delete
33130 @subsubheading Synopsis
33133 -target-file-delete @var{targetfile}
33136 Delete @var{targetfile} from the target system.
33138 @subsubheading @value{GDBN} Command
33140 The corresponding @value{GDBN} command is @samp{remote delete}.
33142 @subsubheading Example
33146 -target-file-delete remotefile
33152 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33153 @node GDB/MI Miscellaneous Commands
33154 @section Miscellaneous @sc{gdb/mi} Commands
33156 @c @subheading -gdb-complete
33158 @subheading The @code{-gdb-exit} Command
33161 @subsubheading Synopsis
33167 Exit @value{GDBN} immediately.
33169 @subsubheading @value{GDBN} Command
33171 Approximately corresponds to @samp{quit}.
33173 @subsubheading Example
33183 @subheading The @code{-exec-abort} Command
33184 @findex -exec-abort
33186 @subsubheading Synopsis
33192 Kill the inferior running program.
33194 @subsubheading @value{GDBN} Command
33196 The corresponding @value{GDBN} command is @samp{kill}.
33198 @subsubheading Example
33203 @subheading The @code{-gdb-set} Command
33206 @subsubheading Synopsis
33212 Set an internal @value{GDBN} variable.
33213 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
33215 @subsubheading @value{GDBN} Command
33217 The corresponding @value{GDBN} command is @samp{set}.
33219 @subsubheading Example
33229 @subheading The @code{-gdb-show} Command
33232 @subsubheading Synopsis
33238 Show the current value of a @value{GDBN} variable.
33240 @subsubheading @value{GDBN} Command
33242 The corresponding @value{GDBN} command is @samp{show}.
33244 @subsubheading Example
33253 @c @subheading -gdb-source
33256 @subheading The @code{-gdb-version} Command
33257 @findex -gdb-version
33259 @subsubheading Synopsis
33265 Show version information for @value{GDBN}. Used mostly in testing.
33267 @subsubheading @value{GDBN} Command
33269 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
33270 default shows this information when you start an interactive session.
33272 @subsubheading Example
33274 @c This example modifies the actual output from GDB to avoid overfull
33280 ~Copyright 2000 Free Software Foundation, Inc.
33281 ~GDB is free software, covered by the GNU General Public License, and
33282 ~you are welcome to change it and/or distribute copies of it under
33283 ~ certain conditions.
33284 ~Type "show copying" to see the conditions.
33285 ~There is absolutely no warranty for GDB. Type "show warranty" for
33287 ~This GDB was configured as
33288 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
33293 @subheading The @code{-list-features} Command
33294 @findex -list-features
33296 Returns a list of particular features of the MI protocol that
33297 this version of gdb implements. A feature can be a command,
33298 or a new field in an output of some command, or even an
33299 important bugfix. While a frontend can sometimes detect presence
33300 of a feature at runtime, it is easier to perform detection at debugger
33303 The command returns a list of strings, with each string naming an
33304 available feature. Each returned string is just a name, it does not
33305 have any internal structure. The list of possible feature names
33311 (gdb) -list-features
33312 ^done,result=["feature1","feature2"]
33315 The current list of features is:
33318 @item frozen-varobjs
33319 Indicates support for the @code{-var-set-frozen} command, as well
33320 as possible presense of the @code{frozen} field in the output
33321 of @code{-varobj-create}.
33322 @item pending-breakpoints
33323 Indicates support for the @option{-f} option to the @code{-break-insert}
33326 Indicates Python scripting support, Python-based
33327 pretty-printing commands, and possible presence of the
33328 @samp{display_hint} field in the output of @code{-var-list-children}
33330 Indicates support for the @code{-thread-info} command.
33331 @item data-read-memory-bytes
33332 Indicates support for the @code{-data-read-memory-bytes} and the
33333 @code{-data-write-memory-bytes} commands.
33334 @item breakpoint-notifications
33335 Indicates that changes to breakpoints and breakpoints created via the
33336 CLI will be announced via async records.
33337 @item ada-task-info
33338 Indicates support for the @code{-ada-task-info} command.
33341 @subheading The @code{-list-target-features} Command
33342 @findex -list-target-features
33344 Returns a list of particular features that are supported by the
33345 target. Those features affect the permitted MI commands, but
33346 unlike the features reported by the @code{-list-features} command, the
33347 features depend on which target GDB is using at the moment. Whenever
33348 a target can change, due to commands such as @code{-target-select},
33349 @code{-target-attach} or @code{-exec-run}, the list of target features
33350 may change, and the frontend should obtain it again.
33354 (gdb) -list-features
33355 ^done,result=["async"]
33358 The current list of features is:
33362 Indicates that the target is capable of asynchronous command
33363 execution, which means that @value{GDBN} will accept further commands
33364 while the target is running.
33367 Indicates that the target is capable of reverse execution.
33368 @xref{Reverse Execution}, for more information.
33372 @subheading The @code{-list-thread-groups} Command
33373 @findex -list-thread-groups
33375 @subheading Synopsis
33378 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
33381 Lists thread groups (@pxref{Thread groups}). When a single thread
33382 group is passed as the argument, lists the children of that group.
33383 When several thread group are passed, lists information about those
33384 thread groups. Without any parameters, lists information about all
33385 top-level thread groups.
33387 Normally, thread groups that are being debugged are reported.
33388 With the @samp{--available} option, @value{GDBN} reports thread groups
33389 available on the target.
33391 The output of this command may have either a @samp{threads} result or
33392 a @samp{groups} result. The @samp{thread} result has a list of tuples
33393 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
33394 Information}). The @samp{groups} result has a list of tuples as value,
33395 each tuple describing a thread group. If top-level groups are
33396 requested (that is, no parameter is passed), or when several groups
33397 are passed, the output always has a @samp{groups} result. The format
33398 of the @samp{group} result is described below.
33400 To reduce the number of roundtrips it's possible to list thread groups
33401 together with their children, by passing the @samp{--recurse} option
33402 and the recursion depth. Presently, only recursion depth of 1 is
33403 permitted. If this option is present, then every reported thread group
33404 will also include its children, either as @samp{group} or
33405 @samp{threads} field.
33407 In general, any combination of option and parameters is permitted, with
33408 the following caveats:
33412 When a single thread group is passed, the output will typically
33413 be the @samp{threads} result. Because threads may not contain
33414 anything, the @samp{recurse} option will be ignored.
33417 When the @samp{--available} option is passed, limited information may
33418 be available. In particular, the list of threads of a process might
33419 be inaccessible. Further, specifying specific thread groups might
33420 not give any performance advantage over listing all thread groups.
33421 The frontend should assume that @samp{-list-thread-groups --available}
33422 is always an expensive operation and cache the results.
33426 The @samp{groups} result is a list of tuples, where each tuple may
33427 have the following fields:
33431 Identifier of the thread group. This field is always present.
33432 The identifier is an opaque string; frontends should not try to
33433 convert it to an integer, even though it might look like one.
33436 The type of the thread group. At present, only @samp{process} is a
33440 The target-specific process identifier. This field is only present
33441 for thread groups of type @samp{process} and only if the process exists.
33444 The number of children this thread group has. This field may be
33445 absent for an available thread group.
33448 This field has a list of tuples as value, each tuple describing a
33449 thread. It may be present if the @samp{--recurse} option is
33450 specified, and it's actually possible to obtain the threads.
33453 This field is a list of integers, each identifying a core that one
33454 thread of the group is running on. This field may be absent if
33455 such information is not available.
33458 The name of the executable file that corresponds to this thread group.
33459 The field is only present for thread groups of type @samp{process},
33460 and only if there is a corresponding executable file.
33464 @subheading Example
33468 -list-thread-groups
33469 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
33470 -list-thread-groups 17
33471 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
33472 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
33473 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
33474 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
33475 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
33476 -list-thread-groups --available
33477 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
33478 -list-thread-groups --available --recurse 1
33479 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33480 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33481 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
33482 -list-thread-groups --available --recurse 1 17 18
33483 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33484 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33485 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
33488 @subheading The @code{-info-os} Command
33491 @subsubheading Synopsis
33494 -info-os [ @var{type} ]
33497 If no argument is supplied, the command returns a table of available
33498 operating-system-specific information types. If one of these types is
33499 supplied as an argument @var{type}, then the command returns a table
33500 of data of that type.
33502 The types of information available depend on the target operating
33505 @subsubheading @value{GDBN} Command
33507 The corresponding @value{GDBN} command is @samp{info os}.
33509 @subsubheading Example
33511 When run on a @sc{gnu}/Linux system, the output will look something
33517 ^done,OSDataTable=@{nr_rows="9",nr_cols="3",
33518 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
33519 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
33520 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
33521 body=[item=@{col0="processes",col1="Listing of all processes",
33522 col2="Processes"@},
33523 item=@{col0="procgroups",col1="Listing of all process groups",
33524 col2="Process groups"@},
33525 item=@{col0="threads",col1="Listing of all threads",
33527 item=@{col0="files",col1="Listing of all file descriptors",
33528 col2="File descriptors"@},
33529 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
33531 item=@{col0="shm",col1="Listing of all shared-memory regions",
33532 col2="Shared-memory regions"@},
33533 item=@{col0="semaphores",col1="Listing of all semaphores",
33534 col2="Semaphores"@},
33535 item=@{col0="msg",col1="Listing of all message queues",
33536 col2="Message queues"@},
33537 item=@{col0="modules",col1="Listing of all loaded kernel modules",
33538 col2="Kernel modules"@}]@}
33541 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
33542 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
33543 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
33544 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
33545 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
33546 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
33547 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
33548 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
33550 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
33551 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
33555 (Note that the MI output here includes a @code{"Title"} column that
33556 does not appear in command-line @code{info os}; this column is useful
33557 for MI clients that want to enumerate the types of data, such as in a
33558 popup menu, but is needless clutter on the command line, and
33559 @code{info os} omits it.)
33561 @subheading The @code{-add-inferior} Command
33562 @findex -add-inferior
33564 @subheading Synopsis
33570 Creates a new inferior (@pxref{Inferiors and Programs}). The created
33571 inferior is not associated with any executable. Such association may
33572 be established with the @samp{-file-exec-and-symbols} command
33573 (@pxref{GDB/MI File Commands}). The command response has a single
33574 field, @samp{thread-group}, whose value is the identifier of the
33575 thread group corresponding to the new inferior.
33577 @subheading Example
33582 ^done,thread-group="i3"
33585 @subheading The @code{-interpreter-exec} Command
33586 @findex -interpreter-exec
33588 @subheading Synopsis
33591 -interpreter-exec @var{interpreter} @var{command}
33593 @anchor{-interpreter-exec}
33595 Execute the specified @var{command} in the given @var{interpreter}.
33597 @subheading @value{GDBN} Command
33599 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
33601 @subheading Example
33605 -interpreter-exec console "break main"
33606 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
33607 &"During symbol reading, bad structure-type format.\n"
33608 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
33613 @subheading The @code{-inferior-tty-set} Command
33614 @findex -inferior-tty-set
33616 @subheading Synopsis
33619 -inferior-tty-set /dev/pts/1
33622 Set terminal for future runs of the program being debugged.
33624 @subheading @value{GDBN} Command
33626 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
33628 @subheading Example
33632 -inferior-tty-set /dev/pts/1
33637 @subheading The @code{-inferior-tty-show} Command
33638 @findex -inferior-tty-show
33640 @subheading Synopsis
33646 Show terminal for future runs of program being debugged.
33648 @subheading @value{GDBN} Command
33650 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
33652 @subheading Example
33656 -inferior-tty-set /dev/pts/1
33660 ^done,inferior_tty_terminal="/dev/pts/1"
33664 @subheading The @code{-enable-timings} Command
33665 @findex -enable-timings
33667 @subheading Synopsis
33670 -enable-timings [yes | no]
33673 Toggle the printing of the wallclock, user and system times for an MI
33674 command as a field in its output. This command is to help frontend
33675 developers optimize the performance of their code. No argument is
33676 equivalent to @samp{yes}.
33678 @subheading @value{GDBN} Command
33682 @subheading Example
33690 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
33691 addr="0x080484ed",func="main",file="myprog.c",
33692 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
33694 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
33702 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
33703 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
33704 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
33705 fullname="/home/nickrob/myprog.c",line="73"@}
33710 @chapter @value{GDBN} Annotations
33712 This chapter describes annotations in @value{GDBN}. Annotations were
33713 designed to interface @value{GDBN} to graphical user interfaces or other
33714 similar programs which want to interact with @value{GDBN} at a
33715 relatively high level.
33717 The annotation mechanism has largely been superseded by @sc{gdb/mi}
33721 This is Edition @value{EDITION}, @value{DATE}.
33725 * Annotations Overview:: What annotations are; the general syntax.
33726 * Server Prefix:: Issuing a command without affecting user state.
33727 * Prompting:: Annotations marking @value{GDBN}'s need for input.
33728 * Errors:: Annotations for error messages.
33729 * Invalidation:: Some annotations describe things now invalid.
33730 * Annotations for Running::
33731 Whether the program is running, how it stopped, etc.
33732 * Source Annotations:: Annotations describing source code.
33735 @node Annotations Overview
33736 @section What is an Annotation?
33737 @cindex annotations
33739 Annotations start with a newline character, two @samp{control-z}
33740 characters, and the name of the annotation. If there is no additional
33741 information associated with this annotation, the name of the annotation
33742 is followed immediately by a newline. If there is additional
33743 information, the name of the annotation is followed by a space, the
33744 additional information, and a newline. The additional information
33745 cannot contain newline characters.
33747 Any output not beginning with a newline and two @samp{control-z}
33748 characters denotes literal output from @value{GDBN}. Currently there is
33749 no need for @value{GDBN} to output a newline followed by two
33750 @samp{control-z} characters, but if there was such a need, the
33751 annotations could be extended with an @samp{escape} annotation which
33752 means those three characters as output.
33754 The annotation @var{level}, which is specified using the
33755 @option{--annotate} command line option (@pxref{Mode Options}), controls
33756 how much information @value{GDBN} prints together with its prompt,
33757 values of expressions, source lines, and other types of output. Level 0
33758 is for no annotations, level 1 is for use when @value{GDBN} is run as a
33759 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
33760 for programs that control @value{GDBN}, and level 2 annotations have
33761 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
33762 Interface, annotate, GDB's Obsolete Annotations}).
33765 @kindex set annotate
33766 @item set annotate @var{level}
33767 The @value{GDBN} command @code{set annotate} sets the level of
33768 annotations to the specified @var{level}.
33770 @item show annotate
33771 @kindex show annotate
33772 Show the current annotation level.
33775 This chapter describes level 3 annotations.
33777 A simple example of starting up @value{GDBN} with annotations is:
33780 $ @kbd{gdb --annotate=3}
33782 Copyright 2003 Free Software Foundation, Inc.
33783 GDB is free software, covered by the GNU General Public License,
33784 and you are welcome to change it and/or distribute copies of it
33785 under certain conditions.
33786 Type "show copying" to see the conditions.
33787 There is absolutely no warranty for GDB. Type "show warranty"
33789 This GDB was configured as "i386-pc-linux-gnu"
33800 Here @samp{quit} is input to @value{GDBN}; the rest is output from
33801 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
33802 denotes a @samp{control-z} character) are annotations; the rest is
33803 output from @value{GDBN}.
33805 @node Server Prefix
33806 @section The Server Prefix
33807 @cindex server prefix
33809 If you prefix a command with @samp{server } then it will not affect
33810 the command history, nor will it affect @value{GDBN}'s notion of which
33811 command to repeat if @key{RET} is pressed on a line by itself. This
33812 means that commands can be run behind a user's back by a front-end in
33813 a transparent manner.
33815 The @code{server } prefix does not affect the recording of values into
33816 the value history; to print a value without recording it into the
33817 value history, use the @code{output} command instead of the
33818 @code{print} command.
33820 Using this prefix also disables confirmation requests
33821 (@pxref{confirmation requests}).
33824 @section Annotation for @value{GDBN} Input
33826 @cindex annotations for prompts
33827 When @value{GDBN} prompts for input, it annotates this fact so it is possible
33828 to know when to send output, when the output from a given command is
33831 Different kinds of input each have a different @dfn{input type}. Each
33832 input type has three annotations: a @code{pre-} annotation, which
33833 denotes the beginning of any prompt which is being output, a plain
33834 annotation, which denotes the end of the prompt, and then a @code{post-}
33835 annotation which denotes the end of any echo which may (or may not) be
33836 associated with the input. For example, the @code{prompt} input type
33837 features the following annotations:
33845 The input types are
33848 @findex pre-prompt annotation
33849 @findex prompt annotation
33850 @findex post-prompt annotation
33852 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
33854 @findex pre-commands annotation
33855 @findex commands annotation
33856 @findex post-commands annotation
33858 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
33859 command. The annotations are repeated for each command which is input.
33861 @findex pre-overload-choice annotation
33862 @findex overload-choice annotation
33863 @findex post-overload-choice annotation
33864 @item overload-choice
33865 When @value{GDBN} wants the user to select between various overloaded functions.
33867 @findex pre-query annotation
33868 @findex query annotation
33869 @findex post-query annotation
33871 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
33873 @findex pre-prompt-for-continue annotation
33874 @findex prompt-for-continue annotation
33875 @findex post-prompt-for-continue annotation
33876 @item prompt-for-continue
33877 When @value{GDBN} is asking the user to press return to continue. Note: Don't
33878 expect this to work well; instead use @code{set height 0} to disable
33879 prompting. This is because the counting of lines is buggy in the
33880 presence of annotations.
33885 @cindex annotations for errors, warnings and interrupts
33887 @findex quit annotation
33892 This annotation occurs right before @value{GDBN} responds to an interrupt.
33894 @findex error annotation
33899 This annotation occurs right before @value{GDBN} responds to an error.
33901 Quit and error annotations indicate that any annotations which @value{GDBN} was
33902 in the middle of may end abruptly. For example, if a
33903 @code{value-history-begin} annotation is followed by a @code{error}, one
33904 cannot expect to receive the matching @code{value-history-end}. One
33905 cannot expect not to receive it either, however; an error annotation
33906 does not necessarily mean that @value{GDBN} is immediately returning all the way
33909 @findex error-begin annotation
33910 A quit or error annotation may be preceded by
33916 Any output between that and the quit or error annotation is the error
33919 Warning messages are not yet annotated.
33920 @c If we want to change that, need to fix warning(), type_error(),
33921 @c range_error(), and possibly other places.
33924 @section Invalidation Notices
33926 @cindex annotations for invalidation messages
33927 The following annotations say that certain pieces of state may have
33931 @findex frames-invalid annotation
33932 @item ^Z^Zframes-invalid
33934 The frames (for example, output from the @code{backtrace} command) may
33937 @findex breakpoints-invalid annotation
33938 @item ^Z^Zbreakpoints-invalid
33940 The breakpoints may have changed. For example, the user just added or
33941 deleted a breakpoint.
33944 @node Annotations for Running
33945 @section Running the Program
33946 @cindex annotations for running programs
33948 @findex starting annotation
33949 @findex stopping annotation
33950 When the program starts executing due to a @value{GDBN} command such as
33951 @code{step} or @code{continue},
33957 is output. When the program stops,
33963 is output. Before the @code{stopped} annotation, a variety of
33964 annotations describe how the program stopped.
33967 @findex exited annotation
33968 @item ^Z^Zexited @var{exit-status}
33969 The program exited, and @var{exit-status} is the exit status (zero for
33970 successful exit, otherwise nonzero).
33972 @findex signalled annotation
33973 @findex signal-name annotation
33974 @findex signal-name-end annotation
33975 @findex signal-string annotation
33976 @findex signal-string-end annotation
33977 @item ^Z^Zsignalled
33978 The program exited with a signal. After the @code{^Z^Zsignalled}, the
33979 annotation continues:
33985 ^Z^Zsignal-name-end
33989 ^Z^Zsignal-string-end
33994 where @var{name} is the name of the signal, such as @code{SIGILL} or
33995 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
33996 as @code{Illegal Instruction} or @code{Segmentation fault}.
33997 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
33998 user's benefit and have no particular format.
34000 @findex signal annotation
34002 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
34003 just saying that the program received the signal, not that it was
34004 terminated with it.
34006 @findex breakpoint annotation
34007 @item ^Z^Zbreakpoint @var{number}
34008 The program hit breakpoint number @var{number}.
34010 @findex watchpoint annotation
34011 @item ^Z^Zwatchpoint @var{number}
34012 The program hit watchpoint number @var{number}.
34015 @node Source Annotations
34016 @section Displaying Source
34017 @cindex annotations for source display
34019 @findex source annotation
34020 The following annotation is used instead of displaying source code:
34023 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
34026 where @var{filename} is an absolute file name indicating which source
34027 file, @var{line} is the line number within that file (where 1 is the
34028 first line in the file), @var{character} is the character position
34029 within the file (where 0 is the first character in the file) (for most
34030 debug formats this will necessarily point to the beginning of a line),
34031 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
34032 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
34033 @var{addr} is the address in the target program associated with the
34034 source which is being displayed. @var{addr} is in the form @samp{0x}
34035 followed by one or more lowercase hex digits (note that this does not
34036 depend on the language).
34038 @node JIT Interface
34039 @chapter JIT Compilation Interface
34040 @cindex just-in-time compilation
34041 @cindex JIT compilation interface
34043 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
34044 interface. A JIT compiler is a program or library that generates native
34045 executable code at runtime and executes it, usually in order to achieve good
34046 performance while maintaining platform independence.
34048 Programs that use JIT compilation are normally difficult to debug because
34049 portions of their code are generated at runtime, instead of being loaded from
34050 object files, which is where @value{GDBN} normally finds the program's symbols
34051 and debug information. In order to debug programs that use JIT compilation,
34052 @value{GDBN} has an interface that allows the program to register in-memory
34053 symbol files with @value{GDBN} at runtime.
34055 If you are using @value{GDBN} to debug a program that uses this interface, then
34056 it should work transparently so long as you have not stripped the binary. If
34057 you are developing a JIT compiler, then the interface is documented in the rest
34058 of this chapter. At this time, the only known client of this interface is the
34061 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
34062 JIT compiler communicates with @value{GDBN} by writing data into a global
34063 variable and calling a fuction at a well-known symbol. When @value{GDBN}
34064 attaches, it reads a linked list of symbol files from the global variable to
34065 find existing code, and puts a breakpoint in the function so that it can find
34066 out about additional code.
34069 * Declarations:: Relevant C struct declarations
34070 * Registering Code:: Steps to register code
34071 * Unregistering Code:: Steps to unregister code
34072 * Custom Debug Info:: Emit debug information in a custom format
34076 @section JIT Declarations
34078 These are the relevant struct declarations that a C program should include to
34079 implement the interface:
34089 struct jit_code_entry
34091 struct jit_code_entry *next_entry;
34092 struct jit_code_entry *prev_entry;
34093 const char *symfile_addr;
34094 uint64_t symfile_size;
34097 struct jit_descriptor
34100 /* This type should be jit_actions_t, but we use uint32_t
34101 to be explicit about the bitwidth. */
34102 uint32_t action_flag;
34103 struct jit_code_entry *relevant_entry;
34104 struct jit_code_entry *first_entry;
34107 /* GDB puts a breakpoint in this function. */
34108 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
34110 /* Make sure to specify the version statically, because the
34111 debugger may check the version before we can set it. */
34112 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
34115 If the JIT is multi-threaded, then it is important that the JIT synchronize any
34116 modifications to this global data properly, which can easily be done by putting
34117 a global mutex around modifications to these structures.
34119 @node Registering Code
34120 @section Registering Code
34122 To register code with @value{GDBN}, the JIT should follow this protocol:
34126 Generate an object file in memory with symbols and other desired debug
34127 information. The file must include the virtual addresses of the sections.
34130 Create a code entry for the file, which gives the start and size of the symbol
34134 Add it to the linked list in the JIT descriptor.
34137 Point the relevant_entry field of the descriptor at the entry.
34140 Set @code{action_flag} to @code{JIT_REGISTER} and call
34141 @code{__jit_debug_register_code}.
34144 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
34145 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
34146 new code. However, the linked list must still be maintained in order to allow
34147 @value{GDBN} to attach to a running process and still find the symbol files.
34149 @node Unregistering Code
34150 @section Unregistering Code
34152 If code is freed, then the JIT should use the following protocol:
34156 Remove the code entry corresponding to the code from the linked list.
34159 Point the @code{relevant_entry} field of the descriptor at the code entry.
34162 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
34163 @code{__jit_debug_register_code}.
34166 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
34167 and the JIT will leak the memory used for the associated symbol files.
34169 @node Custom Debug Info
34170 @section Custom Debug Info
34171 @cindex custom JIT debug info
34172 @cindex JIT debug info reader
34174 Generating debug information in platform-native file formats (like ELF
34175 or COFF) may be an overkill for JIT compilers; especially if all the
34176 debug info is used for is displaying a meaningful backtrace. The
34177 issue can be resolved by having the JIT writers decide on a debug info
34178 format and also provide a reader that parses the debug info generated
34179 by the JIT compiler. This section gives a brief overview on writing
34180 such a parser. More specific details can be found in the source file
34181 @file{gdb/jit-reader.in}, which is also installed as a header at
34182 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
34184 The reader is implemented as a shared object (so this functionality is
34185 not available on platforms which don't allow loading shared objects at
34186 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
34187 @code{jit-reader-unload} are provided, to be used to load and unload
34188 the readers from a preconfigured directory. Once loaded, the shared
34189 object is used the parse the debug information emitted by the JIT
34193 * Using JIT Debug Info Readers:: How to use supplied readers correctly
34194 * Writing JIT Debug Info Readers:: Creating a debug-info reader
34197 @node Using JIT Debug Info Readers
34198 @subsection Using JIT Debug Info Readers
34199 @kindex jit-reader-load
34200 @kindex jit-reader-unload
34202 Readers can be loaded and unloaded using the @code{jit-reader-load}
34203 and @code{jit-reader-unload} commands.
34206 @item jit-reader-load @var{reader}
34207 Load the JIT reader named @var{reader}. @var{reader} is a shared
34208 object specified as either an absolute or a relative file name. In
34209 the latter case, @value{GDBN} will try to load the reader from a
34210 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
34211 system (here @var{libdir} is the system library directory, often
34212 @file{/usr/local/lib}).
34214 Only one reader can be active at a time; trying to load a second
34215 reader when one is already loaded will result in @value{GDBN}
34216 reporting an error. A new JIT reader can be loaded by first unloading
34217 the current one using @code{jit-reader-unload} and then invoking
34218 @code{jit-reader-load}.
34220 @item jit-reader-unload
34221 Unload the currently loaded JIT reader.
34225 @node Writing JIT Debug Info Readers
34226 @subsection Writing JIT Debug Info Readers
34227 @cindex writing JIT debug info readers
34229 As mentioned, a reader is essentially a shared object conforming to a
34230 certain ABI. This ABI is described in @file{jit-reader.h}.
34232 @file{jit-reader.h} defines the structures, macros and functions
34233 required to write a reader. It is installed (along with
34234 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
34235 the system include directory.
34237 Readers need to be released under a GPL compatible license. A reader
34238 can be declared as released under such a license by placing the macro
34239 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
34241 The entry point for readers is the symbol @code{gdb_init_reader},
34242 which is expected to be a function with the prototype
34244 @findex gdb_init_reader
34246 extern struct gdb_reader_funcs *gdb_init_reader (void);
34249 @cindex @code{struct gdb_reader_funcs}
34251 @code{struct gdb_reader_funcs} contains a set of pointers to callback
34252 functions. These functions are executed to read the debug info
34253 generated by the JIT compiler (@code{read}), to unwind stack frames
34254 (@code{unwind}) and to create canonical frame IDs
34255 (@code{get_Frame_id}). It also has a callback that is called when the
34256 reader is being unloaded (@code{destroy}). The struct looks like this
34259 struct gdb_reader_funcs
34261 /* Must be set to GDB_READER_INTERFACE_VERSION. */
34262 int reader_version;
34264 /* For use by the reader. */
34267 gdb_read_debug_info *read;
34268 gdb_unwind_frame *unwind;
34269 gdb_get_frame_id *get_frame_id;
34270 gdb_destroy_reader *destroy;
34274 @cindex @code{struct gdb_symbol_callbacks}
34275 @cindex @code{struct gdb_unwind_callbacks}
34277 The callbacks are provided with another set of callbacks by
34278 @value{GDBN} to do their job. For @code{read}, these callbacks are
34279 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
34280 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
34281 @code{struct gdb_symbol_callbacks} has callbacks to create new object
34282 files and new symbol tables inside those object files. @code{struct
34283 gdb_unwind_callbacks} has callbacks to read registers off the current
34284 frame and to write out the values of the registers in the previous
34285 frame. Both have a callback (@code{target_read}) to read bytes off the
34286 target's address space.
34288 @node In-Process Agent
34289 @chapter In-Process Agent
34290 @cindex debugging agent
34291 The traditional debugging model is conceptually low-speed, but works fine,
34292 because most bugs can be reproduced in debugging-mode execution. However,
34293 as multi-core or many-core processors are becoming mainstream, and
34294 multi-threaded programs become more and more popular, there should be more
34295 and more bugs that only manifest themselves at normal-mode execution, for
34296 example, thread races, because debugger's interference with the program's
34297 timing may conceal the bugs. On the other hand, in some applications,
34298 it is not feasible for the debugger to interrupt the program's execution
34299 long enough for the developer to learn anything helpful about its behavior.
34300 If the program's correctness depends on its real-time behavior, delays
34301 introduced by a debugger might cause the program to fail, even when the
34302 code itself is correct. It is useful to be able to observe the program's
34303 behavior without interrupting it.
34305 Therefore, traditional debugging model is too intrusive to reproduce
34306 some bugs. In order to reduce the interference with the program, we can
34307 reduce the number of operations performed by debugger. The
34308 @dfn{In-Process Agent}, a shared library, is running within the same
34309 process with inferior, and is able to perform some debugging operations
34310 itself. As a result, debugger is only involved when necessary, and
34311 performance of debugging can be improved accordingly. Note that
34312 interference with program can be reduced but can't be removed completely,
34313 because the in-process agent will still stop or slow down the program.
34315 The in-process agent can interpret and execute Agent Expressions
34316 (@pxref{Agent Expressions}) during performing debugging operations. The
34317 agent expressions can be used for different purposes, such as collecting
34318 data in tracepoints, and condition evaluation in breakpoints.
34320 @anchor{Control Agent}
34321 You can control whether the in-process agent is used as an aid for
34322 debugging with the following commands:
34325 @kindex set agent on
34327 Causes the in-process agent to perform some operations on behalf of the
34328 debugger. Just which operations requested by the user will be done
34329 by the in-process agent depends on the its capabilities. For example,
34330 if you request to evaluate breakpoint conditions in the in-process agent,
34331 and the in-process agent has such capability as well, then breakpoint
34332 conditions will be evaluated in the in-process agent.
34334 @kindex set agent off
34335 @item set agent off
34336 Disables execution of debugging operations by the in-process agent. All
34337 of the operations will be performed by @value{GDBN}.
34341 Display the current setting of execution of debugging operations by
34342 the in-process agent.
34346 * In-Process Agent Protocol::
34349 @node In-Process Agent Protocol
34350 @section In-Process Agent Protocol
34351 @cindex in-process agent protocol
34353 The in-process agent is able to communicate with both @value{GDBN} and
34354 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
34355 used for communications between @value{GDBN} or GDBserver and the IPA.
34356 In general, @value{GDBN} or GDBserver sends commands
34357 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
34358 in-process agent replies back with the return result of the command, or
34359 some other information. The data sent to in-process agent is composed
34360 of primitive data types, such as 4-byte or 8-byte type, and composite
34361 types, which are called objects (@pxref{IPA Protocol Objects}).
