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 @item throw @r{[}@var{regexp}@r{]}
4078 @itemx rethrow @r{[}@var{regexp}@r{]}
4079 @itemx catch @r{[}@var{regexp}@r{]}
4080 @cindex stop on C@t{++} exceptions
4081 The throwing, re-throwing, or catching of a C@t{++} exception.
4083 If @var{regexp} is given, then only exceptions whose type matches the
4084 regular expression will be caught.
4086 @vindex $_exception@r{, convenience variable}
4087 The convenience variable @code{$_exception} is available at an
4088 exception-related catchpoint, on some systems. This holds the
4089 exception being thrown.
4091 There are currently some limitations to C@t{++} exception handling in
4096 The support for these commands is system-dependent. Currently, only
4097 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4101 The regular expression feature and the @code{$_exception} convenience
4102 variable rely on the presence of some SDT probes in @code{libstdc++}.
4103 If these probes are not present, then these features cannot be used.
4104 These probes were first available in the GCC 4.8 release, but whether
4105 or not they are available in your GCC also depends on how it was
4109 The @code{$_exception} convenience variable is only valid at the
4110 instruction at which an exception-related catchpoint is set.
4113 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4114 location in the system library which implements runtime exception
4115 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4116 (@pxref{Selection}) to get to your code.
4119 If you call a function interactively, @value{GDBN} normally returns
4120 control to you when the function has finished executing. If the call
4121 raises an exception, however, the call may bypass the mechanism that
4122 returns control to you and cause your program either to abort or to
4123 simply continue running until it hits a breakpoint, catches a signal
4124 that @value{GDBN} is listening for, or exits. This is the case even if
4125 you set a catchpoint for the exception; catchpoints on exceptions are
4126 disabled within interactive calls. @xref{Calling}, for information on
4127 controlling this with @code{set unwind-on-terminating-exception}.
4130 You cannot raise an exception interactively.
4133 You cannot install an exception handler interactively.
4137 @cindex Ada exception catching
4138 @cindex catch Ada exceptions
4139 An Ada exception being raised. If an exception name is specified
4140 at the end of the command (eg @code{catch exception Program_Error}),
4141 the debugger will stop only when this specific exception is raised.
4142 Otherwise, the debugger stops execution when any Ada exception is raised.
4144 When inserting an exception catchpoint on a user-defined exception whose
4145 name is identical to one of the exceptions defined by the language, the
4146 fully qualified name must be used as the exception name. Otherwise,
4147 @value{GDBN} will assume that it should stop on the pre-defined exception
4148 rather than the user-defined one. For instance, assuming an exception
4149 called @code{Constraint_Error} is defined in package @code{Pck}, then
4150 the command to use to catch such exceptions is @kbd{catch exception
4151 Pck.Constraint_Error}.
4153 @item exception unhandled
4154 An exception that was raised but is not handled by the program.
4157 A failed Ada assertion.
4160 @cindex break on fork/exec
4161 A call to @code{exec}. This is currently only available for HP-UX
4165 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4166 @cindex break on a system call.
4167 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4168 syscall is a mechanism for application programs to request a service
4169 from the operating system (OS) or one of the OS system services.
4170 @value{GDBN} can catch some or all of the syscalls issued by the
4171 debuggee, and show the related information for each syscall. If no
4172 argument is specified, calls to and returns from all system calls
4175 @var{name} can be any system call name that is valid for the
4176 underlying OS. Just what syscalls are valid depends on the OS. On
4177 GNU and Unix systems, you can find the full list of valid syscall
4178 names on @file{/usr/include/asm/unistd.h}.
4180 @c For MS-Windows, the syscall names and the corresponding numbers
4181 @c can be found, e.g., on this URL:
4182 @c http://www.metasploit.com/users/opcode/syscalls.html
4183 @c but we don't support Windows syscalls yet.
4185 Normally, @value{GDBN} knows in advance which syscalls are valid for
4186 each OS, so you can use the @value{GDBN} command-line completion
4187 facilities (@pxref{Completion,, command completion}) to list the
4190 You may also specify the system call numerically. A syscall's
4191 number is the value passed to the OS's syscall dispatcher to
4192 identify the requested service. When you specify the syscall by its
4193 name, @value{GDBN} uses its database of syscalls to convert the name
4194 into the corresponding numeric code, but using the number directly
4195 may be useful if @value{GDBN}'s database does not have the complete
4196 list of syscalls on your system (e.g., because @value{GDBN} lags
4197 behind the OS upgrades).
4199 The example below illustrates how this command works if you don't provide
4203 (@value{GDBP}) catch syscall
4204 Catchpoint 1 (syscall)
4206 Starting program: /tmp/catch-syscall
4208 Catchpoint 1 (call to syscall 'close'), \
4209 0xffffe424 in __kernel_vsyscall ()
4213 Catchpoint 1 (returned from syscall 'close'), \
4214 0xffffe424 in __kernel_vsyscall ()
4218 Here is an example of catching a system call by name:
4221 (@value{GDBP}) catch syscall chroot
4222 Catchpoint 1 (syscall 'chroot' [61])
4224 Starting program: /tmp/catch-syscall
4226 Catchpoint 1 (call to syscall 'chroot'), \
4227 0xffffe424 in __kernel_vsyscall ()
4231 Catchpoint 1 (returned from syscall 'chroot'), \
4232 0xffffe424 in __kernel_vsyscall ()
4236 An example of specifying a system call numerically. In the case
4237 below, the syscall number has a corresponding entry in the XML
4238 file, so @value{GDBN} finds its name and prints it:
4241 (@value{GDBP}) catch syscall 252
4242 Catchpoint 1 (syscall(s) 'exit_group')
4244 Starting program: /tmp/catch-syscall
4246 Catchpoint 1 (call to syscall 'exit_group'), \
4247 0xffffe424 in __kernel_vsyscall ()
4251 Program exited normally.
4255 However, there can be situations when there is no corresponding name
4256 in XML file for that syscall number. In this case, @value{GDBN} prints
4257 a warning message saying that it was not able to find the syscall name,
4258 but the catchpoint will be set anyway. See the example below:
4261 (@value{GDBP}) catch syscall 764
4262 warning: The number '764' does not represent a known syscall.
4263 Catchpoint 2 (syscall 764)
4267 If you configure @value{GDBN} using the @samp{--without-expat} option,
4268 it will not be able to display syscall names. Also, if your
4269 architecture does not have an XML file describing its system calls,
4270 you will not be able to see the syscall names. It is important to
4271 notice that these two features are used for accessing the syscall
4272 name database. In either case, you will see a warning like this:
4275 (@value{GDBP}) catch syscall
4276 warning: Could not open "syscalls/i386-linux.xml"
4277 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4278 GDB will not be able to display syscall names.
4279 Catchpoint 1 (syscall)
4283 Of course, the file name will change depending on your architecture and system.
4285 Still using the example above, you can also try to catch a syscall by its
4286 number. In this case, you would see something like:
4289 (@value{GDBP}) catch syscall 252
4290 Catchpoint 1 (syscall(s) 252)
4293 Again, in this case @value{GDBN} would not be able to display syscall's names.
4296 A call to @code{fork}. This is currently only available for HP-UX
4300 A call to @code{vfork}. This is currently only available for HP-UX
4303 @item load @r{[}regexp@r{]}
4304 @itemx unload @r{[}regexp@r{]}
4305 The loading or unloading of a shared library. If @var{regexp} is
4306 given, then the catchpoint will stop only if the regular expression
4307 matches one of the affected libraries.
4309 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4310 The delivery of a signal.
4312 With no arguments, this catchpoint will catch any signal that is not
4313 used internally by @value{GDBN}, specifically, all signals except
4314 @samp{SIGTRAP} and @samp{SIGINT}.
4316 With the argument @samp{all}, all signals, including those used by
4317 @value{GDBN}, will be caught. This argument cannot be used with other
4320 Otherwise, the arguments are a list of signal names as given to
4321 @code{handle} (@pxref{Signals}). Only signals specified in this list
4324 One reason that @code{catch signal} can be more useful than
4325 @code{handle} is that you can attach commands and conditions to the
4328 When a signal is caught by a catchpoint, the signal's @code{stop} and
4329 @code{print} settings, as specified by @code{handle}, are ignored.
4330 However, whether the signal is still delivered to the inferior depends
4331 on the @code{pass} setting; this can be changed in the catchpoint's
4336 @item tcatch @var{event}
4337 Set a catchpoint that is enabled only for one stop. The catchpoint is
4338 automatically deleted after the first time the event is caught.
4342 Use the @code{info break} command to list the current catchpoints.
4346 @subsection Deleting Breakpoints
4348 @cindex clearing breakpoints, watchpoints, catchpoints
4349 @cindex deleting breakpoints, watchpoints, catchpoints
4350 It is often necessary to eliminate a breakpoint, watchpoint, or
4351 catchpoint once it has done its job and you no longer want your program
4352 to stop there. This is called @dfn{deleting} the breakpoint. A
4353 breakpoint that has been deleted no longer exists; it is forgotten.
4355 With the @code{clear} command you can delete breakpoints according to
4356 where they are in your program. With the @code{delete} command you can
4357 delete individual breakpoints, watchpoints, or catchpoints by specifying
4358 their breakpoint numbers.
4360 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4361 automatically ignores breakpoints on the first instruction to be executed
4362 when you continue execution without changing the execution address.
4367 Delete any breakpoints at the next instruction to be executed in the
4368 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4369 the innermost frame is selected, this is a good way to delete a
4370 breakpoint where your program just stopped.
4372 @item clear @var{location}
4373 Delete any breakpoints set at the specified @var{location}.
4374 @xref{Specify Location}, for the various forms of @var{location}; the
4375 most useful ones are listed below:
4378 @item clear @var{function}
4379 @itemx clear @var{filename}:@var{function}
4380 Delete any breakpoints set at entry to the named @var{function}.
4382 @item clear @var{linenum}
4383 @itemx clear @var{filename}:@var{linenum}
4384 Delete any breakpoints set at or within the code of the specified
4385 @var{linenum} of the specified @var{filename}.
4388 @cindex delete breakpoints
4390 @kindex d @r{(@code{delete})}
4391 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4392 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4393 ranges specified as arguments. If no argument is specified, delete all
4394 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4395 confirm off}). You can abbreviate this command as @code{d}.
4399 @subsection Disabling Breakpoints
4401 @cindex enable/disable a breakpoint
4402 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4403 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4404 it had been deleted, but remembers the information on the breakpoint so
4405 that you can @dfn{enable} it again later.
4407 You disable and enable breakpoints, watchpoints, and catchpoints with
4408 the @code{enable} and @code{disable} commands, optionally specifying
4409 one or more breakpoint numbers as arguments. Use @code{info break} to
4410 print a list of all breakpoints, watchpoints, and catchpoints if you
4411 do not know which numbers to use.
4413 Disabling and enabling a breakpoint that has multiple locations
4414 affects all of its locations.
4416 A breakpoint, watchpoint, or catchpoint can have any of several
4417 different states of enablement:
4421 Enabled. The breakpoint stops your program. A breakpoint set
4422 with the @code{break} command starts out in this state.
4424 Disabled. The breakpoint has no effect on your program.
4426 Enabled once. The breakpoint stops your program, but then becomes
4429 Enabled for a count. The breakpoint stops your program for the next
4430 N times, then becomes disabled.
4432 Enabled for deletion. The breakpoint stops your program, but
4433 immediately after it does so it is deleted permanently. A breakpoint
4434 set with the @code{tbreak} command starts out in this state.
4437 You can use the following commands to enable or disable breakpoints,
4438 watchpoints, and catchpoints:
4442 @kindex dis @r{(@code{disable})}
4443 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4444 Disable the specified breakpoints---or all breakpoints, if none are
4445 listed. A disabled breakpoint has no effect but is not forgotten. All
4446 options such as ignore-counts, conditions and commands are remembered in
4447 case the breakpoint is enabled again later. You may abbreviate
4448 @code{disable} as @code{dis}.
4451 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4452 Enable the specified breakpoints (or all defined breakpoints). They
4453 become effective once again in stopping your program.
4455 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4456 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4457 of these breakpoints immediately after stopping your program.
4459 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4460 Enable the specified breakpoints temporarily. @value{GDBN} records
4461 @var{count} with each of the specified breakpoints, and decrements a
4462 breakpoint's count when it is hit. When any count reaches 0,
4463 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4464 count (@pxref{Conditions, ,Break Conditions}), that will be
4465 decremented to 0 before @var{count} is affected.
4467 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4468 Enable the specified breakpoints to work once, then die. @value{GDBN}
4469 deletes any of these breakpoints as soon as your program stops there.
4470 Breakpoints set by the @code{tbreak} command start out in this state.
4473 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4474 @c confusing: tbreak is also initially enabled.
4475 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4476 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4477 subsequently, they become disabled or enabled only when you use one of
4478 the commands above. (The command @code{until} can set and delete a
4479 breakpoint of its own, but it does not change the state of your other
4480 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4484 @subsection Break Conditions
4485 @cindex conditional breakpoints
4486 @cindex breakpoint conditions
4488 @c FIXME what is scope of break condition expr? Context where wanted?
4489 @c in particular for a watchpoint?
4490 The simplest sort of breakpoint breaks every time your program reaches a
4491 specified place. You can also specify a @dfn{condition} for a
4492 breakpoint. A condition is just a Boolean expression in your
4493 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4494 a condition evaluates the expression each time your program reaches it,
4495 and your program stops only if the condition is @emph{true}.
4497 This is the converse of using assertions for program validation; in that
4498 situation, you want to stop when the assertion is violated---that is,
4499 when the condition is false. In C, if you want to test an assertion expressed
4500 by the condition @var{assert}, you should set the condition
4501 @samp{! @var{assert}} on the appropriate breakpoint.
4503 Conditions are also accepted for watchpoints; you may not need them,
4504 since a watchpoint is inspecting the value of an expression anyhow---but
4505 it might be simpler, say, to just set a watchpoint on a variable name,
4506 and specify a condition that tests whether the new value is an interesting
4509 Break conditions can have side effects, and may even call functions in
4510 your program. This can be useful, for example, to activate functions
4511 that log program progress, or to use your own print functions to
4512 format special data structures. The effects are completely predictable
4513 unless there is another enabled breakpoint at the same address. (In
4514 that case, @value{GDBN} might see the other breakpoint first and stop your
4515 program without checking the condition of this one.) Note that
4516 breakpoint commands are usually more convenient and flexible than break
4518 purpose of performing side effects when a breakpoint is reached
4519 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4521 Breakpoint conditions can also be evaluated on the target's side if
4522 the target supports it. Instead of evaluating the conditions locally,
4523 @value{GDBN} encodes the expression into an agent expression
4524 (@pxref{Agent Expressions}) suitable for execution on the target,
4525 independently of @value{GDBN}. Global variables become raw memory
4526 locations, locals become stack accesses, and so forth.
4528 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4529 when its condition evaluates to true. This mechanism may provide faster
4530 response times depending on the performance characteristics of the target
4531 since it does not need to keep @value{GDBN} informed about
4532 every breakpoint trigger, even those with false conditions.
4534 Break conditions can be specified when a breakpoint is set, by using
4535 @samp{if} in the arguments to the @code{break} command. @xref{Set
4536 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4537 with the @code{condition} command.
4539 You can also use the @code{if} keyword with the @code{watch} command.
4540 The @code{catch} command does not recognize the @code{if} keyword;
4541 @code{condition} is the only way to impose a further condition on a
4546 @item condition @var{bnum} @var{expression}
4547 Specify @var{expression} as the break condition for breakpoint,
4548 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4549 breakpoint @var{bnum} stops your program only if the value of
4550 @var{expression} is true (nonzero, in C). When you use
4551 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4552 syntactic correctness, and to determine whether symbols in it have
4553 referents in the context of your breakpoint. If @var{expression} uses
4554 symbols not referenced in the context of the breakpoint, @value{GDBN}
4555 prints an error message:
4558 No symbol "foo" in current context.
4563 not actually evaluate @var{expression} at the time the @code{condition}
4564 command (or a command that sets a breakpoint with a condition, like
4565 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4567 @item condition @var{bnum}
4568 Remove the condition from breakpoint number @var{bnum}. It becomes
4569 an ordinary unconditional breakpoint.
4572 @cindex ignore count (of breakpoint)
4573 A special case of a breakpoint condition is to stop only when the
4574 breakpoint has been reached a certain number of times. This is so
4575 useful that there is a special way to do it, using the @dfn{ignore
4576 count} of the breakpoint. Every breakpoint has an ignore count, which
4577 is an integer. Most of the time, the ignore count is zero, and
4578 therefore has no effect. But if your program reaches a breakpoint whose
4579 ignore count is positive, then instead of stopping, it just decrements
4580 the ignore count by one and continues. As a result, if the ignore count
4581 value is @var{n}, the breakpoint does not stop the next @var{n} times
4582 your program reaches it.
4586 @item ignore @var{bnum} @var{count}
4587 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4588 The next @var{count} times the breakpoint is reached, your program's
4589 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4592 To make the breakpoint stop the next time it is reached, specify
4595 When you use @code{continue} to resume execution of your program from a
4596 breakpoint, you can specify an ignore count directly as an argument to
4597 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4598 Stepping,,Continuing and Stepping}.
4600 If a breakpoint has a positive ignore count and a condition, the
4601 condition is not checked. Once the ignore count reaches zero,
4602 @value{GDBN} resumes checking the condition.
4604 You could achieve the effect of the ignore count with a condition such
4605 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4606 is decremented each time. @xref{Convenience Vars, ,Convenience
4610 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4613 @node Break Commands
4614 @subsection Breakpoint Command Lists
4616 @cindex breakpoint commands
4617 You can give any breakpoint (or watchpoint or catchpoint) a series of
4618 commands to execute when your program stops due to that breakpoint. For
4619 example, you might want to print the values of certain expressions, or
4620 enable other breakpoints.
4624 @kindex end@r{ (breakpoint commands)}
4625 @item commands @r{[}@var{range}@dots{}@r{]}
4626 @itemx @dots{} @var{command-list} @dots{}
4628 Specify a list of commands for the given breakpoints. The commands
4629 themselves appear on the following lines. Type a line containing just
4630 @code{end} to terminate the commands.
4632 To remove all commands from a breakpoint, type @code{commands} and
4633 follow it immediately with @code{end}; that is, give no commands.
4635 With no argument, @code{commands} refers to the last breakpoint,
4636 watchpoint, or catchpoint set (not to the breakpoint most recently
4637 encountered). If the most recent breakpoints were set with a single
4638 command, then the @code{commands} will apply to all the breakpoints
4639 set by that command. This applies to breakpoints set by
4640 @code{rbreak}, and also applies when a single @code{break} command
4641 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4645 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4646 disabled within a @var{command-list}.
4648 You can use breakpoint commands to start your program up again. Simply
4649 use the @code{continue} command, or @code{step}, or any other command
4650 that resumes execution.
4652 Any other commands in the command list, after a command that resumes
4653 execution, are ignored. This is because any time you resume execution
4654 (even with a simple @code{next} or @code{step}), you may encounter
4655 another breakpoint---which could have its own command list, leading to
4656 ambiguities about which list to execute.
4659 If the first command you specify in a command list is @code{silent}, the
4660 usual message about stopping at a breakpoint is not printed. This may
4661 be desirable for breakpoints that are to print a specific message and
4662 then continue. If none of the remaining commands print anything, you
4663 see no sign that the breakpoint was reached. @code{silent} is
4664 meaningful only at the beginning of a breakpoint command list.
4666 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4667 print precisely controlled output, and are often useful in silent
4668 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4670 For example, here is how you could use breakpoint commands to print the
4671 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4677 printf "x is %d\n",x
4682 One application for breakpoint commands is to compensate for one bug so
4683 you can test for another. Put a breakpoint just after the erroneous line
4684 of code, give it a condition to detect the case in which something
4685 erroneous has been done, and give it commands to assign correct values
4686 to any variables that need them. End with the @code{continue} command
4687 so that your program does not stop, and start with the @code{silent}
4688 command so that no output is produced. Here is an example:
4699 @node Dynamic Printf
4700 @subsection Dynamic Printf
4702 @cindex dynamic printf
4704 The dynamic printf command @code{dprintf} combines a breakpoint with
4705 formatted printing of your program's data to give you the effect of
4706 inserting @code{printf} calls into your program on-the-fly, without
4707 having to recompile it.
4709 In its most basic form, the output goes to the GDB console. However,
4710 you can set the variable @code{dprintf-style} for alternate handling.
4711 For instance, you can ask to format the output by calling your
4712 program's @code{printf} function. This has the advantage that the
4713 characters go to the program's output device, so they can recorded in
4714 redirects to files and so forth.
4716 If you are doing remote debugging with a stub or agent, you can also
4717 ask to have the printf handled by the remote agent. In addition to
4718 ensuring that the output goes to the remote program's device along
4719 with any other output the program might produce, you can also ask that
4720 the dprintf remain active even after disconnecting from the remote
4721 target. Using the stub/agent is also more efficient, as it can do
4722 everything without needing to communicate with @value{GDBN}.
4726 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4727 Whenever execution reaches @var{location}, print the values of one or
4728 more @var{expressions} under the control of the string @var{template}.
4729 To print several values, separate them with commas.
4731 @item set dprintf-style @var{style}
4732 Set the dprintf output to be handled in one of several different
4733 styles enumerated below. A change of style affects all existing
4734 dynamic printfs immediately. (If you need individual control over the
4735 print commands, simply define normal breakpoints with
4736 explicitly-supplied command lists.)
4739 @kindex dprintf-style gdb
4740 Handle the output using the @value{GDBN} @code{printf} command.
4743 @kindex dprintf-style call
4744 Handle the output by calling a function in your program (normally
4748 @kindex dprintf-style agent
4749 Have the remote debugging agent (such as @code{gdbserver}) handle
4750 the output itself. This style is only available for agents that
4751 support running commands on the target.
4753 @item set dprintf-function @var{function}
4754 Set the function to call if the dprintf style is @code{call}. By
4755 default its value is @code{printf}. You may set it to any expression.
4756 that @value{GDBN} can evaluate to a function, as per the @code{call}
4759 @item set dprintf-channel @var{channel}
4760 Set a ``channel'' for dprintf. If set to a non-empty value,
4761 @value{GDBN} will evaluate it as an expression and pass the result as
4762 a first argument to the @code{dprintf-function}, in the manner of
4763 @code{fprintf} and similar functions. Otherwise, the dprintf format
4764 string will be the first argument, in the manner of @code{printf}.
4766 As an example, if you wanted @code{dprintf} output to go to a logfile
4767 that is a standard I/O stream assigned to the variable @code{mylog},
4768 you could do the following:
4771 (gdb) set dprintf-style call
4772 (gdb) set dprintf-function fprintf
4773 (gdb) set dprintf-channel mylog
4774 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4775 Dprintf 1 at 0x123456: file main.c, line 25.
4777 1 dprintf keep y 0x00123456 in main at main.c:25
4778 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4783 Note that the @code{info break} displays the dynamic printf commands
4784 as normal breakpoint commands; you can thus easily see the effect of
4785 the variable settings.
4787 @item set disconnected-dprintf on
4788 @itemx set disconnected-dprintf off
4789 @kindex set disconnected-dprintf
4790 Choose whether @code{dprintf} commands should continue to run if
4791 @value{GDBN} has disconnected from the target. This only applies
4792 if the @code{dprintf-style} is @code{agent}.
4794 @item show disconnected-dprintf off
4795 @kindex show disconnected-dprintf
4796 Show the current choice for disconnected @code{dprintf}.
4800 @value{GDBN} does not check the validity of function and channel,
4801 relying on you to supply values that are meaningful for the contexts
4802 in which they are being used. For instance, the function and channel
4803 may be the values of local variables, but if that is the case, then
4804 all enabled dynamic prints must be at locations within the scope of
4805 those locals. If evaluation fails, @value{GDBN} will report an error.
4807 @node Save Breakpoints
4808 @subsection How to save breakpoints to a file
4810 To save breakpoint definitions to a file use the @w{@code{save
4811 breakpoints}} command.
4814 @kindex save breakpoints
4815 @cindex save breakpoints to a file for future sessions
4816 @item save breakpoints [@var{filename}]
4817 This command saves all current breakpoint definitions together with
4818 their commands and ignore counts, into a file @file{@var{filename}}
4819 suitable for use in a later debugging session. This includes all
4820 types of breakpoints (breakpoints, watchpoints, catchpoints,
4821 tracepoints). To read the saved breakpoint definitions, use the
4822 @code{source} command (@pxref{Command Files}). Note that watchpoints
4823 with expressions involving local variables may fail to be recreated
4824 because it may not be possible to access the context where the
4825 watchpoint is valid anymore. Because the saved breakpoint definitions
4826 are simply a sequence of @value{GDBN} commands that recreate the
4827 breakpoints, you can edit the file in your favorite editing program,
4828 and remove the breakpoint definitions you're not interested in, or
4829 that can no longer be recreated.
4832 @node Static Probe Points
4833 @subsection Static Probe Points
4835 @cindex static probe point, SystemTap
4836 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4837 for Statically Defined Tracing, and the probes are designed to have a tiny
4838 runtime code and data footprint, and no dynamic relocations. They are
4839 usable from assembly, C and C@t{++} languages. See
4840 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4841 for a good reference on how the @acronym{SDT} probes are implemented.
4843 Currently, @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4844 @acronym{SDT} probes are supported on ELF-compatible systems. See
4845 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4846 for more information on how to add @code{SystemTap} @acronym{SDT} probes
4847 in your applications.
4849 @cindex semaphores on static probe points
4850 Some probes have an associated semaphore variable; for instance, this
4851 happens automatically if you defined your probe using a DTrace-style
4852 @file{.d} file. If your probe has a semaphore, @value{GDBN} will
4853 automatically enable it when you specify a breakpoint using the
4854 @samp{-probe-stap} notation. But, if you put a breakpoint at a probe's
4855 location by some other method (e.g., @code{break file:line}), then
4856 @value{GDBN} will not automatically set the semaphore.
4858 You can examine the available static static probes using @code{info
4859 probes}, with optional arguments:
4863 @item info probes stap @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
4864 If given, @var{provider} is a regular expression used to match against provider
4865 names when selecting which probes to list. If omitted, probes by all
4866 probes from all providers are listed.
4868 If given, @var{name} is a regular expression to match against probe names
4869 when selecting which probes to list. If omitted, probe names are not
4870 considered when deciding whether to display them.
4872 If given, @var{objfile} is a regular expression used to select which
4873 object files (executable or shared libraries) to examine. If not
4874 given, all object files are considered.
4876 @item info probes all
4877 List the available static probes, from all types.
4880 @vindex $_probe_arg@r{, convenience variable}
4881 A probe may specify up to twelve arguments. These are available at the
4882 point at which the probe is defined---that is, when the current PC is
4883 at the probe's location. The arguments are available using the
4884 convenience variables (@pxref{Convenience Vars})
4885 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. Each probe argument is
4886 an integer of the appropriate size; types are not preserved. The
4887 convenience variable @code{$_probe_argc} holds the number of arguments
4888 at the current probe point.
4890 These variables are always available, but attempts to access them at
4891 any location other than a probe point will cause @value{GDBN} to give
4895 @c @ifclear BARETARGET
4896 @node Error in Breakpoints
4897 @subsection ``Cannot insert breakpoints''
4899 If you request too many active hardware-assisted breakpoints and
4900 watchpoints, you will see this error message:
4902 @c FIXME: the precise wording of this message may change; the relevant
4903 @c source change is not committed yet (Sep 3, 1999).
4905 Stopped; cannot insert breakpoints.
4906 You may have requested too many hardware breakpoints and watchpoints.
4910 This message is printed when you attempt to resume the program, since
4911 only then @value{GDBN} knows exactly how many hardware breakpoints and
4912 watchpoints it needs to insert.
4914 When this message is printed, you need to disable or remove some of the
4915 hardware-assisted breakpoints and watchpoints, and then continue.
4917 @node Breakpoint-related Warnings
4918 @subsection ``Breakpoint address adjusted...''
4919 @cindex breakpoint address adjusted
4921 Some processor architectures place constraints on the addresses at
4922 which breakpoints may be placed. For architectures thus constrained,
4923 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4924 with the constraints dictated by the architecture.
4926 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4927 a VLIW architecture in which a number of RISC-like instructions may be
4928 bundled together for parallel execution. The FR-V architecture
4929 constrains the location of a breakpoint instruction within such a
4930 bundle to the instruction with the lowest address. @value{GDBN}
4931 honors this constraint by adjusting a breakpoint's address to the
4932 first in the bundle.
4934 It is not uncommon for optimized code to have bundles which contain
4935 instructions from different source statements, thus it may happen that
4936 a breakpoint's address will be adjusted from one source statement to
4937 another. Since this adjustment may significantly alter @value{GDBN}'s
4938 breakpoint related behavior from what the user expects, a warning is
4939 printed when the breakpoint is first set and also when the breakpoint
4942 A warning like the one below is printed when setting a breakpoint
4943 that's been subject to address adjustment:
4946 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4949 Such warnings are printed both for user settable and @value{GDBN}'s
4950 internal breakpoints. If you see one of these warnings, you should
4951 verify that a breakpoint set at the adjusted address will have the
4952 desired affect. If not, the breakpoint in question may be removed and
4953 other breakpoints may be set which will have the desired behavior.
4954 E.g., it may be sufficient to place the breakpoint at a later
4955 instruction. A conditional breakpoint may also be useful in some
4956 cases to prevent the breakpoint from triggering too often.
4958 @value{GDBN} will also issue a warning when stopping at one of these
4959 adjusted breakpoints:
4962 warning: Breakpoint 1 address previously adjusted from 0x00010414
4966 When this warning is encountered, it may be too late to take remedial
4967 action except in cases where the breakpoint is hit earlier or more
4968 frequently than expected.
4970 @node Continuing and Stepping
4971 @section Continuing and Stepping
4975 @cindex resuming execution
4976 @dfn{Continuing} means resuming program execution until your program
4977 completes normally. In contrast, @dfn{stepping} means executing just
4978 one more ``step'' of your program, where ``step'' may mean either one
4979 line of source code, or one machine instruction (depending on what
4980 particular command you use). Either when continuing or when stepping,
4981 your program may stop even sooner, due to a breakpoint or a signal. (If
4982 it stops due to a signal, you may want to use @code{handle}, or use
4983 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4987 @kindex c @r{(@code{continue})}
4988 @kindex fg @r{(resume foreground execution)}
4989 @item continue @r{[}@var{ignore-count}@r{]}
4990 @itemx c @r{[}@var{ignore-count}@r{]}
4991 @itemx fg @r{[}@var{ignore-count}@r{]}
4992 Resume program execution, at the address where your program last stopped;
4993 any breakpoints set at that address are bypassed. The optional argument
4994 @var{ignore-count} allows you to specify a further number of times to
4995 ignore a breakpoint at this location; its effect is like that of
4996 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4998 The argument @var{ignore-count} is meaningful only when your program
4999 stopped due to a breakpoint. At other times, the argument to
5000 @code{continue} is ignored.
5002 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5003 debugged program is deemed to be the foreground program) are provided
5004 purely for convenience, and have exactly the same behavior as
5008 To resume execution at a different place, you can use @code{return}
5009 (@pxref{Returning, ,Returning from a Function}) to go back to the
5010 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5011 Different Address}) to go to an arbitrary location in your program.
5013 A typical technique for using stepping is to set a breakpoint
5014 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5015 beginning of the function or the section of your program where a problem
5016 is believed to lie, run your program until it stops at that breakpoint,
5017 and then step through the suspect area, examining the variables that are
5018 interesting, until you see the problem happen.
5022 @kindex s @r{(@code{step})}
5024 Continue running your program until control reaches a different source
5025 line, then stop it and return control to @value{GDBN}. This command is
5026 abbreviated @code{s}.
5029 @c "without debugging information" is imprecise; actually "without line
5030 @c numbers in the debugging information". (gcc -g1 has debugging info but
5031 @c not line numbers). But it seems complex to try to make that
5032 @c distinction here.
5033 @emph{Warning:} If you use the @code{step} command while control is
5034 within a function that was compiled without debugging information,
5035 execution proceeds until control reaches a function that does have
5036 debugging information. Likewise, it will not step into a function which
5037 is compiled without debugging information. To step through functions
5038 without debugging information, use the @code{stepi} command, described
5042 The @code{step} command only stops at the first instruction of a source
5043 line. This prevents the multiple stops that could otherwise occur in
5044 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5045 to stop if a function that has debugging information is called within
5046 the line. In other words, @code{step} @emph{steps inside} any functions
5047 called within the line.
5049 Also, the @code{step} command only enters a function if there is line
5050 number information for the function. Otherwise it acts like the
5051 @code{next} command. This avoids problems when using @code{cc -gl}
5052 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5053 was any debugging information about the routine.
5055 @item step @var{count}
5056 Continue running as in @code{step}, but do so @var{count} times. If a
5057 breakpoint is reached, or a signal not related to stepping occurs before
5058 @var{count} steps, stepping stops right away.
5061 @kindex n @r{(@code{next})}
5062 @item next @r{[}@var{count}@r{]}
5063 Continue to the next source line in the current (innermost) stack frame.
5064 This is similar to @code{step}, but function calls that appear within
5065 the line of code are executed without stopping. Execution stops when
5066 control reaches a different line of code at the original stack level
5067 that was executing when you gave the @code{next} command. This command
5068 is abbreviated @code{n}.
5070 An argument @var{count} is a repeat count, as for @code{step}.
5073 @c FIX ME!! Do we delete this, or is there a way it fits in with
5074 @c the following paragraph? --- Vctoria
5076 @c @code{next} within a function that lacks debugging information acts like
5077 @c @code{step}, but any function calls appearing within the code of the
5078 @c function are executed without stopping.
5080 The @code{next} command only stops at the first instruction of a
5081 source line. This prevents multiple stops that could otherwise occur in
5082 @code{switch} statements, @code{for} loops, etc.
5084 @kindex set step-mode
5086 @cindex functions without line info, and stepping
5087 @cindex stepping into functions with no line info
5088 @itemx set step-mode on
5089 The @code{set step-mode on} command causes the @code{step} command to
5090 stop at the first instruction of a function which contains no debug line
5091 information rather than stepping over it.
5093 This is useful in cases where you may be interested in inspecting the
5094 machine instructions of a function which has no symbolic info and do not
5095 want @value{GDBN} to automatically skip over this function.
5097 @item set step-mode off
5098 Causes the @code{step} command to step over any functions which contains no
5099 debug information. This is the default.
5101 @item show step-mode
5102 Show whether @value{GDBN} will stop in or step over functions without
5103 source line debug information.
5106 @kindex fin @r{(@code{finish})}
5108 Continue running until just after function in the selected stack frame
5109 returns. Print the returned value (if any). This command can be
5110 abbreviated as @code{fin}.
5112 Contrast this with the @code{return} command (@pxref{Returning,
5113 ,Returning from a Function}).
5116 @kindex u @r{(@code{until})}
5117 @cindex run until specified location
5120 Continue running until a source line past the current line, in the
5121 current stack frame, is reached. This command is used to avoid single
5122 stepping through a loop more than once. It is like the @code{next}
5123 command, except that when @code{until} encounters a jump, it
5124 automatically continues execution until the program counter is greater
5125 than the address of the jump.
5127 This means that when you reach the end of a loop after single stepping
5128 though it, @code{until} makes your program continue execution until it
5129 exits the loop. In contrast, a @code{next} command at the end of a loop
5130 simply steps back to the beginning of the loop, which forces you to step
5131 through the next iteration.
5133 @code{until} always stops your program if it attempts to exit the current
5136 @code{until} may produce somewhat counterintuitive results if the order
5137 of machine code does not match the order of the source lines. For
5138 example, in the following excerpt from a debugging session, the @code{f}
5139 (@code{frame}) command shows that execution is stopped at line
5140 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5144 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5146 (@value{GDBP}) until
5147 195 for ( ; argc > 0; NEXTARG) @{
5150 This happened because, for execution efficiency, the compiler had
5151 generated code for the loop closure test at the end, rather than the
5152 start, of the loop---even though the test in a C @code{for}-loop is
5153 written before the body of the loop. The @code{until} command appeared
5154 to step back to the beginning of the loop when it advanced to this
5155 expression; however, it has not really gone to an earlier
5156 statement---not in terms of the actual machine code.
5158 @code{until} with no argument works by means of single
5159 instruction stepping, and hence is slower than @code{until} with an
5162 @item until @var{location}
5163 @itemx u @var{location}
5164 Continue running your program until either the specified location is
5165 reached, or the current stack frame returns. @var{location} is any of
5166 the forms described in @ref{Specify Location}.
5167 This form of the command uses temporary breakpoints, and
5168 hence is quicker than @code{until} without an argument. The specified
5169 location is actually reached only if it is in the current frame. This
5170 implies that @code{until} can be used to skip over recursive function
5171 invocations. For instance in the code below, if the current location is
5172 line @code{96}, issuing @code{until 99} will execute the program up to
5173 line @code{99} in the same invocation of factorial, i.e., after the inner
5174 invocations have returned.
5177 94 int factorial (int value)
5179 96 if (value > 1) @{
5180 97 value *= factorial (value - 1);
5187 @kindex advance @var{location}
5188 @item advance @var{location}
5189 Continue running the program up to the given @var{location}. An argument is
5190 required, which should be of one of the forms described in
5191 @ref{Specify Location}.
5192 Execution will also stop upon exit from the current stack
5193 frame. This command is similar to @code{until}, but @code{advance} will
5194 not skip over recursive function calls, and the target location doesn't
5195 have to be in the same frame as the current one.
5199 @kindex si @r{(@code{stepi})}
5201 @itemx stepi @var{arg}
5203 Execute one machine instruction, then stop and return to the debugger.
5205 It is often useful to do @samp{display/i $pc} when stepping by machine
5206 instructions. This makes @value{GDBN} automatically display the next
5207 instruction to be executed, each time your program stops. @xref{Auto
5208 Display,, Automatic Display}.
5210 An argument is a repeat count, as in @code{step}.
5214 @kindex ni @r{(@code{nexti})}
5216 @itemx nexti @var{arg}
5218 Execute one machine instruction, but if it is a function call,
5219 proceed until the function returns.
5221 An argument is a repeat count, as in @code{next}.
5225 @anchor{range stepping}
5226 @cindex range stepping
5227 @cindex target-assisted range stepping
5228 By default, and if available, @value{GDBN} makes use of
5229 target-assisted @dfn{range stepping}. In other words, whenever you
5230 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5231 tells the target to step the corresponding range of instruction
5232 addresses instead of issuing multiple single-steps. This speeds up
5233 line stepping, particularly for remote targets. Ideally, there should
5234 be no reason you would want to turn range stepping off. However, it's
5235 possible that a bug in the debug info, a bug in the remote stub (for
5236 remote targets), or even a bug in @value{GDBN} could make line
5237 stepping behave incorrectly when target-assisted range stepping is
5238 enabled. You can use the following command to turn off range stepping
5242 @kindex set range-stepping
5243 @kindex show range-stepping
5244 @item set range-stepping
5245 @itemx show range-stepping
5246 Control whether range stepping is enabled.
5248 If @code{on}, and the target supports it, @value{GDBN} tells the
5249 target to step a range of addresses itself, instead of issuing
5250 multiple single-steps. If @code{off}, @value{GDBN} always issues
5251 single-steps, even if range stepping is supported by the target. The
5252 default is @code{on}.
5256 @node Skipping Over Functions and Files
5257 @section Skipping Over Functions and Files
5258 @cindex skipping over functions and files
5260 The program you are debugging may contain some functions which are
5261 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5262 skip a function or all functions in a file when stepping.
5264 For example, consider the following C function:
5275 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5276 are not interested in stepping through @code{boring}. If you run @code{step}
5277 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5278 step over both @code{foo} and @code{boring}!
5280 One solution is to @code{step} into @code{boring} and use the @code{finish}
5281 command to immediately exit it. But this can become tedious if @code{boring}
5282 is called from many places.
5284 A more flexible solution is to execute @kbd{skip boring}. This instructs
5285 @value{GDBN} never to step into @code{boring}. Now when you execute
5286 @code{step} at line 103, you'll step over @code{boring} and directly into
5289 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5290 example, @code{skip file boring.c}.
5293 @kindex skip function
5294 @item skip @r{[}@var{linespec}@r{]}
5295 @itemx skip function @r{[}@var{linespec}@r{]}
5296 After running this command, the function named by @var{linespec} or the
5297 function containing the line named by @var{linespec} will be skipped over when
5298 stepping. @xref{Specify Location}.
5300 If you do not specify @var{linespec}, the function you're currently debugging
5303 (If you have a function called @code{file} that you want to skip, use
5304 @kbd{skip function file}.)
5307 @item skip file @r{[}@var{filename}@r{]}
5308 After running this command, any function whose source lives in @var{filename}
5309 will be skipped over when stepping.
5311 If you do not specify @var{filename}, functions whose source lives in the file
5312 you're currently debugging will be skipped.
5315 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5316 These are the commands for managing your list of skips:
5320 @item info skip @r{[}@var{range}@r{]}
5321 Print details about the specified skip(s). If @var{range} is not specified,
5322 print a table with details about all functions and files marked for skipping.
5323 @code{info skip} prints the following information about each skip:
5327 A number identifying this skip.
5329 The type of this skip, either @samp{function} or @samp{file}.
5330 @item Enabled or Disabled
5331 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5333 For function skips, this column indicates the address in memory of the function
5334 being skipped. If you've set a function skip on a function which has not yet
5335 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5336 which has the function is loaded, @code{info skip} will show the function's
5339 For file skips, this field contains the filename being skipped. For functions
5340 skips, this field contains the function name and its line number in the file
5341 where it is defined.
5345 @item skip delete @r{[}@var{range}@r{]}
5346 Delete the specified skip(s). If @var{range} is not specified, delete all
5350 @item skip enable @r{[}@var{range}@r{]}
5351 Enable the specified skip(s). If @var{range} is not specified, enable all
5354 @kindex skip disable
5355 @item skip disable @r{[}@var{range}@r{]}
5356 Disable the specified skip(s). If @var{range} is not specified, disable all
5365 A signal is an asynchronous event that can happen in a program. The
5366 operating system defines the possible kinds of signals, and gives each
5367 kind a name and a number. For example, in Unix @code{SIGINT} is the
5368 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5369 @code{SIGSEGV} is the signal a program gets from referencing a place in
5370 memory far away from all the areas in use; @code{SIGALRM} occurs when
5371 the alarm clock timer goes off (which happens only if your program has
5372 requested an alarm).
5374 @cindex fatal signals
5375 Some signals, including @code{SIGALRM}, are a normal part of the
5376 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5377 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5378 program has not specified in advance some other way to handle the signal.
5379 @code{SIGINT} does not indicate an error in your program, but it is normally
5380 fatal so it can carry out the purpose of the interrupt: to kill the program.
5382 @value{GDBN} has the ability to detect any occurrence of a signal in your
5383 program. You can tell @value{GDBN} in advance what to do for each kind of
5386 @cindex handling signals
5387 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5388 @code{SIGALRM} be silently passed to your program
5389 (so as not to interfere with their role in the program's functioning)
5390 but to stop your program immediately whenever an error signal happens.
5391 You can change these settings with the @code{handle} command.
5394 @kindex info signals
5398 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5399 handle each one. You can use this to see the signal numbers of all
5400 the defined types of signals.
5402 @item info signals @var{sig}
5403 Similar, but print information only about the specified signal number.
5405 @code{info handle} is an alias for @code{info signals}.
5407 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5408 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5409 for details about this command.
5412 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5413 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5414 can be the number of a signal or its name (with or without the
5415 @samp{SIG} at the beginning); a list of signal numbers of the form
5416 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5417 known signals. Optional arguments @var{keywords}, described below,
5418 say what change to make.
5422 The keywords allowed by the @code{handle} command can be abbreviated.
5423 Their full names are:
5427 @value{GDBN} should not stop your program when this signal happens. It may
5428 still print a message telling you that the signal has come in.
5431 @value{GDBN} should stop your program when this signal happens. This implies
5432 the @code{print} keyword as well.
5435 @value{GDBN} should print a message when this signal happens.
5438 @value{GDBN} should not mention the occurrence of the signal at all. This
5439 implies the @code{nostop} keyword as well.
5443 @value{GDBN} should allow your program to see this signal; your program
5444 can handle the signal, or else it may terminate if the signal is fatal
5445 and not handled. @code{pass} and @code{noignore} are synonyms.
5449 @value{GDBN} should not allow your program to see this signal.
5450 @code{nopass} and @code{ignore} are synonyms.
5454 When a signal stops your program, the signal is not visible to the
5456 continue. Your program sees the signal then, if @code{pass} is in
5457 effect for the signal in question @emph{at that time}. In other words,
5458 after @value{GDBN} reports a signal, you can use the @code{handle}
5459 command with @code{pass} or @code{nopass} to control whether your
5460 program sees that signal when you continue.
5462 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5463 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5464 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5467 You can also use the @code{signal} command to prevent your program from
5468 seeing a signal, or cause it to see a signal it normally would not see,
5469 or to give it any signal at any time. For example, if your program stopped
5470 due to some sort of memory reference error, you might store correct
5471 values into the erroneous variables and continue, hoping to see more
5472 execution; but your program would probably terminate immediately as
5473 a result of the fatal signal once it saw the signal. To prevent this,
5474 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5477 @cindex extra signal information
5478 @anchor{extra signal information}
5480 On some targets, @value{GDBN} can inspect extra signal information
5481 associated with the intercepted signal, before it is actually
5482 delivered to the program being debugged. This information is exported
5483 by the convenience variable @code{$_siginfo}, and consists of data
5484 that is passed by the kernel to the signal handler at the time of the
5485 receipt of a signal. The data type of the information itself is
5486 target dependent. You can see the data type using the @code{ptype
5487 $_siginfo} command. On Unix systems, it typically corresponds to the
5488 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5491 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5492 referenced address that raised a segmentation fault.
5496 (@value{GDBP}) continue
5497 Program received signal SIGSEGV, Segmentation fault.
5498 0x0000000000400766 in main ()
5500 (@value{GDBP}) ptype $_siginfo
5507 struct @{...@} _kill;
5508 struct @{...@} _timer;
5510 struct @{...@} _sigchld;
5511 struct @{...@} _sigfault;
5512 struct @{...@} _sigpoll;
5515 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5519 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5520 $1 = (void *) 0x7ffff7ff7000
5524 Depending on target support, @code{$_siginfo} may also be writable.
5527 @section Stopping and Starting Multi-thread Programs
5529 @cindex stopped threads
5530 @cindex threads, stopped
5532 @cindex continuing threads
5533 @cindex threads, continuing
5535 @value{GDBN} supports debugging programs with multiple threads
5536 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5537 are two modes of controlling execution of your program within the
5538 debugger. In the default mode, referred to as @dfn{all-stop mode},
5539 when any thread in your program stops (for example, at a breakpoint
5540 or while being stepped), all other threads in the program are also stopped by
5541 @value{GDBN}. On some targets, @value{GDBN} also supports
5542 @dfn{non-stop mode}, in which other threads can continue to run freely while
5543 you examine the stopped thread in the debugger.
5546 * All-Stop Mode:: All threads stop when GDB takes control
5547 * Non-Stop Mode:: Other threads continue to execute
5548 * Background Execution:: Running your program asynchronously
5549 * Thread-Specific Breakpoints:: Controlling breakpoints
5550 * Interrupted System Calls:: GDB may interfere with system calls
5551 * Observer Mode:: GDB does not alter program behavior
5555 @subsection All-Stop Mode
5557 @cindex all-stop mode
5559 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5560 @emph{all} threads of execution stop, not just the current thread. This
5561 allows you to examine the overall state of the program, including
5562 switching between threads, without worrying that things may change
5565 Conversely, whenever you restart the program, @emph{all} threads start
5566 executing. @emph{This is true even when single-stepping} with commands
5567 like @code{step} or @code{next}.
5569 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5570 Since thread scheduling is up to your debugging target's operating
5571 system (not controlled by @value{GDBN}), other threads may
5572 execute more than one statement while the current thread completes a
5573 single step. Moreover, in general other threads stop in the middle of a
5574 statement, rather than at a clean statement boundary, when the program
5577 You might even find your program stopped in another thread after
5578 continuing or even single-stepping. This happens whenever some other
5579 thread runs into a breakpoint, a signal, or an exception before the
5580 first thread completes whatever you requested.
5582 @cindex automatic thread selection
5583 @cindex switching threads automatically
5584 @cindex threads, automatic switching
5585 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5586 signal, it automatically selects the thread where that breakpoint or
5587 signal happened. @value{GDBN} alerts you to the context switch with a
5588 message such as @samp{[Switching to Thread @var{n}]} to identify the
5591 On some OSes, you can modify @value{GDBN}'s default behavior by
5592 locking the OS scheduler to allow only a single thread to run.
5595 @item set scheduler-locking @var{mode}
5596 @cindex scheduler locking mode
5597 @cindex lock scheduler
5598 Set the scheduler locking mode. If it is @code{off}, then there is no
5599 locking and any thread may run at any time. If @code{on}, then only the
5600 current thread may run when the inferior is resumed. The @code{step}
5601 mode optimizes for single-stepping; it prevents other threads
5602 from preempting the current thread while you are stepping, so that
5603 the focus of debugging does not change unexpectedly.
5604 Other threads only rarely (or never) get a chance to run
5605 when you step. They are more likely to run when you @samp{next} over a
5606 function call, and they are completely free to run when you use commands
5607 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5608 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5609 the current thread away from the thread that you are debugging.
5611 @item show scheduler-locking
5612 Display the current scheduler locking mode.
5615 @cindex resume threads of multiple processes simultaneously
5616 By default, when you issue one of the execution commands such as
5617 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5618 threads of the current inferior to run. For example, if @value{GDBN}
5619 is attached to two inferiors, each with two threads, the
5620 @code{continue} command resumes only the two threads of the current
5621 inferior. This is useful, for example, when you debug a program that
5622 forks and you want to hold the parent stopped (so that, for instance,
5623 it doesn't run to exit), while you debug the child. In other
5624 situations, you may not be interested in inspecting the current state
5625 of any of the processes @value{GDBN} is attached to, and you may want
5626 to resume them all until some breakpoint is hit. In the latter case,
5627 you can instruct @value{GDBN} to allow all threads of all the
5628 inferiors to run with the @w{@code{set schedule-multiple}} command.
5631 @kindex set schedule-multiple
5632 @item set schedule-multiple
5633 Set the mode for allowing threads of multiple processes to be resumed
5634 when an execution command is issued. When @code{on}, all threads of
5635 all processes are allowed to run. When @code{off}, only the threads
5636 of the current process are resumed. The default is @code{off}. The
5637 @code{scheduler-locking} mode takes precedence when set to @code{on},
5638 or while you are stepping and set to @code{step}.
5640 @item show schedule-multiple
5641 Display the current mode for resuming the execution of threads of
5646 @subsection Non-Stop Mode
5648 @cindex non-stop mode
5650 @c This section is really only a place-holder, and needs to be expanded
5651 @c with more details.
5653 For some multi-threaded targets, @value{GDBN} supports an optional
5654 mode of operation in which you can examine stopped program threads in
5655 the debugger while other threads continue to execute freely. This
5656 minimizes intrusion when debugging live systems, such as programs
5657 where some threads have real-time constraints or must continue to
5658 respond to external events. This is referred to as @dfn{non-stop} mode.
5660 In non-stop mode, when a thread stops to report a debugging event,
5661 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5662 threads as well, in contrast to the all-stop mode behavior. Additionally,
5663 execution commands such as @code{continue} and @code{step} apply by default
5664 only to the current thread in non-stop mode, rather than all threads as
5665 in all-stop mode. This allows you to control threads explicitly in
5666 ways that are not possible in all-stop mode --- for example, stepping
5667 one thread while allowing others to run freely, stepping
5668 one thread while holding all others stopped, or stepping several threads
5669 independently and simultaneously.
5671 To enter non-stop mode, use this sequence of commands before you run
5672 or attach to your program:
5675 # Enable the async interface.
5678 # If using the CLI, pagination breaks non-stop.
5681 # Finally, turn it on!
5685 You can use these commands to manipulate the non-stop mode setting:
5688 @kindex set non-stop
5689 @item set non-stop on
5690 Enable selection of non-stop mode.
5691 @item set non-stop off
5692 Disable selection of non-stop mode.
5693 @kindex show non-stop
5695 Show the current non-stop enablement setting.
5698 Note these commands only reflect whether non-stop mode is enabled,
5699 not whether the currently-executing program is being run in non-stop mode.
5700 In particular, the @code{set non-stop} preference is only consulted when
5701 @value{GDBN} starts or connects to the target program, and it is generally
5702 not possible to switch modes once debugging has started. Furthermore,
5703 since not all targets support non-stop mode, even when you have enabled
5704 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5707 In non-stop mode, all execution commands apply only to the current thread
5708 by default. That is, @code{continue} only continues one thread.
5709 To continue all threads, issue @code{continue -a} or @code{c -a}.
5711 You can use @value{GDBN}'s background execution commands
5712 (@pxref{Background Execution}) to run some threads in the background
5713 while you continue to examine or step others from @value{GDBN}.
5714 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5715 always executed asynchronously in non-stop mode.
5717 Suspending execution is done with the @code{interrupt} command when
5718 running in the background, or @kbd{Ctrl-c} during foreground execution.
5719 In all-stop mode, this stops the whole process;
5720 but in non-stop mode the interrupt applies only to the current thread.
5721 To stop the whole program, use @code{interrupt -a}.
5723 Other execution commands do not currently support the @code{-a} option.
5725 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5726 that thread current, as it does in all-stop mode. This is because the
5727 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5728 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5729 changed to a different thread just as you entered a command to operate on the
5730 previously current thread.
5732 @node Background Execution
5733 @subsection Background Execution
5735 @cindex foreground execution
5736 @cindex background execution
5737 @cindex asynchronous execution
5738 @cindex execution, foreground, background and asynchronous
5740 @value{GDBN}'s execution commands have two variants: the normal
5741 foreground (synchronous) behavior, and a background
5742 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5743 the program to report that some thread has stopped before prompting for
5744 another command. In background execution, @value{GDBN} immediately gives
5745 a command prompt so that you can issue other commands while your program runs.
5747 You need to explicitly enable asynchronous mode before you can use
5748 background execution commands. You can use these commands to
5749 manipulate the asynchronous mode setting:
5752 @kindex set target-async
5753 @item set target-async on
5754 Enable asynchronous mode.
5755 @item set target-async off
5756 Disable asynchronous mode.
5757 @kindex show target-async
5758 @item show target-async
5759 Show the current target-async setting.
5762 If the target doesn't support async mode, @value{GDBN} issues an error
5763 message if you attempt to use the background execution commands.
5765 To specify background execution, add a @code{&} to the command. For example,
5766 the background form of the @code{continue} command is @code{continue&}, or
5767 just @code{c&}. The execution commands that accept background execution
5773 @xref{Starting, , Starting your Program}.
5777 @xref{Attach, , Debugging an Already-running Process}.
5781 @xref{Continuing and Stepping, step}.
5785 @xref{Continuing and Stepping, stepi}.
5789 @xref{Continuing and Stepping, next}.
5793 @xref{Continuing and Stepping, nexti}.
5797 @xref{Continuing and Stepping, continue}.
5801 @xref{Continuing and Stepping, finish}.
5805 @xref{Continuing and Stepping, until}.
5809 Background execution is especially useful in conjunction with non-stop
5810 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5811 However, you can also use these commands in the normal all-stop mode with
5812 the restriction that you cannot issue another execution command until the
5813 previous one finishes. Examples of commands that are valid in all-stop
5814 mode while the program is running include @code{help} and @code{info break}.
5816 You can interrupt your program while it is running in the background by
5817 using the @code{interrupt} command.
5824 Suspend execution of the running program. In all-stop mode,
5825 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5826 only the current thread. To stop the whole program in non-stop mode,
5827 use @code{interrupt -a}.
5830 @node Thread-Specific Breakpoints
5831 @subsection Thread-Specific Breakpoints
5833 When your program has multiple threads (@pxref{Threads,, Debugging
5834 Programs with Multiple Threads}), you can choose whether to set
5835 breakpoints on all threads, or on a particular thread.
5838 @cindex breakpoints and threads
5839 @cindex thread breakpoints
5840 @kindex break @dots{} thread @var{threadno}
5841 @item break @var{linespec} thread @var{threadno}
5842 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5843 @var{linespec} specifies source lines; there are several ways of
5844 writing them (@pxref{Specify Location}), but the effect is always to
5845 specify some source line.
5847 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5848 to specify that you only want @value{GDBN} to stop the program when a
5849 particular thread reaches this breakpoint. @var{threadno} is one of the
5850 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5851 column of the @samp{info threads} display.
5853 If you do not specify @samp{thread @var{threadno}} when you set a
5854 breakpoint, the breakpoint applies to @emph{all} threads of your
5857 You can use the @code{thread} qualifier on conditional breakpoints as
5858 well; in this case, place @samp{thread @var{threadno}} before or
5859 after the breakpoint condition, like this:
5862 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5867 Thread-specific breakpoints are automatically deleted when
5868 @value{GDBN} detects the corresponding thread is no longer in the
5869 thread list. For example:
5873 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
5876 There are several ways for a thread to disappear, such as a regular
5877 thread exit, but also when you detach from the process with the
5878 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
5879 Process}), or if @value{GDBN} loses the remote connection
5880 (@pxref{Remote Debugging}), etc. Note that with some targets,
5881 @value{GDBN} is only able to detect a thread has exited when the user
5882 explictly asks for the thread list with the @code{info threads}
5885 @node Interrupted System Calls
5886 @subsection Interrupted System Calls
5888 @cindex thread breakpoints and system calls
5889 @cindex system calls and thread breakpoints
5890 @cindex premature return from system calls
5891 There is an unfortunate side effect when using @value{GDBN} to debug
5892 multi-threaded programs. If one thread stops for a
5893 breakpoint, or for some other reason, and another thread is blocked in a
5894 system call, then the system call may return prematurely. This is a
5895 consequence of the interaction between multiple threads and the signals
5896 that @value{GDBN} uses to implement breakpoints and other events that
5899 To handle this problem, your program should check the return value of
5900 each system call and react appropriately. This is good programming
5903 For example, do not write code like this:
5909 The call to @code{sleep} will return early if a different thread stops
5910 at a breakpoint or for some other reason.
5912 Instead, write this:
5917 unslept = sleep (unslept);
5920 A system call is allowed to return early, so the system is still
5921 conforming to its specification. But @value{GDBN} does cause your
5922 multi-threaded program to behave differently than it would without
5925 Also, @value{GDBN} uses internal breakpoints in the thread library to
5926 monitor certain events such as thread creation and thread destruction.
5927 When such an event happens, a system call in another thread may return
5928 prematurely, even though your program does not appear to stop.
5931 @subsection Observer Mode
5933 If you want to build on non-stop mode and observe program behavior
5934 without any chance of disruption by @value{GDBN}, you can set
5935 variables to disable all of the debugger's attempts to modify state,
5936 whether by writing memory, inserting breakpoints, etc. These operate
5937 at a low level, intercepting operations from all commands.
5939 When all of these are set to @code{off}, then @value{GDBN} is said to
5940 be @dfn{observer mode}. As a convenience, the variable
5941 @code{observer} can be set to disable these, plus enable non-stop
5944 Note that @value{GDBN} will not prevent you from making nonsensical
5945 combinations of these settings. For instance, if you have enabled
5946 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5947 then breakpoints that work by writing trap instructions into the code
5948 stream will still not be able to be placed.
5953 @item set observer on
5954 @itemx set observer off
5955 When set to @code{on}, this disables all the permission variables
5956 below (except for @code{insert-fast-tracepoints}), plus enables
5957 non-stop debugging. Setting this to @code{off} switches back to
5958 normal debugging, though remaining in non-stop mode.
5961 Show whether observer mode is on or off.
5963 @kindex may-write-registers
5964 @item set may-write-registers on
5965 @itemx set may-write-registers off
5966 This controls whether @value{GDBN} will attempt to alter the values of
5967 registers, such as with assignment expressions in @code{print}, or the
5968 @code{jump} command. It defaults to @code{on}.
5970 @item show may-write-registers
5971 Show the current permission to write registers.
5973 @kindex may-write-memory
5974 @item set may-write-memory on
5975 @itemx set may-write-memory off
5976 This controls whether @value{GDBN} will attempt to alter the contents
5977 of memory, such as with assignment expressions in @code{print}. It
5978 defaults to @code{on}.
5980 @item show may-write-memory
5981 Show the current permission to write memory.
5983 @kindex may-insert-breakpoints
5984 @item set may-insert-breakpoints on
5985 @itemx set may-insert-breakpoints off
5986 This controls whether @value{GDBN} will attempt to insert breakpoints.
5987 This affects all breakpoints, including internal breakpoints defined
5988 by @value{GDBN}. It defaults to @code{on}.
5990 @item show may-insert-breakpoints
5991 Show the current permission to insert breakpoints.
5993 @kindex may-insert-tracepoints
5994 @item set may-insert-tracepoints on
5995 @itemx set may-insert-tracepoints off
5996 This controls whether @value{GDBN} will attempt to insert (regular)
5997 tracepoints at the beginning of a tracing experiment. It affects only
5998 non-fast tracepoints, fast tracepoints being under the control of
5999 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6001 @item show may-insert-tracepoints
6002 Show the current permission to insert tracepoints.
6004 @kindex may-insert-fast-tracepoints
6005 @item set may-insert-fast-tracepoints on
6006 @itemx set may-insert-fast-tracepoints off
6007 This controls whether @value{GDBN} will attempt to insert fast
6008 tracepoints at the beginning of a tracing experiment. It affects only
6009 fast tracepoints, regular (non-fast) tracepoints being under the
6010 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6012 @item show may-insert-fast-tracepoints
6013 Show the current permission to insert fast tracepoints.
6015 @kindex may-interrupt
6016 @item set may-interrupt on
6017 @itemx set may-interrupt off
6018 This controls whether @value{GDBN} will attempt to interrupt or stop
6019 program execution. When this variable is @code{off}, the
6020 @code{interrupt} command will have no effect, nor will
6021 @kbd{Ctrl-c}. It defaults to @code{on}.
6023 @item show may-interrupt
6024 Show the current permission to interrupt or stop the program.
6028 @node Reverse Execution
6029 @chapter Running programs backward
6030 @cindex reverse execution
6031 @cindex running programs backward
6033 When you are debugging a program, it is not unusual to realize that
6034 you have gone too far, and some event of interest has already happened.
6035 If the target environment supports it, @value{GDBN} can allow you to
6036 ``rewind'' the program by running it backward.
6038 A target environment that supports reverse execution should be able
6039 to ``undo'' the changes in machine state that have taken place as the
6040 program was executing normally. Variables, registers etc.@: should
6041 revert to their previous values. Obviously this requires a great
6042 deal of sophistication on the part of the target environment; not
6043 all target environments can support reverse execution.
6045 When a program is executed in reverse, the instructions that
6046 have most recently been executed are ``un-executed'', in reverse
6047 order. The program counter runs backward, following the previous
6048 thread of execution in reverse. As each instruction is ``un-executed'',
6049 the values of memory and/or registers that were changed by that
6050 instruction are reverted to their previous states. After executing
6051 a piece of source code in reverse, all side effects of that code
6052 should be ``undone'', and all variables should be returned to their
6053 prior values@footnote{
6054 Note that some side effects are easier to undo than others. For instance,
6055 memory and registers are relatively easy, but device I/O is hard. Some
6056 targets may be able undo things like device I/O, and some may not.
6058 The contract between @value{GDBN} and the reverse executing target
6059 requires only that the target do something reasonable when
6060 @value{GDBN} tells it to execute backwards, and then report the
6061 results back to @value{GDBN}. Whatever the target reports back to
6062 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6063 assumes that the memory and registers that the target reports are in a
6064 consistant state, but @value{GDBN} accepts whatever it is given.
6067 If you are debugging in a target environment that supports
6068 reverse execution, @value{GDBN} provides the following commands.
6071 @kindex reverse-continue
6072 @kindex rc @r{(@code{reverse-continue})}
6073 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6074 @itemx rc @r{[}@var{ignore-count}@r{]}
6075 Beginning at the point where your program last stopped, start executing
6076 in reverse. Reverse execution will stop for breakpoints and synchronous
6077 exceptions (signals), just like normal execution. Behavior of
6078 asynchronous signals depends on the target environment.
6080 @kindex reverse-step
6081 @kindex rs @r{(@code{step})}
6082 @item reverse-step @r{[}@var{count}@r{]}
6083 Run the program backward until control reaches the start of a
6084 different source line; then stop it, and return control to @value{GDBN}.
6086 Like the @code{step} command, @code{reverse-step} will only stop
6087 at the beginning of a source line. It ``un-executes'' the previously
6088 executed source line. If the previous source line included calls to
6089 debuggable functions, @code{reverse-step} will step (backward) into
6090 the called function, stopping at the beginning of the @emph{last}
6091 statement in the called function (typically a return statement).
6093 Also, as with the @code{step} command, if non-debuggable functions are
6094 called, @code{reverse-step} will run thru them backward without stopping.
6096 @kindex reverse-stepi
6097 @kindex rsi @r{(@code{reverse-stepi})}
6098 @item reverse-stepi @r{[}@var{count}@r{]}
6099 Reverse-execute one machine instruction. Note that the instruction
6100 to be reverse-executed is @emph{not} the one pointed to by the program
6101 counter, but the instruction executed prior to that one. For instance,
6102 if the last instruction was a jump, @code{reverse-stepi} will take you
6103 back from the destination of the jump to the jump instruction itself.
6105 @kindex reverse-next
6106 @kindex rn @r{(@code{reverse-next})}
6107 @item reverse-next @r{[}@var{count}@r{]}
6108 Run backward to the beginning of the previous line executed in
6109 the current (innermost) stack frame. If the line contains function
6110 calls, they will be ``un-executed'' without stopping. Starting from
6111 the first line of a function, @code{reverse-next} will take you back
6112 to the caller of that function, @emph{before} the function was called,
6113 just as the normal @code{next} command would take you from the last
6114 line of a function back to its return to its caller
6115 @footnote{Unless the code is too heavily optimized.}.
6117 @kindex reverse-nexti
6118 @kindex rni @r{(@code{reverse-nexti})}
6119 @item reverse-nexti @r{[}@var{count}@r{]}
6120 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6121 in reverse, except that called functions are ``un-executed'' atomically.
6122 That is, if the previously executed instruction was a return from
6123 another function, @code{reverse-nexti} will continue to execute
6124 in reverse until the call to that function (from the current stack
6127 @kindex reverse-finish
6128 @item reverse-finish
6129 Just as the @code{finish} command takes you to the point where the
6130 current function returns, @code{reverse-finish} takes you to the point
6131 where it was called. Instead of ending up at the end of the current
6132 function invocation, you end up at the beginning.
6134 @kindex set exec-direction
6135 @item set exec-direction
6136 Set the direction of target execution.
6137 @item set exec-direction reverse
6138 @cindex execute forward or backward in time
6139 @value{GDBN} will perform all execution commands in reverse, until the
6140 exec-direction mode is changed to ``forward''. Affected commands include
6141 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6142 command cannot be used in reverse mode.
6143 @item set exec-direction forward
6144 @value{GDBN} will perform all execution commands in the normal fashion.
6145 This is the default.
6149 @node Process Record and Replay
6150 @chapter Recording Inferior's Execution and Replaying It
6151 @cindex process record and replay
6152 @cindex recording inferior's execution and replaying it
6154 On some platforms, @value{GDBN} provides a special @dfn{process record
6155 and replay} target that can record a log of the process execution, and
6156 replay it later with both forward and reverse execution commands.
6159 When this target is in use, if the execution log includes the record
6160 for the next instruction, @value{GDBN} will debug in @dfn{replay
6161 mode}. In the replay mode, the inferior does not really execute code
6162 instructions. Instead, all the events that normally happen during
6163 code execution are taken from the execution log. While code is not
6164 really executed in replay mode, the values of registers (including the
6165 program counter register) and the memory of the inferior are still
6166 changed as they normally would. Their contents are taken from the
6170 If the record for the next instruction is not in the execution log,
6171 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6172 inferior executes normally, and @value{GDBN} records the execution log
6175 The process record and replay target supports reverse execution
6176 (@pxref{Reverse Execution}), even if the platform on which the
6177 inferior runs does not. However, the reverse execution is limited in
6178 this case by the range of the instructions recorded in the execution
6179 log. In other words, reverse execution on platforms that don't
6180 support it directly can only be done in the replay mode.
6182 When debugging in the reverse direction, @value{GDBN} will work in
6183 replay mode as long as the execution log includes the record for the
6184 previous instruction; otherwise, it will work in record mode, if the
6185 platform supports reverse execution, or stop if not.
6187 For architecture environments that support process record and replay,
6188 @value{GDBN} provides the following commands:
6191 @kindex target record
6192 @kindex target record-full
6193 @kindex target record-btrace
6196 @kindex record btrace
6200 @item record @var{method}
6201 This command starts the process record and replay target. The
6202 recording method can be specified as parameter. Without a parameter
6203 the command uses the @code{full} recording method. The following
6204 recording methods are available:
6208 Full record/replay recording using @value{GDBN}'s software record and
6209 replay implementation. This method allows replaying and reverse
6213 Hardware-supported instruction recording. This method does not allow
6214 replaying and reverse execution.
6216 This recording method may not be available on all processors.
6219 The process record and replay target can only debug a process that is
6220 already running. Therefore, you need first to start the process with
6221 the @kbd{run} or @kbd{start} commands, and then start the recording
6222 with the @kbd{record @var{method}} command.
6224 Both @code{record @var{method}} and @code{rec @var{method}} are
6225 aliases of @code{target record-@var{method}}.
6227 @cindex displaced stepping, and process record and replay
6228 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6229 will be automatically disabled when process record and replay target
6230 is started. That's because the process record and replay target
6231 doesn't support displaced stepping.
6233 @cindex non-stop mode, and process record and replay
6234 @cindex asynchronous execution, and process record and replay
6235 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6236 the asynchronous execution mode (@pxref{Background Execution}), not
6237 all recording methods are available. The @code{full} recording method
6238 does not support these two modes.
6243 Stop the process record and replay target. When process record and
6244 replay target stops, the entire execution log will be deleted and the
6245 inferior will either be terminated, or will remain in its final state.
6247 When you stop the process record and replay target in record mode (at
6248 the end of the execution log), the inferior will be stopped at the
6249 next instruction that would have been recorded. In other words, if
6250 you record for a while and then stop recording, the inferior process
6251 will be left in the same state as if the recording never happened.
6253 On the other hand, if the process record and replay target is stopped
6254 while in replay mode (that is, not at the end of the execution log,
6255 but at some earlier point), the inferior process will become ``live''
6256 at that earlier state, and it will then be possible to continue the
6257 usual ``live'' debugging of the process from that state.
6259 When the inferior process exits, or @value{GDBN} detaches from it,
6260 process record and replay target will automatically stop itself.
6264 Go to a specific location in the execution log. There are several
6265 ways to specify the location to go to:
6268 @item record goto begin
6269 @itemx record goto start
6270 Go to the beginning of the execution log.
6272 @item record goto end
6273 Go to the end of the execution log.
6275 @item record goto @var{n}
6276 Go to instruction number @var{n} in the execution log.
6280 @item record save @var{filename}
6281 Save the execution log to a file @file{@var{filename}}.
6282 Default filename is @file{gdb_record.@var{process_id}}, where
6283 @var{process_id} is the process ID of the inferior.
6285 This command may not be available for all recording methods.
6287 @kindex record restore
6288 @item record restore @var{filename}
6289 Restore the execution log from a file @file{@var{filename}}.
6290 File must have been created with @code{record save}.
6292 @kindex set record full
6293 @item set record full insn-number-max @var{limit}
6294 @itemx set record full insn-number-max unlimited
6295 Set the limit of instructions to be recorded for the @code{full}
6296 recording method. Default value is 200000.
6298 If @var{limit} is a positive number, then @value{GDBN} will start
6299 deleting instructions from the log once the number of the record
6300 instructions becomes greater than @var{limit}. For every new recorded
6301 instruction, @value{GDBN} will delete the earliest recorded
6302 instruction to keep the number of recorded instructions at the limit.
6303 (Since deleting recorded instructions loses information, @value{GDBN}
6304 lets you control what happens when the limit is reached, by means of
6305 the @code{stop-at-limit} option, described below.)
6307 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6308 delete recorded instructions from the execution log. The number of
6309 recorded instructions is limited only by the available memory.
6311 @kindex show record full
6312 @item show record full insn-number-max
6313 Show the limit of instructions to be recorded with the @code{full}
6316 @item set record full stop-at-limit
6317 Control the behavior of the @code{full} recording method when the
6318 number of recorded instructions reaches the limit. If ON (the
6319 default), @value{GDBN} will stop when the limit is reached for the
6320 first time and ask you whether you want to stop the inferior or
6321 continue running it and recording the execution log. If you decide
6322 to continue recording, each new recorded instruction will cause the
6323 oldest one to be deleted.
6325 If this option is OFF, @value{GDBN} will automatically delete the
6326 oldest record to make room for each new one, without asking.
6328 @item show record full stop-at-limit
6329 Show the current setting of @code{stop-at-limit}.
6331 @item set record full memory-query
6332 Control the behavior when @value{GDBN} is unable to record memory
6333 changes caused by an instruction for the @code{full} recording method.
6334 If ON, @value{GDBN} will query whether to stop the inferior in that
6337 If this option is OFF (the default), @value{GDBN} will automatically
6338 ignore the effect of such instructions on memory. Later, when
6339 @value{GDBN} replays this execution log, it will mark the log of this
6340 instruction as not accessible, and it will not affect the replay
6343 @item show record full memory-query
6344 Show the current setting of @code{memory-query}.
6348 Show various statistics about the recording depending on the recording
6353 For the @code{full} recording method, it shows the state of process
6354 record and its in-memory execution log buffer, including:
6358 Whether in record mode or replay mode.
6360 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6362 Highest recorded instruction number.
6364 Current instruction about to be replayed (if in replay mode).
6366 Number of instructions contained in the execution log.
6368 Maximum number of instructions that may be contained in the execution log.
6372 For the @code{btrace} recording method, it shows the number of
6373 instructions that have been recorded and the number of blocks of
6374 sequential control-flow that is formed by the recorded instructions.
6377 @kindex record delete
6380 When record target runs in replay mode (``in the past''), delete the
6381 subsequent execution log and begin to record a new execution log starting
6382 from the current address. This means you will abandon the previously
6383 recorded ``future'' and begin recording a new ``future''.
6385 @kindex record instruction-history
6386 @kindex rec instruction-history
6387 @item record instruction-history
6388 Disassembles instructions from the recorded execution log. By
6389 default, ten instructions are disassembled. This can be changed using
6390 the @code{set record instruction-history-size} command. Instructions
6391 are printed in execution order. There are several ways to specify
6392 what part of the execution log to disassemble:
6395 @item record instruction-history @var{insn}
6396 Disassembles ten instructions starting from instruction number
6399 @item record instruction-history @var{insn}, +/-@var{n}
6400 Disassembles @var{n} instructions around instruction number
6401 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6402 @var{n} instructions after instruction number @var{insn}. If
6403 @var{n} is preceded with @code{-}, disassembles @var{n}
6404 instructions before instruction number @var{insn}.
6406 @item record instruction-history
6407 Disassembles ten more instructions after the last disassembly.
6409 @item record instruction-history -
6410 Disassembles ten more instructions before the last disassembly.
6412 @item record instruction-history @var{begin} @var{end}
6413 Disassembles instructions beginning with instruction number
6414 @var{begin} until instruction number @var{end}. The instruction
6415 number @var{end} is not included.
6418 This command may not be available for all recording methods.
6421 @item set record instruction-history-size @var{size}
6422 @itemx set record instruction-history-size unlimited
6423 Define how many instructions to disassemble in the @code{record
6424 instruction-history} command. The default value is 10.
6425 A @var{size} of @code{unlimited} means unlimited instructions.
6428 @item show record instruction-history-size
6429 Show how many instructions to disassemble in the @code{record
6430 instruction-history} command.
6432 @kindex record function-call-history
6433 @kindex rec function-call-history
6434 @item record function-call-history
6435 Prints the execution history at function granularity. It prints one
6436 line for each sequence of instructions that belong to the same
6437 function giving the name of that function, the source lines
6438 for this instruction sequence (if the @code{/l} modifier is
6439 specified), and the instructions numbers that form the sequence (if
6440 the @code{/i} modifier is specified).
6443 (@value{GDBP}) @b{list 1, 10}
6454 (@value{GDBP}) @b{record function-call-history /l}
6460 By default, ten lines are printed. This can be changed using the
6461 @code{set record function-call-history-size} command. Functions are
6462 printed in execution order. There are several ways to specify what
6466 @item record function-call-history @var{func}
6467 Prints ten functions starting from function number @var{func}.
6469 @item record function-call-history @var{func}, +/-@var{n}
6470 Prints @var{n} functions around function number @var{func}. If
6471 @var{n} is preceded with @code{+}, prints @var{n} functions after
6472 function number @var{func}. If @var{n} is preceded with @code{-},
6473 prints @var{n} functions before function number @var{func}.
6475 @item record function-call-history
6476 Prints ten more functions after the last ten-line print.
6478 @item record function-call-history -
6479 Prints ten more functions before the last ten-line print.
6481 @item record function-call-history @var{begin} @var{end}
6482 Prints functions beginning with function number @var{begin} until
6483 function number @var{end}. The function number @var{end} is not
6487 This command may not be available for all recording methods.
6489 @item set record function-call-history-size @var{size}
6490 @itemx set record function-call-history-size unlimited
6491 Define how many lines to print in the
6492 @code{record function-call-history} command. The default value is 10.
6493 A size of @code{unlimited} means unlimited lines.
6495 @item show record function-call-history-size
6496 Show how many lines to print in the
6497 @code{record function-call-history} command.
6502 @chapter Examining the Stack
6504 When your program has stopped, the first thing you need to know is where it
6505 stopped and how it got there.
6508 Each time your program performs a function call, information about the call
6510 That information includes the location of the call in your program,
6511 the arguments of the call,
6512 and the local variables of the function being called.
6513 The information is saved in a block of data called a @dfn{stack frame}.
6514 The stack frames are allocated in a region of memory called the @dfn{call
6517 When your program stops, the @value{GDBN} commands for examining the
6518 stack allow you to see all of this information.
6520 @cindex selected frame
6521 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6522 @value{GDBN} commands refer implicitly to the selected frame. In
6523 particular, whenever you ask @value{GDBN} for the value of a variable in
6524 your program, the value is found in the selected frame. There are
6525 special @value{GDBN} commands to select whichever frame you are
6526 interested in. @xref{Selection, ,Selecting a Frame}.
6528 When your program stops, @value{GDBN} automatically selects the
6529 currently executing frame and describes it briefly, similar to the
6530 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6533 * Frames:: Stack frames
6534 * Backtrace:: Backtraces
6535 * Frame Filter Management:: Managing frame filters
6536 * Selection:: Selecting a frame
6537 * Frame Info:: Information on a frame
6542 @section Stack Frames
6544 @cindex frame, definition
6546 The call stack is divided up into contiguous pieces called @dfn{stack
6547 frames}, or @dfn{frames} for short; each frame is the data associated
6548 with one call to one function. The frame contains the arguments given
6549 to the function, the function's local variables, and the address at
6550 which the function is executing.
6552 @cindex initial frame
6553 @cindex outermost frame
6554 @cindex innermost frame
6555 When your program is started, the stack has only one frame, that of the
6556 function @code{main}. This is called the @dfn{initial} frame or the
6557 @dfn{outermost} frame. Each time a function is called, a new frame is
6558 made. Each time a function returns, the frame for that function invocation
6559 is eliminated. If a function is recursive, there can be many frames for
6560 the same function. The frame for the function in which execution is
6561 actually occurring is called the @dfn{innermost} frame. This is the most
6562 recently created of all the stack frames that still exist.
6564 @cindex frame pointer
6565 Inside your program, stack frames are identified by their addresses. A
6566 stack frame consists of many bytes, each of which has its own address; each
6567 kind of computer has a convention for choosing one byte whose
6568 address serves as the address of the frame. Usually this address is kept
6569 in a register called the @dfn{frame pointer register}
6570 (@pxref{Registers, $fp}) while execution is going on in that frame.
6572 @cindex frame number
6573 @value{GDBN} assigns numbers to all existing stack frames, starting with
6574 zero for the innermost frame, one for the frame that called it,
6575 and so on upward. These numbers do not really exist in your program;
6576 they are assigned by @value{GDBN} to give you a way of designating stack
6577 frames in @value{GDBN} commands.
6579 @c The -fomit-frame-pointer below perennially causes hbox overflow
6580 @c underflow problems.
6581 @cindex frameless execution
6582 Some compilers provide a way to compile functions so that they operate
6583 without stack frames. (For example, the @value{NGCC} option
6585 @samp{-fomit-frame-pointer}
6587 generates functions without a frame.)
6588 This is occasionally done with heavily used library functions to save
6589 the frame setup time. @value{GDBN} has limited facilities for dealing
6590 with these function invocations. If the innermost function invocation
6591 has no stack frame, @value{GDBN} nevertheless regards it as though
6592 it had a separate frame, which is numbered zero as usual, allowing
6593 correct tracing of the function call chain. However, @value{GDBN} has
6594 no provision for frameless functions elsewhere in the stack.
6597 @kindex frame@r{, command}
6598 @cindex current stack frame
6599 @item frame @var{args}
6600 The @code{frame} command allows you to move from one stack frame to another,
6601 and to print the stack frame you select. @var{args} may be either the
6602 address of the frame or the stack frame number. Without an argument,
6603 @code{frame} prints the current stack frame.
6605 @kindex select-frame
6606 @cindex selecting frame silently
6608 The @code{select-frame} command allows you to move from one stack frame
6609 to another without printing the frame. This is the silent version of
6617 @cindex call stack traces
6618 A backtrace is a summary of how your program got where it is. It shows one
6619 line per frame, for many frames, starting with the currently executing
6620 frame (frame zero), followed by its caller (frame one), and on up the
6623 @anchor{backtrace-command}
6626 @kindex bt @r{(@code{backtrace})}
6629 Print a backtrace of the entire stack: one line per frame for all
6630 frames in the stack.
6632 You can stop the backtrace at any time by typing the system interrupt
6633 character, normally @kbd{Ctrl-c}.
6635 @item backtrace @var{n}
6637 Similar, but print only the innermost @var{n} frames.
6639 @item backtrace -@var{n}
6641 Similar, but print only the outermost @var{n} frames.
6643 @item backtrace full
6645 @itemx bt full @var{n}
6646 @itemx bt full -@var{n}
6647 Print the values of the local variables also. @var{n} specifies the
6648 number of frames to print, as described above.
6650 @item backtrace no-filters
6651 @itemx bt no-filters
6652 @itemx bt no-filters @var{n}
6653 @itemx bt no-filters -@var{n}
6654 @itemx bt no-filters full
6655 @itemx bt no-filters full @var{n}
6656 @itemx bt no-filters full -@var{n}
6657 Do not run Python frame filters on this backtrace. @xref{Frame
6658 Filter API}, for more information. Additionally use @ref{disable
6659 frame-filter all} to turn off all frame filters. This is only
6660 relevant when @value{GDBN} has been configured with @code{Python}
6666 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6667 are additional aliases for @code{backtrace}.
6669 @cindex multiple threads, backtrace
6670 In a multi-threaded program, @value{GDBN} by default shows the
6671 backtrace only for the current thread. To display the backtrace for
6672 several or all of the threads, use the command @code{thread apply}
6673 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6674 apply all backtrace}, @value{GDBN} will display the backtrace for all
6675 the threads; this is handy when you debug a core dump of a
6676 multi-threaded program.
6678 Each line in the backtrace shows the frame number and the function name.
6679 The program counter value is also shown---unless you use @code{set
6680 print address off}. The backtrace also shows the source file name and
6681 line number, as well as the arguments to the function. The program
6682 counter value is omitted if it is at the beginning of the code for that
6685 Here is an example of a backtrace. It was made with the command
6686 @samp{bt 3}, so it shows the innermost three frames.
6690 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6692 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6693 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6695 (More stack frames follow...)
6700 The display for frame zero does not begin with a program counter
6701 value, indicating that your program has stopped at the beginning of the
6702 code for line @code{993} of @code{builtin.c}.
6705 The value of parameter @code{data} in frame 1 has been replaced by
6706 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6707 only if it is a scalar (integer, pointer, enumeration, etc). See command
6708 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6709 on how to configure the way function parameter values are printed.
6711 @cindex optimized out, in backtrace
6712 @cindex function call arguments, optimized out
6713 If your program was compiled with optimizations, some compilers will
6714 optimize away arguments passed to functions if those arguments are
6715 never used after the call. Such optimizations generate code that
6716 passes arguments through registers, but doesn't store those arguments
6717 in the stack frame. @value{GDBN} has no way of displaying such
6718 arguments in stack frames other than the innermost one. Here's what
6719 such a backtrace might look like:
6723 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6725 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6726 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6728 (More stack frames follow...)
6733 The values of arguments that were not saved in their stack frames are
6734 shown as @samp{<optimized out>}.
6736 If you need to display the values of such optimized-out arguments,
6737 either deduce that from other variables whose values depend on the one
6738 you are interested in, or recompile without optimizations.
6740 @cindex backtrace beyond @code{main} function
6741 @cindex program entry point
6742 @cindex startup code, and backtrace
6743 Most programs have a standard user entry point---a place where system
6744 libraries and startup code transition into user code. For C this is
6745 @code{main}@footnote{
6746 Note that embedded programs (the so-called ``free-standing''
6747 environment) are not required to have a @code{main} function as the
6748 entry point. They could even have multiple entry points.}.
6749 When @value{GDBN} finds the entry function in a backtrace
6750 it will terminate the backtrace, to avoid tracing into highly
6751 system-specific (and generally uninteresting) code.
6753 If you need to examine the startup code, or limit the number of levels
6754 in a backtrace, you can change this behavior:
6757 @item set backtrace past-main
6758 @itemx set backtrace past-main on
6759 @kindex set backtrace
6760 Backtraces will continue past the user entry point.
6762 @item set backtrace past-main off
6763 Backtraces will stop when they encounter the user entry point. This is the
6766 @item show backtrace past-main
6767 @kindex show backtrace
6768 Display the current user entry point backtrace policy.
6770 @item set backtrace past-entry
6771 @itemx set backtrace past-entry on
6772 Backtraces will continue past the internal entry point of an application.
6773 This entry point is encoded by the linker when the application is built,
6774 and is likely before the user entry point @code{main} (or equivalent) is called.
6776 @item set backtrace past-entry off
6777 Backtraces will stop when they encounter the internal entry point of an
6778 application. This is the default.
6780 @item show backtrace past-entry
6781 Display the current internal entry point backtrace policy.
6783 @item set backtrace limit @var{n}
6784 @itemx set backtrace limit 0
6785 @itemx set backtrace limit unlimited
6786 @cindex backtrace limit
6787 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
6788 or zero means unlimited levels.
6790 @item show backtrace limit
6791 Display the current limit on backtrace levels.
6794 You can control how file names are displayed.
6797 @item set filename-display
6798 @itemx set filename-display relative
6799 @cindex filename-display
6800 Display file names relative to the compilation directory. This is the default.
6802 @item set filename-display basename
6803 Display only basename of a filename.
6805 @item set filename-display absolute
6806 Display an absolute filename.
6808 @item show filename-display
6809 Show the current way to display filenames.
6812 @node Frame Filter Management
6813 @section Management of Frame Filters.
6814 @cindex managing frame filters
6816 Frame filters are Python based utilities to manage and decorate the
6817 output of frames. @xref{Frame Filter API}, for further information.
6819 Managing frame filters is performed by several commands available
6820 within @value{GDBN}, detailed here.
6823 @kindex info frame-filter
6824 @item info frame-filter
6825 Print a list of installed frame filters from all dictionaries, showing
6826 their name, priority and enabled status.
6828 @kindex disable frame-filter
6829 @anchor{disable frame-filter all}
6830 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
6831 Disable a frame filter in the dictionary matching
6832 @var{filter-dictionary}, or @code{all}, and @var{filter-name}.
6833 @var{filter-dictionary} may be @code{all}, @code{global},
6834 @code{progspace} or the name of the object file where the frame filter
6835 dictionary resides. When @code{all} is specified, all frame filters
6836 across all dictionaries are disabled. @var{filter-name} is the name
6837 of the frame filter and is used when @code{all} is not the option for
6838 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
6839 may be enabled again later.
6841 @kindex enable frame-filter
6842 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
6843 Enable a frame filter in the dictionary matching
6844 @var{filter-dictionary}, or @code{all}, and @var{filter-name}.
6845 @var{filter-dictionary} may be @code{all}, @code{global},
6846 @code{progspace} or the name of the object file where the frame filter
6847 dictionary resides. When @code{all} is specified, all frame filters across
6848 all dictionaries are enabled. @var{filter-name} is the name of the frame
6849 filter and is used when @code{all} is not the option for
6850 @var{filter-dictionary}.
6855 (gdb) info frame-filter
6857 global frame-filters:
6858 Priority Enabled Name
6859 1000 No PrimaryFunctionFilter
6862 progspace /build/test frame-filters:
6863 Priority Enabled Name
6864 100 Yes ProgspaceFilter
6866 objfile /build/test frame-filters:
6867 Priority Enabled Name
6868 999 Yes BuildProgra Filter
6870 (gdb) disable frame-filter /build/test BuildProgramFilter
6871 (gdb) info frame-filter
6873 global frame-filters:
6874 Priority Enabled Name
6875 1000 No PrimaryFunctionFilter
6878 progspace /build/test frame-filters:
6879 Priority Enabled Name
6880 100 Yes ProgspaceFilter
6882 objfile /build/test frame-filters:
6883 Priority Enabled Name
6884 999 No BuildProgramFilter
6886 (gdb) enable frame-filter global PrimaryFunctionFilter
6887 (gdb) info frame-filter
6889 global frame-filters:
6890 Priority Enabled Name
6891 1000 Yes PrimaryFunctionFilter
6894 progspace /build/test frame-filters:
6895 Priority Enabled Name
6896 100 Yes ProgspaceFilter
6898 objfile /build/test frame-filters:
6899 Priority Enabled Name
6900 999 No BuildProgramFilter
6903 @kindex set frame-filter priority
6904 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
6905 Set the @var{priority} of a frame filter in the dictionary matching
6906 @var{filter-dictionary}, and the frame filter name matching
6907 @var{filter-name}. @var{filter-dictionary} may be @code{global},
6908 @code{progspace} or the name of the object file where the frame filter
6909 dictionary resides. @var{priority} is an integer.
6911 @kindex show frame-filter priority
6912 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
6913 Show the @var{priority} of a frame filter in the dictionary matching
6914 @var{filter-dictionary}, and the frame filter name matching
6915 @var{filter-name}. @var{filter-dictionary} may be @code{global},
6916 @code{progspace} or the name of the object file where the frame filter
6922 (gdb) info frame-filter
6924 global frame-filters:
6925 Priority Enabled Name
6926 1000 Yes PrimaryFunctionFilter
6929 progspace /build/test frame-filters:
6930 Priority Enabled Name
6931 100 Yes ProgspaceFilter
6933 objfile /build/test frame-filters:
6934 Priority Enabled Name
6935 999 No BuildProgramFilter
6937 (gdb) set frame-filter priority global Reverse 50
6938 (gdb) info frame-filter
6940 global frame-filters:
6941 Priority Enabled Name
6942 1000 Yes PrimaryFunctionFilter
6945 progspace /build/test frame-filters:
6946 Priority Enabled Name
6947 100 Yes ProgspaceFilter
6949 objfile /build/test frame-filters:
6950 Priority Enabled Name
6951 999 No BuildProgramFilter
6956 @section Selecting a Frame
6958 Most commands for examining the stack and other data in your program work on
6959 whichever stack frame is selected at the moment. Here are the commands for
6960 selecting a stack frame; all of them finish by printing a brief description
6961 of the stack frame just selected.
6964 @kindex frame@r{, selecting}
6965 @kindex f @r{(@code{frame})}
6968 Select frame number @var{n}. Recall that frame zero is the innermost
6969 (currently executing) frame, frame one is the frame that called the
6970 innermost one, and so on. The highest-numbered frame is the one for
6973 @item frame @var{addr}
6975 Select the frame at address @var{addr}. This is useful mainly if the
6976 chaining of stack frames has been damaged by a bug, making it
6977 impossible for @value{GDBN} to assign numbers properly to all frames. In
6978 addition, this can be useful when your program has multiple stacks and
6979 switches between them.
6981 On the SPARC architecture, @code{frame} needs two addresses to
6982 select an arbitrary frame: a frame pointer and a stack pointer.
6984 On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack
6985 pointer and a program counter.
6987 On the 29k architecture, it needs three addresses: a register stack
6988 pointer, a program counter, and a memory stack pointer.
6992 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6993 advances toward the outermost frame, to higher frame numbers, to frames
6994 that have existed longer. @var{n} defaults to one.
6997 @kindex do @r{(@code{down})}
6999 Move @var{n} frames down the stack. For positive numbers @var{n}, this
7000 advances toward the innermost frame, to lower frame numbers, to frames
7001 that were created more recently. @var{n} defaults to one. You may
7002 abbreviate @code{down} as @code{do}.
7005 All of these commands end by printing two lines of output describing the
7006 frame. The first line shows the frame number, the function name, the
7007 arguments, and the source file and line number of execution in that
7008 frame. The second line shows the text of that source line.
7016 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7018 10 read_input_file (argv[i]);
7022 After such a printout, the @code{list} command with no arguments
7023 prints ten lines centered on the point of execution in the frame.
7024 You can also edit the program at the point of execution with your favorite
7025 editing program by typing @code{edit}.
7026 @xref{List, ,Printing Source Lines},
7030 @kindex down-silently
7032 @item up-silently @var{n}
7033 @itemx down-silently @var{n}
7034 These two commands are variants of @code{up} and @code{down},
7035 respectively; they differ in that they do their work silently, without
7036 causing display of the new frame. They are intended primarily for use
7037 in @value{GDBN} command scripts, where the output might be unnecessary and
7042 @section Information About a Frame
7044 There are several other commands to print information about the selected
7050 When used without any argument, this command does not change which
7051 frame is selected, but prints a brief description of the currently
7052 selected stack frame. It can be abbreviated @code{f}. With an
7053 argument, this command is used to select a stack frame.
7054 @xref{Selection, ,Selecting a Frame}.
7057 @kindex info f @r{(@code{info frame})}
7060 This command prints a verbose description of the selected stack frame,
7065 the address of the frame
7067 the address of the next frame down (called by this frame)
7069 the address of the next frame up (caller of this frame)
7071 the language in which the source code corresponding to this frame is written
7073 the address of the frame's arguments
7075 the address of the frame's local variables
7077 the program counter saved in it (the address of execution in the caller frame)
7079 which registers were saved in the frame
7082 @noindent The verbose description is useful when
7083 something has gone wrong that has made the stack format fail to fit
7084 the usual conventions.
7086 @item info frame @var{addr}
7087 @itemx info f @var{addr}
7088 Print a verbose description of the frame at address @var{addr}, without
7089 selecting that frame. The selected frame remains unchanged by this
7090 command. This requires the same kind of address (more than one for some
7091 architectures) that you specify in the @code{frame} command.
7092 @xref{Selection, ,Selecting a Frame}.
7096 Print the arguments of the selected frame, each on a separate line.
7100 Print the local variables of the selected frame, each on a separate
7101 line. These are all variables (declared either static or automatic)
7102 accessible at the point of execution of the selected frame.
7108 @chapter Examining Source Files
7110 @value{GDBN} can print parts of your program's source, since the debugging
7111 information recorded in the program tells @value{GDBN} what source files were
7112 used to build it. When your program stops, @value{GDBN} spontaneously prints
7113 the line where it stopped. Likewise, when you select a stack frame
7114 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7115 execution in that frame has stopped. You can print other portions of
7116 source files by explicit command.
7118 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7119 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7120 @value{GDBN} under @sc{gnu} Emacs}.
7123 * List:: Printing source lines
7124 * Specify Location:: How to specify code locations
7125 * Edit:: Editing source files
7126 * Search:: Searching source files
7127 * Source Path:: Specifying source directories
7128 * Machine Code:: Source and machine code
7132 @section Printing Source Lines
7135 @kindex l @r{(@code{list})}
7136 To print lines from a source file, use the @code{list} command
7137 (abbreviated @code{l}). By default, ten lines are printed.
7138 There are several ways to specify what part of the file you want to
7139 print; see @ref{Specify Location}, for the full list.
7141 Here are the forms of the @code{list} command most commonly used:
7144 @item list @var{linenum}
7145 Print lines centered around line number @var{linenum} in the
7146 current source file.
7148 @item list @var{function}
7149 Print lines centered around the beginning of function
7153 Print more lines. If the last lines printed were printed with a
7154 @code{list} command, this prints lines following the last lines
7155 printed; however, if the last line printed was a solitary line printed
7156 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7157 Stack}), this prints lines centered around that line.
7160 Print lines just before the lines last printed.
7163 @cindex @code{list}, how many lines to display
7164 By default, @value{GDBN} prints ten source lines with any of these forms of
7165 the @code{list} command. You can change this using @code{set listsize}:
7168 @kindex set listsize
7169 @item set listsize @var{count}
7170 @itemx set listsize unlimited
7171 Make the @code{list} command display @var{count} source lines (unless
7172 the @code{list} argument explicitly specifies some other number).
7173 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7175 @kindex show listsize
7177 Display the number of lines that @code{list} prints.
7180 Repeating a @code{list} command with @key{RET} discards the argument,
7181 so it is equivalent to typing just @code{list}. This is more useful
7182 than listing the same lines again. An exception is made for an
7183 argument of @samp{-}; that argument is preserved in repetition so that
7184 each repetition moves up in the source file.
7186 In general, the @code{list} command expects you to supply zero, one or two
7187 @dfn{linespecs}. Linespecs specify source lines; there are several ways
7188 of writing them (@pxref{Specify Location}), but the effect is always
7189 to specify some source line.
7191 Here is a complete description of the possible arguments for @code{list}:
7194 @item list @var{linespec}
7195 Print lines centered around the line specified by @var{linespec}.
7197 @item list @var{first},@var{last}
7198 Print lines from @var{first} to @var{last}. Both arguments are
7199 linespecs. When a @code{list} command has two linespecs, and the
7200 source file of the second linespec is omitted, this refers to
7201 the same source file as the first linespec.
7203 @item list ,@var{last}
7204 Print lines ending with @var{last}.
7206 @item list @var{first},
7207 Print lines starting with @var{first}.
7210 Print lines just after the lines last printed.
7213 Print lines just before the lines last printed.
7216 As described in the preceding table.
7219 @node Specify Location
7220 @section Specifying a Location
7221 @cindex specifying location
7224 Several @value{GDBN} commands accept arguments that specify a location
7225 of your program's code. Since @value{GDBN} is a source-level
7226 debugger, a location usually specifies some line in the source code;
7227 for that reason, locations are also known as @dfn{linespecs}.
7229 Here are all the different ways of specifying a code location that
7230 @value{GDBN} understands:
7234 Specifies the line number @var{linenum} of the current source file.
7237 @itemx +@var{offset}
7238 Specifies the line @var{offset} lines before or after the @dfn{current
7239 line}. For the @code{list} command, the current line is the last one
7240 printed; for the breakpoint commands, this is the line at which
7241 execution stopped in the currently selected @dfn{stack frame}
7242 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7243 used as the second of the two linespecs in a @code{list} command,
7244 this specifies the line @var{offset} lines up or down from the first
7247 @item @var{filename}:@var{linenum}
7248 Specifies the line @var{linenum} in the source file @var{filename}.
7249 If @var{filename} is a relative file name, then it will match any
7250 source file name with the same trailing components. For example, if
7251 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7252 name of @file{/build/trunk/gcc/expr.c}, but not
7253 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7255 @item @var{function}
7256 Specifies the line that begins the body of the function @var{function}.
7257 For example, in C, this is the line with the open brace.
7259 @item @var{function}:@var{label}
7260 Specifies the line where @var{label} appears in @var{function}.
7262 @item @var{filename}:@var{function}
7263 Specifies the line that begins the body of the function @var{function}
7264 in the file @var{filename}. You only need the file name with a
7265 function name to avoid ambiguity when there are identically named
7266 functions in different source files.
7269 Specifies the line at which the label named @var{label} appears.
7270 @value{GDBN} searches for the label in the function corresponding to
7271 the currently selected stack frame. If there is no current selected
7272 stack frame (for instance, if the inferior is not running), then
7273 @value{GDBN} will not search for a label.
7275 @item *@var{address}
7276 Specifies the program address @var{address}. For line-oriented
7277 commands, such as @code{list} and @code{edit}, this specifies a source
7278 line that contains @var{address}. For @code{break} and other
7279 breakpoint oriented commands, this can be used to set breakpoints in
7280 parts of your program which do not have debugging information or
7283 Here @var{address} may be any expression valid in the current working
7284 language (@pxref{Languages, working language}) that specifies a code
7285 address. In addition, as a convenience, @value{GDBN} extends the
7286 semantics of expressions used in locations to cover the situations
7287 that frequently happen during debugging. Here are the various forms
7291 @item @var{expression}
7292 Any expression valid in the current working language.
7294 @item @var{funcaddr}
7295 An address of a function or procedure derived from its name. In C,
7296 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7297 simply the function's name @var{function} (and actually a special case
7298 of a valid expression). In Pascal and Modula-2, this is
7299 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7300 (although the Pascal form also works).
7302 This form specifies the address of the function's first instruction,
7303 before the stack frame and arguments have been set up.
7305 @item '@var{filename}'::@var{funcaddr}
7306 Like @var{funcaddr} above, but also specifies the name of the source
7307 file explicitly. This is useful if the name of the function does not
7308 specify the function unambiguously, e.g., if there are several
7309 functions with identical names in different source files.
7312 @cindex breakpoint at static probe point
7313 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7314 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7315 applications to embed static probes. @xref{Static Probe Points}, for more
7316 information on finding and using static probes. This form of linespec
7317 specifies the location of such a static probe.
7319 If @var{objfile} is given, only probes coming from that shared library
7320 or executable matching @var{objfile} as a regular expression are considered.
7321 If @var{provider} is given, then only probes from that provider are considered.
7322 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7323 each one of those probes.
7329 @section Editing Source Files
7330 @cindex editing source files
7333 @kindex e @r{(@code{edit})}
7334 To edit the lines in a source file, use the @code{edit} command.
7335 The editing program of your choice
7336 is invoked with the current line set to
7337 the active line in the program.
7338 Alternatively, there are several ways to specify what part of the file you
7339 want to print if you want to see other parts of the program:
7342 @item edit @var{location}
7343 Edit the source file specified by @code{location}. Editing starts at
7344 that @var{location}, e.g., at the specified source line of the
7345 specified file. @xref{Specify Location}, for all the possible forms
7346 of the @var{location} argument; here are the forms of the @code{edit}
7347 command most commonly used:
7350 @item edit @var{number}
7351 Edit the current source file with @var{number} as the active line number.
7353 @item edit @var{function}
7354 Edit the file containing @var{function} at the beginning of its definition.
7359 @subsection Choosing your Editor
7360 You can customize @value{GDBN} to use any editor you want
7362 The only restriction is that your editor (say @code{ex}), recognizes the
7363 following command-line syntax:
7365 ex +@var{number} file
7367 The optional numeric value +@var{number} specifies the number of the line in
7368 the file where to start editing.}.
7369 By default, it is @file{@value{EDITOR}}, but you can change this
7370 by setting the environment variable @code{EDITOR} before using
7371 @value{GDBN}. For example, to configure @value{GDBN} to use the
7372 @code{vi} editor, you could use these commands with the @code{sh} shell:
7378 or in the @code{csh} shell,
7380 setenv EDITOR /usr/bin/vi
7385 @section Searching Source Files
7386 @cindex searching source files
7388 There are two commands for searching through the current source file for a
7393 @kindex forward-search
7394 @kindex fo @r{(@code{forward-search})}
7395 @item forward-search @var{regexp}
7396 @itemx search @var{regexp}
7397 The command @samp{forward-search @var{regexp}} checks each line,
7398 starting with the one following the last line listed, for a match for
7399 @var{regexp}. It lists the line that is found. You can use the
7400 synonym @samp{search @var{regexp}} or abbreviate the command name as
7403 @kindex reverse-search
7404 @item reverse-search @var{regexp}
7405 The command @samp{reverse-search @var{regexp}} checks each line, starting
7406 with the one before the last line listed and going backward, for a match
7407 for @var{regexp}. It lists the line that is found. You can abbreviate
7408 this command as @code{rev}.
7412 @section Specifying Source Directories
7415 @cindex directories for source files
7416 Executable programs sometimes do not record the directories of the source
7417 files from which they were compiled, just the names. Even when they do,
7418 the directories could be moved between the compilation and your debugging
7419 session. @value{GDBN} has a list of directories to search for source files;
7420 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7421 it tries all the directories in the list, in the order they are present
7422 in the list, until it finds a file with the desired name.
7424 For example, suppose an executable references the file
7425 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7426 @file{/mnt/cross}. The file is first looked up literally; if this
7427 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7428 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7429 message is printed. @value{GDBN} does not look up the parts of the
7430 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7431 Likewise, the subdirectories of the source path are not searched: if
7432 the source path is @file{/mnt/cross}, and the binary refers to
7433 @file{foo.c}, @value{GDBN} would not find it under
7434 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7436 Plain file names, relative file names with leading directories, file
7437 names containing dots, etc.@: are all treated as described above; for
7438 instance, if the source path is @file{/mnt/cross}, and the source file
7439 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7440 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7441 that---@file{/mnt/cross/foo.c}.
7443 Note that the executable search path is @emph{not} used to locate the
7446 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7447 any information it has cached about where source files are found and where
7448 each line is in the file.
7452 When you start @value{GDBN}, its source path includes only @samp{cdir}
7453 and @samp{cwd}, in that order.
7454 To add other directories, use the @code{directory} command.
7456 The search path is used to find both program source files and @value{GDBN}
7457 script files (read using the @samp{-command} option and @samp{source} command).
7459 In addition to the source path, @value{GDBN} provides a set of commands
7460 that manage a list of source path substitution rules. A @dfn{substitution
7461 rule} specifies how to rewrite source directories stored in the program's
7462 debug information in case the sources were moved to a different
7463 directory between compilation and debugging. A rule is made of
7464 two strings, the first specifying what needs to be rewritten in
7465 the path, and the second specifying how it should be rewritten.
7466 In @ref{set substitute-path}, we name these two parts @var{from} and
7467 @var{to} respectively. @value{GDBN} does a simple string replacement
7468 of @var{from} with @var{to} at the start of the directory part of the
7469 source file name, and uses that result instead of the original file
7470 name to look up the sources.
7472 Using the previous example, suppose the @file{foo-1.0} tree has been
7473 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7474 @value{GDBN} to replace @file{/usr/src} in all source path names with
7475 @file{/mnt/cross}. The first lookup will then be
7476 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7477 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7478 substitution rule, use the @code{set substitute-path} command
7479 (@pxref{set substitute-path}).
7481 To avoid unexpected substitution results, a rule is applied only if the
7482 @var{from} part of the directory name ends at a directory separator.
7483 For instance, a rule substituting @file{/usr/source} into
7484 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7485 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7486 is applied only at the beginning of the directory name, this rule will
7487 not be applied to @file{/root/usr/source/baz.c} either.
7489 In many cases, you can achieve the same result using the @code{directory}
7490 command. However, @code{set substitute-path} can be more efficient in
7491 the case where the sources are organized in a complex tree with multiple
7492 subdirectories. With the @code{directory} command, you need to add each
7493 subdirectory of your project. If you moved the entire tree while
7494 preserving its internal organization, then @code{set substitute-path}
7495 allows you to direct the debugger to all the sources with one single
7498 @code{set substitute-path} is also more than just a shortcut command.
7499 The source path is only used if the file at the original location no
7500 longer exists. On the other hand, @code{set substitute-path} modifies
7501 the debugger behavior to look at the rewritten location instead. So, if
7502 for any reason a source file that is not relevant to your executable is
7503 located at the original location, a substitution rule is the only
7504 method available to point @value{GDBN} at the new location.
7506 @cindex @samp{--with-relocated-sources}
7507 @cindex default source path substitution
7508 You can configure a default source path substitution rule by
7509 configuring @value{GDBN} with the
7510 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7511 should be the name of a directory under @value{GDBN}'s configured
7512 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7513 directory names in debug information under @var{dir} will be adjusted
7514 automatically if the installed @value{GDBN} is moved to a new
7515 location. This is useful if @value{GDBN}, libraries or executables
7516 with debug information and corresponding source code are being moved
7520 @item directory @var{dirname} @dots{}
7521 @item dir @var{dirname} @dots{}
7522 Add directory @var{dirname} to the front of the source path. Several
7523 directory names may be given to this command, separated by @samp{:}
7524 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7525 part of absolute file names) or
7526 whitespace. You may specify a directory that is already in the source
7527 path; this moves it forward, so @value{GDBN} searches it sooner.
7531 @vindex $cdir@r{, convenience variable}
7532 @vindex $cwd@r{, convenience variable}
7533 @cindex compilation directory
7534 @cindex current directory
7535 @cindex working directory
7536 @cindex directory, current
7537 @cindex directory, compilation
7538 You can use the string @samp{$cdir} to refer to the compilation
7539 directory (if one is recorded), and @samp{$cwd} to refer to the current
7540 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7541 tracks the current working directory as it changes during your @value{GDBN}
7542 session, while the latter is immediately expanded to the current
7543 directory at the time you add an entry to the source path.
7546 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7548 @c RET-repeat for @code{directory} is explicitly disabled, but since
7549 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7551 @item set directories @var{path-list}
7552 @kindex set directories
7553 Set the source path to @var{path-list}.
7554 @samp{$cdir:$cwd} are added if missing.
7556 @item show directories
7557 @kindex show directories
7558 Print the source path: show which directories it contains.
7560 @anchor{set substitute-path}
7561 @item set substitute-path @var{from} @var{to}
7562 @kindex set substitute-path
7563 Define a source path substitution rule, and add it at the end of the
7564 current list of existing substitution rules. If a rule with the same
7565 @var{from} was already defined, then the old rule is also deleted.
7567 For example, if the file @file{/foo/bar/baz.c} was moved to
7568 @file{/mnt/cross/baz.c}, then the command
7571 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7575 will tell @value{GDBN} to replace @samp{/usr/src} with
7576 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7577 @file{baz.c} even though it was moved.
7579 In the case when more than one substitution rule have been defined,
7580 the rules are evaluated one by one in the order where they have been
7581 defined. The first one matching, if any, is selected to perform
7584 For instance, if we had entered the following commands:
7587 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7588 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7592 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7593 @file{/mnt/include/defs.h} by using the first rule. However, it would
7594 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7595 @file{/mnt/src/lib/foo.c}.
7598 @item unset substitute-path [path]
7599 @kindex unset substitute-path
7600 If a path is specified, search the current list of substitution rules
7601 for a rule that would rewrite that path. Delete that rule if found.
7602 A warning is emitted by the debugger if no rule could be found.
7604 If no path is specified, then all substitution rules are deleted.
7606 @item show substitute-path [path]
7607 @kindex show substitute-path
7608 If a path is specified, then print the source path substitution rule
7609 which would rewrite that path, if any.
7611 If no path is specified, then print all existing source path substitution
7616 If your source path is cluttered with directories that are no longer of
7617 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7618 versions of source. You can correct the situation as follows:
7622 Use @code{directory} with no argument to reset the source path to its default value.
7625 Use @code{directory} with suitable arguments to reinstall the
7626 directories you want in the source path. You can add all the
7627 directories in one command.
7631 @section Source and Machine Code
7632 @cindex source line and its code address
7634 You can use the command @code{info line} to map source lines to program
7635 addresses (and vice versa), and the command @code{disassemble} to display
7636 a range of addresses as machine instructions. You can use the command
7637 @code{set disassemble-next-line} to set whether to disassemble next
7638 source line when execution stops. When run under @sc{gnu} Emacs
7639 mode, the @code{info line} command causes the arrow to point to the
7640 line specified. Also, @code{info line} prints addresses in symbolic form as
7645 @item info line @var{linespec}
7646 Print the starting and ending addresses of the compiled code for
7647 source line @var{linespec}. You can specify source lines in any of
7648 the ways documented in @ref{Specify Location}.
7651 For example, we can use @code{info line} to discover the location of
7652 the object code for the first line of function
7653 @code{m4_changequote}:
7655 @c FIXME: I think this example should also show the addresses in
7656 @c symbolic form, as they usually would be displayed.
7658 (@value{GDBP}) info line m4_changequote
7659 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7663 @cindex code address and its source line
7664 We can also inquire (using @code{*@var{addr}} as the form for
7665 @var{linespec}) what source line covers a particular address:
7667 (@value{GDBP}) info line *0x63ff
7668 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7671 @cindex @code{$_} and @code{info line}
7672 @cindex @code{x} command, default address
7673 @kindex x@r{(examine), and} info line
7674 After @code{info line}, the default address for the @code{x} command
7675 is changed to the starting address of the line, so that @samp{x/i} is
7676 sufficient to begin examining the machine code (@pxref{Memory,
7677 ,Examining Memory}). Also, this address is saved as the value of the
7678 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7683 @cindex assembly instructions
7684 @cindex instructions, assembly
7685 @cindex machine instructions
7686 @cindex listing machine instructions
7688 @itemx disassemble /m
7689 @itemx disassemble /r
7690 This specialized command dumps a range of memory as machine
7691 instructions. It can also print mixed source+disassembly by specifying
7692 the @code{/m} modifier and print the raw instructions in hex as well as
7693 in symbolic form by specifying the @code{/r}.
7694 The default memory range is the function surrounding the
7695 program counter of the selected frame. A single argument to this
7696 command is a program counter value; @value{GDBN} dumps the function
7697 surrounding this value. When two arguments are given, they should
7698 be separated by a comma, possibly surrounded by whitespace. The
7699 arguments specify a range of addresses to dump, in one of two forms:
7702 @item @var{start},@var{end}
7703 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
7704 @item @var{start},+@var{length}
7705 the addresses from @var{start} (inclusive) to
7706 @code{@var{start}+@var{length}} (exclusive).
7710 When 2 arguments are specified, the name of the function is also
7711 printed (since there could be several functions in the given range).
7713 The argument(s) can be any expression yielding a numeric value, such as
7714 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
7716 If the range of memory being disassembled contains current program counter,
7717 the instruction at that location is shown with a @code{=>} marker.
7720 The following example shows the disassembly of a range of addresses of
7721 HP PA-RISC 2.0 code:
7724 (@value{GDBP}) disas 0x32c4, 0x32e4
7725 Dump of assembler code from 0x32c4 to 0x32e4:
7726 0x32c4 <main+204>: addil 0,dp
7727 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
7728 0x32cc <main+212>: ldil 0x3000,r31
7729 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
7730 0x32d4 <main+220>: ldo 0(r31),rp
7731 0x32d8 <main+224>: addil -0x800,dp
7732 0x32dc <main+228>: ldo 0x588(r1),r26
7733 0x32e0 <main+232>: ldil 0x3000,r31
7734 End of assembler dump.
7737 Here is an example showing mixed source+assembly for Intel x86, when the
7738 program is stopped just after function prologue:
7741 (@value{GDBP}) disas /m main
7742 Dump of assembler code for function main:
7744 0x08048330 <+0>: push %ebp
7745 0x08048331 <+1>: mov %esp,%ebp
7746 0x08048333 <+3>: sub $0x8,%esp
7747 0x08048336 <+6>: and $0xfffffff0,%esp
7748 0x08048339 <+9>: sub $0x10,%esp
7750 6 printf ("Hello.\n");
7751 => 0x0804833c <+12>: movl $0x8048440,(%esp)
7752 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7756 0x08048348 <+24>: mov $0x0,%eax
7757 0x0804834d <+29>: leave
7758 0x0804834e <+30>: ret
7760 End of assembler dump.
7763 Here is another example showing raw instructions in hex for AMD x86-64,
7766 (gdb) disas /r 0x400281,+10
7767 Dump of assembler code from 0x400281 to 0x40028b:
7768 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7769 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7770 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7771 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7772 End of assembler dump.
7775 Addresses cannot be specified as a linespec (@pxref{Specify Location}).
7776 So, for example, if you want to disassemble function @code{bar}
7777 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
7778 and not @samp{disassemble foo.c:bar}.
7780 Some architectures have more than one commonly-used set of instruction
7781 mnemonics or other syntax.
7783 For programs that were dynamically linked and use shared libraries,
7784 instructions that call functions or branch to locations in the shared
7785 libraries might show a seemingly bogus location---it's actually a
7786 location of the relocation table. On some architectures, @value{GDBN}
7787 might be able to resolve these to actual function names.
7790 @kindex set disassembly-flavor
7791 @cindex Intel disassembly flavor
7792 @cindex AT&T disassembly flavor
7793 @item set disassembly-flavor @var{instruction-set}
7794 Select the instruction set to use when disassembling the
7795 program via the @code{disassemble} or @code{x/i} commands.
7797 Currently this command is only defined for the Intel x86 family. You
7798 can set @var{instruction-set} to either @code{intel} or @code{att}.
7799 The default is @code{att}, the AT&T flavor used by default by Unix
7800 assemblers for x86-based targets.
7802 @kindex show disassembly-flavor
7803 @item show disassembly-flavor
7804 Show the current setting of the disassembly flavor.
7808 @kindex set disassemble-next-line
7809 @kindex show disassemble-next-line
7810 @item set disassemble-next-line
7811 @itemx show disassemble-next-line
7812 Control whether or not @value{GDBN} will disassemble the next source
7813 line or instruction when execution stops. If ON, @value{GDBN} will
7814 display disassembly of the next source line when execution of the
7815 program being debugged stops. This is @emph{in addition} to
7816 displaying the source line itself, which @value{GDBN} always does if
7817 possible. If the next source line cannot be displayed for some reason
7818 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7819 info in the debug info), @value{GDBN} will display disassembly of the
7820 next @emph{instruction} instead of showing the next source line. If
7821 AUTO, @value{GDBN} will display disassembly of next instruction only
7822 if the source line cannot be displayed. This setting causes
7823 @value{GDBN} to display some feedback when you step through a function
7824 with no line info or whose source file is unavailable. The default is
7825 OFF, which means never display the disassembly of the next line or
7831 @chapter Examining Data
7833 @cindex printing data
7834 @cindex examining data
7837 The usual way to examine data in your program is with the @code{print}
7838 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7839 evaluates and prints the value of an expression of the language your
7840 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7841 Different Languages}). It may also print the expression using a
7842 Python-based pretty-printer (@pxref{Pretty Printing}).
7845 @item print @var{expr}
7846 @itemx print /@var{f} @var{expr}
7847 @var{expr} is an expression (in the source language). By default the
7848 value of @var{expr} is printed in a format appropriate to its data type;
7849 you can choose a different format by specifying @samp{/@var{f}}, where
7850 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7854 @itemx print /@var{f}
7855 @cindex reprint the last value
7856 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7857 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7858 conveniently inspect the same value in an alternative format.
7861 A more low-level way of examining data is with the @code{x} command.
7862 It examines data in memory at a specified address and prints it in a
7863 specified format. @xref{Memory, ,Examining Memory}.
7865 If you are interested in information about types, or about how the
7866 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7867 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7870 @cindex exploring hierarchical data structures
7872 Another way of examining values of expressions and type information is
7873 through the Python extension command @code{explore} (available only if
7874 the @value{GDBN} build is configured with @code{--with-python}). It
7875 offers an interactive way to start at the highest level (or, the most
7876 abstract level) of the data type of an expression (or, the data type
7877 itself) and explore all the way down to leaf scalar values/fields
7878 embedded in the higher level data types.
7881 @item explore @var{arg}
7882 @var{arg} is either an expression (in the source language), or a type
7883 visible in the current context of the program being debugged.
7886 The working of the @code{explore} command can be illustrated with an
7887 example. If a data type @code{struct ComplexStruct} is defined in your
7897 struct ComplexStruct
7899 struct SimpleStruct *ss_p;
7905 followed by variable declarations as
7908 struct SimpleStruct ss = @{ 10, 1.11 @};
7909 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
7913 then, the value of the variable @code{cs} can be explored using the
7914 @code{explore} command as follows.
7918 The value of `cs' is a struct/class of type `struct ComplexStruct' with
7919 the following fields:
7921 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
7922 arr = <Enter 1 to explore this field of type `int [10]'>
7924 Enter the field number of choice:
7928 Since the fields of @code{cs} are not scalar values, you are being
7929 prompted to chose the field you want to explore. Let's say you choose
7930 the field @code{ss_p} by entering @code{0}. Then, since this field is a
7931 pointer, you will be asked if it is pointing to a single value. From
7932 the declaration of @code{cs} above, it is indeed pointing to a single
7933 value, hence you enter @code{y}. If you enter @code{n}, then you will
7934 be asked if it were pointing to an array of values, in which case this
7935 field will be explored as if it were an array.
7938 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
7939 Continue exploring it as a pointer to a single value [y/n]: y
7940 The value of `*(cs.ss_p)' is a struct/class of type `struct
7941 SimpleStruct' with the following fields:
7943 i = 10 .. (Value of type `int')
7944 d = 1.1100000000000001 .. (Value of type `double')
7946 Press enter to return to parent value:
7950 If the field @code{arr} of @code{cs} was chosen for exploration by
7951 entering @code{1} earlier, then since it is as array, you will be
7952 prompted to enter the index of the element in the array that you want
7956 `cs.arr' is an array of `int'.
7957 Enter the index of the element you want to explore in `cs.arr': 5
7959 `(cs.arr)[5]' is a scalar value of type `int'.
7963 Press enter to return to parent value:
7966 In general, at any stage of exploration, you can go deeper towards the
7967 leaf values by responding to the prompts appropriately, or hit the
7968 return key to return to the enclosing data structure (the @i{higher}
7969 level data structure).
7971 Similar to exploring values, you can use the @code{explore} command to
7972 explore types. Instead of specifying a value (which is typically a
7973 variable name or an expression valid in the current context of the
7974 program being debugged), you specify a type name. If you consider the
7975 same example as above, your can explore the type
7976 @code{struct ComplexStruct} by passing the argument
7977 @code{struct ComplexStruct} to the @code{explore} command.
7980 (gdb) explore struct ComplexStruct
7984 By responding to the prompts appropriately in the subsequent interactive
7985 session, you can explore the type @code{struct ComplexStruct} in a
7986 manner similar to how the value @code{cs} was explored in the above
7989 The @code{explore} command also has two sub-commands,
7990 @code{explore value} and @code{explore type}. The former sub-command is
7991 a way to explicitly specify that value exploration of the argument is
7992 being invoked, while the latter is a way to explicitly specify that type
7993 exploration of the argument is being invoked.
7996 @item explore value @var{expr}
7997 @cindex explore value
7998 This sub-command of @code{explore} explores the value of the
7999 expression @var{expr} (if @var{expr} is an expression valid in the
8000 current context of the program being debugged). The behavior of this
8001 command is identical to that of the behavior of the @code{explore}
8002 command being passed the argument @var{expr}.
8004 @item explore type @var{arg}
8005 @cindex explore type
8006 This sub-command of @code{explore} explores the type of @var{arg} (if
8007 @var{arg} is a type visible in the current context of program being
8008 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8009 is an expression valid in the current context of the program being
8010 debugged). If @var{arg} is a type, then the behavior of this command is
8011 identical to that of the @code{explore} command being passed the
8012 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8013 this command will be identical to that of the @code{explore} command
8014 being passed the type of @var{arg} as the argument.
8018 * Expressions:: Expressions
8019 * Ambiguous Expressions:: Ambiguous Expressions
8020 * Variables:: Program variables
8021 * Arrays:: Artificial arrays
8022 * Output Formats:: Output formats
8023 * Memory:: Examining memory
8024 * Auto Display:: Automatic display
8025 * Print Settings:: Print settings
8026 * Pretty Printing:: Python pretty printing
8027 * Value History:: Value history
8028 * Convenience Vars:: Convenience variables
8029 * Convenience Funs:: Convenience functions
8030 * Registers:: Registers
8031 * Floating Point Hardware:: Floating point hardware
8032 * Vector Unit:: Vector Unit
8033 * OS Information:: Auxiliary data provided by operating system
8034 * Memory Region Attributes:: Memory region attributes
8035 * Dump/Restore Files:: Copy between memory and a file
8036 * Core File Generation:: Cause a program dump its core
8037 * Character Sets:: Debugging programs that use a different
8038 character set than GDB does
8039 * Caching Remote Data:: Data caching for remote targets
8040 * Searching Memory:: Searching memory for a sequence of bytes
8044 @section Expressions
8047 @code{print} and many other @value{GDBN} commands accept an expression and
8048 compute its value. Any kind of constant, variable or operator defined
8049 by the programming language you are using is valid in an expression in
8050 @value{GDBN}. This includes conditional expressions, function calls,
8051 casts, and string constants. It also includes preprocessor macros, if
8052 you compiled your program to include this information; see
8055 @cindex arrays in expressions
8056 @value{GDBN} supports array constants in expressions input by
8057 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8058 you can use the command @code{print @{1, 2, 3@}} to create an array
8059 of three integers. If you pass an array to a function or assign it
8060 to a program variable, @value{GDBN} copies the array to memory that
8061 is @code{malloc}ed in the target program.
8063 Because C is so widespread, most of the expressions shown in examples in
8064 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8065 Languages}, for information on how to use expressions in other
8068 In this section, we discuss operators that you can use in @value{GDBN}
8069 expressions regardless of your programming language.
8071 @cindex casts, in expressions
8072 Casts are supported in all languages, not just in C, because it is so
8073 useful to cast a number into a pointer in order to examine a structure
8074 at that address in memory.
8075 @c FIXME: casts supported---Mod2 true?
8077 @value{GDBN} supports these operators, in addition to those common
8078 to programming languages:
8082 @samp{@@} is a binary operator for treating parts of memory as arrays.
8083 @xref{Arrays, ,Artificial Arrays}, for more information.
8086 @samp{::} allows you to specify a variable in terms of the file or
8087 function where it is defined. @xref{Variables, ,Program Variables}.
8089 @cindex @{@var{type}@}
8090 @cindex type casting memory
8091 @cindex memory, viewing as typed object
8092 @cindex casts, to view memory
8093 @item @{@var{type}@} @var{addr}
8094 Refers to an object of type @var{type} stored at address @var{addr} in
8095 memory. @var{addr} may be any expression whose value is an integer or
8096 pointer (but parentheses are required around binary operators, just as in
8097 a cast). This construct is allowed regardless of what kind of data is
8098 normally supposed to reside at @var{addr}.
8101 @node Ambiguous Expressions
8102 @section Ambiguous Expressions
8103 @cindex ambiguous expressions
8105 Expressions can sometimes contain some ambiguous elements. For instance,
8106 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8107 a single function name to be defined several times, for application in
8108 different contexts. This is called @dfn{overloading}. Another example
8109 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8110 templates and is typically instantiated several times, resulting in
8111 the same function name being defined in different contexts.
8113 In some cases and depending on the language, it is possible to adjust
8114 the expression to remove the ambiguity. For instance in C@t{++}, you
8115 can specify the signature of the function you want to break on, as in
8116 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8117 qualified name of your function often makes the expression unambiguous
8120 When an ambiguity that needs to be resolved is detected, the debugger
8121 has the capability to display a menu of numbered choices for each
8122 possibility, and then waits for the selection with the prompt @samp{>}.
8123 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8124 aborts the current command. If the command in which the expression was
8125 used allows more than one choice to be selected, the next option in the
8126 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8129 For example, the following session excerpt shows an attempt to set a
8130 breakpoint at the overloaded symbol @code{String::after}.
8131 We choose three particular definitions of that function name:
8133 @c FIXME! This is likely to change to show arg type lists, at least
8136 (@value{GDBP}) b String::after
8139 [2] file:String.cc; line number:867
8140 [3] file:String.cc; line number:860
8141 [4] file:String.cc; line number:875
8142 [5] file:String.cc; line number:853
8143 [6] file:String.cc; line number:846
8144 [7] file:String.cc; line number:735
8146 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8147 Breakpoint 2 at 0xb344: file String.cc, line 875.
8148 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8149 Multiple breakpoints were set.
8150 Use the "delete" command to delete unwanted
8157 @kindex set multiple-symbols
8158 @item set multiple-symbols @var{mode}
8159 @cindex multiple-symbols menu
8161 This option allows you to adjust the debugger behavior when an expression
8164 By default, @var{mode} is set to @code{all}. If the command with which
8165 the expression is used allows more than one choice, then @value{GDBN}
8166 automatically selects all possible choices. For instance, inserting
8167 a breakpoint on a function using an ambiguous name results in a breakpoint
8168 inserted on each possible match. However, if a unique choice must be made,
8169 then @value{GDBN} uses the menu to help you disambiguate the expression.
8170 For instance, printing the address of an overloaded function will result
8171 in the use of the menu.
8173 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8174 when an ambiguity is detected.
8176 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8177 an error due to the ambiguity and the command is aborted.
8179 @kindex show multiple-symbols
8180 @item show multiple-symbols
8181 Show the current value of the @code{multiple-symbols} setting.
8185 @section Program Variables
8187 The most common kind of expression to use is the name of a variable
8190 Variables in expressions are understood in the selected stack frame
8191 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8195 global (or file-static)
8202 visible according to the scope rules of the
8203 programming language from the point of execution in that frame
8206 @noindent This means that in the function
8221 you can examine and use the variable @code{a} whenever your program is
8222 executing within the function @code{foo}, but you can only use or
8223 examine the variable @code{b} while your program is executing inside
8224 the block where @code{b} is declared.
8226 @cindex variable name conflict
8227 There is an exception: you can refer to a variable or function whose
8228 scope is a single source file even if the current execution point is not
8229 in this file. But it is possible to have more than one such variable or
8230 function with the same name (in different source files). If that
8231 happens, referring to that name has unpredictable effects. If you wish,
8232 you can specify a static variable in a particular function or file by
8233 using the colon-colon (@code{::}) notation:
8235 @cindex colon-colon, context for variables/functions
8237 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8238 @cindex @code{::}, context for variables/functions
8241 @var{file}::@var{variable}
8242 @var{function}::@var{variable}
8246 Here @var{file} or @var{function} is the name of the context for the
8247 static @var{variable}. In the case of file names, you can use quotes to
8248 make sure @value{GDBN} parses the file name as a single word---for example,
8249 to print a global value of @code{x} defined in @file{f2.c}:
8252 (@value{GDBP}) p 'f2.c'::x
8255 The @code{::} notation is normally used for referring to
8256 static variables, since you typically disambiguate uses of local variables
8257 in functions by selecting the appropriate frame and using the
8258 simple name of the variable. However, you may also use this notation
8259 to refer to local variables in frames enclosing the selected frame:
8268 process (a); /* Stop here */
8279 For example, if there is a breakpoint at the commented line,
8280 here is what you might see
8281 when the program stops after executing the call @code{bar(0)}:
8286 (@value{GDBP}) p bar::a
8289 #2 0x080483d0 in foo (a=5) at foobar.c:12
8292 (@value{GDBP}) p bar::a
8296 @cindex C@t{++} scope resolution
8297 These uses of @samp{::} are very rarely in conflict with the very similar
8298 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
8299 scope resolution operator in @value{GDBN} expressions.
8300 @c FIXME: Um, so what happens in one of those rare cases where it's in
8303 @cindex wrong values
8304 @cindex variable values, wrong
8305 @cindex function entry/exit, wrong values of variables
8306 @cindex optimized code, wrong values of variables
8308 @emph{Warning:} Occasionally, a local variable may appear to have the
8309 wrong value at certain points in a function---just after entry to a new
8310 scope, and just before exit.
8312 You may see this problem when you are stepping by machine instructions.
8313 This is because, on most machines, it takes more than one instruction to
8314 set up a stack frame (including local variable definitions); if you are
8315 stepping by machine instructions, variables may appear to have the wrong
8316 values until the stack frame is completely built. On exit, it usually
8317 also takes more than one machine instruction to destroy a stack frame;
8318 after you begin stepping through that group of instructions, local
8319 variable definitions may be gone.
8321 This may also happen when the compiler does significant optimizations.
8322 To be sure of always seeing accurate values, turn off all optimization
8325 @cindex ``No symbol "foo" in current context''
8326 Another possible effect of compiler optimizations is to optimize
8327 unused variables out of existence, or assign variables to registers (as
8328 opposed to memory addresses). Depending on the support for such cases
8329 offered by the debug info format used by the compiler, @value{GDBN}
8330 might not be able to display values for such local variables. If that
8331 happens, @value{GDBN} will print a message like this:
8334 No symbol "foo" in current context.
8337 To solve such problems, either recompile without optimizations, or use a
8338 different debug info format, if the compiler supports several such
8339 formats. @xref{Compilation}, for more information on choosing compiler
8340 options. @xref{C, ,C and C@t{++}}, for more information about debug
8341 info formats that are best suited to C@t{++} programs.
8343 If you ask to print an object whose contents are unknown to
8344 @value{GDBN}, e.g., because its data type is not completely specified
8345 by the debug information, @value{GDBN} will say @samp{<incomplete
8346 type>}. @xref{Symbols, incomplete type}, for more about this.
8348 If you append @kbd{@@entry} string to a function parameter name you get its
8349 value at the time the function got called. If the value is not available an
8350 error message is printed. Entry values are available only with some compilers.
8351 Entry values are normally also printed at the function parameter list according
8352 to @ref{set print entry-values}.
8355 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8361 (gdb) print i@@entry
8365 Strings are identified as arrays of @code{char} values without specified
8366 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8367 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8368 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8369 defines literal string type @code{"char"} as @code{char} without a sign.
8374 signed char var1[] = "A";
8377 You get during debugging
8382 $2 = @{65 'A', 0 '\0'@}
8386 @section Artificial Arrays
8388 @cindex artificial array
8390 @kindex @@@r{, referencing memory as an array}
8391 It is often useful to print out several successive objects of the
8392 same type in memory; a section of an array, or an array of
8393 dynamically determined size for which only a pointer exists in the
8396 You can do this by referring to a contiguous span of memory as an
8397 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8398 operand of @samp{@@} should be the first element of the desired array
8399 and be an individual object. The right operand should be the desired length
8400 of the array. The result is an array value whose elements are all of
8401 the type of the left argument. The first element is actually the left
8402 argument; the second element comes from bytes of memory immediately
8403 following those that hold the first element, and so on. Here is an
8404 example. If a program says
8407 int *array = (int *) malloc (len * sizeof (int));
8411 you can print the contents of @code{array} with
8417 The left operand of @samp{@@} must reside in memory. Array values made
8418 with @samp{@@} in this way behave just like other arrays in terms of
8419 subscripting, and are coerced to pointers when used in expressions.
8420 Artificial arrays most often appear in expressions via the value history
8421 (@pxref{Value History, ,Value History}), after printing one out.
8423 Another way to create an artificial array is to use a cast.
8424 This re-interprets a value as if it were an array.
8425 The value need not be in memory:
8427 (@value{GDBP}) p/x (short[2])0x12345678
8428 $1 = @{0x1234, 0x5678@}
8431 As a convenience, if you leave the array length out (as in
8432 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8433 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8435 (@value{GDBP}) p/x (short[])0x12345678
8436 $2 = @{0x1234, 0x5678@}
8439 Sometimes the artificial array mechanism is not quite enough; in
8440 moderately complex data structures, the elements of interest may not
8441 actually be adjacent---for example, if you are interested in the values
8442 of pointers in an array. One useful work-around in this situation is
8443 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8444 Variables}) as a counter in an expression that prints the first
8445 interesting value, and then repeat that expression via @key{RET}. For
8446 instance, suppose you have an array @code{dtab} of pointers to
8447 structures, and you are interested in the values of a field @code{fv}
8448 in each structure. Here is an example of what you might type:
8458 @node Output Formats
8459 @section Output Formats
8461 @cindex formatted output
8462 @cindex output formats
8463 By default, @value{GDBN} prints a value according to its data type. Sometimes
8464 this is not what you want. For example, you might want to print a number
8465 in hex, or a pointer in decimal. Or you might want to view data in memory
8466 at a certain address as a character string or as an instruction. To do
8467 these things, specify an @dfn{output format} when you print a value.
8469 The simplest use of output formats is to say how to print a value
8470 already computed. This is done by starting the arguments of the
8471 @code{print} command with a slash and a format letter. The format
8472 letters supported are:
8476 Regard the bits of the value as an integer, and print the integer in
8480 Print as integer in signed decimal.
8483 Print as integer in unsigned decimal.
8486 Print as integer in octal.
8489 Print as integer in binary. The letter @samp{t} stands for ``two''.
8490 @footnote{@samp{b} cannot be used because these format letters are also
8491 used with the @code{x} command, where @samp{b} stands for ``byte'';
8492 see @ref{Memory,,Examining Memory}.}
8495 @cindex unknown address, locating
8496 @cindex locate address
8497 Print as an address, both absolute in hexadecimal and as an offset from
8498 the nearest preceding symbol. You can use this format used to discover
8499 where (in what function) an unknown address is located:
8502 (@value{GDBP}) p/a 0x54320
8503 $3 = 0x54320 <_initialize_vx+396>
8507 The command @code{info symbol 0x54320} yields similar results.
8508 @xref{Symbols, info symbol}.
8511 Regard as an integer and print it as a character constant. This
8512 prints both the numerical value and its character representation. The
8513 character representation is replaced with the octal escape @samp{\nnn}
8514 for characters outside the 7-bit @sc{ascii} range.
8516 Without this format, @value{GDBN} displays @code{char},
8517 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8518 constants. Single-byte members of vectors are displayed as integer
8522 Regard the bits of the value as a floating point number and print
8523 using typical floating point syntax.
8526 @cindex printing strings
8527 @cindex printing byte arrays
8528 Regard as a string, if possible. With this format, pointers to single-byte
8529 data are displayed as null-terminated strings and arrays of single-byte data
8530 are displayed as fixed-length strings. Other values are displayed in their
8533 Without this format, @value{GDBN} displays pointers to and arrays of
8534 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8535 strings. Single-byte members of a vector are displayed as an integer
8539 Like @samp{x} formatting, the value is treated as an integer and
8540 printed as hexadecimal, but leading zeros are printed to pad the value
8541 to the size of the integer type.
8544 @cindex raw printing
8545 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8546 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8547 Printing}). This typically results in a higher-level display of the
8548 value's contents. The @samp{r} format bypasses any Python
8549 pretty-printer which might exist.
8552 For example, to print the program counter in hex (@pxref{Registers}), type
8559 Note that no space is required before the slash; this is because command
8560 names in @value{GDBN} cannot contain a slash.
8562 To reprint the last value in the value history with a different format,
8563 you can use the @code{print} command with just a format and no
8564 expression. For example, @samp{p/x} reprints the last value in hex.
8567 @section Examining Memory
8569 You can use the command @code{x} (for ``examine'') to examine memory in
8570 any of several formats, independently of your program's data types.
8572 @cindex examining memory
8574 @kindex x @r{(examine memory)}
8575 @item x/@var{nfu} @var{addr}
8578 Use the @code{x} command to examine memory.
8581 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8582 much memory to display and how to format it; @var{addr} is an
8583 expression giving the address where you want to start displaying memory.
8584 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8585 Several commands set convenient defaults for @var{addr}.
8588 @item @var{n}, the repeat count
8589 The repeat count is a decimal integer; the default is 1. It specifies
8590 how much memory (counting by units @var{u}) to display.
8591 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8594 @item @var{f}, the display format
8595 The display format is one of the formats used by @code{print}
8596 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8597 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8598 The default is @samp{x} (hexadecimal) initially. The default changes
8599 each time you use either @code{x} or @code{print}.
8601 @item @var{u}, the unit size
8602 The unit size is any of
8608 Halfwords (two bytes).
8610 Words (four bytes). This is the initial default.
8612 Giant words (eight bytes).
8615 Each time you specify a unit size with @code{x}, that size becomes the
8616 default unit the next time you use @code{x}. For the @samp{i} format,
8617 the unit size is ignored and is normally not written. For the @samp{s} format,
8618 the unit size defaults to @samp{b}, unless it is explicitly given.
8619 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8620 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8621 Note that the results depend on the programming language of the
8622 current compilation unit. If the language is C, the @samp{s}
8623 modifier will use the UTF-16 encoding while @samp{w} will use
8624 UTF-32. The encoding is set by the programming language and cannot
8627 @item @var{addr}, starting display address
8628 @var{addr} is the address where you want @value{GDBN} to begin displaying
8629 memory. The expression need not have a pointer value (though it may);
8630 it is always interpreted as an integer address of a byte of memory.
8631 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8632 @var{addr} is usually just after the last address examined---but several
8633 other commands also set the default address: @code{info breakpoints} (to
8634 the address of the last breakpoint listed), @code{info line} (to the
8635 starting address of a line), and @code{print} (if you use it to display
8636 a value from memory).
8639 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8640 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8641 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8642 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8643 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8645 Since the letters indicating unit sizes are all distinct from the
8646 letters specifying output formats, you do not have to remember whether
8647 unit size or format comes first; either order works. The output
8648 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8649 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8651 Even though the unit size @var{u} is ignored for the formats @samp{s}
8652 and @samp{i}, you might still want to use a count @var{n}; for example,
8653 @samp{3i} specifies that you want to see three machine instructions,
8654 including any operands. For convenience, especially when used with
8655 the @code{display} command, the @samp{i} format also prints branch delay
8656 slot instructions, if any, beyond the count specified, which immediately
8657 follow the last instruction that is within the count. The command
8658 @code{disassemble} gives an alternative way of inspecting machine
8659 instructions; see @ref{Machine Code,,Source and Machine Code}.
8661 All the defaults for the arguments to @code{x} are designed to make it
8662 easy to continue scanning memory with minimal specifications each time
8663 you use @code{x}. For example, after you have inspected three machine
8664 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8665 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8666 the repeat count @var{n} is used again; the other arguments default as
8667 for successive uses of @code{x}.
8669 When examining machine instructions, the instruction at current program
8670 counter is shown with a @code{=>} marker. For example:
8673 (@value{GDBP}) x/5i $pc-6
8674 0x804837f <main+11>: mov %esp,%ebp
8675 0x8048381 <main+13>: push %ecx
8676 0x8048382 <main+14>: sub $0x4,%esp
8677 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8678 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8681 @cindex @code{$_}, @code{$__}, and value history
8682 The addresses and contents printed by the @code{x} command are not saved
8683 in the value history because there is often too much of them and they
8684 would get in the way. Instead, @value{GDBN} makes these values available for
8685 subsequent use in expressions as values of the convenience variables
8686 @code{$_} and @code{$__}. After an @code{x} command, the last address
8687 examined is available for use in expressions in the convenience variable
8688 @code{$_}. The contents of that address, as examined, are available in
8689 the convenience variable @code{$__}.
8691 If the @code{x} command has a repeat count, the address and contents saved
8692 are from the last memory unit printed; this is not the same as the last
8693 address printed if several units were printed on the last line of output.
8695 @cindex remote memory comparison
8696 @cindex verify remote memory image
8697 When you are debugging a program running on a remote target machine
8698 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
8699 remote machine's memory against the executable file you downloaded to
8700 the target. The @code{compare-sections} command is provided for such
8704 @kindex compare-sections
8705 @item compare-sections @r{[}@var{section-name}@r{]}
8706 Compare the data of a loadable section @var{section-name} in the
8707 executable file of the program being debugged with the same section in
8708 the remote machine's memory, and report any mismatches. With no
8709 arguments, compares all loadable sections. This command's
8710 availability depends on the target's support for the @code{"qCRC"}
8715 @section Automatic Display
8716 @cindex automatic display
8717 @cindex display of expressions
8719 If you find that you want to print the value of an expression frequently
8720 (to see how it changes), you might want to add it to the @dfn{automatic
8721 display list} so that @value{GDBN} prints its value each time your program stops.
8722 Each expression added to the list is given a number to identify it;
8723 to remove an expression from the list, you specify that number.
8724 The automatic display looks like this:
8728 3: bar[5] = (struct hack *) 0x3804
8732 This display shows item numbers, expressions and their current values. As with
8733 displays you request manually using @code{x} or @code{print}, you can
8734 specify the output format you prefer; in fact, @code{display} decides
8735 whether to use @code{print} or @code{x} depending your format
8736 specification---it uses @code{x} if you specify either the @samp{i}
8737 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
8741 @item display @var{expr}
8742 Add the expression @var{expr} to the list of expressions to display
8743 each time your program stops. @xref{Expressions, ,Expressions}.
8745 @code{display} does not repeat if you press @key{RET} again after using it.
8747 @item display/@var{fmt} @var{expr}
8748 For @var{fmt} specifying only a display format and not a size or
8749 count, add the expression @var{expr} to the auto-display list but
8750 arrange to display it each time in the specified format @var{fmt}.
8751 @xref{Output Formats,,Output Formats}.
8753 @item display/@var{fmt} @var{addr}
8754 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
8755 number of units, add the expression @var{addr} as a memory address to
8756 be examined each time your program stops. Examining means in effect
8757 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
8760 For example, @samp{display/i $pc} can be helpful, to see the machine
8761 instruction about to be executed each time execution stops (@samp{$pc}
8762 is a common name for the program counter; @pxref{Registers, ,Registers}).
8765 @kindex delete display
8767 @item undisplay @var{dnums}@dots{}
8768 @itemx delete display @var{dnums}@dots{}
8769 Remove items from the list of expressions to display. Specify the
8770 numbers of the displays that you want affected with the command
8771 argument @var{dnums}. It can be a single display number, one of the
8772 numbers shown in the first field of the @samp{info display} display;
8773 or it could be a range of display numbers, as in @code{2-4}.
8775 @code{undisplay} does not repeat if you press @key{RET} after using it.
8776 (Otherwise you would just get the error @samp{No display number @dots{}}.)
8778 @kindex disable display
8779 @item disable display @var{dnums}@dots{}
8780 Disable the display of item numbers @var{dnums}. A disabled display
8781 item is not printed automatically, but is not forgotten. It may be
8782 enabled again later. Specify the numbers of the displays that you
8783 want affected with the command argument @var{dnums}. It can be a
8784 single display number, one of the numbers shown in the first field of
8785 the @samp{info display} display; or it could be a range of display
8786 numbers, as in @code{2-4}.
8788 @kindex enable display
8789 @item enable display @var{dnums}@dots{}
8790 Enable display of item numbers @var{dnums}. It becomes effective once
8791 again in auto display of its expression, until you specify otherwise.
8792 Specify the numbers of the displays that you want affected with the
8793 command argument @var{dnums}. It can be a single display number, one
8794 of the numbers shown in the first field of the @samp{info display}
8795 display; or it could be a range of display numbers, as in @code{2-4}.
8798 Display the current values of the expressions on the list, just as is
8799 done when your program stops.
8801 @kindex info display
8803 Print the list of expressions previously set up to display
8804 automatically, each one with its item number, but without showing the
8805 values. This includes disabled expressions, which are marked as such.
8806 It also includes expressions which would not be displayed right now
8807 because they refer to automatic variables not currently available.
8810 @cindex display disabled out of scope
8811 If a display expression refers to local variables, then it does not make
8812 sense outside the lexical context for which it was set up. Such an
8813 expression is disabled when execution enters a context where one of its
8814 variables is not defined. For example, if you give the command
8815 @code{display last_char} while inside a function with an argument
8816 @code{last_char}, @value{GDBN} displays this argument while your program
8817 continues to stop inside that function. When it stops elsewhere---where
8818 there is no variable @code{last_char}---the display is disabled
8819 automatically. The next time your program stops where @code{last_char}
8820 is meaningful, you can enable the display expression once again.
8822 @node Print Settings
8823 @section Print Settings
8825 @cindex format options
8826 @cindex print settings
8827 @value{GDBN} provides the following ways to control how arrays, structures,
8828 and symbols are printed.
8831 These settings are useful for debugging programs in any language:
8835 @item set print address
8836 @itemx set print address on
8837 @cindex print/don't print memory addresses
8838 @value{GDBN} prints memory addresses showing the location of stack
8839 traces, structure values, pointer values, breakpoints, and so forth,
8840 even when it also displays the contents of those addresses. The default
8841 is @code{on}. For example, this is what a stack frame display looks like with
8842 @code{set print address on}:
8847 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
8849 530 if (lquote != def_lquote)
8853 @item set print address off
8854 Do not print addresses when displaying their contents. For example,
8855 this is the same stack frame displayed with @code{set print address off}:
8859 (@value{GDBP}) set print addr off
8861 #0 set_quotes (lq="<<", rq=">>") at input.c:530
8862 530 if (lquote != def_lquote)
8866 You can use @samp{set print address off} to eliminate all machine
8867 dependent displays from the @value{GDBN} interface. For example, with
8868 @code{print address off}, you should get the same text for backtraces on
8869 all machines---whether or not they involve pointer arguments.
8872 @item show print address
8873 Show whether or not addresses are to be printed.
8876 When @value{GDBN} prints a symbolic address, it normally prints the
8877 closest earlier symbol plus an offset. If that symbol does not uniquely
8878 identify the address (for example, it is a name whose scope is a single
8879 source file), you may need to clarify. One way to do this is with
8880 @code{info line}, for example @samp{info line *0x4537}. Alternately,
8881 you can set @value{GDBN} to print the source file and line number when
8882 it prints a symbolic address:
8885 @item set print symbol-filename on
8886 @cindex source file and line of a symbol
8887 @cindex symbol, source file and line
8888 Tell @value{GDBN} to print the source file name and line number of a
8889 symbol in the symbolic form of an address.
8891 @item set print symbol-filename off
8892 Do not print source file name and line number of a symbol. This is the
8895 @item show print symbol-filename
8896 Show whether or not @value{GDBN} will print the source file name and
8897 line number of a symbol in the symbolic form of an address.
8900 Another situation where it is helpful to show symbol filenames and line
8901 numbers is when disassembling code; @value{GDBN} shows you the line
8902 number and source file that corresponds to each instruction.
8904 Also, you may wish to see the symbolic form only if the address being
8905 printed is reasonably close to the closest earlier symbol:
8908 @item set print max-symbolic-offset @var{max-offset}
8909 @itemx set print max-symbolic-offset unlimited
8910 @cindex maximum value for offset of closest symbol
8911 Tell @value{GDBN} to only display the symbolic form of an address if the
8912 offset between the closest earlier symbol and the address is less than
8913 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
8914 to always print the symbolic form of an address if any symbol precedes
8915 it. Zero is equivalent to @code{unlimited}.
8917 @item show print max-symbolic-offset
8918 Ask how large the maximum offset is that @value{GDBN} prints in a
8922 @cindex wild pointer, interpreting
8923 @cindex pointer, finding referent
8924 If you have a pointer and you are not sure where it points, try
8925 @samp{set print symbol-filename on}. Then you can determine the name
8926 and source file location of the variable where it points, using
8927 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
8928 For example, here @value{GDBN} shows that a variable @code{ptt} points
8929 at another variable @code{t}, defined in @file{hi2.c}:
8932 (@value{GDBP}) set print symbol-filename on
8933 (@value{GDBP}) p/a ptt
8934 $4 = 0xe008 <t in hi2.c>
8938 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
8939 does not show the symbol name and filename of the referent, even with
8940 the appropriate @code{set print} options turned on.
8943 You can also enable @samp{/a}-like formatting all the time using
8944 @samp{set print symbol on}:
8947 @item set print symbol on
8948 Tell @value{GDBN} to print the symbol corresponding to an address, if
8951 @item set print symbol off
8952 Tell @value{GDBN} not to print the symbol corresponding to an
8953 address. In this mode, @value{GDBN} will still print the symbol
8954 corresponding to pointers to functions. This is the default.
8956 @item show print symbol
8957 Show whether @value{GDBN} will display the symbol corresponding to an
8961 Other settings control how different kinds of objects are printed:
8964 @item set print array
8965 @itemx set print array on
8966 @cindex pretty print arrays
8967 Pretty print arrays. This format is more convenient to read,
8968 but uses more space. The default is off.
8970 @item set print array off
8971 Return to compressed format for arrays.
8973 @item show print array
8974 Show whether compressed or pretty format is selected for displaying
8977 @cindex print array indexes
8978 @item set print array-indexes
8979 @itemx set print array-indexes on
8980 Print the index of each element when displaying arrays. May be more
8981 convenient to locate a given element in the array or quickly find the
8982 index of a given element in that printed array. The default is off.
8984 @item set print array-indexes off
8985 Stop printing element indexes when displaying arrays.
8987 @item show print array-indexes
8988 Show whether the index of each element is printed when displaying
8991 @item set print elements @var{number-of-elements}
8992 @itemx set print elements unlimited
8993 @cindex number of array elements to print
8994 @cindex limit on number of printed array elements
8995 Set a limit on how many elements of an array @value{GDBN} will print.
8996 If @value{GDBN} is printing a large array, it stops printing after it has
8997 printed the number of elements set by the @code{set print elements} command.
8998 This limit also applies to the display of strings.
8999 When @value{GDBN} starts, this limit is set to 200.
9000 Setting @var{number-of-elements} to @code{unlimited} or zero means
9001 that the number of elements to print is unlimited.
9003 @item show print elements
9004 Display the number of elements of a large array that @value{GDBN} will print.
9005 If the number is 0, then the printing is unlimited.
9007 @item set print frame-arguments @var{value}
9008 @kindex set print frame-arguments
9009 @cindex printing frame argument values
9010 @cindex print all frame argument values
9011 @cindex print frame argument values for scalars only
9012 @cindex do not print frame argument values
9013 This command allows to control how the values of arguments are printed
9014 when the debugger prints a frame (@pxref{Frames}). The possible
9019 The values of all arguments are printed.
9022 Print the value of an argument only if it is a scalar. The value of more
9023 complex arguments such as arrays, structures, unions, etc, is replaced
9024 by @code{@dots{}}. This is the default. Here is an example where
9025 only scalar arguments are shown:
9028 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9033 None of the argument values are printed. Instead, the value of each argument
9034 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9037 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9042 By default, only scalar arguments are printed. This command can be used
9043 to configure the debugger to print the value of all arguments, regardless
9044 of their type. However, it is often advantageous to not print the value
9045 of more complex parameters. For instance, it reduces the amount of
9046 information printed in each frame, making the backtrace more readable.
9047 Also, it improves performance when displaying Ada frames, because
9048 the computation of large arguments can sometimes be CPU-intensive,
9049 especially in large applications. Setting @code{print frame-arguments}
9050 to @code{scalars} (the default) or @code{none} avoids this computation,
9051 thus speeding up the display of each Ada frame.
9053 @item show print frame-arguments
9054 Show how the value of arguments should be displayed when printing a frame.
9056 @item set print raw frame-arguments on
9057 Print frame arguments in raw, non pretty-printed, form.
9059 @item set print raw frame-arguments off
9060 Print frame arguments in pretty-printed form, if there is a pretty-printer
9061 for the value (@pxref{Pretty Printing}),
9062 otherwise print the value in raw form.
9063 This is the default.
9065 @item show print raw frame-arguments
9066 Show whether to print frame arguments in raw form.
9068 @anchor{set print entry-values}
9069 @item set print entry-values @var{value}
9070 @kindex set print entry-values
9071 Set printing of frame argument values at function entry. In some cases
9072 @value{GDBN} can determine the value of function argument which was passed by
9073 the function caller, even if the value was modified inside the called function
9074 and therefore is different. With optimized code, the current value could be
9075 unavailable, but the entry value may still be known.
9077 The default value is @code{default} (see below for its description). Older
9078 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9079 this feature will behave in the @code{default} setting the same way as with the
9082 This functionality is currently supported only by DWARF 2 debugging format and
9083 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9084 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9087 The @var{value} parameter can be one of the following:
9091 Print only actual parameter values, never print values from function entry
9095 #0 different (val=6)
9096 #0 lost (val=<optimized out>)
9098 #0 invalid (val=<optimized out>)
9102 Print only parameter values from function entry point. The actual parameter
9103 values are never printed.
9105 #0 equal (val@@entry=5)
9106 #0 different (val@@entry=5)
9107 #0 lost (val@@entry=5)
9108 #0 born (val@@entry=<optimized out>)
9109 #0 invalid (val@@entry=<optimized out>)
9113 Print only parameter values from function entry point. If value from function
9114 entry point is not known while the actual value is known, print the actual
9115 value for such parameter.
9117 #0 equal (val@@entry=5)
9118 #0 different (val@@entry=5)
9119 #0 lost (val@@entry=5)
9121 #0 invalid (val@@entry=<optimized out>)
9125 Print actual parameter values. If actual parameter value is not known while
9126 value from function entry point is known, print the entry point value for such
9130 #0 different (val=6)
9131 #0 lost (val@@entry=5)
9133 #0 invalid (val=<optimized out>)
9137 Always print both the actual parameter value and its value from function entry
9138 point, even if values of one or both are not available due to compiler
9141 #0 equal (val=5, val@@entry=5)
9142 #0 different (val=6, val@@entry=5)
9143 #0 lost (val=<optimized out>, val@@entry=5)
9144 #0 born (val=10, val@@entry=<optimized out>)
9145 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9149 Print the actual parameter value if it is known and also its value from
9150 function entry point if it is known. If neither is known, print for the actual
9151 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9152 values are known and identical, print the shortened
9153 @code{param=param@@entry=VALUE} notation.
9155 #0 equal (val=val@@entry=5)
9156 #0 different (val=6, val@@entry=5)
9157 #0 lost (val@@entry=5)
9159 #0 invalid (val=<optimized out>)
9163 Always print the actual parameter value. Print also its value from function
9164 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9165 if both values are known and identical, print the shortened
9166 @code{param=param@@entry=VALUE} notation.
9168 #0 equal (val=val@@entry=5)
9169 #0 different (val=6, val@@entry=5)
9170 #0 lost (val=<optimized out>, val@@entry=5)
9172 #0 invalid (val=<optimized out>)
9176 For analysis messages on possible failures of frame argument values at function
9177 entry resolution see @ref{set debug entry-values}.
9179 @item show print entry-values
9180 Show the method being used for printing of frame argument values at function
9183 @item set print repeats @var{number-of-repeats}
9184 @itemx set print repeats unlimited
9185 @cindex repeated array elements
9186 Set the threshold for suppressing display of repeated array
9187 elements. When the number of consecutive identical elements of an
9188 array exceeds the threshold, @value{GDBN} prints the string
9189 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9190 identical repetitions, instead of displaying the identical elements
9191 themselves. Setting the threshold to @code{unlimited} or zero will
9192 cause all elements to be individually printed. The default threshold
9195 @item show print repeats
9196 Display the current threshold for printing repeated identical
9199 @item set print null-stop
9200 @cindex @sc{null} elements in arrays
9201 Cause @value{GDBN} to stop printing the characters of an array when the first
9202 @sc{null} is encountered. This is useful when large arrays actually
9203 contain only short strings.
9206 @item show print null-stop
9207 Show whether @value{GDBN} stops printing an array on the first
9208 @sc{null} character.
9210 @item set print pretty on
9211 @cindex print structures in indented form
9212 @cindex indentation in structure display
9213 Cause @value{GDBN} to print structures in an indented format with one member
9214 per line, like this:
9229 @item set print pretty off
9230 Cause @value{GDBN} to print structures in a compact format, like this:
9234 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
9235 meat = 0x54 "Pork"@}
9240 This is the default format.
9242 @item show print pretty
9243 Show which format @value{GDBN} is using to print structures.
9245 @item set print sevenbit-strings on
9246 @cindex eight-bit characters in strings
9247 @cindex octal escapes in strings
9248 Print using only seven-bit characters; if this option is set,
9249 @value{GDBN} displays any eight-bit characters (in strings or
9250 character values) using the notation @code{\}@var{nnn}. This setting is
9251 best if you are working in English (@sc{ascii}) and you use the
9252 high-order bit of characters as a marker or ``meta'' bit.
9254 @item set print sevenbit-strings off
9255 Print full eight-bit characters. This allows the use of more
9256 international character sets, and is the default.
9258 @item show print sevenbit-strings
9259 Show whether or not @value{GDBN} is printing only seven-bit characters.
9261 @item set print union on
9262 @cindex unions in structures, printing
9263 Tell @value{GDBN} to print unions which are contained in structures
9264 and other unions. This is the default setting.
9266 @item set print union off
9267 Tell @value{GDBN} not to print unions which are contained in
9268 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9271 @item show print union
9272 Ask @value{GDBN} whether or not it will print unions which are contained in
9273 structures and other unions.
9275 For example, given the declarations
9278 typedef enum @{Tree, Bug@} Species;
9279 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9280 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9291 struct thing foo = @{Tree, @{Acorn@}@};
9295 with @code{set print union on} in effect @samp{p foo} would print
9298 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9302 and with @code{set print union off} in effect it would print
9305 $1 = @{it = Tree, form = @{...@}@}
9309 @code{set print union} affects programs written in C-like languages
9315 These settings are of interest when debugging C@t{++} programs:
9318 @cindex demangling C@t{++} names
9319 @item set print demangle
9320 @itemx set print demangle on
9321 Print C@t{++} names in their source form rather than in the encoded
9322 (``mangled'') form passed to the assembler and linker for type-safe
9323 linkage. The default is on.
9325 @item show print demangle
9326 Show whether C@t{++} names are printed in mangled or demangled form.
9328 @item set print asm-demangle
9329 @itemx set print asm-demangle on
9330 Print C@t{++} names in their source form rather than their mangled form, even
9331 in assembler code printouts such as instruction disassemblies.
9334 @item show print asm-demangle
9335 Show whether C@t{++} names in assembly listings are printed in mangled
9338 @cindex C@t{++} symbol decoding style
9339 @cindex symbol decoding style, C@t{++}
9340 @kindex set demangle-style
9341 @item set demangle-style @var{style}
9342 Choose among several encoding schemes used by different compilers to
9343 represent C@t{++} names. The choices for @var{style} are currently:
9347 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9348 This is the default.
9351 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9354 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9357 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9360 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9361 @strong{Warning:} this setting alone is not sufficient to allow
9362 debugging @code{cfront}-generated executables. @value{GDBN} would
9363 require further enhancement to permit that.
9366 If you omit @var{style}, you will see a list of possible formats.
9368 @item show demangle-style
9369 Display the encoding style currently in use for decoding C@t{++} symbols.
9371 @item set print object
9372 @itemx set print object on
9373 @cindex derived type of an object, printing
9374 @cindex display derived types
9375 When displaying a pointer to an object, identify the @emph{actual}
9376 (derived) type of the object rather than the @emph{declared} type, using
9377 the virtual function table. Note that the virtual function table is
9378 required---this feature can only work for objects that have run-time
9379 type identification; a single virtual method in the object's declared
9380 type is sufficient. Note that this setting is also taken into account when
9381 working with variable objects via MI (@pxref{GDB/MI}).
9383 @item set print object off
9384 Display only the declared type of objects, without reference to the
9385 virtual function table. This is the default setting.
9387 @item show print object
9388 Show whether actual, or declared, object types are displayed.
9390 @item set print static-members
9391 @itemx set print static-members on
9392 @cindex static members of C@t{++} objects
9393 Print static members when displaying a C@t{++} object. The default is on.
9395 @item set print static-members off
9396 Do not print static members when displaying a C@t{++} object.
9398 @item show print static-members
9399 Show whether C@t{++} static members are printed or not.
9401 @item set print pascal_static-members
9402 @itemx set print pascal_static-members on
9403 @cindex static members of Pascal objects
9404 @cindex Pascal objects, static members display
9405 Print static members when displaying a Pascal object. The default is on.
9407 @item set print pascal_static-members off
9408 Do not print static members when displaying a Pascal object.
9410 @item show print pascal_static-members
9411 Show whether Pascal static members are printed or not.
9413 @c These don't work with HP ANSI C++ yet.
9414 @item set print vtbl
9415 @itemx set print vtbl on
9416 @cindex pretty print C@t{++} virtual function tables
9417 @cindex virtual functions (C@t{++}) display
9418 @cindex VTBL display
9419 Pretty print C@t{++} virtual function tables. The default is off.
9420 (The @code{vtbl} commands do not work on programs compiled with the HP
9421 ANSI C@t{++} compiler (@code{aCC}).)
9423 @item set print vtbl off
9424 Do not pretty print C@t{++} virtual function tables.
9426 @item show print vtbl
9427 Show whether C@t{++} virtual function tables are pretty printed, or not.
9430 @node Pretty Printing
9431 @section Pretty Printing
9433 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9434 Python code. It greatly simplifies the display of complex objects. This
9435 mechanism works for both MI and the CLI.
9438 * Pretty-Printer Introduction:: Introduction to pretty-printers
9439 * Pretty-Printer Example:: An example pretty-printer
9440 * Pretty-Printer Commands:: Pretty-printer commands
9443 @node Pretty-Printer Introduction
9444 @subsection Pretty-Printer Introduction
9446 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9447 registered for the value. If there is then @value{GDBN} invokes the
9448 pretty-printer to print the value. Otherwise the value is printed normally.
9450 Pretty-printers are normally named. This makes them easy to manage.
9451 The @samp{info pretty-printer} command will list all the installed
9452 pretty-printers with their names.
9453 If a pretty-printer can handle multiple data types, then its
9454 @dfn{subprinters} are the printers for the individual data types.
9455 Each such subprinter has its own name.
9456 The format of the name is @var{printer-name};@var{subprinter-name}.
9458 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9459 Typically they are automatically loaded and registered when the corresponding
9460 debug information is loaded, thus making them available without having to
9461 do anything special.
9463 There are three places where a pretty-printer can be registered.
9467 Pretty-printers registered globally are available when debugging
9471 Pretty-printers registered with a program space are available only
9472 when debugging that program.
9473 @xref{Progspaces In Python}, for more details on program spaces in Python.
9476 Pretty-printers registered with an objfile are loaded and unloaded
9477 with the corresponding objfile (e.g., shared library).
9478 @xref{Objfiles In Python}, for more details on objfiles in Python.
9481 @xref{Selecting Pretty-Printers}, for further information on how
9482 pretty-printers are selected,
9484 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9487 @node Pretty-Printer Example
9488 @subsection Pretty-Printer Example
9490 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9493 (@value{GDBP}) print s
9495 static npos = 4294967295,
9497 <std::allocator<char>> = @{
9498 <__gnu_cxx::new_allocator<char>> = @{
9499 <No data fields>@}, <No data fields>
9501 members of std::basic_string<char, std::char_traits<char>,
9502 std::allocator<char> >::_Alloc_hider:
9503 _M_p = 0x804a014 "abcd"
9508 With a pretty-printer for @code{std::string} only the contents are printed:
9511 (@value{GDBP}) print s
9515 @node Pretty-Printer Commands
9516 @subsection Pretty-Printer Commands
9517 @cindex pretty-printer commands
9520 @kindex info pretty-printer
9521 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9522 Print the list of installed pretty-printers.
9523 This includes disabled pretty-printers, which are marked as such.
9525 @var{object-regexp} is a regular expression matching the objects
9526 whose pretty-printers to list.
9527 Objects can be @code{global}, the program space's file
9528 (@pxref{Progspaces In Python}),
9529 and the object files within that program space (@pxref{Objfiles In Python}).
9530 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9531 looks up a printer from these three objects.
9533 @var{name-regexp} is a regular expression matching the name of the printers
9536 @kindex disable pretty-printer
9537 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9538 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9539 A disabled pretty-printer is not forgotten, it may be enabled again later.
9541 @kindex enable pretty-printer
9542 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9543 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9548 Suppose we have three pretty-printers installed: one from library1.so
9549 named @code{foo} that prints objects of type @code{foo}, and
9550 another from library2.so named @code{bar} that prints two types of objects,
9551 @code{bar1} and @code{bar2}.
9554 (gdb) info pretty-printer
9561 (gdb) info pretty-printer library2
9566 (gdb) disable pretty-printer library1
9568 2 of 3 printers enabled
9569 (gdb) info pretty-printer
9576 (gdb) disable pretty-printer library2 bar:bar1
9578 1 of 3 printers enabled
9579 (gdb) info pretty-printer library2
9586 (gdb) disable pretty-printer library2 bar
9588 0 of 3 printers enabled
9589 (gdb) info pretty-printer library2
9598 Note that for @code{bar} the entire printer can be disabled,
9599 as can each individual subprinter.
9602 @section Value History
9604 @cindex value history
9605 @cindex history of values printed by @value{GDBN}
9606 Values printed by the @code{print} command are saved in the @value{GDBN}
9607 @dfn{value history}. This allows you to refer to them in other expressions.
9608 Values are kept until the symbol table is re-read or discarded
9609 (for example with the @code{file} or @code{symbol-file} commands).
9610 When the symbol table changes, the value history is discarded,
9611 since the values may contain pointers back to the types defined in the
9616 @cindex history number
9617 The values printed are given @dfn{history numbers} by which you can
9618 refer to them. These are successive integers starting with one.
9619 @code{print} shows you the history number assigned to a value by
9620 printing @samp{$@var{num} = } before the value; here @var{num} is the
9623 To refer to any previous value, use @samp{$} followed by the value's
9624 history number. The way @code{print} labels its output is designed to
9625 remind you of this. Just @code{$} refers to the most recent value in
9626 the history, and @code{$$} refers to the value before that.
9627 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9628 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9629 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9631 For example, suppose you have just printed a pointer to a structure and
9632 want to see the contents of the structure. It suffices to type
9638 If you have a chain of structures where the component @code{next} points
9639 to the next one, you can print the contents of the next one with this:
9646 You can print successive links in the chain by repeating this
9647 command---which you can do by just typing @key{RET}.
9649 Note that the history records values, not expressions. If the value of
9650 @code{x} is 4 and you type these commands:
9658 then the value recorded in the value history by the @code{print} command
9659 remains 4 even though the value of @code{x} has changed.
9664 Print the last ten values in the value history, with their item numbers.
9665 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9666 values} does not change the history.
9668 @item show values @var{n}
9669 Print ten history values centered on history item number @var{n}.
9672 Print ten history values just after the values last printed. If no more
9673 values are available, @code{show values +} produces no display.
9676 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
9677 same effect as @samp{show values +}.
9679 @node Convenience Vars
9680 @section Convenience Variables
9682 @cindex convenience variables
9683 @cindex user-defined variables
9684 @value{GDBN} provides @dfn{convenience variables} that you can use within
9685 @value{GDBN} to hold on to a value and refer to it later. These variables
9686 exist entirely within @value{GDBN}; they are not part of your program, and
9687 setting a convenience variable has no direct effect on further execution
9688 of your program. That is why you can use them freely.
9690 Convenience variables are prefixed with @samp{$}. Any name preceded by
9691 @samp{$} can be used for a convenience variable, unless it is one of
9692 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
9693 (Value history references, in contrast, are @emph{numbers} preceded
9694 by @samp{$}. @xref{Value History, ,Value History}.)
9696 You can save a value in a convenience variable with an assignment
9697 expression, just as you would set a variable in your program.
9701 set $foo = *object_ptr
9705 would save in @code{$foo} the value contained in the object pointed to by
9708 Using a convenience variable for the first time creates it, but its
9709 value is @code{void} until you assign a new value. You can alter the
9710 value with another assignment at any time.
9712 Convenience variables have no fixed types. You can assign a convenience
9713 variable any type of value, including structures and arrays, even if
9714 that variable already has a value of a different type. The convenience
9715 variable, when used as an expression, has the type of its current value.
9718 @kindex show convenience
9719 @cindex show all user variables and functions
9720 @item show convenience
9721 Print a list of convenience variables used so far, and their values,
9722 as well as a list of the convenience functions.
9723 Abbreviated @code{show conv}.
9725 @kindex init-if-undefined
9726 @cindex convenience variables, initializing
9727 @item init-if-undefined $@var{variable} = @var{expression}
9728 Set a convenience variable if it has not already been set. This is useful
9729 for user-defined commands that keep some state. It is similar, in concept,
9730 to using local static variables with initializers in C (except that
9731 convenience variables are global). It can also be used to allow users to
9732 override default values used in a command script.
9734 If the variable is already defined then the expression is not evaluated so
9735 any side-effects do not occur.
9738 One of the ways to use a convenience variable is as a counter to be
9739 incremented or a pointer to be advanced. For example, to print
9740 a field from successive elements of an array of structures:
9744 print bar[$i++]->contents
9748 Repeat that command by typing @key{RET}.
9750 Some convenience variables are created automatically by @value{GDBN} and given
9751 values likely to be useful.
9754 @vindex $_@r{, convenience variable}
9756 The variable @code{$_} is automatically set by the @code{x} command to
9757 the last address examined (@pxref{Memory, ,Examining Memory}). Other
9758 commands which provide a default address for @code{x} to examine also
9759 set @code{$_} to that address; these commands include @code{info line}
9760 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
9761 except when set by the @code{x} command, in which case it is a pointer
9762 to the type of @code{$__}.
9764 @vindex $__@r{, convenience variable}
9766 The variable @code{$__} is automatically set by the @code{x} command
9767 to the value found in the last address examined. Its type is chosen
9768 to match the format in which the data was printed.
9771 @vindex $_exitcode@r{, convenience variable}
9772 When the program being debugged terminates normally, @value{GDBN}
9773 automatically sets this variable to the exit code of the program, and
9774 resets @code{$_exitsignal} to @code{void}.
9777 @vindex $_exitsignal@r{, convenience variable}
9778 When the program being debugged dies due to an uncaught signal,
9779 @value{GDBN} automatically sets this variable to that signal's number,
9780 and resets @code{$_exitcode} to @code{void}.
9782 To distinguish between whether the program being debugged has exited
9783 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
9784 @code{$_exitsignal} is not @code{void}), the convenience function
9785 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
9786 Functions}). For example, considering the following source code:
9792 main (int argc, char *argv[])
9799 A valid way of telling whether the program being debugged has exited
9800 or signalled would be:
9803 (@value{GDBP}) define has_exited_or_signalled
9804 Type commands for definition of ``has_exited_or_signalled''.
9805 End with a line saying just ``end''.
9806 >if $_isvoid ($_exitsignal)
9807 >echo The program has exited\n
9809 >echo The program has signalled\n
9815 Program terminated with signal SIGALRM, Alarm clock.
9816 The program no longer exists.
9817 (@value{GDBP}) has_exited_or_signalled
9818 The program has signalled
9821 As can be seen, @value{GDBN} correctly informs that the program being
9822 debugged has signalled, since it calls @code{raise} and raises a
9823 @code{SIGALRM} signal. If the program being debugged had not called
9824 @code{raise}, then @value{GDBN} would report a normal exit:
9827 (@value{GDBP}) has_exited_or_signalled
9828 The program has exited
9832 The variable @code{$_exception} is set to the exception object being
9833 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
9836 @itemx $_probe_arg0@dots{}$_probe_arg11
9837 Arguments to a static probe. @xref{Static Probe Points}.
9840 @vindex $_sdata@r{, inspect, convenience variable}
9841 The variable @code{$_sdata} contains extra collected static tracepoint
9842 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
9843 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
9844 if extra static tracepoint data has not been collected.
9847 @vindex $_siginfo@r{, convenience variable}
9848 The variable @code{$_siginfo} contains extra signal information
9849 (@pxref{extra signal information}). Note that @code{$_siginfo}
9850 could be empty, if the application has not yet received any signals.
9851 For example, it will be empty before you execute the @code{run} command.
9854 @vindex $_tlb@r{, convenience variable}
9855 The variable @code{$_tlb} is automatically set when debugging
9856 applications running on MS-Windows in native mode or connected to
9857 gdbserver that supports the @code{qGetTIBAddr} request.
9858 @xref{General Query Packets}.
9859 This variable contains the address of the thread information block.
9863 On HP-UX systems, if you refer to a function or variable name that
9864 begins with a dollar sign, @value{GDBN} searches for a user or system
9865 name first, before it searches for a convenience variable.
9867 @node Convenience Funs
9868 @section Convenience Functions
9870 @cindex convenience functions
9871 @value{GDBN} also supplies some @dfn{convenience functions}. These
9872 have a syntax similar to convenience variables. A convenience
9873 function can be used in an expression just like an ordinary function;
9874 however, a convenience function is implemented internally to
9877 These functions do not require @value{GDBN} to be configured with
9878 @code{Python} support, which means that they are always available.
9882 @item $_isvoid (@var{expr})
9883 @findex $_isvoid@r{, convenience function}
9884 Return one if the expression @var{expr} is @code{void}. Otherwise it
9887 A @code{void} expression is an expression where the type of the result
9888 is @code{void}. For example, you can examine a convenience variable
9889 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
9893 (@value{GDBP}) print $_exitcode
9895 (@value{GDBP}) print $_isvoid ($_exitcode)
9898 Starting program: ./a.out
9899 [Inferior 1 (process 29572) exited normally]
9900 (@value{GDBP}) print $_exitcode
9902 (@value{GDBP}) print $_isvoid ($_exitcode)
9906 In the example above, we used @code{$_isvoid} to check whether
9907 @code{$_exitcode} is @code{void} before and after the execution of the
9908 program being debugged. Before the execution there is no exit code to
9909 be examined, therefore @code{$_exitcode} is @code{void}. After the
9910 execution the program being debugged returned zero, therefore
9911 @code{$_exitcode} is zero, which means that it is not @code{void}
9914 The @code{void} expression can also be a call of a function from the
9915 program being debugged. For example, given the following function:
9924 The result of calling it inside @value{GDBN} is @code{void}:
9927 (@value{GDBP}) print foo ()
9929 (@value{GDBP}) print $_isvoid (foo ())
9931 (@value{GDBP}) set $v = foo ()
9932 (@value{GDBP}) print $v
9934 (@value{GDBP}) print $_isvoid ($v)
9940 These functions require @value{GDBN} to be configured with
9941 @code{Python} support.
9945 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
9946 @findex $_memeq@r{, convenience function}
9947 Returns one if the @var{length} bytes at the addresses given by
9948 @var{buf1} and @var{buf2} are equal.
9949 Otherwise it returns zero.
9951 @item $_regex(@var{str}, @var{regex})
9952 @findex $_regex@r{, convenience function}
9953 Returns one if the string @var{str} matches the regular expression
9954 @var{regex}. Otherwise it returns zero.
9955 The syntax of the regular expression is that specified by @code{Python}'s
9956 regular expression support.
9958 @item $_streq(@var{str1}, @var{str2})
9959 @findex $_streq@r{, convenience function}
9960 Returns one if the strings @var{str1} and @var{str2} are equal.
9961 Otherwise it returns zero.
9963 @item $_strlen(@var{str})
9964 @findex $_strlen@r{, convenience function}
9965 Returns the length of string @var{str}.
9969 @value{GDBN} provides the ability to list and get help on
9970 convenience functions.
9974 @kindex help function
9975 @cindex show all convenience functions
9976 Print a list of all convenience functions.
9983 You can refer to machine register contents, in expressions, as variables
9984 with names starting with @samp{$}. The names of registers are different
9985 for each machine; use @code{info registers} to see the names used on
9989 @kindex info registers
9990 @item info registers
9991 Print the names and values of all registers except floating-point
9992 and vector registers (in the selected stack frame).
9994 @kindex info all-registers
9995 @cindex floating point registers
9996 @item info all-registers
9997 Print the names and values of all registers, including floating-point
9998 and vector registers (in the selected stack frame).
10000 @item info registers @var{regname} @dots{}
10001 Print the @dfn{relativized} value of each specified register @var{regname}.
10002 As discussed in detail below, register values are normally relative to
10003 the selected stack frame. @var{regname} may be any register name valid on
10004 the machine you are using, with or without the initial @samp{$}.
10007 @cindex stack pointer register
10008 @cindex program counter register
10009 @cindex process status register
10010 @cindex frame pointer register
10011 @cindex standard registers
10012 @value{GDBN} has four ``standard'' register names that are available (in
10013 expressions) on most machines---whenever they do not conflict with an
10014 architecture's canonical mnemonics for registers. The register names
10015 @code{$pc} and @code{$sp} are used for the program counter register and
10016 the stack pointer. @code{$fp} is used for a register that contains a
10017 pointer to the current stack frame, and @code{$ps} is used for a
10018 register that contains the processor status. For example,
10019 you could print the program counter in hex with
10026 or print the instruction to be executed next with
10033 or add four to the stack pointer@footnote{This is a way of removing
10034 one word from the stack, on machines where stacks grow downward in
10035 memory (most machines, nowadays). This assumes that the innermost
10036 stack frame is selected; setting @code{$sp} is not allowed when other
10037 stack frames are selected. To pop entire frames off the stack,
10038 regardless of machine architecture, use @code{return};
10039 see @ref{Returning, ,Returning from a Function}.} with
10045 Whenever possible, these four standard register names are available on
10046 your machine even though the machine has different canonical mnemonics,
10047 so long as there is no conflict. The @code{info registers} command
10048 shows the canonical names. For example, on the SPARC, @code{info
10049 registers} displays the processor status register as @code{$psr} but you
10050 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10051 is an alias for the @sc{eflags} register.
10053 @value{GDBN} always considers the contents of an ordinary register as an
10054 integer when the register is examined in this way. Some machines have
10055 special registers which can hold nothing but floating point; these
10056 registers are considered to have floating point values. There is no way
10057 to refer to the contents of an ordinary register as floating point value
10058 (although you can @emph{print} it as a floating point value with
10059 @samp{print/f $@var{regname}}).
10061 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10062 means that the data format in which the register contents are saved by
10063 the operating system is not the same one that your program normally
10064 sees. For example, the registers of the 68881 floating point
10065 coprocessor are always saved in ``extended'' (raw) format, but all C
10066 programs expect to work with ``double'' (virtual) format. In such
10067 cases, @value{GDBN} normally works with the virtual format only (the format
10068 that makes sense for your program), but the @code{info registers} command
10069 prints the data in both formats.
10071 @cindex SSE registers (x86)
10072 @cindex MMX registers (x86)
10073 Some machines have special registers whose contents can be interpreted
10074 in several different ways. For example, modern x86-based machines
10075 have SSE and MMX registers that can hold several values packed
10076 together in several different formats. @value{GDBN} refers to such
10077 registers in @code{struct} notation:
10080 (@value{GDBP}) print $xmm1
10082 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10083 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10084 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10085 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10086 v4_int32 = @{0, 20657912, 11, 13@},
10087 v2_int64 = @{88725056443645952, 55834574859@},
10088 uint128 = 0x0000000d0000000b013b36f800000000
10093 To set values of such registers, you need to tell @value{GDBN} which
10094 view of the register you wish to change, as if you were assigning
10095 value to a @code{struct} member:
10098 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10101 Normally, register values are relative to the selected stack frame
10102 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10103 value that the register would contain if all stack frames farther in
10104 were exited and their saved registers restored. In order to see the
10105 true contents of hardware registers, you must select the innermost
10106 frame (with @samp{frame 0}).
10108 @cindex caller-saved registers
10109 @cindex call-clobbered registers
10110 @cindex volatile registers
10111 @cindex <not saved> values
10112 Usually ABIs reserve some registers as not needed to be saved by the
10113 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10114 registers). It may therefore not be possible for @value{GDBN} to know
10115 the value a register had before the call (in other words, in the outer
10116 frame), if the register value has since been changed by the callee.
10117 @value{GDBN} tries to deduce where the inner frame saved
10118 (``callee-saved'') registers, from the debug info, unwind info, or the
10119 machine code generated by your compiler. If some register is not
10120 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
10121 its own knowledge of the ABI, or because the debug/unwind info
10122 explicitly says the register's value is undefined), @value{GDBN}
10123 displays @w{@samp{<not saved>}} as the register's value. With targets
10124 that @value{GDBN} has no knowledge of the register saving convention,
10125 if a register was not saved by the callee, then its value and location
10126 in the outer frame are assumed to be the same of the inner frame.
10127 This is usually harmless, because if the register is call-clobbered,
10128 the caller either does not care what is in the register after the
10129 call, or has code to restore the value that it does care about. Note,
10130 however, that if you change such a register in the outer frame, you
10131 may also be affecting the inner frame. Also, the more ``outer'' the
10132 frame is you're looking at, the more likely a call-clobbered
10133 register's value is to be wrong, in the sense that it doesn't actually
10134 represent the value the register had just before the call.
10136 @node Floating Point Hardware
10137 @section Floating Point Hardware
10138 @cindex floating point
10140 Depending on the configuration, @value{GDBN} may be able to give
10141 you more information about the status of the floating point hardware.
10146 Display hardware-dependent information about the floating
10147 point unit. The exact contents and layout vary depending on the
10148 floating point chip. Currently, @samp{info float} is supported on
10149 the ARM and x86 machines.
10153 @section Vector Unit
10154 @cindex vector unit
10156 Depending on the configuration, @value{GDBN} may be able to give you
10157 more information about the status of the vector unit.
10160 @kindex info vector
10162 Display information about the vector unit. The exact contents and
10163 layout vary depending on the hardware.
10166 @node OS Information
10167 @section Operating System Auxiliary Information
10168 @cindex OS information
10170 @value{GDBN} provides interfaces to useful OS facilities that can help
10171 you debug your program.
10173 @cindex auxiliary vector
10174 @cindex vector, auxiliary
10175 Some operating systems supply an @dfn{auxiliary vector} to programs at
10176 startup. This is akin to the arguments and environment that you
10177 specify for a program, but contains a system-dependent variety of
10178 binary values that tell system libraries important details about the
10179 hardware, operating system, and process. Each value's purpose is
10180 identified by an integer tag; the meanings are well-known but system-specific.
10181 Depending on the configuration and operating system facilities,
10182 @value{GDBN} may be able to show you this information. For remote
10183 targets, this functionality may further depend on the remote stub's
10184 support of the @samp{qXfer:auxv:read} packet, see
10185 @ref{qXfer auxiliary vector read}.
10190 Display the auxiliary vector of the inferior, which can be either a
10191 live process or a core dump file. @value{GDBN} prints each tag value
10192 numerically, and also shows names and text descriptions for recognized
10193 tags. Some values in the vector are numbers, some bit masks, and some
10194 pointers to strings or other data. @value{GDBN} displays each value in the
10195 most appropriate form for a recognized tag, and in hexadecimal for
10196 an unrecognized tag.
10199 On some targets, @value{GDBN} can access operating system-specific
10200 information and show it to you. The types of information available
10201 will differ depending on the type of operating system running on the
10202 target. The mechanism used to fetch the data is described in
10203 @ref{Operating System Information}. For remote targets, this
10204 functionality depends on the remote stub's support of the
10205 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
10209 @item info os @var{infotype}
10211 Display OS information of the requested type.
10213 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
10215 @anchor{linux info os infotypes}
10217 @kindex info os processes
10219 Display the list of processes on the target. For each process,
10220 @value{GDBN} prints the process identifier, the name of the user, the
10221 command corresponding to the process, and the list of processor cores
10222 that the process is currently running on. (To understand what these
10223 properties mean, for this and the following info types, please consult
10224 the general @sc{gnu}/Linux documentation.)
10226 @kindex info os procgroups
10228 Display the list of process groups on the target. For each process,
10229 @value{GDBN} prints the identifier of the process group that it belongs
10230 to, the command corresponding to the process group leader, the process
10231 identifier, and the command line of the process. The list is sorted
10232 first by the process group identifier, then by the process identifier,
10233 so that processes belonging to the same process group are grouped together
10234 and the process group leader is listed first.
10236 @kindex info os threads
10238 Display the list of threads running on the target. For each thread,
10239 @value{GDBN} prints the identifier of the process that the thread
10240 belongs to, the command of the process, the thread identifier, and the
10241 processor core that it is currently running on. The main thread of a
10242 process is not listed.
10244 @kindex info os files
10246 Display the list of open file descriptors on the target. For each
10247 file descriptor, @value{GDBN} prints the identifier of the process
10248 owning the descriptor, the command of the owning process, the value
10249 of the descriptor, and the target of the descriptor.
10251 @kindex info os sockets
10253 Display the list of Internet-domain sockets on the target. For each
10254 socket, @value{GDBN} prints the address and port of the local and
10255 remote endpoints, the current state of the connection, the creator of
10256 the socket, the IP address family of the socket, and the type of the
10259 @kindex info os shm
10261 Display the list of all System V shared-memory regions on the target.
10262 For each shared-memory region, @value{GDBN} prints the region key,
10263 the shared-memory identifier, the access permissions, the size of the
10264 region, the process that created the region, the process that last
10265 attached to or detached from the region, the current number of live
10266 attaches to the region, and the times at which the region was last
10267 attached to, detach from, and changed.
10269 @kindex info os semaphores
10271 Display the list of all System V semaphore sets on the target. For each
10272 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
10273 set identifier, the access permissions, the number of semaphores in the
10274 set, the user and group of the owner and creator of the semaphore set,
10275 and the times at which the semaphore set was operated upon and changed.
10277 @kindex info os msg
10279 Display the list of all System V message queues on the target. For each
10280 message queue, @value{GDBN} prints the message queue key, the message
10281 queue identifier, the access permissions, the current number of bytes
10282 on the queue, the current number of messages on the queue, the processes
10283 that last sent and received a message on the queue, the user and group
10284 of the owner and creator of the message queue, the times at which a
10285 message was last sent and received on the queue, and the time at which
10286 the message queue was last changed.
10288 @kindex info os modules
10290 Display the list of all loaded kernel modules on the target. For each
10291 module, @value{GDBN} prints the module name, the size of the module in
10292 bytes, the number of times the module is used, the dependencies of the
10293 module, the status of the module, and the address of the loaded module
10298 If @var{infotype} is omitted, then list the possible values for
10299 @var{infotype} and the kind of OS information available for each
10300 @var{infotype}. If the target does not return a list of possible
10301 types, this command will report an error.
10304 @node Memory Region Attributes
10305 @section Memory Region Attributes
10306 @cindex memory region attributes
10308 @dfn{Memory region attributes} allow you to describe special handling
10309 required by regions of your target's memory. @value{GDBN} uses
10310 attributes to determine whether to allow certain types of memory
10311 accesses; whether to use specific width accesses; and whether to cache
10312 target memory. By default the description of memory regions is
10313 fetched from the target (if the current target supports this), but the
10314 user can override the fetched regions.
10316 Defined memory regions can be individually enabled and disabled. When a
10317 memory region is disabled, @value{GDBN} uses the default attributes when
10318 accessing memory in that region. Similarly, if no memory regions have
10319 been defined, @value{GDBN} uses the default attributes when accessing
10322 When a memory region is defined, it is given a number to identify it;
10323 to enable, disable, or remove a memory region, you specify that number.
10327 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
10328 Define a memory region bounded by @var{lower} and @var{upper} with
10329 attributes @var{attributes}@dots{}, and add it to the list of regions
10330 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
10331 case: it is treated as the target's maximum memory address.
10332 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
10335 Discard any user changes to the memory regions and use target-supplied
10336 regions, if available, or no regions if the target does not support.
10339 @item delete mem @var{nums}@dots{}
10340 Remove memory regions @var{nums}@dots{} from the list of regions
10341 monitored by @value{GDBN}.
10343 @kindex disable mem
10344 @item disable mem @var{nums}@dots{}
10345 Disable monitoring of memory regions @var{nums}@dots{}.
10346 A disabled memory region is not forgotten.
10347 It may be enabled again later.
10350 @item enable mem @var{nums}@dots{}
10351 Enable monitoring of memory regions @var{nums}@dots{}.
10355 Print a table of all defined memory regions, with the following columns
10359 @item Memory Region Number
10360 @item Enabled or Disabled.
10361 Enabled memory regions are marked with @samp{y}.
10362 Disabled memory regions are marked with @samp{n}.
10365 The address defining the inclusive lower bound of the memory region.
10368 The address defining the exclusive upper bound of the memory region.
10371 The list of attributes set for this memory region.
10376 @subsection Attributes
10378 @subsubsection Memory Access Mode
10379 The access mode attributes set whether @value{GDBN} may make read or
10380 write accesses to a memory region.
10382 While these attributes prevent @value{GDBN} from performing invalid
10383 memory accesses, they do nothing to prevent the target system, I/O DMA,
10384 etc.@: from accessing memory.
10388 Memory is read only.
10390 Memory is write only.
10392 Memory is read/write. This is the default.
10395 @subsubsection Memory Access Size
10396 The access size attribute tells @value{GDBN} to use specific sized
10397 accesses in the memory region. Often memory mapped device registers
10398 require specific sized accesses. If no access size attribute is
10399 specified, @value{GDBN} may use accesses of any size.
10403 Use 8 bit memory accesses.
10405 Use 16 bit memory accesses.
10407 Use 32 bit memory accesses.
10409 Use 64 bit memory accesses.
10412 @c @subsubsection Hardware/Software Breakpoints
10413 @c The hardware/software breakpoint attributes set whether @value{GDBN}
10414 @c will use hardware or software breakpoints for the internal breakpoints
10415 @c used by the step, next, finish, until, etc. commands.
10419 @c Always use hardware breakpoints
10420 @c @item swbreak (default)
10423 @subsubsection Data Cache
10424 The data cache attributes set whether @value{GDBN} will cache target
10425 memory. While this generally improves performance by reducing debug
10426 protocol overhead, it can lead to incorrect results because @value{GDBN}
10427 does not know about volatile variables or memory mapped device
10432 Enable @value{GDBN} to cache target memory.
10434 Disable @value{GDBN} from caching target memory. This is the default.
10437 @subsection Memory Access Checking
10438 @value{GDBN} can be instructed to refuse accesses to memory that is
10439 not explicitly described. This can be useful if accessing such
10440 regions has undesired effects for a specific target, or to provide
10441 better error checking. The following commands control this behaviour.
10444 @kindex set mem inaccessible-by-default
10445 @item set mem inaccessible-by-default [on|off]
10446 If @code{on} is specified, make @value{GDBN} treat memory not
10447 explicitly described by the memory ranges as non-existent and refuse accesses
10448 to such memory. The checks are only performed if there's at least one
10449 memory range defined. If @code{off} is specified, make @value{GDBN}
10450 treat the memory not explicitly described by the memory ranges as RAM.
10451 The default value is @code{on}.
10452 @kindex show mem inaccessible-by-default
10453 @item show mem inaccessible-by-default
10454 Show the current handling of accesses to unknown memory.
10458 @c @subsubsection Memory Write Verification
10459 @c The memory write verification attributes set whether @value{GDBN}
10460 @c will re-reads data after each write to verify the write was successful.
10464 @c @item noverify (default)
10467 @node Dump/Restore Files
10468 @section Copy Between Memory and a File
10469 @cindex dump/restore files
10470 @cindex append data to a file
10471 @cindex dump data to a file
10472 @cindex restore data from a file
10474 You can use the commands @code{dump}, @code{append}, and
10475 @code{restore} to copy data between target memory and a file. The
10476 @code{dump} and @code{append} commands write data to a file, and the
10477 @code{restore} command reads data from a file back into the inferior's
10478 memory. Files may be in binary, Motorola S-record, Intel hex, or
10479 Tektronix Hex format; however, @value{GDBN} can only append to binary
10485 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10486 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
10487 Dump the contents of memory from @var{start_addr} to @var{end_addr},
10488 or the value of @var{expr}, to @var{filename} in the given format.
10490 The @var{format} parameter may be any one of:
10497 Motorola S-record format.
10499 Tektronix Hex format.
10502 @value{GDBN} uses the same definitions of these formats as the
10503 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
10504 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
10508 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10509 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
10510 Append the contents of memory from @var{start_addr} to @var{end_addr},
10511 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
10512 (@value{GDBN} can only append data to files in raw binary form.)
10515 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
10516 Restore the contents of file @var{filename} into memory. The
10517 @code{restore} command can automatically recognize any known @sc{bfd}
10518 file format, except for raw binary. To restore a raw binary file you
10519 must specify the optional keyword @code{binary} after the filename.
10521 If @var{bias} is non-zero, its value will be added to the addresses
10522 contained in the file. Binary files always start at address zero, so
10523 they will be restored at address @var{bias}. Other bfd files have
10524 a built-in location; they will be restored at offset @var{bias}
10525 from that location.
10527 If @var{start} and/or @var{end} are non-zero, then only data between
10528 file offset @var{start} and file offset @var{end} will be restored.
10529 These offsets are relative to the addresses in the file, before
10530 the @var{bias} argument is applied.
10534 @node Core File Generation
10535 @section How to Produce a Core File from Your Program
10536 @cindex dump core from inferior
10538 A @dfn{core file} or @dfn{core dump} is a file that records the memory
10539 image of a running process and its process status (register values
10540 etc.). Its primary use is post-mortem debugging of a program that
10541 crashed while it ran outside a debugger. A program that crashes
10542 automatically produces a core file, unless this feature is disabled by
10543 the user. @xref{Files}, for information on invoking @value{GDBN} in
10544 the post-mortem debugging mode.
10546 Occasionally, you may wish to produce a core file of the program you
10547 are debugging in order to preserve a snapshot of its state.
10548 @value{GDBN} has a special command for that.
10552 @kindex generate-core-file
10553 @item generate-core-file [@var{file}]
10554 @itemx gcore [@var{file}]
10555 Produce a core dump of the inferior process. The optional argument
10556 @var{file} specifies the file name where to put the core dump. If not
10557 specified, the file name defaults to @file{core.@var{pid}}, where
10558 @var{pid} is the inferior process ID.
10560 Note that this command is implemented only for some systems (as of
10561 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
10564 @node Character Sets
10565 @section Character Sets
10566 @cindex character sets
10568 @cindex translating between character sets
10569 @cindex host character set
10570 @cindex target character set
10572 If the program you are debugging uses a different character set to
10573 represent characters and strings than the one @value{GDBN} uses itself,
10574 @value{GDBN} can automatically translate between the character sets for
10575 you. The character set @value{GDBN} uses we call the @dfn{host
10576 character set}; the one the inferior program uses we call the
10577 @dfn{target character set}.
10579 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
10580 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
10581 remote protocol (@pxref{Remote Debugging}) to debug a program
10582 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
10583 then the host character set is Latin-1, and the target character set is
10584 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
10585 target-charset EBCDIC-US}, then @value{GDBN} translates between
10586 @sc{ebcdic} and Latin 1 as you print character or string values, or use
10587 character and string literals in expressions.
10589 @value{GDBN} has no way to automatically recognize which character set
10590 the inferior program uses; you must tell it, using the @code{set
10591 target-charset} command, described below.
10593 Here are the commands for controlling @value{GDBN}'s character set
10597 @item set target-charset @var{charset}
10598 @kindex set target-charset
10599 Set the current target character set to @var{charset}. To display the
10600 list of supported target character sets, type
10601 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
10603 @item set host-charset @var{charset}
10604 @kindex set host-charset
10605 Set the current host character set to @var{charset}.
10607 By default, @value{GDBN} uses a host character set appropriate to the
10608 system it is running on; you can override that default using the
10609 @code{set host-charset} command. On some systems, @value{GDBN} cannot
10610 automatically determine the appropriate host character set. In this
10611 case, @value{GDBN} uses @samp{UTF-8}.
10613 @value{GDBN} can only use certain character sets as its host character
10614 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
10615 @value{GDBN} will list the host character sets it supports.
10617 @item set charset @var{charset}
10618 @kindex set charset
10619 Set the current host and target character sets to @var{charset}. As
10620 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
10621 @value{GDBN} will list the names of the character sets that can be used
10622 for both host and target.
10625 @kindex show charset
10626 Show the names of the current host and target character sets.
10628 @item show host-charset
10629 @kindex show host-charset
10630 Show the name of the current host character set.
10632 @item show target-charset
10633 @kindex show target-charset
10634 Show the name of the current target character set.
10636 @item set target-wide-charset @var{charset}
10637 @kindex set target-wide-charset
10638 Set the current target's wide character set to @var{charset}. This is
10639 the character set used by the target's @code{wchar_t} type. To
10640 display the list of supported wide character sets, type
10641 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
10643 @item show target-wide-charset
10644 @kindex show target-wide-charset
10645 Show the name of the current target's wide character set.
10648 Here is an example of @value{GDBN}'s character set support in action.
10649 Assume that the following source code has been placed in the file
10650 @file{charset-test.c}:
10656 = @{72, 101, 108, 108, 111, 44, 32, 119,
10657 111, 114, 108, 100, 33, 10, 0@};
10658 char ibm1047_hello[]
10659 = @{200, 133, 147, 147, 150, 107, 64, 166,
10660 150, 153, 147, 132, 90, 37, 0@};
10664 printf ("Hello, world!\n");
10668 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
10669 containing the string @samp{Hello, world!} followed by a newline,
10670 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
10672 We compile the program, and invoke the debugger on it:
10675 $ gcc -g charset-test.c -o charset-test
10676 $ gdb -nw charset-test
10677 GNU gdb 2001-12-19-cvs
10678 Copyright 2001 Free Software Foundation, Inc.
10683 We can use the @code{show charset} command to see what character sets
10684 @value{GDBN} is currently using to interpret and display characters and
10688 (@value{GDBP}) show charset
10689 The current host and target character set is `ISO-8859-1'.
10693 For the sake of printing this manual, let's use @sc{ascii} as our
10694 initial character set:
10696 (@value{GDBP}) set charset ASCII
10697 (@value{GDBP}) show charset
10698 The current host and target character set is `ASCII'.
10702 Let's assume that @sc{ascii} is indeed the correct character set for our
10703 host system --- in other words, let's assume that if @value{GDBN} prints
10704 characters using the @sc{ascii} character set, our terminal will display
10705 them properly. Since our current target character set is also
10706 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
10709 (@value{GDBP}) print ascii_hello
10710 $1 = 0x401698 "Hello, world!\n"
10711 (@value{GDBP}) print ascii_hello[0]
10716 @value{GDBN} uses the target character set for character and string
10717 literals you use in expressions:
10720 (@value{GDBP}) print '+'
10725 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
10728 @value{GDBN} relies on the user to tell it which character set the
10729 target program uses. If we print @code{ibm1047_hello} while our target
10730 character set is still @sc{ascii}, we get jibberish:
10733 (@value{GDBP}) print ibm1047_hello
10734 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
10735 (@value{GDBP}) print ibm1047_hello[0]
10740 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
10741 @value{GDBN} tells us the character sets it supports:
10744 (@value{GDBP}) set target-charset
10745 ASCII EBCDIC-US IBM1047 ISO-8859-1
10746 (@value{GDBP}) set target-charset
10749 We can select @sc{ibm1047} as our target character set, and examine the
10750 program's strings again. Now the @sc{ascii} string is wrong, but
10751 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
10752 target character set, @sc{ibm1047}, to the host character set,
10753 @sc{ascii}, and they display correctly:
10756 (@value{GDBP}) set target-charset IBM1047
10757 (@value{GDBP}) show charset
10758 The current host character set is `ASCII'.
10759 The current target character set is `IBM1047'.
10760 (@value{GDBP}) print ascii_hello
10761 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
10762 (@value{GDBP}) print ascii_hello[0]
10764 (@value{GDBP}) print ibm1047_hello
10765 $8 = 0x4016a8 "Hello, world!\n"
10766 (@value{GDBP}) print ibm1047_hello[0]
10771 As above, @value{GDBN} uses the target character set for character and
10772 string literals you use in expressions:
10775 (@value{GDBP}) print '+'
10780 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
10783 @node Caching Remote Data
10784 @section Caching Data of Remote Targets
10785 @cindex caching data of remote targets
10787 @value{GDBN} caches data exchanged between the debugger and a
10788 remote target (@pxref{Remote Debugging}). Such caching generally improves
10789 performance, because it reduces the overhead of the remote protocol by
10790 bundling memory reads and writes into large chunks. Unfortunately, simply
10791 caching everything would lead to incorrect results, since @value{GDBN}
10792 does not necessarily know anything about volatile values, memory-mapped I/O
10793 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
10794 memory can be changed @emph{while} a gdb command is executing.
10795 Therefore, by default, @value{GDBN} only caches data
10796 known to be on the stack@footnote{In non-stop mode, it is moderately
10797 rare for a running thread to modify the stack of a stopped thread
10798 in a way that would interfere with a backtrace, and caching of
10799 stack reads provides a significant speed up of remote backtraces.}.
10800 Other regions of memory can be explicitly marked as
10801 cacheable; see @pxref{Memory Region Attributes}.
10804 @kindex set remotecache
10805 @item set remotecache on
10806 @itemx set remotecache off
10807 This option no longer does anything; it exists for compatibility
10810 @kindex show remotecache
10811 @item show remotecache
10812 Show the current state of the obsolete remotecache flag.
10814 @kindex set stack-cache
10815 @item set stack-cache on
10816 @itemx set stack-cache off
10817 Enable or disable caching of stack accesses. When @code{ON}, use
10818 caching. By default, this option is @code{ON}.
10820 @kindex show stack-cache
10821 @item show stack-cache
10822 Show the current state of data caching for memory accesses.
10824 @kindex info dcache
10825 @item info dcache @r{[}line@r{]}
10826 Print the information about the data cache performance. The
10827 information displayed includes the dcache width and depth, and for
10828 each cache line, its number, address, and how many times it was
10829 referenced. This command is useful for debugging the data cache
10832 If a line number is specified, the contents of that line will be
10835 @item set dcache size @var{size}
10836 @cindex dcache size
10837 @kindex set dcache size
10838 Set maximum number of entries in dcache (dcache depth above).
10840 @item set dcache line-size @var{line-size}
10841 @cindex dcache line-size
10842 @kindex set dcache line-size
10843 Set number of bytes each dcache entry caches (dcache width above).
10844 Must be a power of 2.
10846 @item show dcache size
10847 @kindex show dcache size
10848 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
10850 @item show dcache line-size
10851 @kindex show dcache line-size
10852 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
10856 @node Searching Memory
10857 @section Search Memory
10858 @cindex searching memory
10860 Memory can be searched for a particular sequence of bytes with the
10861 @code{find} command.
10865 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10866 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10867 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
10868 etc. The search begins at address @var{start_addr} and continues for either
10869 @var{len} bytes or through to @var{end_addr} inclusive.
10872 @var{s} and @var{n} are optional parameters.
10873 They may be specified in either order, apart or together.
10876 @item @var{s}, search query size
10877 The size of each search query value.
10883 halfwords (two bytes)
10887 giant words (eight bytes)
10890 All values are interpreted in the current language.
10891 This means, for example, that if the current source language is C/C@t{++}
10892 then searching for the string ``hello'' includes the trailing '\0'.
10894 If the value size is not specified, it is taken from the
10895 value's type in the current language.
10896 This is useful when one wants to specify the search
10897 pattern as a mixture of types.
10898 Note that this means, for example, that in the case of C-like languages
10899 a search for an untyped 0x42 will search for @samp{(int) 0x42}
10900 which is typically four bytes.
10902 @item @var{n}, maximum number of finds
10903 The maximum number of matches to print. The default is to print all finds.
10906 You can use strings as search values. Quote them with double-quotes
10908 The string value is copied into the search pattern byte by byte,
10909 regardless of the endianness of the target and the size specification.
10911 The address of each match found is printed as well as a count of the
10912 number of matches found.
10914 The address of the last value found is stored in convenience variable
10916 A count of the number of matches is stored in @samp{$numfound}.
10918 For example, if stopped at the @code{printf} in this function:
10924 static char hello[] = "hello-hello";
10925 static struct @{ char c; short s; int i; @}
10926 __attribute__ ((packed)) mixed
10927 = @{ 'c', 0x1234, 0x87654321 @};
10928 printf ("%s\n", hello);
10933 you get during debugging:
10936 (gdb) find &hello[0], +sizeof(hello), "hello"
10937 0x804956d <hello.1620+6>
10939 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
10940 0x8049567 <hello.1620>
10941 0x804956d <hello.1620+6>
10943 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
10944 0x8049567 <hello.1620>
10946 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
10947 0x8049560 <mixed.1625>
10949 (gdb) print $numfound
10952 $2 = (void *) 0x8049560
10955 @node Optimized Code
10956 @chapter Debugging Optimized Code
10957 @cindex optimized code, debugging
10958 @cindex debugging optimized code
10960 Almost all compilers support optimization. With optimization
10961 disabled, the compiler generates assembly code that corresponds
10962 directly to your source code, in a simplistic way. As the compiler
10963 applies more powerful optimizations, the generated assembly code
10964 diverges from your original source code. With help from debugging
10965 information generated by the compiler, @value{GDBN} can map from
10966 the running program back to constructs from your original source.
10968 @value{GDBN} is more accurate with optimization disabled. If you
10969 can recompile without optimization, it is easier to follow the
10970 progress of your program during debugging. But, there are many cases
10971 where you may need to debug an optimized version.
10973 When you debug a program compiled with @samp{-g -O}, remember that the
10974 optimizer has rearranged your code; the debugger shows you what is
10975 really there. Do not be too surprised when the execution path does not
10976 exactly match your source file! An extreme example: if you define a
10977 variable, but never use it, @value{GDBN} never sees that
10978 variable---because the compiler optimizes it out of existence.
10980 Some things do not work as well with @samp{-g -O} as with just
10981 @samp{-g}, particularly on machines with instruction scheduling. If in
10982 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
10983 please report it to us as a bug (including a test case!).
10984 @xref{Variables}, for more information about debugging optimized code.
10987 * Inline Functions:: How @value{GDBN} presents inlining
10988 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
10991 @node Inline Functions
10992 @section Inline Functions
10993 @cindex inline functions, debugging
10995 @dfn{Inlining} is an optimization that inserts a copy of the function
10996 body directly at each call site, instead of jumping to a shared
10997 routine. @value{GDBN} displays inlined functions just like
10998 non-inlined functions. They appear in backtraces. You can view their
10999 arguments and local variables, step into them with @code{step}, skip
11000 them with @code{next}, and escape from them with @code{finish}.
11001 You can check whether a function was inlined by using the
11002 @code{info frame} command.
11004 For @value{GDBN} to support inlined functions, the compiler must
11005 record information about inlining in the debug information ---
11006 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11007 other compilers do also. @value{GDBN} only supports inlined functions
11008 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11009 do not emit two required attributes (@samp{DW_AT_call_file} and
11010 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11011 function calls with earlier versions of @value{NGCC}. It instead
11012 displays the arguments and local variables of inlined functions as
11013 local variables in the caller.
11015 The body of an inlined function is directly included at its call site;
11016 unlike a non-inlined function, there are no instructions devoted to
11017 the call. @value{GDBN} still pretends that the call site and the
11018 start of the inlined function are different instructions. Stepping to
11019 the call site shows the call site, and then stepping again shows
11020 the first line of the inlined function, even though no additional
11021 instructions are executed.
11023 This makes source-level debugging much clearer; you can see both the
11024 context of the call and then the effect of the call. Only stepping by
11025 a single instruction using @code{stepi} or @code{nexti} does not do
11026 this; single instruction steps always show the inlined body.
11028 There are some ways that @value{GDBN} does not pretend that inlined
11029 function calls are the same as normal calls:
11033 Setting breakpoints at the call site of an inlined function may not
11034 work, because the call site does not contain any code. @value{GDBN}
11035 may incorrectly move the breakpoint to the next line of the enclosing
11036 function, after the call. This limitation will be removed in a future
11037 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11038 or inside the inlined function instead.
11041 @value{GDBN} cannot locate the return value of inlined calls after
11042 using the @code{finish} command. This is a limitation of compiler-generated
11043 debugging information; after @code{finish}, you can step to the next line
11044 and print a variable where your program stored the return value.
11048 @node Tail Call Frames
11049 @section Tail Call Frames
11050 @cindex tail call frames, debugging
11052 Function @code{B} can call function @code{C} in its very last statement. In
11053 unoptimized compilation the call of @code{C} is immediately followed by return
11054 instruction at the end of @code{B} code. Optimizing compiler may replace the
11055 call and return in function @code{B} into one jump to function @code{C}
11056 instead. Such use of a jump instruction is called @dfn{tail call}.
11058 During execution of function @code{C}, there will be no indication in the
11059 function call stack frames that it was tail-called from @code{B}. If function
11060 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
11061 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
11062 some cases @value{GDBN} can determine that @code{C} was tail-called from
11063 @code{B}, and it will then create fictitious call frame for that, with the
11064 return address set up as if @code{B} called @code{C} normally.
11066 This functionality is currently supported only by DWARF 2 debugging format and
11067 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
11068 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11071 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
11072 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
11076 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
11078 Stack level 1, frame at 0x7fffffffda30:
11079 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
11080 tail call frame, caller of frame at 0x7fffffffda30
11081 source language c++.
11082 Arglist at unknown address.
11083 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
11086 The detection of all the possible code path executions can find them ambiguous.
11087 There is no execution history stored (possible @ref{Reverse Execution} is never
11088 used for this purpose) and the last known caller could have reached the known
11089 callee by multiple different jump sequences. In such case @value{GDBN} still
11090 tries to show at least all the unambiguous top tail callers and all the
11091 unambiguous bottom tail calees, if any.
11094 @anchor{set debug entry-values}
11095 @item set debug entry-values
11096 @kindex set debug entry-values
11097 When set to on, enables printing of analysis messages for both frame argument
11098 values at function entry and tail calls. It will show all the possible valid
11099 tail calls code paths it has considered. It will also print the intersection
11100 of them with the final unambiguous (possibly partial or even empty) code path
11103 @item show debug entry-values
11104 @kindex show debug entry-values
11105 Show the current state of analysis messages printing for both frame argument
11106 values at function entry and tail calls.
11109 The analysis messages for tail calls can for example show why the virtual tail
11110 call frame for function @code{c} has not been recognized (due to the indirect
11111 reference by variable @code{x}):
11114 static void __attribute__((noinline, noclone)) c (void);
11115 void (*x) (void) = c;
11116 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11117 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
11118 int main (void) @{ x (); return 0; @}
11120 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
11121 DW_TAG_GNU_call_site 0x40039a in main
11123 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11126 #1 0x000000000040039a in main () at t.c:5
11129 Another possibility is an ambiguous virtual tail call frames resolution:
11133 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
11134 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
11135 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
11136 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
11137 static void __attribute__((noinline, noclone)) b (void)
11138 @{ if (i) c (); else e (); @}
11139 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
11140 int main (void) @{ a (); return 0; @}
11142 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
11143 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
11144 tailcall: reduced: 0x4004d2(a) |
11147 #1 0x00000000004004d2 in a () at t.c:8
11148 #2 0x0000000000400395 in main () at t.c:9
11151 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
11152 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
11154 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
11155 @ifset HAVE_MAKEINFO_CLICK
11156 @set ARROW @click{}
11157 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
11158 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
11160 @ifclear HAVE_MAKEINFO_CLICK
11162 @set CALLSEQ1B @value{CALLSEQ1A}
11163 @set CALLSEQ2B @value{CALLSEQ2A}
11166 Frames #0 and #2 are real, #1 is a virtual tail call frame.
11167 The code can have possible execution paths @value{CALLSEQ1B} or
11168 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
11170 @code{initial:} state shows some random possible calling sequence @value{GDBN}
11171 has found. It then finds another possible calling sequcen - that one is
11172 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
11173 printed as the @code{reduced:} calling sequence. That one could have many
11174 futher @code{compare:} and @code{reduced:} statements as long as there remain
11175 any non-ambiguous sequence entries.
11177 For the frame of function @code{b} in both cases there are different possible
11178 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
11179 also ambigous. The only non-ambiguous frame is the one for function @code{a},
11180 therefore this one is displayed to the user while the ambiguous frames are
11183 There can be also reasons why printing of frame argument values at function
11188 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
11189 static void __attribute__((noinline, noclone)) a (int i);
11190 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
11191 static void __attribute__((noinline, noclone)) a (int i)
11192 @{ if (i) b (i - 1); else c (0); @}
11193 int main (void) @{ a (5); return 0; @}
11196 #0 c (i=i@@entry=0) at t.c:2
11197 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
11198 function "a" at 0x400420 can call itself via tail calls
11199 i=<optimized out>) at t.c:6
11200 #2 0x000000000040036e in main () at t.c:7
11203 @value{GDBN} cannot find out from the inferior state if and how many times did
11204 function @code{a} call itself (via function @code{b}) as these calls would be
11205 tail calls. Such tail calls would modify thue @code{i} variable, therefore
11206 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
11207 prints @code{<optimized out>} instead.
11210 @chapter C Preprocessor Macros
11212 Some languages, such as C and C@t{++}, provide a way to define and invoke
11213 ``preprocessor macros'' which expand into strings of tokens.
11214 @value{GDBN} can evaluate expressions containing macro invocations, show
11215 the result of macro expansion, and show a macro's definition, including
11216 where it was defined.
11218 You may need to compile your program specially to provide @value{GDBN}
11219 with information about preprocessor macros. Most compilers do not
11220 include macros in their debugging information, even when you compile
11221 with the @option{-g} flag. @xref{Compilation}.
11223 A program may define a macro at one point, remove that definition later,
11224 and then provide a different definition after that. Thus, at different
11225 points in the program, a macro may have different definitions, or have
11226 no definition at all. If there is a current stack frame, @value{GDBN}
11227 uses the macros in scope at that frame's source code line. Otherwise,
11228 @value{GDBN} uses the macros in scope at the current listing location;
11231 Whenever @value{GDBN} evaluates an expression, it always expands any
11232 macro invocations present in the expression. @value{GDBN} also provides
11233 the following commands for working with macros explicitly.
11237 @kindex macro expand
11238 @cindex macro expansion, showing the results of preprocessor
11239 @cindex preprocessor macro expansion, showing the results of
11240 @cindex expanding preprocessor macros
11241 @item macro expand @var{expression}
11242 @itemx macro exp @var{expression}
11243 Show the results of expanding all preprocessor macro invocations in
11244 @var{expression}. Since @value{GDBN} simply expands macros, but does
11245 not parse the result, @var{expression} need not be a valid expression;
11246 it can be any string of tokens.
11249 @item macro expand-once @var{expression}
11250 @itemx macro exp1 @var{expression}
11251 @cindex expand macro once
11252 @i{(This command is not yet implemented.)} Show the results of
11253 expanding those preprocessor macro invocations that appear explicitly in
11254 @var{expression}. Macro invocations appearing in that expansion are
11255 left unchanged. This command allows you to see the effect of a
11256 particular macro more clearly, without being confused by further
11257 expansions. Since @value{GDBN} simply expands macros, but does not
11258 parse the result, @var{expression} need not be a valid expression; it
11259 can be any string of tokens.
11262 @cindex macro definition, showing
11263 @cindex definition of a macro, showing
11264 @cindex macros, from debug info
11265 @item info macro [-a|-all] [--] @var{macro}
11266 Show the current definition or all definitions of the named @var{macro},
11267 and describe the source location or compiler command-line where that
11268 definition was established. The optional double dash is to signify the end of
11269 argument processing and the beginning of @var{macro} for non C-like macros where
11270 the macro may begin with a hyphen.
11272 @kindex info macros
11273 @item info macros @var{linespec}
11274 Show all macro definitions that are in effect at the location specified
11275 by @var{linespec}, and describe the source location or compiler
11276 command-line where those definitions were established.
11278 @kindex macro define
11279 @cindex user-defined macros
11280 @cindex defining macros interactively
11281 @cindex macros, user-defined
11282 @item macro define @var{macro} @var{replacement-list}
11283 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
11284 Introduce a definition for a preprocessor macro named @var{macro},
11285 invocations of which are replaced by the tokens given in
11286 @var{replacement-list}. The first form of this command defines an
11287 ``object-like'' macro, which takes no arguments; the second form
11288 defines a ``function-like'' macro, which takes the arguments given in
11291 A definition introduced by this command is in scope in every
11292 expression evaluated in @value{GDBN}, until it is removed with the
11293 @code{macro undef} command, described below. The definition overrides
11294 all definitions for @var{macro} present in the program being debugged,
11295 as well as any previous user-supplied definition.
11297 @kindex macro undef
11298 @item macro undef @var{macro}
11299 Remove any user-supplied definition for the macro named @var{macro}.
11300 This command only affects definitions provided with the @code{macro
11301 define} command, described above; it cannot remove definitions present
11302 in the program being debugged.
11306 List all the macros defined using the @code{macro define} command.
11309 @cindex macros, example of debugging with
11310 Here is a transcript showing the above commands in action. First, we
11311 show our source files:
11316 #include "sample.h"
11319 #define ADD(x) (M + x)
11324 printf ("Hello, world!\n");
11326 printf ("We're so creative.\n");
11328 printf ("Goodbye, world!\n");
11335 Now, we compile the program using the @sc{gnu} C compiler,
11336 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
11337 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
11338 and @option{-gdwarf-4}; we recommend always choosing the most recent
11339 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
11340 includes information about preprocessor macros in the debugging
11344 $ gcc -gdwarf-2 -g3 sample.c -o sample
11348 Now, we start @value{GDBN} on our sample program:
11352 GNU gdb 2002-05-06-cvs
11353 Copyright 2002 Free Software Foundation, Inc.
11354 GDB is free software, @dots{}
11358 We can expand macros and examine their definitions, even when the
11359 program is not running. @value{GDBN} uses the current listing position
11360 to decide which macro definitions are in scope:
11363 (@value{GDBP}) list main
11366 5 #define ADD(x) (M + x)
11371 10 printf ("Hello, world!\n");
11373 12 printf ("We're so creative.\n");
11374 (@value{GDBP}) info macro ADD
11375 Defined at /home/jimb/gdb/macros/play/sample.c:5
11376 #define ADD(x) (M + x)
11377 (@value{GDBP}) info macro Q
11378 Defined at /home/jimb/gdb/macros/play/sample.h:1
11379 included at /home/jimb/gdb/macros/play/sample.c:2
11381 (@value{GDBP}) macro expand ADD(1)
11382 expands to: (42 + 1)
11383 (@value{GDBP}) macro expand-once ADD(1)
11384 expands to: once (M + 1)
11388 In the example above, note that @code{macro expand-once} expands only
11389 the macro invocation explicit in the original text --- the invocation of
11390 @code{ADD} --- but does not expand the invocation of the macro @code{M},
11391 which was introduced by @code{ADD}.
11393 Once the program is running, @value{GDBN} uses the macro definitions in
11394 force at the source line of the current stack frame:
11397 (@value{GDBP}) break main
11398 Breakpoint 1 at 0x8048370: file sample.c, line 10.
11400 Starting program: /home/jimb/gdb/macros/play/sample
11402 Breakpoint 1, main () at sample.c:10
11403 10 printf ("Hello, world!\n");
11407 At line 10, the definition of the macro @code{N} at line 9 is in force:
11410 (@value{GDBP}) info macro N
11411 Defined at /home/jimb/gdb/macros/play/sample.c:9
11413 (@value{GDBP}) macro expand N Q M
11414 expands to: 28 < 42
11415 (@value{GDBP}) print N Q M
11420 As we step over directives that remove @code{N}'s definition, and then
11421 give it a new definition, @value{GDBN} finds the definition (or lack
11422 thereof) in force at each point:
11425 (@value{GDBP}) next
11427 12 printf ("We're so creative.\n");
11428 (@value{GDBP}) info macro N
11429 The symbol `N' has no definition as a C/C++ preprocessor macro
11430 at /home/jimb/gdb/macros/play/sample.c:12
11431 (@value{GDBP}) next
11433 14 printf ("Goodbye, world!\n");
11434 (@value{GDBP}) info macro N
11435 Defined at /home/jimb/gdb/macros/play/sample.c:13
11437 (@value{GDBP}) macro expand N Q M
11438 expands to: 1729 < 42
11439 (@value{GDBP}) print N Q M
11444 In addition to source files, macros can be defined on the compilation command
11445 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
11446 such a way, @value{GDBN} displays the location of their definition as line zero
11447 of the source file submitted to the compiler.
11450 (@value{GDBP}) info macro __STDC__
11451 Defined at /home/jimb/gdb/macros/play/sample.c:0
11458 @chapter Tracepoints
11459 @c This chapter is based on the documentation written by Michael
11460 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
11462 @cindex tracepoints
11463 In some applications, it is not feasible for the debugger to interrupt
11464 the program's execution long enough for the developer to learn
11465 anything helpful about its behavior. If the program's correctness
11466 depends on its real-time behavior, delays introduced by a debugger
11467 might cause the program to change its behavior drastically, or perhaps
11468 fail, even when the code itself is correct. It is useful to be able
11469 to observe the program's behavior without interrupting it.
11471 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
11472 specify locations in the program, called @dfn{tracepoints}, and
11473 arbitrary expressions to evaluate when those tracepoints are reached.
11474 Later, using the @code{tfind} command, you can examine the values
11475 those expressions had when the program hit the tracepoints. The
11476 expressions may also denote objects in memory---structures or arrays,
11477 for example---whose values @value{GDBN} should record; while visiting
11478 a particular tracepoint, you may inspect those objects as if they were
11479 in memory at that moment. However, because @value{GDBN} records these
11480 values without interacting with you, it can do so quickly and
11481 unobtrusively, hopefully not disturbing the program's behavior.
11483 The tracepoint facility is currently available only for remote
11484 targets. @xref{Targets}. In addition, your remote target must know
11485 how to collect trace data. This functionality is implemented in the
11486 remote stub; however, none of the stubs distributed with @value{GDBN}
11487 support tracepoints as of this writing. The format of the remote
11488 packets used to implement tracepoints are described in @ref{Tracepoint
11491 It is also possible to get trace data from a file, in a manner reminiscent
11492 of corefiles; you specify the filename, and use @code{tfind} to search
11493 through the file. @xref{Trace Files}, for more details.
11495 This chapter describes the tracepoint commands and features.
11498 * Set Tracepoints::
11499 * Analyze Collected Data::
11500 * Tracepoint Variables::
11504 @node Set Tracepoints
11505 @section Commands to Set Tracepoints
11507 Before running such a @dfn{trace experiment}, an arbitrary number of
11508 tracepoints can be set. A tracepoint is actually a special type of
11509 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
11510 standard breakpoint commands. For instance, as with breakpoints,
11511 tracepoint numbers are successive integers starting from one, and many
11512 of the commands associated with tracepoints take the tracepoint number
11513 as their argument, to identify which tracepoint to work on.
11515 For each tracepoint, you can specify, in advance, some arbitrary set
11516 of data that you want the target to collect in the trace buffer when
11517 it hits that tracepoint. The collected data can include registers,
11518 local variables, or global data. Later, you can use @value{GDBN}
11519 commands to examine the values these data had at the time the
11520 tracepoint was hit.
11522 Tracepoints do not support every breakpoint feature. Ignore counts on
11523 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
11524 commands when they are hit. Tracepoints may not be thread-specific
11527 @cindex fast tracepoints
11528 Some targets may support @dfn{fast tracepoints}, which are inserted in
11529 a different way (such as with a jump instead of a trap), that is
11530 faster but possibly restricted in where they may be installed.
11532 @cindex static tracepoints
11533 @cindex markers, static tracepoints
11534 @cindex probing markers, static tracepoints
11535 Regular and fast tracepoints are dynamic tracing facilities, meaning
11536 that they can be used to insert tracepoints at (almost) any location
11537 in the target. Some targets may also support controlling @dfn{static
11538 tracepoints} from @value{GDBN}. With static tracing, a set of
11539 instrumentation points, also known as @dfn{markers}, are embedded in
11540 the target program, and can be activated or deactivated by name or
11541 address. These are usually placed at locations which facilitate
11542 investigating what the target is actually doing. @value{GDBN}'s
11543 support for static tracing includes being able to list instrumentation
11544 points, and attach them with @value{GDBN} defined high level
11545 tracepoints that expose the whole range of convenience of
11546 @value{GDBN}'s tracepoints support. Namely, support for collecting
11547 registers values and values of global or local (to the instrumentation
11548 point) variables; tracepoint conditions and trace state variables.
11549 The act of installing a @value{GDBN} static tracepoint on an
11550 instrumentation point, or marker, is referred to as @dfn{probing} a
11551 static tracepoint marker.
11553 @code{gdbserver} supports tracepoints on some target systems.
11554 @xref{Server,,Tracepoints support in @code{gdbserver}}.
11556 This section describes commands to set tracepoints and associated
11557 conditions and actions.
11560 * Create and Delete Tracepoints::
11561 * Enable and Disable Tracepoints::
11562 * Tracepoint Passcounts::
11563 * Tracepoint Conditions::
11564 * Trace State Variables::
11565 * Tracepoint Actions::
11566 * Listing Tracepoints::
11567 * Listing Static Tracepoint Markers::
11568 * Starting and Stopping Trace Experiments::
11569 * Tracepoint Restrictions::
11572 @node Create and Delete Tracepoints
11573 @subsection Create and Delete Tracepoints
11576 @cindex set tracepoint
11578 @item trace @var{location}
11579 The @code{trace} command is very similar to the @code{break} command.
11580 Its argument @var{location} can be a source line, a function name, or
11581 an address in the target program. @xref{Specify Location}. The
11582 @code{trace} command defines a tracepoint, which is a point in the
11583 target program where the debugger will briefly stop, collect some
11584 data, and then allow the program to continue. Setting a tracepoint or
11585 changing its actions takes effect immediately if the remote stub
11586 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
11588 If remote stub doesn't support the @samp{InstallInTrace} feature, all
11589 these changes don't take effect until the next @code{tstart}
11590 command, and once a trace experiment is running, further changes will
11591 not have any effect until the next trace experiment starts. In addition,
11592 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
11593 address is not yet resolved. (This is similar to pending breakpoints.)
11594 Pending tracepoints are not downloaded to the target and not installed
11595 until they are resolved. The resolution of pending tracepoints requires
11596 @value{GDBN} support---when debugging with the remote target, and
11597 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
11598 tracing}), pending tracepoints can not be resolved (and downloaded to
11599 the remote stub) while @value{GDBN} is disconnected.
11601 Here are some examples of using the @code{trace} command:
11604 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
11606 (@value{GDBP}) @b{trace +2} // 2 lines forward
11608 (@value{GDBP}) @b{trace my_function} // first source line of function
11610 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
11612 (@value{GDBP}) @b{trace *0x2117c4} // an address
11616 You can abbreviate @code{trace} as @code{tr}.
11618 @item trace @var{location} if @var{cond}
11619 Set a tracepoint with condition @var{cond}; evaluate the expression
11620 @var{cond} each time the tracepoint is reached, and collect data only
11621 if the value is nonzero---that is, if @var{cond} evaluates as true.
11622 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
11623 information on tracepoint conditions.
11625 @item ftrace @var{location} [ if @var{cond} ]
11626 @cindex set fast tracepoint
11627 @cindex fast tracepoints, setting
11629 The @code{ftrace} command sets a fast tracepoint. For targets that
11630 support them, fast tracepoints will use a more efficient but possibly
11631 less general technique to trigger data collection, such as a jump
11632 instruction instead of a trap, or some sort of hardware support. It
11633 may not be possible to create a fast tracepoint at the desired
11634 location, in which case the command will exit with an explanatory
11637 @value{GDBN} handles arguments to @code{ftrace} exactly as for
11640 On 32-bit x86-architecture systems, fast tracepoints normally need to
11641 be placed at an instruction that is 5 bytes or longer, but can be
11642 placed at 4-byte instructions if the low 64K of memory of the target
11643 program is available to install trampolines. Some Unix-type systems,
11644 such as @sc{gnu}/Linux, exclude low addresses from the program's
11645 address space; but for instance with the Linux kernel it is possible
11646 to let @value{GDBN} use this area by doing a @command{sysctl} command
11647 to set the @code{mmap_min_addr} kernel parameter, as in
11650 sudo sysctl -w vm.mmap_min_addr=32768
11654 which sets the low address to 32K, which leaves plenty of room for
11655 trampolines. The minimum address should be set to a page boundary.
11657 @item strace @var{location} [ if @var{cond} ]
11658 @cindex set static tracepoint
11659 @cindex static tracepoints, setting
11660 @cindex probe static tracepoint marker
11662 The @code{strace} command sets a static tracepoint. For targets that
11663 support it, setting a static tracepoint probes a static
11664 instrumentation point, or marker, found at @var{location}. It may not
11665 be possible to set a static tracepoint at the desired location, in
11666 which case the command will exit with an explanatory message.
11668 @value{GDBN} handles arguments to @code{strace} exactly as for
11669 @code{trace}, with the addition that the user can also specify
11670 @code{-m @var{marker}} as @var{location}. This probes the marker
11671 identified by the @var{marker} string identifier. This identifier
11672 depends on the static tracepoint backend library your program is
11673 using. You can find all the marker identifiers in the @samp{ID} field
11674 of the @code{info static-tracepoint-markers} command output.
11675 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
11676 Markers}. For example, in the following small program using the UST
11682 trace_mark(ust, bar33, "str %s", "FOOBAZ");
11687 the marker id is composed of joining the first two arguments to the
11688 @code{trace_mark} call with a slash, which translates to:
11691 (@value{GDBP}) info static-tracepoint-markers
11692 Cnt Enb ID Address What
11693 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
11699 so you may probe the marker above with:
11702 (@value{GDBP}) strace -m ust/bar33
11705 Static tracepoints accept an extra collect action --- @code{collect
11706 $_sdata}. This collects arbitrary user data passed in the probe point
11707 call to the tracing library. In the UST example above, you'll see
11708 that the third argument to @code{trace_mark} is a printf-like format
11709 string. The user data is then the result of running that formating
11710 string against the following arguments. Note that @code{info
11711 static-tracepoint-markers} command output lists that format string in
11712 the @samp{Data:} field.
11714 You can inspect this data when analyzing the trace buffer, by printing
11715 the $_sdata variable like any other variable available to
11716 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
11719 @cindex last tracepoint number
11720 @cindex recent tracepoint number
11721 @cindex tracepoint number
11722 The convenience variable @code{$tpnum} records the tracepoint number
11723 of the most recently set tracepoint.
11725 @kindex delete tracepoint
11726 @cindex tracepoint deletion
11727 @item delete tracepoint @r{[}@var{num}@r{]}
11728 Permanently delete one or more tracepoints. With no argument, the
11729 default is to delete all tracepoints. Note that the regular
11730 @code{delete} command can remove tracepoints also.
11735 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
11737 (@value{GDBP}) @b{delete trace} // remove all tracepoints
11741 You can abbreviate this command as @code{del tr}.
11744 @node Enable and Disable Tracepoints
11745 @subsection Enable and Disable Tracepoints
11747 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
11750 @kindex disable tracepoint
11751 @item disable tracepoint @r{[}@var{num}@r{]}
11752 Disable tracepoint @var{num}, or all tracepoints if no argument
11753 @var{num} is given. A disabled tracepoint will have no effect during
11754 a trace experiment, but it is not forgotten. You can re-enable
11755 a disabled tracepoint using the @code{enable tracepoint} command.
11756 If the command is issued during a trace experiment and the debug target
11757 has support for disabling tracepoints during a trace experiment, then the
11758 change will be effective immediately. Otherwise, it will be applied to the
11759 next trace experiment.
11761 @kindex enable tracepoint
11762 @item enable tracepoint @r{[}@var{num}@r{]}
11763 Enable tracepoint @var{num}, or all tracepoints. If this command is
11764 issued during a trace experiment and the debug target supports enabling
11765 tracepoints during a trace experiment, then the enabled tracepoints will
11766 become effective immediately. Otherwise, they will become effective the
11767 next time a trace experiment is run.
11770 @node Tracepoint Passcounts
11771 @subsection Tracepoint Passcounts
11775 @cindex tracepoint pass count
11776 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
11777 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
11778 automatically stop a trace experiment. If a tracepoint's passcount is
11779 @var{n}, then the trace experiment will be automatically stopped on
11780 the @var{n}'th time that tracepoint is hit. If the tracepoint number
11781 @var{num} is not specified, the @code{passcount} command sets the
11782 passcount of the most recently defined tracepoint. If no passcount is
11783 given, the trace experiment will run until stopped explicitly by the
11789 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
11790 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
11792 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
11793 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
11794 (@value{GDBP}) @b{trace foo}
11795 (@value{GDBP}) @b{pass 3}
11796 (@value{GDBP}) @b{trace bar}
11797 (@value{GDBP}) @b{pass 2}
11798 (@value{GDBP}) @b{trace baz}
11799 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
11800 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
11801 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
11802 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
11806 @node Tracepoint Conditions
11807 @subsection Tracepoint Conditions
11808 @cindex conditional tracepoints
11809 @cindex tracepoint conditions
11811 The simplest sort of tracepoint collects data every time your program
11812 reaches a specified place. You can also specify a @dfn{condition} for
11813 a tracepoint. A condition is just a Boolean expression in your
11814 programming language (@pxref{Expressions, ,Expressions}). A
11815 tracepoint with a condition evaluates the expression each time your
11816 program reaches it, and data collection happens only if the condition
11819 Tracepoint conditions can be specified when a tracepoint is set, by
11820 using @samp{if} in the arguments to the @code{trace} command.
11821 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
11822 also be set or changed at any time with the @code{condition} command,
11823 just as with breakpoints.
11825 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
11826 the conditional expression itself. Instead, @value{GDBN} encodes the
11827 expression into an agent expression (@pxref{Agent Expressions})
11828 suitable for execution on the target, independently of @value{GDBN}.
11829 Global variables become raw memory locations, locals become stack
11830 accesses, and so forth.
11832 For instance, suppose you have a function that is usually called
11833 frequently, but should not be called after an error has occurred. You
11834 could use the following tracepoint command to collect data about calls
11835 of that function that happen while the error code is propagating
11836 through the program; an unconditional tracepoint could end up
11837 collecting thousands of useless trace frames that you would have to
11841 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
11844 @node Trace State Variables
11845 @subsection Trace State Variables
11846 @cindex trace state variables
11848 A @dfn{trace state variable} is a special type of variable that is
11849 created and managed by target-side code. The syntax is the same as
11850 that for GDB's convenience variables (a string prefixed with ``$''),
11851 but they are stored on the target. They must be created explicitly,
11852 using a @code{tvariable} command. They are always 64-bit signed
11855 Trace state variables are remembered by @value{GDBN}, and downloaded
11856 to the target along with tracepoint information when the trace
11857 experiment starts. There are no intrinsic limits on the number of
11858 trace state variables, beyond memory limitations of the target.
11860 @cindex convenience variables, and trace state variables
11861 Although trace state variables are managed by the target, you can use
11862 them in print commands and expressions as if they were convenience
11863 variables; @value{GDBN} will get the current value from the target
11864 while the trace experiment is running. Trace state variables share
11865 the same namespace as other ``$'' variables, which means that you
11866 cannot have trace state variables with names like @code{$23} or
11867 @code{$pc}, nor can you have a trace state variable and a convenience
11868 variable with the same name.
11872 @item tvariable $@var{name} [ = @var{expression} ]
11874 The @code{tvariable} command creates a new trace state variable named
11875 @code{$@var{name}}, and optionally gives it an initial value of
11876 @var{expression}. @var{expression} is evaluated when this command is
11877 entered; the result will be converted to an integer if possible,
11878 otherwise @value{GDBN} will report an error. A subsequent
11879 @code{tvariable} command specifying the same name does not create a
11880 variable, but instead assigns the supplied initial value to the
11881 existing variable of that name, overwriting any previous initial
11882 value. The default initial value is 0.
11884 @item info tvariables
11885 @kindex info tvariables
11886 List all the trace state variables along with their initial values.
11887 Their current values may also be displayed, if the trace experiment is
11890 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
11891 @kindex delete tvariable
11892 Delete the given trace state variables, or all of them if no arguments
11897 @node Tracepoint Actions
11898 @subsection Tracepoint Action Lists
11902 @cindex tracepoint actions
11903 @item actions @r{[}@var{num}@r{]}
11904 This command will prompt for a list of actions to be taken when the
11905 tracepoint is hit. If the tracepoint number @var{num} is not
11906 specified, this command sets the actions for the one that was most
11907 recently defined (so that you can define a tracepoint and then say
11908 @code{actions} without bothering about its number). You specify the
11909 actions themselves on the following lines, one action at a time, and
11910 terminate the actions list with a line containing just @code{end}. So
11911 far, the only defined actions are @code{collect}, @code{teval}, and
11912 @code{while-stepping}.
11914 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
11915 Commands, ,Breakpoint Command Lists}), except that only the defined
11916 actions are allowed; any other @value{GDBN} command is rejected.
11918 @cindex remove actions from a tracepoint
11919 To remove all actions from a tracepoint, type @samp{actions @var{num}}
11920 and follow it immediately with @samp{end}.
11923 (@value{GDBP}) @b{collect @var{data}} // collect some data
11925 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
11927 (@value{GDBP}) @b{end} // signals the end of actions.
11930 In the following example, the action list begins with @code{collect}
11931 commands indicating the things to be collected when the tracepoint is
11932 hit. Then, in order to single-step and collect additional data
11933 following the tracepoint, a @code{while-stepping} command is used,
11934 followed by the list of things to be collected after each step in a
11935 sequence of single steps. The @code{while-stepping} command is
11936 terminated by its own separate @code{end} command. Lastly, the action
11937 list is terminated by an @code{end} command.
11940 (@value{GDBP}) @b{trace foo}
11941 (@value{GDBP}) @b{actions}
11942 Enter actions for tracepoint 1, one per line:
11945 > while-stepping 12
11946 > collect $pc, arr[i]
11951 @kindex collect @r{(tracepoints)}
11952 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
11953 Collect values of the given expressions when the tracepoint is hit.
11954 This command accepts a comma-separated list of any valid expressions.
11955 In addition to global, static, or local variables, the following
11956 special arguments are supported:
11960 Collect all registers.
11963 Collect all function arguments.
11966 Collect all local variables.
11969 Collect the return address. This is helpful if you want to see more
11973 Collects the number of arguments from the static probe at which the
11974 tracepoint is located.
11975 @xref{Static Probe Points}.
11977 @item $_probe_arg@var{n}
11978 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
11979 from the static probe at which the tracepoint is located.
11980 @xref{Static Probe Points}.
11983 @vindex $_sdata@r{, collect}
11984 Collect static tracepoint marker specific data. Only available for
11985 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
11986 Lists}. On the UST static tracepoints library backend, an
11987 instrumentation point resembles a @code{printf} function call. The
11988 tracing library is able to collect user specified data formatted to a
11989 character string using the format provided by the programmer that
11990 instrumented the program. Other backends have similar mechanisms.
11991 Here's an example of a UST marker call:
11994 const char master_name[] = "$your_name";
11995 trace_mark(channel1, marker1, "hello %s", master_name)
11998 In this case, collecting @code{$_sdata} collects the string
11999 @samp{hello $yourname}. When analyzing the trace buffer, you can
12000 inspect @samp{$_sdata} like any other variable available to
12004 You can give several consecutive @code{collect} commands, each one
12005 with a single argument, or one @code{collect} command with several
12006 arguments separated by commas; the effect is the same.
12008 The optional @var{mods} changes the usual handling of the arguments.
12009 @code{s} requests that pointers to chars be handled as strings, in
12010 particular collecting the contents of the memory being pointed at, up
12011 to the first zero. The upper bound is by default the value of the
12012 @code{print elements} variable; if @code{s} is followed by a decimal
12013 number, that is the upper bound instead. So for instance
12014 @samp{collect/s25 mystr} collects as many as 25 characters at
12017 The command @code{info scope} (@pxref{Symbols, info scope}) is
12018 particularly useful for figuring out what data to collect.
12020 @kindex teval @r{(tracepoints)}
12021 @item teval @var{expr1}, @var{expr2}, @dots{}
12022 Evaluate the given expressions when the tracepoint is hit. This
12023 command accepts a comma-separated list of expressions. The results
12024 are discarded, so this is mainly useful for assigning values to trace
12025 state variables (@pxref{Trace State Variables}) without adding those
12026 values to the trace buffer, as would be the case if the @code{collect}
12029 @kindex while-stepping @r{(tracepoints)}
12030 @item while-stepping @var{n}
12031 Perform @var{n} single-step instruction traces after the tracepoint,
12032 collecting new data after each step. The @code{while-stepping}
12033 command is followed by the list of what to collect while stepping
12034 (followed by its own @code{end} command):
12037 > while-stepping 12
12038 > collect $regs, myglobal
12044 Note that @code{$pc} is not automatically collected by
12045 @code{while-stepping}; you need to explicitly collect that register if
12046 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
12049 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
12050 @kindex set default-collect
12051 @cindex default collection action
12052 This variable is a list of expressions to collect at each tracepoint
12053 hit. It is effectively an additional @code{collect} action prepended
12054 to every tracepoint action list. The expressions are parsed
12055 individually for each tracepoint, so for instance a variable named
12056 @code{xyz} may be interpreted as a global for one tracepoint, and a
12057 local for another, as appropriate to the tracepoint's location.
12059 @item show default-collect
12060 @kindex show default-collect
12061 Show the list of expressions that are collected by default at each
12066 @node Listing Tracepoints
12067 @subsection Listing Tracepoints
12070 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
12071 @kindex info tp @r{[}@var{n}@dots{}@r{]}
12072 @cindex information about tracepoints
12073 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
12074 Display information about the tracepoint @var{num}. If you don't
12075 specify a tracepoint number, displays information about all the
12076 tracepoints defined so far. The format is similar to that used for
12077 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
12078 command, simply restricting itself to tracepoints.
12080 A tracepoint's listing may include additional information specific to
12085 its passcount as given by the @code{passcount @var{n}} command
12088 the state about installed on target of each location
12092 (@value{GDBP}) @b{info trace}
12093 Num Type Disp Enb Address What
12094 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
12096 collect globfoo, $regs
12101 2 tracepoint keep y <MULTIPLE>
12103 2.1 y 0x0804859c in func4 at change-loc.h:35
12104 installed on target
12105 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
12106 installed on target
12107 2.3 y <PENDING> set_tracepoint
12108 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
12109 not installed on target
12114 This command can be abbreviated @code{info tp}.
12117 @node Listing Static Tracepoint Markers
12118 @subsection Listing Static Tracepoint Markers
12121 @kindex info static-tracepoint-markers
12122 @cindex information about static tracepoint markers
12123 @item info static-tracepoint-markers
12124 Display information about all static tracepoint markers defined in the
12127 For each marker, the following columns are printed:
12131 An incrementing counter, output to help readability. This is not a
12134 The marker ID, as reported by the target.
12135 @item Enabled or Disabled
12136 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
12137 that are not enabled.
12139 Where the marker is in your program, as a memory address.
12141 Where the marker is in the source for your program, as a file and line
12142 number. If the debug information included in the program does not
12143 allow @value{GDBN} to locate the source of the marker, this column
12144 will be left blank.
12148 In addition, the following information may be printed for each marker:
12152 User data passed to the tracing library by the marker call. In the
12153 UST backend, this is the format string passed as argument to the
12155 @item Static tracepoints probing the marker
12156 The list of static tracepoints attached to the marker.
12160 (@value{GDBP}) info static-tracepoint-markers
12161 Cnt ID Enb Address What
12162 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
12163 Data: number1 %d number2 %d
12164 Probed by static tracepoints: #2
12165 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
12171 @node Starting and Stopping Trace Experiments
12172 @subsection Starting and Stopping Trace Experiments
12175 @kindex tstart [ @var{notes} ]
12176 @cindex start a new trace experiment
12177 @cindex collected data discarded
12179 This command starts the trace experiment, and begins collecting data.
12180 It has the side effect of discarding all the data collected in the
12181 trace buffer during the previous trace experiment. If any arguments
12182 are supplied, they are taken as a note and stored with the trace
12183 experiment's state. The notes may be arbitrary text, and are
12184 especially useful with disconnected tracing in a multi-user context;
12185 the notes can explain what the trace is doing, supply user contact
12186 information, and so forth.
12188 @kindex tstop [ @var{notes} ]
12189 @cindex stop a running trace experiment
12191 This command stops the trace experiment. If any arguments are
12192 supplied, they are recorded with the experiment as a note. This is
12193 useful if you are stopping a trace started by someone else, for
12194 instance if the trace is interfering with the system's behavior and
12195 needs to be stopped quickly.
12197 @strong{Note}: a trace experiment and data collection may stop
12198 automatically if any tracepoint's passcount is reached
12199 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
12202 @cindex status of trace data collection
12203 @cindex trace experiment, status of
12205 This command displays the status of the current trace data
12209 Here is an example of the commands we described so far:
12212 (@value{GDBP}) @b{trace gdb_c_test}
12213 (@value{GDBP}) @b{actions}
12214 Enter actions for tracepoint #1, one per line.
12215 > collect $regs,$locals,$args
12216 > while-stepping 11
12220 (@value{GDBP}) @b{tstart}
12221 [time passes @dots{}]
12222 (@value{GDBP}) @b{tstop}
12225 @anchor{disconnected tracing}
12226 @cindex disconnected tracing
12227 You can choose to continue running the trace experiment even if
12228 @value{GDBN} disconnects from the target, voluntarily or
12229 involuntarily. For commands such as @code{detach}, the debugger will
12230 ask what you want to do with the trace. But for unexpected
12231 terminations (@value{GDBN} crash, network outage), it would be
12232 unfortunate to lose hard-won trace data, so the variable
12233 @code{disconnected-tracing} lets you decide whether the trace should
12234 continue running without @value{GDBN}.
12237 @item set disconnected-tracing on
12238 @itemx set disconnected-tracing off
12239 @kindex set disconnected-tracing
12240 Choose whether a tracing run should continue to run if @value{GDBN}
12241 has disconnected from the target. Note that @code{detach} or
12242 @code{quit} will ask you directly what to do about a running trace no
12243 matter what this variable's setting, so the variable is mainly useful
12244 for handling unexpected situations, such as loss of the network.
12246 @item show disconnected-tracing
12247 @kindex show disconnected-tracing
12248 Show the current choice for disconnected tracing.
12252 When you reconnect to the target, the trace experiment may or may not
12253 still be running; it might have filled the trace buffer in the
12254 meantime, or stopped for one of the other reasons. If it is running,
12255 it will continue after reconnection.
12257 Upon reconnection, the target will upload information about the
12258 tracepoints in effect. @value{GDBN} will then compare that
12259 information to the set of tracepoints currently defined, and attempt
12260 to match them up, allowing for the possibility that the numbers may
12261 have changed due to creation and deletion in the meantime. If one of
12262 the target's tracepoints does not match any in @value{GDBN}, the
12263 debugger will create a new tracepoint, so that you have a number with
12264 which to specify that tracepoint. This matching-up process is
12265 necessarily heuristic, and it may result in useless tracepoints being
12266 created; you may simply delete them if they are of no use.
12268 @cindex circular trace buffer
12269 If your target agent supports a @dfn{circular trace buffer}, then you
12270 can run a trace experiment indefinitely without filling the trace
12271 buffer; when space runs out, the agent deletes already-collected trace
12272 frames, oldest first, until there is enough room to continue
12273 collecting. This is especially useful if your tracepoints are being
12274 hit too often, and your trace gets terminated prematurely because the
12275 buffer is full. To ask for a circular trace buffer, simply set
12276 @samp{circular-trace-buffer} to on. You can set this at any time,
12277 including during tracing; if the agent can do it, it will change
12278 buffer handling on the fly, otherwise it will not take effect until
12282 @item set circular-trace-buffer on
12283 @itemx set circular-trace-buffer off
12284 @kindex set circular-trace-buffer
12285 Choose whether a tracing run should use a linear or circular buffer
12286 for trace data. A linear buffer will not lose any trace data, but may
12287 fill up prematurely, while a circular buffer will discard old trace
12288 data, but it will have always room for the latest tracepoint hits.
12290 @item show circular-trace-buffer
12291 @kindex show circular-trace-buffer
12292 Show the current choice for the trace buffer. Note that this may not
12293 match the agent's current buffer handling, nor is it guaranteed to
12294 match the setting that might have been in effect during a past run,
12295 for instance if you are looking at frames from a trace file.
12300 @item set trace-buffer-size @var{n}
12301 @itemx set trace-buffer-size unlimited
12302 @kindex set trace-buffer-size
12303 Request that the target use a trace buffer of @var{n} bytes. Not all
12304 targets will honor the request; they may have a compiled-in size for
12305 the trace buffer, or some other limitation. Set to a value of
12306 @code{unlimited} or @code{-1} to let the target use whatever size it
12307 likes. This is also the default.
12309 @item show trace-buffer-size
12310 @kindex show trace-buffer-size
12311 Show the current requested size for the trace buffer. Note that this
12312 will only match the actual size if the target supports size-setting,
12313 and was able to handle the requested size. For instance, if the
12314 target can only change buffer size between runs, this variable will
12315 not reflect the change until the next run starts. Use @code{tstatus}
12316 to get a report of the actual buffer size.
12320 @item set trace-user @var{text}
12321 @kindex set trace-user
12323 @item show trace-user
12324 @kindex show trace-user
12326 @item set trace-notes @var{text}
12327 @kindex set trace-notes
12328 Set the trace run's notes.
12330 @item show trace-notes
12331 @kindex show trace-notes
12332 Show the trace run's notes.
12334 @item set trace-stop-notes @var{text}
12335 @kindex set trace-stop-notes
12336 Set the trace run's stop notes. The handling of the note is as for
12337 @code{tstop} arguments; the set command is convenient way to fix a
12338 stop note that is mistaken or incomplete.
12340 @item show trace-stop-notes
12341 @kindex show trace-stop-notes
12342 Show the trace run's stop notes.
12346 @node Tracepoint Restrictions
12347 @subsection Tracepoint Restrictions
12349 @cindex tracepoint restrictions
12350 There are a number of restrictions on the use of tracepoints. As
12351 described above, tracepoint data gathering occurs on the target
12352 without interaction from @value{GDBN}. Thus the full capabilities of
12353 the debugger are not available during data gathering, and then at data
12354 examination time, you will be limited by only having what was
12355 collected. The following items describe some common problems, but it
12356 is not exhaustive, and you may run into additional difficulties not
12362 Tracepoint expressions are intended to gather objects (lvalues). Thus
12363 the full flexibility of GDB's expression evaluator is not available.
12364 You cannot call functions, cast objects to aggregate types, access
12365 convenience variables or modify values (except by assignment to trace
12366 state variables). Some language features may implicitly call
12367 functions (for instance Objective-C fields with accessors), and therefore
12368 cannot be collected either.
12371 Collection of local variables, either individually or in bulk with
12372 @code{$locals} or @code{$args}, during @code{while-stepping} may
12373 behave erratically. The stepping action may enter a new scope (for
12374 instance by stepping into a function), or the location of the variable
12375 may change (for instance it is loaded into a register). The
12376 tracepoint data recorded uses the location information for the
12377 variables that is correct for the tracepoint location. When the
12378 tracepoint is created, it is not possible, in general, to determine
12379 where the steps of a @code{while-stepping} sequence will advance the
12380 program---particularly if a conditional branch is stepped.
12383 Collection of an incompletely-initialized or partially-destroyed object
12384 may result in something that @value{GDBN} cannot display, or displays
12385 in a misleading way.
12388 When @value{GDBN} displays a pointer to character it automatically
12389 dereferences the pointer to also display characters of the string
12390 being pointed to. However, collecting the pointer during tracing does
12391 not automatically collect the string. You need to explicitly
12392 dereference the pointer and provide size information if you want to
12393 collect not only the pointer, but the memory pointed to. For example,
12394 @code{*ptr@@50} can be used to collect the 50 element array pointed to
12398 It is not possible to collect a complete stack backtrace at a
12399 tracepoint. Instead, you may collect the registers and a few hundred
12400 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
12401 (adjust to use the name of the actual stack pointer register on your
12402 target architecture, and the amount of stack you wish to capture).
12403 Then the @code{backtrace} command will show a partial backtrace when
12404 using a trace frame. The number of stack frames that can be examined
12405 depends on the sizes of the frames in the collected stack. Note that
12406 if you ask for a block so large that it goes past the bottom of the
12407 stack, the target agent may report an error trying to read from an
12411 If you do not collect registers at a tracepoint, @value{GDBN} can
12412 infer that the value of @code{$pc} must be the same as the address of
12413 the tracepoint and use that when you are looking at a trace frame
12414 for that tracepoint. However, this cannot work if the tracepoint has
12415 multiple locations (for instance if it was set in a function that was
12416 inlined), or if it has a @code{while-stepping} loop. In those cases
12417 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
12422 @node Analyze Collected Data
12423 @section Using the Collected Data
12425 After the tracepoint experiment ends, you use @value{GDBN} commands
12426 for examining the trace data. The basic idea is that each tracepoint
12427 collects a trace @dfn{snapshot} every time it is hit and another
12428 snapshot every time it single-steps. All these snapshots are
12429 consecutively numbered from zero and go into a buffer, and you can
12430 examine them later. The way you examine them is to @dfn{focus} on a
12431 specific trace snapshot. When the remote stub is focused on a trace
12432 snapshot, it will respond to all @value{GDBN} requests for memory and
12433 registers by reading from the buffer which belongs to that snapshot,
12434 rather than from @emph{real} memory or registers of the program being
12435 debugged. This means that @strong{all} @value{GDBN} commands
12436 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
12437 behave as if we were currently debugging the program state as it was
12438 when the tracepoint occurred. Any requests for data that are not in
12439 the buffer will fail.
12442 * tfind:: How to select a trace snapshot
12443 * tdump:: How to display all data for a snapshot
12444 * save tracepoints:: How to save tracepoints for a future run
12448 @subsection @code{tfind @var{n}}
12451 @cindex select trace snapshot
12452 @cindex find trace snapshot
12453 The basic command for selecting a trace snapshot from the buffer is
12454 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
12455 counting from zero. If no argument @var{n} is given, the next
12456 snapshot is selected.
12458 Here are the various forms of using the @code{tfind} command.
12462 Find the first snapshot in the buffer. This is a synonym for
12463 @code{tfind 0} (since 0 is the number of the first snapshot).
12466 Stop debugging trace snapshots, resume @emph{live} debugging.
12469 Same as @samp{tfind none}.
12472 No argument means find the next trace snapshot.
12475 Find the previous trace snapshot before the current one. This permits
12476 retracing earlier steps.
12478 @item tfind tracepoint @var{num}
12479 Find the next snapshot associated with tracepoint @var{num}. Search
12480 proceeds forward from the last examined trace snapshot. If no
12481 argument @var{num} is given, it means find the next snapshot collected
12482 for the same tracepoint as the current snapshot.
12484 @item tfind pc @var{addr}
12485 Find the next snapshot associated with the value @var{addr} of the
12486 program counter. Search proceeds forward from the last examined trace
12487 snapshot. If no argument @var{addr} is given, it means find the next
12488 snapshot with the same value of PC as the current snapshot.
12490 @item tfind outside @var{addr1}, @var{addr2}
12491 Find the next snapshot whose PC is outside the given range of
12492 addresses (exclusive).
12494 @item tfind range @var{addr1}, @var{addr2}
12495 Find the next snapshot whose PC is between @var{addr1} and
12496 @var{addr2} (inclusive).
12498 @item tfind line @r{[}@var{file}:@r{]}@var{n}
12499 Find the next snapshot associated with the source line @var{n}. If
12500 the optional argument @var{file} is given, refer to line @var{n} in
12501 that source file. Search proceeds forward from the last examined
12502 trace snapshot. If no argument @var{n} is given, it means find the
12503 next line other than the one currently being examined; thus saying
12504 @code{tfind line} repeatedly can appear to have the same effect as
12505 stepping from line to line in a @emph{live} debugging session.
12508 The default arguments for the @code{tfind} commands are specifically
12509 designed to make it easy to scan through the trace buffer. For
12510 instance, @code{tfind} with no argument selects the next trace
12511 snapshot, and @code{tfind -} with no argument selects the previous
12512 trace snapshot. So, by giving one @code{tfind} command, and then
12513 simply hitting @key{RET} repeatedly you can examine all the trace
12514 snapshots in order. Or, by saying @code{tfind -} and then hitting
12515 @key{RET} repeatedly you can examine the snapshots in reverse order.
12516 The @code{tfind line} command with no argument selects the snapshot
12517 for the next source line executed. The @code{tfind pc} command with
12518 no argument selects the next snapshot with the same program counter
12519 (PC) as the current frame. The @code{tfind tracepoint} command with
12520 no argument selects the next trace snapshot collected by the same
12521 tracepoint as the current one.
12523 In addition to letting you scan through the trace buffer manually,
12524 these commands make it easy to construct @value{GDBN} scripts that
12525 scan through the trace buffer and print out whatever collected data
12526 you are interested in. Thus, if we want to examine the PC, FP, and SP
12527 registers from each trace frame in the buffer, we can say this:
12530 (@value{GDBP}) @b{tfind start}
12531 (@value{GDBP}) @b{while ($trace_frame != -1)}
12532 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
12533 $trace_frame, $pc, $sp, $fp
12537 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
12538 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
12539 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
12540 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
12541 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
12542 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
12543 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
12544 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
12545 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
12546 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
12547 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
12550 Or, if we want to examine the variable @code{X} at each source line in
12554 (@value{GDBP}) @b{tfind start}
12555 (@value{GDBP}) @b{while ($trace_frame != -1)}
12556 > printf "Frame %d, X == %d\n", $trace_frame, X
12566 @subsection @code{tdump}
12568 @cindex dump all data collected at tracepoint
12569 @cindex tracepoint data, display
12571 This command takes no arguments. It prints all the data collected at
12572 the current trace snapshot.
12575 (@value{GDBP}) @b{trace 444}
12576 (@value{GDBP}) @b{actions}
12577 Enter actions for tracepoint #2, one per line:
12578 > collect $regs, $locals, $args, gdb_long_test
12581 (@value{GDBP}) @b{tstart}
12583 (@value{GDBP}) @b{tfind line 444}
12584 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
12586 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
12588 (@value{GDBP}) @b{tdump}
12589 Data collected at tracepoint 2, trace frame 1:
12590 d0 0xc4aa0085 -995491707
12594 d4 0x71aea3d 119204413
12597 d7 0x380035 3670069
12598 a0 0x19e24a 1696330
12599 a1 0x3000668 50333288
12601 a3 0x322000 3284992
12602 a4 0x3000698 50333336
12603 a5 0x1ad3cc 1758156
12604 fp 0x30bf3c 0x30bf3c
12605 sp 0x30bf34 0x30bf34
12607 pc 0x20b2c8 0x20b2c8
12611 p = 0x20e5b4 "gdb-test"
12618 gdb_long_test = 17 '\021'
12623 @code{tdump} works by scanning the tracepoint's current collection
12624 actions and printing the value of each expression listed. So
12625 @code{tdump} can fail, if after a run, you change the tracepoint's
12626 actions to mention variables that were not collected during the run.
12628 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
12629 uses the collected value of @code{$pc} to distinguish between trace
12630 frames that were collected at the tracepoint hit, and frames that were
12631 collected while stepping. This allows it to correctly choose whether
12632 to display the basic list of collections, or the collections from the
12633 body of the while-stepping loop. However, if @code{$pc} was not collected,
12634 then @code{tdump} will always attempt to dump using the basic collection
12635 list, and may fail if a while-stepping frame does not include all the
12636 same data that is collected at the tracepoint hit.
12637 @c This is getting pretty arcane, example would be good.
12639 @node save tracepoints
12640 @subsection @code{save tracepoints @var{filename}}
12641 @kindex save tracepoints
12642 @kindex save-tracepoints
12643 @cindex save tracepoints for future sessions
12645 This command saves all current tracepoint definitions together with
12646 their actions and passcounts, into a file @file{@var{filename}}
12647 suitable for use in a later debugging session. To read the saved
12648 tracepoint definitions, use the @code{source} command (@pxref{Command
12649 Files}). The @w{@code{save-tracepoints}} command is a deprecated
12650 alias for @w{@code{save tracepoints}}
12652 @node Tracepoint Variables
12653 @section Convenience Variables for Tracepoints
12654 @cindex tracepoint variables
12655 @cindex convenience variables for tracepoints
12658 @vindex $trace_frame
12659 @item (int) $trace_frame
12660 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
12661 snapshot is selected.
12663 @vindex $tracepoint
12664 @item (int) $tracepoint
12665 The tracepoint for the current trace snapshot.
12667 @vindex $trace_line
12668 @item (int) $trace_line
12669 The line number for the current trace snapshot.
12671 @vindex $trace_file
12672 @item (char []) $trace_file
12673 The source file for the current trace snapshot.
12675 @vindex $trace_func
12676 @item (char []) $trace_func
12677 The name of the function containing @code{$tracepoint}.
12680 Note: @code{$trace_file} is not suitable for use in @code{printf},
12681 use @code{output} instead.
12683 Here's a simple example of using these convenience variables for
12684 stepping through all the trace snapshots and printing some of their
12685 data. Note that these are not the same as trace state variables,
12686 which are managed by the target.
12689 (@value{GDBP}) @b{tfind start}
12691 (@value{GDBP}) @b{while $trace_frame != -1}
12692 > output $trace_file
12693 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
12699 @section Using Trace Files
12700 @cindex trace files
12702 In some situations, the target running a trace experiment may no
12703 longer be available; perhaps it crashed, or the hardware was needed
12704 for a different activity. To handle these cases, you can arrange to
12705 dump the trace data into a file, and later use that file as a source
12706 of trace data, via the @code{target tfile} command.
12711 @item tsave [ -r ] @var{filename}
12712 @itemx tsave [-ctf] @var{dirname}
12713 Save the trace data to @var{filename}. By default, this command
12714 assumes that @var{filename} refers to the host filesystem, so if
12715 necessary @value{GDBN} will copy raw trace data up from the target and
12716 then save it. If the target supports it, you can also supply the
12717 optional argument @code{-r} (``remote'') to direct the target to save
12718 the data directly into @var{filename} in its own filesystem, which may be
12719 more efficient if the trace buffer is very large. (Note, however, that
12720 @code{target tfile} can only read from files accessible to the host.)
12721 By default, this command will save trace frame in tfile format.
12722 You can supply the optional argument @code{-ctf} to save date in CTF
12723 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
12724 that can be shared by multiple debugging and tracing tools. Please go to
12725 @indicateurl{http://www.efficios.com/ctf} to get more information.
12727 @kindex target tfile
12731 @item target tfile @var{filename}
12732 @itemx target ctf @var{dirname}
12733 Use the file named @var{filename} or directory named @var{dirname} as
12734 a source of trace data. Commands that examine data work as they do with
12735 a live target, but it is not possible to run any new trace experiments.
12736 @code{tstatus} will report the state of the trace run at the moment
12737 the data was saved, as well as the current trace frame you are examining.
12738 @var{filename} or @var{dirname} must be on a filesystem accessible to
12742 (@value{GDBP}) target ctf ctf.ctf
12743 (@value{GDBP}) tfind
12744 Found trace frame 0, tracepoint 2
12745 39 ++a; /* set tracepoint 1 here */
12746 (@value{GDBP}) tdump
12747 Data collected at tracepoint 2, trace frame 0:
12751 c = @{"123", "456", "789", "123", "456", "789"@}
12752 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
12760 @chapter Debugging Programs That Use Overlays
12763 If your program is too large to fit completely in your target system's
12764 memory, you can sometimes use @dfn{overlays} to work around this
12765 problem. @value{GDBN} provides some support for debugging programs that
12769 * How Overlays Work:: A general explanation of overlays.
12770 * Overlay Commands:: Managing overlays in @value{GDBN}.
12771 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
12772 mapped by asking the inferior.
12773 * Overlay Sample Program:: A sample program using overlays.
12776 @node How Overlays Work
12777 @section How Overlays Work
12778 @cindex mapped overlays
12779 @cindex unmapped overlays
12780 @cindex load address, overlay's
12781 @cindex mapped address
12782 @cindex overlay area
12784 Suppose you have a computer whose instruction address space is only 64
12785 kilobytes long, but which has much more memory which can be accessed by
12786 other means: special instructions, segment registers, or memory
12787 management hardware, for example. Suppose further that you want to
12788 adapt a program which is larger than 64 kilobytes to run on this system.
12790 One solution is to identify modules of your program which are relatively
12791 independent, and need not call each other directly; call these modules
12792 @dfn{overlays}. Separate the overlays from the main program, and place
12793 their machine code in the larger memory. Place your main program in
12794 instruction memory, but leave at least enough space there to hold the
12795 largest overlay as well.
12797 Now, to call a function located in an overlay, you must first copy that
12798 overlay's machine code from the large memory into the space set aside
12799 for it in the instruction memory, and then jump to its entry point
12802 @c NB: In the below the mapped area's size is greater or equal to the
12803 @c size of all overlays. This is intentional to remind the developer
12804 @c that overlays don't necessarily need to be the same size.
12808 Data Instruction Larger
12809 Address Space Address Space Address Space
12810 +-----------+ +-----------+ +-----------+
12812 +-----------+ +-----------+ +-----------+<-- overlay 1
12813 | program | | main | .----| overlay 1 | load address
12814 | variables | | program | | +-----------+
12815 | and heap | | | | | |
12816 +-----------+ | | | +-----------+<-- overlay 2
12817 | | +-----------+ | | | load address
12818 +-----------+ | | | .-| overlay 2 |
12820 mapped --->+-----------+ | | +-----------+
12821 address | | | | | |
12822 | overlay | <-' | | |
12823 | area | <---' +-----------+<-- overlay 3
12824 | | <---. | | load address
12825 +-----------+ `--| overlay 3 |
12832 @anchor{A code overlay}A code overlay
12836 The diagram (@pxref{A code overlay}) shows a system with separate data
12837 and instruction address spaces. To map an overlay, the program copies
12838 its code from the larger address space to the instruction address space.
12839 Since the overlays shown here all use the same mapped address, only one
12840 may be mapped at a time. For a system with a single address space for
12841 data and instructions, the diagram would be similar, except that the
12842 program variables and heap would share an address space with the main
12843 program and the overlay area.
12845 An overlay loaded into instruction memory and ready for use is called a
12846 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
12847 instruction memory. An overlay not present (or only partially present)
12848 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
12849 is its address in the larger memory. The mapped address is also called
12850 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
12851 called the @dfn{load memory address}, or @dfn{LMA}.
12853 Unfortunately, overlays are not a completely transparent way to adapt a
12854 program to limited instruction memory. They introduce a new set of
12855 global constraints you must keep in mind as you design your program:
12860 Before calling or returning to a function in an overlay, your program
12861 must make sure that overlay is actually mapped. Otherwise, the call or
12862 return will transfer control to the right address, but in the wrong
12863 overlay, and your program will probably crash.
12866 If the process of mapping an overlay is expensive on your system, you
12867 will need to choose your overlays carefully to minimize their effect on
12868 your program's performance.
12871 The executable file you load onto your system must contain each
12872 overlay's instructions, appearing at the overlay's load address, not its
12873 mapped address. However, each overlay's instructions must be relocated
12874 and its symbols defined as if the overlay were at its mapped address.
12875 You can use GNU linker scripts to specify different load and relocation
12876 addresses for pieces of your program; see @ref{Overlay Description,,,
12877 ld.info, Using ld: the GNU linker}.
12880 The procedure for loading executable files onto your system must be able
12881 to load their contents into the larger address space as well as the
12882 instruction and data spaces.
12886 The overlay system described above is rather simple, and could be
12887 improved in many ways:
12892 If your system has suitable bank switch registers or memory management
12893 hardware, you could use those facilities to make an overlay's load area
12894 contents simply appear at their mapped address in instruction space.
12895 This would probably be faster than copying the overlay to its mapped
12896 area in the usual way.
12899 If your overlays are small enough, you could set aside more than one
12900 overlay area, and have more than one overlay mapped at a time.
12903 You can use overlays to manage data, as well as instructions. In
12904 general, data overlays are even less transparent to your design than
12905 code overlays: whereas code overlays only require care when you call or
12906 return to functions, data overlays require care every time you access
12907 the data. Also, if you change the contents of a data overlay, you
12908 must copy its contents back out to its load address before you can copy a
12909 different data overlay into the same mapped area.
12914 @node Overlay Commands
12915 @section Overlay Commands
12917 To use @value{GDBN}'s overlay support, each overlay in your program must
12918 correspond to a separate section of the executable file. The section's
12919 virtual memory address and load memory address must be the overlay's
12920 mapped and load addresses. Identifying overlays with sections allows
12921 @value{GDBN} to determine the appropriate address of a function or
12922 variable, depending on whether the overlay is mapped or not.
12924 @value{GDBN}'s overlay commands all start with the word @code{overlay};
12925 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
12930 Disable @value{GDBN}'s overlay support. When overlay support is
12931 disabled, @value{GDBN} assumes that all functions and variables are
12932 always present at their mapped addresses. By default, @value{GDBN}'s
12933 overlay support is disabled.
12935 @item overlay manual
12936 @cindex manual overlay debugging
12937 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
12938 relies on you to tell it which overlays are mapped, and which are not,
12939 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
12940 commands described below.
12942 @item overlay map-overlay @var{overlay}
12943 @itemx overlay map @var{overlay}
12944 @cindex map an overlay
12945 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
12946 be the name of the object file section containing the overlay. When an
12947 overlay is mapped, @value{GDBN} assumes it can find the overlay's
12948 functions and variables at their mapped addresses. @value{GDBN} assumes
12949 that any other overlays whose mapped ranges overlap that of
12950 @var{overlay} are now unmapped.
12952 @item overlay unmap-overlay @var{overlay}
12953 @itemx overlay unmap @var{overlay}
12954 @cindex unmap an overlay
12955 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
12956 must be the name of the object file section containing the overlay.
12957 When an overlay is unmapped, @value{GDBN} assumes it can find the
12958 overlay's functions and variables at their load addresses.
12961 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
12962 consults a data structure the overlay manager maintains in the inferior
12963 to see which overlays are mapped. For details, see @ref{Automatic
12964 Overlay Debugging}.
12966 @item overlay load-target
12967 @itemx overlay load
12968 @cindex reloading the overlay table
12969 Re-read the overlay table from the inferior. Normally, @value{GDBN}
12970 re-reads the table @value{GDBN} automatically each time the inferior
12971 stops, so this command should only be necessary if you have changed the
12972 overlay mapping yourself using @value{GDBN}. This command is only
12973 useful when using automatic overlay debugging.
12975 @item overlay list-overlays
12976 @itemx overlay list
12977 @cindex listing mapped overlays
12978 Display a list of the overlays currently mapped, along with their mapped
12979 addresses, load addresses, and sizes.
12983 Normally, when @value{GDBN} prints a code address, it includes the name
12984 of the function the address falls in:
12987 (@value{GDBP}) print main
12988 $3 = @{int ()@} 0x11a0 <main>
12991 When overlay debugging is enabled, @value{GDBN} recognizes code in
12992 unmapped overlays, and prints the names of unmapped functions with
12993 asterisks around them. For example, if @code{foo} is a function in an
12994 unmapped overlay, @value{GDBN} prints it this way:
12997 (@value{GDBP}) overlay list
12998 No sections are mapped.
12999 (@value{GDBP}) print foo
13000 $5 = @{int (int)@} 0x100000 <*foo*>
13003 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13007 (@value{GDBP}) overlay list
13008 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13009 mapped at 0x1016 - 0x104a
13010 (@value{GDBP}) print foo
13011 $6 = @{int (int)@} 0x1016 <foo>
13014 When overlay debugging is enabled, @value{GDBN} can find the correct
13015 address for functions and variables in an overlay, whether or not the
13016 overlay is mapped. This allows most @value{GDBN} commands, like
13017 @code{break} and @code{disassemble}, to work normally, even on unmapped
13018 code. However, @value{GDBN}'s breakpoint support has some limitations:
13022 @cindex breakpoints in overlays
13023 @cindex overlays, setting breakpoints in
13024 You can set breakpoints in functions in unmapped overlays, as long as
13025 @value{GDBN} can write to the overlay at its load address.
13027 @value{GDBN} can not set hardware or simulator-based breakpoints in
13028 unmapped overlays. However, if you set a breakpoint at the end of your
13029 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13030 you are using manual overlay management), @value{GDBN} will re-set its
13031 breakpoints properly.
13035 @node Automatic Overlay Debugging
13036 @section Automatic Overlay Debugging
13037 @cindex automatic overlay debugging
13039 @value{GDBN} can automatically track which overlays are mapped and which
13040 are not, given some simple co-operation from the overlay manager in the
13041 inferior. If you enable automatic overlay debugging with the
13042 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
13043 looks in the inferior's memory for certain variables describing the
13044 current state of the overlays.
13046 Here are the variables your overlay manager must define to support
13047 @value{GDBN}'s automatic overlay debugging:
13051 @item @code{_ovly_table}:
13052 This variable must be an array of the following structures:
13057 /* The overlay's mapped address. */
13060 /* The size of the overlay, in bytes. */
13061 unsigned long size;
13063 /* The overlay's load address. */
13066 /* Non-zero if the overlay is currently mapped;
13068 unsigned long mapped;
13072 @item @code{_novlys}:
13073 This variable must be a four-byte signed integer, holding the total
13074 number of elements in @code{_ovly_table}.
13078 To decide whether a particular overlay is mapped or not, @value{GDBN}
13079 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
13080 @code{lma} members equal the VMA and LMA of the overlay's section in the
13081 executable file. When @value{GDBN} finds a matching entry, it consults
13082 the entry's @code{mapped} member to determine whether the overlay is
13085 In addition, your overlay manager may define a function called
13086 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
13087 will silently set a breakpoint there. If the overlay manager then
13088 calls this function whenever it has changed the overlay table, this
13089 will enable @value{GDBN} to accurately keep track of which overlays
13090 are in program memory, and update any breakpoints that may be set
13091 in overlays. This will allow breakpoints to work even if the
13092 overlays are kept in ROM or other non-writable memory while they
13093 are not being executed.
13095 @node Overlay Sample Program
13096 @section Overlay Sample Program
13097 @cindex overlay example program
13099 When linking a program which uses overlays, you must place the overlays
13100 at their load addresses, while relocating them to run at their mapped
13101 addresses. To do this, you must write a linker script (@pxref{Overlay
13102 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
13103 since linker scripts are specific to a particular host system, target
13104 architecture, and target memory layout, this manual cannot provide
13105 portable sample code demonstrating @value{GDBN}'s overlay support.
13107 However, the @value{GDBN} source distribution does contain an overlaid
13108 program, with linker scripts for a few systems, as part of its test
13109 suite. The program consists of the following files from
13110 @file{gdb/testsuite/gdb.base}:
13114 The main program file.
13116 A simple overlay manager, used by @file{overlays.c}.
13121 Overlay modules, loaded and used by @file{overlays.c}.
13124 Linker scripts for linking the test program on the @code{d10v-elf}
13125 and @code{m32r-elf} targets.
13128 You can build the test program using the @code{d10v-elf} GCC
13129 cross-compiler like this:
13132 $ d10v-elf-gcc -g -c overlays.c
13133 $ d10v-elf-gcc -g -c ovlymgr.c
13134 $ d10v-elf-gcc -g -c foo.c
13135 $ d10v-elf-gcc -g -c bar.c
13136 $ d10v-elf-gcc -g -c baz.c
13137 $ d10v-elf-gcc -g -c grbx.c
13138 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
13139 baz.o grbx.o -Wl,-Td10v.ld -o overlays
13142 The build process is identical for any other architecture, except that
13143 you must substitute the appropriate compiler and linker script for the
13144 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
13148 @chapter Using @value{GDBN} with Different Languages
13151 Although programming languages generally have common aspects, they are
13152 rarely expressed in the same manner. For instance, in ANSI C,
13153 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
13154 Modula-2, it is accomplished by @code{p^}. Values can also be
13155 represented (and displayed) differently. Hex numbers in C appear as
13156 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
13158 @cindex working language
13159 Language-specific information is built into @value{GDBN} for some languages,
13160 allowing you to express operations like the above in your program's
13161 native language, and allowing @value{GDBN} to output values in a manner
13162 consistent with the syntax of your program's native language. The
13163 language you use to build expressions is called the @dfn{working
13167 * Setting:: Switching between source languages
13168 * Show:: Displaying the language
13169 * Checks:: Type and range checks
13170 * Supported Languages:: Supported languages
13171 * Unsupported Languages:: Unsupported languages
13175 @section Switching Between Source Languages
13177 There are two ways to control the working language---either have @value{GDBN}
13178 set it automatically, or select it manually yourself. You can use the
13179 @code{set language} command for either purpose. On startup, @value{GDBN}
13180 defaults to setting the language automatically. The working language is
13181 used to determine how expressions you type are interpreted, how values
13184 In addition to the working language, every source file that
13185 @value{GDBN} knows about has its own working language. For some object
13186 file formats, the compiler might indicate which language a particular
13187 source file is in. However, most of the time @value{GDBN} infers the
13188 language from the name of the file. The language of a source file
13189 controls whether C@t{++} names are demangled---this way @code{backtrace} can
13190 show each frame appropriately for its own language. There is no way to
13191 set the language of a source file from within @value{GDBN}, but you can
13192 set the language associated with a filename extension. @xref{Show, ,
13193 Displaying the Language}.
13195 This is most commonly a problem when you use a program, such
13196 as @code{cfront} or @code{f2c}, that generates C but is written in
13197 another language. In that case, make the
13198 program use @code{#line} directives in its C output; that way
13199 @value{GDBN} will know the correct language of the source code of the original
13200 program, and will display that source code, not the generated C code.
13203 * Filenames:: Filename extensions and languages.
13204 * Manually:: Setting the working language manually
13205 * Automatically:: Having @value{GDBN} infer the source language
13209 @subsection List of Filename Extensions and Languages
13211 If a source file name ends in one of the following extensions, then
13212 @value{GDBN} infers that its language is the one indicated.
13230 C@t{++} source file
13236 Objective-C source file
13240 Fortran source file
13243 Modula-2 source file
13247 Assembler source file. This actually behaves almost like C, but
13248 @value{GDBN} does not skip over function prologues when stepping.
13251 In addition, you may set the language associated with a filename
13252 extension. @xref{Show, , Displaying the Language}.
13255 @subsection Setting the Working Language
13257 If you allow @value{GDBN} to set the language automatically,
13258 expressions are interpreted the same way in your debugging session and
13261 @kindex set language
13262 If you wish, you may set the language manually. To do this, issue the
13263 command @samp{set language @var{lang}}, where @var{lang} is the name of
13264 a language, such as
13265 @code{c} or @code{modula-2}.
13266 For a list of the supported languages, type @samp{set language}.
13268 Setting the language manually prevents @value{GDBN} from updating the working
13269 language automatically. This can lead to confusion if you try
13270 to debug a program when the working language is not the same as the
13271 source language, when an expression is acceptable to both
13272 languages---but means different things. For instance, if the current
13273 source file were written in C, and @value{GDBN} was parsing Modula-2, a
13281 might not have the effect you intended. In C, this means to add
13282 @code{b} and @code{c} and place the result in @code{a}. The result
13283 printed would be the value of @code{a}. In Modula-2, this means to compare
13284 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
13286 @node Automatically
13287 @subsection Having @value{GDBN} Infer the Source Language
13289 To have @value{GDBN} set the working language automatically, use
13290 @samp{set language local} or @samp{set language auto}. @value{GDBN}
13291 then infers the working language. That is, when your program stops in a
13292 frame (usually by encountering a breakpoint), @value{GDBN} sets the
13293 working language to the language recorded for the function in that
13294 frame. If the language for a frame is unknown (that is, if the function
13295 or block corresponding to the frame was defined in a source file that
13296 does not have a recognized extension), the current working language is
13297 not changed, and @value{GDBN} issues a warning.
13299 This may not seem necessary for most programs, which are written
13300 entirely in one source language. However, program modules and libraries
13301 written in one source language can be used by a main program written in
13302 a different source language. Using @samp{set language auto} in this
13303 case frees you from having to set the working language manually.
13306 @section Displaying the Language
13308 The following commands help you find out which language is the
13309 working language, and also what language source files were written in.
13312 @item show language
13313 @kindex show language
13314 Display the current working language. This is the
13315 language you can use with commands such as @code{print} to
13316 build and compute expressions that may involve variables in your program.
13319 @kindex info frame@r{, show the source language}
13320 Display the source language for this frame. This language becomes the
13321 working language if you use an identifier from this frame.
13322 @xref{Frame Info, ,Information about a Frame}, to identify the other
13323 information listed here.
13326 @kindex info source@r{, show the source language}
13327 Display the source language of this source file.
13328 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
13329 information listed here.
13332 In unusual circumstances, you may have source files with extensions
13333 not in the standard list. You can then set the extension associated
13334 with a language explicitly:
13337 @item set extension-language @var{ext} @var{language}
13338 @kindex set extension-language
13339 Tell @value{GDBN} that source files with extension @var{ext} are to be
13340 assumed as written in the source language @var{language}.
13342 @item info extensions
13343 @kindex info extensions
13344 List all the filename extensions and the associated languages.
13348 @section Type and Range Checking
13350 Some languages are designed to guard you against making seemingly common
13351 errors through a series of compile- and run-time checks. These include
13352 checking the type of arguments to functions and operators and making
13353 sure mathematical overflows are caught at run time. Checks such as
13354 these help to ensure a program's correctness once it has been compiled
13355 by eliminating type mismatches and providing active checks for range
13356 errors when your program is running.
13358 By default @value{GDBN} checks for these errors according to the
13359 rules of the current source language. Although @value{GDBN} does not check
13360 the statements in your program, it can check expressions entered directly
13361 into @value{GDBN} for evaluation via the @code{print} command, for example.
13364 * Type Checking:: An overview of type checking
13365 * Range Checking:: An overview of range checking
13368 @cindex type checking
13369 @cindex checks, type
13370 @node Type Checking
13371 @subsection An Overview of Type Checking
13373 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
13374 arguments to operators and functions have to be of the correct type,
13375 otherwise an error occurs. These checks prevent type mismatch
13376 errors from ever causing any run-time problems. For example,
13379 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
13381 (@value{GDBP}) print obj.my_method (0)
13384 (@value{GDBP}) print obj.my_method (0x1234)
13385 Cannot resolve method klass::my_method to any overloaded instance
13388 The second example fails because in C@t{++} the integer constant
13389 @samp{0x1234} is not type-compatible with the pointer parameter type.
13391 For the expressions you use in @value{GDBN} commands, you can tell
13392 @value{GDBN} to not enforce strict type checking or
13393 to treat any mismatches as errors and abandon the expression;
13394 When type checking is disabled, @value{GDBN} successfully evaluates
13395 expressions like the second example above.
13397 Even if type checking is off, there may be other reasons
13398 related to type that prevent @value{GDBN} from evaluating an expression.
13399 For instance, @value{GDBN} does not know how to add an @code{int} and
13400 a @code{struct foo}. These particular type errors have nothing to do
13401 with the language in use and usually arise from expressions which make
13402 little sense to evaluate anyway.
13404 @value{GDBN} provides some additional commands for controlling type checking:
13406 @kindex set check type
13407 @kindex show check type
13409 @item set check type on
13410 @itemx set check type off
13411 Set strict type checking on or off. If any type mismatches occur in
13412 evaluating an expression while type checking is on, @value{GDBN} prints a
13413 message and aborts evaluation of the expression.
13415 @item show check type
13416 Show the current setting of type checking and whether @value{GDBN}
13417 is enforcing strict type checking rules.
13420 @cindex range checking
13421 @cindex checks, range
13422 @node Range Checking
13423 @subsection An Overview of Range Checking
13425 In some languages (such as Modula-2), it is an error to exceed the
13426 bounds of a type; this is enforced with run-time checks. Such range
13427 checking is meant to ensure program correctness by making sure
13428 computations do not overflow, or indices on an array element access do
13429 not exceed the bounds of the array.
13431 For expressions you use in @value{GDBN} commands, you can tell
13432 @value{GDBN} to treat range errors in one of three ways: ignore them,
13433 always treat them as errors and abandon the expression, or issue
13434 warnings but evaluate the expression anyway.
13436 A range error can result from numerical overflow, from exceeding an
13437 array index bound, or when you type a constant that is not a member
13438 of any type. Some languages, however, do not treat overflows as an
13439 error. In many implementations of C, mathematical overflow causes the
13440 result to ``wrap around'' to lower values---for example, if @var{m} is
13441 the largest integer value, and @var{s} is the smallest, then
13444 @var{m} + 1 @result{} @var{s}
13447 This, too, is specific to individual languages, and in some cases
13448 specific to individual compilers or machines. @xref{Supported Languages, ,
13449 Supported Languages}, for further details on specific languages.
13451 @value{GDBN} provides some additional commands for controlling the range checker:
13453 @kindex set check range
13454 @kindex show check range
13456 @item set check range auto
13457 Set range checking on or off based on the current working language.
13458 @xref{Supported Languages, ,Supported Languages}, for the default settings for
13461 @item set check range on
13462 @itemx set check range off
13463 Set range checking on or off, overriding the default setting for the
13464 current working language. A warning is issued if the setting does not
13465 match the language default. If a range error occurs and range checking is on,
13466 then a message is printed and evaluation of the expression is aborted.