34364 * IPA Protocol Objects::
34365 * IPA Protocol Commands::
34368 @node IPA Protocol Objects
34369 @subsection IPA Protocol Objects
34370 @cindex ipa protocol objects
34372 The commands sent to and results received from agent may contain some
34373 complex data types called @dfn{objects}.
34375 The in-process agent is running on the same machine with @value{GDBN}
34376 or GDBserver, so it doesn't have to handle as much differences between
34377 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
34378 However, there are still some differences of two ends in two processes:
34382 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
34383 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
34385 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
34386 GDBserver is compiled with one, and in-process agent is compiled with
34390 Here are the IPA Protocol Objects:
34394 agent expression object. It represents an agent expression
34395 (@pxref{Agent Expressions}).
34396 @anchor{agent expression object}
34398 tracepoint action object. It represents a tracepoint action
34399 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
34400 memory, static trace data and to evaluate expression.
34401 @anchor{tracepoint action object}
34403 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
34404 @anchor{tracepoint object}
34408 The following table describes important attributes of each IPA protocol
34411 @multitable @columnfractions .30 .20 .50
34412 @headitem Name @tab Size @tab Description
34413 @item @emph{agent expression object} @tab @tab
34414 @item length @tab 4 @tab length of bytes code
34415 @item byte code @tab @var{length} @tab contents of byte code
34416 @item @emph{tracepoint action for collecting memory} @tab @tab
34417 @item 'M' @tab 1 @tab type of tracepoint action
34418 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
34419 address of the lowest byte to collect, otherwise @var{addr} is the offset
34420 of @var{basereg} for memory collecting.
34421 @item len @tab 8 @tab length of memory for collecting
34422 @item basereg @tab 4 @tab the register number containing the starting
34423 memory address for collecting.
34424 @item @emph{tracepoint action for collecting registers} @tab @tab
34425 @item 'R' @tab 1 @tab type of tracepoint action
34426 @item @emph{tracepoint action for collecting static trace data} @tab @tab
34427 @item 'L' @tab 1 @tab type of tracepoint action
34428 @item @emph{tracepoint action for expression evaluation} @tab @tab
34429 @item 'X' @tab 1 @tab type of tracepoint action
34430 @item agent expression @tab length of @tab @ref{agent expression object}
34431 @item @emph{tracepoint object} @tab @tab
34432 @item number @tab 4 @tab number of tracepoint
34433 @item address @tab 8 @tab address of tracepoint inserted on
34434 @item type @tab 4 @tab type of tracepoint
34435 @item enabled @tab 1 @tab enable or disable of tracepoint
34436 @item step_count @tab 8 @tab step
34437 @item pass_count @tab 8 @tab pass
34438 @item numactions @tab 4 @tab number of tracepoint actions
34439 @item hit count @tab 8 @tab hit count
34440 @item trace frame usage @tab 8 @tab trace frame usage
34441 @item compiled_cond @tab 8 @tab compiled condition
34442 @item orig_size @tab 8 @tab orig size
34443 @item condition @tab 4 if condition is NULL otherwise length of
34444 @ref{agent expression object}
34445 @tab zero if condition is NULL, otherwise is
34446 @ref{agent expression object}
34447 @item actions @tab variable
34448 @tab numactions number of @ref{tracepoint action object}
34451 @node IPA Protocol Commands
34452 @subsection IPA Protocol Commands
34453 @cindex ipa protocol commands
34455 The spaces in each command are delimiters to ease reading this commands
34456 specification. They don't exist in real commands.
34460 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
34461 Installs a new fast tracepoint described by @var{tracepoint_object}
34462 (@pxref{tracepoint object}). @var{gdb_jump_pad_head}, 8-byte long, is the
34463 head of @dfn{jumppad}, which is used to jump to data collection routine
34468 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
34469 @var{target_address} is address of tracepoint in the inferior.
34470 @var{gdb_jump_pad_head} is updated head of jumppad. Both of
34471 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
34472 @var{fjump} contains a sequence of instructions jump to jumppad entry.
34473 @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
34480 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
34481 is about to kill inferiors.
34489 @item probe_marker_at:@var{address}
34490 Asks in-process agent to probe the marker at @var{address}.
34497 @item unprobe_marker_at:@var{address}
34498 Asks in-process agent to unprobe the marker at @var{address}.
34502 @chapter Reporting Bugs in @value{GDBN}
34503 @cindex bugs in @value{GDBN}
34504 @cindex reporting bugs in @value{GDBN}
34506 Your bug reports play an essential role in making @value{GDBN} reliable.
34508 Reporting a bug may help you by bringing a solution to your problem, or it
34509 may not. But in any case the principal function of a bug report is to help
34510 the entire community by making the next version of @value{GDBN} work better. Bug
34511 reports are your contribution to the maintenance of @value{GDBN}.
34513 In order for a bug report to serve its purpose, you must include the
34514 information that enables us to fix the bug.
34517 * Bug Criteria:: Have you found a bug?
34518 * Bug Reporting:: How to report bugs
34522 @section Have You Found a Bug?
34523 @cindex bug criteria
34525 If you are not sure whether you have found a bug, here are some guidelines:
34528 @cindex fatal signal
34529 @cindex debugger crash
34530 @cindex crash of debugger
34532 If the debugger gets a fatal signal, for any input whatever, that is a
34533 @value{GDBN} bug. Reliable debuggers never crash.
34535 @cindex error on valid input
34537 If @value{GDBN} produces an error message for valid input, that is a
34538 bug. (Note that if you're cross debugging, the problem may also be
34539 somewhere in the connection to the target.)
34541 @cindex invalid input
34543 If @value{GDBN} does not produce an error message for invalid input,
34544 that is a bug. However, you should note that your idea of
34545 ``invalid input'' might be our idea of ``an extension'' or ``support
34546 for traditional practice''.
34549 If you are an experienced user of debugging tools, your suggestions
34550 for improvement of @value{GDBN} are welcome in any case.
34553 @node Bug Reporting
34554 @section How to Report Bugs
34555 @cindex bug reports
34556 @cindex @value{GDBN} bugs, reporting
34558 A number of companies and individuals offer support for @sc{gnu} products.
34559 If you obtained @value{GDBN} from a support organization, we recommend you
34560 contact that organization first.
34562 You can find contact information for many support companies and
34563 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
34565 @c should add a web page ref...
34568 @ifset BUGURL_DEFAULT
34569 In any event, we also recommend that you submit bug reports for
34570 @value{GDBN}. The preferred method is to submit them directly using
34571 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
34572 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
34575 @strong{Do not send bug reports to @samp{info-gdb}, or to
34576 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
34577 not want to receive bug reports. Those that do have arranged to receive
34580 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
34581 serves as a repeater. The mailing list and the newsgroup carry exactly
34582 the same messages. Often people think of posting bug reports to the
34583 newsgroup instead of mailing them. This appears to work, but it has one
34584 problem which can be crucial: a newsgroup posting often lacks a mail
34585 path back to the sender. Thus, if we need to ask for more information,
34586 we may be unable to reach you. For this reason, it is better to send
34587 bug reports to the mailing list.
34589 @ifclear BUGURL_DEFAULT
34590 In any event, we also recommend that you submit bug reports for
34591 @value{GDBN} to @value{BUGURL}.
34595 The fundamental principle of reporting bugs usefully is this:
34596 @strong{report all the facts}. If you are not sure whether to state a
34597 fact or leave it out, state it!
34599 Often people omit facts because they think they know what causes the
34600 problem and assume that some details do not matter. Thus, you might
34601 assume that the name of the variable you use in an example does not matter.
34602 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
34603 stray memory reference which happens to fetch from the location where that
34604 name is stored in memory; perhaps, if the name were different, the contents
34605 of that location would fool the debugger into doing the right thing despite
34606 the bug. Play it safe and give a specific, complete example. That is the
34607 easiest thing for you to do, and the most helpful.
34609 Keep in mind that the purpose of a bug report is to enable us to fix the
34610 bug. It may be that the bug has been reported previously, but neither
34611 you nor we can know that unless your bug report is complete and
34614 Sometimes people give a few sketchy facts and ask, ``Does this ring a
34615 bell?'' Those bug reports are useless, and we urge everyone to
34616 @emph{refuse to respond to them} except to chide the sender to report
34619 To enable us to fix the bug, you should include all these things:
34623 The version of @value{GDBN}. @value{GDBN} announces it if you start
34624 with no arguments; you can also print it at any time using @code{show
34627 Without this, we will not know whether there is any point in looking for
34628 the bug in the current version of @value{GDBN}.
34631 The type of machine you are using, and the operating system name and
34635 The details of the @value{GDBN} build-time configuration.
34636 @value{GDBN} shows these details if you invoke it with the
34637 @option{--configuration} command-line option, or if you type
34638 @code{show configuration} at @value{GDBN}'s prompt.
34641 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
34642 ``@value{GCC}--2.8.1''.
34645 What compiler (and its version) was used to compile the program you are
34646 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
34647 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
34648 to get this information; for other compilers, see the documentation for
34652 The command arguments you gave the compiler to compile your example and
34653 observe the bug. For example, did you use @samp{-O}? To guarantee
34654 you will not omit something important, list them all. A copy of the
34655 Makefile (or the output from make) is sufficient.
34657 If we were to try to guess the arguments, we would probably guess wrong
34658 and then we might not encounter the bug.
34661 A complete input script, and all necessary source files, that will
34665 A description of what behavior you observe that you believe is
34666 incorrect. For example, ``It gets a fatal signal.''
34668 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
34669 will certainly notice it. But if the bug is incorrect output, we might
34670 not notice unless it is glaringly wrong. You might as well not give us
34671 a chance to make a mistake.
34673 Even if the problem you experience is a fatal signal, you should still
34674 say so explicitly. Suppose something strange is going on, such as, your
34675 copy of @value{GDBN} is out of synch, or you have encountered a bug in
34676 the C library on your system. (This has happened!) Your copy might
34677 crash and ours would not. If you told us to expect a crash, then when
34678 ours fails to crash, we would know that the bug was not happening for
34679 us. If you had not told us to expect a crash, then we would not be able
34680 to draw any conclusion from our observations.
34683 @cindex recording a session script
34684 To collect all this information, you can use a session recording program
34685 such as @command{script}, which is available on many Unix systems.
34686 Just run your @value{GDBN} session inside @command{script} and then
34687 include the @file{typescript} file with your bug report.
34689 Another way to record a @value{GDBN} session is to run @value{GDBN}
34690 inside Emacs and then save the entire buffer to a file.
34693 If you wish to suggest changes to the @value{GDBN} source, send us context
34694 diffs. If you even discuss something in the @value{GDBN} source, refer to
34695 it by context, not by line number.
34697 The line numbers in our development sources will not match those in your
34698 sources. Your line numbers would convey no useful information to us.
34702 Here are some things that are not necessary:
34706 A description of the envelope of the bug.
34708 Often people who encounter a bug spend a lot of time investigating
34709 which changes to the input file will make the bug go away and which
34710 changes will not affect it.
34712 This is often time consuming and not very useful, because the way we
34713 will find the bug is by running a single example under the debugger
34714 with breakpoints, not by pure deduction from a series of examples.
34715 We recommend that you save your time for something else.
34717 Of course, if you can find a simpler example to report @emph{instead}
34718 of the original one, that is a convenience for us. Errors in the
34719 output will be easier to spot, running under the debugger will take
34720 less time, and so on.
34722 However, simplification is not vital; if you do not want to do this,
34723 report the bug anyway and send us the entire test case you used.
34726 A patch for the bug.
34728 A patch for the bug does help us if it is a good one. But do not omit
34729 the necessary information, such as the test case, on the assumption that
34730 a patch is all we need. We might see problems with your patch and decide
34731 to fix the problem another way, or we might not understand it at all.
34733 Sometimes with a program as complicated as @value{GDBN} it is very hard to
34734 construct an example that will make the program follow a certain path
34735 through the code. If you do not send us the example, we will not be able
34736 to construct one, so we will not be able to verify that the bug is fixed.
34738 And if we cannot understand what bug you are trying to fix, or why your
34739 patch should be an improvement, we will not install it. A test case will
34740 help us to understand.
34743 A guess about what the bug is or what it depends on.
34745 Such guesses are usually wrong. Even we cannot guess right about such
34746 things without first using the debugger to find the facts.
34749 @c The readline documentation is distributed with the readline code
34750 @c and consists of the two following files:
34753 @c Use -I with makeinfo to point to the appropriate directory,
34754 @c environment var TEXINPUTS with TeX.
34755 @ifclear SYSTEM_READLINE
34756 @include rluser.texi
34757 @include hsuser.texi
34761 @appendix In Memoriam
34763 The @value{GDBN} project mourns the loss of the following long-time
34768 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
34769 to Free Software in general. Outside of @value{GDBN}, he was known in
34770 the Amiga world for his series of Fish Disks, and the GeekGadget project.
34772 @item Michael Snyder
34773 Michael was one of the Global Maintainers of the @value{GDBN} project,
34774 with contributions recorded as early as 1996, until 2011. In addition
34775 to his day to day participation, he was a large driving force behind
34776 adding Reverse Debugging to @value{GDBN}.
34779 Beyond their technical contributions to the project, they were also
34780 enjoyable members of the Free Software Community. We will miss them.
34782 @node Formatting Documentation
34783 @appendix Formatting Documentation
34785 @cindex @value{GDBN} reference card
34786 @cindex reference card
34787 The @value{GDBN} 4 release includes an already-formatted reference card, ready
34788 for printing with PostScript or Ghostscript, in the @file{gdb}
34789 subdirectory of the main source directory@footnote{In
34790 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
34791 release.}. If you can use PostScript or Ghostscript with your printer,
34792 you can print the reference card immediately with @file{refcard.ps}.
34794 The release also includes the source for the reference card. You
34795 can format it, using @TeX{}, by typing:
34801 The @value{GDBN} reference card is designed to print in @dfn{landscape}
34802 mode on US ``letter'' size paper;
34803 that is, on a sheet 11 inches wide by 8.5 inches
34804 high. You will need to specify this form of printing as an option to
34805 your @sc{dvi} output program.
34807 @cindex documentation
34809 All the documentation for @value{GDBN} comes as part of the machine-readable
34810 distribution. The documentation is written in Texinfo format, which is
34811 a documentation system that uses a single source file to produce both
34812 on-line information and a printed manual. You can use one of the Info
34813 formatting commands to create the on-line version of the documentation
34814 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
34816 @value{GDBN} includes an already formatted copy of the on-line Info
34817 version of this manual in the @file{gdb} subdirectory. The main Info
34818 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
34819 subordinate files matching @samp{gdb.info*} in the same directory. If
34820 necessary, you can print out these files, or read them with any editor;
34821 but they are easier to read using the @code{info} subsystem in @sc{gnu}
34822 Emacs or the standalone @code{info} program, available as part of the
34823 @sc{gnu} Texinfo distribution.
34825 If you want to format these Info files yourself, you need one of the
34826 Info formatting programs, such as @code{texinfo-format-buffer} or
34829 If you have @code{makeinfo} installed, and are in the top level
34830 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
34831 version @value{GDBVN}), you can make the Info file by typing:
34838 If you want to typeset and print copies of this manual, you need @TeX{},
34839 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
34840 Texinfo definitions file.
34842 @TeX{} is a typesetting program; it does not print files directly, but
34843 produces output files called @sc{dvi} files. To print a typeset
34844 document, you need a program to print @sc{dvi} files. If your system
34845 has @TeX{} installed, chances are it has such a program. The precise
34846 command to use depends on your system; @kbd{lpr -d} is common; another
34847 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
34848 require a file name without any extension or a @samp{.dvi} extension.
34850 @TeX{} also requires a macro definitions file called
34851 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
34852 written in Texinfo format. On its own, @TeX{} cannot either read or
34853 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
34854 and is located in the @file{gdb-@var{version-number}/texinfo}
34857 If you have @TeX{} and a @sc{dvi} printer program installed, you can
34858 typeset and print this manual. First switch to the @file{gdb}
34859 subdirectory of the main source directory (for example, to
34860 @file{gdb-@value{GDBVN}/gdb}) and type:
34866 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
34868 @node Installing GDB
34869 @appendix Installing @value{GDBN}
34870 @cindex installation
34873 * Requirements:: Requirements for building @value{GDBN}
34874 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
34875 * Separate Objdir:: Compiling @value{GDBN} in another directory
34876 * Config Names:: Specifying names for hosts and targets
34877 * Configure Options:: Summary of options for configure
34878 * System-wide configuration:: Having a system-wide init file
34882 @section Requirements for Building @value{GDBN}
34883 @cindex building @value{GDBN}, requirements for
34885 Building @value{GDBN} requires various tools and packages to be available.
34886 Other packages will be used only if they are found.
34888 @heading Tools/Packages Necessary for Building @value{GDBN}
34890 @item ISO C90 compiler
34891 @value{GDBN} is written in ISO C90. It should be buildable with any
34892 working C90 compiler, e.g.@: GCC.
34896 @heading Tools/Packages Optional for Building @value{GDBN}
34900 @value{GDBN} can use the Expat XML parsing library. This library may be
34901 included with your operating system distribution; if it is not, you
34902 can get the latest version from @url{http://expat.sourceforge.net}.
34903 The @file{configure} script will search for this library in several
34904 standard locations; if it is installed in an unusual path, you can
34905 use the @option{--with-libexpat-prefix} option to specify its location.
34911 Remote protocol memory maps (@pxref{Memory Map Format})
34913 Target descriptions (@pxref{Target Descriptions})
34915 Remote shared library lists (@xref{Library List Format},
34916 or alternatively @pxref{Library List Format for SVR4 Targets})
34918 MS-Windows shared libraries (@pxref{Shared Libraries})
34920 Traceframe info (@pxref{Traceframe Info Format})
34922 Branch trace (@pxref{Branch Trace Format})
34926 @cindex compressed debug sections
34927 @value{GDBN} will use the @samp{zlib} library, if available, to read
34928 compressed debug sections. Some linkers, such as GNU gold, are capable
34929 of producing binaries with compressed debug sections. If @value{GDBN}
34930 is compiled with @samp{zlib}, it will be able to read the debug
34931 information in such binaries.
34933 The @samp{zlib} library is likely included with your operating system
34934 distribution; if it is not, you can get the latest version from
34935 @url{http://zlib.net}.
34938 @value{GDBN}'s features related to character sets (@pxref{Character
34939 Sets}) require a functioning @code{iconv} implementation. If you are
34940 on a GNU system, then this is provided by the GNU C Library. Some
34941 other systems also provide a working @code{iconv}.
34943 If @value{GDBN} is using the @code{iconv} program which is installed
34944 in a non-standard place, you will need to tell @value{GDBN} where to find it.
34945 This is done with @option{--with-iconv-bin} which specifies the
34946 directory that contains the @code{iconv} program.
34948 On systems without @code{iconv}, you can install GNU Libiconv. If you
34949 have previously installed Libiconv, you can use the
34950 @option{--with-libiconv-prefix} option to configure.
34952 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
34953 arrange to build Libiconv if a directory named @file{libiconv} appears
34954 in the top-most source directory. If Libiconv is built this way, and
34955 if the operating system does not provide a suitable @code{iconv}
34956 implementation, then the just-built library will automatically be used
34957 by @value{GDBN}. One easy way to set this up is to download GNU
34958 Libiconv, unpack it, and then rename the directory holding the
34959 Libiconv source code to @samp{libiconv}.
34962 @node Running Configure
34963 @section Invoking the @value{GDBN} @file{configure} Script
34964 @cindex configuring @value{GDBN}
34965 @value{GDBN} comes with a @file{configure} script that automates the process
34966 of preparing @value{GDBN} for installation; you can then use @code{make} to
34967 build the @code{gdb} program.
34969 @c irrelevant in info file; it's as current as the code it lives with.
34970 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
34971 look at the @file{README} file in the sources; we may have improved the
34972 installation procedures since publishing this manual.}
34975 The @value{GDBN} distribution includes all the source code you need for
34976 @value{GDBN} in a single directory, whose name is usually composed by
34977 appending the version number to @samp{gdb}.
34979 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
34980 @file{gdb-@value{GDBVN}} directory. That directory contains:
34983 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
34984 script for configuring @value{GDBN} and all its supporting libraries
34986 @item gdb-@value{GDBVN}/gdb
34987 the source specific to @value{GDBN} itself
34989 @item gdb-@value{GDBVN}/bfd
34990 source for the Binary File Descriptor library
34992 @item gdb-@value{GDBVN}/include
34993 @sc{gnu} include files
34995 @item gdb-@value{GDBVN}/libiberty
34996 source for the @samp{-liberty} free software library
34998 @item gdb-@value{GDBVN}/opcodes
34999 source for the library of opcode tables and disassemblers
35001 @item gdb-@value{GDBVN}/readline
35002 source for the @sc{gnu} command-line interface
35004 @item gdb-@value{GDBVN}/glob
35005 source for the @sc{gnu} filename pattern-matching subroutine
35007 @item gdb-@value{GDBVN}/mmalloc
35008 source for the @sc{gnu} memory-mapped malloc package
35011 The simplest way to configure and build @value{GDBN} is to run @file{configure}
35012 from the @file{gdb-@var{version-number}} source directory, which in
35013 this example is the @file{gdb-@value{GDBVN}} directory.
35015 First switch to the @file{gdb-@var{version-number}} source directory
35016 if you are not already in it; then run @file{configure}. Pass the
35017 identifier for the platform on which @value{GDBN} will run as an
35023 cd gdb-@value{GDBVN}
35024 ./configure @var{host}
35029 where @var{host} is an identifier such as @samp{sun4} or
35030 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
35031 (You can often leave off @var{host}; @file{configure} tries to guess the
35032 correct value by examining your system.)
35034 Running @samp{configure @var{host}} and then running @code{make} builds the
35035 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
35036 libraries, then @code{gdb} itself. The configured source files, and the
35037 binaries, are left in the corresponding source directories.
35040 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
35041 system does not recognize this automatically when you run a different
35042 shell, you may need to run @code{sh} on it explicitly:
35045 sh configure @var{host}
35048 If you run @file{configure} from a directory that contains source
35049 directories for multiple libraries or programs, such as the
35050 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
35052 creates configuration files for every directory level underneath (unless
35053 you tell it not to, with the @samp{--norecursion} option).
35055 You should run the @file{configure} script from the top directory in the
35056 source tree, the @file{gdb-@var{version-number}} directory. If you run
35057 @file{configure} from one of the subdirectories, you will configure only
35058 that subdirectory. That is usually not what you want. In particular,
35059 if you run the first @file{configure} from the @file{gdb} subdirectory
35060 of the @file{gdb-@var{version-number}} directory, you will omit the
35061 configuration of @file{bfd}, @file{readline}, and other sibling
35062 directories of the @file{gdb} subdirectory. This leads to build errors
35063 about missing include files such as @file{bfd/bfd.h}.
35065 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
35066 However, you should make sure that the shell on your path (named by
35067 the @samp{SHELL} environment variable) is publicly readable. Remember
35068 that @value{GDBN} uses the shell to start your program---some systems refuse to
35069 let @value{GDBN} debug child processes whose programs are not readable.
35071 @node Separate Objdir
35072 @section Compiling @value{GDBN} in Another Directory
35074 If you want to run @value{GDBN} versions for several host or target machines,
35075 you need a different @code{gdb} compiled for each combination of
35076 host and target. @file{configure} is designed to make this easy by
35077 allowing you to generate each configuration in a separate subdirectory,
35078 rather than in the source directory. If your @code{make} program
35079 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
35080 @code{make} in each of these directories builds the @code{gdb}
35081 program specified there.
35083 To build @code{gdb} in a separate directory, run @file{configure}
35084 with the @samp{--srcdir} option to specify where to find the source.
35085 (You also need to specify a path to find @file{configure}
35086 itself from your working directory. If the path to @file{configure}
35087 would be the same as the argument to @samp{--srcdir}, you can leave out
35088 the @samp{--srcdir} option; it is assumed.)
35090 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
35091 separate directory for a Sun 4 like this:
35095 cd gdb-@value{GDBVN}
35098 ../gdb-@value{GDBVN}/configure sun4
35103 When @file{configure} builds a configuration using a remote source
35104 directory, it creates a tree for the binaries with the same structure
35105 (and using the same names) as the tree under the source directory. In
35106 the example, you'd find the Sun 4 library @file{libiberty.a} in the
35107 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
35108 @file{gdb-sun4/gdb}.
35110 Make sure that your path to the @file{configure} script has just one
35111 instance of @file{gdb} in it. If your path to @file{configure} looks
35112 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
35113 one subdirectory of @value{GDBN}, not the whole package. This leads to
35114 build errors about missing include files such as @file{bfd/bfd.h}.
35116 One popular reason to build several @value{GDBN} configurations in separate
35117 directories is to configure @value{GDBN} for cross-compiling (where
35118 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
35119 programs that run on another machine---the @dfn{target}).
35120 You specify a cross-debugging target by
35121 giving the @samp{--target=@var{target}} option to @file{configure}.
35123 When you run @code{make} to build a program or library, you must run
35124 it in a configured directory---whatever directory you were in when you
35125 called @file{configure} (or one of its subdirectories).
35127 The @code{Makefile} that @file{configure} generates in each source
35128 directory also runs recursively. If you type @code{make} in a source
35129 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
35130 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
35131 will build all the required libraries, and then build GDB.
35133 When you have multiple hosts or targets configured in separate
35134 directories, you can run @code{make} on them in parallel (for example,
35135 if they are NFS-mounted on each of the hosts); they will not interfere
35139 @section Specifying Names for Hosts and Targets
35141 The specifications used for hosts and targets in the @file{configure}
35142 script are based on a three-part naming scheme, but some short predefined
35143 aliases are also supported. The full naming scheme encodes three pieces
35144 of information in the following pattern:
35147 @var{architecture}-@var{vendor}-@var{os}
35150 For example, you can use the alias @code{sun4} as a @var{host} argument,
35151 or as the value for @var{target} in a @code{--target=@var{target}}
35152 option. The equivalent full name is @samp{sparc-sun-sunos4}.
35154 The @file{configure} script accompanying @value{GDBN} does not provide
35155 any query facility to list all supported host and target names or
35156 aliases. @file{configure} calls the Bourne shell script
35157 @code{config.sub} to map abbreviations to full names; you can read the
35158 script, if you wish, or you can use it to test your guesses on
35159 abbreviations---for example:
35162 % sh config.sub i386-linux
35164 % sh config.sub alpha-linux
35165 alpha-unknown-linux-gnu
35166 % sh config.sub hp9k700
35168 % sh config.sub sun4
35169 sparc-sun-sunos4.1.1
35170 % sh config.sub sun3
35171 m68k-sun-sunos4.1.1
35172 % sh config.sub i986v
35173 Invalid configuration `i986v': machine `i986v' not recognized
35177 @code{config.sub} is also distributed in the @value{GDBN} source
35178 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
35180 @node Configure Options
35181 @section @file{configure} Options
35183 Here is a summary of the @file{configure} options and arguments that
35184 are most often useful for building @value{GDBN}. @file{configure} also has
35185 several other options not listed here. @inforef{What Configure
35186 Does,,configure.info}, for a full explanation of @file{configure}.
35189 configure @r{[}--help@r{]}
35190 @r{[}--prefix=@var{dir}@r{]}
35191 @r{[}--exec-prefix=@var{dir}@r{]}
35192 @r{[}--srcdir=@var{dirname}@r{]}
35193 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
35194 @r{[}--target=@var{target}@r{]}
35199 You may introduce options with a single @samp{-} rather than
35200 @samp{--} if you prefer; but you may abbreviate option names if you use
35205 Display a quick summary of how to invoke @file{configure}.
35207 @item --prefix=@var{dir}
35208 Configure the source to install programs and files under directory
35211 @item --exec-prefix=@var{dir}
35212 Configure the source to install programs under directory
35215 @c avoid splitting the warning from the explanation:
35217 @item --srcdir=@var{dirname}
35218 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
35219 @code{make} that implements the @code{VPATH} feature.}@*
35220 Use this option to make configurations in directories separate from the
35221 @value{GDBN} source directories. Among other things, you can use this to
35222 build (or maintain) several configurations simultaneously, in separate
35223 directories. @file{configure} writes configuration-specific files in
35224 the current directory, but arranges for them to use the source in the
35225 directory @var{dirname}. @file{configure} creates directories under
35226 the working directory in parallel to the source directories below
35229 @item --norecursion
35230 Configure only the directory level where @file{configure} is executed; do not
35231 propagate configuration to subdirectories.
35233 @item --target=@var{target}
35234 Configure @value{GDBN} for cross-debugging programs running on the specified
35235 @var{target}. Without this option, @value{GDBN} is configured to debug
35236 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
35238 There is no convenient way to generate a list of all available targets.
35240 @item @var{host} @dots{}
35241 Configure @value{GDBN} to run on the specified @var{host}.
35243 There is no convenient way to generate a list of all available hosts.
35246 There are many other options available as well, but they are generally
35247 needed for special purposes only.
35249 @node System-wide configuration
35250 @section System-wide configuration and settings
35251 @cindex system-wide init file
35253 @value{GDBN} can be configured to have a system-wide init file;
35254 this file will be read and executed at startup (@pxref{Startup, , What
35255 @value{GDBN} does during startup}).
35257 Here is the corresponding configure option:
35260 @item --with-system-gdbinit=@var{file}
35261 Specify that the default location of the system-wide init file is
35265 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
35266 it may be subject to relocation. Two possible cases:
35270 If the default location of this init file contains @file{$prefix},
35271 it will be subject to relocation. Suppose that the configure options
35272 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
35273 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
35274 init file is looked for as @file{$install/etc/gdbinit} instead of
35275 @file{$prefix/etc/gdbinit}.
35278 By contrast, if the default location does not contain the prefix,
35279 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
35280 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
35281 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
35282 wherever @value{GDBN} is installed.
35285 If the configured location of the system-wide init file (as given by the
35286 @option{--with-system-gdbinit} option at configure time) is in the
35287 data-directory (as specified by @option{--with-gdb-datadir} at configure
35288 time) or in one of its subdirectories, then @value{GDBN} will look for the
35289 system-wide init file in the directory specified by the
35290 @option{--data-directory} command-line option.
35291 Note that the system-wide init file is only read once, during @value{GDBN}
35292 initialization. If the data-directory is changed after @value{GDBN} has
35293 started with the @code{set data-directory} command, the file will not be
35296 @node Maintenance Commands
35297 @appendix Maintenance Commands
35298 @cindex maintenance commands
35299 @cindex internal commands
35301 In addition to commands intended for @value{GDBN} users, @value{GDBN}
35302 includes a number of commands intended for @value{GDBN} developers,
35303 that are not documented elsewhere in this manual. These commands are
35304 provided here for reference. (For commands that turn on debugging
35305 messages, see @ref{Debugging Output}.)
35308 @kindex maint agent
35309 @kindex maint agent-eval
35310 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
35311 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
35312 Translate the given @var{expression} into remote agent bytecodes.
35313 This command is useful for debugging the Agent Expression mechanism
35314 (@pxref{Agent Expressions}). The @samp{agent} version produces an
35315 expression useful for data collection, such as by tracepoints, while
35316 @samp{maint agent-eval} produces an expression that evaluates directly
35317 to a result. For instance, a collection expression for @code{globa +
35318 globb} will include bytecodes to record four bytes of memory at each
35319 of the addresses of @code{globa} and @code{globb}, while discarding
35320 the result of the addition, while an evaluation expression will do the
35321 addition and return the sum.
35322 If @code{-at} is given, generate remote agent bytecode for @var{location}.
35323 If not, generate remote agent bytecode for current frame PC address.
35325 @kindex maint agent-printf
35326 @item maint agent-printf @var{format},@var{expr},...