13468 @item set check range warn
13469 Output messages when the @value{GDBN} range checker detects a range error,
13470 but attempt to evaluate the expression anyway. Evaluating the
13471 expression may still be impossible for other reasons, such as accessing
13472 memory that the process does not own (a typical example from many Unix
13476 Show the current setting of the range checker, and whether or not it is
13477 being set automatically by @value{GDBN}.
13480 @node Supported Languages
13481 @section Supported Languages
13483 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
13484 OpenCL C, Pascal, assembly, Modula-2, and Ada.
13485 @c This is false ...
13486 Some @value{GDBN} features may be used in expressions regardless of the
13487 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
13488 and the @samp{@{type@}addr} construct (@pxref{Expressions,
13489 ,Expressions}) can be used with the constructs of any supported
13492 The following sections detail to what degree each source language is
13493 supported by @value{GDBN}. These sections are not meant to be language
13494 tutorials or references, but serve only as a reference guide to what the
13495 @value{GDBN} expression parser accepts, and what input and output
13496 formats should look like for different languages. There are many good
13497 books written on each of these languages; please look to these for a
13498 language reference or tutorial.
13501 * C:: C and C@t{++}
13504 * Objective-C:: Objective-C
13505 * OpenCL C:: OpenCL C
13506 * Fortran:: Fortran
13508 * Modula-2:: Modula-2
13513 @subsection C and C@t{++}
13515 @cindex C and C@t{++}
13516 @cindex expressions in C or C@t{++}
13518 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
13519 to both languages. Whenever this is the case, we discuss those languages
13523 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
13524 @cindex @sc{gnu} C@t{++}
13525 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
13526 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
13527 effectively, you must compile your C@t{++} programs with a supported
13528 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
13529 compiler (@code{aCC}).
13532 * C Operators:: C and C@t{++} operators
13533 * C Constants:: C and C@t{++} constants
13534 * C Plus Plus Expressions:: C@t{++} expressions
13535 * C Defaults:: Default settings for C and C@t{++}
13536 * C Checks:: C and C@t{++} type and range checks
13537 * Debugging C:: @value{GDBN} and C
13538 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
13539 * Decimal Floating Point:: Numbers in Decimal Floating Point format
13543 @subsubsection C and C@t{++} Operators
13545 @cindex C and C@t{++} operators
13547 Operators must be defined on values of specific types. For instance,
13548 @code{+} is defined on numbers, but not on structures. Operators are
13549 often defined on groups of types.
13551 For the purposes of C and C@t{++}, the following definitions hold:
13556 @emph{Integral types} include @code{int} with any of its storage-class
13557 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
13560 @emph{Floating-point types} include @code{float}, @code{double}, and
13561 @code{long double} (if supported by the target platform).
13564 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
13567 @emph{Scalar types} include all of the above.
13572 The following operators are supported. They are listed here
13573 in order of increasing precedence:
13577 The comma or sequencing operator. Expressions in a comma-separated list
13578 are evaluated from left to right, with the result of the entire
13579 expression being the last expression evaluated.
13582 Assignment. The value of an assignment expression is the value
13583 assigned. Defined on scalar types.
13586 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
13587 and translated to @w{@code{@var{a} = @var{a op b}}}.
13588 @w{@code{@var{op}=}} and @code{=} have the same precedence.
13589 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
13590 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
13593 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
13594 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
13598 Logical @sc{or}. Defined on integral types.
13601 Logical @sc{and}. Defined on integral types.
13604 Bitwise @sc{or}. Defined on integral types.
13607 Bitwise exclusive-@sc{or}. Defined on integral types.
13610 Bitwise @sc{and}. Defined on integral types.
13613 Equality and inequality. Defined on scalar types. The value of these
13614 expressions is 0 for false and non-zero for true.
13616 @item <@r{, }>@r{, }<=@r{, }>=
13617 Less than, greater than, less than or equal, greater than or equal.
13618 Defined on scalar types. The value of these expressions is 0 for false
13619 and non-zero for true.
13622 left shift, and right shift. Defined on integral types.
13625 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13628 Addition and subtraction. Defined on integral types, floating-point types and
13631 @item *@r{, }/@r{, }%
13632 Multiplication, division, and modulus. Multiplication and division are
13633 defined on integral and floating-point types. Modulus is defined on
13637 Increment and decrement. When appearing before a variable, the
13638 operation is performed before the variable is used in an expression;
13639 when appearing after it, the variable's value is used before the
13640 operation takes place.
13643 Pointer dereferencing. Defined on pointer types. Same precedence as
13647 Address operator. Defined on variables. Same precedence as @code{++}.
13649 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
13650 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
13651 to examine the address
13652 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
13656 Negative. Defined on integral and floating-point types. Same
13657 precedence as @code{++}.
13660 Logical negation. Defined on integral types. Same precedence as
13664 Bitwise complement operator. Defined on integral types. Same precedence as
13669 Structure member, and pointer-to-structure member. For convenience,
13670 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
13671 pointer based on the stored type information.
13672 Defined on @code{struct} and @code{union} data.
13675 Dereferences of pointers to members.
13678 Array indexing. @code{@var{a}[@var{i}]} is defined as
13679 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
13682 Function parameter list. Same precedence as @code{->}.
13685 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
13686 and @code{class} types.
13689 Doubled colons also represent the @value{GDBN} scope operator
13690 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
13694 If an operator is redefined in the user code, @value{GDBN} usually
13695 attempts to invoke the redefined version instead of using the operator's
13696 predefined meaning.
13699 @subsubsection C and C@t{++} Constants
13701 @cindex C and C@t{++} constants
13703 @value{GDBN} allows you to express the constants of C and C@t{++} in the
13708 Integer constants are a sequence of digits. Octal constants are
13709 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
13710 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
13711 @samp{l}, specifying that the constant should be treated as a
13715 Floating point constants are a sequence of digits, followed by a decimal
13716 point, followed by a sequence of digits, and optionally followed by an
13717 exponent. An exponent is of the form:
13718 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
13719 sequence of digits. The @samp{+} is optional for positive exponents.
13720 A floating-point constant may also end with a letter @samp{f} or
13721 @samp{F}, specifying that the constant should be treated as being of
13722 the @code{float} (as opposed to the default @code{double}) type; or with
13723 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
13727 Enumerated constants consist of enumerated identifiers, or their
13728 integral equivalents.
13731 Character constants are a single character surrounded by single quotes
13732 (@code{'}), or a number---the ordinal value of the corresponding character
13733 (usually its @sc{ascii} value). Within quotes, the single character may
13734 be represented by a letter or by @dfn{escape sequences}, which are of
13735 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
13736 of the character's ordinal value; or of the form @samp{\@var{x}}, where
13737 @samp{@var{x}} is a predefined special character---for example,
13738 @samp{\n} for newline.
13740 Wide character constants can be written by prefixing a character
13741 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
13742 form of @samp{x}. The target wide character set is used when
13743 computing the value of this constant (@pxref{Character Sets}).
13746 String constants are a sequence of character constants surrounded by
13747 double quotes (@code{"}). Any valid character constant (as described
13748 above) may appear. Double quotes within the string must be preceded by
13749 a backslash, so for instance @samp{"a\"b'c"} is a string of five
13752 Wide string constants can be written by prefixing a string constant
13753 with @samp{L}, as in C. The target wide character set is used when
13754 computing the value of this constant (@pxref{Character Sets}).
13757 Pointer constants are an integral value. You can also write pointers
13758 to constants using the C operator @samp{&}.
13761 Array constants are comma-separated lists surrounded by braces @samp{@{}
13762 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
13763 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
13764 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
13767 @node C Plus Plus Expressions
13768 @subsubsection C@t{++} Expressions
13770 @cindex expressions in C@t{++}
13771 @value{GDBN} expression handling can interpret most C@t{++} expressions.
13773 @cindex debugging C@t{++} programs
13774 @cindex C@t{++} compilers
13775 @cindex debug formats and C@t{++}
13776 @cindex @value{NGCC} and C@t{++}
13778 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
13779 the proper compiler and the proper debug format. Currently,
13780 @value{GDBN} works best when debugging C@t{++} code that is compiled
13781 with the most recent version of @value{NGCC} possible. The DWARF
13782 debugging format is preferred; @value{NGCC} defaults to this on most
13783 popular platforms. Other compilers and/or debug formats are likely to
13784 work badly or not at all when using @value{GDBN} to debug C@t{++}
13785 code. @xref{Compilation}.
13790 @cindex member functions
13792 Member function calls are allowed; you can use expressions like
13795 count = aml->GetOriginal(x, y)
13798 @vindex this@r{, inside C@t{++} member functions}
13799 @cindex namespace in C@t{++}
13801 While a member function is active (in the selected stack frame), your
13802 expressions have the same namespace available as the member function;
13803 that is, @value{GDBN} allows implicit references to the class instance
13804 pointer @code{this} following the same rules as C@t{++}. @code{using}
13805 declarations in the current scope are also respected by @value{GDBN}.
13807 @cindex call overloaded functions
13808 @cindex overloaded functions, calling
13809 @cindex type conversions in C@t{++}
13811 You can call overloaded functions; @value{GDBN} resolves the function
13812 call to the right definition, with some restrictions. @value{GDBN} does not
13813 perform overload resolution involving user-defined type conversions,
13814 calls to constructors, or instantiations of templates that do not exist
13815 in the program. It also cannot handle ellipsis argument lists or
13818 It does perform integral conversions and promotions, floating-point
13819 promotions, arithmetic conversions, pointer conversions, conversions of
13820 class objects to base classes, and standard conversions such as those of
13821 functions or arrays to pointers; it requires an exact match on the
13822 number of function arguments.
13824 Overload resolution is always performed, unless you have specified
13825 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
13826 ,@value{GDBN} Features for C@t{++}}.
13828 You must specify @code{set overload-resolution off} in order to use an
13829 explicit function signature to call an overloaded function, as in
13831 p 'foo(char,int)'('x', 13)
13834 The @value{GDBN} command-completion facility can simplify this;
13835 see @ref{Completion, ,Command Completion}.
13837 @cindex reference declarations
13839 @value{GDBN} understands variables declared as C@t{++} references; you can use
13840 them in expressions just as you do in C@t{++} source---they are automatically
13843 In the parameter list shown when @value{GDBN} displays a frame, the values of
13844 reference variables are not displayed (unlike other variables); this
13845 avoids clutter, since references are often used for large structures.
13846 The @emph{address} of a reference variable is always shown, unless
13847 you have specified @samp{set print address off}.
13850 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
13851 expressions can use it just as expressions in your program do. Since
13852 one scope may be defined in another, you can use @code{::} repeatedly if
13853 necessary, for example in an expression like
13854 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
13855 resolving name scope by reference to source files, in both C and C@t{++}
13856 debugging (@pxref{Variables, ,Program Variables}).
13859 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
13864 @subsubsection C and C@t{++} Defaults
13866 @cindex C and C@t{++} defaults
13868 If you allow @value{GDBN} to set range checking automatically, it
13869 defaults to @code{off} whenever the working language changes to
13870 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
13871 selects the working language.
13873 If you allow @value{GDBN} to set the language automatically, it
13874 recognizes source files whose names end with @file{.c}, @file{.C}, or
13875 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
13876 these files, it sets the working language to C or C@t{++}.
13877 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
13878 for further details.
13881 @subsubsection C and C@t{++} Type and Range Checks
13883 @cindex C and C@t{++} checks
13885 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
13886 checking is used. However, if you turn type checking off, @value{GDBN}
13887 will allow certain non-standard conversions, such as promoting integer
13888 constants to pointers.
13890 Range checking, if turned on, is done on mathematical operations. Array
13891 indices are not checked, since they are often used to index a pointer
13892 that is not itself an array.
13895 @subsubsection @value{GDBN} and C
13897 The @code{set print union} and @code{show print union} commands apply to
13898 the @code{union} type. When set to @samp{on}, any @code{union} that is
13899 inside a @code{struct} or @code{class} is also printed. Otherwise, it
13900 appears as @samp{@{...@}}.
13902 The @code{@@} operator aids in the debugging of dynamic arrays, formed
13903 with pointers and a memory allocation function. @xref{Expressions,
13906 @node Debugging C Plus Plus
13907 @subsubsection @value{GDBN} Features for C@t{++}
13909 @cindex commands for C@t{++}
13911 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
13912 designed specifically for use with C@t{++}. Here is a summary:
13915 @cindex break in overloaded functions
13916 @item @r{breakpoint menus}
13917 When you want a breakpoint in a function whose name is overloaded,
13918 @value{GDBN} has the capability to display a menu of possible breakpoint
13919 locations to help you specify which function definition you want.
13920 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
13922 @cindex overloading in C@t{++}
13923 @item rbreak @var{regex}
13924 Setting breakpoints using regular expressions is helpful for setting
13925 breakpoints on overloaded functions that are not members of any special
13927 @xref{Set Breaks, ,Setting Breakpoints}.
13929 @cindex C@t{++} exception handling
13931 @itemx catch rethrow
13933 Debug C@t{++} exception handling using these commands. @xref{Set
13934 Catchpoints, , Setting Catchpoints}.
13936 @cindex inheritance
13937 @item ptype @var{typename}
13938 Print inheritance relationships as well as other information for type
13940 @xref{Symbols, ,Examining the Symbol Table}.
13942 @item info vtbl @var{expression}.
13943 The @code{info vtbl} command can be used to display the virtual
13944 method tables of the object computed by @var{expression}. This shows
13945 one entry per virtual table; there may be multiple virtual tables when
13946 multiple inheritance is in use.
13948 @cindex C@t{++} symbol display
13949 @item set print demangle
13950 @itemx show print demangle
13951 @itemx set print asm-demangle
13952 @itemx show print asm-demangle
13953 Control whether C@t{++} symbols display in their source form, both when
13954 displaying code as C@t{++} source and when displaying disassemblies.
13955 @xref{Print Settings, ,Print Settings}.
13957 @item set print object
13958 @itemx show print object
13959 Choose whether to print derived (actual) or declared types of objects.
13960 @xref{Print Settings, ,Print Settings}.
13962 @item set print vtbl
13963 @itemx show print vtbl
13964 Control the format for printing virtual function tables.
13965 @xref{Print Settings, ,Print Settings}.
13966 (The @code{vtbl} commands do not work on programs compiled with the HP
13967 ANSI C@t{++} compiler (@code{aCC}).)
13969 @kindex set overload-resolution
13970 @cindex overloaded functions, overload resolution
13971 @item set overload-resolution on
13972 Enable overload resolution for C@t{++} expression evaluation. The default
13973 is on. For overloaded functions, @value{GDBN} evaluates the arguments
13974 and searches for a function whose signature matches the argument types,
13975 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
13976 Expressions, ,C@t{++} Expressions}, for details).
13977 If it cannot find a match, it emits a message.
13979 @item set overload-resolution off
13980 Disable overload resolution for C@t{++} expression evaluation. For
13981 overloaded functions that are not class member functions, @value{GDBN}
13982 chooses the first function of the specified name that it finds in the
13983 symbol table, whether or not its arguments are of the correct type. For
13984 overloaded functions that are class member functions, @value{GDBN}
13985 searches for a function whose signature @emph{exactly} matches the
13988 @kindex show overload-resolution
13989 @item show overload-resolution
13990 Show the current setting of overload resolution.
13992 @item @r{Overloaded symbol names}
13993 You can specify a particular definition of an overloaded symbol, using
13994 the same notation that is used to declare such symbols in C@t{++}: type
13995 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
13996 also use the @value{GDBN} command-line word completion facilities to list the
13997 available choices, or to finish the type list for you.
13998 @xref{Completion,, Command Completion}, for details on how to do this.
14001 @node Decimal Floating Point
14002 @subsubsection Decimal Floating Point format
14003 @cindex decimal floating point format
14005 @value{GDBN} can examine, set and perform computations with numbers in
14006 decimal floating point format, which in the C language correspond to the
14007 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14008 specified by the extension to support decimal floating-point arithmetic.
14010 There are two encodings in use, depending on the architecture: BID (Binary
14011 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14012 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14015 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14016 to manipulate decimal floating point numbers, it is not possible to convert
14017 (using a cast, for example) integers wider than 32-bit to decimal float.
14019 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14020 point computations, error checking in decimal float operations ignores
14021 underflow, overflow and divide by zero exceptions.
14023 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14024 to inspect @code{_Decimal128} values stored in floating point registers.
14025 See @ref{PowerPC,,PowerPC} for more details.
14031 @value{GDBN} can be used to debug programs written in D and compiled with
14032 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
14033 specific feature --- dynamic arrays.
14038 @cindex Go (programming language)
14039 @value{GDBN} can be used to debug programs written in Go and compiled with
14040 @file{gccgo} or @file{6g} compilers.
14042 Here is a summary of the Go-specific features and restrictions:
14045 @cindex current Go package
14046 @item The current Go package
14047 The name of the current package does not need to be specified when
14048 specifying global variables and functions.
14050 For example, given the program:
14054 var myglob = "Shall we?"
14060 When stopped inside @code{main} either of these work:
14064 (gdb) p main.myglob
14067 @cindex builtin Go types
14068 @item Builtin Go types
14069 The @code{string} type is recognized by @value{GDBN} and is printed
14072 @cindex builtin Go functions
14073 @item Builtin Go functions
14074 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
14075 function and handles it internally.
14077 @cindex restrictions on Go expressions
14078 @item Restrictions on Go expressions
14079 All Go operators are supported except @code{&^}.
14080 The Go @code{_} ``blank identifier'' is not supported.
14081 Automatic dereferencing of pointers is not supported.
14085 @subsection Objective-C
14087 @cindex Objective-C
14088 This section provides information about some commands and command
14089 options that are useful for debugging Objective-C code. See also
14090 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
14091 few more commands specific to Objective-C support.
14094 * Method Names in Commands::
14095 * The Print Command with Objective-C::
14098 @node Method Names in Commands
14099 @subsubsection Method Names in Commands
14101 The following commands have been extended to accept Objective-C method
14102 names as line specifications:
14104 @kindex clear@r{, and Objective-C}
14105 @kindex break@r{, and Objective-C}
14106 @kindex info line@r{, and Objective-C}
14107 @kindex jump@r{, and Objective-C}
14108 @kindex list@r{, and Objective-C}
14112 @item @code{info line}
14117 A fully qualified Objective-C method name is specified as
14120 -[@var{Class} @var{methodName}]
14123 where the minus sign is used to indicate an instance method and a
14124 plus sign (not shown) is used to indicate a class method. The class
14125 name @var{Class} and method name @var{methodName} are enclosed in
14126 brackets, similar to the way messages are specified in Objective-C
14127 source code. For example, to set a breakpoint at the @code{create}
14128 instance method of class @code{Fruit} in the program currently being
14132 break -[Fruit create]
14135 To list ten program lines around the @code{initialize} class method,
14139 list +[NSText initialize]
14142 In the current version of @value{GDBN}, the plus or minus sign is
14143 required. In future versions of @value{GDBN}, the plus or minus
14144 sign will be optional, but you can use it to narrow the search. It
14145 is also possible to specify just a method name:
14151 You must specify the complete method name, including any colons. If
14152 your program's source files contain more than one @code{create} method,
14153 you'll be presented with a numbered list of classes that implement that
14154 method. Indicate your choice by number, or type @samp{0} to exit if
14157 As another example, to clear a breakpoint established at the
14158 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
14161 clear -[NSWindow makeKeyAndOrderFront:]
14164 @node The Print Command with Objective-C
14165 @subsubsection The Print Command With Objective-C
14166 @cindex Objective-C, print objects
14167 @kindex print-object
14168 @kindex po @r{(@code{print-object})}
14170 The print command has also been extended to accept methods. For example:
14173 print -[@var{object} hash]
14176 @cindex print an Objective-C object description
14177 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
14179 will tell @value{GDBN} to send the @code{hash} message to @var{object}
14180 and print the result. Also, an additional command has been added,
14181 @code{print-object} or @code{po} for short, which is meant to print
14182 the description of an object. However, this command may only work
14183 with certain Objective-C libraries that have a particular hook
14184 function, @code{_NSPrintForDebugger}, defined.
14187 @subsection OpenCL C
14190 This section provides information about @value{GDBN}s OpenCL C support.
14193 * OpenCL C Datatypes::
14194 * OpenCL C Expressions::
14195 * OpenCL C Operators::
14198 @node OpenCL C Datatypes
14199 @subsubsection OpenCL C Datatypes
14201 @cindex OpenCL C Datatypes
14202 @value{GDBN} supports the builtin scalar and vector datatypes specified
14203 by OpenCL 1.1. In addition the half- and double-precision floating point
14204 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
14205 extensions are also known to @value{GDBN}.
14207 @node OpenCL C Expressions
14208 @subsubsection OpenCL C Expressions
14210 @cindex OpenCL C Expressions
14211 @value{GDBN} supports accesses to vector components including the access as
14212 lvalue where possible. Since OpenCL C is based on C99 most C expressions
14213 supported by @value{GDBN} can be used as well.
14215 @node OpenCL C Operators
14216 @subsubsection OpenCL C Operators
14218 @cindex OpenCL C Operators
14219 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
14223 @subsection Fortran
14224 @cindex Fortran-specific support in @value{GDBN}
14226 @value{GDBN} can be used to debug programs written in Fortran, but it
14227 currently supports only the features of Fortran 77 language.
14229 @cindex trailing underscore, in Fortran symbols
14230 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
14231 among them) append an underscore to the names of variables and
14232 functions. When you debug programs compiled by those compilers, you
14233 will need to refer to variables and functions with a trailing
14237 * Fortran Operators:: Fortran operators and expressions
14238 * Fortran Defaults:: Default settings for Fortran
14239 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
14242 @node Fortran Operators
14243 @subsubsection Fortran Operators and Expressions
14245 @cindex Fortran operators and expressions
14247 Operators must be defined on values of specific types. For instance,
14248 @code{+} is defined on numbers, but not on characters or other non-
14249 arithmetic types. Operators are often defined on groups of types.
14253 The exponentiation operator. It raises the first operand to the power
14257 The range operator. Normally used in the form of array(low:high) to
14258 represent a section of array.
14261 The access component operator. Normally used to access elements in derived
14262 types. Also suitable for unions. As unions aren't part of regular Fortran,
14263 this can only happen when accessing a register that uses a gdbarch-defined
14267 @node Fortran Defaults
14268 @subsubsection Fortran Defaults
14270 @cindex Fortran Defaults
14272 Fortran symbols are usually case-insensitive, so @value{GDBN} by
14273 default uses case-insensitive matches for Fortran symbols. You can
14274 change that with the @samp{set case-insensitive} command, see
14275 @ref{Symbols}, for the details.
14277 @node Special Fortran Commands
14278 @subsubsection Special Fortran Commands
14280 @cindex Special Fortran commands
14282 @value{GDBN} has some commands to support Fortran-specific features,
14283 such as displaying common blocks.
14286 @cindex @code{COMMON} blocks, Fortran
14287 @kindex info common
14288 @item info common @r{[}@var{common-name}@r{]}
14289 This command prints the values contained in the Fortran @code{COMMON}
14290 block whose name is @var{common-name}. With no argument, the names of
14291 all @code{COMMON} blocks visible at the current program location are
14298 @cindex Pascal support in @value{GDBN}, limitations
14299 Debugging Pascal programs which use sets, subranges, file variables, or
14300 nested functions does not currently work. @value{GDBN} does not support
14301 entering expressions, printing values, or similar features using Pascal
14304 The Pascal-specific command @code{set print pascal_static-members}
14305 controls whether static members of Pascal objects are displayed.
14306 @xref{Print Settings, pascal_static-members}.
14309 @subsection Modula-2
14311 @cindex Modula-2, @value{GDBN} support
14313 The extensions made to @value{GDBN} to support Modula-2 only support
14314 output from the @sc{gnu} Modula-2 compiler (which is currently being
14315 developed). Other Modula-2 compilers are not currently supported, and
14316 attempting to debug executables produced by them is most likely
14317 to give an error as @value{GDBN} reads in the executable's symbol
14320 @cindex expressions in Modula-2
14322 * M2 Operators:: Built-in operators
14323 * Built-In Func/Proc:: Built-in functions and procedures
14324 * M2 Constants:: Modula-2 constants
14325 * M2 Types:: Modula-2 types
14326 * M2 Defaults:: Default settings for Modula-2
14327 * Deviations:: Deviations from standard Modula-2
14328 * M2 Checks:: Modula-2 type and range checks
14329 * M2 Scope:: The scope operators @code{::} and @code{.}
14330 * GDB/M2:: @value{GDBN} and Modula-2
14334 @subsubsection Operators
14335 @cindex Modula-2 operators
14337 Operators must be defined on values of specific types. For instance,
14338 @code{+} is defined on numbers, but not on structures. Operators are
14339 often defined on groups of types. For the purposes of Modula-2, the
14340 following definitions hold:
14345 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
14349 @emph{Character types} consist of @code{CHAR} and its subranges.
14352 @emph{Floating-point types} consist of @code{REAL}.
14355 @emph{Pointer types} consist of anything declared as @code{POINTER TO
14359 @emph{Scalar types} consist of all of the above.
14362 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
14365 @emph{Boolean types} consist of @code{BOOLEAN}.
14369 The following operators are supported, and appear in order of
14370 increasing precedence:
14374 Function argument or array index separator.
14377 Assignment. The value of @var{var} @code{:=} @var{value} is
14381 Less than, greater than on integral, floating-point, or enumerated
14385 Less than or equal to, greater than or equal to
14386 on integral, floating-point and enumerated types, or set inclusion on
14387 set types. Same precedence as @code{<}.
14389 @item =@r{, }<>@r{, }#
14390 Equality and two ways of expressing inequality, valid on scalar types.
14391 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
14392 available for inequality, since @code{#} conflicts with the script
14396 Set membership. Defined on set types and the types of their members.
14397 Same precedence as @code{<}.
14400 Boolean disjunction. Defined on boolean types.
14403 Boolean conjunction. Defined on boolean types.
14406 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14409 Addition and subtraction on integral and floating-point types, or union
14410 and difference on set types.
14413 Multiplication on integral and floating-point types, or set intersection
14417 Division on floating-point types, or symmetric set difference on set
14418 types. Same precedence as @code{*}.
14421 Integer division and remainder. Defined on integral types. Same
14422 precedence as @code{*}.
14425 Negative. Defined on @code{INTEGER} and @code{REAL} data.
14428 Pointer dereferencing. Defined on pointer types.
14431 Boolean negation. Defined on boolean types. Same precedence as
14435 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
14436 precedence as @code{^}.
14439 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
14442 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
14446 @value{GDBN} and Modula-2 scope operators.
14450 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
14451 treats the use of the operator @code{IN}, or the use of operators
14452 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
14453 @code{<=}, and @code{>=} on sets as an error.
14457 @node Built-In Func/Proc
14458 @subsubsection Built-in Functions and Procedures
14459 @cindex Modula-2 built-ins
14461 Modula-2 also makes available several built-in procedures and functions.
14462 In describing these, the following metavariables are used:
14467 represents an @code{ARRAY} variable.
14470 represents a @code{CHAR} constant or variable.
14473 represents a variable or constant of integral type.
14476 represents an identifier that belongs to a set. Generally used in the
14477 same function with the metavariable @var{s}. The type of @var{s} should
14478 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
14481 represents a variable or constant of integral or floating-point type.
14484 represents a variable or constant of floating-point type.
14490 represents a variable.
14493 represents a variable or constant of one of many types. See the
14494 explanation of the function for details.
14497 All Modula-2 built-in procedures also return a result, described below.
14501 Returns the absolute value of @var{n}.
14504 If @var{c} is a lower case letter, it returns its upper case
14505 equivalent, otherwise it returns its argument.
14508 Returns the character whose ordinal value is @var{i}.
14511 Decrements the value in the variable @var{v} by one. Returns the new value.
14513 @item DEC(@var{v},@var{i})
14514 Decrements the value in the variable @var{v} by @var{i}. Returns the
14517 @item EXCL(@var{m},@var{s})
14518 Removes the element @var{m} from the set @var{s}. Returns the new
14521 @item FLOAT(@var{i})
14522 Returns the floating point equivalent of the integer @var{i}.
14524 @item HIGH(@var{a})
14525 Returns the index of the last member of @var{a}.
14528 Increments the value in the variable @var{v} by one. Returns the new value.
14530 @item INC(@var{v},@var{i})
14531 Increments the value in the variable @var{v} by @var{i}. Returns the
14534 @item INCL(@var{m},@var{s})
14535 Adds the element @var{m} to the set @var{s} if it is not already
14536 there. Returns the new set.
14539 Returns the maximum value of the type @var{t}.
14542 Returns the minimum value of the type @var{t}.
14545 Returns boolean TRUE if @var{i} is an odd number.
14548 Returns the ordinal value of its argument. For example, the ordinal
14549 value of a character is its @sc{ascii} value (on machines supporting the
14550 @sc{ascii} character set). @var{x} must be of an ordered type, which include
14551 integral, character and enumerated types.
14553 @item SIZE(@var{x})
14554 Returns the size of its argument. @var{x} can be a variable or a type.
14556 @item TRUNC(@var{r})
14557 Returns the integral part of @var{r}.
14559 @item TSIZE(@var{x})
14560 Returns the size of its argument. @var{x} can be a variable or a type.
14562 @item VAL(@var{t},@var{i})
14563 Returns the member of the type @var{t} whose ordinal value is @var{i}.
14567 @emph{Warning:} Sets and their operations are not yet supported, so
14568 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
14572 @cindex Modula-2 constants
14574 @subsubsection Constants
14576 @value{GDBN} allows you to express the constants of Modula-2 in the following
14582 Integer constants are simply a sequence of digits. When used in an
14583 expression, a constant is interpreted to be type-compatible with the
14584 rest of the expression. Hexadecimal integers are specified by a
14585 trailing @samp{H}, and octal integers by a trailing @samp{B}.
14588 Floating point constants appear as a sequence of digits, followed by a
14589 decimal point and another sequence of digits. An optional exponent can
14590 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
14591 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
14592 digits of the floating point constant must be valid decimal (base 10)
14596 Character constants consist of a single character enclosed by a pair of
14597 like quotes, either single (@code{'}) or double (@code{"}). They may
14598 also be expressed by their ordinal value (their @sc{ascii} value, usually)
14599 followed by a @samp{C}.
14602 String constants consist of a sequence of characters enclosed by a
14603 pair of like quotes, either single (@code{'}) or double (@code{"}).
14604 Escape sequences in the style of C are also allowed. @xref{C
14605 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
14609 Enumerated constants consist of an enumerated identifier.
14612 Boolean constants consist of the identifiers @code{TRUE} and
14616 Pointer constants consist of integral values only.
14619 Set constants are not yet supported.
14623 @subsubsection Modula-2 Types
14624 @cindex Modula-2 types
14626 Currently @value{GDBN} can print the following data types in Modula-2
14627 syntax: array types, record types, set types, pointer types, procedure
14628 types, enumerated types, subrange types and base types. You can also
14629 print the contents of variables declared using these type.
14630 This section gives a number of simple source code examples together with
14631 sample @value{GDBN} sessions.
14633 The first example contains the following section of code:
14642 and you can request @value{GDBN} to interrogate the type and value of
14643 @code{r} and @code{s}.
14646 (@value{GDBP}) print s
14648 (@value{GDBP}) ptype s
14650 (@value{GDBP}) print r
14652 (@value{GDBP}) ptype r
14657 Likewise if your source code declares @code{s} as:
14661 s: SET ['A'..'Z'] ;
14665 then you may query the type of @code{s} by:
14668 (@value{GDBP}) ptype s
14669 type = SET ['A'..'Z']
14673 Note that at present you cannot interactively manipulate set
14674 expressions using the debugger.
14676 The following example shows how you might declare an array in Modula-2
14677 and how you can interact with @value{GDBN} to print its type and contents:
14681 s: ARRAY [-10..10] OF CHAR ;
14685 (@value{GDBP}) ptype s
14686 ARRAY [-10..10] OF CHAR
14689 Note that the array handling is not yet complete and although the type
14690 is printed correctly, expression handling still assumes that all
14691 arrays have a lower bound of zero and not @code{-10} as in the example
14694 Here are some more type related Modula-2 examples:
14698 colour = (blue, red, yellow, green) ;
14699 t = [blue..yellow] ;
14707 The @value{GDBN} interaction shows how you can query the data type
14708 and value of a variable.
14711 (@value{GDBP}) print s
14713 (@value{GDBP}) ptype t
14714 type = [blue..yellow]
14718 In this example a Modula-2 array is declared and its contents
14719 displayed. Observe that the contents are written in the same way as
14720 their @code{C} counterparts.
14724 s: ARRAY [1..5] OF CARDINAL ;
14730 (@value{GDBP}) print s
14731 $1 = @{1, 0, 0, 0, 0@}
14732 (@value{GDBP}) ptype s
14733 type = ARRAY [1..5] OF CARDINAL
14736 The Modula-2 language interface to @value{GDBN} also understands
14737 pointer types as shown in this example:
14741 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
14748 and you can request that @value{GDBN} describes the type of @code{s}.
14751 (@value{GDBP}) ptype s
14752 type = POINTER TO ARRAY [1..5] OF CARDINAL
14755 @value{GDBN} handles compound types as we can see in this example.
14756 Here we combine array types, record types, pointer types and subrange
14767 myarray = ARRAY myrange OF CARDINAL ;
14768 myrange = [-2..2] ;
14770 s: POINTER TO ARRAY myrange OF foo ;
14774 and you can ask @value{GDBN} to describe the type of @code{s} as shown
14778 (@value{GDBP}) ptype s
14779 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
14782 f3 : ARRAY [-2..2] OF CARDINAL;
14787 @subsubsection Modula-2 Defaults
14788 @cindex Modula-2 defaults
14790 If type and range checking are set automatically by @value{GDBN}, they
14791 both default to @code{on} whenever the working language changes to
14792 Modula-2. This happens regardless of whether you or @value{GDBN}
14793 selected the working language.
14795 If you allow @value{GDBN} to set the language automatically, then entering
14796 code compiled from a file whose name ends with @file{.mod} sets the
14797 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
14798 Infer the Source Language}, for further details.
14801 @subsubsection Deviations from Standard Modula-2
14802 @cindex Modula-2, deviations from
14804 A few changes have been made to make Modula-2 programs easier to debug.
14805 This is done primarily via loosening its type strictness:
14809 Unlike in standard Modula-2, pointer constants can be formed by
14810 integers. This allows you to modify pointer variables during
14811 debugging. (In standard Modula-2, the actual address contained in a
14812 pointer variable is hidden from you; it can only be modified
14813 through direct assignment to another pointer variable or expression that
14814 returned a pointer.)
14817 C escape sequences can be used in strings and characters to represent
14818 non-printable characters. @value{GDBN} prints out strings with these
14819 escape sequences embedded. Single non-printable characters are
14820 printed using the @samp{CHR(@var{nnn})} format.
14823 The assignment operator (@code{:=}) returns the value of its right-hand
14827 All built-in procedures both modify @emph{and} return their argument.
14831 @subsubsection Modula-2 Type and Range Checks
14832 @cindex Modula-2 checks
14835 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
14838 @c FIXME remove warning when type/range checks added
14840 @value{GDBN} considers two Modula-2 variables type equivalent if:
14844 They are of types that have been declared equivalent via a @code{TYPE
14845 @var{t1} = @var{t2}} statement
14848 They have been declared on the same line. (Note: This is true of the
14849 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
14852 As long as type checking is enabled, any attempt to combine variables
14853 whose types are not equivalent is an error.
14855 Range checking is done on all mathematical operations, assignment, array
14856 index bounds, and all built-in functions and procedures.
14859 @subsubsection The Scope Operators @code{::} and @code{.}
14861 @cindex @code{.}, Modula-2 scope operator
14862 @cindex colon, doubled as scope operator
14864 @vindex colon-colon@r{, in Modula-2}
14865 @c Info cannot handle :: but TeX can.
14868 @vindex ::@r{, in Modula-2}
14871 There are a few subtle differences between the Modula-2 scope operator
14872 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
14877 @var{module} . @var{id}
14878 @var{scope} :: @var{id}
14882 where @var{scope} is the name of a module or a procedure,
14883 @var{module} the name of a module, and @var{id} is any declared
14884 identifier within your program, except another module.
14886 Using the @code{::} operator makes @value{GDBN} search the scope
14887 specified by @var{scope} for the identifier @var{id}. If it is not
14888 found in the specified scope, then @value{GDBN} searches all scopes
14889 enclosing the one specified by @var{scope}.
14891 Using the @code{.} operator makes @value{GDBN} search the current scope for
14892 the identifier specified by @var{id} that was imported from the
14893 definition module specified by @var{module}. With this operator, it is
14894 an error if the identifier @var{id} was not imported from definition
14895 module @var{module}, or if @var{id} is not an identifier in
14899 @subsubsection @value{GDBN} and Modula-2
14901 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
14902 Five subcommands of @code{set print} and @code{show print} apply
14903 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
14904 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
14905 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
14906 analogue in Modula-2.
14908 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
14909 with any language, is not useful with Modula-2. Its
14910 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
14911 created in Modula-2 as they can in C or C@t{++}. However, because an
14912 address can be specified by an integral constant, the construct
14913 @samp{@{@var{type}@}@var{adrexp}} is still useful.
14915 @cindex @code{#} in Modula-2
14916 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
14917 interpreted as the beginning of a comment. Use @code{<>} instead.
14923 The extensions made to @value{GDBN} for Ada only support
14924 output from the @sc{gnu} Ada (GNAT) compiler.
14925 Other Ada compilers are not currently supported, and
14926 attempting to debug executables produced by them is most likely
14930 @cindex expressions in Ada
14932 * Ada Mode Intro:: General remarks on the Ada syntax
14933 and semantics supported by Ada mode
14935 * Omissions from Ada:: Restrictions on the Ada expression syntax.
14936 * Additions to Ada:: Extensions of the Ada expression syntax.
14937 * Stopping Before Main Program:: Debugging the program during elaboration.
14938 * Ada Tasks:: Listing and setting breakpoints in tasks.
14939 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
14940 * Ravenscar Profile:: Tasking Support when using the Ravenscar
14942 * Ada Glitches:: Known peculiarities of Ada mode.
14945 @node Ada Mode Intro
14946 @subsubsection Introduction
14947 @cindex Ada mode, general
14949 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
14950 syntax, with some extensions.
14951 The philosophy behind the design of this subset is
14955 That @value{GDBN} should provide basic literals and access to operations for
14956 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
14957 leaving more sophisticated computations to subprograms written into the
14958 program (which therefore may be called from @value{GDBN}).
14961 That type safety and strict adherence to Ada language restrictions
14962 are not particularly important to the @value{GDBN} user.
14965 That brevity is important to the @value{GDBN} user.
14968 Thus, for brevity, the debugger acts as if all names declared in
14969 user-written packages are directly visible, even if they are not visible
14970 according to Ada rules, thus making it unnecessary to fully qualify most
14971 names with their packages, regardless of context. Where this causes
14972 ambiguity, @value{GDBN} asks the user's intent.
14974 The debugger will start in Ada mode if it detects an Ada main program.
14975 As for other languages, it will enter Ada mode when stopped in a program that
14976 was translated from an Ada source file.
14978 While in Ada mode, you may use `@t{--}' for comments. This is useful
14979 mostly for documenting command files. The standard @value{GDBN} comment
14980 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
14981 middle (to allow based literals).
14983 The debugger supports limited overloading. Given a subprogram call in which
14984 the function symbol has multiple definitions, it will use the number of
14985 actual parameters and some information about their types to attempt to narrow
14986 the set of definitions. It also makes very limited use of context, preferring
14987 procedures to functions in the context of the @code{call} command, and
14988 functions to procedures elsewhere.
14990 @node Omissions from Ada
14991 @subsubsection Omissions from Ada
14992 @cindex Ada, omissions from
14994 Here are the notable omissions from the subset:
14998 Only a subset of the attributes are supported:
15002 @t{'First}, @t{'Last}, and @t{'Length}
15003 on array objects (not on types and subtypes).
15006 @t{'Min} and @t{'Max}.
15009 @t{'Pos} and @t{'Val}.
15015 @t{'Range} on array objects (not subtypes), but only as the right
15016 operand of the membership (@code{in}) operator.
15019 @t{'Access}, @t{'Unchecked_Access}, and
15020 @t{'Unrestricted_Access} (a GNAT extension).
15028 @code{Characters.Latin_1} are not available and
15029 concatenation is not implemented. Thus, escape characters in strings are
15030 not currently available.
15033 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
15034 equality of representations. They will generally work correctly
15035 for strings and arrays whose elements have integer or enumeration types.
15036 They may not work correctly for arrays whose element
15037 types have user-defined equality, for arrays of real values
15038 (in particular, IEEE-conformant floating point, because of negative
15039 zeroes and NaNs), and for arrays whose elements contain unused bits with
15040 indeterminate values.
15043 The other component-by-component array operations (@code{and}, @code{or},
15044 @code{xor}, @code{not}, and relational tests other than equality)
15045 are not implemented.
15048 @cindex array aggregates (Ada)
15049 @cindex record aggregates (Ada)
15050 @cindex aggregates (Ada)
15051 There is limited support for array and record aggregates. They are
15052 permitted only on the right sides of assignments, as in these examples:
15055 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
15056 (@value{GDBP}) set An_Array := (1, others => 0)
15057 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
15058 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
15059 (@value{GDBP}) set A_Record := (1, "Peter", True);
15060 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
15064 discriminant's value by assigning an aggregate has an
15065 undefined effect if that discriminant is used within the record.
15066 However, you can first modify discriminants by directly assigning to
15067 them (which normally would not be allowed in Ada), and then performing an
15068 aggregate assignment. For example, given a variable @code{A_Rec}
15069 declared to have a type such as:
15072 type Rec (Len : Small_Integer := 0) is record
15074 Vals : IntArray (1 .. Len);
15078 you can assign a value with a different size of @code{Vals} with two
15082 (@value{GDBP}) set A_Rec.Len := 4
15083 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
15086 As this example also illustrates, @value{GDBN} is very loose about the usual
15087 rules concerning aggregates. You may leave out some of the
15088 components of an array or record aggregate (such as the @code{Len}
15089 component in the assignment to @code{A_Rec} above); they will retain their
15090 original values upon assignment. You may freely use dynamic values as
15091 indices in component associations. You may even use overlapping or
15092 redundant component associations, although which component values are
15093 assigned in such cases is not defined.
15096 Calls to dispatching subprograms are not implemented.
15099 The overloading algorithm is much more limited (i.e., less selective)
15100 than that of real Ada. It makes only limited use of the context in
15101 which a subexpression appears to resolve its meaning, and it is much
15102 looser in its rules for allowing type matches. As a result, some
15103 function calls will be ambiguous, and the user will be asked to choose
15104 the proper resolution.
15107 The @code{new} operator is not implemented.
15110 Entry calls are not implemented.
15113 Aside from printing, arithmetic operations on the native VAX floating-point
15114 formats are not supported.
15117 It is not possible to slice a packed array.
15120 The names @code{True} and @code{False}, when not part of a qualified name,
15121 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
15123 Should your program
15124 redefine these names in a package or procedure (at best a dubious practice),
15125 you will have to use fully qualified names to access their new definitions.
15128 @node Additions to Ada
15129 @subsubsection Additions to Ada
15130 @cindex Ada, deviations from
15132 As it does for other languages, @value{GDBN} makes certain generic
15133 extensions to Ada (@pxref{Expressions}):
15137 If the expression @var{E} is a variable residing in memory (typically
15138 a local variable or array element) and @var{N} is a positive integer,
15139 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
15140 @var{N}-1 adjacent variables following it in memory as an array. In
15141 Ada, this operator is generally not necessary, since its prime use is
15142 in displaying parts of an array, and slicing will usually do this in
15143 Ada. However, there are occasional uses when debugging programs in
15144 which certain debugging information has been optimized away.
15147 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
15148 appears in function or file @var{B}.'' When @var{B} is a file name,
15149 you must typically surround it in single quotes.
15152 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
15153 @var{type} that appears at address @var{addr}.''
15156 A name starting with @samp{$} is a convenience variable
15157 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
15160 In addition, @value{GDBN} provides a few other shortcuts and outright
15161 additions specific to Ada:
15165 The assignment statement is allowed as an expression, returning
15166 its right-hand operand as its value. Thus, you may enter
15169 (@value{GDBP}) set x := y + 3
15170 (@value{GDBP}) print A(tmp := y + 1)
15174 The semicolon is allowed as an ``operator,'' returning as its value
15175 the value of its right-hand operand.
15176 This allows, for example,
15177 complex conditional breaks:
15180 (@value{GDBP}) break f
15181 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
15185 Rather than use catenation and symbolic character names to introduce special
15186 characters into strings, one may instead use a special bracket notation,
15187 which is also used to print strings. A sequence of characters of the form
15188 @samp{["@var{XX}"]} within a string or character literal denotes the
15189 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
15190 sequence of characters @samp{["""]} also denotes a single quotation mark
15191 in strings. For example,
15193 "One line.["0a"]Next line.["0a"]"
15196 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
15200 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
15201 @t{'Max} is optional (and is ignored in any case). For example, it is valid
15205 (@value{GDBP}) print 'max(x, y)
15209 When printing arrays, @value{GDBN} uses positional notation when the
15210 array has a lower bound of 1, and uses a modified named notation otherwise.
15211 For example, a one-dimensional array of three integers with a lower bound
15212 of 3 might print as
15219 That is, in contrast to valid Ada, only the first component has a @code{=>}
15223 You may abbreviate attributes in expressions with any unique,
15224 multi-character subsequence of
15225 their names (an exact match gets preference).
15226 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
15227 in place of @t{a'length}.
15230 @cindex quoting Ada internal identifiers
15231 Since Ada is case-insensitive, the debugger normally maps identifiers you type
15232 to lower case. The GNAT compiler uses upper-case characters for
15233 some of its internal identifiers, which are normally of no interest to users.
15234 For the rare occasions when you actually have to look at them,
15235 enclose them in angle brackets to avoid the lower-case mapping.
15238 (@value{GDBP}) print <JMPBUF_SAVE>[0]
15242 Printing an object of class-wide type or dereferencing an
15243 access-to-class-wide value will display all the components of the object's
15244 specific type (as indicated by its run-time tag). Likewise, component
15245 selection on such a value will operate on the specific type of the
15250 @node Stopping Before Main Program
15251 @subsubsection Stopping at the Very Beginning
15253 @cindex breakpointing Ada elaboration code
15254 It is sometimes necessary to debug the program during elaboration, and
15255 before reaching the main procedure.
15256 As defined in the Ada Reference
15257 Manual, the elaboration code is invoked from a procedure called
15258 @code{adainit}. To run your program up to the beginning of
15259 elaboration, simply use the following two commands:
15260 @code{tbreak adainit} and @code{run}.
15263 @subsubsection Extensions for Ada Tasks
15264 @cindex Ada, tasking
15266 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
15267 @value{GDBN} provides the following task-related commands:
15272 This command shows a list of current Ada tasks, as in the following example:
15279 (@value{GDBP}) info tasks
15280 ID TID P-ID Pri State Name
15281 1 8088000 0 15 Child Activation Wait main_task
15282 2 80a4000 1 15 Accept Statement b
15283 3 809a800 1 15 Child Activation Wait a
15284 * 4 80ae800 3 15 Runnable c
15289 In this listing, the asterisk before the last task indicates it to be the
15290 task currently being inspected.
15294 Represents @value{GDBN}'s internal task number.
15300 The parent's task ID (@value{GDBN}'s internal task number).
15303 The base priority of the task.
15306 Current state of the task.
15310 The task has been created but has not been activated. It cannot be
15314 The task is not blocked for any reason known to Ada. (It may be waiting
15315 for a mutex, though.) It is conceptually "executing" in normal mode.
15318 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
15319 that were waiting on terminate alternatives have been awakened and have
15320 terminated themselves.
15322 @item Child Activation Wait
15323 The task is waiting for created tasks to complete activation.
15325 @item Accept Statement
15326 The task is waiting on an accept or selective wait statement.
15328 @item Waiting on entry call
15329 The task is waiting on an entry call.
15331 @item Async Select Wait
15332 The task is waiting to start the abortable part of an asynchronous
15336 The task is waiting on a select statement with only a delay
15339 @item Child Termination Wait
15340 The task is sleeping having completed a master within itself, and is
15341 waiting for the tasks dependent on that master to become terminated or
15342 waiting on a terminate Phase.
15344 @item Wait Child in Term Alt
15345 The task is sleeping waiting for tasks on terminate alternatives to
15346 finish terminating.
15348 @item Accepting RV with @var{taskno}
15349 The task is accepting a rendez-vous with the task @var{taskno}.
15353 Name of the task in the program.
15357 @kindex info task @var{taskno}
15358 @item info task @var{taskno}
15359 This command shows detailled informations on the specified task, as in
15360 the following example:
15365 (@value{GDBP}) info tasks
15366 ID TID P-ID Pri State Name
15367 1 8077880 0 15 Child Activation Wait main_task
15368 * 2 807c468 1 15 Runnable task_1
15369 (@value{GDBP}) info task 2
15370 Ada Task: 0x807c468
15373 Parent: 1 (main_task)
15379 @kindex task@r{ (Ada)}
15380 @cindex current Ada task ID
15381 This command prints the ID of the current task.
15387 (@value{GDBP}) info tasks
15388 ID TID P-ID Pri State Name
15389 1 8077870 0 15 Child Activation Wait main_task
15390 * 2 807c458 1 15 Runnable t
15391 (@value{GDBP}) task
15392 [Current task is 2]
15395 @item task @var{taskno}
15396 @cindex Ada task switching
15397 This command is like the @code{thread @var{threadno}}
15398 command (@pxref{Threads}). It switches the context of debugging
15399 from the current task to the given task.
15405 (@value{GDBP}) info tasks
15406 ID TID P-ID Pri State Name
15407 1 8077870 0 15 Child Activation Wait main_task
15408 * 2 807c458 1 15 Runnable t
15409 (@value{GDBP}) task 1
15410 [Switching to task 1]
15411 #0 0x8067726 in pthread_cond_wait ()
15413 #0 0x8067726 in pthread_cond_wait ()
15414 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
15415 #2 0x805cb63 in system.task_primitives.operations.sleep ()
15416 #3 0x806153e in system.tasking.stages.activate_tasks ()
15417 #4 0x804aacc in un () at un.adb:5
15420 @item break @var{linespec} task @var{taskno}
15421 @itemx break @var{linespec} task @var{taskno} if @dots{}
15422 @cindex breakpoints and tasks, in Ada
15423 @cindex task breakpoints, in Ada
15424 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
15425 These commands are like the @code{break @dots{} thread @dots{}}
15426 command (@pxref{Thread Stops}).
15427 @var{linespec} specifies source lines, as described
15428 in @ref{Specify Location}.
15430 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
15431 to specify that you only want @value{GDBN} to stop the program when a
15432 particular Ada task reaches this breakpoint. @var{taskno} is one of the
15433 numeric task identifiers assigned by @value{GDBN}, shown in the first
15434 column of the @samp{info tasks} display.
15436 If you do not specify @samp{task @var{taskno}} when you set a
15437 breakpoint, the breakpoint applies to @emph{all} tasks of your
15440 You can use the @code{task} qualifier on conditional breakpoints as
15441 well; in this case, place @samp{task @var{taskno}} before the
15442 breakpoint condition (before the @code{if}).
15450 (@value{GDBP}) info tasks
15451 ID TID P-ID Pri State Name
15452 1 140022020 0 15 Child Activation Wait main_task
15453 2 140045060 1 15 Accept/Select Wait t2
15454 3 140044840 1 15 Runnable t1
15455 * 4 140056040 1 15 Runnable t3
15456 (@value{GDBP}) b 15 task 2
15457 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
15458 (@value{GDBP}) cont
15463 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
15465 (@value{GDBP}) info tasks
15466 ID TID P-ID Pri State Name
15467 1 140022020 0 15 Child Activation Wait main_task
15468 * 2 140045060 1 15 Runnable t2
15469 3 140044840 1 15 Runnable t1
15470 4 140056040 1 15 Delay Sleep t3
15474 @node Ada Tasks and Core Files
15475 @subsubsection Tasking Support when Debugging Core Files
15476 @cindex Ada tasking and core file debugging
15478 When inspecting a core file, as opposed to debugging a live program,
15479 tasking support may be limited or even unavailable, depending on
15480 the platform being used.
15481 For instance, on x86-linux, the list of tasks is available, but task
15482 switching is not supported. On Tru64, however, task switching will work
15485 On certain platforms, including Tru64, the debugger needs to perform some
15486 memory writes in order to provide Ada tasking support. When inspecting
15487 a core file, this means that the core file must be opened with read-write
15488 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
15489 Under these circumstances, you should make a backup copy of the core
15490 file before inspecting it with @value{GDBN}.
15492 @node Ravenscar Profile
15493 @subsubsection Tasking Support when using the Ravenscar Profile
15494 @cindex Ravenscar Profile
15496 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
15497 specifically designed for systems with safety-critical real-time
15501 @kindex set ravenscar task-switching on
15502 @cindex task switching with program using Ravenscar Profile
15503 @item set ravenscar task-switching on
15504 Allows task switching when debugging a program that uses the Ravenscar
15505 Profile. This is the default.
15507 @kindex set ravenscar task-switching off
15508 @item set ravenscar task-switching off
15509 Turn off task switching when debugging a program that uses the Ravenscar
15510 Profile. This is mostly intended to disable the code that adds support
15511 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
15512 the Ravenscar runtime is preventing @value{GDBN} from working properly.
15513 To be effective, this command should be run before the program is started.
15515 @kindex show ravenscar task-switching
15516 @item show ravenscar task-switching
15517 Show whether it is possible to switch from task to task in a program
15518 using the Ravenscar Profile.
15523 @subsubsection Known Peculiarities of Ada Mode
15524 @cindex Ada, problems
15526 Besides the omissions listed previously (@pxref{Omissions from Ada}),
15527 we know of several problems with and limitations of Ada mode in
15529 some of which will be fixed with planned future releases of the debugger
15530 and the GNU Ada compiler.
15534 Static constants that the compiler chooses not to materialize as objects in
15535 storage are invisible to the debugger.
15538 Named parameter associations in function argument lists are ignored (the
15539 argument lists are treated as positional).
15542 Many useful library packages are currently invisible to the debugger.
15545 Fixed-point arithmetic, conversions, input, and output is carried out using
15546 floating-point arithmetic, and may give results that only approximate those on
15550 The GNAT compiler never generates the prefix @code{Standard} for any of
15551 the standard symbols defined by the Ada language. @value{GDBN} knows about
15552 this: it will strip the prefix from names when you use it, and will never
15553 look for a name you have so qualified among local symbols, nor match against
15554 symbols in other packages or subprograms. If you have
15555 defined entities anywhere in your program other than parameters and
15556 local variables whose simple names match names in @code{Standard},
15557 GNAT's lack of qualification here can cause confusion. When this happens,
15558 you can usually resolve the confusion
15559 by qualifying the problematic names with package
15560 @code{Standard} explicitly.
15563 Older versions of the compiler sometimes generate erroneous debugging
15564 information, resulting in the debugger incorrectly printing the value
15565 of affected entities. In some cases, the debugger is able to work
15566 around an issue automatically. In other cases, the debugger is able
15567 to work around the issue, but the work-around has to be specifically
15570 @kindex set ada trust-PAD-over-XVS
15571 @kindex show ada trust-PAD-over-XVS
15574 @item set ada trust-PAD-over-XVS on
15575 Configure GDB to strictly follow the GNAT encoding when computing the
15576 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
15577 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
15578 a complete description of the encoding used by the GNAT compiler).
15579 This is the default.
15581 @item set ada trust-PAD-over-XVS off
15582 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
15583 sometimes prints the wrong value for certain entities, changing @code{ada
15584 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
15585 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
15586 @code{off}, but this incurs a slight performance penalty, so it is
15587 recommended to leave this setting to @code{on} unless necessary.
15591 @node Unsupported Languages
15592 @section Unsupported Languages
15594 @cindex unsupported languages
15595 @cindex minimal language
15596 In addition to the other fully-supported programming languages,
15597 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
15598 It does not represent a real programming language, but provides a set
15599 of capabilities close to what the C or assembly languages provide.
15600 This should allow most simple operations to be performed while debugging
15601 an application that uses a language currently not supported by @value{GDBN}.
15603 If the language is set to @code{auto}, @value{GDBN} will automatically
15604 select this language if the current frame corresponds to an unsupported
15608 @chapter Examining the Symbol Table
15610 The commands described in this chapter allow you to inquire about the
15611 symbols (names of variables, functions and types) defined in your
15612 program. This information is inherent in the text of your program and
15613 does not change as your program executes. @value{GDBN} finds it in your
15614 program's symbol table, in the file indicated when you started @value{GDBN}
15615 (@pxref{File Options, ,Choosing Files}), or by one of the
15616 file-management commands (@pxref{Files, ,Commands to Specify Files}).
15618 @cindex symbol names
15619 @cindex names of symbols
15620 @cindex quoting names
15621 Occasionally, you may need to refer to symbols that contain unusual
15622 characters, which @value{GDBN} ordinarily treats as word delimiters. The
15623 most frequent case is in referring to static variables in other
15624 source files (@pxref{Variables,,Program Variables}). File names
15625 are recorded in object files as debugging symbols, but @value{GDBN} would
15626 ordinarily parse a typical file name, like @file{foo.c}, as the three words
15627 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
15628 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
15635 looks up the value of @code{x} in the scope of the file @file{foo.c}.
15638 @cindex case-insensitive symbol names
15639 @cindex case sensitivity in symbol names
15640 @kindex set case-sensitive
15641 @item set case-sensitive on
15642 @itemx set case-sensitive off
15643 @itemx set case-sensitive auto
15644 Normally, when @value{GDBN} looks up symbols, it matches their names
15645 with case sensitivity determined by the current source language.
15646 Occasionally, you may wish to control that. The command @code{set
15647 case-sensitive} lets you do that by specifying @code{on} for
15648 case-sensitive matches or @code{off} for case-insensitive ones. If
15649 you specify @code{auto}, case sensitivity is reset to the default
15650 suitable for the source language. The default is case-sensitive
15651 matches for all languages except for Fortran, for which the default is
15652 case-insensitive matches.
15654 @kindex show case-sensitive
15655 @item show case-sensitive
15656 This command shows the current setting of case sensitivity for symbols
15659 @kindex set print type methods
15660 @item set print type methods
15661 @itemx set print type methods on
15662 @itemx set print type methods off
15663 Normally, when @value{GDBN} prints a class, it displays any methods
15664 declared in that class. You can control this behavior either by
15665 passing the appropriate flag to @code{ptype}, or using @command{set
15666 print type methods}. Specifying @code{on} will cause @value{GDBN} to
15667 display the methods; this is the default. Specifying @code{off} will
15668 cause @value{GDBN} to omit the methods.
15670 @kindex show print type methods
15671 @item show print type methods
15672 This command shows the current setting of method display when printing
15675 @kindex set print type typedefs
15676 @item set print type typedefs
15677 @itemx set print type typedefs on
15678 @itemx set print type typedefs off
15680 Normally, when @value{GDBN} prints a class, it displays any typedefs
15681 defined in that class. You can control this behavior either by
15682 passing the appropriate flag to @code{ptype}, or using @command{set
15683 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
15684 display the typedef definitions; this is the default. Specifying
15685 @code{off} will cause @value{GDBN} to omit the typedef definitions.
15686 Note that this controls whether the typedef definition itself is
15687 printed, not whether typedef names are substituted when printing other
15690 @kindex show print type typedefs
15691 @item show print type typedefs
15692 This command shows the current setting of typedef display when
15695 @kindex info address
15696 @cindex address of a symbol
15697 @item info address @var{symbol}
15698 Describe where the data for @var{symbol} is stored. For a register
15699 variable, this says which register it is kept in. For a non-register
15700 local variable, this prints the stack-frame offset at which the variable
15703 Note the contrast with @samp{print &@var{symbol}}, which does not work
15704 at all for a register variable, and for a stack local variable prints
15705 the exact address of the current instantiation of the variable.
15707 @kindex info symbol
15708 @cindex symbol from address
15709 @cindex closest symbol and offset for an address
15710 @item info symbol @var{addr}
15711 Print the name of a symbol which is stored at the address @var{addr}.
15712 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
15713 nearest symbol and an offset from it:
15716 (@value{GDBP}) info symbol 0x54320
15717 _initialize_vx + 396 in section .text
15721 This is the opposite of the @code{info address} command. You can use
15722 it to find out the name of a variable or a function given its address.
15724 For dynamically linked executables, the name of executable or shared
15725 library containing the symbol is also printed:
15728 (@value{GDBP}) info symbol 0x400225
15729 _start + 5 in section .text of /tmp/a.out
15730 (@value{GDBP}) info symbol 0x2aaaac2811cf
15731 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
15735 @item whatis[/@var{flags}] [@var{arg}]
15736 Print the data type of @var{arg}, which can be either an expression
15737 or a name of a data type. With no argument, print the data type of
15738 @code{$}, the last value in the value history.
15740 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
15741 is not actually evaluated, and any side-effecting operations (such as
15742 assignments or function calls) inside it do not take place.
15744 If @var{arg} is a variable or an expression, @code{whatis} prints its
15745 literal type as it is used in the source code. If the type was
15746 defined using a @code{typedef}, @code{whatis} will @emph{not} print
15747 the data type underlying the @code{typedef}. If the type of the
15748 variable or the expression is a compound data type, such as
15749 @code{struct} or @code{class}, @code{whatis} never prints their
15750 fields or methods. It just prints the @code{struct}/@code{class}
15751 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
15752 such a compound data type, use @code{ptype}.
15754 If @var{arg} is a type name that was defined using @code{typedef},
15755 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
15756 Unrolling means that @code{whatis} will show the underlying type used
15757 in the @code{typedef} declaration of @var{arg}. However, if that
15758 underlying type is also a @code{typedef}, @code{whatis} will not
15761 For C code, the type names may also have the form @samp{class
15762 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
15763 @var{union-tag}} or @samp{enum @var{enum-tag}}.
15765 @var{flags} can be used to modify how the type is displayed.
15766 Available flags are:
15770 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
15771 parameters and typedefs defined in a class when printing the class'
15772 members. The @code{/r} flag disables this.
15775 Do not print methods defined in the class.
15778 Print methods defined in the class. This is the default, but the flag
15779 exists in case you change the default with @command{set print type methods}.
15782 Do not print typedefs defined in the class. Note that this controls
15783 whether the typedef definition itself is printed, not whether typedef
15784 names are substituted when printing other types.
15787 Print typedefs defined in the class. This is the default, but the flag
15788 exists in case you change the default with @command{set print type typedefs}.
15792 @item ptype[/@var{flags}] [@var{arg}]
15793 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
15794 detailed description of the type, instead of just the name of the type.
15795 @xref{Expressions, ,Expressions}.
15797 Contrary to @code{whatis}, @code{ptype} always unrolls any
15798 @code{typedef}s in its argument declaration, whether the argument is
15799 a variable, expression, or a data type. This means that @code{ptype}
15800 of a variable or an expression will not print literally its type as
15801 present in the source code---use @code{whatis} for that. @code{typedef}s at
15802 the pointer or reference targets are also unrolled. Only @code{typedef}s of
15803 fields, methods and inner @code{class typedef}s of @code{struct}s,
15804 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
15806 For example, for this variable declaration:
15809 typedef double real_t;
15810 struct complex @{ real_t real; double imag; @};
15811 typedef struct complex complex_t;
15813 real_t *real_pointer_var;
15817 the two commands give this output:
15821 (@value{GDBP}) whatis var
15823 (@value{GDBP}) ptype var
15824 type = struct complex @{
15828 (@value{GDBP}) whatis complex_t
15829 type = struct complex
15830 (@value{GDBP}) whatis struct complex
15831 type = struct complex
15832 (@value{GDBP}) ptype struct complex
15833 type = struct complex @{
15837 (@value{GDBP}) whatis real_pointer_var
15839 (@value{GDBP}) ptype real_pointer_var
15845 As with @code{whatis}, using @code{ptype} without an argument refers to
15846 the type of @code{$}, the last value in the value history.
15848 @cindex incomplete type
15849 Sometimes, programs use opaque data types or incomplete specifications
15850 of complex data structure. If the debug information included in the
15851 program does not allow @value{GDBN} to display a full declaration of
15852 the data type, it will say @samp{<incomplete type>}. For example,
15853 given these declarations:
15857 struct foo *fooptr;
15861 but no definition for @code{struct foo} itself, @value{GDBN} will say:
15864 (@value{GDBP}) ptype foo
15865 $1 = <incomplete type>
15869 ``Incomplete type'' is C terminology for data types that are not
15870 completely specified.
15873 @item info types @var{regexp}
15875 Print a brief description of all types whose names match the regular
15876 expression @var{regexp} (or all types in your program, if you supply
15877 no argument). Each complete typename is matched as though it were a
15878 complete line; thus, @samp{i type value} gives information on all
15879 types in your program whose names include the string @code{value}, but
15880 @samp{i type ^value$} gives information only on types whose complete
15881 name is @code{value}.
15883 This command differs from @code{ptype} in two ways: first, like
15884 @code{whatis}, it does not print a detailed description; second, it
15885 lists all source files where a type is defined.
15887 @kindex info type-printers
15888 @item info type-printers
15889 Versions of @value{GDBN} that ship with Python scripting enabled may
15890 have ``type printers'' available. When using @command{ptype} or
15891 @command{whatis}, these printers are consulted when the name of a type
15892 is needed. @xref{Type Printing API}, for more information on writing
15895 @code{info type-printers} displays all the available type printers.
15897 @kindex enable type-printer
15898 @kindex disable type-printer
15899 @item enable type-printer @var{name}@dots{}
15900 @item disable type-printer @var{name}@dots{}
15901 These commands can be used to enable or disable type printers.
15904 @cindex local variables
15905 @item info scope @var{location}
15906 List all the variables local to a particular scope. This command
15907 accepts a @var{location} argument---a function name, a source line, or
15908 an address preceded by a @samp{*}, and prints all the variables local
15909 to the scope defined by that location. (@xref{Specify Location}, for
15910 details about supported forms of @var{location}.) For example:
15913 (@value{GDBP}) @b{info scope command_line_handler}
15914 Scope for command_line_handler:
15915 Symbol rl is an argument at stack/frame offset 8, length 4.
15916 Symbol linebuffer is in static storage at address 0x150a18, length 4.
15917 Symbol linelength is in static storage at address 0x150a1c, length 4.
15918 Symbol p is a local variable in register $esi, length 4.
15919 Symbol p1 is a local variable in register $ebx, length 4.
15920 Symbol nline is a local variable in register $edx, length 4.
15921 Symbol repeat is a local variable at frame offset -8, length 4.
15925 This command is especially useful for determining what data to collect
15926 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
15929 @kindex info source
15931 Show information about the current source file---that is, the source file for
15932 the function containing the current point of execution:
15935 the name of the source file, and the directory containing it,
15937 the directory it was compiled in,
15939 its length, in lines,
15941 which programming language it is written in,
15943 whether the executable includes debugging information for that file, and
15944 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
15946 whether the debugging information includes information about
15947 preprocessor macros.
15951 @kindex info sources
15953 Print the names of all source files in your program for which there is
15954 debugging information, organized into two lists: files whose symbols
15955 have already been read, and files whose symbols will be read when needed.
15957 @kindex info functions
15958 @item info functions
15959 Print the names and data types of all defined functions.
15961 @item info functions @var{regexp}
15962 Print the names and data types of all defined functions
15963 whose names contain a match for regular expression @var{regexp}.
15964 Thus, @samp{info fun step} finds all functions whose names
15965 include @code{step}; @samp{info fun ^step} finds those whose names
15966 start with @code{step}. If a function name contains characters
15967 that conflict with the regular expression language (e.g.@:
15968 @samp{operator*()}), they may be quoted with a backslash.
15970 @kindex info variables
15971 @item info variables
15972 Print the names and data types of all variables that are defined
15973 outside of functions (i.e.@: excluding local variables).
15975 @item info variables @var{regexp}
15976 Print the names and data types of all variables (except for local
15977 variables) whose names contain a match for regular expression
15980 @kindex info classes
15981 @cindex Objective-C, classes and selectors
15983 @itemx info classes @var{regexp}
15984 Display all Objective-C classes in your program, or
15985 (with the @var{regexp} argument) all those matching a particular regular
15988 @kindex info selectors
15989 @item info selectors
15990 @itemx info selectors @var{regexp}
15991 Display all Objective-C selectors in your program, or
15992 (with the @var{regexp} argument) all those matching a particular regular
15996 This was never implemented.
15997 @kindex info methods
15999 @itemx info methods @var{regexp}
16000 The @code{info methods} command permits the user to examine all defined
16001 methods within C@t{++} program, or (with the @var{regexp} argument) a
16002 specific set of methods found in the various C@t{++} classes. Many
16003 C@t{++} classes provide a large number of methods. Thus, the output
16004 from the @code{ptype} command can be overwhelming and hard to use. The
16005 @code{info-methods} command filters the methods, printing only those
16006 which match the regular-expression @var{regexp}.
16009 @cindex opaque data types
16010 @kindex set opaque-type-resolution
16011 @item set opaque-type-resolution on
16012 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
16013 declared as a pointer to a @code{struct}, @code{class}, or
16014 @code{union}---for example, @code{struct MyType *}---that is used in one
16015 source file although the full declaration of @code{struct MyType} is in
16016 another source file. The default is on.
16018 A change in the setting of this subcommand will not take effect until
16019 the next time symbols for a file are loaded.
16021 @item set opaque-type-resolution off
16022 Tell @value{GDBN} not to resolve opaque types. In this case, the type
16023 is printed as follows:
16025 @{<no data fields>@}
16028 @kindex show opaque-type-resolution
16029 @item show opaque-type-resolution
16030 Show whether opaque types are resolved or not.
16032 @kindex maint print symbols
16033 @cindex symbol dump
16034 @kindex maint print psymbols
16035 @cindex partial symbol dump
16036 @kindex maint print msymbols
16037 @cindex minimal symbol dump
16038 @item maint print symbols @var{filename}
16039 @itemx maint print psymbols @var{filename}
16040 @itemx maint print msymbols @var{filename}
16041 Write a dump of debugging symbol data into the file @var{filename}.
16042 These commands are used to debug the @value{GDBN} symbol-reading code. Only
16043 symbols with debugging data are included. If you use @samp{maint print
16044 symbols}, @value{GDBN} includes all the symbols for which it has already
16045 collected full details: that is, @var{filename} reflects symbols for
16046 only those files whose symbols @value{GDBN} has read. You can use the
16047 command @code{info sources} to find out which files these are. If you
16048 use @samp{maint print psymbols} instead, the dump shows information about
16049 symbols that @value{GDBN} only knows partially---that is, symbols defined in
16050 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
16051 @samp{maint print msymbols} dumps just the minimal symbol information
16052 required for each object file from which @value{GDBN} has read some symbols.
16053 @xref{Files, ,Commands to Specify Files}, for a discussion of how
16054 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
16056 @kindex maint info symtabs
16057 @kindex maint info psymtabs
16058 @cindex listing @value{GDBN}'s internal symbol tables
16059 @cindex symbol tables, listing @value{GDBN}'s internal
16060 @cindex full symbol tables, listing @value{GDBN}'s internal
16061 @cindex partial symbol tables, listing @value{GDBN}'s internal
16062 @item maint info symtabs @r{[} @var{regexp} @r{]}
16063 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
16065 List the @code{struct symtab} or @code{struct partial_symtab}
16066 structures whose names match @var{regexp}. If @var{regexp} is not
16067 given, list them all. The output includes expressions which you can
16068 copy into a @value{GDBN} debugging this one to examine a particular
16069 structure in more detail. For example:
16072 (@value{GDBP}) maint info psymtabs dwarf2read
16073 @{ objfile /home/gnu/build/gdb/gdb
16074 ((struct objfile *) 0x82e69d0)
16075 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
16076 ((struct partial_symtab *) 0x8474b10)
16079 text addresses 0x814d3c8 -- 0x8158074
16080 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
16081 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
16082 dependencies (none)
16085 (@value{GDBP}) maint info symtabs
16089 We see that there is one partial symbol table whose filename contains
16090 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
16091 and we see that @value{GDBN} has not read in any symtabs yet at all.
16092 If we set a breakpoint on a function, that will cause @value{GDBN} to
16093 read the symtab for the compilation unit containing that function:
16096 (@value{GDBP}) break dwarf2_psymtab_to_symtab
16097 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
16099 (@value{GDBP}) maint info symtabs
16100 @{ objfile /home/gnu/build/gdb/gdb
16101 ((struct objfile *) 0x82e69d0)
16102 @{ symtab /home/gnu/src/gdb/dwarf2read.c
16103 ((struct symtab *) 0x86c1f38)
16106 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
16107 linetable ((struct linetable *) 0x8370fa0)
16108 debugformat DWARF 2
16117 @chapter Altering Execution
16119 Once you think you have found an error in your program, you might want to
16120 find out for certain whether correcting the apparent error would lead to
16121 correct results in the rest of the run. You can find the answer by
16122 experiment, using the @value{GDBN} features for altering execution of the
16125 For example, you can store new values into variables or memory
16126 locations, give your program a signal, restart it at a different
16127 address, or even return prematurely from a function.
16130 * Assignment:: Assignment to variables
16131 * Jumping:: Continuing at a different address
16132 * Signaling:: Giving your program a signal
16133 * Returning:: Returning from a function
16134 * Calling:: Calling your program's functions
16135 * Patching:: Patching your program
16139 @section Assignment to Variables
16142 @cindex setting variables
16143 To alter the value of a variable, evaluate an assignment expression.
16144 @xref{Expressions, ,Expressions}. For example,
16151 stores the value 4 into the variable @code{x}, and then prints the
16152 value of the assignment expression (which is 4).
16153 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
16154 information on operators in supported languages.
16156 @kindex set variable
16157 @cindex variables, setting
16158 If you are not interested in seeing the value of the assignment, use the
16159 @code{set} command instead of the @code{print} command. @code{set} is
16160 really the same as @code{print} except that the expression's value is
16161 not printed and is not put in the value history (@pxref{Value History,
16162 ,Value History}). The expression is evaluated only for its effects.
16164 If the beginning of the argument string of the @code{set} command
16165 appears identical to a @code{set} subcommand, use the @code{set
16166 variable} command instead of just @code{set}. This command is identical
16167 to @code{set} except for its lack of subcommands. For example, if your
16168 program has a variable @code{width}, you get an error if you try to set
16169 a new value with just @samp{set width=13}, because @value{GDBN} has the
16170 command @code{set width}:
16173 (@value{GDBP}) whatis width
16175 (@value{GDBP}) p width
16177 (@value{GDBP}) set width=47
16178 Invalid syntax in expression.
16182 The invalid expression, of course, is @samp{=47}. In
16183 order to actually set the program's variable @code{width}, use
16186 (@value{GDBP}) set var width=47
16189 Because the @code{set} command has many subcommands that can conflict
16190 with the names of program variables, it is a good idea to use the
16191 @code{set variable} command instead of just @code{set}. For example, if
16192 your program has a variable @code{g}, you run into problems if you try
16193 to set a new value with just @samp{set g=4}, because @value{GDBN} has
16194 the command @code{set gnutarget}, abbreviated @code{set g}:
16198 (@value{GDBP}) whatis g
16202 (@value{GDBP}) set g=4
16206 The program being debugged has been started already.
16207 Start it from the beginning? (y or n) y
16208 Starting program: /home/smith/cc_progs/a.out
16209 "/home/smith/cc_progs/a.out": can't open to read symbols:
16210 Invalid bfd target.
16211 (@value{GDBP}) show g
16212 The current BFD target is "=4".
16217 The program variable @code{g} did not change, and you silently set the
16218 @code{gnutarget} to an invalid value. In order to set the variable
16222 (@value{GDBP}) set var g=4
16225 @value{GDBN} allows more implicit conversions in assignments than C; you can
16226 freely store an integer value into a pointer variable or vice versa,
16227 and you can convert any structure to any other structure that is the
16228 same length or shorter.
16229 @comment FIXME: how do structs align/pad in these conversions?
16230 @comment /doc@cygnus.com 18dec1990
16232 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
16233 construct to generate a value of specified type at a specified address
16234 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
16235 to memory location @code{0x83040} as an integer (which implies a certain size
16236 and representation in memory), and
16239 set @{int@}0x83040 = 4
16243 stores the value 4 into that memory location.
16246 @section Continuing at a Different Address
16248 Ordinarily, when you continue your program, you do so at the place where
16249 it stopped, with the @code{continue} command. You can instead continue at
16250 an address of your own choosing, with the following commands:
16254 @kindex j @r{(@code{jump})}
16255 @item jump @var{linespec}
16256 @itemx j @var{linespec}
16257 @itemx jump @var{location}
16258 @itemx j @var{location}
16259 Resume execution at line @var{linespec} or at address given by
16260 @var{location}. Execution stops again immediately if there is a
16261 breakpoint there. @xref{Specify Location}, for a description of the
16262 different forms of @var{linespec} and @var{location}. It is common
16263 practice to use the @code{tbreak} command in conjunction with
16264 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
16266 The @code{jump} command does not change the current stack frame, or
16267 the stack pointer, or the contents of any memory location or any
16268 register other than the program counter. If line @var{linespec} is in
16269 a different function from the one currently executing, the results may
16270 be bizarre if the two functions expect different patterns of arguments or
16271 of local variables. For this reason, the @code{jump} command requests
16272 confirmation if the specified line is not in the function currently
16273 executing. However, even bizarre results are predictable if you are
16274 well acquainted with the machine-language code of your program.
16277 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
16278 On many systems, you can get much the same effect as the @code{jump}
16279 command by storing a new value into the register @code{$pc}. The
16280 difference is that this does not start your program running; it only
16281 changes the address of where it @emph{will} run when you continue. For
16289 makes the next @code{continue} command or stepping command execute at
16290 address @code{0x485}, rather than at the address where your program stopped.
16291 @xref{Continuing and Stepping, ,Continuing and Stepping}.
16293 The most common occasion to use the @code{jump} command is to back
16294 up---perhaps with more breakpoints set---over a portion of a program
16295 that has already executed, in order to examine its execution in more
16300 @section Giving your Program a Signal
16301 @cindex deliver a signal to a program
16305 @item signal @var{signal}
16306 Resume execution where your program stopped, but immediately give it the
16307 signal @var{signal}. @var{signal} can be the name or the number of a
16308 signal. For example, on many systems @code{signal 2} and @code{signal
16309 SIGINT} are both ways of sending an interrupt signal.
16311 Alternatively, if @var{signal} is zero, continue execution without
16312 giving a signal. This is useful when your program stopped on account of
16313 a signal and would ordinarily see the signal when resumed with the
16314 @code{continue} command; @samp{signal 0} causes it to resume without a
16317 @code{signal} does not repeat when you press @key{RET} a second time
16318 after executing the command.
16322 Invoking the @code{signal} command is not the same as invoking the
16323 @code{kill} utility from the shell. Sending a signal with @code{kill}
16324 causes @value{GDBN} to decide what to do with the signal depending on
16325 the signal handling tables (@pxref{Signals}). The @code{signal} command
16326 passes the signal directly to your program.
16330 @section Returning from a Function
16333 @cindex returning from a function
16336 @itemx return @var{expression}
16337 You can cancel execution of a function call with the @code{return}
16338 command. If you give an
16339 @var{expression} argument, its value is used as the function's return
16343 When you use @code{return}, @value{GDBN} discards the selected stack frame
16344 (and all frames within it). You can think of this as making the
16345 discarded frame return prematurely. If you wish to specify a value to
16346 be returned, give that value as the argument to @code{return}.
16348 This pops the selected stack frame (@pxref{Selection, ,Selecting a
16349 Frame}), and any other frames inside of it, leaving its caller as the
16350 innermost remaining frame. That frame becomes selected. The
16351 specified value is stored in the registers used for returning values
16354 The @code{return} command does not resume execution; it leaves the
16355 program stopped in the state that would exist if the function had just
16356 returned. In contrast, the @code{finish} command (@pxref{Continuing
16357 and Stepping, ,Continuing and Stepping}) resumes execution until the
16358 selected stack frame returns naturally.
16360 @value{GDBN} needs to know how the @var{expression} argument should be set for
16361 the inferior. The concrete registers assignment depends on the OS ABI and the
16362 type being returned by the selected stack frame. For example it is common for
16363 OS ABI to return floating point values in FPU registers while integer values in
16364 CPU registers. Still some ABIs return even floating point values in CPU
16365 registers. Larger integer widths (such as @code{long long int}) also have
16366 specific placement rules. @value{GDBN} already knows the OS ABI from its
16367 current target so it needs to find out also the type being returned to make the
16368 assignment into the right register(s).
16370 Normally, the selected stack frame has debug info. @value{GDBN} will always
16371 use the debug info instead of the implicit type of @var{expression} when the
16372 debug info is available. For example, if you type @kbd{return -1}, and the
16373 function in the current stack frame is declared to return a @code{long long
16374 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
16375 into a @code{long long int}:
16378 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
16380 (@value{GDBP}) return -1
16381 Make func return now? (y or n) y
16382 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
16383 43 printf ("result=%lld\n", func ());
16387 However, if the selected stack frame does not have a debug info, e.g., if the
16388 function was compiled without debug info, @value{GDBN} has to find out the type
16389 to return from user. Specifying a different type by mistake may set the value
16390 in different inferior registers than the caller code expects. For example,
16391 typing @kbd{return -1} with its implicit type @code{int} would set only a part
16392 of a @code{long long int} result for a debug info less function (on 32-bit
16393 architectures). Therefore the user is required to specify the return type by
16394 an appropriate cast explicitly:
16397 Breakpoint 2, 0x0040050b in func ()
16398 (@value{GDBP}) return -1
16399 Return value type not available for selected stack frame.
16400 Please use an explicit cast of the value to return.
16401 (@value{GDBP}) return (long long int) -1
16402 Make selected stack frame return now? (y or n) y
16403 #0 0x00400526 in main ()
16408 @section Calling Program Functions
16411 @cindex calling functions
16412 @cindex inferior functions, calling
16413 @item print @var{expr}
16414 Evaluate the expression @var{expr} and display the resulting value.
16415 @var{expr} may include calls to functions in the program being
16419 @item call @var{expr}
16420 Evaluate the expression @var{expr} without displaying @code{void}
16423 You can use this variant of the @code{print} command if you want to
16424 execute a function from your program that does not return anything
16425 (a.k.a.@: @dfn{a void function}), but without cluttering the output
16426 with @code{void} returned values that @value{GDBN} will otherwise
16427 print. If the result is not void, it is printed and saved in the
16431 It is possible for the function you call via the @code{print} or
16432 @code{call} command to generate a signal (e.g., if there's a bug in
16433 the function, or if you passed it incorrect arguments). What happens
16434 in that case is controlled by the @code{set unwindonsignal} command.
16436 Similarly, with a C@t{++} program it is possible for the function you
16437 call via the @code{print} or @code{call} command to generate an
16438 exception that is not handled due to the constraints of the dummy
16439 frame. In this case, any exception that is raised in the frame, but has
16440 an out-of-frame exception handler will not be found. GDB builds a
16441 dummy-frame for the inferior function call, and the unwinder cannot
16442 seek for exception handlers outside of this dummy-frame. What happens
16443 in that case is controlled by the
16444 @code{set unwind-on-terminating-exception} command.
16447 @item set unwindonsignal
16448 @kindex set unwindonsignal
16449 @cindex unwind stack in called functions
16450 @cindex call dummy stack unwinding
16451 Set unwinding of the stack if a signal is received while in a function
16452 that @value{GDBN} called in the program being debugged. If set to on,
16453 @value{GDBN} unwinds the stack it created for the call and restores
16454 the context to what it was before the call. If set to off (the
16455 default), @value{GDBN} stops in the frame where the signal was
16458 @item show unwindonsignal
16459 @kindex show unwindonsignal
16460 Show the current setting of stack unwinding in the functions called by
16463 @item set unwind-on-terminating-exception
16464 @kindex set unwind-on-terminating-exception
16465 @cindex unwind stack in called functions with unhandled exceptions
16466 @cindex call dummy stack unwinding on unhandled exception.
16467 Set unwinding of the stack if a C@t{++} exception is raised, but left
16468 unhandled while in a function that @value{GDBN} called in the program being
16469 debugged. If set to on (the default), @value{GDBN} unwinds the stack
16470 it created for the call and restores the context to what it was before
16471 the call. If set to off, @value{GDBN} the exception is delivered to
16472 the default C@t{++} exception handler and the inferior terminated.
16474 @item show unwind-on-terminating-exception
16475 @kindex show unwind-on-terminating-exception
16476 Show the current setting of stack unwinding in the functions called by
16481 @cindex weak alias functions
16482 Sometimes, a function you wish to call is actually a @dfn{weak alias}
16483 for another function. In such case, @value{GDBN} might not pick up
16484 the type information, including the types of the function arguments,
16485 which causes @value{GDBN} to call the inferior function incorrectly.
16486 As a result, the called function will function erroneously and may
16487 even crash. A solution to that is to use the name of the aliased
16491 @section Patching Programs
16493 @cindex patching binaries
16494 @cindex writing into executables
16495 @cindex writing into corefiles
16497 By default, @value{GDBN} opens the file containing your program's
16498 executable code (or the corefile) read-only. This prevents accidental
16499 alterations to machine code; but it also prevents you from intentionally
16500 patching your program's binary.
16502 If you'd like to be able to patch the binary, you can specify that
16503 explicitly with the @code{set write} command. For example, you might
16504 want to turn on internal debugging flags, or even to make emergency
16510 @itemx set write off
16511 If you specify @samp{set write on}, @value{GDBN} opens executable and
16512 core files for both reading and writing; if you specify @kbd{set write
16513 off} (the default), @value{GDBN} opens them read-only.
16515 If you have already loaded a file, you must load it again (using the
16516 @code{exec-file} or @code{core-file} command) after changing @code{set
16517 write}, for your new setting to take effect.
16521 Display whether executable files and core files are opened for writing
16522 as well as reading.
16526 @chapter @value{GDBN} Files
16528 @value{GDBN} needs to know the file name of the program to be debugged,
16529 both in order to read its symbol table and in order to start your
16530 program. To debug a core dump of a previous run, you must also tell
16531 @value{GDBN} the name of the core dump file.
16534 * Files:: Commands to specify files
16535 * Separate Debug Files:: Debugging information in separate files
16536 * MiniDebugInfo:: Debugging information in a special section
16537 * Index Files:: Index files speed up GDB
16538 * Symbol Errors:: Errors reading symbol files
16539 * Data Files:: GDB data files
16543 @section Commands to Specify Files
16545 @cindex symbol table
16546 @cindex core dump file
16548 You may want to specify executable and core dump file names. The usual
16549 way to do this is at start-up time, using the arguments to
16550 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
16551 Out of @value{GDBN}}).
16553 Occasionally it is necessary to change to a different file during a
16554 @value{GDBN} session. Or you may run @value{GDBN} and forget to
16555 specify a file you want to use. Or you are debugging a remote target
16556 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
16557 Program}). In these situations the @value{GDBN} commands to specify
16558 new files are useful.
16561 @cindex executable file
16563 @item file @var{filename}
16564 Use @var{filename} as the program to be debugged. It is read for its
16565 symbols and for the contents of pure memory. It is also the program
16566 executed when you use the @code{run} command. If you do not specify a
16567 directory and the file is not found in the @value{GDBN} working directory,
16568 @value{GDBN} uses the environment variable @code{PATH} as a list of
16569 directories to search, just as the shell does when looking for a program
16570 to run. You can change the value of this variable, for both @value{GDBN}
16571 and your program, using the @code{path} command.
16573 @cindex unlinked object files
16574 @cindex patching object files
16575 You can load unlinked object @file{.o} files into @value{GDBN} using
16576 the @code{file} command. You will not be able to ``run'' an object
16577 file, but you can disassemble functions and inspect variables. Also,
16578 if the underlying BFD functionality supports it, you could use
16579 @kbd{gdb -write} to patch object files using this technique. Note
16580 that @value{GDBN} can neither interpret nor modify relocations in this
16581 case, so branches and some initialized variables will appear to go to
16582 the wrong place. But this feature is still handy from time to time.
16585 @code{file} with no argument makes @value{GDBN} discard any information it
16586 has on both executable file and the symbol table.
16589 @item exec-file @r{[} @var{filename} @r{]}
16590 Specify that the program to be run (but not the symbol table) is found
16591 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
16592 if necessary to locate your program. Omitting @var{filename} means to
16593 discard information on the executable file.
16595 @kindex symbol-file
16596 @item symbol-file @r{[} @var{filename} @r{]}
16597 Read symbol table information from file @var{filename}. @code{PATH} is
16598 searched when necessary. Use the @code{file} command to get both symbol
16599 table and program to run from the same file.
16601 @code{symbol-file} with no argument clears out @value{GDBN} information on your
16602 program's symbol table.
16604 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
16605 some breakpoints and auto-display expressions. This is because they may
16606 contain pointers to the internal data recording symbols and data types,
16607 which are part of the old symbol table data being discarded inside
16610 @code{symbol-file} does not repeat if you press @key{RET} again after
16613 When @value{GDBN} is configured for a particular environment, it
16614 understands debugging information in whatever format is the standard
16615 generated for that environment; you may use either a @sc{gnu} compiler, or
16616 other compilers that adhere to the local conventions.
16617 Best results are usually obtained from @sc{gnu} compilers; for example,
16618 using @code{@value{NGCC}} you can generate debugging information for
16621 For most kinds of object files, with the exception of old SVR3 systems
16622 using COFF, the @code{symbol-file} command does not normally read the
16623 symbol table in full right away. Instead, it scans the symbol table
16624 quickly to find which source files and which symbols are present. The
16625 details are read later, one source file at a time, as they are needed.
16627 The purpose of this two-stage reading strategy is to make @value{GDBN}
16628 start up faster. For the most part, it is invisible except for
16629 occasional pauses while the symbol table details for a particular source
16630 file are being read. (The @code{set verbose} command can turn these
16631 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
16632 Warnings and Messages}.)
16634 We have not implemented the two-stage strategy for COFF yet. When the
16635 symbol table is stored in COFF format, @code{symbol-file} reads the
16636 symbol table data in full right away. Note that ``stabs-in-COFF''
16637 still does the two-stage strategy, since the debug info is actually
16641 @cindex reading symbols immediately
16642 @cindex symbols, reading immediately
16643 @item symbol-file @r{[} -readnow @r{]} @var{filename}
16644 @itemx file @r{[} -readnow @r{]} @var{filename}
16645 You can override the @value{GDBN} two-stage strategy for reading symbol
16646 tables by using the @samp{-readnow} option with any of the commands that
16647 load symbol table information, if you want to be sure @value{GDBN} has the
16648 entire symbol table available.
16650 @c FIXME: for now no mention of directories, since this seems to be in
16651 @c flux. 13mar1992 status is that in theory GDB would look either in
16652 @c current dir or in same dir as myprog; but issues like competing
16653 @c GDB's, or clutter in system dirs, mean that in practice right now
16654 @c only current dir is used. FFish says maybe a special GDB hierarchy
16655 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
16659 @item core-file @r{[}@var{filename}@r{]}
16661 Specify the whereabouts of a core dump file to be used as the ``contents
16662 of memory''. Traditionally, core files contain only some parts of the
16663 address space of the process that generated them; @value{GDBN} can access the
16664 executable file itself for other parts.
16666 @code{core-file} with no argument specifies that no core file is
16669 Note that the core file is ignored when your program is actually running
16670 under @value{GDBN}. So, if you have been running your program and you
16671 wish to debug a core file instead, you must kill the subprocess in which
16672 the program is running. To do this, use the @code{kill} command
16673 (@pxref{Kill Process, ,Killing the Child Process}).
16675 @kindex add-symbol-file
16676 @cindex dynamic linking
16677 @item add-symbol-file @var{filename} @var{address}
16678 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
16679 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
16680 The @code{add-symbol-file} command reads additional symbol table
16681 information from the file @var{filename}. You would use this command
16682 when @var{filename} has been dynamically loaded (by some other means)
16683 into the program that is running. @var{address} should be the memory
16684 address at which the file has been loaded; @value{GDBN} cannot figure
16685 this out for itself. You can additionally specify an arbitrary number
16686 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
16687 section name and base address for that section. You can specify any
16688 @var{address} as an expression.
16690 The symbol table of the file @var{filename} is added to the symbol table
16691 originally read with the @code{symbol-file} command. You can use the
16692 @code{add-symbol-file} command any number of times; the new symbol data
16693 thus read keeps adding to the old. To discard all old symbol data
16694 instead, use the @code{symbol-file} command without any arguments.
16696 @cindex relocatable object files, reading symbols from
16697 @cindex object files, relocatable, reading symbols from
16698 @cindex reading symbols from relocatable object files
16699 @cindex symbols, reading from relocatable object files
16700 @cindex @file{.o} files, reading symbols from
16701 Although @var{filename} is typically a shared library file, an
16702 executable file, or some other object file which has been fully
16703 relocated for loading into a process, you can also load symbolic
16704 information from relocatable @file{.o} files, as long as:
16708 the file's symbolic information refers only to linker symbols defined in
16709 that file, not to symbols defined by other object files,
16711 every section the file's symbolic information refers to has actually
16712 been loaded into the inferior, as it appears in the file, and
16714 you can determine the address at which every section was loaded, and
16715 provide these to the @code{add-symbol-file} command.
16719 Some embedded operating systems, like Sun Chorus and VxWorks, can load
16720 relocatable files into an already running program; such systems
16721 typically make the requirements above easy to meet. However, it's
16722 important to recognize that many native systems use complex link
16723 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
16724 assembly, for example) that make the requirements difficult to meet. In
16725 general, one cannot assume that using @code{add-symbol-file} to read a
16726 relocatable object file's symbolic information will have the same effect
16727 as linking the relocatable object file into the program in the normal
16730 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
16732 @kindex add-symbol-file-from-memory
16733 @cindex @code{syscall DSO}
16734 @cindex load symbols from memory
16735 @item add-symbol-file-from-memory @var{address}
16736 Load symbols from the given @var{address} in a dynamically loaded
16737 object file whose image is mapped directly into the inferior's memory.
16738 For example, the Linux kernel maps a @code{syscall DSO} into each
16739 process's address space; this DSO provides kernel-specific code for
16740 some system calls. The argument can be any expression whose
16741 evaluation yields the address of the file's shared object file header.
16742 For this command to work, you must have used @code{symbol-file} or
16743 @code{exec-file} commands in advance.
16745 @kindex add-shared-symbol-files
16747 @item add-shared-symbol-files @var{library-file}
16748 @itemx assf @var{library-file}
16749 The @code{add-shared-symbol-files} command can currently be used only
16750 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
16751 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
16752 @value{GDBN} automatically looks for shared libraries, however if
16753 @value{GDBN} does not find yours, you can invoke
16754 @code{add-shared-symbol-files}. It takes one argument: the shared
16755 library's file name. @code{assf} is a shorthand alias for
16756 @code{add-shared-symbol-files}.
16759 @item section @var{section} @var{addr}
16760 The @code{section} command changes the base address of the named
16761 @var{section} of the exec file to @var{addr}. This can be used if the
16762 exec file does not contain section addresses, (such as in the
16763 @code{a.out} format), or when the addresses specified in the file
16764 itself are wrong. Each section must be changed separately. The
16765 @code{info files} command, described below, lists all the sections and
16769 @kindex info target
16772 @code{info files} and @code{info target} are synonymous; both print the
16773 current target (@pxref{Targets, ,Specifying a Debugging Target}),
16774 including the names of the executable and core dump files currently in
16775 use by @value{GDBN}, and the files from which symbols were loaded. The
16776 command @code{help target} lists all possible targets rather than
16779 @kindex maint info sections
16780 @item maint info sections
16781 Another command that can give you extra information about program sections
16782 is @code{maint info sections}. In addition to the section information
16783 displayed by @code{info files}, this command displays the flags and file
16784 offset of each section in the executable and core dump files. In addition,
16785 @code{maint info sections} provides the following command options (which
16786 may be arbitrarily combined):
16790 Display sections for all loaded object files, including shared libraries.
16791 @item @var{sections}
16792 Display info only for named @var{sections}.
16793 @item @var{section-flags}
16794 Display info only for sections for which @var{section-flags} are true.
16795 The section flags that @value{GDBN} currently knows about are:
16798 Section will have space allocated in the process when loaded.
16799 Set for all sections except those containing debug information.
16801 Section will be loaded from the file into the child process memory.
16802 Set for pre-initialized code and data, clear for @code{.bss} sections.
16804 Section needs to be relocated before loading.
16806 Section cannot be modified by the child process.
16808 Section contains executable code only.
16810 Section contains data only (no executable code).
16812 Section will reside in ROM.
16814 Section contains data for constructor/destructor lists.
16816 Section is not empty.
16818 An instruction to the linker to not output the section.
16819 @item COFF_SHARED_LIBRARY
16820 A notification to the linker that the section contains
16821 COFF shared library information.
16823 Section contains common symbols.
16826 @kindex set trust-readonly-sections
16827 @cindex read-only sections
16828 @item set trust-readonly-sections on
16829 Tell @value{GDBN} that readonly sections in your object file
16830 really are read-only (i.e.@: that their contents will not change).
16831 In that case, @value{GDBN} can fetch values from these sections
16832 out of the object file, rather than from the target program.
16833 For some targets (notably embedded ones), this can be a significant
16834 enhancement to debugging performance.
16836 The default is off.
16838 @item set trust-readonly-sections off
16839 Tell @value{GDBN} not to trust readonly sections. This means that
16840 the contents of the section might change while the program is running,
16841 and must therefore be fetched from the target when needed.
16843 @item show trust-readonly-sections
16844 Show the current setting of trusting readonly sections.
16847 All file-specifying commands allow both absolute and relative file names
16848 as arguments. @value{GDBN} always converts the file name to an absolute file
16849 name and remembers it that way.
16851 @cindex shared libraries
16852 @anchor{Shared Libraries}
16853 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
16854 and IBM RS/6000 AIX shared libraries.
16856 On MS-Windows @value{GDBN} must be linked with the Expat library to support
16857 shared libraries. @xref{Expat}.
16859 @value{GDBN} automatically loads symbol definitions from shared libraries
16860 when you use the @code{run} command, or when you examine a core file.
16861 (Before you issue the @code{run} command, @value{GDBN} does not understand
16862 references to a function in a shared library, however---unless you are
16863 debugging a core file).
16865 On HP-UX, if the program loads a library explicitly, @value{GDBN}
16866 automatically loads the symbols at the time of the @code{shl_load} call.
16868 @c FIXME: some @value{GDBN} release may permit some refs to undef
16869 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
16870 @c FIXME...lib; check this from time to time when updating manual
16872 There are times, however, when you may wish to not automatically load
16873 symbol definitions from shared libraries, such as when they are
16874 particularly large or there are many of them.
16876 To control the automatic loading of shared library symbols, use the
16880 @kindex set auto-solib-add
16881 @item set auto-solib-add @var{mode}
16882 If @var{mode} is @code{on}, symbols from all shared object libraries
16883 will be loaded automatically when the inferior begins execution, you
16884 attach to an independently started inferior, or when the dynamic linker
16885 informs @value{GDBN} that a new library has been loaded. If @var{mode}
16886 is @code{off}, symbols must be loaded manually, using the
16887 @code{sharedlibrary} command. The default value is @code{on}.
16889 @cindex memory used for symbol tables
16890 If your program uses lots of shared libraries with debug info that
16891 takes large amounts of memory, you can decrease the @value{GDBN}
16892 memory footprint by preventing it from automatically loading the
16893 symbols from shared libraries. To that end, type @kbd{set
16894 auto-solib-add off} before running the inferior, then load each
16895 library whose debug symbols you do need with @kbd{sharedlibrary
16896 @var{regexp}}, where @var{regexp} is a regular expression that matches
16897 the libraries whose symbols you want to be loaded.
16899 @kindex show auto-solib-add
16900 @item show auto-solib-add
16901 Display the current autoloading mode.
16904 @cindex load shared library
16905 To explicitly load shared library symbols, use the @code{sharedlibrary}
16909 @kindex info sharedlibrary
16911 @item info share @var{regex}
16912 @itemx info sharedlibrary @var{regex}
16913 Print the names of the shared libraries which are currently loaded
16914 that match @var{regex}. If @var{regex} is omitted then print
16915 all shared libraries that are loaded.
16917 @kindex sharedlibrary
16919 @item sharedlibrary @var{regex}
16920 @itemx share @var{regex}
16921 Load shared object library symbols for files matching a
16922 Unix regular expression.
16923 As with files loaded automatically, it only loads shared libraries
16924 required by your program for a core file or after typing @code{run}. If
16925 @var{regex} is omitted all shared libraries required by your program are
16928 @item nosharedlibrary
16929 @kindex nosharedlibrary
16930 @cindex unload symbols from shared libraries
16931 Unload all shared object library symbols. This discards all symbols
16932 that have been loaded from all shared libraries. Symbols from shared
16933 libraries that were loaded by explicit user requests are not
16937 Sometimes you may wish that @value{GDBN} stops and gives you control
16938 when any of shared library events happen. The best way to do this is
16939 to use @code{catch load} and @code{catch unload} (@pxref{Set
16942 @value{GDBN} also supports the the @code{set stop-on-solib-events}
16943 command for this. This command exists for historical reasons. It is
16944 less useful than setting a catchpoint, because it does not allow for
16945 conditions or commands as a catchpoint does.
16948 @item set stop-on-solib-events
16949 @kindex set stop-on-solib-events
16950 This command controls whether @value{GDBN} should give you control
16951 when the dynamic linker notifies it about some shared library event.
16952 The most common event of interest is loading or unloading of a new
16955 @item show stop-on-solib-events
16956 @kindex show stop-on-solib-events
16957 Show whether @value{GDBN} stops and gives you control when shared
16958 library events happen.
16961 Shared libraries are also supported in many cross or remote debugging
16962 configurations. @value{GDBN} needs to have access to the target's libraries;
16963 this can be accomplished either by providing copies of the libraries
16964 on the host system, or by asking @value{GDBN} to automatically retrieve the
16965 libraries from the target. If copies of the target libraries are
16966 provided, they need to be the same as the target libraries, although the
16967 copies on the target can be stripped as long as the copies on the host are
16970 @cindex where to look for shared libraries
16971 For remote debugging, you need to tell @value{GDBN} where the target
16972 libraries are, so that it can load the correct copies---otherwise, it
16973 may try to load the host's libraries. @value{GDBN} has two variables
16974 to specify the search directories for target libraries.
16977 @cindex prefix for shared library file names
16978 @cindex system root, alternate
16979 @kindex set solib-absolute-prefix
16980 @kindex set sysroot
16981 @item set sysroot @var{path}
16982 Use @var{path} as the system root for the program being debugged. Any
16983 absolute shared library paths will be prefixed with @var{path}; many
16984 runtime loaders store the absolute paths to the shared library in the
16985 target program's memory. If you use @code{set sysroot} to find shared
16986 libraries, they need to be laid out in the same way that they are on
16987 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
16990 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
16991 retrieve the target libraries from the remote system. This is only
16992 supported when using a remote target that supports the @code{remote get}
16993 command (@pxref{File Transfer,,Sending files to a remote system}).
16994 The part of @var{path} following the initial @file{remote:}
16995 (if present) is used as system root prefix on the remote file system.
16996 @footnote{If you want to specify a local system root using a directory
16997 that happens to be named @file{remote:}, you need to use some equivalent
16998 variant of the name like @file{./remote:}.}
17000 For targets with an MS-DOS based filesystem, such as MS-Windows and
17001 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
17002 absolute file name with @var{path}. But first, on Unix hosts,
17003 @value{GDBN} converts all backslash directory separators into forward
17004 slashes, because the backslash is not a directory separator on Unix:
17007 c:\foo\bar.dll @result{} c:/foo/bar.dll
17010 Then, @value{GDBN} attempts prefixing the target file name with
17011 @var{path}, and looks for the resulting file name in the host file
17015 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
17018 If that does not find the shared library, @value{GDBN} tries removing
17019 the @samp{:} character from the drive spec, both for convenience, and,
17020 for the case of the host file system not supporting file names with
17024 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
17027 This makes it possible to have a system root that mirrors a target
17028 with more than one drive. E.g., you may want to setup your local
17029 copies of the target system shared libraries like so (note @samp{c} vs
17033 @file{/path/to/sysroot/c/sys/bin/foo.dll}
17034 @file{/path/to/sysroot/c/sys/bin/bar.dll}
17035 @file{/path/to/sysroot/z/sys/bin/bar.dll}
17039 and point the system root at @file{/path/to/sysroot}, so that
17040 @value{GDBN} can find the correct copies of both
17041 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
17043 If that still does not find the shared library, @value{GDBN} tries
17044 removing the whole drive spec from the target file name:
17047 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
17050 This last lookup makes it possible to not care about the drive name,
17051 if you don't want or need to.
17053 The @code{set solib-absolute-prefix} command is an alias for @code{set
17056 @cindex default system root
17057 @cindex @samp{--with-sysroot}
17058 You can set the default system root by using the configure-time
17059 @samp{--with-sysroot} option. If the system root is inside
17060 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17061 @samp{--exec-prefix}), then the default system root will be updated
17062 automatically if the installed @value{GDBN} is moved to a new
17065 @kindex show sysroot
17067 Display the current shared library prefix.
17069 @kindex set solib-search-path
17070 @item set solib-search-path @var{path}
17071 If this variable is set, @var{path} is a colon-separated list of
17072 directories to search for shared libraries. @samp{solib-search-path}
17073 is used after @samp{sysroot} fails to locate the library, or if the
17074 path to the library is relative instead of absolute. If you want to
17075 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
17076 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
17077 finding your host's libraries. @samp{sysroot} is preferred; setting
17078 it to a nonexistent directory may interfere with automatic loading
17079 of shared library symbols.
17081 @kindex show solib-search-path
17082 @item show solib-search-path
17083 Display the current shared library search path.
17085 @cindex DOS file-name semantics of file names.
17086 @kindex set target-file-system-kind (unix|dos-based|auto)
17087 @kindex show target-file-system-kind
17088 @item set target-file-system-kind @var{kind}
17089 Set assumed file system kind for target reported file names.
17091 Shared library file names as reported by the target system may not
17092 make sense as is on the system @value{GDBN} is running on. For
17093 example, when remote debugging a target that has MS-DOS based file
17094 system semantics, from a Unix host, the target may be reporting to
17095 @value{GDBN} a list of loaded shared libraries with file names such as
17096 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
17097 drive letters, so the @samp{c:\} prefix is not normally understood as
17098 indicating an absolute file name, and neither is the backslash
17099 normally considered a directory separator character. In that case,
17100 the native file system would interpret this whole absolute file name
17101 as a relative file name with no directory components. This would make
17102 it impossible to point @value{GDBN} at a copy of the remote target's
17103 shared libraries on the host using @code{set sysroot}, and impractical
17104 with @code{set solib-search-path}. Setting
17105 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
17106 to interpret such file names similarly to how the target would, and to
17107 map them to file names valid on @value{GDBN}'s native file system
17108 semantics. The value of @var{kind} can be @code{"auto"}, in addition
17109 to one of the supported file system kinds. In that case, @value{GDBN}
17110 tries to determine the appropriate file system variant based on the
17111 current target's operating system (@pxref{ABI, ,Configuring the
17112 Current ABI}). The supported file system settings are:
17116 Instruct @value{GDBN} to assume the target file system is of Unix
17117 kind. Only file names starting the forward slash (@samp{/}) character
17118 are considered absolute, and the directory separator character is also
17122 Instruct @value{GDBN} to assume the target file system is DOS based.
17123 File names starting with either a forward slash, or a drive letter
17124 followed by a colon (e.g., @samp{c:}), are considered absolute, and
17125 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
17126 considered directory separators.
17129 Instruct @value{GDBN} to use the file system kind associated with the
17130 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
17131 This is the default.
17135 @cindex file name canonicalization
17136 @cindex base name differences
17137 When processing file names provided by the user, @value{GDBN}
17138 frequently needs to compare them to the file names recorded in the
17139 program's debug info. Normally, @value{GDBN} compares just the
17140 @dfn{base names} of the files as strings, which is reasonably fast
17141 even for very large programs. (The base name of a file is the last
17142 portion of its name, after stripping all the leading directories.)
17143 This shortcut in comparison is based upon the assumption that files
17144 cannot have more than one base name. This is usually true, but
17145 references to files that use symlinks or similar filesystem
17146 facilities violate that assumption. If your program records files
17147 using such facilities, or if you provide file names to @value{GDBN}
17148 using symlinks etc., you can set @code{basenames-may-differ} to
17149 @code{true} to instruct @value{GDBN} to completely canonicalize each
17150 pair of file names it needs to compare. This will make file-name
17151 comparisons accurate, but at a price of a significant slowdown.
17154 @item set basenames-may-differ
17155 @kindex set basenames-may-differ
17156 Set whether a source file may have multiple base names.
17158 @item show basenames-may-differ
17159 @kindex show basenames-may-differ
17160 Show whether a source file may have multiple base names.
17163 @node Separate Debug Files
17164 @section Debugging Information in Separate Files
17165 @cindex separate debugging information files
17166 @cindex debugging information in separate files
17167 @cindex @file{.debug} subdirectories
17168 @cindex debugging information directory, global
17169 @cindex global debugging information directories
17170 @cindex build ID, and separate debugging files
17171 @cindex @file{.build-id} directory
17173 @value{GDBN} allows you to put a program's debugging information in a
17174 file separate from the executable itself, in a way that allows
17175 @value{GDBN} to find and load the debugging information automatically.
17176 Since debugging information can be very large---sometimes larger
17177 than the executable code itself---some systems distribute debugging
17178 information for their executables in separate files, which users can
17179 install only when they need to debug a problem.
17181 @value{GDBN} supports two ways of specifying the separate debug info
17186 The executable contains a @dfn{debug link} that specifies the name of
17187 the separate debug info file. The separate debug file's name is
17188 usually @file{@var{executable}.debug}, where @var{executable} is the
17189 name of the corresponding executable file without leading directories
17190 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
17191 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
17192 checksum for the debug file, which @value{GDBN} uses to validate that
17193 the executable and the debug file came from the same build.
17196 The executable contains a @dfn{build ID}, a unique bit string that is
17197 also present in the corresponding debug info file. (This is supported
17198 only on some operating systems, notably those which use the ELF format
17199 for binary files and the @sc{gnu} Binutils.) For more details about
17200 this feature, see the description of the @option{--build-id}
17201 command-line option in @ref{Options, , Command Line Options, ld.info,
17202 The GNU Linker}. The debug info file's name is not specified
17203 explicitly by the build ID, but can be computed from the build ID, see
17207 Depending on the way the debug info file is specified, @value{GDBN}
17208 uses two different methods of looking for the debug file:
17212 For the ``debug link'' method, @value{GDBN} looks up the named file in
17213 the directory of the executable file, then in a subdirectory of that
17214 directory named @file{.debug}, and finally under each one of the global debug
17215 directories, in a subdirectory whose name is identical to the leading
17216 directories of the executable's absolute file name.
17219 For the ``build ID'' method, @value{GDBN} looks in the
17220 @file{.build-id} subdirectory of each one of the global debug directories for
17221 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
17222 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
17223 are the rest of the bit string. (Real build ID strings are 32 or more
17224 hex characters, not 10.)
17227 So, for example, suppose you ask @value{GDBN} to debug
17228 @file{/usr/bin/ls}, which has a debug link that specifies the
17229 file @file{ls.debug}, and a build ID whose value in hex is
17230 @code{abcdef1234}. If the list of the global debug directories includes
17231 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
17232 debug information files, in the indicated order:
17236 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
17238 @file{/usr/bin/ls.debug}
17240 @file{/usr/bin/.debug/ls.debug}
17242 @file{/usr/lib/debug/usr/bin/ls.debug}.
17245 @anchor{debug-file-directory}
17246 Global debugging info directories default to what is set by @value{GDBN}
17247 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
17248 you can also set the global debugging info directories, and view the list
17249 @value{GDBN} is currently using.
17253 @kindex set debug-file-directory
17254 @item set debug-file-directory @var{directories}
17255 Set the directories which @value{GDBN} searches for separate debugging
17256 information files to @var{directory}. Multiple path components can be set
17257 concatenating them by a path separator.
17259 @kindex show debug-file-directory
17260 @item show debug-file-directory
17261 Show the directories @value{GDBN} searches for separate debugging
17266 @cindex @code{.gnu_debuglink} sections
17267 @cindex debug link sections
17268 A debug link is a special section of the executable file named
17269 @code{.gnu_debuglink}. The section must contain:
17273 A filename, with any leading directory components removed, followed by
17276 zero to three bytes of padding, as needed to reach the next four-byte
17277 boundary within the section, and
17279 a four-byte CRC checksum, stored in the same endianness used for the
17280 executable file itself. The checksum is computed on the debugging
17281 information file's full contents by the function given below, passing
17282 zero as the @var{crc} argument.
17285 Any executable file format can carry a debug link, as long as it can
17286 contain a section named @code{.gnu_debuglink} with the contents
17289 @cindex @code{.note.gnu.build-id} sections
17290 @cindex build ID sections
17291 The build ID is a special section in the executable file (and in other
17292 ELF binary files that @value{GDBN} may consider). This section is
17293 often named @code{.note.gnu.build-id}, but that name is not mandatory.
17294 It contains unique identification for the built files---the ID remains
17295 the same across multiple builds of the same build tree. The default
17296 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
17297 content for the build ID string. The same section with an identical
17298 value is present in the original built binary with symbols, in its
17299 stripped variant, and in the separate debugging information file.
17301 The debugging information file itself should be an ordinary
17302 executable, containing a full set of linker symbols, sections, and
17303 debugging information. The sections of the debugging information file
17304 should have the same names, addresses, and sizes as the original file,
17305 but they need not contain any data---much like a @code{.bss} section
17306 in an ordinary executable.
17308 The @sc{gnu} binary utilities (Binutils) package includes the
17309 @samp{objcopy} utility that can produce
17310 the separated executable / debugging information file pairs using the
17311 following commands:
17314 @kbd{objcopy --only-keep-debug foo foo.debug}
17319 These commands remove the debugging
17320 information from the executable file @file{foo} and place it in the file
17321 @file{foo.debug}. You can use the first, second or both methods to link the
17326 The debug link method needs the following additional command to also leave
17327 behind a debug link in @file{foo}:
17330 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
17333 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
17334 a version of the @code{strip} command such that the command @kbd{strip foo -f
17335 foo.debug} has the same functionality as the two @code{objcopy} commands and
17336 the @code{ln -s} command above, together.
17339 Build ID gets embedded into the main executable using @code{ld --build-id} or
17340 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
17341 compatibility fixes for debug files separation are present in @sc{gnu} binary
17342 utilities (Binutils) package since version 2.18.
17347 @cindex CRC algorithm definition
17348 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
17349 IEEE 802.3 using the polynomial:
17351 @c TexInfo requires naked braces for multi-digit exponents for Tex
17352 @c output, but this causes HTML output to barf. HTML has to be set using
17353 @c raw commands. So we end up having to specify this equation in 2
17358 <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>
17359 + <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
17365 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
17366 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
17370 The function is computed byte at a time, taking the least
17371 significant bit of each byte first. The initial pattern
17372 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
17373 the final result is inverted to ensure trailing zeros also affect the
17376 @emph{Note:} This is the same CRC polynomial as used in handling the
17377 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
17378 , @value{GDBN} Remote Serial Protocol}). However in the
17379 case of the Remote Serial Protocol, the CRC is computed @emph{most}
17380 significant bit first, and the result is not inverted, so trailing
17381 zeros have no effect on the CRC value.
17383 To complete the description, we show below the code of the function
17384 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
17385 initially supplied @code{crc} argument means that an initial call to
17386 this function passing in zero will start computing the CRC using
17389 @kindex gnu_debuglink_crc32
17392 gnu_debuglink_crc32 (unsigned long crc,
17393 unsigned char *buf, size_t len)
17395 static const unsigned long crc32_table[256] =
17397 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
17398 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
17399 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
17400 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
17401 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
17402 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
17403 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
17404 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
17405 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
17406 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
17407 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
17408 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
17409 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
17410 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
17411 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
17412 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
17413 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
17414 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
17415 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
17416 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
17417 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
17418 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
17419 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
17420 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
17421 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
17422 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
17423 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
17424 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
17425 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
17426 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
17427 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
17428 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
17429 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
17430 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
17431 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
17432 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
17433 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
17434 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
17435 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
17436 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
17437 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
17438 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
17439 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
17440 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
17441 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
17442 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
17443 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
17444 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
17445 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
17446 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
17447 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
17450 unsigned char *end;
17452 crc = ~crc & 0xffffffff;
17453 for (end = buf + len; buf < end; ++buf)
17454 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
17455 return ~crc & 0xffffffff;
17460 This computation does not apply to the ``build ID'' method.
17462 @node MiniDebugInfo
17463 @section Debugging information in a special section
17464 @cindex separate debug sections
17465 @cindex @samp{.gnu_debugdata} section
17467 Some systems ship pre-built executables and libraries that have a
17468 special @samp{.gnu_debugdata} section. This feature is called
17469 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
17470 is used to supply extra symbols for backtraces.
17472 The intent of this section is to provide extra minimal debugging
17473 information for use in simple backtraces. It is not intended to be a
17474 replacement for full separate debugging information (@pxref{Separate
17475 Debug Files}). The example below shows the intended use; however,
17476 @value{GDBN} does not currently put restrictions on what sort of
17477 debugging information might be included in the section.
17479 @value{GDBN} has support for this extension. If the section exists,
17480 then it is used provided that no other source of debugging information
17481 can be found, and that @value{GDBN} was configured with LZMA support.
17483 This section can be easily created using @command{objcopy} and other
17484 standard utilities:
17487 # Extract the dynamic symbols from the main binary, there is no need
17488 # to also have these in the normal symbol table.
17489 nm -D @var{binary} --format=posix --defined-only \
17490 | awk '@{ print $1 @}' | sort > dynsyms
17492 # Extract all the text (i.e. function) symbols from the debuginfo.
17493 # (Note that we actually also accept "D" symbols, for the benefit
17494 # of platforms like PowerPC64 that use function descriptors.)
17495 nm @var{binary} --format=posix --defined-only \
17496 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
17499 # Keep all the function symbols not already in the dynamic symbol
17501 comm -13 dynsyms funcsyms > keep_symbols
17503 # Separate full debug info into debug binary.
17504 objcopy --only-keep-debug @var{binary} debug
17506 # Copy the full debuginfo, keeping only a minimal set of symbols and
17507 # removing some unnecessary sections.
17508 objcopy -S --remove-section .gdb_index --remove-section .comment \
17509 --keep-symbols=keep_symbols debug mini_debuginfo
17511 # Drop the full debug info from the original binary.
17512 strip --strip-all -R .comment @var{binary}
17514 # Inject the compressed data into the .gnu_debugdata section of the
17517 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
17521 @section Index Files Speed Up @value{GDBN}
17522 @cindex index files
17523 @cindex @samp{.gdb_index} section
17525 When @value{GDBN} finds a symbol file, it scans the symbols in the
17526 file in order to construct an internal symbol table. This lets most
17527 @value{GDBN} operations work quickly---at the cost of a delay early
17528 on. For large programs, this delay can be quite lengthy, so
17529 @value{GDBN} provides a way to build an index, which speeds up
17532 The index is stored as a section in the symbol file. @value{GDBN} can
17533 write the index to a file, then you can put it into the symbol file
17534 using @command{objcopy}.
17536 To create an index file, use the @code{save gdb-index} command:
17539 @item save gdb-index @var{directory}
17540 @kindex save gdb-index
17541 Create an index file for each symbol file currently known by
17542 @value{GDBN}. Each file is named after its corresponding symbol file,
17543 with @samp{.gdb-index} appended, and is written into the given
17547 Once you have created an index file you can merge it into your symbol
17548 file, here named @file{symfile}, using @command{objcopy}:
17551 $ objcopy --add-section .gdb_index=symfile.gdb-index \
17552 --set-section-flags .gdb_index=readonly symfile symfile
17555 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
17556 sections that have been deprecated. Usually they are deprecated because
17557 they are missing a new feature or have performance issues.
17558 To tell @value{GDBN} to use a deprecated index section anyway
17559 specify @code{set use-deprecated-index-sections on}.
17560 The default is @code{off}.
17561 This can speed up startup, but may result in some functionality being lost.
17562 @xref{Index Section Format}.
17564 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
17565 must be done before gdb reads the file. The following will not work:
17568 $ gdb -ex "set use-deprecated-index-sections on" <program>
17571 Instead you must do, for example,
17574 $ gdb -iex "set use-deprecated-index-sections on" <program>
17577 There are currently some limitation on indices. They only work when
17578 for DWARF debugging information, not stabs. And, they do not
17579 currently work for programs using Ada.
17581 @node Symbol Errors
17582 @section Errors Reading Symbol Files
17584 While reading a symbol file, @value{GDBN} occasionally encounters problems,
17585 such as symbol types it does not recognize, or known bugs in compiler
17586 output. By default, @value{GDBN} does not notify you of such problems, since
17587 they are relatively common and primarily of interest to people
17588 debugging compilers. If you are interested in seeing information
17589 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
17590 only one message about each such type of problem, no matter how many
17591 times the problem occurs; or you can ask @value{GDBN} to print more messages,
17592 to see how many times the problems occur, with the @code{set
17593 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
17596 The messages currently printed, and their meanings, include:
17599 @item inner block not inside outer block in @var{symbol}
17601 The symbol information shows where symbol scopes begin and end
17602 (such as at the start of a function or a block of statements). This
17603 error indicates that an inner scope block is not fully contained
17604 in its outer scope blocks.
17606 @value{GDBN} circumvents the problem by treating the inner block as if it had
17607 the same scope as the outer block. In the error message, @var{symbol}
17608 may be shown as ``@code{(don't know)}'' if the outer block is not a
17611 @item block at @var{address} out of order
17613 The symbol information for symbol scope blocks should occur in
17614 order of increasing addresses. This error indicates that it does not
17617 @value{GDBN} does not circumvent this problem, and has trouble
17618 locating symbols in the source file whose symbols it is reading. (You
17619 can often determine what source file is affected by specifying
17620 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
17623 @item bad block start address patched
17625 The symbol information for a symbol scope block has a start address
17626 smaller than the address of the preceding source line. This is known
17627 to occur in the SunOS 4.1.1 (and earlier) C compiler.
17629 @value{GDBN} circumvents the problem by treating the symbol scope block as
17630 starting on the previous source line.
17632 @item bad string table offset in symbol @var{n}
17635 Symbol number @var{n} contains a pointer into the string table which is
17636 larger than the size of the string table.
17638 @value{GDBN} circumvents the problem by considering the symbol to have the
17639 name @code{foo}, which may cause other problems if many symbols end up
17642 @item unknown symbol type @code{0x@var{nn}}
17644 The symbol information contains new data types that @value{GDBN} does
17645 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
17646 uncomprehended information, in hexadecimal.
17648 @value{GDBN} circumvents the error by ignoring this symbol information.
17649 This usually allows you to debug your program, though certain symbols
17650 are not accessible. If you encounter such a problem and feel like
17651 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
17652 on @code{complain}, then go up to the function @code{read_dbx_symtab}
17653 and examine @code{*bufp} to see the symbol.
17655 @item stub type has NULL name
17657 @value{GDBN} could not find the full definition for a struct or class.
17659 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
17660 The symbol information for a C@t{++} member function is missing some
17661 information that recent versions of the compiler should have output for
17664 @item info mismatch between compiler and debugger
17666 @value{GDBN} could not parse a type specification output by the compiler.
17671 @section GDB Data Files
17673 @cindex prefix for data files
17674 @value{GDBN} will sometimes read an auxiliary data file. These files
17675 are kept in a directory known as the @dfn{data directory}.
17677 You can set the data directory's name, and view the name @value{GDBN}
17678 is currently using.
17681 @kindex set data-directory
17682 @item set data-directory @var{directory}
17683 Set the directory which @value{GDBN} searches for auxiliary data files
17684 to @var{directory}.
17686 @kindex show data-directory
17687 @item show data-directory
17688 Show the directory @value{GDBN} searches for auxiliary data files.
17691 @cindex default data directory
17692 @cindex @samp{--with-gdb-datadir}
17693 You can set the default data directory by using the configure-time
17694 @samp{--with-gdb-datadir} option. If the data directory is inside
17695 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17696 @samp{--exec-prefix}), then the default data directory will be updated
17697 automatically if the installed @value{GDBN} is moved to a new
17700 The data directory may also be specified with the
17701 @code{--data-directory} command line option.
17702 @xref{Mode Options}.
17705 @chapter Specifying a Debugging Target
17707 @cindex debugging target
17708 A @dfn{target} is the execution environment occupied by your program.
17710 Often, @value{GDBN} runs in the same host environment as your program;
17711 in that case, the debugging target is specified as a side effect when
17712 you use the @code{file} or @code{core} commands. When you need more
17713 flexibility---for example, running @value{GDBN} on a physically separate
17714 host, or controlling a standalone system over a serial port or a
17715 realtime system over a TCP/IP connection---you can use the @code{target}
17716 command to specify one of the target types configured for @value{GDBN}
17717 (@pxref{Target Commands, ,Commands for Managing Targets}).
17719 @cindex target architecture
17720 It is possible to build @value{GDBN} for several different @dfn{target
17721 architectures}. When @value{GDBN} is built like that, you can choose
17722 one of the available architectures with the @kbd{set architecture}
17726 @kindex set architecture
17727 @kindex show architecture
17728 @item set architecture @var{arch}
17729 This command sets the current target architecture to @var{arch}. The
17730 value of @var{arch} can be @code{"auto"}, in addition to one of the
17731 supported architectures.
17733 @item show architecture
17734 Show the current target architecture.
17736 @item set processor
17738 @kindex set processor
17739 @kindex show processor
17740 These are alias commands for, respectively, @code{set architecture}
17741 and @code{show architecture}.
17745 * Active Targets:: Active targets
17746 * Target Commands:: Commands for managing targets
17747 * Byte Order:: Choosing target byte order
17750 @node Active Targets
17751 @section Active Targets
17753 @cindex stacking targets
17754 @cindex active targets
17755 @cindex multiple targets
17757 There are multiple classes of targets such as: processes, executable files or
17758 recording sessions. Core files belong to the process class, making core file
17759 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
17760 on multiple active targets, one in each class. This allows you to (for
17761 example) start a process and inspect its activity, while still having access to
17762 the executable file after the process finishes. Or if you start process
17763 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
17764 presented a virtual layer of the recording target, while the process target
17765 remains stopped at the chronologically last point of the process execution.
17767 Use the @code{core-file} and @code{exec-file} commands to select a new core
17768 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
17769 specify as a target a process that is already running, use the @code{attach}
17770 command (@pxref{Attach, ,Debugging an Already-running Process}).
17772 @node Target Commands
17773 @section Commands for Managing Targets
17776 @item target @var{type} @var{parameters}
17777 Connects the @value{GDBN} host environment to a target machine or
17778 process. A target is typically a protocol for talking to debugging
17779 facilities. You use the argument @var{type} to specify the type or
17780 protocol of the target machine.
17782 Further @var{parameters} are interpreted by the target protocol, but
17783 typically include things like device names or host names to connect
17784 with, process numbers, and baud rates.
17786 The @code{target} command does not repeat if you press @key{RET} again
17787 after executing the command.
17789 @kindex help target
17791 Displays the names of all targets available. To display targets
17792 currently selected, use either @code{info target} or @code{info files}
17793 (@pxref{Files, ,Commands to Specify Files}).
17795 @item help target @var{name}
17796 Describe a particular target, including any parameters necessary to
17799 @kindex set gnutarget
17800 @item set gnutarget @var{args}
17801 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
17802 knows whether it is reading an @dfn{executable},
17803 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
17804 with the @code{set gnutarget} command. Unlike most @code{target} commands,
17805 with @code{gnutarget} the @code{target} refers to a program, not a machine.
17808 @emph{Warning:} To specify a file format with @code{set gnutarget},
17809 you must know the actual BFD name.
17813 @xref{Files, , Commands to Specify Files}.
17815 @kindex show gnutarget
17816 @item show gnutarget
17817 Use the @code{show gnutarget} command to display what file format
17818 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
17819 @value{GDBN} will determine the file format for each file automatically,
17820 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
17823 @cindex common targets
17824 Here are some common targets (available, or not, depending on the GDB
17829 @item target exec @var{program}
17830 @cindex executable file target
17831 An executable file. @samp{target exec @var{program}} is the same as
17832 @samp{exec-file @var{program}}.
17834 @item target core @var{filename}
17835 @cindex core dump file target
17836 A core dump file. @samp{target core @var{filename}} is the same as
17837 @samp{core-file @var{filename}}.
17839 @item target remote @var{medium}
17840 @cindex remote target
17841 A remote system connected to @value{GDBN} via a serial line or network
17842 connection. This command tells @value{GDBN} to use its own remote
17843 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
17845 For example, if you have a board connected to @file{/dev/ttya} on the
17846 machine running @value{GDBN}, you could say:
17849 target remote /dev/ttya
17852 @code{target remote} supports the @code{load} command. This is only
17853 useful if you have some other way of getting the stub to the target
17854 system, and you can put it somewhere in memory where it won't get
17855 clobbered by the download.
17857 @item target sim @r{[}@var{simargs}@r{]} @dots{}
17858 @cindex built-in simulator target
17859 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
17867 works; however, you cannot assume that a specific memory map, device
17868 drivers, or even basic I/O is available, although some simulators do
17869 provide these. For info about any processor-specific simulator details,
17870 see the appropriate section in @ref{Embedded Processors, ,Embedded
17875 Different targets are available on different configurations of @value{GDBN};
17876 your configuration may have more or fewer targets.
17878 Many remote targets require you to download the executable's code once
17879 you've successfully established a connection. You may wish to control
17880 various aspects of this process.
17885 @kindex set hash@r{, for remote monitors}
17886 @cindex hash mark while downloading
17887 This command controls whether a hash mark @samp{#} is displayed while
17888 downloading a file to the remote monitor. If on, a hash mark is
17889 displayed after each S-record is successfully downloaded to the
17893 @kindex show hash@r{, for remote monitors}
17894 Show the current status of displaying the hash mark.
17896 @item set debug monitor
17897 @kindex set debug monitor
17898 @cindex display remote monitor communications
17899 Enable or disable display of communications messages between
17900 @value{GDBN} and the remote monitor.
17902 @item show debug monitor
17903 @kindex show debug monitor
17904 Show the current status of displaying communications between
17905 @value{GDBN} and the remote monitor.
17910 @kindex load @var{filename}
17911 @item load @var{filename}
17913 Depending on what remote debugging facilities are configured into
17914 @value{GDBN}, the @code{load} command may be available. Where it exists, it
17915 is meant to make @var{filename} (an executable) available for debugging
17916 on the remote system---by downloading, or dynamic linking, for example.
17917 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
17918 the @code{add-symbol-file} command.
17920 If your @value{GDBN} does not have a @code{load} command, attempting to
17921 execute it gets the error message ``@code{You can't do that when your
17922 target is @dots{}}''
17924 The file is loaded at whatever address is specified in the executable.
17925 For some object file formats, you can specify the load address when you
17926 link the program; for other formats, like a.out, the object file format
17927 specifies a fixed address.
17928 @c FIXME! This would be a good place for an xref to the GNU linker doc.
17930 Depending on the remote side capabilities, @value{GDBN} may be able to
17931 load programs into flash memory.
17933 @code{load} does not repeat if you press @key{RET} again after using it.
17937 @section Choosing Target Byte Order
17939 @cindex choosing target byte order
17940 @cindex target byte order
17942 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
17943 offer the ability to run either big-endian or little-endian byte
17944 orders. Usually the executable or symbol will include a bit to
17945 designate the endian-ness, and you will not need to worry about
17946 which to use. However, you may still find it useful to adjust
17947 @value{GDBN}'s idea of processor endian-ness manually.
17951 @item set endian big
17952 Instruct @value{GDBN} to assume the target is big-endian.
17954 @item set endian little
17955 Instruct @value{GDBN} to assume the target is little-endian.
17957 @item set endian auto
17958 Instruct @value{GDBN} to use the byte order associated with the
17962 Display @value{GDBN}'s current idea of the target byte order.
17966 Note that these commands merely adjust interpretation of symbolic
17967 data on the host, and that they have absolutely no effect on the
17971 @node Remote Debugging
17972 @chapter Debugging Remote Programs
17973 @cindex remote debugging
17975 If you are trying to debug a program running on a machine that cannot run
17976 @value{GDBN} in the usual way, it is often useful to use remote debugging.
17977 For example, you might use remote debugging on an operating system kernel,
17978 or on a small system which does not have a general purpose operating system
17979 powerful enough to run a full-featured debugger.
17981 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
17982 to make this work with particular debugging targets. In addition,
17983 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
17984 but not specific to any particular target system) which you can use if you
17985 write the remote stubs---the code that runs on the remote system to
17986 communicate with @value{GDBN}.
17988 Other remote targets may be available in your
17989 configuration of @value{GDBN}; use @code{help target} to list them.
17992 * Connecting:: Connecting to a remote target
17993 * File Transfer:: Sending files to a remote system
17994 * Server:: Using the gdbserver program
17995 * Remote Configuration:: Remote configuration
17996 * Remote Stub:: Implementing a remote stub
18000 @section Connecting to a Remote Target
18002 On the @value{GDBN} host machine, you will need an unstripped copy of
18003 your program, since @value{GDBN} needs symbol and debugging information.
18004 Start up @value{GDBN} as usual, using the name of the local copy of your
18005 program as the first argument.
18007 @cindex @code{target remote}
18008 @value{GDBN} can communicate with the target over a serial line, or
18009 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
18010 each case, @value{GDBN} uses the same protocol for debugging your
18011 program; only the medium carrying the debugging packets varies. The
18012 @code{target remote} command establishes a connection to the target.
18013 Its arguments indicate which medium to use:
18017 @item target remote @var{serial-device}
18018 @cindex serial line, @code{target remote}
18019 Use @var{serial-device} to communicate with the target. For example,
18020 to use a serial line connected to the device named @file{/dev/ttyb}:
18023 target remote /dev/ttyb
18026 If you're using a serial line, you may want to give @value{GDBN} the
18027 @samp{--baud} option, or use the @code{set serial baud} command
18028 (@pxref{Remote Configuration, set serial baud}) before the
18029 @code{target} command.
18031 @item target remote @code{@var{host}:@var{port}}
18032 @itemx target remote @code{tcp:@var{host}:@var{port}}
18033 @cindex @acronym{TCP} port, @code{target remote}
18034 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
18035 The @var{host} may be either a host name or a numeric @acronym{IP}
18036 address; @var{port} must be a decimal number. The @var{host} could be
18037 the target machine itself, if it is directly connected to the net, or
18038 it might be a terminal server which in turn has a serial line to the
18041 For example, to connect to port 2828 on a terminal server named
18045 target remote manyfarms:2828
18048 If your remote target is actually running on the same machine as your
18049 debugger session (e.g.@: a simulator for your target running on the
18050 same host), you can omit the hostname. For example, to connect to
18051 port 1234 on your local machine:
18054 target remote :1234
18058 Note that the colon is still required here.
18060 @item target remote @code{udp:@var{host}:@var{port}}
18061 @cindex @acronym{UDP} port, @code{target remote}
18062 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
18063 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
18066 target remote udp:manyfarms:2828
18069 When using a @acronym{UDP} connection for remote debugging, you should
18070 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
18071 can silently drop packets on busy or unreliable networks, which will
18072 cause havoc with your debugging session.
18074 @item target remote | @var{command}
18075 @cindex pipe, @code{target remote} to
18076 Run @var{command} in the background and communicate with it using a
18077 pipe. The @var{command} is a shell command, to be parsed and expanded
18078 by the system's command shell, @code{/bin/sh}; it should expect remote
18079 protocol packets on its standard input, and send replies on its
18080 standard output. You could use this to run a stand-alone simulator
18081 that speaks the remote debugging protocol, to make net connections
18082 using programs like @code{ssh}, or for other similar tricks.
18084 If @var{command} closes its standard output (perhaps by exiting),
18085 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
18086 program has already exited, this will have no effect.)
18090 Once the connection has been established, you can use all the usual
18091 commands to examine and change data. The remote program is already
18092 running; you can use @kbd{step} and @kbd{continue}, and you do not
18093 need to use @kbd{run}.
18095 @cindex interrupting remote programs
18096 @cindex remote programs, interrupting
18097 Whenever @value{GDBN} is waiting for the remote program, if you type the
18098 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
18099 program. This may or may not succeed, depending in part on the hardware
18100 and the serial drivers the remote system uses. If you type the
18101 interrupt character once again, @value{GDBN} displays this prompt:
18104 Interrupted while waiting for the program.
18105 Give up (and stop debugging it)? (y or n)
18108 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
18109 (If you decide you want to try again later, you can use @samp{target
18110 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
18111 goes back to waiting.
18114 @kindex detach (remote)
18116 When you have finished debugging the remote program, you can use the
18117 @code{detach} command to release it from @value{GDBN} control.
18118 Detaching from the target normally resumes its execution, but the results
18119 will depend on your particular remote stub. After the @code{detach}
18120 command, @value{GDBN} is free to connect to another target.
18124 The @code{disconnect} command behaves like @code{detach}, except that
18125 the target is generally not resumed. It will wait for @value{GDBN}
18126 (this instance or another one) to connect and continue debugging. After
18127 the @code{disconnect} command, @value{GDBN} is again free to connect to
18130 @cindex send command to remote monitor
18131 @cindex extend @value{GDBN} for remote targets
18132 @cindex add new commands for external monitor
18134 @item monitor @var{cmd}
18135 This command allows you to send arbitrary commands directly to the
18136 remote monitor. Since @value{GDBN} doesn't care about the commands it
18137 sends like this, this command is the way to extend @value{GDBN}---you
18138 can add new commands that only the external monitor will understand
18142 @node File Transfer
18143 @section Sending files to a remote system
18144 @cindex remote target, file transfer
18145 @cindex file transfer
18146 @cindex sending files to remote systems
18148 Some remote targets offer the ability to transfer files over the same
18149 connection used to communicate with @value{GDBN}. This is convenient
18150 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
18151 running @code{gdbserver} over a network interface. For other targets,
18152 e.g.@: embedded devices with only a single serial port, this may be
18153 the only way to upload or download files.
18155 Not all remote targets support these commands.
18159 @item remote put @var{hostfile} @var{targetfile}
18160 Copy file @var{hostfile} from the host system (the machine running
18161 @value{GDBN}) to @var{targetfile} on the target system.
18164 @item remote get @var{targetfile} @var{hostfile}
18165 Copy file @var{targetfile} from the target system to @var{hostfile}
18166 on the host system.
18168 @kindex remote delete
18169 @item remote delete @var{targetfile}
18170 Delete @var{targetfile} from the target system.
18175 @section Using the @code{gdbserver} Program
18178 @cindex remote connection without stubs
18179 @code{gdbserver} is a control program for Unix-like systems, which
18180 allows you to connect your program with a remote @value{GDBN} via
18181 @code{target remote}---but without linking in the usual debugging stub.
18183 @code{gdbserver} is not a complete replacement for the debugging stubs,
18184 because it requires essentially the same operating-system facilities
18185 that @value{GDBN} itself does. In fact, a system that can run
18186 @code{gdbserver} to connect to a remote @value{GDBN} could also run
18187 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
18188 because it is a much smaller program than @value{GDBN} itself. It is
18189 also easier to port than all of @value{GDBN}, so you may be able to get
18190 started more quickly on a new system by using @code{gdbserver}.
18191 Finally, if you develop code for real-time systems, you may find that
18192 the tradeoffs involved in real-time operation make it more convenient to
18193 do as much development work as possible on another system, for example
18194 by cross-compiling. You can use @code{gdbserver} to make a similar
18195 choice for debugging.
18197 @value{GDBN} and @code{gdbserver} communicate via either a serial line
18198 or a TCP connection, using the standard @value{GDBN} remote serial
18202 @emph{Warning:} @code{gdbserver} does not have any built-in security.
18203 Do not run @code{gdbserver} connected to any public network; a
18204 @value{GDBN} connection to @code{gdbserver} provides access to the
18205 target system with the same privileges as the user running
18209 @subsection Running @code{gdbserver}
18210 @cindex arguments, to @code{gdbserver}
18211 @cindex @code{gdbserver}, command-line arguments
18213 Run @code{gdbserver} on the target system. You need a copy of the
18214 program you want to debug, including any libraries it requires.
18215 @code{gdbserver} does not need your program's symbol table, so you can
18216 strip the program if necessary to save space. @value{GDBN} on the host
18217 system does all the symbol handling.
18219 To use the server, you must tell it how to communicate with @value{GDBN};
18220 the name of your program; and the arguments for your program. The usual
18224 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
18227 @var{comm} is either a device name (to use a serial line), or a TCP
18228 hostname and portnumber, or @code{-} or @code{stdio} to use
18229 stdin/stdout of @code{gdbserver}.
18230 For example, to debug Emacs with the argument
18231 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
18235 target> gdbserver /dev/com1 emacs foo.txt
18238 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
18241 To use a TCP connection instead of a serial line:
18244 target> gdbserver host:2345 emacs foo.txt
18247 The only difference from the previous example is the first argument,
18248 specifying that you are communicating with the host @value{GDBN} via
18249 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
18250 expect a TCP connection from machine @samp{host} to local TCP port 2345.
18251 (Currently, the @samp{host} part is ignored.) You can choose any number
18252 you want for the port number as long as it does not conflict with any
18253 TCP ports already in use on the target system (for example, @code{23} is
18254 reserved for @code{telnet}).@footnote{If you choose a port number that
18255 conflicts with another service, @code{gdbserver} prints an error message
18256 and exits.} You must use the same port number with the host @value{GDBN}
18257 @code{target remote} command.
18259 The @code{stdio} connection is useful when starting @code{gdbserver}
18263 (gdb) target remote | ssh -T hostname gdbserver - hello
18266 The @samp{-T} option to ssh is provided because we don't need a remote pty,
18267 and we don't want escape-character handling. Ssh does this by default when
18268 a command is provided, the flag is provided to make it explicit.
18269 You could elide it if you want to.
18271 Programs started with stdio-connected gdbserver have @file{/dev/null} for
18272 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
18273 display through a pipe connected to gdbserver.
18274 Both @code{stdout} and @code{stderr} use the same pipe.
18276 @subsubsection Attaching to a Running Program
18277 @cindex attach to a program, @code{gdbserver}
18278 @cindex @option{--attach}, @code{gdbserver} option
18280 On some targets, @code{gdbserver} can also attach to running programs.
18281 This is accomplished via the @code{--attach} argument. The syntax is:
18284 target> gdbserver --attach @var{comm} @var{pid}
18287 @var{pid} is the process ID of a currently running process. It isn't necessary
18288 to point @code{gdbserver} at a binary for the running process.
18291 You can debug processes by name instead of process ID if your target has the
18292 @code{pidof} utility:
18295 target> gdbserver --attach @var{comm} `pidof @var{program}`
18298 In case more than one copy of @var{program} is running, or @var{program}
18299 has multiple threads, most versions of @code{pidof} support the
18300 @code{-s} option to only return the first process ID.
18302 @subsubsection Multi-Process Mode for @code{gdbserver}
18303 @cindex @code{gdbserver}, multiple processes
18304 @cindex multiple processes with @code{gdbserver}
18306 When you connect to @code{gdbserver} using @code{target remote},
18307 @code{gdbserver} debugs the specified program only once. When the
18308 program exits, or you detach from it, @value{GDBN} closes the connection
18309 and @code{gdbserver} exits.