35327 Translate the given format string and list of argument expressions
35328 into remote agent bytecodes and display them as a disassembled list.
35329 This command is useful for debugging the agent version of dynamic
35330 printf (@pxref{Dynamic Printf}).
35332 @kindex maint info breakpoints
35333 @item @anchor{maint info breakpoints}maint info breakpoints
35334 Using the same format as @samp{info breakpoints}, display both the
35335 breakpoints you've set explicitly, and those @value{GDBN} is using for
35336 internal purposes. Internal breakpoints are shown with negative
35337 breakpoint numbers. The type column identifies what kind of breakpoint
35342 Normal, explicitly set breakpoint.
35345 Normal, explicitly set watchpoint.
35348 Internal breakpoint, used to handle correctly stepping through
35349 @code{longjmp} calls.
35351 @item longjmp resume
35352 Internal breakpoint at the target of a @code{longjmp}.
35355 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
35358 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
35361 Shared library events.
35365 @kindex maint info bfds
35366 @item maint info bfds
35367 This prints information about each @code{bfd} object that is known to
35368 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
35370 @kindex set displaced-stepping
35371 @kindex show displaced-stepping
35372 @cindex displaced stepping support
35373 @cindex out-of-line single-stepping
35374 @item set displaced-stepping
35375 @itemx show displaced-stepping
35376 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
35377 if the target supports it. Displaced stepping is a way to single-step
35378 over breakpoints without removing them from the inferior, by executing
35379 an out-of-line copy of the instruction that was originally at the
35380 breakpoint location. It is also known as out-of-line single-stepping.
35383 @item set displaced-stepping on
35384 If the target architecture supports it, @value{GDBN} will use
35385 displaced stepping to step over breakpoints.
35387 @item set displaced-stepping off
35388 @value{GDBN} will not use displaced stepping to step over breakpoints,
35389 even if such is supported by the target architecture.
35391 @cindex non-stop mode, and @samp{set displaced-stepping}
35392 @item set displaced-stepping auto
35393 This is the default mode. @value{GDBN} will use displaced stepping
35394 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
35395 architecture supports displaced stepping.
35398 @kindex maint check-symtabs
35399 @item maint check-symtabs
35400 Check the consistency of psymtabs and symtabs.
35402 @kindex maint cplus first_component
35403 @item maint cplus first_component @var{name}
35404 Print the first C@t{++} class/namespace component of @var{name}.
35406 @kindex maint cplus namespace
35407 @item maint cplus namespace
35408 Print the list of possible C@t{++} namespaces.
35410 @kindex maint demangle
35411 @item maint demangle @var{name}
35412 Demangle a C@t{++} or Objective-C mangled @var{name}.
35414 @kindex maint deprecate
35415 @kindex maint undeprecate
35416 @cindex deprecated commands
35417 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
35418 @itemx maint undeprecate @var{command}
35419 Deprecate or undeprecate the named @var{command}. Deprecated commands
35420 cause @value{GDBN} to issue a warning when you use them. The optional
35421 argument @var{replacement} says which newer command should be used in
35422 favor of the deprecated one; if it is given, @value{GDBN} will mention
35423 the replacement as part of the warning.
35425 @kindex maint dump-me
35426 @item maint dump-me
35427 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
35428 Cause a fatal signal in the debugger and force it to dump its core.
35429 This is supported only on systems which support aborting a program
35430 with the @code{SIGQUIT} signal.
35432 @kindex maint internal-error
35433 @kindex maint internal-warning
35434 @item maint internal-error @r{[}@var{message-text}@r{]}
35435 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
35436 Cause @value{GDBN} to call the internal function @code{internal_error}
35437 or @code{internal_warning} and hence behave as though an internal error
35438 or internal warning has been detected. In addition to reporting the
35439 internal problem, these functions give the user the opportunity to
35440 either quit @value{GDBN} or create a core file of the current
35441 @value{GDBN} session.
35443 These commands take an optional parameter @var{message-text} that is
35444 used as the text of the error or warning message.
35446 Here's an example of using @code{internal-error}:
35449 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
35450 @dots{}/maint.c:121: internal-error: testing, 1, 2
35451 A problem internal to GDB has been detected. Further
35452 debugging may prove unreliable.
35453 Quit this debugging session? (y or n) @kbd{n}
35454 Create a core file? (y or n) @kbd{n}
35458 @cindex @value{GDBN} internal error
35459 @cindex internal errors, control of @value{GDBN} behavior
35461 @kindex maint set internal-error
35462 @kindex maint show internal-error
35463 @kindex maint set internal-warning
35464 @kindex maint show internal-warning
35465 @item maint set internal-error @var{action} [ask|yes|no]
35466 @itemx maint show internal-error @var{action}
35467 @itemx maint set internal-warning @var{action} [ask|yes|no]
35468 @itemx maint show internal-warning @var{action}
35469 When @value{GDBN} reports an internal problem (error or warning) it
35470 gives the user the opportunity to both quit @value{GDBN} and create a
35471 core file of the current @value{GDBN} session. These commands let you
35472 override the default behaviour for each particular @var{action},
35473 described in the table below.
35477 You can specify that @value{GDBN} should always (yes) or never (no)
35478 quit. The default is to ask the user what to do.
35481 You can specify that @value{GDBN} should always (yes) or never (no)
35482 create a core file. The default is to ask the user what to do.
35485 @kindex maint packet
35486 @item maint packet @var{text}
35487 If @value{GDBN} is talking to an inferior via the serial protocol,
35488 then this command sends the string @var{text} to the inferior, and
35489 displays the response packet. @value{GDBN} supplies the initial
35490 @samp{$} character, the terminating @samp{#} character, and the
35493 @kindex maint print architecture
35494 @item maint print architecture @r{[}@var{file}@r{]}
35495 Print the entire architecture configuration. The optional argument
35496 @var{file} names the file where the output goes.
35498 @kindex maint print c-tdesc
35499 @item maint print c-tdesc
35500 Print the current target description (@pxref{Target Descriptions}) as
35501 a C source file. The created source file can be used in @value{GDBN}
35502 when an XML parser is not available to parse the description.
35504 @kindex maint print dummy-frames
35505 @item maint print dummy-frames
35506 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
35509 (@value{GDBP}) @kbd{b add}
35511 (@value{GDBP}) @kbd{print add(2,3)}
35512 Breakpoint 2, add (a=2, b=3) at @dots{}
35514 The program being debugged stopped while in a function called from GDB.
35516 (@value{GDBP}) @kbd{maint print dummy-frames}
35517 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
35518 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
35519 call_lo=0x01014000 call_hi=0x01014001
35523 Takes an optional file parameter.
35525 @kindex maint print registers
35526 @kindex maint print raw-registers
35527 @kindex maint print cooked-registers
35528 @kindex maint print register-groups
35529 @kindex maint print remote-registers
35530 @item maint print registers @r{[}@var{file}@r{]}
35531 @itemx maint print raw-registers @r{[}@var{file}@r{]}
35532 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
35533 @itemx maint print register-groups @r{[}@var{file}@r{]}
35534 @itemx maint print remote-registers @r{[}@var{file}@r{]}
35535 Print @value{GDBN}'s internal register data structures.
35537 The command @code{maint print raw-registers} includes the contents of
35538 the raw register cache; the command @code{maint print
35539 cooked-registers} includes the (cooked) value of all registers,
35540 including registers which aren't available on the target nor visible
35541 to user; the command @code{maint print register-groups} includes the
35542 groups that each register is a member of; and the command @code{maint
35543 print remote-registers} includes the remote target's register numbers
35544 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
35545 @value{GDBN} Internals}.
35547 These commands take an optional parameter, a file name to which to
35548 write the information.
35550 @kindex maint print reggroups
35551 @item maint print reggroups @r{[}@var{file}@r{]}
35552 Print @value{GDBN}'s internal register group data structures. The
35553 optional argument @var{file} tells to what file to write the
35556 The register groups info looks like this:
35559 (@value{GDBP}) @kbd{maint print reggroups}
35572 This command forces @value{GDBN} to flush its internal register cache.
35574 @kindex maint print objfiles
35575 @cindex info for known object files
35576 @item maint print objfiles
35577 Print a dump of all known object files. For each object file, this
35578 command prints its name, address in memory, and all of its psymtabs
35581 @kindex maint print section-scripts
35582 @cindex info for known .debug_gdb_scripts-loaded scripts
35583 @item maint print section-scripts [@var{regexp}]
35584 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
35585 If @var{regexp} is specified, only print scripts loaded by object files
35586 matching @var{regexp}.
35587 For each script, this command prints its name as specified in the objfile,
35588 and the full path if known.
35589 @xref{dotdebug_gdb_scripts section}.
35591 @kindex maint print statistics
35592 @cindex bcache statistics
35593 @item maint print statistics
35594 This command prints, for each object file in the program, various data
35595 about that object file followed by the byte cache (@dfn{bcache})
35596 statistics for the object file. The objfile data includes the number
35597 of minimal, partial, full, and stabs symbols, the number of types
35598 defined by the objfile, the number of as yet unexpanded psym tables,
35599 the number of line tables and string tables, and the amount of memory
35600 used by the various tables. The bcache statistics include the counts,
35601 sizes, and counts of duplicates of all and unique objects, max,
35602 average, and median entry size, total memory used and its overhead and
35603 savings, and various measures of the hash table size and chain
35606 @kindex maint print target-stack
35607 @cindex target stack description
35608 @item maint print target-stack
35609 A @dfn{target} is an interface between the debugger and a particular
35610 kind of file or process. Targets can be stacked in @dfn{strata},
35611 so that more than one target can potentially respond to a request.
35612 In particular, memory accesses will walk down the stack of targets
35613 until they find a target that is interested in handling that particular
35616 This command prints a short description of each layer that was pushed on
35617 the @dfn{target stack}, starting from the top layer down to the bottom one.
35619 @kindex maint print type
35620 @cindex type chain of a data type
35621 @item maint print type @var{expr}
35622 Print the type chain for a type specified by @var{expr}. The argument
35623 can be either a type name or a symbol. If it is a symbol, the type of
35624 that symbol is described. The type chain produced by this command is
35625 a recursive definition of the data type as stored in @value{GDBN}'s
35626 data structures, including its flags and contained types.
35628 @kindex maint set dwarf2 always-disassemble
35629 @kindex maint show dwarf2 always-disassemble
35630 @item maint set dwarf2 always-disassemble
35631 @item maint show dwarf2 always-disassemble
35632 Control the behavior of @code{info address} when using DWARF debugging
35635 The default is @code{off}, which means that @value{GDBN} should try to
35636 describe a variable's location in an easily readable format. When
35637 @code{on}, @value{GDBN} will instead display the DWARF location
35638 expression in an assembly-like format. Note that some locations are
35639 too complex for @value{GDBN} to describe simply; in this case you will
35640 always see the disassembly form.
35642 Here is an example of the resulting disassembly:
35645 (gdb) info addr argc
35646 Symbol "argc" is a complex DWARF expression:
35650 For more information on these expressions, see
35651 @uref{http://www.dwarfstd.org/, the DWARF standard}.
35653 @kindex maint set dwarf2 max-cache-age
35654 @kindex maint show dwarf2 max-cache-age
35655 @item maint set dwarf2 max-cache-age
35656 @itemx maint show dwarf2 max-cache-age
35657 Control the DWARF 2 compilation unit cache.
35659 @cindex DWARF 2 compilation units cache
35660 In object files with inter-compilation-unit references, such as those
35661 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
35662 reader needs to frequently refer to previously read compilation units.
35663 This setting controls how long a compilation unit will remain in the
35664 cache if it is not referenced. A higher limit means that cached
35665 compilation units will be stored in memory longer, and more total
35666 memory will be used. Setting it to zero disables caching, which will
35667 slow down @value{GDBN} startup, but reduce memory consumption.
35669 @kindex maint set profile
35670 @kindex maint show profile
35671 @cindex profiling GDB
35672 @item maint set profile
35673 @itemx maint show profile
35674 Control profiling of @value{GDBN}.
35676 Profiling will be disabled until you use the @samp{maint set profile}
35677 command to enable it. When you enable profiling, the system will begin
35678 collecting timing and execution count data; when you disable profiling or
35679 exit @value{GDBN}, the results will be written to a log file. Remember that
35680 if you use profiling, @value{GDBN} will overwrite the profiling log file
35681 (often called @file{gmon.out}). If you have a record of important profiling
35682 data in a @file{gmon.out} file, be sure to move it to a safe location.
35684 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
35685 compiled with the @samp{-pg} compiler option.
35687 @kindex maint set show-debug-regs
35688 @kindex maint show show-debug-regs
35689 @cindex hardware debug registers
35690 @item maint set show-debug-regs
35691 @itemx maint show show-debug-regs
35692 Control whether to show variables that mirror the hardware debug
35693 registers. Use @code{ON} to enable, @code{OFF} to disable. If
35694 enabled, the debug registers values are shown when @value{GDBN} inserts or
35695 removes a hardware breakpoint or watchpoint, and when the inferior
35696 triggers a hardware-assisted breakpoint or watchpoint.
35698 @kindex maint set show-all-tib
35699 @kindex maint show show-all-tib
35700 @item maint set show-all-tib
35701 @itemx maint show show-all-tib
35702 Control whether to show all non zero areas within a 1k block starting
35703 at thread local base, when using the @samp{info w32 thread-information-block}
35706 @kindex maint set per-command
35707 @kindex maint show per-command
35708 @item maint set per-command
35709 @itemx maint show per-command
35710 @cindex resources used by commands
35712 @value{GDBN} can display the resources used by each command.
35713 This is useful in debugging performance problems.
35716 @item maint set per-command space [on|off]
35717 @itemx maint show per-command space
35718 Enable or disable the printing of the memory used by GDB for each command.
35719 If enabled, @value{GDBN} will display how much memory each command
35720 took, following the command's own output.
35721 This can also be requested by invoking @value{GDBN} with the
35722 @option{--statistics} command-line switch (@pxref{Mode Options}).
35724 @item maint set per-command time [on|off]
35725 @itemx maint show per-command time
35726 Enable or disable the printing of the execution time of @value{GDBN}
35728 If enabled, @value{GDBN} will display how much time it
35729 took to execute each command, following the command's own output.
35730 Both CPU time and wallclock time are printed.
35731 Printing both is useful when trying to determine whether the cost is
35732 CPU or, e.g., disk/network latency.
35733 Note that the CPU time printed is for @value{GDBN} only, it does not include
35734 the execution time of the inferior because there's no mechanism currently
35735 to compute how much time was spent by @value{GDBN} and how much time was
35736 spent by the program been debugged.
35737 This can also be requested by invoking @value{GDBN} with the
35738 @option{--statistics} command-line switch (@pxref{Mode Options}).
35740 @item maint set per-command symtab [on|off]
35741 @itemx maint show per-command symtab
35742 Enable or disable the printing of basic symbol table statistics
35744 If enabled, @value{GDBN} will display the following information:
35748 number of symbol tables
35750 number of primary symbol tables
35752 number of blocks in the blockvector
35756 @kindex maint space
35757 @cindex memory used by commands
35758 @item maint space @var{value}
35759 An alias for @code{maint set per-command space}.
35760 A non-zero value enables it, zero disables it.
35763 @cindex time of command execution
35764 @item maint time @var{value}
35765 An alias for @code{maint set per-command time}.
35766 A non-zero value enables it, zero disables it.
35768 @kindex maint translate-address
35769 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
35770 Find the symbol stored at the location specified by the address
35771 @var{addr} and an optional section name @var{section}. If found,
35772 @value{GDBN} prints the name of the closest symbol and an offset from
35773 the symbol's location to the specified address. This is similar to
35774 the @code{info address} command (@pxref{Symbols}), except that this
35775 command also allows to find symbols in other sections.
35777 If section was not specified, the section in which the symbol was found
35778 is also printed. For dynamically linked executables, the name of
35779 executable or shared library containing the symbol is printed as well.
35783 The following command is useful for non-interactive invocations of
35784 @value{GDBN}, such as in the test suite.
35787 @item set watchdog @var{nsec}
35788 @kindex set watchdog
35789 @cindex watchdog timer
35790 @cindex timeout for commands
35791 Set the maximum number of seconds @value{GDBN} will wait for the
35792 target operation to finish. If this time expires, @value{GDBN}
35793 reports and error and the command is aborted.
35795 @item show watchdog
35796 Show the current setting of the target wait timeout.
35799 @node Remote Protocol
35800 @appendix @value{GDBN} Remote Serial Protocol
35805 * Stop Reply Packets::
35806 * General Query Packets::
35807 * Architecture-Specific Protocol Details::
35808 * Tracepoint Packets::
35809 * Host I/O Packets::
35811 * Notification Packets::
35812 * Remote Non-Stop::
35813 * Packet Acknowledgment::
35815 * File-I/O Remote Protocol Extension::
35816 * Library List Format::
35817 * Library List Format for SVR4 Targets::
35818 * Memory Map Format::
35819 * Thread List Format::
35820 * Traceframe Info Format::
35821 * Branch Trace Format::
35827 There may be occasions when you need to know something about the
35828 protocol---for example, if there is only one serial port to your target
35829 machine, you might want your program to do something special if it
35830 recognizes a packet meant for @value{GDBN}.
35832 In the examples below, @samp{->} and @samp{<-} are used to indicate
35833 transmitted and received data, respectively.
35835 @cindex protocol, @value{GDBN} remote serial
35836 @cindex serial protocol, @value{GDBN} remote
35837 @cindex remote serial protocol
35838 All @value{GDBN} commands and responses (other than acknowledgments
35839 and notifications, see @ref{Notification Packets}) are sent as a
35840 @var{packet}. A @var{packet} is introduced with the character
35841 @samp{$}, the actual @var{packet-data}, and the terminating character
35842 @samp{#} followed by a two-digit @var{checksum}:
35845 @code{$}@var{packet-data}@code{#}@var{checksum}
35849 @cindex checksum, for @value{GDBN} remote
35851 The two-digit @var{checksum} is computed as the modulo 256 sum of all
35852 characters between the leading @samp{$} and the trailing @samp{#} (an
35853 eight bit unsigned checksum).
35855 Implementors should note that prior to @value{GDBN} 5.0 the protocol
35856 specification also included an optional two-digit @var{sequence-id}:
35859 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
35862 @cindex sequence-id, for @value{GDBN} remote
35864 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
35865 has never output @var{sequence-id}s. Stubs that handle packets added
35866 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
35868 When either the host or the target machine receives a packet, the first
35869 response expected is an acknowledgment: either @samp{+} (to indicate
35870 the package was received correctly) or @samp{-} (to request
35874 -> @code{$}@var{packet-data}@code{#}@var{checksum}
35879 The @samp{+}/@samp{-} acknowledgments can be disabled
35880 once a connection is established.
35881 @xref{Packet Acknowledgment}, for details.
35883 The host (@value{GDBN}) sends @var{command}s, and the target (the
35884 debugging stub incorporated in your program) sends a @var{response}. In
35885 the case of step and continue @var{command}s, the response is only sent
35886 when the operation has completed, and the target has again stopped all
35887 threads in all attached processes. This is the default all-stop mode
35888 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
35889 execution mode; see @ref{Remote Non-Stop}, for details.
35891 @var{packet-data} consists of a sequence of characters with the
35892 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
35895 @cindex remote protocol, field separator
35896 Fields within the packet should be separated using @samp{,} @samp{;} or
35897 @samp{:}. Except where otherwise noted all numbers are represented in
35898 @sc{hex} with leading zeros suppressed.
35900 Implementors should note that prior to @value{GDBN} 5.0, the character
35901 @samp{:} could not appear as the third character in a packet (as it
35902 would potentially conflict with the @var{sequence-id}).
35904 @cindex remote protocol, binary data
35905 @anchor{Binary Data}
35906 Binary data in most packets is encoded either as two hexadecimal
35907 digits per byte of binary data. This allowed the traditional remote
35908 protocol to work over connections which were only seven-bit clean.
35909 Some packets designed more recently assume an eight-bit clean
35910 connection, and use a more efficient encoding to send and receive
35913 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
35914 as an escape character. Any escaped byte is transmitted as the escape
35915 character followed by the original character XORed with @code{0x20}.
35916 For example, the byte @code{0x7d} would be transmitted as the two
35917 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
35918 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
35919 @samp{@}}) must always be escaped. Responses sent by the stub
35920 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
35921 is not interpreted as the start of a run-length encoded sequence
35924 Response @var{data} can be run-length encoded to save space.
35925 Run-length encoding replaces runs of identical characters with one
35926 instance of the repeated character, followed by a @samp{*} and a
35927 repeat count. The repeat count is itself sent encoded, to avoid
35928 binary characters in @var{data}: a value of @var{n} is sent as
35929 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
35930 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
35931 code 32) for a repeat count of 3. (This is because run-length
35932 encoding starts to win for counts 3 or more.) Thus, for example,
35933 @samp{0* } is a run-length encoding of ``0000'': the space character
35934 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
35937 The printable characters @samp{#} and @samp{$} or with a numeric value
35938 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
35939 seven repeats (@samp{$}) can be expanded using a repeat count of only
35940 five (@samp{"}). For example, @samp{00000000} can be encoded as
35943 The error response returned for some packets includes a two character
35944 error number. That number is not well defined.
35946 @cindex empty response, for unsupported packets
35947 For any @var{command} not supported by the stub, an empty response
35948 (@samp{$#00}) should be returned. That way it is possible to extend the
35949 protocol. A newer @value{GDBN} can tell if a packet is supported based
35952 At a minimum, a stub is required to support the @samp{g} and @samp{G}
35953 commands for register access, and the @samp{m} and @samp{M} commands
35954 for memory access. Stubs that only control single-threaded targets
35955 can implement run control with the @samp{c} (continue), and @samp{s}
35956 (step) commands. Stubs that support multi-threading targets should
35957 support the @samp{vCont} command. All other commands are optional.
35962 The following table provides a complete list of all currently defined
35963 @var{command}s and their corresponding response @var{data}.
35964 @xref{File-I/O Remote Protocol Extension}, for details about the File
35965 I/O extension of the remote protocol.
35967 Each packet's description has a template showing the packet's overall
35968 syntax, followed by an explanation of the packet's meaning. We
35969 include spaces in some of the templates for clarity; these are not
35970 part of the packet's syntax. No @value{GDBN} packet uses spaces to
35971 separate its components. For example, a template like @samp{foo
35972 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
35973 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
35974 @var{baz}. @value{GDBN} does not transmit a space character between the
35975 @samp{foo} and the @var{bar}, or between the @var{bar} and the
35978 @cindex @var{thread-id}, in remote protocol
35979 @anchor{thread-id syntax}
35980 Several packets and replies include a @var{thread-id} field to identify
35981 a thread. Normally these are positive numbers with a target-specific
35982 interpretation, formatted as big-endian hex strings. A @var{thread-id}
35983 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
35986 In addition, the remote protocol supports a multiprocess feature in
35987 which the @var{thread-id} syntax is extended to optionally include both
35988 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
35989 The @var{pid} (process) and @var{tid} (thread) components each have the
35990 format described above: a positive number with target-specific
35991 interpretation formatted as a big-endian hex string, literal @samp{-1}
35992 to indicate all processes or threads (respectively), or @samp{0} to
35993 indicate an arbitrary process or thread. Specifying just a process, as
35994 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
35995 error to specify all processes but a specific thread, such as
35996 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
35997 for those packets and replies explicitly documented to include a process
35998 ID, rather than a @var{thread-id}.
36000 The multiprocess @var{thread-id} syntax extensions are only used if both
36001 @value{GDBN} and the stub report support for the @samp{multiprocess}
36002 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
36005 Note that all packet forms beginning with an upper- or lower-case
36006 letter, other than those described here, are reserved for future use.
36008 Here are the packet descriptions.
36013 @cindex @samp{!} packet
36014 @anchor{extended mode}
36015 Enable extended mode. In extended mode, the remote server is made
36016 persistent. The @samp{R} packet is used to restart the program being
36022 The remote target both supports and has enabled extended mode.
36026 @cindex @samp{?} packet
36027 Indicate the reason the target halted. The reply is the same as for
36028 step and continue. This packet has a special interpretation when the
36029 target is in non-stop mode; see @ref{Remote Non-Stop}.
36032 @xref{Stop Reply Packets}, for the reply specifications.
36034 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
36035 @cindex @samp{A} packet
36036 Initialized @code{argv[]} array passed into program. @var{arglen}
36037 specifies the number of bytes in the hex encoded byte stream
36038 @var{arg}. See @code{gdbserver} for more details.
36043 The arguments were set.
36049 @cindex @samp{b} packet
36050 (Don't use this packet; its behavior is not well-defined.)
36051 Change the serial line speed to @var{baud}.
36053 JTC: @emph{When does the transport layer state change? When it's
36054 received, or after the ACK is transmitted. In either case, there are
36055 problems if the command or the acknowledgment packet is dropped.}
36057 Stan: @emph{If people really wanted to add something like this, and get
36058 it working for the first time, they ought to modify ser-unix.c to send
36059 some kind of out-of-band message to a specially-setup stub and have the
36060 switch happen "in between" packets, so that from remote protocol's point
36061 of view, nothing actually happened.}
36063 @item B @var{addr},@var{mode}
36064 @cindex @samp{B} packet
36065 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
36066 breakpoint at @var{addr}.
36068 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
36069 (@pxref{insert breakpoint or watchpoint packet}).
36071 @cindex @samp{bc} packet
36074 Backward continue. Execute the target system in reverse. No parameter.
36075 @xref{Reverse Execution}, for more information.
36078 @xref{Stop Reply Packets}, for the reply specifications.
36080 @cindex @samp{bs} packet
36083 Backward single step. Execute one instruction in reverse. No parameter.
36084 @xref{Reverse Execution}, for more information.
36087 @xref{Stop Reply Packets}, for the reply specifications.
36089 @item c @r{[}@var{addr}@r{]}
36090 @cindex @samp{c} packet
36091 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
36092 resume at current address.
36094 This packet is deprecated for multi-threading support. @xref{vCont
36098 @xref{Stop Reply Packets}, for the reply specifications.
36100 @item C @var{sig}@r{[};@var{addr}@r{]}
36101 @cindex @samp{C} packet
36102 Continue with signal @var{sig} (hex signal number). If
36103 @samp{;@var{addr}} is omitted, resume at same address.
36105 This packet is deprecated for multi-threading support. @xref{vCont
36109 @xref{Stop Reply Packets}, for the reply specifications.
36112 @cindex @samp{d} packet
36115 Don't use this packet; instead, define a general set packet
36116 (@pxref{General Query Packets}).
36120 @cindex @samp{D} packet
36121 The first form of the packet is used to detach @value{GDBN} from the
36122 remote system. It is sent to the remote target
36123 before @value{GDBN} disconnects via the @code{detach} command.
36125 The second form, including a process ID, is used when multiprocess
36126 protocol extensions are enabled (@pxref{multiprocess extensions}), to
36127 detach only a specific process. The @var{pid} is specified as a
36128 big-endian hex string.
36138 @item F @var{RC},@var{EE},@var{CF};@var{XX}
36139 @cindex @samp{F} packet
36140 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
36141 This is part of the File-I/O protocol extension. @xref{File-I/O
36142 Remote Protocol Extension}, for the specification.
36145 @anchor{read registers packet}
36146 @cindex @samp{g} packet
36147 Read general registers.
36151 @item @var{XX@dots{}}
36152 Each byte of register data is described by two hex digits. The bytes
36153 with the register are transmitted in target byte order. The size of
36154 each register and their position within the @samp{g} packet are
36155 determined by the @value{GDBN} internal gdbarch functions
36156 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
36157 specification of several standard @samp{g} packets is specified below.
36159 When reading registers from a trace frame (@pxref{Analyze Collected
36160 Data,,Using the Collected Data}), the stub may also return a string of
36161 literal @samp{x}'s in place of the register data digits, to indicate
36162 that the corresponding register has not been collected, thus its value
36163 is unavailable. For example, for an architecture with 4 registers of
36164 4 bytes each, the following reply indicates to @value{GDBN} that
36165 registers 0 and 2 have not been collected, while registers 1 and 3
36166 have been collected, and both have zero value:
36170 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
36177 @item G @var{XX@dots{}}
36178 @cindex @samp{G} packet
36179 Write general registers. @xref{read registers packet}, for a
36180 description of the @var{XX@dots{}} data.
36190 @item H @var{op} @var{thread-id}
36191 @cindex @samp{H} packet
36192 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
36193 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
36194 it should be @samp{c} for step and continue operations (note that this
36195 is deprecated, supporting the @samp{vCont} command is a better
36196 option), @samp{g} for other operations. The thread designator
36197 @var{thread-id} has the format and interpretation described in
36198 @ref{thread-id syntax}.
36209 @c 'H': How restrictive (or permissive) is the thread model. If a
36210 @c thread is selected and stopped, are other threads allowed
36211 @c to continue to execute? As I mentioned above, I think the
36212 @c semantics of each command when a thread is selected must be
36213 @c described. For example:
36215 @c 'g': If the stub supports threads and a specific thread is
36216 @c selected, returns the register block from that thread;
36217 @c otherwise returns current registers.
36219 @c 'G' If the stub supports threads and a specific thread is
36220 @c selected, sets the registers of the register block of
36221 @c that thread; otherwise sets current registers.
36223 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
36224 @anchor{cycle step packet}
36225 @cindex @samp{i} packet
36226 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
36227 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
36228 step starting at that address.
36231 @cindex @samp{I} packet
36232 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
36236 @cindex @samp{k} packet
36239 FIXME: @emph{There is no description of how to operate when a specific
36240 thread context has been selected (i.e.@: does 'k' kill only that
36243 @item m @var{addr},@var{length}
36244 @cindex @samp{m} packet
36245 Read @var{length} bytes of memory starting at address @var{addr}.
36246 Note that @var{addr} may not be aligned to any particular boundary.
36248 The stub need not use any particular size or alignment when gathering
36249 data from memory for the response; even if @var{addr} is word-aligned
36250 and @var{length} is a multiple of the word size, the stub is free to
36251 use byte accesses, or not. For this reason, this packet may not be
36252 suitable for accessing memory-mapped I/O devices.
36253 @cindex alignment of remote memory accesses
36254 @cindex size of remote memory accesses
36255 @cindex memory, alignment and size of remote accesses
36259 @item @var{XX@dots{}}
36260 Memory contents; each byte is transmitted as a two-digit hexadecimal
36261 number. The reply may contain fewer bytes than requested if the
36262 server was able to read only part of the region of memory.
36267 @item M @var{addr},@var{length}:@var{XX@dots{}}
36268 @cindex @samp{M} packet
36269 Write @var{length} bytes of memory starting at address @var{addr}.
36270 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
36271 hexadecimal number.
36278 for an error (this includes the case where only part of the data was
36283 @cindex @samp{p} packet
36284 Read the value of register @var{n}; @var{n} is in hex.
36285 @xref{read registers packet}, for a description of how the returned
36286 register value is encoded.
36290 @item @var{XX@dots{}}
36291 the register's value
36295 Indicating an unrecognized @var{query}.
36298 @item P @var{n@dots{}}=@var{r@dots{}}
36299 @anchor{write register packet}
36300 @cindex @samp{P} packet
36301 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
36302 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
36303 digits for each byte in the register (target byte order).
36313 @item q @var{name} @var{params}@dots{}
36314 @itemx Q @var{name} @var{params}@dots{}
36315 @cindex @samp{q} packet
36316 @cindex @samp{Q} packet
36317 General query (@samp{q}) and set (@samp{Q}). These packets are
36318 described fully in @ref{General Query Packets}.