18311 If you connect using @kbd{target extended-remote}, @code{gdbserver}
18312 enters multi-process mode. When the debugged program exits, or you
18313 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
18314 though no program is running. The @code{run} and @code{attach}
18315 commands instruct @code{gdbserver} to run or attach to a new program.
18316 The @code{run} command uses @code{set remote exec-file} (@pxref{set
18317 remote exec-file}) to select the program to run. Command line
18318 arguments are supported, except for wildcard expansion and I/O
18319 redirection (@pxref{Arguments}).
18321 @cindex @option{--multi}, @code{gdbserver} option
18322 To start @code{gdbserver} without supplying an initial command to run
18323 or process ID to attach, use the @option{--multi} command line option.
18324 Then you can connect using @kbd{target extended-remote} and start
18325 the program you want to debug.
18327 In multi-process mode @code{gdbserver} does not automatically exit unless you
18328 use the option @option{--once}. You can terminate it by using
18329 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
18330 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
18331 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
18332 @option{--multi} option to @code{gdbserver} has no influence on that.
18334 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
18336 This section applies only when @code{gdbserver} is run to listen on a TCP port.
18338 @code{gdbserver} normally terminates after all of its debugged processes have
18339 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
18340 extended-remote}, @code{gdbserver} stays running even with no processes left.
18341 @value{GDBN} normally terminates the spawned debugged process on its exit,
18342 which normally also terminates @code{gdbserver} in the @kbd{target remote}
18343 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
18344 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
18345 stays running even in the @kbd{target remote} mode.
18347 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
18348 Such reconnecting is useful for features like @ref{disconnected tracing}. For
18349 completeness, at most one @value{GDBN} can be connected at a time.
18351 @cindex @option{--once}, @code{gdbserver} option
18352 By default, @code{gdbserver} keeps the listening TCP port open, so that
18353 subsequent connections are possible. However, if you start @code{gdbserver}
18354 with the @option{--once} option, it will stop listening for any further
18355 connection attempts after connecting to the first @value{GDBN} session. This
18356 means no further connections to @code{gdbserver} will be possible after the
18357 first one. It also means @code{gdbserver} will terminate after the first
18358 connection with remote @value{GDBN} has closed, even for unexpectedly closed
18359 connections and even in the @kbd{target extended-remote} mode. The
18360 @option{--once} option allows reusing the same port number for connecting to
18361 multiple instances of @code{gdbserver} running on the same host, since each
18362 instance closes its port after the first connection.
18364 @subsubsection Other Command-Line Arguments for @code{gdbserver}
18366 @cindex @option{--debug}, @code{gdbserver} option
18367 The @option{--debug} option tells @code{gdbserver} to display extra
18368 status information about the debugging process.
18369 @cindex @option{--remote-debug}, @code{gdbserver} option
18370 The @option{--remote-debug} option tells @code{gdbserver} to display
18371 remote protocol debug output. These options are intended for
18372 @code{gdbserver} development and for bug reports to the developers.
18374 @cindex @option{--wrapper}, @code{gdbserver} option
18375 The @option{--wrapper} option specifies a wrapper to launch programs
18376 for debugging. The option should be followed by the name of the
18377 wrapper, then any command-line arguments to pass to the wrapper, then
18378 @kbd{--} indicating the end of the wrapper arguments.
18380 @code{gdbserver} runs the specified wrapper program with a combined
18381 command line including the wrapper arguments, then the name of the
18382 program to debug, then any arguments to the program. The wrapper
18383 runs until it executes your program, and then @value{GDBN} gains control.
18385 You can use any program that eventually calls @code{execve} with
18386 its arguments as a wrapper. Several standard Unix utilities do
18387 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
18388 with @code{exec "$@@"} will also work.
18390 For example, you can use @code{env} to pass an environment variable to
18391 the debugged program, without setting the variable in @code{gdbserver}'s
18395 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
18398 @subsection Connecting to @code{gdbserver}
18400 Run @value{GDBN} on the host system.
18402 First make sure you have the necessary symbol files. Load symbols for
18403 your application using the @code{file} command before you connect. Use
18404 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
18405 was compiled with the correct sysroot using @code{--with-sysroot}).
18407 The symbol file and target libraries must exactly match the executable
18408 and libraries on the target, with one exception: the files on the host
18409 system should not be stripped, even if the files on the target system
18410 are. Mismatched or missing files will lead to confusing results
18411 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
18412 files may also prevent @code{gdbserver} from debugging multi-threaded
18415 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
18416 For TCP connections, you must start up @code{gdbserver} prior to using
18417 the @code{target remote} command. Otherwise you may get an error whose
18418 text depends on the host system, but which usually looks something like
18419 @samp{Connection refused}. Don't use the @code{load}
18420 command in @value{GDBN} when using @code{gdbserver}, since the program is
18421 already on the target.
18423 @subsection Monitor Commands for @code{gdbserver}
18424 @cindex monitor commands, for @code{gdbserver}
18425 @anchor{Monitor Commands for gdbserver}
18427 During a @value{GDBN} session using @code{gdbserver}, you can use the
18428 @code{monitor} command to send special requests to @code{gdbserver}.
18429 Here are the available commands.
18433 List the available monitor commands.
18435 @item monitor set debug 0
18436 @itemx monitor set debug 1
18437 Disable or enable general debugging messages.
18439 @item monitor set remote-debug 0
18440 @itemx monitor set remote-debug 1
18441 Disable or enable specific debugging messages associated with the remote
18442 protocol (@pxref{Remote Protocol}).
18444 @item monitor set libthread-db-search-path [PATH]
18445 @cindex gdbserver, search path for @code{libthread_db}
18446 When this command is issued, @var{path} is a colon-separated list of
18447 directories to search for @code{libthread_db} (@pxref{Threads,,set
18448 libthread-db-search-path}). If you omit @var{path},
18449 @samp{libthread-db-search-path} will be reset to its default value.
18451 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
18452 not supported in @code{gdbserver}.
18455 Tell gdbserver to exit immediately. This command should be followed by
18456 @code{disconnect} to close the debugging session. @code{gdbserver} will
18457 detach from any attached processes and kill any processes it created.
18458 Use @code{monitor exit} to terminate @code{gdbserver} at the end
18459 of a multi-process mode debug session.
18463 @subsection Tracepoints support in @code{gdbserver}
18464 @cindex tracepoints support in @code{gdbserver}
18466 On some targets, @code{gdbserver} supports tracepoints, fast
18467 tracepoints and static tracepoints.
18469 For fast or static tracepoints to work, a special library called the
18470 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
18471 This library is built and distributed as an integral part of
18472 @code{gdbserver}. In addition, support for static tracepoints
18473 requires building the in-process agent library with static tracepoints
18474 support. At present, the UST (LTTng Userspace Tracer,
18475 @url{http://lttng.org/ust}) tracing engine is supported. This support
18476 is automatically available if UST development headers are found in the
18477 standard include path when @code{gdbserver} is built, or if
18478 @code{gdbserver} was explicitly configured using @option{--with-ust}
18479 to point at such headers. You can explicitly disable the support
18480 using @option{--with-ust=no}.
18482 There are several ways to load the in-process agent in your program:
18485 @item Specifying it as dependency at link time
18487 You can link your program dynamically with the in-process agent
18488 library. On most systems, this is accomplished by adding
18489 @code{-linproctrace} to the link command.
18491 @item Using the system's preloading mechanisms
18493 You can force loading the in-process agent at startup time by using
18494 your system's support for preloading shared libraries. Many Unixes
18495 support the concept of preloading user defined libraries. In most
18496 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
18497 in the environment. See also the description of @code{gdbserver}'s
18498 @option{--wrapper} command line option.
18500 @item Using @value{GDBN} to force loading the agent at run time
18502 On some systems, you can force the inferior to load a shared library,
18503 by calling a dynamic loader function in the inferior that takes care
18504 of dynamically looking up and loading a shared library. On most Unix
18505 systems, the function is @code{dlopen}. You'll use the @code{call}
18506 command for that. For example:
18509 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
18512 Note that on most Unix systems, for the @code{dlopen} function to be
18513 available, the program needs to be linked with @code{-ldl}.
18516 On systems that have a userspace dynamic loader, like most Unix
18517 systems, when you connect to @code{gdbserver} using @code{target
18518 remote}, you'll find that the program is stopped at the dynamic
18519 loader's entry point, and no shared library has been loaded in the
18520 program's address space yet, including the in-process agent. In that
18521 case, before being able to use any of the fast or static tracepoints
18522 features, you need to let the loader run and load the shared
18523 libraries. The simplest way to do that is to run the program to the
18524 main procedure. E.g., if debugging a C or C@t{++} program, start
18525 @code{gdbserver} like so:
18528 $ gdbserver :9999 myprogram
18531 Start GDB and connect to @code{gdbserver} like so, and run to main:
18535 (@value{GDBP}) target remote myhost:9999
18536 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
18537 (@value{GDBP}) b main
18538 (@value{GDBP}) continue
18541 The in-process tracing agent library should now be loaded into the
18542 process; you can confirm it with the @code{info sharedlibrary}
18543 command, which will list @file{libinproctrace.so} as loaded in the
18544 process. You are now ready to install fast tracepoints, list static
18545 tracepoint markers, probe static tracepoints markers, and start
18548 @node Remote Configuration
18549 @section Remote Configuration
18552 @kindex show remote
18553 This section documents the configuration options available when
18554 debugging remote programs. For the options related to the File I/O
18555 extensions of the remote protocol, see @ref{system,
18556 system-call-allowed}.
18559 @item set remoteaddresssize @var{bits}
18560 @cindex address size for remote targets
18561 @cindex bits in remote address
18562 Set the maximum size of address in a memory packet to the specified
18563 number of bits. @value{GDBN} will mask off the address bits above
18564 that number, when it passes addresses to the remote target. The
18565 default value is the number of bits in the target's address.
18567 @item show remoteaddresssize
18568 Show the current value of remote address size in bits.
18570 @item set serial baud @var{n}
18571 @cindex baud rate for remote targets
18572 Set the baud rate for the remote serial I/O to @var{n} baud. The
18573 value is used to set the speed of the serial port used for debugging
18576 @item show serial baud
18577 Show the current speed of the remote connection.
18579 @item set remotebreak
18580 @cindex interrupt remote programs
18581 @cindex BREAK signal instead of Ctrl-C
18582 @anchor{set remotebreak}
18583 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
18584 when you type @kbd{Ctrl-c} to interrupt the program running
18585 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
18586 character instead. The default is off, since most remote systems
18587 expect to see @samp{Ctrl-C} as the interrupt signal.
18589 @item show remotebreak
18590 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
18591 interrupt the remote program.
18593 @item set remoteflow on
18594 @itemx set remoteflow off
18595 @kindex set remoteflow
18596 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
18597 on the serial port used to communicate to the remote target.
18599 @item show remoteflow
18600 @kindex show remoteflow
18601 Show the current setting of hardware flow control.
18603 @item set remotelogbase @var{base}
18604 Set the base (a.k.a.@: radix) of logging serial protocol
18605 communications to @var{base}. Supported values of @var{base} are:
18606 @code{ascii}, @code{octal}, and @code{hex}. The default is
18609 @item show remotelogbase
18610 Show the current setting of the radix for logging remote serial
18613 @item set remotelogfile @var{file}
18614 @cindex record serial communications on file
18615 Record remote serial communications on the named @var{file}. The
18616 default is not to record at all.
18618 @item show remotelogfile.
18619 Show the current setting of the file name on which to record the
18620 serial communications.
18622 @item set remotetimeout @var{num}
18623 @cindex timeout for serial communications
18624 @cindex remote timeout
18625 Set the timeout limit to wait for the remote target to respond to
18626 @var{num} seconds. The default is 2 seconds.
18628 @item show remotetimeout
18629 Show the current number of seconds to wait for the remote target
18632 @cindex limit hardware breakpoints and watchpoints
18633 @cindex remote target, limit break- and watchpoints
18634 @anchor{set remote hardware-watchpoint-limit}
18635 @anchor{set remote hardware-breakpoint-limit}
18636 @item set remote hardware-watchpoint-limit @var{limit}
18637 @itemx set remote hardware-breakpoint-limit @var{limit}
18638 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
18639 watchpoints. A limit of -1, the default, is treated as unlimited.
18641 @cindex limit hardware watchpoints length
18642 @cindex remote target, limit watchpoints length
18643 @anchor{set remote hardware-watchpoint-length-limit}
18644 @item set remote hardware-watchpoint-length-limit @var{limit}
18645 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
18646 a remote hardware watchpoint. A limit of -1, the default, is treated
18649 @item show remote hardware-watchpoint-length-limit
18650 Show the current limit (in bytes) of the maximum length of
18651 a remote hardware watchpoint.
18653 @item set remote exec-file @var{filename}
18654 @itemx show remote exec-file
18655 @anchor{set remote exec-file}
18656 @cindex executable file, for remote target
18657 Select the file used for @code{run} with @code{target
18658 extended-remote}. This should be set to a filename valid on the
18659 target system. If it is not set, the target will use a default
18660 filename (e.g.@: the last program run).
18662 @item set remote interrupt-sequence
18663 @cindex interrupt remote programs
18664 @cindex select Ctrl-C, BREAK or BREAK-g
18665 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
18666 @samp{BREAK-g} as the
18667 sequence to the remote target in order to interrupt the execution.
18668 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
18669 is high level of serial line for some certain time.
18670 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
18671 It is @code{BREAK} signal followed by character @code{g}.
18673 @item show interrupt-sequence
18674 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
18675 is sent by @value{GDBN} to interrupt the remote program.
18676 @code{BREAK-g} is BREAK signal followed by @code{g} and
18677 also known as Magic SysRq g.
18679 @item set remote interrupt-on-connect
18680 @cindex send interrupt-sequence on start
18681 Specify whether interrupt-sequence is sent to remote target when
18682 @value{GDBN} connects to it. This is mostly needed when you debug
18683 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
18684 which is known as Magic SysRq g in order to connect @value{GDBN}.
18686 @item show interrupt-on-connect
18687 Show whether interrupt-sequence is sent
18688 to remote target when @value{GDBN} connects to it.
18692 @item set tcp auto-retry on
18693 @cindex auto-retry, for remote TCP target
18694 Enable auto-retry for remote TCP connections. This is useful if the remote
18695 debugging agent is launched in parallel with @value{GDBN}; there is a race
18696 condition because the agent may not become ready to accept the connection
18697 before @value{GDBN} attempts to connect. When auto-retry is
18698 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
18699 to establish the connection using the timeout specified by
18700 @code{set tcp connect-timeout}.
18702 @item set tcp auto-retry off
18703 Do not auto-retry failed TCP connections.
18705 @item show tcp auto-retry
18706 Show the current auto-retry setting.
18708 @item set tcp connect-timeout @var{seconds}
18709 @itemx set tcp connect-timeout unlimited
18710 @cindex connection timeout, for remote TCP target
18711 @cindex timeout, for remote target connection
18712 Set the timeout for establishing a TCP connection to the remote target to
18713 @var{seconds}. The timeout affects both polling to retry failed connections
18714 (enabled by @code{set tcp auto-retry on}) and waiting for connections
18715 that are merely slow to complete, and represents an approximate cumulative
18716 value. If @var{seconds} is @code{unlimited}, there is no timeout and
18717 @value{GDBN} will keep attempting to establish a connection forever,
18718 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
18720 @item show tcp connect-timeout
18721 Show the current connection timeout setting.
18724 @cindex remote packets, enabling and disabling
18725 The @value{GDBN} remote protocol autodetects the packets supported by
18726 your debugging stub. If you need to override the autodetection, you
18727 can use these commands to enable or disable individual packets. Each
18728 packet can be set to @samp{on} (the remote target supports this
18729 packet), @samp{off} (the remote target does not support this packet),
18730 or @samp{auto} (detect remote target support for this packet). They
18731 all default to @samp{auto}. For more information about each packet,
18732 see @ref{Remote Protocol}.
18734 During normal use, you should not have to use any of these commands.
18735 If you do, that may be a bug in your remote debugging stub, or a bug
18736 in @value{GDBN}. You may want to report the problem to the
18737 @value{GDBN} developers.
18739 For each packet @var{name}, the command to enable or disable the
18740 packet is @code{set remote @var{name}-packet}. The available settings
18743 @multitable @columnfractions 0.28 0.32 0.25
18746 @tab Related Features
18748 @item @code{fetch-register}
18750 @tab @code{info registers}
18752 @item @code{set-register}
18756 @item @code{binary-download}
18758 @tab @code{load}, @code{set}
18760 @item @code{read-aux-vector}
18761 @tab @code{qXfer:auxv:read}
18762 @tab @code{info auxv}
18764 @item @code{symbol-lookup}
18765 @tab @code{qSymbol}
18766 @tab Detecting multiple threads
18768 @item @code{attach}
18769 @tab @code{vAttach}
18772 @item @code{verbose-resume}
18774 @tab Stepping or resuming multiple threads
18780 @item @code{software-breakpoint}
18784 @item @code{hardware-breakpoint}
18788 @item @code{write-watchpoint}
18792 @item @code{read-watchpoint}
18796 @item @code{access-watchpoint}
18800 @item @code{target-features}
18801 @tab @code{qXfer:features:read}
18802 @tab @code{set architecture}
18804 @item @code{library-info}
18805 @tab @code{qXfer:libraries:read}
18806 @tab @code{info sharedlibrary}
18808 @item @code{memory-map}
18809 @tab @code{qXfer:memory-map:read}
18810 @tab @code{info mem}
18812 @item @code{read-sdata-object}
18813 @tab @code{qXfer:sdata:read}
18814 @tab @code{print $_sdata}
18816 @item @code{read-spu-object}
18817 @tab @code{qXfer:spu:read}
18818 @tab @code{info spu}
18820 @item @code{write-spu-object}
18821 @tab @code{qXfer:spu:write}
18822 @tab @code{info spu}
18824 @item @code{read-siginfo-object}
18825 @tab @code{qXfer:siginfo:read}
18826 @tab @code{print $_siginfo}
18828 @item @code{write-siginfo-object}
18829 @tab @code{qXfer:siginfo:write}
18830 @tab @code{set $_siginfo}
18832 @item @code{threads}
18833 @tab @code{qXfer:threads:read}
18834 @tab @code{info threads}
18836 @item @code{get-thread-local-@*storage-address}
18837 @tab @code{qGetTLSAddr}
18838 @tab Displaying @code{__thread} variables
18840 @item @code{get-thread-information-block-address}
18841 @tab @code{qGetTIBAddr}
18842 @tab Display MS-Windows Thread Information Block.
18844 @item @code{search-memory}
18845 @tab @code{qSearch:memory}
18848 @item @code{supported-packets}
18849 @tab @code{qSupported}
18850 @tab Remote communications parameters
18852 @item @code{pass-signals}
18853 @tab @code{QPassSignals}
18854 @tab @code{handle @var{signal}}
18856 @item @code{program-signals}
18857 @tab @code{QProgramSignals}
18858 @tab @code{handle @var{signal}}
18860 @item @code{hostio-close-packet}
18861 @tab @code{vFile:close}
18862 @tab @code{remote get}, @code{remote put}
18864 @item @code{hostio-open-packet}
18865 @tab @code{vFile:open}
18866 @tab @code{remote get}, @code{remote put}
18868 @item @code{hostio-pread-packet}
18869 @tab @code{vFile:pread}
18870 @tab @code{remote get}, @code{remote put}
18872 @item @code{hostio-pwrite-packet}
18873 @tab @code{vFile:pwrite}
18874 @tab @code{remote get}, @code{remote put}
18876 @item @code{hostio-unlink-packet}
18877 @tab @code{vFile:unlink}
18878 @tab @code{remote delete}
18880 @item @code{hostio-readlink-packet}
18881 @tab @code{vFile:readlink}
18884 @item @code{noack-packet}
18885 @tab @code{QStartNoAckMode}
18886 @tab Packet acknowledgment
18888 @item @code{osdata}
18889 @tab @code{qXfer:osdata:read}
18890 @tab @code{info os}
18892 @item @code{query-attached}
18893 @tab @code{qAttached}
18894 @tab Querying remote process attach state.
18896 @item @code{trace-buffer-size}
18897 @tab @code{QTBuffer:size}
18898 @tab @code{set trace-buffer-size}
18900 @item @code{trace-status}
18901 @tab @code{qTStatus}
18902 @tab @code{tstatus}
18904 @item @code{traceframe-info}
18905 @tab @code{qXfer:traceframe-info:read}
18906 @tab Traceframe info
18908 @item @code{install-in-trace}
18909 @tab @code{InstallInTrace}
18910 @tab Install tracepoint in tracing
18912 @item @code{disable-randomization}
18913 @tab @code{QDisableRandomization}
18914 @tab @code{set disable-randomization}
18916 @item @code{conditional-breakpoints-packet}
18917 @tab @code{Z0 and Z1}
18918 @tab @code{Support for target-side breakpoint condition evaluation}
18922 @section Implementing a Remote Stub
18924 @cindex debugging stub, example
18925 @cindex remote stub, example
18926 @cindex stub example, remote debugging
18927 The stub files provided with @value{GDBN} implement the target side of the
18928 communication protocol, and the @value{GDBN} side is implemented in the
18929 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
18930 these subroutines to communicate, and ignore the details. (If you're
18931 implementing your own stub file, you can still ignore the details: start
18932 with one of the existing stub files. @file{sparc-stub.c} is the best
18933 organized, and therefore the easiest to read.)
18935 @cindex remote serial debugging, overview
18936 To debug a program running on another machine (the debugging
18937 @dfn{target} machine), you must first arrange for all the usual
18938 prerequisites for the program to run by itself. For example, for a C
18943 A startup routine to set up the C runtime environment; these usually
18944 have a name like @file{crt0}. The startup routine may be supplied by
18945 your hardware supplier, or you may have to write your own.
18948 A C subroutine library to support your program's
18949 subroutine calls, notably managing input and output.
18952 A way of getting your program to the other machine---for example, a
18953 download program. These are often supplied by the hardware
18954 manufacturer, but you may have to write your own from hardware
18958 The next step is to arrange for your program to use a serial port to
18959 communicate with the machine where @value{GDBN} is running (the @dfn{host}
18960 machine). In general terms, the scheme looks like this:
18964 @value{GDBN} already understands how to use this protocol; when everything
18965 else is set up, you can simply use the @samp{target remote} command
18966 (@pxref{Targets,,Specifying a Debugging Target}).
18968 @item On the target,
18969 you must link with your program a few special-purpose subroutines that
18970 implement the @value{GDBN} remote serial protocol. The file containing these
18971 subroutines is called a @dfn{debugging stub}.
18973 On certain remote targets, you can use an auxiliary program
18974 @code{gdbserver} instead of linking a stub into your program.
18975 @xref{Server,,Using the @code{gdbserver} Program}, for details.
18978 The debugging stub is specific to the architecture of the remote
18979 machine; for example, use @file{sparc-stub.c} to debug programs on
18982 @cindex remote serial stub list
18983 These working remote stubs are distributed with @value{GDBN}:
18988 @cindex @file{i386-stub.c}
18991 For Intel 386 and compatible architectures.
18994 @cindex @file{m68k-stub.c}
18995 @cindex Motorola 680x0
18997 For Motorola 680x0 architectures.
19000 @cindex @file{sh-stub.c}
19003 For Renesas SH architectures.
19006 @cindex @file{sparc-stub.c}
19008 For @sc{sparc} architectures.
19010 @item sparcl-stub.c
19011 @cindex @file{sparcl-stub.c}
19014 For Fujitsu @sc{sparclite} architectures.
19018 The @file{README} file in the @value{GDBN} distribution may list other
19019 recently added stubs.
19022 * Stub Contents:: What the stub can do for you
19023 * Bootstrapping:: What you must do for the stub
19024 * Debug Session:: Putting it all together
19027 @node Stub Contents
19028 @subsection What the Stub Can Do for You
19030 @cindex remote serial stub
19031 The debugging stub for your architecture supplies these three
19035 @item set_debug_traps
19036 @findex set_debug_traps
19037 @cindex remote serial stub, initialization
19038 This routine arranges for @code{handle_exception} to run when your
19039 program stops. You must call this subroutine explicitly in your
19040 program's startup code.
19042 @item handle_exception
19043 @findex handle_exception
19044 @cindex remote serial stub, main routine
19045 This is the central workhorse, but your program never calls it
19046 explicitly---the setup code arranges for @code{handle_exception} to
19047 run when a trap is triggered.
19049 @code{handle_exception} takes control when your program stops during
19050 execution (for example, on a breakpoint), and mediates communications
19051 with @value{GDBN} on the host machine. This is where the communications
19052 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
19053 representative on the target machine. It begins by sending summary
19054 information on the state of your program, then continues to execute,
19055 retrieving and transmitting any information @value{GDBN} needs, until you
19056 execute a @value{GDBN} command that makes your program resume; at that point,
19057 @code{handle_exception} returns control to your own code on the target
19061 @cindex @code{breakpoint} subroutine, remote
19062 Use this auxiliary subroutine to make your program contain a
19063 breakpoint. Depending on the particular situation, this may be the only
19064 way for @value{GDBN} to get control. For instance, if your target
19065 machine has some sort of interrupt button, you won't need to call this;
19066 pressing the interrupt button transfers control to
19067 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
19068 simply receiving characters on the serial port may also trigger a trap;
19069 again, in that situation, you don't need to call @code{breakpoint} from
19070 your own program---simply running @samp{target remote} from the host
19071 @value{GDBN} session gets control.
19073 Call @code{breakpoint} if none of these is true, or if you simply want
19074 to make certain your program stops at a predetermined point for the
19075 start of your debugging session.
19078 @node Bootstrapping
19079 @subsection What You Must Do for the Stub
19081 @cindex remote stub, support routines
19082 The debugging stubs that come with @value{GDBN} are set up for a particular
19083 chip architecture, but they have no information about the rest of your
19084 debugging target machine.
19086 First of all you need to tell the stub how to communicate with the
19090 @item int getDebugChar()
19091 @findex getDebugChar
19092 Write this subroutine to read a single character from the serial port.
19093 It may be identical to @code{getchar} for your target system; a
19094 different name is used to allow you to distinguish the two if you wish.
19096 @item void putDebugChar(int)
19097 @findex putDebugChar
19098 Write this subroutine to write a single character to the serial port.
19099 It may be identical to @code{putchar} for your target system; a
19100 different name is used to allow you to distinguish the two if you wish.
19103 @cindex control C, and remote debugging
19104 @cindex interrupting remote targets
19105 If you want @value{GDBN} to be able to stop your program while it is
19106 running, you need to use an interrupt-driven serial driver, and arrange
19107 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
19108 character). That is the character which @value{GDBN} uses to tell the
19109 remote system to stop.
19111 Getting the debugging target to return the proper status to @value{GDBN}
19112 probably requires changes to the standard stub; one quick and dirty way
19113 is to just execute a breakpoint instruction (the ``dirty'' part is that
19114 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
19116 Other routines you need to supply are:
19119 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
19120 @findex exceptionHandler
19121 Write this function to install @var{exception_address} in the exception
19122 handling tables. You need to do this because the stub does not have any
19123 way of knowing what the exception handling tables on your target system
19124 are like (for example, the processor's table might be in @sc{rom},
19125 containing entries which point to a table in @sc{ram}).
19126 @var{exception_number} is the exception number which should be changed;
19127 its meaning is architecture-dependent (for example, different numbers
19128 might represent divide by zero, misaligned access, etc). When this
19129 exception occurs, control should be transferred directly to
19130 @var{exception_address}, and the processor state (stack, registers,
19131 and so on) should be just as it is when a processor exception occurs. So if
19132 you want to use a jump instruction to reach @var{exception_address}, it
19133 should be a simple jump, not a jump to subroutine.
19135 For the 386, @var{exception_address} should be installed as an interrupt
19136 gate so that interrupts are masked while the handler runs. The gate
19137 should be at privilege level 0 (the most privileged level). The
19138 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
19139 help from @code{exceptionHandler}.
19141 @item void flush_i_cache()
19142 @findex flush_i_cache
19143 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
19144 instruction cache, if any, on your target machine. If there is no
19145 instruction cache, this subroutine may be a no-op.
19147 On target machines that have instruction caches, @value{GDBN} requires this
19148 function to make certain that the state of your program is stable.
19152 You must also make sure this library routine is available:
19155 @item void *memset(void *, int, int)
19157 This is the standard library function @code{memset} that sets an area of
19158 memory to a known value. If you have one of the free versions of
19159 @code{libc.a}, @code{memset} can be found there; otherwise, you must
19160 either obtain it from your hardware manufacturer, or write your own.
19163 If you do not use the GNU C compiler, you may need other standard
19164 library subroutines as well; this varies from one stub to another,
19165 but in general the stubs are likely to use any of the common library
19166 subroutines which @code{@value{NGCC}} generates as inline code.
19169 @node Debug Session
19170 @subsection Putting it All Together
19172 @cindex remote serial debugging summary
19173 In summary, when your program is ready to debug, you must follow these
19178 Make sure you have defined the supporting low-level routines
19179 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
19181 @code{getDebugChar}, @code{putDebugChar},
19182 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
19186 Insert these lines in your program's startup code, before the main
19187 procedure is called:
19194 On some machines, when a breakpoint trap is raised, the hardware
19195 automatically makes the PC point to the instruction after the
19196 breakpoint. If your machine doesn't do that, you may need to adjust
19197 @code{handle_exception} to arrange for it to return to the instruction
19198 after the breakpoint on this first invocation, so that your program
19199 doesn't keep hitting the initial breakpoint instead of making
19203 For the 680x0 stub only, you need to provide a variable called
19204 @code{exceptionHook}. Normally you just use:
19207 void (*exceptionHook)() = 0;
19211 but if before calling @code{set_debug_traps}, you set it to point to a
19212 function in your program, that function is called when
19213 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
19214 error). The function indicated by @code{exceptionHook} is called with
19215 one parameter: an @code{int} which is the exception number.
19218 Compile and link together: your program, the @value{GDBN} debugging stub for
19219 your target architecture, and the supporting subroutines.
19222 Make sure you have a serial connection between your target machine and
19223 the @value{GDBN} host, and identify the serial port on the host.
19226 @c The "remote" target now provides a `load' command, so we should
19227 @c document that. FIXME.
19228 Download your program to your target machine (or get it there by
19229 whatever means the manufacturer provides), and start it.
19232 Start @value{GDBN} on the host, and connect to the target
19233 (@pxref{Connecting,,Connecting to a Remote Target}).
19237 @node Configurations
19238 @chapter Configuration-Specific Information
19240 While nearly all @value{GDBN} commands are available for all native and
19241 cross versions of the debugger, there are some exceptions. This chapter
19242 describes things that are only available in certain configurations.
19244 There are three major categories of configurations: native
19245 configurations, where the host and target are the same, embedded
19246 operating system configurations, which are usually the same for several
19247 different processor architectures, and bare embedded processors, which
19248 are quite different from each other.
19253 * Embedded Processors::
19260 This section describes details specific to particular native
19265 * BSD libkvm Interface:: Debugging BSD kernel memory images
19266 * SVR4 Process Information:: SVR4 process information
19267 * DJGPP Native:: Features specific to the DJGPP port
19268 * Cygwin Native:: Features specific to the Cygwin port
19269 * Hurd Native:: Features specific to @sc{gnu} Hurd
19270 * Darwin:: Features specific to Darwin
19276 On HP-UX systems, if you refer to a function or variable name that
19277 begins with a dollar sign, @value{GDBN} searches for a user or system
19278 name first, before it searches for a convenience variable.
19281 @node BSD libkvm Interface
19282 @subsection BSD libkvm Interface
19285 @cindex kernel memory image
19286 @cindex kernel crash dump
19288 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
19289 interface that provides a uniform interface for accessing kernel virtual
19290 memory images, including live systems and crash dumps. @value{GDBN}
19291 uses this interface to allow you to debug live kernels and kernel crash
19292 dumps on many native BSD configurations. This is implemented as a
19293 special @code{kvm} debugging target. For debugging a live system, load
19294 the currently running kernel into @value{GDBN} and connect to the
19298 (@value{GDBP}) @b{target kvm}
19301 For debugging crash dumps, provide the file name of the crash dump as an
19305 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
19308 Once connected to the @code{kvm} target, the following commands are
19314 Set current context from the @dfn{Process Control Block} (PCB) address.
19317 Set current context from proc address. This command isn't available on
19318 modern FreeBSD systems.
19321 @node SVR4 Process Information
19322 @subsection SVR4 Process Information
19324 @cindex examine process image
19325 @cindex process info via @file{/proc}
19327 Many versions of SVR4 and compatible systems provide a facility called
19328 @samp{/proc} that can be used to examine the image of a running
19329 process using file-system subroutines.
19331 If @value{GDBN} is configured for an operating system with this
19332 facility, the command @code{info proc} is available to report
19333 information about the process running your program, or about any
19334 process running on your system. This includes, as of this writing,
19335 @sc{gnu}/Linux, OSF/1 (Digital Unix), Solaris, and Irix, but
19336 not HP-UX, for example.
19338 This command may also work on core files that were created on a system
19339 that has the @samp{/proc} facility.
19345 @itemx info proc @var{process-id}
19346 Summarize available information about any running process. If a
19347 process ID is specified by @var{process-id}, display information about
19348 that process; otherwise display information about the program being
19349 debugged. The summary includes the debugged process ID, the command
19350 line used to invoke it, its current working directory, and its
19351 executable file's absolute file name.
19353 On some systems, @var{process-id} can be of the form
19354 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
19355 within a process. If the optional @var{pid} part is missing, it means
19356 a thread from the process being debugged (the leading @samp{/} still
19357 needs to be present, or else @value{GDBN} will interpret the number as
19358 a process ID rather than a thread ID).
19360 @item info proc cmdline
19361 @cindex info proc cmdline
19362 Show the original command line of the process. This command is
19363 specific to @sc{gnu}/Linux.
19365 @item info proc cwd
19366 @cindex info proc cwd
19367 Show the current working directory of the process. This command is
19368 specific to @sc{gnu}/Linux.
19370 @item info proc exe
19371 @cindex info proc exe
19372 Show the name of executable of the process. This command is specific
19375 @item info proc mappings
19376 @cindex memory address space mappings
19377 Report the memory address space ranges accessible in the program, with
19378 information on whether the process has read, write, or execute access
19379 rights to each range. On @sc{gnu}/Linux systems, each memory range
19380 includes the object file which is mapped to that range, instead of the
19381 memory access rights to that range.
19383 @item info proc stat
19384 @itemx info proc status
19385 @cindex process detailed status information
19386 These subcommands are specific to @sc{gnu}/Linux systems. They show
19387 the process-related information, including the user ID and group ID;
19388 how many threads are there in the process; its virtual memory usage;
19389 the signals that are pending, blocked, and ignored; its TTY; its
19390 consumption of system and user time; its stack size; its @samp{nice}
19391 value; etc. For more information, see the @samp{proc} man page
19392 (type @kbd{man 5 proc} from your shell prompt).
19394 @item info proc all
19395 Show all the information about the process described under all of the
19396 above @code{info proc} subcommands.
19399 @comment These sub-options of 'info proc' were not included when
19400 @comment procfs.c was re-written. Keep their descriptions around
19401 @comment against the day when someone finds the time to put them back in.
19402 @kindex info proc times
19403 @item info proc times
19404 Starting time, user CPU time, and system CPU time for your program and
19407 @kindex info proc id
19409 Report on the process IDs related to your program: its own process ID,
19410 the ID of its parent, the process group ID, and the session ID.
19413 @item set procfs-trace
19414 @kindex set procfs-trace
19415 @cindex @code{procfs} API calls
19416 This command enables and disables tracing of @code{procfs} API calls.
19418 @item show procfs-trace
19419 @kindex show procfs-trace
19420 Show the current state of @code{procfs} API call tracing.
19422 @item set procfs-file @var{file}
19423 @kindex set procfs-file
19424 Tell @value{GDBN} to write @code{procfs} API trace to the named
19425 @var{file}. @value{GDBN} appends the trace info to the previous
19426 contents of the file. The default is to display the trace on the
19429 @item show procfs-file
19430 @kindex show procfs-file
19431 Show the file to which @code{procfs} API trace is written.
19433 @item proc-trace-entry
19434 @itemx proc-trace-exit
19435 @itemx proc-untrace-entry
19436 @itemx proc-untrace-exit
19437 @kindex proc-trace-entry
19438 @kindex proc-trace-exit
19439 @kindex proc-untrace-entry
19440 @kindex proc-untrace-exit
19441 These commands enable and disable tracing of entries into and exits
19442 from the @code{syscall} interface.
19445 @kindex info pidlist
19446 @cindex process list, QNX Neutrino
19447 For QNX Neutrino only, this command displays the list of all the
19448 processes and all the threads within each process.
19451 @kindex info meminfo
19452 @cindex mapinfo list, QNX Neutrino
19453 For QNX Neutrino only, this command displays the list of all mapinfos.
19457 @subsection Features for Debugging @sc{djgpp} Programs
19458 @cindex @sc{djgpp} debugging
19459 @cindex native @sc{djgpp} debugging
19460 @cindex MS-DOS-specific commands
19463 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
19464 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
19465 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
19466 top of real-mode DOS systems and their emulations.
19468 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
19469 defines a few commands specific to the @sc{djgpp} port. This
19470 subsection describes those commands.
19475 This is a prefix of @sc{djgpp}-specific commands which print
19476 information about the target system and important OS structures.
19479 @cindex MS-DOS system info
19480 @cindex free memory information (MS-DOS)
19481 @item info dos sysinfo
19482 This command displays assorted information about the underlying
19483 platform: the CPU type and features, the OS version and flavor, the
19484 DPMI version, and the available conventional and DPMI memory.
19489 @cindex segment descriptor tables
19490 @cindex descriptor tables display
19492 @itemx info dos ldt
19493 @itemx info dos idt
19494 These 3 commands display entries from, respectively, Global, Local,
19495 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
19496 tables are data structures which store a descriptor for each segment
19497 that is currently in use. The segment's selector is an index into a
19498 descriptor table; the table entry for that index holds the
19499 descriptor's base address and limit, and its attributes and access
19502 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
19503 segment (used for both data and the stack), and a DOS segment (which
19504 allows access to DOS/BIOS data structures and absolute addresses in
19505 conventional memory). However, the DPMI host will usually define
19506 additional segments in order to support the DPMI environment.
19508 @cindex garbled pointers
19509 These commands allow to display entries from the descriptor tables.
19510 Without an argument, all entries from the specified table are
19511 displayed. An argument, which should be an integer expression, means
19512 display a single entry whose index is given by the argument. For
19513 example, here's a convenient way to display information about the
19514 debugged program's data segment:
19517 @exdent @code{(@value{GDBP}) info dos ldt $ds}
19518 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
19522 This comes in handy when you want to see whether a pointer is outside
19523 the data segment's limit (i.e.@: @dfn{garbled}).
19525 @cindex page tables display (MS-DOS)
19527 @itemx info dos pte
19528 These two commands display entries from, respectively, the Page
19529 Directory and the Page Tables. Page Directories and Page Tables are
19530 data structures which control how virtual memory addresses are mapped
19531 into physical addresses. A Page Table includes an entry for every
19532 page of memory that is mapped into the program's address space; there
19533 may be several Page Tables, each one holding up to 4096 entries. A
19534 Page Directory has up to 4096 entries, one each for every Page Table
19535 that is currently in use.
19537 Without an argument, @kbd{info dos pde} displays the entire Page
19538 Directory, and @kbd{info dos pte} displays all the entries in all of
19539 the Page Tables. An argument, an integer expression, given to the
19540 @kbd{info dos pde} command means display only that entry from the Page
19541 Directory table. An argument given to the @kbd{info dos pte} command
19542 means display entries from a single Page Table, the one pointed to by
19543 the specified entry in the Page Directory.
19545 @cindex direct memory access (DMA) on MS-DOS
19546 These commands are useful when your program uses @dfn{DMA} (Direct
19547 Memory Access), which needs physical addresses to program the DMA
19550 These commands are supported only with some DPMI servers.
19552 @cindex physical address from linear address
19553 @item info dos address-pte @var{addr}
19554 This command displays the Page Table entry for a specified linear
19555 address. The argument @var{addr} is a linear address which should
19556 already have the appropriate segment's base address added to it,
19557 because this command accepts addresses which may belong to @emph{any}
19558 segment. For example, here's how to display the Page Table entry for
19559 the page where a variable @code{i} is stored:
19562 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
19563 @exdent @code{Page Table entry for address 0x11a00d30:}
19564 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
19568 This says that @code{i} is stored at offset @code{0xd30} from the page
19569 whose physical base address is @code{0x02698000}, and shows all the
19570 attributes of that page.
19572 Note that you must cast the addresses of variables to a @code{char *},
19573 since otherwise the value of @code{__djgpp_base_address}, the base
19574 address of all variables and functions in a @sc{djgpp} program, will
19575 be added using the rules of C pointer arithmetics: if @code{i} is
19576 declared an @code{int}, @value{GDBN} will add 4 times the value of
19577 @code{__djgpp_base_address} to the address of @code{i}.
19579 Here's another example, it displays the Page Table entry for the
19583 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
19584 @exdent @code{Page Table entry for address 0x29110:}
19585 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
19589 (The @code{+ 3} offset is because the transfer buffer's address is the
19590 3rd member of the @code{_go32_info_block} structure.) The output
19591 clearly shows that this DPMI server maps the addresses in conventional
19592 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
19593 linear (@code{0x29110}) addresses are identical.
19595 This command is supported only with some DPMI servers.
19598 @cindex DOS serial data link, remote debugging
19599 In addition to native debugging, the DJGPP port supports remote
19600 debugging via a serial data link. The following commands are specific
19601 to remote serial debugging in the DJGPP port of @value{GDBN}.
19604 @kindex set com1base
19605 @kindex set com1irq
19606 @kindex set com2base
19607 @kindex set com2irq
19608 @kindex set com3base
19609 @kindex set com3irq
19610 @kindex set com4base
19611 @kindex set com4irq
19612 @item set com1base @var{addr}
19613 This command sets the base I/O port address of the @file{COM1} serial
19616 @item set com1irq @var{irq}
19617 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
19618 for the @file{COM1} serial port.
19620 There are similar commands @samp{set com2base}, @samp{set com3irq},
19621 etc.@: for setting the port address and the @code{IRQ} lines for the
19624 @kindex show com1base
19625 @kindex show com1irq
19626 @kindex show com2base
19627 @kindex show com2irq
19628 @kindex show com3base
19629 @kindex show com3irq
19630 @kindex show com4base
19631 @kindex show com4irq
19632 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
19633 display the current settings of the base address and the @code{IRQ}
19634 lines used by the COM ports.
19637 @kindex info serial
19638 @cindex DOS serial port status
19639 This command prints the status of the 4 DOS serial ports. For each
19640 port, it prints whether it's active or not, its I/O base address and
19641 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
19642 counts of various errors encountered so far.
19646 @node Cygwin Native
19647 @subsection Features for Debugging MS Windows PE Executables
19648 @cindex MS Windows debugging
19649 @cindex native Cygwin debugging
19650 @cindex Cygwin-specific commands
19652 @value{GDBN} supports native debugging of MS Windows programs, including
19653 DLLs with and without symbolic debugging information.
19655 @cindex Ctrl-BREAK, MS-Windows
19656 @cindex interrupt debuggee on MS-Windows
19657 MS-Windows programs that call @code{SetConsoleMode} to switch off the
19658 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
19659 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
19660 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
19661 sequence, which can be used to interrupt the debuggee even if it
19664 There are various additional Cygwin-specific commands, described in
19665 this section. Working with DLLs that have no debugging symbols is
19666 described in @ref{Non-debug DLL Symbols}.
19671 This is a prefix of MS Windows-specific commands which print
19672 information about the target system and important OS structures.
19674 @item info w32 selector
19675 This command displays information returned by
19676 the Win32 API @code{GetThreadSelectorEntry} function.
19677 It takes an optional argument that is evaluated to
19678 a long value to give the information about this given selector.
19679 Without argument, this command displays information
19680 about the six segment registers.
19682 @item info w32 thread-information-block
19683 This command displays thread specific information stored in the
19684 Thread Information Block (readable on the X86 CPU family using @code{$fs}
19685 selector for 32-bit programs and @code{$gs} for 64-bit programs).
19689 This is a Cygwin-specific alias of @code{info shared}.
19691 @kindex dll-symbols
19693 This command loads symbols from a dll similarly to
19694 add-sym command but without the need to specify a base address.
19696 @kindex set cygwin-exceptions
19697 @cindex debugging the Cygwin DLL
19698 @cindex Cygwin DLL, debugging
19699 @item set cygwin-exceptions @var{mode}
19700 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
19701 happen inside the Cygwin DLL. If @var{mode} is @code{off},
19702 @value{GDBN} will delay recognition of exceptions, and may ignore some
19703 exceptions which seem to be caused by internal Cygwin DLL
19704 ``bookkeeping''. This option is meant primarily for debugging the
19705 Cygwin DLL itself; the default value is @code{off} to avoid annoying
19706 @value{GDBN} users with false @code{SIGSEGV} signals.
19708 @kindex show cygwin-exceptions
19709 @item show cygwin-exceptions
19710 Displays whether @value{GDBN} will break on exceptions that happen
19711 inside the Cygwin DLL itself.
19713 @kindex set new-console
19714 @item set new-console @var{mode}
19715 If @var{mode} is @code{on} the debuggee will
19716 be started in a new console on next start.
19717 If @var{mode} is @code{off}, the debuggee will
19718 be started in the same console as the debugger.
19720 @kindex show new-console
19721 @item show new-console
19722 Displays whether a new console is used
19723 when the debuggee is started.
19725 @kindex set new-group
19726 @item set new-group @var{mode}
19727 This boolean value controls whether the debuggee should
19728 start a new group or stay in the same group as the debugger.
19729 This affects the way the Windows OS handles
19732 @kindex show new-group
19733 @item show new-group
19734 Displays current value of new-group boolean.
19736 @kindex set debugevents
19737 @item set debugevents
19738 This boolean value adds debug output concerning kernel events related
19739 to the debuggee seen by the debugger. This includes events that
19740 signal thread and process creation and exit, DLL loading and
19741 unloading, console interrupts, and debugging messages produced by the
19742 Windows @code{OutputDebugString} API call.
19744 @kindex set debugexec
19745 @item set debugexec
19746 This boolean value adds debug output concerning execute events
19747 (such as resume thread) seen by the debugger.
19749 @kindex set debugexceptions
19750 @item set debugexceptions
19751 This boolean value adds debug output concerning exceptions in the
19752 debuggee seen by the debugger.
19754 @kindex set debugmemory
19755 @item set debugmemory
19756 This boolean value adds debug output concerning debuggee memory reads
19757 and writes by the debugger.
19761 This boolean values specifies whether the debuggee is called
19762 via a shell or directly (default value is on).
19766 Displays if the debuggee will be started with a shell.
19771 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
19774 @node Non-debug DLL Symbols
19775 @subsubsection Support for DLLs without Debugging Symbols
19776 @cindex DLLs with no debugging symbols
19777 @cindex Minimal symbols and DLLs
19779 Very often on windows, some of the DLLs that your program relies on do
19780 not include symbolic debugging information (for example,
19781 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
19782 symbols in a DLL, it relies on the minimal amount of symbolic
19783 information contained in the DLL's export table. This section
19784 describes working with such symbols, known internally to @value{GDBN} as
19785 ``minimal symbols''.
19787 Note that before the debugged program has started execution, no DLLs
19788 will have been loaded. The easiest way around this problem is simply to
19789 start the program --- either by setting a breakpoint or letting the
19790 program run once to completion. It is also possible to force
19791 @value{GDBN} to load a particular DLL before starting the executable ---
19792 see the shared library information in @ref{Files}, or the
19793 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
19794 explicitly loading symbols from a DLL with no debugging information will
19795 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
19796 which may adversely affect symbol lookup performance.
19798 @subsubsection DLL Name Prefixes
19800 In keeping with the naming conventions used by the Microsoft debugging
19801 tools, DLL export symbols are made available with a prefix based on the
19802 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
19803 also entered into the symbol table, so @code{CreateFileA} is often
19804 sufficient. In some cases there will be name clashes within a program
19805 (particularly if the executable itself includes full debugging symbols)
19806 necessitating the use of the fully qualified name when referring to the
19807 contents of the DLL. Use single-quotes around the name to avoid the
19808 exclamation mark (``!'') being interpreted as a language operator.
19810 Note that the internal name of the DLL may be all upper-case, even
19811 though the file name of the DLL is lower-case, or vice-versa. Since
19812 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
19813 some confusion. If in doubt, try the @code{info functions} and
19814 @code{info variables} commands or even @code{maint print msymbols}
19815 (@pxref{Symbols}). Here's an example:
19818 (@value{GDBP}) info function CreateFileA
19819 All functions matching regular expression "CreateFileA":
19821 Non-debugging symbols:
19822 0x77e885f4 CreateFileA
19823 0x77e885f4 KERNEL32!CreateFileA
19827 (@value{GDBP}) info function !
19828 All functions matching regular expression "!":
19830 Non-debugging symbols:
19831 0x6100114c cygwin1!__assert
19832 0x61004034 cygwin1!_dll_crt0@@0
19833 0x61004240 cygwin1!dll_crt0(per_process *)
19837 @subsubsection Working with Minimal Symbols
19839 Symbols extracted from a DLL's export table do not contain very much
19840 type information. All that @value{GDBN} can do is guess whether a symbol
19841 refers to a function or variable depending on the linker section that
19842 contains the symbol. Also note that the actual contents of the memory
19843 contained in a DLL are not available unless the program is running. This
19844 means that you cannot examine the contents of a variable or disassemble
19845 a function within a DLL without a running program.
19847 Variables are generally treated as pointers and dereferenced
19848 automatically. For this reason, it is often necessary to prefix a
19849 variable name with the address-of operator (``&'') and provide explicit
19850 type information in the command. Here's an example of the type of
19854 (@value{GDBP}) print 'cygwin1!__argv'
19859 (@value{GDBP}) x 'cygwin1!__argv'
19860 0x10021610: "\230y\""
19863 And two possible solutions:
19866 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
19867 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
19871 (@value{GDBP}) x/2x &'cygwin1!__argv'
19872 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
19873 (@value{GDBP}) x/x 0x10021608
19874 0x10021608: 0x0022fd98
19875 (@value{GDBP}) x/s 0x0022fd98
19876 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
19879 Setting a break point within a DLL is possible even before the program
19880 starts execution. However, under these circumstances, @value{GDBN} can't
19881 examine the initial instructions of the function in order to skip the
19882 function's frame set-up code. You can work around this by using ``*&''
19883 to set the breakpoint at a raw memory address:
19886 (@value{GDBP}) break *&'python22!PyOS_Readline'
19887 Breakpoint 1 at 0x1e04eff0
19890 The author of these extensions is not entirely convinced that setting a
19891 break point within a shared DLL like @file{kernel32.dll} is completely
19895 @subsection Commands Specific to @sc{gnu} Hurd Systems
19896 @cindex @sc{gnu} Hurd debugging
19898 This subsection describes @value{GDBN} commands specific to the
19899 @sc{gnu} Hurd native debugging.
19904 @kindex set signals@r{, Hurd command}
19905 @kindex set sigs@r{, Hurd command}
19906 This command toggles the state of inferior signal interception by
19907 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
19908 affected by this command. @code{sigs} is a shorthand alias for
19913 @kindex show signals@r{, Hurd command}
19914 @kindex show sigs@r{, Hurd command}
19915 Show the current state of intercepting inferior's signals.
19917 @item set signal-thread
19918 @itemx set sigthread
19919 @kindex set signal-thread
19920 @kindex set sigthread
19921 This command tells @value{GDBN} which thread is the @code{libc} signal
19922 thread. That thread is run when a signal is delivered to a running
19923 process. @code{set sigthread} is the shorthand alias of @code{set
19926 @item show signal-thread
19927 @itemx show sigthread
19928 @kindex show signal-thread
19929 @kindex show sigthread
19930 These two commands show which thread will run when the inferior is
19931 delivered a signal.
19934 @kindex set stopped@r{, Hurd command}
19935 This commands tells @value{GDBN} that the inferior process is stopped,
19936 as with the @code{SIGSTOP} signal. The stopped process can be
19937 continued by delivering a signal to it.
19940 @kindex show stopped@r{, Hurd command}
19941 This command shows whether @value{GDBN} thinks the debuggee is
19944 @item set exceptions
19945 @kindex set exceptions@r{, Hurd command}
19946 Use this command to turn off trapping of exceptions in the inferior.
19947 When exception trapping is off, neither breakpoints nor
19948 single-stepping will work. To restore the default, set exception
19951 @item show exceptions
19952 @kindex show exceptions@r{, Hurd command}
19953 Show the current state of trapping exceptions in the inferior.
19955 @item set task pause
19956 @kindex set task@r{, Hurd commands}
19957 @cindex task attributes (@sc{gnu} Hurd)
19958 @cindex pause current task (@sc{gnu} Hurd)
19959 This command toggles task suspension when @value{GDBN} has control.
19960 Setting it to on takes effect immediately, and the task is suspended
19961 whenever @value{GDBN} gets control. Setting it to off will take
19962 effect the next time the inferior is continued. If this option is set
19963 to off, you can use @code{set thread default pause on} or @code{set
19964 thread pause on} (see below) to pause individual threads.
19966 @item show task pause
19967 @kindex show task@r{, Hurd commands}
19968 Show the current state of task suspension.
19970 @item set task detach-suspend-count
19971 @cindex task suspend count
19972 @cindex detach from task, @sc{gnu} Hurd
19973 This command sets the suspend count the task will be left with when
19974 @value{GDBN} detaches from it.
19976 @item show task detach-suspend-count
19977 Show the suspend count the task will be left with when detaching.
19979 @item set task exception-port
19980 @itemx set task excp
19981 @cindex task exception port, @sc{gnu} Hurd
19982 This command sets the task exception port to which @value{GDBN} will
19983 forward exceptions. The argument should be the value of the @dfn{send
19984 rights} of the task. @code{set task excp} is a shorthand alias.
19986 @item set noninvasive
19987 @cindex noninvasive task options
19988 This command switches @value{GDBN} to a mode that is the least
19989 invasive as far as interfering with the inferior is concerned. This
19990 is the same as using @code{set task pause}, @code{set exceptions}, and
19991 @code{set signals} to values opposite to the defaults.
19993 @item info send-rights
19994 @itemx info receive-rights
19995 @itemx info port-rights
19996 @itemx info port-sets
19997 @itemx info dead-names
20000 @cindex send rights, @sc{gnu} Hurd
20001 @cindex receive rights, @sc{gnu} Hurd
20002 @cindex port rights, @sc{gnu} Hurd
20003 @cindex port sets, @sc{gnu} Hurd
20004 @cindex dead names, @sc{gnu} Hurd
20005 These commands display information about, respectively, send rights,
20006 receive rights, port rights, port sets, and dead names of a task.
20007 There are also shorthand aliases: @code{info ports} for @code{info
20008 port-rights} and @code{info psets} for @code{info port-sets}.
20010 @item set thread pause
20011 @kindex set thread@r{, Hurd command}
20012 @cindex thread properties, @sc{gnu} Hurd
20013 @cindex pause current thread (@sc{gnu} Hurd)
20014 This command toggles current thread suspension when @value{GDBN} has
20015 control. Setting it to on takes effect immediately, and the current
20016 thread is suspended whenever @value{GDBN} gets control. Setting it to
20017 off will take effect the next time the inferior is continued.
20018 Normally, this command has no effect, since when @value{GDBN} has
20019 control, the whole task is suspended. However, if you used @code{set
20020 task pause off} (see above), this command comes in handy to suspend
20021 only the current thread.
20023 @item show thread pause
20024 @kindex show thread@r{, Hurd command}
20025 This command shows the state of current thread suspension.
20027 @item set thread run
20028 This command sets whether the current thread is allowed to run.
20030 @item show thread run
20031 Show whether the current thread is allowed to run.
20033 @item set thread detach-suspend-count
20034 @cindex thread suspend count, @sc{gnu} Hurd
20035 @cindex detach from thread, @sc{gnu} Hurd
20036 This command sets the suspend count @value{GDBN} will leave on a
20037 thread when detaching. This number is relative to the suspend count
20038 found by @value{GDBN} when it notices the thread; use @code{set thread
20039 takeover-suspend-count} to force it to an absolute value.
20041 @item show thread detach-suspend-count
20042 Show the suspend count @value{GDBN} will leave on the thread when
20045 @item set thread exception-port
20046 @itemx set thread excp
20047 Set the thread exception port to which to forward exceptions. This
20048 overrides the port set by @code{set task exception-port} (see above).
20049 @code{set thread excp} is the shorthand alias.
20051 @item set thread takeover-suspend-count
20052 Normally, @value{GDBN}'s thread suspend counts are relative to the
20053 value @value{GDBN} finds when it notices each thread. This command
20054 changes the suspend counts to be absolute instead.
20056 @item set thread default
20057 @itemx show thread default
20058 @cindex thread default settings, @sc{gnu} Hurd
20059 Each of the above @code{set thread} commands has a @code{set thread
20060 default} counterpart (e.g., @code{set thread default pause}, @code{set
20061 thread default exception-port}, etc.). The @code{thread default}
20062 variety of commands sets the default thread properties for all
20063 threads; you can then change the properties of individual threads with
20064 the non-default commands.
20071 @value{GDBN} provides the following commands specific to the Darwin target:
20074 @item set debug darwin @var{num}
20075 @kindex set debug darwin
20076 When set to a non zero value, enables debugging messages specific to
20077 the Darwin support. Higher values produce more verbose output.
20079 @item show debug darwin
20080 @kindex show debug darwin
20081 Show the current state of Darwin messages.
20083 @item set debug mach-o @var{num}
20084 @kindex set debug mach-o
20085 When set to a non zero value, enables debugging messages while
20086 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
20087 file format used on Darwin for object and executable files.) Higher
20088 values produce more verbose output. This is a command to diagnose
20089 problems internal to @value{GDBN} and should not be needed in normal
20092 @item show debug mach-o
20093 @kindex show debug mach-o
20094 Show the current state of Mach-O file messages.
20096 @item set mach-exceptions on
20097 @itemx set mach-exceptions off
20098 @kindex set mach-exceptions
20099 On Darwin, faults are first reported as a Mach exception and are then
20100 mapped to a Posix signal. Use this command to turn on trapping of
20101 Mach exceptions in the inferior. This might be sometimes useful to
20102 better understand the cause of a fault. The default is off.
20104 @item show mach-exceptions
20105 @kindex show mach-exceptions
20106 Show the current state of exceptions trapping.
20111 @section Embedded Operating Systems
20113 This section describes configurations involving the debugging of
20114 embedded operating systems that are available for several different
20118 * VxWorks:: Using @value{GDBN} with VxWorks
20121 @value{GDBN} includes the ability to debug programs running on
20122 various real-time operating systems.
20125 @subsection Using @value{GDBN} with VxWorks
20131 @kindex target vxworks
20132 @item target vxworks @var{machinename}
20133 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
20134 is the target system's machine name or IP address.
20138 On VxWorks, @code{load} links @var{filename} dynamically on the
20139 current target system as well as adding its symbols in @value{GDBN}.
20141 @value{GDBN} enables developers to spawn and debug tasks running on networked
20142 VxWorks targets from a Unix host. Already-running tasks spawned from
20143 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
20144 both the Unix host and on the VxWorks target. The program
20145 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
20146 installed with the name @code{vxgdb}, to distinguish it from a
20147 @value{GDBN} for debugging programs on the host itself.)
20150 @item VxWorks-timeout @var{args}
20151 @kindex vxworks-timeout
20152 All VxWorks-based targets now support the option @code{vxworks-timeout}.
20153 This option is set by the user, and @var{args} represents the number of
20154 seconds @value{GDBN} waits for responses to rpc's. You might use this if
20155 your VxWorks target is a slow software simulator or is on the far side
20156 of a thin network line.
20159 The following information on connecting to VxWorks was current when
20160 this manual was produced; newer releases of VxWorks may use revised
20163 @findex INCLUDE_RDB
20164 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
20165 to include the remote debugging interface routines in the VxWorks
20166 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
20167 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
20168 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
20169 source debugging task @code{tRdbTask} when VxWorks is booted. For more
20170 information on configuring and remaking VxWorks, see the manufacturer's
20172 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
20174 Once you have included @file{rdb.a} in your VxWorks system image and set
20175 your Unix execution search path to find @value{GDBN}, you are ready to
20176 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
20177 @code{vxgdb}, depending on your installation).
20179 @value{GDBN} comes up showing the prompt:
20186 * VxWorks Connection:: Connecting to VxWorks
20187 * VxWorks Download:: VxWorks download
20188 * VxWorks Attach:: Running tasks
20191 @node VxWorks Connection
20192 @subsubsection Connecting to VxWorks
20194 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
20195 network. To connect to a target whose host name is ``@code{tt}'', type:
20198 (vxgdb) target vxworks tt
20202 @value{GDBN} displays messages like these:
20205 Attaching remote machine across net...
20210 @value{GDBN} then attempts to read the symbol tables of any object modules
20211 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
20212 these files by searching the directories listed in the command search
20213 path (@pxref{Environment, ,Your Program's Environment}); if it fails
20214 to find an object file, it displays a message such as:
20217 prog.o: No such file or directory.
20220 When this happens, add the appropriate directory to the search path with
20221 the @value{GDBN} command @code{path}, and execute the @code{target}
20224 @node VxWorks Download
20225 @subsubsection VxWorks Download
20227 @cindex download to VxWorks
20228 If you have connected to the VxWorks target and you want to debug an
20229 object that has not yet been loaded, you can use the @value{GDBN}
20230 @code{load} command to download a file from Unix to VxWorks
20231 incrementally. The object file given as an argument to the @code{load}
20232 command is actually opened twice: first by the VxWorks target in order
20233 to download the code, then by @value{GDBN} in order to read the symbol
20234 table. This can lead to problems if the current working directories on
20235 the two systems differ. If both systems have NFS mounted the same
20236 filesystems, you can avoid these problems by using absolute paths.
20237 Otherwise, it is simplest to set the working directory on both systems
20238 to the directory in which the object file resides, and then to reference
20239 the file by its name, without any path. For instance, a program
20240 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
20241 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
20242 program, type this on VxWorks:
20245 -> cd "@var{vxpath}/vw/demo/rdb"
20249 Then, in @value{GDBN}, type:
20252 (vxgdb) cd @var{hostpath}/vw/demo/rdb
20253 (vxgdb) load prog.o
20256 @value{GDBN} displays a response similar to this:
20259 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
20262 You can also use the @code{load} command to reload an object module
20263 after editing and recompiling the corresponding source file. Note that
20264 this makes @value{GDBN} delete all currently-defined breakpoints,
20265 auto-displays, and convenience variables, and to clear the value
20266 history. (This is necessary in order to preserve the integrity of
20267 debugger's data structures that reference the target system's symbol
20270 @node VxWorks Attach
20271 @subsubsection Running Tasks
20273 @cindex running VxWorks tasks
20274 You can also attach to an existing task using the @code{attach} command as
20278 (vxgdb) attach @var{task}
20282 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
20283 or suspended when you attach to it. Running tasks are suspended at
20284 the time of attachment.
20286 @node Embedded Processors
20287 @section Embedded Processors
20289 This section goes into details specific to particular embedded
20292 @cindex send command to simulator
20293 Whenever a specific embedded processor has a simulator, @value{GDBN}
20294 allows to send an arbitrary command to the simulator.
20297 @item sim @var{command}
20298 @kindex sim@r{, a command}
20299 Send an arbitrary @var{command} string to the simulator. Consult the
20300 documentation for the specific simulator in use for information about
20301 acceptable commands.
20307 * M32R/D:: Renesas M32R/D
20308 * M68K:: Motorola M68K
20309 * MicroBlaze:: Xilinx MicroBlaze
20310 * MIPS Embedded:: MIPS Embedded
20311 * PowerPC Embedded:: PowerPC Embedded
20312 * PA:: HP PA Embedded
20313 * Sparclet:: Tsqware Sparclet
20314 * Sparclite:: Fujitsu Sparclite
20315 * Z8000:: Zilog Z8000
20318 * Super-H:: Renesas Super-H
20327 @item target rdi @var{dev}
20328 ARM Angel monitor, via RDI library interface to ADP protocol. You may
20329 use this target to communicate with both boards running the Angel
20330 monitor, or with the EmbeddedICE JTAG debug device.
20333 @item target rdp @var{dev}
20338 @value{GDBN} provides the following ARM-specific commands:
20341 @item set arm disassembler
20343 This commands selects from a list of disassembly styles. The
20344 @code{"std"} style is the standard style.
20346 @item show arm disassembler
20348 Show the current disassembly style.
20350 @item set arm apcs32
20351 @cindex ARM 32-bit mode
20352 This command toggles ARM operation mode between 32-bit and 26-bit.
20354 @item show arm apcs32
20355 Display the current usage of the ARM 32-bit mode.
20357 @item set arm fpu @var{fputype}
20358 This command sets the ARM floating-point unit (FPU) type. The
20359 argument @var{fputype} can be one of these:
20363 Determine the FPU type by querying the OS ABI.
20365 Software FPU, with mixed-endian doubles on little-endian ARM
20368 GCC-compiled FPA co-processor.
20370 Software FPU with pure-endian doubles.
20376 Show the current type of the FPU.
20379 This command forces @value{GDBN} to use the specified ABI.
20382 Show the currently used ABI.
20384 @item set arm fallback-mode (arm|thumb|auto)
20385 @value{GDBN} uses the symbol table, when available, to determine
20386 whether instructions are ARM or Thumb. This command controls
20387 @value{GDBN}'s default behavior when the symbol table is not
20388 available. The default is @samp{auto}, which causes @value{GDBN} to
20389 use the current execution mode (from the @code{T} bit in the @code{CPSR}
20392 @item show arm fallback-mode
20393 Show the current fallback instruction mode.
20395 @item set arm force-mode (arm|thumb|auto)
20396 This command overrides use of the symbol table to determine whether
20397 instructions are ARM or Thumb. The default is @samp{auto}, which
20398 causes @value{GDBN} to use the symbol table and then the setting
20399 of @samp{set arm fallback-mode}.
20401 @item show arm force-mode
20402 Show the current forced instruction mode.
20404 @item set debug arm
20405 Toggle whether to display ARM-specific debugging messages from the ARM
20406 target support subsystem.
20408 @item show debug arm
20409 Show whether ARM-specific debugging messages are enabled.
20412 The following commands are available when an ARM target is debugged
20413 using the RDI interface:
20416 @item rdilogfile @r{[}@var{file}@r{]}
20418 @cindex ADP (Angel Debugger Protocol) logging
20419 Set the filename for the ADP (Angel Debugger Protocol) packet log.
20420 With an argument, sets the log file to the specified @var{file}. With
20421 no argument, show the current log file name. The default log file is
20424 @item rdilogenable @r{[}@var{arg}@r{]}
20425 @kindex rdilogenable
20426 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
20427 enables logging, with an argument 0 or @code{"no"} disables it. With
20428 no arguments displays the current setting. When logging is enabled,
20429 ADP packets exchanged between @value{GDBN} and the RDI target device
20430 are logged to a file.
20432 @item set rdiromatzero
20433 @kindex set rdiromatzero
20434 @cindex ROM at zero address, RDI
20435 Tell @value{GDBN} whether the target has ROM at address 0. If on,
20436 vector catching is disabled, so that zero address can be used. If off
20437 (the default), vector catching is enabled. For this command to take
20438 effect, it needs to be invoked prior to the @code{target rdi} command.
20440 @item show rdiromatzero
20441 @kindex show rdiromatzero
20442 Show the current setting of ROM at zero address.
20444 @item set rdiheartbeat
20445 @kindex set rdiheartbeat
20446 @cindex RDI heartbeat
20447 Enable or disable RDI heartbeat packets. It is not recommended to
20448 turn on this option, since it confuses ARM and EPI JTAG interface, as
20449 well as the Angel monitor.
20451 @item show rdiheartbeat
20452 @kindex show rdiheartbeat
20453 Show the setting of RDI heartbeat packets.
20457 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20458 The @value{GDBN} ARM simulator accepts the following optional arguments.
20461 @item --swi-support=@var{type}
20462 Tell the simulator which SWI interfaces to support.
20463 @var{type} may be a comma separated list of the following values.
20464 The default value is @code{all}.
20477 @subsection Renesas M32R/D and M32R/SDI
20480 @kindex target m32r
20481 @item target m32r @var{dev}
20482 Renesas M32R/D ROM monitor.
20484 @kindex target m32rsdi
20485 @item target m32rsdi @var{dev}
20486 Renesas M32R SDI server, connected via parallel port to the board.
20489 The following @value{GDBN} commands are specific to the M32R monitor:
20492 @item set download-path @var{path}
20493 @kindex set download-path
20494 @cindex find downloadable @sc{srec} files (M32R)
20495 Set the default path for finding downloadable @sc{srec} files.
20497 @item show download-path
20498 @kindex show download-path
20499 Show the default path for downloadable @sc{srec} files.
20501 @item set board-address @var{addr}
20502 @kindex set board-address
20503 @cindex M32-EVA target board address
20504 Set the IP address for the M32R-EVA target board.
20506 @item show board-address
20507 @kindex show board-address
20508 Show the current IP address of the target board.
20510 @item set server-address @var{addr}
20511 @kindex set server-address
20512 @cindex download server address (M32R)
20513 Set the IP address for the download server, which is the @value{GDBN}'s
20516 @item show server-address
20517 @kindex show server-address
20518 Display the IP address of the download server.
20520 @item upload @r{[}@var{file}@r{]}
20521 @kindex upload@r{, M32R}
20522 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
20523 upload capability. If no @var{file} argument is given, the current
20524 executable file is uploaded.
20526 @item tload @r{[}@var{file}@r{]}
20527 @kindex tload@r{, M32R}
20528 Test the @code{upload} command.
20531 The following commands are available for M32R/SDI:
20536 @cindex reset SDI connection, M32R
20537 This command resets the SDI connection.
20541 This command shows the SDI connection status.
20544 @kindex debug_chaos
20545 @cindex M32R/Chaos debugging
20546 Instructs the remote that M32R/Chaos debugging is to be used.
20548 @item use_debug_dma
20549 @kindex use_debug_dma
20550 Instructs the remote to use the DEBUG_DMA method of accessing memory.
20553 @kindex use_mon_code
20554 Instructs the remote to use the MON_CODE method of accessing memory.
20557 @kindex use_ib_break
20558 Instructs the remote to set breakpoints by IB break.
20560 @item use_dbt_break
20561 @kindex use_dbt_break
20562 Instructs the remote to set breakpoints by DBT.
20568 The Motorola m68k configuration includes ColdFire support, and a
20569 target command for the following ROM monitor.
20573 @kindex target dbug
20574 @item target dbug @var{dev}
20575 dBUG ROM monitor for Motorola ColdFire.
20580 @subsection MicroBlaze
20581 @cindex Xilinx MicroBlaze
20582 @cindex XMD, Xilinx Microprocessor Debugger
20584 The MicroBlaze is a soft-core processor supported on various Xilinx
20585 FPGAs, such as Spartan or Virtex series. Boards with these processors
20586 usually have JTAG ports which connect to a host system running the Xilinx
20587 Embedded Development Kit (EDK) or Software Development Kit (SDK).
20588 This host system is used to download the configuration bitstream to
20589 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
20590 communicates with the target board using the JTAG interface and
20591 presents a @code{gdbserver} interface to the board. By default
20592 @code{xmd} uses port @code{1234}. (While it is possible to change
20593 this default port, it requires the use of undocumented @code{xmd}
20594 commands. Contact Xilinx support if you need to do this.)
20596 Use these GDB commands to connect to the MicroBlaze target processor.
20599 @item target remote :1234
20600 Use this command to connect to the target if you are running @value{GDBN}
20601 on the same system as @code{xmd}.
20603 @item target remote @var{xmd-host}:1234
20604 Use this command to connect to the target if it is connected to @code{xmd}
20605 running on a different system named @var{xmd-host}.
20608 Use this command to download a program to the MicroBlaze target.
20610 @item set debug microblaze @var{n}
20611 Enable MicroBlaze-specific debugging messages if non-zero.
20613 @item show debug microblaze @var{n}
20614 Show MicroBlaze-specific debugging level.
20617 @node MIPS Embedded
20618 @subsection @acronym{MIPS} Embedded
20620 @cindex @acronym{MIPS} boards
20621 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
20622 @acronym{MIPS} board attached to a serial line. This is available when
20623 you configure @value{GDBN} with @samp{--target=mips-elf}.
20626 Use these @value{GDBN} commands to specify the connection to your target board:
20629 @item target mips @var{port}
20630 @kindex target mips @var{port}
20631 To run a program on the board, start up @code{@value{GDBP}} with the
20632 name of your program as the argument. To connect to the board, use the
20633 command @samp{target mips @var{port}}, where @var{port} is the name of
20634 the serial port connected to the board. If the program has not already
20635 been downloaded to the board, you may use the @code{load} command to
20636 download it. You can then use all the usual @value{GDBN} commands.
20638 For example, this sequence connects to the target board through a serial
20639 port, and loads and runs a program called @var{prog} through the
20643 host$ @value{GDBP} @var{prog}
20644 @value{GDBN} is free software and @dots{}
20645 (@value{GDBP}) target mips /dev/ttyb
20646 (@value{GDBP}) load @var{prog}
20650 @item target mips @var{hostname}:@var{portnumber}
20651 On some @value{GDBN} host configurations, you can specify a TCP
20652 connection (for instance, to a serial line managed by a terminal
20653 concentrator) instead of a serial port, using the syntax
20654 @samp{@var{hostname}:@var{portnumber}}.
20656 @item target pmon @var{port}
20657 @kindex target pmon @var{port}
20660 @item target ddb @var{port}
20661 @kindex target ddb @var{port}
20662 NEC's DDB variant of PMON for Vr4300.
20664 @item target lsi @var{port}
20665 @kindex target lsi @var{port}
20666 LSI variant of PMON.
20668 @kindex target r3900
20669 @item target r3900 @var{dev}
20670 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
20672 @kindex target array
20673 @item target array @var{dev}
20674 Array Tech LSI33K RAID controller board.
20680 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
20683 @item set mipsfpu double
20684 @itemx set mipsfpu single
20685 @itemx set mipsfpu none
20686 @itemx set mipsfpu auto
20687 @itemx show mipsfpu
20688 @kindex set mipsfpu
20689 @kindex show mipsfpu
20690 @cindex @acronym{MIPS} remote floating point
20691 @cindex floating point, @acronym{MIPS} remote
20692 If your target board does not support the @acronym{MIPS} floating point
20693 coprocessor, you should use the command @samp{set mipsfpu none} (if you
20694 need this, you may wish to put the command in your @value{GDBN} init
20695 file). This tells @value{GDBN} how to find the return value of
20696 functions which return floating point values. It also allows
20697 @value{GDBN} to avoid saving the floating point registers when calling
20698 functions on the board. If you are using a floating point coprocessor
20699 with only single precision floating point support, as on the @sc{r4650}
20700 processor, use the command @samp{set mipsfpu single}. The default
20701 double precision floating point coprocessor may be selected using
20702 @samp{set mipsfpu double}.
20704 In previous versions the only choices were double precision or no
20705 floating point, so @samp{set mipsfpu on} will select double precision
20706 and @samp{set mipsfpu off} will select no floating point.
20708 As usual, you can inquire about the @code{mipsfpu} variable with
20709 @samp{show mipsfpu}.
20711 @item set timeout @var{seconds}
20712 @itemx set retransmit-timeout @var{seconds}
20713 @itemx show timeout
20714 @itemx show retransmit-timeout
20715 @cindex @code{timeout}, @acronym{MIPS} protocol
20716 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
20717 @kindex set timeout
20718 @kindex show timeout
20719 @kindex set retransmit-timeout
20720 @kindex show retransmit-timeout
20721 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
20722 remote protocol, with the @code{set timeout @var{seconds}} command. The
20723 default is 5 seconds. Similarly, you can control the timeout used while
20724 waiting for an acknowledgment of a packet with the @code{set
20725 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
20726 You can inspect both values with @code{show timeout} and @code{show
20727 retransmit-timeout}. (These commands are @emph{only} available when
20728 @value{GDBN} is configured for @samp{--target=mips-elf}.)
20730 The timeout set by @code{set timeout} does not apply when @value{GDBN}
20731 is waiting for your program to stop. In that case, @value{GDBN} waits
20732 forever because it has no way of knowing how long the program is going
20733 to run before stopping.
20735 @item set syn-garbage-limit @var{num}
20736 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
20737 @cindex synchronize with remote @acronym{MIPS} target
20738 Limit the maximum number of characters @value{GDBN} should ignore when
20739 it tries to synchronize with the remote target. The default is 10
20740 characters. Setting the limit to -1 means there's no limit.
20742 @item show syn-garbage-limit
20743 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
20744 Show the current limit on the number of characters to ignore when
20745 trying to synchronize with the remote system.
20747 @item set monitor-prompt @var{prompt}
20748 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
20749 @cindex remote monitor prompt
20750 Tell @value{GDBN} to expect the specified @var{prompt} string from the
20751 remote monitor. The default depends on the target:
20761 @item show monitor-prompt
20762 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
20763 Show the current strings @value{GDBN} expects as the prompt from the
20766 @item set monitor-warnings
20767 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
20768 Enable or disable monitor warnings about hardware breakpoints. This
20769 has effect only for the @code{lsi} target. When on, @value{GDBN} will
20770 display warning messages whose codes are returned by the @code{lsi}
20771 PMON monitor for breakpoint commands.
20773 @item show monitor-warnings
20774 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
20775 Show the current setting of printing monitor warnings.
20777 @item pmon @var{command}
20778 @kindex pmon@r{, @acronym{MIPS} remote}
20779 @cindex send PMON command
20780 This command allows sending an arbitrary @var{command} string to the
20781 monitor. The monitor must be in debug mode for this to work.
20784 @node PowerPC Embedded
20785 @subsection PowerPC Embedded
20787 @cindex DVC register
20788 @value{GDBN} supports using the DVC (Data Value Compare) register to
20789 implement in hardware simple hardware watchpoint conditions of the form:
20792 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
20793 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
20796 The DVC register will be automatically used when @value{GDBN} detects
20797 such pattern in a condition expression, and the created watchpoint uses one
20798 debug register (either the @code{exact-watchpoints} option is on and the
20799 variable is scalar, or the variable has a length of one byte). This feature
20800 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
20803 When running on PowerPC embedded processors, @value{GDBN} automatically uses
20804 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
20805 in which case watchpoints using only one debug register are created when
20806 watching variables of scalar types.
20808 You can create an artificial array to watch an arbitrary memory
20809 region using one of the following commands (@pxref{Expressions}):
20812 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
20813 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
20816 PowerPC embedded processors support masked watchpoints. See the discussion
20817 about the @code{mask} argument in @ref{Set Watchpoints}.
20819 @cindex ranged breakpoint
20820 PowerPC embedded processors support hardware accelerated
20821 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
20822 the inferior whenever it executes an instruction at any address within
20823 the range it specifies. To set a ranged breakpoint in @value{GDBN},
20824 use the @code{break-range} command.
20826 @value{GDBN} provides the following PowerPC-specific commands:
20829 @kindex break-range
20830 @item break-range @var{start-location}, @var{end-location}
20831 Set a breakpoint for an address range.
20832 @var{start-location} and @var{end-location} can specify a function name,
20833 a line number, an offset of lines from the current line or from the start
20834 location, or an address of an instruction (see @ref{Specify Location},
20835 for a list of all the possible ways to specify a @var{location}.)
20836 The breakpoint will stop execution of the inferior whenever it
20837 executes an instruction at any address within the specified range,
20838 (including @var{start-location} and @var{end-location}.)
20840 @kindex set powerpc
20841 @item set powerpc soft-float
20842 @itemx show powerpc soft-float
20843 Force @value{GDBN} to use (or not use) a software floating point calling
20844 convention. By default, @value{GDBN} selects the calling convention based
20845 on the selected architecture and the provided executable file.
20847 @item set powerpc vector-abi
20848 @itemx show powerpc vector-abi
20849 Force @value{GDBN} to use the specified calling convention for vector
20850 arguments and return values. The valid options are @samp{auto};
20851 @samp{generic}, to avoid vector registers even if they are present;
20852 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
20853 registers. By default, @value{GDBN} selects the calling convention
20854 based on the selected architecture and the provided executable file.
20856 @item set powerpc exact-watchpoints
20857 @itemx show powerpc exact-watchpoints
20858 Allow @value{GDBN} to use only one debug register when watching a variable
20859 of scalar type, thus assuming that the variable is accessed through the
20860 address of its first byte.
20862 @kindex target dink32
20863 @item target dink32 @var{dev}
20864 DINK32 ROM monitor.
20866 @kindex target ppcbug
20867 @item target ppcbug @var{dev}
20868 @kindex target ppcbug1
20869 @item target ppcbug1 @var{dev}
20870 PPCBUG ROM monitor for PowerPC.
20873 @item target sds @var{dev}
20874 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
20877 @cindex SDS protocol
20878 The following commands specific to the SDS protocol are supported
20882 @item set sdstimeout @var{nsec}
20883 @kindex set sdstimeout
20884 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
20885 default is 2 seconds.
20887 @item show sdstimeout
20888 @kindex show sdstimeout
20889 Show the current value of the SDS timeout.
20891 @item sds @var{command}
20892 @kindex sds@r{, a command}
20893 Send the specified @var{command} string to the SDS monitor.
20898 @subsection HP PA Embedded
20902 @kindex target op50n
20903 @item target op50n @var{dev}
20904 OP50N monitor, running on an OKI HPPA board.
20906 @kindex target w89k
20907 @item target w89k @var{dev}
20908 W89K monitor, running on a Winbond HPPA board.
20913 @subsection Tsqware Sparclet
20917 @value{GDBN} enables developers to debug tasks running on
20918 Sparclet targets from a Unix host.
20919 @value{GDBN} uses code that runs on
20920 both the Unix host and on the Sparclet target. The program
20921 @code{@value{GDBP}} is installed and executed on the Unix host.
20924 @item remotetimeout @var{args}
20925 @kindex remotetimeout
20926 @value{GDBN} supports the option @code{remotetimeout}.
20927 This option is set by the user, and @var{args} represents the number of
20928 seconds @value{GDBN} waits for responses.
20931 @cindex compiling, on Sparclet
20932 When compiling for debugging, include the options @samp{-g} to get debug
20933 information and @samp{-Ttext} to relocate the program to where you wish to
20934 load it on the target. You may also want to add the options @samp{-n} or
20935 @samp{-N} in order to reduce the size of the sections. Example:
20938 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
20941 You can use @code{objdump} to verify that the addresses are what you intended:
20944 sparclet-aout-objdump --headers --syms prog
20947 @cindex running, on Sparclet
20949 your Unix execution search path to find @value{GDBN}, you are ready to
20950 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
20951 (or @code{sparclet-aout-gdb}, depending on your installation).
20953 @value{GDBN} comes up showing the prompt:
20960 * Sparclet File:: Setting the file to debug
20961 * Sparclet Connection:: Connecting to Sparclet
20962 * Sparclet Download:: Sparclet download
20963 * Sparclet Execution:: Running and debugging
20966 @node Sparclet File
20967 @subsubsection Setting File to Debug
20969 The @value{GDBN} command @code{file} lets you choose with program to debug.
20972 (gdbslet) file prog
20976 @value{GDBN} then attempts to read the symbol table of @file{prog}.
20977 @value{GDBN} locates
20978 the file by searching the directories listed in the command search
20980 If the file was compiled with debug information (option @samp{-g}), source
20981 files will be searched as well.
20982 @value{GDBN} locates
20983 the source files by searching the directories listed in the directory search
20984 path (@pxref{Environment, ,Your Program's Environment}).
20986 to find a file, it displays a message such as:
20989 prog: No such file or directory.
20992 When this happens, add the appropriate directories to the search paths with
20993 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
20994 @code{target} command again.
20996 @node Sparclet Connection
20997 @subsubsection Connecting to Sparclet
20999 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
21000 To connect to a target on serial port ``@code{ttya}'', type:
21003 (gdbslet) target sparclet /dev/ttya
21004 Remote target sparclet connected to /dev/ttya
21005 main () at ../prog.c:3
21009 @value{GDBN} displays messages like these:
21015 @node Sparclet Download
21016 @subsubsection Sparclet Download
21018 @cindex download to Sparclet
21019 Once connected to the Sparclet target,
21020 you can use the @value{GDBN}
21021 @code{load} command to download the file from the host to the target.
21022 The file name and load offset should be given as arguments to the @code{load}
21024 Since the file format is aout, the program must be loaded to the starting
21025 address. You can use @code{objdump} to find out what this value is. The load
21026 offset is an offset which is added to the VMA (virtual memory address)
21027 of each of the file's sections.
21028 For instance, if the program
21029 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
21030 and bss at 0x12010170, in @value{GDBN}, type:
21033 (gdbslet) load prog 0x12010000
21034 Loading section .text, size 0xdb0 vma 0x12010000
21037 If the code is loaded at a different address then what the program was linked
21038 to, you may need to use the @code{section} and @code{add-symbol-file} commands
21039 to tell @value{GDBN} where to map the symbol table.
21041 @node Sparclet Execution
21042 @subsubsection Running and Debugging
21044 @cindex running and debugging Sparclet programs
21045 You can now begin debugging the task using @value{GDBN}'s execution control
21046 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
21047 manual for the list of commands.
21051 Breakpoint 1 at 0x12010000: file prog.c, line 3.
21053 Starting program: prog
21054 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
21055 3 char *symarg = 0;
21057 4 char *execarg = "hello!";
21062 @subsection Fujitsu Sparclite
21066 @kindex target sparclite
21067 @item target sparclite @var{dev}
21068 Fujitsu sparclite boards, used only for the purpose of loading.
21069 You must use an additional command to debug the program.
21070 For example: target remote @var{dev} using @value{GDBN} standard
21076 @subsection Zilog Z8000
21079 @cindex simulator, Z8000
21080 @cindex Zilog Z8000 simulator
21082 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
21085 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
21086 unsegmented variant of the Z8000 architecture) or the Z8001 (the
21087 segmented variant). The simulator recognizes which architecture is
21088 appropriate by inspecting the object code.
21091 @item target sim @var{args}
21093 @kindex target sim@r{, with Z8000}
21094 Debug programs on a simulated CPU. If the simulator supports setup
21095 options, specify them via @var{args}.
21099 After specifying this target, you can debug programs for the simulated
21100 CPU in the same style as programs for your host computer; use the
21101 @code{file} command to load a new program image, the @code{run} command
21102 to run your program, and so on.
21104 As well as making available all the usual machine registers
21105 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
21106 additional items of information as specially named registers:
21111 Counts clock-ticks in the simulator.
21114 Counts instructions run in the simulator.
21117 Execution time in 60ths of a second.
21121 You can refer to these values in @value{GDBN} expressions with the usual
21122 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
21123 conditional breakpoint that suspends only after at least 5000
21124 simulated clock ticks.
21127 @subsection Atmel AVR
21130 When configured for debugging the Atmel AVR, @value{GDBN} supports the
21131 following AVR-specific commands:
21134 @item info io_registers
21135 @kindex info io_registers@r{, AVR}
21136 @cindex I/O registers (Atmel AVR)
21137 This command displays information about the AVR I/O registers. For
21138 each register, @value{GDBN} prints its number and value.
21145 When configured for debugging CRIS, @value{GDBN} provides the
21146 following CRIS-specific commands:
21149 @item set cris-version @var{ver}
21150 @cindex CRIS version
21151 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
21152 The CRIS version affects register names and sizes. This command is useful in
21153 case autodetection of the CRIS version fails.
21155 @item show cris-version
21156 Show the current CRIS version.
21158 @item set cris-dwarf2-cfi
21159 @cindex DWARF-2 CFI and CRIS
21160 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
21161 Change to @samp{off} when using @code{gcc-cris} whose version is below
21164 @item show cris-dwarf2-cfi
21165 Show the current state of using DWARF-2 CFI.
21167 @item set cris-mode @var{mode}
21169 Set the current CRIS mode to @var{mode}. It should only be changed when
21170 debugging in guru mode, in which case it should be set to
21171 @samp{guru} (the default is @samp{normal}).
21173 @item show cris-mode
21174 Show the current CRIS mode.
21178 @subsection Renesas Super-H
21181 For the Renesas Super-H processor, @value{GDBN} provides these
21185 @item set sh calling-convention @var{convention}
21186 @kindex set sh calling-convention
21187 Set the calling-convention used when calling functions from @value{GDBN}.
21188 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
21189 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
21190 convention. If the DWARF-2 information of the called function specifies
21191 that the function follows the Renesas calling convention, the function
21192 is called using the Renesas calling convention. If the calling convention
21193 is set to @samp{renesas}, the Renesas calling convention is always used,
21194 regardless of the DWARF-2 information. This can be used to override the
21195 default of @samp{gcc} if debug information is missing, or the compiler
21196 does not emit the DWARF-2 calling convention entry for a function.
21198 @item show sh calling-convention
21199 @kindex show sh calling-convention
21200 Show the current calling convention setting.
21205 @node Architectures
21206 @section Architectures
21208 This section describes characteristics of architectures that affect
21209 all uses of @value{GDBN} with the architecture, both native and cross.
21216 * HPPA:: HP PA architecture
21217 * SPU:: Cell Broadband Engine SPU architecture
21223 @subsection AArch64
21224 @cindex AArch64 support
21226 When @value{GDBN} is debugging the AArch64 architecture, it provides the
21227 following special commands:
21230 @item set debug aarch64
21231 @kindex set debug aarch64
21232 This command determines whether AArch64 architecture-specific debugging
21233 messages are to be displayed.
21235 @item show debug aarch64
21236 Show whether AArch64 debugging messages are displayed.
21241 @subsection x86 Architecture-specific Issues
21244 @item set struct-convention @var{mode}
21245 @kindex set struct-convention
21246 @cindex struct return convention
21247 @cindex struct/union returned in registers
21248 Set the convention used by the inferior to return @code{struct}s and
21249 @code{union}s from functions to @var{mode}. Possible values of
21250 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
21251 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
21252 are returned on the stack, while @code{"reg"} means that a
21253 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
21254 be returned in a register.
21256 @item show struct-convention
21257 @kindex show struct-convention
21258 Show the current setting of the convention to return @code{struct}s
21265 See the following section.
21268 @subsection @acronym{MIPS}
21270 @cindex stack on Alpha
21271 @cindex stack on @acronym{MIPS}
21272 @cindex Alpha stack
21273 @cindex @acronym{MIPS} stack
21274 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
21275 sometimes requires @value{GDBN} to search backward in the object code to
21276 find the beginning of a function.
21278 @cindex response time, @acronym{MIPS} debugging
21279 To improve response time (especially for embedded applications, where
21280 @value{GDBN} may be restricted to a slow serial line for this search)
21281 you may want to limit the size of this search, using one of these
21285 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
21286 @item set heuristic-fence-post @var{limit}
21287 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
21288 search for the beginning of a function. A value of @var{0} (the
21289 default) means there is no limit. However, except for @var{0}, the
21290 larger the limit the more bytes @code{heuristic-fence-post} must search
21291 and therefore the longer it takes to run. You should only need to use
21292 this command when debugging a stripped executable.
21294 @item show heuristic-fence-post
21295 Display the current limit.
21299 These commands are available @emph{only} when @value{GDBN} is configured
21300 for debugging programs on Alpha or @acronym{MIPS} processors.
21302 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
21306 @item set mips abi @var{arg}
21307 @kindex set mips abi
21308 @cindex set ABI for @acronym{MIPS}
21309 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
21310 values of @var{arg} are:
21314 The default ABI associated with the current binary (this is the
21324 @item show mips abi
21325 @kindex show mips abi
21326 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
21328 @item set mips compression @var{arg}
21329 @kindex set mips compression
21330 @cindex code compression, @acronym{MIPS}
21331 Tell @value{GDBN} which @acronym{MIPS} compressed
21332 @acronym{ISA, Instruction Set Architecture} encoding is used by the
21333 inferior. @value{GDBN} uses this for code disassembly and other
21334 internal interpretation purposes. This setting is only referred to
21335 when no executable has been associated with the debugging session or
21336 the executable does not provide information about the encoding it uses.
21337 Otherwise this setting is automatically updated from information
21338 provided by the executable.
21340 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
21341 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
21342 executables containing @acronym{MIPS16} code frequently are not
21343 identified as such.
21345 This setting is ``sticky''; that is, it retains its value across
21346 debugging sessions until reset either explicitly with this command or
21347 implicitly from an executable.
21349 The compiler and/or assembler typically add symbol table annotations to
21350 identify functions compiled for the @acronym{MIPS16} or
21351 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
21352 are present, @value{GDBN} uses them in preference to the global
21353 compressed @acronym{ISA} encoding setting.
21355 @item show mips compression
21356 @kindex show mips compression
21357 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
21358 @value{GDBN} to debug the inferior.
21361 @itemx show mipsfpu
21362 @xref{MIPS Embedded, set mipsfpu}.
21364 @item set mips mask-address @var{arg}
21365 @kindex set mips mask-address
21366 @cindex @acronym{MIPS} addresses, masking
21367 This command determines whether the most-significant 32 bits of 64-bit
21368 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
21369 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
21370 setting, which lets @value{GDBN} determine the correct value.
21372 @item show mips mask-address
21373 @kindex show mips mask-address
21374 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
21377 @item set remote-mips64-transfers-32bit-regs
21378 @kindex set remote-mips64-transfers-32bit-regs
21379 This command controls compatibility with 64-bit @acronym{MIPS} targets that
21380 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
21381 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
21382 and 64 bits for other registers, set this option to @samp{on}.
21384 @item show remote-mips64-transfers-32bit-regs
21385 @kindex show remote-mips64-transfers-32bit-regs
21386 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
21388 @item set debug mips
21389 @kindex set debug mips
21390 This command turns on and off debugging messages for the @acronym{MIPS}-specific
21391 target code in @value{GDBN}.
21393 @item show debug mips
21394 @kindex show debug mips
21395 Show the current setting of @acronym{MIPS} debugging messages.
21401 @cindex HPPA support
21403 When @value{GDBN} is debugging the HP PA architecture, it provides the
21404 following special commands:
21407 @item set debug hppa
21408 @kindex set debug hppa
21409 This command determines whether HPPA architecture-specific debugging
21410 messages are to be displayed.
21412 @item show debug hppa
21413 Show whether HPPA debugging messages are displayed.
21415 @item maint print unwind @var{address}
21416 @kindex maint print unwind@r{, HPPA}
21417 This command displays the contents of the unwind table entry at the
21418 given @var{address}.
21424 @subsection Cell Broadband Engine SPU architecture
21425 @cindex Cell Broadband Engine
21428 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
21429 it provides the following special commands:
21432 @item info spu event
21434 Display SPU event facility status. Shows current event mask
21435 and pending event status.
21437 @item info spu signal
21438 Display SPU signal notification facility status. Shows pending
21439 signal-control word and signal notification mode of both signal
21440 notification channels.
21442 @item info spu mailbox
21443 Display SPU mailbox facility status. Shows all pending entries,
21444 in order of processing, in each of the SPU Write Outbound,
21445 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
21448 Display MFC DMA status. Shows all pending commands in the MFC
21449 DMA queue. For each entry, opcode, tag, class IDs, effective
21450 and local store addresses and transfer size are shown.
21452 @item info spu proxydma
21453 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
21454 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
21455 and local store addresses and transfer size are shown.
21459 When @value{GDBN} is debugging a combined PowerPC/SPU application
21460 on the Cell Broadband Engine, it provides in addition the following
21464 @item set spu stop-on-load @var{arg}
21466 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
21467 will give control to the user when a new SPE thread enters its @code{main}
21468 function. The default is @code{off}.
21470 @item show spu stop-on-load
21472 Show whether to stop for new SPE threads.
21474 @item set spu auto-flush-cache @var{arg}
21475 Set whether to automatically flush the software-managed cache. When set to
21476 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
21477 cache to be flushed whenever SPE execution stops. This provides a consistent
21478 view of PowerPC memory that is accessed via the cache. If an application
21479 does not use the software-managed cache, this option has no effect.
21481 @item show spu auto-flush-cache
21482 Show whether to automatically flush the software-managed cache.
21487 @subsection PowerPC
21488 @cindex PowerPC architecture
21490 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
21491 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
21492 numbers stored in the floating point registers. These values must be stored
21493 in two consecutive registers, always starting at an even register like
21494 @code{f0} or @code{f2}.
21496 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
21497 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
21498 @code{f2} and @code{f3} for @code{$dl1} and so on.
21500 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
21501 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
21504 @subsection Nios II
21505 @cindex Nios II architecture
21507 When @value{GDBN} is debugging the Nios II architecture,
21508 it provides the following special commands:
21512 @item set debug nios2
21513 @kindex set debug nios2
21514 This command turns on and off debugging messages for the Nios II
21515 target code in @value{GDBN}.
21517 @item show debug nios2
21518 @kindex show debug nios2
21519 Show the current setting of Nios II debugging messages.
21522 @node Controlling GDB
21523 @chapter Controlling @value{GDBN}
21525 You can alter the way @value{GDBN} interacts with you by using the
21526 @code{set} command. For commands controlling how @value{GDBN} displays
21527 data, see @ref{Print Settings, ,Print Settings}. Other settings are
21532 * Editing:: Command editing
21533 * Command History:: Command history
21534 * Screen Size:: Screen size
21535 * Numbers:: Numbers
21536 * ABI:: Configuring the current ABI
21537 * Auto-loading:: Automatically loading associated files
21538 * Messages/Warnings:: Optional warnings and messages
21539 * Debugging Output:: Optional messages about internal happenings
21540 * Other Misc Settings:: Other Miscellaneous Settings
21548 @value{GDBN} indicates its readiness to read a command by printing a string
21549 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
21550 can change the prompt string with the @code{set prompt} command. For
21551 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
21552 the prompt in one of the @value{GDBN} sessions so that you can always tell
21553 which one you are talking to.
21555 @emph{Note:} @code{set prompt} does not add a space for you after the
21556 prompt you set. This allows you to set a prompt which ends in a space
21557 or a prompt that does not.
21561 @item set prompt @var{newprompt}
21562 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
21564 @kindex show prompt
21566 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
21569 Versions of @value{GDBN} that ship with Python scripting enabled have
21570 prompt extensions. The commands for interacting with these extensions
21574 @kindex set extended-prompt
21575 @item set extended-prompt @var{prompt}
21576 Set an extended prompt that allows for substitutions.
21577 @xref{gdb.prompt}, for a list of escape sequences that can be used for
21578 substitution. Any escape sequences specified as part of the prompt
21579 string are replaced with the corresponding strings each time the prompt
21585 set extended-prompt Current working directory: \w (gdb)
21588 Note that when an extended-prompt is set, it takes control of the
21589 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
21591 @kindex show extended-prompt
21592 @item show extended-prompt
21593 Prints the extended prompt. Any escape sequences specified as part of
21594 the prompt string with @code{set extended-prompt}, are replaced with the
21595 corresponding strings each time the prompt is displayed.
21599 @section Command Editing
21601 @cindex command line editing
21603 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
21604 @sc{gnu} library provides consistent behavior for programs which provide a
21605 command line interface to the user. Advantages are @sc{gnu} Emacs-style
21606 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
21607 substitution, and a storage and recall of command history across
21608 debugging sessions.
21610 You may control the behavior of command line editing in @value{GDBN} with the
21611 command @code{set}.
21614 @kindex set editing
21617 @itemx set editing on
21618 Enable command line editing (enabled by default).
21620 @item set editing off
21621 Disable command line editing.
21623 @kindex show editing
21625 Show whether command line editing is enabled.
21628 @ifset SYSTEM_READLINE
21629 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
21631 @ifclear SYSTEM_READLINE
21632 @xref{Command Line Editing},
21634 for more details about the Readline
21635 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
21636 encouraged to read that chapter.
21638 @node Command History
21639 @section Command History
21640 @cindex command history
21642 @value{GDBN} can keep track of the commands you type during your
21643 debugging sessions, so that you can be certain of precisely what
21644 happened. Use these commands to manage the @value{GDBN} command
21647 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
21648 package, to provide the history facility.
21649 @ifset SYSTEM_READLINE
21650 @xref{Using History Interactively, , , history, GNU History Library},
21652 @ifclear SYSTEM_READLINE
21653 @xref{Using History Interactively},
21655 for the detailed description of the History library.
21657 To issue a command to @value{GDBN} without affecting certain aspects of
21658 the state which is seen by users, prefix it with @samp{server }
21659 (@pxref{Server Prefix}). This
21660 means that this command will not affect the command history, nor will it
21661 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
21662 pressed on a line by itself.
21664 @cindex @code{server}, command prefix
21665 The server prefix does not affect the recording of values into the value
21666 history; to print a value without recording it into the value history,
21667 use the @code{output} command instead of the @code{print} command.
21669 Here is the description of @value{GDBN} commands related to command
21673 @cindex history substitution
21674 @cindex history file
21675 @kindex set history filename
21676 @cindex @env{GDBHISTFILE}, environment variable
21677 @item set history filename @var{fname}
21678 Set the name of the @value{GDBN} command history file to @var{fname}.
21679 This is the file where @value{GDBN} reads an initial command history
21680 list, and where it writes the command history from this session when it
21681 exits. You can access this list through history expansion or through
21682 the history command editing characters listed below. This file defaults
21683 to the value of the environment variable @code{GDBHISTFILE}, or to
21684 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
21687 @cindex save command history
21688 @kindex set history save
21689 @item set history save
21690 @itemx set history save on
21691 Record command history in a file, whose name may be specified with the
21692 @code{set history filename} command. By default, this option is disabled.
21694 @item set history save off
21695 Stop recording command history in a file.
21697 @cindex history size
21698 @kindex set history size
21699 @cindex @env{HISTSIZE}, environment variable
21700 @item set history size @var{size}
21701 @itemx set history size unlimited
21702 Set the number of commands which @value{GDBN} keeps in its history list.
21703 This defaults to the value of the environment variable
21704 @code{HISTSIZE}, or to 256 if this variable is not set. If @var{size}
21705 is @code{unlimited}, the number of commands @value{GDBN} keeps in the
21706 history list is unlimited.
21709 History expansion assigns special meaning to the character @kbd{!}.
21710 @ifset SYSTEM_READLINE
21711 @xref{Event Designators, , , history, GNU History Library},
21713 @ifclear SYSTEM_READLINE
21714 @xref{Event Designators},
21718 @cindex history expansion, turn on/off
21719 Since @kbd{!} is also the logical not operator in C, history expansion
21720 is off by default. If you decide to enable history expansion with the
21721 @code{set history expansion on} command, you may sometimes need to
21722 follow @kbd{!} (when it is used as logical not, in an expression) with
21723 a space or a tab to prevent it from being expanded. The readline
21724 history facilities do not attempt substitution on the strings
21725 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
21727 The commands to control history expansion are:
21730 @item set history expansion on
21731 @itemx set history expansion
21732 @kindex set history expansion
21733 Enable history expansion. History expansion is off by default.
21735 @item set history expansion off
21736 Disable history expansion.
21739 @kindex show history
21741 @itemx show history filename
21742 @itemx show history save
21743 @itemx show history size
21744 @itemx show history expansion
21745 These commands display the state of the @value{GDBN} history parameters.
21746 @code{show history} by itself displays all four states.
21751 @kindex show commands
21752 @cindex show last commands
21753 @cindex display command history
21754 @item show commands
21755 Display the last ten commands in the command history.
21757 @item show commands @var{n}
21758 Print ten commands centered on command number @var{n}.
21760 @item show commands +
21761 Print ten commands just after the commands last printed.
21765 @section Screen Size
21766 @cindex size of screen
21767 @cindex pauses in output
21769 Certain commands to @value{GDBN} may produce large amounts of
21770 information output to the screen. To help you read all of it,
21771 @value{GDBN} pauses and asks you for input at the end of each page of
21772 output. Type @key{RET} when you want to continue the output, or @kbd{q}
21773 to discard the remaining output. Also, the screen width setting
21774 determines when to wrap lines of output. Depending on what is being
21775 printed, @value{GDBN} tries to break the line at a readable place,
21776 rather than simply letting it overflow onto the following line.
21778 Normally @value{GDBN} knows the size of the screen from the terminal
21779 driver software. For example, on Unix @value{GDBN} uses the termcap data base
21780 together with the value of the @code{TERM} environment variable and the
21781 @code{stty rows} and @code{stty cols} settings. If this is not correct,
21782 you can override it with the @code{set height} and @code{set
21789 @kindex show height
21790 @item set height @var{lpp}
21791 @itemx set height unlimited
21793 @itemx set width @var{cpl}
21794 @itemx set width unlimited
21796 These @code{set} commands specify a screen height of @var{lpp} lines and
21797 a screen width of @var{cpl} characters. The associated @code{show}
21798 commands display the current settings.
21800 If you specify a height of either @code{unlimited} or zero lines,
21801 @value{GDBN} does not pause during output no matter how long the
21802 output is. This is useful if output is to a file or to an editor
21805 Likewise, you can specify @samp{set width unlimited} or @samp{set
21806 width 0} to prevent @value{GDBN} from wrapping its output.
21808 @item set pagination on
21809 @itemx set pagination off
21810 @kindex set pagination
21811 Turn the output pagination on or off; the default is on. Turning
21812 pagination off is the alternative to @code{set height unlimited}. Note that
21813 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
21814 Options, -batch}) also automatically disables pagination.
21816 @item show pagination
21817 @kindex show pagination
21818 Show the current pagination mode.
21823 @cindex number representation
21824 @cindex entering numbers
21826 You can always enter numbers in octal, decimal, or hexadecimal in
21827 @value{GDBN} by the usual conventions: octal numbers begin with
21828 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
21829 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
21830 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
21831 10; likewise, the default display for numbers---when no particular
21832 format is specified---is base 10. You can change the default base for
21833 both input and output with the commands described below.
21836 @kindex set input-radix
21837 @item set input-radix @var{base}
21838 Set the default base for numeric input. Supported choices
21839 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21840 specified either unambiguously or using the current input radix; for
21844 set input-radix 012
21845 set input-radix 10.
21846 set input-radix 0xa
21850 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
21851 leaves the input radix unchanged, no matter what it was, since
21852 @samp{10}, being without any leading or trailing signs of its base, is
21853 interpreted in the current radix. Thus, if the current radix is 16,
21854 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
21857 @kindex set output-radix
21858 @item set output-radix @var{base}
21859 Set the default base for numeric display. Supported choices
21860 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21861 specified either unambiguously or using the current input radix.
21863 @kindex show input-radix
21864 @item show input-radix
21865 Display the current default base for numeric input.
21867 @kindex show output-radix
21868 @item show output-radix
21869 Display the current default base for numeric display.
21871 @item set radix @r{[}@var{base}@r{]}
21875 These commands set and show the default base for both input and output
21876 of numbers. @code{set radix} sets the radix of input and output to
21877 the same base; without an argument, it resets the radix back to its
21878 default value of 10.
21883 @section Configuring the Current ABI
21885 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
21886 application automatically. However, sometimes you need to override its
21887 conclusions. Use these commands to manage @value{GDBN}'s view of the
21893 @cindex Newlib OS ABI and its influence on the longjmp handling
21895 One @value{GDBN} configuration can debug binaries for multiple operating
21896 system targets, either via remote debugging or native emulation.
21897 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
21898 but you can override its conclusion using the @code{set osabi} command.
21899 One example where this is useful is in debugging of binaries which use
21900 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
21901 not have the same identifying marks that the standard C library for your
21904 When @value{GDBN} is debugging the AArch64 architecture, it provides a
21905 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
21906 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
21907 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
21911 Show the OS ABI currently in use.
21914 With no argument, show the list of registered available OS ABI's.
21916 @item set osabi @var{abi}
21917 Set the current OS ABI to @var{abi}.
21920 @cindex float promotion
21922 Generally, the way that an argument of type @code{float} is passed to a
21923 function depends on whether the function is prototyped. For a prototyped
21924 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
21925 according to the architecture's convention for @code{float}. For unprototyped
21926 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
21927 @code{double} and then passed.
21929 Unfortunately, some forms of debug information do not reliably indicate whether
21930 a function is prototyped. If @value{GDBN} calls a function that is not marked
21931 as prototyped, it consults @kbd{set coerce-float-to-double}.
21934 @kindex set coerce-float-to-double
21935 @item set coerce-float-to-double
21936 @itemx set coerce-float-to-double on
21937 Arguments of type @code{float} will be promoted to @code{double} when passed
21938 to an unprototyped function. This is the default setting.
21940 @item set coerce-float-to-double off
21941 Arguments of type @code{float} will be passed directly to unprototyped
21944 @kindex show coerce-float-to-double
21945 @item show coerce-float-to-double
21946 Show the current setting of promoting @code{float} to @code{double}.
21950 @kindex show cp-abi
21951 @value{GDBN} needs to know the ABI used for your program's C@t{++}
21952 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
21953 used to build your application. @value{GDBN} only fully supports
21954 programs with a single C@t{++} ABI; if your program contains code using
21955 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
21956 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
21957 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
21958 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
21959 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
21960 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
21965 Show the C@t{++} ABI currently in use.
21968 With no argument, show the list of supported C@t{++} ABI's.
21970 @item set cp-abi @var{abi}
21971 @itemx set cp-abi auto
21972 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
21976 @section Automatically loading associated files
21977 @cindex auto-loading
21979 @value{GDBN} sometimes reads files with commands and settings automatically,
21980 without being explicitly told so by the user. We call this feature
21981 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
21982 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
21983 results or introduce security risks (e.g., if the file comes from untrusted
21986 Note that loading of these associated files (including the local @file{.gdbinit}
21987 file) requires accordingly configured @code{auto-load safe-path}
21988 (@pxref{Auto-loading safe path}).
21990 For these reasons, @value{GDBN} includes commands and options to let you
21991 control when to auto-load files and which files should be auto-loaded.
21994 @anchor{set auto-load off}
21995 @kindex set auto-load off
21996 @item set auto-load off
21997 Globally disable loading of all auto-loaded files.
21998 You may want to use this command with the @samp{-iex} option
21999 (@pxref{Option -init-eval-command}) such as:
22001 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
22004 Be aware that system init file (@pxref{System-wide configuration})
22005 and init files from your home directory (@pxref{Home Directory Init File})
22006 still get read (as they come from generally trusted directories).
22007 To prevent @value{GDBN} from auto-loading even those init files, use the
22008 @option{-nx} option (@pxref{Mode Options}), in addition to
22009 @code{set auto-load no}.
22011 @anchor{show auto-load}
22012 @kindex show auto-load
22013 @item show auto-load
22014 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
22018 (gdb) show auto-load
22019 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
22020 libthread-db: Auto-loading of inferior specific libthread_db is on.
22021 local-gdbinit: Auto-loading of .gdbinit script from current directory
22023 python-scripts: Auto-loading of Python scripts is on.
22024 safe-path: List of directories from which it is safe to auto-load files
22025 is $debugdir:$datadir/auto-load.
22026 scripts-directory: List of directories from which to load auto-loaded scripts
22027 is $debugdir:$datadir/auto-load.
22030 @anchor{info auto-load}
22031 @kindex info auto-load
22032 @item info auto-load
22033 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
22037 (gdb) info auto-load
22040 Yes /home/user/gdb/gdb-gdb.gdb
22041 libthread-db: No auto-loaded libthread-db.
22042 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
22046 Yes /home/user/gdb/gdb-gdb.py
22050 These are various kinds of files @value{GDBN} can automatically load:
22054 @xref{objfile-gdb.py file}, controlled by @ref{set auto-load python-scripts}.
22056 @xref{objfile-gdb.gdb file}, controlled by @ref{set auto-load gdb-scripts}.
22058 @xref{dotdebug_gdb_scripts section},
22059 controlled by @ref{set auto-load python-scripts}.
22061 @xref{Init File in the Current Directory},
22062 controlled by @ref{set auto-load local-gdbinit}.
22064 @xref{libthread_db.so.1 file}, controlled by @ref{set auto-load libthread-db}.
22067 These are @value{GDBN} control commands for the auto-loading:
22069 @multitable @columnfractions .5 .5
22070 @item @xref{set auto-load off}.
22071 @tab Disable auto-loading globally.
22072 @item @xref{show auto-load}.
22073 @tab Show setting of all kinds of files.
22074 @item @xref{info auto-load}.
22075 @tab Show state of all kinds of files.
22076 @item @xref{set auto-load gdb-scripts}.
22077 @tab Control for @value{GDBN} command scripts.
22078 @item @xref{show auto-load gdb-scripts}.
22079 @tab Show setting of @value{GDBN} command scripts.
22080 @item @xref{info auto-load gdb-scripts}.
22081 @tab Show state of @value{GDBN} command scripts.
22082 @item @xref{set auto-load python-scripts}.
22083 @tab Control for @value{GDBN} Python scripts.
22084 @item @xref{show auto-load python-scripts}.
22085 @tab Show setting of @value{GDBN} Python scripts.
22086 @item @xref{info auto-load python-scripts}.
22087 @tab Show state of @value{GDBN} Python scripts.
22088 @item @xref{set auto-load scripts-directory}.
22089 @tab Control for @value{GDBN} auto-loaded scripts location.
22090 @item @xref{show auto-load scripts-directory}.
22091 @tab Show @value{GDBN} auto-loaded scripts location.
22092 @item @xref{set auto-load local-gdbinit}.
22093 @tab Control for init file in the current directory.
22094 @item @xref{show auto-load local-gdbinit}.
22095 @tab Show setting of init file in the current directory.
22096 @item @xref{info auto-load local-gdbinit}.
22097 @tab Show state of init file in the current directory.
22098 @item @xref{set auto-load libthread-db}.
22099 @tab Control for thread debugging library.
22100 @item @xref{show auto-load libthread-db}.
22101 @tab Show setting of thread debugging library.
22102 @item @xref{info auto-load libthread-db}.
22103 @tab Show state of thread debugging library.
22104 @item @xref{set auto-load safe-path}.
22105 @tab Control directories trusted for automatic loading.
22106 @item @xref{show auto-load safe-path}.
22107 @tab Show directories trusted for automatic loading.
22108 @item @xref{add-auto-load-safe-path}.
22109 @tab Add directory trusted for automatic loading.
22113 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
22114 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
22115 * objfile-gdb.gdb file:: @samp{set/show/info auto-load gdb-script}
22116 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
22117 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
22118 @xref{Python Auto-loading}.
22121 @node Init File in the Current Directory
22122 @subsection Automatically loading init file in the current directory
22123 @cindex auto-loading init file in the current directory
22125 By default, @value{GDBN} reads and executes the canned sequences of commands
22126 from init file (if any) in the current working directory,
22127 see @ref{Init File in the Current Directory during Startup}.
22129 Note that loading of this local @file{.gdbinit} file also requires accordingly
22130 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22133 @anchor{set auto-load local-gdbinit}
22134 @kindex set auto-load local-gdbinit
22135 @item set auto-load local-gdbinit [on|off]
22136 Enable or disable the auto-loading of canned sequences of commands
22137 (@pxref{Sequences}) found in init file in the current directory.
22139 @anchor{show auto-load local-gdbinit}
22140 @kindex show auto-load local-gdbinit
22141 @item show auto-load local-gdbinit
22142 Show whether auto-loading of canned sequences of commands from init file in the
22143 current directory is enabled or disabled.
22145 @anchor{info auto-load local-gdbinit}
22146 @kindex info auto-load local-gdbinit
22147 @item info auto-load local-gdbinit
22148 Print whether canned sequences of commands from init file in the
22149 current directory have been auto-loaded.
22152 @node libthread_db.so.1 file
22153 @subsection Automatically loading thread debugging library
22154 @cindex auto-loading libthread_db.so.1
22156 This feature is currently present only on @sc{gnu}/Linux native hosts.
22158 @value{GDBN} reads in some cases thread debugging library from places specific
22159 to the inferior (@pxref{set libthread-db-search-path}).
22161 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
22162 without checking this @samp{set auto-load libthread-db} switch as system
22163 libraries have to be trusted in general. In all other cases of
22164 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
22165 auto-load libthread-db} is enabled before trying to open such thread debugging
22168 Note that loading of this debugging library also requires accordingly configured
22169 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22172 @anchor{set auto-load libthread-db}
22173 @kindex set auto-load libthread-db
22174 @item set auto-load libthread-db [on|off]
22175 Enable or disable the auto-loading of inferior specific thread debugging library.
22177 @anchor{show auto-load libthread-db}
22178 @kindex show auto-load libthread-db
22179 @item show auto-load libthread-db
22180 Show whether auto-loading of inferior specific thread debugging library is
22181 enabled or disabled.
22183 @anchor{info auto-load libthread-db}
22184 @kindex info auto-load libthread-db
22185 @item info auto-load libthread-db
22186 Print the list of all loaded inferior specific thread debugging libraries and
22187 for each such library print list of inferior @var{pid}s using it.
22190 @node objfile-gdb.gdb file
22191 @subsection The @file{@var{objfile}-gdb.gdb} file
22192 @cindex auto-loading @file{@var{objfile}-gdb.gdb}
22194 @value{GDBN} tries to load an @file{@var{objfile}-gdb.gdb} file containing
22195 canned sequences of commands (@pxref{Sequences}), as long as @samp{set
22196 auto-load gdb-scripts} is set to @samp{on}.
22198 Note that loading of this script file also requires accordingly configured
22199 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22201 For more background refer to the similar Python scripts auto-loading
22202 description (@pxref{objfile-gdb.py file}).
22205 @anchor{set auto-load gdb-scripts}
22206 @kindex set auto-load gdb-scripts
22207 @item set auto-load gdb-scripts [on|off]
22208 Enable or disable the auto-loading of canned sequences of commands scripts.
22210 @anchor{show auto-load gdb-scripts}
22211 @kindex show auto-load gdb-scripts
22212 @item show auto-load gdb-scripts
22213 Show whether auto-loading of canned sequences of commands scripts is enabled or
22216 @anchor{info auto-load gdb-scripts}
22217 @kindex info auto-load gdb-scripts
22218 @cindex print list of auto-loaded canned sequences of commands scripts
22219 @item info auto-load gdb-scripts [@var{regexp}]
22220 Print the list of all canned sequences of commands scripts that @value{GDBN}
22224 If @var{regexp} is supplied only canned sequences of commands scripts with
22225 matching names are printed.
22227 @node Auto-loading safe path
22228 @subsection Security restriction for auto-loading
22229 @cindex auto-loading safe-path
22231 As the files of inferior can come from untrusted source (such as submitted by
22232 an application user) @value{GDBN} does not always load any files automatically.
22233 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
22234 directories trusted for loading files not explicitly requested by user.
22235 Each directory can also be a shell wildcard pattern.
22237 If the path is not set properly you will see a warning and the file will not
22242 Reading symbols from /home/user/gdb/gdb...done.
22243 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
22244 declined by your `auto-load safe-path' set
22245 to "$debugdir:$datadir/auto-load".
22246 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
22247 declined by your `auto-load safe-path' set
22248 to "$debugdir:$datadir/auto-load".
22252 To instruct @value{GDBN} to go ahead and use the init files anyway,
22253 invoke @value{GDBN} like this:
22256 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
22259 The list of trusted directories is controlled by the following commands:
22262 @anchor{set auto-load safe-path}
22263 @kindex set auto-load safe-path
22264 @item set auto-load safe-path @r{[}@var{directories}@r{]}
22265 Set the list of directories (and their subdirectories) trusted for automatic
22266 loading and execution of scripts. You can also enter a specific trusted file.
22267 Each directory can also be a shell wildcard pattern; wildcards do not match
22268 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
22269 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
22270 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
22271 its default value as specified during @value{GDBN} compilation.
22273 The list of directories uses path separator (@samp{:} on GNU and Unix
22274 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
22275 to the @env{PATH} environment variable.
22277 @anchor{show auto-load safe-path}
22278 @kindex show auto-load safe-path
22279 @item show auto-load safe-path
22280 Show the list of directories trusted for automatic loading and execution of
22283 @anchor{add-auto-load-safe-path}
22284 @kindex add-auto-load-safe-path
22285 @item add-auto-load-safe-path
22286 Add an entry (or list of entries) the list of directories trusted for automatic
22287 loading and execution of scripts. Multiple entries may be delimited by the
22288 host platform path separator in use.
22291 This variable defaults to what @code{--with-auto-load-dir} has been configured
22292 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
22293 substitution applies the same as for @ref{set auto-load scripts-directory}.
22294 The default @code{set auto-load safe-path} value can be also overriden by
22295 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
22297 Setting this variable to @file{/} disables this security protection,
22298 corresponding @value{GDBN} configuration option is
22299 @option{--without-auto-load-safe-path}.
22300 This variable is supposed to be set to the system directories writable by the
22301 system superuser only. Users can add their source directories in init files in
22302 their home directories (@pxref{Home Directory Init File}). See also deprecated
22303 init file in the current directory
22304 (@pxref{Init File in the Current Directory during Startup}).
22306 To force @value{GDBN} to load the files it declined to load in the previous
22307 example, you could use one of the following ways:
22310 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
22311 Specify this trusted directory (or a file) as additional component of the list.
22312 You have to specify also any existing directories displayed by
22313 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
22315 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
22316 Specify this directory as in the previous case but just for a single
22317 @value{GDBN} session.
22319 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
22320 Disable auto-loading safety for a single @value{GDBN} session.
22321 This assumes all the files you debug during this @value{GDBN} session will come
22322 from trusted sources.
22324 @item @kbd{./configure --without-auto-load-safe-path}
22325 During compilation of @value{GDBN} you may disable any auto-loading safety.
22326 This assumes all the files you will ever debug with this @value{GDBN} come from
22330 On the other hand you can also explicitly forbid automatic files loading which
22331 also suppresses any such warning messages:
22334 @item @kbd{gdb -iex "set auto-load no" @dots{}}
22335 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
22337 @item @file{~/.gdbinit}: @samp{set auto-load no}
22338 Disable auto-loading globally for the user
22339 (@pxref{Home Directory Init File}). While it is improbable, you could also
22340 use system init file instead (@pxref{System-wide configuration}).
22343 This setting applies to the file names as entered by user. If no entry matches
22344 @value{GDBN} tries as a last resort to also resolve all the file names into
22345 their canonical form (typically resolving symbolic links) and compare the
22346 entries again. @value{GDBN} already canonicalizes most of the filenames on its
22347 own before starting the comparison so a canonical form of directories is
22348 recommended to be entered.
22350 @node Auto-loading verbose mode
22351 @subsection Displaying files tried for auto-load
22352 @cindex auto-loading verbose mode
22354 For better visibility of all the file locations where you can place scripts to
22355 be auto-loaded with inferior --- or to protect yourself against accidental
22356 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
22357 all the files attempted to be loaded. Both existing and non-existing files may
22360 For example the list of directories from which it is safe to auto-load files
22361 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
22362 may not be too obvious while setting it up.
22365 (gdb) set debug auto-load on
22366 (gdb) file ~/src/t/true
22367 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
22368 for objfile "/tmp/true".
22369 auto-load: Updating directories of "/usr:/opt".
22370 auto-load: Using directory "/usr".
22371 auto-load: Using directory "/opt".
22372 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
22373 by your `auto-load safe-path' set to "/usr:/opt".
22377 @anchor{set debug auto-load}
22378 @kindex set debug auto-load
22379 @item set debug auto-load [on|off]
22380 Set whether to print the filenames attempted to be auto-loaded.
22382 @anchor{show debug auto-load}
22383 @kindex show debug auto-load
22384 @item show debug auto-load
22385 Show whether printing of the filenames attempted to be auto-loaded is turned
22389 @node Messages/Warnings
22390 @section Optional Warnings and Messages
22392 @cindex verbose operation
22393 @cindex optional warnings
22394 By default, @value{GDBN} is silent about its inner workings. If you are
22395 running on a slow machine, you may want to use the @code{set verbose}
22396 command. This makes @value{GDBN} tell you when it does a lengthy
22397 internal operation, so you will not think it has crashed.
22399 Currently, the messages controlled by @code{set verbose} are those
22400 which announce that the symbol table for a source file is being read;
22401 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
22404 @kindex set verbose
22405 @item set verbose on
22406 Enables @value{GDBN} output of certain informational messages.
22408 @item set verbose off
22409 Disables @value{GDBN} output of certain informational messages.
22411 @kindex show verbose
22413 Displays whether @code{set verbose} is on or off.
22416 By default, if @value{GDBN} encounters bugs in the symbol table of an
22417 object file, it is silent; but if you are debugging a compiler, you may
22418 find this information useful (@pxref{Symbol Errors, ,Errors Reading
22423 @kindex set complaints
22424 @item set complaints @var{limit}
22425 Permits @value{GDBN} to output @var{limit} complaints about each type of
22426 unusual symbols before becoming silent about the problem. Set
22427 @var{limit} to zero to suppress all complaints; set it to a large number
22428 to prevent complaints from being suppressed.
22430 @kindex show complaints
22431 @item show complaints
22432 Displays how many symbol complaints @value{GDBN} is permitted to produce.
22436 @anchor{confirmation requests}
22437 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
22438 lot of stupid questions to confirm certain commands. For example, if
22439 you try to run a program which is already running:
22443 The program being debugged has been started already.
22444 Start it from the beginning? (y or n)
22447 If you are willing to unflinchingly face the consequences of your own
22448 commands, you can disable this ``feature'':
22452 @kindex set confirm
22454 @cindex confirmation
22455 @cindex stupid questions
22456 @item set confirm off
22457 Disables confirmation requests. Note that running @value{GDBN} with
22458 the @option{--batch} option (@pxref{Mode Options, -batch}) also
22459 automatically disables confirmation requests.
22461 @item set confirm on
22462 Enables confirmation requests (the default).
22464 @kindex show confirm
22466 Displays state of confirmation requests.
22470 @cindex command tracing
22471 If you need to debug user-defined commands or sourced files you may find it
22472 useful to enable @dfn{command tracing}. In this mode each command will be
22473 printed as it is executed, prefixed with one or more @samp{+} symbols, the
22474 quantity denoting the call depth of each command.
22477 @kindex set trace-commands
22478 @cindex command scripts, debugging
22479 @item set trace-commands on
22480 Enable command tracing.
22481 @item set trace-commands off
22482 Disable command tracing.
22483 @item show trace-commands
22484 Display the current state of command tracing.
22487 @node Debugging Output
22488 @section Optional Messages about Internal Happenings
22489 @cindex optional debugging messages
22491 @value{GDBN} has commands that enable optional debugging messages from
22492 various @value{GDBN} subsystems; normally these commands are of
22493 interest to @value{GDBN} maintainers, or when reporting a bug. This
22494 section documents those commands.
22497 @kindex set exec-done-display
22498 @item set exec-done-display
22499 Turns on or off the notification of asynchronous commands'
22500 completion. When on, @value{GDBN} will print a message when an
22501 asynchronous command finishes its execution. The default is off.
22502 @kindex show exec-done-display
22503 @item show exec-done-display
22504 Displays the current setting of asynchronous command completion
22507 @cindex ARM AArch64
22508 @item set debug aarch64
22509 Turns on or off display of debugging messages related to ARM AArch64.
22510 The default is off.
22512 @item show debug aarch64
22513 Displays the current state of displaying debugging messages related to
22515 @cindex gdbarch debugging info
22516 @cindex architecture debugging info
22517 @item set debug arch
22518 Turns on or off display of gdbarch debugging info. The default is off
22519 @item show debug arch
22520 Displays the current state of displaying gdbarch debugging info.
22521 @item set debug aix-solib
22522 @cindex AIX shared library debugging
22523 Control display of debugging messages from the AIX shared library
22524 support module. The default is off.
22525 @item show debug aix-thread
22526 Show the current state of displaying AIX shared library debugging messages.
22527 @item set debug aix-thread
22528 @cindex AIX threads
22529 Display debugging messages about inner workings of the AIX thread
22531 @item show debug aix-thread
22532 Show the current state of AIX thread debugging info display.
22533 @item set debug check-physname
22535 Check the results of the ``physname'' computation. When reading DWARF
22536 debugging information for C@t{++}, @value{GDBN} attempts to compute
22537 each entity's name. @value{GDBN} can do this computation in two
22538 different ways, depending on exactly what information is present.
22539 When enabled, this setting causes @value{GDBN} to compute the names
22540 both ways and display any discrepancies.
22541 @item show debug check-physname
22542 Show the current state of ``physname'' checking.
22543 @item set debug coff-pe-read
22544 @cindex COFF/PE exported symbols
22545 Control display of debugging messages related to reading of COFF/PE
22546 exported symbols. The default is off.
22547 @item show debug coff-pe-read
22548 Displays the current state of displaying debugging messages related to
22549 reading of COFF/PE exported symbols.
22550 @item set debug dwarf2-die
22551 @cindex DWARF2 DIEs
22552 Dump DWARF2 DIEs after they are read in.
22553 The value is the number of nesting levels to print.
22554 A value of zero turns off the display.
22555 @item show debug dwarf2-die
22556 Show the current state of DWARF2 DIE debugging.
22557 @item set debug dwarf2-read
22558 @cindex DWARF2 Reading
22559 Turns on or off display of debugging messages related to reading
22560 DWARF debug info. The default is off.
22561 @item show debug dwarf2-read
22562 Show the current state of DWARF2 reader debugging.
22563 @item set debug displaced
22564 @cindex displaced stepping debugging info
22565 Turns on or off display of @value{GDBN} debugging info for the
22566 displaced stepping support. The default is off.
22567 @item show debug displaced
22568 Displays the current state of displaying @value{GDBN} debugging info
22569 related to displaced stepping.
22570 @item set debug event
22571 @cindex event debugging info
22572 Turns on or off display of @value{GDBN} event debugging info. The
22574 @item show debug event
22575 Displays the current state of displaying @value{GDBN} event debugging
22577 @item set debug expression
22578 @cindex expression debugging info
22579 Turns on or off display of debugging info about @value{GDBN}
22580 expression parsing. The default is off.
22581 @item show debug expression
22582 Displays the current state of displaying debugging info about
22583 @value{GDBN} expression parsing.
22584 @item set debug frame
22585 @cindex frame debugging info
22586 Turns on or off display of @value{GDBN} frame debugging info. The
22588 @item show debug frame
22589 Displays the current state of displaying @value{GDBN} frame debugging
22591 @item set debug gnu-nat
22592 @cindex @sc{gnu}/Hurd debug messages
22593 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
22594 @item show debug gnu-nat
22595 Show the current state of @sc{gnu}/Hurd debugging messages.
22596 @item set debug infrun
22597 @cindex inferior debugging info
22598 Turns on or off display of @value{GDBN} debugging info for running the inferior.
22599 The default is off. @file{infrun.c} contains GDB's runtime state machine used
22600 for implementing operations such as single-stepping the inferior.
22601 @item show debug infrun
22602 Displays the current state of @value{GDBN} inferior debugging.
22603 @item set debug jit
22604 @cindex just-in-time compilation, debugging messages
22605 Turns on or off debugging messages from JIT debug support.
22606 @item show debug jit
22607 Displays the current state of @value{GDBN} JIT debugging.
22608 @item set debug lin-lwp
22609 @cindex @sc{gnu}/Linux LWP debug messages
22610 @cindex Linux lightweight processes
22611 Turns on or off debugging messages from the Linux LWP debug support.
22612 @item show debug lin-lwp
22613 Show the current state of Linux LWP debugging messages.
22614 @item set debug mach-o
22615 @cindex Mach-O symbols processing
22616 Control display of debugging messages related to Mach-O symbols
22617 processing. The default is off.
22618 @item show debug mach-o
22619 Displays the current state of displaying debugging messages related to
22620 reading of COFF/PE exported symbols.
22621 @item set debug notification
22622 @cindex remote async notification debugging info
22623 Turns on or off debugging messages about remote async notification.
22624 The default is off.
22625 @item show debug notification
22626 Displays the current state of remote async notification debugging messages.
22627 @item set debug observer
22628 @cindex observer debugging info
22629 Turns on or off display of @value{GDBN} observer debugging. This
22630 includes info such as the notification of observable events.
22631 @item show debug observer
22632 Displays the current state of observer debugging.
22633 @item set debug overload
22634 @cindex C@t{++} overload debugging info
22635 Turns on or off display of @value{GDBN} C@t{++} overload debugging
22636 info. This includes info such as ranking of functions, etc. The default
22638 @item show debug overload
22639 Displays the current state of displaying @value{GDBN} C@t{++} overload
22641 @cindex expression parser, debugging info
22642 @cindex debug expression parser
22643 @item set debug parser
22644 Turns on or off the display of expression parser debugging output.
22645 Internally, this sets the @code{yydebug} variable in the expression
22646 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
22647 details. The default is off.
22648 @item show debug parser
22649 Show the current state of expression parser debugging.
22650 @cindex packets, reporting on stdout
22651 @cindex serial connections, debugging
22652 @cindex debug remote protocol
22653 @cindex remote protocol debugging
22654 @cindex display remote packets
22655 @item set debug remote
22656 Turns on or off display of reports on all packets sent back and forth across
22657 the serial line to the remote machine. The info is printed on the
22658 @value{GDBN} standard output stream. The default is off.
22659 @item show debug remote
22660 Displays the state of display of remote packets.
22661 @item set debug serial
22662 Turns on or off display of @value{GDBN} serial debugging info. The
22664 @item show debug serial
22665 Displays the current state of displaying @value{GDBN} serial debugging
22667 @item set debug solib-frv
22668 @cindex FR-V shared-library debugging
22669 Turns on or off debugging messages for FR-V shared-library code.
22670 @item show debug solib-frv
22671 Display the current state of FR-V shared-library code debugging
22673 @item set debug symfile
22674 @cindex symbol file functions
22675 Turns on or off display of debugging messages related to symbol file functions.
22676 The default is off. @xref{Files}.
22677 @item show debug symfile
22678 Show the current state of symbol file debugging messages.
22679 @item set debug symtab-create
22680 @cindex symbol table creation
22681 Turns on or off display of debugging messages related to symbol table creation.
22682 The default is off.
22683 @item show debug symtab-create
22684 Show the current state of symbol table creation debugging.
22685 @item set debug target
22686 @cindex target debugging info
22687 Turns on or off display of @value{GDBN} target debugging info. This info
22688 includes what is going on at the target level of GDB, as it happens. The
22689 default is 0. Set it to 1 to track events, and to 2 to also track the
22690 value of large memory transfers. Changes to this flag do not take effect
22691 until the next time you connect to a target or use the @code{run} command.
22692 @item show debug target
22693 Displays the current state of displaying @value{GDBN} target debugging
22695 @item set debug timestamp
22696 @cindex timestampping debugging info
22697 Turns on or off display of timestamps with @value{GDBN} debugging info.
22698 When enabled, seconds and microseconds are displayed before each debugging
22700 @item show debug timestamp
22701 Displays the current state of displaying timestamps with @value{GDBN}
22703 @item set debugvarobj
22704 @cindex variable object debugging info
22705 Turns on or off display of @value{GDBN} variable object debugging
22706 info. The default is off.
22707 @item show debugvarobj
22708 Displays the current state of displaying @value{GDBN} variable object
22710 @item set debug xml
22711 @cindex XML parser debugging
22712 Turns on or off debugging messages for built-in XML parsers.
22713 @item show debug xml
22714 Displays the current state of XML debugging messages.
22717 @node Other Misc Settings
22718 @section Other Miscellaneous Settings
22719 @cindex miscellaneous settings
22722 @kindex set interactive-mode
22723 @item set interactive-mode
22724 If @code{on}, forces @value{GDBN} to assume that GDB was started
22725 in a terminal. In practice, this means that @value{GDBN} should wait
22726 for the user to answer queries generated by commands entered at
22727 the command prompt. If @code{off}, forces @value{GDBN} to operate
22728 in the opposite mode, and it uses the default answers to all queries.
22729 If @code{auto} (the default), @value{GDBN} tries to determine whether
22730 its standard input is a terminal, and works in interactive-mode if it
22731 is, non-interactively otherwise.
22733 In the vast majority of cases, the debugger should be able to guess
22734 correctly which mode should be used. But this setting can be useful
22735 in certain specific cases, such as running a MinGW @value{GDBN}
22736 inside a cygwin window.
22738 @kindex show interactive-mode
22739 @item show interactive-mode
22740 Displays whether the debugger is operating in interactive mode or not.
22743 @node Extending GDB
22744 @chapter Extending @value{GDBN}
22745 @cindex extending GDB
22747 @value{GDBN} provides three mechanisms for extension. The first is based
22748 on composition of @value{GDBN} commands, the second is based on the
22749 Python scripting language, and the third is for defining new aliases of
22752 To facilitate the use of the first two extensions, @value{GDBN} is capable
22753 of evaluating the contents of a file. When doing so, @value{GDBN}
22754 can recognize which scripting language is being used by looking at
22755 the filename extension. Files with an unrecognized filename extension
22756 are always treated as a @value{GDBN} Command Files.
22757 @xref{Command Files,, Command files}.
22759 You can control how @value{GDBN} evaluates these files with the following
22763 @kindex set script-extension
22764 @kindex show script-extension
22765 @item set script-extension off
22766 All scripts are always evaluated as @value{GDBN} Command Files.
22768 @item set script-extension soft
22769 The debugger determines the scripting language based on filename
22770 extension. If this scripting language is supported, @value{GDBN}
22771 evaluates the script using that language. Otherwise, it evaluates
22772 the file as a @value{GDBN} Command File.
22774 @item set script-extension strict
22775 The debugger determines the scripting language based on filename
22776 extension, and evaluates the script using that language. If the
22777 language is not supported, then the evaluation fails.
22779 @item show script-extension
22780 Display the current value of the @code{script-extension} option.
22785 * Sequences:: Canned Sequences of Commands
22786 * Python:: Scripting @value{GDBN} using Python
22787 * Aliases:: Creating new spellings of existing commands
22791 @section Canned Sequences of Commands
22793 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
22794 Command Lists}), @value{GDBN} provides two ways to store sequences of
22795 commands for execution as a unit: user-defined commands and command
22799 * Define:: How to define your own commands
22800 * Hooks:: Hooks for user-defined commands
22801 * Command Files:: How to write scripts of commands to be stored in a file
22802 * Output:: Commands for controlled output
22806 @subsection User-defined Commands
22808 @cindex user-defined command
22809 @cindex arguments, to user-defined commands
22810 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
22811 which you assign a new name as a command. This is done with the
22812 @code{define} command. User commands may accept up to 10 arguments
22813 separated by whitespace. Arguments are accessed within the user command
22814 via @code{$arg0@dots{}$arg9}. A trivial example:
22818 print $arg0 + $arg1 + $arg2
22823 To execute the command use:
22830 This defines the command @code{adder}, which prints the sum of
22831 its three arguments. Note the arguments are text substitutions, so they may
22832 reference variables, use complex expressions, or even perform inferior
22835 @cindex argument count in user-defined commands
22836 @cindex how many arguments (user-defined commands)
22837 In addition, @code{$argc} may be used to find out how many arguments have
22838 been passed. This expands to a number in the range 0@dots{}10.
22843 print $arg0 + $arg1
22846 print $arg0 + $arg1 + $arg2
22854 @item define @var{commandname}
22855 Define a command named @var{commandname}. If there is already a command
22856 by that name, you are asked to confirm that you want to redefine it.
22857 @var{commandname} may be a bare command name consisting of letters,
22858 numbers, dashes, and underscores. It may also start with any predefined
22859 prefix command. For example, @samp{define target my-target} creates
22860 a user-defined @samp{target my-target} command.
22862 The definition of the command is made up of other @value{GDBN} command lines,
22863 which are given following the @code{define} command. The end of these
22864 commands is marked by a line containing @code{end}.
22867 @kindex end@r{ (user-defined commands)}
22868 @item document @var{commandname}
22869 Document the user-defined command @var{commandname}, so that it can be
22870 accessed by @code{help}. The command @var{commandname} must already be
22871 defined. This command reads lines of documentation just as @code{define}
22872 reads the lines of the command definition, ending with @code{end}.
22873 After the @code{document} command is finished, @code{help} on command
22874 @var{commandname} displays the documentation you have written.
22876 You may use the @code{document} command again to change the
22877 documentation of a command. Redefining the command with @code{define}
22878 does not change the documentation.
22880 @kindex dont-repeat
22881 @cindex don't repeat command
22883 Used inside a user-defined command, this tells @value{GDBN} that this
22884 command should not be repeated when the user hits @key{RET}
22885 (@pxref{Command Syntax, repeat last command}).
22887 @kindex help user-defined
22888 @item help user-defined
22889 List all user-defined commands and all python commands defined in class
22890 COMAND_USER. The first line of the documentation or docstring is
22895 @itemx show user @var{commandname}
22896 Display the @value{GDBN} commands used to define @var{commandname} (but
22897 not its documentation). If no @var{commandname} is given, display the
22898 definitions for all user-defined commands.
22899 This does not work for user-defined python commands.
22901 @cindex infinite recursion in user-defined commands
22902 @kindex show max-user-call-depth
22903 @kindex set max-user-call-depth
22904 @item show max-user-call-depth
22905 @itemx set max-user-call-depth
22906 The value of @code{max-user-call-depth} controls how many recursion
22907 levels are allowed in user-defined commands before @value{GDBN} suspects an
22908 infinite recursion and aborts the command.
22909 This does not apply to user-defined python commands.
22912 In addition to the above commands, user-defined commands frequently
22913 use control flow commands, described in @ref{Command Files}.
22915 When user-defined commands are executed, the
22916 commands of the definition are not printed. An error in any command
22917 stops execution of the user-defined command.
22919 If used interactively, commands that would ask for confirmation proceed
22920 without asking when used inside a user-defined command. Many @value{GDBN}
22921 commands that normally print messages to say what they are doing omit the
22922 messages when used in a user-defined command.
22925 @subsection User-defined Command Hooks
22926 @cindex command hooks
22927 @cindex hooks, for commands
22928 @cindex hooks, pre-command
22931 You may define @dfn{hooks}, which are a special kind of user-defined
22932 command. Whenever you run the command @samp{foo}, if the user-defined
22933 command @samp{hook-foo} exists, it is executed (with no arguments)
22934 before that command.
22936 @cindex hooks, post-command
22938 A hook may also be defined which is run after the command you executed.
22939 Whenever you run the command @samp{foo}, if the user-defined command
22940 @samp{hookpost-foo} exists, it is executed (with no arguments) after
22941 that command. Post-execution hooks may exist simultaneously with
22942 pre-execution hooks, for the same command.
22944 It is valid for a hook to call the command which it hooks. If this
22945 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
22947 @c It would be nice if hookpost could be passed a parameter indicating
22948 @c if the command it hooks executed properly or not. FIXME!
22950 @kindex stop@r{, a pseudo-command}
22951 In addition, a pseudo-command, @samp{stop} exists. Defining
22952 (@samp{hook-stop}) makes the associated commands execute every time
22953 execution stops in your program: before breakpoint commands are run,
22954 displays are printed, or the stack frame is printed.
22956 For example, to ignore @code{SIGALRM} signals while
22957 single-stepping, but treat them normally during normal execution,
22962 handle SIGALRM nopass
22966 handle SIGALRM pass
22969 define hook-continue
22970 handle SIGALRM pass
22974 As a further example, to hook at the beginning and end of the @code{echo}
22975 command, and to add extra text to the beginning and end of the message,
22983 define hookpost-echo
22987 (@value{GDBP}) echo Hello World
22988 <<<---Hello World--->>>
22993 You can define a hook for any single-word command in @value{GDBN}, but
22994 not for command aliases; you should define a hook for the basic command
22995 name, e.g.@: @code{backtrace} rather than @code{bt}.
22996 @c FIXME! So how does Joe User discover whether a command is an alias
22998 You can hook a multi-word command by adding @code{hook-} or
22999 @code{hookpost-} to the last word of the command, e.g.@:
23000 @samp{define target hook-remote} to add a hook to @samp{target remote}.
23002 If an error occurs during the execution of your hook, execution of
23003 @value{GDBN} commands stops and @value{GDBN} issues a prompt
23004 (before the command that you actually typed had a chance to run).
23006 If you try to define a hook which does not match any known command, you
23007 get a warning from the @code{define} command.
23009 @node Command Files
23010 @subsection Command Files
23012 @cindex command files
23013 @cindex scripting commands
23014 A command file for @value{GDBN} is a text file made of lines that are
23015 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
23016 also be included. An empty line in a command file does nothing; it
23017 does not mean to repeat the last command, as it would from the
23020 You can request the execution of a command file with the @code{source}
23021 command. Note that the @code{source} command is also used to evaluate
23022 scripts that are not Command Files. The exact behavior can be configured
23023 using the @code{script-extension} setting.
23024 @xref{Extending GDB,, Extending GDB}.
23028 @cindex execute commands from a file
23029 @item source [-s] [-v] @var{filename}
23030 Execute the command file @var{filename}.
23033 The lines in a command file are generally executed sequentially,
23034 unless the order of execution is changed by one of the
23035 @emph{flow-control commands} described below. The commands are not
23036 printed as they are executed. An error in any command terminates
23037 execution of the command file and control is returned to the console.
23039 @value{GDBN} first searches for @var{filename} in the current directory.
23040 If the file is not found there, and @var{filename} does not specify a
23041 directory, then @value{GDBN} also looks for the file on the source search path
23042 (specified with the @samp{directory} command);
23043 except that @file{$cdir} is not searched because the compilation directory
23044 is not relevant to scripts.
23046 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
23047 on the search path even if @var{filename} specifies a directory.
23048 The search is done by appending @var{filename} to each element of the
23049 search path. So, for example, if @var{filename} is @file{mylib/myscript}
23050 and the search path contains @file{/home/user} then @value{GDBN} will
23051 look for the script @file{/home/user/mylib/myscript}.
23052 The search is also done if @var{filename} is an absolute path.
23053 For example, if @var{filename} is @file{/tmp/myscript} and
23054 the search path contains @file{/home/user} then @value{GDBN} will
23055 look for the script @file{/home/user/tmp/myscript}.
23056 For DOS-like systems, if @var{filename} contains a drive specification,
23057 it is stripped before concatenation. For example, if @var{filename} is
23058 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
23059 will look for the script @file{c:/tmp/myscript}.
23061 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
23062 each command as it is executed. The option must be given before
23063 @var{filename}, and is interpreted as part of the filename anywhere else.
23065 Commands that would ask for confirmation if used interactively proceed
23066 without asking when used in a command file. Many @value{GDBN} commands that
23067 normally print messages to say what they are doing omit the messages
23068 when called from command files.
23070 @value{GDBN} also accepts command input from standard input. In this
23071 mode, normal output goes to standard output and error output goes to
23072 standard error. Errors in a command file supplied on standard input do
23073 not terminate execution of the command file---execution continues with
23077 gdb < cmds > log 2>&1
23080 (The syntax above will vary depending on the shell used.) This example
23081 will execute commands from the file @file{cmds}. All output and errors
23082 would be directed to @file{log}.
23084 Since commands stored on command files tend to be more general than
23085 commands typed interactively, they frequently need to deal with
23086 complicated situations, such as different or unexpected values of
23087 variables and symbols, changes in how the program being debugged is
23088 built, etc. @value{GDBN} provides a set of flow-control commands to
23089 deal with these complexities. Using these commands, you can write
23090 complex scripts that loop over data structures, execute commands
23091 conditionally, etc.
23098 This command allows to include in your script conditionally executed
23099 commands. The @code{if} command takes a single argument, which is an
23100 expression to evaluate. It is followed by a series of commands that
23101 are executed only if the expression is true (its value is nonzero).
23102 There can then optionally be an @code{else} line, followed by a series
23103 of commands that are only executed if the expression was false. The
23104 end of the list is marked by a line containing @code{end}.
23108 This command allows to write loops. Its syntax is similar to
23109 @code{if}: the command takes a single argument, which is an expression
23110 to evaluate, and must be followed by the commands to execute, one per
23111 line, terminated by an @code{end}. These commands are called the
23112 @dfn{body} of the loop. The commands in the body of @code{while} are
23113 executed repeatedly as long as the expression evaluates to true.
23117 This command exits the @code{while} loop in whose body it is included.
23118 Execution of the script continues after that @code{while}s @code{end}
23121 @kindex loop_continue
23122 @item loop_continue
23123 This command skips the execution of the rest of the body of commands
23124 in the @code{while} loop in whose body it is included. Execution
23125 branches to the beginning of the @code{while} loop, where it evaluates
23126 the controlling expression.
23128 @kindex end@r{ (if/else/while commands)}
23130 Terminate the block of commands that are the body of @code{if},
23131 @code{else}, or @code{while} flow-control commands.
23136 @subsection Commands for Controlled Output
23138 During the execution of a command file or a user-defined command, normal
23139 @value{GDBN} output is suppressed; the only output that appears is what is
23140 explicitly printed by the commands in the definition. This section
23141 describes three commands useful for generating exactly the output you
23146 @item echo @var{text}
23147 @c I do not consider backslash-space a standard C escape sequence
23148 @c because it is not in ANSI.
23149 Print @var{text}. Nonprinting characters can be included in
23150 @var{text} using C escape sequences, such as @samp{\n} to print a
23151 newline. @strong{No newline is printed unless you specify one.}
23152 In addition to the standard C escape sequences, a backslash followed
23153 by a space stands for a space. This is useful for displaying a
23154 string with spaces at the beginning or the end, since leading and
23155 trailing spaces are otherwise trimmed from all arguments.
23156 To print @samp{@w{ }and foo =@w{ }}, use the command
23157 @samp{echo \@w{ }and foo = \@w{ }}.
23159 A backslash at the end of @var{text} can be used, as in C, to continue
23160 the command onto subsequent lines. For example,
23163 echo This is some text\n\
23164 which is continued\n\
23165 onto several lines.\n
23168 produces the same output as
23171 echo This is some text\n
23172 echo which is continued\n
23173 echo onto several lines.\n
23177 @item output @var{expression}
23178 Print the value of @var{expression} and nothing but that value: no
23179 newlines, no @samp{$@var{nn} = }. The value is not entered in the
23180 value history either. @xref{Expressions, ,Expressions}, for more information
23183 @item output/@var{fmt} @var{expression}
23184 Print the value of @var{expression} in format @var{fmt}. You can use
23185 the same formats as for @code{print}. @xref{Output Formats,,Output
23186 Formats}, for more information.
23189 @item printf @var{template}, @var{expressions}@dots{}
23190 Print the values of one or more @var{expressions} under the control of
23191 the string @var{template}. To print several values, make
23192 @var{expressions} be a comma-separated list of individual expressions,
23193 which may be either numbers or pointers. Their values are printed as
23194 specified by @var{template}, exactly as a C program would do by
23195 executing the code below:
23198 printf (@var{template}, @var{expressions}@dots{});
23201 As in @code{C} @code{printf}, ordinary characters in @var{template}
23202 are printed verbatim, while @dfn{conversion specification} introduced
23203 by the @samp{%} character cause subsequent @var{expressions} to be
23204 evaluated, their values converted and formatted according to type and
23205 style information encoded in the conversion specifications, and then
23208 For example, you can print two values in hex like this:
23211 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
23214 @code{printf} supports all the standard @code{C} conversion
23215 specifications, including the flags and modifiers between the @samp{%}
23216 character and the conversion letter, with the following exceptions:
23220 The argument-ordering modifiers, such as @samp{2$}, are not supported.
23223 The modifier @samp{*} is not supported for specifying precision or
23227 The @samp{'} flag (for separation of digits into groups according to
23228 @code{LC_NUMERIC'}) is not supported.
23231 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
23235 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
23238 The conversion letters @samp{a} and @samp{A} are not supported.
23242 Note that the @samp{ll} type modifier is supported only if the
23243 underlying @code{C} implementation used to build @value{GDBN} supports
23244 the @code{long long int} type, and the @samp{L} type modifier is
23245 supported only if @code{long double} type is available.
23247 As in @code{C}, @code{printf} supports simple backslash-escape
23248 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
23249 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
23250 single character. Octal and hexadecimal escape sequences are not
23253 Additionally, @code{printf} supports conversion specifications for DFP
23254 (@dfn{Decimal Floating Point}) types using the following length modifiers
23255 together with a floating point specifier.
23260 @samp{H} for printing @code{Decimal32} types.
23263 @samp{D} for printing @code{Decimal64} types.
23266 @samp{DD} for printing @code{Decimal128} types.
23269 If the underlying @code{C} implementation used to build @value{GDBN} has
23270 support for the three length modifiers for DFP types, other modifiers
23271 such as width and precision will also be available for @value{GDBN} to use.
23273 In case there is no such @code{C} support, no additional modifiers will be
23274 available and the value will be printed in the standard way.
23276 Here's an example of printing DFP types using the above conversion letters:
23278 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
23282 @item eval @var{template}, @var{expressions}@dots{}
23283 Convert the values of one or more @var{expressions} under the control of
23284 the string @var{template} to a command line, and call it.
23289 @section Scripting @value{GDBN} using Python
23290 @cindex python scripting
23291 @cindex scripting with python
23293 You can script @value{GDBN} using the @uref{http://www.python.org/,
23294 Python programming language}. This feature is available only if
23295 @value{GDBN} was configured using @option{--with-python}.
23297 @cindex python directory
23298 Python scripts used by @value{GDBN} should be installed in
23299 @file{@var{data-directory}/python}, where @var{data-directory} is
23300 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
23301 This directory, known as the @dfn{python directory},
23302 is automatically added to the Python Search Path in order to allow
23303 the Python interpreter to locate all scripts installed at this location.
23305 Additionally, @value{GDBN} commands and convenience functions which
23306 are written in Python and are located in the
23307 @file{@var{data-directory}/python/gdb/command} or
23308 @file{@var{data-directory}/python/gdb/function} directories are
23309 automatically imported when @value{GDBN} starts.
23312 * Python Commands:: Accessing Python from @value{GDBN}.
23313 * Python API:: Accessing @value{GDBN} from Python.
23314 * Python Auto-loading:: Automatically loading Python code.
23315 * Python modules:: Python modules provided by @value{GDBN}.
23318 @node Python Commands
23319 @subsection Python Commands
23320 @cindex python commands
23321 @cindex commands to access python
23323 @value{GDBN} provides two commands for accessing the Python interpreter,
23324 and one related setting:
23327 @kindex python-interactive
23329 @item python-interactive @r{[}@var{command}@r{]}
23330 @itemx pi @r{[}@var{command}@r{]}
23331 Without an argument, the @code{python-interactive} command can be used
23332 to start an interactive Python prompt. To return to @value{GDBN},
23333 type the @code{EOF} character (e.g., @kbd{Ctrl-D} on an empty prompt).
23335 Alternatively, a single-line Python command can be given as an
23336 argument and evaluated. If the command is an expression, the result
23337 will be printed; otherwise, nothing will be printed. For example:
23340 (@value{GDBP}) python-interactive 2 + 3
23346 @item python @r{[}@var{command}@r{]}
23347 @itemx py @r{[}@var{command}@r{]}
23348 The @code{python} command can be used to evaluate Python code.
23350 If given an argument, the @code{python} command will evaluate the
23351 argument as a Python command. For example:
23354 (@value{GDBP}) python print 23
23358 If you do not provide an argument to @code{python}, it will act as a
23359 multi-line command, like @code{define}. In this case, the Python
23360 script is made up of subsequent command lines, given after the
23361 @code{python} command. This command list is terminated using a line
23362 containing @code{end}. For example:
23365 (@value{GDBP}) python
23367 End with a line saying just "end".
23373 @kindex set python print-stack
23374 @item set python print-stack
23375 By default, @value{GDBN} will print only the message component of a
23376 Python exception when an error occurs in a Python script. This can be
23377 controlled using @code{set python print-stack}: if @code{full}, then
23378 full Python stack printing is enabled; if @code{none}, then Python stack
23379 and message printing is disabled; if @code{message}, the default, only
23380 the message component of the error is printed.
23383 It is also possible to execute a Python script from the @value{GDBN}
23387 @item source @file{script-name}
23388 The script name must end with @samp{.py} and @value{GDBN} must be configured
23389 to recognize the script language based on filename extension using
23390 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
23392 @item python execfile ("script-name")
23393 This method is based on the @code{execfile} Python built-in function,
23394 and thus is always available.
23398 @subsection Python API
23400 @cindex programming in python
23402 You can get quick online help for @value{GDBN}'s Python API by issuing
23403 the command @w{@kbd{python help (gdb)}}.
23405 Functions and methods which have two or more optional arguments allow
23406 them to be specified using keyword syntax. This allows passing some
23407 optional arguments while skipping others. Example:
23408 @w{@code{gdb.some_function ('foo', bar = 1, baz = 2)}}.
23411 * Basic Python:: Basic Python Functions.
23412 * Exception Handling:: How Python exceptions are translated.
23413 * Values From Inferior:: Python representation of values.
23414 * Types In Python:: Python representation of types.
23415 * Pretty Printing API:: Pretty-printing values.
23416 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
23417 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
23418 * Type Printing API:: Pretty-printing types.
23419 * Frame Filter API:: Filtering Frames.
23420 * Frame Decorator API:: Decorating Frames.
23421 * Writing a Frame Filter:: Writing a Frame Filter.
23422 * Inferiors In Python:: Python representation of inferiors (processes)
23423 * Events In Python:: Listening for events from @value{GDBN}.
23424 * Threads In Python:: Accessing inferior threads from Python.
23425 * Commands In Python:: Implementing new commands in Python.
23426 * Parameters In Python:: Adding new @value{GDBN} parameters.
23427 * Functions In Python:: Writing new convenience functions.
23428 * Progspaces In Python:: Program spaces.
23429 * Objfiles In Python:: Object files.
23430 * Frames In Python:: Accessing inferior stack frames from Python.
23431 * Blocks In Python:: Accessing blocks from Python.
23432 * Symbols In Python:: Python representation of symbols.
23433 * Symbol Tables In Python:: Python representation of symbol tables.
23434 * Breakpoints In Python:: Manipulating breakpoints using Python.
23435 * Finish Breakpoints in Python:: Setting Breakpoints on function return
23437 * Lazy Strings In Python:: Python representation of lazy strings.
23438 * Architectures In Python:: Python representation of architectures.
23442 @subsubsection Basic Python
23444 @cindex python stdout
23445 @cindex python pagination
23446 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
23447 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
23448 A Python program which outputs to one of these streams may have its
23449 output interrupted by the user (@pxref{Screen Size}). In this
23450 situation, a Python @code{KeyboardInterrupt} exception is thrown.
23452 Some care must be taken when writing Python code to run in
23453 @value{GDBN}. Two things worth noting in particular:
23457 @value{GDBN} install handlers for @code{SIGCHLD} and @code{SIGINT}.
23458 Python code must not override these, or even change the options using
23459 @code{sigaction}. If your program changes the handling of these
23460 signals, @value{GDBN} will most likely stop working correctly. Note
23461 that it is unfortunately common for GUI toolkits to install a
23462 @code{SIGCHLD} handler.
23465 @value{GDBN} takes care to mark its internal file descriptors as
23466 close-on-exec. However, this cannot be done in a thread-safe way on
23467 all platforms. Your Python programs should be aware of this and
23468 should both create new file descriptors with the close-on-exec flag
23469 set and arrange to close unneeded file descriptors before starting a
23473 @cindex python functions
23474 @cindex python module
23476 @value{GDBN} introduces a new Python module, named @code{gdb}. All
23477 methods and classes added by @value{GDBN} are placed in this module.
23478 @value{GDBN} automatically @code{import}s the @code{gdb} module for
23479 use in all scripts evaluated by the @code{python} command.
23481 @findex gdb.PYTHONDIR
23482 @defvar gdb.PYTHONDIR
23483 A string containing the python directory (@pxref{Python}).
23486 @findex gdb.execute
23487 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
23488 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
23489 If a GDB exception happens while @var{command} runs, it is
23490 translated as described in @ref{Exception Handling,,Exception Handling}.
23492 @var{from_tty} specifies whether @value{GDBN} ought to consider this
23493 command as having originated from the user invoking it interactively.
23494 It must be a boolean value. If omitted, it defaults to @code{False}.
23496 By default, any output produced by @var{command} is sent to
23497 @value{GDBN}'s standard output. If the @var{to_string} parameter is
23498 @code{True}, then output will be collected by @code{gdb.execute} and
23499 returned as a string. The default is @code{False}, in which case the
23500 return value is @code{None}. If @var{to_string} is @code{True}, the
23501 @value{GDBN} virtual terminal will be temporarily set to unlimited width
23502 and height, and its pagination will be disabled; @pxref{Screen Size}.
23505 @findex gdb.breakpoints
23506 @defun gdb.breakpoints ()
23507 Return a sequence holding all of @value{GDBN}'s breakpoints.
23508 @xref{Breakpoints In Python}, for more information.
23511 @findex gdb.parameter
23512 @defun gdb.parameter (parameter)
23513 Return the value of a @value{GDBN} parameter. @var{parameter} is a
23514 string naming the parameter to look up; @var{parameter} may contain
23515 spaces if the parameter has a multi-part name. For example,
23516 @samp{print object} is a valid parameter name.
23518 If the named parameter does not exist, this function throws a
23519 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
23520 parameter's value is converted to a Python value of the appropriate
23521 type, and returned.
23524 @findex gdb.history
23525 @defun gdb.history (number)
23526 Return a value from @value{GDBN}'s value history (@pxref{Value
23527 History}). @var{number} indicates which history element to return.
23528 If @var{number} is negative, then @value{GDBN} will take its absolute value
23529 and count backward from the last element (i.e., the most recent element) to
23530 find the value to return. If @var{number} is zero, then @value{GDBN} will
23531 return the most recent element. If the element specified by @var{number}
23532 doesn't exist in the value history, a @code{gdb.error} exception will be
23535 If no exception is raised, the return value is always an instance of
23536 @code{gdb.Value} (@pxref{Values From Inferior}).
23539 @findex gdb.parse_and_eval
23540 @defun gdb.parse_and_eval (expression)
23541 Parse @var{expression} as an expression in the current language,
23542 evaluate it, and return the result as a @code{gdb.Value}.
23543 @var{expression} must be a string.
23545 This function can be useful when implementing a new command
23546 (@pxref{Commands In Python}), as it provides a way to parse the
23547 command's argument as an expression. It is also useful simply to
23548 compute values, for example, it is the only way to get the value of a
23549 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
23552 @findex gdb.find_pc_line
23553 @defun gdb.find_pc_line (pc)
23554 Return the @code{gdb.Symtab_and_line} object corresponding to the
23555 @var{pc} value. @xref{Symbol Tables In Python}. If an invalid
23556 value of @var{pc} is passed as an argument, then the @code{symtab} and
23557 @code{line} attributes of the returned @code{gdb.Symtab_and_line} object
23558 will be @code{None} and 0 respectively.
23561 @findex gdb.post_event
23562 @defun gdb.post_event (event)
23563 Put @var{event}, a callable object taking no arguments, into
23564 @value{GDBN}'s internal event queue. This callable will be invoked at
23565 some later point, during @value{GDBN}'s event processing. Events
23566 posted using @code{post_event} will be run in the order in which they
23567 were posted; however, there is no way to know when they will be
23568 processed relative to other events inside @value{GDBN}.
23570 @value{GDBN} is not thread-safe. If your Python program uses multiple
23571 threads, you must be careful to only call @value{GDBN}-specific
23572 functions in the main @value{GDBN} thread. @code{post_event} ensures
23576 (@value{GDBP}) python
23580 > def __init__(self, message):
23581 > self.message = message;
23582 > def __call__(self):
23583 > gdb.write(self.message)
23585 >class MyThread1 (threading.Thread):
23587 > gdb.post_event(Writer("Hello "))
23589 >class MyThread2 (threading.Thread):
23591 > gdb.post_event(Writer("World\n"))
23593 >MyThread1().start()
23594 >MyThread2().start()
23596 (@value{GDBP}) Hello World
23601 @defun gdb.write (string @r{[}, stream{]})
23602 Print a string to @value{GDBN}'s paginated output stream. The
23603 optional @var{stream} determines the stream to print to. The default
23604 stream is @value{GDBN}'s standard output stream. Possible stream
23611 @value{GDBN}'s standard output stream.
23616 @value{GDBN}'s standard error stream.
23621 @value{GDBN}'s log stream (@pxref{Logging Output}).
23624 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
23625 call this function and will automatically direct the output to the
23630 @defun gdb.flush ()
23631 Flush the buffer of a @value{GDBN} paginated stream so that the
23632 contents are displayed immediately. @value{GDBN} will flush the
23633 contents of a stream automatically when it encounters a newline in the
23634 buffer. The optional @var{stream} determines the stream to flush. The
23635 default stream is @value{GDBN}'s standard output stream. Possible
23642 @value{GDBN}'s standard output stream.
23647 @value{GDBN}'s standard error stream.
23652 @value{GDBN}'s log stream (@pxref{Logging Output}).
23656 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
23657 call this function for the relevant stream.
23660 @findex gdb.target_charset
23661 @defun gdb.target_charset ()
23662 Return the name of the current target character set (@pxref{Character
23663 Sets}). This differs from @code{gdb.parameter('target-charset')} in
23664 that @samp{auto} is never returned.
23667 @findex gdb.target_wide_charset
23668 @defun gdb.target_wide_charset ()
23669 Return the name of the current target wide character set
23670 (@pxref{Character Sets}). This differs from
23671 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
23675 @findex gdb.solib_name
23676 @defun gdb.solib_name (address)
23677 Return the name of the shared library holding the given @var{address}
23678 as a string, or @code{None}.
23681 @findex gdb.decode_line
23682 @defun gdb.decode_line @r{[}expression@r{]}
23683 Return locations of the line specified by @var{expression}, or of the
23684 current line if no argument was given. This function returns a Python
23685 tuple containing two elements. The first element contains a string
23686 holding any unparsed section of @var{expression} (or @code{None} if
23687 the expression has been fully parsed). The second element contains
23688 either @code{None} or another tuple that contains all the locations
23689 that match the expression represented as @code{gdb.Symtab_and_line}
23690 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
23691 provided, it is decoded the way that @value{GDBN}'s inbuilt
23692 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
23695 @defun gdb.prompt_hook (current_prompt)
23696 @anchor{prompt_hook}
23698 If @var{prompt_hook} is callable, @value{GDBN} will call the method
23699 assigned to this operation before a prompt is displayed by
23702 The parameter @code{current_prompt} contains the current @value{GDBN}
23703 prompt. This method must return a Python string, or @code{None}. If
23704 a string is returned, the @value{GDBN} prompt will be set to that
23705 string. If @code{None} is returned, @value{GDBN} will continue to use
23706 the current prompt.
23708 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
23709 such as those used by readline for command input, and annotation
23710 related prompts are prohibited from being changed.
23713 @node Exception Handling
23714 @subsubsection Exception Handling
23715 @cindex python exceptions
23716 @cindex exceptions, python
23718 When executing the @code{python} command, Python exceptions
23719 uncaught within the Python code are translated to calls to
23720 @value{GDBN} error-reporting mechanism. If the command that called
23721 @code{python} does not handle the error, @value{GDBN} will
23722 terminate it and print an error message containing the Python
23723 exception name, the associated value, and the Python call stack
23724 backtrace at the point where the exception was raised. Example:
23727 (@value{GDBP}) python print foo
23728 Traceback (most recent call last):
23729 File "<string>", line 1, in <module>
23730 NameError: name 'foo' is not defined
23733 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
23734 Python code are converted to Python exceptions. The type of the
23735 Python exception depends on the error.
23739 This is the base class for most exceptions generated by @value{GDBN}.
23740 It is derived from @code{RuntimeError}, for compatibility with earlier
23741 versions of @value{GDBN}.
23743 If an error occurring in @value{GDBN} does not fit into some more
23744 specific category, then the generated exception will have this type.
23746 @item gdb.MemoryError
23747 This is a subclass of @code{gdb.error} which is thrown when an
23748 operation tried to access invalid memory in the inferior.
23750 @item KeyboardInterrupt
23751 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
23752 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
23755 In all cases, your exception handler will see the @value{GDBN} error
23756 message as its value and the Python call stack backtrace at the Python
23757 statement closest to where the @value{GDBN} error occured as the
23760 @findex gdb.GdbError
23761 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
23762 it is useful to be able to throw an exception that doesn't cause a
23763 traceback to be printed. For example, the user may have invoked the
23764 command incorrectly. Use the @code{gdb.GdbError} exception
23765 to handle this case. Example:
23769 >class HelloWorld (gdb.Command):
23770 > """Greet the whole world."""
23771 > def __init__ (self):
23772 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
23773 > def invoke (self, args, from_tty):
23774 > argv = gdb.string_to_argv (args)
23775 > if len (argv) != 0:
23776 > raise gdb.GdbError ("hello-world takes no arguments")
23777 > print "Hello, World!"
23780 (gdb) hello-world 42
23781 hello-world takes no arguments
23784 @node Values From Inferior
23785 @subsubsection Values From Inferior
23786 @cindex values from inferior, with Python
23787 @cindex python, working with values from inferior
23789 @cindex @code{gdb.Value}
23790 @value{GDBN} provides values it obtains from the inferior program in
23791 an object of type @code{gdb.Value}. @value{GDBN} uses this object
23792 for its internal bookkeeping of the inferior's values, and for
23793 fetching values when necessary.
23795 Inferior values that are simple scalars can be used directly in
23796 Python expressions that are valid for the value's data type. Here's
23797 an example for an integer or floating-point value @code{some_val}:
23804 As result of this, @code{bar} will also be a @code{gdb.Value} object
23805 whose values are of the same type as those of @code{some_val}.
23807 Inferior values that are structures or instances of some class can
23808 be accessed using the Python @dfn{dictionary syntax}. For example, if
23809 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
23810 can access its @code{foo} element with:
23813 bar = some_val['foo']
23816 Again, @code{bar} will also be a @code{gdb.Value} object.
23818 A @code{gdb.Value} that represents a function can be executed via
23819 inferior function call. Any arguments provided to the call must match
23820 the function's prototype, and must be provided in the order specified
23823 For example, @code{some_val} is a @code{gdb.Value} instance
23824 representing a function that takes two integers as arguments. To
23825 execute this function, call it like so:
23828 result = some_val (10,20)
23831 Any values returned from a function call will be stored as a
23834 The following attributes are provided:
23836 @defvar Value.address
23837 If this object is addressable, this read-only attribute holds a
23838 @code{gdb.Value} object representing the address. Otherwise,
23839 this attribute holds @code{None}.
23842 @cindex optimized out value in Python
23843 @defvar Value.is_optimized_out
23844 This read-only boolean attribute is true if the compiler optimized out
23845 this value, thus it is not available for fetching from the inferior.
23849 The type of this @code{gdb.Value}. The value of this attribute is a
23850 @code{gdb.Type} object (@pxref{Types In Python}).
23853 @defvar Value.dynamic_type
23854 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
23855 type information (@acronym{RTTI}) to determine the dynamic type of the
23856 value. If this value is of class type, it will return the class in
23857 which the value is embedded, if any. If this value is of pointer or
23858 reference to a class type, it will compute the dynamic type of the
23859 referenced object, and return a pointer or reference to that type,
23860 respectively. In all other cases, it will return the value's static
23863 Note that this feature will only work when debugging a C@t{++} program
23864 that includes @acronym{RTTI} for the object in question. Otherwise,
23865 it will just return the static type of the value as in @kbd{ptype foo}
23866 (@pxref{Symbols, ptype}).
23869 @defvar Value.is_lazy
23870 The value of this read-only boolean attribute is @code{True} if this
23871 @code{gdb.Value} has not yet been fetched from the inferior.
23872 @value{GDBN} does not fetch values until necessary, for efficiency.
23876 myval = gdb.parse_and_eval ('somevar')
23879 The value of @code{somevar} is not fetched at this time. It will be
23880 fetched when the value is needed, or when the @code{fetch_lazy}
23884 The following methods are provided:
23886 @defun Value.__init__ (@var{val})
23887 Many Python values can be converted directly to a @code{gdb.Value} via
23888 this object initializer. Specifically:
23891 @item Python boolean
23892 A Python boolean is converted to the boolean type from the current
23895 @item Python integer
23896 A Python integer is converted to the C @code{long} type for the
23897 current architecture.
23900 A Python long is converted to the C @code{long long} type for the
23901 current architecture.
23904 A Python float is converted to the C @code{double} type for the
23905 current architecture.
23907 @item Python string
23908 A Python string is converted to a target string, using the current
23911 @item @code{gdb.Value}
23912 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
23914 @item @code{gdb.LazyString}
23915 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
23916 Python}), then the lazy string's @code{value} method is called, and
23917 its result is used.
23921 @defun Value.cast (type)
23922 Return a new instance of @code{gdb.Value} that is the result of
23923 casting this instance to the type described by @var{type}, which must
23924 be a @code{gdb.Type} object. If the cast cannot be performed for some
23925 reason, this method throws an exception.
23928 @defun Value.dereference ()
23929 For pointer data types, this method returns a new @code{gdb.Value} object
23930 whose contents is the object pointed to by the pointer. For example, if
23931 @code{foo} is a C pointer to an @code{int}, declared in your C program as
23938 then you can use the corresponding @code{gdb.Value} to access what
23939 @code{foo} points to like this:
23942 bar = foo.dereference ()
23945 The result @code{bar} will be a @code{gdb.Value} object holding the
23946 value pointed to by @code{foo}.
23948 A similar function @code{Value.referenced_value} exists which also
23949 returns @code{gdb.Value} objects corresonding to the values pointed to
23950 by pointer values (and additionally, values referenced by reference
23951 values). However, the behavior of @code{Value.dereference}
23952 differs from @code{Value.referenced_value} by the fact that the
23953 behavior of @code{Value.dereference} is identical to applying the C
23954 unary operator @code{*} on a given value. For example, consider a
23955 reference to a pointer @code{ptrref}, declared in your C@t{++} program
23959 typedef int *intptr;
23963 intptr &ptrref = ptr;
23966 Though @code{ptrref} is a reference value, one can apply the method
23967 @code{Value.dereference} to the @code{gdb.Value} object corresponding
23968 to it and obtain a @code{gdb.Value} which is identical to that
23969 corresponding to @code{val}. However, if you apply the method
23970 @code{Value.referenced_value}, the result would be a @code{gdb.Value}
23971 object identical to that corresponding to @code{ptr}.
23974 py_ptrref = gdb.parse_and_eval ("ptrref")
23975 py_val = py_ptrref.dereference ()
23976 py_ptr = py_ptrref.referenced_value ()
23979 The @code{gdb.Value} object @code{py_val} is identical to that
23980 corresponding to @code{val}, and @code{py_ptr} is identical to that
23981 corresponding to @code{ptr}. In general, @code{Value.dereference} can
23982 be applied whenever the C unary operator @code{*} can be applied
23983 to the corresponding C value. For those cases where applying both
23984 @code{Value.dereference} and @code{Value.referenced_value} is allowed,
23985 the results obtained need not be identical (as we have seen in the above
23986 example). The results are however identical when applied on
23987 @code{gdb.Value} objects corresponding to pointers (@code{gdb.Value}
23988 objects with type code @code{TYPE_CODE_PTR}) in a C/C@t{++} program.
23991 @defun Value.referenced_value ()
23992 For pointer or reference data types, this method returns a new
23993 @code{gdb.Value} object corresponding to the value referenced by the
23994 pointer/reference value. For pointer data types,
23995 @code{Value.dereference} and @code{Value.referenced_value} produce
23996 identical results. The difference between these methods is that
23997 @code{Value.dereference} cannot get the values referenced by reference
23998 values. For example, consider a reference to an @code{int}, declared
23999 in your C@t{++} program as
24007 then applying @code{Value.dereference} to the @code{gdb.Value} object
24008 corresponding to @code{ref} will result in an error, while applying
24009 @code{Value.referenced_value} will result in a @code{gdb.Value} object
24010 identical to that corresponding to @code{val}.
24013 py_ref = gdb.parse_and_eval ("ref")
24014 er_ref = py_ref.dereference () # Results in error
24015 py_val = py_ref.referenced_value () # Returns the referenced value
24018 The @code{gdb.Value} object @code{py_val} is identical to that
24019 corresponding to @code{val}.
24022 @defun Value.dynamic_cast (type)
24023 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
24024 operator were used. Consult a C@t{++} reference for details.
24027 @defun Value.reinterpret_cast (type)
24028 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
24029 operator were used. Consult a C@t{++} reference for details.
24032 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
24033 If this @code{gdb.Value} represents a string, then this method
24034 converts the contents to a Python string. Otherwise, this method will
24035 throw an exception.
24037 Strings are recognized in a language-specific way; whether a given
24038 @code{gdb.Value} represents a string is determined by the current
24041 For C-like languages, a value is a string if it is a pointer to or an
24042 array of characters or ints. The string is assumed to be terminated
24043 by a zero of the appropriate width. However if the optional length
24044 argument is given, the string will be converted to that given length,
24045 ignoring any embedded zeros that the string may contain.
24047 If the optional @var{encoding} argument is given, it must be a string
24048 naming the encoding of the string in the @code{gdb.Value}, such as
24049 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
24050 the same encodings as the corresponding argument to Python's
24051 @code{string.decode} method, and the Python codec machinery will be used
24052 to convert the string. If @var{encoding} is not given, or if
24053 @var{encoding} is the empty string, then either the @code{target-charset}
24054 (@pxref{Character Sets}) will be used, or a language-specific encoding
24055 will be used, if the current language is able to supply one.
24057 The optional @var{errors} argument is the same as the corresponding
24058 argument to Python's @code{string.decode} method.
24060 If the optional @var{length} argument is given, the string will be
24061 fetched and converted to the given length.
24064 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
24065 If this @code{gdb.Value} represents a string, then this method
24066 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
24067 In Python}). Otherwise, this method will throw an exception.
24069 If the optional @var{encoding} argument is given, it must be a string
24070 naming the encoding of the @code{gdb.LazyString}. Some examples are:
24071 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
24072 @var{encoding} argument is an encoding that @value{GDBN} does
24073 recognize, @value{GDBN} will raise an error.
24075 When a lazy string is printed, the @value{GDBN} encoding machinery is
24076 used to convert the string during printing. If the optional
24077 @var{encoding} argument is not provided, or is an empty string,
24078 @value{GDBN} will automatically select the encoding most suitable for
24079 the string type. For further information on encoding in @value{GDBN}
24080 please see @ref{Character Sets}.
24082 If the optional @var{length} argument is given, the string will be
24083 fetched and encoded to the length of characters specified. If
24084 the @var{length} argument is not provided, the string will be fetched
24085 and encoded until a null of appropriate width is found.
24088 @defun Value.fetch_lazy ()
24089 If the @code{gdb.Value} object is currently a lazy value
24090 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
24091 fetched from the inferior. Any errors that occur in the process
24092 will produce a Python exception.
24094 If the @code{gdb.Value} object is not a lazy value, this method
24097 This method does not return a value.
24101 @node Types In Python
24102 @subsubsection Types In Python
24103 @cindex types in Python
24104 @cindex Python, working with types
24107 @value{GDBN} represents types from the inferior using the class
24110 The following type-related functions are available in the @code{gdb}
24113 @findex gdb.lookup_type
24114 @defun gdb.lookup_type (name @r{[}, block@r{]})
24115 This function looks up a type by name. @var{name} is the name of the
24116 type to look up. It must be a string.
24118 If @var{block} is given, then @var{name} is looked up in that scope.
24119 Otherwise, it is searched for globally.
24121 Ordinarily, this function will return an instance of @code{gdb.Type}.
24122 If the named type cannot be found, it will throw an exception.
24125 If the type is a structure or class type, or an enum type, the fields
24126 of that type can be accessed using the Python @dfn{dictionary syntax}.
24127 For example, if @code{some_type} is a @code{gdb.Type} instance holding
24128 a structure type, you can access its @code{foo} field with:
24131 bar = some_type['foo']
24134 @code{bar} will be a @code{gdb.Field} object; see below under the
24135 description of the @code{Type.fields} method for a description of the
24136 @code{gdb.Field} class.
24138 An instance of @code{Type} has the following attributes:
24141 The type code for this type. The type code will be one of the
24142 @code{TYPE_CODE_} constants defined below.
24145 @defvar Type.sizeof
24146 The size of this type, in target @code{char} units. Usually, a
24147 target's @code{char} type will be an 8-bit byte. However, on some
24148 unusual platforms, this type may have a different size.
24152 The tag name for this type. The tag name is the name after
24153 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
24154 languages have this concept. If this type has no tag name, then
24155 @code{None} is returned.
24158 The following methods are provided:
24160 @defun Type.fields ()
24161 For structure and union types, this method returns the fields. Range
24162 types have two fields, the minimum and maximum values. Enum types
24163 have one field per enum constant. Function and method types have one
24164 field per parameter. The base types of C@t{++} classes are also
24165 represented as fields. If the type has no fields, or does not fit
24166 into one of these categories, an empty sequence will be returned.
24168 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
24171 This attribute is not available for @code{static} fields (as in
24172 C@t{++} or Java). For non-@code{static} fields, the value is the bit
24173 position of the field. For @code{enum} fields, the value is the
24174 enumeration member's integer representation.
24177 The name of the field, or @code{None} for anonymous fields.
24180 This is @code{True} if the field is artificial, usually meaning that
24181 it was provided by the compiler and not the user. This attribute is
24182 always provided, and is @code{False} if the field is not artificial.
24184 @item is_base_class
24185 This is @code{True} if the field represents a base class of a C@t{++}
24186 structure. This attribute is always provided, and is @code{False}
24187 if the field is not a base class of the type that is the argument of
24188 @code{fields}, or if that type was not a C@t{++} class.
24191 If the field is packed, or is a bitfield, then this will have a
24192 non-zero value, which is the size of the field in bits. Otherwise,
24193 this will be zero; in this case the field's size is given by its type.
24196 The type of the field. This is usually an instance of @code{Type},
24197 but it can be @code{None} in some situations.
24201 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
24202 Return a new @code{gdb.Type} object which represents an array of this
24203 type. If one argument is given, it is the inclusive upper bound of
24204 the array; in this case the lower bound is zero. If two arguments are
24205 given, the first argument is the lower bound of the array, and the
24206 second argument is the upper bound of the array. An array's length
24207 must not be negative, but the bounds can be.
24210 @defun Type.vector (@var{n1} @r{[}, @var{n2}@r{]})
24211 Return a new @code{gdb.Type} object which represents a vector of this
24212 type. If one argument is given, it is the inclusive upper bound of
24213 the vector; in this case the lower bound is zero. If two arguments are
24214 given, the first argument is the lower bound of the vector, and the
24215 second argument is the upper bound of the vector. A vector's length
24216 must not be negative, but the bounds can be.
24218 The difference between an @code{array} and a @code{vector} is that
24219 arrays behave like in C: when used in expressions they decay to a pointer
24220 to the first element whereas vectors are treated as first class values.
24223 @defun Type.const ()
24224 Return a new @code{gdb.Type} object which represents a
24225 @code{const}-qualified variant of this type.
24228 @defun Type.volatile ()
24229 Return a new @code{gdb.Type} object which represents a
24230 @code{volatile}-qualified variant of this type.
24233 @defun Type.unqualified ()
24234 Return a new @code{gdb.Type} object which represents an unqualified
24235 variant of this type. That is, the result is neither @code{const} nor
24239 @defun Type.range ()
24240 Return a Python @code{Tuple} object that contains two elements: the
24241 low bound of the argument type and the high bound of that type. If
24242 the type does not have a range, @value{GDBN} will raise a
24243 @code{gdb.error} exception (@pxref{Exception Handling}).
24246 @defun Type.reference ()
24247 Return a new @code{gdb.Type} object which represents a reference to this
24251 @defun Type.pointer ()
24252 Return a new @code{gdb.Type} object which represents a pointer to this
24256 @defun Type.strip_typedefs ()
24257 Return a new @code{gdb.Type} that represents the real type,
24258 after removing all layers of typedefs.
24261 @defun Type.target ()
24262 Return a new @code{gdb.Type} object which represents the target type
24265 For a pointer type, the target type is the type of the pointed-to
24266 object. For an array type (meaning C-like arrays), the target type is
24267 the type of the elements of the array. For a function or method type,
24268 the target type is the type of the return value. For a complex type,
24269 the target type is the type of the elements. For a typedef, the
24270 target type is the aliased type.
24272 If the type does not have a target, this method will throw an
24276 @defun Type.template_argument (n @r{[}, block@r{]})
24277 If this @code{gdb.Type} is an instantiation of a template, this will
24278 return a new @code{gdb.Type} which represents the type of the
24279 @var{n}th template argument.
24281 If this @code{gdb.Type} is not a template type, this will throw an
24282 exception. Ordinarily, only C@t{++} code will have template types.
24284 If @var{block} is given, then @var{name} is looked up in that scope.
24285 Otherwise, it is searched for globally.
24289 Each type has a code, which indicates what category this type falls
24290 into. The available type categories are represented by constants
24291 defined in the @code{gdb} module:
24294 @findex TYPE_CODE_PTR
24295 @findex gdb.TYPE_CODE_PTR
24296 @item gdb.TYPE_CODE_PTR
24297 The type is a pointer.
24299 @findex TYPE_CODE_ARRAY
24300 @findex gdb.TYPE_CODE_ARRAY
24301 @item gdb.TYPE_CODE_ARRAY
24302 The type is an array.
24304 @findex TYPE_CODE_STRUCT
24305 @findex gdb.TYPE_CODE_STRUCT
24306 @item gdb.TYPE_CODE_STRUCT
24307 The type is a structure.
24309 @findex TYPE_CODE_UNION
24310 @findex gdb.TYPE_CODE_UNION
24311 @item gdb.TYPE_CODE_UNION
24312 The type is a union.
24314 @findex TYPE_CODE_ENUM
24315 @findex gdb.TYPE_CODE_ENUM
24316 @item gdb.TYPE_CODE_ENUM
24317 The type is an enum.
24319 @findex TYPE_CODE_FLAGS
24320 @findex gdb.TYPE_CODE_FLAGS
24321 @item gdb.TYPE_CODE_FLAGS
24322 A bit flags type, used for things such as status registers.
24324 @findex TYPE_CODE_FUNC
24325 @findex gdb.TYPE_CODE_FUNC
24326 @item gdb.TYPE_CODE_FUNC
24327 The type is a function.
24329 @findex TYPE_CODE_INT
24330 @findex gdb.TYPE_CODE_INT
24331 @item gdb.TYPE_CODE_INT
24332 The type is an integer type.
24334 @findex TYPE_CODE_FLT
24335 @findex gdb.TYPE_CODE_FLT
24336 @item gdb.TYPE_CODE_FLT
24337 A floating point type.
24339 @findex TYPE_CODE_VOID
24340 @findex gdb.TYPE_CODE_VOID
24341 @item gdb.TYPE_CODE_VOID
24342 The special type @code{void}.
24344 @findex TYPE_CODE_SET
24345 @findex gdb.TYPE_CODE_SET
24346 @item gdb.TYPE_CODE_SET
24349 @findex TYPE_CODE_RANGE
24350 @findex gdb.TYPE_CODE_RANGE
24351 @item gdb.TYPE_CODE_RANGE
24352 A range type, that is, an integer type with bounds.
24354 @findex TYPE_CODE_STRING
24355 @findex gdb.TYPE_CODE_STRING
24356 @item gdb.TYPE_CODE_STRING
24357 A string type. Note that this is only used for certain languages with
24358 language-defined string types; C strings are not represented this way.
24360 @findex TYPE_CODE_BITSTRING
24361 @findex gdb.TYPE_CODE_BITSTRING
24362 @item gdb.TYPE_CODE_BITSTRING
24363 A string of bits. It is deprecated.
24365 @findex TYPE_CODE_ERROR
24366 @findex gdb.TYPE_CODE_ERROR
24367 @item gdb.TYPE_CODE_ERROR
24368 An unknown or erroneous type.
24370 @findex TYPE_CODE_METHOD
24371 @findex gdb.TYPE_CODE_METHOD
24372 @item gdb.TYPE_CODE_METHOD
24373 A method type, as found in C@t{++} or Java.
24375 @findex TYPE_CODE_METHODPTR
24376 @findex gdb.TYPE_CODE_METHODPTR
24377 @item gdb.TYPE_CODE_METHODPTR
24378 A pointer-to-member-function.
24380 @findex TYPE_CODE_MEMBERPTR
24381 @findex gdb.TYPE_CODE_MEMBERPTR
24382 @item gdb.TYPE_CODE_MEMBERPTR
24383 A pointer-to-member.
24385 @findex TYPE_CODE_REF
24386 @findex gdb.TYPE_CODE_REF
24387 @item gdb.TYPE_CODE_REF
24390 @findex TYPE_CODE_CHAR
24391 @findex gdb.TYPE_CODE_CHAR
24392 @item gdb.TYPE_CODE_CHAR
24395 @findex TYPE_CODE_BOOL
24396 @findex gdb.TYPE_CODE_BOOL
24397 @item gdb.TYPE_CODE_BOOL
24400 @findex TYPE_CODE_COMPLEX
24401 @findex gdb.TYPE_CODE_COMPLEX
24402 @item gdb.TYPE_CODE_COMPLEX
24403 A complex float type.
24405 @findex TYPE_CODE_TYPEDEF
24406 @findex gdb.TYPE_CODE_TYPEDEF
24407 @item gdb.TYPE_CODE_TYPEDEF
24408 A typedef to some other type.
24410 @findex TYPE_CODE_NAMESPACE
24411 @findex gdb.TYPE_CODE_NAMESPACE
24412 @item gdb.TYPE_CODE_NAMESPACE
24413 A C@t{++} namespace.
24415 @findex TYPE_CODE_DECFLOAT
24416 @findex gdb.TYPE_CODE_DECFLOAT
24417 @item gdb.TYPE_CODE_DECFLOAT
24418 A decimal floating point type.
24420 @findex TYPE_CODE_INTERNAL_FUNCTION
24421 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
24422 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
24423 A function internal to @value{GDBN}. This is the type used to represent
24424 convenience functions.
24427 Further support for types is provided in the @code{gdb.types}
24428 Python module (@pxref{gdb.types}).
24430 @node Pretty Printing API
24431 @subsubsection Pretty Printing API
24433 An example output is provided (@pxref{Pretty Printing}).
24435 A pretty-printer is just an object that holds a value and implements a
24436 specific interface, defined here.
24438 @defun pretty_printer.children (self)
24439 @value{GDBN} will call this method on a pretty-printer to compute the
24440 children of the pretty-printer's value.
24442 This method must return an object conforming to the Python iterator
24443 protocol. Each item returned by the iterator must be a tuple holding
24444 two elements. The first element is the ``name'' of the child; the
24445 second element is the child's value. The value can be any Python
24446 object which is convertible to a @value{GDBN} value.
24448 This method is optional. If it does not exist, @value{GDBN} will act
24449 as though the value has no children.
24452 @defun pretty_printer.display_hint (self)
24453 The CLI may call this method and use its result to change the
24454 formatting of a value. The result will also be supplied to an MI
24455 consumer as a @samp{displayhint} attribute of the variable being
24458 This method is optional. If it does exist, this method must return a
24461 Some display hints are predefined by @value{GDBN}:
24465 Indicate that the object being printed is ``array-like''. The CLI
24466 uses this to respect parameters such as @code{set print elements} and
24467 @code{set print array}.
24470 Indicate that the object being printed is ``map-like'', and that the
24471 children of this value can be assumed to alternate between keys and
24475 Indicate that the object being printed is ``string-like''. If the
24476 printer's @code{to_string} method returns a Python string of some
24477 kind, then @value{GDBN} will call its internal language-specific
24478 string-printing function to format the string. For the CLI this means
24479 adding quotation marks, possibly escaping some characters, respecting
24480 @code{set print elements}, and the like.
24484 @defun pretty_printer.to_string (self)
24485 @value{GDBN} will call this method to display the string
24486 representation of the value passed to the object's constructor.
24488 When printing from the CLI, if the @code{to_string} method exists,
24489 then @value{GDBN} will prepend its result to the values returned by
24490 @code{children}. Exactly how this formatting is done is dependent on
24491 the display hint, and may change as more hints are added. Also,
24492 depending on the print settings (@pxref{Print Settings}), the CLI may
24493 print just the result of @code{to_string} in a stack trace, omitting
24494 the result of @code{children}.
24496 If this method returns a string, it is printed verbatim.
24498 Otherwise, if this method returns an instance of @code{gdb.Value},
24499 then @value{GDBN} prints this value. This may result in a call to
24500 another pretty-printer.
24502 If instead the method returns a Python value which is convertible to a
24503 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
24504 the resulting value. Again, this may result in a call to another
24505 pretty-printer. Python scalars (integers, floats, and booleans) and
24506 strings are convertible to @code{gdb.Value}; other types are not.
24508 Finally, if this method returns @code{None} then no further operations
24509 are peformed in this method and nothing is printed.
24511 If the result is not one of these types, an exception is raised.
24514 @value{GDBN} provides a function which can be used to look up the
24515 default pretty-printer for a @code{gdb.Value}:
24517 @findex gdb.default_visualizer
24518 @defun gdb.default_visualizer (value)
24519 This function takes a @code{gdb.Value} object as an argument. If a
24520 pretty-printer for this value exists, then it is returned. If no such
24521 printer exists, then this returns @code{None}.
24524 @node Selecting Pretty-Printers
24525 @subsubsection Selecting Pretty-Printers
24527 The Python list @code{gdb.pretty_printers} contains an array of
24528 functions or callable objects that have been registered via addition
24529 as a pretty-printer. Printers in this list are called @code{global}
24530 printers, they're available when debugging all inferiors.
24531 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
24532 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
24535 Each function on these lists is passed a single @code{gdb.Value}
24536 argument and should return a pretty-printer object conforming to the
24537 interface definition above (@pxref{Pretty Printing API}). If a function
24538 cannot create a pretty-printer for the value, it should return
24541 @value{GDBN} first checks the @code{pretty_printers} attribute of each
24542 @code{gdb.Objfile} in the current program space and iteratively calls
24543 each enabled lookup routine in the list for that @code{gdb.Objfile}
24544 until it receives a pretty-printer object.
24545 If no pretty-printer is found in the objfile lists, @value{GDBN} then
24546 searches the pretty-printer list of the current program space,
24547 calling each enabled function until an object is returned.
24548 After these lists have been exhausted, it tries the global
24549 @code{gdb.pretty_printers} list, again calling each enabled function until an
24550 object is returned.
24552 The order in which the objfiles are searched is not specified. For a
24553 given list, functions are always invoked from the head of the list,
24554 and iterated over sequentially until the end of the list, or a printer
24555 object is returned.
24557 For various reasons a pretty-printer may not work.
24558 For example, the underlying data structure may have changed and
24559 the pretty-printer is out of date.
24561 The consequences of a broken pretty-printer are severe enough that
24562 @value{GDBN} provides support for enabling and disabling individual
24563 printers. For example, if @code{print frame-arguments} is on,
24564 a backtrace can become highly illegible if any argument is printed
24565 with a broken printer.
24567 Pretty-printers are enabled and disabled by attaching an @code{enabled}
24568 attribute to the registered function or callable object. If this attribute
24569 is present and its value is @code{False}, the printer is disabled, otherwise
24570 the printer is enabled.
24572 @node Writing a Pretty-Printer
24573 @subsubsection Writing a Pretty-Printer
24574 @cindex writing a pretty-printer
24576 A pretty-printer consists of two parts: a lookup function to detect
24577 if the type is supported, and the printer itself.
24579 Here is an example showing how a @code{std::string} printer might be
24580 written. @xref{Pretty Printing API}, for details on the API this class
24584 class StdStringPrinter(object):
24585 "Print a std::string"
24587 def __init__(self, val):
24590 def to_string(self):
24591 return self.val['_M_dataplus']['_M_p']
24593 def display_hint(self):
24597 And here is an example showing how a lookup function for the printer
24598 example above might be written.
24601 def str_lookup_function(val):
24602 lookup_tag = val.type.tag
24603 if lookup_tag == None:
24605 regex = re.compile("^std::basic_string<char,.*>$")
24606 if regex.match(lookup_tag):
24607 return StdStringPrinter(val)
24611 The example lookup function extracts the value's type, and attempts to
24612 match it to a type that it can pretty-print. If it is a type the
24613 printer can pretty-print, it will return a printer object. If not, it
24614 returns @code{None}.
24616 We recommend that you put your core pretty-printers into a Python
24617 package. If your pretty-printers are for use with a library, we
24618 further recommend embedding a version number into the package name.
24619 This practice will enable @value{GDBN} to load multiple versions of
24620 your pretty-printers at the same time, because they will have
24623 You should write auto-loaded code (@pxref{Python Auto-loading}) such that it
24624 can be evaluated multiple times without changing its meaning. An
24625 ideal auto-load file will consist solely of @code{import}s of your
24626 printer modules, followed by a call to a register pretty-printers with
24627 the current objfile.
24629 Taken as a whole, this approach will scale nicely to multiple
24630 inferiors, each potentially using a different library version.
24631 Embedding a version number in the Python package name will ensure that
24632 @value{GDBN} is able to load both sets of printers simultaneously.
24633 Then, because the search for pretty-printers is done by objfile, and
24634 because your auto-loaded code took care to register your library's
24635 printers with a specific objfile, @value{GDBN} will find the correct
24636 printers for the specific version of the library used by each
24639 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
24640 this code might appear in @code{gdb.libstdcxx.v6}:
24643 def register_printers(objfile):
24644 objfile.pretty_printers.append(str_lookup_function)
24648 And then the corresponding contents of the auto-load file would be:
24651 import gdb.libstdcxx.v6
24652 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
24655 The previous example illustrates a basic pretty-printer.
24656 There are a few things that can be improved on.
24657 The printer doesn't have a name, making it hard to identify in a
24658 list of installed printers. The lookup function has a name, but
24659 lookup functions can have arbitrary, even identical, names.
24661 Second, the printer only handles one type, whereas a library typically has
24662 several types. One could install a lookup function for each desired type
24663 in the library, but one could also have a single lookup function recognize
24664 several types. The latter is the conventional way this is handled.
24665 If a pretty-printer can handle multiple data types, then its
24666 @dfn{subprinters} are the printers for the individual data types.
24668 The @code{gdb.printing} module provides a formal way of solving these
24669 problems (@pxref{gdb.printing}).
24670 Here is another example that handles multiple types.
24672 These are the types we are going to pretty-print:
24675 struct foo @{ int a, b; @};
24676 struct bar @{ struct foo x, y; @};
24679 Here are the printers:
24683 """Print a foo object."""
24685 def __init__(self, val):
24688 def to_string(self):
24689 return ("a=<" + str(self.val["a"]) +
24690 "> b=<" + str(self.val["b"]) + ">")
24693 """Print a bar object."""
24695 def __init__(self, val):
24698 def to_string(self):
24699 return ("x=<" + str(self.val["x"]) +
24700 "> y=<" + str(self.val["y"]) + ">")
24703 This example doesn't need a lookup function, that is handled by the
24704 @code{gdb.printing} module. Instead a function is provided to build up
24705 the object that handles the lookup.
24708 import gdb.printing
24710 def build_pretty_printer():
24711 pp = gdb.printing.RegexpCollectionPrettyPrinter(
24713 pp.add_printer('foo', '^foo$', fooPrinter)
24714 pp.add_printer('bar', '^bar$', barPrinter)
24718 And here is the autoload support:
24721 import gdb.printing
24723 gdb.printing.register_pretty_printer(
24724 gdb.current_objfile(),
24725 my_library.build_pretty_printer())
24728 Finally, when this printer is loaded into @value{GDBN}, here is the
24729 corresponding output of @samp{info pretty-printer}:
24732 (gdb) info pretty-printer
24739 @node Type Printing API
24740 @subsubsection Type Printing API
24741 @cindex type printing API for Python
24743 @value{GDBN} provides a way for Python code to customize type display.
24744 This is mainly useful for substituting canonical typedef names for
24747 @cindex type printer
24748 A @dfn{type printer} is just a Python object conforming to a certain
24749 protocol. A simple base class implementing the protocol is provided;
24750 see @ref{gdb.types}. A type printer must supply at least:
24752 @defivar type_printer enabled
24753 A boolean which is True if the printer is enabled, and False
24754 otherwise. This is manipulated by the @code{enable type-printer}
24755 and @code{disable type-printer} commands.
24758 @defivar type_printer name
24759 The name of the type printer. This must be a string. This is used by
24760 the @code{enable type-printer} and @code{disable type-printer}
24764 @defmethod type_printer instantiate (self)
24765 This is called by @value{GDBN} at the start of type-printing. It is
24766 only called if the type printer is enabled. This method must return a
24767 new object that supplies a @code{recognize} method, as described below.
24771 When displaying a type, say via the @code{ptype} command, @value{GDBN}
24772 will compute a list of type recognizers. This is done by iterating
24773 first over the per-objfile type printers (@pxref{Objfiles In Python}),
24774 followed by the per-progspace type printers (@pxref{Progspaces In
24775 Python}), and finally the global type printers.
24777 @value{GDBN} will call the @code{instantiate} method of each enabled
24778 type printer. If this method returns @code{None}, then the result is
24779 ignored; otherwise, it is appended to the list of recognizers.
24781 Then, when @value{GDBN} is going to display a type name, it iterates
24782 over the list of recognizers. For each one, it calls the recognition
24783 function, stopping if the function returns a non-@code{None} value.
24784 The recognition function is defined as:
24786 @defmethod type_recognizer recognize (self, type)
24787 If @var{type} is not recognized, return @code{None}. Otherwise,
24788 return a string which is to be printed as the name of @var{type}.
24789 @var{type} will be an instance of @code{gdb.Type} (@pxref{Types In
24793 @value{GDBN} uses this two-pass approach so that type printers can
24794 efficiently cache information without holding on to it too long. For
24795 example, it can be convenient to look up type information in a type
24796 printer and hold it for a recognizer's lifetime; if a single pass were
24797 done then type printers would have to make use of the event system in
24798 order to avoid holding information that could become stale as the
24801 @node Frame Filter API
24802 @subsubsection Filtering Frames.
24803 @cindex frame filters api
24805 Frame filters are Python objects that manipulate the visibility of a
24806 frame or frames when a backtrace (@pxref{Backtrace}) is printed by
24809 Only commands that print a backtrace, or, in the case of @sc{gdb/mi}
24810 commands (@pxref{GDB/MI}), those that return a collection of frames
24811 are affected. The commands that work with frame filters are:
24813 @code{backtrace} (@pxref{backtrace-command,, The backtrace command}),
24814 @code{-stack-list-frames}
24815 (@pxref{-stack-list-frames,, The -stack-list-frames command}),
24816 @code{-stack-list-variables} (@pxref{-stack-list-variables,, The
24817 -stack-list-variables command}), @code{-stack-list-arguments}
24818 @pxref{-stack-list-arguments,, The -stack-list-arguments command}) and
24819 @code{-stack-list-locals} (@pxref{-stack-list-locals,, The
24820 -stack-list-locals command}).
24822 A frame filter works by taking an iterator as an argument, applying
24823 actions to the contents of that iterator, and returning another
24824 iterator (or, possibly, the same iterator it was provided in the case
24825 where the filter does not perform any operations). Typically, frame
24826 filters utilize tools such as the Python's @code{itertools} module to
24827 work with and create new iterators from the source iterator.
24828 Regardless of how a filter chooses to apply actions, it must not alter
24829 the underlying @value{GDBN} frame or frames, or attempt to alter the
24830 call-stack within @value{GDBN}. This preserves data integrity within
24831 @value{GDBN}. Frame filters are executed on a priority basis and care
24832 should be taken that some frame filters may have been executed before,
24833 and that some frame filters will be executed after.
24835 An important consideration when designing frame filters, and well
24836 worth reflecting upon, is that frame filters should avoid unwinding
24837 the call stack if possible. Some stacks can run very deep, into the
24838 tens of thousands in some cases. To search every frame when a frame
24839 filter executes may be too expensive at that step. The frame filter
24840 cannot know how many frames it has to iterate over, and it may have to
24841 iterate through them all. This ends up duplicating effort as
24842 @value{GDBN} performs this iteration when it prints the frames. If
24843 the filter can defer unwinding frames until frame decorators are
24844 executed, after the last filter has executed, it should. @xref{Frame
24845 Decorator API}, for more information on decorators. Also, there are
24846 examples for both frame decorators and filters in later chapters.
24847 @xref{Writing a Frame Filter}, for more information.
24849 The Python dictionary @code{gdb.frame_filters} contains key/object
24850 pairings that comprise a frame filter. Frame filters in this
24851 dictionary are called @code{global} frame filters, and they are
24852 available when debugging all inferiors. These frame filters must
24853 register with the dictionary directly. In addition to the
24854 @code{global} dictionary, there are other dictionaries that are loaded
24855 with different inferiors via auto-loading (@pxref{Python
24856 Auto-loading}). The two other areas where frame filter dictionaries
24857 can be found are: @code{gdb.Progspace} which contains a
24858 @code{frame_filters} dictionary attribute, and each @code{gdb.Objfile}
24859 object which also contains a @code{frame_filters} dictionary
24862 When a command is executed from @value{GDBN} that is compatible with
24863 frame filters, @value{GDBN} combines the @code{global},
24864 @code{gdb.Progspace} and all @code{gdb.Objfile} dictionaries currently
24865 loaded. All of the @code{gdb.Objfile} dictionaries are combined, as
24866 several frames, and thus several object files, might be in use.
24867 @value{GDBN} then prunes any frame filter whose @code{enabled}
24868 attribute is @code{False}. This pruned list is then sorted according
24869 to the @code{priority} attribute in each filter.
24871 Once the dictionaries are combined, pruned and sorted, @value{GDBN}
24872 creates an iterator which wraps each frame in the call stack in a
24873 @code{FrameDecorator} object, and calls each filter in order. The
24874 output from the previous filter will always be the input to the next
24877 Frame filters have a mandatory interface which each frame filter must
24878 implement, defined here:
24880 @defun FrameFilter.filter (iterator)
24881 @value{GDBN} will call this method on a frame filter when it has
24882 reached the order in the priority list for that filter.
24884 For example, if there are four frame filters:
24895 The order that the frame filters will be called is:
24898 Filter3 -> Filter2 -> Filter1 -> Filter4
24901 Note that the output from @code{Filter3} is passed to the input of
24902 @code{Filter2}, and so on.
24904 This @code{filter} method is passed a Python iterator. This iterator
24905 contains a sequence of frame decorators that wrap each
24906 @code{gdb.Frame}, or a frame decorator that wraps another frame
24907 decorator. The first filter that is executed in the sequence of frame
24908 filters will receive an iterator entirely comprised of default
24909 @code{FrameDecorator} objects. However, after each frame filter is
24910 executed, the previous frame filter may have wrapped some or all of
24911 the frame decorators with their own frame decorator. As frame
24912 decorators must also conform to a mandatory interface, these
24913 decorators can be assumed to act in a uniform manner (@pxref{Frame
24916 This method must return an object conforming to the Python iterator
24917 protocol. Each item in the iterator must be an object conforming to
24918 the frame decorator interface. If a frame filter does not wish to
24919 perform any operations on this iterator, it should return that
24920 iterator untouched.
24922 This method is not optional. If it does not exist, @value{GDBN} will
24923 raise and print an error.
24926 @defvar FrameFilter.name
24927 The @code{name} attribute must be Python string which contains the
24928 name of the filter displayed by @value{GDBN} (@pxref{Frame Filter
24929 Management}). This attribute may contain any combination of letters
24930 or numbers. Care should be taken to ensure that it is unique. This
24931 attribute is mandatory.
24934 @defvar FrameFilter.enabled
24935 The @code{enabled} attribute must be Python boolean. This attribute
24936 indicates to @value{GDBN} whether the frame filter is enabled, and
24937 should be considered when frame filters are executed. If
24938 @code{enabled} is @code{True}, then the frame filter will be executed
24939 when any of the backtrace commands detailed earlier in this chapter
24940 are executed. If @code{enabled} is @code{False}, then the frame
24941 filter will not be executed. This attribute is mandatory.
24944 @defvar FrameFilter.priority
24945 The @code{priority} attribute must be Python integer. This attribute
24946 controls the order of execution in relation to other frame filters.
24947 There are no imposed limits on the range of @code{priority} other than
24948 it must be a valid integer. The higher the @code{priority} attribute,
24949 the sooner the frame filter will be executed in relation to other
24950 frame filters. Although @code{priority} can be negative, it is
24951 recommended practice to assume zero is the lowest priority that a
24952 frame filter can be assigned. Frame filters that have the same
24953 priority are executed in unsorted order in that priority slot. This
24954 attribute is mandatory.
24957 @node Frame Decorator API
24958 @subsubsection Decorating Frames.
24959 @cindex frame decorator api
24961 Frame decorators are sister objects to frame filters (@pxref{Frame
24962 Filter API}). Frame decorators are applied by a frame filter and can
24963 only be used in conjunction with frame filters.
24965 The purpose of a frame decorator is to customize the printed content
24966 of each @code{gdb.Frame} in commands where frame filters are executed.
24967 This concept is called decorating a frame. Frame decorators decorate
24968 a @code{gdb.Frame} with Python code contained within each API call.
24969 This separates the actual data contained in a @code{gdb.Frame} from
24970 the decorated data produced by a frame decorator. This abstraction is
24971 necessary to maintain integrity of the data contained in each
24974 Frame decorators have a mandatory interface, defined below.
24976 @value{GDBN} already contains a frame decorator called
24977 @code{FrameDecorator}. This contains substantial amounts of
24978 boilerplate code to decorate the content of a @code{gdb.Frame}. It is
24979 recommended that other frame decorators inherit and extend this
24980 object, and only to override the methods needed.
24982 @defun FrameDecorator.elided (self)
24984 The @code{elided} method groups frames together in a hierarchical
24985 system. An example would be an interpreter, where multiple low-level
24986 frames make up a single call in the interpreted language. In this
24987 example, the frame filter would elide the low-level frames and present
24988 a single high-level frame, representing the call in the interpreted
24989 language, to the user.
24991 The @code{elided} function must return an iterable and this iterable
24992 must contain the frames that are being elided wrapped in a suitable
24993 frame decorator. If no frames are being elided this function may
24994 return an empty iterable, or @code{None}. Elided frames are indented
24995 from normal frames in a @code{CLI} backtrace, or in the case of
24996 @code{GDB/MI}, are placed in the @code{children} field of the eliding
24999 It is the frame filter's task to also filter out the elided frames from
25000 the source iterator. This will avoid printing the frame twice.
25003 @defun FrameDecorator.function (self)
25005 This method returns the name of the function in the frame that is to
25008 This method must return a Python string describing the function, or
25011 If this function returns @code{None}, @value{GDBN} will not print any
25012 data for this field.
25015 @defun FrameDecorator.address (self)
25017 This method returns the address of the frame that is to be printed.
25019 This method must return a Python numeric integer type of sufficient
25020 size to describe the address of the frame, or @code{None}.
25022 If this function returns a @code{None}, @value{GDBN} will not print
25023 any data for this field.
25026 @defun FrameDecorator.filename (self)
25028 This method returns the filename and path associated with this frame.
25030 This method must return a Python string containing the filename and
25031 the path to the object file backing the frame, or @code{None}.
25033 If this function returns a @code{None}, @value{GDBN} will not print
25034 any data for this field.
25037 @defun FrameDecorator.line (self):
25039 This method returns the line number associated with the current
25040 position within the function addressed by this frame.
25042 This method must return a Python integer type, or @code{None}.
25044 If this function returns a @code{None}, @value{GDBN} will not print
25045 any data for this field.
25048 @defun FrameDecorator.frame_args (self)
25049 @anchor{frame_args}
25051 This method must return an iterable, or @code{None}. Returning an
25052 empty iterable, or @code{None} means frame arguments will not be
25053 printed for this frame. This iterable must contain objects that
25054 implement two methods, described here.
25056 This object must implement a @code{argument} method which takes a
25057 single @code{self} parameter and must return a @code{gdb.Symbol}
25058 (@pxref{Symbols In Python}), or a Python string. The object must also
25059 implement a @code{value} method which takes a single @code{self}
25060 parameter and must return a @code{gdb.Value} (@pxref{Values From
25061 Inferior}), a Python value, or @code{None}. If the @code{value}
25062 method returns @code{None}, and the @code{argument} method returns a
25063 @code{gdb.Symbol}, @value{GDBN} will look-up and print the value of
25064 the @code{gdb.Symbol} automatically.
25069 class SymValueWrapper():
25071 def __init__(self, symbol, value):
25081 class SomeFrameDecorator()
25084 def frame_args(self):
25087 block = self.inferior_frame.block()
25091 # Iterate over all symbols in a block. Only add
25092 # symbols that are arguments.
25094 if not sym.is_argument:
25096 args.append(SymValueWrapper(sym,None))
25098 # Add example synthetic argument.
25099 args.append(SymValueWrapper(``foo'', 42))
25105 @defun FrameDecorator.frame_locals (self)
25107 This method must return an iterable or @code{None}. Returning an
25108 empty iterable, or @code{None} means frame local arguments will not be
25109 printed for this frame.
25111 The object interface, the description of the various strategies for
25112 reading frame locals, and the example are largely similar to those
25113 described in the @code{frame_args} function, (@pxref{frame_args,,The
25114 frame filter frame_args function}). Below is a modified example:
25117 class SomeFrameDecorator()
25120 def frame_locals(self):
25123 block = self.inferior_frame.block()
25127 # Iterate over all symbols in a block. Add all
25128 # symbols, except arguments.
25130 if sym.is_argument:
25132 vars.append(SymValueWrapper(sym,None))
25134 # Add an example of a synthetic local variable.
25135 vars.append(SymValueWrapper(``bar'', 99))
25141 @defun FrameDecorator.inferior_frame (self):
25143 This method must return the underlying @code{gdb.Frame} that this
25144 frame decorator is decorating. @value{GDBN} requires the underlying
25145 frame for internal frame information to determine how to print certain
25146 values when printing a frame.
25149 @node Writing a Frame Filter
25150 @subsubsection Writing a Frame Filter
25151 @cindex writing a frame filter
25153 There are three basic elements that a frame filter must implement: it
25154 must correctly implement the documented interface (@pxref{Frame Filter
25155 API}), it must register itself with @value{GDBN}, and finally, it must
25156 decide if it is to work on the data provided by @value{GDBN}. In all
25157 cases, whether it works on the iterator or not, each frame filter must
25158 return an iterator. A bare-bones frame filter follows the pattern in
25159 the following example.
25164 class FrameFilter():
25166 def __init__(self):
25167 # Frame filter attribute creation.
25169 # 'name' is the name of the filter that GDB will display.
25171 # 'priority' is the priority of the filter relative to other
25174 # 'enabled' is a boolean that indicates whether this filter is
25175 # enabled and should be executed.
25178 self.priority = 100
25179 self.enabled = True
25181 # Register this frame filter with the global frame_filters
25183 gdb.frame_filters[self.name] = self
25185 def filter(self, frame_iter):
25186 # Just return the iterator.
25190 The frame filter in the example above implements the three
25191 requirements for all frame filters. It implements the API, self
25192 registers, and makes a decision on the iterator (in this case, it just
25193 returns the iterator untouched).
25195 The first step is attribute creation and assignment, and as shown in
25196 the comments the filter assigns the following attributes: @code{name},
25197 @code{priority} and whether the filter should be enabled with the
25198 @code{enabled} attribute.
25200 The second step is registering the frame filter with the dictionary or
25201 dictionaries that the frame filter has interest in. As shown in the
25202 comments, this filter just registers itself with the global dictionary
25203 @code{gdb.frame_filters}. As noted earlier, @code{gdb.frame_filters}
25204 is a dictionary that is initialized in the @code{gdb} module when
25205 @value{GDBN} starts. What dictionary a filter registers with is an
25206 important consideration. Generally, if a filter is specific to a set
25207 of code, it should be registered either in the @code{objfile} or
25208 @code{progspace} dictionaries as they are specific to the program
25209 currently loaded in @value{GDBN}. The global dictionary is always
25210 present in @value{GDBN} and is never unloaded. Any filters registered
25211 with the global dictionary will exist until @value{GDBN} exits. To
25212 avoid filters that may conflict, it is generally better to register
25213 frame filters against the dictionaries that more closely align with
25214 the usage of the filter currently in question. @xref{Python
25215 Auto-loading}, for further information on auto-loading Python scripts.
25217 @value{GDBN} takes a hands-off approach to frame filter registration,
25218 therefore it is the frame filter's responsibility to ensure
25219 registration has occurred, and that any exceptions are handled
25220 appropriately. In particular, you may wish to handle exceptions
25221 relating to Python dictionary key uniqueness. It is mandatory that
25222 the dictionary key is the same as frame filter's @code{name}
25223 attribute. When a user manages frame filters (@pxref{Frame Filter
25224 Management}), the names @value{GDBN} will display are those contained
25225 in the @code{name} attribute.
25227 The final step of this example is the implementation of the
25228 @code{filter} method. As shown in the example comments, we define the
25229 @code{filter} method and note that the method must take an iterator,
25230 and also must return an iterator. In this bare-bones example, the
25231 frame filter is not very useful as it just returns the iterator
25232 untouched. However this is a valid operation for frame filters that
25233 have the @code{enabled} attribute set, but decide not to operate on
25236 In the next example, the frame filter operates on all frames and
25237 utilizes a frame decorator to perform some work on the frames.
25238 @xref{Frame Decorator API}, for further information on the frame
25239 decorator interface.
25241 This example works on inlined frames. It highlights frames which are
25242 inlined by tagging them with an ``[inlined]'' tag. By applying a
25243 frame decorator to all frames with the Python @code{itertools imap}
25244 method, the example defers actions to the frame decorator. Frame
25245 decorators are only processed when @value{GDBN} prints the backtrace.
25247 This introduces a new decision making topic: whether to perform
25248 decision making operations at the filtering step, or at the printing
25249 step. In this example's approach, it does not perform any filtering
25250 decisions at the filtering step beyond mapping a frame decorator to
25251 each frame. This allows the actual decision making to be performed
25252 when each frame is printed. This is an important consideration, and
25253 well worth reflecting upon when designing a frame filter. An issue
25254 that frame filters should avoid is unwinding the stack if possible.
25255 Some stacks can run very deep, into the tens of thousands in some
25256 cases. To search every frame to determine if it is inlined ahead of
25257 time may be too expensive at the filtering step. The frame filter
25258 cannot know how many frames it has to iterate over, and it would have
25259 to iterate through them all. This ends up duplicating effort as
25260 @value{GDBN} performs this iteration when it prints the frames.
25262 In this example decision making can be deferred to the printing step.
25263 As each frame is printed, the frame decorator can examine each frame
25264 in turn when @value{GDBN} iterates. From a performance viewpoint,
25265 this is the most appropriate decision to make as it avoids duplicating
25266 the effort that the printing step would undertake anyway. Also, if
25267 there are many frame filters unwinding the stack during filtering, it
25268 can substantially delay the printing of the backtrace which will
25269 result in large memory usage, and a poor user experience.
25272 class InlineFilter():
25274 def __init__(self):
25275 self.name = "InlinedFrameFilter"
25276 self.priority = 100
25277 self.enabled = True
25278 gdb.frame_filters[self.name] = self
25280 def filter(self, frame_iter):
25281 frame_iter = itertools.imap(InlinedFrameDecorator,
25286 This frame filter is somewhat similar to the earlier example, except
25287 that the @code{filter} method applies a frame decorator object called
25288 @code{InlinedFrameDecorator} to each element in the iterator. The
25289 @code{imap} Python method is light-weight. It does not proactively
25290 iterate over the iterator, but rather creates a new iterator which
25291 wraps the existing one.
25293 Below is the frame decorator for this example.
25296 class InlinedFrameDecorator(FrameDecorator):
25298 def __init__(self, fobj):
25299 super(InlinedFrameDecorator, self).__init__(fobj)
25301 def function(self):
25302 frame = fobj.inferior_frame()
25303 name = str(frame.name())
25305 if frame.type() == gdb.INLINE_FRAME:
25306 name = name + " [inlined]"
25311 This frame decorator only defines and overrides the @code{function}
25312 method. It lets the supplied @code{FrameDecorator}, which is shipped
25313 with @value{GDBN}, perform the other work associated with printing
25316 The combination of these two objects create this output from a
25320 #0 0x004004e0 in bar () at inline.c:11
25321 #1 0x00400566 in max [inlined] (b=6, a=12) at inline.c:21
25322 #2 0x00400566 in main () at inline.c:31
25325 So in the case of this example, a frame decorator is applied to all
25326 frames, regardless of whether they may be inlined or not. As
25327 @value{GDBN} iterates over the iterator produced by the frame filters,
25328 @value{GDBN} executes each frame decorator which then makes a decision
25329 on what to print in the @code{function} callback. Using a strategy
25330 like this is a way to defer decisions on the frame content to printing
25333 @subheading Eliding Frames
25335 It might be that the above example is not desirable for representing
25336 inlined frames, and a hierarchical approach may be preferred. If we
25337 want to hierarchically represent frames, the @code{elided} frame
25338 decorator interface might be preferable.
25340 This example approaches the issue with the @code{elided} method. This
25341 example is quite long, but very simplistic. It is out-of-scope for
25342 this section to write a complete example that comprehensively covers
25343 all approaches of finding and printing inlined frames. However, this
25344 example illustrates the approach an author might use.
25346 This example comprises of three sections.
25349 class InlineFrameFilter():
25351 def __init__(self):
25352 self.name = "InlinedFrameFilter"
25353 self.priority = 100
25354 self.enabled = True
25355 gdb.frame_filters[self.name] = self
25357 def filter(self, frame_iter):
25358 return ElidingInlineIterator(frame_iter)
25361 This frame filter is very similar to the other examples. The only
25362 difference is this frame filter is wrapping the iterator provided to
25363 it (@code{frame_iter}) with a custom iterator called
25364 @code{ElidingInlineIterator}. This again defers actions to when
25365 @value{GDBN} prints the backtrace, as the iterator is not traversed
25368 The iterator for this example is as follows. It is in this section of
25369 the example where decisions are made on the content of the backtrace.
25372 class ElidingInlineIterator:
25373 def __init__(self, ii):
25374 self.input_iterator = ii
25376 def __iter__(self):
25380 frame = next(self.input_iterator)
25382 if frame.inferior_frame().type() != gdb.INLINE_FRAME:
25386 eliding_frame = next(self.input_iterator)
25387 except StopIteration:
25389 return ElidingFrameDecorator(eliding_frame, [frame])
25392 This iterator implements the Python iterator protocol. When the
25393 @code{next} function is called (when @value{GDBN} prints each frame),
25394 the iterator checks if this frame decorator, @code{frame}, is wrapping
25395 an inlined frame. If it is not, it returns the existing frame decorator
25396 untouched. If it is wrapping an inlined frame, it assumes that the
25397 inlined frame was contained within the next oldest frame,
25398 @code{eliding_frame}, which it fetches. It then creates and returns a
25399 frame decorator, @code{ElidingFrameDecorator}, which contains both the
25400 elided frame, and the eliding frame.
25403 class ElidingInlineDecorator(FrameDecorator):
25405 def __init__(self, frame, elided_frames):
25406 super(ElidingInlineDecorator, self).__init__(frame)
25408 self.elided_frames = elided_frames
25411 return iter(self.elided_frames)
25414 This frame decorator overrides one function and returns the inlined
25415 frame in the @code{elided} method. As before it lets
25416 @code{FrameDecorator} do the rest of the work involved in printing
25417 this frame. This produces the following output.
25420 #0 0x004004e0 in bar () at inline.c:11
25421 #2 0x00400529 in main () at inline.c:25
25422 #1 0x00400529 in max (b=6, a=12) at inline.c:15
25425 In that output, @code{max} which has been inlined into @code{main} is
25426 printed hierarchically. Another approach would be to combine the
25427 @code{function} method, and the @code{elided} method to both print a
25428 marker in the inlined frame, and also show the hierarchical
25431 @node Inferiors In Python
25432 @subsubsection Inferiors In Python
25433 @cindex inferiors in Python
25435 @findex gdb.Inferior
25436 Programs which are being run under @value{GDBN} are called inferiors
25437 (@pxref{Inferiors and Programs}). Python scripts can access
25438 information about and manipulate inferiors controlled by @value{GDBN}
25439 via objects of the @code{gdb.Inferior} class.
25441 The following inferior-related functions are available in the @code{gdb}
25444 @defun gdb.inferiors ()
25445 Return a tuple containing all inferior objects.
25448 @defun gdb.selected_inferior ()
25449 Return an object representing the current inferior.
25452 A @code{gdb.Inferior} object has the following attributes:
25454 @defvar Inferior.num
25455 ID of inferior, as assigned by GDB.
25458 @defvar Inferior.pid
25459 Process ID of the inferior, as assigned by the underlying operating
25463 @defvar Inferior.was_attached
25464 Boolean signaling whether the inferior was created using `attach', or
25465 started by @value{GDBN} itself.
25468 A @code{gdb.Inferior} object has the following methods:
25470 @defun Inferior.is_valid ()
25471 Returns @code{True} if the @code{gdb.Inferior} object is valid,
25472 @code{False} if not. A @code{gdb.Inferior} object will become invalid
25473 if the inferior no longer exists within @value{GDBN}. All other
25474 @code{gdb.Inferior} methods will throw an exception if it is invalid
25475 at the time the method is called.
25478 @defun Inferior.threads ()
25479 This method returns a tuple holding all the threads which are valid
25480 when it is called. If there are no valid threads, the method will
25481 return an empty tuple.
25484 @findex Inferior.read_memory
25485 @defun Inferior.read_memory (address, length)
25486 Read @var{length} bytes of memory from the inferior, starting at
25487 @var{address}. Returns a buffer object, which behaves much like an array
25488 or a string. It can be modified and given to the
25489 @code{Inferior.write_memory} function. In @code{Python} 3, the return
25490 value is a @code{memoryview} object.
25493 @findex Inferior.write_memory
25494 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
25495 Write the contents of @var{buffer} to the inferior, starting at
25496 @var{address}. The @var{buffer} parameter must be a Python object
25497 which supports the buffer protocol, i.e., a string, an array or the
25498 object returned from @code{Inferior.read_memory}. If given, @var{length}
25499 determines the number of bytes from @var{buffer} to be written.
25502 @findex gdb.search_memory
25503 @defun Inferior.search_memory (address, length, pattern)
25504 Search a region of the inferior memory starting at @var{address} with
25505 the given @var{length} using the search pattern supplied in
25506 @var{pattern}. The @var{pattern} parameter must be a Python object
25507 which supports the buffer protocol, i.e., a string, an array or the
25508 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
25509 containing the address where the pattern was found, or @code{None} if
25510 the pattern could not be found.
25513 @node Events In Python
25514 @subsubsection Events In Python
25515 @cindex inferior events in Python
25517 @value{GDBN} provides a general event facility so that Python code can be
25518 notified of various state changes, particularly changes that occur in
25521 An @dfn{event} is just an object that describes some state change. The
25522 type of the object and its attributes will vary depending on the details
25523 of the change. All the existing events are described below.
25525 In order to be notified of an event, you must register an event handler
25526 with an @dfn{event registry}. An event registry is an object in the
25527 @code{gdb.events} module which dispatches particular events. A registry
25528 provides methods to register and unregister event handlers:
25530 @defun EventRegistry.connect (object)
25531 Add the given callable @var{object} to the registry. This object will be
25532 called when an event corresponding to this registry occurs.
25535 @defun EventRegistry.disconnect (object)
25536 Remove the given @var{object} from the registry. Once removed, the object
25537 will no longer receive notifications of events.
25540 Here is an example:
25543 def exit_handler (event):
25544 print "event type: exit"
25545 print "exit code: %d" % (event.exit_code)
25547 gdb.events.exited.connect (exit_handler)
25550 In the above example we connect our handler @code{exit_handler} to the
25551 registry @code{events.exited}. Once connected, @code{exit_handler} gets
25552 called when the inferior exits. The argument @dfn{event} in this example is
25553 of type @code{gdb.ExitedEvent}. As you can see in the example the
25554 @code{ExitedEvent} object has an attribute which indicates the exit code of
25557 The following is a listing of the event registries that are available and
25558 details of the events they emit:
25563 Emits @code{gdb.ThreadEvent}.
25565 Some events can be thread specific when @value{GDBN} is running in non-stop
25566 mode. When represented in Python, these events all extend
25567 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
25568 events which are emitted by this or other modules might extend this event.
25569 Examples of these events are @code{gdb.BreakpointEvent} and
25570 @code{gdb.ContinueEvent}.
25572 @defvar ThreadEvent.inferior_thread
25573 In non-stop mode this attribute will be set to the specific thread which was
25574 involved in the emitted event. Otherwise, it will be set to @code{None}.
25577 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
25579 This event indicates that the inferior has been continued after a stop. For
25580 inherited attribute refer to @code{gdb.ThreadEvent} above.
25582 @item events.exited
25583 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
25584 @code{events.ExitedEvent} has two attributes:
25585 @defvar ExitedEvent.exit_code
25586 An integer representing the exit code, if available, which the inferior
25587 has returned. (The exit code could be unavailable if, for example,
25588 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
25589 the attribute does not exist.
25591 @defvar ExitedEvent inferior
25592 A reference to the inferior which triggered the @code{exited} event.
25596 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
25598 Indicates that the inferior has stopped. All events emitted by this registry
25599 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
25600 will indicate the stopped thread when @value{GDBN} is running in non-stop
25601 mode. Refer to @code{gdb.ThreadEvent} above for more details.
25603 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
25605 This event indicates that the inferior or one of its threads has received as
25606 signal. @code{gdb.SignalEvent} has the following attributes:
25608 @defvar SignalEvent.stop_signal
25609 A string representing the signal received by the inferior. A list of possible
25610 signal values can be obtained by running the command @code{info signals} in
25611 the @value{GDBN} command prompt.
25614 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
25616 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
25617 been hit, and has the following attributes:
25619 @defvar BreakpointEvent.breakpoints
25620 A sequence containing references to all the breakpoints (type
25621 @code{gdb.Breakpoint}) that were hit.
25622 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
25624 @defvar BreakpointEvent.breakpoint
25625 A reference to the first breakpoint that was hit.
25626 This function is maintained for backward compatibility and is now deprecated
25627 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
25630 @item events.new_objfile
25631 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
25632 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
25634 @defvar NewObjFileEvent.new_objfile
25635 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
25636 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
25641 @node Threads In Python
25642 @subsubsection Threads In Python
25643 @cindex threads in python
25645 @findex gdb.InferiorThread
25646 Python scripts can access information about, and manipulate inferior threads
25647 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
25649 The following thread-related functions are available in the @code{gdb}
25652 @findex gdb.selected_thread
25653 @defun gdb.selected_thread ()
25654 This function returns the thread object for the selected thread. If there
25655 is no selected thread, this will return @code{None}.
25658 A @code{gdb.InferiorThread} object has the following attributes:
25660 @defvar InferiorThread.name
25661 The name of the thread. If the user specified a name using
25662 @code{thread name}, then this returns that name. Otherwise, if an
25663 OS-supplied name is available, then it is returned. Otherwise, this
25664 returns @code{None}.
25666 This attribute can be assigned to. The new value must be a string
25667 object, which sets the new name, or @code{None}, which removes any
25668 user-specified thread name.
25671 @defvar InferiorThread.num
25672 ID of the thread, as assigned by GDB.
25675 @defvar InferiorThread.ptid
25676 ID of the thread, as assigned by the operating system. This attribute is a
25677 tuple containing three integers. The first is the Process ID (PID); the second
25678 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
25679 Either the LWPID or TID may be 0, which indicates that the operating system
25680 does not use that identifier.
25683 A @code{gdb.InferiorThread} object has the following methods:
25685 @defun InferiorThread.is_valid ()
25686 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
25687 @code{False} if not. A @code{gdb.InferiorThread} object will become
25688 invalid if the thread exits, or the inferior that the thread belongs
25689 is deleted. All other @code{gdb.InferiorThread} methods will throw an
25690 exception if it is invalid at the time the method is called.
25693 @defun InferiorThread.switch ()
25694 This changes @value{GDBN}'s currently selected thread to the one represented
25698 @defun InferiorThread.is_stopped ()
25699 Return a Boolean indicating whether the thread is stopped.
25702 @defun InferiorThread.is_running ()
25703 Return a Boolean indicating whether the thread is running.
25706 @defun InferiorThread.is_exited ()
25707 Return a Boolean indicating whether the thread is exited.
25710 @node Commands In Python
25711 @subsubsection Commands In Python
25713 @cindex commands in python
25714 @cindex python commands
25715 You can implement new @value{GDBN} CLI commands in Python. A CLI
25716 command is implemented using an instance of the @code{gdb.Command}
25717 class, most commonly using a subclass.
25719 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
25720 The object initializer for @code{Command} registers the new command
25721 with @value{GDBN}. This initializer is normally invoked from the
25722 subclass' own @code{__init__} method.
25724 @var{name} is the name of the command. If @var{name} consists of
25725 multiple words, then the initial words are looked for as prefix
25726 commands. In this case, if one of the prefix commands does not exist,
25727 an exception is raised.
25729 There is no support for multi-line commands.
25731 @var{command_class} should be one of the @samp{COMMAND_} constants
25732 defined below. This argument tells @value{GDBN} how to categorize the
25733 new command in the help system.
25735 @var{completer_class} is an optional argument. If given, it should be
25736 one of the @samp{COMPLETE_} constants defined below. This argument
25737 tells @value{GDBN} how to perform completion for this command. If not
25738 given, @value{GDBN} will attempt to complete using the object's
25739 @code{complete} method (see below); if no such method is found, an
25740 error will occur when completion is attempted.
25742 @var{prefix} is an optional argument. If @code{True}, then the new
25743 command is a prefix command; sub-commands of this command may be
25746 The help text for the new command is taken from the Python
25747 documentation string for the command's class, if there is one. If no
25748 documentation string is provided, the default value ``This command is
25749 not documented.'' is used.
25752 @cindex don't repeat Python command
25753 @defun Command.dont_repeat ()
25754 By default, a @value{GDBN} command is repeated when the user enters a
25755 blank line at the command prompt. A command can suppress this
25756 behavior by invoking the @code{dont_repeat} method. This is similar
25757 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
25760 @defun Command.invoke (argument, from_tty)
25761 This method is called by @value{GDBN} when this command is invoked.
25763 @var{argument} is a string. It is the argument to the command, after
25764 leading and trailing whitespace has been stripped.
25766 @var{from_tty} is a boolean argument. When true, this means that the
25767 command was entered by the user at the terminal; when false it means
25768 that the command came from elsewhere.
25770 If this method throws an exception, it is turned into a @value{GDBN}
25771 @code{error} call. Otherwise, the return value is ignored.
25773 @findex gdb.string_to_argv
25774 To break @var{argument} up into an argv-like string use
25775 @code{gdb.string_to_argv}. This function behaves identically to
25776 @value{GDBN}'s internal argument lexer @code{buildargv}.
25777 It is recommended to use this for consistency.
25778 Arguments are separated by spaces and may be quoted.
25782 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
25783 ['1', '2 "3', '4 "5', "6 '7"]
25788 @cindex completion of Python commands
25789 @defun Command.complete (text, word)
25790 This method is called by @value{GDBN} when the user attempts
25791 completion on this command. All forms of completion are handled by
25792 this method, that is, the @key{TAB} and @key{M-?} key bindings
25793 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
25796 The arguments @var{text} and @var{word} are both strings. @var{text}
25797 holds the complete command line up to the cursor's location.
25798 @var{word} holds the last word of the command line; this is computed
25799 using a word-breaking heuristic.
25801 The @code{complete} method can return several values:
25804 If the return value is a sequence, the contents of the sequence are
25805 used as the completions. It is up to @code{complete} to ensure that the
25806 contents actually do complete the word. A zero-length sequence is
25807 allowed, it means that there were no completions available. Only
25808 string elements of the sequence are used; other elements in the
25809 sequence are ignored.
25812 If the return value is one of the @samp{COMPLETE_} constants defined
25813 below, then the corresponding @value{GDBN}-internal completion
25814 function is invoked, and its result is used.
25817 All other results are treated as though there were no available
25822 When a new command is registered, it must be declared as a member of
25823 some general class of commands. This is used to classify top-level
25824 commands in the on-line help system; note that prefix commands are not
25825 listed under their own category but rather that of their top-level
25826 command. The available classifications are represented by constants
25827 defined in the @code{gdb} module:
25830 @findex COMMAND_NONE
25831 @findex gdb.COMMAND_NONE
25832 @item gdb.COMMAND_NONE
25833 The command does not belong to any particular class. A command in
25834 this category will not be displayed in any of the help categories.
25836 @findex COMMAND_RUNNING
25837 @findex gdb.COMMAND_RUNNING
25838 @item gdb.COMMAND_RUNNING
25839 The command is related to running the inferior. For example,
25840 @code{start}, @code{step}, and @code{continue} are in this category.
25841 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
25842 commands in this category.
25844 @findex COMMAND_DATA
25845 @findex gdb.COMMAND_DATA
25846 @item gdb.COMMAND_DATA
25847 The command is related to data or variables. For example,
25848 @code{call}, @code{find}, and @code{print} are in this category. Type
25849 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
25852 @findex COMMAND_STACK
25853 @findex gdb.COMMAND_STACK
25854 @item gdb.COMMAND_STACK
25855 The command has to do with manipulation of the stack. For example,
25856 @code{backtrace}, @code{frame}, and @code{return} are in this
25857 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
25858 list of commands in this category.
25860 @findex COMMAND_FILES
25861 @findex gdb.COMMAND_FILES
25862 @item gdb.COMMAND_FILES
25863 This class is used for file-related commands. For example,
25864 @code{file}, @code{list} and @code{section} are in this category.
25865 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
25866 commands in this category.
25868 @findex COMMAND_SUPPORT
25869 @findex gdb.COMMAND_SUPPORT
25870 @item gdb.COMMAND_SUPPORT
25871 This should be used for ``support facilities'', generally meaning
25872 things that are useful to the user when interacting with @value{GDBN},
25873 but not related to the state of the inferior. For example,
25874 @code{help}, @code{make}, and @code{shell} are in this category. Type
25875 @kbd{help support} at the @value{GDBN} prompt to see a list of
25876 commands in this category.
25878 @findex COMMAND_STATUS
25879 @findex gdb.COMMAND_STATUS
25880 @item gdb.COMMAND_STATUS
25881 The command is an @samp{info}-related command, that is, related to the
25882 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
25883 and @code{show} are in this category. Type @kbd{help status} at the
25884 @value{GDBN} prompt to see a list of commands in this category.
25886 @findex COMMAND_BREAKPOINTS
25887 @findex gdb.COMMAND_BREAKPOINTS
25888 @item gdb.COMMAND_BREAKPOINTS
25889 The command has to do with breakpoints. For example, @code{break},
25890 @code{clear}, and @code{delete} are in this category. Type @kbd{help
25891 breakpoints} at the @value{GDBN} prompt to see a list of commands in
25894 @findex COMMAND_TRACEPOINTS
25895 @findex gdb.COMMAND_TRACEPOINTS
25896 @item gdb.COMMAND_TRACEPOINTS
25897 The command has to do with tracepoints. For example, @code{trace},
25898 @code{actions}, and @code{tfind} are in this category. Type
25899 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
25900 commands in this category.
25902 @findex COMMAND_USER
25903 @findex gdb.COMMAND_USER
25904 @item gdb.COMMAND_USER
25905 The command is a general purpose command for the user, and typically
25906 does not fit in one of the other categories.
25907 Type @kbd{help user-defined} at the @value{GDBN} prompt to see
25908 a list of commands in this category, as well as the list of gdb macros
25909 (@pxref{Sequences}).
25911 @findex COMMAND_OBSCURE
25912 @findex gdb.COMMAND_OBSCURE
25913 @item gdb.COMMAND_OBSCURE
25914 The command is only used in unusual circumstances, or is not of
25915 general interest to users. For example, @code{checkpoint},
25916 @code{fork}, and @code{stop} are in this category. Type @kbd{help
25917 obscure} at the @value{GDBN} prompt to see a list of commands in this
25920 @findex COMMAND_MAINTENANCE
25921 @findex gdb.COMMAND_MAINTENANCE
25922 @item gdb.COMMAND_MAINTENANCE
25923 The command is only useful to @value{GDBN} maintainers. The
25924 @code{maintenance} and @code{flushregs} commands are in this category.
25925 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
25926 commands in this category.
25929 A new command can use a predefined completion function, either by
25930 specifying it via an argument at initialization, or by returning it
25931 from the @code{complete} method. These predefined completion
25932 constants are all defined in the @code{gdb} module:
25935 @findex COMPLETE_NONE
25936 @findex gdb.COMPLETE_NONE
25937 @item gdb.COMPLETE_NONE
25938 This constant means that no completion should be done.
25940 @findex COMPLETE_FILENAME
25941 @findex gdb.COMPLETE_FILENAME
25942 @item gdb.COMPLETE_FILENAME
25943 This constant means that filename completion should be performed.
25945 @findex COMPLETE_LOCATION
25946 @findex gdb.COMPLETE_LOCATION
25947 @item gdb.COMPLETE_LOCATION
25948 This constant means that location completion should be done.
25949 @xref{Specify Location}.
25951 @findex COMPLETE_COMMAND
25952 @findex gdb.COMPLETE_COMMAND
25953 @item gdb.COMPLETE_COMMAND
25954 This constant means that completion should examine @value{GDBN}
25957 @findex COMPLETE_SYMBOL
25958 @findex gdb.COMPLETE_SYMBOL
25959 @item gdb.COMPLETE_SYMBOL
25960 This constant means that completion should be done using symbol names
25964 The following code snippet shows how a trivial CLI command can be
25965 implemented in Python:
25968 class HelloWorld (gdb.Command):
25969 """Greet the whole world."""
25971 def __init__ (self):
25972 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
25974 def invoke (self, arg, from_tty):
25975 print "Hello, World!"
25980 The last line instantiates the class, and is necessary to trigger the
25981 registration of the command with @value{GDBN}. Depending on how the
25982 Python code is read into @value{GDBN}, you may need to import the
25983 @code{gdb} module explicitly.
25985 @node Parameters In Python
25986 @subsubsection Parameters In Python
25988 @cindex parameters in python
25989 @cindex python parameters
25990 @tindex gdb.Parameter
25992 You can implement new @value{GDBN} parameters using Python. A new
25993 parameter is implemented as an instance of the @code{gdb.Parameter}
25996 Parameters are exposed to the user via the @code{set} and
25997 @code{show} commands. @xref{Help}.
25999 There are many parameters that already exist and can be set in
26000 @value{GDBN}. Two examples are: @code{set follow fork} and
26001 @code{set charset}. Setting these parameters influences certain
26002 behavior in @value{GDBN}. Similarly, you can define parameters that
26003 can be used to influence behavior in custom Python scripts and commands.
26005 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
26006 The object initializer for @code{Parameter} registers the new
26007 parameter with @value{GDBN}. This initializer is normally invoked
26008 from the subclass' own @code{__init__} method.
26010 @var{name} is the name of the new parameter. If @var{name} consists
26011 of multiple words, then the initial words are looked for as prefix
26012 parameters. An example of this can be illustrated with the
26013 @code{set print} set of parameters. If @var{name} is
26014 @code{print foo}, then @code{print} will be searched as the prefix
26015 parameter. In this case the parameter can subsequently be accessed in
26016 @value{GDBN} as @code{set print foo}.
26018 If @var{name} consists of multiple words, and no prefix parameter group
26019 can be found, an exception is raised.
26021 @var{command-class} should be one of the @samp{COMMAND_} constants
26022 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
26023 categorize the new parameter in the help system.
26025 @var{parameter-class} should be one of the @samp{PARAM_} constants
26026 defined below. This argument tells @value{GDBN} the type of the new
26027 parameter; this information is used for input validation and
26030 If @var{parameter-class} is @code{PARAM_ENUM}, then
26031 @var{enum-sequence} must be a sequence of strings. These strings
26032 represent the possible values for the parameter.
26034 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
26035 of a fourth argument will cause an exception to be thrown.
26037 The help text for the new parameter is taken from the Python
26038 documentation string for the parameter's class, if there is one. If
26039 there is no documentation string, a default value is used.
26042 @defvar Parameter.set_doc
26043 If this attribute exists, and is a string, then its value is used as
26044 the help text for this parameter's @code{set} command. The value is
26045 examined when @code{Parameter.__init__} is invoked; subsequent changes
26049 @defvar Parameter.show_doc
26050 If this attribute exists, and is a string, then its value is used as
26051 the help text for this parameter's @code{show} command. The value is
26052 examined when @code{Parameter.__init__} is invoked; subsequent changes
26056 @defvar Parameter.value
26057 The @code{value} attribute holds the underlying value of the
26058 parameter. It can be read and assigned to just as any other
26059 attribute. @value{GDBN} does validation when assignments are made.
26062 There are two methods that should be implemented in any
26063 @code{Parameter} class. These are:
26065 @defun Parameter.get_set_string (self)
26066 @value{GDBN} will call this method when a @var{parameter}'s value has
26067 been changed via the @code{set} API (for example, @kbd{set foo off}).
26068 The @code{value} attribute has already been populated with the new
26069 value and may be used in output. This method must return a string.
26072 @defun Parameter.get_show_string (self, svalue)
26073 @value{GDBN} will call this method when a @var{parameter}'s
26074 @code{show} API has been invoked (for example, @kbd{show foo}). The
26075 argument @code{svalue} receives the string representation of the
26076 current value. This method must return a string.
26079 When a new parameter is defined, its type must be specified. The
26080 available types are represented by constants defined in the @code{gdb}
26084 @findex PARAM_BOOLEAN
26085 @findex gdb.PARAM_BOOLEAN
26086 @item gdb.PARAM_BOOLEAN
26087 The value is a plain boolean. The Python boolean values, @code{True}
26088 and @code{False} are the only valid values.
26090 @findex PARAM_AUTO_BOOLEAN
26091 @findex gdb.PARAM_AUTO_BOOLEAN
26092 @item gdb.PARAM_AUTO_BOOLEAN
26093 The value has three possible states: true, false, and @samp{auto}. In
26094 Python, true and false are represented using boolean constants, and
26095 @samp{auto} is represented using @code{None}.
26097 @findex PARAM_UINTEGER
26098 @findex gdb.PARAM_UINTEGER
26099 @item gdb.PARAM_UINTEGER
26100 The value is an unsigned integer. The value of 0 should be
26101 interpreted to mean ``unlimited''.
26103 @findex PARAM_INTEGER
26104 @findex gdb.PARAM_INTEGER
26105 @item gdb.PARAM_INTEGER
26106 The value is a signed integer. The value of 0 should be interpreted
26107 to mean ``unlimited''.
26109 @findex PARAM_STRING
26110 @findex gdb.PARAM_STRING
26111 @item gdb.PARAM_STRING
26112 The value is a string. When the user modifies the string, any escape
26113 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
26114 translated into corresponding characters and encoded into the current
26117 @findex PARAM_STRING_NOESCAPE
26118 @findex gdb.PARAM_STRING_NOESCAPE
26119 @item gdb.PARAM_STRING_NOESCAPE
26120 The value is a string. When the user modifies the string, escapes are
26121 passed through untranslated.
26123 @findex PARAM_OPTIONAL_FILENAME
26124 @findex gdb.PARAM_OPTIONAL_FILENAME
26125 @item gdb.PARAM_OPTIONAL_FILENAME
26126 The value is a either a filename (a string), or @code{None}.
26128 @findex PARAM_FILENAME
26129 @findex gdb.PARAM_FILENAME
26130 @item gdb.PARAM_FILENAME
26131 The value is a filename. This is just like
26132 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
26134 @findex PARAM_ZINTEGER
26135 @findex gdb.PARAM_ZINTEGER
26136 @item gdb.PARAM_ZINTEGER
26137 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
26138 is interpreted as itself.
26141 @findex gdb.PARAM_ENUM
26142 @item gdb.PARAM_ENUM
26143 The value is a string, which must be one of a collection string
26144 constants provided when the parameter is created.
26147 @node Functions In Python
26148 @subsubsection Writing new convenience functions
26150 @cindex writing convenience functions
26151 @cindex convenience functions in python
26152 @cindex python convenience functions
26153 @tindex gdb.Function
26155 You can implement new convenience functions (@pxref{Convenience Vars})
26156 in Python. A convenience function is an instance of a subclass of the
26157 class @code{gdb.Function}.
26159 @defun Function.__init__ (name)
26160 The initializer for @code{Function} registers the new function with
26161 @value{GDBN}. The argument @var{name} is the name of the function,
26162 a string. The function will be visible to the user as a convenience
26163 variable of type @code{internal function}, whose name is the same as
26164 the given @var{name}.
26166 The documentation for the new function is taken from the documentation
26167 string for the new class.
26170 @defun Function.invoke (@var{*args})
26171 When a convenience function is evaluated, its arguments are converted
26172 to instances of @code{gdb.Value}, and then the function's
26173 @code{invoke} method is called. Note that @value{GDBN} does not
26174 predetermine the arity of convenience functions. Instead, all
26175 available arguments are passed to @code{invoke}, following the
26176 standard Python calling convention. In particular, a convenience
26177 function can have default values for parameters without ill effect.
26179 The return value of this method is used as its value in the enclosing
26180 expression. If an ordinary Python value is returned, it is converted
26181 to a @code{gdb.Value} following the usual rules.
26184 The following code snippet shows how a trivial convenience function can
26185 be implemented in Python:
26188 class Greet (gdb.Function):
26189 """Return string to greet someone.
26190 Takes a name as argument."""
26192 def __init__ (self):
26193 super (Greet, self).__init__ ("greet")
26195 def invoke (self, name):
26196 return "Hello, %s!" % name.string ()
26201 The last line instantiates the class, and is necessary to trigger the
26202 registration of the function with @value{GDBN}. Depending on how the
26203 Python code is read into @value{GDBN}, you may need to import the
26204 @code{gdb} module explicitly.
26206 Now you can use the function in an expression:
26209 (gdb) print $greet("Bob")
26213 @node Progspaces In Python
26214 @subsubsection Program Spaces In Python
26216 @cindex progspaces in python
26217 @tindex gdb.Progspace
26219 A program space, or @dfn{progspace}, represents a symbolic view
26220 of an address space.
26221 It consists of all of the objfiles of the program.
26222 @xref{Objfiles In Python}.
26223 @xref{Inferiors and Programs, program spaces}, for more details
26224 about program spaces.
26226 The following progspace-related functions are available in the
26229 @findex gdb.current_progspace
26230 @defun gdb.current_progspace ()
26231 This function returns the program space of the currently selected inferior.
26232 @xref{Inferiors and Programs}.
26235 @findex gdb.progspaces
26236 @defun gdb.progspaces ()
26237 Return a sequence of all the progspaces currently known to @value{GDBN}.
26240 Each progspace is represented by an instance of the @code{gdb.Progspace}
26243 @defvar Progspace.filename
26244 The file name of the progspace as a string.
26247 @defvar Progspace.pretty_printers
26248 The @code{pretty_printers} attribute is a list of functions. It is
26249 used to look up pretty-printers. A @code{Value} is passed to each
26250 function in order; if the function returns @code{None}, then the
26251 search continues. Otherwise, the return value should be an object
26252 which is used to format the value. @xref{Pretty Printing API}, for more
26256 @defvar Progspace.type_printers
26257 The @code{type_printers} attribute is a list of type printer objects.
26258 @xref{Type Printing API}, for more information.
26261 @defvar Progspace.frame_filters
26262 The @code{frame_filters} attribute is a dictionary of frame filter
26263 objects. @xref{Frame Filter API}, for more information.
26266 @node Objfiles In Python
26267 @subsubsection Objfiles In Python
26269 @cindex objfiles in python
26270 @tindex gdb.Objfile
26272 @value{GDBN} loads symbols for an inferior from various
26273 symbol-containing files (@pxref{Files}). These include the primary
26274 executable file, any shared libraries used by the inferior, and any
26275 separate debug info files (@pxref{Separate Debug Files}).
26276 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
26278 The following objfile-related functions are available in the
26281 @findex gdb.current_objfile
26282 @defun gdb.current_objfile ()
26283 When auto-loading a Python script (@pxref{Python Auto-loading}), @value{GDBN}
26284 sets the ``current objfile'' to the corresponding objfile. This
26285 function returns the current objfile. If there is no current objfile,
26286 this function returns @code{None}.
26289 @findex gdb.objfiles
26290 @defun gdb.objfiles ()
26291 Return a sequence of all the objfiles current known to @value{GDBN}.
26292 @xref{Objfiles In Python}.
26295 Each objfile is represented by an instance of the @code{gdb.Objfile}
26298 @defvar Objfile.filename
26299 The file name of the objfile as a string.
26302 @defvar Objfile.pretty_printers
26303 The @code{pretty_printers} attribute is a list of functions. It is
26304 used to look up pretty-printers. A @code{Value} is passed to each
26305 function in order; if the function returns @code{None}, then the
26306 search continues. Otherwise, the return value should be an object
26307 which is used to format the value. @xref{Pretty Printing API}, for more
26311 @defvar Objfile.type_printers
26312 The @code{type_printers} attribute is a list of type printer objects.
26313 @xref{Type Printing API}, for more information.
26316 @defvar Objfile.frame_filters
26317 The @code{frame_filters} attribute is a dictionary of frame filter
26318 objects. @xref{Frame Filter API}, for more information.
26321 A @code{gdb.Objfile} object has the following methods:
26323 @defun Objfile.is_valid ()
26324 Returns @code{True} if the @code{gdb.Objfile} object is valid,
26325 @code{False} if not. A @code{gdb.Objfile} object can become invalid
26326 if the object file it refers to is not loaded in @value{GDBN} any
26327 longer. All other @code{gdb.Objfile} methods will throw an exception
26328 if it is invalid at the time the method is called.
26331 @node Frames In Python
26332 @subsubsection Accessing inferior stack frames from Python.
26334 @cindex frames in python
26335 When the debugged program stops, @value{GDBN} is able to analyze its call
26336 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
26337 represents a frame in the stack. A @code{gdb.Frame} object is only valid
26338 while its corresponding frame exists in the inferior's stack. If you try
26339 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
26340 exception (@pxref{Exception Handling}).
26342 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
26346 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
26350 The following frame-related functions are available in the @code{gdb} module:
26352 @findex gdb.selected_frame
26353 @defun gdb.selected_frame ()
26354 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
26357 @findex gdb.newest_frame
26358 @defun gdb.newest_frame ()
26359 Return the newest frame object for the selected thread.
26362 @defun gdb.frame_stop_reason_string (reason)
26363 Return a string explaining the reason why @value{GDBN} stopped unwinding
26364 frames, as expressed by the given @var{reason} code (an integer, see the
26365 @code{unwind_stop_reason} method further down in this section).
26368 A @code{gdb.Frame} object has the following methods:
26370 @defun Frame.is_valid ()
26371 Returns true if the @code{gdb.Frame} object is valid, false if not.
26372 A frame object can become invalid if the frame it refers to doesn't
26373 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
26374 an exception if it is invalid at the time the method is called.
26377 @defun Frame.name ()
26378 Returns the function name of the frame, or @code{None} if it can't be
26382 @defun Frame.architecture ()
26383 Returns the @code{gdb.Architecture} object corresponding to the frame's
26384 architecture. @xref{Architectures In Python}.
26387 @defun Frame.type ()
26388 Returns the type of the frame. The value can be one of:
26390 @item gdb.NORMAL_FRAME
26391 An ordinary stack frame.
26393 @item gdb.DUMMY_FRAME
26394 A fake stack frame that was created by @value{GDBN} when performing an
26395 inferior function call.
26397 @item gdb.INLINE_FRAME
26398 A frame representing an inlined function. The function was inlined
26399 into a @code{gdb.NORMAL_FRAME} that is older than this one.
26401 @item gdb.TAILCALL_FRAME
26402 A frame representing a tail call. @xref{Tail Call Frames}.
26404 @item gdb.SIGTRAMP_FRAME
26405 A signal trampoline frame. This is the frame created by the OS when
26406 it calls into a signal handler.
26408 @item gdb.ARCH_FRAME
26409 A fake stack frame representing a cross-architecture call.
26411 @item gdb.SENTINEL_FRAME
26412 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
26417 @defun Frame.unwind_stop_reason ()
26418 Return an integer representing the reason why it's not possible to find
26419 more frames toward the outermost frame. Use
26420 @code{gdb.frame_stop_reason_string} to convert the value returned by this
26421 function to a string. The value can be one of:
26424 @item gdb.FRAME_UNWIND_NO_REASON
26425 No particular reason (older frames should be available).
26427 @item gdb.FRAME_UNWIND_NULL_ID
26428 The previous frame's analyzer returns an invalid result.
26430 @item gdb.FRAME_UNWIND_OUTERMOST
26431 This frame is the outermost.
26433 @item gdb.FRAME_UNWIND_UNAVAILABLE
26434 Cannot unwind further, because that would require knowing the
26435 values of registers or memory that have not been collected.
26437 @item gdb.FRAME_UNWIND_INNER_ID
26438 This frame ID looks like it ought to belong to a NEXT frame,
26439 but we got it for a PREV frame. Normally, this is a sign of
26440 unwinder failure. It could also indicate stack corruption.
26442 @item gdb.FRAME_UNWIND_SAME_ID
26443 This frame has the same ID as the previous one. That means
26444 that unwinding further would almost certainly give us another
26445 frame with exactly the same ID, so break the chain. Normally,
26446 this is a sign of unwinder failure. It could also indicate
26449 @item gdb.FRAME_UNWIND_NO_SAVED_PC
26450 The frame unwinder did not find any saved PC, but we needed
26451 one to unwind further.
26453 @item gdb.FRAME_UNWIND_FIRST_ERROR
26454 Any stop reason greater or equal to this value indicates some kind
26455 of error. This special value facilitates writing code that tests
26456 for errors in unwinding in a way that will work correctly even if
26457 the list of the other values is modified in future @value{GDBN}
26458 versions. Using it, you could write:
26460 reason = gdb.selected_frame().unwind_stop_reason ()
26461 reason_str = gdb.frame_stop_reason_string (reason)
26462 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
26463 print "An error occured: %s" % reason_str
26470 Returns the frame's resume address.
26473 @defun Frame.block ()
26474 Return the frame's code block. @xref{Blocks In Python}.
26477 @defun Frame.function ()
26478 Return the symbol for the function corresponding to this frame.
26479 @xref{Symbols In Python}.
26482 @defun Frame.older ()
26483 Return the frame that called this frame.
26486 @defun Frame.newer ()
26487 Return the frame called by this frame.
26490 @defun Frame.find_sal ()
26491 Return the frame's symtab and line object.
26492 @xref{Symbol Tables In Python}.
26495 @defun Frame.read_var (variable @r{[}, block@r{]})
26496 Return the value of @var{variable} in this frame. If the optional
26497 argument @var{block} is provided, search for the variable from that
26498 block; otherwise start at the frame's current block (which is
26499 determined by the frame's current program counter). @var{variable}
26500 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
26501 @code{gdb.Block} object.
26504 @defun Frame.select ()
26505 Set this frame to be the selected frame. @xref{Stack, ,Examining the
26509 @node Blocks In Python
26510 @subsubsection Accessing blocks from Python.
26512 @cindex blocks in python
26515 In @value{GDBN}, symbols are stored in blocks. A block corresponds
26516 roughly to a scope in the source code. Blocks are organized
26517 hierarchically, and are represented individually in Python as a
26518 @code{gdb.Block}. Blocks rely on debugging information being
26521 A frame has a block. Please see @ref{Frames In Python}, for a more
26522 in-depth discussion of frames.
26524 The outermost block is known as the @dfn{global block}. The global
26525 block typically holds public global variables and functions.
26527 The block nested just inside the global block is the @dfn{static
26528 block}. The static block typically holds file-scoped variables and
26531 @value{GDBN} provides a method to get a block's superblock, but there
26532 is currently no way to examine the sub-blocks of a block, or to
26533 iterate over all the blocks in a symbol table (@pxref{Symbol Tables In
26536 Here is a short example that should help explain blocks:
26539 /* This is in the global block. */
26542 /* This is in the static block. */
26543 static int file_scope;
26545 /* 'function' is in the global block, and 'argument' is
26546 in a block nested inside of 'function'. */
26547 int function (int argument)
26549 /* 'local' is in a block inside 'function'. It may or may
26550 not be in the same block as 'argument'. */
26554 /* 'inner' is in a block whose superblock is the one holding
26558 /* If this call is expanded by the compiler, you may see
26559 a nested block here whose function is 'inline_function'
26560 and whose superblock is the one holding 'inner'. */
26561 inline_function ();
26566 A @code{gdb.Block} is iterable. The iterator returns the symbols
26567 (@pxref{Symbols In Python}) local to the block. Python programs
26568 should not assume that a specific block object will always contain a
26569 given symbol, since changes in @value{GDBN} features and
26570 infrastructure may cause symbols move across blocks in a symbol
26573 The following block-related functions are available in the @code{gdb}
26576 @findex gdb.block_for_pc
26577 @defun gdb.block_for_pc (pc)
26578 Return the innermost @code{gdb.Block} containing the given @var{pc}
26579 value. If the block cannot be found for the @var{pc} value specified,
26580 the function will return @code{None}.
26583 A @code{gdb.Block} object has the following methods:
26585 @defun Block.is_valid ()
26586 Returns @code{True} if the @code{gdb.Block} object is valid,
26587 @code{False} if not. A block object can become invalid if the block it
26588 refers to doesn't exist anymore in the inferior. All other
26589 @code{gdb.Block} methods will throw an exception if it is invalid at
26590 the time the method is called. The block's validity is also checked
26591 during iteration over symbols of the block.
26594 A @code{gdb.Block} object has the following attributes:
26596 @defvar Block.start
26597 The start address of the block. This attribute is not writable.
26601 The end address of the block. This attribute is not writable.
26604 @defvar Block.function
26605 The name of the block represented as a @code{gdb.Symbol}. If the
26606 block is not named, then this attribute holds @code{None}. This
26607 attribute is not writable.
26609 For ordinary function blocks, the superblock is the static block.
26610 However, you should note that it is possible for a function block to
26611 have a superblock that is not the static block -- for instance this
26612 happens for an inlined function.
26615 @defvar Block.superblock
26616 The block containing this block. If this parent block does not exist,
26617 this attribute holds @code{None}. This attribute is not writable.
26620 @defvar Block.global_block
26621 The global block associated with this block. This attribute is not
26625 @defvar Block.static_block
26626 The static block associated with this block. This attribute is not
26630 @defvar Block.is_global
26631 @code{True} if the @code{gdb.Block} object is a global block,
26632 @code{False} if not. This attribute is not
26636 @defvar Block.is_static
26637 @code{True} if the @code{gdb.Block} object is a static block,
26638 @code{False} if not. This attribute is not writable.
26641 @node Symbols In Python
26642 @subsubsection Python representation of Symbols.
26644 @cindex symbols in python
26647 @value{GDBN} represents every variable, function and type as an
26648 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
26649 Similarly, Python represents these symbols in @value{GDBN} with the
26650 @code{gdb.Symbol} object.
26652 The following symbol-related functions are available in the @code{gdb}
26655 @findex gdb.lookup_symbol
26656 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
26657 This function searches for a symbol by name. The search scope can be
26658 restricted to the parameters defined in the optional domain and block
26661 @var{name} is the name of the symbol. It must be a string. The
26662 optional @var{block} argument restricts the search to symbols visible
26663 in that @var{block}. The @var{block} argument must be a
26664 @code{gdb.Block} object. If omitted, the block for the current frame
26665 is used. The optional @var{domain} argument restricts
26666 the search to the domain type. The @var{domain} argument must be a
26667 domain constant defined in the @code{gdb} module and described later
26670 The result is a tuple of two elements.
26671 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
26673 If the symbol is found, the second element is @code{True} if the symbol
26674 is a field of a method's object (e.g., @code{this} in C@t{++}),
26675 otherwise it is @code{False}.
26676 If the symbol is not found, the second element is @code{False}.
26679 @findex gdb.lookup_global_symbol
26680 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
26681 This function searches for a global symbol by name.
26682 The search scope can be restricted to by the domain argument.
26684 @var{name} is the name of the symbol. It must be a string.
26685 The optional @var{domain} argument restricts the search to the domain type.
26686 The @var{domain} argument must be a domain constant defined in the @code{gdb}
26687 module and described later in this chapter.
26689 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
26693 A @code{gdb.Symbol} object has the following attributes:
26695 @defvar Symbol.type
26696 The type of the symbol or @code{None} if no type is recorded.
26697 This attribute is represented as a @code{gdb.Type} object.
26698 @xref{Types In Python}. This attribute is not writable.
26701 @defvar Symbol.symtab
26702 The symbol table in which the symbol appears. This attribute is
26703 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
26704 Python}. This attribute is not writable.
26707 @defvar Symbol.line
26708 The line number in the source code at which the symbol was defined.
26709 This is an integer.
26712 @defvar Symbol.name
26713 The name of the symbol as a string. This attribute is not writable.
26716 @defvar Symbol.linkage_name
26717 The name of the symbol, as used by the linker (i.e., may be mangled).
26718 This attribute is not writable.
26721 @defvar Symbol.print_name
26722 The name of the symbol in a form suitable for output. This is either
26723 @code{name} or @code{linkage_name}, depending on whether the user
26724 asked @value{GDBN} to display demangled or mangled names.
26727 @defvar Symbol.addr_class
26728 The address class of the symbol. This classifies how to find the value
26729 of a symbol. Each address class is a constant defined in the
26730 @code{gdb} module and described later in this chapter.
26733 @defvar Symbol.needs_frame
26734 This is @code{True} if evaluating this symbol's value requires a frame
26735 (@pxref{Frames In Python}) and @code{False} otherwise. Typically,
26736 local variables will require a frame, but other symbols will not.
26739 @defvar Symbol.is_argument
26740 @code{True} if the symbol is an argument of a function.
26743 @defvar Symbol.is_constant
26744 @code{True} if the symbol is a constant.
26747 @defvar Symbol.is_function
26748 @code{True} if the symbol is a function or a method.
26751 @defvar Symbol.is_variable
26752 @code{True} if the symbol is a variable.
26755 A @code{gdb.Symbol} object has the following methods:
26757 @defun Symbol.is_valid ()
26758 Returns @code{True} if the @code{gdb.Symbol} object is valid,
26759 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
26760 the symbol it refers to does not exist in @value{GDBN} any longer.
26761 All other @code{gdb.Symbol} methods will throw an exception if it is
26762 invalid at the time the method is called.
26765 @defun Symbol.value (@r{[}frame@r{]})
26766 Compute the value of the symbol, as a @code{gdb.Value}. For
26767 functions, this computes the address of the function, cast to the
26768 appropriate type. If the symbol requires a frame in order to compute
26769 its value, then @var{frame} must be given. If @var{frame} is not
26770 given, or if @var{frame} is invalid, then this method will throw an
26774 The available domain categories in @code{gdb.Symbol} are represented
26775 as constants in the @code{gdb} module:
26778 @findex SYMBOL_UNDEF_DOMAIN
26779 @findex gdb.SYMBOL_UNDEF_DOMAIN
26780 @item gdb.SYMBOL_UNDEF_DOMAIN
26781 This is used when a domain has not been discovered or none of the
26782 following domains apply. This usually indicates an error either
26783 in the symbol information or in @value{GDBN}'s handling of symbols.
26784 @findex SYMBOL_VAR_DOMAIN
26785 @findex gdb.SYMBOL_VAR_DOMAIN
26786 @item gdb.SYMBOL_VAR_DOMAIN
26787 This domain contains variables, function names, typedef names and enum
26789 @findex SYMBOL_STRUCT_DOMAIN
26790 @findex gdb.SYMBOL_STRUCT_DOMAIN
26791 @item gdb.SYMBOL_STRUCT_DOMAIN
26792 This domain holds struct, union and enum type names.
26793 @findex SYMBOL_LABEL_DOMAIN
26794 @findex gdb.SYMBOL_LABEL_DOMAIN
26795 @item gdb.SYMBOL_LABEL_DOMAIN
26796 This domain contains names of labels (for gotos).
26797 @findex SYMBOL_VARIABLES_DOMAIN
26798 @findex gdb.SYMBOL_VARIABLES_DOMAIN
26799 @item gdb.SYMBOL_VARIABLES_DOMAIN
26800 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
26801 contains everything minus functions and types.
26802 @findex SYMBOL_FUNCTIONS_DOMAIN
26803 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
26804 @item gdb.SYMBOL_FUNCTION_DOMAIN
26805 This domain contains all functions.
26806 @findex SYMBOL_TYPES_DOMAIN
26807 @findex gdb.SYMBOL_TYPES_DOMAIN
26808 @item gdb.SYMBOL_TYPES_DOMAIN
26809 This domain contains all types.
26812 The available address class categories in @code{gdb.Symbol} are represented
26813 as constants in the @code{gdb} module:
26816 @findex SYMBOL_LOC_UNDEF
26817 @findex gdb.SYMBOL_LOC_UNDEF
26818 @item gdb.SYMBOL_LOC_UNDEF
26819 If this is returned by address class, it indicates an error either in
26820 the symbol information or in @value{GDBN}'s handling of symbols.
26821 @findex SYMBOL_LOC_CONST
26822 @findex gdb.SYMBOL_LOC_CONST
26823 @item gdb.SYMBOL_LOC_CONST
26824 Value is constant int.
26825 @findex SYMBOL_LOC_STATIC
26826 @findex gdb.SYMBOL_LOC_STATIC
26827 @item gdb.SYMBOL_LOC_STATIC
26828 Value is at a fixed address.
26829 @findex SYMBOL_LOC_REGISTER
26830 @findex gdb.SYMBOL_LOC_REGISTER
26831 @item gdb.SYMBOL_LOC_REGISTER
26832 Value is in a register.
26833 @findex SYMBOL_LOC_ARG
26834 @findex gdb.SYMBOL_LOC_ARG
26835 @item gdb.SYMBOL_LOC_ARG
26836 Value is an argument. This value is at the offset stored within the
26837 symbol inside the frame's argument list.
26838 @findex SYMBOL_LOC_REF_ARG
26839 @findex gdb.SYMBOL_LOC_REF_ARG
26840 @item gdb.SYMBOL_LOC_REF_ARG
26841 Value address is stored in the frame's argument list. Just like
26842 @code{LOC_ARG} except that the value's address is stored at the
26843 offset, not the value itself.
26844 @findex SYMBOL_LOC_REGPARM_ADDR
26845 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
26846 @item gdb.SYMBOL_LOC_REGPARM_ADDR
26847 Value is a specified register. Just like @code{LOC_REGISTER} except
26848 the register holds the address of the argument instead of the argument
26850 @findex SYMBOL_LOC_LOCAL
26851 @findex gdb.SYMBOL_LOC_LOCAL
26852 @item gdb.SYMBOL_LOC_LOCAL
26853 Value is a local variable.
26854 @findex SYMBOL_LOC_TYPEDEF
26855 @findex gdb.SYMBOL_LOC_TYPEDEF
26856 @item gdb.SYMBOL_LOC_TYPEDEF
26857 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
26859 @findex SYMBOL_LOC_BLOCK
26860 @findex gdb.SYMBOL_LOC_BLOCK
26861 @item gdb.SYMBOL_LOC_BLOCK
26863 @findex SYMBOL_LOC_CONST_BYTES
26864 @findex gdb.SYMBOL_LOC_CONST_BYTES
26865 @item gdb.SYMBOL_LOC_CONST_BYTES
26866 Value is a byte-sequence.
26867 @findex SYMBOL_LOC_UNRESOLVED
26868 @findex gdb.SYMBOL_LOC_UNRESOLVED
26869 @item gdb.SYMBOL_LOC_UNRESOLVED
26870 Value is at a fixed address, but the address of the variable has to be
26871 determined from the minimal symbol table whenever the variable is
26873 @findex SYMBOL_LOC_OPTIMIZED_OUT
26874 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
26875 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
26876 The value does not actually exist in the program.
26877 @findex SYMBOL_LOC_COMPUTED
26878 @findex gdb.SYMBOL_LOC_COMPUTED
26879 @item gdb.SYMBOL_LOC_COMPUTED
26880 The value's address is a computed location.
26883 @node Symbol Tables In Python
26884 @subsubsection Symbol table representation in Python.
26886 @cindex symbol tables in python
26888 @tindex gdb.Symtab_and_line
26890 Access to symbol table data maintained by @value{GDBN} on the inferior
26891 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
26892 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
26893 from the @code{find_sal} method in @code{gdb.Frame} object.
26894 @xref{Frames In Python}.
26896 For more information on @value{GDBN}'s symbol table management, see
26897 @ref{Symbols, ,Examining the Symbol Table}, for more information.
26899 A @code{gdb.Symtab_and_line} object has the following attributes:
26901 @defvar Symtab_and_line.symtab
26902 The symbol table object (@code{gdb.Symtab}) for this frame.
26903 This attribute is not writable.
26906 @defvar Symtab_and_line.pc
26907 Indicates the start of the address range occupied by code for the
26908 current source line. This attribute is not writable.
26911 @defvar Symtab_and_line.last
26912 Indicates the end of the address range occupied by code for the current
26913 source line. This attribute is not writable.
26916 @defvar Symtab_and_line.line
26917 Indicates the current line number for this object. This
26918 attribute is not writable.
26921 A @code{gdb.Symtab_and_line} object has the following methods:
26923 @defun Symtab_and_line.is_valid ()
26924 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
26925 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
26926 invalid if the Symbol table and line object it refers to does not
26927 exist in @value{GDBN} any longer. All other
26928 @code{gdb.Symtab_and_line} methods will throw an exception if it is
26929 invalid at the time the method is called.
26932 A @code{gdb.Symtab} object has the following attributes:
26934 @defvar Symtab.filename
26935 The symbol table's source filename. This attribute is not writable.
26938 @defvar Symtab.objfile
26939 The symbol table's backing object file. @xref{Objfiles In Python}.
26940 This attribute is not writable.
26943 A @code{gdb.Symtab} object has the following methods:
26945 @defun Symtab.is_valid ()
26946 Returns @code{True} if the @code{gdb.Symtab} object is valid,
26947 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
26948 the symbol table it refers to does not exist in @value{GDBN} any
26949 longer. All other @code{gdb.Symtab} methods will throw an exception
26950 if it is invalid at the time the method is called.
26953 @defun Symtab.fullname ()
26954 Return the symbol table's source absolute file name.
26957 @defun Symtab.global_block ()
26958 Return the global block of the underlying symbol table.
26959 @xref{Blocks In Python}.
26962 @defun Symtab.static_block ()
26963 Return the static block of the underlying symbol table.
26964 @xref{Blocks In Python}.
26967 @node Breakpoints In Python
26968 @subsubsection Manipulating breakpoints using Python
26970 @cindex breakpoints in python
26971 @tindex gdb.Breakpoint
26973 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
26976 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
26977 Create a new breakpoint. @var{spec} is a string naming the
26978 location of the breakpoint, or an expression that defines a
26979 watchpoint. The contents can be any location recognized by the
26980 @code{break} command, or in the case of a watchpoint, by the @code{watch}
26981 command. The optional @var{type} denotes the breakpoint to create
26982 from the types defined later in this chapter. This argument can be
26983 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
26984 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
26985 allows the breakpoint to become invisible to the user. The breakpoint
26986 will neither be reported when created, nor will it be listed in the
26987 output from @code{info breakpoints} (but will be listed with the
26988 @code{maint info breakpoints} command). The optional @var{wp_class}
26989 argument defines the class of watchpoint to create, if @var{type} is
26990 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
26991 assumed to be a @code{gdb.WP_WRITE} class.
26994 @defun Breakpoint.stop (self)
26995 The @code{gdb.Breakpoint} class can be sub-classed and, in
26996 particular, you may choose to implement the @code{stop} method.
26997 If this method is defined as a sub-class of @code{gdb.Breakpoint},
26998 it will be called when the inferior reaches any location of a
26999 breakpoint which instantiates that sub-class. If the method returns
27000 @code{True}, the inferior will be stopped at the location of the
27001 breakpoint, otherwise the inferior will continue.
27003 If there are multiple breakpoints at the same location with a
27004 @code{stop} method, each one will be called regardless of the
27005 return status of the previous. This ensures that all @code{stop}
27006 methods have a chance to execute at that location. In this scenario
27007 if one of the methods returns @code{True} but the others return
27008 @code{False}, the inferior will still be stopped.
27010 You should not alter the execution state of the inferior (i.e.@:, step,
27011 next, etc.), alter the current frame context (i.e.@:, change the current
27012 active frame), or alter, add or delete any breakpoint. As a general
27013 rule, you should not alter any data within @value{GDBN} or the inferior
27016 Example @code{stop} implementation:
27019 class MyBreakpoint (gdb.Breakpoint):
27021 inf_val = gdb.parse_and_eval("foo")
27028 The available watchpoint types represented by constants are defined in the
27033 @findex gdb.WP_READ
27035 Read only watchpoint.
27038 @findex gdb.WP_WRITE
27040 Write only watchpoint.
27043 @findex gdb.WP_ACCESS
27044 @item gdb.WP_ACCESS
27045 Read/Write watchpoint.
27048 @defun Breakpoint.is_valid ()
27049 Return @code{True} if this @code{Breakpoint} object is valid,
27050 @code{False} otherwise. A @code{Breakpoint} object can become invalid
27051 if the user deletes the breakpoint. In this case, the object still
27052 exists, but the underlying breakpoint does not. In the cases of
27053 watchpoint scope, the watchpoint remains valid even if execution of the
27054 inferior leaves the scope of that watchpoint.
27057 @defun Breakpoint.delete
27058 Permanently deletes the @value{GDBN} breakpoint. This also
27059 invalidates the Python @code{Breakpoint} object. Any further access
27060 to this object's attributes or methods will raise an error.
27063 @defvar Breakpoint.enabled
27064 This attribute is @code{True} if the breakpoint is enabled, and
27065 @code{False} otherwise. This attribute is writable.
27068 @defvar Breakpoint.silent
27069 This attribute is @code{True} if the breakpoint is silent, and
27070 @code{False} otherwise. This attribute is writable.
27072 Note that a breakpoint can also be silent if it has commands and the
27073 first command is @code{silent}. This is not reported by the
27074 @code{silent} attribute.
27077 @defvar Breakpoint.thread
27078 If the breakpoint is thread-specific, this attribute holds the thread
27079 id. If the breakpoint is not thread-specific, this attribute is
27080 @code{None}. This attribute is writable.
27083 @defvar Breakpoint.task
27084 If the breakpoint is Ada task-specific, this attribute holds the Ada task
27085 id. If the breakpoint is not task-specific (or the underlying
27086 language is not Ada), this attribute is @code{None}. This attribute
27090 @defvar Breakpoint.ignore_count
27091 This attribute holds the ignore count for the breakpoint, an integer.
27092 This attribute is writable.
27095 @defvar Breakpoint.number
27096 This attribute holds the breakpoint's number --- the identifier used by
27097 the user to manipulate the breakpoint. This attribute is not writable.
27100 @defvar Breakpoint.type
27101 This attribute holds the breakpoint's type --- the identifier used to
27102 determine the actual breakpoint type or use-case. This attribute is not
27106 @defvar Breakpoint.visible
27107 This attribute tells whether the breakpoint is visible to the user
27108 when set, or when the @samp{info breakpoints} command is run. This
27109 attribute is not writable.
27112 The available types are represented by constants defined in the @code{gdb}
27116 @findex BP_BREAKPOINT
27117 @findex gdb.BP_BREAKPOINT
27118 @item gdb.BP_BREAKPOINT
27119 Normal code breakpoint.
27121 @findex BP_WATCHPOINT
27122 @findex gdb.BP_WATCHPOINT
27123 @item gdb.BP_WATCHPOINT
27124 Watchpoint breakpoint.
27126 @findex BP_HARDWARE_WATCHPOINT
27127 @findex gdb.BP_HARDWARE_WATCHPOINT
27128 @item gdb.BP_HARDWARE_WATCHPOINT
27129 Hardware assisted watchpoint.
27131 @findex BP_READ_WATCHPOINT
27132 @findex gdb.BP_READ_WATCHPOINT
27133 @item gdb.BP_READ_WATCHPOINT
27134 Hardware assisted read watchpoint.
27136 @findex BP_ACCESS_WATCHPOINT
27137 @findex gdb.BP_ACCESS_WATCHPOINT
27138 @item gdb.BP_ACCESS_WATCHPOINT
27139 Hardware assisted access watchpoint.
27142 @defvar Breakpoint.hit_count
27143 This attribute holds the hit count for the breakpoint, an integer.
27144 This attribute is writable, but currently it can only be set to zero.
27147 @defvar Breakpoint.location
27148 This attribute holds the location of the breakpoint, as specified by
27149 the user. It is a string. If the breakpoint does not have a location
27150 (that is, it is a watchpoint) the attribute's value is @code{None}. This
27151 attribute is not writable.
27154 @defvar Breakpoint.expression
27155 This attribute holds a breakpoint expression, as specified by
27156 the user. It is a string. If the breakpoint does not have an
27157 expression (the breakpoint is not a watchpoint) the attribute's value
27158 is @code{None}. This attribute is not writable.
27161 @defvar Breakpoint.condition
27162 This attribute holds the condition of the breakpoint, as specified by
27163 the user. It is a string. If there is no condition, this attribute's
27164 value is @code{None}. This attribute is writable.
27167 @defvar Breakpoint.commands
27168 This attribute holds the commands attached to the breakpoint. If
27169 there are commands, this attribute's value is a string holding all the
27170 commands, separated by newlines. If there are no commands, this
27171 attribute is @code{None}. This attribute is not writable.
27174 @node Finish Breakpoints in Python
27175 @subsubsection Finish Breakpoints
27177 @cindex python finish breakpoints
27178 @tindex gdb.FinishBreakpoint
27180 A finish breakpoint is a temporary breakpoint set at the return address of
27181 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
27182 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
27183 and deleted when the execution will run out of the breakpoint scope (i.e.@:
27184 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
27185 Finish breakpoints are thread specific and must be create with the right
27188 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
27189 Create a finish breakpoint at the return address of the @code{gdb.Frame}
27190 object @var{frame}. If @var{frame} is not provided, this defaults to the
27191 newest frame. The optional @var{internal} argument allows the breakpoint to
27192 become invisible to the user. @xref{Breakpoints In Python}, for further
27193 details about this argument.
27196 @defun FinishBreakpoint.out_of_scope (self)
27197 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
27198 @code{return} command, @dots{}), a function may not properly terminate, and
27199 thus never hit the finish breakpoint. When @value{GDBN} notices such a
27200 situation, the @code{out_of_scope} callback will be triggered.
27202 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
27206 class MyFinishBreakpoint (gdb.FinishBreakpoint)
27208 print "normal finish"
27211 def out_of_scope ():
27212 print "abnormal finish"
27216 @defvar FinishBreakpoint.return_value
27217 When @value{GDBN} is stopped at a finish breakpoint and the frame
27218 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
27219 attribute will contain a @code{gdb.Value} object corresponding to the return
27220 value of the function. The value will be @code{None} if the function return
27221 type is @code{void} or if the return value was not computable. This attribute
27225 @node Lazy Strings In Python
27226 @subsubsection Python representation of lazy strings.
27228 @cindex lazy strings in python
27229 @tindex gdb.LazyString
27231 A @dfn{lazy string} is a string whose contents is not retrieved or
27232 encoded until it is needed.
27234 A @code{gdb.LazyString} is represented in @value{GDBN} as an
27235 @code{address} that points to a region of memory, an @code{encoding}
27236 that will be used to encode that region of memory, and a @code{length}
27237 to delimit the region of memory that represents the string. The
27238 difference between a @code{gdb.LazyString} and a string wrapped within
27239 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
27240 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
27241 retrieved and encoded during printing, while a @code{gdb.Value}
27242 wrapping a string is immediately retrieved and encoded on creation.
27244 A @code{gdb.LazyString} object has the following functions:
27246 @defun LazyString.value ()
27247 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
27248 will point to the string in memory, but will lose all the delayed
27249 retrieval, encoding and handling that @value{GDBN} applies to a
27250 @code{gdb.LazyString}.
27253 @defvar LazyString.address
27254 This attribute holds the address of the string. This attribute is not
27258 @defvar LazyString.length
27259 This attribute holds the length of the string in characters. If the
27260 length is -1, then the string will be fetched and encoded up to the
27261 first null of appropriate width. This attribute is not writable.
27264 @defvar LazyString.encoding
27265 This attribute holds the encoding that will be applied to the string
27266 when the string is printed by @value{GDBN}. If the encoding is not
27267 set, or contains an empty string, then @value{GDBN} will select the
27268 most appropriate encoding when the string is printed. This attribute
27272 @defvar LazyString.type
27273 This attribute holds the type that is represented by the lazy string's
27274 type. For a lazy string this will always be a pointer type. To
27275 resolve this to the lazy string's character type, use the type's
27276 @code{target} method. @xref{Types In Python}. This attribute is not
27280 @node Architectures In Python
27281 @subsubsection Python representation of architectures
27282 @cindex Python architectures
27284 @value{GDBN} uses architecture specific parameters and artifacts in a
27285 number of its various computations. An architecture is represented
27286 by an instance of the @code{gdb.Architecture} class.
27288 A @code{gdb.Architecture} class has the following methods:
27290 @defun Architecture.name ()
27291 Return the name (string value) of the architecture.
27294 @defun Architecture.disassemble (@var{start_pc} @r{[}, @var{end_pc} @r{[}, @var{count}@r{]]})
27295 Return a list of disassembled instructions starting from the memory
27296 address @var{start_pc}. The optional arguments @var{end_pc} and
27297 @var{count} determine the number of instructions in the returned list.
27298 If both the optional arguments @var{end_pc} and @var{count} are
27299 specified, then a list of at most @var{count} disassembled instructions
27300 whose start address falls in the closed memory address interval from
27301 @var{start_pc} to @var{end_pc} are returned. If @var{end_pc} is not
27302 specified, but @var{count} is specified, then @var{count} number of
27303 instructions starting from the address @var{start_pc} are returned. If
27304 @var{count} is not specified but @var{end_pc} is specified, then all
27305 instructions whose start address falls in the closed memory address
27306 interval from @var{start_pc} to @var{end_pc} are returned. If neither
27307 @var{end_pc} nor @var{count} are specified, then a single instruction at
27308 @var{start_pc} is returned. For all of these cases, each element of the
27309 returned list is a Python @code{dict} with the following string keys:
27314 The value corresponding to this key is a Python long integer capturing
27315 the memory address of the instruction.
27318 The value corresponding to this key is a string value which represents
27319 the instruction with assembly language mnemonics. The assembly
27320 language flavor used is the same as that specified by the current CLI
27321 variable @code{disassembly-flavor}. @xref{Machine Code}.
27324 The value corresponding to this key is the length (integer value) of the
27325 instruction in bytes.
27330 @node Python Auto-loading
27331 @subsection Python Auto-loading
27332 @cindex Python auto-loading
27334 When a new object file is read (for example, due to the @code{file}
27335 command, or because the inferior has loaded a shared library),
27336 @value{GDBN} will look for Python support scripts in several ways:
27337 @file{@var{objfile}-gdb.py} (@pxref{objfile-gdb.py file})
27338 and @code{.debug_gdb_scripts} section
27339 (@pxref{dotdebug_gdb_scripts section}).
27341 The auto-loading feature is useful for supplying application-specific
27342 debugging commands and scripts.
27344 Auto-loading can be enabled or disabled,
27345 and the list of auto-loaded scripts can be printed.
27348 @anchor{set auto-load python-scripts}
27349 @kindex set auto-load python-scripts
27350 @item set auto-load python-scripts [on|off]
27351 Enable or disable the auto-loading of Python scripts.
27353 @anchor{show auto-load python-scripts}
27354 @kindex show auto-load python-scripts
27355 @item show auto-load python-scripts
27356 Show whether auto-loading of Python scripts is enabled or disabled.
27358 @anchor{info auto-load python-scripts}
27359 @kindex info auto-load python-scripts
27360 @cindex print list of auto-loaded Python scripts
27361 @item info auto-load python-scripts [@var{regexp}]
27362 Print the list of all Python scripts that @value{GDBN} auto-loaded.
27364 Also printed is the list of Python scripts that were mentioned in
27365 the @code{.debug_gdb_scripts} section and were not found
27366 (@pxref{dotdebug_gdb_scripts section}).