36321 @cindex @samp{r} packet
36322 Reset the entire system.
36324 Don't use this packet; use the @samp{R} packet instead.
36327 @cindex @samp{R} packet
36328 Restart the program being debugged. @var{XX}, while needed, is ignored.
36329 This packet is only available in extended mode (@pxref{extended mode}).
36331 The @samp{R} packet has no reply.
36333 @item s @r{[}@var{addr}@r{]}
36334 @cindex @samp{s} packet
36335 Single step. @var{addr} is the address at which to resume. If
36336 @var{addr} is omitted, resume at same address.
36338 This packet is deprecated for multi-threading support. @xref{vCont
36342 @xref{Stop Reply Packets}, for the reply specifications.
36344 @item S @var{sig}@r{[};@var{addr}@r{]}
36345 @anchor{step with signal packet}
36346 @cindex @samp{S} packet
36347 Step with signal. This is analogous to the @samp{C} packet, but
36348 requests a single-step, rather than a normal resumption of execution.
36350 This packet is deprecated for multi-threading support. @xref{vCont
36354 @xref{Stop Reply Packets}, for the reply specifications.
36356 @item t @var{addr}:@var{PP},@var{MM}
36357 @cindex @samp{t} packet
36358 Search backwards starting at address @var{addr} for a match with pattern
36359 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
36360 @var{addr} must be at least 3 digits.
36362 @item T @var{thread-id}
36363 @cindex @samp{T} packet
36364 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
36369 thread is still alive
36375 Packets starting with @samp{v} are identified by a multi-letter name,
36376 up to the first @samp{;} or @samp{?} (or the end of the packet).
36378 @item vAttach;@var{pid}
36379 @cindex @samp{vAttach} packet
36380 Attach to a new process with the specified process ID @var{pid}.
36381 The process ID is a
36382 hexadecimal integer identifying the process. In all-stop mode, all
36383 threads in the attached process are stopped; in non-stop mode, it may be
36384 attached without being stopped if that is supported by the target.
36386 @c In non-stop mode, on a successful vAttach, the stub should set the
36387 @c current thread to a thread of the newly-attached process. After
36388 @c attaching, GDB queries for the attached process's thread ID with qC.
36389 @c Also note that, from a user perspective, whether or not the
36390 @c target is stopped on attach in non-stop mode depends on whether you
36391 @c use the foreground or background version of the attach command, not
36392 @c on what vAttach does; GDB does the right thing with respect to either
36393 @c stopping or restarting threads.
36395 This packet is only available in extended mode (@pxref{extended mode}).
36401 @item @r{Any stop packet}
36402 for success in all-stop mode (@pxref{Stop Reply Packets})
36404 for success in non-stop mode (@pxref{Remote Non-Stop})
36407 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
36408 @cindex @samp{vCont} packet
36409 @anchor{vCont packet}
36410 Resume the inferior, specifying different actions for each thread.
36411 If an action is specified with no @var{thread-id}, then it is applied to any
36412 threads that don't have a specific action specified; if no default action is
36413 specified then other threads should remain stopped in all-stop mode and
36414 in their current state in non-stop mode.
36415 Specifying multiple
36416 default actions is an error; specifying no actions is also an error.
36417 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
36419 Currently supported actions are:
36425 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
36429 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
36434 The optional argument @var{addr} normally associated with the
36435 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
36436 not supported in @samp{vCont}.
36438 The @samp{t} action is only relevant in non-stop mode
36439 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
36440 A stop reply should be generated for any affected thread not already stopped.
36441 When a thread is stopped by means of a @samp{t} action,
36442 the corresponding stop reply should indicate that the thread has stopped with
36443 signal @samp{0}, regardless of whether the target uses some other signal
36444 as an implementation detail.
36446 The stub must support @samp{vCont} if it reports support for
36447 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
36448 this case @samp{vCont} actions can be specified to apply to all threads
36449 in a process by using the @samp{p@var{pid}.-1} form of the
36453 @xref{Stop Reply Packets}, for the reply specifications.
36456 @cindex @samp{vCont?} packet
36457 Request a list of actions supported by the @samp{vCont} packet.
36461 @item vCont@r{[};@var{action}@dots{}@r{]}
36462 The @samp{vCont} packet is supported. Each @var{action} is a supported
36463 command in the @samp{vCont} packet.
36465 The @samp{vCont} packet is not supported.
36468 @item vFile:@var{operation}:@var{parameter}@dots{}
36469 @cindex @samp{vFile} packet
36470 Perform a file operation on the target system. For details,
36471 see @ref{Host I/O Packets}.
36473 @item vFlashErase:@var{addr},@var{length}
36474 @cindex @samp{vFlashErase} packet
36475 Direct the stub to erase @var{length} bytes of flash starting at
36476 @var{addr}. The region may enclose any number of flash blocks, but
36477 its start and end must fall on block boundaries, as indicated by the
36478 flash block size appearing in the memory map (@pxref{Memory Map
36479 Format}). @value{GDBN} groups flash memory programming operations
36480 together, and sends a @samp{vFlashDone} request after each group; the
36481 stub is allowed to delay erase operation until the @samp{vFlashDone}
36482 packet is received.
36492 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
36493 @cindex @samp{vFlashWrite} packet
36494 Direct the stub to write data to flash address @var{addr}. The data
36495 is passed in binary form using the same encoding as for the @samp{X}
36496 packet (@pxref{Binary Data}). The memory ranges specified by
36497 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
36498 not overlap, and must appear in order of increasing addresses
36499 (although @samp{vFlashErase} packets for higher addresses may already
36500 have been received; the ordering is guaranteed only between
36501 @samp{vFlashWrite} packets). If a packet writes to an address that was
36502 neither erased by a preceding @samp{vFlashErase} packet nor by some other
36503 target-specific method, the results are unpredictable.
36511 for vFlashWrite addressing non-flash memory
36517 @cindex @samp{vFlashDone} packet
36518 Indicate to the stub that flash programming operation is finished.
36519 The stub is permitted to delay or batch the effects of a group of
36520 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
36521 @samp{vFlashDone} packet is received. The contents of the affected
36522 regions of flash memory are unpredictable until the @samp{vFlashDone}
36523 request is completed.
36525 @item vKill;@var{pid}
36526 @cindex @samp{vKill} packet
36527 Kill the process with the specified process ID. @var{pid} is a
36528 hexadecimal integer identifying the process. This packet is used in
36529 preference to @samp{k} when multiprocess protocol extensions are
36530 supported; see @ref{multiprocess extensions}.
36540 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
36541 @cindex @samp{vRun} packet
36542 Run the program @var{filename}, passing it each @var{argument} on its
36543 command line. The file and arguments are hex-encoded strings. If
36544 @var{filename} is an empty string, the stub may use a default program
36545 (e.g.@: the last program run). The program is created in the stopped
36548 @c FIXME: What about non-stop mode?
36550 This packet is only available in extended mode (@pxref{extended mode}).
36556 @item @r{Any stop packet}
36557 for success (@pxref{Stop Reply Packets})
36561 @cindex @samp{vStopped} packet
36562 @xref{Notification Packets}.
36564 @item X @var{addr},@var{length}:@var{XX@dots{}}
36566 @cindex @samp{X} packet
36567 Write data to memory, where the data is transmitted in binary.
36568 @var{addr} is address, @var{length} is number of bytes,
36569 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
36579 @item z @var{type},@var{addr},@var{kind}
36580 @itemx Z @var{type},@var{addr},@var{kind}
36581 @anchor{insert breakpoint or watchpoint packet}
36582 @cindex @samp{z} packet
36583 @cindex @samp{Z} packets
36584 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
36585 watchpoint starting at address @var{address} of kind @var{kind}.
36587 Each breakpoint and watchpoint packet @var{type} is documented
36590 @emph{Implementation notes: A remote target shall return an empty string
36591 for an unrecognized breakpoint or watchpoint packet @var{type}. A
36592 remote target shall support either both or neither of a given
36593 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
36594 avoid potential problems with duplicate packets, the operations should
36595 be implemented in an idempotent way.}
36597 @item z0,@var{addr},@var{kind}
36598 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
36599 @cindex @samp{z0} packet
36600 @cindex @samp{Z0} packet
36601 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
36602 @var{addr} of type @var{kind}.
36604 A memory breakpoint is implemented by replacing the instruction at
36605 @var{addr} with a software breakpoint or trap instruction. The
36606 @var{kind} is target-specific and typically indicates the size of
36607 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
36608 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
36609 architectures have additional meanings for @var{kind};
36610 @var{cond_list} is an optional list of conditional expressions in bytecode
36611 form that should be evaluated on the target's side. These are the
36612 conditions that should be taken into consideration when deciding if
36613 the breakpoint trigger should be reported back to @var{GDBN}.
36615 The @var{cond_list} parameter is comprised of a series of expressions,
36616 concatenated without separators. Each expression has the following form:
36620 @item X @var{len},@var{expr}
36621 @var{len} is the length of the bytecode expression and @var{expr} is the
36622 actual conditional expression in bytecode form.
36626 The optional @var{cmd_list} parameter introduces commands that may be
36627 run on the target, rather than being reported back to @value{GDBN}.
36628 The parameter starts with a numeric flag @var{persist}; if the flag is
36629 nonzero, then the breakpoint may remain active and the commands
36630 continue to be run even when @value{GDBN} disconnects from the target.
36631 Following this flag is a series of expressions concatenated with no
36632 separators. Each expression has the following form:
36636 @item X @var{len},@var{expr}
36637 @var{len} is the length of the bytecode expression and @var{expr} is the
36638 actual conditional expression in bytecode form.
36642 see @ref{Architecture-Specific Protocol Details}.
36644 @emph{Implementation note: It is possible for a target to copy or move
36645 code that contains memory breakpoints (e.g., when implementing
36646 overlays). The behavior of this packet, in the presence of such a
36647 target, is not defined.}
36659 @item z1,@var{addr},@var{kind}
36660 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
36661 @cindex @samp{z1} packet
36662 @cindex @samp{Z1} packet
36663 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
36664 address @var{addr}.
36666 A hardware breakpoint is implemented using a mechanism that is not
36667 dependant on being able to modify the target's memory. @var{kind}
36668 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
36670 @emph{Implementation note: A hardware breakpoint is not affected by code
36683 @item z2,@var{addr},@var{kind}
36684 @itemx Z2,@var{addr},@var{kind}
36685 @cindex @samp{z2} packet
36686 @cindex @samp{Z2} packet
36687 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
36688 @var{kind} is interpreted as the number of bytes to watch.
36700 @item z3,@var{addr},@var{kind}
36701 @itemx Z3,@var{addr},@var{kind}
36702 @cindex @samp{z3} packet
36703 @cindex @samp{Z3} packet
36704 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
36705 @var{kind} is interpreted as the number of bytes to watch.
36717 @item z4,@var{addr},@var{kind}
36718 @itemx Z4,@var{addr},@var{kind}
36719 @cindex @samp{z4} packet
36720 @cindex @samp{Z4} packet
36721 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
36722 @var{kind} is interpreted as the number of bytes to watch.
36736 @node Stop Reply Packets
36737 @section Stop Reply Packets
36738 @cindex stop reply packets
36740 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
36741 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
36742 receive any of the below as a reply. Except for @samp{?}
36743 and @samp{vStopped}, that reply is only returned
36744 when the target halts. In the below the exact meaning of @dfn{signal
36745 number} is defined by the header @file{include/gdb/signals.h} in the
36746 @value{GDBN} source code.
36748 As in the description of request packets, we include spaces in the
36749 reply templates for clarity; these are not part of the reply packet's
36750 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
36756 The program received signal number @var{AA} (a two-digit hexadecimal
36757 number). This is equivalent to a @samp{T} response with no
36758 @var{n}:@var{r} pairs.
36760 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
36761 @cindex @samp{T} packet reply
36762 The program received signal number @var{AA} (a two-digit hexadecimal
36763 number). This is equivalent to an @samp{S} response, except that the
36764 @samp{@var{n}:@var{r}} pairs can carry values of important registers
36765 and other information directly in the stop reply packet, reducing
36766 round-trip latency. Single-step and breakpoint traps are reported
36767 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
36771 If @var{n} is a hexadecimal number, it is a register number, and the
36772 corresponding @var{r} gives that register's value. @var{r} is a
36773 series of bytes in target byte order, with each byte given by a
36774 two-digit hex number.
36777 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
36778 the stopped thread, as specified in @ref{thread-id syntax}.
36781 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
36782 the core on which the stop event was detected.
36785 If @var{n} is a recognized @dfn{stop reason}, it describes a more
36786 specific event that stopped the target. The currently defined stop
36787 reasons are listed below. @var{aa} should be @samp{05}, the trap
36788 signal. At most one stop reason should be present.
36791 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
36792 and go on to the next; this allows us to extend the protocol in the
36796 The currently defined stop reasons are:
36802 The packet indicates a watchpoint hit, and @var{r} is the data address, in
36805 @cindex shared library events, remote reply
36807 The packet indicates that the loaded libraries have changed.
36808 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
36809 list of loaded libraries. @var{r} is ignored.
36811 @cindex replay log events, remote reply
36813 The packet indicates that the target cannot continue replaying
36814 logged execution events, because it has reached the end (or the
36815 beginning when executing backward) of the log. The value of @var{r}
36816 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
36817 for more information.
36821 @itemx W @var{AA} ; process:@var{pid}
36822 The process exited, and @var{AA} is the exit status. This is only
36823 applicable to certain targets.
36825 The second form of the response, including the process ID of the exited
36826 process, can be used only when @value{GDBN} has reported support for
36827 multiprocess protocol extensions; see @ref{multiprocess extensions}.
36828 The @var{pid} is formatted as a big-endian hex string.
36831 @itemx X @var{AA} ; process:@var{pid}
36832 The process terminated with signal @var{AA}.
36834 The second form of the response, including the process ID of the
36835 terminated process, can be used only when @value{GDBN} has reported
36836 support for multiprocess protocol extensions; see @ref{multiprocess
36837 extensions}. The @var{pid} is formatted as a big-endian hex string.
36839 @item O @var{XX}@dots{}
36840 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
36841 written as the program's console output. This can happen at any time
36842 while the program is running and the debugger should continue to wait
36843 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
36845 @item F @var{call-id},@var{parameter}@dots{}
36846 @var{call-id} is the identifier which says which host system call should
36847 be called. This is just the name of the function. Translation into the
36848 correct system call is only applicable as it's defined in @value{GDBN}.
36849 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
36852 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
36853 this very system call.
36855 The target replies with this packet when it expects @value{GDBN} to
36856 call a host system call on behalf of the target. @value{GDBN} replies
36857 with an appropriate @samp{F} packet and keeps up waiting for the next
36858 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
36859 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
36860 Protocol Extension}, for more details.
36864 @node General Query Packets
36865 @section General Query Packets
36866 @cindex remote query requests
36868 Packets starting with @samp{q} are @dfn{general query packets};
36869 packets starting with @samp{Q} are @dfn{general set packets}. General
36870 query and set packets are a semi-unified form for retrieving and
36871 sending information to and from the stub.
36873 The initial letter of a query or set packet is followed by a name
36874 indicating what sort of thing the packet applies to. For example,
36875 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
36876 definitions with the stub. These packet names follow some
36881 The name must not contain commas, colons or semicolons.
36883 Most @value{GDBN} query and set packets have a leading upper case
36886 The names of custom vendor packets should use a company prefix, in
36887 lower case, followed by a period. For example, packets designed at
36888 the Acme Corporation might begin with @samp{qacme.foo} (for querying
36889 foos) or @samp{Qacme.bar} (for setting bars).
36892 The name of a query or set packet should be separated from any
36893 parameters by a @samp{:}; the parameters themselves should be
36894 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
36895 full packet name, and check for a separator or the end of the packet,
36896 in case two packet names share a common prefix. New packets should not begin
36897 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
36898 packets predate these conventions, and have arguments without any terminator
36899 for the packet name; we suspect they are in widespread use in places that
36900 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
36901 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
36904 Like the descriptions of the other packets, each description here
36905 has a template showing the packet's overall syntax, followed by an
36906 explanation of the packet's meaning. We include spaces in some of the
36907 templates for clarity; these are not part of the packet's syntax. No
36908 @value{GDBN} packet uses spaces to separate its components.
36910 Here are the currently defined query and set packets:
36916 Turn on or off the agent as a helper to perform some debugging operations
36917 delegated from @value{GDBN} (@pxref{Control Agent}).
36919 @item QAllow:@var{op}:@var{val}@dots{}
36920 @cindex @samp{QAllow} packet
36921 Specify which operations @value{GDBN} expects to request of the
36922 target, as a semicolon-separated list of operation name and value
36923 pairs. Possible values for @var{op} include @samp{WriteReg},
36924 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
36925 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
36926 indicating that @value{GDBN} will not request the operation, or 1,
36927 indicating that it may. (The target can then use this to set up its
36928 own internals optimally, for instance if the debugger never expects to
36929 insert breakpoints, it may not need to install its own trap handler.)
36932 @cindex current thread, remote request
36933 @cindex @samp{qC} packet
36934 Return the current thread ID.
36938 @item QC @var{thread-id}
36939 Where @var{thread-id} is a thread ID as documented in
36940 @ref{thread-id syntax}.
36941 @item @r{(anything else)}
36942 Any other reply implies the old thread ID.
36945 @item qCRC:@var{addr},@var{length}
36946 @cindex CRC of memory block, remote request
36947 @cindex @samp{qCRC} packet
36948 Compute the CRC checksum of a block of memory using CRC-32 defined in
36949 IEEE 802.3. The CRC is computed byte at a time, taking the most
36950 significant bit of each byte first. The initial pattern code
36951 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
36953 @emph{Note:} This is the same CRC used in validating separate debug
36954 files (@pxref{Separate Debug Files, , Debugging Information in Separate
36955 Files}). However the algorithm is slightly different. When validating
36956 separate debug files, the CRC is computed taking the @emph{least}
36957 significant bit of each byte first, and the final result is inverted to
36958 detect trailing zeros.
36963 An error (such as memory fault)
36964 @item C @var{crc32}
36965 The specified memory region's checksum is @var{crc32}.
36968 @item QDisableRandomization:@var{value}
36969 @cindex disable address space randomization, remote request
36970 @cindex @samp{QDisableRandomization} packet
36971 Some target operating systems will randomize the virtual address space
36972 of the inferior process as a security feature, but provide a feature
36973 to disable such randomization, e.g.@: to allow for a more deterministic
36974 debugging experience. On such systems, this packet with a @var{value}
36975 of 1 directs the target to disable address space randomization for
36976 processes subsequently started via @samp{vRun} packets, while a packet
36977 with a @var{value} of 0 tells the target to enable address space
36980 This packet is only available in extended mode (@pxref{extended mode}).
36985 The request succeeded.
36988 An error occurred. @var{nn} are hex digits.
36991 An empty reply indicates that @samp{QDisableRandomization} is not supported
36995 This packet is not probed by default; the remote stub must request it,
36996 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36997 This should only be done on targets that actually support disabling
36998 address space randomization.
37001 @itemx qsThreadInfo
37002 @cindex list active threads, remote request
37003 @cindex @samp{qfThreadInfo} packet
37004 @cindex @samp{qsThreadInfo} packet
37005 Obtain a list of all active thread IDs from the target (OS). Since there
37006 may be too many active threads to fit into one reply packet, this query
37007 works iteratively: it may require more than one query/reply sequence to
37008 obtain the entire list of threads. The first query of the sequence will
37009 be the @samp{qfThreadInfo} query; subsequent queries in the
37010 sequence will be the @samp{qsThreadInfo} query.
37012 NOTE: This packet replaces the @samp{qL} query (see below).
37016 @item m @var{thread-id}
37018 @item m @var{thread-id},@var{thread-id}@dots{}
37019 a comma-separated list of thread IDs
37021 (lower case letter @samp{L}) denotes end of list.
37024 In response to each query, the target will reply with a list of one or
37025 more thread IDs, separated by commas.
37026 @value{GDBN} will respond to each reply with a request for more thread
37027 ids (using the @samp{qs} form of the query), until the target responds
37028 with @samp{l} (lower-case ell, for @dfn{last}).
37029 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
37032 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
37033 @cindex get thread-local storage address, remote request
37034 @cindex @samp{qGetTLSAddr} packet
37035 Fetch the address associated with thread local storage specified
37036 by @var{thread-id}, @var{offset}, and @var{lm}.
37038 @var{thread-id} is the thread ID associated with the
37039 thread for which to fetch the TLS address. @xref{thread-id syntax}.
37041 @var{offset} is the (big endian, hex encoded) offset associated with the
37042 thread local variable. (This offset is obtained from the debug
37043 information associated with the variable.)
37045 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
37046 load module associated with the thread local storage. For example,
37047 a @sc{gnu}/Linux system will pass the link map address of the shared
37048 object associated with the thread local storage under consideration.
37049 Other operating environments may choose to represent the load module
37050 differently, so the precise meaning of this parameter will vary.
37054 @item @var{XX}@dots{}
37055 Hex encoded (big endian) bytes representing the address of the thread
37056 local storage requested.
37059 An error occurred. @var{nn} are hex digits.
37062 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
37065 @item qGetTIBAddr:@var{thread-id}
37066 @cindex get thread information block address
37067 @cindex @samp{qGetTIBAddr} packet
37068 Fetch address of the Windows OS specific Thread Information Block.
37070 @var{thread-id} is the thread ID associated with the thread.
37074 @item @var{XX}@dots{}
37075 Hex encoded (big endian) bytes representing the linear address of the
37076 thread information block.
37079 An error occured. This means that either the thread was not found, or the
37080 address could not be retrieved.
37083 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
37086 @item qL @var{startflag} @var{threadcount} @var{nextthread}
37087 Obtain thread information from RTOS. Where: @var{startflag} (one hex
37088 digit) is one to indicate the first query and zero to indicate a
37089 subsequent query; @var{threadcount} (two hex digits) is the maximum
37090 number of threads the response packet can contain; and @var{nextthread}
37091 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
37092 returned in the response as @var{argthread}.
37094 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
37098 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
37099 Where: @var{count} (two hex digits) is the number of threads being
37100 returned; @var{done} (one hex digit) is zero to indicate more threads
37101 and one indicates no further threads; @var{argthreadid} (eight hex
37102 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
37103 is a sequence of thread IDs from the target. @var{threadid} (eight hex
37104 digits). See @code{remote.c:parse_threadlist_response()}.
37108 @cindex section offsets, remote request
37109 @cindex @samp{qOffsets} packet
37110 Get section offsets that the target used when relocating the downloaded
37115 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
37116 Relocate the @code{Text} section by @var{xxx} from its original address.
37117 Relocate the @code{Data} section by @var{yyy} from its original address.
37118 If the object file format provides segment information (e.g.@: @sc{elf}
37119 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
37120 segments by the supplied offsets.
37122 @emph{Note: while a @code{Bss} offset may be included in the response,
37123 @value{GDBN} ignores this and instead applies the @code{Data} offset
37124 to the @code{Bss} section.}
37126 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
37127 Relocate the first segment of the object file, which conventionally
37128 contains program code, to a starting address of @var{xxx}. If
37129 @samp{DataSeg} is specified, relocate the second segment, which
37130 conventionally contains modifiable data, to a starting address of
37131 @var{yyy}. @value{GDBN} will report an error if the object file
37132 does not contain segment information, or does not contain at least
37133 as many segments as mentioned in the reply. Extra segments are
37134 kept at fixed offsets relative to the last relocated segment.
37137 @item qP @var{mode} @var{thread-id}
37138 @cindex thread information, remote request
37139 @cindex @samp{qP} packet
37140 Returns information on @var{thread-id}. Where: @var{mode} is a hex
37141 encoded 32 bit mode; @var{thread-id} is a thread ID
37142 (@pxref{thread-id syntax}).
37144 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
37147 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
37151 @cindex non-stop mode, remote request
37152 @cindex @samp{QNonStop} packet
37154 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
37155 @xref{Remote Non-Stop}, for more information.
37160 The request succeeded.
37163 An error occurred. @var{nn} are hex digits.
37166 An empty reply indicates that @samp{QNonStop} is not supported by
37170 This packet is not probed by default; the remote stub must request it,
37171 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37172 Use of this packet is controlled by the @code{set non-stop} command;
37173 @pxref{Non-Stop Mode}.
37175 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37176 @cindex pass signals to inferior, remote request
37177 @cindex @samp{QPassSignals} packet
37178 @anchor{QPassSignals}
37179 Each listed @var{signal} should be passed directly to the inferior process.
37180 Signals are numbered identically to continue packets and stop replies
37181 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37182 strictly greater than the previous item. These signals do not need to stop
37183 the inferior, or be reported to @value{GDBN}. All other signals should be
37184 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
37185 combine; any earlier @samp{QPassSignals} list is completely replaced by the
37186 new list. This packet improves performance when using @samp{handle
37187 @var{signal} nostop noprint pass}.
37192 The request succeeded.
37195 An error occurred. @var{nn} are hex digits.
37198 An empty reply indicates that @samp{QPassSignals} is not supported by
37202 Use of this packet is controlled by the @code{set remote pass-signals}
37203 command (@pxref{Remote Configuration, set remote pass-signals}).
37204 This packet is not probed by default; the remote stub must request it,
37205 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37207 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37208 @cindex signals the inferior may see, remote request
37209 @cindex @samp{QProgramSignals} packet
37210 @anchor{QProgramSignals}
37211 Each listed @var{signal} may be delivered to the inferior process.
37212 Others should be silently discarded.
37214 In some cases, the remote stub may need to decide whether to deliver a
37215 signal to the program or not without @value{GDBN} involvement. One
37216 example of that is while detaching --- the program's threads may have
37217 stopped for signals that haven't yet had a chance of being reported to
37218 @value{GDBN}, and so the remote stub can use the signal list specified
37219 by this packet to know whether to deliver or ignore those pending
37222 This does not influence whether to deliver a signal as requested by a
37223 resumption packet (@pxref{vCont packet}).
37225 Signals are numbered identically to continue packets and stop replies
37226 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37227 strictly greater than the previous item. Multiple
37228 @samp{QProgramSignals} packets do not combine; any earlier
37229 @samp{QProgramSignals} list is completely replaced by the new list.
37234 The request succeeded.
37237 An error occurred. @var{nn} are hex digits.
37240 An empty reply indicates that @samp{QProgramSignals} is not supported
37244 Use of this packet is controlled by the @code{set remote program-signals}
37245 command (@pxref{Remote Configuration, set remote program-signals}).
37246 This packet is not probed by default; the remote stub must request it,
37247 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37249 @item qRcmd,@var{command}
37250 @cindex execute remote command, remote request
37251 @cindex @samp{qRcmd} packet
37252 @var{command} (hex encoded) is passed to the local interpreter for
37253 execution. Invalid commands should be reported using the output
37254 string. Before the final result packet, the target may also respond
37255 with a number of intermediate @samp{O@var{output}} console output
37256 packets. @emph{Implementors should note that providing access to a
37257 stubs's interpreter may have security implications}.
37262 A command response with no output.
37264 A command response with the hex encoded output string @var{OUTPUT}.
37266 Indicate a badly formed request.
37268 An empty reply indicates that @samp{qRcmd} is not recognized.
37271 (Note that the @code{qRcmd} packet's name is separated from the
37272 command by a @samp{,}, not a @samp{:}, contrary to the naming
37273 conventions above. Please don't use this packet as a model for new
37276 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
37277 @cindex searching memory, in remote debugging
37279 @cindex @samp{qSearch:memory} packet
37281 @cindex @samp{qSearch memory} packet
37282 @anchor{qSearch memory}
37283 Search @var{length} bytes at @var{address} for @var{search-pattern}.
37284 @var{address} and @var{length} are encoded in hex.
37285 @var{search-pattern} is a sequence of bytes, hex encoded.
37290 The pattern was not found.
37292 The pattern was found at @var{address}.
37294 A badly formed request or an error was encountered while searching memory.
37296 An empty reply indicates that @samp{qSearch:memory} is not recognized.
37299 @item QStartNoAckMode
37300 @cindex @samp{QStartNoAckMode} packet
37301 @anchor{QStartNoAckMode}
37302 Request that the remote stub disable the normal @samp{+}/@samp{-}
37303 protocol acknowledgments (@pxref{Packet Acknowledgment}).
37308 The stub has switched to no-acknowledgment mode.
37309 @value{GDBN} acknowledges this reponse,
37310 but neither the stub nor @value{GDBN} shall send or expect further
37311 @samp{+}/@samp{-} acknowledgments in the current connection.
37313 An empty reply indicates that the stub does not support no-acknowledgment mode.
37316 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
37317 @cindex supported packets, remote query
37318 @cindex features of the remote protocol
37319 @cindex @samp{qSupported} packet
37320 @anchor{qSupported}
37321 Tell the remote stub about features supported by @value{GDBN}, and
37322 query the stub for features it supports. This packet allows
37323 @value{GDBN} and the remote stub to take advantage of each others'
37324 features. @samp{qSupported} also consolidates multiple feature probes
37325 at startup, to improve @value{GDBN} performance---a single larger
37326 packet performs better than multiple smaller probe packets on
37327 high-latency links. Some features may enable behavior which must not
37328 be on by default, e.g.@: because it would confuse older clients or
37329 stubs. Other features may describe packets which could be
37330 automatically probed for, but are not. These features must be
37331 reported before @value{GDBN} will use them. This ``default
37332 unsupported'' behavior is not appropriate for all packets, but it
37333 helps to keep the initial connection time under control with new
37334 versions of @value{GDBN} which support increasing numbers of packets.
37338 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
37339 The stub supports or does not support each returned @var{stubfeature},
37340 depending on the form of each @var{stubfeature} (see below for the
37343 An empty reply indicates that @samp{qSupported} is not recognized,
37344 or that no features needed to be reported to @value{GDBN}.
37347 The allowed forms for each feature (either a @var{gdbfeature} in the
37348 @samp{qSupported} packet, or a @var{stubfeature} in the response)
37352 @item @var{name}=@var{value}
37353 The remote protocol feature @var{name} is supported, and associated
37354 with the specified @var{value}. The format of @var{value} depends
37355 on the feature, but it must not include a semicolon.
37357 The remote protocol feature @var{name} is supported, and does not
37358 need an associated value.
37360 The remote protocol feature @var{name} is not supported.
37362 The remote protocol feature @var{name} may be supported, and
37363 @value{GDBN} should auto-detect support in some other way when it is
37364 needed. This form will not be used for @var{gdbfeature} notifications,
37365 but may be used for @var{stubfeature} responses.
37368 Whenever the stub receives a @samp{qSupported} request, the
37369 supplied set of @value{GDBN} features should override any previous
37370 request. This allows @value{GDBN} to put the stub in a known
37371 state, even if the stub had previously been communicating with
37372 a different version of @value{GDBN}.
37374 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
37379 This feature indicates whether @value{GDBN} supports multiprocess
37380 extensions to the remote protocol. @value{GDBN} does not use such
37381 extensions unless the stub also reports that it supports them by
37382 including @samp{multiprocess+} in its @samp{qSupported} reply.
37383 @xref{multiprocess extensions}, for details.
37386 This feature indicates that @value{GDBN} supports the XML target
37387 description. If the stub sees @samp{xmlRegisters=} with target
37388 specific strings separated by a comma, it will report register
37392 This feature indicates whether @value{GDBN} supports the
37393 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
37394 instruction reply packet}).
37397 Stubs should ignore any unknown values for
37398 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
37399 packet supports receiving packets of unlimited length (earlier
37400 versions of @value{GDBN} may reject overly long responses). Additional values
37401 for @var{gdbfeature} may be defined in the future to let the stub take
37402 advantage of new features in @value{GDBN}, e.g.@: incompatible
37403 improvements in the remote protocol---the @samp{multiprocess} feature is
37404 an example of such a feature. The stub's reply should be independent
37405 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
37406 describes all the features it supports, and then the stub replies with
37407 all the features it supports.
37409 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
37410 responses, as long as each response uses one of the standard forms.
37412 Some features are flags. A stub which supports a flag feature
37413 should respond with a @samp{+} form response. Other features
37414 require values, and the stub should respond with an @samp{=}
37417 Each feature has a default value, which @value{GDBN} will use if
37418 @samp{qSupported} is not available or if the feature is not mentioned
37419 in the @samp{qSupported} response. The default values are fixed; a
37420 stub is free to omit any feature responses that match the defaults.
37422 Not all features can be probed, but for those which can, the probing
37423 mechanism is useful: in some cases, a stub's internal
37424 architecture may not allow the protocol layer to know some information
37425 about the underlying target in advance. This is especially common in
37426 stubs which may be configured for multiple targets.
37428 These are the currently defined stub features and their properties:
37430 @multitable @columnfractions 0.35 0.2 0.12 0.2
37431 @c NOTE: The first row should be @headitem, but we do not yet require
37432 @c a new enough version of Texinfo (4.7) to use @headitem.
37434 @tab Value Required
37438 @item @samp{PacketSize}
37443 @item @samp{qXfer:auxv:read}
37448 @item @samp{qXfer:btrace:read}
37453 @item @samp{qXfer:features:read}
37458 @item @samp{qXfer:libraries:read}
37463 @item @samp{qXfer:memory-map:read}
37468 @item @samp{qXfer:sdata:read}
37473 @item @samp{qXfer:spu:read}
37478 @item @samp{qXfer:spu:write}
37483 @item @samp{qXfer:siginfo:read}
37488 @item @samp{qXfer:siginfo:write}
37493 @item @samp{qXfer:threads:read}
37498 @item @samp{qXfer:traceframe-info:read}
37503 @item @samp{qXfer:uib:read}
37508 @item @samp{qXfer:fdpic:read}
37513 @item @samp{Qbtrace:off}
37518 @item @samp{Qbtrace:bts}
37523 @item @samp{QNonStop}
37528 @item @samp{QPassSignals}
37533 @item @samp{QStartNoAckMode}
37538 @item @samp{multiprocess}
37543 @item @samp{ConditionalBreakpoints}
37548 @item @samp{ConditionalTracepoints}
37553 @item @samp{ReverseContinue}
37558 @item @samp{ReverseStep}
37563 @item @samp{TracepointSource}
37568 @item @samp{QAgent}
37573 @item @samp{QAllow}
37578 @item @samp{QDisableRandomization}
37583 @item @samp{EnableDisableTracepoints}
37588 @item @samp{QTBuffer:size}
37593 @item @samp{tracenz}
37598 @item @samp{BreakpointCommands}
37605 These are the currently defined stub features, in more detail:
37608 @cindex packet size, remote protocol
37609 @item PacketSize=@var{bytes}
37610 The remote stub can accept packets up to at least @var{bytes} in
37611 length. @value{GDBN} will send packets up to this size for bulk
37612 transfers, and will never send larger packets. This is a limit on the
37613 data characters in the packet, including the frame and checksum.
37614 There is no trailing NUL byte in a remote protocol packet; if the stub
37615 stores packets in a NUL-terminated format, it should allow an extra
37616 byte in its buffer for the NUL. If this stub feature is not supported,
37617 @value{GDBN} guesses based on the size of the @samp{g} packet response.
37619 @item qXfer:auxv:read
37620 The remote stub understands the @samp{qXfer:auxv:read} packet
37621 (@pxref{qXfer auxiliary vector read}).
37623 @item qXfer:btrace:read
37624 The remote stub understands the @samp{qXfer:btrace:read}
37625 packet (@pxref{qXfer btrace read}).
37627 @item qXfer:features:read
37628 The remote stub understands the @samp{qXfer:features:read} packet
37629 (@pxref{qXfer target description read}).
37631 @item qXfer:libraries:read
37632 The remote stub understands the @samp{qXfer:libraries:read} packet
37633 (@pxref{qXfer library list read}).
37635 @item qXfer:libraries-svr4:read
37636 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
37637 (@pxref{qXfer svr4 library list read}).
37639 @item qXfer:memory-map:read
37640 The remote stub understands the @samp{qXfer:memory-map:read} packet
37641 (@pxref{qXfer memory map read}).
37643 @item qXfer:sdata:read
37644 The remote stub understands the @samp{qXfer:sdata:read} packet
37645 (@pxref{qXfer sdata read}).
37647 @item qXfer:spu:read
37648 The remote stub understands the @samp{qXfer:spu:read} packet
37649 (@pxref{qXfer spu read}).
37651 @item qXfer:spu:write
37652 The remote stub understands the @samp{qXfer:spu:write} packet
37653 (@pxref{qXfer spu write}).
37655 @item qXfer:siginfo:read
37656 The remote stub understands the @samp{qXfer:siginfo:read} packet
37657 (@pxref{qXfer siginfo read}).
37659 @item qXfer:siginfo:write
37660 The remote stub understands the @samp{qXfer:siginfo:write} packet
37661 (@pxref{qXfer siginfo write}).
37663 @item qXfer:threads:read
37664 The remote stub understands the @samp{qXfer:threads:read} packet
37665 (@pxref{qXfer threads read}).
37667 @item qXfer:traceframe-info:read
37668 The remote stub understands the @samp{qXfer:traceframe-info:read}
37669 packet (@pxref{qXfer traceframe info read}).
37671 @item qXfer:uib:read
37672 The remote stub understands the @samp{qXfer:uib:read}
37673 packet (@pxref{qXfer unwind info block}).
37675 @item qXfer:fdpic:read
37676 The remote stub understands the @samp{qXfer:fdpic:read}
37677 packet (@pxref{qXfer fdpic loadmap read}).
37680 The remote stub understands the @samp{QNonStop} packet
37681 (@pxref{QNonStop}).
37684 The remote stub understands the @samp{QPassSignals} packet
37685 (@pxref{QPassSignals}).
37687 @item QStartNoAckMode
37688 The remote stub understands the @samp{QStartNoAckMode} packet and
37689 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
37692 @anchor{multiprocess extensions}
37693 @cindex multiprocess extensions, in remote protocol
37694 The remote stub understands the multiprocess extensions to the remote
37695 protocol syntax. The multiprocess extensions affect the syntax of
37696 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
37697 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
37698 replies. Note that reporting this feature indicates support for the
37699 syntactic extensions only, not that the stub necessarily supports
37700 debugging of more than one process at a time. The stub must not use
37701 multiprocess extensions in packet replies unless @value{GDBN} has also
37702 indicated it supports them in its @samp{qSupported} request.
37704 @item qXfer:osdata:read
37705 The remote stub understands the @samp{qXfer:osdata:read} packet
37706 ((@pxref{qXfer osdata read}).
37708 @item ConditionalBreakpoints
37709 The target accepts and implements evaluation of conditional expressions
37710 defined for breakpoints. The target will only report breakpoint triggers
37711 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
37713 @item ConditionalTracepoints
37714 The remote stub accepts and implements conditional expressions defined
37715 for tracepoints (@pxref{Tracepoint Conditions}).
37717 @item ReverseContinue
37718 The remote stub accepts and implements the reverse continue packet
37722 The remote stub accepts and implements the reverse step packet
37725 @item TracepointSource
37726 The remote stub understands the @samp{QTDPsrc} packet that supplies
37727 the source form of tracepoint definitions.
37730 The remote stub understands the @samp{QAgent} packet.
37733 The remote stub understands the @samp{QAllow} packet.
37735 @item QDisableRandomization
37736 The remote stub understands the @samp{QDisableRandomization} packet.
37738 @item StaticTracepoint
37739 @cindex static tracepoints, in remote protocol
37740 The remote stub supports static tracepoints.
37742 @item InstallInTrace
37743 @anchor{install tracepoint in tracing}
37744 The remote stub supports installing tracepoint in tracing.
37746 @item EnableDisableTracepoints
37747 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
37748 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
37749 to be enabled and disabled while a trace experiment is running.
37751 @item QTBuffer:size
37752 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
37753 packet that allows to change the size of the trace buffer.
37756 @cindex string tracing, in remote protocol
37757 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
37758 See @ref{Bytecode Descriptions} for details about the bytecode.
37760 @item BreakpointCommands
37761 @cindex breakpoint commands, in remote protocol
37762 The remote stub supports running a breakpoint's command list itself,
37763 rather than reporting the hit to @value{GDBN}.
37766 The remote stub understands the @samp{Qbtrace:off} packet.
37769 The remote stub understands the @samp{Qbtrace:bts} packet.
37774 @cindex symbol lookup, remote request
37775 @cindex @samp{qSymbol} packet
37776 Notify the target that @value{GDBN} is prepared to serve symbol lookup
37777 requests. Accept requests from the target for the values of symbols.
37782 The target does not need to look up any (more) symbols.
37783 @item qSymbol:@var{sym_name}
37784 The target requests the value of symbol @var{sym_name} (hex encoded).
37785 @value{GDBN} may provide the value by using the
37786 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
37790 @item qSymbol:@var{sym_value}:@var{sym_name}
37791 Set the value of @var{sym_name} to @var{sym_value}.
37793 @var{sym_name} (hex encoded) is the name of a symbol whose value the
37794 target has previously requested.
37796 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
37797 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
37803 The target does not need to look up any (more) symbols.
37804 @item qSymbol:@var{sym_name}
37805 The target requests the value of a new symbol @var{sym_name} (hex
37806 encoded). @value{GDBN} will continue to supply the values of symbols
37807 (if available), until the target ceases to request them.
37812 @itemx QTDisconnected
37819 @itemx qTMinFTPILen
37821 @xref{Tracepoint Packets}.
37823 @item qThreadExtraInfo,@var{thread-id}
37824 @cindex thread attributes info, remote request
37825 @cindex @samp{qThreadExtraInfo} packet
37826 Obtain a printable string description of a thread's attributes from
37827 the target OS. @var{thread-id} is a thread ID;
37828 see @ref{thread-id syntax}. This
37829 string may contain anything that the target OS thinks is interesting
37830 for @value{GDBN} to tell the user about the thread. The string is
37831 displayed in @value{GDBN}'s @code{info threads} display. Some
37832 examples of possible thread extra info strings are @samp{Runnable}, or
37833 @samp{Blocked on Mutex}.
37837 @item @var{XX}@dots{}
37838 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
37839 comprising the printable string containing the extra information about
37840 the thread's attributes.
37843 (Note that the @code{qThreadExtraInfo} packet's name is separated from
37844 the command by a @samp{,}, not a @samp{:}, contrary to the naming
37845 conventions above. Please don't use this packet as a model for new
37864 @xref{Tracepoint Packets}.
37866 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
37867 @cindex read special object, remote request
37868 @cindex @samp{qXfer} packet
37869 @anchor{qXfer read}
37870 Read uninterpreted bytes from the target's special data area
37871 identified by the keyword @var{object}. Request @var{length} bytes
37872 starting at @var{offset} bytes into the data. The content and
37873 encoding of @var{annex} is specific to @var{object}; it can supply
37874 additional details about what data to access.
37876 Here are the specific requests of this form defined so far. All
37877 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
37878 formats, listed below.
37881 @item qXfer:auxv:read::@var{offset},@var{length}
37882 @anchor{qXfer auxiliary vector read}
37883 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
37884 auxiliary vector}. Note @var{annex} must be empty.
37886 This packet is not probed by default; the remote stub must request it,
37887 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37889 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
37890 @anchor{qXfer btrace read}
37892 Return a description of the current branch trace.
37893 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
37894 packet may have one of the following values:
37898 Returns all available branch trace.
37901 Returns all available branch trace if the branch trace changed since
37902 the last read request.
37905 This packet is not probed by default; the remote stub must request it
37906 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37908 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
37909 @anchor{qXfer target description read}
37910 Access the @dfn{target description}. @xref{Target Descriptions}. The
37911 annex specifies which XML document to access. The main description is
37912 always loaded from the @samp{target.xml} annex.
37914 This packet is not probed by default; the remote stub must request it,
37915 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37917 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
37918 @anchor{qXfer library list read}
37919 Access the target's list of loaded libraries. @xref{Library List Format}.
37920 The annex part of the generic @samp{qXfer} packet must be empty
37921 (@pxref{qXfer read}).
37923 Targets which maintain a list of libraries in the program's memory do
37924 not need to implement this packet; it is designed for platforms where
37925 the operating system manages the list of loaded libraries.
37927 This packet is not probed by default; the remote stub must request it,
37928 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37930 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
37931 @anchor{qXfer svr4 library list read}
37932 Access the target's list of loaded libraries when the target is an SVR4
37933 platform. @xref{Library List Format for SVR4 Targets}. The annex part
37934 of the generic @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37936 This packet is optional for better performance on SVR4 targets.
37937 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
37939 This packet is not probed by default; the remote stub must request it,
37940 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37942 @item qXfer:memory-map:read::@var{offset},@var{length}
37943 @anchor{qXfer memory map read}
37944 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
37945 annex part of the generic @samp{qXfer} packet must be empty
37946 (@pxref{qXfer read}).
37948 This packet is not probed by default; the remote stub must request it,
37949 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37951 @item qXfer:sdata:read::@var{offset},@var{length}
37952 @anchor{qXfer sdata read}
37954 Read contents of the extra collected static tracepoint marker
37955 information. The annex part of the generic @samp{qXfer} packet must
37956 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
37959 This packet is not probed by default; the remote stub must request it,
37960 by supplying an appropriate @samp{qSupported} response
37961 (@pxref{qSupported}).
37963 @item qXfer:siginfo:read::@var{offset},@var{length}
37964 @anchor{qXfer siginfo read}
37965 Read contents of the extra signal information on the target
37966 system. The annex part of the generic @samp{qXfer} packet must be
37967 empty (@pxref{qXfer read}).
37969 This packet is not probed by default; the remote stub must request it,
37970 by supplying an appropriate @samp{qSupported} response
37971 (@pxref{qSupported}).
37973 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
37974 @anchor{qXfer spu read}
37975 Read contents of an @code{spufs} file on the target system. The
37976 annex specifies which file to read; it must be of the form
37977 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37978 in the target process, and @var{name} identifes the @code{spufs} file
37979 in that context to be accessed.
37981 This packet is not probed by default; the remote stub must request it,
37982 by supplying an appropriate @samp{qSupported} response
37983 (@pxref{qSupported}).
37985 @item qXfer:threads:read::@var{offset},@var{length}
37986 @anchor{qXfer threads read}
37987 Access the list of threads on target. @xref{Thread List Format}. The
37988 annex part of the generic @samp{qXfer} packet must be empty
37989 (@pxref{qXfer read}).
37991 This packet is not probed by default; the remote stub must request it,
37992 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37994 @item qXfer:traceframe-info:read::@var{offset},@var{length}
37995 @anchor{qXfer traceframe info read}
37997 Return a description of the current traceframe's contents.
37998 @xref{Traceframe Info Format}. The annex part of the generic
37999 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
38001 This packet is not probed by default; the remote stub must request it,
38002 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38004 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
38005 @anchor{qXfer unwind info block}
38007 Return the unwind information block for @var{pc}. This packet is used
38008 on OpenVMS/ia64 to ask the kernel unwind information.
38010 This packet is not probed by default.
38012 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
38013 @anchor{qXfer fdpic loadmap read}
38014 Read contents of @code{loadmap}s on the target system. The
38015 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
38016 executable @code{loadmap} or interpreter @code{loadmap} to read.
38018 This packet is not probed by default; the remote stub must request it,
38019 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38021 @item qXfer:osdata:read::@var{offset},@var{length}
38022 @anchor{qXfer osdata read}
38023 Access the target's @dfn{operating system information}.
38024 @xref{Operating System Information}.
38031 Data @var{data} (@pxref{Binary Data}) has been read from the
38032 target. There may be more data at a higher address (although
38033 it is permitted to return @samp{m} even for the last valid
38034 block of data, as long as at least one byte of data was read).
38035 @var{data} may have fewer bytes than the @var{length} in the
38039 Data @var{data} (@pxref{Binary Data}) has been read from the target.
38040 There is no more data to be read. @var{data} may have fewer bytes
38041 than the @var{length} in the request.
38044 The @var{offset} in the request is at the end of the data.
38045 There is no more data to be read.
38048 The request was malformed, or @var{annex} was invalid.
38051 The offset was invalid, or there was an error encountered reading the data.
38052 @var{nn} is a hex-encoded @code{errno} value.
38055 An empty reply indicates the @var{object} string was not recognized by
38056 the stub, or that the object does not support reading.
38059 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
38060 @cindex write data into object, remote request
38061 @anchor{qXfer write}
38062 Write uninterpreted bytes into the target's special data area
38063 identified by the keyword @var{object}, starting at @var{offset} bytes
38064 into the data. @var{data}@dots{} is the binary-encoded data
38065 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
38066 is specific to @var{object}; it can supply additional details about what data
38069 Here are the specific requests of this form defined so far. All
38070 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
38071 formats, listed below.
38074 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
38075 @anchor{qXfer siginfo write}
38076 Write @var{data} to the extra signal information on the target system.
38077 The annex part of the generic @samp{qXfer} packet must be
38078 empty (@pxref{qXfer write}).
38080 This packet is not probed by default; the remote stub must request it,
38081 by supplying an appropriate @samp{qSupported} response
38082 (@pxref{qSupported}).
38084 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
38085 @anchor{qXfer spu write}
38086 Write @var{data} to an @code{spufs} file on the target system. The
38087 annex specifies which file to write; it must be of the form
38088 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
38089 in the target process, and @var{name} identifes the @code{spufs} file
38090 in that context to be accessed.
38092 This packet is not probed by default; the remote stub must request it,
38093 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38099 @var{nn} (hex encoded) is the number of bytes written.
38100 This may be fewer bytes than supplied in the request.
38103 The request was malformed, or @var{annex} was invalid.
38106 The offset was invalid, or there was an error encountered writing the data.
38107 @var{nn} is a hex-encoded @code{errno} value.
38110 An empty reply indicates the @var{object} string was not
38111 recognized by the stub, or that the object does not support writing.
38114 @item qXfer:@var{object}:@var{operation}:@dots{}
38115 Requests of this form may be added in the future. When a stub does
38116 not recognize the @var{object} keyword, or its support for
38117 @var{object} does not recognize the @var{operation} keyword, the stub
38118 must respond with an empty packet.
38120 @item qAttached:@var{pid}
38121 @cindex query attached, remote request
38122 @cindex @samp{qAttached} packet
38123 Return an indication of whether the remote server attached to an
38124 existing process or created a new process. When the multiprocess
38125 protocol extensions are supported (@pxref{multiprocess extensions}),
38126 @var{pid} is an integer in hexadecimal format identifying the target
38127 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
38128 the query packet will be simplified as @samp{qAttached}.
38130 This query is used, for example, to know whether the remote process
38131 should be detached or killed when a @value{GDBN} session is ended with
38132 the @code{quit} command.
38137 The remote server attached to an existing process.
38139 The remote server created a new process.
38141 A badly formed request or an error was encountered.
38145 Enable branch tracing for the current thread using bts tracing.
38150 Branch tracing has been enabled.
38152 A badly formed request or an error was encountered.
38156 Disable branch tracing for the current thread.
38161 Branch tracing has been disabled.
38163 A badly formed request or an error was encountered.
38168 @node Architecture-Specific Protocol Details
38169 @section Architecture-Specific Protocol Details
38171 This section describes how the remote protocol is applied to specific
38172 target architectures. Also see @ref{Standard Target Features}, for
38173 details of XML target descriptions for each architecture.
38176 * ARM-Specific Protocol Details::
38177 * MIPS-Specific Protocol Details::
38180 @node ARM-Specific Protocol Details
38181 @subsection @acronym{ARM}-specific Protocol Details
38184 * ARM Breakpoint Kinds::
38187 @node ARM Breakpoint Kinds
38188 @subsubsection @acronym{ARM} Breakpoint Kinds
38189 @cindex breakpoint kinds, @acronym{ARM}
38191 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38196 16-bit Thumb mode breakpoint.
38199 32-bit Thumb mode (Thumb-2) breakpoint.
38202 32-bit @acronym{ARM} mode breakpoint.
38206 @node MIPS-Specific Protocol Details
38207 @subsection @acronym{MIPS}-specific Protocol Details
38210 * MIPS Register packet Format::
38211 * MIPS Breakpoint Kinds::
38214 @node MIPS Register packet Format
38215 @subsubsection @acronym{MIPS} Register Packet Format
38216 @cindex register packet format, @acronym{MIPS}
38218 The following @code{g}/@code{G} packets have previously been defined.
38219 In the below, some thirty-two bit registers are transferred as
38220 sixty-four bits. Those registers should be zero/sign extended (which?)
38221 to fill the space allocated. Register bytes are transferred in target
38222 byte order. The two nibbles within a register byte are transferred
38223 most-significant -- least-significant.
38228 All registers are transferred as thirty-two bit quantities in the order:
38229 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
38230 registers; fsr; fir; fp.
38233 All registers are transferred as sixty-four bit quantities (including
38234 thirty-two bit registers such as @code{sr}). The ordering is the same
38239 @node MIPS Breakpoint Kinds
38240 @subsubsection @acronym{MIPS} Breakpoint Kinds
38241 @cindex breakpoint kinds, @acronym{MIPS}
38243 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38248 16-bit @acronym{MIPS16} mode breakpoint.
38251 16-bit @acronym{microMIPS} mode breakpoint.
38254 32-bit standard @acronym{MIPS} mode breakpoint.
38257 32-bit @acronym{microMIPS} mode breakpoint.
38261 @node Tracepoint Packets
38262 @section Tracepoint Packets
38263 @cindex tracepoint packets
38264 @cindex packets, tracepoint
38266 Here we describe the packets @value{GDBN} uses to implement
38267 tracepoints (@pxref{Tracepoints}).
38271 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
38272 @cindex @samp{QTDP} packet
38273 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
38274 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
38275 the tracepoint is disabled. @var{step} is the tracepoint's step
38276 count, and @var{pass} is its pass count. If an @samp{F} is present,
38277 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
38278 the number of bytes that the target should copy elsewhere to make room
38279 for the tracepoint. If an @samp{X} is present, it introduces a
38280 tracepoint condition, which consists of a hexadecimal length, followed
38281 by a comma and hex-encoded bytes, in a manner similar to action
38282 encodings as described below. If the trailing @samp{-} is present,
38283 further @samp{QTDP} packets will follow to specify this tracepoint's
38289 The packet was understood and carried out.
38291 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38293 The packet was not recognized.
38296 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
38297 Define actions to be taken when a tracepoint is hit. @var{n} and
38298 @var{addr} must be the same as in the initial @samp{QTDP} packet for
38299 this tracepoint. This packet may only be sent immediately after
38300 another @samp{QTDP} packet that ended with a @samp{-}. If the
38301 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
38302 specifying more actions for this tracepoint.
38304 In the series of action packets for a given tracepoint, at most one
38305 can have an @samp{S} before its first @var{action}. If such a packet
38306 is sent, it and the following packets define ``while-stepping''
38307 actions. Any prior packets define ordinary actions --- that is, those
38308 taken when the tracepoint is first hit. If no action packet has an
38309 @samp{S}, then all the packets in the series specify ordinary
38310 tracepoint actions.
38312 The @samp{@var{action}@dots{}} portion of the packet is a series of
38313 actions, concatenated without separators. Each action has one of the
38319 Collect the registers whose bits are set in @var{mask}. @var{mask} is
38320 a hexadecimal number whose @var{i}'th bit is set if register number
38321 @var{i} should be collected. (The least significant bit is numbered
38322 zero.) Note that @var{mask} may be any number of digits long; it may
38323 not fit in a 32-bit word.
38325 @item M @var{basereg},@var{offset},@var{len}
38326 Collect @var{len} bytes of memory starting at the address in register
38327 number @var{basereg}, plus @var{offset}. If @var{basereg} is
38328 @samp{-1}, then the range has a fixed address: @var{offset} is the
38329 address of the lowest byte to collect. The @var{basereg},
38330 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
38331 values (the @samp{-1} value for @var{basereg} is a special case).
38333 @item X @var{len},@var{expr}
38334 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
38335 it directs. @var{expr} is an agent expression, as described in
38336 @ref{Agent Expressions}. Each byte of the expression is encoded as a
38337 two-digit hex number in the packet; @var{len} is the number of bytes
38338 in the expression (and thus one-half the number of hex digits in the
38343 Any number of actions may be packed together in a single @samp{QTDP}
38344 packet, as long as the packet does not exceed the maximum packet
38345 length (400 bytes, for many stubs). There may be only one @samp{R}
38346 action per tracepoint, and it must precede any @samp{M} or @samp{X}
38347 actions. Any registers referred to by @samp{M} and @samp{X} actions
38348 must be collected by a preceding @samp{R} action. (The
38349 ``while-stepping'' actions are treated as if they were attached to a
38350 separate tracepoint, as far as these restrictions are concerned.)
38355 The packet was understood and carried out.
38357 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38359 The packet was not recognized.
38362 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
38363 @cindex @samp{QTDPsrc} packet
38364 Specify a source string of tracepoint @var{n} at address @var{addr}.
38365 This is useful to get accurate reproduction of the tracepoints
38366 originally downloaded at the beginning of the trace run. @var{type}
38367 is the name of the tracepoint part, such as @samp{cond} for the
38368 tracepoint's conditional expression (see below for a list of types), while
38369 @var{bytes} is the string, encoded in hexadecimal.
38371 @var{start} is the offset of the @var{bytes} within the overall source
38372 string, while @var{slen} is the total length of the source string.
38373 This is intended for handling source strings that are longer than will
38374 fit in a single packet.
38375 @c Add detailed example when this info is moved into a dedicated
38376 @c tracepoint descriptions section.
38378 The available string types are @samp{at} for the location,
38379 @samp{cond} for the conditional, and @samp{cmd} for an action command.
38380 @value{GDBN} sends a separate packet for each command in the action
38381 list, in the same order in which the commands are stored in the list.
38383 The target does not need to do anything with source strings except
38384 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
38387 Although this packet is optional, and @value{GDBN} will only send it
38388 if the target replies with @samp{TracepointSource} @xref{General
38389 Query Packets}, it makes both disconnected tracing and trace files
38390 much easier to use. Otherwise the user must be careful that the
38391 tracepoints in effect while looking at trace frames are identical to
38392 the ones in effect during the trace run; even a small discrepancy
38393 could cause @samp{tdump} not to work, or a particular trace frame not
38396 @item QTDV:@var{n}:@var{value}
38397 @cindex define trace state variable, remote request
38398 @cindex @samp{QTDV} packet
38399 Create a new trace state variable, number @var{n}, with an initial
38400 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
38401 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
38402 the option of not using this packet for initial values of zero; the
38403 target should simply create the trace state variables as they are
38404 mentioned in expressions.
38406 @item QTFrame:@var{n}
38407 @cindex @samp{QTFrame} packet
38408 Select the @var{n}'th tracepoint frame from the buffer, and use the
38409 register and memory contents recorded there to answer subsequent
38410 request packets from @value{GDBN}.
38412 A successful reply from the stub indicates that the stub has found the
38413 requested frame. The response is a series of parts, concatenated
38414 without separators, describing the frame we selected. Each part has
38415 one of the following forms:
38419 The selected frame is number @var{n} in the trace frame buffer;
38420 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
38421 was no frame matching the criteria in the request packet.
38424 The selected trace frame records a hit of tracepoint number @var{t};
38425 @var{t} is a hexadecimal number.
38429 @item QTFrame:pc:@var{addr}
38430 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38431 currently selected frame whose PC is @var{addr};
38432 @var{addr} is a hexadecimal number.
38434 @item QTFrame:tdp:@var{t}
38435 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38436 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
38437 is a hexadecimal number.
38439 @item QTFrame:range:@var{start}:@var{end}
38440 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38441 currently selected frame whose PC is between @var{start} (inclusive)
38442 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
38445 @item QTFrame:outside:@var{start}:@var{end}
38446 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
38447 frame @emph{outside} the given range of addresses (exclusive).
38450 @cindex @samp{qTMinFTPILen} packet
38451 This packet requests the minimum length of instruction at which a fast
38452 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
38453 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
38454 it depends on the target system being able to create trampolines in
38455 the first 64K of memory, which might or might not be possible for that
38456 system. So the reply to this packet will be 4 if it is able to
38463 The minimum instruction length is currently unknown.
38465 The minimum instruction length is @var{length}, where @var{length} is greater
38466 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
38467 that a fast tracepoint may be placed on any instruction regardless of size.
38469 An error has occurred.
38471 An empty reply indicates that the request is not supported by the stub.
38475 @cindex @samp{QTStart} packet
38476 Begin the tracepoint experiment. Begin collecting data from
38477 tracepoint hits in the trace frame buffer. This packet supports the
38478 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
38479 instruction reply packet}).
38482 @cindex @samp{QTStop} packet
38483 End the tracepoint experiment. Stop collecting trace frames.
38485 @item QTEnable:@var{n}:@var{addr}
38487 @cindex @samp{QTEnable} packet
38488 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
38489 experiment. If the tracepoint was previously disabled, then collection
38490 of data from it will resume.
38492 @item QTDisable:@var{n}:@var{addr}
38494 @cindex @samp{QTDisable} packet
38495 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
38496 experiment. No more data will be collected from the tracepoint unless
38497 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
38500 @cindex @samp{QTinit} packet
38501 Clear the table of tracepoints, and empty the trace frame buffer.
38503 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
38504 @cindex @samp{QTro} packet
38505 Establish the given ranges of memory as ``transparent''. The stub
38506 will answer requests for these ranges from memory's current contents,
38507 if they were not collected as part of the tracepoint hit.
38509 @value{GDBN} uses this to mark read-only regions of memory, like those
38510 containing program code. Since these areas never change, they should
38511 still have the same contents they did when the tracepoint was hit, so
38512 there's no reason for the stub to refuse to provide their contents.
38514 @item QTDisconnected:@var{value}
38515 @cindex @samp{QTDisconnected} packet
38516 Set the choice to what to do with the tracing run when @value{GDBN}
38517 disconnects from the target. A @var{value} of 1 directs the target to
38518 continue the tracing run, while 0 tells the target to stop tracing if
38519 @value{GDBN} is no longer in the picture.
38522 @cindex @samp{qTStatus} packet
38523 Ask the stub if there is a trace experiment running right now.
38525 The reply has the form:
38529 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
38530 @var{running} is a single digit @code{1} if the trace is presently
38531 running, or @code{0} if not. It is followed by semicolon-separated
38532 optional fields that an agent may use to report additional status.
38536 If the trace is not running, the agent may report any of several
38537 explanations as one of the optional fields:
38542 No trace has been run yet.
38544 @item tstop[:@var{text}]:0
38545 The trace was stopped by a user-originated stop command. The optional
38546 @var{text} field is a user-supplied string supplied as part of the
38547 stop command (for instance, an explanation of why the trace was
38548 stopped manually). It is hex-encoded.
38551 The trace stopped because the trace buffer filled up.
38553 @item tdisconnected:0
38554 The trace stopped because @value{GDBN} disconnected from the target.
38556 @item tpasscount:@var{tpnum}
38557 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
38559 @item terror:@var{text}:@var{tpnum}
38560 The trace stopped because tracepoint @var{tpnum} had an error. The
38561 string @var{text} is available to describe the nature of the error
38562 (for instance, a divide by zero in the condition expression).
38563 @var{text} is hex encoded.
38566 The trace stopped for some other reason.
38570 Additional optional fields supply statistical and other information.
38571 Although not required, they are extremely useful for users monitoring
38572 the progress of a trace run. If a trace has stopped, and these
38573 numbers are reported, they must reflect the state of the just-stopped
38578 @item tframes:@var{n}
38579 The number of trace frames in the buffer.
38581 @item tcreated:@var{n}
38582 The total number of trace frames created during the run. This may
38583 be larger than the trace frame count, if the buffer is circular.