27367 This is useful because their names are not printed when @value{GDBN}
27368 tries to load them and fails. There may be many of them, and printing
27369 an error message for each one is problematic.
27371 If @var{regexp} is supplied only Python scripts with matching names are printed.
27376 (gdb) info auto-load python-scripts
27378 Yes py-section-script.py
27379 full name: /tmp/py-section-script.py
27380 No my-foo-pretty-printers.py
27384 When reading an auto-loaded file, @value{GDBN} sets the
27385 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
27386 function (@pxref{Objfiles In Python}). This can be useful for
27387 registering objfile-specific pretty-printers and frame-filters.
27390 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
27391 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
27392 * Which flavor to choose?::
27395 @node objfile-gdb.py file
27396 @subsubsection The @file{@var{objfile}-gdb.py} file
27397 @cindex @file{@var{objfile}-gdb.py}
27399 When a new object file is read, @value{GDBN} looks for
27400 a file named @file{@var{objfile}-gdb.py} (we call it @var{script-name} below),
27401 where @var{objfile} is the object file's real name, formed by ensuring
27402 that the file name is absolute, following all symlinks, and resolving
27403 @code{.} and @code{..} components. If this file exists and is
27404 readable, @value{GDBN} will evaluate it as a Python script.
27406 If this file does not exist, then @value{GDBN} will look for
27407 @var{script-name} file in all of the directories as specified below.
27409 Note that loading of this script file also requires accordingly configured
27410 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27412 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
27413 scripts normally according to its @file{.exe} filename. But if no scripts are
27414 found @value{GDBN} also tries script filenames matching the object file without
27415 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
27416 is attempted on any platform. This makes the script filenames compatible
27417 between Unix and MS-Windows hosts.
27420 @anchor{set auto-load scripts-directory}
27421 @kindex set auto-load scripts-directory
27422 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
27423 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
27424 may be delimited by the host platform path separator in use
27425 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
27427 Each entry here needs to be covered also by the security setting
27428 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
27430 @anchor{with-auto-load-dir}
27431 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
27432 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
27433 configuration option @option{--with-auto-load-dir}.
27435 Any reference to @file{$debugdir} will get replaced by
27436 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
27437 reference to @file{$datadir} will get replaced by @var{data-directory} which is
27438 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
27439 @file{$datadir} must be placed as a directory component --- either alone or
27440 delimited by @file{/} or @file{\} directory separators, depending on the host
27443 The list of directories uses path separator (@samp{:} on GNU and Unix
27444 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
27445 to the @env{PATH} environment variable.
27447 @anchor{show auto-load scripts-directory}
27448 @kindex show auto-load scripts-directory
27449 @item show auto-load scripts-directory
27450 Show @value{GDBN} auto-loaded scripts location.
27453 @value{GDBN} does not track which files it has already auto-loaded this way.
27454 @value{GDBN} will load the associated script every time the corresponding
27455 @var{objfile} is opened.
27456 So your @file{-gdb.py} file should be careful to avoid errors if it
27457 is evaluated more than once.
27459 @node dotdebug_gdb_scripts section
27460 @subsubsection The @code{.debug_gdb_scripts} section
27461 @cindex @code{.debug_gdb_scripts} section
27463 For systems using file formats like ELF and COFF,
27464 when @value{GDBN} loads a new object file
27465 it will look for a special section named @samp{.debug_gdb_scripts}.
27466 If this section exists, its contents is a list of names of scripts to load.
27468 @value{GDBN} will look for each specified script file first in the
27469 current directory and then along the source search path
27470 (@pxref{Source Path, ,Specifying Source Directories}),
27471 except that @file{$cdir} is not searched, since the compilation
27472 directory is not relevant to scripts.
27474 Entries can be placed in section @code{.debug_gdb_scripts} with,
27475 for example, this GCC macro:
27478 /* Note: The "MS" section flags are to remove duplicates. */
27479 #define DEFINE_GDB_SCRIPT(script_name) \
27481 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
27483 .asciz \"" script_name "\"\n\
27489 Then one can reference the macro in a header or source file like this:
27492 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
27495 The script name may include directories if desired.
27497 Note that loading of this script file also requires accordingly configured
27498 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27500 If the macro is put in a header, any application or library
27501 using this header will get a reference to the specified script.
27503 @node Which flavor to choose?
27504 @subsubsection Which flavor to choose?
27506 Given the multiple ways of auto-loading Python scripts, it might not always
27507 be clear which one to choose. This section provides some guidance.
27509 Benefits of the @file{-gdb.py} way:
27513 Can be used with file formats that don't support multiple sections.
27516 Ease of finding scripts for public libraries.
27518 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
27519 in the source search path.
27520 For publicly installed libraries, e.g., @file{libstdc++}, there typically
27521 isn't a source directory in which to find the script.
27524 Doesn't require source code additions.
27527 Benefits of the @code{.debug_gdb_scripts} way:
27531 Works with static linking.
27533 Scripts for libraries done the @file{-gdb.py} way require an objfile to
27534 trigger their loading. When an application is statically linked the only
27535 objfile available is the executable, and it is cumbersome to attach all the
27536 scripts from all the input libraries to the executable's @file{-gdb.py} script.
27539 Works with classes that are entirely inlined.
27541 Some classes can be entirely inlined, and thus there may not be an associated
27542 shared library to attach a @file{-gdb.py} script to.
27545 Scripts needn't be copied out of the source tree.
27547 In some circumstances, apps can be built out of large collections of internal
27548 libraries, and the build infrastructure necessary to install the
27549 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
27550 cumbersome. It may be easier to specify the scripts in the
27551 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
27552 top of the source tree to the source search path.
27555 @node Python modules
27556 @subsection Python modules
27557 @cindex python modules
27559 @value{GDBN} comes with several modules to assist writing Python code.
27562 * gdb.printing:: Building and registering pretty-printers.
27563 * gdb.types:: Utilities for working with types.
27564 * gdb.prompt:: Utilities for prompt value substitution.
27568 @subsubsection gdb.printing
27569 @cindex gdb.printing
27571 This module provides a collection of utilities for working with
27575 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
27576 This class specifies the API that makes @samp{info pretty-printer},
27577 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
27578 Pretty-printers should generally inherit from this class.
27580 @item SubPrettyPrinter (@var{name})
27581 For printers that handle multiple types, this class specifies the
27582 corresponding API for the subprinters.
27584 @item RegexpCollectionPrettyPrinter (@var{name})
27585 Utility class for handling multiple printers, all recognized via
27586 regular expressions.
27587 @xref{Writing a Pretty-Printer}, for an example.
27589 @item FlagEnumerationPrinter (@var{name})
27590 A pretty-printer which handles printing of @code{enum} values. Unlike
27591 @value{GDBN}'s built-in @code{enum} printing, this printer attempts to
27592 work properly when there is some overlap between the enumeration
27593 constants. @var{name} is the name of the printer and also the name of
27594 the @code{enum} type to look up.
27596 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
27597 Register @var{printer} with the pretty-printer list of @var{obj}.
27598 If @var{replace} is @code{True} then any existing copy of the printer
27599 is replaced. Otherwise a @code{RuntimeError} exception is raised
27600 if a printer with the same name already exists.
27604 @subsubsection gdb.types
27607 This module provides a collection of utilities for working with
27608 @code{gdb.Type} objects.
27611 @item get_basic_type (@var{type})
27612 Return @var{type} with const and volatile qualifiers stripped,
27613 and with typedefs and C@t{++} references converted to the underlying type.
27618 typedef const int const_int;
27620 const_int& foo_ref (foo);
27621 int main () @{ return 0; @}
27628 (gdb) python import gdb.types
27629 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
27630 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
27634 @item has_field (@var{type}, @var{field})
27635 Return @code{True} if @var{type}, assumed to be a type with fields
27636 (e.g., a structure or union), has field @var{field}.
27638 @item make_enum_dict (@var{enum_type})
27639 Return a Python @code{dictionary} type produced from @var{enum_type}.
27641 @item deep_items (@var{type})
27642 Returns a Python iterator similar to the standard
27643 @code{gdb.Type.iteritems} method, except that the iterator returned
27644 by @code{deep_items} will recursively traverse anonymous struct or
27645 union fields. For example:
27659 Then in @value{GDBN}:
27661 (@value{GDBP}) python import gdb.types
27662 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
27663 (@value{GDBP}) python print struct_a.keys ()
27665 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
27666 @{['a', 'b0', 'b1']@}
27669 @item get_type_recognizers ()
27670 Return a list of the enabled type recognizers for the current context.
27671 This is called by @value{GDBN} during the type-printing process
27672 (@pxref{Type Printing API}).
27674 @item apply_type_recognizers (recognizers, type_obj)
27675 Apply the type recognizers, @var{recognizers}, to the type object
27676 @var{type_obj}. If any recognizer returns a string, return that
27677 string. Otherwise, return @code{None}. This is called by
27678 @value{GDBN} during the type-printing process (@pxref{Type Printing
27681 @item register_type_printer (locus, printer)
27682 This is a convenience function to register a type printer.
27683 @var{printer} is the type printer to register. It must implement the
27684 type printer protocol. @var{locus} is either a @code{gdb.Objfile}, in
27685 which case the printer is registered with that objfile; a
27686 @code{gdb.Progspace}, in which case the printer is registered with
27687 that progspace; or @code{None}, in which case the printer is
27688 registered globally.
27691 This is a base class that implements the type printer protocol. Type
27692 printers are encouraged, but not required, to derive from this class.
27693 It defines a constructor:
27695 @defmethod TypePrinter __init__ (self, name)
27696 Initialize the type printer with the given name. The new printer
27697 starts in the enabled state.
27703 @subsubsection gdb.prompt
27706 This module provides a method for prompt value-substitution.
27709 @item substitute_prompt (@var{string})
27710 Return @var{string} with escape sequences substituted by values. Some
27711 escape sequences take arguments. You can specify arguments inside
27712 ``@{@}'' immediately following the escape sequence.
27714 The escape sequences you can pass to this function are:
27718 Substitute a backslash.
27720 Substitute an ESC character.
27722 Substitute the selected frame; an argument names a frame parameter.
27724 Substitute a newline.
27726 Substitute a parameter's value; the argument names the parameter.
27728 Substitute a carriage return.
27730 Substitute the selected thread; an argument names a thread parameter.
27732 Substitute the version of GDB.
27734 Substitute the current working directory.
27736 Begin a sequence of non-printing characters. These sequences are
27737 typically used with the ESC character, and are not counted in the string
27738 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
27739 blue-colored ``(gdb)'' prompt where the length is five.
27741 End a sequence of non-printing characters.
27747 substitute_prompt (``frame: \f,
27748 print arguments: \p@{print frame-arguments@}'')
27751 @exdent will return the string:
27754 "frame: main, print arguments: scalars"
27759 @section Creating new spellings of existing commands
27760 @cindex aliases for commands
27762 It is often useful to define alternate spellings of existing commands.
27763 For example, if a new @value{GDBN} command defined in Python has
27764 a long name to type, it is handy to have an abbreviated version of it
27765 that involves less typing.
27767 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
27768 of the @samp{step} command even though it is otherwise an ambiguous
27769 abbreviation of other commands like @samp{set} and @samp{show}.
27771 Aliases are also used to provide shortened or more common versions
27772 of multi-word commands. For example, @value{GDBN} provides the
27773 @samp{tty} alias of the @samp{set inferior-tty} command.
27775 You can define a new alias with the @samp{alias} command.
27780 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
27784 @var{ALIAS} specifies the name of the new alias.
27785 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
27788 @var{COMMAND} specifies the name of an existing command
27789 that is being aliased.
27791 The @samp{-a} option specifies that the new alias is an abbreviation
27792 of the command. Abbreviations are not shown in command
27793 lists displayed by the @samp{help} command.
27795 The @samp{--} option specifies the end of options,
27796 and is useful when @var{ALIAS} begins with a dash.
27798 Here is a simple example showing how to make an abbreviation
27799 of a command so that there is less to type.
27800 Suppose you were tired of typing @samp{disas}, the current
27801 shortest unambiguous abbreviation of the @samp{disassemble} command
27802 and you wanted an even shorter version named @samp{di}.
27803 The following will accomplish this.
27806 (gdb) alias -a di = disas
27809 Note that aliases are different from user-defined commands.
27810 With a user-defined command, you also need to write documentation
27811 for it with the @samp{document} command.
27812 An alias automatically picks up the documentation of the existing command.
27814 Here is an example where we make @samp{elms} an abbreviation of
27815 @samp{elements} in the @samp{set print elements} command.
27816 This is to show that you can make an abbreviation of any part
27820 (gdb) alias -a set print elms = set print elements
27821 (gdb) alias -a show print elms = show print elements
27822 (gdb) set p elms 20
27824 Limit on string chars or array elements to print is 200.
27827 Note that if you are defining an alias of a @samp{set} command,
27828 and you want to have an alias for the corresponding @samp{show}
27829 command, then you need to define the latter separately.
27831 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
27832 @var{ALIAS}, just as they are normally.
27835 (gdb) alias -a set pr elms = set p ele
27838 Finally, here is an example showing the creation of a one word
27839 alias for a more complex command.
27840 This creates alias @samp{spe} of the command @samp{set print elements}.
27843 (gdb) alias spe = set print elements
27848 @chapter Command Interpreters
27849 @cindex command interpreters
27851 @value{GDBN} supports multiple command interpreters, and some command
27852 infrastructure to allow users or user interface writers to switch
27853 between interpreters or run commands in other interpreters.
27855 @value{GDBN} currently supports two command interpreters, the console
27856 interpreter (sometimes called the command-line interpreter or @sc{cli})
27857 and the machine interface interpreter (or @sc{gdb/mi}). This manual
27858 describes both of these interfaces in great detail.
27860 By default, @value{GDBN} will start with the console interpreter.
27861 However, the user may choose to start @value{GDBN} with another
27862 interpreter by specifying the @option{-i} or @option{--interpreter}
27863 startup options. Defined interpreters include:
27867 @cindex console interpreter
27868 The traditional console or command-line interpreter. This is the most often
27869 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
27870 @value{GDBN} will use this interpreter.
27873 @cindex mi interpreter
27874 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
27875 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
27876 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
27880 @cindex mi2 interpreter
27881 The current @sc{gdb/mi} interface.
27884 @cindex mi1 interpreter
27885 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
27889 @cindex invoke another interpreter
27890 The interpreter being used by @value{GDBN} may not be dynamically
27891 switched at runtime. Although possible, this could lead to a very
27892 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
27893 enters the command "interpreter-set console" in a console view,
27894 @value{GDBN} would switch to using the console interpreter, rendering
27895 the IDE inoperable!
27897 @kindex interpreter-exec
27898 Although you may only choose a single interpreter at startup, you may execute
27899 commands in any interpreter from the current interpreter using the appropriate
27900 command. If you are running the console interpreter, simply use the
27901 @code{interpreter-exec} command:
27904 interpreter-exec mi "-data-list-register-names"
27907 @sc{gdb/mi} has a similar command, although it is only available in versions of
27908 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
27911 @chapter @value{GDBN} Text User Interface
27913 @cindex Text User Interface
27916 * TUI Overview:: TUI overview
27917 * TUI Keys:: TUI key bindings
27918 * TUI Single Key Mode:: TUI single key mode
27919 * TUI Commands:: TUI-specific commands
27920 * TUI Configuration:: TUI configuration variables
27923 The @value{GDBN} Text User Interface (TUI) is a terminal
27924 interface which uses the @code{curses} library to show the source
27925 file, the assembly output, the program registers and @value{GDBN}
27926 commands in separate text windows. The TUI mode is supported only
27927 on platforms where a suitable version of the @code{curses} library
27930 The TUI mode is enabled by default when you invoke @value{GDBN} as
27931 @samp{@value{GDBP} -tui}.
27932 You can also switch in and out of TUI mode while @value{GDBN} runs by
27933 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
27934 @xref{TUI Keys, ,TUI Key Bindings}.
27937 @section TUI Overview
27939 In TUI mode, @value{GDBN} can display several text windows:
27943 This window is the @value{GDBN} command window with the @value{GDBN}
27944 prompt and the @value{GDBN} output. The @value{GDBN} input is still
27945 managed using readline.
27948 The source window shows the source file of the program. The current
27949 line and active breakpoints are displayed in this window.
27952 The assembly window shows the disassembly output of the program.
27955 This window shows the processor registers. Registers are highlighted
27956 when their values change.
27959 The source and assembly windows show the current program position
27960 by highlighting the current line and marking it with a @samp{>} marker.
27961 Breakpoints are indicated with two markers. The first marker
27962 indicates the breakpoint type:
27966 Breakpoint which was hit at least once.
27969 Breakpoint which was never hit.
27972 Hardware breakpoint which was hit at least once.
27975 Hardware breakpoint which was never hit.
27978 The second marker indicates whether the breakpoint is enabled or not:
27982 Breakpoint is enabled.
27985 Breakpoint is disabled.
27988 The source, assembly and register windows are updated when the current
27989 thread changes, when the frame changes, or when the program counter
27992 These windows are not all visible at the same time. The command
27993 window is always visible. The others can be arranged in several
28004 source and assembly,
28007 source and registers, or
28010 assembly and registers.
28013 A status line above the command window shows the following information:
28017 Indicates the current @value{GDBN} target.
28018 (@pxref{Targets, ,Specifying a Debugging Target}).
28021 Gives the current process or thread number.
28022 When no process is being debugged, this field is set to @code{No process}.
28025 Gives the current function name for the selected frame.
28026 The name is demangled if demangling is turned on (@pxref{Print Settings}).
28027 When there is no symbol corresponding to the current program counter,
28028 the string @code{??} is displayed.
28031 Indicates the current line number for the selected frame.
28032 When the current line number is not known, the string @code{??} is displayed.
28035 Indicates the current program counter address.
28039 @section TUI Key Bindings
28040 @cindex TUI key bindings
28042 The TUI installs several key bindings in the readline keymaps
28043 @ifset SYSTEM_READLINE
28044 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
28046 @ifclear SYSTEM_READLINE
28047 (@pxref{Command Line Editing}).
28049 The following key bindings are installed for both TUI mode and the
28050 @value{GDBN} standard mode.
28059 Enter or leave the TUI mode. When leaving the TUI mode,
28060 the curses window management stops and @value{GDBN} operates using
28061 its standard mode, writing on the terminal directly. When reentering
28062 the TUI mode, control is given back to the curses windows.
28063 The screen is then refreshed.
28067 Use a TUI layout with only one window. The layout will
28068 either be @samp{source} or @samp{assembly}. When the TUI mode
28069 is not active, it will switch to the TUI mode.
28071 Think of this key binding as the Emacs @kbd{C-x 1} binding.
28075 Use a TUI layout with at least two windows. When the current
28076 layout already has two windows, the next layout with two windows is used.
28077 When a new layout is chosen, one window will always be common to the
28078 previous layout and the new one.
28080 Think of it as the Emacs @kbd{C-x 2} binding.
28084 Change the active window. The TUI associates several key bindings
28085 (like scrolling and arrow keys) with the active window. This command
28086 gives the focus to the next TUI window.
28088 Think of it as the Emacs @kbd{C-x o} binding.
28092 Switch in and out of the TUI SingleKey mode that binds single
28093 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
28096 The following key bindings only work in the TUI mode:
28101 Scroll the active window one page up.
28105 Scroll the active window one page down.
28109 Scroll the active window one line up.
28113 Scroll the active window one line down.
28117 Scroll the active window one column left.
28121 Scroll the active window one column right.
28125 Refresh the screen.
28128 Because the arrow keys scroll the active window in the TUI mode, they
28129 are not available for their normal use by readline unless the command
28130 window has the focus. When another window is active, you must use
28131 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
28132 and @kbd{C-f} to control the command window.
28134 @node TUI Single Key Mode
28135 @section TUI Single Key Mode
28136 @cindex TUI single key mode
28138 The TUI also provides a @dfn{SingleKey} mode, which binds several
28139 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
28140 switch into this mode, where the following key bindings are used:
28143 @kindex c @r{(SingleKey TUI key)}
28147 @kindex d @r{(SingleKey TUI key)}
28151 @kindex f @r{(SingleKey TUI key)}
28155 @kindex n @r{(SingleKey TUI key)}
28159 @kindex q @r{(SingleKey TUI key)}
28161 exit the SingleKey mode.
28163 @kindex r @r{(SingleKey TUI key)}
28167 @kindex s @r{(SingleKey TUI key)}
28171 @kindex u @r{(SingleKey TUI key)}
28175 @kindex v @r{(SingleKey TUI key)}
28179 @kindex w @r{(SingleKey TUI key)}
28184 Other keys temporarily switch to the @value{GDBN} command prompt.
28185 The key that was pressed is inserted in the editing buffer so that
28186 it is possible to type most @value{GDBN} commands without interaction
28187 with the TUI SingleKey mode. Once the command is entered the TUI
28188 SingleKey mode is restored. The only way to permanently leave
28189 this mode is by typing @kbd{q} or @kbd{C-x s}.
28193 @section TUI-specific Commands
28194 @cindex TUI commands
28196 The TUI has specific commands to control the text windows.
28197 These commands are always available, even when @value{GDBN} is not in
28198 the TUI mode. When @value{GDBN} is in the standard mode, most
28199 of these commands will automatically switch to the TUI mode.
28201 Note that if @value{GDBN}'s @code{stdout} is not connected to a
28202 terminal, or @value{GDBN} has been started with the machine interface
28203 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
28204 these commands will fail with an error, because it would not be
28205 possible or desirable to enable curses window management.
28210 List and give the size of all displayed windows.
28214 Display the next layout.
28217 Display the previous layout.
28220 Display the source window only.
28223 Display the assembly window only.
28226 Display the source and assembly window.
28229 Display the register window together with the source or assembly window.
28233 Make the next window active for scrolling.
28236 Make the previous window active for scrolling.
28239 Make the source window active for scrolling.
28242 Make the assembly window active for scrolling.
28245 Make the register window active for scrolling.
28248 Make the command window active for scrolling.
28252 Refresh the screen. This is similar to typing @kbd{C-L}.
28254 @item tui reg float
28256 Show the floating point registers in the register window.
28258 @item tui reg general
28259 Show the general registers in the register window.
28262 Show the next register group. The list of register groups as well as
28263 their order is target specific. The predefined register groups are the
28264 following: @code{general}, @code{float}, @code{system}, @code{vector},
28265 @code{all}, @code{save}, @code{restore}.
28267 @item tui reg system
28268 Show the system registers in the register window.
28272 Update the source window and the current execution point.
28274 @item winheight @var{name} +@var{count}
28275 @itemx winheight @var{name} -@var{count}
28277 Change the height of the window @var{name} by @var{count}
28278 lines. Positive counts increase the height, while negative counts
28281 @item tabset @var{nchars}
28283 Set the width of tab stops to be @var{nchars} characters.
28286 @node TUI Configuration
28287 @section TUI Configuration Variables
28288 @cindex TUI configuration variables
28290 Several configuration variables control the appearance of TUI windows.
28293 @item set tui border-kind @var{kind}
28294 @kindex set tui border-kind
28295 Select the border appearance for the source, assembly and register windows.
28296 The possible values are the following:
28299 Use a space character to draw the border.
28302 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
28305 Use the Alternate Character Set to draw the border. The border is
28306 drawn using character line graphics if the terminal supports them.
28309 @item set tui border-mode @var{mode}
28310 @kindex set tui border-mode
28311 @itemx set tui active-border-mode @var{mode}
28312 @kindex set tui active-border-mode
28313 Select the display attributes for the borders of the inactive windows
28314 or the active window. The @var{mode} can be one of the following:
28317 Use normal attributes to display the border.
28323 Use reverse video mode.
28326 Use half bright mode.
28328 @item half-standout
28329 Use half bright and standout mode.
28332 Use extra bright or bold mode.
28334 @item bold-standout
28335 Use extra bright or bold and standout mode.
28340 @chapter Using @value{GDBN} under @sc{gnu} Emacs
28343 @cindex @sc{gnu} Emacs
28344 A special interface allows you to use @sc{gnu} Emacs to view (and
28345 edit) the source files for the program you are debugging with
28348 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
28349 executable file you want to debug as an argument. This command starts
28350 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
28351 created Emacs buffer.
28352 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
28354 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
28359 All ``terminal'' input and output goes through an Emacs buffer, called
28362 This applies both to @value{GDBN} commands and their output, and to the input
28363 and output done by the program you are debugging.
28365 This is useful because it means that you can copy the text of previous
28366 commands and input them again; you can even use parts of the output
28369 All the facilities of Emacs' Shell mode are available for interacting
28370 with your program. In particular, you can send signals the usual
28371 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
28375 @value{GDBN} displays source code through Emacs.
28377 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
28378 source file for that frame and puts an arrow (@samp{=>}) at the
28379 left margin of the current line. Emacs uses a separate buffer for
28380 source display, and splits the screen to show both your @value{GDBN} session
28383 Explicit @value{GDBN} @code{list} or search commands still produce output as
28384 usual, but you probably have no reason to use them from Emacs.
28387 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
28388 a graphical mode, enabled by default, which provides further buffers
28389 that can control the execution and describe the state of your program.
28390 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
28392 If you specify an absolute file name when prompted for the @kbd{M-x
28393 gdb} argument, then Emacs sets your current working directory to where
28394 your program resides. If you only specify the file name, then Emacs
28395 sets your current working directory to the directory associated
28396 with the previous buffer. In this case, @value{GDBN} may find your
28397 program by searching your environment's @code{PATH} variable, but on
28398 some operating systems it might not find the source. So, although the
28399 @value{GDBN} input and output session proceeds normally, the auxiliary
28400 buffer does not display the current source and line of execution.
28402 The initial working directory of @value{GDBN} is printed on the top
28403 line of the GUD buffer and this serves as a default for the commands
28404 that specify files for @value{GDBN} to operate on. @xref{Files,
28405 ,Commands to Specify Files}.
28407 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
28408 need to call @value{GDBN} by a different name (for example, if you
28409 keep several configurations around, with different names) you can
28410 customize the Emacs variable @code{gud-gdb-command-name} to run the
28413 In the GUD buffer, you can use these special Emacs commands in
28414 addition to the standard Shell mode commands:
28418 Describe the features of Emacs' GUD Mode.
28421 Execute to another source line, like the @value{GDBN} @code{step} command; also
28422 update the display window to show the current file and location.
28425 Execute to next source line in this function, skipping all function
28426 calls, like the @value{GDBN} @code{next} command. Then update the display window
28427 to show the current file and location.
28430 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
28431 display window accordingly.
28434 Execute until exit from the selected stack frame, like the @value{GDBN}
28435 @code{finish} command.
28438 Continue execution of your program, like the @value{GDBN} @code{continue}
28442 Go up the number of frames indicated by the numeric argument
28443 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
28444 like the @value{GDBN} @code{up} command.
28447 Go down the number of frames indicated by the numeric argument, like the
28448 @value{GDBN} @code{down} command.
28451 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
28452 tells @value{GDBN} to set a breakpoint on the source line point is on.
28454 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
28455 separate frame which shows a backtrace when the GUD buffer is current.
28456 Move point to any frame in the stack and type @key{RET} to make it
28457 become the current frame and display the associated source in the
28458 source buffer. Alternatively, click @kbd{Mouse-2} to make the
28459 selected frame become the current one. In graphical mode, the
28460 speedbar displays watch expressions.
28462 If you accidentally delete the source-display buffer, an easy way to get
28463 it back is to type the command @code{f} in the @value{GDBN} buffer, to
28464 request a frame display; when you run under Emacs, this recreates
28465 the source buffer if necessary to show you the context of the current
28468 The source files displayed in Emacs are in ordinary Emacs buffers
28469 which are visiting the source files in the usual way. You can edit
28470 the files with these buffers if you wish; but keep in mind that @value{GDBN}
28471 communicates with Emacs in terms of line numbers. If you add or
28472 delete lines from the text, the line numbers that @value{GDBN} knows cease
28473 to correspond properly with the code.
28475 A more detailed description of Emacs' interaction with @value{GDBN} is
28476 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
28480 @chapter The @sc{gdb/mi} Interface
28482 @unnumberedsec Function and Purpose
28484 @cindex @sc{gdb/mi}, its purpose
28485 @sc{gdb/mi} is a line based machine oriented text interface to
28486 @value{GDBN} and is activated by specifying using the
28487 @option{--interpreter} command line option (@pxref{Mode Options}). It
28488 is specifically intended to support the development of systems which
28489 use the debugger as just one small component of a larger system.
28491 This chapter is a specification of the @sc{gdb/mi} interface. It is written
28492 in the form of a reference manual.
28494 Note that @sc{gdb/mi} is still under construction, so some of the
28495 features described below are incomplete and subject to change
28496 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
28498 @unnumberedsec Notation and Terminology
28500 @cindex notational conventions, for @sc{gdb/mi}
28501 This chapter uses the following notation:
28505 @code{|} separates two alternatives.
28508 @code{[ @var{something} ]} indicates that @var{something} is optional:
28509 it may or may not be given.
28512 @code{( @var{group} )*} means that @var{group} inside the parentheses
28513 may repeat zero or more times.
28516 @code{( @var{group} )+} means that @var{group} inside the parentheses
28517 may repeat one or more times.
28520 @code{"@var{string}"} means a literal @var{string}.
28524 @heading Dependencies
28528 * GDB/MI General Design::
28529 * GDB/MI Command Syntax::
28530 * GDB/MI Compatibility with CLI::
28531 * GDB/MI Development and Front Ends::
28532 * GDB/MI Output Records::
28533 * GDB/MI Simple Examples::
28534 * GDB/MI Command Description Format::
28535 * GDB/MI Breakpoint Commands::
28536 * GDB/MI Catchpoint Commands::
28537 * GDB/MI Program Context::
28538 * GDB/MI Thread Commands::
28539 * GDB/MI Ada Tasking Commands::
28540 * GDB/MI Program Execution::
28541 * GDB/MI Stack Manipulation::
28542 * GDB/MI Variable Objects::
28543 * GDB/MI Data Manipulation::
28544 * GDB/MI Tracepoint Commands::
28545 * GDB/MI Symbol Query::
28546 * GDB/MI File Commands::
28548 * GDB/MI Kod Commands::
28549 * GDB/MI Memory Overlay Commands::
28550 * GDB/MI Signal Handling Commands::
28552 * GDB/MI Target Manipulation::
28553 * GDB/MI File Transfer Commands::
28554 * GDB/MI Miscellaneous Commands::
28557 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28558 @node GDB/MI General Design
28559 @section @sc{gdb/mi} General Design
28560 @cindex GDB/MI General Design
28562 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
28563 parts---commands sent to @value{GDBN}, responses to those commands
28564 and notifications. Each command results in exactly one response,
28565 indicating either successful completion of the command, or an error.
28566 For the commands that do not resume the target, the response contains the
28567 requested information. For the commands that resume the target, the
28568 response only indicates whether the target was successfully resumed.
28569 Notifications is the mechanism for reporting changes in the state of the
28570 target, or in @value{GDBN} state, that cannot conveniently be associated with
28571 a command and reported as part of that command response.
28573 The important examples of notifications are:
28577 Exec notifications. These are used to report changes in
28578 target state---when a target is resumed, or stopped. It would not
28579 be feasible to include this information in response of resuming
28580 commands, because one resume commands can result in multiple events in
28581 different threads. Also, quite some time may pass before any event
28582 happens in the target, while a frontend needs to know whether the resuming
28583 command itself was successfully executed.
28586 Console output, and status notifications. Console output
28587 notifications are used to report output of CLI commands, as well as
28588 diagnostics for other commands. Status notifications are used to
28589 report the progress of a long-running operation. Naturally, including
28590 this information in command response would mean no output is produced
28591 until the command is finished, which is undesirable.
28594 General notifications. Commands may have various side effects on
28595 the @value{GDBN} or target state beyond their official purpose. For example,
28596 a command may change the selected thread. Although such changes can
28597 be included in command response, using notification allows for more
28598 orthogonal frontend design.
28602 There's no guarantee that whenever an MI command reports an error,
28603 @value{GDBN} or the target are in any specific state, and especially,
28604 the state is not reverted to the state before the MI command was
28605 processed. Therefore, whenever an MI command results in an error,
28606 we recommend that the frontend refreshes all the information shown in
28607 the user interface.
28611 * Context management::
28612 * Asynchronous and non-stop modes::
28616 @node Context management
28617 @subsection Context management
28619 In most cases when @value{GDBN} accesses the target, this access is
28620 done in context of a specific thread and frame (@pxref{Frames}).
28621 Often, even when accessing global data, the target requires that a thread
28622 be specified. The CLI interface maintains the selected thread and frame,
28623 and supplies them to target on each command. This is convenient,
28624 because a command line user would not want to specify that information
28625 explicitly on each command, and because user interacts with
28626 @value{GDBN} via a single terminal, so no confusion is possible as
28627 to what thread and frame are the current ones.
28629 In the case of MI, the concept of selected thread and frame is less
28630 useful. First, a frontend can easily remember this information
28631 itself. Second, a graphical frontend can have more than one window,
28632 each one used for debugging a different thread, and the frontend might
28633 want to access additional threads for internal purposes. This
28634 increases the risk that by relying on implicitly selected thread, the
28635 frontend may be operating on a wrong one. Therefore, each MI command
28636 should explicitly specify which thread and frame to operate on. To
28637 make it possible, each MI command accepts the @samp{--thread} and
28638 @samp{--frame} options, the value to each is @value{GDBN} identifier
28639 for thread and frame to operate on.
28641 Usually, each top-level window in a frontend allows the user to select
28642 a thread and a frame, and remembers the user selection for further
28643 operations. However, in some cases @value{GDBN} may suggest that the
28644 current thread be changed. For example, when stopping on a breakpoint
28645 it is reasonable to switch to the thread where breakpoint is hit. For
28646 another example, if the user issues the CLI @samp{thread} command via
28647 the frontend, it is desirable to change the frontend's selected thread to the
28648 one specified by user. @value{GDBN} communicates the suggestion to
28649 change current thread using the @samp{=thread-selected} notification.
28650 No such notification is available for the selected frame at the moment.
28652 Note that historically, MI shares the selected thread with CLI, so
28653 frontends used the @code{-thread-select} to execute commands in the
28654 right context. However, getting this to work right is cumbersome. The
28655 simplest way is for frontend to emit @code{-thread-select} command
28656 before every command. This doubles the number of commands that need
28657 to be sent. The alternative approach is to suppress @code{-thread-select}
28658 if the selected thread in @value{GDBN} is supposed to be identical to the
28659 thread the frontend wants to operate on. However, getting this
28660 optimization right can be tricky. In particular, if the frontend
28661 sends several commands to @value{GDBN}, and one of the commands changes the
28662 selected thread, then the behaviour of subsequent commands will
28663 change. So, a frontend should either wait for response from such
28664 problematic commands, or explicitly add @code{-thread-select} for
28665 all subsequent commands. No frontend is known to do this exactly
28666 right, so it is suggested to just always pass the @samp{--thread} and
28667 @samp{--frame} options.
28669 @node Asynchronous and non-stop modes
28670 @subsection Asynchronous command execution and non-stop mode
28672 On some targets, @value{GDBN} is capable of processing MI commands
28673 even while the target is running. This is called @dfn{asynchronous
28674 command execution} (@pxref{Background Execution}). The frontend may
28675 specify a preferrence for asynchronous execution using the
28676 @code{-gdb-set target-async 1} command, which should be emitted before
28677 either running the executable or attaching to the target. After the
28678 frontend has started the executable or attached to the target, it can
28679 find if asynchronous execution is enabled using the
28680 @code{-list-target-features} command.
28682 Even if @value{GDBN} can accept a command while target is running,
28683 many commands that access the target do not work when the target is
28684 running. Therefore, asynchronous command execution is most useful
28685 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
28686 it is possible to examine the state of one thread, while other threads
28689 When a given thread is running, MI commands that try to access the
28690 target in the context of that thread may not work, or may work only on
28691 some targets. In particular, commands that try to operate on thread's
28692 stack will not work, on any target. Commands that read memory, or
28693 modify breakpoints, may work or not work, depending on the target. Note
28694 that even commands that operate on global state, such as @code{print},
28695 @code{set}, and breakpoint commands, still access the target in the
28696 context of a specific thread, so frontend should try to find a
28697 stopped thread and perform the operation on that thread (using the
28698 @samp{--thread} option).
28700 Which commands will work in the context of a running thread is
28701 highly target dependent. However, the two commands
28702 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
28703 to find the state of a thread, will always work.
28705 @node Thread groups
28706 @subsection Thread groups
28707 @value{GDBN} may be used to debug several processes at the same time.
28708 On some platfroms, @value{GDBN} may support debugging of several
28709 hardware systems, each one having several cores with several different
28710 processes running on each core. This section describes the MI
28711 mechanism to support such debugging scenarios.
28713 The key observation is that regardless of the structure of the
28714 target, MI can have a global list of threads, because most commands that
28715 accept the @samp{--thread} option do not need to know what process that
28716 thread belongs to. Therefore, it is not necessary to introduce
28717 neither additional @samp{--process} option, nor an notion of the
28718 current process in the MI interface. The only strictly new feature
28719 that is required is the ability to find how the threads are grouped
28722 To allow the user to discover such grouping, and to support arbitrary
28723 hierarchy of machines/cores/processes, MI introduces the concept of a
28724 @dfn{thread group}. Thread group is a collection of threads and other
28725 thread groups. A thread group always has a string identifier, a type,
28726 and may have additional attributes specific to the type. A new
28727 command, @code{-list-thread-groups}, returns the list of top-level
28728 thread groups, which correspond to processes that @value{GDBN} is
28729 debugging at the moment. By passing an identifier of a thread group
28730 to the @code{-list-thread-groups} command, it is possible to obtain
28731 the members of specific thread group.
28733 To allow the user to easily discover processes, and other objects, he
28734 wishes to debug, a concept of @dfn{available thread group} is
28735 introduced. Available thread group is an thread group that
28736 @value{GDBN} is not debugging, but that can be attached to, using the
28737 @code{-target-attach} command. The list of available top-level thread
28738 groups can be obtained using @samp{-list-thread-groups --available}.
28739 In general, the content of a thread group may be only retrieved only
28740 after attaching to that thread group.
28742 Thread groups are related to inferiors (@pxref{Inferiors and
28743 Programs}). Each inferior corresponds to a thread group of a special
28744 type @samp{process}, and some additional operations are permitted on
28745 such thread groups.
28747 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28748 @node GDB/MI Command Syntax
28749 @section @sc{gdb/mi} Command Syntax
28752 * GDB/MI Input Syntax::
28753 * GDB/MI Output Syntax::
28756 @node GDB/MI Input Syntax
28757 @subsection @sc{gdb/mi} Input Syntax
28759 @cindex input syntax for @sc{gdb/mi}
28760 @cindex @sc{gdb/mi}, input syntax
28762 @item @var{command} @expansion{}
28763 @code{@var{cli-command} | @var{mi-command}}
28765 @item @var{cli-command} @expansion{}
28766 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
28767 @var{cli-command} is any existing @value{GDBN} CLI command.
28769 @item @var{mi-command} @expansion{}
28770 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
28771 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
28773 @item @var{token} @expansion{}
28774 "any sequence of digits"
28776 @item @var{option} @expansion{}
28777 @code{"-" @var{parameter} [ " " @var{parameter} ]}
28779 @item @var{parameter} @expansion{}
28780 @code{@var{non-blank-sequence} | @var{c-string}}
28782 @item @var{operation} @expansion{}
28783 @emph{any of the operations described in this chapter}
28785 @item @var{non-blank-sequence} @expansion{}
28786 @emph{anything, provided it doesn't contain special characters such as
28787 "-", @var{nl}, """ and of course " "}
28789 @item @var{c-string} @expansion{}
28790 @code{""" @var{seven-bit-iso-c-string-content} """}
28792 @item @var{nl} @expansion{}
28801 The CLI commands are still handled by the @sc{mi} interpreter; their
28802 output is described below.
28805 The @code{@var{token}}, when present, is passed back when the command
28809 Some @sc{mi} commands accept optional arguments as part of the parameter
28810 list. Each option is identified by a leading @samp{-} (dash) and may be
28811 followed by an optional argument parameter. Options occur first in the
28812 parameter list and can be delimited from normal parameters using
28813 @samp{--} (this is useful when some parameters begin with a dash).
28820 We want easy access to the existing CLI syntax (for debugging).
28823 We want it to be easy to spot a @sc{mi} operation.
28826 @node GDB/MI Output Syntax
28827 @subsection @sc{gdb/mi} Output Syntax
28829 @cindex output syntax of @sc{gdb/mi}
28830 @cindex @sc{gdb/mi}, output syntax
28831 The output from @sc{gdb/mi} consists of zero or more out-of-band records
28832 followed, optionally, by a single result record. This result record
28833 is for the most recent command. The sequence of output records is
28834 terminated by @samp{(gdb)}.
28836 If an input command was prefixed with a @code{@var{token}} then the
28837 corresponding output for that command will also be prefixed by that same
28841 @item @var{output} @expansion{}
28842 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
28844 @item @var{result-record} @expansion{}
28845 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
28847 @item @var{out-of-band-record} @expansion{}
28848 @code{@var{async-record} | @var{stream-record}}
28850 @item @var{async-record} @expansion{}
28851 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
28853 @item @var{exec-async-output} @expansion{}
28854 @code{[ @var{token} ] "*" @var{async-output}}
28856 @item @var{status-async-output} @expansion{}
28857 @code{[ @var{token} ] "+" @var{async-output}}
28859 @item @var{notify-async-output} @expansion{}
28860 @code{[ @var{token} ] "=" @var{async-output}}
28862 @item @var{async-output} @expansion{}
28863 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
28865 @item @var{result-class} @expansion{}
28866 @code{"done" | "running" | "connected" | "error" | "exit"}
28868 @item @var{async-class} @expansion{}
28869 @code{"stopped" | @var{others}} (where @var{others} will be added
28870 depending on the needs---this is still in development).
28872 @item @var{result} @expansion{}
28873 @code{ @var{variable} "=" @var{value}}
28875 @item @var{variable} @expansion{}
28876 @code{ @var{string} }
28878 @item @var{value} @expansion{}
28879 @code{ @var{const} | @var{tuple} | @var{list} }
28881 @item @var{const} @expansion{}
28882 @code{@var{c-string}}
28884 @item @var{tuple} @expansion{}
28885 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
28887 @item @var{list} @expansion{}
28888 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
28889 @var{result} ( "," @var{result} )* "]" }
28891 @item @var{stream-record} @expansion{}
28892 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
28894 @item @var{console-stream-output} @expansion{}
28895 @code{"~" @var{c-string}}
28897 @item @var{target-stream-output} @expansion{}
28898 @code{"@@" @var{c-string}}
28900 @item @var{log-stream-output} @expansion{}
28901 @code{"&" @var{c-string}}
28903 @item @var{nl} @expansion{}
28906 @item @var{token} @expansion{}
28907 @emph{any sequence of digits}.
28915 All output sequences end in a single line containing a period.
28918 The @code{@var{token}} is from the corresponding request. Note that
28919 for all async output, while the token is allowed by the grammar and
28920 may be output by future versions of @value{GDBN} for select async
28921 output messages, it is generally omitted. Frontends should treat
28922 all async output as reporting general changes in the state of the
28923 target and there should be no need to associate async output to any
28927 @cindex status output in @sc{gdb/mi}
28928 @var{status-async-output} contains on-going status information about the
28929 progress of a slow operation. It can be discarded. All status output is
28930 prefixed by @samp{+}.
28933 @cindex async output in @sc{gdb/mi}
28934 @var{exec-async-output} contains asynchronous state change on the target
28935 (stopped, started, disappeared). All async output is prefixed by
28939 @cindex notify output in @sc{gdb/mi}
28940 @var{notify-async-output} contains supplementary information that the
28941 client should handle (e.g., a new breakpoint information). All notify
28942 output is prefixed by @samp{=}.
28945 @cindex console output in @sc{gdb/mi}
28946 @var{console-stream-output} is output that should be displayed as is in the
28947 console. It is the textual response to a CLI command. All the console
28948 output is prefixed by @samp{~}.
28951 @cindex target output in @sc{gdb/mi}
28952 @var{target-stream-output} is the output produced by the target program.
28953 All the target output is prefixed by @samp{@@}.
28956 @cindex log output in @sc{gdb/mi}
28957 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
28958 instance messages that should be displayed as part of an error log. All
28959 the log output is prefixed by @samp{&}.
28962 @cindex list output in @sc{gdb/mi}
28963 New @sc{gdb/mi} commands should only output @var{lists} containing
28969 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
28970 details about the various output records.
28972 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28973 @node GDB/MI Compatibility with CLI
28974 @section @sc{gdb/mi} Compatibility with CLI
28976 @cindex compatibility, @sc{gdb/mi} and CLI
28977 @cindex @sc{gdb/mi}, compatibility with CLI
28979 For the developers convenience CLI commands can be entered directly,
28980 but there may be some unexpected behaviour. For example, commands
28981 that query the user will behave as if the user replied yes, breakpoint
28982 command lists are not executed and some CLI commands, such as
28983 @code{if}, @code{when} and @code{define}, prompt for further input with
28984 @samp{>}, which is not valid MI output.
28986 This feature may be removed at some stage in the future and it is
28987 recommended that front ends use the @code{-interpreter-exec} command
28988 (@pxref{-interpreter-exec}).
28990 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28991 @node GDB/MI Development and Front Ends
28992 @section @sc{gdb/mi} Development and Front Ends
28993 @cindex @sc{gdb/mi} development
28995 The application which takes the MI output and presents the state of the
28996 program being debugged to the user is called a @dfn{front end}.
28998 Although @sc{gdb/mi} is still incomplete, it is currently being used
28999 by a variety of front ends to @value{GDBN}. This makes it difficult
29000 to introduce new functionality without breaking existing usage. This
29001 section tries to minimize the problems by describing how the protocol
29004 Some changes in MI need not break a carefully designed front end, and
29005 for these the MI version will remain unchanged. The following is a
29006 list of changes that may occur within one level, so front ends should
29007 parse MI output in a way that can handle them:
29011 New MI commands may be added.
29014 New fields may be added to the output of any MI command.
29017 The range of values for fields with specified values, e.g.,
29018 @code{in_scope} (@pxref{-var-update}) may be extended.
29020 @c The format of field's content e.g type prefix, may change so parse it
29021 @c at your own risk. Yes, in general?
29023 @c The order of fields may change? Shouldn't really matter but it might
29024 @c resolve inconsistencies.
29027 If the changes are likely to break front ends, the MI version level
29028 will be increased by one. This will allow the front end to parse the
29029 output according to the MI version. Apart from mi0, new versions of
29030 @value{GDBN} will not support old versions of MI and it will be the
29031 responsibility of the front end to work with the new one.
29033 @c Starting with mi3, add a new command -mi-version that prints the MI
29036 The best way to avoid unexpected changes in MI that might break your front
29037 end is to make your project known to @value{GDBN} developers and
29038 follow development on @email{gdb@@sourceware.org} and
29039 @email{gdb-patches@@sourceware.org}.
29040 @cindex mailing lists
29042 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29043 @node GDB/MI Output Records
29044 @section @sc{gdb/mi} Output Records
29047 * GDB/MI Result Records::
29048 * GDB/MI Stream Records::
29049 * GDB/MI Async Records::
29050 * GDB/MI Breakpoint Information::
29051 * GDB/MI Frame Information::
29052 * GDB/MI Thread Information::
29053 * GDB/MI Ada Exception Information::
29056 @node GDB/MI Result Records
29057 @subsection @sc{gdb/mi} Result Records
29059 @cindex result records in @sc{gdb/mi}
29060 @cindex @sc{gdb/mi}, result records
29061 In addition to a number of out-of-band notifications, the response to a
29062 @sc{gdb/mi} command includes one of the following result indications:
29066 @item "^done" [ "," @var{results} ]
29067 The synchronous operation was successful, @code{@var{results}} are the return
29072 This result record is equivalent to @samp{^done}. Historically, it
29073 was output instead of @samp{^done} if the command has resumed the
29074 target. This behaviour is maintained for backward compatibility, but
29075 all frontends should treat @samp{^done} and @samp{^running}
29076 identically and rely on the @samp{*running} output record to determine
29077 which threads are resumed.
29081 @value{GDBN} has connected to a remote target.
29083 @item "^error" "," @var{c-string}
29085 The operation failed. The @code{@var{c-string}} contains the corresponding
29090 @value{GDBN} has terminated.
29094 @node GDB/MI Stream Records
29095 @subsection @sc{gdb/mi} Stream Records
29097 @cindex @sc{gdb/mi}, stream records
29098 @cindex stream records in @sc{gdb/mi}
29099 @value{GDBN} internally maintains a number of output streams: the console, the
29100 target, and the log. The output intended for each of these streams is
29101 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
29103 Each stream record begins with a unique @dfn{prefix character} which
29104 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
29105 Syntax}). In addition to the prefix, each stream record contains a
29106 @code{@var{string-output}}. This is either raw text (with an implicit new
29107 line) or a quoted C string (which does not contain an implicit newline).
29110 @item "~" @var{string-output}
29111 The console output stream contains text that should be displayed in the
29112 CLI console window. It contains the textual responses to CLI commands.
29114 @item "@@" @var{string-output}
29115 The target output stream contains any textual output from the running
29116 target. This is only present when GDB's event loop is truly
29117 asynchronous, which is currently only the case for remote targets.
29119 @item "&" @var{string-output}
29120 The log stream contains debugging messages being produced by @value{GDBN}'s
29124 @node GDB/MI Async Records
29125 @subsection @sc{gdb/mi} Async Records
29127 @cindex async records in @sc{gdb/mi}
29128 @cindex @sc{gdb/mi}, async records
29129 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
29130 additional changes that have occurred. Those changes can either be a
29131 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
29132 target activity (e.g., target stopped).
29134 The following is the list of possible async records:
29138 @item *running,thread-id="@var{thread}"
29139 The target is now running. The @var{thread} field tells which
29140 specific thread is now running, and can be @samp{all} if all threads
29141 are running. The frontend should assume that no interaction with a
29142 running thread is possible after this notification is produced.
29143 The frontend should not assume that this notification is output
29144 only once for any command. @value{GDBN} may emit this notification
29145 several times, either for different threads, because it cannot resume
29146 all threads together, or even for a single thread, if the thread must
29147 be stepped though some code before letting it run freely.
29149 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
29150 The target has stopped. The @var{reason} field can have one of the
29154 @item breakpoint-hit
29155 A breakpoint was reached.
29156 @item watchpoint-trigger
29157 A watchpoint was triggered.
29158 @item read-watchpoint-trigger
29159 A read watchpoint was triggered.
29160 @item access-watchpoint-trigger
29161 An access watchpoint was triggered.
29162 @item function-finished
29163 An -exec-finish or similar CLI command was accomplished.
29164 @item location-reached
29165 An -exec-until or similar CLI command was accomplished.
29166 @item watchpoint-scope
29167 A watchpoint has gone out of scope.
29168 @item end-stepping-range
29169 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
29170 similar CLI command was accomplished.
29171 @item exited-signalled
29172 The inferior exited because of a signal.
29174 The inferior exited.
29175 @item exited-normally
29176 The inferior exited normally.
29177 @item signal-received
29178 A signal was received by the inferior.
29180 The inferior has stopped due to a library being loaded or unloaded.
29181 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
29182 set or when a @code{catch load} or @code{catch unload} catchpoint is
29183 in use (@pxref{Set Catchpoints}).
29185 The inferior has forked. This is reported when @code{catch fork}
29186 (@pxref{Set Catchpoints}) has been used.
29188 The inferior has vforked. This is reported in when @code{catch vfork}
29189 (@pxref{Set Catchpoints}) has been used.
29190 @item syscall-entry
29191 The inferior entered a system call. This is reported when @code{catch
29192 syscall} (@pxref{Set Catchpoints}) has been used.
29193 @item syscall-entry
29194 The inferior returned from a system call. This is reported when
29195 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
29197 The inferior called @code{exec}. This is reported when @code{catch exec}
29198 (@pxref{Set Catchpoints}) has been used.
29201 The @var{id} field identifies the thread that directly caused the stop
29202 -- for example by hitting a breakpoint. Depending on whether all-stop
29203 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
29204 stop all threads, or only the thread that directly triggered the stop.
29205 If all threads are stopped, the @var{stopped} field will have the
29206 value of @code{"all"}. Otherwise, the value of the @var{stopped}
29207 field will be a list of thread identifiers. Presently, this list will
29208 always include a single thread, but frontend should be prepared to see
29209 several threads in the list. The @var{core} field reports the
29210 processor core on which the stop event has happened. This field may be absent
29211 if such information is not available.
29213 @item =thread-group-added,id="@var{id}"
29214 @itemx =thread-group-removed,id="@var{id}"
29215 A thread group was either added or removed. The @var{id} field
29216 contains the @value{GDBN} identifier of the thread group. When a thread
29217 group is added, it generally might not be associated with a running
29218 process. When a thread group is removed, its id becomes invalid and
29219 cannot be used in any way.
29221 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
29222 A thread group became associated with a running program,
29223 either because the program was just started or the thread group
29224 was attached to a program. The @var{id} field contains the
29225 @value{GDBN} identifier of the thread group. The @var{pid} field
29226 contains process identifier, specific to the operating system.
29228 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
29229 A thread group is no longer associated with a running program,
29230 either because the program has exited, or because it was detached
29231 from. The @var{id} field contains the @value{GDBN} identifier of the
29232 thread group. @var{code} is the exit code of the inferior; it exists
29233 only when the inferior exited with some code.
29235 @item =thread-created,id="@var{id}",group-id="@var{gid}"
29236 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
29237 A thread either was created, or has exited. The @var{id} field
29238 contains the @value{GDBN} identifier of the thread. The @var{gid}
29239 field identifies the thread group this thread belongs to.
29241 @item =thread-selected,id="@var{id}"
29242 Informs that the selected thread was changed as result of the last
29243 command. This notification is not emitted as result of @code{-thread-select}
29244 command but is emitted whenever an MI command that is not documented
29245 to change the selected thread actually changes it. In particular,
29246 invoking, directly or indirectly (via user-defined command), the CLI
29247 @code{thread} command, will generate this notification.
29249 We suggest that in response to this notification, front ends
29250 highlight the selected thread and cause subsequent commands to apply to
29253 @item =library-loaded,...
29254 Reports that a new library file was loaded by the program. This
29255 notification has 4 fields---@var{id}, @var{target-name},
29256 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
29257 opaque identifier of the library. For remote debugging case,
29258 @var{target-name} and @var{host-name} fields give the name of the
29259 library file on the target, and on the host respectively. For native
29260 debugging, both those fields have the same value. The
29261 @var{symbols-loaded} field is emitted only for backward compatibility
29262 and should not be relied on to convey any useful information. The
29263 @var{thread-group} field, if present, specifies the id of the thread
29264 group in whose context the library was loaded. If the field is
29265 absent, it means the library was loaded in the context of all present
29268 @item =library-unloaded,...
29269 Reports that a library was unloaded by the program. This notification
29270 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
29271 the same meaning as for the @code{=library-loaded} notification.
29272 The @var{thread-group} field, if present, specifies the id of the
29273 thread group in whose context the library was unloaded. If the field is
29274 absent, it means the library was unloaded in the context of all present
29277 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
29278 @itemx =traceframe-changed,end
29279 Reports that the trace frame was changed and its new number is
29280 @var{tfnum}. The number of the tracepoint associated with this trace
29281 frame is @var{tpnum}.
29283 @item =tsv-created,name=@var{name},initial=@var{initial}
29284 Reports that the new trace state variable @var{name} is created with
29285 initial value @var{initial}.
29287 @item =tsv-deleted,name=@var{name}
29288 @itemx =tsv-deleted
29289 Reports that the trace state variable @var{name} is deleted or all
29290 trace state variables are deleted.
29292 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
29293 Reports that the trace state variable @var{name} is modified with
29294 the initial value @var{initial}. The current value @var{current} of
29295 trace state variable is optional and is reported if the current
29296 value of trace state variable is known.
29298 @item =breakpoint-created,bkpt=@{...@}
29299 @itemx =breakpoint-modified,bkpt=@{...@}
29300 @itemx =breakpoint-deleted,id=@var{number}
29301 Reports that a breakpoint was created, modified, or deleted,
29302 respectively. Only user-visible breakpoints are reported to the MI
29305 The @var{bkpt} argument is of the same form as returned by the various
29306 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
29307 @var{number} is the ordinal number of the breakpoint.
29309 Note that if a breakpoint is emitted in the result record of a
29310 command, then it will not also be emitted in an async record.
29312 @item =record-started,thread-group="@var{id}"
29313 @itemx =record-stopped,thread-group="@var{id}"
29314 Execution log recording was either started or stopped on an
29315 inferior. The @var{id} is the @value{GDBN} identifier of the thread
29316 group corresponding to the affected inferior.
29318 @item =cmd-param-changed,param=@var{param},value=@var{value}
29319 Reports that a parameter of the command @code{set @var{param}} is
29320 changed to @var{value}. In the multi-word @code{set} command,
29321 the @var{param} is the whole parameter list to @code{set} command.
29322 For example, In command @code{set check type on}, @var{param}
29323 is @code{check type} and @var{value} is @code{on}.
29325 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
29326 Reports that bytes from @var{addr} to @var{data} + @var{len} were
29327 written in an inferior. The @var{id} is the identifier of the
29328 thread group corresponding to the affected inferior. The optional
29329 @code{type="code"} part is reported if the memory written to holds
29333 @node GDB/MI Breakpoint Information
29334 @subsection @sc{gdb/mi} Breakpoint Information
29336 When @value{GDBN} reports information about a breakpoint, a
29337 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
29342 The breakpoint number. For a breakpoint that represents one location
29343 of a multi-location breakpoint, this will be a dotted pair, like
29347 The type of the breakpoint. For ordinary breakpoints this will be
29348 @samp{breakpoint}, but many values are possible.
29351 If the type of the breakpoint is @samp{catchpoint}, then this
29352 indicates the exact type of catchpoint.
29355 This is the breakpoint disposition---either @samp{del}, meaning that
29356 the breakpoint will be deleted at the next stop, or @samp{keep},
29357 meaning that the breakpoint will not be deleted.
29360 This indicates whether the breakpoint is enabled, in which case the
29361 value is @samp{y}, or disabled, in which case the value is @samp{n}.
29362 Note that this is not the same as the field @code{enable}.
29365 The address of the breakpoint. This may be a hexidecimal number,
29366 giving the address; or the string @samp{<PENDING>}, for a pending
29367 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
29368 multiple locations. This field will not be present if no address can
29369 be determined. For example, a watchpoint does not have an address.
29372 If known, the function in which the breakpoint appears.
29373 If not known, this field is not present.
29376 The name of the source file which contains this function, if known.
29377 If not known, this field is not present.
29380 The full file name of the source file which contains this function, if
29381 known. If not known, this field is not present.
29384 The line number at which this breakpoint appears, if known.
29385 If not known, this field is not present.
29388 If the source file is not known, this field may be provided. If
29389 provided, this holds the address of the breakpoint, possibly followed
29393 If this breakpoint is pending, this field is present and holds the
29394 text used to set the breakpoint, as entered by the user.
29397 Where this breakpoint's condition is evaluated, either @samp{host} or
29401 If this is a thread-specific breakpoint, then this identifies the
29402 thread in which the breakpoint can trigger.
29405 If this breakpoint is restricted to a particular Ada task, then this
29406 field will hold the task identifier.
29409 If the breakpoint is conditional, this is the condition expression.
29412 The ignore count of the breakpoint.
29415 The enable count of the breakpoint.
29417 @item traceframe-usage
29420 @item static-tracepoint-marker-string-id
29421 For a static tracepoint, the name of the static tracepoint marker.
29424 For a masked watchpoint, this is the mask.
29427 A tracepoint's pass count.
29429 @item original-location
29430 The location of the breakpoint as originally specified by the user.
29431 This field is optional.
29434 The number of times the breakpoint has been hit.
29437 This field is only given for tracepoints. This is either @samp{y},
29438 meaning that the tracepoint is installed, or @samp{n}, meaning that it
29442 Some extra data, the exact contents of which are type-dependent.
29446 For example, here is what the output of @code{-break-insert}
29447 (@pxref{GDB/MI Breakpoint Commands}) might be:
29450 -> -break-insert main
29451 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29452 enabled="y",addr="0x08048564",func="main",file="myprog.c",
29453 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
29458 @node GDB/MI Frame Information
29459 @subsection @sc{gdb/mi} Frame Information
29461 Response from many MI commands includes an information about stack
29462 frame. This information is a tuple that may have the following
29467 The level of the stack frame. The innermost frame has the level of
29468 zero. This field is always present.
29471 The name of the function corresponding to the frame. This field may
29472 be absent if @value{GDBN} is unable to determine the function name.
29475 The code address for the frame. This field is always present.
29478 The name of the source files that correspond to the frame's code
29479 address. This field may be absent.
29482 The source line corresponding to the frames' code address. This field
29486 The name of the binary file (either executable or shared library) the
29487 corresponds to the frame's code address. This field may be absent.
29491 @node GDB/MI Thread Information
29492 @subsection @sc{gdb/mi} Thread Information
29494 Whenever @value{GDBN} has to report an information about a thread, it
29495 uses a tuple with the following fields:
29499 The numeric id assigned to the thread by @value{GDBN}. This field is
29503 Target-specific string identifying the thread. This field is always present.
29506 Additional information about the thread provided by the target.
29507 It is supposed to be human-readable and not interpreted by the
29508 frontend. This field is optional.
29511 Either @samp{stopped} or @samp{running}, depending on whether the
29512 thread is presently running. This field is always present.
29515 The value of this field is an integer number of the processor core the
29516 thread was last seen on. This field is optional.
29519 @node GDB/MI Ada Exception Information
29520 @subsection @sc{gdb/mi} Ada Exception Information
29522 Whenever a @code{*stopped} record is emitted because the program
29523 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
29524 @value{GDBN} provides the name of the exception that was raised via
29525 the @code{exception-name} field.
29527 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29528 @node GDB/MI Simple Examples
29529 @section Simple Examples of @sc{gdb/mi} Interaction
29530 @cindex @sc{gdb/mi}, simple examples
29532 This subsection presents several simple examples of interaction using
29533 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
29534 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
29535 the output received from @sc{gdb/mi}.
29537 Note the line breaks shown in the examples are here only for
29538 readability, they don't appear in the real output.
29540 @subheading Setting a Breakpoint
29542 Setting a breakpoint generates synchronous output which contains detailed
29543 information of the breakpoint.
29546 -> -break-insert main
29547 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29548 enabled="y",addr="0x08048564",func="main",file="myprog.c",
29549 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
29554 @subheading Program Execution
29556 Program execution generates asynchronous records and MI gives the
29557 reason that execution stopped.
29563 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
29564 frame=@{addr="0x08048564",func="main",
29565 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
29566 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
29571 <- *stopped,reason="exited-normally"
29575 @subheading Quitting @value{GDBN}
29577 Quitting @value{GDBN} just prints the result class @samp{^exit}.
29585 Please note that @samp{^exit} is printed immediately, but it might
29586 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
29587 performs necessary cleanups, including killing programs being debugged
29588 or disconnecting from debug hardware, so the frontend should wait till
29589 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
29590 fails to exit in reasonable time.
29592 @subheading A Bad Command
29594 Here's what happens if you pass a non-existent command:
29598 <- ^error,msg="Undefined MI command: rubbish"
29603 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29604 @node GDB/MI Command Description Format
29605 @section @sc{gdb/mi} Command Description Format
29607 The remaining sections describe blocks of commands. Each block of
29608 commands is laid out in a fashion similar to this section.
29610 @subheading Motivation
29612 The motivation for this collection of commands.
29614 @subheading Introduction
29616 A brief introduction to this collection of commands as a whole.
29618 @subheading Commands
29620 For each command in the block, the following is described:
29622 @subsubheading Synopsis
29625 -command @var{args}@dots{}
29628 @subsubheading Result
29630 @subsubheading @value{GDBN} Command
29632 The corresponding @value{GDBN} CLI command(s), if any.
29634 @subsubheading Example
29636 Example(s) formatted for readability. Some of the described commands have
29637 not been implemented yet and these are labeled N.A.@: (not available).
29640 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29641 @node GDB/MI Breakpoint Commands
29642 @section @sc{gdb/mi} Breakpoint Commands
29644 @cindex breakpoint commands for @sc{gdb/mi}
29645 @cindex @sc{gdb/mi}, breakpoint commands
29646 This section documents @sc{gdb/mi} commands for manipulating
29649 @subheading The @code{-break-after} Command
29650 @findex -break-after
29652 @subsubheading Synopsis
29655 -break-after @var{number} @var{count}
29658 The breakpoint number @var{number} is not in effect until it has been
29659 hit @var{count} times. To see how this is reflected in the output of
29660 the @samp{-break-list} command, see the description of the
29661 @samp{-break-list} command below.
29663 @subsubheading @value{GDBN} Command
29665 The corresponding @value{GDBN} command is @samp{ignore}.
29667 @subsubheading Example
29672 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29673 enabled="y",addr="0x000100d0",func="main",file="hello.c",
29674 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
29682 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29683 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29684 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29685 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29686 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29687 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29688 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29689 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29690 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
29691 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
29696 @subheading The @code{-break-catch} Command
29697 @findex -break-catch
29700 @subheading The @code{-break-commands} Command
29701 @findex -break-commands
29703 @subsubheading Synopsis
29706 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
29709 Specifies the CLI commands that should be executed when breakpoint
29710 @var{number} is hit. The parameters @var{command1} to @var{commandN}
29711 are the commands. If no command is specified, any previously-set
29712 commands are cleared. @xref{Break Commands}. Typical use of this
29713 functionality is tracing a program, that is, printing of values of
29714 some variables whenever breakpoint is hit and then continuing.
29716 @subsubheading @value{GDBN} Command
29718 The corresponding @value{GDBN} command is @samp{commands}.
29720 @subsubheading Example
29725 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29726 enabled="y",addr="0x000100d0",func="main",file="hello.c",
29727 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
29730 -break-commands 1 "print v" "continue"
29735 @subheading The @code{-break-condition} Command
29736 @findex -break-condition
29738 @subsubheading Synopsis
29741 -break-condition @var{number} @var{expr}
29744 Breakpoint @var{number} will stop the program only if the condition in
29745 @var{expr} is true. The condition becomes part of the
29746 @samp{-break-list} output (see the description of the @samp{-break-list}
29749 @subsubheading @value{GDBN} Command
29751 The corresponding @value{GDBN} command is @samp{condition}.
29753 @subsubheading Example
29757 -break-condition 1 1
29761 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29762 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29763 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29764 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29765 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29766 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29767 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29768 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29769 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
29770 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
29774 @subheading The @code{-break-delete} Command
29775 @findex -break-delete
29777 @subsubheading Synopsis
29780 -break-delete ( @var{breakpoint} )+
29783 Delete the breakpoint(s) whose number(s) are specified in the argument
29784 list. This is obviously reflected in the breakpoint list.
29786 @subsubheading @value{GDBN} Command
29788 The corresponding @value{GDBN} command is @samp{delete}.
29790 @subsubheading Example
29798 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
29799 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29800 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29801 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29802 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29803 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29804 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29809 @subheading The @code{-break-disable} Command
29810 @findex -break-disable
29812 @subsubheading Synopsis
29815 -break-disable ( @var{breakpoint} )+
29818 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
29819 break list is now set to @samp{n} for the named @var{breakpoint}(s).
29821 @subsubheading @value{GDBN} Command
29823 The corresponding @value{GDBN} command is @samp{disable}.
29825 @subsubheading Example
29833 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29834 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29835 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29836 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29837 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29838 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29839 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29840 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
29841 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
29842 line="5",thread-groups=["i1"],times="0"@}]@}
29846 @subheading The @code{-break-enable} Command
29847 @findex -break-enable
29849 @subsubheading Synopsis
29852 -break-enable ( @var{breakpoint} )+
29855 Enable (previously disabled) @var{breakpoint}(s).
29857 @subsubheading @value{GDBN} Command
29859 The corresponding @value{GDBN} command is @samp{enable}.
29861 @subsubheading Example
29869 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29870 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29871 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29872 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29873 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29874 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29875 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29876 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
29877 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
29878 line="5",thread-groups=["i1"],times="0"@}]@}
29882 @subheading The @code{-break-info} Command
29883 @findex -break-info
29885 @subsubheading Synopsis
29888 -break-info @var{breakpoint}
29892 Get information about a single breakpoint.
29894 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
29895 Information}, for details on the format of each breakpoint in the
29898 @subsubheading @value{GDBN} Command
29900 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
29902 @subsubheading Example
29905 @subheading The @code{-break-insert} Command
29906 @findex -break-insert
29908 @subsubheading Synopsis
29911 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
29912 [ -c @var{condition} ] [ -i @var{ignore-count} ]
29913 [ -p @var{thread-id} ] [ @var{location} ]
29917 If specified, @var{location}, can be one of:
29924 @item filename:linenum
29925 @item filename:function
29929 The possible optional parameters of this command are:
29933 Insert a temporary breakpoint.
29935 Insert a hardware breakpoint.
29937 If @var{location} cannot be parsed (for example if it
29938 refers to unknown files or functions), create a pending
29939 breakpoint. Without this flag, @value{GDBN} will report
29940 an error, and won't create a breakpoint, if @var{location}
29943 Create a disabled breakpoint.
29945 Create a tracepoint. @xref{Tracepoints}. When this parameter
29946 is used together with @samp{-h}, a fast tracepoint is created.
29947 @item -c @var{condition}
29948 Make the breakpoint conditional on @var{condition}.
29949 @item -i @var{ignore-count}
29950 Initialize the @var{ignore-count}.
29951 @item -p @var{thread-id}
29952 Restrict the breakpoint to the specified @var{thread-id}.
29955 @subsubheading Result
29957 @xref{GDB/MI Breakpoint Information}, for details on the format of the
29958 resulting breakpoint.
29960 Note: this format is open to change.
29961 @c An out-of-band breakpoint instead of part of the result?
29963 @subsubheading @value{GDBN} Command
29965 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
29966 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
29968 @subsubheading Example
29973 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
29974 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
29977 -break-insert -t foo
29978 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
29979 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
29983 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29984 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29985 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29986 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29987 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29988 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29989 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29990 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29991 addr="0x0001072c", func="main",file="recursive2.c",
29992 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
29994 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
29995 addr="0x00010774",func="foo",file="recursive2.c",
29996 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
29999 @c -break-insert -r foo.*
30000 @c ~int foo(int, int);
30001 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
30002 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
30007 @subheading The @code{-dprintf-insert} Command
30008 @findex -dprintf-insert
30010 @subsubheading Synopsis
30013 -dprintf-insert [ -t ] [ -f ] [ -d ]
30014 [ -c @var{condition} ] [ -i @var{ignore-count} ]
30015 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
30020 If specified, @var{location}, can be one of:
30023 @item @var{function}
30026 @c @item @var{linenum}
30027 @item @var{filename}:@var{linenum}
30028 @item @var{filename}:function
30029 @item *@var{address}
30032 The possible optional parameters of this command are:
30036 Insert a temporary breakpoint.
30038 If @var{location} cannot be parsed (for example, if it
30039 refers to unknown files or functions), create a pending
30040 breakpoint. Without this flag, @value{GDBN} will report
30041 an error, and won't create a breakpoint, if @var{location}
30044 Create a disabled breakpoint.
30045 @item -c @var{condition}
30046 Make the breakpoint conditional on @var{condition}.
30047 @item -i @var{ignore-count}
30048 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
30049 to @var{ignore-count}.
30050 @item -p @var{thread-id}
30051 Restrict the breakpoint to the specified @var{thread-id}.
30054 @subsubheading Result
30056 @xref{GDB/MI Breakpoint Information}, for details on the format of the
30057 resulting breakpoint.
30059 @c An out-of-band breakpoint instead of part of the result?
30061 @subsubheading @value{GDBN} Command
30063 The corresponding @value{GDBN} command is @samp{dprintf}.
30065 @subsubheading Example
30069 4-dprintf-insert foo "At foo entry\n"
30070 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
30071 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
30072 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
30073 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
30074 original-location="foo"@}
30076 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
30077 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
30078 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
30079 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
30080 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
30081 original-location="mi-dprintf.c:26"@}
30085 @subheading The @code{-break-list} Command
30086 @findex -break-list
30088 @subsubheading Synopsis
30094 Displays the list of inserted breakpoints, showing the following fields:
30098 number of the breakpoint
30100 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
30102 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
30105 is the breakpoint enabled or no: @samp{y} or @samp{n}
30107 memory location at which the breakpoint is set
30109 logical location of the breakpoint, expressed by function name, file
30111 @item Thread-groups
30112 list of thread groups to which this breakpoint applies
30114 number of times the breakpoint has been hit
30117 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
30118 @code{body} field is an empty list.
30120 @subsubheading @value{GDBN} Command
30122 The corresponding @value{GDBN} command is @samp{info break}.
30124 @subsubheading Example
30129 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30130 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30131 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30132 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30133 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30134 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30135 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30136 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30137 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
30139 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
30140 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
30141 line="13",thread-groups=["i1"],times="0"@}]@}
30145 Here's an example of the result when there are no breakpoints:
30150 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
30151 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30152 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30153 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30154 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30155 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30156 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30161 @subheading The @code{-break-passcount} Command
30162 @findex -break-passcount
30164 @subsubheading Synopsis
30167 -break-passcount @var{tracepoint-number} @var{passcount}
30170 Set the passcount for tracepoint @var{tracepoint-number} to
30171 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
30172 is not a tracepoint, error is emitted. This corresponds to CLI
30173 command @samp{passcount}.
30175 @subheading The @code{-break-watch} Command
30176 @findex -break-watch
30178 @subsubheading Synopsis
30181 -break-watch [ -a | -r ]
30184 Create a watchpoint. With the @samp{-a} option it will create an
30185 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
30186 read from or on a write to the memory location. With the @samp{-r}
30187 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
30188 trigger only when the memory location is accessed for reading. Without
30189 either of the options, the watchpoint created is a regular watchpoint,
30190 i.e., it will trigger when the memory location is accessed for writing.
30191 @xref{Set Watchpoints, , Setting Watchpoints}.
30193 Note that @samp{-break-list} will report a single list of watchpoints and
30194 breakpoints inserted.
30196 @subsubheading @value{GDBN} Command
30198 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
30201 @subsubheading Example
30203 Setting a watchpoint on a variable in the @code{main} function:
30208 ^done,wpt=@{number="2",exp="x"@}
30213 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
30214 value=@{old="-268439212",new="55"@},
30215 frame=@{func="main",args=[],file="recursive2.c",
30216 fullname="/home/foo/bar/recursive2.c",line="5"@}
30220 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
30221 the program execution twice: first for the variable changing value, then
30222 for the watchpoint going out of scope.
30227 ^done,wpt=@{number="5",exp="C"@}
30232 *stopped,reason="watchpoint-trigger",
30233 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
30234 frame=@{func="callee4",args=[],
30235 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30236 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
30241 *stopped,reason="watchpoint-scope",wpnum="5",
30242 frame=@{func="callee3",args=[@{name="strarg",
30243 value="0x11940 \"A string argument.\""@}],
30244 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30245 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
30249 Listing breakpoints and watchpoints, at different points in the program
30250 execution. Note that once the watchpoint goes out of scope, it is
30256 ^done,wpt=@{number="2",exp="C"@}
30259 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30260 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30261 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30262 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30263 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30264 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30265 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30266 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30267 addr="0x00010734",func="callee4",
30268 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30269 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
30271 bkpt=@{number="2",type="watchpoint",disp="keep",
30272 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
30277 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
30278 value=@{old="-276895068",new="3"@},
30279 frame=@{func="callee4",args=[],
30280 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30281 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
30284 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30285 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30286 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30287 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30288 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30289 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30290 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30291 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30292 addr="0x00010734",func="callee4",
30293 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30294 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
30296 bkpt=@{number="2",type="watchpoint",disp="keep",
30297 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
30301 ^done,reason="watchpoint-scope",wpnum="2",
30302 frame=@{func="callee3",args=[@{name="strarg",
30303 value="0x11940 \"A string argument.\""@}],
30304 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30305 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
30308 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30309 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30310 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30311 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30312 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30313 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30314 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30315 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30316 addr="0x00010734",func="callee4",
30317 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30318 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
30319 thread-groups=["i1"],times="1"@}]@}
30324 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30325 @node GDB/MI Catchpoint Commands
30326 @section @sc{gdb/mi} Catchpoint Commands
30328 This section documents @sc{gdb/mi} commands for manipulating
30332 * Shared Library GDB/MI Catchpoint Commands::
30333 * Ada Exception GDB/MI Catchpoint Commands::
30336 @node Shared Library GDB/MI Catchpoint Commands
30337 @subsection Shared Library @sc{gdb/mi} Catchpoints
30339 @subheading The @code{-catch-load} Command
30340 @findex -catch-load
30342 @subsubheading Synopsis
30345 -catch-load [ -t ] [ -d ] @var{regexp}
30348 Add a catchpoint for library load events. If the @samp{-t} option is used,
30349 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
30350 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
30351 in a disabled state. The @samp{regexp} argument is a regular
30352 expression used to match the name of the loaded library.
30355 @subsubheading @value{GDBN} Command
30357 The corresponding @value{GDBN} command is @samp{catch load}.
30359 @subsubheading Example
30362 -catch-load -t foo.so
30363 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
30364 what="load of library matching foo.so",catch-type="load",times="0"@}
30369 @subheading The @code{-catch-unload} Command
30370 @findex -catch-unload
30372 @subsubheading Synopsis
30375 -catch-unload [ -t ] [ -d ] @var{regexp}
30378 Add a catchpoint for library unload events. If the @samp{-t} option is
30379 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
30380 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
30381 created in a disabled state. The @samp{regexp} argument is a regular
30382 expression used to match the name of the unloaded library.
30384 @subsubheading @value{GDBN} Command
30386 The corresponding @value{GDBN} command is @samp{catch unload}.
30388 @subsubheading Example
30391 -catch-unload -d bar.so
30392 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
30393 what="load of library matching bar.so",catch-type="unload",times="0"@}
30397 @node Ada Exception GDB/MI Catchpoint Commands
30398 @subsection Ada Exception @sc{gdb/mi} Catchpoints
30400 The following @sc{gdb/mi} commands can be used to create catchpoints
30401 that stop the execution when Ada exceptions are being raised.
30403 @subheading The @code{-catch-assert} Command
30404 @findex -catch-assert
30406 @subsubheading Synopsis
30409 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
30412 Add a catchpoint for failed Ada assertions.
30414 The possible optional parameters for this command are:
30417 @item -c @var{condition}
30418 Make the catchpoint conditional on @var{condition}.
30420 Create a disabled catchpoint.
30422 Create a temporary catchpoint.
30425 @subsubheading @value{GDBN} Command
30427 The corresponding @value{GDBN} command is @samp{catch assert}.
30429 @subsubheading Example
30433 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
30434 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
30435 thread-groups=["i1"],times="0",
30436 original-location="__gnat_debug_raise_assert_failure"@}
30440 @subheading The @code{-catch-exception} Command
30441 @findex -catch-exception
30443 @subsubheading Synopsis
30446 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
30450 Add a catchpoint stopping when Ada exceptions are raised.
30451 By default, the command stops the program when any Ada exception
30452 gets raised. But it is also possible, by using some of the
30453 optional parameters described below, to create more selective
30456 The possible optional parameters for this command are:
30459 @item -c @var{condition}
30460 Make the catchpoint conditional on @var{condition}.
30462 Create a disabled catchpoint.
30463 @item -e @var{exception-name}
30464 Only stop when @var{exception-name} is raised. This option cannot
30465 be used combined with @samp{-u}.
30467 Create a temporary catchpoint.
30469 Stop only when an unhandled exception gets raised. This option
30470 cannot be used combined with @samp{-e}.
30473 @subsubheading @value{GDBN} Command
30475 The corresponding @value{GDBN} commands are @samp{catch exception}
30476 and @samp{catch exception unhandled}.
30478 @subsubheading Example
30481 -catch-exception -e Program_Error
30482 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
30483 enabled="y",addr="0x0000000000404874",
30484 what="`Program_Error' Ada exception", thread-groups=["i1"],
30485 times="0",original-location="__gnat_debug_raise_exception"@}
30489 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30490 @node GDB/MI Program Context
30491 @section @sc{gdb/mi} Program Context
30493 @subheading The @code{-exec-arguments} Command
30494 @findex -exec-arguments
30497 @subsubheading Synopsis
30500 -exec-arguments @var{args}
30503 Set the inferior program arguments, to be used in the next
30506 @subsubheading @value{GDBN} Command
30508 The corresponding @value{GDBN} command is @samp{set args}.
30510 @subsubheading Example
30514 -exec-arguments -v word
30521 @subheading The @code{-exec-show-arguments} Command
30522 @findex -exec-show-arguments
30524 @subsubheading Synopsis
30527 -exec-show-arguments
30530 Print the arguments of the program.
30532 @subsubheading @value{GDBN} Command
30534 The corresponding @value{GDBN} command is @samp{show args}.
30536 @subsubheading Example
30541 @subheading The @code{-environment-cd} Command
30542 @findex -environment-cd
30544 @subsubheading Synopsis
30547 -environment-cd @var{pathdir}
30550 Set @value{GDBN}'s working directory.
30552 @subsubheading @value{GDBN} Command
30554 The corresponding @value{GDBN} command is @samp{cd}.
30556 @subsubheading Example
30560 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
30566 @subheading The @code{-environment-directory} Command
30567 @findex -environment-directory
30569 @subsubheading Synopsis
30572 -environment-directory [ -r ] [ @var{pathdir} ]+
30575 Add directories @var{pathdir} to beginning of search path for source files.
30576 If the @samp{-r} option is used, the search path is reset to the default
30577 search path. If directories @var{pathdir} are supplied in addition to the
30578 @samp{-r} option, the search path is first reset and then addition
30580 Multiple directories may be specified, separated by blanks. Specifying
30581 multiple directories in a single command
30582 results in the directories added to the beginning of the
30583 search path in the same order they were presented in the command.
30584 If blanks are needed as
30585 part of a directory name, double-quotes should be used around
30586 the name. In the command output, the path will show up separated
30587 by the system directory-separator character. The directory-separator
30588 character must not be used
30589 in any directory name.
30590 If no directories are specified, the current search path is displayed.
30592 @subsubheading @value{GDBN} Command
30594 The corresponding @value{GDBN} command is @samp{dir}.
30596 @subsubheading Example
30600 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
30601 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
30603 -environment-directory ""
30604 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
30606 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
30607 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
30609 -environment-directory -r
30610 ^done,source-path="$cdir:$cwd"
30615 @subheading The @code{-environment-path} Command
30616 @findex -environment-path
30618 @subsubheading Synopsis
30621 -environment-path [ -r ] [ @var{pathdir} ]+
30624 Add directories @var{pathdir} to beginning of search path for object files.
30625 If the @samp{-r} option is used, the search path is reset to the original
30626 search path that existed at gdb start-up. If directories @var{pathdir} are
30627 supplied in addition to the
30628 @samp{-r} option, the search path is first reset and then addition
30630 Multiple directories may be specified, separated by blanks. Specifying
30631 multiple directories in a single command
30632 results in the directories added to the beginning of the
30633 search path in the same order they were presented in the command.
30634 If blanks are needed as
30635 part of a directory name, double-quotes should be used around
30636 the name. In the command output, the path will show up separated
30637 by the system directory-separator character. The directory-separator
30638 character must not be used
30639 in any directory name.
30640 If no directories are specified, the current path is displayed.
30643 @subsubheading @value{GDBN} Command
30645 The corresponding @value{GDBN} command is @samp{path}.
30647 @subsubheading Example
30652 ^done,path="/usr/bin"
30654 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
30655 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
30657 -environment-path -r /usr/local/bin
30658 ^done,path="/usr/local/bin:/usr/bin"
30663 @subheading The @code{-environment-pwd} Command
30664 @findex -environment-pwd
30666 @subsubheading Synopsis
30672 Show the current working directory.
30674 @subsubheading @value{GDBN} Command
30676 The corresponding @value{GDBN} command is @samp{pwd}.
30678 @subsubheading Example
30683 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
30687 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30688 @node GDB/MI Thread Commands
30689 @section @sc{gdb/mi} Thread Commands
30692 @subheading The @code{-thread-info} Command
30693 @findex -thread-info
30695 @subsubheading Synopsis
30698 -thread-info [ @var{thread-id} ]
30701 Reports information about either a specific thread, if
30702 the @var{thread-id} parameter is present, or about all
30703 threads. When printing information about all threads,
30704 also reports the current thread.
30706 @subsubheading @value{GDBN} Command
30708 The @samp{info thread} command prints the same information
30711 @subsubheading Result
30713 The result is a list of threads. The following attributes are
30714 defined for a given thread:
30718 This field exists only for the current thread. It has the value @samp{*}.
30721 The identifier that @value{GDBN} uses to refer to the thread.
30724 The identifier that the target uses to refer to the thread.
30727 Extra information about the thread, in a target-specific format. This
30731 The name of the thread. If the user specified a name using the
30732 @code{thread name} command, then this name is given. Otherwise, if
30733 @value{GDBN} can extract the thread name from the target, then that
30734 name is given. If @value{GDBN} cannot find the thread name, then this
30738 The stack frame currently executing in the thread.
30741 The thread's state. The @samp{state} field may have the following
30746 The thread is stopped. Frame information is available for stopped
30750 The thread is running. There's no frame information for running
30756 If @value{GDBN} can find the CPU core on which this thread is running,
30757 then this field is the core identifier. This field is optional.
30761 @subsubheading Example
30766 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
30767 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
30768 args=[]@},state="running"@},
30769 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
30770 frame=@{level="0",addr="0x0804891f",func="foo",
30771 args=[@{name="i",value="10"@}],
30772 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
30773 state="running"@}],
30774 current-thread-id="1"
30778 @subheading The @code{-thread-list-ids} Command
30779 @findex -thread-list-ids
30781 @subsubheading Synopsis
30787 Produces a list of the currently known @value{GDBN} thread ids. At the
30788 end of the list it also prints the total number of such threads.
30790 This command is retained for historical reasons, the
30791 @code{-thread-info} command should be used instead.
30793 @subsubheading @value{GDBN} Command
30795 Part of @samp{info threads} supplies the same information.
30797 @subsubheading Example
30802 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
30803 current-thread-id="1",number-of-threads="3"
30808 @subheading The @code{-thread-select} Command
30809 @findex -thread-select
30811 @subsubheading Synopsis
30814 -thread-select @var{threadnum}
30817 Make @var{threadnum} the current thread. It prints the number of the new
30818 current thread, and the topmost frame for that thread.
30820 This command is deprecated in favor of explicitly using the
30821 @samp{--thread} option to each command.
30823 @subsubheading @value{GDBN} Command
30825 The corresponding @value{GDBN} command is @samp{thread}.
30827 @subsubheading Example
30834 *stopped,reason="end-stepping-range",thread-id="2",line="187",
30835 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
30839 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
30840 number-of-threads="3"
30843 ^done,new-thread-id="3",
30844 frame=@{level="0",func="vprintf",
30845 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
30846 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
30850 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30851 @node GDB/MI Ada Tasking Commands
30852 @section @sc{gdb/mi} Ada Tasking Commands
30854 @subheading The @code{-ada-task-info} Command
30855 @findex -ada-task-info
30857 @subsubheading Synopsis
30860 -ada-task-info [ @var{task-id} ]
30863 Reports information about either a specific Ada task, if the
30864 @var{task-id} parameter is present, or about all Ada tasks.
30866 @subsubheading @value{GDBN} Command
30868 The @samp{info tasks} command prints the same information
30869 about all Ada tasks (@pxref{Ada Tasks}).
30871 @subsubheading Result
30873 The result is a table of Ada tasks. The following columns are
30874 defined for each Ada task:
30878 This field exists only for the current thread. It has the value @samp{*}.
30881 The identifier that @value{GDBN} uses to refer to the Ada task.
30884 The identifier that the target uses to refer to the Ada task.
30887 The identifier of the thread corresponding to the Ada task.
30889 This field should always exist, as Ada tasks are always implemented
30890 on top of a thread. But if @value{GDBN} cannot find this corresponding
30891 thread for any reason, the field is omitted.
30894 This field exists only when the task was created by another task.
30895 In this case, it provides the ID of the parent task.
30898 The base priority of the task.
30901 The current state of the task. For a detailed description of the
30902 possible states, see @ref{Ada Tasks}.
30905 The name of the task.
30909 @subsubheading Example
30913 ^done,tasks=@{nr_rows="3",nr_cols="8",
30914 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
30915 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
30916 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
30917 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
30918 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
30919 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
30920 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
30921 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
30922 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
30923 state="Child Termination Wait",name="main_task"@}]@}
30927 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30928 @node GDB/MI Program Execution
30929 @section @sc{gdb/mi} Program Execution
30931 These are the asynchronous commands which generate the out-of-band
30932 record @samp{*stopped}. Currently @value{GDBN} only really executes
30933 asynchronously with remote targets and this interaction is mimicked in
30936 @subheading The @code{-exec-continue} Command
30937 @findex -exec-continue
30939 @subsubheading Synopsis
30942 -exec-continue [--reverse] [--all|--thread-group N]
30945 Resumes the execution of the inferior program, which will continue
30946 to execute until it reaches a debugger stop event. If the
30947 @samp{--reverse} option is specified, execution resumes in reverse until
30948 it reaches a stop event. Stop events may include
30951 breakpoints or watchpoints
30953 signals or exceptions
30955 the end of the process (or its beginning under @samp{--reverse})
30957 the end or beginning of a replay log if one is being used.
30959 In all-stop mode (@pxref{All-Stop
30960 Mode}), may resume only one thread, or all threads, depending on the
30961 value of the @samp{scheduler-locking} variable. If @samp{--all} is
30962 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
30963 ignored in all-stop mode. If the @samp{--thread-group} options is
30964 specified, then all threads in that thread group are resumed.
30966 @subsubheading @value{GDBN} Command
30968 The corresponding @value{GDBN} corresponding is @samp{continue}.
30970 @subsubheading Example
30977 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
30978 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
30984 @subheading The @code{-exec-finish} Command
30985 @findex -exec-finish
30987 @subsubheading Synopsis
30990 -exec-finish [--reverse]
30993 Resumes the execution of the inferior program until the current
30994 function is exited. Displays the results returned by the function.
30995 If the @samp{--reverse} option is specified, resumes the reverse
30996 execution of the inferior program until the point where current
30997 function was called.
30999 @subsubheading @value{GDBN} Command
31001 The corresponding @value{GDBN} command is @samp{finish}.
31003 @subsubheading Example
31005 Function returning @code{void}.
31012 *stopped,reason="function-finished",frame=@{func="main",args=[],
31013 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
31017 Function returning other than @code{void}. The name of the internal
31018 @value{GDBN} variable storing the result is printed, together with the
31025 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
31026 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
31027 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31028 gdb-result-var="$1",return-value="0"
31033 @subheading The @code{-exec-interrupt} Command
31034 @findex -exec-interrupt
31036 @subsubheading Synopsis
31039 -exec-interrupt [--all|--thread-group N]
31042 Interrupts the background execution of the target. Note how the token
31043 associated with the stop message is the one for the execution command
31044 that has been interrupted. The token for the interrupt itself only
31045 appears in the @samp{^done} output. If the user is trying to
31046 interrupt a non-running program, an error message will be printed.
31048 Note that when asynchronous execution is enabled, this command is
31049 asynchronous just like other execution commands. That is, first the
31050 @samp{^done} response will be printed, and the target stop will be
31051 reported after that using the @samp{*stopped} notification.
31053 In non-stop mode, only the context thread is interrupted by default.
31054 All threads (in all inferiors) will be interrupted if the
31055 @samp{--all} option is specified. If the @samp{--thread-group}
31056 option is specified, all threads in that group will be interrupted.
31058 @subsubheading @value{GDBN} Command
31060 The corresponding @value{GDBN} command is @samp{interrupt}.
31062 @subsubheading Example
31073 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
31074 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
31075 fullname="/home/foo/bar/try.c",line="13"@}
31080 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
31084 @subheading The @code{-exec-jump} Command
31087 @subsubheading Synopsis
31090 -exec-jump @var{location}
31093 Resumes execution of the inferior program at the location specified by
31094 parameter. @xref{Specify Location}, for a description of the
31095 different forms of @var{location}.
31097 @subsubheading @value{GDBN} Command
31099 The corresponding @value{GDBN} command is @samp{jump}.
31101 @subsubheading Example
31104 -exec-jump foo.c:10
31105 *running,thread-id="all"
31110 @subheading The @code{-exec-next} Command
31113 @subsubheading Synopsis
31116 -exec-next [--reverse]
31119 Resumes execution of the inferior program, stopping when the beginning
31120 of the next source line is reached.
31122 If the @samp{--reverse} option is specified, resumes reverse execution
31123 of the inferior program, stopping at the beginning of the previous
31124 source line. If you issue this command on the first line of a
31125 function, it will take you back to the caller of that function, to the
31126 source line where the function was called.
31129 @subsubheading @value{GDBN} Command
31131 The corresponding @value{GDBN} command is @samp{next}.
31133 @subsubheading Example
31139 *stopped,reason="end-stepping-range",line="8",file="hello.c"
31144 @subheading The @code{-exec-next-instruction} Command
31145 @findex -exec-next-instruction
31147 @subsubheading Synopsis
31150 -exec-next-instruction [--reverse]
31153 Executes one machine instruction. If the instruction is a function
31154 call, continues until the function returns. If the program stops at an
31155 instruction in the middle of a source line, the address will be
31158 If the @samp{--reverse} option is specified, resumes reverse execution
31159 of the inferior program, stopping at the previous instruction. If the
31160 previously executed instruction was a return from another function,
31161 it will continue to execute in reverse until the call to that function
31162 (from the current stack frame) is reached.
31164 @subsubheading @value{GDBN} Command
31166 The corresponding @value{GDBN} command is @samp{nexti}.
31168 @subsubheading Example
31172 -exec-next-instruction
31176 *stopped,reason="end-stepping-range",
31177 addr="0x000100d4",line="5",file="hello.c"
31182 @subheading The @code{-exec-return} Command
31183 @findex -exec-return
31185 @subsubheading Synopsis
31191 Makes current function return immediately. Doesn't execute the inferior.
31192 Displays the new current frame.
31194 @subsubheading @value{GDBN} Command
31196 The corresponding @value{GDBN} command is @samp{return}.
31198 @subsubheading Example
31202 200-break-insert callee4
31203 200^done,bkpt=@{number="1",addr="0x00010734",
31204 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
31209 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
31210 frame=@{func="callee4",args=[],
31211 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31212 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
31218 111^done,frame=@{level="0",func="callee3",
31219 args=[@{name="strarg",
31220 value="0x11940 \"A string argument.\""@}],
31221 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31222 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
31227 @subheading The @code{-exec-run} Command
31230 @subsubheading Synopsis
31233 -exec-run [ --all | --thread-group N ] [ --start ]
31236 Starts execution of the inferior from the beginning. The inferior
31237 executes until either a breakpoint is encountered or the program
31238 exits. In the latter case the output will include an exit code, if
31239 the program has exited exceptionally.
31241 When neither the @samp{--all} nor the @samp{--thread-group} option
31242 is specified, the current inferior is started. If the
31243 @samp{--thread-group} option is specified, it should refer to a thread
31244 group of type @samp{process}, and that thread group will be started.
31245 If the @samp{--all} option is specified, then all inferiors will be started.
31247 Using the @samp{--start} option instructs the debugger to stop
31248 the execution at the start of the inferior's main subprogram,
31249 following the same behavior as the @code{start} command
31250 (@pxref{Starting}).
31252 @subsubheading @value{GDBN} Command
31254 The corresponding @value{GDBN} command is @samp{run}.
31256 @subsubheading Examples
31261 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
31266 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
31267 frame=@{func="main",args=[],file="recursive2.c",
31268 fullname="/home/foo/bar/recursive2.c",line="4"@}
31273 Program exited normally:
31281 *stopped,reason="exited-normally"
31286 Program exited exceptionally:
31294 *stopped,reason="exited",exit-code="01"
31298 Another way the program can terminate is if it receives a signal such as
31299 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
31303 *stopped,reason="exited-signalled",signal-name="SIGINT",
31304 signal-meaning="Interrupt"
31308 @c @subheading -exec-signal
31311 @subheading The @code{-exec-step} Command
31314 @subsubheading Synopsis
31317 -exec-step [--reverse]
31320 Resumes execution of the inferior program, stopping when the beginning
31321 of the next source line is reached, if the next source line is not a
31322 function call. If it is, stop at the first instruction of the called
31323 function. If the @samp{--reverse} option is specified, resumes reverse
31324 execution of the inferior program, stopping at the beginning of the
31325 previously executed source line.
31327 @subsubheading @value{GDBN} Command
31329 The corresponding @value{GDBN} command is @samp{step}.
31331 @subsubheading Example
31333 Stepping into a function:
31339 *stopped,reason="end-stepping-range",
31340 frame=@{func="foo",args=[@{name="a",value="10"@},
31341 @{name="b",value="0"@}],file="recursive2.c",
31342 fullname="/home/foo/bar/recursive2.c",line="11"@}
31352 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
31357 @subheading The @code{-exec-step-instruction} Command
31358 @findex -exec-step-instruction
31360 @subsubheading Synopsis
31363 -exec-step-instruction [--reverse]
31366 Resumes the inferior which executes one machine instruction. If the
31367 @samp{--reverse} option is specified, resumes reverse execution of the
31368 inferior program, stopping at the previously executed instruction.
31369 The output, once @value{GDBN} has stopped, will vary depending on
31370 whether we have stopped in the middle of a source line or not. In the
31371 former case, the address at which the program stopped will be printed
31374 @subsubheading @value{GDBN} Command
31376 The corresponding @value{GDBN} command is @samp{stepi}.
31378 @subsubheading Example
31382 -exec-step-instruction
31386 *stopped,reason="end-stepping-range",
31387 frame=@{func="foo",args=[],file="try.c",
31388 fullname="/home/foo/bar/try.c",line="10"@}
31390 -exec-step-instruction
31394 *stopped,reason="end-stepping-range",
31395 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
31396 fullname="/home/foo/bar/try.c",line="10"@}
31401 @subheading The @code{-exec-until} Command
31402 @findex -exec-until
31404 @subsubheading Synopsis
31407 -exec-until [ @var{location} ]
31410 Executes the inferior until the @var{location} specified in the
31411 argument is reached. If there is no argument, the inferior executes
31412 until a source line greater than the current one is reached. The
31413 reason for stopping in this case will be @samp{location-reached}.
31415 @subsubheading @value{GDBN} Command
31417 The corresponding @value{GDBN} command is @samp{until}.
31419 @subsubheading Example
31423 -exec-until recursive2.c:6
31427 *stopped,reason="location-reached",frame=@{func="main",args=[],
31428 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
31433 @subheading -file-clear
31434 Is this going away????
31437 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31438 @node GDB/MI Stack Manipulation
31439 @section @sc{gdb/mi} Stack Manipulation Commands
31441 @subheading The @code{-enable-frame-filters} Command
31442 @findex -enable-frame-filters
31445 -enable-frame-filters
31448 @value{GDBN} allows Python-based frame filters to affect the output of
31449 the MI commands relating to stack traces. As there is no way to
31450 implement this in a fully backward-compatible way, a front end must
31451 request that this functionality be enabled.
31453 Once enabled, this feature cannot be disabled.
31455 Note that if Python support has not been compiled into @value{GDBN},
31456 this command will still succeed (and do nothing).
31458 @subheading The @code{-stack-info-frame} Command
31459 @findex -stack-info-frame
31461 @subsubheading Synopsis
31467 Get info on the selected frame.
31469 @subsubheading @value{GDBN} Command
31471 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
31472 (without arguments).
31474 @subsubheading Example
31479 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
31480 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31481 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
31485 @subheading The @code{-stack-info-depth} Command
31486 @findex -stack-info-depth
31488 @subsubheading Synopsis
31491 -stack-info-depth [ @var{max-depth} ]
31494 Return the depth of the stack. If the integer argument @var{max-depth}
31495 is specified, do not count beyond @var{max-depth} frames.
31497 @subsubheading @value{GDBN} Command
31499 There's no equivalent @value{GDBN} command.
31501 @subsubheading Example
31503 For a stack with frame levels 0 through 11:
31510 -stack-info-depth 4
31513 -stack-info-depth 12
31516 -stack-info-depth 11
31519 -stack-info-depth 13
31524 @anchor{-stack-list-arguments}
31525 @subheading The @code{-stack-list-arguments} Command
31526 @findex -stack-list-arguments
31528 @subsubheading Synopsis
31531 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
31532 [ @var{low-frame} @var{high-frame} ]
31535 Display a list of the arguments for the frames between @var{low-frame}
31536 and @var{high-frame} (inclusive). If @var{low-frame} and
31537 @var{high-frame} are not provided, list the arguments for the whole
31538 call stack. If the two arguments are equal, show the single frame
31539 at the corresponding level. It is an error if @var{low-frame} is
31540 larger than the actual number of frames. On the other hand,
31541 @var{high-frame} may be larger than the actual number of frames, in
31542 which case only existing frames will be returned.
31544 If @var{print-values} is 0 or @code{--no-values}, print only the names of
31545 the variables; if it is 1 or @code{--all-values}, print also their
31546 values; and if it is 2 or @code{--simple-values}, print the name,
31547 type and value for simple data types, and the name and type for arrays,
31548 structures and unions. If the option @code{--no-frame-filters} is
31549 supplied, then Python frame filters will not be executed.
31551 If the @code{--skip-unavailable} option is specified, arguments that
31552 are not available are not listed. Partially available arguments
31553 are still displayed, however.
31555 Use of this command to obtain arguments in a single frame is
31556 deprecated in favor of the @samp{-stack-list-variables} command.
31558 @subsubheading @value{GDBN} Command
31560 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
31561 @samp{gdb_get_args} command which partially overlaps with the
31562 functionality of @samp{-stack-list-arguments}.
31564 @subsubheading Example
31571 frame=@{level="0",addr="0x00010734",func="callee4",
31572 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31573 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
31574 frame=@{level="1",addr="0x0001076c",func="callee3",
31575 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31576 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
31577 frame=@{level="2",addr="0x0001078c",func="callee2",
31578 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31579 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
31580 frame=@{level="3",addr="0x000107b4",func="callee1",
31581 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31582 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
31583 frame=@{level="4",addr="0x000107e0",func="main",
31584 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31585 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
31587 -stack-list-arguments 0
31590 frame=@{level="0",args=[]@},
31591 frame=@{level="1",args=[name="strarg"]@},
31592 frame=@{level="2",args=[name="intarg",name="strarg"]@},
31593 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
31594 frame=@{level="4",args=[]@}]
31596 -stack-list-arguments 1
31599 frame=@{level="0",args=[]@},
31601 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
31602 frame=@{level="2",args=[
31603 @{name="intarg",value="2"@},
31604 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
31605 @{frame=@{level="3",args=[
31606 @{name="intarg",value="2"@},
31607 @{name="strarg",value="0x11940 \"A string argument.\""@},
31608 @{name="fltarg",value="3.5"@}]@},
31609 frame=@{level="4",args=[]@}]
31611 -stack-list-arguments 0 2 2
31612 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
31614 -stack-list-arguments 1 2 2
31615 ^done,stack-args=[frame=@{level="2",
31616 args=[@{name="intarg",value="2"@},
31617 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
31621 @c @subheading -stack-list-exception-handlers
31624 @anchor{-stack-list-frames}
31625 @subheading The @code{-stack-list-frames} Command
31626 @findex -stack-list-frames
31628 @subsubheading Synopsis
31631 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
31634 List the frames currently on the stack. For each frame it displays the
31639 The frame number, 0 being the topmost frame, i.e., the innermost function.
31641 The @code{$pc} value for that frame.
31645 File name of the source file where the function lives.
31646 @item @var{fullname}
31647 The full file name of the source file where the function lives.
31649 Line number corresponding to the @code{$pc}.
31651 The shared library where this function is defined. This is only given
31652 if the frame's function is not known.
31655 If invoked without arguments, this command prints a backtrace for the
31656 whole stack. If given two integer arguments, it shows the frames whose
31657 levels are between the two arguments (inclusive). If the two arguments
31658 are equal, it shows the single frame at the corresponding level. It is
31659 an error if @var{low-frame} is larger than the actual number of
31660 frames. On the other hand, @var{high-frame} may be larger than the
31661 actual number of frames, in which case only existing frames will be
31662 returned. If the option @code{--no-frame-filters} is supplied, then
31663 Python frame filters will not be executed.
31665 @subsubheading @value{GDBN} Command
31667 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
31669 @subsubheading Example
31671 Full stack backtrace:
31677 [frame=@{level="0",addr="0x0001076c",func="foo",
31678 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
31679 frame=@{level="1",addr="0x000107a4",func="foo",
31680 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31681 frame=@{level="2",addr="0x000107a4",func="foo",
31682 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31683 frame=@{level="3",addr="0x000107a4",func="foo",
31684 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31685 frame=@{level="4",addr="0x000107a4",func="foo",
31686 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31687 frame=@{level="5",addr="0x000107a4",func="foo",
31688 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31689 frame=@{level="6",addr="0x000107a4",func="foo",
31690 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31691 frame=@{level="7",addr="0x000107a4",func="foo",
31692 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31693 frame=@{level="8",addr="0x000107a4",func="foo",
31694 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31695 frame=@{level="9",addr="0x000107a4",func="foo",
31696 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31697 frame=@{level="10",addr="0x000107a4",func="foo",
31698 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31699 frame=@{level="11",addr="0x00010738",func="main",
31700 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
31704 Show frames between @var{low_frame} and @var{high_frame}:
31708 -stack-list-frames 3 5
31710 [frame=@{level="3",addr="0x000107a4",func="foo",
31711 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31712 frame=@{level="4",addr="0x000107a4",func="foo",
31713 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31714 frame=@{level="5",addr="0x000107a4",func="foo",
31715 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
31719 Show a single frame:
31723 -stack-list-frames 3 3
31725 [frame=@{level="3",addr="0x000107a4",func="foo",
31726 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
31731 @subheading The @code{-stack-list-locals} Command
31732 @findex -stack-list-locals
31733 @anchor{-stack-list-locals}
31735 @subsubheading Synopsis
31738 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
31741 Display the local variable names for the selected frame. If
31742 @var{print-values} is 0 or @code{--no-values}, print only the names of
31743 the variables; if it is 1 or @code{--all-values}, print also their
31744 values; and if it is 2 or @code{--simple-values}, print the name,
31745 type and value for simple data types, and the name and type for arrays,
31746 structures and unions. In this last case, a frontend can immediately
31747 display the value of simple data types and create variable objects for
31748 other data types when the user wishes to explore their values in
31749 more detail. If the option @code{--no-frame-filters} is supplied, then
31750 Python frame filters will not be executed.
31752 If the @code{--skip-unavailable} option is specified, local variables
31753 that are not available are not listed. Partially available local
31754 variables are still displayed, however.
31756 This command is deprecated in favor of the
31757 @samp{-stack-list-variables} command.
31759 @subsubheading @value{GDBN} Command
31761 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
31763 @subsubheading Example
31767 -stack-list-locals 0
31768 ^done,locals=[name="A",name="B",name="C"]
31770 -stack-list-locals --all-values
31771 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
31772 @{name="C",value="@{1, 2, 3@}"@}]
31773 -stack-list-locals --simple-values
31774 ^done,locals=[@{name="A",type="int",value="1"@},
31775 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
31779 @anchor{-stack-list-variables}
31780 @subheading The @code{-stack-list-variables} Command
31781 @findex -stack-list-variables
31783 @subsubheading Synopsis
31786 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
31789 Display the names of local variables and function arguments for the selected frame. If
31790 @var{print-values} is 0 or @code{--no-values}, print only the names of
31791 the variables; if it is 1 or @code{--all-values}, print also their
31792 values; and if it is 2 or @code{--simple-values}, print the name,
31793 type and value for simple data types, and the name and type for arrays,
31794 structures and unions. If the option @code{--no-frame-filters} is
31795 supplied, then Python frame filters will not be executed.
31797 If the @code{--skip-unavailable} option is specified, local variables
31798 and arguments that are not available are not listed. Partially
31799 available arguments and local variables are still displayed, however.
31801 @subsubheading Example
31805 -stack-list-variables --thread 1 --frame 0 --all-values
31806 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
31811 @subheading The @code{-stack-select-frame} Command
31812 @findex -stack-select-frame
31814 @subsubheading Synopsis
31817 -stack-select-frame @var{framenum}
31820 Change the selected frame. Select a different frame @var{framenum} on
31823 This command in deprecated in favor of passing the @samp{--frame}
31824 option to every command.
31826 @subsubheading @value{GDBN} Command
31828 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
31829 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
31831 @subsubheading Example
31835 -stack-select-frame 2
31840 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31841 @node GDB/MI Variable Objects
31842 @section @sc{gdb/mi} Variable Objects
31846 @subheading Motivation for Variable Objects in @sc{gdb/mi}
31848 For the implementation of a variable debugger window (locals, watched
31849 expressions, etc.), we are proposing the adaptation of the existing code
31850 used by @code{Insight}.
31852 The two main reasons for that are:
31856 It has been proven in practice (it is already on its second generation).
31859 It will shorten development time (needless to say how important it is
31863 The original interface was designed to be used by Tcl code, so it was
31864 slightly changed so it could be used through @sc{gdb/mi}. This section
31865 describes the @sc{gdb/mi} operations that will be available and gives some
31866 hints about their use.
31868 @emph{Note}: In addition to the set of operations described here, we
31869 expect the @sc{gui} implementation of a variable window to require, at
31870 least, the following operations:
31873 @item @code{-gdb-show} @code{output-radix}
31874 @item @code{-stack-list-arguments}
31875 @item @code{-stack-list-locals}
31876 @item @code{-stack-select-frame}
31881 @subheading Introduction to Variable Objects
31883 @cindex variable objects in @sc{gdb/mi}
31885 Variable objects are "object-oriented" MI interface for examining and
31886 changing values of expressions. Unlike some other MI interfaces that
31887 work with expressions, variable objects are specifically designed for
31888 simple and efficient presentation in the frontend. A variable object
31889 is identified by string name. When a variable object is created, the
31890 frontend specifies the expression for that variable object. The
31891 expression can be a simple variable, or it can be an arbitrary complex
31892 expression, and can even involve CPU registers. After creating a
31893 variable object, the frontend can invoke other variable object
31894 operations---for example to obtain or change the value of a variable
31895 object, or to change display format.
31897 Variable objects have hierarchical tree structure. Any variable object
31898 that corresponds to a composite type, such as structure in C, has
31899 a number of child variable objects, for example corresponding to each
31900 element of a structure. A child variable object can itself have
31901 children, recursively. Recursion ends when we reach
31902 leaf variable objects, which always have built-in types. Child variable
31903 objects are created only by explicit request, so if a frontend
31904 is not interested in the children of a particular variable object, no
31905 child will be created.
31907 For a leaf variable object it is possible to obtain its value as a
31908 string, or set the value from a string. String value can be also
31909 obtained for a non-leaf variable object, but it's generally a string
31910 that only indicates the type of the object, and does not list its
31911 contents. Assignment to a non-leaf variable object is not allowed.
31913 A frontend does not need to read the values of all variable objects each time
31914 the program stops. Instead, MI provides an update command that lists all
31915 variable objects whose values has changed since the last update
31916 operation. This considerably reduces the amount of data that must
31917 be transferred to the frontend. As noted above, children variable
31918 objects are created on demand, and only leaf variable objects have a
31919 real value. As result, gdb will read target memory only for leaf
31920 variables that frontend has created.
31922 The automatic update is not always desirable. For example, a frontend
31923 might want to keep a value of some expression for future reference,
31924 and never update it. For another example, fetching memory is
31925 relatively slow for embedded targets, so a frontend might want
31926 to disable automatic update for the variables that are either not
31927 visible on the screen, or ``closed''. This is possible using so
31928 called ``frozen variable objects''. Such variable objects are never
31929 implicitly updated.
31931 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
31932 fixed variable object, the expression is parsed when the variable
31933 object is created, including associating identifiers to specific
31934 variables. The meaning of expression never changes. For a floating
31935 variable object the values of variables whose names appear in the
31936 expressions are re-evaluated every time in the context of the current
31937 frame. Consider this example:
31942 struct work_state state;
31949 If a fixed variable object for the @code{state} variable is created in
31950 this function, and we enter the recursive call, the variable
31951 object will report the value of @code{state} in the top-level
31952 @code{do_work} invocation. On the other hand, a floating variable
31953 object will report the value of @code{state} in the current frame.
31955 If an expression specified when creating a fixed variable object
31956 refers to a local variable, the variable object becomes bound to the
31957 thread and frame in which the variable object is created. When such
31958 variable object is updated, @value{GDBN} makes sure that the
31959 thread/frame combination the variable object is bound to still exists,
31960 and re-evaluates the variable object in context of that thread/frame.
31962 The following is the complete set of @sc{gdb/mi} operations defined to
31963 access this functionality:
31965 @multitable @columnfractions .4 .6
31966 @item @strong{Operation}
31967 @tab @strong{Description}
31969 @item @code{-enable-pretty-printing}
31970 @tab enable Python-based pretty-printing
31971 @item @code{-var-create}
31972 @tab create a variable object
31973 @item @code{-var-delete}
31974 @tab delete the variable object and/or its children
31975 @item @code{-var-set-format}
31976 @tab set the display format of this variable
31977 @item @code{-var-show-format}
31978 @tab show the display format of this variable
31979 @item @code{-var-info-num-children}
31980 @tab tells how many children this object has
31981 @item @code{-var-list-children}
31982 @tab return a list of the object's children
31983 @item @code{-var-info-type}
31984 @tab show the type of this variable object
31985 @item @code{-var-info-expression}
31986 @tab print parent-relative expression that this variable object represents
31987 @item @code{-var-info-path-expression}
31988 @tab print full expression that this variable object represents
31989 @item @code{-var-show-attributes}
31990 @tab is this variable editable? does it exist here?
31991 @item @code{-var-evaluate-expression}
31992 @tab get the value of this variable
31993 @item @code{-var-assign}
31994 @tab set the value of this variable
31995 @item @code{-var-update}
31996 @tab update the variable and its children
31997 @item @code{-var-set-frozen}
31998 @tab set frozeness attribute
31999 @item @code{-var-set-update-range}
32000 @tab set range of children to display on update
32003 In the next subsection we describe each operation in detail and suggest
32004 how it can be used.
32006 @subheading Description And Use of Operations on Variable Objects
32008 @subheading The @code{-enable-pretty-printing} Command
32009 @findex -enable-pretty-printing
32012 -enable-pretty-printing
32015 @value{GDBN} allows Python-based visualizers to affect the output of the
32016 MI variable object commands. However, because there was no way to
32017 implement this in a fully backward-compatible way, a front end must
32018 request that this functionality be enabled.
32020 Once enabled, this feature cannot be disabled.
32022 Note that if Python support has not been compiled into @value{GDBN},
32023 this command will still succeed (and do nothing).
32025 This feature is currently (as of @value{GDBN} 7.0) experimental, and
32026 may work differently in future versions of @value{GDBN}.
32028 @subheading The @code{-var-create} Command
32029 @findex -var-create
32031 @subsubheading Synopsis
32034 -var-create @{@var{name} | "-"@}
32035 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
32038 This operation creates a variable object, which allows the monitoring of
32039 a variable, the result of an expression, a memory cell or a CPU
32042 The @var{name} parameter is the string by which the object can be
32043 referenced. It must be unique. If @samp{-} is specified, the varobj
32044 system will generate a string ``varNNNNNN'' automatically. It will be
32045 unique provided that one does not specify @var{name} of that format.
32046 The command fails if a duplicate name is found.
32048 The frame under which the expression should be evaluated can be
32049 specified by @var{frame-addr}. A @samp{*} indicates that the current
32050 frame should be used. A @samp{@@} indicates that a floating variable
32051 object must be created.
32053 @var{expression} is any expression valid on the current language set (must not
32054 begin with a @samp{*}), or one of the following:
32058 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
32061 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
32064 @samp{$@var{regname}} --- a CPU register name
32067 @cindex dynamic varobj
32068 A varobj's contents may be provided by a Python-based pretty-printer. In this
32069 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
32070 have slightly different semantics in some cases. If the
32071 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
32072 will never create a dynamic varobj. This ensures backward
32073 compatibility for existing clients.
32075 @subsubheading Result
32077 This operation returns attributes of the newly-created varobj. These
32082 The name of the varobj.
32085 The number of children of the varobj. This number is not necessarily
32086 reliable for a dynamic varobj. Instead, you must examine the
32087 @samp{has_more} attribute.
32090 The varobj's scalar value. For a varobj whose type is some sort of
32091 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
32092 will not be interesting.
32095 The varobj's type. This is a string representation of the type, as
32096 would be printed by the @value{GDBN} CLI. If @samp{print object}
32097 (@pxref{Print Settings, set print object}) is set to @code{on}, the
32098 @emph{actual} (derived) type of the object is shown rather than the
32099 @emph{declared} one.
32102 If a variable object is bound to a specific thread, then this is the
32103 thread's identifier.
32106 For a dynamic varobj, this indicates whether there appear to be any
32107 children available. For a non-dynamic varobj, this will be 0.
32110 This attribute will be present and have the value @samp{1} if the
32111 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32112 then this attribute will not be present.
32115 A dynamic varobj can supply a display hint to the front end. The
32116 value comes directly from the Python pretty-printer object's
32117 @code{display_hint} method. @xref{Pretty Printing API}.
32120 Typical output will look like this:
32123 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
32124 has_more="@var{has_more}"
32128 @subheading The @code{-var-delete} Command
32129 @findex -var-delete
32131 @subsubheading Synopsis
32134 -var-delete [ -c ] @var{name}
32137 Deletes a previously created variable object and all of its children.
32138 With the @samp{-c} option, just deletes the children.
32140 Returns an error if the object @var{name} is not found.
32143 @subheading The @code{-var-set-format} Command
32144 @findex -var-set-format
32146 @subsubheading Synopsis
32149 -var-set-format @var{name} @var{format-spec}
32152 Sets the output format for the value of the object @var{name} to be
32155 @anchor{-var-set-format}
32156 The syntax for the @var{format-spec} is as follows:
32159 @var{format-spec} @expansion{}
32160 @{binary | decimal | hexadecimal | octal | natural@}
32163 The natural format is the default format choosen automatically
32164 based on the variable type (like decimal for an @code{int}, hex
32165 for pointers, etc.).
32167 For a variable with children, the format is set only on the
32168 variable itself, and the children are not affected.
32170 @subheading The @code{-var-show-format} Command
32171 @findex -var-show-format
32173 @subsubheading Synopsis
32176 -var-show-format @var{name}
32179 Returns the format used to display the value of the object @var{name}.
32182 @var{format} @expansion{}
32187 @subheading The @code{-var-info-num-children} Command
32188 @findex -var-info-num-children
32190 @subsubheading Synopsis
32193 -var-info-num-children @var{name}
32196 Returns the number of children of a variable object @var{name}:
32202 Note that this number is not completely reliable for a dynamic varobj.
32203 It will return the current number of children, but more children may
32207 @subheading The @code{-var-list-children} Command
32208 @findex -var-list-children
32210 @subsubheading Synopsis
32213 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
32215 @anchor{-var-list-children}
32217 Return a list of the children of the specified variable object and
32218 create variable objects for them, if they do not already exist. With
32219 a single argument or if @var{print-values} has a value of 0 or
32220 @code{--no-values}, print only the names of the variables; if
32221 @var{print-values} is 1 or @code{--all-values}, also print their
32222 values; and if it is 2 or @code{--simple-values} print the name and
32223 value for simple data types and just the name for arrays, structures
32226 @var{from} and @var{to}, if specified, indicate the range of children
32227 to report. If @var{from} or @var{to} is less than zero, the range is
32228 reset and all children will be reported. Otherwise, children starting
32229 at @var{from} (zero-based) and up to and excluding @var{to} will be
32232 If a child range is requested, it will only affect the current call to
32233 @code{-var-list-children}, but not future calls to @code{-var-update}.
32234 For this, you must instead use @code{-var-set-update-range}. The
32235 intent of this approach is to enable a front end to implement any
32236 update approach it likes; for example, scrolling a view may cause the
32237 front end to request more children with @code{-var-list-children}, and
32238 then the front end could call @code{-var-set-update-range} with a
32239 different range to ensure that future updates are restricted to just
32242 For each child the following results are returned:
32247 Name of the variable object created for this child.
32250 The expression to be shown to the user by the front end to designate this child.
32251 For example this may be the name of a structure member.
32253 For a dynamic varobj, this value cannot be used to form an
32254 expression. There is no way to do this at all with a dynamic varobj.
32256 For C/C@t{++} structures there are several pseudo children returned to
32257 designate access qualifiers. For these pseudo children @var{exp} is
32258 @samp{public}, @samp{private}, or @samp{protected}. In this case the
32259 type and value are not present.
32261 A dynamic varobj will not report the access qualifying
32262 pseudo-children, regardless of the language. This information is not
32263 available at all with a dynamic varobj.
32266 Number of children this child has. For a dynamic varobj, this will be
32270 The type of the child. If @samp{print object}
32271 (@pxref{Print Settings, set print object}) is set to @code{on}, the
32272 @emph{actual} (derived) type of the object is shown rather than the
32273 @emph{declared} one.
32276 If values were requested, this is the value.
32279 If this variable object is associated with a thread, this is the thread id.
32280 Otherwise this result is not present.
32283 If the variable object is frozen, this variable will be present with a value of 1.
32286 The result may have its own attributes:
32290 A dynamic varobj can supply a display hint to the front end. The
32291 value comes directly from the Python pretty-printer object's
32292 @code{display_hint} method. @xref{Pretty Printing API}.
32295 This is an integer attribute which is nonzero if there are children
32296 remaining after the end of the selected range.
32299 @subsubheading Example
32303 -var-list-children n
32304 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
32305 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
32307 -var-list-children --all-values n
32308 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
32309 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
32313 @subheading The @code{-var-info-type} Command
32314 @findex -var-info-type
32316 @subsubheading Synopsis
32319 -var-info-type @var{name}
32322 Returns the type of the specified variable @var{name}. The type is
32323 returned as a string in the same format as it is output by the
32327 type=@var{typename}
32331 @subheading The @code{-var-info-expression} Command
32332 @findex -var-info-expression
32334 @subsubheading Synopsis
32337 -var-info-expression @var{name}
32340 Returns a string that is suitable for presenting this
32341 variable object in user interface. The string is generally
32342 not valid expression in the current language, and cannot be evaluated.
32344 For example, if @code{a} is an array, and variable object
32345 @code{A} was created for @code{a}, then we'll get this output:
32348 (gdb) -var-info-expression A.1
32349 ^done,lang="C",exp="1"
32353 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
32355 Note that the output of the @code{-var-list-children} command also
32356 includes those expressions, so the @code{-var-info-expression} command
32359 @subheading The @code{-var-info-path-expression} Command
32360 @findex -var-info-path-expression
32362 @subsubheading Synopsis
32365 -var-info-path-expression @var{name}
32368 Returns an expression that can be evaluated in the current
32369 context and will yield the same value that a variable object has.
32370 Compare this with the @code{-var-info-expression} command, which
32371 result can be used only for UI presentation. Typical use of
32372 the @code{-var-info-path-expression} command is creating a
32373 watchpoint from a variable object.
32375 This command is currently not valid for children of a dynamic varobj,
32376 and will give an error when invoked on one.
32378 For example, suppose @code{C} is a C@t{++} class, derived from class
32379 @code{Base}, and that the @code{Base} class has a member called
32380 @code{m_size}. Assume a variable @code{c} is has the type of
32381 @code{C} and a variable object @code{C} was created for variable
32382 @code{c}. Then, we'll get this output:
32384 (gdb) -var-info-path-expression C.Base.public.m_size
32385 ^done,path_expr=((Base)c).m_size)
32388 @subheading The @code{-var-show-attributes} Command
32389 @findex -var-show-attributes
32391 @subsubheading Synopsis
32394 -var-show-attributes @var{name}
32397 List attributes of the specified variable object @var{name}:
32400 status=@var{attr} [ ( ,@var{attr} )* ]
32404 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
32406 @subheading The @code{-var-evaluate-expression} Command
32407 @findex -var-evaluate-expression
32409 @subsubheading Synopsis
32412 -var-evaluate-expression [-f @var{format-spec}] @var{name}
32415 Evaluates the expression that is represented by the specified variable
32416 object and returns its value as a string. The format of the string
32417 can be specified with the @samp{-f} option. The possible values of
32418 this option are the same as for @code{-var-set-format}
32419 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
32420 the current display format will be used. The current display format
32421 can be changed using the @code{-var-set-format} command.
32427 Note that one must invoke @code{-var-list-children} for a variable
32428 before the value of a child variable can be evaluated.
32430 @subheading The @code{-var-assign} Command
32431 @findex -var-assign
32433 @subsubheading Synopsis
32436 -var-assign @var{name} @var{expression}
32439 Assigns the value of @var{expression} to the variable object specified
32440 by @var{name}. The object must be @samp{editable}. If the variable's
32441 value is altered by the assign, the variable will show up in any
32442 subsequent @code{-var-update} list.
32444 @subsubheading Example
32452 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
32456 @subheading The @code{-var-update} Command
32457 @findex -var-update
32459 @subsubheading Synopsis
32462 -var-update [@var{print-values}] @{@var{name} | "*"@}
32465 Reevaluate the expressions corresponding to the variable object
32466 @var{name} and all its direct and indirect children, and return the
32467 list of variable objects whose values have changed; @var{name} must
32468 be a root variable object. Here, ``changed'' means that the result of
32469 @code{-var-evaluate-expression} before and after the
32470 @code{-var-update} is different. If @samp{*} is used as the variable
32471 object names, all existing variable objects are updated, except
32472 for frozen ones (@pxref{-var-set-frozen}). The option
32473 @var{print-values} determines whether both names and values, or just
32474 names are printed. The possible values of this option are the same
32475 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
32476 recommended to use the @samp{--all-values} option, to reduce the
32477 number of MI commands needed on each program stop.
32479 With the @samp{*} parameter, if a variable object is bound to a
32480 currently running thread, it will not be updated, without any
32483 If @code{-var-set-update-range} was previously used on a varobj, then
32484 only the selected range of children will be reported.
32486 @code{-var-update} reports all the changed varobjs in a tuple named
32489 Each item in the change list is itself a tuple holding:
32493 The name of the varobj.
32496 If values were requested for this update, then this field will be
32497 present and will hold the value of the varobj.
32500 @anchor{-var-update}
32501 This field is a string which may take one of three values:
32505 The variable object's current value is valid.
32508 The variable object does not currently hold a valid value but it may
32509 hold one in the future if its associated expression comes back into
32513 The variable object no longer holds a valid value.
32514 This can occur when the executable file being debugged has changed,
32515 either through recompilation or by using the @value{GDBN} @code{file}
32516 command. The front end should normally choose to delete these variable
32520 In the future new values may be added to this list so the front should
32521 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
32524 This is only present if the varobj is still valid. If the type
32525 changed, then this will be the string @samp{true}; otherwise it will
32528 When a varobj's type changes, its children are also likely to have
32529 become incorrect. Therefore, the varobj's children are automatically
32530 deleted when this attribute is @samp{true}. Also, the varobj's update
32531 range, when set using the @code{-var-set-update-range} command, is
32535 If the varobj's type changed, then this field will be present and will
32538 @item new_num_children
32539 For a dynamic varobj, if the number of children changed, or if the
32540 type changed, this will be the new number of children.
32542 The @samp{numchild} field in other varobj responses is generally not
32543 valid for a dynamic varobj -- it will show the number of children that
32544 @value{GDBN} knows about, but because dynamic varobjs lazily
32545 instantiate their children, this will not reflect the number of
32546 children which may be available.
32548 The @samp{new_num_children} attribute only reports changes to the
32549 number of children known by @value{GDBN}. This is the only way to
32550 detect whether an update has removed children (which necessarily can
32551 only happen at the end of the update range).
32554 The display hint, if any.
32557 This is an integer value, which will be 1 if there are more children
32558 available outside the varobj's update range.
32561 This attribute will be present and have the value @samp{1} if the
32562 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32563 then this attribute will not be present.
32566 If new children were added to a dynamic varobj within the selected
32567 update range (as set by @code{-var-set-update-range}), then they will
32568 be listed in this attribute.
32571 @subsubheading Example
32578 -var-update --all-values var1
32579 ^done,changelist=[@{name="var1",value="3",in_scope="true",
32580 type_changed="false"@}]
32584 @subheading The @code{-var-set-frozen} Command
32585 @findex -var-set-frozen
32586 @anchor{-var-set-frozen}
32588 @subsubheading Synopsis
32591 -var-set-frozen @var{name} @var{flag}
32594 Set the frozenness flag on the variable object @var{name}. The
32595 @var{flag} parameter should be either @samp{1} to make the variable
32596 frozen or @samp{0} to make it unfrozen. If a variable object is
32597 frozen, then neither itself, nor any of its children, are
32598 implicitly updated by @code{-var-update} of
32599 a parent variable or by @code{-var-update *}. Only
32600 @code{-var-update} of the variable itself will update its value and
32601 values of its children. After a variable object is unfrozen, it is
32602 implicitly updated by all subsequent @code{-var-update} operations.
32603 Unfreezing a variable does not update it, only subsequent
32604 @code{-var-update} does.
32606 @subsubheading Example
32610 -var-set-frozen V 1
32615 @subheading The @code{-var-set-update-range} command
32616 @findex -var-set-update-range
32617 @anchor{-var-set-update-range}
32619 @subsubheading Synopsis
32622 -var-set-update-range @var{name} @var{from} @var{to}
32625 Set the range of children to be returned by future invocations of
32626 @code{-var-update}.
32628 @var{from} and @var{to} indicate the range of children to report. If
32629 @var{from} or @var{to} is less than zero, the range is reset and all
32630 children will be reported. Otherwise, children starting at @var{from}
32631 (zero-based) and up to and excluding @var{to} will be reported.
32633 @subsubheading Example
32637 -var-set-update-range V 1 2
32641 @subheading The @code{-var-set-visualizer} command
32642 @findex -var-set-visualizer
32643 @anchor{-var-set-visualizer}
32645 @subsubheading Synopsis
32648 -var-set-visualizer @var{name} @var{visualizer}
32651 Set a visualizer for the variable object @var{name}.
32653 @var{visualizer} is the visualizer to use. The special value
32654 @samp{None} means to disable any visualizer in use.
32656 If not @samp{None}, @var{visualizer} must be a Python expression.
32657 This expression must evaluate to a callable object which accepts a
32658 single argument. @value{GDBN} will call this object with the value of
32659 the varobj @var{name} as an argument (this is done so that the same
32660 Python pretty-printing code can be used for both the CLI and MI).
32661 When called, this object must return an object which conforms to the
32662 pretty-printing interface (@pxref{Pretty Printing API}).
32664 The pre-defined function @code{gdb.default_visualizer} may be used to
32665 select a visualizer by following the built-in process
32666 (@pxref{Selecting Pretty-Printers}). This is done automatically when
32667 a varobj is created, and so ordinarily is not needed.
32669 This feature is only available if Python support is enabled. The MI
32670 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
32671 can be used to check this.
32673 @subsubheading Example
32675 Resetting the visualizer:
32679 -var-set-visualizer V None
32683 Reselecting the default (type-based) visualizer:
32687 -var-set-visualizer V gdb.default_visualizer
32691 Suppose @code{SomeClass} is a visualizer class. A lambda expression
32692 can be used to instantiate this class for a varobj:
32696 -var-set-visualizer V "lambda val: SomeClass()"
32700 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32701 @node GDB/MI Data Manipulation
32702 @section @sc{gdb/mi} Data Manipulation
32704 @cindex data manipulation, in @sc{gdb/mi}
32705 @cindex @sc{gdb/mi}, data manipulation
32706 This section describes the @sc{gdb/mi} commands that manipulate data:
32707 examine memory and registers, evaluate expressions, etc.
32709 @c REMOVED FROM THE INTERFACE.
32710 @c @subheading -data-assign
32711 @c Change the value of a program variable. Plenty of side effects.
32712 @c @subsubheading GDB Command
32714 @c @subsubheading Example
32717 @subheading The @code{-data-disassemble} Command
32718 @findex -data-disassemble
32720 @subsubheading Synopsis
32724 [ -s @var{start-addr} -e @var{end-addr} ]
32725 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
32733 @item @var{start-addr}
32734 is the beginning address (or @code{$pc})
32735 @item @var{end-addr}
32737 @item @var{filename}
32738 is the name of the file to disassemble
32739 @item @var{linenum}
32740 is the line number to disassemble around
32742 is the number of disassembly lines to be produced. If it is -1,
32743 the whole function will be disassembled, in case no @var{end-addr} is
32744 specified. If @var{end-addr} is specified as a non-zero value, and
32745 @var{lines} is lower than the number of disassembly lines between
32746 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
32747 displayed; if @var{lines} is higher than the number of lines between
32748 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
32751 is either 0 (meaning only disassembly), 1 (meaning mixed source and
32752 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
32753 mixed source and disassembly with raw opcodes).
32756 @subsubheading Result
32758 The result of the @code{-data-disassemble} command will be a list named
32759 @samp{asm_insns}, the contents of this list depend on the @var{mode}
32760 used with the @code{-data-disassemble} command.
32762 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
32767 The address at which this instruction was disassembled.
32770 The name of the function this instruction is within.
32773 The decimal offset in bytes from the start of @samp{func-name}.
32776 The text disassembly for this @samp{address}.
32779 This field is only present for mode 2. This contains the raw opcode
32780 bytes for the @samp{inst} field.
32784 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
32785 @samp{src_and_asm_line}, each of which has the following fields:
32789 The line number within @samp{file}.
32792 The file name from the compilation unit. This might be an absolute
32793 file name or a relative file name depending on the compile command
32797 Absolute file name of @samp{file}. It is converted to a canonical form
32798 using the source file search path
32799 (@pxref{Source Path, ,Specifying Source Directories})
32800 and after resolving all the symbolic links.
32802 If the source file is not found this field will contain the path as
32803 present in the debug information.
32805 @item line_asm_insn
32806 This is a list of tuples containing the disassembly for @samp{line} in
32807 @samp{file}. The fields of each tuple are the same as for
32808 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
32809 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
32814 Note that whatever included in the @samp{inst} field, is not
32815 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
32818 @subsubheading @value{GDBN} Command
32820 The corresponding @value{GDBN} command is @samp{disassemble}.
32822 @subsubheading Example
32824 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
32828 -data-disassemble -s $pc -e "$pc + 20" -- 0
32831 @{address="0x000107c0",func-name="main",offset="4",
32832 inst="mov 2, %o0"@},
32833 @{address="0x000107c4",func-name="main",offset="8",
32834 inst="sethi %hi(0x11800), %o2"@},
32835 @{address="0x000107c8",func-name="main",offset="12",
32836 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
32837 @{address="0x000107cc",func-name="main",offset="16",
32838 inst="sethi %hi(0x11800), %o2"@},
32839 @{address="0x000107d0",func-name="main",offset="20",
32840 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
32844 Disassemble the whole @code{main} function. Line 32 is part of
32848 -data-disassemble -f basics.c -l 32 -- 0
32850 @{address="0x000107bc",func-name="main",offset="0",
32851 inst="save %sp, -112, %sp"@},
32852 @{address="0x000107c0",func-name="main",offset="4",
32853 inst="mov 2, %o0"@},
32854 @{address="0x000107c4",func-name="main",offset="8",
32855 inst="sethi %hi(0x11800), %o2"@},
32857 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
32858 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
32862 Disassemble 3 instructions from the start of @code{main}:
32866 -data-disassemble -f basics.c -l 32 -n 3 -- 0
32868 @{address="0x000107bc",func-name="main",offset="0",
32869 inst="save %sp, -112, %sp"@},
32870 @{address="0x000107c0",func-name="main",offset="4",
32871 inst="mov 2, %o0"@},
32872 @{address="0x000107c4",func-name="main",offset="8",
32873 inst="sethi %hi(0x11800), %o2"@}]
32877 Disassemble 3 instructions from the start of @code{main} in mixed mode:
32881 -data-disassemble -f basics.c -l 32 -n 3 -- 1
32883 src_and_asm_line=@{line="31",
32884 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
32885 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
32886 line_asm_insn=[@{address="0x000107bc",
32887 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
32888 src_and_asm_line=@{line="32",
32889 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
32890 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
32891 line_asm_insn=[@{address="0x000107c0",
32892 func-name="main",offset="4",inst="mov 2, %o0"@},
32893 @{address="0x000107c4",func-name="main",offset="8",
32894 inst="sethi %hi(0x11800), %o2"@}]@}]
32899 @subheading The @code{-data-evaluate-expression} Command
32900 @findex -data-evaluate-expression
32902 @subsubheading Synopsis
32905 -data-evaluate-expression @var{expr}
32908 Evaluate @var{expr} as an expression. The expression could contain an
32909 inferior function call. The function call will execute synchronously.
32910 If the expression contains spaces, it must be enclosed in double quotes.
32912 @subsubheading @value{GDBN} Command
32914 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
32915 @samp{call}. In @code{gdbtk} only, there's a corresponding
32916 @samp{gdb_eval} command.
32918 @subsubheading Example
32920 In the following example, the numbers that precede the commands are the
32921 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
32922 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
32926 211-data-evaluate-expression A
32929 311-data-evaluate-expression &A
32930 311^done,value="0xefffeb7c"
32932 411-data-evaluate-expression A+3
32935 511-data-evaluate-expression "A + 3"
32941 @subheading The @code{-data-list-changed-registers} Command
32942 @findex -data-list-changed-registers
32944 @subsubheading Synopsis
32947 -data-list-changed-registers
32950 Display a list of the registers that have changed.
32952 @subsubheading @value{GDBN} Command
32954 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
32955 has the corresponding command @samp{gdb_changed_register_list}.
32957 @subsubheading Example
32959 On a PPC MBX board:
32967 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
32968 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
32971 -data-list-changed-registers
32972 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
32973 "10","11","13","14","15","16","17","18","19","20","21","22","23",
32974 "24","25","26","27","28","30","31","64","65","66","67","69"]
32979 @subheading The @code{-data-list-register-names} Command
32980 @findex -data-list-register-names
32982 @subsubheading Synopsis
32985 -data-list-register-names [ ( @var{regno} )+ ]
32988 Show a list of register names for the current target. If no arguments
32989 are given, it shows a list of the names of all the registers. If
32990 integer numbers are given as arguments, it will print a list of the
32991 names of the registers corresponding to the arguments. To ensure
32992 consistency between a register name and its number, the output list may
32993 include empty register names.
32995 @subsubheading @value{GDBN} Command
32997 @value{GDBN} does not have a command which corresponds to
32998 @samp{-data-list-register-names}. In @code{gdbtk} there is a
32999 corresponding command @samp{gdb_regnames}.
33001 @subsubheading Example
33003 For the PPC MBX board:
33006 -data-list-register-names
33007 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
33008 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
33009 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
33010 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
33011 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
33012 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
33013 "", "pc","ps","cr","lr","ctr","xer"]
33015 -data-list-register-names 1 2 3
33016 ^done,register-names=["r1","r2","r3"]
33020 @subheading The @code{-data-list-register-values} Command
33021 @findex -data-list-register-values
33023 @subsubheading Synopsis
33026 -data-list-register-values
33027 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
33030 Display the registers' contents. @var{fmt} is the format according to
33031 which the registers' contents are to be returned, followed by an optional
33032 list of numbers specifying the registers to display. A missing list of
33033 numbers indicates that the contents of all the registers must be
33034 returned. The @code{--skip-unavailable} option indicates that only
33035 the available registers are to be returned.
33037 Allowed formats for @var{fmt} are:
33054 @subsubheading @value{GDBN} Command
33056 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
33057 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
33059 @subsubheading Example
33061 For a PPC MBX board (note: line breaks are for readability only, they
33062 don't appear in the actual output):
33066 -data-list-register-values r 64 65
33067 ^done,register-values=[@{number="64",value="0xfe00a300"@},
33068 @{number="65",value="0x00029002"@}]
33070 -data-list-register-values x
33071 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
33072 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
33073 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
33074 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
33075 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
33076 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
33077 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
33078 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
33079 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
33080 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
33081 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
33082 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
33083 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
33084 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
33085 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
33086 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
33087 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
33088 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
33089 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
33090 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
33091 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
33092 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
33093 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
33094 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
33095 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
33096 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
33097 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
33098 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
33099 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
33100 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
33101 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
33102 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
33103 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
33104 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
33105 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
33106 @{number="69",value="0x20002b03"@}]
33111 @subheading The @code{-data-read-memory} Command
33112 @findex -data-read-memory
33114 This command is deprecated, use @code{-data-read-memory-bytes} instead.
33116 @subsubheading Synopsis
33119 -data-read-memory [ -o @var{byte-offset} ]
33120 @var{address} @var{word-format} @var{word-size}
33121 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
33128 @item @var{address}
33129 An expression specifying the address of the first memory word to be
33130 read. Complex expressions containing embedded white space should be
33131 quoted using the C convention.
33133 @item @var{word-format}
33134 The format to be used to print the memory words. The notation is the
33135 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
33138 @item @var{word-size}
33139 The size of each memory word in bytes.
33141 @item @var{nr-rows}
33142 The number of rows in the output table.
33144 @item @var{nr-cols}
33145 The number of columns in the output table.
33148 If present, indicates that each row should include an @sc{ascii} dump. The
33149 value of @var{aschar} is used as a padding character when a byte is not a
33150 member of the printable @sc{ascii} character set (printable @sc{ascii}
33151 characters are those whose code is between 32 and 126, inclusively).
33153 @item @var{byte-offset}
33154 An offset to add to the @var{address} before fetching memory.
33157 This command displays memory contents as a table of @var{nr-rows} by
33158 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
33159 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
33160 (returned as @samp{total-bytes}). Should less than the requested number
33161 of bytes be returned by the target, the missing words are identified
33162 using @samp{N/A}. The number of bytes read from the target is returned
33163 in @samp{nr-bytes} and the starting address used to read memory in
33166 The address of the next/previous row or page is available in
33167 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
33170 @subsubheading @value{GDBN} Command
33172 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
33173 @samp{gdb_get_mem} memory read command.
33175 @subsubheading Example
33177 Read six bytes of memory starting at @code{bytes+6} but then offset by
33178 @code{-6} bytes. Format as three rows of two columns. One byte per
33179 word. Display each word in hex.
33183 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
33184 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
33185 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
33186 prev-page="0x0000138a",memory=[
33187 @{addr="0x00001390",data=["0x00","0x01"]@},
33188 @{addr="0x00001392",data=["0x02","0x03"]@},
33189 @{addr="0x00001394",data=["0x04","0x05"]@}]
33193 Read two bytes of memory starting at address @code{shorts + 64} and
33194 display as a single word formatted in decimal.
33198 5-data-read-memory shorts+64 d 2 1 1
33199 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
33200 next-row="0x00001512",prev-row="0x0000150e",
33201 next-page="0x00001512",prev-page="0x0000150e",memory=[
33202 @{addr="0x00001510",data=["128"]@}]
33206 Read thirty two bytes of memory starting at @code{bytes+16} and format
33207 as eight rows of four columns. Include a string encoding with @samp{x}
33208 used as the non-printable character.
33212 4-data-read-memory bytes+16 x 1 8 4 x
33213 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
33214 next-row="0x000013c0",prev-row="0x0000139c",
33215 next-page="0x000013c0",prev-page="0x00001380",memory=[
33216 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
33217 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
33218 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
33219 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
33220 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
33221 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
33222 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
33223 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
33227 @subheading The @code{-data-read-memory-bytes} Command
33228 @findex -data-read-memory-bytes
33230 @subsubheading Synopsis
33233 -data-read-memory-bytes [ -o @var{byte-offset} ]
33234 @var{address} @var{count}
33241 @item @var{address}
33242 An expression specifying the address of the first memory word to be
33243 read. Complex expressions containing embedded white space should be
33244 quoted using the C convention.
33247 The number of bytes to read. This should be an integer literal.
33249 @item @var{byte-offset}
33250 The offsets in bytes relative to @var{address} at which to start
33251 reading. This should be an integer literal. This option is provided
33252 so that a frontend is not required to first evaluate address and then
33253 perform address arithmetics itself.
33257 This command attempts to read all accessible memory regions in the
33258 specified range. First, all regions marked as unreadable in the memory
33259 map (if one is defined) will be skipped. @xref{Memory Region
33260 Attributes}. Second, @value{GDBN} will attempt to read the remaining
33261 regions. For each one, if reading full region results in an errors,
33262 @value{GDBN} will try to read a subset of the region.
33264 In general, every single byte in the region may be readable or not,
33265 and the only way to read every readable byte is to try a read at
33266 every address, which is not practical. Therefore, @value{GDBN} will
33267 attempt to read all accessible bytes at either beginning or the end
33268 of the region, using a binary division scheme. This heuristic works
33269 well for reading accross a memory map boundary. Note that if a region
33270 has a readable range that is neither at the beginning or the end,
33271 @value{GDBN} will not read it.
33273 The result record (@pxref{GDB/MI Result Records}) that is output of
33274 the command includes a field named @samp{memory} whose content is a
33275 list of tuples. Each tuple represent a successfully read memory block
33276 and has the following fields:
33280 The start address of the memory block, as hexadecimal literal.
33283 The end address of the memory block, as hexadecimal literal.
33286 The offset of the memory block, as hexadecimal literal, relative to
33287 the start address passed to @code{-data-read-memory-bytes}.
33290 The contents of the memory block, in hex.
33296 @subsubheading @value{GDBN} Command
33298 The corresponding @value{GDBN} command is @samp{x}.
33300 @subsubheading Example
33304 -data-read-memory-bytes &a 10
33305 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
33307 contents="01000000020000000300"@}]
33312 @subheading The @code{-data-write-memory-bytes} Command
33313 @findex -data-write-memory-bytes
33315 @subsubheading Synopsis
33318 -data-write-memory-bytes @var{address} @var{contents}
33319 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
33326 @item @var{address}
33327 An expression specifying the address of the first memory word to be
33328 read. Complex expressions containing embedded white space should be
33329 quoted using the C convention.
33331 @item @var{contents}
33332 The hex-encoded bytes to write.
33335 Optional argument indicating the number of bytes to be written. If @var{count}
33336 is greater than @var{contents}' length, @value{GDBN} will repeatedly
33337 write @var{contents} until it fills @var{count} bytes.
33341 @subsubheading @value{GDBN} Command
33343 There's no corresponding @value{GDBN} command.
33345 @subsubheading Example
33349 -data-write-memory-bytes &a "aabbccdd"
33356 -data-write-memory-bytes &a "aabbccdd" 16e
33361 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33362 @node GDB/MI Tracepoint Commands
33363 @section @sc{gdb/mi} Tracepoint Commands
33365 The commands defined in this section implement MI support for
33366 tracepoints. For detailed introduction, see @ref{Tracepoints}.
33368 @subheading The @code{-trace-find} Command
33369 @findex -trace-find
33371 @subsubheading Synopsis
33374 -trace-find @var{mode} [@var{parameters}@dots{}]
33377 Find a trace frame using criteria defined by @var{mode} and
33378 @var{parameters}. The following table lists permissible
33379 modes and their parameters. For details of operation, see @ref{tfind}.
33384 No parameters are required. Stops examining trace frames.
33387 An integer is required as parameter. Selects tracepoint frame with
33390 @item tracepoint-number
33391 An integer is required as parameter. Finds next
33392 trace frame that corresponds to tracepoint with the specified number.
33395 An address is required as parameter. Finds
33396 next trace frame that corresponds to any tracepoint at the specified
33399 @item pc-inside-range
33400 Two addresses are required as parameters. Finds next trace
33401 frame that corresponds to a tracepoint at an address inside the
33402 specified range. Both bounds are considered to be inside the range.
33404 @item pc-outside-range
33405 Two addresses are required as parameters. Finds
33406 next trace frame that corresponds to a tracepoint at an address outside
33407 the specified range. Both bounds are considered to be inside the range.
33410 Line specification is required as parameter. @xref{Specify Location}.
33411 Finds next trace frame that corresponds to a tracepoint at
33412 the specified location.
33416 If @samp{none} was passed as @var{mode}, the response does not
33417 have fields. Otherwise, the response may have the following fields:
33421 This field has either @samp{0} or @samp{1} as the value, depending
33422 on whether a matching tracepoint was found.
33425 The index of the found traceframe. This field is present iff
33426 the @samp{found} field has value of @samp{1}.
33429 The index of the found tracepoint. This field is present iff
33430 the @samp{found} field has value of @samp{1}.
33433 The information about the frame corresponding to the found trace
33434 frame. This field is present only if a trace frame was found.
33435 @xref{GDB/MI Frame Information}, for description of this field.
33439 @subsubheading @value{GDBN} Command
33441 The corresponding @value{GDBN} command is @samp{tfind}.
33443 @subheading -trace-define-variable
33444 @findex -trace-define-variable
33446 @subsubheading Synopsis
33449 -trace-define-variable @var{name} [ @var{value} ]
33452 Create trace variable @var{name} if it does not exist. If
33453 @var{value} is specified, sets the initial value of the specified
33454 trace variable to that value. Note that the @var{name} should start
33455 with the @samp{$} character.
33457 @subsubheading @value{GDBN} Command
33459 The corresponding @value{GDBN} command is @samp{tvariable}.
33461 @subheading The @code{-trace-frame-collected} Command
33462 @findex -trace-frame-collected
33464 @subsubheading Synopsis
33467 -trace-frame-collected
33468 [--var-print-values @var{var_pval}]
33469 [--comp-print-values @var{comp_pval}]
33470 [--registers-format @var{regformat}]
33471 [--memory-contents]
33474 This command returns the set of collected objects, register names,
33475 trace state variable names, memory ranges and computed expressions
33476 that have been collected at a particular trace frame. The optional
33477 parameters to the command affect the output format in different ways.
33478 See the output description table below for more details.
33480 The reported names can be used in the normal manner to create
33481 varobjs and inspect the objects themselves. The items returned by
33482 this command are categorized so that it is clear which is a variable,
33483 which is a register, which is a trace state variable, which is a
33484 memory range and which is a computed expression.
33486 For instance, if the actions were
33488 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
33489 collect *(int*)0xaf02bef0@@40
33493 the object collected in its entirety would be @code{myVar}. The
33494 object @code{myArray} would be partially collected, because only the
33495 element at index @code{myIndex} would be collected. The remaining
33496 objects would be computed expressions.
33498 An example output would be:
33502 -trace-frame-collected
33504 explicit-variables=[@{name="myVar",value="1"@}],
33505 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
33506 @{name="myObj.field",value="0"@},
33507 @{name="myPtr->field",value="1"@},
33508 @{name="myCount + 2",value="3"@},
33509 @{name="$tvar1 + 1",value="43970027"@}],
33510 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
33511 @{number="1",value="0x0"@},
33512 @{number="2",value="0x4"@},
33514 @{number="125",value="0x0"@}],
33515 tvars=[@{name="$tvar1",current="43970026"@}],
33516 memory=[@{address="0x0000000000602264",length="4"@},
33517 @{address="0x0000000000615bc0",length="4"@}]
33524 @item explicit-variables
33525 The set of objects that have been collected in their entirety (as
33526 opposed to collecting just a few elements of an array or a few struct
33527 members). For each object, its name and value are printed.
33528 The @code{--var-print-values} option affects how or whether the value
33529 field is output. If @var{var_pval} is 0, then print only the names;
33530 if it is 1, print also their values; and if it is 2, print the name,
33531 type and value for simple data types, and the name and type for
33532 arrays, structures and unions.
33534 @item computed-expressions
33535 The set of computed expressions that have been collected at the
33536 current trace frame. The @code{--comp-print-values} option affects
33537 this set like the @code{--var-print-values} option affects the
33538 @code{explicit-variables} set. See above.
33541 The registers that have been collected at the current trace frame.
33542 For each register collected, the name and current value are returned.
33543 The value is formatted according to the @code{--registers-format}
33544 option. See the @command{-data-list-register-values} command for a
33545 list of the allowed formats. The default is @samp{x}.
33548 The trace state variables that have been collected at the current
33549 trace frame. For each trace state variable collected, the name and
33550 current value are returned.
33553 The set of memory ranges that have been collected at the current trace
33554 frame. Its content is a list of tuples. Each tuple represents a
33555 collected memory range and has the following fields:
33559 The start address of the memory range, as hexadecimal literal.
33562 The length of the memory range, as decimal literal.
33565 The contents of the memory block, in hex. This field is only present
33566 if the @code{--memory-contents} option is specified.
33572 @subsubheading @value{GDBN} Command
33574 There is no corresponding @value{GDBN} command.
33576 @subsubheading Example
33578 @subheading -trace-list-variables
33579 @findex -trace-list-variables
33581 @subsubheading Synopsis
33584 -trace-list-variables
33587 Return a table of all defined trace variables. Each element of the
33588 table has the following fields:
33592 The name of the trace variable. This field is always present.
33595 The initial value. This is a 64-bit signed integer. This
33596 field is always present.
33599 The value the trace variable has at the moment. This is a 64-bit
33600 signed integer. This field is absent iff current value is
33601 not defined, for example if the trace was never run, or is
33606 @subsubheading @value{GDBN} Command
33608 The corresponding @value{GDBN} command is @samp{tvariables}.
33610 @subsubheading Example
33614 -trace-list-variables
33615 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
33616 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
33617 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
33618 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
33619 body=[variable=@{name="$trace_timestamp",initial="0"@}
33620 variable=@{name="$foo",initial="10",current="15"@}]@}
33624 @subheading -trace-save
33625 @findex -trace-save
33627 @subsubheading Synopsis
33630 -trace-save [-r ] @var{filename}
33633 Saves the collected trace data to @var{filename}. Without the
33634 @samp{-r} option, the data is downloaded from the target and saved
33635 in a local file. With the @samp{-r} option the target is asked
33636 to perform the save.
33638 @subsubheading @value{GDBN} Command
33640 The corresponding @value{GDBN} command is @samp{tsave}.
33643 @subheading -trace-start
33644 @findex -trace-start
33646 @subsubheading Synopsis
33652 Starts a tracing experiments. The result of this command does not
33655 @subsubheading @value{GDBN} Command
33657 The corresponding @value{GDBN} command is @samp{tstart}.
33659 @subheading -trace-status
33660 @findex -trace-status
33662 @subsubheading Synopsis
33668 Obtains the status of a tracing experiment. The result may include
33669 the following fields:
33674 May have a value of either @samp{0}, when no tracing operations are
33675 supported, @samp{1}, when all tracing operations are supported, or
33676 @samp{file} when examining trace file. In the latter case, examining
33677 of trace frame is possible but new tracing experiement cannot be
33678 started. This field is always present.
33681 May have a value of either @samp{0} or @samp{1} depending on whether
33682 tracing experiement is in progress on target. This field is present
33683 if @samp{supported} field is not @samp{0}.
33686 Report the reason why the tracing was stopped last time. This field
33687 may be absent iff tracing was never stopped on target yet. The
33688 value of @samp{request} means the tracing was stopped as result of
33689 the @code{-trace-stop} command. The value of @samp{overflow} means
33690 the tracing buffer is full. The value of @samp{disconnection} means
33691 tracing was automatically stopped when @value{GDBN} has disconnected.
33692 The value of @samp{passcount} means tracing was stopped when a
33693 tracepoint was passed a maximal number of times for that tracepoint.
33694 This field is present if @samp{supported} field is not @samp{0}.
33696 @item stopping-tracepoint
33697 The number of tracepoint whose passcount as exceeded. This field is
33698 present iff the @samp{stop-reason} field has the value of
33702 @itemx frames-created
33703 The @samp{frames} field is a count of the total number of trace frames
33704 in the trace buffer, while @samp{frames-created} is the total created
33705 during the run, including ones that were discarded, such as when a
33706 circular trace buffer filled up. Both fields are optional.
33710 These fields tell the current size of the tracing buffer and the
33711 remaining space. These fields are optional.
33714 The value of the circular trace buffer flag. @code{1} means that the
33715 trace buffer is circular and old trace frames will be discarded if
33716 necessary to make room, @code{0} means that the trace buffer is linear
33720 The value of the disconnected tracing flag. @code{1} means that
33721 tracing will continue after @value{GDBN} disconnects, @code{0} means
33722 that the trace run will stop.
33725 The filename of the trace file being examined. This field is
33726 optional, and only present when examining a trace file.
33730 @subsubheading @value{GDBN} Command
33732 The corresponding @value{GDBN} command is @samp{tstatus}.
33734 @subheading -trace-stop
33735 @findex -trace-stop
33737 @subsubheading Synopsis
33743 Stops a tracing experiment. The result of this command has the same
33744 fields as @code{-trace-status}, except that the @samp{supported} and
33745 @samp{running} fields are not output.
33747 @subsubheading @value{GDBN} Command
33749 The corresponding @value{GDBN} command is @samp{tstop}.
33752 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33753 @node GDB/MI Symbol Query
33754 @section @sc{gdb/mi} Symbol Query Commands
33758 @subheading The @code{-symbol-info-address} Command
33759 @findex -symbol-info-address
33761 @subsubheading Synopsis
33764 -symbol-info-address @var{symbol}
33767 Describe where @var{symbol} is stored.
33769 @subsubheading @value{GDBN} Command
33771 The corresponding @value{GDBN} command is @samp{info address}.
33773 @subsubheading Example
33777 @subheading The @code{-symbol-info-file} Command
33778 @findex -symbol-info-file
33780 @subsubheading Synopsis
33786 Show the file for the symbol.
33788 @subsubheading @value{GDBN} Command
33790 There's no equivalent @value{GDBN} command. @code{gdbtk} has
33791 @samp{gdb_find_file}.
33793 @subsubheading Example
33797 @subheading The @code{-symbol-info-function} Command
33798 @findex -symbol-info-function
33800 @subsubheading Synopsis
33803 -symbol-info-function
33806 Show which function the symbol lives in.
33808 @subsubheading @value{GDBN} Command
33810 @samp{gdb_get_function} in @code{gdbtk}.
33812 @subsubheading Example
33816 @subheading The @code{-symbol-info-line} Command
33817 @findex -symbol-info-line
33819 @subsubheading Synopsis
33825 Show the core addresses of the code for a source line.
33827 @subsubheading @value{GDBN} Command
33829 The corresponding @value{GDBN} command is @samp{info line}.
33830 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
33832 @subsubheading Example
33836 @subheading The @code{-symbol-info-symbol} Command
33837 @findex -symbol-info-symbol
33839 @subsubheading Synopsis
33842 -symbol-info-symbol @var{addr}
33845 Describe what symbol is at location @var{addr}.
33847 @subsubheading @value{GDBN} Command
33849 The corresponding @value{GDBN} command is @samp{info symbol}.
33851 @subsubheading Example
33855 @subheading The @code{-symbol-list-functions} Command
33856 @findex -symbol-list-functions
33858 @subsubheading Synopsis
33861 -symbol-list-functions
33864 List the functions in the executable.
33866 @subsubheading @value{GDBN} Command
33868 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
33869 @samp{gdb_search} in @code{gdbtk}.
33871 @subsubheading Example
33876 @subheading The @code{-symbol-list-lines} Command
33877 @findex -symbol-list-lines
33879 @subsubheading Synopsis
33882 -symbol-list-lines @var{filename}
33885 Print the list of lines that contain code and their associated program
33886 addresses for the given source filename. The entries are sorted in
33887 ascending PC order.
33889 @subsubheading @value{GDBN} Command
33891 There is no corresponding @value{GDBN} command.
33893 @subsubheading Example
33896 -symbol-list-lines basics.c
33897 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
33903 @subheading The @code{-symbol-list-types} Command
33904 @findex -symbol-list-types
33906 @subsubheading Synopsis
33912 List all the type names.
33914 @subsubheading @value{GDBN} Command
33916 The corresponding commands are @samp{info types} in @value{GDBN},
33917 @samp{gdb_search} in @code{gdbtk}.
33919 @subsubheading Example
33923 @subheading The @code{-symbol-list-variables} Command
33924 @findex -symbol-list-variables
33926 @subsubheading Synopsis
33929 -symbol-list-variables
33932 List all the global and static variable names.
33934 @subsubheading @value{GDBN} Command
33936 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
33938 @subsubheading Example
33942 @subheading The @code{-symbol-locate} Command
33943 @findex -symbol-locate
33945 @subsubheading Synopsis
33951 @subsubheading @value{GDBN} Command
33953 @samp{gdb_loc} in @code{gdbtk}.
33955 @subsubheading Example
33959 @subheading The @code{-symbol-type} Command
33960 @findex -symbol-type
33962 @subsubheading Synopsis
33965 -symbol-type @var{variable}
33968 Show type of @var{variable}.
33970 @subsubheading @value{GDBN} Command
33972 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
33973 @samp{gdb_obj_variable}.
33975 @subsubheading Example
33980 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33981 @node GDB/MI File Commands
33982 @section @sc{gdb/mi} File Commands
33984 This section describes the GDB/MI commands to specify executable file names
33985 and to read in and obtain symbol table information.
33987 @subheading The @code{-file-exec-and-symbols} Command
33988 @findex -file-exec-and-symbols
33990 @subsubheading Synopsis
33993 -file-exec-and-symbols @var{file}
33996 Specify the executable file to be debugged. This file is the one from
33997 which the symbol table is also read. If no file is specified, the
33998 command clears the executable and symbol information. If breakpoints
33999 are set when using this command with no arguments, @value{GDBN} will produce
34000 error messages. Otherwise, no output is produced, except a completion
34003 @subsubheading @value{GDBN} Command
34005 The corresponding @value{GDBN} command is @samp{file}.
34007 @subsubheading Example
34011 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
34017 @subheading The @code{-file-exec-file} Command
34018 @findex -file-exec-file
34020 @subsubheading Synopsis
34023 -file-exec-file @var{file}
34026 Specify the executable file to be debugged. Unlike
34027 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
34028 from this file. If used without argument, @value{GDBN} clears the information
34029 about the executable file. No output is produced, except a completion
34032 @subsubheading @value{GDBN} Command
34034 The corresponding @value{GDBN} command is @samp{exec-file}.
34036 @subsubheading Example
34040 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
34047 @subheading The @code{-file-list-exec-sections} Command
34048 @findex -file-list-exec-sections
34050 @subsubheading Synopsis
34053 -file-list-exec-sections
34056 List the sections of the current executable file.
34058 @subsubheading @value{GDBN} Command
34060 The @value{GDBN} command @samp{info file} shows, among the rest, the same
34061 information as this command. @code{gdbtk} has a corresponding command
34062 @samp{gdb_load_info}.
34064 @subsubheading Example
34069 @subheading The @code{-file-list-exec-source-file} Command
34070 @findex -file-list-exec-source-file
34072 @subsubheading Synopsis
34075 -file-list-exec-source-file
34078 List the line number, the current source file, and the absolute path
34079 to the current source file for the current executable. The macro
34080 information field has a value of @samp{1} or @samp{0} depending on
34081 whether or not the file includes preprocessor macro information.
34083 @subsubheading @value{GDBN} Command
34085 The @value{GDBN} equivalent is @samp{info source}
34087 @subsubheading Example
34091 123-file-list-exec-source-file
34092 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
34097 @subheading The @code{-file-list-exec-source-files} Command
34098 @findex -file-list-exec-source-files
34100 @subsubheading Synopsis
34103 -file-list-exec-source-files
34106 List the source files for the current executable.
34108 It will always output both the filename and fullname (absolute file
34109 name) of a source file.
34111 @subsubheading @value{GDBN} Command
34113 The @value{GDBN} equivalent is @samp{info sources}.
34114 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
34116 @subsubheading Example
34119 -file-list-exec-source-files
34121 @{file=foo.c,fullname=/home/foo.c@},
34122 @{file=/home/bar.c,fullname=/home/bar.c@},
34123 @{file=gdb_could_not_find_fullpath.c@}]
34128 @subheading The @code{-file-list-shared-libraries} Command
34129 @findex -file-list-shared-libraries
34131 @subsubheading Synopsis
34134 -file-list-shared-libraries
34137 List the shared libraries in the program.
34139 @subsubheading @value{GDBN} Command
34141 The corresponding @value{GDBN} command is @samp{info shared}.
34143 @subsubheading Example
34147 @subheading The @code{-file-list-symbol-files} Command
34148 @findex -file-list-symbol-files
34150 @subsubheading Synopsis
34153 -file-list-symbol-files
34158 @subsubheading @value{GDBN} Command
34160 The corresponding @value{GDBN} command is @samp{info file} (part of it).
34162 @subsubheading Example
34167 @subheading The @code{-file-symbol-file} Command
34168 @findex -file-symbol-file
34170 @subsubheading Synopsis
34173 -file-symbol-file @var{file}
34176 Read symbol table info from the specified @var{file} argument. When
34177 used without arguments, clears @value{GDBN}'s symbol table info. No output is
34178 produced, except for a completion notification.
34180 @subsubheading @value{GDBN} Command
34182 The corresponding @value{GDBN} command is @samp{symbol-file}.
34184 @subsubheading Example
34188 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
34194 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34195 @node GDB/MI Memory Overlay Commands
34196 @section @sc{gdb/mi} Memory Overlay Commands
34198 The memory overlay commands are not implemented.
34200 @c @subheading -overlay-auto
34202 @c @subheading -overlay-list-mapping-state
34204 @c @subheading -overlay-list-overlays
34206 @c @subheading -overlay-map
34208 @c @subheading -overlay-off
34210 @c @subheading -overlay-on
34212 @c @subheading -overlay-unmap
34214 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34215 @node GDB/MI Signal Handling Commands
34216 @section @sc{gdb/mi} Signal Handling Commands
34218 Signal handling commands are not implemented.
34220 @c @subheading -signal-handle
34222 @c @subheading -signal-list-handle-actions
34224 @c @subheading -signal-list-signal-types
34228 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34229 @node GDB/MI Target Manipulation
34230 @section @sc{gdb/mi} Target Manipulation Commands
34233 @subheading The @code{-target-attach} Command
34234 @findex -target-attach
34236 @subsubheading Synopsis
34239 -target-attach @var{pid} | @var{gid} | @var{file}
34242 Attach to a process @var{pid} or a file @var{file} outside of
34243 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
34244 group, the id previously returned by
34245 @samp{-list-thread-groups --available} must be used.
34247 @subsubheading @value{GDBN} Command
34249 The corresponding @value{GDBN} command is @samp{attach}.
34251 @subsubheading Example
34255 =thread-created,id="1"
34256 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
34262 @subheading The @code{-target-compare-sections} Command
34263 @findex -target-compare-sections
34265 @subsubheading Synopsis
34268 -target-compare-sections [ @var{section} ]
34271 Compare data of section @var{section} on target to the exec file.
34272 Without the argument, all sections are compared.
34274 @subsubheading @value{GDBN} Command
34276 The @value{GDBN} equivalent is @samp{compare-sections}.
34278 @subsubheading Example
34283 @subheading The @code{-target-detach} Command
34284 @findex -target-detach
34286 @subsubheading Synopsis
34289 -target-detach [ @var{pid} | @var{gid} ]
34292 Detach from the remote target which normally resumes its execution.
34293 If either @var{pid} or @var{gid} is specified, detaches from either
34294 the specified process, or specified thread group. There's no output.
34296 @subsubheading @value{GDBN} Command
34298 The corresponding @value{GDBN} command is @samp{detach}.
34300 @subsubheading Example
34310 @subheading The @code{-target-disconnect} Command
34311 @findex -target-disconnect
34313 @subsubheading Synopsis
34319 Disconnect from the remote target. There's no output and the target is
34320 generally not resumed.
34322 @subsubheading @value{GDBN} Command
34324 The corresponding @value{GDBN} command is @samp{disconnect}.
34326 @subsubheading Example
34336 @subheading The @code{-target-download} Command
34337 @findex -target-download
34339 @subsubheading Synopsis
34345 Loads the executable onto the remote target.
34346 It prints out an update message every half second, which includes the fields:
34350 The name of the section.
34352 The size of what has been sent so far for that section.
34354 The size of the section.
34356 The total size of what was sent so far (the current and the previous sections).
34358 The size of the overall executable to download.
34362 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
34363 @sc{gdb/mi} Output Syntax}).
34365 In addition, it prints the name and size of the sections, as they are
34366 downloaded. These messages include the following fields:
34370 The name of the section.
34372 The size of the section.
34374 The size of the overall executable to download.
34378 At the end, a summary is printed.
34380 @subsubheading @value{GDBN} Command
34382 The corresponding @value{GDBN} command is @samp{load}.
34384 @subsubheading Example
34386 Note: each status message appears on a single line. Here the messages
34387 have been broken down so that they can fit onto a page.
34392 +download,@{section=".text",section-size="6668",total-size="9880"@}
34393 +download,@{section=".text",section-sent="512",section-size="6668",
34394 total-sent="512",total-size="9880"@}
34395 +download,@{section=".text",section-sent="1024",section-size="6668",
34396 total-sent="1024",total-size="9880"@}
34397 +download,@{section=".text",section-sent="1536",section-size="6668",
34398 total-sent="1536",total-size="9880"@}
34399 +download,@{section=".text",section-sent="2048",section-size="6668",
34400 total-sent="2048",total-size="9880"@}
34401 +download,@{section=".text",section-sent="2560",section-size="6668",
34402 total-sent="2560",total-size="9880"@}
34403 +download,@{section=".text",section-sent="3072",section-size="6668",
34404 total-sent="3072",total-size="9880"@}
34405 +download,@{section=".text",section-sent="3584",section-size="6668",
34406 total-sent="3584",total-size="9880"@}
34407 +download,@{section=".text",section-sent="4096",section-size="6668",
34408 total-sent="4096",total-size="9880"@}
34409 +download,@{section=".text",section-sent="4608",section-size="6668",
34410 total-sent="4608",total-size="9880"@}
34411 +download,@{section=".text",section-sent="5120",section-size="6668",
34412 total-sent="5120",total-size="9880"@}
34413 +download,@{section=".text",section-sent="5632",section-size="6668",
34414 total-sent="5632",total-size="9880"@}
34415 +download,@{section=".text",section-sent="6144",section-size="6668",
34416 total-sent="6144",total-size="9880"@}
34417 +download,@{section=".text",section-sent="6656",section-size="6668",
34418 total-sent="6656",total-size="9880"@}
34419 +download,@{section=".init",section-size="28",total-size="9880"@}
34420 +download,@{section=".fini",section-size="28",total-size="9880"@}
34421 +download,@{section=".data",section-size="3156",total-size="9880"@}
34422 +download,@{section=".data",section-sent="512",section-size="3156",
34423 total-sent="7236",total-size="9880"@}
34424 +download,@{section=".data",section-sent="1024",section-size="3156",
34425 total-sent="7748",total-size="9880"@}
34426 +download,@{section=".data",section-sent="1536",section-size="3156",
34427 total-sent="8260",total-size="9880"@}
34428 +download,@{section=".data",section-sent="2048",section-size="3156",
34429 total-sent="8772",total-size="9880"@}
34430 +download,@{section=".data",section-sent="2560",section-size="3156",
34431 total-sent="9284",total-size="9880"@}
34432 +download,@{section=".data",section-sent="3072",section-size="3156",
34433 total-sent="9796",total-size="9880"@}
34434 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
34441 @subheading The @code{-target-exec-status} Command
34442 @findex -target-exec-status
34444 @subsubheading Synopsis
34447 -target-exec-status
34450 Provide information on the state of the target (whether it is running or
34451 not, for instance).
34453 @subsubheading @value{GDBN} Command
34455 There's no equivalent @value{GDBN} command.
34457 @subsubheading Example
34461 @subheading The @code{-target-list-available-targets} Command
34462 @findex -target-list-available-targets
34464 @subsubheading Synopsis
34467 -target-list-available-targets
34470 List the possible targets to connect to.
34472 @subsubheading @value{GDBN} Command
34474 The corresponding @value{GDBN} command is @samp{help target}.
34476 @subsubheading Example
34480 @subheading The @code{-target-list-current-targets} Command
34481 @findex -target-list-current-targets
34483 @subsubheading Synopsis
34486 -target-list-current-targets
34489 Describe the current target.
34491 @subsubheading @value{GDBN} Command
34493 The corresponding information is printed by @samp{info file} (among
34496 @subsubheading Example
34500 @subheading The @code{-target-list-parameters} Command
34501 @findex -target-list-parameters
34503 @subsubheading Synopsis
34506 -target-list-parameters
34512 @subsubheading @value{GDBN} Command
34516 @subsubheading Example
34520 @subheading The @code{-target-select} Command
34521 @findex -target-select
34523 @subsubheading Synopsis
34526 -target-select @var{type} @var{parameters @dots{}}
34529 Connect @value{GDBN} to the remote target. This command takes two args:
34533 The type of target, for instance @samp{remote}, etc.
34534 @item @var{parameters}
34535 Device names, host names and the like. @xref{Target Commands, ,
34536 Commands for Managing Targets}, for more details.
34539 The output is a connection notification, followed by the address at
34540 which the target program is, in the following form:
34543 ^connected,addr="@var{address}",func="@var{function name}",
34544 args=[@var{arg list}]
34547 @subsubheading @value{GDBN} Command
34549 The corresponding @value{GDBN} command is @samp{target}.
34551 @subsubheading Example
34555 -target-select remote /dev/ttya
34556 ^connected,addr="0xfe00a300",func="??",args=[]
34560 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34561 @node GDB/MI File Transfer Commands
34562 @section @sc{gdb/mi} File Transfer Commands
34565 @subheading The @code{-target-file-put} Command
34566 @findex -target-file-put
34568 @subsubheading Synopsis
34571 -target-file-put @var{hostfile} @var{targetfile}
34574 Copy file @var{hostfile} from the host system (the machine running
34575 @value{GDBN}) to @var{targetfile} on the target system.
34577 @subsubheading @value{GDBN} Command
34579 The corresponding @value{GDBN} command is @samp{remote put}.
34581 @subsubheading Example
34585 -target-file-put localfile remotefile
34591 @subheading The @code{-target-file-get} Command
34592 @findex -target-file-get
34594 @subsubheading Synopsis
34597 -target-file-get @var{targetfile} @var{hostfile}
34600 Copy file @var{targetfile} from the target system to @var{hostfile}
34601 on the host system.
34603 @subsubheading @value{GDBN} Command
34605 The corresponding @value{GDBN} command is @samp{remote get}.
34607 @subsubheading Example
34611 -target-file-get remotefile localfile
34617 @subheading The @code{-target-file-delete} Command
34618 @findex -target-file-delete
34620 @subsubheading Synopsis
34623 -target-file-delete @var{targetfile}
34626 Delete @var{targetfile} from the target system.
34628 @subsubheading @value{GDBN} Command
34630 The corresponding @value{GDBN} command is @samp{remote delete}.
34632 @subsubheading Example
34636 -target-file-delete remotefile
34642 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34643 @node GDB/MI Miscellaneous Commands
34644 @section Miscellaneous @sc{gdb/mi} Commands
34646 @c @subheading -gdb-complete
34648 @subheading The @code{-gdb-exit} Command
34651 @subsubheading Synopsis
34657 Exit @value{GDBN} immediately.
34659 @subsubheading @value{GDBN} Command
34661 Approximately corresponds to @samp{quit}.
34663 @subsubheading Example
34673 @subheading The @code{-exec-abort} Command
34674 @findex -exec-abort
34676 @subsubheading Synopsis
34682 Kill the inferior running program.
34684 @subsubheading @value{GDBN} Command
34686 The corresponding @value{GDBN} command is @samp{kill}.
34688 @subsubheading Example
34693 @subheading The @code{-gdb-set} Command
34696 @subsubheading Synopsis
34702 Set an internal @value{GDBN} variable.
34703 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
34705 @subsubheading @value{GDBN} Command
34707 The corresponding @value{GDBN} command is @samp{set}.
34709 @subsubheading Example
34719 @subheading The @code{-gdb-show} Command
34722 @subsubheading Synopsis
34728 Show the current value of a @value{GDBN} variable.
34730 @subsubheading @value{GDBN} Command
34732 The corresponding @value{GDBN} command is @samp{show}.
34734 @subsubheading Example
34743 @c @subheading -gdb-source
34746 @subheading The @code{-gdb-version} Command
34747 @findex -gdb-version
34749 @subsubheading Synopsis
34755 Show version information for @value{GDBN}. Used mostly in testing.
34757 @subsubheading @value{GDBN} Command
34759 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
34760 default shows this information when you start an interactive session.
34762 @subsubheading Example
34764 @c This example modifies the actual output from GDB to avoid overfull
34770 ~Copyright 2000 Free Software Foundation, Inc.
34771 ~GDB is free software, covered by the GNU General Public License, and
34772 ~you are welcome to change it and/or distribute copies of it under
34773 ~ certain conditions.
34774 ~Type "show copying" to see the conditions.
34775 ~There is absolutely no warranty for GDB. Type "show warranty" for
34777 ~This GDB was configured as
34778 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
34783 @subheading The @code{-list-features} Command
34784 @findex -list-features
34786 Returns a list of particular features of the MI protocol that
34787 this version of gdb implements. A feature can be a command,
34788 or a new field in an output of some command, or even an
34789 important bugfix. While a frontend can sometimes detect presence
34790 of a feature at runtime, it is easier to perform detection at debugger
34793 The command returns a list of strings, with each string naming an
34794 available feature. Each returned string is just a name, it does not
34795 have any internal structure. The list of possible feature names
34801 (gdb) -list-features
34802 ^done,result=["feature1","feature2"]
34805 The current list of features is:
34808 @item frozen-varobjs
34809 Indicates support for the @code{-var-set-frozen} command, as well
34810 as possible presense of the @code{frozen} field in the output
34811 of @code{-varobj-create}.
34812 @item pending-breakpoints
34813 Indicates support for the @option{-f} option to the @code{-break-insert}
34816 Indicates Python scripting support, Python-based
34817 pretty-printing commands, and possible presence of the
34818 @samp{display_hint} field in the output of @code{-var-list-children}
34820 Indicates support for the @code{-thread-info} command.
34821 @item data-read-memory-bytes
34822 Indicates support for the @code{-data-read-memory-bytes} and the
34823 @code{-data-write-memory-bytes} commands.
34824 @item breakpoint-notifications
34825 Indicates that changes to breakpoints and breakpoints created via the
34826 CLI will be announced via async records.
34827 @item ada-task-info
34828 Indicates support for the @code{-ada-task-info} command.
34831 @subheading The @code{-list-target-features} Command
34832 @findex -list-target-features
34834 Returns a list of particular features that are supported by the
34835 target. Those features affect the permitted MI commands, but
34836 unlike the features reported by the @code{-list-features} command, the
34837 features depend on which target GDB is using at the moment. Whenever
34838 a target can change, due to commands such as @code{-target-select},
34839 @code{-target-attach} or @code{-exec-run}, the list of target features
34840 may change, and the frontend should obtain it again.
34844 (gdb) -list-target-features
34845 ^done,result=["async"]
34848 The current list of features is:
34852 Indicates that the target is capable of asynchronous command
34853 execution, which means that @value{GDBN} will accept further commands
34854 while the target is running.
34857 Indicates that the target is capable of reverse execution.
34858 @xref{Reverse Execution}, for more information.
34862 @subheading The @code{-list-thread-groups} Command
34863 @findex -list-thread-groups
34865 @subheading Synopsis
34868 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
34871 Lists thread groups (@pxref{Thread groups}). When a single thread
34872 group is passed as the argument, lists the children of that group.
34873 When several thread group are passed, lists information about those
34874 thread groups. Without any parameters, lists information about all
34875 top-level thread groups.
34877 Normally, thread groups that are being debugged are reported.
34878 With the @samp{--available} option, @value{GDBN} reports thread groups
34879 available on the target.
34881 The output of this command may have either a @samp{threads} result or
34882 a @samp{groups} result. The @samp{thread} result has a list of tuples
34883 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
34884 Information}). The @samp{groups} result has a list of tuples as value,
34885 each tuple describing a thread group. If top-level groups are
34886 requested (that is, no parameter is passed), or when several groups
34887 are passed, the output always has a @samp{groups} result. The format
34888 of the @samp{group} result is described below.
34890 To reduce the number of roundtrips it's possible to list thread groups
34891 together with their children, by passing the @samp{--recurse} option
34892 and the recursion depth. Presently, only recursion depth of 1 is
34893 permitted. If this option is present, then every reported thread group
34894 will also include its children, either as @samp{group} or
34895 @samp{threads} field.
34897 In general, any combination of option and parameters is permitted, with
34898 the following caveats:
34902 When a single thread group is passed, the output will typically
34903 be the @samp{threads} result. Because threads may not contain
34904 anything, the @samp{recurse} option will be ignored.
34907 When the @samp{--available} option is passed, limited information may
34908 be available. In particular, the list of threads of a process might
34909 be inaccessible. Further, specifying specific thread groups might
34910 not give any performance advantage over listing all thread groups.
34911 The frontend should assume that @samp{-list-thread-groups --available}
34912 is always an expensive operation and cache the results.
34916 The @samp{groups} result is a list of tuples, where each tuple may
34917 have the following fields:
34921 Identifier of the thread group. This field is always present.
34922 The identifier is an opaque string; frontends should not try to
34923 convert it to an integer, even though it might look like one.
34926 The type of the thread group. At present, only @samp{process} is a
34930 The target-specific process identifier. This field is only present
34931 for thread groups of type @samp{process} and only if the process exists.
34934 The number of children this thread group has. This field may be
34935 absent for an available thread group.
34938 This field has a list of tuples as value, each tuple describing a
34939 thread. It may be present if the @samp{--recurse} option is
34940 specified, and it's actually possible to obtain the threads.
34943 This field is a list of integers, each identifying a core that one
34944 thread of the group is running on. This field may be absent if
34945 such information is not available.
34948 The name of the executable file that corresponds to this thread group.
34949 The field is only present for thread groups of type @samp{process},
34950 and only if there is a corresponding executable file.
34954 @subheading Example
34958 -list-thread-groups
34959 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
34960 -list-thread-groups 17
34961 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
34962 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
34963 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
34964 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
34965 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
34966 -list-thread-groups --available
34967 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
34968 -list-thread-groups --available --recurse 1
34969 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
34970 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
34971 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
34972 -list-thread-groups --available --recurse 1 17 18
34973 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
34974 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
34975 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
34978 @subheading The @code{-info-os} Command
34981 @subsubheading Synopsis
34984 -info-os [ @var{type} ]
34987 If no argument is supplied, the command returns a table of available
34988 operating-system-specific information types. If one of these types is
34989 supplied as an argument @var{type}, then the command returns a table
34990 of data of that type.
34992 The types of information available depend on the target operating
34995 @subsubheading @value{GDBN} Command
34997 The corresponding @value{GDBN} command is @samp{info os}.
34999 @subsubheading Example
35001 When run on a @sc{gnu}/Linux system, the output will look something
35007 ^done,OSDataTable=@{nr_rows="9",nr_cols="3",
35008 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
35009 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
35010 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
35011 body=[item=@{col0="processes",col1="Listing of all processes",
35012 col2="Processes"@},
35013 item=@{col0="procgroups",col1="Listing of all process groups",
35014 col2="Process groups"@},
35015 item=@{col0="threads",col1="Listing of all threads",
35017 item=@{col0="files",col1="Listing of all file descriptors",
35018 col2="File descriptors"@},
35019 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
35021 item=@{col0="shm",col1="Listing of all shared-memory regions",
35022 col2="Shared-memory regions"@},
35023 item=@{col0="semaphores",col1="Listing of all semaphores",
35024 col2="Semaphores"@},
35025 item=@{col0="msg",col1="Listing of all message queues",
35026 col2="Message queues"@},
35027 item=@{col0="modules",col1="Listing of all loaded kernel modules",
35028 col2="Kernel modules"@}]@}
35031 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
35032 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
35033 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
35034 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
35035 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
35036 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
35037 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
35038 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
35040 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
35041 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
35045 (Note that the MI output here includes a @code{"Title"} column that
35046 does not appear in command-line @code{info os}; this column is useful
35047 for MI clients that want to enumerate the types of data, such as in a
35048 popup menu, but is needless clutter on the command line, and
35049 @code{info os} omits it.)
35051 @subheading The @code{-add-inferior} Command
35052 @findex -add-inferior
35054 @subheading Synopsis
35060 Creates a new inferior (@pxref{Inferiors and Programs}). The created
35061 inferior is not associated with any executable. Such association may
35062 be established with the @samp{-file-exec-and-symbols} command
35063 (@pxref{GDB/MI File Commands}). The command response has a single
35064 field, @samp{inferior}, whose value is the identifier of the
35065 thread group corresponding to the new inferior.
35067 @subheading Example
35072 ^done,inferior="i3"
35075 @subheading The @code{-interpreter-exec} Command
35076 @findex -interpreter-exec
35078 @subheading Synopsis
35081 -interpreter-exec @var{interpreter} @var{command}
35083 @anchor{-interpreter-exec}
35085 Execute the specified @var{command} in the given @var{interpreter}.
35087 @subheading @value{GDBN} Command
35089 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
35091 @subheading Example
35095 -interpreter-exec console "break main"
35096 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
35097 &"During symbol reading, bad structure-type format.\n"
35098 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
35103 @subheading The @code{-inferior-tty-set} Command
35104 @findex -inferior-tty-set
35106 @subheading Synopsis
35109 -inferior-tty-set /dev/pts/1
35112 Set terminal for future runs of the program being debugged.
35114 @subheading @value{GDBN} Command
35116 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
35118 @subheading Example
35122 -inferior-tty-set /dev/pts/1
35127 @subheading The @code{-inferior-tty-show} Command
35128 @findex -inferior-tty-show
35130 @subheading Synopsis
35136 Show terminal for future runs of program being debugged.
35138 @subheading @value{GDBN} Command
35140 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
35142 @subheading Example
35146 -inferior-tty-set /dev/pts/1
35150 ^done,inferior_tty_terminal="/dev/pts/1"
35154 @subheading The @code{-enable-timings} Command
35155 @findex -enable-timings
35157 @subheading Synopsis
35160 -enable-timings [yes | no]
35163 Toggle the printing of the wallclock, user and system times for an MI
35164 command as a field in its output. This command is to help frontend
35165 developers optimize the performance of their code. No argument is
35166 equivalent to @samp{yes}.
35168 @subheading @value{GDBN} Command
35172 @subheading Example
35180 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
35181 addr="0x080484ed",func="main",file="myprog.c",
35182 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
35184 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
35192 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
35193 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
35194 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
35195 fullname="/home/nickrob/myprog.c",line="73"@}
35200 @chapter @value{GDBN} Annotations
35202 This chapter describes annotations in @value{GDBN}. Annotations were
35203 designed to interface @value{GDBN} to graphical user interfaces or other
35204 similar programs which want to interact with @value{GDBN} at a
35205 relatively high level.
35207 The annotation mechanism has largely been superseded by @sc{gdb/mi}
35211 This is Edition @value{EDITION}, @value{DATE}.
35215 * Annotations Overview:: What annotations are; the general syntax.
35216 * Server Prefix:: Issuing a command without affecting user state.
35217 * Prompting:: Annotations marking @value{GDBN}'s need for input.
35218 * Errors:: Annotations for error messages.
35219 * Invalidation:: Some annotations describe things now invalid.
35220 * Annotations for Running::
35221 Whether the program is running, how it stopped, etc.
35222 * Source Annotations:: Annotations describing source code.
35225 @node Annotations Overview
35226 @section What is an Annotation?
35227 @cindex annotations
35229 Annotations start with a newline character, two @samp{control-z}
35230 characters, and the name of the annotation. If there is no additional
35231 information associated with this annotation, the name of the annotation
35232 is followed immediately by a newline. If there is additional
35233 information, the name of the annotation is followed by a space, the
35234 additional information, and a newline. The additional information
35235 cannot contain newline characters.
35237 Any output not beginning with a newline and two @samp{control-z}
35238 characters denotes literal output from @value{GDBN}. Currently there is
35239 no need for @value{GDBN} to output a newline followed by two
35240 @samp{control-z} characters, but if there was such a need, the
35241 annotations could be extended with an @samp{escape} annotation which
35242 means those three characters as output.
35244 The annotation @var{level}, which is specified using the
35245 @option{--annotate} command line option (@pxref{Mode Options}), controls
35246 how much information @value{GDBN} prints together with its prompt,
35247 values of expressions, source lines, and other types of output. Level 0
35248 is for no annotations, level 1 is for use when @value{GDBN} is run as a
35249 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
35250 for programs that control @value{GDBN}, and level 2 annotations have
35251 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
35252 Interface, annotate, GDB's Obsolete Annotations}).
35255 @kindex set annotate
35256 @item set annotate @var{level}
35257 The @value{GDBN} command @code{set annotate} sets the level of
35258 annotations to the specified @var{level}.
35260 @item show annotate
35261 @kindex show annotate
35262 Show the current annotation level.
35265 This chapter describes level 3 annotations.
35267 A simple example of starting up @value{GDBN} with annotations is:
35270 $ @kbd{gdb --annotate=3}
35272 Copyright 2003 Free Software Foundation, Inc.
35273 GDB is free software, covered by the GNU General Public License,
35274 and you are welcome to change it and/or distribute copies of it
35275 under certain conditions.
35276 Type "show copying" to see the conditions.
35277 There is absolutely no warranty for GDB. Type "show warranty"
35279 This GDB was configured as "i386-pc-linux-gnu"
35290 Here @samp{quit} is input to @value{GDBN}; the rest is output from
35291 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
35292 denotes a @samp{control-z} character) are annotations; the rest is
35293 output from @value{GDBN}.
35295 @node Server Prefix
35296 @section The Server Prefix
35297 @cindex server prefix
35299 If you prefix a command with @samp{server } then it will not affect
35300 the command history, nor will it affect @value{GDBN}'s notion of which
35301 command to repeat if @key{RET} is pressed on a line by itself. This
35302 means that commands can be run behind a user's back by a front-end in
35303 a transparent manner.
35305 The @code{server } prefix does not affect the recording of values into
35306 the value history; to print a value without recording it into the
35307 value history, use the @code{output} command instead of the
35308 @code{print} command.
35310 Using this prefix also disables confirmation requests
35311 (@pxref{confirmation requests}).
35314 @section Annotation for @value{GDBN} Input
35316 @cindex annotations for prompts
35317 When @value{GDBN} prompts for input, it annotates this fact so it is possible
35318 to know when to send output, when the output from a given command is
35321 Different kinds of input each have a different @dfn{input type}. Each
35322 input type has three annotations: a @code{pre-} annotation, which
35323 denotes the beginning of any prompt which is being output, a plain
35324 annotation, which denotes the end of the prompt, and then a @code{post-}
35325 annotation which denotes the end of any echo which may (or may not) be
35326 associated with the input. For example, the @code{prompt} input type
35327 features the following annotations:
35335 The input types are
35338 @findex pre-prompt annotation
35339 @findex prompt annotation
35340 @findex post-prompt annotation
35342 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
35344 @findex pre-commands annotation
35345 @findex commands annotation
35346 @findex post-commands annotation
35348 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
35349 command. The annotations are repeated for each command which is input.
35351 @findex pre-overload-choice annotation
35352 @findex overload-choice annotation
35353 @findex post-overload-choice annotation
35354 @item overload-choice
35355 When @value{GDBN} wants the user to select between various overloaded functions.
35357 @findex pre-query annotation
35358 @findex query annotation
35359 @findex post-query annotation
35361 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
35363 @findex pre-prompt-for-continue annotation
35364 @findex prompt-for-continue annotation
35365 @findex post-prompt-for-continue annotation
35366 @item prompt-for-continue
35367 When @value{GDBN} is asking the user to press return to continue. Note: Don't
35368 expect this to work well; instead use @code{set height 0} to disable
35369 prompting. This is because the counting of lines is buggy in the
35370 presence of annotations.
35375 @cindex annotations for errors, warnings and interrupts
35377 @findex quit annotation
35382 This annotation occurs right before @value{GDBN} responds to an interrupt.
35384 @findex error annotation
35389 This annotation occurs right before @value{GDBN} responds to an error.
35391 Quit and error annotations indicate that any annotations which @value{GDBN} was
35392 in the middle of may end abruptly. For example, if a
35393 @code{value-history-begin} annotation is followed by a @code{error}, one
35394 cannot expect to receive the matching @code{value-history-end}. One
35395 cannot expect not to receive it either, however; an error annotation
35396 does not necessarily mean that @value{GDBN} is immediately returning all the way
35399 @findex error-begin annotation
35400 A quit or error annotation may be preceded by
35406 Any output between that and the quit or error annotation is the error
35409 Warning messages are not yet annotated.
35410 @c If we want to change that, need to fix warning(), type_error(),
35411 @c range_error(), and possibly other places.
35414 @section Invalidation Notices
35416 @cindex annotations for invalidation messages
35417 The following annotations say that certain pieces of state may have
35421 @findex frames-invalid annotation
35422 @item ^Z^Zframes-invalid
35424 The frames (for example, output from the @code{backtrace} command) may
35427 @findex breakpoints-invalid annotation
35428 @item ^Z^Zbreakpoints-invalid
35430 The breakpoints may have changed. For example, the user just added or
35431 deleted a breakpoint.
35434 @node Annotations for Running
35435 @section Running the Program
35436 @cindex annotations for running programs
35438 @findex starting annotation
35439 @findex stopping annotation
35440 When the program starts executing due to a @value{GDBN} command such as
35441 @code{step} or @code{continue},
35447 is output. When the program stops,
35453 is output. Before the @code{stopped} annotation, a variety of
35454 annotations describe how the program stopped.
35457 @findex exited annotation
35458 @item ^Z^Zexited @var{exit-status}
35459 The program exited, and @var{exit-status} is the exit status (zero for
35460 successful exit, otherwise nonzero).
35462 @findex signalled annotation
35463 @findex signal-name annotation
35464 @findex signal-name-end annotation
35465 @findex signal-string annotation
35466 @findex signal-string-end annotation
35467 @item ^Z^Zsignalled
35468 The program exited with a signal. After the @code{^Z^Zsignalled}, the
35469 annotation continues:
35475 ^Z^Zsignal-name-end
35479 ^Z^Zsignal-string-end
35484 where @var{name} is the name of the signal, such as @code{SIGILL} or
35485 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
35486 as @code{Illegal Instruction} or @code{Segmentation fault}.
35487 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
35488 user's benefit and have no particular format.
35490 @findex signal annotation
35492 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
35493 just saying that the program received the signal, not that it was
35494 terminated with it.
35496 @findex breakpoint annotation
35497 @item ^Z^Zbreakpoint @var{number}
35498 The program hit breakpoint number @var{number}.
35500 @findex watchpoint annotation
35501 @item ^Z^Zwatchpoint @var{number}
35502 The program hit watchpoint number @var{number}.
35505 @node Source Annotations
35506 @section Displaying Source
35507 @cindex annotations for source display
35509 @findex source annotation
35510 The following annotation is used instead of displaying source code:
35513 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
35516 where @var{filename} is an absolute file name indicating which source
35517 file, @var{line} is the line number within that file (where 1 is the
35518 first line in the file), @var{character} is the character position
35519 within the file (where 0 is the first character in the file) (for most
35520 debug formats this will necessarily point to the beginning of a line),
35521 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
35522 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
35523 @var{addr} is the address in the target program associated with the
35524 source which is being displayed. @var{addr} is in the form @samp{0x}
35525 followed by one or more lowercase hex digits (note that this does not
35526 depend on the language).
35528 @node JIT Interface
35529 @chapter JIT Compilation Interface
35530 @cindex just-in-time compilation
35531 @cindex JIT compilation interface
35533 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
35534 interface. A JIT compiler is a program or library that generates native
35535 executable code at runtime and executes it, usually in order to achieve good
35536 performance while maintaining platform independence.
35538 Programs that use JIT compilation are normally difficult to debug because
35539 portions of their code are generated at runtime, instead of being loaded from
35540 object files, which is where @value{GDBN} normally finds the program's symbols
35541 and debug information. In order to debug programs that use JIT compilation,
35542 @value{GDBN} has an interface that allows the program to register in-memory
35543 symbol files with @value{GDBN} at runtime.
35545 If you are using @value{GDBN} to debug a program that uses this interface, then
35546 it should work transparently so long as you have not stripped the binary. If
35547 you are developing a JIT compiler, then the interface is documented in the rest
35548 of this chapter. At this time, the only known client of this interface is the
35551 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
35552 JIT compiler communicates with @value{GDBN} by writing data into a global
35553 variable and calling a fuction at a well-known symbol. When @value{GDBN}
35554 attaches, it reads a linked list of symbol files from the global variable to
35555 find existing code, and puts a breakpoint in the function so that it can find
35556 out about additional code.
35559 * Declarations:: Relevant C struct declarations
35560 * Registering Code:: Steps to register code
35561 * Unregistering Code:: Steps to unregister code
35562 * Custom Debug Info:: Emit debug information in a custom format
35566 @section JIT Declarations
35568 These are the relevant struct declarations that a C program should include to
35569 implement the interface:
35579 struct jit_code_entry
35581 struct jit_code_entry *next_entry;
35582 struct jit_code_entry *prev_entry;
35583 const char *symfile_addr;
35584 uint64_t symfile_size;
35587 struct jit_descriptor
35590 /* This type should be jit_actions_t, but we use uint32_t
35591 to be explicit about the bitwidth. */
35592 uint32_t action_flag;
35593 struct jit_code_entry *relevant_entry;
35594 struct jit_code_entry *first_entry;
35597 /* GDB puts a breakpoint in this function. */
35598 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
35600 /* Make sure to specify the version statically, because the
35601 debugger may check the version before we can set it. */
35602 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
35605 If the JIT is multi-threaded, then it is important that the JIT synchronize any
35606 modifications to this global data properly, which can easily be done by putting
35607 a global mutex around modifications to these structures.
35609 @node Registering Code
35610 @section Registering Code
35612 To register code with @value{GDBN}, the JIT should follow this protocol:
35616 Generate an object file in memory with symbols and other desired debug
35617 information. The file must include the virtual addresses of the sections.
35620 Create a code entry for the file, which gives the start and size of the symbol
35624 Add it to the linked list in the JIT descriptor.
35627 Point the relevant_entry field of the descriptor at the entry.
35630 Set @code{action_flag} to @code{JIT_REGISTER} and call
35631 @code{__jit_debug_register_code}.
35634 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
35635 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
35636 new code. However, the linked list must still be maintained in order to allow
35637 @value{GDBN} to attach to a running process and still find the symbol files.
35639 @node Unregistering Code
35640 @section Unregistering Code
35642 If code is freed, then the JIT should use the following protocol:
35646 Remove the code entry corresponding to the code from the linked list.
35649 Point the @code{relevant_entry} field of the descriptor at the code entry.
35652 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
35653 @code{__jit_debug_register_code}.
35656 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
35657 and the JIT will leak the memory used for the associated symbol files.
35659 @node Custom Debug Info
35660 @section Custom Debug Info
35661 @cindex custom JIT debug info
35662 @cindex JIT debug info reader
35664 Generating debug information in platform-native file formats (like ELF
35665 or COFF) may be an overkill for JIT compilers; especially if all the
35666 debug info is used for is displaying a meaningful backtrace. The
35667 issue can be resolved by having the JIT writers decide on a debug info
35668 format and also provide a reader that parses the debug info generated
35669 by the JIT compiler. This section gives a brief overview on writing
35670 such a parser. More specific details can be found in the source file
35671 @file{gdb/jit-reader.in}, which is also installed as a header at
35672 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
35674 The reader is implemented as a shared object (so this functionality is
35675 not available on platforms which don't allow loading shared objects at
35676 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
35677 @code{jit-reader-unload} are provided, to be used to load and unload
35678 the readers from a preconfigured directory. Once loaded, the shared
35679 object is used the parse the debug information emitted by the JIT
35683 * Using JIT Debug Info Readers:: How to use supplied readers correctly
35684 * Writing JIT Debug Info Readers:: Creating a debug-info reader
35687 @node Using JIT Debug Info Readers
35688 @subsection Using JIT Debug Info Readers
35689 @kindex jit-reader-load
35690 @kindex jit-reader-unload
35692 Readers can be loaded and unloaded using the @code{jit-reader-load}
35693 and @code{jit-reader-unload} commands.
35696 @item jit-reader-load @var{reader}
35697 Load the JIT reader named @var{reader}. @var{reader} is a shared
35698 object specified as either an absolute or a relative file name. In
35699 the latter case, @value{GDBN} will try to load the reader from a
35700 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
35701 system (here @var{libdir} is the system library directory, often
35702 @file{/usr/local/lib}).
35704 Only one reader can be active at a time; trying to load a second
35705 reader when one is already loaded will result in @value{GDBN}
35706 reporting an error. A new JIT reader can be loaded by first unloading
35707 the current one using @code{jit-reader-unload} and then invoking
35708 @code{jit-reader-load}.
35710 @item jit-reader-unload
35711 Unload the currently loaded JIT reader.
35715 @node Writing JIT Debug Info Readers
35716 @subsection Writing JIT Debug Info Readers
35717 @cindex writing JIT debug info readers
35719 As mentioned, a reader is essentially a shared object conforming to a
35720 certain ABI. This ABI is described in @file{jit-reader.h}.
35722 @file{jit-reader.h} defines the structures, macros and functions
35723 required to write a reader. It is installed (along with
35724 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
35725 the system include directory.
35727 Readers need to be released under a GPL compatible license. A reader
35728 can be declared as released under such a license by placing the macro
35729 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
35731 The entry point for readers is the symbol @code{gdb_init_reader},
35732 which is expected to be a function with the prototype
35734 @findex gdb_init_reader
35736 extern struct gdb_reader_funcs *gdb_init_reader (void);
35739 @cindex @code{struct gdb_reader_funcs}
35741 @code{struct gdb_reader_funcs} contains a set of pointers to callback
35742 functions. These functions are executed to read the debug info
35743 generated by the JIT compiler (@code{read}), to unwind stack frames
35744 (@code{unwind}) and to create canonical frame IDs
35745 (@code{get_Frame_id}). It also has a callback that is called when the
35746 reader is being unloaded (@code{destroy}). The struct looks like this
35749 struct gdb_reader_funcs
35751 /* Must be set to GDB_READER_INTERFACE_VERSION. */
35752 int reader_version;
35754 /* For use by the reader. */
35757 gdb_read_debug_info *read;
35758 gdb_unwind_frame *unwind;
35759 gdb_get_frame_id *get_frame_id;
35760 gdb_destroy_reader *destroy;
35764 @cindex @code{struct gdb_symbol_callbacks}
35765 @cindex @code{struct gdb_unwind_callbacks}
35767 The callbacks are provided with another set of callbacks by
35768 @value{GDBN} to do their job. For @code{read}, these callbacks are
35769 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
35770 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
35771 @code{struct gdb_symbol_callbacks} has callbacks to create new object
35772 files and new symbol tables inside those object files. @code{struct
35773 gdb_unwind_callbacks} has callbacks to read registers off the current
35774 frame and to write out the values of the registers in the previous
35775 frame. Both have a callback (@code{target_read}) to read bytes off the
35776 target's address space.
35778 @node In-Process Agent
35779 @chapter In-Process Agent
35780 @cindex debugging agent
35781 The traditional debugging model is conceptually low-speed, but works fine,
35782 because most bugs can be reproduced in debugging-mode execution. However,
35783 as multi-core or many-core processors are becoming mainstream, and
35784 multi-threaded programs become more and more popular, there should be more
35785 and more bugs that only manifest themselves at normal-mode execution, for
35786 example, thread races, because debugger's interference with the program's
35787 timing may conceal the bugs. On the other hand, in some applications,
35788 it is not feasible for the debugger to interrupt the program's execution
35789 long enough for the developer to learn anything helpful about its behavior.
35790 If the program's correctness depends on its real-time behavior, delays
35791 introduced by a debugger might cause the program to fail, even when the
35792 code itself is correct. It is useful to be able to observe the program's
35793 behavior without interrupting it.
35795 Therefore, traditional debugging model is too intrusive to reproduce
35796 some bugs. In order to reduce the interference with the program, we can
35797 reduce the number of operations performed by debugger. The
35798 @dfn{In-Process Agent}, a shared library, is running within the same
35799 process with inferior, and is able to perform some debugging operations
35800 itself. As a result, debugger is only involved when necessary, and
35801 performance of debugging can be improved accordingly. Note that
35802 interference with program can be reduced but can't be removed completely,
35803 because the in-process agent will still stop or slow down the program.
35805 The in-process agent can interpret and execute Agent Expressions
35806 (@pxref{Agent Expressions}) during performing debugging operations. The
35807 agent expressions can be used for different purposes, such as collecting
35808 data in tracepoints, and condition evaluation in breakpoints.
35810 @anchor{Control Agent}
35811 You can control whether the in-process agent is used as an aid for
35812 debugging with the following commands:
35815 @kindex set agent on
35817 Causes the in-process agent to perform some operations on behalf of the
35818 debugger. Just which operations requested by the user will be done
35819 by the in-process agent depends on the its capabilities. For example,
35820 if you request to evaluate breakpoint conditions in the in-process agent,
35821 and the in-process agent has such capability as well, then breakpoint
35822 conditions will be evaluated in the in-process agent.
35824 @kindex set agent off
35825 @item set agent off
35826 Disables execution of debugging operations by the in-process agent. All
35827 of the operations will be performed by @value{GDBN}.
35831 Display the current setting of execution of debugging operations by
35832 the in-process agent.
35836 * In-Process Agent Protocol::
35839 @node In-Process Agent Protocol
35840 @section In-Process Agent Protocol
35841 @cindex in-process agent protocol
35843 The in-process agent is able to communicate with both @value{GDBN} and
35844 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
35845 used for communications between @value{GDBN} or GDBserver and the IPA.
35846 In general, @value{GDBN} or GDBserver sends commands
35847 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
35848 in-process agent replies back with the return result of the command, or
35849 some other information. The data sent to in-process agent is composed
35850 of primitive data types, such as 4-byte or 8-byte type, and composite
35851 types, which are called objects (@pxref{IPA Protocol Objects}).
35854 * IPA Protocol Objects::
35855 * IPA Protocol Commands::
35858 @node IPA Protocol Objects
35859 @subsection IPA Protocol Objects
35860 @cindex ipa protocol objects
35862 The commands sent to and results received from agent may contain some
35863 complex data types called @dfn{objects}.
35865 The in-process agent is running on the same machine with @value{GDBN}
35866 or GDBserver, so it doesn't have to handle as much differences between
35867 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
35868 However, there are still some differences of two ends in two processes:
35872 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
35873 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
35875 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
35876 GDBserver is compiled with one, and in-process agent is compiled with
35880 Here are the IPA Protocol Objects:
35884 agent expression object. It represents an agent expression
35885 (@pxref{Agent Expressions}).
35886 @anchor{agent expression object}
35888 tracepoint action object. It represents a tracepoint action
35889 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
35890 memory, static trace data and to evaluate expression.
35891 @anchor{tracepoint action object}
35893 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
35894 @anchor{tracepoint object}
35898 The following table describes important attributes of each IPA protocol
35901 @multitable @columnfractions .30 .20 .50
35902 @headitem Name @tab Size @tab Description
35903 @item @emph{agent expression object} @tab @tab
35904 @item length @tab 4 @tab length of bytes code
35905 @item byte code @tab @var{length} @tab contents of byte code
35906 @item @emph{tracepoint action for collecting memory} @tab @tab
35907 @item 'M' @tab 1 @tab type of tracepoint action
35908 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
35909 address of the lowest byte to collect, otherwise @var{addr} is the offset
35910 of @var{basereg} for memory collecting.
35911 @item len @tab 8 @tab length of memory for collecting
35912 @item basereg @tab 4 @tab the register number containing the starting
35913 memory address for collecting.
35914 @item @emph{tracepoint action for collecting registers} @tab @tab
35915 @item 'R' @tab 1 @tab type of tracepoint action
35916 @item @emph{tracepoint action for collecting static trace data} @tab @tab
35917 @item 'L' @tab 1 @tab type of tracepoint action
35918 @item @emph{tracepoint action for expression evaluation} @tab @tab
35919 @item 'X' @tab 1 @tab type of tracepoint action
35920 @item agent expression @tab length of @tab @ref{agent expression object}
35921 @item @emph{tracepoint object} @tab @tab
35922 @item number @tab 4 @tab number of tracepoint
35923 @item address @tab 8 @tab address of tracepoint inserted on
35924 @item type @tab 4 @tab type of tracepoint
35925 @item enabled @tab 1 @tab enable or disable of tracepoint
35926 @item step_count @tab 8 @tab step
35927 @item pass_count @tab 8 @tab pass
35928 @item numactions @tab 4 @tab number of tracepoint actions
35929 @item hit count @tab 8 @tab hit count
35930 @item trace frame usage @tab 8 @tab trace frame usage
35931 @item compiled_cond @tab 8 @tab compiled condition
35932 @item orig_size @tab 8 @tab orig size
35933 @item condition @tab 4 if condition is NULL otherwise length of
35934 @ref{agent expression object}
35935 @tab zero if condition is NULL, otherwise is
35936 @ref{agent expression object}
35937 @item actions @tab variable
35938 @tab numactions number of @ref{tracepoint action object}
35941 @node IPA Protocol Commands
35942 @subsection IPA Protocol Commands
35943 @cindex ipa protocol commands
35945 The spaces in each command are delimiters to ease reading this commands
35946 specification. They don't exist in real commands.
35950 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
35951 Installs a new fast tracepoint described by @var{tracepoint_object}
35952 (@pxref{tracepoint object}). @var{gdb_jump_pad_head}, 8-byte long, is the
35953 head of @dfn{jumppad}, which is used to jump to data collection routine
35958 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
35959 @var{target_address} is address of tracepoint in the inferior.
35960 @var{gdb_jump_pad_head} is updated head of jumppad. Both of
35961 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
35962 @var{fjump} contains a sequence of instructions jump to jumppad entry.
35963 @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
35970 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
35971 is about to kill inferiors.
35979 @item probe_marker_at:@var{address}
35980 Asks in-process agent to probe the marker at @var{address}.
35987 @item unprobe_marker_at:@var{address}
35988 Asks in-process agent to unprobe the marker at @var{address}.
35992 @chapter Reporting Bugs in @value{GDBN}
35993 @cindex bugs in @value{GDBN}
35994 @cindex reporting bugs in @value{GDBN}
35996 Your bug reports play an essential role in making @value{GDBN} reliable.
35998 Reporting a bug may help you by bringing a solution to your problem, or it
35999 may not. But in any case the principal function of a bug report is to help
36000 the entire community by making the next version of @value{GDBN} work better. Bug
36001 reports are your contribution to the maintenance of @value{GDBN}.
36003 In order for a bug report to serve its purpose, you must include the
36004 information that enables us to fix the bug.
36007 * Bug Criteria:: Have you found a bug?
36008 * Bug Reporting:: How to report bugs
36012 @section Have You Found a Bug?
36013 @cindex bug criteria
36015 If you are not sure whether you have found a bug, here are some guidelines:
36018 @cindex fatal signal
36019 @cindex debugger crash
36020 @cindex crash of debugger
36022 If the debugger gets a fatal signal, for any input whatever, that is a
36023 @value{GDBN} bug. Reliable debuggers never crash.
36025 @cindex error on valid input
36027 If @value{GDBN} produces an error message for valid input, that is a
36028 bug. (Note that if you're cross debugging, the problem may also be
36029 somewhere in the connection to the target.)
36031 @cindex invalid input
36033 If @value{GDBN} does not produce an error message for invalid input,
36034 that is a bug. However, you should note that your idea of
36035 ``invalid input'' might be our idea of ``an extension'' or ``support
36036 for traditional practice''.
36039 If you are an experienced user of debugging tools, your suggestions
36040 for improvement of @value{GDBN} are welcome in any case.
36043 @node Bug Reporting
36044 @section How to Report Bugs
36045 @cindex bug reports
36046 @cindex @value{GDBN} bugs, reporting
36048 A number of companies and individuals offer support for @sc{gnu} products.
36049 If you obtained @value{GDBN} from a support organization, we recommend you
36050 contact that organization first.
36052 You can find contact information for many support companies and
36053 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
36055 @c should add a web page ref...
36058 @ifset BUGURL_DEFAULT
36059 In any event, we also recommend that you submit bug reports for
36060 @value{GDBN}. The preferred method is to submit them directly using
36061 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
36062 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
36065 @strong{Do not send bug reports to @samp{info-gdb}, or to
36066 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
36067 not want to receive bug reports. Those that do have arranged to receive
36070 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
36071 serves as a repeater. The mailing list and the newsgroup carry exactly
36072 the same messages. Often people think of posting bug reports to the
36073 newsgroup instead of mailing them. This appears to work, but it has one
36074 problem which can be crucial: a newsgroup posting often lacks a mail
36075 path back to the sender. Thus, if we need to ask for more information,
36076 we may be unable to reach you. For this reason, it is better to send
36077 bug reports to the mailing list.
36079 @ifclear BUGURL_DEFAULT
36080 In any event, we also recommend that you submit bug reports for
36081 @value{GDBN} to @value{BUGURL}.
36085 The fundamental principle of reporting bugs usefully is this:
36086 @strong{report all the facts}. If you are not sure whether to state a
36087 fact or leave it out, state it!
36089 Often people omit facts because they think they know what causes the
36090 problem and assume that some details do not matter. Thus, you might
36091 assume that the name of the variable you use in an example does not matter.
36092 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
36093 stray memory reference which happens to fetch from the location where that
36094 name is stored in memory; perhaps, if the name were different, the contents
36095 of that location would fool the debugger into doing the right thing despite
36096 the bug. Play it safe and give a specific, complete example. That is the
36097 easiest thing for you to do, and the most helpful.
36099 Keep in mind that the purpose of a bug report is to enable us to fix the
36100 bug. It may be that the bug has been reported previously, but neither
36101 you nor we can know that unless your bug report is complete and
36104 Sometimes people give a few sketchy facts and ask, ``Does this ring a
36105 bell?'' Those bug reports are useless, and we urge everyone to
36106 @emph{refuse to respond to them} except to chide the sender to report
36109 To enable us to fix the bug, you should include all these things:
36113 The version of @value{GDBN}. @value{GDBN} announces it if you start
36114 with no arguments; you can also print it at any time using @code{show
36117 Without this, we will not know whether there is any point in looking for
36118 the bug in the current version of @value{GDBN}.
36121 The type of machine you are using, and the operating system name and
36125 The details of the @value{GDBN} build-time configuration.
36126 @value{GDBN} shows these details if you invoke it with the
36127 @option{--configuration} command-line option, or if you type
36128 @code{show configuration} at @value{GDBN}'s prompt.
36131 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
36132 ``@value{GCC}--2.8.1''.
36135 What compiler (and its version) was used to compile the program you are
36136 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
36137 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
36138 to get this information; for other compilers, see the documentation for
36142 The command arguments you gave the compiler to compile your example and
36143 observe the bug. For example, did you use @samp{-O}? To guarantee
36144 you will not omit something important, list them all. A copy of the
36145 Makefile (or the output from make) is sufficient.
36147 If we were to try to guess the arguments, we would probably guess wrong
36148 and then we might not encounter the bug.
36151 A complete input script, and all necessary source files, that will
36155 A description of what behavior you observe that you believe is
36156 incorrect. For example, ``It gets a fatal signal.''
36158 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
36159 will certainly notice it. But if the bug is incorrect output, we might
36160 not notice unless it is glaringly wrong. You might as well not give us
36161 a chance to make a mistake.
36163 Even if the problem you experience is a fatal signal, you should still
36164 say so explicitly. Suppose something strange is going on, such as, your
36165 copy of @value{GDBN} is out of synch, or you have encountered a bug in
36166 the C library on your system. (This has happened!) Your copy might
36167 crash and ours would not. If you told us to expect a crash, then when
36168 ours fails to crash, we would know that the bug was not happening for
36169 us. If you had not told us to expect a crash, then we would not be able
36170 to draw any conclusion from our observations.
36173 @cindex recording a session script
36174 To collect all this information, you can use a session recording program
36175 such as @command{script}, which is available on many Unix systems.
36176 Just run your @value{GDBN} session inside @command{script} and then
36177 include the @file{typescript} file with your bug report.
36179 Another way to record a @value{GDBN} session is to run @value{GDBN}
36180 inside Emacs and then save the entire buffer to a file.
36183 If you wish to suggest changes to the @value{GDBN} source, send us context
36184 diffs. If you even discuss something in the @value{GDBN} source, refer to
36185 it by context, not by line number.
36187 The line numbers in our development sources will not match those in your
36188 sources. Your line numbers would convey no useful information to us.
36192 Here are some things that are not necessary:
36196 A description of the envelope of the bug.
36198 Often people who encounter a bug spend a lot of time investigating
36199 which changes to the input file will make the bug go away and which
36200 changes will not affect it.
36202 This is often time consuming and not very useful, because the way we
36203 will find the bug is by running a single example under the debugger
36204 with breakpoints, not by pure deduction from a series of examples.
36205 We recommend that you save your time for something else.
36207 Of course, if you can find a simpler example to report @emph{instead}
36208 of the original one, that is a convenience for us. Errors in the
36209 output will be easier to spot, running under the debugger will take
36210 less time, and so on.
36212 However, simplification is not vital; if you do not want to do this,
36213 report the bug anyway and send us the entire test case you used.
36216 A patch for the bug.
36218 A patch for the bug does help us if it is a good one. But do not omit
36219 the necessary information, such as the test case, on the assumption that
36220 a patch is all we need. We might see problems with your patch and decide
36221 to fix the problem another way, or we might not understand it at all.
36223 Sometimes with a program as complicated as @value{GDBN} it is very hard to
36224 construct an example that will make the program follow a certain path
36225 through the code. If you do not send us the example, we will not be able
36226 to construct one, so we will not be able to verify that the bug is fixed.
36228 And if we cannot understand what bug you are trying to fix, or why your
36229 patch should be an improvement, we will not install it. A test case will
36230 help us to understand.
36233 A guess about what the bug is or what it depends on.
36235 Such guesses are usually wrong. Even we cannot guess right about such
36236 things without first using the debugger to find the facts.
36239 @c The readline documentation is distributed with the readline code
36240 @c and consists of the two following files:
36243 @c Use -I with makeinfo to point to the appropriate directory,
36244 @c environment var TEXINPUTS with TeX.
36245 @ifclear SYSTEM_READLINE
36246 @include rluser.texi
36247 @include hsuser.texi
36251 @appendix In Memoriam
36253 The @value{GDBN} project mourns the loss of the following long-time
36258 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
36259 to Free Software in general. Outside of @value{GDBN}, he was known in
36260 the Amiga world for his series of Fish Disks, and the GeekGadget project.
36262 @item Michael Snyder
36263 Michael was one of the Global Maintainers of the @value{GDBN} project,
36264 with contributions recorded as early as 1996, until 2011. In addition
36265 to his day to day participation, he was a large driving force behind
36266 adding Reverse Debugging to @value{GDBN}.
36269 Beyond their technical contributions to the project, they were also
36270 enjoyable members of the Free Software Community. We will miss them.
36272 @node Formatting Documentation
36273 @appendix Formatting Documentation
36275 @cindex @value{GDBN} reference card
36276 @cindex reference card
36277 The @value{GDBN} 4 release includes an already-formatted reference card, ready
36278 for printing with PostScript or Ghostscript, in the @file{gdb}
36279 subdirectory of the main source directory@footnote{In
36280 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
36281 release.}. If you can use PostScript or Ghostscript with your printer,
36282 you can print the reference card immediately with @file{refcard.ps}.
36284 The release also includes the source for the reference card. You
36285 can format it, using @TeX{}, by typing:
36291 The @value{GDBN} reference card is designed to print in @dfn{landscape}
36292 mode on US ``letter'' size paper;
36293 that is, on a sheet 11 inches wide by 8.5 inches
36294 high. You will need to specify this form of printing as an option to
36295 your @sc{dvi} output program.
36297 @cindex documentation
36299 All the documentation for @value{GDBN} comes as part of the machine-readable
36300 distribution. The documentation is written in Texinfo format, which is
36301 a documentation system that uses a single source file to produce both
36302 on-line information and a printed manual. You can use one of the Info
36303 formatting commands to create the on-line version of the documentation
36304 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
36306 @value{GDBN} includes an already formatted copy of the on-line Info
36307 version of this manual in the @file{gdb} subdirectory. The main Info
36308 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
36309 subordinate files matching @samp{gdb.info*} in the same directory. If
36310 necessary, you can print out these files, or read them with any editor;
36311 but they are easier to read using the @code{info} subsystem in @sc{gnu}
36312 Emacs or the standalone @code{info} program, available as part of the
36313 @sc{gnu} Texinfo distribution.
36315 If you want to format these Info files yourself, you need one of the
36316 Info formatting programs, such as @code{texinfo-format-buffer} or
36319 If you have @code{makeinfo} installed, and are in the top level
36320 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
36321 version @value{GDBVN}), you can make the Info file by typing:
36328 If you want to typeset and print copies of this manual, you need @TeX{},
36329 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
36330 Texinfo definitions file.
36332 @TeX{} is a typesetting program; it does not print files directly, but
36333 produces output files called @sc{dvi} files. To print a typeset
36334 document, you need a program to print @sc{dvi} files. If your system
36335 has @TeX{} installed, chances are it has such a program. The precise
36336 command to use depends on your system; @kbd{lpr -d} is common; another
36337 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
36338 require a file name without any extension or a @samp{.dvi} extension.
36340 @TeX{} also requires a macro definitions file called
36341 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
36342 written in Texinfo format. On its own, @TeX{} cannot either read or
36343 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
36344 and is located in the @file{gdb-@var{version-number}/texinfo}
36347 If you have @TeX{} and a @sc{dvi} printer program installed, you can
36348 typeset and print this manual. First switch to the @file{gdb}
36349 subdirectory of the main source directory (for example, to
36350 @file{gdb-@value{GDBVN}/gdb}) and type:
36356 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
36358 @node Installing GDB
36359 @appendix Installing @value{GDBN}
36360 @cindex installation
36363 * Requirements:: Requirements for building @value{GDBN}
36364 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
36365 * Separate Objdir:: Compiling @value{GDBN} in another directory
36366 * Config Names:: Specifying names for hosts and targets
36367 * Configure Options:: Summary of options for configure
36368 * System-wide configuration:: Having a system-wide init file
36372 @section Requirements for Building @value{GDBN}
36373 @cindex building @value{GDBN}, requirements for
36375 Building @value{GDBN} requires various tools and packages to be available.
36376 Other packages will be used only if they are found.
36378 @heading Tools/Packages Necessary for Building @value{GDBN}
36380 @item ISO C90 compiler
36381 @value{GDBN} is written in ISO C90. It should be buildable with any
36382 working C90 compiler, e.g.@: GCC.
36386 @heading Tools/Packages Optional for Building @value{GDBN}
36390 @value{GDBN} can use the Expat XML parsing library. This library may be
36391 included with your operating system distribution; if it is not, you
36392 can get the latest version from @url{http://expat.sourceforge.net}.
36393 The @file{configure} script will search for this library in several
36394 standard locations; if it is installed in an unusual path, you can
36395 use the @option{--with-libexpat-prefix} option to specify its location.
36401 Remote protocol memory maps (@pxref{Memory Map Format})
36403 Target descriptions (@pxref{Target Descriptions})
36405 Remote shared library lists (@xref{Library List Format},
36406 or alternatively @pxref{Library List Format for SVR4 Targets})
36408 MS-Windows shared libraries (@pxref{Shared Libraries})
36410 Traceframe info (@pxref{Traceframe Info Format})
36412 Branch trace (@pxref{Branch Trace Format})
36416 @cindex compressed debug sections
36417 @value{GDBN} will use the @samp{zlib} library, if available, to read
36418 compressed debug sections. Some linkers, such as GNU gold, are capable
36419 of producing binaries with compressed debug sections. If @value{GDBN}
36420 is compiled with @samp{zlib}, it will be able to read the debug
36421 information in such binaries.
36423 The @samp{zlib} library is likely included with your operating system
36424 distribution; if it is not, you can get the latest version from
36425 @url{http://zlib.net}.
36428 @value{GDBN}'s features related to character sets (@pxref{Character
36429 Sets}) require a functioning @code{iconv} implementation. If you are
36430 on a GNU system, then this is provided by the GNU C Library. Some
36431 other systems also provide a working @code{iconv}.
36433 If @value{GDBN} is using the @code{iconv} program which is installed
36434 in a non-standard place, you will need to tell @value{GDBN} where to find it.
36435 This is done with @option{--with-iconv-bin} which specifies the
36436 directory that contains the @code{iconv} program.
36438 On systems without @code{iconv}, you can install GNU Libiconv. If you
36439 have previously installed Libiconv, you can use the
36440 @option{--with-libiconv-prefix} option to configure.
36442 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
36443 arrange to build Libiconv if a directory named @file{libiconv} appears
36444 in the top-most source directory. If Libiconv is built this way, and
36445 if the operating system does not provide a suitable @code{iconv}
36446 implementation, then the just-built library will automatically be used
36447 by @value{GDBN}. One easy way to set this up is to download GNU
36448 Libiconv, unpack it, and then rename the directory holding the
36449 Libiconv source code to @samp{libiconv}.
36452 @node Running Configure
36453 @section Invoking the @value{GDBN} @file{configure} Script
36454 @cindex configuring @value{GDBN}
36455 @value{GDBN} comes with a @file{configure} script that automates the process
36456 of preparing @value{GDBN} for installation; you can then use @code{make} to
36457 build the @code{gdb} program.
36459 @c irrelevant in info file; it's as current as the code it lives with.
36460 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
36461 look at the @file{README} file in the sources; we may have improved the
36462 installation procedures since publishing this manual.}
36465 The @value{GDBN} distribution includes all the source code you need for
36466 @value{GDBN} in a single directory, whose name is usually composed by
36467 appending the version number to @samp{gdb}.
36469 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
36470 @file{gdb-@value{GDBVN}} directory. That directory contains:
36473 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
36474 script for configuring @value{GDBN} and all its supporting libraries
36476 @item gdb-@value{GDBVN}/gdb
36477 the source specific to @value{GDBN} itself
36479 @item gdb-@value{GDBVN}/bfd
36480 source for the Binary File Descriptor library
36482 @item gdb-@value{GDBVN}/include
36483 @sc{gnu} include files
36485 @item gdb-@value{GDBVN}/libiberty
36486 source for the @samp{-liberty} free software library
36488 @item gdb-@value{GDBVN}/opcodes
36489 source for the library of opcode tables and disassemblers
36491 @item gdb-@value{GDBVN}/readline
36492 source for the @sc{gnu} command-line interface
36494 @item gdb-@value{GDBVN}/glob
36495 source for the @sc{gnu} filename pattern-matching subroutine
36497 @item gdb-@value{GDBVN}/mmalloc
36498 source for the @sc{gnu} memory-mapped malloc package
36501 The simplest way to configure and build @value{GDBN} is to run @file{configure}
36502 from the @file{gdb-@var{version-number}} source directory, which in
36503 this example is the @file{gdb-@value{GDBVN}} directory.
36505 First switch to the @file{gdb-@var{version-number}} source directory
36506 if you are not already in it; then run @file{configure}. Pass the
36507 identifier for the platform on which @value{GDBN} will run as an
36513 cd gdb-@value{GDBVN}
36514 ./configure @var{host}
36519 where @var{host} is an identifier such as @samp{sun4} or
36520 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
36521 (You can often leave off @var{host}; @file{configure} tries to guess the
36522 correct value by examining your system.)
36524 Running @samp{configure @var{host}} and then running @code{make} builds the
36525 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
36526 libraries, then @code{gdb} itself. The configured source files, and the
36527 binaries, are left in the corresponding source directories.
36530 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
36531 system does not recognize this automatically when you run a different
36532 shell, you may need to run @code{sh} on it explicitly:
36535 sh configure @var{host}
36538 If you run @file{configure} from a directory that contains source
36539 directories for multiple libraries or programs, such as the
36540 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
36542 creates configuration files for every directory level underneath (unless
36543 you tell it not to, with the @samp{--norecursion} option).
36545 You should run the @file{configure} script from the top directory in the
36546 source tree, the @file{gdb-@var{version-number}} directory. If you run
36547 @file{configure} from one of the subdirectories, you will configure only
36548 that subdirectory. That is usually not what you want. In particular,
36549 if you run the first @file{configure} from the @file{gdb} subdirectory
36550 of the @file{gdb-@var{version-number}} directory, you will omit the
36551 configuration of @file{bfd}, @file{readline}, and other sibling
36552 directories of the @file{gdb} subdirectory. This leads to build errors
36553 about missing include files such as @file{bfd/bfd.h}.
36555 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
36556 However, you should make sure that the shell on your path (named by
36557 the @samp{SHELL} environment variable) is publicly readable. Remember
36558 that @value{GDBN} uses the shell to start your program---some systems refuse to
36559 let @value{GDBN} debug child processes whose programs are not readable.
36561 @node Separate Objdir
36562 @section Compiling @value{GDBN} in Another Directory
36564 If you want to run @value{GDBN} versions for several host or target machines,
36565 you need a different @code{gdb} compiled for each combination of
36566 host and target. @file{configure} is designed to make this easy by
36567 allowing you to generate each configuration in a separate subdirectory,
36568 rather than in the source directory. If your @code{make} program
36569 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
36570 @code{make} in each of these directories builds the @code{gdb}
36571 program specified there.
36573 To build @code{gdb} in a separate directory, run @file{configure}
36574 with the @samp{--srcdir} option to specify where to find the source.
36575 (You also need to specify a path to find @file{configure}
36576 itself from your working directory. If the path to @file{configure}
36577 would be the same as the argument to @samp{--srcdir}, you can leave out
36578 the @samp{--srcdir} option; it is assumed.)
36580 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
36581 separate directory for a Sun 4 like this:
36585 cd gdb-@value{GDBVN}
36588 ../gdb-@value{GDBVN}/configure sun4
36593 When @file{configure} builds a configuration using a remote source
36594 directory, it creates a tree for the binaries with the same structure
36595 (and using the same names) as the tree under the source directory. In
36596 the example, you'd find the Sun 4 library @file{libiberty.a} in the
36597 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
36598 @file{gdb-sun4/gdb}.
36600 Make sure that your path to the @file{configure} script has just one
36601 instance of @file{gdb} in it. If your path to @file{configure} looks
36602 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
36603 one subdirectory of @value{GDBN}, not the whole package. This leads to
36604 build errors about missing include files such as @file{bfd/bfd.h}.
36606 One popular reason to build several @value{GDBN} configurations in separate
36607 directories is to configure @value{GDBN} for cross-compiling (where
36608 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
36609 programs that run on another machine---the @dfn{target}).
36610 You specify a cross-debugging target by
36611 giving the @samp{--target=@var{target}} option to @file{configure}.
36613 When you run @code{make} to build a program or library, you must run
36614 it in a configured directory---whatever directory you were in when you
36615 called @file{configure} (or one of its subdirectories).
36617 The @code{Makefile} that @file{configure} generates in each source
36618 directory also runs recursively. If you type @code{make} in a source
36619 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
36620 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
36621 will build all the required libraries, and then build GDB.
36623 When you have multiple hosts or targets configured in separate
36624 directories, you can run @code{make} on them in parallel (for example,
36625 if they are NFS-mounted on each of the hosts); they will not interfere
36629 @section Specifying Names for Hosts and Targets
36631 The specifications used for hosts and targets in the @file{configure}
36632 script are based on a three-part naming scheme, but some short predefined
36633 aliases are also supported. The full naming scheme encodes three pieces
36634 of information in the following pattern:
36637 @var{architecture}-@var{vendor}-@var{os}
36640 For example, you can use the alias @code{sun4} as a @var{host} argument,
36641 or as the value for @var{target} in a @code{--target=@var{target}}
36642 option. The equivalent full name is @samp{sparc-sun-sunos4}.
36644 The @file{configure} script accompanying @value{GDBN} does not provide
36645 any query facility to list all supported host and target names or
36646 aliases. @file{configure} calls the Bourne shell script
36647 @code{config.sub} to map abbreviations to full names; you can read the
36648 script, if you wish, or you can use it to test your guesses on
36649 abbreviations---for example:
36652 % sh config.sub i386-linux
36654 % sh config.sub alpha-linux
36655 alpha-unknown-linux-gnu
36656 % sh config.sub hp9k700
36658 % sh config.sub sun4
36659 sparc-sun-sunos4.1.1
36660 % sh config.sub sun3
36661 m68k-sun-sunos4.1.1
36662 % sh config.sub i986v
36663 Invalid configuration `i986v': machine `i986v' not recognized
36667 @code{config.sub} is also distributed in the @value{GDBN} source
36668 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
36670 @node Configure Options
36671 @section @file{configure} Options
36673 Here is a summary of the @file{configure} options and arguments that
36674 are most often useful for building @value{GDBN}. @file{configure} also has
36675 several other options not listed here. @inforef{What Configure
36676 Does,,configure.info}, for a full explanation of @file{configure}.
36679 configure @r{[}--help@r{]}
36680 @r{[}--prefix=@var{dir}@r{]}
36681 @r{[}--exec-prefix=@var{dir}@r{]}
36682 @r{[}--srcdir=@var{dirname}@r{]}
36683 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
36684 @r{[}--target=@var{target}@r{]}
36689 You may introduce options with a single @samp{-} rather than
36690 @samp{--} if you prefer; but you may abbreviate option names if you use
36695 Display a quick summary of how to invoke @file{configure}.
36697 @item --prefix=@var{dir}
36698 Configure the source to install programs and files under directory
36701 @item --exec-prefix=@var{dir}
36702 Configure the source to install programs under directory
36705 @c avoid splitting the warning from the explanation:
36707 @item --srcdir=@var{dirname}
36708 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
36709 @code{make} that implements the @code{VPATH} feature.}@*
36710 Use this option to make configurations in directories separate from the
36711 @value{GDBN} source directories. Among other things, you can use this to
36712 build (or maintain) several configurations simultaneously, in separate
36713 directories. @file{configure} writes configuration-specific files in
36714 the current directory, but arranges for them to use the source in the
36715 directory @var{dirname}. @file{configure} creates directories under
36716 the working directory in parallel to the source directories below
36719 @item --norecursion
36720 Configure only the directory level where @file{configure} is executed; do not
36721 propagate configuration to subdirectories.
36723 @item --target=@var{target}
36724 Configure @value{GDBN} for cross-debugging programs running on the specified
36725 @var{target}. Without this option, @value{GDBN} is configured to debug
36726 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
36728 There is no convenient way to generate a list of all available targets.
36730 @item @var{host} @dots{}
36731 Configure @value{GDBN} to run on the specified @var{host}.
36733 There is no convenient way to generate a list of all available hosts.
36736 There are many other options available as well, but they are generally
36737 needed for special purposes only.
36739 @node System-wide configuration
36740 @section System-wide configuration and settings
36741 @cindex system-wide init file
36743 @value{GDBN} can be configured to have a system-wide init file;
36744 this file will be read and executed at startup (@pxref{Startup, , What
36745 @value{GDBN} does during startup}).
36747 Here is the corresponding configure option:
36750 @item --with-system-gdbinit=@var{file}
36751 Specify that the default location of the system-wide init file is
36755 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
36756 it may be subject to relocation. Two possible cases:
36760 If the default location of this init file contains @file{$prefix},
36761 it will be subject to relocation. Suppose that the configure options
36762 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
36763 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
36764 init file is looked for as @file{$install/etc/gdbinit} instead of
36765 @file{$prefix/etc/gdbinit}.
36768 By contrast, if the default location does not contain the prefix,
36769 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
36770 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
36771 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
36772 wherever @value{GDBN} is installed.
36775 If the configured location of the system-wide init file (as given by the
36776 @option{--with-system-gdbinit} option at configure time) is in the
36777 data-directory (as specified by @option{--with-gdb-datadir} at configure
36778 time) or in one of its subdirectories, then @value{GDBN} will look for the
36779 system-wide init file in the directory specified by the
36780 @option{--data-directory} command-line option.
36781 Note that the system-wide init file is only read once, during @value{GDBN}
36782 initialization. If the data-directory is changed after @value{GDBN} has
36783 started with the @code{set data-directory} command, the file will not be
36787 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
36790 @node System-wide Configuration Scripts
36791 @subsection Installed System-wide Configuration Scripts
36792 @cindex system-wide configuration scripts
36794 The @file{system-gdbinit} directory, located inside the data-directory
36795 (as specified by @option{--with-gdb-datadir} at configure time) contains
36796 a number of scripts which can be used as system-wide init files. To
36797 automatically source those scripts at startup, @value{GDBN} should be
36798 configured with @option{--with-system-gdbinit}. Otherwise, any user
36799 should be able to source them by hand as needed.
36801 The following scripts are currently available:
36804 @item @file{elinos.py}
36806 @cindex ELinOS system-wide configuration script
36807 This script is useful when debugging a program on an ELinOS target.
36808 It takes advantage of the environment variables defined in a standard
36809 ELinOS environment in order to determine the location of the system
36810 shared libraries, and then sets the @samp{solib-absolute-prefix}
36811 and @samp{solib-search-path} variables appropriately.
36813 @item @file{wrs-linux.py}
36814 @pindex wrs-linux.py
36815 @cindex Wind River Linux system-wide configuration script
36816 This script is useful when debugging a program on a target running
36817 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
36818 the host-side sysroot used by the target system.
36822 @node Maintenance Commands
36823 @appendix Maintenance Commands
36824 @cindex maintenance commands
36825 @cindex internal commands
36827 In addition to commands intended for @value{GDBN} users, @value{GDBN}
36828 includes a number of commands intended for @value{GDBN} developers,
36829 that are not documented elsewhere in this manual. These commands are
36830 provided here for reference. (For commands that turn on debugging
36831 messages, see @ref{Debugging Output}.)
36834 @kindex maint agent
36835 @kindex maint agent-eval
36836 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
36837 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
36838 Translate the given @var{expression} into remote agent bytecodes.
36839 This command is useful for debugging the Agent Expression mechanism
36840 (@pxref{Agent Expressions}). The @samp{agent} version produces an
36841 expression useful for data collection, such as by tracepoints, while
36842 @samp{maint agent-eval} produces an expression that evaluates directly
36843 to a result. For instance, a collection expression for @code{globa +
36844 globb} will include bytecodes to record four bytes of memory at each
36845 of the addresses of @code{globa} and @code{globb}, while discarding
36846 the result of the addition, while an evaluation expression will do the
36847 addition and return the sum.
36848 If @code{-at} is given, generate remote agent bytecode for @var{location}.
36849 If not, generate remote agent bytecode for current frame PC address.
36851 @kindex maint agent-printf
36852 @item maint agent-printf @var{format},@var{expr},...
36853 Translate the given format string and list of argument expressions
36854 into remote agent bytecodes and display them as a disassembled list.
36855 This command is useful for debugging the agent version of dynamic
36856 printf (@pxref{Dynamic Printf}).
36858 @kindex maint info breakpoints
36859 @item @anchor{maint info breakpoints}maint info breakpoints
36860 Using the same format as @samp{info breakpoints}, display both the
36861 breakpoints you've set explicitly, and those @value{GDBN} is using for
36862 internal purposes. Internal breakpoints are shown with negative
36863 breakpoint numbers. The type column identifies what kind of breakpoint
36868 Normal, explicitly set breakpoint.
36871 Normal, explicitly set watchpoint.
36874 Internal breakpoint, used to handle correctly stepping through
36875 @code{longjmp} calls.
36877 @item longjmp resume
36878 Internal breakpoint at the target of a @code{longjmp}.
36881 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
36884 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
36887 Shared library events.
36891 @kindex maint info bfds
36892 @item maint info bfds
36893 This prints information about each @code{bfd} object that is known to
36894 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
36896 @kindex set displaced-stepping
36897 @kindex show displaced-stepping
36898 @cindex displaced stepping support
36899 @cindex out-of-line single-stepping
36900 @item set displaced-stepping
36901 @itemx show displaced-stepping
36902 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
36903 if the target supports it. Displaced stepping is a way to single-step
36904 over breakpoints without removing them from the inferior, by executing
36905 an out-of-line copy of the instruction that was originally at the
36906 breakpoint location. It is also known as out-of-line single-stepping.
36909 @item set displaced-stepping on
36910 If the target architecture supports it, @value{GDBN} will use
36911 displaced stepping to step over breakpoints.
36913 @item set displaced-stepping off
36914 @value{GDBN} will not use displaced stepping to step over breakpoints,
36915 even if such is supported by the target architecture.
36917 @cindex non-stop mode, and @samp{set displaced-stepping}
36918 @item set displaced-stepping auto
36919 This is the default mode. @value{GDBN} will use displaced stepping
36920 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
36921 architecture supports displaced stepping.
36924 @kindex maint check-psymtabs
36925 @item maint check-psymtabs
36926 Check the consistency of currently expanded psymtabs versus symtabs.
36927 Use this to check, for example, whether a symbol is in one but not the other.
36929 @kindex maint check-symtabs
36930 @item maint check-symtabs
36931 Check the consistency of currently expanded symtabs.
36933 @kindex maint expand-symtabs
36934 @item maint expand-symtabs [@var{regexp}]
36935 Expand symbol tables.
36936 If @var{regexp} is specified, only expand symbol tables for file
36937 names matching @var{regexp}.
36939 @kindex maint cplus first_component
36940 @item maint cplus first_component @var{name}
36941 Print the first C@t{++} class/namespace component of @var{name}.
36943 @kindex maint cplus namespace
36944 @item maint cplus namespace
36945 Print the list of possible C@t{++} namespaces.
36947 @kindex maint demangle
36948 @item maint demangle @var{name}
36949 Demangle a C@t{++} or Objective-C mangled @var{name}.
36951 @kindex maint deprecate
36952 @kindex maint undeprecate
36953 @cindex deprecated commands
36954 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
36955 @itemx maint undeprecate @var{command}
36956 Deprecate or undeprecate the named @var{command}. Deprecated commands
36957 cause @value{GDBN} to issue a warning when you use them. The optional
36958 argument @var{replacement} says which newer command should be used in
36959 favor of the deprecated one; if it is given, @value{GDBN} will mention
36960 the replacement as part of the warning.
36962 @kindex maint dump-me
36963 @item maint dump-me
36964 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
36965 Cause a fatal signal in the debugger and force it to dump its core.
36966 This is supported only on systems which support aborting a program
36967 with the @code{SIGQUIT} signal.
36969 @kindex maint internal-error
36970 @kindex maint internal-warning
36971 @item maint internal-error @r{[}@var{message-text}@r{]}
36972 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
36973 Cause @value{GDBN} to call the internal function @code{internal_error}
36974 or @code{internal_warning} and hence behave as though an internal error
36975 or internal warning has been detected. In addition to reporting the
36976 internal problem, these functions give the user the opportunity to
36977 either quit @value{GDBN} or create a core file of the current
36978 @value{GDBN} session.
36980 These commands take an optional parameter @var{message-text} that is
36981 used as the text of the error or warning message.
36983 Here's an example of using @code{internal-error}:
36986 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
36987 @dots{}/maint.c:121: internal-error: testing, 1, 2
36988 A problem internal to GDB has been detected. Further
36989 debugging may prove unreliable.
36990 Quit this debugging session? (y or n) @kbd{n}
36991 Create a core file? (y or n) @kbd{n}
36995 @cindex @value{GDBN} internal error
36996 @cindex internal errors, control of @value{GDBN} behavior
36998 @kindex maint set internal-error
36999 @kindex maint show internal-error
37000 @kindex maint set internal-warning
37001 @kindex maint show internal-warning
37002 @item maint set internal-error @var{action} [ask|yes|no]
37003 @itemx maint show internal-error @var{action}
37004 @itemx maint set internal-warning @var{action} [ask|yes|no]
37005 @itemx maint show internal-warning @var{action}
37006 When @value{GDBN} reports an internal problem (error or warning) it
37007 gives the user the opportunity to both quit @value{GDBN} and create a
37008 core file of the current @value{GDBN} session. These commands let you
37009 override the default behaviour for each particular @var{action},
37010 described in the table below.
37014 You can specify that @value{GDBN} should always (yes) or never (no)
37015 quit. The default is to ask the user what to do.
37018 You can specify that @value{GDBN} should always (yes) or never (no)
37019 create a core file. The default is to ask the user what to do.
37022 @kindex maint packet
37023 @item maint packet @var{text}
37024 If @value{GDBN} is talking to an inferior via the serial protocol,
37025 then this command sends the string @var{text} to the inferior, and
37026 displays the response packet. @value{GDBN} supplies the initial
37027 @samp{$} character, the terminating @samp{#} character, and the
37030 @kindex maint print architecture
37031 @item maint print architecture @r{[}@var{file}@r{]}
37032 Print the entire architecture configuration. The optional argument
37033 @var{file} names the file where the output goes.
37035 @kindex maint print c-tdesc
37036 @item maint print c-tdesc
37037 Print the current target description (@pxref{Target Descriptions}) as
37038 a C source file. The created source file can be used in @value{GDBN}
37039 when an XML parser is not available to parse the description.
37041 @kindex maint print dummy-frames
37042 @item maint print dummy-frames
37043 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
37046 (@value{GDBP}) @kbd{b add}
37048 (@value{GDBP}) @kbd{print add(2,3)}
37049 Breakpoint 2, add (a=2, b=3) at @dots{}
37051 The program being debugged stopped while in a function called from GDB.
37053 (@value{GDBP}) @kbd{maint print dummy-frames}
37054 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
37055 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
37056 call_lo=0x01014000 call_hi=0x01014001
37060 Takes an optional file parameter.
37062 @kindex maint print registers
37063 @kindex maint print raw-registers
37064 @kindex maint print cooked-registers
37065 @kindex maint print register-groups
37066 @kindex maint print remote-registers
37067 @item maint print registers @r{[}@var{file}@r{]}
37068 @itemx maint print raw-registers @r{[}@var{file}@r{]}
37069 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
37070 @itemx maint print register-groups @r{[}@var{file}@r{]}
37071 @itemx maint print remote-registers @r{[}@var{file}@r{]}
37072 Print @value{GDBN}'s internal register data structures.
37074 The command @code{maint print raw-registers} includes the contents of
37075 the raw register cache; the command @code{maint print
37076 cooked-registers} includes the (cooked) value of all registers,
37077 including registers which aren't available on the target nor visible
37078 to user; the command @code{maint print register-groups} includes the
37079 groups that each register is a member of; and the command @code{maint
37080 print remote-registers} includes the remote target's register numbers
37081 and offsets in the `G' packets.
37083 These commands take an optional parameter, a file name to which to
37084 write the information.
37086 @kindex maint print reggroups
37087 @item maint print reggroups @r{[}@var{file}@r{]}
37088 Print @value{GDBN}'s internal register group data structures. The
37089 optional argument @var{file} tells to what file to write the
37092 The register groups info looks like this:
37095 (@value{GDBP}) @kbd{maint print reggroups}
37108 This command forces @value{GDBN} to flush its internal register cache.
37110 @kindex maint print objfiles
37111 @cindex info for known object files
37112 @item maint print objfiles @r{[}@var{regexp}@r{]}
37113 Print a dump of all known object files.
37114 If @var{regexp} is specified, only print object files whose names
37115 match @var{regexp}. For each object file, this command prints its name,
37116 address in memory, and all of its psymtabs and symtabs.
37118 @kindex maint print section-scripts
37119 @cindex info for known .debug_gdb_scripts-loaded scripts
37120 @item maint print section-scripts [@var{regexp}]
37121 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
37122 If @var{regexp} is specified, only print scripts loaded by object files
37123 matching @var{regexp}.
37124 For each script, this command prints its name as specified in the objfile,
37125 and the full path if known.
37126 @xref{dotdebug_gdb_scripts section}.
37128 @kindex maint print statistics
37129 @cindex bcache statistics
37130 @item maint print statistics
37131 This command prints, for each object file in the program, various data
37132 about that object file followed by the byte cache (@dfn{bcache})
37133 statistics for the object file. The objfile data includes the number
37134 of minimal, partial, full, and stabs symbols, the number of types
37135 defined by the objfile, the number of as yet unexpanded psym tables,
37136 the number of line tables and string tables, and the amount of memory
37137 used by the various tables. The bcache statistics include the counts,
37138 sizes, and counts of duplicates of all and unique objects, max,
37139 average, and median entry size, total memory used and its overhead and
37140 savings, and various measures of the hash table size and chain
37143 @kindex maint print target-stack
37144 @cindex target stack description
37145 @item maint print target-stack
37146 A @dfn{target} is an interface between the debugger and a particular
37147 kind of file or process. Targets can be stacked in @dfn{strata},
37148 so that more than one target can potentially respond to a request.
37149 In particular, memory accesses will walk down the stack of targets
37150 until they find a target that is interested in handling that particular
37153 This command prints a short description of each layer that was pushed on
37154 the @dfn{target stack}, starting from the top layer down to the bottom one.
37156 @kindex maint print type
37157 @cindex type chain of a data type
37158 @item maint print type @var{expr}
37159 Print the type chain for a type specified by @var{expr}. The argument
37160 can be either a type name or a symbol. If it is a symbol, the type of
37161 that symbol is described. The type chain produced by this command is
37162 a recursive definition of the data type as stored in @value{GDBN}'s
37163 data structures, including its flags and contained types.
37165 @kindex maint set dwarf2 always-disassemble
37166 @kindex maint show dwarf2 always-disassemble
37167 @item maint set dwarf2 always-disassemble
37168 @item maint show dwarf2 always-disassemble
37169 Control the behavior of @code{info address} when using DWARF debugging
37172 The default is @code{off}, which means that @value{GDBN} should try to
37173 describe a variable's location in an easily readable format. When
37174 @code{on}, @value{GDBN} will instead display the DWARF location
37175 expression in an assembly-like format. Note that some locations are
37176 too complex for @value{GDBN} to describe simply; in this case you will
37177 always see the disassembly form.
37179 Here is an example of the resulting disassembly:
37182 (gdb) info addr argc
37183 Symbol "argc" is a complex DWARF expression:
37187 For more information on these expressions, see
37188 @uref{http://www.dwarfstd.org/, the DWARF standard}.
37190 @kindex maint set dwarf2 max-cache-age
37191 @kindex maint show dwarf2 max-cache-age
37192 @item maint set dwarf2 max-cache-age
37193 @itemx maint show dwarf2 max-cache-age
37194 Control the DWARF 2 compilation unit cache.
37196 @cindex DWARF 2 compilation units cache
37197 In object files with inter-compilation-unit references, such as those
37198 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
37199 reader needs to frequently refer to previously read compilation units.
37200 This setting controls how long a compilation unit will remain in the
37201 cache if it is not referenced. A higher limit means that cached
37202 compilation units will be stored in memory longer, and more total
37203 memory will be used. Setting it to zero disables caching, which will
37204 slow down @value{GDBN} startup, but reduce memory consumption.
37206 @kindex maint set profile
37207 @kindex maint show profile
37208 @cindex profiling GDB
37209 @item maint set profile
37210 @itemx maint show profile
37211 Control profiling of @value{GDBN}.
37213 Profiling will be disabled until you use the @samp{maint set profile}
37214 command to enable it. When you enable profiling, the system will begin
37215 collecting timing and execution count data; when you disable profiling or
37216 exit @value{GDBN}, the results will be written to a log file. Remember that
37217 if you use profiling, @value{GDBN} will overwrite the profiling log file
37218 (often called @file{gmon.out}). If you have a record of important profiling
37219 data in a @file{gmon.out} file, be sure to move it to a safe location.
37221 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
37222 compiled with the @samp{-pg} compiler option.
37224 @kindex maint set show-debug-regs
37225 @kindex maint show show-debug-regs
37226 @cindex hardware debug registers
37227 @item maint set show-debug-regs
37228 @itemx maint show show-debug-regs
37229 Control whether to show variables that mirror the hardware debug
37230 registers. Use @code{ON} to enable, @code{OFF} to disable. If
37231 enabled, the debug registers values are shown when @value{GDBN} inserts or
37232 removes a hardware breakpoint or watchpoint, and when the inferior
37233 triggers a hardware-assisted breakpoint or watchpoint.
37235 @kindex maint set show-all-tib
37236 @kindex maint show show-all-tib
37237 @item maint set show-all-tib
37238 @itemx maint show show-all-tib
37239 Control whether to show all non zero areas within a 1k block starting
37240 at thread local base, when using the @samp{info w32 thread-information-block}
37243 @kindex maint set per-command
37244 @kindex maint show per-command
37245 @item maint set per-command
37246 @itemx maint show per-command
37247 @cindex resources used by commands
37249 @value{GDBN} can display the resources used by each command.
37250 This is useful in debugging performance problems.
37253 @item maint set per-command space [on|off]
37254 @itemx maint show per-command space
37255 Enable or disable the printing of the memory used by GDB for each command.
37256 If enabled, @value{GDBN} will display how much memory each command
37257 took, following the command's own output.
37258 This can also be requested by invoking @value{GDBN} with the
37259 @option{--statistics} command-line switch (@pxref{Mode Options}).
37261 @item maint set per-command time [on|off]
37262 @itemx maint show per-command time
37263 Enable or disable the printing of the execution time of @value{GDBN}
37265 If enabled, @value{GDBN} will display how much time it
37266 took to execute each command, following the command's own output.
37267 Both CPU time and wallclock time are printed.
37268 Printing both is useful when trying to determine whether the cost is
37269 CPU or, e.g., disk/network latency.
37270 Note that the CPU time printed is for @value{GDBN} only, it does not include
37271 the execution time of the inferior because there's no mechanism currently
37272 to compute how much time was spent by @value{GDBN} and how much time was
37273 spent by the program been debugged.
37274 This can also be requested by invoking @value{GDBN} with the
37275 @option{--statistics} command-line switch (@pxref{Mode Options}).
37277 @item maint set per-command symtab [on|off]
37278 @itemx maint show per-command symtab
37279 Enable or disable the printing of basic symbol table statistics
37281 If enabled, @value{GDBN} will display the following information:
37285 number of symbol tables
37287 number of primary symbol tables
37289 number of blocks in the blockvector
37293 @kindex maint space
37294 @cindex memory used by commands
37295 @item maint space @var{value}
37296 An alias for @code{maint set per-command space}.
37297 A non-zero value enables it, zero disables it.
37300 @cindex time of command execution
37301 @item maint time @var{value}
37302 An alias for @code{maint set per-command time}.
37303 A non-zero value enables it, zero disables it.
37305 @kindex maint translate-address
37306 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
37307 Find the symbol stored at the location specified by the address
37308 @var{addr} and an optional section name @var{section}. If found,
37309 @value{GDBN} prints the name of the closest symbol and an offset from
37310 the symbol's location to the specified address. This is similar to
37311 the @code{info address} command (@pxref{Symbols}), except that this
37312 command also allows to find symbols in other sections.
37314 If section was not specified, the section in which the symbol was found
37315 is also printed. For dynamically linked executables, the name of
37316 executable or shared library containing the symbol is printed as well.
37320 The following command is useful for non-interactive invocations of
37321 @value{GDBN}, such as in the test suite.
37324 @item set watchdog @var{nsec}
37325 @kindex set watchdog
37326 @cindex watchdog timer
37327 @cindex timeout for commands
37328 Set the maximum number of seconds @value{GDBN} will wait for the
37329 target operation to finish. If this time expires, @value{GDBN}
37330 reports and error and the command is aborted.
37332 @item show watchdog
37333 Show the current setting of the target wait timeout.
37336 @node Remote Protocol
37337 @appendix @value{GDBN} Remote Serial Protocol
37342 * Stop Reply Packets::
37343 * General Query Packets::
37344 * Architecture-Specific Protocol Details::
37345 * Tracepoint Packets::
37346 * Host I/O Packets::
37348 * Notification Packets::
37349 * Remote Non-Stop::
37350 * Packet Acknowledgment::
37352 * File-I/O Remote Protocol Extension::
37353 * Library List Format::
37354 * Library List Format for SVR4 Targets::
37355 * Memory Map Format::
37356 * Thread List Format::
37357 * Traceframe Info Format::
37358 * Branch Trace Format::
37364 There may be occasions when you need to know something about the
37365 protocol---for example, if there is only one serial port to your target
37366 machine, you might want your program to do something special if it
37367 recognizes a packet meant for @value{GDBN}.
37369 In the examples below, @samp{->} and @samp{<-} are used to indicate
37370 transmitted and received data, respectively.
37372 @cindex protocol, @value{GDBN} remote serial
37373 @cindex serial protocol, @value{GDBN} remote
37374 @cindex remote serial protocol
37375 All @value{GDBN} commands and responses (other than acknowledgments
37376 and notifications, see @ref{Notification Packets}) are sent as a
37377 @var{packet}. A @var{packet} is introduced with the character
37378 @samp{$}, the actual @var{packet-data}, and the terminating character
37379 @samp{#} followed by a two-digit @var{checksum}:
37382 @code{$}@var{packet-data}@code{#}@var{checksum}
37386 @cindex checksum, for @value{GDBN} remote
37388 The two-digit @var{checksum} is computed as the modulo 256 sum of all
37389 characters between the leading @samp{$} and the trailing @samp{#} (an
37390 eight bit unsigned checksum).
37392 Implementors should note that prior to @value{GDBN} 5.0 the protocol
37393 specification also included an optional two-digit @var{sequence-id}:
37396 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
37399 @cindex sequence-id, for @value{GDBN} remote
37401 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
37402 has never output @var{sequence-id}s. Stubs that handle packets added
37403 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
37405 When either the host or the target machine receives a packet, the first
37406 response expected is an acknowledgment: either @samp{+} (to indicate
37407 the package was received correctly) or @samp{-} (to request
37411 -> @code{$}@var{packet-data}@code{#}@var{checksum}
37416 The @samp{+}/@samp{-} acknowledgments can be disabled
37417 once a connection is established.
37418 @xref{Packet Acknowledgment}, for details.
37420 The host (@value{GDBN}) sends @var{command}s, and the target (the
37421 debugging stub incorporated in your program) sends a @var{response}. In
37422 the case of step and continue @var{command}s, the response is only sent
37423 when the operation has completed, and the target has again stopped all
37424 threads in all attached processes. This is the default all-stop mode
37425 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
37426 execution mode; see @ref{Remote Non-Stop}, for details.
37428 @var{packet-data} consists of a sequence of characters with the
37429 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
37432 @cindex remote protocol, field separator
37433 Fields within the packet should be separated using @samp{,} @samp{;} or
37434 @samp{:}. Except where otherwise noted all numbers are represented in
37435 @sc{hex} with leading zeros suppressed.
37437 Implementors should note that prior to @value{GDBN} 5.0, the character
37438 @samp{:} could not appear as the third character in a packet (as it
37439 would potentially conflict with the @var{sequence-id}).
37441 @cindex remote protocol, binary data
37442 @anchor{Binary Data}
37443 Binary data in most packets is encoded either as two hexadecimal
37444 digits per byte of binary data. This allowed the traditional remote
37445 protocol to work over connections which were only seven-bit clean.
37446 Some packets designed more recently assume an eight-bit clean
37447 connection, and use a more efficient encoding to send and receive
37450 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
37451 as an escape character. Any escaped byte is transmitted as the escape
37452 character followed by the original character XORed with @code{0x20}.
37453 For example, the byte @code{0x7d} would be transmitted as the two
37454 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
37455 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
37456 @samp{@}}) must always be escaped. Responses sent by the stub
37457 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
37458 is not interpreted as the start of a run-length encoded sequence
37461 Response @var{data} can be run-length encoded to save space.
37462 Run-length encoding replaces runs of identical characters with one
37463 instance of the repeated character, followed by a @samp{*} and a
37464 repeat count. The repeat count is itself sent encoded, to avoid
37465 binary characters in @var{data}: a value of @var{n} is sent as
37466 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
37467 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
37468 code 32) for a repeat count of 3. (This is because run-length
37469 encoding starts to win for counts 3 or more.) Thus, for example,
37470 @samp{0* } is a run-length encoding of ``0000'': the space character
37471 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
37474 The printable characters @samp{#} and @samp{$} or with a numeric value
37475 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
37476 seven repeats (@samp{$}) can be expanded using a repeat count of only
37477 five (@samp{"}). For example, @samp{00000000} can be encoded as
37480 The error response returned for some packets includes a two character
37481 error number. That number is not well defined.
37483 @cindex empty response, for unsupported packets
37484 For any @var{command} not supported by the stub, an empty response
37485 (@samp{$#00}) should be returned. That way it is possible to extend the
37486 protocol. A newer @value{GDBN} can tell if a packet is supported based
37489 At a minimum, a stub is required to support the @samp{g} and @samp{G}
37490 commands for register access, and the @samp{m} and @samp{M} commands
37491 for memory access. Stubs that only control single-threaded targets
37492 can implement run control with the @samp{c} (continue), and @samp{s}
37493 (step) commands. Stubs that support multi-threading targets should
37494 support the @samp{vCont} command. All other commands are optional.
37499 The following table provides a complete list of all currently defined
37500 @var{command}s and their corresponding response @var{data}.
37501 @xref{File-I/O Remote Protocol Extension}, for details about the File
37502 I/O extension of the remote protocol.
37504 Each packet's description has a template showing the packet's overall
37505 syntax, followed by an explanation of the packet's meaning. We
37506 include spaces in some of the templates for clarity; these are not
37507 part of the packet's syntax. No @value{GDBN} packet uses spaces to
37508 separate its components. For example, a template like @samp{foo
37509 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
37510 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
37511 @var{baz}. @value{GDBN} does not transmit a space character between the
37512 @samp{foo} and the @var{bar}, or between the @var{bar} and the
37515 @cindex @var{thread-id}, in remote protocol
37516 @anchor{thread-id syntax}
37517 Several packets and replies include a @var{thread-id} field to identify
37518 a thread. Normally these are positive numbers with a target-specific
37519 interpretation, formatted as big-endian hex strings. A @var{thread-id}
37520 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
37523 In addition, the remote protocol supports a multiprocess feature in
37524 which the @var{thread-id} syntax is extended to optionally include both
37525 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
37526 The @var{pid} (process) and @var{tid} (thread) components each have the
37527 format described above: a positive number with target-specific
37528 interpretation formatted as a big-endian hex string, literal @samp{-1}
37529 to indicate all processes or threads (respectively), or @samp{0} to
37530 indicate an arbitrary process or thread. Specifying just a process, as
37531 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
37532 error to specify all processes but a specific thread, such as
37533 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
37534 for those packets and replies explicitly documented to include a process
37535 ID, rather than a @var{thread-id}.
37537 The multiprocess @var{thread-id} syntax extensions are only used if both
37538 @value{GDBN} and the stub report support for the @samp{multiprocess}
37539 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
37542 Note that all packet forms beginning with an upper- or lower-case
37543 letter, other than those described here, are reserved for future use.
37545 Here are the packet descriptions.
37550 @cindex @samp{!} packet
37551 @anchor{extended mode}
37552 Enable extended mode. In extended mode, the remote server is made
37553 persistent. The @samp{R} packet is used to restart the program being
37559 The remote target both supports and has enabled extended mode.
37563 @cindex @samp{?} packet
37564 Indicate the reason the target halted. The reply is the same as for
37565 step and continue. This packet has a special interpretation when the
37566 target is in non-stop mode; see @ref{Remote Non-Stop}.
37569 @xref{Stop Reply Packets}, for the reply specifications.
37571 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
37572 @cindex @samp{A} packet
37573 Initialized @code{argv[]} array passed into program. @var{arglen}
37574 specifies the number of bytes in the hex encoded byte stream
37575 @var{arg}. See @code{gdbserver} for more details.
37580 The arguments were set.
37586 @cindex @samp{b} packet
37587 (Don't use this packet; its behavior is not well-defined.)
37588 Change the serial line speed to @var{baud}.
37590 JTC: @emph{When does the transport layer state change? When it's
37591 received, or after the ACK is transmitted. In either case, there are
37592 problems if the command or the acknowledgment packet is dropped.}
37594 Stan: @emph{If people really wanted to add something like this, and get
37595 it working for the first time, they ought to modify ser-unix.c to send
37596 some kind of out-of-band message to a specially-setup stub and have the
37597 switch happen "in between" packets, so that from remote protocol's point
37598 of view, nothing actually happened.}
37600 @item B @var{addr},@var{mode}
37601 @cindex @samp{B} packet
37602 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
37603 breakpoint at @var{addr}.
37605 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
37606 (@pxref{insert breakpoint or watchpoint packet}).
37608 @cindex @samp{bc} packet
37611 Backward continue. Execute the target system in reverse. No parameter.
37612 @xref{Reverse Execution}, for more information.
37615 @xref{Stop Reply Packets}, for the reply specifications.
37617 @cindex @samp{bs} packet
37620 Backward single step. Execute one instruction in reverse. No parameter.
37621 @xref{Reverse Execution}, for more information.
37624 @xref{Stop Reply Packets}, for the reply specifications.
37626 @item c @r{[}@var{addr}@r{]}
37627 @cindex @samp{c} packet
37628 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
37629 resume at current address.
37631 This packet is deprecated for multi-threading support. @xref{vCont
37635 @xref{Stop Reply Packets}, for the reply specifications.
37637 @item C @var{sig}@r{[};@var{addr}@r{]}
37638 @cindex @samp{C} packet
37639 Continue with signal @var{sig} (hex signal number). If
37640 @samp{;@var{addr}} is omitted, resume at same address.
37642 This packet is deprecated for multi-threading support. @xref{vCont
37646 @xref{Stop Reply Packets}, for the reply specifications.
37649 @cindex @samp{d} packet
37652 Don't use this packet; instead, define a general set packet
37653 (@pxref{General Query Packets}).
37657 @cindex @samp{D} packet
37658 The first form of the packet is used to detach @value{GDBN} from the
37659 remote system. It is sent to the remote target
37660 before @value{GDBN} disconnects via the @code{detach} command.
37662 The second form, including a process ID, is used when multiprocess
37663 protocol extensions are enabled (@pxref{multiprocess extensions}), to
37664 detach only a specific process. The @var{pid} is specified as a
37665 big-endian hex string.
37675 @item F @var{RC},@var{EE},@var{CF};@var{XX}
37676 @cindex @samp{F} packet
37677 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
37678 This is part of the File-I/O protocol extension. @xref{File-I/O
37679 Remote Protocol Extension}, for the specification.
37682 @anchor{read registers packet}
37683 @cindex @samp{g} packet
37684 Read general registers.
37688 @item @var{XX@dots{}}
37689 Each byte of register data is described by two hex digits. The bytes
37690 with the register are transmitted in target byte order. The size of
37691 each register and their position within the @samp{g} packet are
37692 determined by the @value{GDBN} internal gdbarch functions
37693 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
37694 specification of several standard @samp{g} packets is specified below.
37696 When reading registers from a trace frame (@pxref{Analyze Collected
37697 Data,,Using the Collected Data}), the stub may also return a string of
37698 literal @samp{x}'s in place of the register data digits, to indicate
37699 that the corresponding register has not been collected, thus its value
37700 is unavailable. For example, for an architecture with 4 registers of
37701 4 bytes each, the following reply indicates to @value{GDBN} that
37702 registers 0 and 2 have not been collected, while registers 1 and 3
37703 have been collected, and both have zero value:
37707 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
37714 @item G @var{XX@dots{}}
37715 @cindex @samp{G} packet
37716 Write general registers. @xref{read registers packet}, for a
37717 description of the @var{XX@dots{}} data.
37727 @item H @var{op} @var{thread-id}
37728 @cindex @samp{H} packet
37729 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
37730 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
37731 it should be @samp{c} for step and continue operations (note that this
37732 is deprecated, supporting the @samp{vCont} command is a better
37733 option), @samp{g} for other operations. The thread designator
37734 @var{thread-id} has the format and interpretation described in
37735 @ref{thread-id syntax}.
37746 @c 'H': How restrictive (or permissive) is the thread model. If a
37747 @c thread is selected and stopped, are other threads allowed
37748 @c to continue to execute? As I mentioned above, I think the
37749 @c semantics of each command when a thread is selected must be
37750 @c described. For example:
37752 @c 'g': If the stub supports threads and a specific thread is
37753 @c selected, returns the register block from that thread;
37754 @c otherwise returns current registers.
37756 @c 'G' If the stub supports threads and a specific thread is
37757 @c selected, sets the registers of the register block of
37758 @c that thread; otherwise sets current registers.
37760 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
37761 @anchor{cycle step packet}
37762 @cindex @samp{i} packet
37763 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
37764 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
37765 step starting at that address.
37768 @cindex @samp{I} packet
37769 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
37773 @cindex @samp{k} packet
37776 FIXME: @emph{There is no description of how to operate when a specific
37777 thread context has been selected (i.e.@: does 'k' kill only that
37780 @item m @var{addr},@var{length}
37781 @cindex @samp{m} packet
37782 Read @var{length} bytes of memory starting at address @var{addr}.
37783 Note that @var{addr} may not be aligned to any particular boundary.
37785 The stub need not use any particular size or alignment when gathering
37786 data from memory for the response; even if @var{addr} is word-aligned
37787 and @var{length} is a multiple of the word size, the stub is free to
37788 use byte accesses, or not. For this reason, this packet may not be
37789 suitable for accessing memory-mapped I/O devices.
37790 @cindex alignment of remote memory accesses
37791 @cindex size of remote memory accesses
37792 @cindex memory, alignment and size of remote accesses
37796 @item @var{XX@dots{}}
37797 Memory contents; each byte is transmitted as a two-digit hexadecimal
37798 number. The reply may contain fewer bytes than requested if the
37799 server was able to read only part of the region of memory.
37804 @item M @var{addr},@var{length}:@var{XX@dots{}}
37805 @cindex @samp{M} packet
37806 Write @var{length} bytes of memory starting at address @var{addr}.
37807 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
37808 hexadecimal number.
37815 for an error (this includes the case where only part of the data was
37820 @cindex @samp{p} packet
37821 Read the value of register @var{n}; @var{n} is in hex.
37822 @xref{read registers packet}, for a description of how the returned
37823 register value is encoded.
37827 @item @var{XX@dots{}}
37828 the register's value
37832 Indicating an unrecognized @var{query}.
37835 @item P @var{n@dots{}}=@var{r@dots{}}
37836 @anchor{write register packet}
37837 @cindex @samp{P} packet
37838 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
37839 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
37840 digits for each byte in the register (target byte order).
37850 @item q @var{name} @var{params}@dots{}
37851 @itemx Q @var{name} @var{params}@dots{}
37852 @cindex @samp{q} packet
37853 @cindex @samp{Q} packet
37854 General query (@samp{q}) and set (@samp{Q}). These packets are
37855 described fully in @ref{General Query Packets}.
37858 @cindex @samp{r} packet
37859 Reset the entire system.
37861 Don't use this packet; use the @samp{R} packet instead.
37864 @cindex @samp{R} packet
37865 Restart the program being debugged. @var{XX}, while needed, is ignored.
37866 This packet is only available in extended mode (@pxref{extended mode}).
37868 The @samp{R} packet has no reply.
37870 @item s @r{[}@var{addr}@r{]}
37871 @cindex @samp{s} packet
37872 Single step. @var{addr} is the address at which to resume. If
37873 @var{addr} is omitted, resume at same address.
37875 This packet is deprecated for multi-threading support. @xref{vCont
37879 @xref{Stop Reply Packets}, for the reply specifications.
37881 @item S @var{sig}@r{[};@var{addr}@r{]}
37882 @anchor{step with signal packet}
37883 @cindex @samp{S} packet
37884 Step with signal. This is analogous to the @samp{C} packet, but
37885 requests a single-step, rather than a normal resumption of execution.
37887 This packet is deprecated for multi-threading support. @xref{vCont
37891 @xref{Stop Reply Packets}, for the reply specifications.
37893 @item t @var{addr}:@var{PP},@var{MM}
37894 @cindex @samp{t} packet
37895 Search backwards starting at address @var{addr} for a match with pattern
37896 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
37897 @var{addr} must be at least 3 digits.
37899 @item T @var{thread-id}
37900 @cindex @samp{T} packet
37901 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
37906 thread is still alive
37912 Packets starting with @samp{v} are identified by a multi-letter name,
37913 up to the first @samp{;} or @samp{?} (or the end of the packet).
37915 @item vAttach;@var{pid}
37916 @cindex @samp{vAttach} packet
37917 Attach to a new process with the specified process ID @var{pid}.
37918 The process ID is a
37919 hexadecimal integer identifying the process. In all-stop mode, all
37920 threads in the attached process are stopped; in non-stop mode, it may be
37921 attached without being stopped if that is supported by the target.
37923 @c In non-stop mode, on a successful vAttach, the stub should set the
37924 @c current thread to a thread of the newly-attached process. After
37925 @c attaching, GDB queries for the attached process's thread ID with qC.
37926 @c Also note that, from a user perspective, whether or not the
37927 @c target is stopped on attach in non-stop mode depends on whether you
37928 @c use the foreground or background version of the attach command, not
37929 @c on what vAttach does; GDB does the right thing with respect to either
37930 @c stopping or restarting threads.
37932 This packet is only available in extended mode (@pxref{extended mode}).
37938 @item @r{Any stop packet}
37939 for success in all-stop mode (@pxref{Stop Reply Packets})
37941 for success in non-stop mode (@pxref{Remote Non-Stop})
37944 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
37945 @cindex @samp{vCont} packet
37946 @anchor{vCont packet}
37947 Resume the inferior, specifying different actions for each thread.
37948 If an action is specified with no @var{thread-id}, then it is applied to any
37949 threads that don't have a specific action specified; if no default action is
37950 specified then other threads should remain stopped in all-stop mode and
37951 in their current state in non-stop mode.
37952 Specifying multiple
37953 default actions is an error; specifying no actions is also an error.
37954 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
37956 Currently supported actions are:
37962 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
37966 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
37969 @item r @var{start},@var{end}
37970 Step once, and then keep stepping as long as the thread stops at
37971 addresses between @var{start} (inclusive) and @var{end} (exclusive).
37972 The remote stub reports a stop reply when either the thread goes out
37973 of the range or is stopped due to an unrelated reason, such as hitting
37974 a breakpoint. @xref{range stepping}.
37976 If the range is empty (@var{start} == @var{end}), then the action
37977 becomes equivalent to the @samp{s} action. In other words,
37978 single-step once, and report the stop (even if the stepped instruction
37979 jumps to @var{start}).
37981 (A stop reply may be sent at any point even if the PC is still within
37982 the stepping range; for example, it is valid to implement this packet
37983 in a degenerate way as a single instruction step operation.)
37987 The optional argument @var{addr} normally associated with the
37988 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
37989 not supported in @samp{vCont}.
37991 The @samp{t} action is only relevant in non-stop mode
37992 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
37993 A stop reply should be generated for any affected thread not already stopped.
37994 When a thread is stopped by means of a @samp{t} action,
37995 the corresponding stop reply should indicate that the thread has stopped with
37996 signal @samp{0}, regardless of whether the target uses some other signal
37997 as an implementation detail.
37999 The stub must support @samp{vCont} if it reports support for
38000 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
38001 this case @samp{vCont} actions can be specified to apply to all threads
38002 in a process by using the @samp{p@var{pid}.-1} form of the
38006 @xref{Stop Reply Packets}, for the reply specifications.
38009 @cindex @samp{vCont?} packet
38010 Request a list of actions supported by the @samp{vCont} packet.
38014 @item vCont@r{[};@var{action}@dots{}@r{]}
38015 The @samp{vCont} packet is supported. Each @var{action} is a supported
38016 command in the @samp{vCont} packet.
38018 The @samp{vCont} packet is not supported.
38021 @item vFile:@var{operation}:@var{parameter}@dots{}
38022 @cindex @samp{vFile} packet
38023 Perform a file operation on the target system. For details,
38024 see @ref{Host I/O Packets}.
38026 @item vFlashErase:@var{addr},@var{length}
38027 @cindex @samp{vFlashErase} packet
38028 Direct the stub to erase @var{length} bytes of flash starting at
38029 @var{addr}. The region may enclose any number of flash blocks, but
38030 its start and end must fall on block boundaries, as indicated by the
38031 flash block size appearing in the memory map (@pxref{Memory Map
38032 Format}). @value{GDBN} groups flash memory programming operations
38033 together, and sends a @samp{vFlashDone} request after each group; the
38034 stub is allowed to delay erase operation until the @samp{vFlashDone}
38035 packet is received.
38045 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
38046 @cindex @samp{vFlashWrite} packet
38047 Direct the stub to write data to flash address @var{addr}. The data
38048 is passed in binary form using the same encoding as for the @samp{X}
38049 packet (@pxref{Binary Data}). The memory ranges specified by
38050 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
38051 not overlap, and must appear in order of increasing addresses
38052 (although @samp{vFlashErase} packets for higher addresses may already
38053 have been received; the ordering is guaranteed only between
38054 @samp{vFlashWrite} packets). If a packet writes to an address that was
38055 neither erased by a preceding @samp{vFlashErase} packet nor by some other
38056 target-specific method, the results are unpredictable.
38064 for vFlashWrite addressing non-flash memory
38070 @cindex @samp{vFlashDone} packet
38071 Indicate to the stub that flash programming operation is finished.
38072 The stub is permitted to delay or batch the effects of a group of
38073 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
38074 @samp{vFlashDone} packet is received. The contents of the affected
38075 regions of flash memory are unpredictable until the @samp{vFlashDone}
38076 request is completed.
38078 @item vKill;@var{pid}
38079 @cindex @samp{vKill} packet
38080 Kill the process with the specified process ID. @var{pid} is a
38081 hexadecimal integer identifying the process. This packet is used in
38082 preference to @samp{k} when multiprocess protocol extensions are
38083 supported; see @ref{multiprocess extensions}.
38093 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
38094 @cindex @samp{vRun} packet
38095 Run the program @var{filename}, passing it each @var{argument} on its
38096 command line. The file and arguments are hex-encoded strings. If
38097 @var{filename} is an empty string, the stub may use a default program
38098 (e.g.@: the last program run). The program is created in the stopped
38101 @c FIXME: What about non-stop mode?
38103 This packet is only available in extended mode (@pxref{extended mode}).
38109 @item @r{Any stop packet}
38110 for success (@pxref{Stop Reply Packets})
38114 @cindex @samp{vStopped} packet
38115 @xref{Notification Packets}.
38117 @item X @var{addr},@var{length}:@var{XX@dots{}}
38119 @cindex @samp{X} packet
38120 Write data to memory, where the data is transmitted in binary.
38121 @var{addr} is address, @var{length} is number of bytes,
38122 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
38132 @item z @var{type},@var{addr},@var{kind}
38133 @itemx Z @var{type},@var{addr},@var{kind}
38134 @anchor{insert breakpoint or watchpoint packet}
38135 @cindex @samp{z} packet
38136 @cindex @samp{Z} packets
38137 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
38138 watchpoint starting at address @var{address} of kind @var{kind}.
38140 Each breakpoint and watchpoint packet @var{type} is documented
38143 @emph{Implementation notes: A remote target shall return an empty string
38144 for an unrecognized breakpoint or watchpoint packet @var{type}. A
38145 remote target shall support either both or neither of a given
38146 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
38147 avoid potential problems with duplicate packets, the operations should
38148 be implemented in an idempotent way.}
38150 @item z0,@var{addr},@var{kind}
38151 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
38152 @cindex @samp{z0} packet
38153 @cindex @samp{Z0} packet
38154 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
38155 @var{addr} of type @var{kind}.
38157 A memory breakpoint is implemented by replacing the instruction at
38158 @var{addr} with a software breakpoint or trap instruction. The
38159 @var{kind} is target-specific and typically indicates the size of
38160 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
38161 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
38162 architectures have additional meanings for @var{kind};
38163 @var{cond_list} is an optional list of conditional expressions in bytecode
38164 form that should be evaluated on the target's side. These are the
38165 conditions that should be taken into consideration when deciding if
38166 the breakpoint trigger should be reported back to @var{GDBN}.
38168 The @var{cond_list} parameter is comprised of a series of expressions,
38169 concatenated without separators. Each expression has the following form:
38173 @item X @var{len},@var{expr}
38174 @var{len} is the length of the bytecode expression and @var{expr} is the
38175 actual conditional expression in bytecode form.
38179 The optional @var{cmd_list} parameter introduces commands that may be
38180 run on the target, rather than being reported back to @value{GDBN}.
38181 The parameter starts with a numeric flag @var{persist}; if the flag is
38182 nonzero, then the breakpoint may remain active and the commands
38183 continue to be run even when @value{GDBN} disconnects from the target.
38184 Following this flag is a series of expressions concatenated with no
38185 separators. Each expression has the following form:
38189 @item X @var{len},@var{expr}
38190 @var{len} is the length of the bytecode expression and @var{expr} is the
38191 actual conditional expression in bytecode form.
38195 see @ref{Architecture-Specific Protocol Details}.
38197 @emph{Implementation note: It is possible for a target to copy or move
38198 code that contains memory breakpoints (e.g., when implementing
38199 overlays). The behavior of this packet, in the presence of such a
38200 target, is not defined.}
38212 @item z1,@var{addr},@var{kind}
38213 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
38214 @cindex @samp{z1} packet
38215 @cindex @samp{Z1} packet
38216 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
38217 address @var{addr}.
38219 A hardware breakpoint is implemented using a mechanism that is not
38220 dependant on being able to modify the target's memory. @var{kind}
38221 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
38223 @emph{Implementation note: A hardware breakpoint is not affected by code
38236 @item z2,@var{addr},@var{kind}
38237 @itemx Z2,@var{addr},@var{kind}
38238 @cindex @samp{z2} packet
38239 @cindex @samp{Z2} packet
38240 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
38241 @var{kind} is interpreted as the number of bytes to watch.
38253 @item z3,@var{addr},@var{kind}
38254 @itemx Z3,@var{addr},@var{kind}
38255 @cindex @samp{z3} packet
38256 @cindex @samp{Z3} packet
38257 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
38258 @var{kind} is interpreted as the number of bytes to watch.
38270 @item z4,@var{addr},@var{kind}
38271 @itemx Z4,@var{addr},@var{kind}
38272 @cindex @samp{z4} packet
38273 @cindex @samp{Z4} packet
38274 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
38275 @var{kind} is interpreted as the number of bytes to watch.
38289 @node Stop Reply Packets
38290 @section Stop Reply Packets
38291 @cindex stop reply packets
38293 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
38294 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
38295 receive any of the below as a reply. Except for @samp{?}
38296 and @samp{vStopped}, that reply is only returned
38297 when the target halts. In the below the exact meaning of @dfn{signal
38298 number} is defined by the header @file{include/gdb/signals.h} in the
38299 @value{GDBN} source code.
38301 As in the description of request packets, we include spaces in the
38302 reply templates for clarity; these are not part of the reply packet's
38303 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
38309 The program received signal number @var{AA} (a two-digit hexadecimal
38310 number). This is equivalent to a @samp{T} response with no
38311 @var{n}:@var{r} pairs.
38313 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
38314 @cindex @samp{T} packet reply
38315 The program received signal number @var{AA} (a two-digit hexadecimal
38316 number). This is equivalent to an @samp{S} response, except that the
38317 @samp{@var{n}:@var{r}} pairs can carry values of important registers
38318 and other information directly in the stop reply packet, reducing
38319 round-trip latency. Single-step and breakpoint traps are reported
38320 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
38324 If @var{n} is a hexadecimal number, it is a register number, and the
38325 corresponding @var{r} gives that register's value. @var{r} is a
38326 series of bytes in target byte order, with each byte given by a
38327 two-digit hex number.
38330 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
38331 the stopped thread, as specified in @ref{thread-id syntax}.
38334 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
38335 the core on which the stop event was detected.
38338 If @var{n} is a recognized @dfn{stop reason}, it describes a more
38339 specific event that stopped the target. The currently defined stop
38340 reasons are listed below. @var{aa} should be @samp{05}, the trap
38341 signal. At most one stop reason should be present.
38344 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
38345 and go on to the next; this allows us to extend the protocol in the
38349 The currently defined stop reasons are:
38355 The packet indicates a watchpoint hit, and @var{r} is the data address, in
38358 @cindex shared library events, remote reply
38360 The packet indicates that the loaded libraries have changed.
38361 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
38362 list of loaded libraries. @var{r} is ignored.
38364 @cindex replay log events, remote reply
38366 The packet indicates that the target cannot continue replaying
38367 logged execution events, because it has reached the end (or the
38368 beginning when executing backward) of the log. The value of @var{r}
38369 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
38370 for more information.
38374 @itemx W @var{AA} ; process:@var{pid}
38375 The process exited, and @var{AA} is the exit status. This is only
38376 applicable to certain targets.
38378 The second form of the response, including the process ID of the exited
38379 process, can be used only when @value{GDBN} has reported support for
38380 multiprocess protocol extensions; see @ref{multiprocess extensions}.
38381 The @var{pid} is formatted as a big-endian hex string.
38384 @itemx X @var{AA} ; process:@var{pid}
38385 The process terminated with signal @var{AA}.
38387 The second form of the response, including the process ID of the
38388 terminated process, can be used only when @value{GDBN} has reported
38389 support for multiprocess protocol extensions; see @ref{multiprocess
38390 extensions}. The @var{pid} is formatted as a big-endian hex string.
38392 @item O @var{XX}@dots{}
38393 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
38394 written as the program's console output. This can happen at any time
38395 while the program is running and the debugger should continue to wait
38396 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
38398 @item F @var{call-id},@var{parameter}@dots{}
38399 @var{call-id} is the identifier which says which host system call should
38400 be called. This is just the name of the function. Translation into the
38401 correct system call is only applicable as it's defined in @value{GDBN}.
38402 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
38405 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
38406 this very system call.
38408 The target replies with this packet when it expects @value{GDBN} to
38409 call a host system call on behalf of the target. @value{GDBN} replies
38410 with an appropriate @samp{F} packet and keeps up waiting for the next
38411 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
38412 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
38413 Protocol Extension}, for more details.
38417 @node General Query Packets
38418 @section General Query Packets
38419 @cindex remote query requests
38421 Packets starting with @samp{q} are @dfn{general query packets};
38422 packets starting with @samp{Q} are @dfn{general set packets}. General
38423 query and set packets are a semi-unified form for retrieving and
38424 sending information to and from the stub.
38426 The initial letter of a query or set packet is followed by a name
38427 indicating what sort of thing the packet applies to. For example,
38428 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
38429 definitions with the stub. These packet names follow some
38434 The name must not contain commas, colons or semicolons.
38436 Most @value{GDBN} query and set packets have a leading upper case
38439 The names of custom vendor packets should use a company prefix, in
38440 lower case, followed by a period. For example, packets designed at
38441 the Acme Corporation might begin with @samp{qacme.foo} (for querying
38442 foos) or @samp{Qacme.bar} (for setting bars).
38445 The name of a query or set packet should be separated from any
38446 parameters by a @samp{:}; the parameters themselves should be
38447 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
38448 full packet name, and check for a separator or the end of the packet,
38449 in case two packet names share a common prefix. New packets should not begin
38450 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
38451 packets predate these conventions, and have arguments without any terminator
38452 for the packet name; we suspect they are in widespread use in places that
38453 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
38454 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
38457 Like the descriptions of the other packets, each description here
38458 has a template showing the packet's overall syntax, followed by an
38459 explanation of the packet's meaning. We include spaces in some of the
38460 templates for clarity; these are not part of the packet's syntax. No
38461 @value{GDBN} packet uses spaces to separate its components.
38463 Here are the currently defined query and set packets:
38469 Turn on or off the agent as a helper to perform some debugging operations
38470 delegated from @value{GDBN} (@pxref{Control Agent}).
38472 @item QAllow:@var{op}:@var{val}@dots{}
38473 @cindex @samp{QAllow} packet
38474 Specify which operations @value{GDBN} expects to request of the
38475 target, as a semicolon-separated list of operation name and value
38476 pairs. Possible values for @var{op} include @samp{WriteReg},
38477 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
38478 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
38479 indicating that @value{GDBN} will not request the operation, or 1,
38480 indicating that it may. (The target can then use this to set up its
38481 own internals optimally, for instance if the debugger never expects to
38482 insert breakpoints, it may not need to install its own trap handler.)