38585 @item tsize:@var{n}
38586 The total size of the trace buffer, in bytes.
38588 @item tfree:@var{n}
38589 The number of bytes still unused in the buffer.
38591 @item circular:@var{n}
38592 The value of the circular trace buffer flag. @code{1} means that the
38593 trace buffer is circular and old trace frames will be discarded if
38594 necessary to make room, @code{0} means that the trace buffer is linear
38597 @item disconn:@var{n}
38598 The value of the disconnected tracing flag. @code{1} means that
38599 tracing will continue after @value{GDBN} disconnects, @code{0} means
38600 that the trace run will stop.
38604 @item qTP:@var{tp}:@var{addr}
38605 @cindex tracepoint status, remote request
38606 @cindex @samp{qTP} packet
38607 Ask the stub for the current state of tracepoint number @var{tp} at
38608 address @var{addr}.
38612 @item V@var{hits}:@var{usage}
38613 The tracepoint has been hit @var{hits} times so far during the trace
38614 run, and accounts for @var{usage} in the trace buffer. Note that
38615 @code{while-stepping} steps are not counted as separate hits, but the
38616 steps' space consumption is added into the usage number.
38620 @item qTV:@var{var}
38621 @cindex trace state variable value, remote request
38622 @cindex @samp{qTV} packet
38623 Ask the stub for the value of the trace state variable number @var{var}.
38628 The value of the variable is @var{value}. This will be the current
38629 value of the variable if the user is examining a running target, or a
38630 saved value if the variable was collected in the trace frame that the
38631 user is looking at. Note that multiple requests may result in
38632 different reply values, such as when requesting values while the
38633 program is running.
38636 The value of the variable is unknown. This would occur, for example,
38637 if the user is examining a trace frame in which the requested variable
38642 @cindex @samp{qTfP} packet
38644 @cindex @samp{qTsP} packet
38645 These packets request data about tracepoints that are being used by
38646 the target. @value{GDBN} sends @code{qTfP} to get the first piece
38647 of data, and multiple @code{qTsP} to get additional pieces. Replies
38648 to these packets generally take the form of the @code{QTDP} packets
38649 that define tracepoints. (FIXME add detailed syntax)
38652 @cindex @samp{qTfV} packet
38654 @cindex @samp{qTsV} packet
38655 These packets request data about trace state variables that are on the
38656 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
38657 and multiple @code{qTsV} to get additional variables. Replies to
38658 these packets follow the syntax of the @code{QTDV} packets that define
38659 trace state variables.
38665 @cindex @samp{qTfSTM} packet
38666 @cindex @samp{qTsSTM} packet
38667 These packets request data about static tracepoint markers that exist
38668 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
38669 first piece of data, and multiple @code{qTsSTM} to get additional
38670 pieces. Replies to these packets take the following form:
38674 @item m @var{address}:@var{id}:@var{extra}
38676 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
38677 a comma-separated list of markers
38679 (lower case letter @samp{L}) denotes end of list.
38681 An error occurred. @var{nn} are hex digits.
38683 An empty reply indicates that the request is not supported by the
38687 @var{address} is encoded in hex.
38688 @var{id} and @var{extra} are strings encoded in hex.
38690 In response to each query, the target will reply with a list of one or
38691 more markers, separated by commas. @value{GDBN} will respond to each
38692 reply with a request for more markers (using the @samp{qs} form of the
38693 query), until the target responds with @samp{l} (lower-case ell, for
38696 @item qTSTMat:@var{address}
38698 @cindex @samp{qTSTMat} packet
38699 This packets requests data about static tracepoint markers in the
38700 target program at @var{address}. Replies to this packet follow the
38701 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
38702 tracepoint markers.
38704 @item QTSave:@var{filename}
38705 @cindex @samp{QTSave} packet
38706 This packet directs the target to save trace data to the file name
38707 @var{filename} in the target's filesystem. @var{filename} is encoded
38708 as a hex string; the interpretation of the file name (relative vs
38709 absolute, wild cards, etc) is up to the target.
38711 @item qTBuffer:@var{offset},@var{len}
38712 @cindex @samp{qTBuffer} packet
38713 Return up to @var{len} bytes of the current contents of trace buffer,
38714 starting at @var{offset}. The trace buffer is treated as if it were
38715 a contiguous collection of traceframes, as per the trace file format.
38716 The reply consists as many hex-encoded bytes as the target can deliver
38717 in a packet; it is not an error to return fewer than were asked for.
38718 A reply consisting of just @code{l} indicates that no bytes are
38721 @item QTBuffer:circular:@var{value}
38722 This packet directs the target to use a circular trace buffer if
38723 @var{value} is 1, or a linear buffer if the value is 0.
38725 @item QTBuffer:size:@var{size}
38726 @anchor{QTBuffer-size}
38727 @cindex @samp{QTBuffer size} packet
38728 This packet directs the target to make the trace buffer be of size
38729 @var{size} if possible. A value of @code{-1} tells the target to
38730 use whatever size it prefers.
38732 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
38733 @cindex @samp{QTNotes} packet
38734 This packet adds optional textual notes to the trace run. Allowable
38735 types include @code{user}, @code{notes}, and @code{tstop}, the
38736 @var{text} fields are arbitrary strings, hex-encoded.
38740 @subsection Relocate instruction reply packet
38741 When installing fast tracepoints in memory, the target may need to
38742 relocate the instruction currently at the tracepoint address to a
38743 different address in memory. For most instructions, a simple copy is
38744 enough, but, for example, call instructions that implicitly push the
38745 return address on the stack, and relative branches or other
38746 PC-relative instructions require offset adjustment, so that the effect
38747 of executing the instruction at a different address is the same as if
38748 it had executed in the original location.
38750 In response to several of the tracepoint packets, the target may also
38751 respond with a number of intermediate @samp{qRelocInsn} request
38752 packets before the final result packet, to have @value{GDBN} handle
38753 this relocation operation. If a packet supports this mechanism, its
38754 documentation will explicitly say so. See for example the above
38755 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
38756 format of the request is:
38759 @item qRelocInsn:@var{from};@var{to}
38761 This requests @value{GDBN} to copy instruction at address @var{from}
38762 to address @var{to}, possibly adjusted so that executing the
38763 instruction at @var{to} has the same effect as executing it at
38764 @var{from}. @value{GDBN} writes the adjusted instruction to target
38765 memory starting at @var{to}.
38770 @item qRelocInsn:@var{adjusted_size}
38771 Informs the stub the relocation is complete. @var{adjusted_size} is
38772 the length in bytes of resulting relocated instruction sequence.
38774 A badly formed request was detected, or an error was encountered while
38775 relocating the instruction.
38778 @node Host I/O Packets
38779 @section Host I/O Packets
38780 @cindex Host I/O, remote protocol
38781 @cindex file transfer, remote protocol
38783 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
38784 operations on the far side of a remote link. For example, Host I/O is
38785 used to upload and download files to a remote target with its own
38786 filesystem. Host I/O uses the same constant values and data structure
38787 layout as the target-initiated File-I/O protocol. However, the
38788 Host I/O packets are structured differently. The target-initiated
38789 protocol relies on target memory to store parameters and buffers.
38790 Host I/O requests are initiated by @value{GDBN}, and the
38791 target's memory is not involved. @xref{File-I/O Remote Protocol
38792 Extension}, for more details on the target-initiated protocol.
38794 The Host I/O request packets all encode a single operation along with
38795 its arguments. They have this format:
38799 @item vFile:@var{operation}: @var{parameter}@dots{}
38800 @var{operation} is the name of the particular request; the target
38801 should compare the entire packet name up to the second colon when checking
38802 for a supported operation. The format of @var{parameter} depends on
38803 the operation. Numbers are always passed in hexadecimal. Negative
38804 numbers have an explicit minus sign (i.e.@: two's complement is not
38805 used). Strings (e.g.@: filenames) are encoded as a series of
38806 hexadecimal bytes. The last argument to a system call may be a
38807 buffer of escaped binary data (@pxref{Binary Data}).
38811 The valid responses to Host I/O packets are:
38815 @item F @var{result} [, @var{errno}] [; @var{attachment}]
38816 @var{result} is the integer value returned by this operation, usually
38817 non-negative for success and -1 for errors. If an error has occured,
38818 @var{errno} will be included in the result. @var{errno} will have a
38819 value defined by the File-I/O protocol (@pxref{Errno Values}). For
38820 operations which return data, @var{attachment} supplies the data as a
38821 binary buffer. Binary buffers in response packets are escaped in the
38822 normal way (@pxref{Binary Data}). See the individual packet
38823 documentation for the interpretation of @var{result} and
38827 An empty response indicates that this operation is not recognized.
38831 These are the supported Host I/O operations:
38834 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
38835 Open a file at @var{pathname} and return a file descriptor for it, or
38836 return -1 if an error occurs. @var{pathname} is a string,
38837 @var{flags} is an integer indicating a mask of open flags
38838 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
38839 of mode bits to use if the file is created (@pxref{mode_t Values}).
38840 @xref{open}, for details of the open flags and mode values.
38842 @item vFile:close: @var{fd}
38843 Close the open file corresponding to @var{fd} and return 0, or
38844 -1 if an error occurs.
38846 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
38847 Read data from the open file corresponding to @var{fd}. Up to
38848 @var{count} bytes will be read from the file, starting at @var{offset}
38849 relative to the start of the file. The target may read fewer bytes;
38850 common reasons include packet size limits and an end-of-file
38851 condition. The number of bytes read is returned. Zero should only be
38852 returned for a successful read at the end of the file, or if
38853 @var{count} was zero.
38855 The data read should be returned as a binary attachment on success.
38856 If zero bytes were read, the response should include an empty binary
38857 attachment (i.e.@: a trailing semicolon). The return value is the
38858 number of target bytes read; the binary attachment may be longer if
38859 some characters were escaped.
38861 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
38862 Write @var{data} (a binary buffer) to the open file corresponding
38863 to @var{fd}. Start the write at @var{offset} from the start of the
38864 file. Unlike many @code{write} system calls, there is no
38865 separate @var{count} argument; the length of @var{data} in the
38866 packet is used. @samp{vFile:write} returns the number of bytes written,
38867 which may be shorter than the length of @var{data}, or -1 if an
38870 @item vFile:unlink: @var{pathname}
38871 Delete the file at @var{pathname} on the target. Return 0,
38872 or -1 if an error occurs. @var{pathname} is a string.
38874 @item vFile:readlink: @var{filename}
38875 Read value of symbolic link @var{filename} on the target. Return
38876 the number of bytes read, or -1 if an error occurs.
38878 The data read should be returned as a binary attachment on success.
38879 If zero bytes were read, the response should include an empty binary
38880 attachment (i.e.@: a trailing semicolon). The return value is the
38881 number of target bytes read; the binary attachment may be longer if
38882 some characters were escaped.
38887 @section Interrupts
38888 @cindex interrupts (remote protocol)
38890 When a program on the remote target is running, @value{GDBN} may
38891 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
38892 a @code{BREAK} followed by @code{g},
38893 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
38895 The precise meaning of @code{BREAK} is defined by the transport
38896 mechanism and may, in fact, be undefined. @value{GDBN} does not
38897 currently define a @code{BREAK} mechanism for any of the network
38898 interfaces except for TCP, in which case @value{GDBN} sends the
38899 @code{telnet} BREAK sequence.
38901 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
38902 transport mechanisms. It is represented by sending the single byte
38903 @code{0x03} without any of the usual packet overhead described in
38904 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
38905 transmitted as part of a packet, it is considered to be packet data
38906 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
38907 (@pxref{X packet}), used for binary downloads, may include an unescaped
38908 @code{0x03} as part of its packet.
38910 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
38911 When Linux kernel receives this sequence from serial port,
38912 it stops execution and connects to gdb.
38914 Stubs are not required to recognize these interrupt mechanisms and the
38915 precise meaning associated with receipt of the interrupt is
38916 implementation defined. If the target supports debugging of multiple
38917 threads and/or processes, it should attempt to interrupt all
38918 currently-executing threads and processes.
38919 If the stub is successful at interrupting the
38920 running program, it should send one of the stop
38921 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
38922 of successfully stopping the program in all-stop mode, and a stop reply
38923 for each stopped thread in non-stop mode.
38924 Interrupts received while the
38925 program is stopped are discarded.
38927 @node Notification Packets
38928 @section Notification Packets
38929 @cindex notification packets
38930 @cindex packets, notification
38932 The @value{GDBN} remote serial protocol includes @dfn{notifications},
38933 packets that require no acknowledgment. Both the GDB and the stub
38934 may send notifications (although the only notifications defined at
38935 present are sent by the stub). Notifications carry information
38936 without incurring the round-trip latency of an acknowledgment, and so
38937 are useful for low-impact communications where occasional packet loss
38940 A notification packet has the form @samp{% @var{data} #
38941 @var{checksum}}, where @var{data} is the content of the notification,
38942 and @var{checksum} is a checksum of @var{data}, computed and formatted
38943 as for ordinary @value{GDBN} packets. A notification's @var{data}
38944 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
38945 receiving a notification, the recipient sends no @samp{+} or @samp{-}
38946 to acknowledge the notification's receipt or to report its corruption.
38948 Every notification's @var{data} begins with a name, which contains no
38949 colon characters, followed by a colon character.
38951 Recipients should silently ignore corrupted notifications and
38952 notifications they do not understand. Recipients should restart
38953 timeout periods on receipt of a well-formed notification, whether or
38954 not they understand it.
38956 Senders should only send the notifications described here when this
38957 protocol description specifies that they are permitted. In the
38958 future, we may extend the protocol to permit existing notifications in
38959 new contexts; this rule helps older senders avoid confusing newer
38962 (Older versions of @value{GDBN} ignore bytes received until they see
38963 the @samp{$} byte that begins an ordinary packet, so new stubs may
38964 transmit notifications without fear of confusing older clients. There
38965 are no notifications defined for @value{GDBN} to send at the moment, but we
38966 assume that most older stubs would ignore them, as well.)
38968 Each notification is comprised of three parts:
38970 @item @var{name}:@var{event}
38971 The notification packet is sent by the side that initiates the
38972 exchange (currently, only the stub does that), with @var{event}
38973 carrying the specific information about the notification.
38974 @var{name} is the name of the notification.
38976 The acknowledge sent by the other side, usually @value{GDBN}, to
38977 acknowledge the exchange and request the event.
38980 The purpose of an asynchronous notification mechanism is to report to
38981 @value{GDBN} that something interesting happened in the remote stub.
38983 The remote stub may send notification @var{name}:@var{event}
38984 at any time, but @value{GDBN} acknowledges the notification when
38985 appropriate. The notification event is pending before @value{GDBN}
38986 acknowledges. Only one notification at a time may be pending; if
38987 additional events occur before @value{GDBN} has acknowledged the
38988 previous notification, they must be queued by the stub for later
38989 synchronous transmission in response to @var{ack} packets from
38990 @value{GDBN}. Because the notification mechanism is unreliable,
38991 the stub is permitted to resend a notification if it believes
38992 @value{GDBN} may not have received it.
38994 Specifically, notifications may appear when @value{GDBN} is not
38995 otherwise reading input from the stub, or when @value{GDBN} is
38996 expecting to read a normal synchronous response or a
38997 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
38998 Notification packets are distinct from any other communication from
38999 the stub so there is no ambiguity.
39001 After receiving a notification, @value{GDBN} shall acknowledge it by
39002 sending a @var{ack} packet as a regular, synchronous request to the
39003 stub. Such acknowledgment is not required to happen immediately, as
39004 @value{GDBN} is permitted to send other, unrelated packets to the
39005 stub first, which the stub should process normally.
39007 Upon receiving a @var{ack} packet, if the stub has other queued
39008 events to report to @value{GDBN}, it shall respond by sending a
39009 normal @var{event}. @value{GDBN} shall then send another @var{ack}
39010 packet to solicit further responses; again, it is permitted to send
39011 other, unrelated packets as well which the stub should process
39014 If the stub receives a @var{ack} packet and there are no additional
39015 @var{event} to report, the stub shall return an @samp{OK} response.
39016 At this point, @value{GDBN} has finished processing a notification
39017 and the stub has completed sending any queued events. @value{GDBN}
39018 won't accept any new notifications until the final @samp{OK} is
39019 received . If further notification events occur, the stub shall send
39020 a new notification, @value{GDBN} shall accept the notification, and
39021 the process shall be repeated.
39023 The process of asynchronous notification can be illustrated by the
39026 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
39029 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
39031 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
39036 The following notifications are defined:
39037 @multitable @columnfractions 0.12 0.12 0.38 0.38
39046 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
39047 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
39048 for information on how these notifications are acknowledged by
39050 @tab Report an asynchronous stop event in non-stop mode.
39054 @node Remote Non-Stop
39055 @section Remote Protocol Support for Non-Stop Mode
39057 @value{GDBN}'s remote protocol supports non-stop debugging of
39058 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
39059 supports non-stop mode, it should report that to @value{GDBN} by including
39060 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
39062 @value{GDBN} typically sends a @samp{QNonStop} packet only when
39063 establishing a new connection with the stub. Entering non-stop mode
39064 does not alter the state of any currently-running threads, but targets
39065 must stop all threads in any already-attached processes when entering
39066 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
39067 probe the target state after a mode change.
39069 In non-stop mode, when an attached process encounters an event that
39070 would otherwise be reported with a stop reply, it uses the
39071 asynchronous notification mechanism (@pxref{Notification Packets}) to
39072 inform @value{GDBN}. In contrast to all-stop mode, where all threads
39073 in all processes are stopped when a stop reply is sent, in non-stop
39074 mode only the thread reporting the stop event is stopped. That is,
39075 when reporting a @samp{S} or @samp{T} response to indicate completion
39076 of a step operation, hitting a breakpoint, or a fault, only the
39077 affected thread is stopped; any other still-running threads continue
39078 to run. When reporting a @samp{W} or @samp{X} response, all running
39079 threads belonging to other attached processes continue to run.
39081 In non-stop mode, the target shall respond to the @samp{?} packet as
39082 follows. First, any incomplete stop reply notification/@samp{vStopped}
39083 sequence in progress is abandoned. The target must begin a new
39084 sequence reporting stop events for all stopped threads, whether or not
39085 it has previously reported those events to @value{GDBN}. The first
39086 stop reply is sent as a synchronous reply to the @samp{?} packet, and
39087 subsequent stop replies are sent as responses to @samp{vStopped} packets
39088 using the mechanism described above. The target must not send
39089 asynchronous stop reply notifications until the sequence is complete.
39090 If all threads are running when the target receives the @samp{?} packet,
39091 or if the target is not attached to any process, it shall respond
39094 @node Packet Acknowledgment
39095 @section Packet Acknowledgment
39097 @cindex acknowledgment, for @value{GDBN} remote
39098 @cindex packet acknowledgment, for @value{GDBN} remote
39099 By default, when either the host or the target machine receives a packet,
39100 the first response expected is an acknowledgment: either @samp{+} (to indicate
39101 the package was received correctly) or @samp{-} (to request retransmission).
39102 This mechanism allows the @value{GDBN} remote protocol to operate over
39103 unreliable transport mechanisms, such as a serial line.
39105 In cases where the transport mechanism is itself reliable (such as a pipe or
39106 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
39107 It may be desirable to disable them in that case to reduce communication
39108 overhead, or for other reasons. This can be accomplished by means of the
39109 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
39111 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
39112 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
39113 and response format still includes the normal checksum, as described in
39114 @ref{Overview}, but the checksum may be ignored by the receiver.
39116 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
39117 no-acknowledgment mode, it should report that to @value{GDBN}
39118 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
39119 @pxref{qSupported}.
39120 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
39121 disabled via the @code{set remote noack-packet off} command
39122 (@pxref{Remote Configuration}),
39123 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
39124 Only then may the stub actually turn off packet acknowledgments.
39125 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
39126 response, which can be safely ignored by the stub.
39128 Note that @code{set remote noack-packet} command only affects negotiation
39129 between @value{GDBN} and the stub when subsequent connections are made;
39130 it does not affect the protocol acknowledgment state for any current
39132 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
39133 new connection is established,
39134 there is also no protocol request to re-enable the acknowledgments
39135 for the current connection, once disabled.
39140 Example sequence of a target being re-started. Notice how the restart
39141 does not get any direct output:
39146 @emph{target restarts}
39149 <- @code{T001:1234123412341234}
39153 Example sequence of a target being stepped by a single instruction:
39156 -> @code{G1445@dots{}}
39161 <- @code{T001:1234123412341234}
39165 <- @code{1455@dots{}}
39169 @node File-I/O Remote Protocol Extension
39170 @section File-I/O Remote Protocol Extension
39171 @cindex File-I/O remote protocol extension
39174 * File-I/O Overview::
39175 * Protocol Basics::
39176 * The F Request Packet::
39177 * The F Reply Packet::
39178 * The Ctrl-C Message::
39180 * List of Supported Calls::
39181 * Protocol-specific Representation of Datatypes::
39183 * File-I/O Examples::
39186 @node File-I/O Overview
39187 @subsection File-I/O Overview
39188 @cindex file-i/o overview
39190 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
39191 target to use the host's file system and console I/O to perform various
39192 system calls. System calls on the target system are translated into a
39193 remote protocol packet to the host system, which then performs the needed
39194 actions and returns a response packet to the target system.
39195 This simulates file system operations even on targets that lack file systems.
39197 The protocol is defined to be independent of both the host and target systems.
39198 It uses its own internal representation of datatypes and values. Both
39199 @value{GDBN} and the target's @value{GDBN} stub are responsible for
39200 translating the system-dependent value representations into the internal
39201 protocol representations when data is transmitted.
39203 The communication is synchronous. A system call is possible only when
39204 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
39205 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
39206 the target is stopped to allow deterministic access to the target's
39207 memory. Therefore File-I/O is not interruptible by target signals. On
39208 the other hand, it is possible to interrupt File-I/O by a user interrupt
39209 (@samp{Ctrl-C}) within @value{GDBN}.
39211 The target's request to perform a host system call does not finish
39212 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
39213 after finishing the system call, the target returns to continuing the
39214 previous activity (continue, step). No additional continue or step
39215 request from @value{GDBN} is required.
39218 (@value{GDBP}) continue
39219 <- target requests 'system call X'
39220 target is stopped, @value{GDBN} executes system call
39221 -> @value{GDBN} returns result
39222 ... target continues, @value{GDBN} returns to wait for the target
39223 <- target hits breakpoint and sends a Txx packet
39226 The protocol only supports I/O on the console and to regular files on
39227 the host file system. Character or block special devices, pipes,
39228 named pipes, sockets or any other communication method on the host
39229 system are not supported by this protocol.
39231 File I/O is not supported in non-stop mode.
39233 @node Protocol Basics
39234 @subsection Protocol Basics
39235 @cindex protocol basics, file-i/o
39237 The File-I/O protocol uses the @code{F} packet as the request as well
39238 as reply packet. Since a File-I/O system call can only occur when
39239 @value{GDBN} is waiting for a response from the continuing or stepping target,
39240 the File-I/O request is a reply that @value{GDBN} has to expect as a result
39241 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
39242 This @code{F} packet contains all information needed to allow @value{GDBN}
39243 to call the appropriate host system call:
39247 A unique identifier for the requested system call.
39250 All parameters to the system call. Pointers are given as addresses
39251 in the target memory address space. Pointers to strings are given as
39252 pointer/length pair. Numerical values are given as they are.
39253 Numerical control flags are given in a protocol-specific representation.
39257 At this point, @value{GDBN} has to perform the following actions.
39261 If the parameters include pointer values to data needed as input to a
39262 system call, @value{GDBN} requests this data from the target with a
39263 standard @code{m} packet request. This additional communication has to be
39264 expected by the target implementation and is handled as any other @code{m}
39268 @value{GDBN} translates all value from protocol representation to host
39269 representation as needed. Datatypes are coerced into the host types.
39272 @value{GDBN} calls the system call.
39275 It then coerces datatypes back to protocol representation.
39278 If the system call is expected to return data in buffer space specified
39279 by pointer parameters to the call, the data is transmitted to the
39280 target using a @code{M} or @code{X} packet. This packet has to be expected
39281 by the target implementation and is handled as any other @code{M} or @code{X}
39286 Eventually @value{GDBN} replies with another @code{F} packet which contains all
39287 necessary information for the target to continue. This at least contains
39294 @code{errno}, if has been changed by the system call.
39301 After having done the needed type and value coercion, the target continues
39302 the latest continue or step action.
39304 @node The F Request Packet
39305 @subsection The @code{F} Request Packet
39306 @cindex file-i/o request packet
39307 @cindex @code{F} request packet
39309 The @code{F} request packet has the following format:
39312 @item F@var{call-id},@var{parameter@dots{}}
39314 @var{call-id} is the identifier to indicate the host system call to be called.
39315 This is just the name of the function.
39317 @var{parameter@dots{}} are the parameters to the system call.
39318 Parameters are hexadecimal integer values, either the actual values in case
39319 of scalar datatypes, pointers to target buffer space in case of compound
39320 datatypes and unspecified memory areas, or pointer/length pairs in case
39321 of string parameters. These are appended to the @var{call-id} as a
39322 comma-delimited list. All values are transmitted in ASCII
39323 string representation, pointer/length pairs separated by a slash.
39329 @node The F Reply Packet
39330 @subsection The @code{F} Reply Packet
39331 @cindex file-i/o reply packet
39332 @cindex @code{F} reply packet
39334 The @code{F} reply packet has the following format:
39338 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
39340 @var{retcode} is the return code of the system call as hexadecimal value.
39342 @var{errno} is the @code{errno} set by the call, in protocol-specific
39344 This parameter can be omitted if the call was successful.
39346 @var{Ctrl-C flag} is only sent if the user requested a break. In this
39347 case, @var{errno} must be sent as well, even if the call was successful.
39348 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
39355 or, if the call was interrupted before the host call has been performed:
39362 assuming 4 is the protocol-specific representation of @code{EINTR}.
39367 @node The Ctrl-C Message
39368 @subsection The @samp{Ctrl-C} Message
39369 @cindex ctrl-c message, in file-i/o protocol
39371 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
39372 reply packet (@pxref{The F Reply Packet}),
39373 the target should behave as if it had
39374 gotten a break message. The meaning for the target is ``system call
39375 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
39376 (as with a break message) and return to @value{GDBN} with a @code{T02}
39379 It's important for the target to know in which
39380 state the system call was interrupted. There are two possible cases:
39384 The system call hasn't been performed on the host yet.
39387 The system call on the host has been finished.
39391 These two states can be distinguished by the target by the value of the
39392 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
39393 call hasn't been performed. This is equivalent to the @code{EINTR} handling
39394 on POSIX systems. In any other case, the target may presume that the
39395 system call has been finished --- successfully or not --- and should behave
39396 as if the break message arrived right after the system call.
39398 @value{GDBN} must behave reliably. If the system call has not been called
39399 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
39400 @code{errno} in the packet. If the system call on the host has been finished
39401 before the user requests a break, the full action must be finished by
39402 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
39403 The @code{F} packet may only be sent when either nothing has happened
39404 or the full action has been completed.
39407 @subsection Console I/O
39408 @cindex console i/o as part of file-i/o
39410 By default and if not explicitly closed by the target system, the file
39411 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
39412 on the @value{GDBN} console is handled as any other file output operation
39413 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
39414 by @value{GDBN} so that after the target read request from file descriptor
39415 0 all following typing is buffered until either one of the following
39420 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
39422 system call is treated as finished.
39425 The user presses @key{RET}. This is treated as end of input with a trailing
39429 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
39430 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
39434 If the user has typed more characters than fit in the buffer given to
39435 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
39436 either another @code{read(0, @dots{})} is requested by the target, or debugging
39437 is stopped at the user's request.
39440 @node List of Supported Calls
39441 @subsection List of Supported Calls
39442 @cindex list of supported file-i/o calls
39459 @unnumberedsubsubsec open
39460 @cindex open, file-i/o system call
39465 int open(const char *pathname, int flags);
39466 int open(const char *pathname, int flags, mode_t mode);
39470 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
39473 @var{flags} is the bitwise @code{OR} of the following values:
39477 If the file does not exist it will be created. The host
39478 rules apply as far as file ownership and time stamps
39482 When used with @code{O_CREAT}, if the file already exists it is
39483 an error and open() fails.
39486 If the file already exists and the open mode allows
39487 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
39488 truncated to zero length.
39491 The file is opened in append mode.
39494 The file is opened for reading only.
39497 The file is opened for writing only.
39500 The file is opened for reading and writing.
39504 Other bits are silently ignored.
39508 @var{mode} is the bitwise @code{OR} of the following values:
39512 User has read permission.
39515 User has write permission.
39518 Group has read permission.
39521 Group has write permission.
39524 Others have read permission.
39527 Others have write permission.
39531 Other bits are silently ignored.
39534 @item Return value:
39535 @code{open} returns the new file descriptor or -1 if an error
39542 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
39545 @var{pathname} refers to a directory.
39548 The requested access is not allowed.
39551 @var{pathname} was too long.
39554 A directory component in @var{pathname} does not exist.
39557 @var{pathname} refers to a device, pipe, named pipe or socket.
39560 @var{pathname} refers to a file on a read-only filesystem and
39561 write access was requested.
39564 @var{pathname} is an invalid pointer value.
39567 No space on device to create the file.
39570 The process already has the maximum number of files open.
39573 The limit on the total number of files open on the system
39577 The call was interrupted by the user.
39583 @unnumberedsubsubsec close
39584 @cindex close, file-i/o system call
39593 @samp{Fclose,@var{fd}}
39595 @item Return value:
39596 @code{close} returns zero on success, or -1 if an error occurred.
39602 @var{fd} isn't a valid open file descriptor.
39605 The call was interrupted by the user.
39611 @unnumberedsubsubsec read
39612 @cindex read, file-i/o system call
39617 int read(int fd, void *buf, unsigned int count);
39621 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
39623 @item Return value:
39624 On success, the number of bytes read is returned.
39625 Zero indicates end of file. If count is zero, read
39626 returns zero as well. On error, -1 is returned.
39632 @var{fd} is not a valid file descriptor or is not open for
39636 @var{bufptr} is an invalid pointer value.
39639 The call was interrupted by the user.
39645 @unnumberedsubsubsec write
39646 @cindex write, file-i/o system call
39651 int write(int fd, const void *buf, unsigned int count);
39655 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
39657 @item Return value:
39658 On success, the number of bytes written are returned.
39659 Zero indicates nothing was written. On error, -1
39666 @var{fd} is not a valid file descriptor or is not open for
39670 @var{bufptr} is an invalid pointer value.
39673 An attempt was made to write a file that exceeds the
39674 host-specific maximum file size allowed.
39677 No space on device to write the data.
39680 The call was interrupted by the user.
39686 @unnumberedsubsubsec lseek
39687 @cindex lseek, file-i/o system call
39692 long lseek (int fd, long offset, int flag);
39696 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
39698 @var{flag} is one of:
39702 The offset is set to @var{offset} bytes.
39705 The offset is set to its current location plus @var{offset}
39709 The offset is set to the size of the file plus @var{offset}
39713 @item Return value:
39714 On success, the resulting unsigned offset in bytes from
39715 the beginning of the file is returned. Otherwise, a
39716 value of -1 is returned.
39722 @var{fd} is not a valid open file descriptor.
39725 @var{fd} is associated with the @value{GDBN} console.
39728 @var{flag} is not a proper value.
39731 The call was interrupted by the user.
39737 @unnumberedsubsubsec rename
39738 @cindex rename, file-i/o system call
39743 int rename(const char *oldpath, const char *newpath);
39747 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
39749 @item Return value:
39750 On success, zero is returned. On error, -1 is returned.
39756 @var{newpath} is an existing directory, but @var{oldpath} is not a
39760 @var{newpath} is a non-empty directory.
39763 @var{oldpath} or @var{newpath} is a directory that is in use by some
39767 An attempt was made to make a directory a subdirectory
39771 A component used as a directory in @var{oldpath} or new
39772 path is not a directory. Or @var{oldpath} is a directory
39773 and @var{newpath} exists but is not a directory.
39776 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
39779 No access to the file or the path of the file.
39783 @var{oldpath} or @var{newpath} was too long.
39786 A directory component in @var{oldpath} or @var{newpath} does not exist.
39789 The file is on a read-only filesystem.
39792 The device containing the file has no room for the new
39796 The call was interrupted by the user.
39802 @unnumberedsubsubsec unlink
39803 @cindex unlink, file-i/o system call
39808 int unlink(const char *pathname);
39812 @samp{Funlink,@var{pathnameptr}/@var{len}}
39814 @item Return value:
39815 On success, zero is returned. On error, -1 is returned.
39821 No access to the file or the path of the file.
39824 The system does not allow unlinking of directories.
39827 The file @var{pathname} cannot be unlinked because it's
39828 being used by another process.
39831 @var{pathnameptr} is an invalid pointer value.
39834 @var{pathname} was too long.
39837 A directory component in @var{pathname} does not exist.
39840 A component of the path is not a directory.
39843 The file is on a read-only filesystem.
39846 The call was interrupted by the user.
39852 @unnumberedsubsubsec stat/fstat
39853 @cindex fstat, file-i/o system call
39854 @cindex stat, file-i/o system call
39859 int stat(const char *pathname, struct stat *buf);
39860 int fstat(int fd, struct stat *buf);
39864 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
39865 @samp{Ffstat,@var{fd},@var{bufptr}}
39867 @item Return value:
39868 On success, zero is returned. On error, -1 is returned.
39874 @var{fd} is not a valid open file.
39877 A directory component in @var{pathname} does not exist or the
39878 path is an empty string.
39881 A component of the path is not a directory.
39884 @var{pathnameptr} is an invalid pointer value.
39887 No access to the file or the path of the file.
39890 @var{pathname} was too long.
39893 The call was interrupted by the user.
39899 @unnumberedsubsubsec gettimeofday
39900 @cindex gettimeofday, file-i/o system call
39905 int gettimeofday(struct timeval *tv, void *tz);
39909 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
39911 @item Return value:
39912 On success, 0 is returned, -1 otherwise.
39918 @var{tz} is a non-NULL pointer.
39921 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
39927 @unnumberedsubsubsec isatty
39928 @cindex isatty, file-i/o system call
39933 int isatty(int fd);
39937 @samp{Fisatty,@var{fd}}
39939 @item Return value:
39940 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
39946 The call was interrupted by the user.
39951 Note that the @code{isatty} call is treated as a special case: it returns
39952 1 to the target if the file descriptor is attached
39953 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
39954 would require implementing @code{ioctl} and would be more complex than
39959 @unnumberedsubsubsec system
39960 @cindex system, file-i/o system call
39965 int system(const char *command);
39969 @samp{Fsystem,@var{commandptr}/@var{len}}
39971 @item Return value:
39972 If @var{len} is zero, the return value indicates whether a shell is
39973 available. A zero return value indicates a shell is not available.
39974 For non-zero @var{len}, the value returned is -1 on error and the
39975 return status of the command otherwise. Only the exit status of the
39976 command is returned, which is extracted from the host's @code{system}
39977 return value by calling @code{WEXITSTATUS(retval)}. In case
39978 @file{/bin/sh} could not be executed, 127 is returned.
39984 The call was interrupted by the user.
39989 @value{GDBN} takes over the full task of calling the necessary host calls
39990 to perform the @code{system} call. The return value of @code{system} on
39991 the host is simplified before it's returned
39992 to the target. Any termination signal information from the child process
39993 is discarded, and the return value consists
39994 entirely of the exit status of the called command.
39996 Due to security concerns, the @code{system} call is by default refused
39997 by @value{GDBN}. The user has to allow this call explicitly with the
39998 @code{set remote system-call-allowed 1} command.
40001 @item set remote system-call-allowed
40002 @kindex set remote system-call-allowed
40003 Control whether to allow the @code{system} calls in the File I/O
40004 protocol for the remote target. The default is zero (disabled).
40006 @item show remote system-call-allowed
40007 @kindex show remote system-call-allowed
40008 Show whether the @code{system} calls are allowed in the File I/O
40012 @node Protocol-specific Representation of Datatypes
40013 @subsection Protocol-specific Representation of Datatypes
40014 @cindex protocol-specific representation of datatypes, in file-i/o protocol
40017 * Integral Datatypes::
40019 * Memory Transfer::
40024 @node Integral Datatypes
40025 @unnumberedsubsubsec Integral Datatypes
40026 @cindex integral datatypes, in file-i/o protocol
40028 The integral datatypes used in the system calls are @code{int},
40029 @code{unsigned int}, @code{long}, @code{unsigned long},
40030 @code{mode_t}, and @code{time_t}.
40032 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
40033 implemented as 32 bit values in this protocol.
40035 @code{long} and @code{unsigned long} are implemented as 64 bit types.
40037 @xref{Limits}, for corresponding MIN and MAX values (similar to those
40038 in @file{limits.h}) to allow range checking on host and target.
40040 @code{time_t} datatypes are defined as seconds since the Epoch.
40042 All integral datatypes transferred as part of a memory read or write of a
40043 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
40046 @node Pointer Values
40047 @unnumberedsubsubsec Pointer Values
40048 @cindex pointer values, in file-i/o protocol
40050 Pointers to target data are transmitted as they are. An exception
40051 is made for pointers to buffers for which the length isn't
40052 transmitted as part of the function call, namely strings. Strings
40053 are transmitted as a pointer/length pair, both as hex values, e.g.@:
40060 which is a pointer to data of length 18 bytes at position 0x1aaf.
40061 The length is defined as the full string length in bytes, including
40062 the trailing null byte. For example, the string @code{"hello world"}
40063 at address 0x123456 is transmitted as
40069 @node Memory Transfer
40070 @unnumberedsubsubsec Memory Transfer
40071 @cindex memory transfer, in file-i/o protocol
40073 Structured data which is transferred using a memory read or write (for
40074 example, a @code{struct stat}) is expected to be in a protocol-specific format
40075 with all scalar multibyte datatypes being big endian. Translation to
40076 this representation needs to be done both by the target before the @code{F}
40077 packet is sent, and by @value{GDBN} before
40078 it transfers memory to the target. Transferred pointers to structured
40079 data should point to the already-coerced data at any time.
40083 @unnumberedsubsubsec struct stat
40084 @cindex struct stat, in file-i/o protocol
40086 The buffer of type @code{struct stat} used by the target and @value{GDBN}
40087 is defined as follows:
40091 unsigned int st_dev; /* device */
40092 unsigned int st_ino; /* inode */
40093 mode_t st_mode; /* protection */
40094 unsigned int st_nlink; /* number of hard links */
40095 unsigned int st_uid; /* user ID of owner */
40096 unsigned int st_gid; /* group ID of owner */
40097 unsigned int st_rdev; /* device type (if inode device) */
40098 unsigned long st_size; /* total size, in bytes */
40099 unsigned long st_blksize; /* blocksize for filesystem I/O */
40100 unsigned long st_blocks; /* number of blocks allocated */
40101 time_t st_atime; /* time of last access */
40102 time_t st_mtime; /* time of last modification */
40103 time_t st_ctime; /* time of last change */
40107 The integral datatypes conform to the definitions given in the
40108 appropriate section (see @ref{Integral Datatypes}, for details) so this
40109 structure is of size 64 bytes.
40111 The values of several fields have a restricted meaning and/or
40117 A value of 0 represents a file, 1 the console.
40120 No valid meaning for the target. Transmitted unchanged.
40123 Valid mode bits are described in @ref{Constants}. Any other
40124 bits have currently no meaning for the target.
40129 No valid meaning for the target. Transmitted unchanged.
40134 These values have a host and file system dependent
40135 accuracy. Especially on Windows hosts, the file system may not
40136 support exact timing values.
40139 The target gets a @code{struct stat} of the above representation and is
40140 responsible for coercing it to the target representation before
40143 Note that due to size differences between the host, target, and protocol
40144 representations of @code{struct stat} members, these members could eventually
40145 get truncated on the target.
40147 @node struct timeval
40148 @unnumberedsubsubsec struct timeval
40149 @cindex struct timeval, in file-i/o protocol
40151 The buffer of type @code{struct timeval} used by the File-I/O protocol
40152 is defined as follows:
40156 time_t tv_sec; /* second */
40157 long tv_usec; /* microsecond */
40161 The integral datatypes conform to the definitions given in the
40162 appropriate section (see @ref{Integral Datatypes}, for details) so this
40163 structure is of size 8 bytes.
40166 @subsection Constants
40167 @cindex constants, in file-i/o protocol
40169 The following values are used for the constants inside of the
40170 protocol. @value{GDBN} and target are responsible for translating these
40171 values before and after the call as needed.
40182 @unnumberedsubsubsec Open Flags
40183 @cindex open flags, in file-i/o protocol
40185 All values are given in hexadecimal representation.
40197 @node mode_t Values
40198 @unnumberedsubsubsec mode_t Values
40199 @cindex mode_t values, in file-i/o protocol
40201 All values are given in octal representation.
40218 @unnumberedsubsubsec Errno Values
40219 @cindex errno values, in file-i/o protocol
40221 All values are given in decimal representation.
40246 @code{EUNKNOWN} is used as a fallback error value if a host system returns
40247 any error value not in the list of supported error numbers.
40250 @unnumberedsubsubsec Lseek Flags
40251 @cindex lseek flags, in file-i/o protocol
40260 @unnumberedsubsubsec Limits
40261 @cindex limits, in file-i/o protocol
40263 All values are given in decimal representation.
40266 INT_MIN -2147483648
40268 UINT_MAX 4294967295
40269 LONG_MIN -9223372036854775808
40270 LONG_MAX 9223372036854775807
40271 ULONG_MAX 18446744073709551615
40274 @node File-I/O Examples
40275 @subsection File-I/O Examples
40276 @cindex file-i/o examples
40278 Example sequence of a write call, file descriptor 3, buffer is at target
40279 address 0x1234, 6 bytes should be written:
40282 <- @code{Fwrite,3,1234,6}
40283 @emph{request memory read from target}
40286 @emph{return "6 bytes written"}
40290 Example sequence of a read call, file descriptor 3, buffer is at target
40291 address 0x1234, 6 bytes should be read:
40294 <- @code{Fread,3,1234,6}
40295 @emph{request memory write to target}
40296 -> @code{X1234,6:XXXXXX}
40297 @emph{return "6 bytes read"}
40301 Example sequence of a read call, call fails on the host due to invalid
40302 file descriptor (@code{EBADF}):
40305 <- @code{Fread,3,1234,6}
40309 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
40313 <- @code{Fread,3,1234,6}
40318 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
40322 <- @code{Fread,3,1234,6}
40323 -> @code{X1234,6:XXXXXX}
40327 @node Library List Format
40328 @section Library List Format
40329 @cindex library list format, remote protocol
40331 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
40332 same process as your application to manage libraries. In this case,
40333 @value{GDBN} can use the loader's symbol table and normal memory
40334 operations to maintain a list of shared libraries. On other
40335 platforms, the operating system manages loaded libraries.
40336 @value{GDBN} can not retrieve the list of currently loaded libraries
40337 through memory operations, so it uses the @samp{qXfer:libraries:read}
40338 packet (@pxref{qXfer library list read}) instead. The remote stub
40339 queries the target's operating system and reports which libraries
40342 The @samp{qXfer:libraries:read} packet returns an XML document which
40343 lists loaded libraries and their offsets. Each library has an
40344 associated name and one or more segment or section base addresses,
40345 which report where the library was loaded in memory.
40347 For the common case of libraries that are fully linked binaries, the
40348 library should have a list of segments. If the target supports
40349 dynamic linking of a relocatable object file, its library XML element
40350 should instead include a list of allocated sections. The segment or
40351 section bases are start addresses, not relocation offsets; they do not
40352 depend on the library's link-time base addresses.
40354 @value{GDBN} must be linked with the Expat library to support XML
40355 library lists. @xref{Expat}.
40357 A simple memory map, with one loaded library relocated by a single
40358 offset, looks like this:
40362 <library name="/lib/libc.so.6">
40363 <segment address="0x10000000"/>
40368 Another simple memory map, with one loaded library with three
40369 allocated sections (.text, .data, .bss), looks like this:
40373 <library name="sharedlib.o">
40374 <section address="0x10000000"/>
40375 <section address="0x20000000"/>
40376 <section address="0x30000000"/>
40381 The format of a library list is described by this DTD:
40384 <!-- library-list: Root element with versioning -->
40385 <!ELEMENT library-list (library)*>
40386 <!ATTLIST library-list version CDATA #FIXED "1.0">
40387 <!ELEMENT library (segment*, section*)>
40388 <!ATTLIST library name CDATA #REQUIRED>
40389 <!ELEMENT segment EMPTY>
40390 <!ATTLIST segment address CDATA #REQUIRED>
40391 <!ELEMENT section EMPTY>
40392 <!ATTLIST section address CDATA #REQUIRED>
40395 In addition, segments and section descriptors cannot be mixed within a
40396 single library element, and you must supply at least one segment or
40397 section for each library.
40399 @node Library List Format for SVR4 Targets
40400 @section Library List Format for SVR4 Targets
40401 @cindex library list format, remote protocol
40403 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
40404 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
40405 shared libraries. Still a special library list provided by this packet is
40406 more efficient for the @value{GDBN} remote protocol.
40408 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
40409 loaded libraries and their SVR4 linker parameters. For each library on SVR4
40410 target, the following parameters are reported:
40414 @code{name}, the absolute file name from the @code{l_name} field of
40415 @code{struct link_map}.
40417 @code{lm} with address of @code{struct link_map} used for TLS
40418 (Thread Local Storage) access.
40420 @code{l_addr}, the displacement as read from the field @code{l_addr} of
40421 @code{struct link_map}. For prelinked libraries this is not an absolute
40422 memory address. It is a displacement of absolute memory address against
40423 address the file was prelinked to during the library load.
40425 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
40428 Additionally the single @code{main-lm} attribute specifies address of
40429 @code{struct link_map} used for the main executable. This parameter is used
40430 for TLS access and its presence is optional.
40432 @value{GDBN} must be linked with the Expat library to support XML
40433 SVR4 library lists. @xref{Expat}.
40435 A simple memory map, with two loaded libraries (which do not use prelink),
40439 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
40440 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
40442 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
40444 </library-list-svr>
40447 The format of an SVR4 library list is described by this DTD:
40450 <!-- library-list-svr4: Root element with versioning -->
40451 <!ELEMENT library-list-svr4 (library)*>
40452 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
40453 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
40454 <!ELEMENT library EMPTY>
40455 <!ATTLIST library name CDATA #REQUIRED>
40456 <!ATTLIST library lm CDATA #REQUIRED>
40457 <!ATTLIST library l_addr CDATA #REQUIRED>
40458 <!ATTLIST library l_ld CDATA #REQUIRED>
40461 @node Memory Map Format
40462 @section Memory Map Format
40463 @cindex memory map format
40465 To be able to write into flash memory, @value{GDBN} needs to obtain a
40466 memory map from the target. This section describes the format of the
40469 The memory map is obtained using the @samp{qXfer:memory-map:read}
40470 (@pxref{qXfer memory map read}) packet and is an XML document that
40471 lists memory regions.
40473 @value{GDBN} must be linked with the Expat library to support XML
40474 memory maps. @xref{Expat}.
40476 The top-level structure of the document is shown below:
40479 <?xml version="1.0"?>
40480 <!DOCTYPE memory-map
40481 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40482 "http://sourceware.org/gdb/gdb-memory-map.dtd">
40488 Each region can be either:
40493 A region of RAM starting at @var{addr} and extending for @var{length}
40497 <memory type="ram" start="@var{addr}" length="@var{length}"/>
40502 A region of read-only memory:
40505 <memory type="rom" start="@var{addr}" length="@var{length}"/>
40510 A region of flash memory, with erasure blocks @var{blocksize}
40514 <memory type="flash" start="@var{addr}" length="@var{length}">
40515 <property name="blocksize">@var{blocksize}</property>
40521 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
40522 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
40523 packets to write to addresses in such ranges.
40525 The formal DTD for memory map format is given below:
40528 <!-- ................................................... -->
40529 <!-- Memory Map XML DTD ................................ -->
40530 <!-- File: memory-map.dtd .............................. -->
40531 <!-- .................................... .............. -->
40532 <!-- memory-map.dtd -->
40533 <!-- memory-map: Root element with versioning -->
40534 <!ELEMENT memory-map (memory | property)>
40535 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
40536 <!ELEMENT memory (property)>
40537 <!-- memory: Specifies a memory region,
40538 and its type, or device. -->
40539 <!ATTLIST memory type CDATA #REQUIRED
40540 start CDATA #REQUIRED
40541 length CDATA #REQUIRED
40542 device CDATA #IMPLIED>
40543 <!-- property: Generic attribute tag -->
40544 <!ELEMENT property (#PCDATA | property)*>
40545 <!ATTLIST property name CDATA #REQUIRED>
40548 @node Thread List Format
40549 @section Thread List Format
40550 @cindex thread list format
40552 To efficiently update the list of threads and their attributes,
40553 @value{GDBN} issues the @samp{qXfer:threads:read} packet
40554 (@pxref{qXfer threads read}) and obtains the XML document with
40555 the following structure:
40558 <?xml version="1.0"?>
40560 <thread id="id" core="0">
40561 ... description ...
40566 Each @samp{thread} element must have the @samp{id} attribute that
40567 identifies the thread (@pxref{thread-id syntax}). The
40568 @samp{core} attribute, if present, specifies which processor core
40569 the thread was last executing on. The content of the of @samp{thread}
40570 element is interpreted as human-readable auxilliary information.
40572 @node Traceframe Info Format
40573 @section Traceframe Info Format
40574 @cindex traceframe info format
40576 To be able to know which objects in the inferior can be examined when
40577 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
40578 memory ranges, registers and trace state variables that have been
40579 collected in a traceframe.
40581 This list is obtained using the @samp{qXfer:traceframe-info:read}
40582 (@pxref{qXfer traceframe info read}) packet and is an XML document.
40584 @value{GDBN} must be linked with the Expat library to support XML
40585 traceframe info discovery. @xref{Expat}.
40587 The top-level structure of the document is shown below:
40590 <?xml version="1.0"?>
40591 <!DOCTYPE traceframe-info
40592 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40593 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
40599 Each traceframe block can be either:
40604 A region of collected memory starting at @var{addr} and extending for
40605 @var{length} bytes from there:
40608 <memory start="@var{addr}" length="@var{length}"/>
40613 The formal DTD for the traceframe info format is given below:
40616 <!ELEMENT traceframe-info (memory)* >
40617 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
40619 <!ELEMENT memory EMPTY>
40620 <!ATTLIST memory start CDATA #REQUIRED
40621 length CDATA #REQUIRED>
40624 @node Branch Trace Format
40625 @section Branch Trace Format
40626 @cindex branch trace format
40628 In order to display the branch trace of an inferior thread,
40629 @value{GDBN} needs to obtain the list of branches. This list is
40630 represented as list of sequential code blocks that are connected via
40631 branches. The code in each block has been executed sequentially.
40633 This list is obtained using the @samp{qXfer:btrace:read}
40634 (@pxref{qXfer btrace read}) packet and is an XML document.
40636 @value{GDBN} must be linked with the Expat library to support XML
40637 traceframe info discovery. @xref{Expat}.
40639 The top-level structure of the document is shown below:
40642 <?xml version="1.0"?>
40644 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
40645 "http://sourceware.org/gdb/gdb-btrace.dtd">
40654 A block of sequentially executed instructions starting at @var{begin}
40655 and ending at @var{end}:
40658 <block begin="@var{begin}" end="@var{end}"/>
40663 The formal DTD for the branch trace format is given below:
40666 <!ELEMENT btrace (block)* >
40667 <!ATTLIST btrace version CDATA #FIXED "1.0">
40669 <!ELEMENT block EMPTY>
40670 <!ATTLIST block begin CDATA #REQUIRED
40671 end CDATA #REQUIRED>
40674 @include agentexpr.texi
40676 @node Target Descriptions
40677 @appendix Target Descriptions
40678 @cindex target descriptions
40680 One of the challenges of using @value{GDBN} to debug embedded systems
40681 is that there are so many minor variants of each processor
40682 architecture in use. It is common practice for vendors to start with
40683 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
40684 and then make changes to adapt it to a particular market niche. Some
40685 architectures have hundreds of variants, available from dozens of
40686 vendors. This leads to a number of problems:
40690 With so many different customized processors, it is difficult for
40691 the @value{GDBN} maintainers to keep up with the changes.
40693 Since individual variants may have short lifetimes or limited
40694 audiences, it may not be worthwhile to carry information about every
40695 variant in the @value{GDBN} source tree.
40697 When @value{GDBN} does support the architecture of the embedded system
40698 at hand, the task of finding the correct architecture name to give the
40699 @command{set architecture} command can be error-prone.
40702 To address these problems, the @value{GDBN} remote protocol allows a
40703 target system to not only identify itself to @value{GDBN}, but to
40704 actually describe its own features. This lets @value{GDBN} support
40705 processor variants it has never seen before --- to the extent that the
40706 descriptions are accurate, and that @value{GDBN} understands them.
40708 @value{GDBN} must be linked with the Expat library to support XML
40709 target descriptions. @xref{Expat}.
40712 * Retrieving Descriptions:: How descriptions are fetched from a target.
40713 * Target Description Format:: The contents of a target description.
40714 * Predefined Target Types:: Standard types available for target
40716 * Standard Target Features:: Features @value{GDBN} knows about.
40719 @node Retrieving Descriptions
40720 @section Retrieving Descriptions
40722 Target descriptions can be read from the target automatically, or
40723 specified by the user manually. The default behavior is to read the
40724 description from the target. @value{GDBN} retrieves it via the remote
40725 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
40726 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
40727 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
40728 XML document, of the form described in @ref{Target Description
40731 Alternatively, you can specify a file to read for the target description.
40732 If a file is set, the target will not be queried. The commands to
40733 specify a file are:
40736 @cindex set tdesc filename
40737 @item set tdesc filename @var{path}
40738 Read the target description from @var{path}.
40740 @cindex unset tdesc filename
40741 @item unset tdesc filename
40742 Do not read the XML target description from a file. @value{GDBN}
40743 will use the description supplied by the current target.
40745 @cindex show tdesc filename
40746 @item show tdesc filename
40747 Show the filename to read for a target description, if any.
40751 @node Target Description Format
40752 @section Target Description Format
40753 @cindex target descriptions, XML format
40755 A target description annex is an @uref{http://www.w3.org/XML/, XML}
40756 document which complies with the Document Type Definition provided in
40757 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
40758 means you can use generally available tools like @command{xmllint} to
40759 check that your feature descriptions are well-formed and valid.
40760 However, to help people unfamiliar with XML write descriptions for
40761 their targets, we also describe the grammar here.
40763 Target descriptions can identify the architecture of the remote target
40764 and (for some architectures) provide information about custom register
40765 sets. They can also identify the OS ABI of the remote target.
40766 @value{GDBN} can use this information to autoconfigure for your
40767 target, or to warn you if you connect to an unsupported target.
40769 Here is a simple target description:
40772 <target version="1.0">
40773 <architecture>i386:x86-64</architecture>
40778 This minimal description only says that the target uses
40779 the x86-64 architecture.
40781 A target description has the following overall form, with [ ] marking
40782 optional elements and @dots{} marking repeatable elements. The elements
40783 are explained further below.
40786 <?xml version="1.0"?>
40787 <!DOCTYPE target SYSTEM "gdb-target.dtd">
40788 <target version="1.0">
40789 @r{[}@var{architecture}@r{]}
40790 @r{[}@var{osabi}@r{]}
40791 @r{[}@var{compatible}@r{]}
40792 @r{[}@var{feature}@dots{}@r{]}
40797 The description is generally insensitive to whitespace and line
40798 breaks, under the usual common-sense rules. The XML version
40799 declaration and document type declaration can generally be omitted
40800 (@value{GDBN} does not require them), but specifying them may be
40801 useful for XML validation tools. The @samp{version} attribute for
40802 @samp{<target>} may also be omitted, but we recommend
40803 including it; if future versions of @value{GDBN} use an incompatible
40804 revision of @file{gdb-target.dtd}, they will detect and report
40805 the version mismatch.
40807 @subsection Inclusion
40808 @cindex target descriptions, inclusion
40811 @cindex <xi:include>
40814 It can sometimes be valuable to split a target description up into
40815 several different annexes, either for organizational purposes, or to
40816 share files between different possible target descriptions. You can
40817 divide a description into multiple files by replacing any element of
40818 the target description with an inclusion directive of the form:
40821 <xi:include href="@var{document}"/>
40825 When @value{GDBN} encounters an element of this form, it will retrieve
40826 the named XML @var{document}, and replace the inclusion directive with
40827 the contents of that document. If the current description was read
40828 using @samp{qXfer}, then so will be the included document;
40829 @var{document} will be interpreted as the name of an annex. If the
40830 current description was read from a file, @value{GDBN} will look for
40831 @var{document} as a file in the same directory where it found the
40832 original description.
40834 @subsection Architecture
40835 @cindex <architecture>
40837 An @samp{<architecture>} element has this form:
40840 <architecture>@var{arch}</architecture>
40843 @var{arch} is one of the architectures from the set accepted by
40844 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40847 @cindex @code{<osabi>}
40849 This optional field was introduced in @value{GDBN} version 7.0.
40850 Previous versions of @value{GDBN} ignore it.
40852 An @samp{<osabi>} element has this form:
40855 <osabi>@var{abi-name}</osabi>
40858 @var{abi-name} is an OS ABI name from the same selection accepted by
40859 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
40861 @subsection Compatible Architecture
40862 @cindex @code{<compatible>}
40864 This optional field was introduced in @value{GDBN} version 7.0.
40865 Previous versions of @value{GDBN} ignore it.
40867 A @samp{<compatible>} element has this form:
40870 <compatible>@var{arch}</compatible>
40873 @var{arch} is one of the architectures from the set accepted by
40874 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40876 A @samp{<compatible>} element is used to specify that the target
40877 is able to run binaries in some other than the main target architecture
40878 given by the @samp{<architecture>} element. For example, on the
40879 Cell Broadband Engine, the main architecture is @code{powerpc:common}
40880 or @code{powerpc:common64}, but the system is able to run binaries
40881 in the @code{spu} architecture as well. The way to describe this
40882 capability with @samp{<compatible>} is as follows:
40885 <architecture>powerpc:common</architecture>
40886 <compatible>spu</compatible>
40889 @subsection Features
40892 Each @samp{<feature>} describes some logical portion of the target
40893 system. Features are currently used to describe available CPU
40894 registers and the types of their contents. A @samp{<feature>} element
40898 <feature name="@var{name}">
40899 @r{[}@var{type}@dots{}@r{]}
40905 Each feature's name should be unique within the description. The name
40906 of a feature does not matter unless @value{GDBN} has some special
40907 knowledge of the contents of that feature; if it does, the feature
40908 should have its standard name. @xref{Standard Target Features}.
40912 Any register's value is a collection of bits which @value{GDBN} must
40913 interpret. The default interpretation is a two's complement integer,
40914 but other types can be requested by name in the register description.
40915 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
40916 Target Types}), and the description can define additional composite types.
40918 Each type element must have an @samp{id} attribute, which gives
40919 a unique (within the containing @samp{<feature>}) name to the type.
40920 Types must be defined before they are used.
40923 Some targets offer vector registers, which can be treated as arrays
40924 of scalar elements. These types are written as @samp{<vector>} elements,
40925 specifying the array element type, @var{type}, and the number of elements,
40929 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
40933 If a register's value is usefully viewed in multiple ways, define it
40934 with a union type containing the useful representations. The
40935 @samp{<union>} element contains one or more @samp{<field>} elements,
40936 each of which has a @var{name} and a @var{type}:
40939 <union id="@var{id}">
40940 <field name="@var{name}" type="@var{type}"/>
40946 If a register's value is composed from several separate values, define
40947 it with a structure type. There are two forms of the @samp{<struct>}
40948 element; a @samp{<struct>} element must either contain only bitfields
40949 or contain no bitfields. If the structure contains only bitfields,
40950 its total size in bytes must be specified, each bitfield must have an
40951 explicit start and end, and bitfields are automatically assigned an
40952 integer type. The field's @var{start} should be less than or
40953 equal to its @var{end}, and zero represents the least significant bit.
40956 <struct id="@var{id}" size="@var{size}">
40957 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40962 If the structure contains no bitfields, then each field has an
40963 explicit type, and no implicit padding is added.
40966 <struct id="@var{id}">
40967 <field name="@var{name}" type="@var{type}"/>
40973 If a register's value is a series of single-bit flags, define it with
40974 a flags type. The @samp{<flags>} element has an explicit @var{size}
40975 and contains one or more @samp{<field>} elements. Each field has a
40976 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
40980 <flags id="@var{id}" size="@var{size}">
40981 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40986 @subsection Registers
40989 Each register is represented as an element with this form:
40992 <reg name="@var{name}"
40993 bitsize="@var{size}"
40994 @r{[}regnum="@var{num}"@r{]}
40995 @r{[}save-restore="@var{save-restore}"@r{]}
40996 @r{[}type="@var{type}"@r{]}
40997 @r{[}group="@var{group}"@r{]}/>
41001 The components are as follows:
41006 The register's name; it must be unique within the target description.
41009 The register's size, in bits.
41012 The register's number. If omitted, a register's number is one greater
41013 than that of the previous register (either in the current feature or in
41014 a preceding feature); the first register in the target description
41015 defaults to zero. This register number is used to read or write
41016 the register; e.g.@: it is used in the remote @code{p} and @code{P}
41017 packets, and registers appear in the @code{g} and @code{G} packets
41018 in order of increasing register number.
41021 Whether the register should be preserved across inferior function
41022 calls; this must be either @code{yes} or @code{no}. The default is
41023 @code{yes}, which is appropriate for most registers except for
41024 some system control registers; this is not related to the target's
41028 The type of the register. @var{type} may be a predefined type, a type
41029 defined in the current feature, or one of the special types @code{int}
41030 and @code{float}. @code{int} is an integer type of the correct size
41031 for @var{bitsize}, and @code{float} is a floating point type (in the
41032 architecture's normal floating point format) of the correct size for
41033 @var{bitsize}. The default is @code{int}.
41036 The register group to which this register belongs. @var{group} must
41037 be either @code{general}, @code{float}, or @code{vector}. If no
41038 @var{group} is specified, @value{GDBN} will not display the register
41039 in @code{info registers}.
41043 @node Predefined Target Types
41044 @section Predefined Target Types
41045 @cindex target descriptions, predefined types
41047 Type definitions in the self-description can build up composite types
41048 from basic building blocks, but can not define fundamental types. Instead,
41049 standard identifiers are provided by @value{GDBN} for the fundamental
41050 types. The currently supported types are:
41059 Signed integer types holding the specified number of bits.
41066 Unsigned integer types holding the specified number of bits.
41070 Pointers to unspecified code and data. The program counter and
41071 any dedicated return address register may be marked as code
41072 pointers; printing a code pointer converts it into a symbolic
41073 address. The stack pointer and any dedicated address registers
41074 may be marked as data pointers.
41077 Single precision IEEE floating point.
41080 Double precision IEEE floating point.
41083 The 12-byte extended precision format used by ARM FPA registers.
41086 The 10-byte extended precision format used by x87 registers.
41089 32bit @sc{eflags} register used by x86.