38485 @cindex current thread, remote request
38486 @cindex @samp{qC} packet
38487 Return the current thread ID.
38491 @item QC @var{thread-id}
38492 Where @var{thread-id} is a thread ID as documented in
38493 @ref{thread-id syntax}.
38494 @item @r{(anything else)}
38495 Any other reply implies the old thread ID.
38498 @item qCRC:@var{addr},@var{length}
38499 @cindex CRC of memory block, remote request
38500 @cindex @samp{qCRC} packet
38501 Compute the CRC checksum of a block of memory using CRC-32 defined in
38502 IEEE 802.3. The CRC is computed byte at a time, taking the most
38503 significant bit of each byte first. The initial pattern code
38504 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
38506 @emph{Note:} This is the same CRC used in validating separate debug
38507 files (@pxref{Separate Debug Files, , Debugging Information in Separate
38508 Files}). However the algorithm is slightly different. When validating
38509 separate debug files, the CRC is computed taking the @emph{least}
38510 significant bit of each byte first, and the final result is inverted to
38511 detect trailing zeros.
38516 An error (such as memory fault)
38517 @item C @var{crc32}
38518 The specified memory region's checksum is @var{crc32}.
38521 @item QDisableRandomization:@var{value}
38522 @cindex disable address space randomization, remote request
38523 @cindex @samp{QDisableRandomization} packet
38524 Some target operating systems will randomize the virtual address space
38525 of the inferior process as a security feature, but provide a feature
38526 to disable such randomization, e.g.@: to allow for a more deterministic
38527 debugging experience. On such systems, this packet with a @var{value}
38528 of 1 directs the target to disable address space randomization for
38529 processes subsequently started via @samp{vRun} packets, while a packet
38530 with a @var{value} of 0 tells the target to enable address space
38533 This packet is only available in extended mode (@pxref{extended mode}).
38538 The request succeeded.
38541 An error occurred. @var{nn} are hex digits.
38544 An empty reply indicates that @samp{QDisableRandomization} is not supported
38548 This packet is not probed by default; the remote stub must request it,
38549 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38550 This should only be done on targets that actually support disabling
38551 address space randomization.
38554 @itemx qsThreadInfo
38555 @cindex list active threads, remote request
38556 @cindex @samp{qfThreadInfo} packet
38557 @cindex @samp{qsThreadInfo} packet
38558 Obtain a list of all active thread IDs from the target (OS). Since there
38559 may be too many active threads to fit into one reply packet, this query
38560 works iteratively: it may require more than one query/reply sequence to
38561 obtain the entire list of threads. The first query of the sequence will
38562 be the @samp{qfThreadInfo} query; subsequent queries in the
38563 sequence will be the @samp{qsThreadInfo} query.
38565 NOTE: This packet replaces the @samp{qL} query (see below).
38569 @item m @var{thread-id}
38571 @item m @var{thread-id},@var{thread-id}@dots{}
38572 a comma-separated list of thread IDs
38574 (lower case letter @samp{L}) denotes end of list.
38577 In response to each query, the target will reply with a list of one or
38578 more thread IDs, separated by commas.
38579 @value{GDBN} will respond to each reply with a request for more thread
38580 ids (using the @samp{qs} form of the query), until the target responds
38581 with @samp{l} (lower-case ell, for @dfn{last}).
38582 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
38585 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
38586 @cindex get thread-local storage address, remote request
38587 @cindex @samp{qGetTLSAddr} packet
38588 Fetch the address associated with thread local storage specified
38589 by @var{thread-id}, @var{offset}, and @var{lm}.
38591 @var{thread-id} is the thread ID associated with the
38592 thread for which to fetch the TLS address. @xref{thread-id syntax}.
38594 @var{offset} is the (big endian, hex encoded) offset associated with the
38595 thread local variable. (This offset is obtained from the debug
38596 information associated with the variable.)
38598 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
38599 load module associated with the thread local storage. For example,
38600 a @sc{gnu}/Linux system will pass the link map address of the shared
38601 object associated with the thread local storage under consideration.
38602 Other operating environments may choose to represent the load module
38603 differently, so the precise meaning of this parameter will vary.
38607 @item @var{XX}@dots{}
38608 Hex encoded (big endian) bytes representing the address of the thread
38609 local storage requested.
38612 An error occurred. @var{nn} are hex digits.
38615 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
38618 @item qGetTIBAddr:@var{thread-id}
38619 @cindex get thread information block address
38620 @cindex @samp{qGetTIBAddr} packet
38621 Fetch address of the Windows OS specific Thread Information Block.
38623 @var{thread-id} is the thread ID associated with the thread.
38627 @item @var{XX}@dots{}
38628 Hex encoded (big endian) bytes representing the linear address of the
38629 thread information block.
38632 An error occured. This means that either the thread was not found, or the
38633 address could not be retrieved.
38636 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
38639 @item qL @var{startflag} @var{threadcount} @var{nextthread}
38640 Obtain thread information from RTOS. Where: @var{startflag} (one hex
38641 digit) is one to indicate the first query and zero to indicate a
38642 subsequent query; @var{threadcount} (two hex digits) is the maximum
38643 number of threads the response packet can contain; and @var{nextthread}
38644 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
38645 returned in the response as @var{argthread}.
38647 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
38651 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
38652 Where: @var{count} (two hex digits) is the number of threads being
38653 returned; @var{done} (one hex digit) is zero to indicate more threads
38654 and one indicates no further threads; @var{argthreadid} (eight hex
38655 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
38656 is a sequence of thread IDs from the target. @var{threadid} (eight hex
38657 digits). See @code{remote.c:parse_threadlist_response()}.
38661 @cindex section offsets, remote request
38662 @cindex @samp{qOffsets} packet
38663 Get section offsets that the target used when relocating the downloaded
38668 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
38669 Relocate the @code{Text} section by @var{xxx} from its original address.
38670 Relocate the @code{Data} section by @var{yyy} from its original address.
38671 If the object file format provides segment information (e.g.@: @sc{elf}
38672 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
38673 segments by the supplied offsets.
38675 @emph{Note: while a @code{Bss} offset may be included in the response,
38676 @value{GDBN} ignores this and instead applies the @code{Data} offset
38677 to the @code{Bss} section.}
38679 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
38680 Relocate the first segment of the object file, which conventionally
38681 contains program code, to a starting address of @var{xxx}. If
38682 @samp{DataSeg} is specified, relocate the second segment, which
38683 conventionally contains modifiable data, to a starting address of
38684 @var{yyy}. @value{GDBN} will report an error if the object file
38685 does not contain segment information, or does not contain at least
38686 as many segments as mentioned in the reply. Extra segments are
38687 kept at fixed offsets relative to the last relocated segment.
38690 @item qP @var{mode} @var{thread-id}
38691 @cindex thread information, remote request
38692 @cindex @samp{qP} packet
38693 Returns information on @var{thread-id}. Where: @var{mode} is a hex
38694 encoded 32 bit mode; @var{thread-id} is a thread ID
38695 (@pxref{thread-id syntax}).
38697 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
38700 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
38704 @cindex non-stop mode, remote request
38705 @cindex @samp{QNonStop} packet
38707 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
38708 @xref{Remote Non-Stop}, for more information.
38713 The request succeeded.
38716 An error occurred. @var{nn} are hex digits.
38719 An empty reply indicates that @samp{QNonStop} is not supported by
38723 This packet is not probed by default; the remote stub must request it,
38724 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38725 Use of this packet is controlled by the @code{set non-stop} command;
38726 @pxref{Non-Stop Mode}.
38728 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
38729 @cindex pass signals to inferior, remote request
38730 @cindex @samp{QPassSignals} packet
38731 @anchor{QPassSignals}
38732 Each listed @var{signal} should be passed directly to the inferior process.
38733 Signals are numbered identically to continue packets and stop replies
38734 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
38735 strictly greater than the previous item. These signals do not need to stop
38736 the inferior, or be reported to @value{GDBN}. All other signals should be
38737 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
38738 combine; any earlier @samp{QPassSignals} list is completely replaced by the
38739 new list. This packet improves performance when using @samp{handle
38740 @var{signal} nostop noprint pass}.
38745 The request succeeded.
38748 An error occurred. @var{nn} are hex digits.
38751 An empty reply indicates that @samp{QPassSignals} is not supported by
38755 Use of this packet is controlled by the @code{set remote pass-signals}
38756 command (@pxref{Remote Configuration, set remote pass-signals}).
38757 This packet is not probed by default; the remote stub must request it,
38758 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38760 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
38761 @cindex signals the inferior may see, remote request
38762 @cindex @samp{QProgramSignals} packet
38763 @anchor{QProgramSignals}
38764 Each listed @var{signal} may be delivered to the inferior process.
38765 Others should be silently discarded.
38767 In some cases, the remote stub may need to decide whether to deliver a
38768 signal to the program or not without @value{GDBN} involvement. One
38769 example of that is while detaching --- the program's threads may have
38770 stopped for signals that haven't yet had a chance of being reported to
38771 @value{GDBN}, and so the remote stub can use the signal list specified
38772 by this packet to know whether to deliver or ignore those pending
38775 This does not influence whether to deliver a signal as requested by a
38776 resumption packet (@pxref{vCont packet}).
38778 Signals are numbered identically to continue packets and stop replies
38779 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
38780 strictly greater than the previous item. Multiple
38781 @samp{QProgramSignals} packets do not combine; any earlier
38782 @samp{QProgramSignals} list is completely replaced by the new list.
38787 The request succeeded.
38790 An error occurred. @var{nn} are hex digits.
38793 An empty reply indicates that @samp{QProgramSignals} is not supported
38797 Use of this packet is controlled by the @code{set remote program-signals}
38798 command (@pxref{Remote Configuration, set remote program-signals}).
38799 This packet is not probed by default; the remote stub must request it,
38800 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38802 @item qRcmd,@var{command}
38803 @cindex execute remote command, remote request
38804 @cindex @samp{qRcmd} packet
38805 @var{command} (hex encoded) is passed to the local interpreter for
38806 execution. Invalid commands should be reported using the output
38807 string. Before the final result packet, the target may also respond
38808 with a number of intermediate @samp{O@var{output}} console output
38809 packets. @emph{Implementors should note that providing access to a
38810 stubs's interpreter may have security implications}.
38815 A command response with no output.
38817 A command response with the hex encoded output string @var{OUTPUT}.
38819 Indicate a badly formed request.
38821 An empty reply indicates that @samp{qRcmd} is not recognized.
38824 (Note that the @code{qRcmd} packet's name is separated from the
38825 command by a @samp{,}, not a @samp{:}, contrary to the naming
38826 conventions above. Please don't use this packet as a model for new
38829 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
38830 @cindex searching memory, in remote debugging
38832 @cindex @samp{qSearch:memory} packet
38834 @cindex @samp{qSearch memory} packet
38835 @anchor{qSearch memory}
38836 Search @var{length} bytes at @var{address} for @var{search-pattern}.
38837 @var{address} and @var{length} are encoded in hex.
38838 @var{search-pattern} is a sequence of bytes, hex encoded.
38843 The pattern was not found.
38845 The pattern was found at @var{address}.
38847 A badly formed request or an error was encountered while searching memory.
38849 An empty reply indicates that @samp{qSearch:memory} is not recognized.
38852 @item QStartNoAckMode
38853 @cindex @samp{QStartNoAckMode} packet
38854 @anchor{QStartNoAckMode}
38855 Request that the remote stub disable the normal @samp{+}/@samp{-}
38856 protocol acknowledgments (@pxref{Packet Acknowledgment}).
38861 The stub has switched to no-acknowledgment mode.
38862 @value{GDBN} acknowledges this reponse,
38863 but neither the stub nor @value{GDBN} shall send or expect further
38864 @samp{+}/@samp{-} acknowledgments in the current connection.
38866 An empty reply indicates that the stub does not support no-acknowledgment mode.
38869 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
38870 @cindex supported packets, remote query
38871 @cindex features of the remote protocol
38872 @cindex @samp{qSupported} packet
38873 @anchor{qSupported}
38874 Tell the remote stub about features supported by @value{GDBN}, and
38875 query the stub for features it supports. This packet allows
38876 @value{GDBN} and the remote stub to take advantage of each others'
38877 features. @samp{qSupported} also consolidates multiple feature probes
38878 at startup, to improve @value{GDBN} performance---a single larger
38879 packet performs better than multiple smaller probe packets on
38880 high-latency links. Some features may enable behavior which must not
38881 be on by default, e.g.@: because it would confuse older clients or
38882 stubs. Other features may describe packets which could be
38883 automatically probed for, but are not. These features must be
38884 reported before @value{GDBN} will use them. This ``default
38885 unsupported'' behavior is not appropriate for all packets, but it
38886 helps to keep the initial connection time under control with new
38887 versions of @value{GDBN} which support increasing numbers of packets.
38891 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
38892 The stub supports or does not support each returned @var{stubfeature},
38893 depending on the form of each @var{stubfeature} (see below for the
38896 An empty reply indicates that @samp{qSupported} is not recognized,
38897 or that no features needed to be reported to @value{GDBN}.
38900 The allowed forms for each feature (either a @var{gdbfeature} in the
38901 @samp{qSupported} packet, or a @var{stubfeature} in the response)
38905 @item @var{name}=@var{value}
38906 The remote protocol feature @var{name} is supported, and associated
38907 with the specified @var{value}. The format of @var{value} depends
38908 on the feature, but it must not include a semicolon.
38910 The remote protocol feature @var{name} is supported, and does not
38911 need an associated value.
38913 The remote protocol feature @var{name} is not supported.
38915 The remote protocol feature @var{name} may be supported, and
38916 @value{GDBN} should auto-detect support in some other way when it is
38917 needed. This form will not be used for @var{gdbfeature} notifications,
38918 but may be used for @var{stubfeature} responses.
38921 Whenever the stub receives a @samp{qSupported} request, the
38922 supplied set of @value{GDBN} features should override any previous
38923 request. This allows @value{GDBN} to put the stub in a known
38924 state, even if the stub had previously been communicating with
38925 a different version of @value{GDBN}.
38927 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
38932 This feature indicates whether @value{GDBN} supports multiprocess
38933 extensions to the remote protocol. @value{GDBN} does not use such
38934 extensions unless the stub also reports that it supports them by
38935 including @samp{multiprocess+} in its @samp{qSupported} reply.
38936 @xref{multiprocess extensions}, for details.
38939 This feature indicates that @value{GDBN} supports the XML target
38940 description. If the stub sees @samp{xmlRegisters=} with target
38941 specific strings separated by a comma, it will report register
38945 This feature indicates whether @value{GDBN} supports the
38946 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
38947 instruction reply packet}).
38950 Stubs should ignore any unknown values for
38951 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
38952 packet supports receiving packets of unlimited length (earlier
38953 versions of @value{GDBN} may reject overly long responses). Additional values
38954 for @var{gdbfeature} may be defined in the future to let the stub take
38955 advantage of new features in @value{GDBN}, e.g.@: incompatible
38956 improvements in the remote protocol---the @samp{multiprocess} feature is
38957 an example of such a feature. The stub's reply should be independent
38958 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
38959 describes all the features it supports, and then the stub replies with
38960 all the features it supports.
38962 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
38963 responses, as long as each response uses one of the standard forms.
38965 Some features are flags. A stub which supports a flag feature
38966 should respond with a @samp{+} form response. Other features
38967 require values, and the stub should respond with an @samp{=}
38970 Each feature has a default value, which @value{GDBN} will use if
38971 @samp{qSupported} is not available or if the feature is not mentioned
38972 in the @samp{qSupported} response. The default values are fixed; a
38973 stub is free to omit any feature responses that match the defaults.
38975 Not all features can be probed, but for those which can, the probing
38976 mechanism is useful: in some cases, a stub's internal
38977 architecture may not allow the protocol layer to know some information
38978 about the underlying target in advance. This is especially common in
38979 stubs which may be configured for multiple targets.
38981 These are the currently defined stub features and their properties:
38983 @multitable @columnfractions 0.35 0.2 0.12 0.2
38984 @c NOTE: The first row should be @headitem, but we do not yet require
38985 @c a new enough version of Texinfo (4.7) to use @headitem.
38987 @tab Value Required
38991 @item @samp{PacketSize}
38996 @item @samp{qXfer:auxv:read}
39001 @item @samp{qXfer:btrace:read}
39006 @item @samp{qXfer:features:read}
39011 @item @samp{qXfer:libraries:read}
39016 @item @samp{qXfer:libraries-svr4:read}
39021 @item @samp{augmented-libraries-svr4-read}
39026 @item @samp{qXfer:memory-map:read}
39031 @item @samp{qXfer:sdata:read}
39036 @item @samp{qXfer:spu:read}
39041 @item @samp{qXfer:spu:write}
39046 @item @samp{qXfer:siginfo:read}
39051 @item @samp{qXfer:siginfo:write}
39056 @item @samp{qXfer:threads:read}
39061 @item @samp{qXfer:traceframe-info:read}
39066 @item @samp{qXfer:uib:read}
39071 @item @samp{qXfer:fdpic:read}
39076 @item @samp{Qbtrace:off}
39081 @item @samp{Qbtrace:bts}
39086 @item @samp{QNonStop}
39091 @item @samp{QPassSignals}
39096 @item @samp{QStartNoAckMode}
39101 @item @samp{multiprocess}
39106 @item @samp{ConditionalBreakpoints}
39111 @item @samp{ConditionalTracepoints}
39116 @item @samp{ReverseContinue}
39121 @item @samp{ReverseStep}
39126 @item @samp{TracepointSource}
39131 @item @samp{QAgent}
39136 @item @samp{QAllow}
39141 @item @samp{QDisableRandomization}
39146 @item @samp{EnableDisableTracepoints}
39151 @item @samp{QTBuffer:size}
39156 @item @samp{tracenz}
39161 @item @samp{BreakpointCommands}
39168 These are the currently defined stub features, in more detail:
39171 @cindex packet size, remote protocol
39172 @item PacketSize=@var{bytes}
39173 The remote stub can accept packets up to at least @var{bytes} in
39174 length. @value{GDBN} will send packets up to this size for bulk
39175 transfers, and will never send larger packets. This is a limit on the
39176 data characters in the packet, including the frame and checksum.
39177 There is no trailing NUL byte in a remote protocol packet; if the stub
39178 stores packets in a NUL-terminated format, it should allow an extra
39179 byte in its buffer for the NUL. If this stub feature is not supported,
39180 @value{GDBN} guesses based on the size of the @samp{g} packet response.
39182 @item qXfer:auxv:read
39183 The remote stub understands the @samp{qXfer:auxv:read} packet
39184 (@pxref{qXfer auxiliary vector read}).
39186 @item qXfer:btrace:read
39187 The remote stub understands the @samp{qXfer:btrace:read}
39188 packet (@pxref{qXfer btrace read}).
39190 @item qXfer:features:read
39191 The remote stub understands the @samp{qXfer:features:read} packet
39192 (@pxref{qXfer target description read}).
39194 @item qXfer:libraries:read
39195 The remote stub understands the @samp{qXfer:libraries:read} packet
39196 (@pxref{qXfer library list read}).
39198 @item qXfer:libraries-svr4:read
39199 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
39200 (@pxref{qXfer svr4 library list read}).
39202 @item augmented-libraries-svr4-read
39203 The remote stub understands the augmented form of the
39204 @samp{qXfer:libraries-svr4:read} packet
39205 (@pxref{qXfer svr4 library list read}).
39207 @item qXfer:memory-map:read
39208 The remote stub understands the @samp{qXfer:memory-map:read} packet
39209 (@pxref{qXfer memory map read}).
39211 @item qXfer:sdata:read
39212 The remote stub understands the @samp{qXfer:sdata:read} packet
39213 (@pxref{qXfer sdata read}).
39215 @item qXfer:spu:read
39216 The remote stub understands the @samp{qXfer:spu:read} packet
39217 (@pxref{qXfer spu read}).
39219 @item qXfer:spu:write
39220 The remote stub understands the @samp{qXfer:spu:write} packet
39221 (@pxref{qXfer spu write}).
39223 @item qXfer:siginfo:read
39224 The remote stub understands the @samp{qXfer:siginfo:read} packet
39225 (@pxref{qXfer siginfo read}).
39227 @item qXfer:siginfo:write
39228 The remote stub understands the @samp{qXfer:siginfo:write} packet
39229 (@pxref{qXfer siginfo write}).
39231 @item qXfer:threads:read
39232 The remote stub understands the @samp{qXfer:threads:read} packet
39233 (@pxref{qXfer threads read}).
39235 @item qXfer:traceframe-info:read
39236 The remote stub understands the @samp{qXfer:traceframe-info:read}
39237 packet (@pxref{qXfer traceframe info read}).
39239 @item qXfer:uib:read
39240 The remote stub understands the @samp{qXfer:uib:read}
39241 packet (@pxref{qXfer unwind info block}).
39243 @item qXfer:fdpic:read
39244 The remote stub understands the @samp{qXfer:fdpic:read}
39245 packet (@pxref{qXfer fdpic loadmap read}).
39248 The remote stub understands the @samp{QNonStop} packet
39249 (@pxref{QNonStop}).
39252 The remote stub understands the @samp{QPassSignals} packet
39253 (@pxref{QPassSignals}).
39255 @item QStartNoAckMode
39256 The remote stub understands the @samp{QStartNoAckMode} packet and
39257 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
39260 @anchor{multiprocess extensions}
39261 @cindex multiprocess extensions, in remote protocol
39262 The remote stub understands the multiprocess extensions to the remote
39263 protocol syntax. The multiprocess extensions affect the syntax of
39264 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
39265 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
39266 replies. Note that reporting this feature indicates support for the
39267 syntactic extensions only, not that the stub necessarily supports
39268 debugging of more than one process at a time. The stub must not use
39269 multiprocess extensions in packet replies unless @value{GDBN} has also
39270 indicated it supports them in its @samp{qSupported} request.
39272 @item qXfer:osdata:read
39273 The remote stub understands the @samp{qXfer:osdata:read} packet
39274 ((@pxref{qXfer osdata read}).
39276 @item ConditionalBreakpoints
39277 The target accepts and implements evaluation of conditional expressions
39278 defined for breakpoints. The target will only report breakpoint triggers
39279 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
39281 @item ConditionalTracepoints
39282 The remote stub accepts and implements conditional expressions defined
39283 for tracepoints (@pxref{Tracepoint Conditions}).
39285 @item ReverseContinue
39286 The remote stub accepts and implements the reverse continue packet
39290 The remote stub accepts and implements the reverse step packet
39293 @item TracepointSource
39294 The remote stub understands the @samp{QTDPsrc} packet that supplies
39295 the source form of tracepoint definitions.
39298 The remote stub understands the @samp{QAgent} packet.
39301 The remote stub understands the @samp{QAllow} packet.
39303 @item QDisableRandomization
39304 The remote stub understands the @samp{QDisableRandomization} packet.
39306 @item StaticTracepoint
39307 @cindex static tracepoints, in remote protocol
39308 The remote stub supports static tracepoints.
39310 @item InstallInTrace
39311 @anchor{install tracepoint in tracing}
39312 The remote stub supports installing tracepoint in tracing.
39314 @item EnableDisableTracepoints
39315 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
39316 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
39317 to be enabled and disabled while a trace experiment is running.
39319 @item QTBuffer:size
39320 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
39321 packet that allows to change the size of the trace buffer.
39324 @cindex string tracing, in remote protocol
39325 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
39326 See @ref{Bytecode Descriptions} for details about the bytecode.
39328 @item BreakpointCommands
39329 @cindex breakpoint commands, in remote protocol
39330 The remote stub supports running a breakpoint's command list itself,
39331 rather than reporting the hit to @value{GDBN}.
39334 The remote stub understands the @samp{Qbtrace:off} packet.
39337 The remote stub understands the @samp{Qbtrace:bts} packet.
39342 @cindex symbol lookup, remote request
39343 @cindex @samp{qSymbol} packet
39344 Notify the target that @value{GDBN} is prepared to serve symbol lookup
39345 requests. Accept requests from the target for the values of symbols.
39350 The target does not need to look up any (more) symbols.
39351 @item qSymbol:@var{sym_name}
39352 The target requests the value of symbol @var{sym_name} (hex encoded).
39353 @value{GDBN} may provide the value by using the
39354 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
39358 @item qSymbol:@var{sym_value}:@var{sym_name}
39359 Set the value of @var{sym_name} to @var{sym_value}.
39361 @var{sym_name} (hex encoded) is the name of a symbol whose value the
39362 target has previously requested.
39364 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
39365 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
39371 The target does not need to look up any (more) symbols.
39372 @item qSymbol:@var{sym_name}
39373 The target requests the value of a new symbol @var{sym_name} (hex
39374 encoded). @value{GDBN} will continue to supply the values of symbols
39375 (if available), until the target ceases to request them.
39380 @itemx QTDisconnected
39387 @itemx qTMinFTPILen
39389 @xref{Tracepoint Packets}.
39391 @item qThreadExtraInfo,@var{thread-id}
39392 @cindex thread attributes info, remote request
39393 @cindex @samp{qThreadExtraInfo} packet
39394 Obtain a printable string description of a thread's attributes from
39395 the target OS. @var{thread-id} is a thread ID;
39396 see @ref{thread-id syntax}. This
39397 string may contain anything that the target OS thinks is interesting
39398 for @value{GDBN} to tell the user about the thread. The string is
39399 displayed in @value{GDBN}'s @code{info threads} display. Some
39400 examples of possible thread extra info strings are @samp{Runnable}, or
39401 @samp{Blocked on Mutex}.
39405 @item @var{XX}@dots{}
39406 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
39407 comprising the printable string containing the extra information about
39408 the thread's attributes.
39411 (Note that the @code{qThreadExtraInfo} packet's name is separated from
39412 the command by a @samp{,}, not a @samp{:}, contrary to the naming
39413 conventions above. Please don't use this packet as a model for new
39432 @xref{Tracepoint Packets}.
39434 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
39435 @cindex read special object, remote request
39436 @cindex @samp{qXfer} packet
39437 @anchor{qXfer read}
39438 Read uninterpreted bytes from the target's special data area
39439 identified by the keyword @var{object}. Request @var{length} bytes
39440 starting at @var{offset} bytes into the data. The content and
39441 encoding of @var{annex} is specific to @var{object}; it can supply
39442 additional details about what data to access.
39444 Here are the specific requests of this form defined so far. All
39445 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
39446 formats, listed below.
39449 @item qXfer:auxv:read::@var{offset},@var{length}
39450 @anchor{qXfer auxiliary vector read}
39451 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
39452 auxiliary vector}. Note @var{annex} must be empty.
39454 This packet is not probed by default; the remote stub must request it,
39455 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39457 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
39458 @anchor{qXfer btrace read}
39460 Return a description of the current branch trace.
39461 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
39462 packet may have one of the following values:
39466 Returns all available branch trace.
39469 Returns all available branch trace if the branch trace changed since
39470 the last read request.
39473 This packet is not probed by default; the remote stub must request it
39474 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39476 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
39477 @anchor{qXfer target description read}
39478 Access the @dfn{target description}. @xref{Target Descriptions}. The
39479 annex specifies which XML document to access. The main description is
39480 always loaded from the @samp{target.xml} annex.
39482 This packet is not probed by default; the remote stub must request it,
39483 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39485 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
39486 @anchor{qXfer library list read}
39487 Access the target's list of loaded libraries. @xref{Library List Format}.
39488 The annex part of the generic @samp{qXfer} packet must be empty
39489 (@pxref{qXfer read}).
39491 Targets which maintain a list of libraries in the program's memory do
39492 not need to implement this packet; it is designed for platforms where
39493 the operating system manages the list of loaded libraries.
39495 This packet is not probed by default; the remote stub must request it,
39496 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39498 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
39499 @anchor{qXfer svr4 library list read}
39500 Access the target's list of loaded libraries when the target is an SVR4
39501 platform. @xref{Library List Format for SVR4 Targets}. The annex part
39502 of the generic @samp{qXfer} packet must be empty unless the remote
39503 stub indicated it supports the augmented form of this packet
39504 by supplying an appropriate @samp{qSupported} response
39505 (@pxref{qXfer read}, @ref{qSupported}).
39507 This packet is optional for better performance on SVR4 targets.
39508 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
39510 This packet is not probed by default; the remote stub must request it,
39511 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39513 If the remote stub indicates it supports the augmented form of this
39514 packet then the annex part of the generic @samp{qXfer} packet may
39515 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
39516 arguments. The currently supported arguments are:
39519 @item start=@var{address}
39520 A hexadecimal number specifying the address of the @samp{struct
39521 link_map} to start reading the library list from. If unset or zero
39522 then the first @samp{struct link_map} in the library list will be
39523 chosen as the starting point.
39525 @item prev=@var{address}
39526 A hexadecimal number specifying the address of the @samp{struct
39527 link_map} immediately preceding the @samp{struct link_map}
39528 specified by the @samp{start} argument. If unset or zero then
39529 the remote stub will expect that no @samp{struct link_map}
39530 exists prior to the starting point.
39534 Arguments that are not understood by the remote stub will be silently
39537 @item qXfer:memory-map:read::@var{offset},@var{length}
39538 @anchor{qXfer memory map read}
39539 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
39540 annex part of the generic @samp{qXfer} packet must be empty
39541 (@pxref{qXfer read}).
39543 This packet is not probed by default; the remote stub must request it,
39544 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39546 @item qXfer:sdata:read::@var{offset},@var{length}
39547 @anchor{qXfer sdata read}
39549 Read contents of the extra collected static tracepoint marker
39550 information. The annex part of the generic @samp{qXfer} packet must
39551 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
39554 This packet is not probed by default; the remote stub must request it,
39555 by supplying an appropriate @samp{qSupported} response
39556 (@pxref{qSupported}).
39558 @item qXfer:siginfo:read::@var{offset},@var{length}
39559 @anchor{qXfer siginfo read}
39560 Read contents of the extra signal information on the target
39561 system. The annex part of the generic @samp{qXfer} packet must be
39562 empty (@pxref{qXfer read}).
39564 This packet is not probed by default; the remote stub must request it,
39565 by supplying an appropriate @samp{qSupported} response
39566 (@pxref{qSupported}).
39568 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
39569 @anchor{qXfer spu read}
39570 Read contents of an @code{spufs} file on the target system. The
39571 annex specifies which file to read; it must be of the form
39572 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
39573 in the target process, and @var{name} identifes the @code{spufs} file
39574 in that context to be accessed.
39576 This packet is not probed by default; the remote stub must request it,
39577 by supplying an appropriate @samp{qSupported} response
39578 (@pxref{qSupported}).
39580 @item qXfer:threads:read::@var{offset},@var{length}
39581 @anchor{qXfer threads read}
39582 Access the list of threads on target. @xref{Thread List Format}. The
39583 annex part of the generic @samp{qXfer} packet must be empty
39584 (@pxref{qXfer read}).
39586 This packet is not probed by default; the remote stub must request it,
39587 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39589 @item qXfer:traceframe-info:read::@var{offset},@var{length}
39590 @anchor{qXfer traceframe info read}
39592 Return a description of the current traceframe's contents.
39593 @xref{Traceframe Info Format}. The annex part of the generic
39594 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
39596 This packet is not probed by default; the remote stub must request it,
39597 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39599 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
39600 @anchor{qXfer unwind info block}
39602 Return the unwind information block for @var{pc}. This packet is used
39603 on OpenVMS/ia64 to ask the kernel unwind information.
39605 This packet is not probed by default.
39607 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
39608 @anchor{qXfer fdpic loadmap read}
39609 Read contents of @code{loadmap}s on the target system. The
39610 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
39611 executable @code{loadmap} or interpreter @code{loadmap} to read.
39613 This packet is not probed by default; the remote stub must request it,
39614 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39616 @item qXfer:osdata:read::@var{offset},@var{length}
39617 @anchor{qXfer osdata read}
39618 Access the target's @dfn{operating system information}.
39619 @xref{Operating System Information}.
39626 Data @var{data} (@pxref{Binary Data}) has been read from the
39627 target. There may be more data at a higher address (although
39628 it is permitted to return @samp{m} even for the last valid
39629 block of data, as long as at least one byte of data was read).
39630 @var{data} may have fewer bytes than the @var{length} in the
39634 Data @var{data} (@pxref{Binary Data}) has been read from the target.
39635 There is no more data to be read. @var{data} may have fewer bytes
39636 than the @var{length} in the request.
39639 The @var{offset} in the request is at the end of the data.
39640 There is no more data to be read.
39643 The request was malformed, or @var{annex} was invalid.
39646 The offset was invalid, or there was an error encountered reading the data.
39647 @var{nn} is a hex-encoded @code{errno} value.
39650 An empty reply indicates the @var{object} string was not recognized by
39651 the stub, or that the object does not support reading.
39654 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
39655 @cindex write data into object, remote request
39656 @anchor{qXfer write}
39657 Write uninterpreted bytes into the target's special data area
39658 identified by the keyword @var{object}, starting at @var{offset} bytes
39659 into the data. @var{data}@dots{} is the binary-encoded data
39660 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
39661 is specific to @var{object}; it can supply additional details about what data
39664 Here are the specific requests of this form defined so far. All
39665 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
39666 formats, listed below.
39669 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
39670 @anchor{qXfer siginfo write}
39671 Write @var{data} to the extra signal information on the target system.
39672 The annex part of the generic @samp{qXfer} packet must be
39673 empty (@pxref{qXfer write}).
39675 This packet is not probed by default; the remote stub must request it,
39676 by supplying an appropriate @samp{qSupported} response
39677 (@pxref{qSupported}).
39679 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
39680 @anchor{qXfer spu write}
39681 Write @var{data} to an @code{spufs} file on the target system. The
39682 annex specifies which file to write; it must be of the form
39683 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
39684 in the target process, and @var{name} identifes the @code{spufs} file
39685 in that context to be accessed.
39687 This packet is not probed by default; the remote stub must request it,
39688 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39694 @var{nn} (hex encoded) is the number of bytes written.
39695 This may be fewer bytes than supplied in the request.
39698 The request was malformed, or @var{annex} was invalid.
39701 The offset was invalid, or there was an error encountered writing the data.
39702 @var{nn} is a hex-encoded @code{errno} value.
39705 An empty reply indicates the @var{object} string was not
39706 recognized by the stub, or that the object does not support writing.
39709 @item qXfer:@var{object}:@var{operation}:@dots{}
39710 Requests of this form may be added in the future. When a stub does
39711 not recognize the @var{object} keyword, or its support for
39712 @var{object} does not recognize the @var{operation} keyword, the stub
39713 must respond with an empty packet.
39715 @item qAttached:@var{pid}
39716 @cindex query attached, remote request
39717 @cindex @samp{qAttached} packet
39718 Return an indication of whether the remote server attached to an
39719 existing process or created a new process. When the multiprocess
39720 protocol extensions are supported (@pxref{multiprocess extensions}),
39721 @var{pid} is an integer in hexadecimal format identifying the target
39722 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
39723 the query packet will be simplified as @samp{qAttached}.
39725 This query is used, for example, to know whether the remote process
39726 should be detached or killed when a @value{GDBN} session is ended with
39727 the @code{quit} command.
39732 The remote server attached to an existing process.
39734 The remote server created a new process.
39736 A badly formed request or an error was encountered.
39740 Enable branch tracing for the current thread using bts tracing.
39745 Branch tracing has been enabled.
39747 A badly formed request or an error was encountered.
39751 Disable branch tracing for the current thread.
39756 Branch tracing has been disabled.
39758 A badly formed request or an error was encountered.
39763 @node Architecture-Specific Protocol Details
39764 @section Architecture-Specific Protocol Details
39766 This section describes how the remote protocol is applied to specific
39767 target architectures. Also see @ref{Standard Target Features}, for
39768 details of XML target descriptions for each architecture.
39771 * ARM-Specific Protocol Details::
39772 * MIPS-Specific Protocol Details::
39775 @node ARM-Specific Protocol Details
39776 @subsection @acronym{ARM}-specific Protocol Details
39779 * ARM Breakpoint Kinds::
39782 @node ARM Breakpoint Kinds
39783 @subsubsection @acronym{ARM} Breakpoint Kinds
39784 @cindex breakpoint kinds, @acronym{ARM}
39786 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
39791 16-bit Thumb mode breakpoint.
39794 32-bit Thumb mode (Thumb-2) breakpoint.
39797 32-bit @acronym{ARM} mode breakpoint.
39801 @node MIPS-Specific Protocol Details
39802 @subsection @acronym{MIPS}-specific Protocol Details
39805 * MIPS Register packet Format::
39806 * MIPS Breakpoint Kinds::
39809 @node MIPS Register packet Format
39810 @subsubsection @acronym{MIPS} Register Packet Format
39811 @cindex register packet format, @acronym{MIPS}
39813 The following @code{g}/@code{G} packets have previously been defined.
39814 In the below, some thirty-two bit registers are transferred as
39815 sixty-four bits. Those registers should be zero/sign extended (which?)
39816 to fill the space allocated. Register bytes are transferred in target
39817 byte order. The two nibbles within a register byte are transferred
39818 most-significant -- least-significant.
39823 All registers are transferred as thirty-two bit quantities in the order:
39824 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
39825 registers; fsr; fir; fp.
39828 All registers are transferred as sixty-four bit quantities (including
39829 thirty-two bit registers such as @code{sr}). The ordering is the same
39834 @node MIPS Breakpoint Kinds
39835 @subsubsection @acronym{MIPS} Breakpoint Kinds
39836 @cindex breakpoint kinds, @acronym{MIPS}
39838 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
39843 16-bit @acronym{MIPS16} mode breakpoint.
39846 16-bit @acronym{microMIPS} mode breakpoint.
39849 32-bit standard @acronym{MIPS} mode breakpoint.
39852 32-bit @acronym{microMIPS} mode breakpoint.
39856 @node Tracepoint Packets
39857 @section Tracepoint Packets
39858 @cindex tracepoint packets
39859 @cindex packets, tracepoint
39861 Here we describe the packets @value{GDBN} uses to implement
39862 tracepoints (@pxref{Tracepoints}).
39866 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
39867 @cindex @samp{QTDP} packet
39868 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
39869 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
39870 the tracepoint is disabled. @var{step} is the tracepoint's step
39871 count, and @var{pass} is its pass count. If an @samp{F} is present,
39872 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
39873 the number of bytes that the target should copy elsewhere to make room
39874 for the tracepoint. If an @samp{X} is present, it introduces a
39875 tracepoint condition, which consists of a hexadecimal length, followed
39876 by a comma and hex-encoded bytes, in a manner similar to action
39877 encodings as described below. If the trailing @samp{-} is present,
39878 further @samp{QTDP} packets will follow to specify this tracepoint's
39884 The packet was understood and carried out.
39886 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
39888 The packet was not recognized.
39891 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
39892 Define actions to be taken when a tracepoint is hit. @var{n} and
39893 @var{addr} must be the same as in the initial @samp{QTDP} packet for
39894 this tracepoint. This packet may only be sent immediately after
39895 another @samp{QTDP} packet that ended with a @samp{-}. If the
39896 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
39897 specifying more actions for this tracepoint.
39899 In the series of action packets for a given tracepoint, at most one
39900 can have an @samp{S} before its first @var{action}. If such a packet
39901 is sent, it and the following packets define ``while-stepping''
39902 actions. Any prior packets define ordinary actions --- that is, those
39903 taken when the tracepoint is first hit. If no action packet has an
39904 @samp{S}, then all the packets in the series specify ordinary
39905 tracepoint actions.
39907 The @samp{@var{action}@dots{}} portion of the packet is a series of
39908 actions, concatenated without separators. Each action has one of the
39914 Collect the registers whose bits are set in @var{mask}. @var{mask} is
39915 a hexadecimal number whose @var{i}'th bit is set if register number
39916 @var{i} should be collected. (The least significant bit is numbered
39917 zero.) Note that @var{mask} may be any number of digits long; it may
39918 not fit in a 32-bit word.
39920 @item M @var{basereg},@var{offset},@var{len}
39921 Collect @var{len} bytes of memory starting at the address in register
39922 number @var{basereg}, plus @var{offset}. If @var{basereg} is
39923 @samp{-1}, then the range has a fixed address: @var{offset} is the
39924 address of the lowest byte to collect. The @var{basereg},
39925 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
39926 values (the @samp{-1} value for @var{basereg} is a special case).
39928 @item X @var{len},@var{expr}
39929 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
39930 it directs. @var{expr} is an agent expression, as described in
39931 @ref{Agent Expressions}. Each byte of the expression is encoded as a
39932 two-digit hex number in the packet; @var{len} is the number of bytes
39933 in the expression (and thus one-half the number of hex digits in the
39938 Any number of actions may be packed together in a single @samp{QTDP}
39939 packet, as long as the packet does not exceed the maximum packet
39940 length (400 bytes, for many stubs). There may be only one @samp{R}
39941 action per tracepoint, and it must precede any @samp{M} or @samp{X}
39942 actions. Any registers referred to by @samp{M} and @samp{X} actions
39943 must be collected by a preceding @samp{R} action. (The
39944 ``while-stepping'' actions are treated as if they were attached to a
39945 separate tracepoint, as far as these restrictions are concerned.)
39950 The packet was understood and carried out.
39952 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
39954 The packet was not recognized.
39957 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
39958 @cindex @samp{QTDPsrc} packet
39959 Specify a source string of tracepoint @var{n} at address @var{addr}.
39960 This is useful to get accurate reproduction of the tracepoints
39961 originally downloaded at the beginning of the trace run. @var{type}
39962 is the name of the tracepoint part, such as @samp{cond} for the
39963 tracepoint's conditional expression (see below for a list of types), while
39964 @var{bytes} is the string, encoded in hexadecimal.
39966 @var{start} is the offset of the @var{bytes} within the overall source
39967 string, while @var{slen} is the total length of the source string.
39968 This is intended for handling source strings that are longer than will
39969 fit in a single packet.
39970 @c Add detailed example when this info is moved into a dedicated
39971 @c tracepoint descriptions section.
39973 The available string types are @samp{at} for the location,
39974 @samp{cond} for the conditional, and @samp{cmd} for an action command.
39975 @value{GDBN} sends a separate packet for each command in the action
39976 list, in the same order in which the commands are stored in the list.
39978 The target does not need to do anything with source strings except
39979 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
39982 Although this packet is optional, and @value{GDBN} will only send it
39983 if the target replies with @samp{TracepointSource} @xref{General
39984 Query Packets}, it makes both disconnected tracing and trace files
39985 much easier to use. Otherwise the user must be careful that the
39986 tracepoints in effect while looking at trace frames are identical to
39987 the ones in effect during the trace run; even a small discrepancy
39988 could cause @samp{tdump} not to work, or a particular trace frame not
39991 @item QTDV:@var{n}:@var{value}
39992 @cindex define trace state variable, remote request
39993 @cindex @samp{QTDV} packet
39994 Create a new trace state variable, number @var{n}, with an initial
39995 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
39996 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
39997 the option of not using this packet for initial values of zero; the
39998 target should simply create the trace state variables as they are
39999 mentioned in expressions.
40001 @item QTFrame:@var{n}
40002 @cindex @samp{QTFrame} packet
40003 Select the @var{n}'th tracepoint frame from the buffer, and use the
40004 register and memory contents recorded there to answer subsequent
40005 request packets from @value{GDBN}.
40007 A successful reply from the stub indicates that the stub has found the
40008 requested frame. The response is a series of parts, concatenated
40009 without separators, describing the frame we selected. Each part has
40010 one of the following forms:
40014 The selected frame is number @var{n} in the trace frame buffer;
40015 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
40016 was no frame matching the criteria in the request packet.
40019 The selected trace frame records a hit of tracepoint number @var{t};
40020 @var{t} is a hexadecimal number.
40024 @item QTFrame:pc:@var{addr}
40025 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40026 currently selected frame whose PC is @var{addr};
40027 @var{addr} is a hexadecimal number.
40029 @item QTFrame:tdp:@var{t}
40030 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40031 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
40032 is a hexadecimal number.
40034 @item QTFrame:range:@var{start}:@var{end}
40035 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40036 currently selected frame whose PC is between @var{start} (inclusive)
40037 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
40040 @item QTFrame:outside:@var{start}:@var{end}
40041 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
40042 frame @emph{outside} the given range of addresses (exclusive).
40045 @cindex @samp{qTMinFTPILen} packet
40046 This packet requests the minimum length of instruction at which a fast
40047 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
40048 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
40049 it depends on the target system being able to create trampolines in
40050 the first 64K of memory, which might or might not be possible for that
40051 system. So the reply to this packet will be 4 if it is able to
40058 The minimum instruction length is currently unknown.
40060 The minimum instruction length is @var{length}, where @var{length} is greater
40061 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
40062 that a fast tracepoint may be placed on any instruction regardless of size.
40064 An error has occurred.
40066 An empty reply indicates that the request is not supported by the stub.
40070 @cindex @samp{QTStart} packet
40071 Begin the tracepoint experiment. Begin collecting data from
40072 tracepoint hits in the trace frame buffer. This packet supports the
40073 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
40074 instruction reply packet}).
40077 @cindex @samp{QTStop} packet
40078 End the tracepoint experiment. Stop collecting trace frames.
40080 @item QTEnable:@var{n}:@var{addr}
40082 @cindex @samp{QTEnable} packet
40083 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
40084 experiment. If the tracepoint was previously disabled, then collection
40085 of data from it will resume.
40087 @item QTDisable:@var{n}:@var{addr}
40089 @cindex @samp{QTDisable} packet
40090 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
40091 experiment. No more data will be collected from the tracepoint unless
40092 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
40095 @cindex @samp{QTinit} packet
40096 Clear the table of tracepoints, and empty the trace frame buffer.
40098 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
40099 @cindex @samp{QTro} packet
40100 Establish the given ranges of memory as ``transparent''. The stub
40101 will answer requests for these ranges from memory's current contents,
40102 if they were not collected as part of the tracepoint hit.
40104 @value{GDBN} uses this to mark read-only regions of memory, like those
40105 containing program code. Since these areas never change, they should
40106 still have the same contents they did when the tracepoint was hit, so
40107 there's no reason for the stub to refuse to provide their contents.
40109 @item QTDisconnected:@var{value}
40110 @cindex @samp{QTDisconnected} packet
40111 Set the choice to what to do with the tracing run when @value{GDBN}
40112 disconnects from the target. A @var{value} of 1 directs the target to
40113 continue the tracing run, while 0 tells the target to stop tracing if
40114 @value{GDBN} is no longer in the picture.
40117 @cindex @samp{qTStatus} packet
40118 Ask the stub if there is a trace experiment running right now.
40120 The reply has the form:
40124 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
40125 @var{running} is a single digit @code{1} if the trace is presently
40126 running, or @code{0} if not. It is followed by semicolon-separated
40127 optional fields that an agent may use to report additional status.
40131 If the trace is not running, the agent may report any of several
40132 explanations as one of the optional fields:
40137 No trace has been run yet.
40139 @item tstop[:@var{text}]:0
40140 The trace was stopped by a user-originated stop command. The optional
40141 @var{text} field is a user-supplied string supplied as part of the
40142 stop command (for instance, an explanation of why the trace was
40143 stopped manually). It is hex-encoded.
40146 The trace stopped because the trace buffer filled up.
40148 @item tdisconnected:0
40149 The trace stopped because @value{GDBN} disconnected from the target.
40151 @item tpasscount:@var{tpnum}
40152 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
40154 @item terror:@var{text}:@var{tpnum}
40155 The trace stopped because tracepoint @var{tpnum} had an error. The
40156 string @var{text} is available to describe the nature of the error
40157 (for instance, a divide by zero in the condition expression).
40158 @var{text} is hex encoded.
40161 The trace stopped for some other reason.
40165 Additional optional fields supply statistical and other information.
40166 Although not required, they are extremely useful for users monitoring
40167 the progress of a trace run. If a trace has stopped, and these
40168 numbers are reported, they must reflect the state of the just-stopped
40173 @item tframes:@var{n}
40174 The number of trace frames in the buffer.
40176 @item tcreated:@var{n}
40177 The total number of trace frames created during the run. This may
40178 be larger than the trace frame count, if the buffer is circular.
40180 @item tsize:@var{n}
40181 The total size of the trace buffer, in bytes.
40183 @item tfree:@var{n}
40184 The number of bytes still unused in the buffer.
40186 @item circular:@var{n}
40187 The value of the circular trace buffer flag. @code{1} means that the
40188 trace buffer is circular and old trace frames will be discarded if
40189 necessary to make room, @code{0} means that the trace buffer is linear
40192 @item disconn:@var{n}
40193 The value of the disconnected tracing flag. @code{1} means that
40194 tracing will continue after @value{GDBN} disconnects, @code{0} means
40195 that the trace run will stop.
40199 @item qTP:@var{tp}:@var{addr}
40200 @cindex tracepoint status, remote request
40201 @cindex @samp{qTP} packet
40202 Ask the stub for the current state of tracepoint number @var{tp} at
40203 address @var{addr}.
40207 @item V@var{hits}:@var{usage}
40208 The tracepoint has been hit @var{hits} times so far during the trace
40209 run, and accounts for @var{usage} in the trace buffer. Note that
40210 @code{while-stepping} steps are not counted as separate hits, but the
40211 steps' space consumption is added into the usage number.
40215 @item qTV:@var{var}
40216 @cindex trace state variable value, remote request
40217 @cindex @samp{qTV} packet
40218 Ask the stub for the value of the trace state variable number @var{var}.
40223 The value of the variable is @var{value}. This will be the current
40224 value of the variable if the user is examining a running target, or a
40225 saved value if the variable was collected in the trace frame that the
40226 user is looking at. Note that multiple requests may result in
40227 different reply values, such as when requesting values while the
40228 program is running.
40231 The value of the variable is unknown. This would occur, for example,
40232 if the user is examining a trace frame in which the requested variable
40237 @cindex @samp{qTfP} packet
40239 @cindex @samp{qTsP} packet
40240 These packets request data about tracepoints that are being used by
40241 the target. @value{GDBN} sends @code{qTfP} to get the first piece
40242 of data, and multiple @code{qTsP} to get additional pieces. Replies
40243 to these packets generally take the form of the @code{QTDP} packets
40244 that define tracepoints. (FIXME add detailed syntax)
40247 @cindex @samp{qTfV} packet
40249 @cindex @samp{qTsV} packet
40250 These packets request data about trace state variables that are on the
40251 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
40252 and multiple @code{qTsV} to get additional variables. Replies to
40253 these packets follow the syntax of the @code{QTDV} packets that define
40254 trace state variables.
40260 @cindex @samp{qTfSTM} packet
40261 @cindex @samp{qTsSTM} packet
40262 These packets request data about static tracepoint markers that exist
40263 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
40264 first piece of data, and multiple @code{qTsSTM} to get additional
40265 pieces. Replies to these packets take the following form:
40269 @item m @var{address}:@var{id}:@var{extra}
40271 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
40272 a comma-separated list of markers
40274 (lower case letter @samp{L}) denotes end of list.
40276 An error occurred. @var{nn} are hex digits.
40278 An empty reply indicates that the request is not supported by the
40282 @var{address} is encoded in hex.
40283 @var{id} and @var{extra} are strings encoded in hex.
40285 In response to each query, the target will reply with a list of one or
40286 more markers, separated by commas. @value{GDBN} will respond to each
40287 reply with a request for more markers (using the @samp{qs} form of the
40288 query), until the target responds with @samp{l} (lower-case ell, for
40291 @item qTSTMat:@var{address}
40293 @cindex @samp{qTSTMat} packet
40294 This packets requests data about static tracepoint markers in the
40295 target program at @var{address}. Replies to this packet follow the
40296 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
40297 tracepoint markers.
40299 @item QTSave:@var{filename}
40300 @cindex @samp{QTSave} packet
40301 This packet directs the target to save trace data to the file name
40302 @var{filename} in the target's filesystem. @var{filename} is encoded
40303 as a hex string; the interpretation of the file name (relative vs
40304 absolute, wild cards, etc) is up to the target.
40306 @item qTBuffer:@var{offset},@var{len}
40307 @cindex @samp{qTBuffer} packet
40308 Return up to @var{len} bytes of the current contents of trace buffer,
40309 starting at @var{offset}. The trace buffer is treated as if it were
40310 a contiguous collection of traceframes, as per the trace file format.
40311 The reply consists as many hex-encoded bytes as the target can deliver
40312 in a packet; it is not an error to return fewer than were asked for.
40313 A reply consisting of just @code{l} indicates that no bytes are
40316 @item QTBuffer:circular:@var{value}
40317 This packet directs the target to use a circular trace buffer if
40318 @var{value} is 1, or a linear buffer if the value is 0.
40320 @item QTBuffer:size:@var{size}
40321 @anchor{QTBuffer-size}
40322 @cindex @samp{QTBuffer size} packet
40323 This packet directs the target to make the trace buffer be of size
40324 @var{size} if possible. A value of @code{-1} tells the target to
40325 use whatever size it prefers.
40327 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
40328 @cindex @samp{QTNotes} packet
40329 This packet adds optional textual notes to the trace run. Allowable
40330 types include @code{user}, @code{notes}, and @code{tstop}, the
40331 @var{text} fields are arbitrary strings, hex-encoded.
40335 @subsection Relocate instruction reply packet
40336 When installing fast tracepoints in memory, the target may need to
40337 relocate the instruction currently at the tracepoint address to a
40338 different address in memory. For most instructions, a simple copy is
40339 enough, but, for example, call instructions that implicitly push the
40340 return address on the stack, and relative branches or other
40341 PC-relative instructions require offset adjustment, so that the effect
40342 of executing the instruction at a different address is the same as if
40343 it had executed in the original location.
40345 In response to several of the tracepoint packets, the target may also
40346 respond with a number of intermediate @samp{qRelocInsn} request
40347 packets before the final result packet, to have @value{GDBN} handle
40348 this relocation operation. If a packet supports this mechanism, its
40349 documentation will explicitly say so. See for example the above
40350 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
40351 format of the request is:
40354 @item qRelocInsn:@var{from};@var{to}
40356 This requests @value{GDBN} to copy instruction at address @var{from}
40357 to address @var{to}, possibly adjusted so that executing the
40358 instruction at @var{to} has the same effect as executing it at
40359 @var{from}. @value{GDBN} writes the adjusted instruction to target
40360 memory starting at @var{to}.
40365 @item qRelocInsn:@var{adjusted_size}
40366 Informs the stub the relocation is complete. @var{adjusted_size} is
40367 the length in bytes of resulting relocated instruction sequence.
40369 A badly formed request was detected, or an error was encountered while
40370 relocating the instruction.
40373 @node Host I/O Packets
40374 @section Host I/O Packets
40375 @cindex Host I/O, remote protocol
40376 @cindex file transfer, remote protocol
40378 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
40379 operations on the far side of a remote link. For example, Host I/O is
40380 used to upload and download files to a remote target with its own
40381 filesystem. Host I/O uses the same constant values and data structure
40382 layout as the target-initiated File-I/O protocol. However, the
40383 Host I/O packets are structured differently. The target-initiated
40384 protocol relies on target memory to store parameters and buffers.
40385 Host I/O requests are initiated by @value{GDBN}, and the
40386 target's memory is not involved. @xref{File-I/O Remote Protocol
40387 Extension}, for more details on the target-initiated protocol.
40389 The Host I/O request packets all encode a single operation along with
40390 its arguments. They have this format:
40394 @item vFile:@var{operation}: @var{parameter}@dots{}
40395 @var{operation} is the name of the particular request; the target
40396 should compare the entire packet name up to the second colon when checking
40397 for a supported operation. The format of @var{parameter} depends on
40398 the operation. Numbers are always passed in hexadecimal. Negative
40399 numbers have an explicit minus sign (i.e.@: two's complement is not
40400 used). Strings (e.g.@: filenames) are encoded as a series of
40401 hexadecimal bytes. The last argument to a system call may be a
40402 buffer of escaped binary data (@pxref{Binary Data}).
40406 The valid responses to Host I/O packets are:
40410 @item F @var{result} [, @var{errno}] [; @var{attachment}]
40411 @var{result} is the integer value returned by this operation, usually
40412 non-negative for success and -1 for errors. If an error has occured,
40413 @var{errno} will be included in the result. @var{errno} will have a
40414 value defined by the File-I/O protocol (@pxref{Errno Values}). For
40415 operations which return data, @var{attachment} supplies the data as a
40416 binary buffer. Binary buffers in response packets are escaped in the
40417 normal way (@pxref{Binary Data}). See the individual packet
40418 documentation for the interpretation of @var{result} and
40422 An empty response indicates that this operation is not recognized.
40426 These are the supported Host I/O operations:
40429 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
40430 Open a file at @var{pathname} and return a file descriptor for it, or
40431 return -1 if an error occurs. @var{pathname} is a string,
40432 @var{flags} is an integer indicating a mask of open flags
40433 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
40434 of mode bits to use if the file is created (@pxref{mode_t Values}).
40435 @xref{open}, for details of the open flags and mode values.
40437 @item vFile:close: @var{fd}
40438 Close the open file corresponding to @var{fd} and return 0, or
40439 -1 if an error occurs.
40441 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
40442 Read data from the open file corresponding to @var{fd}. Up to
40443 @var{count} bytes will be read from the file, starting at @var{offset}
40444 relative to the start of the file. The target may read fewer bytes;
40445 common reasons include packet size limits and an end-of-file
40446 condition. The number of bytes read is returned. Zero should only be
40447 returned for a successful read at the end of the file, or if
40448 @var{count} was zero.
40450 The data read should be returned as a binary attachment on success.
40451 If zero bytes were read, the response should include an empty binary
40452 attachment (i.e.@: a trailing semicolon). The return value is the
40453 number of target bytes read; the binary attachment may be longer if
40454 some characters were escaped.
40456 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
40457 Write @var{data} (a binary buffer) to the open file corresponding
40458 to @var{fd}. Start the write at @var{offset} from the start of the
40459 file. Unlike many @code{write} system calls, there is no
40460 separate @var{count} argument; the length of @var{data} in the
40461 packet is used. @samp{vFile:write} returns the number of bytes written,
40462 which may be shorter than the length of @var{data}, or -1 if an
40465 @item vFile:unlink: @var{pathname}
40466 Delete the file at @var{pathname} on the target. Return 0,
40467 or -1 if an error occurs. @var{pathname} is a string.
40469 @item vFile:readlink: @var{filename}
40470 Read value of symbolic link @var{filename} on the target. Return
40471 the number of bytes read, or -1 if an error occurs.
40473 The data read should be returned as a binary attachment on success.
40474 If zero bytes were read, the response should include an empty binary
40475 attachment (i.e.@: a trailing semicolon). The return value is the
40476 number of target bytes read; the binary attachment may be longer if
40477 some characters were escaped.
40482 @section Interrupts
40483 @cindex interrupts (remote protocol)
40485 When a program on the remote target is running, @value{GDBN} may
40486 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
40487 a @code{BREAK} followed by @code{g},
40488 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
40490 The precise meaning of @code{BREAK} is defined by the transport
40491 mechanism and may, in fact, be undefined. @value{GDBN} does not
40492 currently define a @code{BREAK} mechanism for any of the network
40493 interfaces except for TCP, in which case @value{GDBN} sends the
40494 @code{telnet} BREAK sequence.
40496 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
40497 transport mechanisms. It is represented by sending the single byte
40498 @code{0x03} without any of the usual packet overhead described in
40499 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
40500 transmitted as part of a packet, it is considered to be packet data
40501 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
40502 (@pxref{X packet}), used for binary downloads, may include an unescaped
40503 @code{0x03} as part of its packet.
40505 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
40506 When Linux kernel receives this sequence from serial port,
40507 it stops execution and connects to gdb.
40509 Stubs are not required to recognize these interrupt mechanisms and the
40510 precise meaning associated with receipt of the interrupt is
40511 implementation defined. If the target supports debugging of multiple
40512 threads and/or processes, it should attempt to interrupt all
40513 currently-executing threads and processes.
40514 If the stub is successful at interrupting the
40515 running program, it should send one of the stop
40516 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
40517 of successfully stopping the program in all-stop mode, and a stop reply
40518 for each stopped thread in non-stop mode.
40519 Interrupts received while the
40520 program is stopped are discarded.
40522 @node Notification Packets
40523 @section Notification Packets
40524 @cindex notification packets
40525 @cindex packets, notification
40527 The @value{GDBN} remote serial protocol includes @dfn{notifications},
40528 packets that require no acknowledgment. Both the GDB and the stub
40529 may send notifications (although the only notifications defined at
40530 present are sent by the stub). Notifications carry information
40531 without incurring the round-trip latency of an acknowledgment, and so
40532 are useful for low-impact communications where occasional packet loss
40535 A notification packet has the form @samp{% @var{data} #
40536 @var{checksum}}, where @var{data} is the content of the notification,
40537 and @var{checksum} is a checksum of @var{data}, computed and formatted
40538 as for ordinary @value{GDBN} packets. A notification's @var{data}
40539 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
40540 receiving a notification, the recipient sends no @samp{+} or @samp{-}
40541 to acknowledge the notification's receipt or to report its corruption.
40543 Every notification's @var{data} begins with a name, which contains no
40544 colon characters, followed by a colon character.
40546 Recipients should silently ignore corrupted notifications and
40547 notifications they do not understand. Recipients should restart
40548 timeout periods on receipt of a well-formed notification, whether or
40549 not they understand it.
40551 Senders should only send the notifications described here when this
40552 protocol description specifies that they are permitted. In the
40553 future, we may extend the protocol to permit existing notifications in
40554 new contexts; this rule helps older senders avoid confusing newer
40557 (Older versions of @value{GDBN} ignore bytes received until they see
40558 the @samp{$} byte that begins an ordinary packet, so new stubs may
40559 transmit notifications without fear of confusing older clients. There
40560 are no notifications defined for @value{GDBN} to send at the moment, but we
40561 assume that most older stubs would ignore them, as well.)
40563 Each notification is comprised of three parts:
40565 @item @var{name}:@var{event}
40566 The notification packet is sent by the side that initiates the
40567 exchange (currently, only the stub does that), with @var{event}
40568 carrying the specific information about the notification.
40569 @var{name} is the name of the notification.
40571 The acknowledge sent by the other side, usually @value{GDBN}, to
40572 acknowledge the exchange and request the event.
40575 The purpose of an asynchronous notification mechanism is to report to
40576 @value{GDBN} that something interesting happened in the remote stub.
40578 The remote stub may send notification @var{name}:@var{event}
40579 at any time, but @value{GDBN} acknowledges the notification when
40580 appropriate. The notification event is pending before @value{GDBN}
40581 acknowledges. Only one notification at a time may be pending; if
40582 additional events occur before @value{GDBN} has acknowledged the
40583 previous notification, they must be queued by the stub for later
40584 synchronous transmission in response to @var{ack} packets from
40585 @value{GDBN}. Because the notification mechanism is unreliable,
40586 the stub is permitted to resend a notification if it believes
40587 @value{GDBN} may not have received it.
40589 Specifically, notifications may appear when @value{GDBN} is not
40590 otherwise reading input from the stub, or when @value{GDBN} is
40591 expecting to read a normal synchronous response or a
40592 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
40593 Notification packets are distinct from any other communication from
40594 the stub so there is no ambiguity.
40596 After receiving a notification, @value{GDBN} shall acknowledge it by
40597 sending a @var{ack} packet as a regular, synchronous request to the
40598 stub. Such acknowledgment is not required to happen immediately, as
40599 @value{GDBN} is permitted to send other, unrelated packets to the
40600 stub first, which the stub should process normally.
40602 Upon receiving a @var{ack} packet, if the stub has other queued
40603 events to report to @value{GDBN}, it shall respond by sending a
40604 normal @var{event}. @value{GDBN} shall then send another @var{ack}
40605 packet to solicit further responses; again, it is permitted to send
40606 other, unrelated packets as well which the stub should process
40609 If the stub receives a @var{ack} packet and there are no additional
40610 @var{event} to report, the stub shall return an @samp{OK} response.
40611 At this point, @value{GDBN} has finished processing a notification
40612 and the stub has completed sending any queued events. @value{GDBN}
40613 won't accept any new notifications until the final @samp{OK} is
40614 received . If further notification events occur, the stub shall send
40615 a new notification, @value{GDBN} shall accept the notification, and
40616 the process shall be repeated.
40618 The process of asynchronous notification can be illustrated by the
40621 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
40624 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
40626 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
40631 The following notifications are defined:
40632 @multitable @columnfractions 0.12 0.12 0.38 0.38
40641 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
40642 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
40643 for information on how these notifications are acknowledged by
40645 @tab Report an asynchronous stop event in non-stop mode.
40649 @node Remote Non-Stop
40650 @section Remote Protocol Support for Non-Stop Mode
40652 @value{GDBN}'s remote protocol supports non-stop debugging of
40653 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
40654 supports non-stop mode, it should report that to @value{GDBN} by including
40655 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
40657 @value{GDBN} typically sends a @samp{QNonStop} packet only when
40658 establishing a new connection with the stub. Entering non-stop mode
40659 does not alter the state of any currently-running threads, but targets
40660 must stop all threads in any already-attached processes when entering
40661 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
40662 probe the target state after a mode change.
40664 In non-stop mode, when an attached process encounters an event that
40665 would otherwise be reported with a stop reply, it uses the
40666 asynchronous notification mechanism (@pxref{Notification Packets}) to
40667 inform @value{GDBN}. In contrast to all-stop mode, where all threads
40668 in all processes are stopped when a stop reply is sent, in non-stop
40669 mode only the thread reporting the stop event is stopped. That is,
40670 when reporting a @samp{S} or @samp{T} response to indicate completion
40671 of a step operation, hitting a breakpoint, or a fault, only the
40672 affected thread is stopped; any other still-running threads continue
40673 to run. When reporting a @samp{W} or @samp{X} response, all running
40674 threads belonging to other attached processes continue to run.
40676 In non-stop mode, the target shall respond to the @samp{?} packet as
40677 follows. First, any incomplete stop reply notification/@samp{vStopped}
40678 sequence in progress is abandoned. The target must begin a new
40679 sequence reporting stop events for all stopped threads, whether or not
40680 it has previously reported those events to @value{GDBN}. The first
40681 stop reply is sent as a synchronous reply to the @samp{?} packet, and
40682 subsequent stop replies are sent as responses to @samp{vStopped} packets
40683 using the mechanism described above. The target must not send
40684 asynchronous stop reply notifications until the sequence is complete.
40685 If all threads are running when the target receives the @samp{?} packet,
40686 or if the target is not attached to any process, it shall respond
40689 @node Packet Acknowledgment
40690 @section Packet Acknowledgment
40692 @cindex acknowledgment, for @value{GDBN} remote
40693 @cindex packet acknowledgment, for @value{GDBN} remote
40694 By default, when either the host or the target machine receives a packet,
40695 the first response expected is an acknowledgment: either @samp{+} (to indicate
40696 the package was received correctly) or @samp{-} (to request retransmission).
40697 This mechanism allows the @value{GDBN} remote protocol to operate over
40698 unreliable transport mechanisms, such as a serial line.
40700 In cases where the transport mechanism is itself reliable (such as a pipe or
40701 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
40702 It may be desirable to disable them in that case to reduce communication
40703 overhead, or for other reasons. This can be accomplished by means of the
40704 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
40706 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
40707 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
40708 and response format still includes the normal checksum, as described in
40709 @ref{Overview}, but the checksum may be ignored by the receiver.
40711 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
40712 no-acknowledgment mode, it should report that to @value{GDBN}
40713 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
40714 @pxref{qSupported}.
40715 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
40716 disabled via the @code{set remote noack-packet off} command
40717 (@pxref{Remote Configuration}),
40718 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
40719 Only then may the stub actually turn off packet acknowledgments.
40720 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
40721 response, which can be safely ignored by the stub.
40723 Note that @code{set remote noack-packet} command only affects negotiation
40724 between @value{GDBN} and the stub when subsequent connections are made;
40725 it does not affect the protocol acknowledgment state for any current
40727 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
40728 new connection is established,
40729 there is also no protocol request to re-enable the acknowledgments
40730 for the current connection, once disabled.
40735 Example sequence of a target being re-started. Notice how the restart
40736 does not get any direct output:
40741 @emph{target restarts}
40744 <- @code{T001:1234123412341234}
40748 Example sequence of a target being stepped by a single instruction:
40751 -> @code{G1445@dots{}}
40756 <- @code{T001:1234123412341234}
40760 <- @code{1455@dots{}}
40764 @node File-I/O Remote Protocol Extension
40765 @section File-I/O Remote Protocol Extension
40766 @cindex File-I/O remote protocol extension
40769 * File-I/O Overview::
40770 * Protocol Basics::
40771 * The F Request Packet::
40772 * The F Reply Packet::
40773 * The Ctrl-C Message::
40775 * List of Supported Calls::
40776 * Protocol-specific Representation of Datatypes::
40778 * File-I/O Examples::
40781 @node File-I/O Overview
40782 @subsection File-I/O Overview
40783 @cindex file-i/o overview
40785 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
40786 target to use the host's file system and console I/O to perform various
40787 system calls. System calls on the target system are translated into a
40788 remote protocol packet to the host system, which then performs the needed
40789 actions and returns a response packet to the target system.
40790 This simulates file system operations even on targets that lack file systems.
40792 The protocol is defined to be independent of both the host and target systems.
40793 It uses its own internal representation of datatypes and values. Both
40794 @value{GDBN} and the target's @value{GDBN} stub are responsible for
40795 translating the system-dependent value representations into the internal
40796 protocol representations when data is transmitted.
40798 The communication is synchronous. A system call is possible only when
40799 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
40800 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
40801 the target is stopped to allow deterministic access to the target's
40802 memory. Therefore File-I/O is not interruptible by target signals. On
40803 the other hand, it is possible to interrupt File-I/O by a user interrupt
40804 (@samp{Ctrl-C}) within @value{GDBN}.
40806 The target's request to perform a host system call does not finish
40807 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
40808 after finishing the system call, the target returns to continuing the
40809 previous activity (continue, step). No additional continue or step
40810 request from @value{GDBN} is required.
40813 (@value{GDBP}) continue
40814 <- target requests 'system call X'
40815 target is stopped, @value{GDBN} executes system call
40816 -> @value{GDBN} returns result
40817 ... target continues, @value{GDBN} returns to wait for the target
40818 <- target hits breakpoint and sends a Txx packet
40821 The protocol only supports I/O on the console and to regular files on
40822 the host file system. Character or block special devices, pipes,
40823 named pipes, sockets or any other communication method on the host
40824 system are not supported by this protocol.
40826 File I/O is not supported in non-stop mode.
40828 @node Protocol Basics
40829 @subsection Protocol Basics
40830 @cindex protocol basics, file-i/o
40832 The File-I/O protocol uses the @code{F} packet as the request as well
40833 as reply packet. Since a File-I/O system call can only occur when
40834 @value{GDBN} is waiting for a response from the continuing or stepping target,
40835 the File-I/O request is a reply that @value{GDBN} has to expect as a result
40836 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
40837 This @code{F} packet contains all information needed to allow @value{GDBN}
40838 to call the appropriate host system call:
40842 A unique identifier for the requested system call.
40845 All parameters to the system call. Pointers are given as addresses
40846 in the target memory address space. Pointers to strings are given as
40847 pointer/length pair. Numerical values are given as they are.
40848 Numerical control flags are given in a protocol-specific representation.
40852 At this point, @value{GDBN} has to perform the following actions.
40856 If the parameters include pointer values to data needed as input to a
40857 system call, @value{GDBN} requests this data from the target with a
40858 standard @code{m} packet request. This additional communication has to be
40859 expected by the target implementation and is handled as any other @code{m}
40863 @value{GDBN} translates all value from protocol representation to host
40864 representation as needed. Datatypes are coerced into the host types.
40867 @value{GDBN} calls the system call.
40870 It then coerces datatypes back to protocol representation.
40873 If the system call is expected to return data in buffer space specified
40874 by pointer parameters to the call, the data is transmitted to the
40875 target using a @code{M} or @code{X} packet. This packet has to be expected
40876 by the target implementation and is handled as any other @code{M} or @code{X}
40881 Eventually @value{GDBN} replies with another @code{F} packet which contains all
40882 necessary information for the target to continue. This at least contains
40889 @code{errno}, if has been changed by the system call.
40896 After having done the needed type and value coercion, the target continues
40897 the latest continue or step action.
40899 @node The F Request Packet
40900 @subsection The @code{F} Request Packet
40901 @cindex file-i/o request packet
40902 @cindex @code{F} request packet
40904 The @code{F} request packet has the following format:
40907 @item F@var{call-id},@var{parameter@dots{}}
40909 @var{call-id} is the identifier to indicate the host system call to be called.
40910 This is just the name of the function.
40912 @var{parameter@dots{}} are the parameters to the system call.
40913 Parameters are hexadecimal integer values, either the actual values in case
40914 of scalar datatypes, pointers to target buffer space in case of compound
40915 datatypes and unspecified memory areas, or pointer/length pairs in case
40916 of string parameters. These are appended to the @var{call-id} as a
40917 comma-delimited list. All values are transmitted in ASCII
40918 string representation, pointer/length pairs separated by a slash.
40924 @node The F Reply Packet
40925 @subsection The @code{F} Reply Packet
40926 @cindex file-i/o reply packet
40927 @cindex @code{F} reply packet
40929 The @code{F} reply packet has the following format:
40933 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
40935 @var{retcode} is the return code of the system call as hexadecimal value.
40937 @var{errno} is the @code{errno} set by the call, in protocol-specific
40939 This parameter can be omitted if the call was successful.
40941 @var{Ctrl-C flag} is only sent if the user requested a break. In this
40942 case, @var{errno} must be sent as well, even if the call was successful.
40943 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
40950 or, if the call was interrupted before the host call has been performed:
40957 assuming 4 is the protocol-specific representation of @code{EINTR}.
40962 @node The Ctrl-C Message
40963 @subsection The @samp{Ctrl-C} Message
40964 @cindex ctrl-c message, in file-i/o protocol
40966 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
40967 reply packet (@pxref{The F Reply Packet}),
40968 the target should behave as if it had
40969 gotten a break message. The meaning for the target is ``system call
40970 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
40971 (as with a break message) and return to @value{GDBN} with a @code{T02}
40974 It's important for the target to know in which
40975 state the system call was interrupted. There are two possible cases:
40979 The system call hasn't been performed on the host yet.
40982 The system call on the host has been finished.
40986 These two states can be distinguished by the target by the value of the
40987 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
40988 call hasn't been performed. This is equivalent to the @code{EINTR} handling
40989 on POSIX systems. In any other case, the target may presume that the
40990 system call has been finished --- successfully or not --- and should behave
40991 as if the break message arrived right after the system call.
40993 @value{GDBN} must behave reliably. If the system call has not been called
40994 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
40995 @code{errno} in the packet. If the system call on the host has been finished
40996 before the user requests a break, the full action must be finished by
40997 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
40998 The @code{F} packet may only be sent when either nothing has happened
40999 or the full action has been completed.
41002 @subsection Console I/O
41003 @cindex console i/o as part of file-i/o
41005 By default and if not explicitly closed by the target system, the file
41006 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
41007 on the @value{GDBN} console is handled as any other file output operation
41008 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
41009 by @value{GDBN} so that after the target read request from file descriptor
41010 0 all following typing is buffered until either one of the following
41015 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
41017 system call is treated as finished.
41020 The user presses @key{RET}. This is treated as end of input with a trailing
41024 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
41025 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
41029 If the user has typed more characters than fit in the buffer given to
41030 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
41031 either another @code{read(0, @dots{})} is requested by the target, or debugging
41032 is stopped at the user's request.
41035 @node List of Supported Calls
41036 @subsection List of Supported Calls
41037 @cindex list of supported file-i/o calls
41054 @unnumberedsubsubsec open
41055 @cindex open, file-i/o system call
41060 int open(const char *pathname, int flags);
41061 int open(const char *pathname, int flags, mode_t mode);
41065 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
41068 @var{flags} is the bitwise @code{OR} of the following values:
41072 If the file does not exist it will be created. The host
41073 rules apply as far as file ownership and time stamps
41077 When used with @code{O_CREAT}, if the file already exists it is
41078 an error and open() fails.
41081 If the file already exists and the open mode allows
41082 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
41083 truncated to zero length.
41086 The file is opened in append mode.
41089 The file is opened for reading only.
41092 The file is opened for writing only.
41095 The file is opened for reading and writing.
41099 Other bits are silently ignored.
41103 @var{mode} is the bitwise @code{OR} of the following values:
41107 User has read permission.
41110 User has write permission.
41113 Group has read permission.
41116 Group has write permission.
41119 Others have read permission.
41122 Others have write permission.
41126 Other bits are silently ignored.
41129 @item Return value:
41130 @code{open} returns the new file descriptor or -1 if an error
41137 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
41140 @var{pathname} refers to a directory.
41143 The requested access is not allowed.
41146 @var{pathname} was too long.
41149 A directory component in @var{pathname} does not exist.
41152 @var{pathname} refers to a device, pipe, named pipe or socket.
41155 @var{pathname} refers to a file on a read-only filesystem and
41156 write access was requested.
41159 @var{pathname} is an invalid pointer value.
41162 No space on device to create the file.
41165 The process already has the maximum number of files open.
41168 The limit on the total number of files open on the system
41172 The call was interrupted by the user.
41178 @unnumberedsubsubsec close
41179 @cindex close, file-i/o system call
41188 @samp{Fclose,@var{fd}}
41190 @item Return value:
41191 @code{close} returns zero on success, or -1 if an error occurred.
41197 @var{fd} isn't a valid open file descriptor.
41200 The call was interrupted by the user.
41206 @unnumberedsubsubsec read
41207 @cindex read, file-i/o system call
41212 int read(int fd, void *buf, unsigned int count);
41216 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
41218 @item Return value:
41219 On success, the number of bytes read is returned.
41220 Zero indicates end of file. If count is zero, read
41221 returns zero as well. On error, -1 is returned.
41227 @var{fd} is not a valid file descriptor or is not open for
41231 @var{bufptr} is an invalid pointer value.
41234 The call was interrupted by the user.
41240 @unnumberedsubsubsec write
41241 @cindex write, file-i/o system call
41246 int write(int fd, const void *buf, unsigned int count);
41250 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
41252 @item Return value:
41253 On success, the number of bytes written are returned.
41254 Zero indicates nothing was written. On error, -1
41261 @var{fd} is not a valid file descriptor or is not open for
41265 @var{bufptr} is an invalid pointer value.
41268 An attempt was made to write a file that exceeds the
41269 host-specific maximum file size allowed.
41272 No space on device to write the data.
41275 The call was interrupted by the user.
41281 @unnumberedsubsubsec lseek
41282 @cindex lseek, file-i/o system call
41287 long lseek (int fd, long offset, int flag);
41291 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
41293 @var{flag} is one of:
41297 The offset is set to @var{offset} bytes.
41300 The offset is set to its current location plus @var{offset}
41304 The offset is set to the size of the file plus @var{offset}
41308 @item Return value:
41309 On success, the resulting unsigned offset in bytes from
41310 the beginning of the file is returned. Otherwise, a
41311 value of -1 is returned.
41317 @var{fd} is not a valid open file descriptor.
41320 @var{fd} is associated with the @value{GDBN} console.
41323 @var{flag} is not a proper value.
41326 The call was interrupted by the user.
41332 @unnumberedsubsubsec rename
41333 @cindex rename, file-i/o system call
41338 int rename(const char *oldpath, const char *newpath);
41342 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
41344 @item Return value:
41345 On success, zero is returned. On error, -1 is returned.
41351 @var{newpath} is an existing directory, but @var{oldpath} is not a
41355 @var{newpath} is a non-empty directory.
41358 @var{oldpath} or @var{newpath} is a directory that is in use by some
41362 An attempt was made to make a directory a subdirectory
41366 A component used as a directory in @var{oldpath} or new
41367 path is not a directory. Or @var{oldpath} is a directory
41368 and @var{newpath} exists but is not a directory.
41371 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
41374 No access to the file or the path of the file.
41378 @var{oldpath} or @var{newpath} was too long.
41381 A directory component in @var{oldpath} or @var{newpath} does not exist.
41384 The file is on a read-only filesystem.
41387 The device containing the file has no room for the new
41391 The call was interrupted by the user.
41397 @unnumberedsubsubsec unlink
41398 @cindex unlink, file-i/o system call
41403 int unlink(const char *pathname);
41407 @samp{Funlink,@var{pathnameptr}/@var{len}}
41409 @item Return value:
41410 On success, zero is returned. On error, -1 is returned.
41416 No access to the file or the path of the file.
41419 The system does not allow unlinking of directories.
41422 The file @var{pathname} cannot be unlinked because it's
41423 being used by another process.
41426 @var{pathnameptr} is an invalid pointer value.
41429 @var{pathname} was too long.
41432 A directory component in @var{pathname} does not exist.
41435 A component of the path is not a directory.
41438 The file is on a read-only filesystem.
41441 The call was interrupted by the user.
41447 @unnumberedsubsubsec stat/fstat
41448 @cindex fstat, file-i/o system call
41449 @cindex stat, file-i/o system call
41454 int stat(const char *pathname, struct stat *buf);
41455 int fstat(int fd, struct stat *buf);
41459 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
41460 @samp{Ffstat,@var{fd},@var{bufptr}}
41462 @item Return value:
41463 On success, zero is returned. On error, -1 is returned.
41469 @var{fd} is not a valid open file.
41472 A directory component in @var{pathname} does not exist or the
41473 path is an empty string.
41476 A component of the path is not a directory.
41479 @var{pathnameptr} is an invalid pointer value.
41482 No access to the file or the path of the file.
41485 @var{pathname} was too long.
41488 The call was interrupted by the user.
41494 @unnumberedsubsubsec gettimeofday
41495 @cindex gettimeofday, file-i/o system call
41500 int gettimeofday(struct timeval *tv, void *tz);
41504 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
41506 @item Return value:
41507 On success, 0 is returned, -1 otherwise.
41513 @var{tz} is a non-NULL pointer.
41516 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
41522 @unnumberedsubsubsec isatty
41523 @cindex isatty, file-i/o system call
41528 int isatty(int fd);
41532 @samp{Fisatty,@var{fd}}
41534 @item Return value:
41535 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
41541 The call was interrupted by the user.
41546 Note that the @code{isatty} call is treated as a special case: it returns
41547 1 to the target if the file descriptor is attached
41548 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
41549 would require implementing @code{ioctl} and would be more complex than
41554 @unnumberedsubsubsec system
41555 @cindex system, file-i/o system call
41560 int system(const char *command);
41564 @samp{Fsystem,@var{commandptr}/@var{len}}
41566 @item Return value:
41567 If @var{len} is zero, the return value indicates whether a shell is
41568 available. A zero return value indicates a shell is not available.
41569 For non-zero @var{len}, the value returned is -1 on error and the
41570 return status of the command otherwise. Only the exit status of the
41571 command is returned, which is extracted from the host's @code{system}
41572 return value by calling @code{WEXITSTATUS(retval)}. In case
41573 @file{/bin/sh} could not be executed, 127 is returned.
41579 The call was interrupted by the user.
41584 @value{GDBN} takes over the full task of calling the necessary host calls
41585 to perform the @code{system} call. The return value of @code{system} on
41586 the host is simplified before it's returned
41587 to the target. Any termination signal information from the child process
41588 is discarded, and the return value consists
41589 entirely of the exit status of the called command.
41591 Due to security concerns, the @code{system} call is by default refused
41592 by @value{GDBN}. The user has to allow this call explicitly with the
41593 @code{set remote system-call-allowed 1} command.
41596 @item set remote system-call-allowed
41597 @kindex set remote system-call-allowed
41598 Control whether to allow the @code{system} calls in the File I/O
41599 protocol for the remote target. The default is zero (disabled).
41601 @item show remote system-call-allowed
41602 @kindex show remote system-call-allowed
41603 Show whether the @code{system} calls are allowed in the File I/O
41607 @node Protocol-specific Representation of Datatypes
41608 @subsection Protocol-specific Representation of Datatypes
41609 @cindex protocol-specific representation of datatypes, in file-i/o protocol
41612 * Integral Datatypes::
41614 * Memory Transfer::
41619 @node Integral Datatypes
41620 @unnumberedsubsubsec Integral Datatypes
41621 @cindex integral datatypes, in file-i/o protocol
41623 The integral datatypes used in the system calls are @code{int},
41624 @code{unsigned int}, @code{long}, @code{unsigned long},
41625 @code{mode_t}, and @code{time_t}.
41627 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
41628 implemented as 32 bit values in this protocol.
41630 @code{long} and @code{unsigned long} are implemented as 64 bit types.
41632 @xref{Limits}, for corresponding MIN and MAX values (similar to those
41633 in @file{limits.h}) to allow range checking on host and target.
41635 @code{time_t} datatypes are defined as seconds since the Epoch.
41637 All integral datatypes transferred as part of a memory read or write of a
41638 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
41641 @node Pointer Values
41642 @unnumberedsubsubsec Pointer Values
41643 @cindex pointer values, in file-i/o protocol
41645 Pointers to target data are transmitted as they are. An exception
41646 is made for pointers to buffers for which the length isn't
41647 transmitted as part of the function call, namely strings. Strings
41648 are transmitted as a pointer/length pair, both as hex values, e.g.@:
41655 which is a pointer to data of length 18 bytes at position 0x1aaf.
41656 The length is defined as the full string length in bytes, including
41657 the trailing null byte. For example, the string @code{"hello world"}
41658 at address 0x123456 is transmitted as
41664 @node Memory Transfer
41665 @unnumberedsubsubsec Memory Transfer
41666 @cindex memory transfer, in file-i/o protocol
41668 Structured data which is transferred using a memory read or write (for
41669 example, a @code{struct stat}) is expected to be in a protocol-specific format
41670 with all scalar multibyte datatypes being big endian. Translation to
41671 this representation needs to be done both by the target before the @code{F}
41672 packet is sent, and by @value{GDBN} before
41673 it transfers memory to the target. Transferred pointers to structured
41674 data should point to the already-coerced data at any time.
41678 @unnumberedsubsubsec struct stat
41679 @cindex struct stat, in file-i/o protocol
41681 The buffer of type @code{struct stat} used by the target and @value{GDBN}
41682 is defined as follows:
41686 unsigned int st_dev; /* device */
41687 unsigned int st_ino; /* inode */
41688 mode_t st_mode; /* protection */
41689 unsigned int st_nlink; /* number of hard links */
41690 unsigned int st_uid; /* user ID of owner */
41691 unsigned int st_gid; /* group ID of owner */
41692 unsigned int st_rdev; /* device type (if inode device) */
41693 unsigned long st_size; /* total size, in bytes */
41694 unsigned long st_blksize; /* blocksize for filesystem I/O */
41695 unsigned long st_blocks; /* number of blocks allocated */
41696 time_t st_atime; /* time of last access */
41697 time_t st_mtime; /* time of last modification */
41698 time_t st_ctime; /* time of last change */
41702 The integral datatypes conform to the definitions given in the
41703 appropriate section (see @ref{Integral Datatypes}, for details) so this
41704 structure is of size 64 bytes.
41706 The values of several fields have a restricted meaning and/or
41712 A value of 0 represents a file, 1 the console.
41715 No valid meaning for the target. Transmitted unchanged.
41718 Valid mode bits are described in @ref{Constants}. Any other
41719 bits have currently no meaning for the target.
41724 No valid meaning for the target. Transmitted unchanged.
41729 These values have a host and file system dependent
41730 accuracy. Especially on Windows hosts, the file system may not
41731 support exact timing values.
41734 The target gets a @code{struct stat} of the above representation and is
41735 responsible for coercing it to the target representation before
41738 Note that due to size differences between the host, target, and protocol
41739 representations of @code{struct stat} members, these members could eventually
41740 get truncated on the target.
41742 @node struct timeval
41743 @unnumberedsubsubsec struct timeval
41744 @cindex struct timeval, in file-i/o protocol
41746 The buffer of type @code{struct timeval} used by the File-I/O protocol
41747 is defined as follows:
41751 time_t tv_sec; /* second */
41752 long tv_usec; /* microsecond */
41756 The integral datatypes conform to the definitions given in the
41757 appropriate section (see @ref{Integral Datatypes}, for details) so this
41758 structure is of size 8 bytes.
41761 @subsection Constants
41762 @cindex constants, in file-i/o protocol
41764 The following values are used for the constants inside of the
41765 protocol. @value{GDBN} and target are responsible for translating these
41766 values before and after the call as needed.
41777 @unnumberedsubsubsec Open Flags
41778 @cindex open flags, in file-i/o protocol
41780 All values are given in hexadecimal representation.
41792 @node mode_t Values
41793 @unnumberedsubsubsec mode_t Values
41794 @cindex mode_t values, in file-i/o protocol
41796 All values are given in octal representation.
41813 @unnumberedsubsubsec Errno Values
41814 @cindex errno values, in file-i/o protocol
41816 All values are given in decimal representation.
41841 @code{EUNKNOWN} is used as a fallback error value if a host system returns
41842 any error value not in the list of supported error numbers.
41845 @unnumberedsubsubsec Lseek Flags
41846 @cindex lseek flags, in file-i/o protocol
41855 @unnumberedsubsubsec Limits
41856 @cindex limits, in file-i/o protocol
41858 All values are given in decimal representation.
41861 INT_MIN -2147483648
41863 UINT_MAX 4294967295
41864 LONG_MIN -9223372036854775808
41865 LONG_MAX 9223372036854775807
41866 ULONG_MAX 18446744073709551615
41869 @node File-I/O Examples
41870 @subsection File-I/O Examples
41871 @cindex file-i/o examples
41873 Example sequence of a write call, file descriptor 3, buffer is at target
41874 address 0x1234, 6 bytes should be written:
41877 <- @code{Fwrite,3,1234,6}
41878 @emph{request memory read from target}
41881 @emph{return "6 bytes written"}
41885 Example sequence of a read call, file descriptor 3, buffer is at target
41886 address 0x1234, 6 bytes should be read:
41889 <- @code{Fread,3,1234,6}
41890 @emph{request memory write to target}
41891 -> @code{X1234,6:XXXXXX}
41892 @emph{return "6 bytes read"}
41896 Example sequence of a read call, call fails on the host due to invalid
41897 file descriptor (@code{EBADF}):
41900 <- @code{Fread,3,1234,6}
41904 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
41908 <- @code{Fread,3,1234,6}
41913 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
41917 <- @code{Fread,3,1234,6}
41918 -> @code{X1234,6:XXXXXX}
41922 @node Library List Format
41923 @section Library List Format
41924 @cindex library list format, remote protocol
41926 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
41927 same process as your application to manage libraries. In this case,
41928 @value{GDBN} can use the loader's symbol table and normal memory
41929 operations to maintain a list of shared libraries. On other
41930 platforms, the operating system manages loaded libraries.
41931 @value{GDBN} can not retrieve the list of currently loaded libraries
41932 through memory operations, so it uses the @samp{qXfer:libraries:read}
41933 packet (@pxref{qXfer library list read}) instead. The remote stub
41934 queries the target's operating system and reports which libraries
41937 The @samp{qXfer:libraries:read} packet returns an XML document which
41938 lists loaded libraries and their offsets. Each library has an
41939 associated name and one or more segment or section base addresses,
41940 which report where the library was loaded in memory.
41942 For the common case of libraries that are fully linked binaries, the
41943 library should have a list of segments. If the target supports
41944 dynamic linking of a relocatable object file, its library XML element
41945 should instead include a list of allocated sections. The segment or
41946 section bases are start addresses, not relocation offsets; they do not
41947 depend on the library's link-time base addresses.
41949 @value{GDBN} must be linked with the Expat library to support XML
41950 library lists. @xref{Expat}.
41952 A simple memory map, with one loaded library relocated by a single
41953 offset, looks like this:
41957 <library name="/lib/libc.so.6">
41958 <segment address="0x10000000"/>
41963 Another simple memory map, with one loaded library with three
41964 allocated sections (.text, .data, .bss), looks like this:
41968 <library name="sharedlib.o">
41969 <section address="0x10000000"/>
41970 <section address="0x20000000"/>
41971 <section address="0x30000000"/>
41976 The format of a library list is described by this DTD:
41979 <!-- library-list: Root element with versioning -->
41980 <!ELEMENT library-list (library)*>
41981 <!ATTLIST library-list version CDATA #FIXED "1.0">
41982 <!ELEMENT library (segment*, section*)>
41983 <!ATTLIST library name CDATA #REQUIRED>
41984 <!ELEMENT segment EMPTY>
41985 <!ATTLIST segment address CDATA #REQUIRED>
41986 <!ELEMENT section EMPTY>
41987 <!ATTLIST section address CDATA #REQUIRED>
41990 In addition, segments and section descriptors cannot be mixed within a
41991 single library element, and you must supply at least one segment or
41992 section for each library.
41994 @node Library List Format for SVR4 Targets
41995 @section Library List Format for SVR4 Targets
41996 @cindex library list format, remote protocol
41998 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
41999 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
42000 shared libraries. Still a special library list provided by this packet is
42001 more efficient for the @value{GDBN} remote protocol.
42003 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
42004 loaded libraries and their SVR4 linker parameters. For each library on SVR4
42005 target, the following parameters are reported:
42009 @code{name}, the absolute file name from the @code{l_name} field of
42010 @code{struct link_map}.
42012 @code{lm} with address of @code{struct link_map} used for TLS
42013 (Thread Local Storage) access.
42015 @code{l_addr}, the displacement as read from the field @code{l_addr} of
42016 @code{struct link_map}. For prelinked libraries this is not an absolute
42017 memory address. It is a displacement of absolute memory address against
42018 address the file was prelinked to during the library load.
42020 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
42023 Additionally the single @code{main-lm} attribute specifies address of
42024 @code{struct link_map} used for the main executable. This parameter is used
42025 for TLS access and its presence is optional.
42027 @value{GDBN} must be linked with the Expat library to support XML
42028 SVR4 library lists. @xref{Expat}.
42030 A simple memory map, with two loaded libraries (which do not use prelink),
42034 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
42035 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
42037 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
42039 </library-list-svr>
42042 The format of an SVR4 library list is described by this DTD:
42045 <!-- library-list-svr4: Root element with versioning -->
42046 <!ELEMENT library-list-svr4 (library)*>
42047 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
42048 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
42049 <!ELEMENT library EMPTY>
42050 <!ATTLIST library name CDATA #REQUIRED>
42051 <!ATTLIST library lm CDATA #REQUIRED>
42052 <!ATTLIST library l_addr CDATA #REQUIRED>
42053 <!ATTLIST library l_ld CDATA #REQUIRED>
42056 @node Memory Map Format
42057 @section Memory Map Format
42058 @cindex memory map format
42060 To be able to write into flash memory, @value{GDBN} needs to obtain a
42061 memory map from the target. This section describes the format of the
42064 The memory map is obtained using the @samp{qXfer:memory-map:read}
42065 (@pxref{qXfer memory map read}) packet and is an XML document that
42066 lists memory regions.
42068 @value{GDBN} must be linked with the Expat library to support XML
42069 memory maps. @xref{Expat}.
42071 The top-level structure of the document is shown below:
42074 <?xml version="1.0"?>
42075 <!DOCTYPE memory-map
42076 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
42077 "http://sourceware.org/gdb/gdb-memory-map.dtd">
42083 Each region can be either:
42088 A region of RAM starting at @var{addr} and extending for @var{length}
42092 <memory type="ram" start="@var{addr}" length="@var{length}"/>
42097 A region of read-only memory:
42100 <memory type="rom" start="@var{addr}" length="@var{length}"/>
42105 A region of flash memory, with erasure blocks @var{blocksize}
42109 <memory type="flash" start="@var{addr}" length="@var{length}">
42110 <property name="blocksize">@var{blocksize}</property>
42116 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
42117 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
42118 packets to write to addresses in such ranges.
42120 The formal DTD for memory map format is given below:
42123 <!-- ................................................... -->
42124 <!-- Memory Map XML DTD ................................ -->
42125 <!-- File: memory-map.dtd .............................. -->
42126 <!-- .................................... .............. -->
42127 <!-- memory-map.dtd -->
42128 <!-- memory-map: Root element with versioning -->
42129 <!ELEMENT memory-map (memory | property)>
42130 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
42131 <!ELEMENT memory (property)>
42132 <!-- memory: Specifies a memory region,
42133 and its type, or device. -->
42134 <!ATTLIST memory type CDATA #REQUIRED
42135 start CDATA #REQUIRED
42136 length CDATA #REQUIRED
42137 device CDATA #IMPLIED>
42138 <!-- property: Generic attribute tag -->
42139 <!ELEMENT property (#PCDATA | property)*>
42140 <!ATTLIST property name CDATA #REQUIRED>
42143 @node Thread List Format
42144 @section Thread List Format
42145 @cindex thread list format
42147 To efficiently update the list of threads and their attributes,
42148 @value{GDBN} issues the @samp{qXfer:threads:read} packet
42149 (@pxref{qXfer threads read}) and obtains the XML document with
42150 the following structure:
42153 <?xml version="1.0"?>
42155 <thread id="id" core="0">
42156 ... description ...
42161 Each @samp{thread} element must have the @samp{id} attribute that
42162 identifies the thread (@pxref{thread-id syntax}). The
42163 @samp{core} attribute, if present, specifies which processor core
42164 the thread was last executing on. The content of the of @samp{thread}
42165 element is interpreted as human-readable auxilliary information.
42167 @node Traceframe Info Format
42168 @section Traceframe Info Format
42169 @cindex traceframe info format
42171 To be able to know which objects in the inferior can be examined when
42172 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
42173 memory ranges, registers and trace state variables that have been
42174 collected in a traceframe.
42176 This list is obtained using the @samp{qXfer:traceframe-info:read}
42177 (@pxref{qXfer traceframe info read}) packet and is an XML document.
42179 @value{GDBN} must be linked with the Expat library to support XML
42180 traceframe info discovery. @xref{Expat}.
42182 The top-level structure of the document is shown below:
42185 <?xml version="1.0"?>
42186 <!DOCTYPE traceframe-info
42187 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
42188 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
42194 Each traceframe block can be either:
42199 A region of collected memory starting at @var{addr} and extending for
42200 @var{length} bytes from there:
42203 <memory start="@var{addr}" length="@var{length}"/>
42207 A block indicating trace state variable numbered @var{number} has been
42211 <tvar id="@var{number}"/>
42216 The formal DTD for the traceframe info format is given below:
42219 <!ELEMENT traceframe-info (memory | tvar)* >
42220 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
42222 <!ELEMENT memory EMPTY>
42223 <!ATTLIST memory start CDATA #REQUIRED
42224 length CDATA #REQUIRED>
42226 <!ATTLIST tvar id CDATA #REQUIRED>
42229 @node Branch Trace Format
42230 @section Branch Trace Format
42231 @cindex branch trace format
42233 In order to display the branch trace of an inferior thread,
42234 @value{GDBN} needs to obtain the list of branches. This list is
42235 represented as list of sequential code blocks that are connected via
42236 branches. The code in each block has been executed sequentially.
42238 This list is obtained using the @samp{qXfer:btrace:read}
42239 (@pxref{qXfer btrace read}) packet and is an XML document.
42241 @value{GDBN} must be linked with the Expat library to support XML
42242 traceframe info discovery. @xref{Expat}.
42244 The top-level structure of the document is shown below:
42247 <?xml version="1.0"?>
42249 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
42250 "http://sourceware.org/gdb/gdb-btrace.dtd">
42259 A block of sequentially executed instructions starting at @var{begin}
42260 and ending at @var{end}:
42263 <block begin="@var{begin}" end="@var{end}"/>
42268 The formal DTD for the branch trace format is given below:
42271 <!ELEMENT btrace (block)* >
42272 <!ATTLIST btrace version CDATA #FIXED "1.0">
42274 <!ELEMENT block EMPTY>
42275 <!ATTLIST block begin CDATA #REQUIRED
42276 end CDATA #REQUIRED>
42279 @include agentexpr.texi
42281 @node Target Descriptions
42282 @appendix Target Descriptions
42283 @cindex target descriptions
42285 One of the challenges of using @value{GDBN} to debug embedded systems
42286 is that there are so many minor variants of each processor
42287 architecture in use. It is common practice for vendors to start with
42288 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
42289 and then make changes to adapt it to a particular market niche. Some
42290 architectures have hundreds of variants, available from dozens of
42291 vendors. This leads to a number of problems:
42295 With so many different customized processors, it is difficult for
42296 the @value{GDBN} maintainers to keep up with the changes.
42298 Since individual variants may have short lifetimes or limited
42299 audiences, it may not be worthwhile to carry information about every
42300 variant in the @value{GDBN} source tree.
42302 When @value{GDBN} does support the architecture of the embedded system
42303 at hand, the task of finding the correct architecture name to give the
42304 @command{set architecture} command can be error-prone.
42307 To address these problems, the @value{GDBN} remote protocol allows a
42308 target system to not only identify itself to @value{GDBN}, but to
42309 actually describe its own features. This lets @value{GDBN} support
42310 processor variants it has never seen before --- to the extent that the
42311 descriptions are accurate, and that @value{GDBN} understands them.
42313 @value{GDBN} must be linked with the Expat library to support XML
42314 target descriptions. @xref{Expat}.
42317 * Retrieving Descriptions:: How descriptions are fetched from a target.
42318 * Target Description Format:: The contents of a target description.
42319 * Predefined Target Types:: Standard types available for target
42321 * Standard Target Features:: Features @value{GDBN} knows about.
42324 @node Retrieving Descriptions
42325 @section Retrieving Descriptions
42327 Target descriptions can be read from the target automatically, or
42328 specified by the user manually. The default behavior is to read the
42329 description from the target. @value{GDBN} retrieves it via the remote
42330 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
42331 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
42332 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
42333 XML document, of the form described in @ref{Target Description
42336 Alternatively, you can specify a file to read for the target description.
42337 If a file is set, the target will not be queried. The commands to
42338 specify a file are:
42341 @cindex set tdesc filename
42342 @item set tdesc filename @var{path}
42343 Read the target description from @var{path}.
42345 @cindex unset tdesc filename
42346 @item unset tdesc filename
42347 Do not read the XML target description from a file. @value{GDBN}
42348 will use the description supplied by the current target.
42350 @cindex show tdesc filename
42351 @item show tdesc filename
42352 Show the filename to read for a target description, if any.
42356 @node Target Description Format
42357 @section Target Description Format
42358 @cindex target descriptions, XML format
42360 A target description annex is an @uref{http://www.w3.org/XML/, XML}
42361 document which complies with the Document Type Definition provided in
42362 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
42363 means you can use generally available tools like @command{xmllint} to
42364 check that your feature descriptions are well-formed and valid.
42365 However, to help people unfamiliar with XML write descriptions for
42366 their targets, we also describe the grammar here.
42368 Target descriptions can identify the architecture of the remote target
42369 and (for some architectures) provide information about custom register
42370 sets. They can also identify the OS ABI of the remote target.
42371 @value{GDBN} can use this information to autoconfigure for your
42372 target, or to warn you if you connect to an unsupported target.
42374 Here is a simple target description:
42377 <target version="1.0">
42378 <architecture>i386:x86-64</architecture>
42383 This minimal description only says that the target uses
42384 the x86-64 architecture.
42386 A target description has the following overall form, with [ ] marking
42387 optional elements and @dots{} marking repeatable elements. The elements
42388 are explained further below.
42391 <?xml version="1.0"?>
42392 <!DOCTYPE target SYSTEM "gdb-target.dtd">
42393 <target version="1.0">
42394 @r{[}@var{architecture}@r{]}
42395 @r{[}@var{osabi}@r{]}
42396 @r{[}@var{compatible}@r{]}
42397 @r{[}@var{feature}@dots{}@r{]}
42402 The description is generally insensitive to whitespace and line
42403 breaks, under the usual common-sense rules. The XML version
42404 declaration and document type declaration can generally be omitted
42405 (@value{GDBN} does not require them), but specifying them may be
42406 useful for XML validation tools. The @samp{version} attribute for
42407 @samp{<target>} may also be omitted, but we recommend
42408 including it; if future versions of @value{GDBN} use an incompatible
42409 revision of @file{gdb-target.dtd}, they will detect and report
42410 the version mismatch.
42412 @subsection Inclusion
42413 @cindex target descriptions, inclusion
42416 @cindex <xi:include>
42419 It can sometimes be valuable to split a target description up into
42420 several different annexes, either for organizational purposes, or to
42421 share files between different possible target descriptions. You can
42422 divide a description into multiple files by replacing any element of
42423 the target description with an inclusion directive of the form:
42426 <xi:include href="@var{document}"/>
42430 When @value{GDBN} encounters an element of this form, it will retrieve
42431 the named XML @var{document}, and replace the inclusion directive with
42432 the contents of that document. If the current description was read
42433 using @samp{qXfer}, then so will be the included document;
42434 @var{document} will be interpreted as the name of an annex. If the
42435 current description was read from a file, @value{GDBN} will look for
42436 @var{document} as a file in the same directory where it found the
42437 original description.
42439 @subsection Architecture
42440 @cindex <architecture>
42442 An @samp{<architecture>} element has this form:
42445 <architecture>@var{arch}</architecture>
42448 @var{arch} is one of the architectures from the set accepted by
42449 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42452 @cindex @code{<osabi>}
42454 This optional field was introduced in @value{GDBN} version 7.0.
42455 Previous versions of @value{GDBN} ignore it.
42457 An @samp{<osabi>} element has this form:
42460 <osabi>@var{abi-name}</osabi>
42463 @var{abi-name} is an OS ABI name from the same selection accepted by
42464 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
42466 @subsection Compatible Architecture
42467 @cindex @code{<compatible>}
42469 This optional field was introduced in @value{GDBN} version 7.0.
42470 Previous versions of @value{GDBN} ignore it.
42472 A @samp{<compatible>} element has this form:
42475 <compatible>@var{arch}</compatible>
42478 @var{arch} is one of the architectures from the set accepted by
42479 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42481 A @samp{<compatible>} element is used to specify that the target
42482 is able to run binaries in some other than the main target architecture
42483 given by the @samp{<architecture>} element. For example, on the
42484 Cell Broadband Engine, the main architecture is @code{powerpc:common}
42485 or @code{powerpc:common64}, but the system is able to run binaries
42486 in the @code{spu} architecture as well. The way to describe this
42487 capability with @samp{<compatible>} is as follows:
42490 <architecture>powerpc:common</architecture>
42491 <compatible>spu</compatible>
42494 @subsection Features
42497 Each @samp{<feature>} describes some logical portion of the target
42498 system. Features are currently used to describe available CPU
42499 registers and the types of their contents. A @samp{<feature>} element
42503 <feature name="@var{name}">
42504 @r{[}@var{type}@dots{}@r{]}
42510 Each feature's name should be unique within the description. The name
42511 of a feature does not matter unless @value{GDBN} has some special
42512 knowledge of the contents of that feature; if it does, the feature
42513 should have its standard name. @xref{Standard Target Features}.
42517 Any register's value is a collection of bits which @value{GDBN} must
42518 interpret. The default interpretation is a two's complement integer,
42519 but other types can be requested by name in the register description.
42520 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
42521 Target Types}), and the description can define additional composite types.
42523 Each type element must have an @samp{id} attribute, which gives
42524 a unique (within the containing @samp{<feature>}) name to the type.
42525 Types must be defined before they are used.
42528 Some targets offer vector registers, which can be treated as arrays
42529 of scalar elements. These types are written as @samp{<vector>} elements,
42530 specifying the array element type, @var{type}, and the number of elements,
42534 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
42538 If a register's value is usefully viewed in multiple ways, define it
42539 with a union type containing the useful representations. The
42540 @samp{<union>} element contains one or more @samp{<field>} elements,
42541 each of which has a @var{name} and a @var{type}:
42544 <union id="@var{id}">
42545 <field name="@var{name}" type="@var{type}"/>
42551 If a register's value is composed from several separate values, define
42552 it with a structure type. There are two forms of the @samp{<struct>}
42553 element; a @samp{<struct>} element must either contain only bitfields
42554 or contain no bitfields. If the structure contains only bitfields,
42555 its total size in bytes must be specified, each bitfield must have an
42556 explicit start and end, and bitfields are automatically assigned an
42557 integer type. The field's @var{start} should be less than or
42558 equal to its @var{end}, and zero represents the least significant bit.
42561 <struct id="@var{id}" size="@var{size}">
42562 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
42567 If the structure contains no bitfields, then each field has an
42568 explicit type, and no implicit padding is added.
42571 <struct id="@var{id}">
42572 <field name="@var{name}" type="@var{type}"/>
42578 If a register's value is a series of single-bit flags, define it with
42579 a flags type. The @samp{<flags>} element has an explicit @var{size}
42580 and contains one or more @samp{<field>} elements. Each field has a
42581 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
42585 <flags id="@var{id}" size="@var{size}">
42586 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
42591 @subsection Registers
42594 Each register is represented as an element with this form:
42597 <reg name="@var{name}"
42598 bitsize="@var{size}"
42599 @r{[}regnum="@var{num}"@r{]}
42600 @r{[}save-restore="@var{save-restore}"@r{]}
42601 @r{[}type="@var{type}"@r{]}
42602 @r{[}group="@var{group}"@r{]}/>
42606 The components are as follows:
42611 The register's name; it must be unique within the target description.
42614 The register's size, in bits.
42617 The register's number. If omitted, a register's number is one greater
42618 than that of the previous register (either in the current feature or in
42619 a preceding feature); the first register in the target description
42620 defaults to zero. This register number is used to read or write
42621 the register; e.g.@: it is used in the remote @code{p} and @code{P}
42622 packets, and registers appear in the @code{g} and @code{G} packets
42623 in order of increasing register number.
42626 Whether the register should be preserved across inferior function
42627 calls; this must be either @code{yes} or @code{no}. The default is
42628 @code{yes}, which is appropriate for most registers except for
42629 some system control registers; this is not related to the target's
42633 The type of the register. @var{type} may be a predefined type, a type
42634 defined in the current feature, or one of the special types @code{int}
42635 and @code{float}. @code{int} is an integer type of the correct size
42636 for @var{bitsize}, and @code{float} is a floating point type (in the
42637 architecture's normal floating point format) of the correct size for
42638 @var{bitsize}. The default is @code{int}.
42641 The register group to which this register belongs. @var{group} must
42642 be either @code{general}, @code{float}, or @code{vector}. If no
42643 @var{group} is specified, @value{GDBN} will not display the register
42644 in @code{info registers}.
42648 @node Predefined Target Types
42649 @section Predefined Target Types
42650 @cindex target descriptions, predefined types
42652 Type definitions in the self-description can build up composite types
42653 from basic building blocks, but can not define fundamental types. Instead,
42654 standard identifiers are provided by @value{GDBN} for the fundamental
42655 types. The currently supported types are:
42664 Signed integer types holding the specified number of bits.
42671 Unsigned integer types holding the specified number of bits.
42675 Pointers to unspecified code and data. The program counter and
42676 any dedicated return address register may be marked as code
42677 pointers; printing a code pointer converts it into a symbolic
42678 address. The stack pointer and any dedicated address registers
42679 may be marked as data pointers.
42682 Single precision IEEE floating point.
42685 Double precision IEEE floating point.
42688 The 12-byte extended precision format used by ARM FPA registers.
42691 The 10-byte extended precision format used by x87 registers.
42694 32bit @sc{eflags} register used by x86.
42697 32bit @sc{mxcsr} register used by x86.
42701 @node Standard Target Features
42702 @section Standard Target Features
42703 @cindex target descriptions, standard features
42705 A target description must contain either no registers or all the
42706 target's registers. If the description contains no registers, then
42707 @value{GDBN} will assume a default register layout, selected based on
42708 the architecture. If the description contains any registers, the
42709 default layout will not be used; the standard registers must be
42710 described in the target description, in such a way that @value{GDBN}
42711 can recognize them.
42713 This is accomplished by giving specific names to feature elements
42714 which contain standard registers. @value{GDBN} will look for features
42715 with those names and verify that they contain the expected registers;
42716 if any known feature is missing required registers, or if any required
42717 feature is missing, @value{GDBN} will reject the target
42718 description. You can add additional registers to any of the
42719 standard features --- @value{GDBN} will display them just as if
42720 they were added to an unrecognized feature.
42722 This section lists the known features and their expected contents.
42723 Sample XML documents for these features are included in the
42724 @value{GDBN} source tree, in the directory @file{gdb/features}.
42726 Names recognized by @value{GDBN} should include the name of the
42727 company or organization which selected the name, and the overall
42728 architecture to which the feature applies; so e.g.@: the feature
42729 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
42731 The names of registers are not case sensitive for the purpose
42732 of recognizing standard features, but @value{GDBN} will only display
42733 registers using the capitalization used in the description.
42736 * AArch64 Features::
42741 * Nios II Features::
42742 * PowerPC Features::
42743 * S/390 and System z Features::
42748 @node AArch64 Features
42749 @subsection AArch64 Features
42750 @cindex target descriptions, AArch64 features
42752 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
42753 targets. It should contain registers @samp{x0} through @samp{x30},
42754 @samp{sp}, @samp{pc}, and @samp{cpsr}.
42756 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
42757 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
42761 @subsection ARM Features
42762 @cindex target descriptions, ARM features
42764 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
42766 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
42767 @samp{lr}, @samp{pc}, and @samp{cpsr}.
42769 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
42770 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
42771 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
42774 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
42775 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
42777 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
42778 it should contain at least registers @samp{wR0} through @samp{wR15} and
42779 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
42780 @samp{wCSSF}, and @samp{wCASF} registers are optional.
42782 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
42783 should contain at least registers @samp{d0} through @samp{d15}. If
42784 they are present, @samp{d16} through @samp{d31} should also be included.
42785 @value{GDBN} will synthesize the single-precision registers from
42786 halves of the double-precision registers.
42788 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
42789 need to contain registers; it instructs @value{GDBN} to display the
42790 VFP double-precision registers as vectors and to synthesize the
42791 quad-precision registers from pairs of double-precision registers.
42792 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
42793 be present and include 32 double-precision registers.
42795 @node i386 Features
42796 @subsection i386 Features
42797 @cindex target descriptions, i386 features
42799 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
42800 targets. It should describe the following registers:
42804 @samp{eax} through @samp{edi} plus @samp{eip} for i386
42806 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
42808 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
42809 @samp{fs}, @samp{gs}
42811 @samp{st0} through @samp{st7}
42813 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
42814 @samp{foseg}, @samp{fooff} and @samp{fop}
42817 The register sets may be different, depending on the target.
42819 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
42820 describe registers:
42824 @samp{xmm0} through @samp{xmm7} for i386
42826 @samp{xmm0} through @samp{xmm15} for amd64
42831 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
42832 @samp{org.gnu.gdb.i386.sse} feature. It should
42833 describe the upper 128 bits of @sc{ymm} registers:
42837 @samp{ymm0h} through @samp{ymm7h} for i386
42839 @samp{ymm0h} through @samp{ymm15h} for amd64
42842 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
42843 describe a single register, @samp{orig_eax}.
42845 @node MIPS Features
42846 @subsection @acronym{MIPS} Features
42847 @cindex target descriptions, @acronym{MIPS} features
42849 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
42850 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
42851 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
42854 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
42855 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
42856 registers. They may be 32-bit or 64-bit depending on the target.
42858 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
42859 it may be optional in a future version of @value{GDBN}. It should
42860 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
42861 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
42863 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
42864 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
42865 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
42866 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
42868 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
42869 contain a single register, @samp{restart}, which is used by the
42870 Linux kernel to control restartable syscalls.
42872 @node M68K Features
42873 @subsection M68K Features
42874 @cindex target descriptions, M68K features
42877 @item @samp{org.gnu.gdb.m68k.core}
42878 @itemx @samp{org.gnu.gdb.coldfire.core}
42879 @itemx @samp{org.gnu.gdb.fido.core}
42880 One of those features must be always present.
42881 The feature that is present determines which flavor of m68k is
42882 used. The feature that is present should contain registers
42883 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
42884 @samp{sp}, @samp{ps} and @samp{pc}.
42886 @item @samp{org.gnu.gdb.coldfire.fp}
42887 This feature is optional. If present, it should contain registers
42888 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
42892 @node Nios II Features
42893 @subsection Nios II Features
42894 @cindex target descriptions, Nios II features
42896 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
42897 targets. It should contain the 32 core registers (@samp{zero},
42898 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
42899 @samp{pc}, and the 16 control registers (@samp{status} through
42902 @node PowerPC Features
42903 @subsection PowerPC Features
42904 @cindex target descriptions, PowerPC features
42906 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
42907 targets. It should contain registers @samp{r0} through @samp{r31},
42908 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
42909 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
42911 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
42912 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
42914 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
42915 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
42918 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
42919 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
42920 will combine these registers with the floating point registers
42921 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
42922 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
42923 through @samp{vs63}, the set of vector registers for POWER7.
42925 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
42926 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
42927 @samp{spefscr}. SPE targets should provide 32-bit registers in
42928 @samp{org.gnu.gdb.power.core} and provide the upper halves in
42929 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
42930 these to present registers @samp{ev0} through @samp{ev31} to the
42933 @node S/390 and System z Features
42934 @subsection S/390 and System z Features
42935 @cindex target descriptions, S/390 features
42936 @cindex target descriptions, System z features
42938 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
42939 System z targets. It should contain the PSW and the 16 general
42940 registers. In particular, System z targets should provide the 64-bit
42941 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
42942 S/390 targets should provide the 32-bit versions of these registers.
42943 A System z target that runs in 31-bit addressing mode should provide
42944 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
42945 register's upper halves @samp{r0h} through @samp{r15h}, and their
42946 lower halves @samp{r0l} through @samp{r15l}.
42948 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
42949 contain the 64-bit registers @samp{f0} through @samp{f15}, and
42952 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
42953 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
42955 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
42956 contain the register @samp{orig_r2}, which is 64-bit wide on System z
42957 targets and 32-bit otherwise. In addition, the feature may contain
42958 the @samp{last_break} register, whose width depends on the addressing
42959 mode, as well as the @samp{system_call} register, which is always
42962 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
42963 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
42964 @samp{atia}, and @samp{tr0} through @samp{tr15}.
42966 @node TIC6x Features
42967 @subsection TMS320C6x Features
42968 @cindex target descriptions, TIC6x features
42969 @cindex target descriptions, TMS320C6x features
42970 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
42971 targets. It should contain registers @samp{A0} through @samp{A15},
42972 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
42974 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
42975 contain registers @samp{A16} through @samp{A31} and @samp{B16}
42976 through @samp{B31}.
42978 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
42979 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
42981 @node Operating System Information
42982 @appendix Operating System Information
42983 @cindex operating system information
42989 Users of @value{GDBN} often wish to obtain information about the state of
42990 the operating system running on the target---for example the list of
42991 processes, or the list of open files. This section describes the
42992 mechanism that makes it possible. This mechanism is similar to the
42993 target features mechanism (@pxref{Target Descriptions}), but focuses
42994 on a different aspect of target.
42996 Operating system information is retrived from the target via the
42997 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
42998 read}). The object name in the request should be @samp{osdata}, and
42999 the @var{annex} identifies the data to be fetched.
43002 @appendixsection Process list
43003 @cindex operating system information, process list
43005 When requesting the process list, the @var{annex} field in the
43006 @samp{qXfer} request should be @samp{processes}. The returned data is
43007 an XML document. The formal syntax of this document is defined in
43008 @file{gdb/features/osdata.dtd}.
43010 An example document is:
43013 <?xml version="1.0"?>
43014 <!DOCTYPE target SYSTEM "osdata.dtd">
43015 <osdata type="processes">
43017 <column name="pid">1</column>
43018 <column name="user">root</column>
43019 <column name="command">/sbin/init</column>
43020 <column name="cores">1,2,3</column>
43025 Each item should include a column whose name is @samp{pid}. The value
43026 of that column should identify the process on the target. The
43027 @samp{user} and @samp{command} columns are optional, and will be
43028 displayed by @value{GDBN}. The @samp{cores} column, if present,
43029 should contain a comma-separated list of cores that this process
43030 is running on. Target may provide additional columns,
43031 which @value{GDBN} currently ignores.
43033 @node Trace File Format
43034 @appendix Trace File Format
43035 @cindex trace file format
43037 The trace file comes in three parts: a header, a textual description
43038 section, and a trace frame section with binary data.
43040 The header has the form @code{\x7fTRACE0\n}. The first byte is
43041 @code{0x7f} so as to indicate that the file contains binary data,
43042 while the @code{0} is a version number that may have different values
43045 The description section consists of multiple lines of @sc{ascii} text
43046 separated by newline characters (@code{0xa}). The lines may include a
43047 variety of optional descriptive or context-setting information, such
43048 as tracepoint definitions or register set size. @value{GDBN} will
43049 ignore any line that it does not recognize. An empty line marks the end
43052 @c FIXME add some specific types of data
43054 The trace frame section consists of a number of consecutive frames.
43055 Each frame begins with a two-byte tracepoint number, followed by a
43056 four-byte size giving the amount of data in the frame. The data in
43057 the frame consists of a number of blocks, each introduced by a
43058 character indicating its type (at least register, memory, and trace
43059 state variable). The data in this section is raw binary, not a
43060 hexadecimal or other encoding; its endianness matches the target's
43063 @c FIXME bi-arch may require endianness/arch info in description section
43066 @item R @var{bytes}
43067 Register block. The number and ordering of bytes matches that of a
43068 @code{g} packet in the remote protocol. Note that these are the
43069 actual bytes, in target order and @value{GDBN} register order, not a
43070 hexadecimal encoding.
43072 @item M @var{address} @var{length} @var{bytes}...
43073 Memory block. This is a contiguous block of memory, at the 8-byte
43074 address @var{address}, with a 2-byte length @var{length}, followed by
43075 @var{length} bytes.
43077 @item V @var{number} @var{value}
43078 Trace state variable block. This records the 8-byte signed value
43079 @var{value} of trace state variable numbered @var{number}.
43083 Future enhancements of the trace file format may include additional types
43086 @node Index Section Format
43087 @appendix @code{.gdb_index} section format
43088 @cindex .gdb_index section format
43089 @cindex index section format
43091 This section documents the index section that is created by @code{save
43092 gdb-index} (@pxref{Index Files}). The index section is
43093 DWARF-specific; some knowledge of DWARF is assumed in this
43096 The mapped index file format is designed to be directly
43097 @code{mmap}able on any architecture. In most cases, a datum is
43098 represented using a little-endian 32-bit integer value, called an
43099 @code{offset_type}. Big endian machines must byte-swap the values
43100 before using them. Exceptions to this rule are noted. The data is
43101 laid out such that alignment is always respected.
43103 A mapped index consists of several areas, laid out in order.
43107 The file header. This is a sequence of values, of @code{offset_type}
43108 unless otherwise noted:
43112 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
43113 Version 4 uses a different hashing function from versions 5 and 6.
43114 Version 6 includes symbols for inlined functions, whereas versions 4
43115 and 5 do not. Version 7 adds attributes to the CU indices in the
43116 symbol table. Version 8 specifies that symbols from DWARF type units
43117 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
43118 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
43120 @value{GDBN} will only read version 4, 5, or 6 indices
43121 by specifying @code{set use-deprecated-index-sections on}.
43122 GDB has a workaround for potentially broken version 7 indices so it is
43123 currently not flagged as deprecated.
43126 The offset, from the start of the file, of the CU list.
43129 The offset, from the start of the file, of the types CU list. Note
43130 that this area can be empty, in which case this offset will be equal
43131 to the next offset.
43134 The offset, from the start of the file, of the address area.
43137 The offset, from the start of the file, of the symbol table.
43140 The offset, from the start of the file, of the constant pool.
43144 The CU list. This is a sequence of pairs of 64-bit little-endian
43145 values, sorted by the CU offset. The first element in each pair is
43146 the offset of a CU in the @code{.debug_info} section. The second
43147 element in each pair is the length of that CU. References to a CU
43148 elsewhere in the map are done using a CU index, which is just the
43149 0-based index into this table. Note that if there are type CUs, then
43150 conceptually CUs and type CUs form a single list for the purposes of
43154 The types CU list. This is a sequence of triplets of 64-bit
43155 little-endian values. In a triplet, the first value is the CU offset,
43156 the second value is the type offset in the CU, and the third value is
43157 the type signature. The types CU list is not sorted.
43160 The address area. The address area consists of a sequence of address
43161 entries. Each address entry has three elements:
43165 The low address. This is a 64-bit little-endian value.
43168 The high address. This is a 64-bit little-endian value. Like
43169 @code{DW_AT_high_pc}, the value is one byte beyond the end.
43172 The CU index. This is an @code{offset_type} value.
43176 The symbol table. This is an open-addressed hash table. The size of
43177 the hash table is always a power of 2.
43179 Each slot in the hash table consists of a pair of @code{offset_type}
43180 values. The first value is the offset of the symbol's name in the
43181 constant pool. The second value is the offset of the CU vector in the
43184 If both values are 0, then this slot in the hash table is empty. This
43185 is ok because while 0 is a valid constant pool index, it cannot be a
43186 valid index for both a string and a CU vector.
43188 The hash value for a table entry is computed by applying an
43189 iterative hash function to the symbol's name. Starting with an
43190 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
43191 the string is incorporated into the hash using the formula depending on the
43196 The formula is @code{r = r * 67 + c - 113}.
43198 @item Versions 5 to 7
43199 The formula is @code{r = r * 67 + tolower (c) - 113}.
43202 The terminating @samp{\0} is not incorporated into the hash.
43204 The step size used in the hash table is computed via
43205 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
43206 value, and @samp{size} is the size of the hash table. The step size
43207 is used to find the next candidate slot when handling a hash
43210 The names of C@t{++} symbols in the hash table are canonicalized. We
43211 don't currently have a simple description of the canonicalization
43212 algorithm; if you intend to create new index sections, you must read
43216 The constant pool. This is simply a bunch of bytes. It is organized
43217 so that alignment is correct: CU vectors are stored first, followed by
43220 A CU vector in the constant pool is a sequence of @code{offset_type}
43221 values. The first value is the number of CU indices in the vector.
43222 Each subsequent value is the index and symbol attributes of a CU in
43223 the CU list. This element in the hash table is used to indicate which
43224 CUs define the symbol and how the symbol is used.
43225 See below for the format of each CU index+attributes entry.
43227 A string in the constant pool is zero-terminated.
43230 Attributes were added to CU index values in @code{.gdb_index} version 7.
43231 If a symbol has multiple uses within a CU then there is one
43232 CU index+attributes value for each use.
43234 The format of each CU index+attributes entry is as follows
43240 This is the index of the CU in the CU list.
43242 These bits are reserved for future purposes and must be zero.
43244 The kind of the symbol in the CU.
43248 This value is reserved and should not be used.
43249 By reserving zero the full @code{offset_type} value is backwards compatible
43250 with previous versions of the index.
43252 The symbol is a type.
43254 The symbol is a variable or an enum value.
43256 The symbol is a function.
43258 Any other kind of symbol.
43260 These values are reserved.
43264 This bit is zero if the value is global and one if it is static.
43266 The determination of whether a symbol is global or static is complicated.
43267 The authorative reference is the file @file{dwarf2read.c} in
43268 @value{GDBN} sources.
43272 This pseudo-code describes the computation of a symbol's kind and
43273 global/static attributes in the index.
43276 is_external = get_attribute (die, DW_AT_external);
43277 language = get_attribute (cu_die, DW_AT_language);
43280 case DW_TAG_typedef:
43281 case DW_TAG_base_type:
43282 case DW_TAG_subrange_type:
43286 case DW_TAG_enumerator:
43288 is_static = (language != CPLUS && language != JAVA);
43290 case DW_TAG_subprogram:
43292 is_static = ! (is_external || language == ADA);
43294 case DW_TAG_constant:
43296 is_static = ! is_external;
43298 case DW_TAG_variable:
43300 is_static = ! is_external;
43302 case DW_TAG_namespace:
43306 case DW_TAG_class_type:
43307 case DW_TAG_interface_type:
43308 case DW_TAG_structure_type:
43309 case DW_TAG_union_type:
43310 case DW_TAG_enumeration_type:
43312 is_static = (language != CPLUS && language != JAVA);
43320 @appendix Manual pages
43324 * gdb man:: The GNU Debugger man page
43325 * gdbserver man:: Remote Server for the GNU Debugger man page
43326 * gcore man:: Generate a core file of a running program
43327 * gdbinit man:: gdbinit scripts
43333 @c man title gdb The GNU Debugger
43335 @c man begin SYNOPSIS gdb
43336 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
43337 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
43338 [@option{-b}@w{ }@var{bps}]
43339 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
43340 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
43341 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
43342 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
43343 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
43346 @c man begin DESCRIPTION gdb
43347 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
43348 going on ``inside'' another program while it executes -- or what another
43349 program was doing at the moment it crashed.
43351 @value{GDBN} can do four main kinds of things (plus other things in support of
43352 these) to help you catch bugs in the act:
43356 Start your program, specifying anything that might affect its behavior.
43359 Make your program stop on specified conditions.
43362 Examine what has happened, when your program has stopped.
43365 Change things in your program, so you can experiment with correcting the
43366 effects of one bug and go on to learn about another.
43369 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
43372 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
43373 commands from the terminal until you tell it to exit with the @value{GDBN}
43374 command @code{quit}. You can get online help from @value{GDBN} itself
43375 by using the command @code{help}.
43377 You can run @code{gdb} with no arguments or options; but the most
43378 usual way to start @value{GDBN} is with one argument or two, specifying an
43379 executable program as the argument:
43385 You can also start with both an executable program and a core file specified:
43391 You can, instead, specify a process ID as a second argument, if you want
43392 to debug a running process:
43400 would attach @value{GDBN} to process @code{1234} (unless you also have a file
43401 named @file{1234}; @value{GDBN} does check for a core file first).
43402 With option @option{-p} you can omit the @var{program} filename.
43404 Here are some of the most frequently needed @value{GDBN} commands:
43406 @c pod2man highlights the right hand side of the @item lines.
43408 @item break [@var{file}:]@var{functiop}
43409 Set a breakpoint at @var{function} (in @var{file}).
43411 @item run [@var{arglist}]
43412 Start your program (with @var{arglist}, if specified).
43415 Backtrace: display the program stack.
43417 @item print @var{expr}
43418 Display the value of an expression.
43421 Continue running your program (after stopping, e.g. at a breakpoint).
43424 Execute next program line (after stopping); step @emph{over} any
43425 function calls in the line.
43427 @item edit [@var{file}:]@var{function}
43428 look at the program line where it is presently stopped.
43430 @item list [@var{file}:]@var{function}
43431 type the text of the program in the vicinity of where it is presently stopped.
43434 Execute next program line (after stopping); step @emph{into} any
43435 function calls in the line.
43437 @item help [@var{name}]
43438 Show information about @value{GDBN} command @var{name}, or general information
43439 about using @value{GDBN}.
43442 Exit from @value{GDBN}.
43446 For full details on @value{GDBN},
43447 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43448 by Richard M. Stallman and Roland H. Pesch. The same text is available online
43449 as the @code{gdb} entry in the @code{info} program.
43453 @c man begin OPTIONS gdb
43454 Any arguments other than options specify an executable
43455 file and core file (or process ID); that is, the first argument
43456 encountered with no
43457 associated option flag is equivalent to a @option{-se} option, and the second,
43458 if any, is equivalent to a @option{-c} option if it's the name of a file.
43460 both long and short forms; both are shown here. The long forms are also
43461 recognized if you truncate them, so long as enough of the option is
43462 present to be unambiguous. (If you prefer, you can flag option
43463 arguments with @option{+} rather than @option{-}, though we illustrate the
43464 more usual convention.)
43466 All the options and command line arguments you give are processed
43467 in sequential order. The order makes a difference when the @option{-x}
43473 List all options, with brief explanations.
43475 @item -symbols=@var{file}
43476 @itemx -s @var{file}
43477 Read symbol table from file @var{file}.
43480 Enable writing into executable and core files.
43482 @item -exec=@var{file}
43483 @itemx -e @var{file}
43484 Use file @var{file} as the executable file to execute when
43485 appropriate, and for examining pure data in conjunction with a core
43488 @item -se=@var{file}
43489 Read symbol table from file @var{file} and use it as the executable
43492 @item -core=@var{file}
43493 @itemx -c @var{file}
43494 Use file @var{file} as a core dump to examine.
43496 @item -command=@var{file}
43497 @itemx -x @var{file}
43498 Execute @value{GDBN} commands from file @var{file}.
43500 @item -ex @var{command}
43501 Execute given @value{GDBN} @var{command}.
43503 @item -directory=@var{directory}
43504 @itemx -d @var{directory}
43505 Add @var{directory} to the path to search for source files.
43508 Do not execute commands from @file{~/.gdbinit}.
43512 Do not execute commands from any @file{.gdbinit} initialization files.
43516 ``Quiet''. Do not print the introductory and copyright messages. These
43517 messages are also suppressed in batch mode.
43520 Run in batch mode. Exit with status @code{0} after processing all the command
43521 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
43522 Exit with nonzero status if an error occurs in executing the @value{GDBN}
43523 commands in the command files.
43525 Batch mode may be useful for running @value{GDBN} as a filter, for example to
43526 download and run a program on another computer; in order to make this
43527 more useful, the message
43530 Program exited normally.
43534 (which is ordinarily issued whenever a program running under @value{GDBN} control
43535 terminates) is not issued when running in batch mode.
43537 @item -cd=@var{directory}
43538 Run @value{GDBN} using @var{directory} as its working directory,
43539 instead of the current directory.
43543 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
43544 @value{GDBN} to output the full file name and line number in a standard,
43545 recognizable fashion each time a stack frame is displayed (which
43546 includes each time the program stops). This recognizable format looks
43547 like two @samp{\032} characters, followed by the file name, line number
43548 and character position separated by colons, and a newline. The
43549 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
43550 characters as a signal to display the source code for the frame.
43553 Set the line speed (baud rate or bits per second) of any serial
43554 interface used by @value{GDBN} for remote debugging.
43556 @item -tty=@var{device}
43557 Run using @var{device} for your program's standard input and output.
43561 @c man begin SEEALSO gdb
43563 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43564 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43565 documentation are properly installed at your site, the command
43572 should give you access to the complete manual.
43574 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43575 Richard M. Stallman and Roland H. Pesch, July 1991.
43579 @node gdbserver man
43580 @heading gdbserver man
43582 @c man title gdbserver Remote Server for the GNU Debugger
43584 @c man begin SYNOPSIS gdbserver
43585 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
43587 gdbserver --attach @var{comm} @var{pid}
43589 gdbserver --multi @var{comm}
43593 @c man begin DESCRIPTION gdbserver
43594 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
43595 than the one which is running the program being debugged.
43598 @subheading Usage (server (target) side)
43601 Usage (server (target) side):
43604 First, you need to have a copy of the program you want to debug put onto
43605 the target system. The program can be stripped to save space if needed, as
43606 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
43607 the @value{GDBN} running on the host system.
43609 To use the server, you log on to the target system, and run the @command{gdbserver}
43610 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
43611 your program, and (c) its arguments. The general syntax is:
43614 target> gdbserver @var{comm} @var{program} [@var{args} ...]
43617 For example, using a serial port, you might say:
43621 @c @file would wrap it as F</dev/com1>.
43622 target> gdbserver /dev/com1 emacs foo.txt
43625 target> gdbserver @file{/dev/com1} emacs foo.txt
43629 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
43630 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
43631 waits patiently for the host @value{GDBN} to communicate with it.
43633 To use a TCP connection, you could say:
43636 target> gdbserver host:2345 emacs foo.txt
43639 This says pretty much the same thing as the last example, except that we are
43640 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
43641 that we are expecting to see a TCP connection from @code{host} to local TCP port
43642 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
43643 want for the port number as long as it does not conflict with any existing TCP
43644 ports on the target system. This same port number must be used in the host
43645 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
43646 you chose a port number that conflicts with another service, @command{gdbserver} will
43647 print an error message and exit.
43649 @command{gdbserver} can also attach to running programs.
43650 This is accomplished via the @option{--attach} argument. The syntax is:
43653 target> gdbserver --attach @var{comm} @var{pid}
43656 @var{pid} is the process ID of a currently running process. It isn't
43657 necessary to point @command{gdbserver} at a binary for the running process.
43659 To start @code{gdbserver} without supplying an initial command to run
43660 or process ID to attach, use the @option{--multi} command line option.
43661 In such case you should connect using @kbd{target extended-remote} to start
43662 the program you want to debug.
43665 target> gdbserver --multi @var{comm}
43669 @subheading Usage (host side)
43675 You need an unstripped copy of the target program on your host system, since
43676 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
43677 would, with the target program as the first argument. (You may need to use the
43678 @option{--baud} option if the serial line is running at anything except 9600 baud.)
43679 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
43680 new command you need to know about is @code{target remote}
43681 (or @code{target extended-remote}). Its argument is either
43682 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
43683 descriptor. For example:
43687 @c @file would wrap it as F</dev/ttyb>.
43688 (gdb) target remote /dev/ttyb
43691 (gdb) target remote @file{/dev/ttyb}
43696 communicates with the server via serial line @file{/dev/ttyb}, and:
43699 (gdb) target remote the-target:2345
43703 communicates via a TCP connection to port 2345 on host `the-target', where
43704 you previously started up @command{gdbserver} with the same port number. Note that for
43705 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
43706 command, otherwise you may get an error that looks something like
43707 `Connection refused'.
43709 @command{gdbserver} can also debug multiple inferiors at once,
43712 the @value{GDBN} manual in node @code{Inferiors and Programs}
43713 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
43716 @ref{Inferiors and Programs}.
43718 In such case use the @code{extended-remote} @value{GDBN} command variant:
43721 (gdb) target extended-remote the-target:2345
43724 The @command{gdbserver} option @option{--multi} may or may not be used in such
43728 @c man begin OPTIONS gdbserver
43729 There are three different modes for invoking @command{gdbserver}:
43734 Debug a specific program specified by its program name:
43737 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
43740 The @var{comm} parameter specifies how should the server communicate
43741 with @value{GDBN}; it is either a device name (to use a serial line),
43742 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
43743 stdin/stdout of @code{gdbserver}. Specify the name of the program to
43744 debug in @var{prog}. Any remaining arguments will be passed to the
43745 program verbatim. When the program exits, @value{GDBN} will close the
43746 connection, and @code{gdbserver} will exit.
43749 Debug a specific program by specifying the process ID of a running
43753 gdbserver --attach @var{comm} @var{pid}
43756 The @var{comm} parameter is as described above. Supply the process ID
43757 of a running program in @var{pid}; @value{GDBN} will do everything
43758 else. Like with the previous mode, when the process @var{pid} exits,
43759 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
43762 Multi-process mode -- debug more than one program/process:
43765 gdbserver --multi @var{comm}
43768 In this mode, @value{GDBN} can instruct @command{gdbserver} which
43769 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
43770 close the connection when a process being debugged exits, so you can
43771 debug several processes in the same session.
43774 In each of the modes you may specify these options:
43779 List all options, with brief explanations.
43782 This option causes @command{gdbserver} to print its version number and exit.
43785 @command{gdbserver} will attach to a running program. The syntax is:
43788 target> gdbserver --attach @var{comm} @var{pid}
43791 @var{pid} is the process ID of a currently running process. It isn't
43792 necessary to point @command{gdbserver} at a binary for the running process.
43795 To start @code{gdbserver} without supplying an initial command to run
43796 or process ID to attach, use this command line option.
43797 Then you can connect using @kbd{target extended-remote} and start
43798 the program you want to debug. The syntax is:
43801 target> gdbserver --multi @var{comm}
43805 Instruct @code{gdbserver} to display extra status information about the debugging
43807 This option is intended for @code{gdbserver} development and for bug reports to
43810 @item --remote-debug
43811 Instruct @code{gdbserver} to display remote protocol debug output.
43812 This option is intended for @code{gdbserver} development and for bug reports to
43816 Specify a wrapper to launch programs
43817 for debugging. The option should be followed by the name of the
43818 wrapper, then any command-line arguments to pass to the wrapper, then
43819 @kbd{--} indicating the end of the wrapper arguments.
43822 By default, @command{gdbserver} keeps the listening TCP port open, so that
43823 additional connections are possible. However, if you start @code{gdbserver}
43824 with the @option{--once} option, it will stop listening for any further
43825 connection attempts after connecting to the first @value{GDBN} session.
43827 @c --disable-packet is not documented for users.
43829 @c --disable-randomization and --no-disable-randomization are superseded by
43830 @c QDisableRandomization.
43835 @c man begin SEEALSO gdbserver
43837 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43838 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43839 documentation are properly installed at your site, the command
43845 should give you access to the complete manual.
43847 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43848 Richard M. Stallman and Roland H. Pesch, July 1991.
43855 @c man title gcore Generate a core file of a running program
43858 @c man begin SYNOPSIS gcore
43859 gcore [-o @var{filename}] @var{pid}
43863 @c man begin DESCRIPTION gcore
43864 Generate a core dump of a running program with process ID @var{pid}.
43865 Produced file is equivalent to a kernel produced core file as if the process
43866 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
43867 limit). Unlike after a crash, after @command{gcore} the program remains
43868 running without any change.
43871 @c man begin OPTIONS gcore
43873 @item -o @var{filename}
43874 The optional argument
43875 @var{filename} specifies the file name where to put the core dump.
43876 If not specified, the file name defaults to @file{core.@var{pid}},
43877 where @var{pid} is the running program process ID.
43881 @c man begin SEEALSO gcore
43883 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43884 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43885 documentation are properly installed at your site, the command
43892 should give you access to the complete manual.
43894 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43895 Richard M. Stallman and Roland H. Pesch, July 1991.
43902 @c man title gdbinit GDB initialization scripts
43905 @c man begin SYNOPSIS gdbinit
43906 @ifset SYSTEM_GDBINIT
43907 @value{SYSTEM_GDBINIT}
43916 @c man begin DESCRIPTION gdbinit
43917 These files contain @value{GDBN} commands to automatically execute during
43918 @value{GDBN} startup. The lines of contents are canned sequences of commands,
43921 the @value{GDBN} manual in node @code{Sequences}
43922 -- shell command @code{info -f gdb -n Sequences}.
43928 Please read more in
43930 the @value{GDBN} manual in node @code{Startup}
43931 -- shell command @code{info -f gdb -n Startup}.
43938 @ifset SYSTEM_GDBINIT
43939 @item @value{SYSTEM_GDBINIT}
43941 @ifclear SYSTEM_GDBINIT
43942 @item (not enabled with @code{--with-system-gdbinit} during compilation)
43944 System-wide initialization file. It is executed unless user specified
43945 @value{GDBN} option @code{-nx} or @code{-n}.
43948 the @value{GDBN} manual in node @code{System-wide configuration}
43949 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
43952 @ref{System-wide configuration}.
43956 User initialization file. It is executed unless user specified
43957 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
43960 Initialization file for current directory. It may need to be enabled with
43961 @value{GDBN} security command @code{set auto-load local-gdbinit}.
43964 the @value{GDBN} manual in node @code{Init File in the Current Directory}
43965 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
43968 @ref{Init File in the Current Directory}.
43973 @c man begin SEEALSO gdbinit
43975 gdb(1), @code{info -f gdb -n Startup}
43977 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43978 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43979 documentation are properly installed at your site, the command
43985 should give you access to the complete manual.
43987 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43988 Richard M. Stallman and Roland H. Pesch, July 1991.
43994 @node GNU Free Documentation License
43995 @appendix GNU Free Documentation License
43998 @node Concept Index
43999 @unnumbered Concept Index
44003 @node Command and Variable Index
44004 @unnumbered Command, Variable, and Function Index
44009 % I think something like @@colophon should be in texinfo. In the
44011 \long\def\colophon{\hbox to0pt{}\vfill
44012 \centerline{The body of this manual is set in}
44013 \centerline{\fontname\tenrm,}
44014 \centerline{with headings in {\bf\fontname\tenbf}}
44015 \centerline{and examples in {\tt\fontname\tentt}.}
44016 \centerline{{\it\fontname\tenit\/},}
44017 \centerline{{\bf\fontname\tenbf}, and}
44018 \centerline{{\sl\fontname\tensl\/}}
44019 \centerline{are used for emphasis.}\vfill}
44021 % Blame: doc@@cygnus.com, 1991.