41092 32bit @sc{mxcsr} register used by x86.
41096 @node Standard Target Features
41097 @section Standard Target Features
41098 @cindex target descriptions, standard features
41100 A target description must contain either no registers or all the
41101 target's registers. If the description contains no registers, then
41102 @value{GDBN} will assume a default register layout, selected based on
41103 the architecture. If the description contains any registers, the
41104 default layout will not be used; the standard registers must be
41105 described in the target description, in such a way that @value{GDBN}
41106 can recognize them.
41108 This is accomplished by giving specific names to feature elements
41109 which contain standard registers. @value{GDBN} will look for features
41110 with those names and verify that they contain the expected registers;
41111 if any known feature is missing required registers, or if any required
41112 feature is missing, @value{GDBN} will reject the target
41113 description. You can add additional registers to any of the
41114 standard features --- @value{GDBN} will display them just as if
41115 they were added to an unrecognized feature.
41117 This section lists the known features and their expected contents.
41118 Sample XML documents for these features are included in the
41119 @value{GDBN} source tree, in the directory @file{gdb/features}.
41121 Names recognized by @value{GDBN} should include the name of the
41122 company or organization which selected the name, and the overall
41123 architecture to which the feature applies; so e.g.@: the feature
41124 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
41126 The names of registers are not case sensitive for the purpose
41127 of recognizing standard features, but @value{GDBN} will only display
41128 registers using the capitalization used in the description.
41131 * AArch64 Features::
41136 * PowerPC Features::
41141 @node AArch64 Features
41142 @subsection AArch64 Features
41143 @cindex target descriptions, AArch64 features
41145 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
41146 targets. It should contain registers @samp{x0} through @samp{x30},
41147 @samp{sp}, @samp{pc}, and @samp{cpsr}.
41149 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
41150 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
41154 @subsection ARM Features
41155 @cindex target descriptions, ARM features
41157 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
41159 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
41160 @samp{lr}, @samp{pc}, and @samp{cpsr}.
41162 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
41163 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
41164 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
41167 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
41168 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
41170 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
41171 it should contain at least registers @samp{wR0} through @samp{wR15} and
41172 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
41173 @samp{wCSSF}, and @samp{wCASF} registers are optional.
41175 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
41176 should contain at least registers @samp{d0} through @samp{d15}. If
41177 they are present, @samp{d16} through @samp{d31} should also be included.
41178 @value{GDBN} will synthesize the single-precision registers from
41179 halves of the double-precision registers.
41181 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
41182 need to contain registers; it instructs @value{GDBN} to display the
41183 VFP double-precision registers as vectors and to synthesize the
41184 quad-precision registers from pairs of double-precision registers.
41185 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
41186 be present and include 32 double-precision registers.
41188 @node i386 Features
41189 @subsection i386 Features
41190 @cindex target descriptions, i386 features
41192 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
41193 targets. It should describe the following registers:
41197 @samp{eax} through @samp{edi} plus @samp{eip} for i386
41199 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
41201 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
41202 @samp{fs}, @samp{gs}
41204 @samp{st0} through @samp{st7}
41206 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
41207 @samp{foseg}, @samp{fooff} and @samp{fop}
41210 The register sets may be different, depending on the target.
41212 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
41213 describe registers:
41217 @samp{xmm0} through @samp{xmm7} for i386
41219 @samp{xmm0} through @samp{xmm15} for amd64
41224 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
41225 @samp{org.gnu.gdb.i386.sse} feature. It should
41226 describe the upper 128 bits of @sc{ymm} registers:
41230 @samp{ymm0h} through @samp{ymm7h} for i386
41232 @samp{ymm0h} through @samp{ymm15h} for amd64
41235 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
41236 describe a single register, @samp{orig_eax}.
41238 @node MIPS Features
41239 @subsection @acronym{MIPS} Features
41240 @cindex target descriptions, @acronym{MIPS} features
41242 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
41243 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
41244 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
41247 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
41248 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
41249 registers. They may be 32-bit or 64-bit depending on the target.
41251 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
41252 it may be optional in a future version of @value{GDBN}. It should
41253 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
41254 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
41256 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
41257 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
41258 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
41259 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
41261 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
41262 contain a single register, @samp{restart}, which is used by the
41263 Linux kernel to control restartable syscalls.
41265 @node M68K Features
41266 @subsection M68K Features
41267 @cindex target descriptions, M68K features
41270 @item @samp{org.gnu.gdb.m68k.core}
41271 @itemx @samp{org.gnu.gdb.coldfire.core}
41272 @itemx @samp{org.gnu.gdb.fido.core}
41273 One of those features must be always present.
41274 The feature that is present determines which flavor of m68k is
41275 used. The feature that is present should contain registers
41276 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
41277 @samp{sp}, @samp{ps} and @samp{pc}.
41279 @item @samp{org.gnu.gdb.coldfire.fp}
41280 This feature is optional. If present, it should contain registers
41281 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
41285 @node PowerPC Features
41286 @subsection PowerPC Features
41287 @cindex target descriptions, PowerPC features
41289 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
41290 targets. It should contain registers @samp{r0} through @samp{r31},
41291 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
41292 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
41294 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
41295 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
41297 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
41298 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
41301 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
41302 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
41303 will combine these registers with the floating point registers
41304 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
41305 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
41306 through @samp{vs63}, the set of vector registers for POWER7.
41308 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
41309 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
41310 @samp{spefscr}. SPE targets should provide 32-bit registers in
41311 @samp{org.gnu.gdb.power.core} and provide the upper halves in
41312 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
41313 these to present registers @samp{ev0} through @samp{ev31} to the
41316 @node TIC6x Features
41317 @subsection TMS320C6x Features
41318 @cindex target descriptions, TIC6x features
41319 @cindex target descriptions, TMS320C6x features
41320 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
41321 targets. It should contain registers @samp{A0} through @samp{A15},
41322 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
41324 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
41325 contain registers @samp{A16} through @samp{A31} and @samp{B16}
41326 through @samp{B31}.
41328 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
41329 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
41331 @node Operating System Information
41332 @appendix Operating System Information
41333 @cindex operating system information
41339 Users of @value{GDBN} often wish to obtain information about the state of
41340 the operating system running on the target---for example the list of
41341 processes, or the list of open files. This section describes the
41342 mechanism that makes it possible. This mechanism is similar to the
41343 target features mechanism (@pxref{Target Descriptions}), but focuses
41344 on a different aspect of target.
41346 Operating system information is retrived from the target via the
41347 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
41348 read}). The object name in the request should be @samp{osdata}, and
41349 the @var{annex} identifies the data to be fetched.
41352 @appendixsection Process list
41353 @cindex operating system information, process list
41355 When requesting the process list, the @var{annex} field in the
41356 @samp{qXfer} request should be @samp{processes}. The returned data is
41357 an XML document. The formal syntax of this document is defined in
41358 @file{gdb/features/osdata.dtd}.
41360 An example document is:
41363 <?xml version="1.0"?>
41364 <!DOCTYPE target SYSTEM "osdata.dtd">
41365 <osdata type="processes">
41367 <column name="pid">1</column>
41368 <column name="user">root</column>
41369 <column name="command">/sbin/init</column>
41370 <column name="cores">1,2,3</column>
41375 Each item should include a column whose name is @samp{pid}. The value
41376 of that column should identify the process on the target. The
41377 @samp{user} and @samp{command} columns are optional, and will be
41378 displayed by @value{GDBN}. The @samp{cores} column, if present,
41379 should contain a comma-separated list of cores that this process
41380 is running on. Target may provide additional columns,
41381 which @value{GDBN} currently ignores.
41383 @node Trace File Format
41384 @appendix Trace File Format
41385 @cindex trace file format
41387 The trace file comes in three parts: a header, a textual description
41388 section, and a trace frame section with binary data.
41390 The header has the form @code{\x7fTRACE0\n}. The first byte is
41391 @code{0x7f} so as to indicate that the file contains binary data,
41392 while the @code{0} is a version number that may have different values
41395 The description section consists of multiple lines of @sc{ascii} text
41396 separated by newline characters (@code{0xa}). The lines may include a
41397 variety of optional descriptive or context-setting information, such
41398 as tracepoint definitions or register set size. @value{GDBN} will
41399 ignore any line that it does not recognize. An empty line marks the end
41402 @c FIXME add some specific types of data
41404 The trace frame section consists of a number of consecutive frames.
41405 Each frame begins with a two-byte tracepoint number, followed by a
41406 four-byte size giving the amount of data in the frame. The data in
41407 the frame consists of a number of blocks, each introduced by a
41408 character indicating its type (at least register, memory, and trace
41409 state variable). The data in this section is raw binary, not a
41410 hexadecimal or other encoding; its endianness matches the target's
41413 @c FIXME bi-arch may require endianness/arch info in description section
41416 @item R @var{bytes}
41417 Register block. The number and ordering of bytes matches that of a
41418 @code{g} packet in the remote protocol. Note that these are the
41419 actual bytes, in target order and @value{GDBN} register order, not a
41420 hexadecimal encoding.
41422 @item M @var{address} @var{length} @var{bytes}...
41423 Memory block. This is a contiguous block of memory, at the 8-byte
41424 address @var{address}, with a 2-byte length @var{length}, followed by
41425 @var{length} bytes.
41427 @item V @var{number} @var{value}
41428 Trace state variable block. This records the 8-byte signed value
41429 @var{value} of trace state variable numbered @var{number}.
41433 Future enhancements of the trace file format may include additional types
41436 @node Index Section Format
41437 @appendix @code{.gdb_index} section format
41438 @cindex .gdb_index section format
41439 @cindex index section format
41441 This section documents the index section that is created by @code{save
41442 gdb-index} (@pxref{Index Files}). The index section is
41443 DWARF-specific; some knowledge of DWARF is assumed in this
41446 The mapped index file format is designed to be directly
41447 @code{mmap}able on any architecture. In most cases, a datum is
41448 represented using a little-endian 32-bit integer value, called an
41449 @code{offset_type}. Big endian machines must byte-swap the values
41450 before using them. Exceptions to this rule are noted. The data is
41451 laid out such that alignment is always respected.
41453 A mapped index consists of several areas, laid out in order.
41457 The file header. This is a sequence of values, of @code{offset_type}
41458 unless otherwise noted:
41462 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
41463 Version 4 uses a different hashing function from versions 5 and 6.
41464 Version 6 includes symbols for inlined functions, whereas versions 4
41465 and 5 do not. Version 7 adds attributes to the CU indices in the
41466 symbol table. Version 8 specifies that symbols from DWARF type units
41467 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
41468 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
41470 @value{GDBN} will only read version 4, 5, or 6 indices
41471 by specifying @code{set use-deprecated-index-sections on}.
41472 GDB has a workaround for potentially broken version 7 indices so it is
41473 currently not flagged as deprecated.
41476 The offset, from the start of the file, of the CU list.
41479 The offset, from the start of the file, of the types CU list. Note
41480 that this area can be empty, in which case this offset will be equal
41481 to the next offset.
41484 The offset, from the start of the file, of the address area.
41487 The offset, from the start of the file, of the symbol table.
41490 The offset, from the start of the file, of the constant pool.
41494 The CU list. This is a sequence of pairs of 64-bit little-endian
41495 values, sorted by the CU offset. The first element in each pair is
41496 the offset of a CU in the @code{.debug_info} section. The second
41497 element in each pair is the length of that CU. References to a CU
41498 elsewhere in the map are done using a CU index, which is just the
41499 0-based index into this table. Note that if there are type CUs, then
41500 conceptually CUs and type CUs form a single list for the purposes of
41504 The types CU list. This is a sequence of triplets of 64-bit
41505 little-endian values. In a triplet, the first value is the CU offset,
41506 the second value is the type offset in the CU, and the third value is
41507 the type signature. The types CU list is not sorted.
41510 The address area. The address area consists of a sequence of address
41511 entries. Each address entry has three elements:
41515 The low address. This is a 64-bit little-endian value.
41518 The high address. This is a 64-bit little-endian value. Like
41519 @code{DW_AT_high_pc}, the value is one byte beyond the end.
41522 The CU index. This is an @code{offset_type} value.
41526 The symbol table. This is an open-addressed hash table. The size of
41527 the hash table is always a power of 2.
41529 Each slot in the hash table consists of a pair of @code{offset_type}
41530 values. The first value is the offset of the symbol's name in the
41531 constant pool. The second value is the offset of the CU vector in the
41534 If both values are 0, then this slot in the hash table is empty. This
41535 is ok because while 0 is a valid constant pool index, it cannot be a
41536 valid index for both a string and a CU vector.
41538 The hash value for a table entry is computed by applying an
41539 iterative hash function to the symbol's name. Starting with an
41540 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
41541 the string is incorporated into the hash using the formula depending on the
41546 The formula is @code{r = r * 67 + c - 113}.
41548 @item Versions 5 to 7
41549 The formula is @code{r = r * 67 + tolower (c) - 113}.
41552 The terminating @samp{\0} is not incorporated into the hash.
41554 The step size used in the hash table is computed via
41555 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
41556 value, and @samp{size} is the size of the hash table. The step size
41557 is used to find the next candidate slot when handling a hash
41560 The names of C@t{++} symbols in the hash table are canonicalized. We
41561 don't currently have a simple description of the canonicalization
41562 algorithm; if you intend to create new index sections, you must read
41566 The constant pool. This is simply a bunch of bytes. It is organized
41567 so that alignment is correct: CU vectors are stored first, followed by
41570 A CU vector in the constant pool is a sequence of @code{offset_type}
41571 values. The first value is the number of CU indices in the vector.
41572 Each subsequent value is the index and symbol attributes of a CU in
41573 the CU list. This element in the hash table is used to indicate which
41574 CUs define the symbol and how the symbol is used.
41575 See below for the format of each CU index+attributes entry.
41577 A string in the constant pool is zero-terminated.
41580 Attributes were added to CU index values in @code{.gdb_index} version 7.
41581 If a symbol has multiple uses within a CU then there is one
41582 CU index+attributes value for each use.
41584 The format of each CU index+attributes entry is as follows
41590 This is the index of the CU in the CU list.
41592 These bits are reserved for future purposes and must be zero.
41594 The kind of the symbol in the CU.
41598 This value is reserved and should not be used.
41599 By reserving zero the full @code{offset_type} value is backwards compatible
41600 with previous versions of the index.
41602 The symbol is a type.
41604 The symbol is a variable or an enum value.
41606 The symbol is a function.
41608 Any other kind of symbol.
41610 These values are reserved.
41614 This bit is zero if the value is global and one if it is static.
41616 The determination of whether a symbol is global or static is complicated.
41617 The authorative reference is the file @file{dwarf2read.c} in
41618 @value{GDBN} sources.
41622 This pseudo-code describes the computation of a symbol's kind and
41623 global/static attributes in the index.
41626 is_external = get_attribute (die, DW_AT_external);
41627 language = get_attribute (cu_die, DW_AT_language);
41630 case DW_TAG_typedef:
41631 case DW_TAG_base_type:
41632 case DW_TAG_subrange_type:
41636 case DW_TAG_enumerator:
41638 is_static = (language != CPLUS && language != JAVA);
41640 case DW_TAG_subprogram:
41642 is_static = ! (is_external || language == ADA);
41644 case DW_TAG_constant:
41646 is_static = ! is_external;
41648 case DW_TAG_variable:
41650 is_static = ! is_external;
41652 case DW_TAG_namespace:
41656 case DW_TAG_class_type:
41657 case DW_TAG_interface_type:
41658 case DW_TAG_structure_type:
41659 case DW_TAG_union_type:
41660 case DW_TAG_enumeration_type:
41662 is_static = (language != CPLUS && language != JAVA);
41670 @appendix Manual pages
41674 * gdb man:: The GNU Debugger man page
41675 * gdbserver man:: Remote Server for the GNU Debugger man page
41676 * gcore man:: Generate a core file of a running program
41677 * gdbinit man:: gdbinit scripts
41683 @c man title gdb The GNU Debugger
41685 @c man begin SYNOPSIS gdb
41686 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
41687 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
41688 [@option{-b}@w{ }@var{bps}]
41689 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
41690 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
41691 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
41692 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
41693 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
41696 @c man begin DESCRIPTION gdb
41697 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
41698 going on ``inside'' another program while it executes -- or what another
41699 program was doing at the moment it crashed.
41701 @value{GDBN} can do four main kinds of things (plus other things in support of
41702 these) to help you catch bugs in the act:
41706 Start your program, specifying anything that might affect its behavior.
41709 Make your program stop on specified conditions.
41712 Examine what has happened, when your program has stopped.
41715 Change things in your program, so you can experiment with correcting the
41716 effects of one bug and go on to learn about another.
41719 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
41722 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
41723 commands from the terminal until you tell it to exit with the @value{GDBN}
41724 command @code{quit}. You can get online help from @value{GDBN} itself
41725 by using the command @code{help}.
41727 You can run @code{gdb} with no arguments or options; but the most
41728 usual way to start @value{GDBN} is with one argument or two, specifying an
41729 executable program as the argument:
41735 You can also start with both an executable program and a core file specified:
41741 You can, instead, specify a process ID as a second argument, if you want
41742 to debug a running process:
41750 would attach @value{GDBN} to process @code{1234} (unless you also have a file
41751 named @file{1234}; @value{GDBN} does check for a core file first).
41752 With option @option{-p} you can omit the @var{program} filename.
41754 Here are some of the most frequently needed @value{GDBN} commands:
41756 @c pod2man highlights the right hand side of the @item lines.
41758 @item break [@var{file}:]@var{functiop}
41759 Set a breakpoint at @var{function} (in @var{file}).
41761 @item run [@var{arglist}]
41762 Start your program (with @var{arglist}, if specified).
41765 Backtrace: display the program stack.
41767 @item print @var{expr}
41768 Display the value of an expression.
41771 Continue running your program (after stopping, e.g. at a breakpoint).
41774 Execute next program line (after stopping); step @emph{over} any
41775 function calls in the line.
41777 @item edit [@var{file}:]@var{function}
41778 look at the program line where it is presently stopped.
41780 @item list [@var{file}:]@var{function}
41781 type the text of the program in the vicinity of where it is presently stopped.
41784 Execute next program line (after stopping); step @emph{into} any
41785 function calls in the line.
41787 @item help [@var{name}]
41788 Show information about @value{GDBN} command @var{name}, or general information
41789 about using @value{GDBN}.
41792 Exit from @value{GDBN}.
41796 For full details on @value{GDBN},
41797 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41798 by Richard M. Stallman and Roland H. Pesch. The same text is available online
41799 as the @code{gdb} entry in the @code{info} program.
41803 @c man begin OPTIONS gdb
41804 Any arguments other than options specify an executable
41805 file and core file (or process ID); that is, the first argument
41806 encountered with no
41807 associated option flag is equivalent to a @option{-se} option, and the second,
41808 if any, is equivalent to a @option{-c} option if it's the name of a file.
41810 both long and short forms; both are shown here. The long forms are also
41811 recognized if you truncate them, so long as enough of the option is
41812 present to be unambiguous. (If you prefer, you can flag option
41813 arguments with @option{+} rather than @option{-}, though we illustrate the
41814 more usual convention.)
41816 All the options and command line arguments you give are processed
41817 in sequential order. The order makes a difference when the @option{-x}
41823 List all options, with brief explanations.
41825 @item -symbols=@var{file}
41826 @itemx -s @var{file}
41827 Read symbol table from file @var{file}.
41830 Enable writing into executable and core files.
41832 @item -exec=@var{file}
41833 @itemx -e @var{file}
41834 Use file @var{file} as the executable file to execute when
41835 appropriate, and for examining pure data in conjunction with a core
41838 @item -se=@var{file}
41839 Read symbol table from file @var{file} and use it as the executable
41842 @item -core=@var{file}
41843 @itemx -c @var{file}
41844 Use file @var{file} as a core dump to examine.
41846 @item -command=@var{file}
41847 @itemx -x @var{file}
41848 Execute @value{GDBN} commands from file @var{file}.
41850 @item -ex @var{command}
41851 Execute given @value{GDBN} @var{command}.
41853 @item -directory=@var{directory}
41854 @itemx -d @var{directory}
41855 Add @var{directory} to the path to search for source files.
41858 Do not execute commands from @file{~/.gdbinit}.
41862 Do not execute commands from any @file{.gdbinit} initialization files.
41866 ``Quiet''. Do not print the introductory and copyright messages. These
41867 messages are also suppressed in batch mode.
41870 Run in batch mode. Exit with status @code{0} after processing all the command
41871 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
41872 Exit with nonzero status if an error occurs in executing the @value{GDBN}
41873 commands in the command files.
41875 Batch mode may be useful for running @value{GDBN} as a filter, for example to
41876 download and run a program on another computer; in order to make this
41877 more useful, the message
41880 Program exited normally.
41884 (which is ordinarily issued whenever a program running under @value{GDBN} control
41885 terminates) is not issued when running in batch mode.
41887 @item -cd=@var{directory}
41888 Run @value{GDBN} using @var{directory} as its working directory,
41889 instead of the current directory.
41893 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
41894 @value{GDBN} to output the full file name and line number in a standard,
41895 recognizable fashion each time a stack frame is displayed (which
41896 includes each time the program stops). This recognizable format looks
41897 like two @samp{\032} characters, followed by the file name, line number
41898 and character position separated by colons, and a newline. The
41899 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
41900 characters as a signal to display the source code for the frame.
41903 Set the line speed (baud rate or bits per second) of any serial
41904 interface used by @value{GDBN} for remote debugging.
41906 @item -tty=@var{device}
41907 Run using @var{device} for your program's standard input and output.
41911 @c man begin SEEALSO gdb
41913 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41914 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41915 documentation are properly installed at your site, the command
41922 should give you access to the complete manual.
41924 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41925 Richard M. Stallman and Roland H. Pesch, July 1991.
41929 @node gdbserver man
41930 @heading gdbserver man
41932 @c man title gdbserver Remote Server for the GNU Debugger
41934 @c man begin SYNOPSIS gdbserver
41935 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
41937 gdbserver --attach @var{comm} @var{pid}
41939 gdbserver --multi @var{comm}
41943 @c man begin DESCRIPTION gdbserver
41944 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
41945 than the one which is running the program being debugged.
41948 @subheading Usage (server (target) side)
41951 Usage (server (target) side):
41954 First, you need to have a copy of the program you want to debug put onto
41955 the target system. The program can be stripped to save space if needed, as
41956 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
41957 the @value{GDBN} running on the host system.
41959 To use the server, you log on to the target system, and run the @command{gdbserver}
41960 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
41961 your program, and (c) its arguments. The general syntax is:
41964 target> gdbserver @var{comm} @var{program} [@var{args} ...]
41967 For example, using a serial port, you might say:
41971 @c @file would wrap it as F</dev/com1>.
41972 target> gdbserver /dev/com1 emacs foo.txt
41975 target> gdbserver @file{/dev/com1} emacs foo.txt
41979 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
41980 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
41981 waits patiently for the host @value{GDBN} to communicate with it.
41983 To use a TCP connection, you could say:
41986 target> gdbserver host:2345 emacs foo.txt
41989 This says pretty much the same thing as the last example, except that we are
41990 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
41991 that we are expecting to see a TCP connection from @code{host} to local TCP port
41992 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
41993 want for the port number as long as it does not conflict with any existing TCP
41994 ports on the target system. This same port number must be used in the host
41995 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
41996 you chose a port number that conflicts with another service, @command{gdbserver} will
41997 print an error message and exit.
41999 @command{gdbserver} can also attach to running programs.
42000 This is accomplished via the @option{--attach} argument. The syntax is:
42003 target> gdbserver --attach @var{comm} @var{pid}
42006 @var{pid} is the process ID of a currently running process. It isn't
42007 necessary to point @command{gdbserver} at a binary for the running process.
42009 To start @code{gdbserver} without supplying an initial command to run
42010 or process ID to attach, use the @option{--multi} command line option.
42011 In such case you should connect using @kbd{target extended-remote} to start
42012 the program you want to debug.
42015 target> gdbserver --multi @var{comm}
42019 @subheading Usage (host side)
42025 You need an unstripped copy of the target program on your host system, since
42026 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
42027 would, with the target program as the first argument. (You may need to use the
42028 @option{--baud} option if the serial line is running at anything except 9600 baud.)
42029 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
42030 new command you need to know about is @code{target remote}
42031 (or @code{target extended-remote}). Its argument is either
42032 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
42033 descriptor. For example:
42037 @c @file would wrap it as F</dev/ttyb>.
42038 (gdb) target remote /dev/ttyb
42041 (gdb) target remote @file{/dev/ttyb}
42046 communicates with the server via serial line @file{/dev/ttyb}, and:
42049 (gdb) target remote the-target:2345
42053 communicates via a TCP connection to port 2345 on host `the-target', where
42054 you previously started up @command{gdbserver} with the same port number. Note that for
42055 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
42056 command, otherwise you may get an error that looks something like
42057 `Connection refused'.
42059 @command{gdbserver} can also debug multiple inferiors at once,
42062 the @value{GDBN} manual in node @code{Inferiors and Programs}
42063 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
42066 @ref{Inferiors and Programs}.
42068 In such case use the @code{extended-remote} @value{GDBN} command variant:
42071 (gdb) target extended-remote the-target:2345
42074 The @command{gdbserver} option @option{--multi} may or may not be used in such
42078 @c man begin OPTIONS gdbserver
42079 There are three different modes for invoking @command{gdbserver}:
42084 Debug a specific program specified by its program name:
42087 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
42090 The @var{comm} parameter specifies how should the server communicate
42091 with @value{GDBN}; it is either a device name (to use a serial line),
42092 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
42093 stdin/stdout of @code{gdbserver}. Specify the name of the program to
42094 debug in @var{prog}. Any remaining arguments will be passed to the
42095 program verbatim. When the program exits, @value{GDBN} will close the
42096 connection, and @code{gdbserver} will exit.
42099 Debug a specific program by specifying the process ID of a running
42103 gdbserver --attach @var{comm} @var{pid}
42106 The @var{comm} parameter is as described above. Supply the process ID
42107 of a running program in @var{pid}; @value{GDBN} will do everything
42108 else. Like with the previous mode, when the process @var{pid} exits,
42109 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
42112 Multi-process mode -- debug more than one program/process:
42115 gdbserver --multi @var{comm}
42118 In this mode, @value{GDBN} can instruct @command{gdbserver} which
42119 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
42120 close the connection when a process being debugged exits, so you can
42121 debug several processes in the same session.
42124 In each of the modes you may specify these options:
42129 List all options, with brief explanations.
42132 This option causes @command{gdbserver} to print its version number and exit.
42135 @command{gdbserver} will attach to a running program. The syntax is:
42138 target> gdbserver --attach @var{comm} @var{pid}
42141 @var{pid} is the process ID of a currently running process. It isn't
42142 necessary to point @command{gdbserver} at a binary for the running process.
42145 To start @code{gdbserver} without supplying an initial command to run
42146 or process ID to attach, use this command line option.
42147 Then you can connect using @kbd{target extended-remote} and start
42148 the program you want to debug. The syntax is:
42151 target> gdbserver --multi @var{comm}
42155 Instruct @code{gdbserver} to display extra status information about the debugging
42157 This option is intended for @code{gdbserver} development and for bug reports to
42160 @item --remote-debug
42161 Instruct @code{gdbserver} to display remote protocol debug output.
42162 This option is intended for @code{gdbserver} development and for bug reports to
42166 Specify a wrapper to launch programs
42167 for debugging. The option should be followed by the name of the
42168 wrapper, then any command-line arguments to pass to the wrapper, then
42169 @kbd{--} indicating the end of the wrapper arguments.
42172 By default, @command{gdbserver} keeps the listening TCP port open, so that
42173 additional connections are possible. However, if you start @code{gdbserver}
42174 with the @option{--once} option, it will stop listening for any further
42175 connection attempts after connecting to the first @value{GDBN} session.
42177 @c --disable-packet is not documented for users.
42179 @c --disable-randomization and --no-disable-randomization are superseded by
42180 @c QDisableRandomization.
42185 @c man begin SEEALSO gdbserver
42187 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42188 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42189 documentation are properly installed at your site, the command
42195 should give you access to the complete manual.
42197 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42198 Richard M. Stallman and Roland H. Pesch, July 1991.
42205 @c man title gcore Generate a core file of a running program
42208 @c man begin SYNOPSIS gcore
42209 gcore [-o @var{filename}] @var{pid}
42213 @c man begin DESCRIPTION gcore
42214 Generate a core dump of a running program with process ID @var{pid}.
42215 Produced file is equivalent to a kernel produced core file as if the process
42216 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
42217 limit). Unlike after a crash, after @command{gcore} the program remains
42218 running without any change.
42221 @c man begin OPTIONS gcore
42223 @item -o @var{filename}
42224 The optional argument
42225 @var{filename} specifies the file name where to put the core dump.
42226 If not specified, the file name defaults to @file{core.@var{pid}},
42227 where @var{pid} is the running program process ID.
42231 @c man begin SEEALSO gcore
42233 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42234 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42235 documentation are properly installed at your site, the command
42242 should give you access to the complete manual.
42244 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42245 Richard M. Stallman and Roland H. Pesch, July 1991.
42252 @c man title gdbinit GDB initialization scripts
42255 @c man begin SYNOPSIS gdbinit
42256 @ifset SYSTEM_GDBINIT
42257 @value{SYSTEM_GDBINIT}
42266 @c man begin DESCRIPTION gdbinit
42267 These files contain @value{GDBN} commands to automatically execute during
42268 @value{GDBN} startup. The lines of contents are canned sequences of commands,
42271 the @value{GDBN} manual in node @code{Sequences}
42272 -- shell command @code{info -f gdb -n Sequences}.
42278 Please read more in
42280 the @value{GDBN} manual in node @code{Startup}
42281 -- shell command @code{info -f gdb -n Startup}.
42288 @ifset SYSTEM_GDBINIT
42289 @item @value{SYSTEM_GDBINIT}
42291 @ifclear SYSTEM_GDBINIT
42292 @item (not enabled with @code{--with-system-gdbinit} during compilation)
42294 System-wide initialization file. It is executed unless user specified
42295 @value{GDBN} option @code{-nx} or @code{-n}.
42298 the @value{GDBN} manual in node @code{System-wide configuration}
42299 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
42302 @ref{System-wide configuration}.
42306 User initialization file. It is executed unless user specified
42307 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
42310 Initialization file for current directory. It may need to be enabled with
42311 @value{GDBN} security command @code{set auto-load local-gdbinit}.
42314 the @value{GDBN} manual in node @code{Init File in the Current Directory}
42315 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
42318 @ref{Init File in the Current Directory}.
42323 @c man begin SEEALSO gdbinit
42325 gdb(1), @code{info -f gdb -n Startup}
42327 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42328 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42329 documentation are properly installed at your site, the command
42335 should give you access to the complete manual.
42337 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42338 Richard M. Stallman and Roland H. Pesch, July 1991.
42344 @node GNU Free Documentation License
42345 @appendix GNU Free Documentation License
42348 @node Concept Index
42349 @unnumbered Concept Index
42353 @node Command and Variable Index
42354 @unnumbered Command, Variable, and Function Index
42359 % I think something like @@colophon should be in texinfo. In the
42361 \long\def\colophon{\hbox to0pt{}\vfill
42362 \centerline{The body of this manual is set in}
42363 \centerline{\fontname\tenrm,}
42364 \centerline{with headings in {\bf\fontname\tenbf}}
42365 \centerline{and examples in {\tt\fontname\tentt}.}
42366 \centerline{{\it\fontname\tenit\/},}
42367 \centerline{{\bf\fontname\tenbf}, and}
42368 \centerline{{\sl\fontname\tensl\/}}
42369 \centerline{are used for emphasis.}\vfill}
42371 % Blame: doc@@cygnus.com, 1991.